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Geology and geochronometry of the eocene Tatla Lake metamorphic core complex, western edge of the intermontane… Friedman, Richard M. 1988

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GEOLOGY AND GEOCHRONOMETRY OF THE EOCENE TATLA LAKE MET AMORPHIC CORE COMPLEX, WESTERN EDGE OF THE INTERMONTANE BELT, BRITISH COLUMBIA by RICHARD M. FRIEDMAN M.S., University of Chicago, 1983 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSPHY in THE FACULTY OF GRADUATE STUDIES Department of Geological Sciences We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA October, 1988 ® Richard M. Friedman, 1988 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at The University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of Geological Sciences The University of British Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 Date: October, 1988 ABSTRACT The Tatla Lake Metamorphic Complex (TLMC) underlies 1000 km 2 on the western side of the Intermontane Belt (1MB) northeast of the Yalakom fault Three fault-bounded lithotectonic assemblages are recognized in the area studied: an amphibolite grade gneissic and migmatitic core, structurally overlain by a 1 to 2.5 + km-thick zone of amphibolite and greenschist grade mylonite and ductilely sheared metamorphic rocks, the ductilely sheared assemblage (DSA), which is in turn structurally overlain by weakly deformed to unstrained subgreenschist grade rocks of the upper plate which flank the TLMC on three sides. Structures in the gneissic core include a gneissic foliation and schistosity (Sic), which has been deformed by west to northwest-trending tight to isoclinal folds (F2c). Tectonic fabrics observed throughout the DSA which formed during Ds deformation include a gently dipping mylonitic foliation (Ss), containing a mineral elongation (stretching) lineation (Ls) which trends towards 280° ± 20°. Minor folds of variable trend (Fs), almost exclusively confined to DSA metasedimentary rocks, are interpreted as coeval with ductile shear. Vergence of these folds defines movement sense and direction of top towards 290° ± 20°. Kinematic indicators from DSA rocks which have not been deformed by syn-ductile shear folds indicate a top-to-the-west sense of shear while those deformed by Fs folds yield conflicting results, with a top-to-the-west sense predominating. The entire lower plate comprising the TLMC has been deformed by broad, upright, west to west-northwest trending, shallowly plunging map-scale folds (F3) during D3, which deform Sic and Ss surfaces. The steeply dipping, northwest-trending Yalakom fault truncates all units and structures of the TLMC. Gently to moderately dipping normal faults of Ds and post-D3 relative age are the southern and eastern boundaries between DSA upper plate rocks and 1MB lower plate ii rocks. U-Pb zircon dates from igneous arid meta- igneous rocks from the lower plate range from Late Jurassic (157 Ma) through Eocene (47 Ma). These dates bracket the timing of Cretaceous (107 Ma to 79 Ma, in the core) and Eocene (55 Ma to 47 Ma, in the DSA) deformation and metamorphism in the lower plate. Biotite and hornblende K - A i dates of 53.4 Ma to 45.6 Ma for lower plate rocks are in sharp contrast to Jurassic dates from nearby upper plate rocks; they record the uplift and cooling of the TLMC. Whole rock initial 8 7Sr/ 8 6Sr ratios (and for most samples present-day values) of less <0.704 have been determined for igneous and meta-igneous rocks of the TLMC; such values are typical of magmatic arc rocks of the 1MB and Coast Plutonic Complex of B.C. Whole rock major and trace element chemistry of lower plate igneous and meta-igneous rocks indicate sub-alkaline, calcalkaline, volcanic arc affinities. Garnet-biotite temperatures (interpreted as Eocene in age), from pelitic schist in the southern part of the DSA increase from about 400 + 50 to 650+50 C with increasing structural depth. A GT-BI-QZ-Al 2Si0 5 pressure of 8+3 kb has been calculated for one of these samples. A T-P of 650 ±50 C and 5.3+3 kb, calculated from inclusions and garnet cores in a small pelitic pendant in the northwest part of the DSA, reflects conditions during intrusion of the surrounding 71 ±3 Ma igneous body. A pressure of 7.2 ± 1.4 kb, based on the total Al in hornblende, has been calculated for this body. Cretaceous ductile deformation in the gneissic core may be related to folding and thrusting which occured in high level rocks to the west and east of the field area. During Early Eocene time (55-47 Ma) the TLMC acquired the characteristics of iii a Cordilleran metamorphic core complex. Mylonites of the DSA were emplaced by faulting beneath weakly deformed, low metamorphic grade rocks of the upper plate. Synchronously, metamorphic rocks of the gneissic and migmatitic core of the TLMC were moved to higher crustal levels along the footwall of the DSA normal ductile shear zone. The formation of F3 folds and final uplift of the TLMC (47-35 Ma) is postulated to be the consequence of transpression related to later Eocene dextral motion along the Yalakom fault The TLMC has structural style and timing of deformation similar to metamorphic core complexes in southeastern B.C. Local and regional evidence is consistent with the formation of the TLMC in a regional extensional setting within a vigorous magmatic arc. iv TABLE OF CONTENTS Abstract ii Acknowledgments xiii 1. INTRODUCTION 1 1.1. Location 1 1.2. Previous Work 1 1.3. Regional Geology 3 2. MAP UNITS 8 2.1. Gneissic Core 8 2.1.1. Migmatitic Gneiss (mg) 8 2.1.2. Granoblastic Gneiss (gg) 10 2.1.3. One Eye Tonalite (LKoe) 16 2.2. Ductilely-Sheared Assemblage (DSA) 16 2.2.1. Mylonitic Orthogneiss (og) 18 2.2.2. Metasedimentary Rocks (Jms) 26 2.2.3. Metavolcanic Rocks (Jmv) 31 2.2.4. Eagle Lake Tonalite (Eel) 33 2.2.5. Deformed Sills (LKgsi. LJasi and Edsi) 35 2.2.6. Tatla Lake Stock (Etl) 35 2.2.7. Maclntyre Island Dykes (Td) 39 2.3. Upper Plate Rocks 39 2.3.1. Jurassic Volcanic Rocks (Iv) 39 2.3.2. Early Tertiary Volcanic Rocks (Tv) 41 2.3.3. Quartz Diorite (LJqd) 41 2.4. Rocks West of the Yalakom Fault 43 2.4.1. Early Cretaceous Volcanic Rocks (IKvs) 43 2.4.2. Quartz Diorite of the Coast Plutonic Complex (EJqd) 43 3. STRUCTURE 45 3.1. Mesoscopic Structures 48 3.1.1. Gneissic Core 48 3.1.2. Ductilely-Sheared Assemblage 54 3.1.3. Phase 3 67 3.1.4. Faults and Fractures 70 3.2. Microscopic Structures 77 3.2.1. Gneissic Core 77 3.2.2. Ductilely-Sheared Assemblage 84 3.3. Summary 96 4. GEOCHRONOMETRY 101 4.1. U-Pb Zircon Geochronometry 101 4.1.1. Late Jurassic - Early Cretaceous U-Pb Dates 102 4.1.2. Cretaceous U-Pb Dates (70-110 Ma) 102 4.1.3. Eocene U-Pb Dates 105 4.1.4. Geological Significance of U-Pb Zircon Data 109 4.2. K-Ar Geochronometry 112 v 4.2.1. Discussion and Interpretation of K-Ar Dates 1.14 4.2.2. Regional Significance of K-Ar Dates from the TLMC 116 4.3. Rb/Sr and Sr Isotopic Study 116 4.3.1. Whole-Rock Data 116 4.3.2. Calculated Initial Ratios 118 4.3.3. Discussion .-. 121 5. METAMORPHISM 122 5.1. Gneissic Core: Mc Prograde Metamorphism 123 5.2. Ductilely-Sheared Assemblage: Ms Metamorphsm 129 5.2.1. Intermediate to Mafic Metavolcanic Rocks 131 5.2.2. Metapelitic Rocks 135 5.2.3. Ms Metamorphism: Mineral Reactions 152 5.2.4. Ms Metamorphism: Conditions of Metamorphism 160 5.3. M3 Metamorphism 177 5.4. Metamorphism in the Upper Plate 180 5.5. Summary and Discussion 182 5.5.1. Summary 182 5.5.2. Discussion 184 6. GEOCHEMISTRY 188 6.1. Classification and Tectonic Setting 188 7. GEOLOGIC EVOLUTION AND TECTONIC MODELS FOR THE TLMC 195 7.1. Summary of Results which bear on the Geologic Evolution of the TLMC 195 7.1.1. Mapping and Structure 195 7.1.2. Metamorphism 196 7.1.3. Geochemistry 198 7.1.4. Dating of TLMC Magmatism, Structural Fabric/Metamorphism, and Cooling/Uplift 199 7.2. The Geological Evolution of the TLMC 200 7.2.1. Pre-Eocene compression 201 7.2.2. Eocene tectonic development of the TLMC 201 7.3. Regional Perspectives and Tectonic Models 205 7.3.1. Regional Cretaceous Compression 205 7.3.2. Eocene extensional deformation in southern B.C. and the northwestern U.S 206 7.3.3. The TLMC and Eocene regional tectonics of southern B.C. and northern Washington 207 REFERENCES CITED 213 APPENDICES 230 1. Appendix 1. List of chemical, isotopic and microstructural samples from the TLMC 230 2. Appendix 2. Microstructural data from the DSA 234 3. Appendix 3. Geochronometric data 237 4. Appendix 4. Geochronometric and geochemical sample preparation and analytical techniques 248 vi 4.1. U-Pb sample preparation and analytical techniques 248 4.2. K-Ar sample preparation and analytical techniques 249 4.3. Rb-Sr sample preparation and analytical techniques 250 4.4. XRF sample preparation 251 5. Appendix 5. Petrographic data from the TLMC 252 6. Appendix 6. Electron microprobe analytical procedures, mineral analyses and calculated thermobarometry 290 6.1. Electron microprobe analytical procedures 290 6.2. Mineral analytical data 290 6.3. Calculated thermobarometric results 320 7. Appendix 7. Computer modeling of metamorphic reactions 337 8. Appendix 8. Geochemical analyses and associated precision and accuracy 342 vii List of Figures 1. Major tectonic belts of the Canadian Cordillera 2 2. Regional geologic map of southern B.C. and the northwestern U.S 4 3. Lithotectonic assemblage map of the TLMC ..9 4. Outcrop photos of migmatitic gneiss 11 5. Outcrop photos of garnet in granoblastic gneiss 13 6. Outcrop photo of granoblastic gneiss 14 7. Outcrop photos of late pegmatitic rocks in granoblastic gneiss 15 8. Photos of the One Eye tonalite 17 9. Outcrop photos of mylonitic orthogneiss subunit 1 20 10. Photo of pendant within subunit 1 of mylonitic orthogneiss 21 11. Photos of mylonitic orthogneiss subunit 2 (JK.og2) 22 12. Photo of mylonitic orthogneiss subunit 3 (LJog3) 24 13. Photo of mylonitic orthogneiss subunit 4 (LJog4) 25 14. Outcrop photos of quartzofeldspathic metasedimantary rocks 27 15. Photos of pelitic metasedimantary rocks 28 16. Metavolcanic rocks (unit am) within the metasedimentary map unit. 29 17. Outcrop photos of rocks within the metavolcanic map unit 32 18. Eagle Lake tonalite slab showing C-S fabrics 34 19. Outcrop photos of Type 2 aplitic sill (LJasi) 36 20. Cut slab of Type 3 Eocene metadacitic sill from sation 84-711-2 37 21. Photo of cut slab of Tatla Lake granodioritic stock 38 22. Photos of Maclntyre Island rhyolitic dyke 40 23. Photo of quartz diorite slab from map unit LJqd : 42 24. Photo of quartz diorite slab from map unit EJqd 44 25. Structural sub-areas in the lower plate of the TLMC 47 26. Photos showing gneissic layering and schistosity (Sic) 49 27. Photo of "rootless" isoclinal folds (Flc) 51 28. Stereoplots of L2c lineations and poles to Sic foliation subdivided by structural sub-area 52 29. Stereoplots of F2c fold axes and poles to F2c axial surfaces subdivided by structural sub-area 53 30. Photos of mesoscopic F2c folds 55 31. Stereoplots of Ds structural elements subdivided by structural sub-area 56 32. Cut slab showing showing Ss foliation 61 33. Photos of "rootless" isoclinal hinges in metasedimentary rocks 62 34. Outcrop photos of Ls mineral elongation lineations 63 35. Photos of Fs folds which are truncated by later Ss foliation 65 36. Outcrop photos of Fs fold forms 66 37. Stereograms showing calculated a-directions for Fs folds 68 38. S2s axial planar crenulation cleavage in metasedimentary rocks 69 39. Stereograms showing F3 fold axes and axial planes 71 40. Photos of F2c structures deformed by F3 folds 72 41. Stereogram showing fracture and dyke orientation data from the TLMC 75 42. Photos of mineral-filled extension fractures oriented parallel to the Ls lineation .76 43. Photomicrograph of granoblastic gneiss parallel to L2c 78 44. Photomicrograph of granoblastic gneiss perpendicular to L2c 79 45. Photomicrograph showing deformation lamellae in quartz: Granoblastic gneiss 80 46. Photomicrograph showing microcracks in plagioclase and subgrains in quartz 82 viii 47. Photomicrograph showing fracture cutting F3 microfolds 83 48. Photomicrograph showing S-C fabrics 85 49. Photomicrographs of quartz ribbon grains in map unit JKog2 87 50. Photomicrograph showing chlorite-filled pull-aparts in plagioclase 89 51. Photomicrograph showing microfaulted plagioclase in felsic meta volcanic rock 90 52. Photomicrograph showing recrystallization of plagioclase, map unit JKog2 91 53. Photomicrographs showing assymetric pressure shadows around a plagioclase porphyroclast 93 54. Photomicrographs showing quartz porphyroclasts in quartz-rich type-II S-C mylonite 94 55. Photomicrographs showing quartz ribbon grains in quartz-rich type II S-C mylonite 95 56. Photomicrographs showing retort shaped mica bounded by shear bands 97 57. Photomicrographs showing late brittle features in ductilely sheared rocks 98 58. Concordia plot of Late Jurassic and Early Cretaceous U-Pb zircon data from the TLMC (DSA) 103 59. Concordia plot of Mid and Late Cretaceous U-Pb zircon data from the TLMC 104 60. Concordia plot of Cretaceous U-Pb zircon data from the TLMC gneissic core ..106 61. Concordia plot of Eocene U-Pb zircon data from the TLMC (DSA) 107 62. Photo showing contact between Sucker Creek sill/dyke and gneissic country rock 110 63. Concordia plot of U-Pb zircon data from the Sucker Creek sill/dyke I l l 64. Map showing locations and dates for TLMC K-Ar dated samples 113 65. Whole rock Rb-Sr isotopic data from rocks of the TLMC 117 66. Rb-Sr isotopic data for whole rock suite from station 84-83-5 119 67. Rb-Sr isotopic data for whole rock suite from station 84-711-3 120 68. Mineral crystallization with respect to deformation in the gneissic core 124 69. Photomicrographs of magmatic epidote in map unit gg2 : 125 70. Photomicrograph of myrmekitic textures in map unit gg2 128 71. Solidus P-T data determined with natural rocks as starting materials and in the pure system QZ-OR-AB-H 20 130 72. Mineral crystallization with respect to deformation: mafic to intermediate metavolcanic rocks, DSA 132 73. Photomicrographs of garnet in metavolcanic rocks at station 84—622—5 134 74. Photomicrographs of epidote in metavolcanic rocks at station 85-726-4 136 75. Photomicrographs of biotite in pulled-apart and necked amphibole, map unit Jmvl ; 137 76. Recrystallization with respect to deformation: metapelitic rocks, map unit Jmsp ...139 77. Photomicrographs of quartz ribbon grains in metapelitic rocks, map unit Jmsp ...140 78. Biotite fringing garnet, map unit Jmsp, station 85-610-1 142 79. Photomicrograph of mica in isoclinally folded metapelitic schist 143 80. Photomicrograph of Ms chlorite in CHL-BI grade metapelitic schist 144 81. Photomicrograph of chloritoid in metapelitic schist, station 85-68-3 145 82. Photomicrographs of rotated garnet in metapelitic schist 147 83. Photomicrographs of Ms staurolite in metapelitic schist 149 84. Photomicrographs of Ms kyanite in metapelitic schist 151 85. Photomicrographs of Ms sillimanite in TLMC metapelitic schist 153 86. Photomicrographs of andalusite in TLMC metapelitic schist 154 ix 87. Photomicrographs of replacement assemblage in partially resorbed garnet, pelitic schist 158 88. Phase equilibria which constrain Ms conditions of metamorphism in TLMC pelitic schist 161 89. Hypothetical T-P path and GT-BI, GT-PL-Al 2Si0 5-QZ thermobarometric determinations 166 90. Thermobarometric data from rocks of the DSA plotted over modeled reaction net .- 168 91. Photomicrographs of M3 chlorite in TLMC pelitic schist 179 92. Photomicrographs of nonfoliated siltstone from TLMC upper plate 181 93. Generalized metamorphic grade of the TLMC 185 94. T-P-t path for rocks of the TLMC 186 95. Modes of geochemically analysed samples plotted on IUGS plutonic rock diagram 189 96. Chemically analysed samples plotted on alkali vs silica diagram 190 97. Chemically analysed samples plotted on AFM diagram 191 98. Trace element bulk earth normalized diagram (BEND) 193 99. Chemically analysed samples plotted on Rb vs Y + Nb tectonic setting dicriminant diagram 194 100. Eocene tectonic development of the TLMC 202 101. Schematic diagram depicting D3 transpression 204 102. Regional Eocene magmatism and extension in southwestern Canada and the northwestern U.S 209 103. Schematic Eocene Cordilleran cross-section, circa 55-47.5 Ma 211 x List of Tables Table 1. Terminology for structural elements in the metamorphic core of the TLMC 46 Table 2. Explanation of samples plotted on sample location map and discussed in text 231 Table 3. Sense of shear indicators in oriented X-Z sections, TLMC ductilely sheared rocks 235 Table 4. U-Pb zircon dates from the Tatla Lake Metamorphic Complex 238 Table 5. Dominant characteristics of zircon populations 243 Table 6. K-Ar dates from the Tatla Lake Metamorphic Complex and vicinity 245 Table 7. Rb-Sr analytical data from the Tatla Lake Metamorphic Complex 246 Table 8. Rb-Sr sample locations and descriptions 247 Table 9. Mineral abbreviations and formulae 254 Table 10. Petrographic data from the gneissic core of the TLMC 255 Table 11. Petrographic data from the ductilely sheared assemblage of the TLMC 264 Table 12. Electron microprobe standards for mineral analyses 291 Table 13. Electron microprobe mineral analytical data 292 Table 14. Thermobarometric data from the TLMC 322 Table 15. Equilibria which have been modeled in pressure-temperature space 340 Table 16. Activities of phases used to model equilibria shown in Figure 88 341 Table 17. Major element analytical precision 343 Table 18. Major element analytical accuracy 344 Table 19. Major and trace element geochemical data from the TLMC 345 Table 20. Normalization factors for BEND 348 xi List of Plates (Back Poolcot) Plate 1. Geology of the Tatla Lake Metamorphic Complex, southwestern British Columbia Plate 2. Structure: Foliations and Mineral Lineations / Plate 3. Structure: Folds and Fractures \ Plate 4. Sample Location Map / Plate 5. Mineral Assemblage Map j Plate 6. Geologic Cross Sections I / xii ACKNOWLEDGMENTS I would like to acknowledge the unending support of R. L. Armstrong. In addition, H. Trenchard and A. Jung assisted in the field; Krista Scott, J. Harakal, P. van der Heyden, J. Mortensen, D. Parkinson, S. Horsky, and D. Runkle helped in the lab. Discussions with W. H. Mathews, G. J. Woodsworth, H. J. Greenwood, J. V. Ross, J. K. Russell, P. van der Heyden, D. Murphy, D. McMullin, R. R. Parrish, J. A. Fillipone, H. W. Tipper, J. O. Wheeler, and H. Gabrielse greatly improved this project Thanks to the Geological Sciences Techies for their expertise and patience. Finally, I gratefully acknowledge the moral support of Ana and all the folks at 4630. Funding for this project came from NSERC grant A-8841 to R. L. Armstrong. xiii 1. I N T R O D U C T I O N 1.1. L O C A T I O N The Tatla Lake area lies approximately 200 km west of Williams Lake in southwestern interior British Columbia, along the southwestern edge of the Interior (Chilcotin) Plateau. The Williams Lake - Bella Coola highway (B.C. route 20), a well maintained paved/gravel road, runs through the centre of, and provides easy access to the Tatla Lake area. Logging and ranch roads of various qualities branch from route 20 and allow day-trip access to virtually all portions of the study area. Figure 1 shows the limit of the study area, which was mapped at 1:50,000 and 1:20,000 scales during the summers of 1984 and 1985. The area is almost completly within the Interior Plateau physiographic belt, a region of subdued topographic relief. Broad valley bottoms in the study area are between about 900 and 1050 metres elevation (about 2950 to 3500 feet), with rounded hilltops between 1375 and 1900 metres (about 4500 to 6200 feet). The entire mapped area is below timberline, and with the exception of open grassland directly north of Tatla Lake, has abundant stands of jackpine, fir and alder. Most of the bedrock exposures occur near the tops of hills. 1.2. P R E V I O U S W O R K The earliest mention of rocks in the Tatla Lake area was by Dawson (1876). He observed schistose and gneissic rocks adjacent to Eagle and Tatla Lakes. Dolmage (1926) reported on the general geology and economic geology of the Tatla - Bella Coola area. A reconnaissance map published in that report included the southwestern portion of the present study area. Dolmage (1926) mapped gneissic rocks 1 INTRODUCTION / 2 Figure 1. Major tectonic belts of the Canadian Cordillera showing the location of the study area. INTRODUCTION / 3 on Tatla Hill and southeast of Kleena Kleene. He noted the occurrence of what he termed banded quartz, feldspar, garnet, biotite gneiss and a more massive quartz diorite gneiss. Geological Survey of Canada (GSC) reconnaissance mapping of the present study area was carried out in the early 1950s north of 52° N (Anahim Lake sheet; 93C, Tipper, 1969A) and in the middle 1960s south of 52° N (Mt Waddington sheet; 92N, Tipper, 1969B). Although the metamorphic rocks were shown as a single unit on these maps, Tipper (1969B) noted the location of augen gneiss, metavolcanic, metasedimentary, and high grade gneissic rocks in the text of the report Detailed structural analysis was beyond the mandate of the GSC reconnaissance studies. Tipper did however identify the amphibolite grade rocks of the Tatla Lake area as anomalous (and unique) with respect to typical subgreenschist fades rocks of the Intermontane Belt (1MB), and pointed out the need for more detailed study. 1.3. REGIONAL GEOLOGY The study area lies along the southwestern edge of the 1MB, separated from the Coast Plutonic Complex by the Yalakom fault (Figure 2). Regionally, the 1MB is characterized by rocks which - only rarely are penetratively deformed or exceed subgreenschist metamorphic grade (Monger and Hutchison, 1971). At the general latitude of the study area (51° - 53° N), stratified rocks of the 1MB include Late Triassic volcanic and sedimentary rocks tentatively correlated with the Nicola Group, Jurassic volcanic flows, breccias and sediments correlated with the Hazelton Group (Tipper et al., 1981), Cretaceous clastic sedimentary rocks in the Nechako and Tyaughton (which straddles the Yalakom fault) basins (Jeletzky and Tipper 1968; Kleinspehn, 1985), Early Tertiary Ootsa Lake Group volcanics (Souther, 1977) and Miocene Chilcotin Group INTRODUCTION / 4 Legend for Rocks East of the Coast Plutonic Complex MIOCENE and PLIOCENE |: - .'I Chilcotln Group Basalt OLIGOCENE pc"i Chilliwack Batholith EARLY TERTIARY Volcanic and Sedimentary Rocks Plutonic Rocks CRETACEOUS and JURASSIC g Sedimentary and Volcanic Rocks Plutonic Rocks Lower and Middle Jurassic Hazelton Group Volcanics • CRETACEOUS and Older Sedimentary and Volcanic Rocks of Greenschist and Lower Grade Middle to Upper Amphibolite Grade Rocks of Proterozoic to Cretaceous Age Figure 2. Geological map of southern British Columbia and the extreme northwestern United States east of the Coast Plutonic Complex. Eocene faults are highlighted. Normal faults: balls on upper plate; Thrust faults: teeth on upper plate. Modified from Tipper et al. (1981); Gabites (1985); Carr et al. (1987); and Wheeler and McFeely, (1987). BRT: Bridge River Terrane; CCT: Cache Creek Terrane; F: Fraser Fault; HA: Harrison Lake Fault; HO: Hozameen Fault; HV: Hungry Valley Fault; ICPC: Intra Coast Plutonic Complex Fault; K: Kettle Complex; M: Methow Basin; NC: North Cascades; NRMT: Northern Rocky Mountain Trench fault System, southern splays; O: Okanagan Complex; P: Pasayten Fault; PC: Phair Creek Fault; PI: Pinchi Fault; PR: Priest River Complex; RL: Ross Lake Shear Zone; S: Shuswap Complex; SC: Straight Creek Fault; T: Tyaughton Basin; TZ: Tchaikazan Fault V: Valhalla Complex; Y: Yalakom Fault INTRODUCTION / 5 Figure 2 . Continued: Regional geologic map of southern B.C. and the northwestern U.S. See caption on previous page for details. INTRODUCTION / 6 basalts (Bevier, 1983). Granitic plutons of Mesozoic and Cenozoic age also occur in the region (Tipper et al., 1981). The Tertiary volcanic rocks, especially the Chilcotin Group basalts, cover most of the 1MB near the study area, in this portion of the 1MB. Higher grade metamorphic rocks in the study area occur in a structural window and are unique in the 1MB in that they are penetratively deformed and locally attain upper amphibolite fades metamorphic grade. The steeply dipping Yalakom fault, cuts metamorphic rocks of the Tatla Lake area and is the boundary between the 1MB and Coast Belt to the southwest. This fault has commonly been interpreted as a dextral transcurrent system (Tipper, 1969A; Kleinspehn, 1985). Tipper (1969B) has suggested that about 150 km of dextral offset occurred along the segment of the Yalakom adjacent to the TLMC based on a correlation of Jurassic stratified rocks on both sides of the fault Miller (1986) has suggested that the Yalakom was a sinistral fault during the Mesozoic time, based on small scale structures near Lillooet B.C. The rocks directly to the southwest of the Yalakom fault near the TLMC include a Late Triassic marine volcanic arc assemblage, Jura-Cretaceous clastic sediments of the Tyaughton trough and Jurassic to Eocene granitic intrusions of the CPC (Tipper, 1969A; Kleinspehn, 1985; Rusmore, 1985). Stratified rocks as young as Hauterivian in age have been deformed by dominantly northeasterly verging folds and thrusts (Tipper, 1969B; Rusmore and Woodsworth, 1988). Published terrane maps have included the TLMC and vicinity east of the Yalakom fault as part of Stikinia (Monger and Berg, 1984; Wheeler and McFeely, 1987). The distinctve Stikinian Paleozoic sequence has not been recognized in this area. The correlation with Stikinia is tentative and based only on a lithologic correlation of Jurassic volcanic (and metavolcanic) rocks in the vicinity of the TLMC with the INTRODUCTION / 7 Hazelton Group volcanics to the north. Rocks near the study area southwest of the Yalakom fault have recently also been included as part of Stikinia, based on a detailed comparison of Upper Triassic basaltic volcanic rocks with the Takla Volcanics of northern B.C. (Rusmore and Woodsworth, 1988). 2. MAP UNITS Three distinct lithotectonic assemblages have been recognized in the study area: a gneissic and migmatitic core (refered to as the gneissic core), mylonitic and ductilely-sheared metamorphic rocks (refered to as the ductilely-sheared assemblage or DSA), and undeformed to weakly deformed subgreenschist grade cover rocks. The first two assemblages comprise the lower plate or metamorphic core of the Tatla Lake Metamorphic Complex (TLMC), and the latter the upper plate (Fig. 3). These assemblages are discussed separately in this chapter. The descriptions which follow emphasize the lithologic character, areal distribution, and contact relationships. 2.1. GNEISSIC CORE Rocks of the gneissic core are exposed in the cores of map-scale (F3) antiforms (see Table 1 for structural teminology) and occupy the deepest structural level of the TLMC (Plate 1). These rocks are identified in the field by their mesoscopic gneissic foliation and granoblastic elongate texture (Spry, 1969, p. 263), which contrast sharply with structurally overlying mylonitic and ductilely-sheared metamorphic, rocks. Core gneisses have been subdivided into granoblastic (map units ggl, gg2) and migmatitic (map unit mg) gneissic units based on the percentage of migmatitic veins. 2.1.1. Migmatitic Gneiss (mg) Migmatitic gneiss is exposed in the deepest structural level of the core gneiss assemblage in the axial region of the northwestern map-scale (F3) antiform shown on Plate 1. The contact between migmatite and overlying gneiss is gradational and is based on the proportion of neosome (migmatitic veins; Ashworth, 1985) to the total 8 MAP UNITS / 9 L O W E R P L A T E 0 UPPER PLATE ROCKS Q DUCTILELY SHEARED ROCKS fV^n COAST BELT ROCKS GNEISSIC CORE Figure 3. Uthotectonic assemblage map of the TLMC and vicinity. See Plate 1 for fault symbols. MAP UNITS / 10 rock. An arbitrary value of 10% neosome was chosen as minimum for the migmatitic gneiss unit Migmatitic rocks of the TLMC are dominantly of the stromatic (layered; Ashworth, 1985) structural type (Fig. 4A, 4B), with rare examples of agmatic material also present. Overall, the migmatitic gneiss is tonalitic. Neosomes comprise 10% to over 50% of the rock. Leucosomes are commonly 1 to 10 cm thick, tonalitic to granodioritic in composition, and contain less than 10% mafics. They are fine to medium grained and have an aplitic texture (Fig. 4B). Melanosomes up to 20 cm thick have been observed and are commonly up to 50% biotite + hornblende. They are medium grained and contain a schistosity primarily defined by biotite which is subparallel to the gneissic layering in the rock (Fig. 4B). Mesosomes (Ashworth, 1985) comprise from less than half to about 90% of the migmatitic gneiss and are similar to rocks of the overlying gneiss unit Based on modal minerals these horizons are quartz dioritic to tonalitic in composition with up to 30% hornblende ± biotite. They are medium to coarse grained with granoblastic elongate texture, and a foliation similar to that described above in melanosomes (Fig. 4B). 2.1.2. Granoblastic Gneiss (gg) The distribution of the granoblastic gneiss unit, which areally comprises the bulk of the core gneiss assemblage, is shown on Plate 1, (map units ggl, EKggl, gg2). This unit is compositionally homogenous across the study area, dominantly quartz dioritic to tonalitic based on modal minerals. The mafic minerals biotite and hornblende occurring alone or together comprise 15 to 30% of the gneiss. Fist sized pegmatitic clots of hornblende have been rarely observed. Almandine garnet has been locally observed in the granoblastic gneiss (Plate 6). It is commonly fine grained and National Library of Canada Biblioth&que nationale du Canada Canadian Theses Service Service des th&ses canadiennes NOTICE AVIS THE QUALITY OF THIS MICROFICHE IS HEAVILY DEPENDENT UPON THE QUALITY OF THE THESIS SUBMITTED FOR MICROFILMING. LA QUALITE DE CETTE MICROFICHE DEPEND GRANDEMENT DE LA QUALITE DE LA THESE SOUMISE AU MICROFILMAGE. UNFORTUNATELY THE COLOURED ILLUSTRATIONS OF THIS THESIS CAN ONLY YIELD DIFFERENT TONES OF GREY. MALHEUREUSEMENT, LES DIFFERENTES ILLUSTRATIONS EN COULEURS DE CETTE THESE NE PEUVENT DONNER QUE DES TEINTES DE GRIS. / 11 MAP UNITS / 12 comprises much less than 1% of the rock. At one locality however, garnet glomeroporphyroblasts up to 4 cm in diameter with well developed depletion haloes have been observed (Fig. 5A, 5B). The granoblastic gneiss unit owes its name to the granoblastic elongate texture which can be observed throughout its areal extent (Fig. 6A, 6B). Grain sizes range from medium and coarse in the northwestern part of the study area, to fine and medium grained towards the east These rocks contain one penetrative foliation (Sic, Table 1), defined by biotite, which is subparallel to mesoscopic gneissic layering. At least 2 generations of mesoscopic folds (also recognized in the underlying migmatitic gneisses) deform this foliation (Fig. 6B). Centimetre- to metre-scale post-tectonic pegmatitic bodies, sometimes exhibiting graphic texture, comprise a minor constituent of the granoblastic gneiss unit They occur as two distinct mineralogical types: plagioclase + alkali feldspar + biotite + muscovite + quartz + garnet and plagioclase + hornblende + biotite + quartz. The latter type do not exceed about 10 cm in width (Fig. 7). The granoblastic gneiss unit is bounded below by migmatitic gneiss and above by mylonitic orthogneiss and metasedimentary rocks of the ductilely-sheared assemblage (DSA). As previously noted, the lower contact is gradational, and has been placed where migmatitic veining comprises about 10% of the total rock volume. The upper contact has not been observed due to the presence of cover in the area. Exposures of granoblastic gneiss and mylonitic orthogneiss occur less than 50 m apart at several localities, suggesting that the transition between these two contrasting units is abrupt The contact is interpreted as a fault / 13 Figure 5. Outcrop photos of garnet in granoblastic gneiss unit at station 85-720-3. A. Large garnet glomeroporphyroblasts. Pencil is about 18 cm long. B. Depletion halos developed around garnet coin is about 18 mm in diameter. See Plate 5 for garnet localities in the gneissic core. / 14 Figure 6. Outcrop photos of granoblastic gneiss. A. Station 85-712-9; Note isoclinally folded felsic layer. Pencil is about 15 cm in length. B. Station 85-711-3; Hammerhead is about 17 cm long. Figure 7. Photos of late pegmatitic rocks in granoblastic gneiss. A. Contact of relatively large (several square metres) pegmatite body with gneissic country rock from station 84-89-IB. Righthand slab has been stained for potassium feldspar. Coin is about 18 mm in diameter. B. Hornblende-plagioclase pematitic knots at station 85-717-7. Hammerhead is about 17 cm long. MAP UNITS / 16 2.1.3. One Eye Tonalite (LKoe) A tonalitic to rarely quartz dioritic body about 4 x 2 km in dimension, which intrudes the granoblastic gneiss unit, has been informally named the One Eye Tonalite. Mineralogically, this intrusion consists of medium to coarse grained plagioclase (An 3 0_ 3 2) + biotite + hornblende and accessory epidote, zircon, apatite and magnetite. Along the margin of this body a schistosity, subparallel to the gneissic foliation (Sic), has been observed. The intensity of this fabric diminishes towards the interior, becoming indistinct in the core (Fig. 8). The One Eye tonalite is less strained than the surrounding gneiss and is interpreted as a late syn-kinematic body. It is thought that it was intruded during D2c deformation (see Table 1 for structural terminology). 2.2. DUCTILELY-SHEARED ASSEMBLAGE (DSA) The upper lithotectonic assemblage in the lower plate of the TLMC consists of mylonitic and ductilely-sheared metamorphic rocks, interpreted to be part of a major crustal, 1 to 2+ km thick ductile shear zone. A wide variety of rock types are present and metamorphic grade varies from upper greenschist to middle amphibolite facies. The unifying characteristics of this assemblage are the structural elements; a regionally developed mineral-elongation lineation (Ls) and mylonitic foliation (Ss). These structures will be briefly alluded to in this chapter but are described in detail in chapter 3 (see Table 1 for structural terminology). Plate 1 shows the areal extent of the ductilely-sheared assemblage and its subunits. Metasedimentary and metavolcanic rocks dominate the southeastern part of the map-area and also occur in the cores of map-scale F3 synforms. Towards the northwestern portion of the map-area structurally deeper mylonitic orthogneiss is the most common rock type exposed. Pre- to post-tectonic igneous rocks with compositions / 17 Figure 8. Photos of the One Eye tonalite. A. Mafic xenolith in coarse grained tonalite at station 84-87-3. Hammer is about 33 cm long. B. Coarse grained hornblende-biotite tonalite to quartz diorite from station 84-87-2. Slab on right has been stained for potassium feldspar. Coin is about 18 mm in diameter. MAP UNITS / 18 varying from quartz diorite to rhyolite intrude and cut rocks of the DSA. Faults separate the DSA (lower plate rocks) from upper plate rocks of the 1MB and Coast Plutonic Complex. A shallowly to moderately dipping fault which strikes parallel to mylonitic foliation occurs along the southern margin, and a poorly exposed, apparently crosscutting structure is locally recognized along the eastern and northeastern margins of the ductilely-sheared assemblage. The Yalakom fault truncates lower plate rocks and all internal metamorphic fabrics, separating the TLMC from the Coast Plutonic Complex to the southwest. 2.2.1. Mylonitic Orthogneiss (og) Mylonitic orthogneiss has been mapped as a composite unit with distinct lithologic variation recognized across the study area. Plate 1 shows the location of the various mylonitic orthogneiss subunits described below. Although variations in the unit are significant, it is important to note that the total compositional range is narrow; quartz diorite to granodiorite, with tonalite occurring most commonly. U-Pb zircon dating of these rocks corroborate their composite nature, with dates ranging from Late Jurassic to Late Cretaceous in age (Sec. 4.1, Table 4). The contacts of mylonitic orthogneiss with underlying granoblastic gneiss and overlying metasedimentary and metavolcanic rocks are interpreted as ductile faults, Evidence discussed below suggests that portions of the upper contact were originally intrusive in character. Subunit 1 of the mylonitic orthogneiss map unit (LKogl) is located in the northwestern portion of the map-area (Plate 1). These rocks are quartz dioritic to rarely tonalitic, based on mineral modes, with 20-30% biotite plus hornblende. They contain a distinctive pale red purple (5 RP 6/2) coloured plagioclase (An 3o- 3 7), which has not been observed in other mylonitic orthogneiss subunits. From south to north MAP UNITS / 19 over a 4 km distance there is a marked decrease in plagioclase porphyroclast size and number in the rock (Fig. 9). The southern exposures are best described as possessing a foliated, granitic texture, (Fig. 9A), with a gradational change to foliated porphyritic textures towards the north (Fig. 9B). Because there is no obvious increase in strain towards the north this textural variation is thought to reflect primary heterogeneities rather than variable grain size reduction related to deformation. A small (less than 100 m2) pendant consisting of garnet-plagioclase- biotite— sillimanite± kyanite schist, containing the regional mylonitic foliation and lineation, occurs about 1 km north of One Eye Lookout station (Plate 1, Fig. 10). The metamorphic index minerals in this pendant give pressure-temperature information which is discussed in section 5.2 Subunit 2, (JKog2) the most extensively exposed variant of the mylonitic orthogneiss unit occurs locally from the western to northeastern parts of the study area (Plate 1). These rocks are tonalitic in composition, contain about 10% biotite, and lack hornblende. They have the best developed mylonitic foliation and mineral-elongation lineation in the orthogneiss unit Ribbon quartz grains exceeding 3 cm in length and rotated plagioclase porphyroclasts with asymmetric pressure shadows are common (Fig. 11). Near Martin Mountain, mylonitic orthogneiss of subunit 2 is in contact with overlying metasedimentary rocks. The contact occurs across a zone where sheets of mylonitic orthogneiss are intercalated with metasedimentary rocks. This zone is interpreted as a complex, ductilely deformed intrusive contact Subunit 3 of the mylonitic orthogneiss map unit (og3) occurs north and west of the northernmost map-scale (F3) synform in the study area (Plate 1). Based on mineral modes it ranges from tonalitic to granodioritic composition, with 10-15% biotite Figure 9. Outcrop photos of mylonitic orthogneiss subunit 1 (LKogl). A. Ductilely sheared quartz diorite augen gneiss at station 85-76—1, shot towards 200° Blue portion of hammer handle is about 19 cm long. B. Interlayering of augen gneiss and fine grained sills at station 85-713-4. Pen is about 14 cm long. Ss (mylonitic) foliation is well displayed in both photos. MAP UNITS / 21 Figure 10. Coarse grained garnet in pelitic pendant within map unit LKogl, at station 85-76-3. Chisel is about 16 cm long. / 22 Figure 11. Photos of mylonitic orthogneiss subunit 2 (JKog2). A. Tonalite mylonitic augen gneiss shot towards the south at station 84-719-5. Vertical axis of photo is about 15 cm long. B. Slab of tonalite mylonitic orthogneiss from station 84-815-3. Coin is about 21 mm in diameter. MAP UNITS / 23 and no hornblende. It has blastomylonitic texture with medium grained feldspar in a fine grained matrix consisting of quartz and biotite. Subunit 3 can be distinguished from other mylonitic orthogneiss subunits by the relatively high proportion of modal alkali feldspar (up to at least 15%) and the relatively fine grained porphyroclast size (Fig. 12). The contact of unit og3 with overlying metavolcanic rocks of unit Jmvl has been ductilely deformed during Ds mylonitization. The centimetre- to metre-scale interlayering of these two lithologies in the contact zone may not, however, be completely tectonic in nature and is consistent with subunit 3 originating as a high level stock, intruding, or possibly comagmatic with overlying metavolcanic rocks. Subunit 4 of the mylonitic orthogneiss (LJog4) is an approximately 50 m thick sheetlike body located on the south dipping limb of the southern map-scale (F3) antiform, on Splinter and Tatla hills. Compositionally, it is tonalitic to rarely granodioritic, and is distinguished from other mylonitic orthogneiss subunits by the presence of two micas, biotite and muscovite, as well as a flaggy appearance in outcrop (Fig. 13). As is the case for the other of the mylonitic orthogneiss subunits, both mylonitic foliation (Ss) and mineral-elongation lineation (Ls) are well developed. This body crops out between the metasedimentary (Jmsq) and metavolcanic (Jmvl) map units for a portion of its length and is thought to intrude them. This contact zone is an area of localized high ductile strain, and all contacts of subunit 4 have been subsequently modified during deformation. / 24 Figure 12. Granodiorite mylonitic orthogneiss of map unit og3. Slab on right has been stained for potassium feldspar. Coin is about 18 mm in diameter. / Figure 13. Mylonitic orthogneiss of subunit 4 (LJog4). Slabs of two-mica granodiorite mylonitic augen gneiss from station 84-818-2. Slab on right has been stained for potassium feldspar. Coin is about 18 mm in diameter. MAP UNITS / 26 2.2.2. Metasedimentary Rocks (Jms) A map unit composed of metasedimentary and subordinate metavolcanic rocks has been recognized within the ductilely-sheared assemblage. It is exposed in the southern part of the map area and within a relatively small area on Martin Mountain (Plate 1). Metasedimentary rocks range from dominantly quartzofeldspathic to pelitic in composition (Plate 1). Quartzofeldspathic schist (Jmsq), the dominant compositional type, commonly contains subequal amounts of quartz and plagioclase, minor biotite with or without muscovite and/or garnet. Locally, the quartzofeldspathic rocks become very quartz-rich, with quartz to plagioclase ratios as high as 4 to 1. Compositional layering on the mm- and cm-scales is defined by mica-rich and mica-poor horizons (Fig. 14). Metapelitic schist (Jmsp) occurs in the central portion of the southern outcrop belt, mainly west of Whitesand Lake. Metamorphic minerals in these rocks include quartz, garnet, biotite, muscovite, plagioclase, staurolite, kyanite and sillimanite, with an apparent increase in metamorphic grade towards the north with increasing structural depth. Garnet, biotite and muscovite are commonly medium to coarse grained, and easily recognized in handspecimens, (Fig. 15) whereas sillimanite, kyanite and staurolite are fine to very fine grained and have been identified only in thin section. Furthermore, kyanite and sillimanite are very rare in these rocks. Compositional layering is well developed in the metapelitic subunit Sharp compositional contrasts between cm scale horizons of very micaceous schist quartzofeldspathic schist amphibolitic and felsic horizons characterize this subunit Rocks inferred to be metavolcanic in origin on the basis of their composition occur throughout the metasedimentary map unit as felsic or hornblende + plagioclase ± quartz + garnet-bearing layers 10 cm to 1 m thick. They comprise an estimated 10 to 15% of the section (Fig. 16). On much of the south face of Tatia hill / 27 Figure 14. Outcrop photos of quartzofeldspathic metasedimantary rocks (Jmsq). A. Compositional layering in metasedimentary rocks at station 85-727-7, defined by cm- and mm-scale biotite-rich layers. Hammerhead is about 17 cm long. B. Siliceous mylonite at station 84-78-3A, shot towards 020°. Vertical axis of photo is about 18 cm. / 28 Figure 15. Photos of pelitic metasedimantary rocks (Jmsp). A. Garnetiferous pelitic schist at station 84-621-1. Lens cover is about 5 cm in diameter. Slab of pelitic schist from station 85-68-3, cut parallel to Ls and perpendicular to Ss. Coin is about 18 mm in diameter. MAP UNITS / 29 Figure 16. Metavolcanic rocks (unit am) within the metasedimentary map unit A. Dark coloured amphibolites, interpreted as metavolcanic rocks, are interlayered with metasedimentary schist at station 84-819-1. Chisel is about 17 cm long. B. Contact of amphibolite and quartz-feldspathic schist at station 85-819-2. Chisel is about 17 cm long. MAP UNITS / 30 hornblende-plagioclase schist comprises an estimated 50% of the section. Primary depositional and volcanic features have not been recognized in metasedimentary rocks of the TLMC. A schistosity (Ss; mylonitic foliation), parallel to compositional layering, and primarily defined by micas is well developed throughout the map unit In addition, a pervasive mineral-elongation lineation, (Ls), defined by quartz, feldspar and amphibole is obvious in all but the most micaceous schist Shallowly plunging mesoscopic folds of variable trend deform the schistosity (Ss), compositional layering, and locally the mineral lineation. A crenulation cleavage, (Ss2), axial planar to these folds has locally been developed (structural elements are discussed in Chapter 3). The lower contact of the metasedimentary map unit is not exposed along the southern outcrop belt. In the Martin Mountain area, the mylonitic orthogneiss-metasedimentary rock contact is interpreted as a ductilely-sheared intrusive contact (Sec. 2.2.1). In the southern belt and Martin Mountain area metasedimentary rocks are structurally overlain by amphibole-bearing metavolcanic rocks. This contact zone is typified by the intensely developed mineral lineation (Ls) and mylonitic foliation (Ss) and centimetre-scale interlayering of lithologies from above and below the contact. The metasedimentary-metavolcanic unit contact is interpreted as a layer-parallel ductile/brittle fault Rocks of the metasedimentary map unit are lithologically correlated with sedimentary lenses occurring in lower to middle Jurassic volcanic rocks to the east of the study area (Tipper, 1969A, map units 2, 3; 1969B, map unit 7) and west of the Yalakom fault in the Bella Coola map area (Baer, 1973, map unit 10). A late Jurassic minimum age of deposition for the protoliths of the metasedimentary unit has been constrained by a 157+4 Ma U-Pb zircon date from a mylonitic orthogneiss body (LJog4, Sec. 2.2.1.) which intrudes the metasedimentary-metavolcanic unit contact MAP UNITS / 31 2.2.3. Metavolcanic Rocks (Jmv) Amphibolitic schist and phyllitic rocks of volcanic origin (Jmvl, Jmv2) occupy the highest structural position in the ductilely-sheared assemblage. These rocks occur in the cores of map scale F3 synforms and in the southern portion of the lower plate (Plate 1). This map unit is relatively homogenous across the study area. Mineralogically, rocks of the metavolcanic map unit (Jmvl) are composed of actinolite, chlorite, albite, quartz, biotite and accessory phases. In the Martin Mountain area, actinolite and albite have been upgraded to hornblende and oligoclase, respectively (Jmv2). Rocks from map unit Jmv are dark green to gray green, well foliated and lineated, and schistose to less commonly phyllitic. The foliation (Ss, mylonitic foliation) is defined by about 1 mm thick alternating layers of dark green fibrous actinolite (actinolitic hornblende for Jmv2) and gray green elongate plagioclase and quartz clasts. In the plane of the foliation, fibrous actinolite crystals up to 2 cm in length define the mineral lineation (Ls) (Fig. 17). A common small scale structure in the metavolcanic rocks is extension fractures (Fig. 17). These structures are oriented normal to both lineation and foliation, striking approximately north-south and dipping steeply. They are commonly filled with fibrous actinolite, however similarly oriented fractures only partially filled with vuggy quartz have have also been (rarely) observed. As discussed in the preceeding sections (2.2.1., 2.2.2.) the metavolcanic map unit is thought to be in ductile fault contact with structurally underlying mylonitic orthogneiss and metasedimentary rocks. The upper contact of the metavolcanic map unit is faulted or covered/unexposed. Along the southern exposures actinolite-chlorite-albite schist is bounded by a fault that is parallel in strike direction to the well developed / 32 Figure 17. Outcrop photos of rocks within the metavolcanic map unit (Jmv). A. Green, well-foliated chlorite-actinolite-albite schist of unit Jmvl at station 84-627-7. Clipboard is about 32 cm long. B. Rockface in mylonitic chlorite-actinolite-albite schist at station 84-621-8, oriented approximately parallel to Ls and perpendicular to Ss. Actinolite-Filled, Ls-normal extensional fractures are well displayed at this locality. Hammerhead is about 17 cm long. MAP UNITS / 33 mylonitic (Ss) foliation in underlying rocks. This fault is poorly exposed, but clearly juxtaposes undeformed, subgreenschist facies volcaniclastic rocks against structurally underlying, penetratively deformed metavolcanic rocks, and is inferred to be a shallowly to moderately dipping fault parallel to mylonitic foliation (Plate 1). The metavolcanic map unit is lithologically correlated with unamed Jurassic volcanic rocks exposed to the east of the study area (Tipper, 1969B, map unit 7; Tipper, 1969A, map unit 2), and in a general way with Early to Middle Jurassic Hazelton Group volcanic rocks of the 1MB. 2.2.4. Eagle Lake Tonalite (Eel) The Eagle Lake tonalite is an approximately 4 x 3 km deformed tonalite body, which intrudes metasedimentary rocks in the southeastern part of the study area. It is poorly exposed on the north face of an unamed 1917 metre (6288 foot) mountain (informally called Edmunds Mt.) and an unamed east-west trending ridge 1.5 km to the north, and is inferred to underlie the intervening drift covered valley (Plate 1). The Eagle Lake tonalite consists of medium grained plagioclase, quartz and biotite, with accessory allanite (rimmed by epidote), zircon, opaques, and distinctive honey coloured sphene, which is easily identifiable in hand specimen. It has been strongly deformed, containing the regional mylonitic fabrics, manifested as S-C foliations (Berthe et al., 1979; Fig. 18, this report) and mineral-elongation lineation. Although the geometry and precise contact relationships are obscure due to poor exposure, deformed intrusive contacts with surrounding metasedimentary rocks are inferred based on the Eocene crystallization age of the intrusion (55+3 Ma; Sec. 4.1.3 and Table 4), compared to the late Jurassic minimum sedimentary protolith depositional age, and the pervasive ductile-brittle deformation suffered by both intrusion and MAP UNITS / 34 Figure 18. Slab of Eagle Lake tonalite from station 84-714-10 cut approximately parallel to. Ls and perpendicular to Ss. Upper slab has been stained for potassium feldspar. C-S fabrics are well displayed in lower, unstained, slab. The C- or shear-plane is approximately parallel to horizontal axis of the photo, and the S-surface, or schistosity dips at about 30° from upper right to lower left and is defined by the long axes of plagioclase grains. Coin is about 18 mm in diameter. / 35 country rock, which intensifes adjacent to the contact zone. 2.2.5. Deformed Sills (LKgsi, LJasi and Edsi) There are at least three compositional types of foliated sills, which locally attain a thickness as great as 1.5 m, that intrude metasedimentary rocks in the ductilely-sheared assemblage (Plate 1). Type 1 (LKgsi) is medium grained, biotite granodiorite and intrudes quartzofeldspathic schist adjacent to the Yalakom fault in the southwestern portion of the study area (Plate 1). Type 2 (LJasi) is fine grained, aplitic in texture, and composed of quartz, plagioclase and minor white mica. These leucotonalite sills intrude metasedimentary and metavolcanic rocks east of Eagle Lake, and have been deformed by mesoscopic (Fs) folds (Plate 1, Fig. 19). Type 3 (Edsi), which likewise occur east of Eagle Lake (Plate 1), are metadacite; they are pervasively foliated, lineated and locally boudined. Porphyritic textures are still recognizable, with zoned plagioclase and biotite pophyroclasts (originally phenocrysts) in a matrix of fine grained quartz, plagioclase and biotite (Fig. 20). Type 3 sills have been dated as Eocene in age (55± 3 Ma; see section 4.1.3, Table 4). 2.2.6. Tatla Lake Stock (Etl) The Tatla Lake stock is a post-tectonic granodioritic body approximately 2 x 1 km in dimension, which intrudes mylonitic orthogneiss in the extreme northeast portion of the lower plate (Plate 1). This compositionally homogenous intrusion has medium grained hypidiomorphic texture, and is mineralogically made of quartz, plagioclase, alkali feldspar, biotite and accessory apatite, zircon and opaques (Fig. 21). The southern contact is locally exposed and is clearly intrusive in character. The Tatla Lake stock has been dated as Eocene (47+1 Ma, Sec. 4.1.3., Table 4) which constrains the / 36 Figure 19. Outcrop photos of Type 2 aplitic sill (LJasi). A. Aplitic sill at station 84-617-2 deformed by Fs fold. Notebook in the foreground slightly right of centre is about 18 mm long. B. Close-up of fold in Fig. 19A showing deformed sill-countryrock contact MAP UNITS / 37 Figure 20. Cut slab of Type 3 Eocene metadacitic sill from station 84-711-2. Coin is about 18 mm in diameter. MAP UNITS / 38 Figure 21. Cut slab of medium grained Tatla Lake granodiorite stock (Etl) from station 85-817-2. Portion at left has been stained for potassium feldspar. Coin is about 18 mm in diameter. MAP UNITS / 39 minimum age of deformation in the ductilely-sheared assemblage. 2.2.7. Maclntyre Island Dykes (Td) Post-tectonic, nonfoliated rhyolitic dykes intrude the ductilely-sheared assemblage along the north shore of Tatla Lake, adjacent Maclntyre Island and on the east face of Martin Mountain. They intrude both mylonitic orthogneiss and metavolcanic rocks and are concentrated near the contact zone between these two map units (Plate 1). These dykes strike approximately north-south, dip nearly vertically; the same orientation as extensional fractures in the ductilely-sheared assemblage. They vary in thickness from 1 to about 10 m (Fig. 22). Texturally, the Maclntyre Island dykes are porphyritic, with medium grained alkali feldspar, plagioclase and partially resorbed quartz phenocrysts in a fine grained matrix consisting of the same minerals. Biotite is commonly replaced by chlorite. 2.3. UPPER PLATE ROCKS Rocks described in this section occur in the 1MB, within, or directly adjacent to the study area proper. Plate 1 shows the extent of upper plate rocks in the study area. They occur northeast, east and south of the metamorphic core, in the upper plate of core/cover bounding faults. 2.3.1. Jurassic Volcanic Rocks (Jv) Volcanic breccia, tuff and flows of basaltic to dacitic composition, and minor water-laid shale or shaley tuff occur within, and east of the study area (Plate 1, Fig. 3 and Tipper, 1969B, map unit 7; 1969A, map units 2, 3). These rocks have been dated as Bajocian (Middle Jurassic), based on one ammonite recovered from tuffaceous MAP UNITS / 40 Figure 22. A. Contact of fractured Maclntyre Island rhyolitic dyke (Td) with, mylonitic metavolcanic rock (Jvl) at station 84-719-1. Long axis of notebook is about 18 cm long. B. Photo of slabs of Td dyke rock from station 84-817-1. Left hand slab has been stained for potassium feldspar. Coin is about 18 mm in diameter. MAP UNITS / 41 beds along the north shore of Puntzi Lake (Tipper, 1969B) about 40 km northeast of the study area. Within the study area exposures are poor and limited to the tops of ridges (Plate 1). South of the TLMC detachment fault, on Little Meadow mountain, massive, light green volcaniclastic siltstone crops out (Plate 1). It is featurless and fine grained in hand sample, and in thin section contains quartz, albite, calcite, epdote and sericite, a non-diagnostic prehnite-pumpellyite facies assemblage. Volcanic breccia, with fragments up to 12 cm in diameter occur on an unamed hill about 7 km east-northeast of the east end of Eagle Lake (Plate 1 and Tipper, 1969B). 2.3.2. Early Tertiary Volcanic Rocks (Tv) Volcanic rocks correlated with the Eocene Ootsa Lake Group are exposed in a narrow belt along the northern edge of the Study area (Plate 1). They consist mainly of rhyolite, dacite and associated tuff and breccia. Minor andesite, basalt and volcaniclastic sediments have also been observed (Tipper, 1969A, map unit 9). These rocks have been described by Tipper (1969A) as a flat lying to very gently folded nonmarine sequence up to 500 m thick, which rest with angular discordance on Jurassic volcanic rocks. 2.3.3. Quartz Diorite (LJqd) An unamed quartz diorite body, at least 4 x 2 km in dimension, intrudes Jurassic volcanic rocks in the north-central portion of the study area (Plate 1). It is nonfoliated, and consists of medium grained plagioclase, hornblende and minor quartz (Fig. 23). MAP UNITS / 42 Figure 23. Quartz diorite cut slab from map unit LJqd from station 85-725-3 Upper portion has been stained for potassium feldspar. Coin is about 18 mm in diameter. MAP UNITS / 43 2.4. ROCKS WEST OF THE YALAKOM FAULT As briefly outlined at the begining of this chapter, a wide range of rocks are exposed southwest of the Yalakom fault adjacent to the study area. In this section only those rocks within the study area proper will be discussed. 2.4.1. Early Cretaceous Volcanic Rocks (IKvs) Pyroclastic rocks, volcanic breccia, tuff and minor siltstone occur in the northern portion of the study area west of the Yalakom fault (Tipper, 1969B, map unit 13). They are exposed in a panel extending from west of One Eye Lake to about 2 km north of Little Sapeye Lake (Plate 1). These marine volcanic rocks are considered by Tipper (1969B) to be Hauterivian (Early Cretaceous) or younger, based on rare fragments of Inoceramus fragments found in sedimentary interbeds. One of the fossil localities occurs within the present study area, along route 20, about 4.5 km west of One Eye Lake (Plate 1). 2.4.2. Quartz Diorite of the Coast Plutonic Complex (EJqd) Unamed quartz diorite rocks occurs in the southern part of the study area west of the Yalakom fault (Tipper, 1969B, map unit B). It is in fault contact with early Cretaceous volcanic rocks about 2 km north of Little Sapeye Lake, and is exposed on several small hills extending southeastward towards the Homathko River (Plate 1). A sample collected from about 2 km east of Suds Lake is representative of these rocks. It is nonfoliated and contains the major minerals plagioclase, hornblende and quartz (Fig. 24). MAP UNITS / 44 Figure 24. Quartz diorite slab from map unit FJqd in the Coast Plutonic Complex. Upper portion has been stained for potassium feldspar. Coin is about 18 mm in diameter. 3. STRUCTURE The rocks of the study area have been divided into 3 fault-bound lithotectonic assemblages based on intensities and styles of deformation, lithologic character and degree of metamorphism. The upper plate, structurally highest of the assemblages, is characterized by rocks that usually lack penetrative-deformation fabrics. The lower plate or metamorphic core of the TLMC contains the gneissic core and overlying ductilely-sheared assemblage (DSA). These rocks have undergone a polyphase deformational history involving folding, ductile shearing, and fracturing. Primary structures have been obliterated. Migmatite and granoblastic gneiss of the gneissic core contrast markedly with mylonitic rocks of the DSA. Field studies concentrated on determining the nature, geometry and overprinting relationships of structural elements, including planar and linear features as well as fold sets (Table 1). With these observations, a relative timing for the development of mesoscopic structures within lithotectonic assemblages was established. Geochronometric studies (especially U-Pb zircon dating; Chapter 4.1.2) placed these relative ages in an absolute framework. Cretaceous (107-78 Ma) ductile deformation has been documented in the gneissic core of the TLMC where the rocks may also have an Eocene fabric. Development of mylonitic fabrics in the DSA, possibly related to crustal extension, has been dated as Eocene (55-47 Ma) in age (Chapter 4.1.3). The terminology of deformational phases and associated stuctural elements is listed in Table 1. The lower plate of the TLMC has been divided into structural sub-areas, (Fig. 25), based on faults and parts of late, map-scale (F3) folds, which deform earlier structures in the area. Each sub-area is considered separately for analysis of structural data associated with D3 and earlier deformations. Petrographic studies aided in correlation of microstructures with mesoscopic 45 T a b l e 1: Te r m i n o l o g y f o r s t r u c t u r a l elements i n the TLMC GNEISSIC CORE: S u b s c r i p t 'c' denotes s t r u c t u r a l element observed e x c l u s i v e l y i n the g n e i s s i c c o r e , d a ted at l e a s t i n p a r t as Cretaceous (Chapter 4 ) . S 1c S c h i s t o s i t y ( d e f i n e d by b i o t i t e ) and g n e i s s o s i t y i n the g n e i s s i c c o r e F2c Dominantly northwest t r e n d i n g , s h a l l o w l y p l u n g i n g , t i g h t to i s o c l i n a l f o l d s which deform S1c; not r e c o g n i z e d at map s c a l e . S2c R a r e l y observed a x i a l p lane c l e a v a g e a s s o c i a t e d with minor F2c f o l d s . L2c Northwest t r e n d i n g mineral l i n e a t i o n d e f i n e d by hornblende, p l a g i o c l a s e and q u a r t z and a s s o c i a t e d with F2c s t r u c t u r e s . DUCTILELY-SHEARED ROCKS: S u b s c r i p t 's' r e f e r s to s t r u c t u r e s observed throughout the d u c t i l e l y s h e a r e d u n i t and at one l o c a l i t y s t r u c t u r a l l y h i g h i n the g n e i s s i c c o r e . The 's' s t r u c t u r e s have been dated as Eocene (Chapter 4 ) . Ss P e r v a s i v e s h a l l o w l y d i p p i n g m y l o n i t i c f o l i a t i o n d e f i n e d by mica and r i b b o n q u a r t z . Ls M i n e r a l e l o n g a t i o n ( s t r e t c h i n g ) l i n e a t i o n d e f i n e d by q u a r t z , f e l d s p a r and amphibole t r e n d i n g towards 280' ± 20'. Fs T i g h t to i s o c l i n a l , s h a l l o w l y p l u n g i n g , v a r i a b l y t r e n d i n g mesoscopic f o l d s . S2s L o c a l i z e d a x i a l p l a n e c r e n u l a t i o n c l e a v a g e a s s o c i a t e d with Fs f o l d s ; r e s t r i c t e d to metasedimentary rocks and most well d eveloped i n m e t a p e l i t i c l i t h o l o g i e s . ENTIRE METAMORPHIC COMPLEX: F3 Open to normal east-west to n o r t h w e s t - s o u t h e a s t t r e n d i n g map s c a l e f o l d s which d e f i n e the map p a t t e r n i n the metamorphic c o r e of the TLMC. Mesoscopic F3 f o l d s a r e common i n the g n e i s s i c c o r e . STRUCTURE / 47 Figure 25. Structural sub-areas in the lower plate of the TLMC. Orientation data for structural elements are plotted on stereonets in Figs. 29, 29, 31 and 39. STRUCTURE / 48 structures observed in the field, yielded information pertaining to the relative timing of deformation and recrystallization, and allowed inferences to be made about possible deformation mechanisms operative during the structural development of the TLMC. In this chapter, mesoscopic structures are described for each of the 3 lithotectonic assemblages in turn, then mesoscopic structures common to the entire lower plate are described, and finally microstructures are described in the same order of occurrence. 3.1. MESOSCOPIC STRUCTURES 3.1.1. Gneissic Core Two generations of structures are identified in rocks of the gneissic core, and these are designated by numbers and the suffix 'c' (Table 1). A Cretaceous age for much of this fabric is established by dating of variably deformed igneous rocks (Chapter 4). Die Regionally developed gneissic layering and parallel schistosity defined by biotite and hornblende (Sic, Fig. 26, Plate 2) are associated with the earliest deformational event (Die) recognized in the gneissic core of the TLMC. The most common lithology containing Sic is tonalitic to quartz dioritic orthogneiss (Fig. 6). The subdued banding in this rock is defined by mm- to cm-scale alternating layers, relatively enriched in quartz-plagioclase versus biotite and/or hornblende. Marked gneissic layering, most common in map unit mg (Plates 1, 2), migmatitic gneiss, is defined by mm- to cm-scale pre- to syn-deformation sills (neosones), in addition to banding described above (Fig. 4). Rarely, gneissic layering is thought to represent transposed primary STRUCTURE / 49 Figure 26. Gneissic layering and schistosity (Sic) defined by relatively felsic and mafic layers, aligned mica and the long axes of hornblende and plagioclase grains. Upper slab: station 85-714-3; lower slab: station 84-81-8. Both are cut parallel to L2c lineation and perpendicular to Sic foliation. Coin is about 18 mm in diameter. STRUCTURE / 50 stratification. The presence of rare "rootless" isoclinal hinges (Flc) within the Sic foliation, which fold early sills, quartz veins and compositional layering inferred to represent primary stratification, provide evidence for transposition of early "layered" elements (Fig. 27). F l c folds have been identified only at the outcrop scale and have not been associated with map-scale structures. A regionally developed lineation associated the Die deformation has not been recognized within the gneissic core. Stereographic projections containing poles to Sic foliation, plotted by structural sub-area, are illustrated in Figure 28. The distribution and orientation of the Sic foliation across the map-area is plotted on Plate 2. D2c Mesoscopic structural elements associated with the D2c phase of deformation are: 1. Tight to isoclinal (F2c) folds, which deform regional Sic gneissic foliation and schistosity (Plate 3), 2. A rarely observed non-penetrative schistosity, (S2c), locally associated with, and axial planar to F2c folds, and 3. A regionally developed mineral elongation lineation, (L2c), parallel to F2c fold axes (Plate 2). Orientation data for D2c structural data are plotted on stereograms in Figure 29. The distribution and orientation of these structures are shown on Plates 2 and 3. The trends of F2c folds vary from about 320°-140° in the northwestern part of the map-area, to about 250°-70° at the eastern limit of gneissic exposure. They most commonly trend towards 270°-90° (Plate 3, Fig. 29). Fold axes are horizontal to shallowly plunging and subparallel to L2c (Plate 3, Fig. 29). Fold hinges are thickened relative to limbs, and are subrounded ttr subangular in shape. Associated axial surfaces, / 51 Figure 27. "Rootless" isoclinal fold (Flc) at station 84-83-5. Pencil is about 18 cm long. STRUCTURE / 52 N Sub -Area 7 . n = l 4 7 Po les to S 1 c Fo l ia t ion o n= 47 L2c L ineat ions Figure 28. Stereoplots of L2c lineations and poles to Sic foliation subdivided by structural sub-area. See Fig. 25 for location and bounds of structural sub-areas. STRUCTURE / 53 N Sub - A r e a 7 P o l e s to A x i a l P l a n e s : • F 2 c : n = 16 Fo l d A x e s : - F2c: n = 15 N Sub - A r e a s 8A , 8B Poles to Axial Planes: • F2c: n= 176 Fold Axes: ' F2c: n=180 Figure 29. Stereoplots of F2c fold axes and poles to F2c axial surfaces subdivided by structural sub-area. See Fig. 25 for location and bounds of structural sub-areas. STRUCTURE / 54 (with rarely developed S2c), are oriented subparallel or at small angles to Sic (0° to 30° dihedral angles; Fig. 30). F2c folds are sometimes asymmetric, but regional vergence patterns were not recognized and map-scale D2c structures could not be identified (Plate 3). The L2c mineral elongation lineation is defined by aligned hornblende, quartz and plagioclase crystals. Although this structural element has been recognized throughout the gneissic core, it is not intensly developed in these rocks with granoblastic elongate texture. L2c has been found to be consistently oriented parallel to F2c fold axes (Fig. 29). Deformation of these relatively early structures in the gneissic core by later F3 folds is discussed in section 3.1.3. 3.1.2. Ductilely-Sheared Assemblage Structures in dominantly mylonitic rocks of the ductilely-sheared assemblage (DSA) have been analysed independently of those in the gneissic core, based on their contrasting structural styles and timing of deformation: Eocene versus Cretaceous, respectively (Chapter 5.1). The suffix V refers to a structural element or phase of deformation observed in, or associated with the DSA (Table 1). Orientation data for Ds structures are plotted, by structural sub-area, (see Fig. 25 for sub-area boundaries) on stereograms in Figure 31. The distribution and orientation of Ds structures are plotted on Plates 2 and 3. The DSA, a major crustal ductile shear zone of Eocene age, is composed of mylonitic rocks derived from a wide variety of protoliths (Section 2.2, Plate 1). In the northwestern part of the study area the ductilely-sheared rocks had a plutonic protolith and in the southeastern part a largely stratified protolith. The involvement of structurally deeper plutonic rocks towards the northwest suggests that the shear zone STRUCTURE / 56 o o Sub-Area 2 . n=64 Poles to Ss Foliation o n=5 1 Ls Lineations Sub-Area 3 • n=61 Poles to Ss Foliation ° n=29 Ls Lineations Figure 31. Stereoplots of Ds structural elements subdivided by structural sub-area. See Fig. 25 for location and bounds of sub-areas. STRUCTURE / 57 Sub-Area 6 • n=93 Poles to Ss F o l i a t i o n ° n=38 Ls Lineations Figure 31. Continued: Stereoplots of Ds structural elements subdivided by structural sub-area. See Fig. 25 for location and bounds of sub-areas. STRUCTURE / 58 N o n = 1 8 5 F s F o l d A x e s • n = 1 7 8 P o l e s t o F s A x i a l P l a n e s Figure 31. Continued: Stereoplots of Ds structural elements subdivided by structural sub-area: Arrows denote sense of fold vergence. See Fig. 25 for location and bounds of sub-areas. STRUCTURE / 59 cuts downsection towards the northwest Unifying elements of the DSA include regionally developed structures; a well-developed mylonitic foliation (Ss) and mineral elongation lineation (Ls). Mesoscopic folds (Fs) and associated schistosity (S2s) are locally important, but largely confined to metasedimentary map sub-units (Plates 2, 3, Table 1). Mylonitic fabrics present throughout the DSA indicate that these rocks underwent significant strain during Ds deformation. Although present throughout he DSA, these fabrics are most intensely developed adjacent to the margins of the assemblage, and along internal lithologic contacts. Ss The nature of Ss, the regional compositional layering and schistosity recognized throughout the DSA, varies as a function of rock type. It is manifested as an intensely developed schistosity in very micaceous metapelitic rocks (Fig. 15B). In quartzofeldspathic rocks, including both metasedimentary and granitic variants, Ss is defined by ribbon quartz grains up to 4 cm in length, and aligned mica and/or amphibole (Fig. 9A, 10, 11, 12, 13 and 14). Rotated feldspar porphyroclasts are also very common in these rocks. In some mylonitic granitoids a second, poorly defined foliation, outlined by the long axes of feldspar porphyroclasts, and aligned mica, intersects Ss at angles of commonly 0°-5° to rarely about 25° (Fig. 18). These two fabrics are interpreted as S-C surfaces (Berthe et al., 1979). In rocks where two fabrics can be distinguished the dominant surface is interpreted as the C-plane (shear surface). Hand sample analysis (in the field and on oriented specimens) of kinimatic indicators such as S-C fabrics and more commonly asymmetric porphyroclasts (Simpson and Schmid, 1983) observed in mylonitic granitiods throughout the DSA (in x-z plane of rock face or oriented slab; STRUCTURE / 60 parallel to Ls lineation and perpendicular to Ss foliation) indicates a predominant top-to-the-west sense of shear (see Table 3 and Sec. 3.2.2. for a discussion of microscopic and hand sample-scale kinimatic indicators). Compositional layering, oriented parallel to the Ss schistosity, is especially well-developed in metasedimentary rocks. These layers, marked by relative enrichments and depletions in micaceous, felsic and/or mafic minerals (Figs. 14, 16, 17B and 32), are inferred to represent transposed older layering, perhaps original bedding. "Rootless" isoclinal hinges rarely observed within the Ss foliation, provide evidence for syn-Ds transposition of layering in metasedimentary rocks (Fig. 33). Ss has been deformed by syn-Ds, Fs folds (discussed below) and open to normal map-scale folds (F3, discussed in section 3.1.3.) and dips are usually moderate (Plate 2). Ls Ls, a mineral elongation lineation regionally developed within the DSA, commonly plunges shallowly towards 280° -110° ± 20° (Plate 2, Fig. 31). It is defined by the long dimension of aligned ribbon quartz, feldspar, and amphibole grains (Fig. 34). Ls occurs within or on the Ss foliation plane, and formed synchronously with this surface during Ds deformation. Ls is a stretching lineation, parallel to the movement direction within the DSA (evidence discussed below). Fs Folds Mesoscopic folds (Fs) associated with Ds deformation occur in the DSA, and are largely confined to metasedimentary rocks (Jms, Jmsq and especially Jmsp; Plate 1). Map-scale Fs folds have not been recognized in the study area. Evidence, outlined below, indicates that Fs folds formed within the active DSA shear zone. Fs folds occur within the metasedimentary map unit, yet do not regionally / 61 / 62 Figure 33. "Rootless" isoclinal hinges in metasedimentary rocks: A. Station 85-610-1; Hammerhead is about 17 cm long. B. Station 84-626-3; Clipboard is about 32 cm long. STRUCTURE / 63 Figure 34. Ls mineral elongation lineations on Ss foliation surface: A. Map-unit LKogl at station 85-76-4; Notebook is about 21 cm long. B. Map-unit JKog2 at station 84-815-3; Parallel to hammer handle which is about 25 cm long. / 64 deform the contacts of this unit and its internal subunits, or the DSA ductile shear zone as a whole. They deform, and are in some places truncated by mylonitic foliation (Ss), a feature common to folds developed in active ductile shear zones (Fig. 35; Bell, 1978; Bell and Hammond, 1984). Gently-dipping axial surfaces are oriented sub-parallel to regional mylonitic foliation (Ss) and the boundaries of the DSA ductile shear zone (Fig. 31). Fold axis trends are variable; a plot of all Fs fold axes defines a horizontal girdle (Fig. 31). Within a single outcrop Fs fold trends vary up to 70° and up to 40° variations have been measured for single folds. Fs folds are commonly asymmetric and vary from normal, angular hinged structures with little or no hinge-to-rim relative thickening (chevrons), to tight, rounded hinged folds with significant hinge thickening relative to limbs (Fig.36). The tightest Fs folds (isoclinal) have axes which trend at small angles to the mineral elongation lineation direction (290°, for structural sub-area 1; Figs. 25, 31), while folds with axes oblique to the lineation direction (north-south trending) are more open (dihedral angles of 30° -70°). The former may have developed early in the history of the shear zone, oblique to the movement direction, and during progressive shear been reoriented into parallelism with i t The latter folds, which are common in the TLMC, are thought to have formed late in the history of the shear zone. Folds of the latter geometry are reported to be rare in other ductile shear zones (Bell and Hammond, 1984). Most Fs folds verge westerly; towards the bulk mineral elongation lineation direction (290°, Fig. 31). Fs fold vergence defines a movement sense and direction of top towards 290° ±20° (Christie, 1963; Hansen, 1971). Fold vergence is most reliable as a kinematic indicator in areas where fold axes are commonly oblique to the bulk elongation lineation direction (Bell and Hammond, 1984) as is the case for the TLMC. A few Fs folds (commonly north-south trending) have been observed to deform / 65 Figure 35. Fs folds, which deform Ss and are truncated by later Ss (mylonitic) foliation. A. Station 85-68-2; Pencil is about 18 cm long. B. Fold-normal slab faces cut parallel to Ls, mineral elongation lineation. Upper specimen from station 84-77-5; lower specimen from station 84-817-1. Coin is about 18 mm in diameter. Figure 36. Outcrop photos of Fs folds: A. Round-hinged structure which deforms mylonitic foliation (Ss) and mineral elongation lineation (Ls) in metasedimentary rocks at station 84-78-3. Lineation is parallel to chisel which is about 17 cm long. B. Portion of north-south trending recumbent fold in metasedimentary and amphibolitic rocks at station 84-626-7, which exhibits thickening at the hinge. Hammerhead is about 17 cm long. STRUCTURE / 67 the Ls mineral elongation lineation. Where possible, the trend and plunge of Ls has been measured around these Fs structures. In all cases, the intersection of Fs axial surface and deformed Ls locus (movement direction, or a-direction; Ramsay, 1967) occurs adjacent to the Ls lineation maxima for structural sub-area 1 (Figs. 25, 31, and 37). The similarity in orientations of Fs fold calculated a-directions and Ls lineations is consistent with the proposition that these structures (and Ss) developed during the same deformation, (Ds), within a ductile shear zone. This further supports the suggestion that the tectonic transport direction of the DSA dutile shear zone is parallel to the Ls lineation, making it a true stretching lineation. S2s S2s is a locally developed schistosity, observed only in close association with Fs folds. It is manifested as an axial planar crenulation cleavage in rocks of quartzofeldspathic composition (Fig. 38) . In rare, very micaceous metapelitic horizons where isoclinal Fs microfolds have been observed, S2s is well-developed parallel to transposed Ss schistosity (Fig. 79 and Sec. 3.2.2). 3.1.3. P h a s e 3 Map- and outcrop-scale, open to normal upright folds, (F3), which affect the lower plate of the TLMC, developed during D3 deformation (Plate 1). The regional distribution and orientation of deformed Ss (Fig. 31) and Sic (Fig. 28) surfaces outline map-scale F3 fold forms (Plates 2, 7). F3 folds also deform F2c axial surfaces (Fig. 29) F3 fold traces curve from approximately east-west trends in the east, to northwesterly adjacent to the Yalakom fault in the northwestern part of the map-area (Plates 1, 3). Fold intensity diminishes from northwest to southeast across the map-area. Figure 37. Stereograms showing calculated a-directions for individual mesoscopic Fs folds. Symbols: Triangles: measured lineations; Dashed curves: loci of deformed lineations; Solid curves: measured axial surfaces. Solid circles: (with symbol "f") measured and calculated fold axes; (with symbol "fc") calculated fold axes; Open circle with dot: (with symbol "fm") measured fold axis; Open circle: (with symbol "a") calculated a-direction. / 69 Figure 38. S2s axial planar crenulation cleavage in metasedimentary rocks at Station 84-819-2 (map unit Jmsq). A. Outcrop photo; visible portion of pencil is about 16 cm long. B. Slab face normal to Fs fold. Coin is about 18 mm in diameter. STRUCTURE / 70 Mesoscopic F3 structures are common in the gneissic core (especially structural sub-area 8; Fig. 25) and are rare elsewhere in the lower plate. They are concentric, have nearly vertically dipping axial surfaces, (as do megascopic equivalents; Plate 7), and have no associated penetrative deformation fabrics. Mesoscopic F3 fold axes and axial surfaces are plotted on stereograms in Figure 39. Superposition of mesoscopic F3 upon approximately colinear F2c fold sets has resulted in the development of type 3 fold interference patterns (Ramsay, 1967; and Fig. 40). F3 fold trends are subparallel to earlier L2c and Ls lineations throughout the map-area, and do not significantly deform them (Figs. 29, 31). The geometry of map-scale F3 folds is consistent with their formation as drag, or transpression-related structures associated with dextral transcurrent slip along the Yalakom fault (Sec. 7.2, 7.3). 3.1.4. Faults and Fractures Faults bounding the Lower Plate Syn-Ds and post-D3 faults, recognized on the basis differences in structural metamorphic grade, and often rock type form the boundary between lower plate and 1MB upper plate rocks (Plate 1). The Yalakom fault is the southwestern boundary of the TLMC, separating lower plate rocks from low-grade rocks of the Coast Belt The observed fault post-dates Ds deformation. Earlier movement may have occured (Tipper, 1969B; Kleinspehn, 1985) but there is no evidence for this in the study area. The southern, east-west trending segment of the Core/Cover fault is parallel in strike to mylonitic foliation in underlying metamorphic core rocks (Ss dips southerly at about 30° to 35°, Plate 2). It places subgreenschist grade, undeformed volcanic and sedimentary rocks over greenschist facies mylonitic metavolcanic rocks (Plate 1). About / 71 N Sub -Area 7 Poles to Axial Planes: • F 3 : n=17 Fold Axes: * F 3 : n=15 N Sub -Areas 8 A , 8 B Poles to Axial Planes: • F3: n=61 Fold Axes: * F3: n=62 Figure 39. Stereograms showing F3 fold axes and axial planes See Fig. 25 for location and bounds of structural sub-areas. Figure 40. Type 3 interference patterns resulting from the deformation of F2c structures by F3 folds. A. Outcrop photo at station 84-814-5. Hammer handle is about 0.75 metres long. B. Fold-normal slab face displaying refolded felsic sill from station 84-89-IB. STRUCTURE / 73 7 km to the north, pelitic schist containing syn-Ds kyanite and sillimanite which crystallized at a minimum depth of 10 km, is now at a maximum of 4 structural km below the Core/Cover fault (assuming a 30°-35° southerly regional dip; Calculated pressures indicate a depth of greater than 15 km; Sec. 5.2.4). This structural and metamorphic omission (or attenuated metamorphic gradient) is most reasonably explained by a combination of normal ductile shear within the DSA (especially near the metasedimentary/metavolcanic contact) and normal displacement along a mylonitic foliation-parallel fault On the basis of these relationships the southern Core/Cover fault segment is interpreted as a syn-Ds mylonitic-foliation parallel normal fault with a sense of displacement similar to the underlying DSA shear zone (approximately east-west displacement; top-to-the-west sense of shear). A poorly exposed fault which cuts a map-scale F3 fold and locally brecciates mylonitic rocks defines the northeastern and eastern margins of the TLMC lower plate (Plate 1). The trace of this surface was determined largely by interpolating between mylonitic lower plate and low-grade upper plate rocks. The sinuosity of this fault in map view (Plate 1) and its relationship to local topography indicate gentle to moderate east to northeasterly dips. Relatively low-grade rocks in the hanging wall provide evidence favouring down to the east normal motion. The truncation of the southern syn-Ds Core/Cover fault segment by the north-south trending post-D3 segment (Plate 1) is covered in the field, but is geometrically required if, as suggested, the former structure cuts up-section towards the southeast Another geometric consequence of the syn-Ds fault cutting up-section towards the southeast is that a breakaway must be present in the hanging wall of the latter structure to the east of the study area (presently unrecognized). The Yalakom fault forms the southwestern margin of the TLMC lower plate. It STRUCTURE / 74 is not well exposed in the study area, and is defined by a 2 to 3 km wide topographic depression across which unlike rock types are juxtaposed. The Yalakom fault is thought to. be steeply dipping, based on its remarkably straight trace (Tipper et al., 1981). It has not been observed north of the study area, and appears to suddenly die north of 53° N (G.J. Woodsworth, oral comm., 1987). This structure truncates both Sic gneissic layering and Ss mylonitic foliation. The only documentable motion within this fault zone in the study area is therefore post-Ds in relative age. Fractures Steeply dipping, approximately north-south trending fractures, and similarly oriented nonfoliated dykes (plotted on stereograms in Fig. 41) occur in TLMC lower plate rocks. As detailed in Chapter 5, the minerals chlorite, epidote, sphene, carbonate and quartz fill fractures. In the gneissic core fracture density increases in the vicinity of the Yalakom fault Based on orientation, these late structures are interpreted as extensional fractures related to dextral transcurrent motion along the Yalakom fault As discussed above, final Yalakom movement post-dates Ds deformation and is thought to be related to the development of D3 folds. Fractures in the DSA are concentrated in mylonitic metavolcanic rocks (Jmv, Plate 1). These structues are well developed perpendicular to the Ls mineral elogation lineation and are considered to be extensional in nature and associated with Ds deformation. They are often filled with fibrous actinolite and chlorite. (Fig. 42). Nonfoliated rhyolitic dykes also intrude DSA rocks perpendicular to the Ls lineation. They occur near the north shore of Tatla Lake, and on Martin Mountain; adjacent to the contact between metavolcanic and metasedimentary rocks (Jmv, Jms). These dykes cut Ss foliation and are therefore postdate Ds deformation. These could N STRUCTURE / 75 • • • n= 92 Poles to Fractures A n= 9 Poles to Post-Ds Dykes Stereogram showing all fracture and dyke orientation data from the TLMC. / 76 Figure 42. Ls-normal, actinolite filled extension fractures in metavolcanic map unit Jmvl. A. Viewed on Ss foliation surface at station 84-621-3. Lens cover in about 5 cm in diameter. STRUCTURE / 77 be syn-D3 or later and controlled by Ds anisotropic fabric and/or reactivated Ds-age a-c fractures in DSA rocks. 3.2. MICROSCOPIC STRUCTURES Textural analysis of deformed rocks in thin section allows the correlation of fabric elements on the microscopic and mesoscopic scales and can yield information pertaining to the relative timing of recrystallization and deformation. Microstructures also allow inferences to be made about possible deformation mechanisms operative during their formation. 3.2.1. Gneissic Core Textures observed in rocks of the gneissic core are best described as granoblastic elongate (Spry, 1969; p. 263, 267). Figures 43 and 44, photos of thin sections cut parallel and perpendicular to the L2c lineation, display textural relationships typical in rocks of the gneissic core. In Figure 43 (section parallel to L2c) long axes of hornblende, plagioclase and quartz lie parallel to the lineation and within the Sic foliation. Sic is also defined by alternating quartzofeldspathic and hornblende-biotite rich horizons. Grains often meet at 120° angles and have straight boundaries. In Figure 44, cut perpendicular to L2c, mineral grains appear less elongate and also commonly meet at 120° grain boundaries. The long axes of hornblende grains are largely perpendicular to the orientation of this thin section. Throughout the gneissic core (Figs. 43, 44 and 45) widespread subgrain development and kink banding has been observed in quartz. Subgrains are equant or elongate parallel to kink band boundaries which are often parallel to Sic (Fig. 45). Polygonization and subgrain development provide evidence of diffusion climb as a STRUCTURE / 78 Figure 43. Photomicrograph of granoblastic gneiss from station 84-89-1 parallel to L2c mineral elongation lineation. Width of photo is about 4.5 mm Cross polarized light STRUCTURE / 79 Figure 44. Photomicrograph of granoblastic gneiss from station 84-88-2 perpendicular to the L2c mineral elongation lineation. Width of photo is about 4.5 mm. Cross polarized light STRUCTURE / 80 Figure 45. Photomicrograph showing deformation lamellae in quartz from granoblastic gneiss, map unit Ekggl, at station 84-89-1A. Kink band boundaries are oriented approximately parallel to Sic foliation. Field of view is about 2.4 x 3.6 mm. Cross polarized light STRUCTURE / 81 deformation mechanism (Nicolas and Poirier, 1976; White, 1977; Schmid, 1986). This deformation is thought to postdate the development of Sic gneissic foliation because subgrains and kinkbands in quartz are just as common in the post-Die One Eye Tonalite as in gneissic country rock. Partially healed microcracks have been observed within core gniessic rocks and the One Eye Tonalite which intrudes them. These microstructures, which commonly occur in quartz and plagioclase, are defined by planar patterns of gas filled spheroidal and/or cylindrical shaped inclusions which formed due to lattice mismatch during crystal healing (Smith and Evans 1984; Wanamaker and Evans, 1985). In the One Eye tonalite, where microcracks are most common, they have a high density in plagioclase crystals but do not continue across grain boundaries into neighbouring subgrain and kinkband rich quartz grains (Fig. 46). Plagioclase crystals may have deformed brittlely while adjacent quartz grains behaved in a ductile manner and/or microcracks in quartz were more completely healed. Extension fractures have been observed in gneissic core rocks, commonly in thin sections cut parallel to L2c and perpendicular to Sic. These fractures are oriented normal to L2c and F3 fold axes, and at high angles to Sic. They are filled with randomly oriented chlorite and subordinate quartz, epidote and sphene (Fig. 47). Similar chlorite filled fractures have rarely been observed in other orientations. A gently-dipping fracture shown in Figure 47 cuts a D3 microfold. These fractures and associated vein material are thought to be syn- to post-D3 in age, based on their geometry and mineralogy. / 82 Figure 46. Photomicrographs of One Eye tonalite from station 84-812-2 showing plagioclase with a high concentration of microcracks which do not continue into adjacent quartz grain. A. Plane polarized light; B. Cross polarized light; Note well developed subgrains in quartz. Fields of view are 0.6 x 0.9 mm. STRUCTURE / 83 Figure 47. Photornicrograph showing chlorite-filled fractures in granoblastic gneiss at station 84-89-IB. A. Fracture cutting F3 folds which deform Sic foliation. Short axis of photo is about 4.5 mm. Cross polarized light B. Fracture oriented perpendicular to Sic foliation. Field of view is about 2.4 x 3.6 mm. Plane polarized light STRUCTURE / 84 3.2.2. Ductilely-Sheared Assemblage In this section on microstructures in mylonitic rocks of the DSA emphasis has been placed on asymmetric structures, which have been used to determine the sense of shear (Simpson and Schmid, 1983; Lister and Snoke, 1984). Kinematic indicators were analysed in oriented thin sections cut parallel to Ls and normal to Ss; the approximate the x-z plane (see Sec. 3.1.2. for a discussion of evidence which indicates that Ls is a stretching lineation). A top-to-the-west sense of shear was overwhelmingly determined for rocks not deformed by syn-shear zone Fs folds (see Table 3 for results of kinematic analysis). Microstructures in quartzofeldspathic and quartz-mica rich rocks, which correspond to type I and II S-C mylonites, respectively, (in the terminology of Lister and Snoke, 1984), are discussed in separate sections below. Quartzofeldspathic Mylonitic Rocks The majority of DSA mylonites are broadly of quartzofeldspathic composition. Quartz dioritic to granodioritic mylonitic orthogneiss (MKqd, all og subunits), metasedimentary (Jmsq) and metavolcanic (Jmv) rocks are included in this discussion. Shear bands and S-C fabrics (Berthe et al., 1979) have been identified in thin section in a variety of rocks of the DSA (especially rocks of units Jmv, LKogl and Eel). S-surfaces, which approximate the plane of flattening (schistosite of Berthe et al., 1979) are commonly defined by mineral shape preferred orientation of plagioclase in DSA type I S-C mylonites (Figs. 21, 48). C-planes or shear bands (c=cisaillement or shear; Berthe et al., 1979) are spaced surfaces along which shear has been accomodated. They are generally oriented parallel to shear zone boundaries. In DSA rocks they are defined by mica (Fig. 48), quartz ribbons (Fig. 49) and amphibole (Fig. 48). Shear bands and S-C fabrics, (in addition to assymetric pressure shadows around Figure 48. Shear bands, dipping from upper right to lower left, and Ss. foliation, parallel to the length of photos, in these oriented x-z sections. These fabrics are interpreted as C and S surfaces, respectively. A. Metavolcanic rock from station 84-621-4. Short axis of photo is about 6 mm. B. Fine grained sill from station 84-719-5. Field of view is about 2.4 x 3.6 mm. Both photos taken in plane polarized light; east:right, west:left, top:structural top. STRUCTURE / 86 porphyroclasts, retort-shaped porphroclasts, and shape fabric in recrystallized quartz ribbons), used as a shear sense indicators in DSA quartzofeldspathic rocks dominantly indicate a top-to-the-west sense of shear (Figs. 49-51, 53; Table 3). The most intensely deformed quartzofeldspathic mylonites of the DSA shear zone occur in map units JKog2, LJog4 and Jmsq. These rocks contain a single penetrative mylonitic foliation defined by quartz ribbons (see below), mica and to a lesser extent, plagioclase porphyroclasts. S-surfaces in these rocks are inferred to have rotated into parallelism with C- planes. In the following paragraphs microstructures associated with quartz and plagioclase are discussed. Quartz Quartz occurs as polycrystalline ribbon grains with aspect ratios of 10 to greater than 30. Quartz crystals internal to ribbons occur as very fine grained, strain-free, equant neoblasts, and more commonly as elongate crystals (aspect ratios of 3-10) with sutured edges, undulatory extinction and in relatively coarse grains, deformation lamellae. Subgrains are commonly observed in elongate crystals (Fig. 49). These features indicate that quartz has undergone dynamic recrystallization (White, 1977). Elongate, and to a lesser extent equant quartz neoblasts in ribbons define a shape fabric which is slightly oblique to ribbon grain boundaries (Fig. 49). This shape fabric is thought to have formed normal to the flattening direction (interpreted as an S-surface) relatively late in the development of quartz ribbons (Simpson and Schmid, 1983; Burg, 1986). Ribbon grain boundaries are subparallel to C- surfaces in samples which oblique internal shape fabric has been observed. The relationship between quartz shape fabric and ribbon boundaries observed in the x-z plane consistently indicates a top-to-the-west sense of shear (Table 3). / 87 Figure 49. Photomicrographs from x-z sections showing quartz ribbon grains in mylonitic orthogneiss, map unit JKog2, station 84-817-3. A. Plane polarized light; B. Cross polarized light; Note internal shape fabric oblique to ribbon grain boundaries. Fields of view are 2.4 x 3.6 mm. STRUCTURE / 88 Plagioclase Plagioclase feldspar occurs as fine to coarse grained porphyroclasts in type I S-C mylonites. Brittle deformation of plagioclase is commonly marked by pull-apart structures (Fig. 50), filled with quartz, potassium feldspar or chlorite, and rarely by domino style faulting of crystals (Fig. 51). The latter feature, which has been proposed as a shear sense indicator, (Etchecopar, 1974, 1977; Simpson and Schmid, 1983), has yielded consistent top-to-the-west vorticities where observed (Table 3). Microstructures recognized in unit JKog2, (structurally deep in the DSA shear zone) which are similar to those described by Brown et al. (1980), provide evidence for partial dynamic recrystallization of plagioclase porphyroclasts. Strain in porphyroclasts is recognized by bent and deformed twin lamallae (Fig. 52). Relatively strain-free, fine grained, equant plagioclase neoblasts occur along grain boundaries of relict crystals. The degree of recrystallization observed is variable; festoon, mortar and rare heterogenous polygonal textures (terminology of Brown et al., 1980) may occur in a single thin section (Fig. 52). Asymmetric pressure shadows (possessing monoclinic symmetry), which consist of fine grained quartz, potassium feldspar and mica, are commonly developed around plagioclase porphyroclasts. Studies of naturally deformed rocks and experimental data suggest that these asymmetric structures may develop in non-coaxial flow regimes (Ghosh and Ramberg, 1976; Schoneveld, 1979; Passchier and Simpson, 1986). Pressure shadows in quartzofeldspathic rocks of the DSA shear zone belong to the a-type porphyroclast system of Passchier and Simpson (1986). In a porphyroclast systems median lines of wedge shaped pressure shadows lie on opposite sides of, and do not cross a reference line parallel to tails and containing the symmetry axis of the system. Many of the porphyroclasts observed in these mylonitic rocks can be further Figure 50. Photomicrograph showing chlorite-filled pullaparts in plagioclase. x-z section from a deformed felsic sill at station 84-621-2. Field of view is about 2.4 x 3.6 mm. Cross polarized light / 90 Figure 51. Photomicrograph showing a domino-style microfaulted plagioclase grain from felsic metavolcanic rock, map unit Jmvl, station 84-724-8; oriented x-z section, to Ss foliation. This microstxucture indicates a top-to-the-west sense of shear; westrright, east: left, top structural top. Cross polarized light Field of view is about 2.4 x 3.6 mm. Figure 52. Photomicrograph showing deformation and recrystallization of plagioclase, map unit JKog2. A. Note deformation of twin lamallae in interior, and relatively fine grained, strain-free neoblasts around the edge of the porphyroclast Short axis of photo is about 5mm; sample from station 84-817-3. B. Fine grained plagioclase neoblasts concentrated along the margin of porphyroclast Short axis of photo is about 3 mm; sample from station 85-721-5. Both photos from x-z sections and taken in cross polarized light STRUCTURE / 92 subdivided into the a B- type of Passchier and Simpson (1986), which indicates that they are associated with shear bands or C-planes (Fig. 48, 53). Porphyroclast systems in type II S-C mylonites of the DSA shear zone overwhelmingly indicate a top-to-the-west sense of shear (Table 3). Quartz-Mica Rocks Quartz-rich, mica bearing rocks (type II S-C mylonites of Lister and Snoke, 1984) are relatively rare in the DSA ductile shear zone. They occur as centimetre to metre scale compositional horizons in metasedimentary (Jmsq) and metavolcanic (Jmv) map units. DSA quartz-mica mylonites are similar to other type II S-C mylonites in that there is commonly only one dominant (discernable) mesoscopic foliation, which usually corresponds to the C-surface. Microstructures associated with quartz and mica in these rocks are discussed below. Quartz Quartz occurs as fine to medium grained porphyroclasts and very fine grained dynamically recrystallized material in ribbons. Figure 54 shows relict quartz porphyroclasts in quartz-muscovite-garnet mylonite The internal portion of these crystals display undulatory extinction, and contain deformation lamallae which are parallel to C-surfaces in the matrix (defined by muscovite rich surfaces). Relatively fine grained, equant, strain-free neoblasts have nucleated along porphyroclast margins. The long axis of the porphyroclast is parallel to S- surfaces, which are well defined by shape fabric of dynamically recrystallized fine grained matrix quartz. Figure 55 shows typical quartz ribbons in DSA type II S-C mylonites. They have aspect ratios of 15-30 (less than 1mm thick in x-z section) and are composed of very fine grained dynamically recrystallized quartz. Ribbons are separated by very thin white mica-rich horizons. / 93 Figure 53. Photomicrograph showing assymetric pressure shadows around a plagioclase porphyroclast Oriented x-z section from metavolcanic map unit Jmvl, station 85-67-5. Texture indicates a top-to-the-west sense of shear; west: right east: left top structural top. Cross polarized light Width of photo is about 3mm. Figure 54. Photomicrographs showing quartz porphyroclasts in quartz-rich type-II S-C mylonite. x-z sections from metasedimentary map unit Jmsq at station 84-78-3A. Long axes of porphyroclasts parallel to S-planes; deformation lamallae sub-parallel to C-surfaces. Note strained porphyroblast core and relatively strain-free rim neoblasts in photo B. Fields of view are 2.4 x 3.6 mm; Cross polarized light STRUCTURE / 95 Figure 55. Photomicrographs showing quartz ribbon grains in type II S-C mylonite. Oriented thin section from metasedimentary map unit Jmsq, station 84-714-13, cut parallel to Ls and perpendicular to mylonitic foliation, Ss. A. Plane polarized light; B. Cross polarized light Fields of view are about 2.4 x 3.6 mm. / 96 Mica In addition to defining C-surfaces (Fig. 54) and bounding quartz ribbons (Fig. 55), mica occurs as asymmetric porphyroclasts (Eisbacher, 1970) or mica fish (Lister and Snoke, 1984). Mica fish or retort-shaped mica porphyroclasts commonly occur in mylonitic rocks; especially type II S-C mylonites and are considered to be a reliable kinematic indicator (Lister and Snoke, 1984; Simpson and Schmid, 1983). Figure 56 shows a retort-shaped white mica grain bounded by shear bands. The sense of asymmetry indicates a top-to-the-west sense of shear. Note that the mica (001) cleavage is tilted back against the sense of shear and the ends of crystals are bent into parallelism with the shear bands (Table 3). Overprinting Brittle Fabrics Mylonitic fabrics have been progressively overprinted by brittle deformational features approaching the northeast fault strand which separates lower plate and 1MB upper plate rocks. Figure 57A shows a felsic metavolcanic mylonite located aproximately 2 km from this fault zone. Note the spaced brittle microfaults in this sample. Figure 56B is a photomicrograph of a brecciated felsic mylonite from within the fault zone. Angular clasts in this sample are composed dominantly of quartz ribbons. The syn- to post-Ds relative age of the northeast core/cover fault derived from the above microstructural relationships are consistent with map data that indicates a post-D3 relative age (Plate 1, Sec. 3.1.4.). 3.3. S U M M A R Y The Tatla Lake study area has been divided into 3 fault-bounded lithotectonic assemblages. In ascending order these are (1) a gneissic and migmatitic core, (2) a 1 to 2.5+ km-thick package of mylonite and ductilely-sheared metamorphic rocks (DSA), Figure 56. Photornicrographs of oriented x-z thin section showing retort shaped white mica grain bounded by shear bands. The asymmetry indicates a top-to-the-west sense of shear; east:right, west:left, top:structural top. Sample is mica-rich boudin from the contact zone of map units Jmsq and Jmvl, station 85-611-2. A. Plane polarized light B. Cross polarized light Fields of view are about 2.4 x 3.6 mm. / 98 Figure 57. Photomicrographs showing late brittle features in ductilely sheared rocks. A. Fractures in felsic metavolcanic mylonite from station 85-724-8. Short axis of photo is about 6 mm. B. Mylonite breccia from post D3 fault zone at station 85-724-3. Field of view is about 2.4 x 3.6 mm. Both photos taken in cross polarized light STRUCTURE / 99 which together comprise a lower plate, and (3) an undeformed to weakly deformed upper plate. Pervasive structural elements in the gneissic core are gneissic layering and subparallel schistosity (Sic), which has been deformed in west to northwest trending tight to isoclinal folds (F2c). A mineral elongation lineation (L2c) associated with, and parallel to F2c fold axes is also regionally recognized in the gneissic core (L2c). U-Pb zircon dating has bracketed Die ± D2c deformation to between 107+3 Ma (age of a granoblastic orthogneiss sample from unit ggl) and 79±6 Ma (age of late-D2c One Eye tonalite). The DSA is a km-scale ductile shear zone. It involves rocks of increasing structural depth towards the northwest and is therefore inferred to have originally dipped towards the northwest or west Structural elements in the DSA include a gently dipping mylonitic foliation (Ss) and shallowly plunging mineral elongation lineation (Ls) which trends towards 280° (110° )± 20°. Mesoscopic folds (Fs) of syn-Ds relative age occur almost exclusively in metasedimentary rocks. These folds deform and are locally truncated by mylonitic foliation. They occur within the DSA shear zone but do not deform shear zone boundaries or internal lithologic contacts. Fs fold axes have variable trend and plunge gently; axial surfaces are subparallel to shear zone boundaries. Vergence of these folds defines a movement sense and direction of top towards 290° ±20°. Tectonic movement or a-directions determined for Fs folds which which deform Ls lineations are approximately coincident with the regional Ls maxima (mainly from areas not deformed by Fs folds). These observations are consistent with the proposition that Ls is a stretching lineation, parallel to the movement direction within the DSA shear zone. Microstructures observed in oriented thin sections from DSA rocks not deformed by Fs folds overwhelmingly indicate a top-to-the-west sense of STRUCTURE / 100 shear. U-Pb dating has bracketed Ds deformation to between 55±3 Ma (age of pre-to syn Ds Eagle Lake tonalite and unit Edsi sills) and 47.5 Ma (post-Ds Tatla Lake stock). Open to normal map-scale F3 folds deform both Ss and Sic foliations and define the map pattern of units in the TLMC lower plate. They trend west to northwesterly and curve towards the trace of the Yalakom fault in the northwestern portion of the study area. They are thought to be drag or transpression-related structures associated with early stages of dextral transcurrent motion along the Yalakom fault The orientation of late fractures in the gneissic core adjacent to the Yalakom fault are consistent with dextral motion along this structure. Normal faults separate the upper and lower plates of the TLMC. A fault segment along the southern margin of the DSA is parallel in strike to underlying mylonitic foliation and is interpreted as a syn-Ds detachment fault related to the DSA ductile shear zone. The northeastern and eastern edge of the lower plate is a gently to moderately dipping down to the east normal fault which cuts a map-scale F3 fold. 4. GEOCHRONOMETRY 4.1. U-Pb ZIRCON GEOCHRONOMETRY Igneous and meta-igneous rocks within the study area have been sampled for U-Pb zircon dating. For simple systems this technique has been interpreted to date the time of crystallization of zircons analysed (Gebaur and Grunenfelder, 1979; Faure, 1977) The aim of this study was to obtain zircon dates from pre- through post-tectonic igneous (and meta-igneous) rocks, thereby bracketing the timing(s) of magmatic activity and deformational events in the study area. The following sections describe dated samples, report analytical results and discuss the geological significance of U-Pb zircon dates. Analytical techniques are described in Appendix 4.1, analytical data are listed in Table 4 and physical descriptions of zircon populations appear in Table 5. U-Pb zircon analytical data are also plotted on a series of concordia diagrams (Wetherill, 1956) with 2a error envelopes. In the following discussion of U-Pb zircon data a 'concordant date' refers to zircon fractions from a single sample which overlap each other and concordia at the 2a level of confidence. A concordant date is interpreted as the crystallization age of the analysed material. Some fractions plot slightly below concordia, perhaps due to the presence of inherited radiogenic Pb, Pb loss, or a combination of both effects. Pb loss is probably not important when fractions of differing size, magnetic susceptibility and U, Pb concentrations from a single rock sample are nearly coincident but slightly below concordia (Chen and Moore, 1982; Saleeby, 1982). In that case the 2 0 6Pb/ 2 3 8U dates are considered the best approximation of crystallization age. This is because small amounts of inherited old Pb give exaggerated 2 0 7Pb/ 2 0 6Pb and 2 0 7Pb/ 2 3 5U dates but 101 GEOCHRONOMETRY / 102 2 0 6 p D / 2 3 8 T j datgg increase only slightly. 4.1.1. Late Jurassic - Early Cretaceous U-Pb Dates The oldest zircon dated rocks in the study area are Late Jurassic and Early Cretaceous mylonitic tonalite orthogneiss of the DSA (Sec. 2.1.2.). Samples 84-71-7 (map unit LJog4, on Splinter Hill; Plate 1) and 84-726-5 (map unit JKog2, on Martin Mountain; Plate 1) occur as pre-or syn-Ds sheets, containing a well-developed mylonitic foliation and mineral elongation lineation (Ss and Ls; Table 1; Cha. 3). U-Pb zircon data from samples 84-71-7 and 84-726-5 are plotted on the concordia diagram" in Figure 58. Error envelopes (2a) for fractions from sample 84-71-7 overlap each other and slightly intersect concordia. These data are considered marginally concordant, and indicate a date of 157+4 Ma; Late Jurassic. Sample 84-726-5, is clearly concordant at 131+4 Ma, Early Cretaceous, with both analysed fractions coincident on concordia. 4.1.2. Cretaceous U-Pb Dates (70-110 Ma) Cretaceous (70-110 Ma) U-Pb zircon data from the DSA (samples 84-82-2 and 85-714-3) and Gneissic Core (samples 84-89-1C, 84-812-2 and 84-87-2) of the TLMC are plotted on concordia diagrams in Figures 59 and 60, respectively. The two dated samples from the DSA are pre-or syn-Ds in relative age, containing both Ss and Ls fabric elements. Two zircon fractions from sample 84-82-2, a small, foliated quartz diorite stock (MKqd) exposed east of One Eye Lake that intrudes mylonitic tonalite orthogneiss (JKog2; Plate 1), plot adjacent to each other on concordia at about 106 and 109 Ma (Fig. 59). These data cannot be considered concordant (and are difficult to interpret) because 2a error envelopes do not overlap. GEOCHRONOMETRY / 103 Figure 58. Concordia plot of Late Jurassic and Early Cretaceous U-Pb zircon data from the TLMC ductilely sheared assemblage. Dated samples are from map units JKog4 (station 84-71-7) and Uog2 (station 84-726-5). See Appendix 3, Table 4 for analytical data and Plates 1, 4 for sample locations. GEOCHRONOMETRY / 104 Figure 59. Concordia plot of Mid and Late Cretaceous U-Pb zircon data from the TLMC ductilely sheared assemblage. Dated samples are from map units MKqd (station 84-82-2) and LKogl (station 85-714-3). See Appendix 3, Table 4 for analytical data and Plates 1, 4 for sample locations. GEOCHRONOMETRY / 105 The age of this rock is cautiously interpreted as 108 ±4 Ma; the quoted error encompasses the entire range of errors for 2 0 6Pb/ 2 3 8U and 2 0 7Pb/ 2 3 5U dates for individual fractions (Table 4). Sample 84-714-3 is composed of mylonitic tonalite orthogneiss (LKogl) collected from the vicinitiy of One Eye Lake Forest Lookout Station (Plate 1). Two analysed fractions from this rock are very nearly concordant at 71+2 Ma (Fig. 59). Three Cretaceous samples from the gneissic core are plotted on Figure 60. Three zircon fractions from sample 84-89-1C, a granoblastic tonalite orthogneiss (EKggl) of pre- or syn-Die relative age (Plate 1), are nearly concordant at about 107 ±3 Ma (Fig. 60). Three fractions from each of two samples (84-812-2 and 84-87-2) of the weakly to undeformed (late-D2c to pre-D3) One Eye tonalite, which intrudes granoblastic gneiss of the gneissic core, are nearly concordant at 76 ± 3 Ma and 82 ± 3 Ma, respectively (Fig. 60, Table 4). A conservative interpretation for the crystallization age of the One Eye tonalite, incorporating dates and errors for both samples, is 79±6 Ma. A maximum age is given by the 2 0 7Pb/ 2 0 6Pb upper intercept date for the suite, 115 ±13 Ma, assuming Pb loss at about 50 Ma. 4.1.3. Eocene U-Pb Dates Eocene U-Pb zircon dates (Figs. 61 and 62) have been determined for pre- or syn- to post-tectonic rocks from the DSA and gneissic core of the TLMC. Three of the samples from the DSA are pre- to syn-Ds in relative age, and contain Ss and Ls, the regional mylonitic foliation and elongation lineation. Two of these samples, (84-714-10 and 85-812-2) were collected from the mylonitic Eagle Lake Tonalite (Plate 1, 6). Two fractions from sample 84-714-10 are concordant at about 56+2 Ma (Fig. 61, Table 4). Fractions from sample 85-812-2 are GEOCHRONOMETRY / 106 Figure 60. Concordia plot Cretaceous U-Pb zircon data from the TLMC gneissic core. Dated samples are from map units EKggl (station 84-89-1C) and LKoe (One Eye tonalite, stations 84-87-2 and 84-812-2). See Appendix 3, Table 4 for analytical data and Plates 1, 4 for sample locations. Asterisks indicate that fraction was run with 2 0 5Pb spike. GEOCHRONOMETRY / 107 Figure 61. Concordia plot of Eocene U-Pb zircon data from the TLMC ductilely sheared assemblage. Dated samples are from map units Eel (Eagle Lake tonalite, stations 84-714-10 and 85-812-2), Edsi (station 84-711-2) and Etl (Tatla Lake stock, station 85-817-2). See Appendix 3, Table 4 for analytical data and Plates 1, 4 for sample locations. GEOCHRONOMETRY / 108 more difficult to interpret because both fractions intersect concordia but their error ellipses do not overlap one another. An age of 54 ±2 Ma is assigned by computing the range and mean of 2 0 6Pb/ 2 3 8U and 2 0 7Pb/ 2 3 5U dates from this sample. A conservative estimate for the crystallization age of the Eagle Lake Tonalite incorporating data and errors from both samples is 55+3 Ma. U-Pb zircon data is interpreted to indicate an Eocene crystallization age for a pre- to syn-E)s metadacitic sill (Edsi, sample 84-711-2A) which intrudes metasedimentary rocks near the east end of Eagle Lake. As shown on Figure 61, the three fractions analysed from sample 84-711-2A are somewhat scattered. Two fractions (C and F*. Table 4) intersect concordia but do not overlap one another at the 2a level of confidence, while a third fraction plots significantly below concordia. Analytical data from the discordant fraction (F, Table 4) are somewhat suspect as indicated by its large error ellipse. U and Pb concentrations determined for this fine, magnetic fraction are anomalously low relative to the coarse/nonmagnetic and third (duplicate) fraction which was picked from the same fine, magnetic population (Table 4). While no obvious xenocrystic cores were observed, a small population of subhedral, cloudy zircons were recognized in fractions of 84-711-2A, which may have been derived from metasedimentary country rocks adjacent to this less than 1 m thick sill. These zircons were easily excluded from the coarse, nonmagnetic fraction, but may have been present in the discordant fine fraction. The duplicate (F*. concordant; Table 4, Fig. 61) fine fraction was carefully picked after analytical results from the other fractions were known, and included only euhedral, clear, crack-free zircons. Due to uncertainties relating to analytical data quality and/or zircon purity, the discordant fraction is not considered in the present age interpretation of sample 84-711-2A. On the basis of the two fractions that intersect concordia, a conservative GEOCHRONOMETRY / 109 estimate for the crystallization of the metadacitic sill is 55+3 Ma. These data are not truly concordant, because error envelopes of the two fractions considered do not overlap each other (Fig. 61). A post-tectonic (post-Ds) body, the Tatla Lake Granodioritic stock (Etl) intrudes mylonitic orthogneiss north of the northeastern end of Tatla Lake (Plate 1). Two fractions analysed from this rock are plotted on Figure 61. The relatively coarse, nonmagnetic fraction barely overlaps concordia, while the fine, magnetic fraction plots slightly' below concordia and has a minor area of intersection with the former. These data are not rigorously concordant, but are interpreted to indicate a crystallization age of 47+1.5 Ma for the Tatla Lake stock. U-Pb data from the post-tectonic granodioritic sill/dyke of Sucker Creek (Plate 1), which intrudes granoblastic gneiss of the gneissic core (Fig. 62), is plotted on Figure 63. Two relatively fine, magnetic fractions are nearly concordant at 50 ± 2 Ma, which is interpreted as the crystallization age of the body. Abraded, coarse and fine nonmagnetic fractions yield dates as old as 70 Ma, and appear to include inherited zircons (minor population, Table 5). Data from these fractions are too scattered to indicate a date for the inherited zircon population. 4.1.4. Geological Significance of U-Pb Zircon Data U-Pb data presented above (Figs. 58-61, 63; Table 4) bracket the timing of magmatism, deformation and sedimentation in the study area. U-Pb dates from igneous and meta-igneous rocks in the study area (interpreted as crystallization ages), range from 157 ±4 Ma to 47 ±1.5 Ma indicating the long duration of magmatism; Late Jurassic through medial Eocene. Die + D2c deformation in the gneissic core is bracketed between 107 ±3 Ma, GEOCHRONOMETRY / 110 Figure 62. Photo showing the contact between the nonfoliated Sucker Creek sill/dyke and gneissic country rock at station 85-717-7. Hammerhead is about 17 cm long. G E O C H R O N O M E T R Y / 111 0. 014 • , - i -S U C K E R 1 ' "I ' C R E E K S T O C K 1 ' —I 0. 012 8 5 - 7 1 7 - 7 75 C.HBR Z ) CD m 0. 010 -OJ \ J3 Q_ CD O OJ S^~^> f.HBR 5 5 - ^ • 0 . 008 0 . 00G E R R O R S R R E 2 S I G M R 0 . 004 i I . I . i . i 0 . 0 3 5 0 . 0 4 5 0 . 0 5 5 0 . 0 G 5 0 . 0 7 5 0 . 0 8 5 2 0 7 P b / 2 3 5 u Figure 63. Concordia plot of U-Pb zircon data from the Sucker Creek sill/dyke at station 85-717-7. See Appendix 3. Table 4 for analytical data and Plates 1, 4 for sample locations. GEOCHRONOMETRY / 112 a date from granoblastic tonalite orthogneiss (EKggl) containing Sic foliation and F2c folds, and 79+6 Ma, the interpreted crystallization age of the weakly to undeformed (late-D2c to pre-D3) One Eye tonalite. As shown on Plate 1, the One Eye tonalite intrudes granoblastic tonalite orthogneiss. The time of Ds deformation (shear zone activity) in the DSA can be bracketed between 55+3 Ma, interpreted age of the pre-to syn-Ds Eagle Lake Tonalite (Eel) and a metadacitic sill (Edsi), and 47± 1.5 Ma, the date from the post-Ds (post-tectonic) Tatla Lake Granodiorite (Etl). The 157+3 Ma mylonitic tonalite orthogneiss of Splinter Hill (LJog4), which is interpreted to intrude metasedimentary rocks (Jmsq) and the contact between metasedimentary and metavolcanic rocks (Jmvl, Plate 1) provides a minimum age for these strata. 4.2. K-Ar GEOCHRONOMETRY Conventional K-Ar dates determined for 12 biotite, hornblende, and whole rock samples within and adjacent to the TLMC are reported in this section. There is one previously published K-Ar date from the area (Wanless et al., 1979). The K-Ar dates give the time respective minerals passed through their closure temperature (Dodson, 1979). Experimentally determined estimates for hornblende and biotite closure temperatures for moderately fast uplift rates are about 550 C and 300 C, respectively (Harrison, 1981; Harrison and McDougall, 1980). K-Ar dates and their l a errors in and near the TLMC are listed in Table 6 and plotted on Figure 64 and Plate 1. K-Ar analytical techniques employed in this study are given in Appendix 4.2. Nine of ten K-Ar dates from samples from throughout the lower plate of the TLMC are between 45.6 and 53.4 Ma, with a tight cluster of seven dates at slightly GEOCHRONOMETRY / 113 1 2 4 ° 5 4 ' 1 2 4 ° 0 8 ' 5 2 ° 06 ' 5 1 ° 4 7 ' 1 2 4 ° 0 8 ' TLMC K-AR COOLING DATES Figure 64. Map showing locations and dates for K-Ar dated samples from the TLMC and vicinity. H: hornblende; B: biotite; Dates in millions of years with associated l a errors. GEOCHRONOMETRY / 114 less than 50 Ma. The single older date from the lower plate is 61 Ma for hornblende from a foliated hornblende tonalite within the mylonitic orthogneiss unit (sample 85-714-3; LKogl). K-Ar dates from the TLMC are further interpreted in Section 4.2.1. Two samples from the upper plate and one from west of the Yalakom fault have also been dated by K-Ar (Table 6, last three samples) for comparison with samples from within the metamorphic core. Both hornblende fractions (CPC-1 and 85-725-3) from just outside the metamorphic core come from undeformed to very weakly foliated quartz diorite bodies (Figs. 23, 24). Their dates are vastly older than any from lower plate samples, indicating that these bodies did not share thermal histories with rocks of the TLMC, as argued in more detail later. Sample PYP-1 is a volcanic rock of intermediate composition; part of a poorly dated belt of Jurassic (?) volcanic rocks located east and south of the TLMC (outside the bounds of Fig. 64; Tipper, 1969A, map unit 7; 1969B, map units 2, 3). The 67.8 ±2.7 Ma whole rock date determined for PYP-1 is evidence that these rocks may be Cretaceous rather than Jurassic. 4.2.1. Discussion and Interpretation of K-Ar Dates The lower plate of the TLMC cooled through hornblende and biotite closure temperatures between about 45 and 50 Ma. The data are quite consistent; the numerical result should be considered a maximum value due to the possibility of partial rather than total resetting or the possibility of addition of excess radiogenic 4 0Ar, which cannot be easily identified in conventional K-Ar analyses (Brewer, 1969). Partial resetting or addition of excess argon may account for the one older K-Ar date from the TLMC (sample 84-714-3). GEOCHRONOMETRY / 115 Samples dated by both K-Ar and U-Pb techniques can provide some information about cooling rates (See Tables 4, 6). In all cases the U-Pb dates are significantly older than the K-Ar dates. For sample 84-89-1C more than 60 Ma separates the 108±3 Ma U-Pb zircon date and the 46.4+1.6 Ma K-Ar hornblende date, indicating that final cooling occurred well after crystallization. It is not possible to say whether the rock remained above the closure temperature for the entire interval between the K-Ar and zircon dates or if it cooled and was reheated one or several times during that time interval. Samples 85-725-3 and CPC-1 lie just outside the metamorphic core across bounding faults (Fig. 64), and both of these samples have. Jurassic rather than Eocene K-Ar dates. Neither rock contains metamorphic fabrics or any other evidence of post-igneous reheating so that the K-Ar dates may approximate igneous ages for these bodies. It should be noted however, that the 190 ±7 Ma date for CPC-1 is uncommonly old for intrusives of the Coast Plutonic Complex (Armstrong, 1988). The upper plate apparently remained at high crustal levels during Eocene metamorphism of lower plate rocks. Sample PYP-1 was collected from a belt of marine and subaerial volcanic rocks to the east and south of the TLMC which are nearly devoid of index fossils and have been tenatively paleontologically dated as Jurassic in age (Tipper, 1969A; 1969B). It was not within the scope of this project to date rocks of this volcanic belt with the U-Pb zircon method (although it is suggested for further work); the K-Ar whole rock date of 67.8 ±2.7 Ma from this sub-greenschist facies volcanic rock suggests a Late Cretaceous age. GEOCHRONOMETRY / 116 4.2.2. Regional Significance of K-Ar Dates from the TLMC Eocene K-Ar cooling dates from the TLMC are interesting in that they match dates determined from several other metamorphic core complexes located across southern B.C. and the Pacific Northwest of the U.S. (Armstrong, 1982; fully referenced in Sec. 7.3.2). An additional feature in common with other Eocene core complexes is the fault juxtaposition of rapidly cooled lower plate (deformed and metamorphosed) rocks against undeformed to weakly deformed upper plate rocks with much older K-Ar dates (Fig. 64). The tectonic setting of Eocene-reset metamorphic complexes is discussed in Sec. 7.3.3. 4.3. Rb/Sr AND Sr ISOTOPIC STUDY A series of TLMC samples were collected during the 1984 and 1985 field seasons for whole-rock Rb/Sr and Sr isotopic analysis. These include two whole rock suites from the gneissic core and the igneous and meta- igneous rocks from which zircons were separated. The aims of this Rb-Sr study included whole rock isochrons and initial ! 7Sr/ uRb ratios. Sample locations and descriptions appear in Table 8 and analytical data in Table 7. The analytical techniques employed are described in Appendix 4.3. In the following section Rb-Sr data are graphically presented on strontium isochron diagrams. 4.3.1. Whole-Rock Data Figure 65 plots most of the Rb-Sr whole-rock analyses from the TLMC (whole-rock suites are plotted on Figs. 66, 67 and discussed below). The predominance of low 8 7Sr/ ! 6Sr ratios and the narrow range of 8 7Rb/ 8 6Sr values is typical of whole-rock samples from Stikinia (Preto et al., 1979; Morrison et al., 1979; Armstrong, 1988). GEOCHRONOMETRY / 117 CO <£> co CO CO 0.7055 —f 0.7050 — . 0.7045 — 0.7040 — 0.7035 — 0.7030 + + • area of Figure 66 A J "areaof Figure 67 0.7025 0.0 0.2 0.4 8 7 R b / 8 6 S r " i — " — r 0.6 0.8 Figure 65. Whole rock Rb-Sr isotopic data from the TLMC. All data except whole rock suites from stations 84-83-5 and 85-711-3 are plotted above. These suites appear on Figs. 66 and 67, respectively. Crosses indicate positions of data points and associated l a errors (see Table 7 and Appendix 4.3 for Rb-Sr analytical data and techniques). Other symbols: circles: Jurassic rocks; squares: Cretaceous rocks; diamonds: Tertiary rocks. Solid symbols: zircon dated rocks; Open symbols: samples lithologically correlated with a zircon dated rocks; Unadorned cross: poor age control. GEOCHRONOMETRY / 118 Samples of known U-Pb age, or those which can be confidently correlated with zircon dated rocks have been identified with symbols as Jurassic, Cretaceous or Tertiary (Eocene) age. Cretaceous samples are characterized by uniformly low 8 7Rb/ 8 6Sr (<0.15) and 8 7Sr/ uSr ratios (0.7034-0.7037), while Jurassic and Tertiary (Eocene) rocks have higher 8 7Rb/ 8 6Sr (>0.15) and 8 7Rb/ 8 6Sr (0.7038 to 0.7049, today) ratios. Whole-Rock Suites Rb-Sr data from two migmatitic gneiss whole-rock suites, 85-83-5 and 84-711-3, are plotted on Figures 66 and 67 respectively. Both suites span the apparent compositional range of the gneiss yet define only small ranges in both 8 7Sr/ 8 6Sr and 8 7Rb/ 8 6Sr values. A poorly constrained isochron of 289±94 Ma, with an initial 8 7Sr/ 8 6Sr ratio of 0.70327 ± 0.00009 (la) has been calculated for suite 84-83-5 (Fig. 66). This date is given little credence suspect due to the large error and poorly distributed data points. Because no zircon sample was collected at this locality the validity of this whole-rock isochron date cannot be tested with U-Pb data. A late Paleozoic to Jurassic age is compatible with possible Stikinian protoliths for this gneiss (Monger, 1977). The samples of suite 84-711-3 all have low 8 7Sr/ 8 6Sr (0.7034-0.7035) and 8 7Rb/ 8 6Sr (0.1-0.7) ratios. No isochron calculation is advisable for such data (Fig. 67). 4.3.2. Calculated Initial Ratios Calculated initial 8 7Sr/ 8 6Sr ratios vary from 0.70335 to 0.70415 (Table 7) The difference between calculated initial and present-day ratios in no case exceeds 0.001 and is significantly less for most samples.. GEOCHRONOMETRY / 119 0.0 0.1 0.2 0.3 7 R b / 8 6 S r Figure 66. Rb-Sr isotopic data for whole rock suite from station 84-83-5 (map unit mg, migmatitic gneiss). Crosses indicate locations of data points and associated l a errors (see Table 7 and Appendix 4.3 for Rb-Sr analytical data and errors). The isochron was fitted according to the technique of York (1967). GEOCHRONOMETRY / 120 0 . 7 0 3 8 C O co CO C O N. 00 0 . 7 0 3 6 — 0 . 7 0 3 4 0 . 7 0 3 2 — 0 . 7 0 3 0 — 8 7 R b / 8 6 S r Figure 67. Rb-Sr isotopic data for whole rock suite from station 84-711-3 (map unit mg, migmatitic gneiss). Crosses indicate locations of data points and associated l a errors (see Table 7 and Appendix 4.3 for Rb-Sr analytical data and errors). GEOCHRONOMETRY / 121 4.3.3. Discussion As expected, igneous rocks of the TLMC have initial 8 7Sr/ 8 6Sr ratios of about 0.704 and lower. This indicates that Precambrian continental crust does not underlie the area, which is in accordance with other Rb-Sr studies of the central and northern Intermontane Belt (Preto et al., 1979; Morrison et al., 1979) and with regional studies of the Canadian Cordillera (Armstrong, 1988). As noted by Armstrong (1988) the Eocene initial ratios are higher and more variable than Mesozoic initial ratios. This is presumably due to the incorporation about 52 Ma ago, of more evolved and therefore more radiogenic crust in the younger igneous suite. At an average crustal Rb/Sr of 0.15 (Armstrong, 1968) an increase in 8 7Sr/ 8 6Sr of 0.0006/100 Ma can be calculated. 5. METAMORPHISM The study of metamorphism in the TLMC is divided into a number of sections including: prograde metamorphism of the Gneissic Core (Mc) and DSA (Ms), retrograde metamorphism of the entire lower plate (M3) and metamorphism of the upper plate. Although prograde metamorphism in the gneissic core (Mc) and DSA (Ms) are discussed separately, they clearly have some overlap in time as discussed later. Subordinate topics include the documentation of mineral assemblages (Appendix 5, Tables 10 and 11), descriptions of textural relationships, order of metamorphic mineral growth with respect to deformation, and for metapelites, the suggestion of possible metamorphic reactions in the area. Estimates of T-P conditions during metamorphism are made on the basis of evidence from the above qualitative observations and quantitative thermobarometry of analysed minerals (Appendix 6, Tables 12, 13 and 14). Implications for the geological history of the TLMC, based on metamorphic evidence, are discussed in a final section. 122 METAMORPHISM / 123 5.1. GNEISSIC CORE: Mc PROGRADE METAMORPHISM Amphibolite grade metamorphism of granitic gneiss (units mg, ggl, EKggl and gg2; Plate 1) in the core of the TLMC (broadly termed Mc) proceeded from Cretaceous through Eocene time. The early stage of Mc metamorphism (termed Mlc), which is largely associated with the development of the regional gneissic layering, (Sic; Fig. 26), was synchronous with or post-dated the igneous crystallization of the granitic protoliths of these gneissic rocks. U-Pb zircon dating of igneous and meta-igneous rocks in the gneissic core have bracketed the age of Mlc metamorphism as 79 to 107 Ma (Sec. 4.1.2. and 4.1.4.). Based on mesoscopic and microtextural relationships discussed below, Mc metamorphism continued within and outlasted D2c deformation. Gneissic rocks were still experiencing amphibolite facies T-P conditions during Eocene Ds metamorphism of the DSA. Eocene K-Ar hornblende and biotite dates record the final cooling of gneissic core rocks. The timing of mineral growth with respect to deformation in the gneissic core is summarized on Figure 68. Minerals present in all core gneisses studied are (in order of general decreasing abundance), plagioclase (An 2 0-Ari4 0), hornblende, quartz, biotite, magnetite, apatite and zircon (Figs. 43, 44). Garnet and/or alkali feldspar (Fig. 70) are present in some samples, the latter most common in eastern exposures of gneissic rocks. Minor occurrences of epidote interpreted to be magmatic in origin have been recognized in some samples. This epidote displays sharp, well defined zoning and straight, clean boundaries with biotite (Fig. 69). General descriptions of minerals which occur in gneissic core rocks and a tabulated list of phases for all thin sections studied are presented in Table 10. Gneissic core mineral occurrences are plotted on Plate 6 and generalized metamorphic grade of the TLMC is shown on Figure 93. Ubiquitous granoblastic elongate textures observed in core gneissic rocks are / 124 CO Q C O O 0. CO LU CC CL > > - 3 -> > > > > > - 5 --n—5 5-> > > co > > > > > > > > > CD > > > m > > > 2 > CO CO Q LU Q. o CM Q 2 > CO LU cr UJ > L U g m cr L U t-u. < Q Z < L U > 2 > C O > > > LU QC 0 . Q L U > L T L U C O m O Q L U cr cr L U < QC LU Z N I-cr < ZD o L U C O < o o o < L U Q 2 L U - I C D Z cr o 1 2 C O L U z cr < cr o -i 1 o i I 0. 0. L U C O 5 3 cr 55 5 C O C O £ 3 O L U C L U . Figure 68. Mineral crystallization with respect to deformation in the gneissic core of the TLMC. / 125 Figure 69. Photomicrographs of magmatic epidote in map unit gg2, station 84-723-1. Note the sharp contacts with adjacent biotite. A. Plane polarized light; B. Cross polarized light Distinct zoning is visible in above grain. Fields of view are 0.6 x 0.9 mm. METAMORPHISM / 126 thought to have largely developed during the formation of the regional gneissic layering (Sic, during Die deformation). Biotite flakes and the long axes of plagioclase, hornblende and quartz lie within, and help to define the Sic foliation (Figs. 43, 44). The association of L2c, a regionally recognized mineral elongation lineation in core gneissic rocks, with F2c folds (which deform Sic gneissic foliation) provides evidence for continued metamorphic recrystallization during D2c deformation. The presence of small (< 2m3) pegmatitic clots (Fig. 7), which cut folded Sic gneissic layering and indicate that Mc metamorphism outlasted D2c deformation. These clots, many of which display graphic texture, consist of plagioclase + quartz + muscovite + garnet ± biotite ± alkali feldspar or plagioclase + hornblende + biotite + quartz and are interpreted as the crystallized products of partial melts. Thin section analysis of granoblastic textures in core gneissic rocks has revealed few crosscutting relationships between minerals (Figs. 43, 44, Sec. 3.2.1). This is interpreted to indicate that significant annealing occurred during or throughout Mc metamorphism, obliterating earlier textural relationships. As shown on Figure 68, the relative timing for crystallization of most major phases with respect to deformation can be bracketed no more precisely than Die through D2c, with exceptions discussed below. Gamet clearly post-dates the crystallization of hornblende and early biotite, forming at their expense and developing mesoscopic depletion haloes (Fig. 5, Sec. 2.1.2). It is therefore no older than intra-Die in relative age (Fig. 68). The syn- or late-D2c and pre-Ds One Eye tonalite, which intrudes gneissic rocks, is used as a gauge for evaluating the extent to which recrystallization occurred in the gneissic core during Ds deformation. Recrystallization in the One Eye tonalite is only clearly displayed in quartz, where subgrain and kinkband formation has been observed (Fig. 46). As discussed in Section 3.2.1, plagioclase suffered brittle deformation, METAMORPHISM / 127 with the development of microcracks (Fig. 46, Sec. 3.2.1). The near absence of gneissic layering and the occurrence of unoriented biotite and hornblende grains in the One Eye tonalite suggests that these minerals did not recrystallize during Ds deformation, although they were clearly above the hornblende argon retention temperature (550 C) during this time. By analogy with the One Eye tonalite, it is inferred that subgrain and kinkband formation in quartz were the main 'recrystallization' processes operative in core gneissic rocks during Ds deformation. Another relatively late textural feature, common in core gneissic rocks containing alkali feldspar, is the intergrowth of vermicular quartz and sodic plagioclase (myrmekite). These microstructures are observed along the margins of plagioclase crystals which abut alkali feldspar grains, and less commonly as intergranular masses between alkali feldspar grains (Fig. 70). They overprint granoblastic fabric and are thus are probably post-D2c in age. A model such as that first proposed by Becke (1908, p. 386, as discussed in Phillips, 1980), is favoured for the development of these myrmekitic textures. In this so-called replacement model, intergrown oligoclase and quartz are generated as products of dual reactions between alkali feldspar and both Ca- and Na-rich fluids. This model is consistent with textural evidence indicating that myrmekite formed at the expense of alkali feldspar (Fig. 70). T-P conditions in the gneissic core during Mc metamorphism have not been precisely determined, but several lines of evidence outlined below suggest that this event was probably medium to high grade; in the amphibolite facies. The minerals plagioclase (>An 2 0) and hornblende, which occur throughout the gneissic core, are generally considered to be indicative of the amphibolite facies (Turner and Verhoogen, 1960; Winkler, 1976). These minerals were, however, probably METAMORPHISM / 128 Figure 70. Photomicrograph of myrmekitic textures in map unit gg2, station 84-721-10. See text for details Cross polarized light Field of view are 0.6 x 0.9 mm. METAMORPHISM / 129 present in the intermediate granitic protoliths of the core gneisses and it cannot be proven that they were significantly modified during the Mlc event The presence of pegmatitic clots, (Fig. 7), interpreted as the crystallized products of partial melts, place some constraints on minimum temperatures attained during the late stages of Mc (age of clots: post-D2c to Ds; about 75-50 Ma). As shown on Figure 71, which summarizes data from melting experiments on natural and synthetic materials of granitic composition, solidus temperatures are in the neighbourhood of 650 C at pressures between about 4 and 8 kb. Magmatic epidote in hornblende-bearing granoblastic gneiss indicates pre- to syn-Dlc crystallization pressures of >8 kb for the TLMC gneissic core (Zen and Hammarstrom, 1984; 1986; Zen, 1985). 5.2. DUCTILELY-SHEARED ASSEMBLAGE: Ms METAMORPHISM Ms refers to metamorphism which affected rocks of the DSA largely during Ds deformation (textures allow a pre-Ds inception). Metamorphic grade increases from greenschist through middle amphibolite grade with increasing structural depth. Widespread recrystallization appears to be confined to rocks of the DSA although structurally underlying core gneissic rocks were certainly subjected to amphibolite grade T-P conditions during Ms metamorphism. Other than possible annealing of early fabrics and minor ductile deformation of quartz, granitic gneiss of the gneissic core appears to have been largely unaffected by Ms metamorphism. This may be due to the combined effects of 'resistant' quartzofeldspathic bulk compositions, a lack of volatiles, and much lower strain rates. The majority of DSA rocks are also quartzofeldspathic in composition and although they were subjected to pervasive dynamic recrystallization during Ms/Ds, their mineralogies are not useful in precisely determining metamorphic grade. As a result METAMORPHISM / 130 i i i i 1 i 1 1 i 600 650 700 750T(°C) Figure 71. Solidus P-T data determined with natural rocks as starting material and in the pure system QZ-OR-AB-H 20; from Johannes (1985). Data sources: (1) Turtle and Bowen (1958), pure system; (2) Luth et al. (1964), pure system; (3) Johannes (1984), pure system; (4) Winkler (1976), starting composition: alkali feldspar-free paragneiss; (5) Winkler (1976), starting composition: metagreywacke; (6) Piwinskii and Wyllie (1968), starting composition: granodiorite 779; (7) Piwinskii (1973), starting composition: quartz monzonite MO-IB; Piwinskii (1968), starting composition: granite 104. Curves 1, 2 and 3, determined in the pure granite system, are plotted as relatively fine lines with associated ruled lines. METAMORPHISM / 131 rocks approximating pelitic and mafic to intermediate bulk compositions were used to establish metamorphic grade, as discussed below. Generalised metamorphic grade is shown on Figure 93. 5.2.1. Intermediate to Mafic Metavolcanic Rocks Rocks of intermediate to mafic composition are exposed as metavolcanic rocks of unit Jmv and less commonly as Ss-parallel compositional layers and/or sills in metasedimentary (units Jmsp, Jmsq) and metaplutonic (units og) rocks (Plate 1). With increasing metamorphic grade mineral assemblages in these rocks change from albite-epidote-chlorite-sericite to albi te-epidote-sericite-chlorite-biotite ± actinolite to oligoclase/andesine-actinolitic hornblende-biotite ± garnet These assemblages and one other, albite-sericite-epidote-calcite, (only seen in undeformed upper plate rocks) are plotted on a metamorphic assemblage map of the study area (Plate 5). The most important mineralogical change recorded in these rocks is the alibite to oligoclase transition, which can be optically determined and marks the greenschist-amphibolite facies boundary (Winkler, 1976). This transition is recognized in the southern part of the map-area, near the metasedimentary (Jmsp, Jmsq)/metavolcanic (Jmv) contact as, shown on Plate 5. Figure 72 summarizes the timing of metamorphic crystallization in mafic to intermediate rocks with respect to deformation. This diagram is useful to refer to in connection with Ms mineral descriptions which appear below. Amphibole Amphibole is medium to less commonly fine grained, fibrous and moderately to very poikiloblastic. Crystals are dark green and exhibit marked pleochroism: o-pale yellow, greenish yellow; £-pale green; r-pale green to deep blueish green. In METAMORPHISM / CO O 0. CO Q > > > > > > CO > > > 03 > > > > > CO > > > > > CD > > > > > CO > > > > > > > •5-> > > > > > > > > CO O 0_ > > co > > > CO > CO > > > > > > > > > > > > > CO Q > CO • ^ T ^ r >: 5: > >: «: >i >: >• $1 >: > > > > > > > > z o CO CJ o oc a i 0 < c r o LU g CD CC 111 H = < Q Z < Z LU > CO > CO > LU CC CL < HI N ac < o LU CO < —I o g < LU -I o ffl X a . < LU g CO LU z QC < < o LU X 5 LU t LU LU c r o X o o a Q. Ill o _l < o LU z LU X a. CO Q LU > QC 111 CO CO O a LU QC QC 111 Z £ LU > > > > Figure 72. Mineral crystallization with respect to deformation: mafic to intermediate metavolcanic rocks of the ductilely sheared assemblage. METAMORPHISM / 133 longitudinal sections maximum extinction angles do not exceed 20° in albite bearing assemblages and reach 26° in oligoclase bearing rocks. C-axes commonly lie within the Ss foliation and define the Ls lineation (Figs. 48, 53), although unoriented crystals have been rarely observed. This amphibole has been optically identified as actinolite to actinolitic hornblende. Electron microprobe analyses of amphibole in orthogneiss (LKogl) are characteristic of hornblende (Appendix 6). Plagioclase Plagioclase occurs as medium to coarse grained porphyroclasts/porphyroblasts and as a fine grained idioblastic matrix mineral. Compositions determined optically and by electron microprobe analysis (Appendix 6) are similar for both textural types, varying between about An3.7 and An 2 0- 42. Coarser grained plagioclase is replaced to varying degrees by epidote and chlorite (Figs. 48, 53). Chlorite Chlorite is green with light green to light yellow pleochroism and anomalous blue birefringence. It occurs in low-grade assemblages as a matrix mineral parallel to Ss foliation (Figs. 48, 53), in late-Ds, Ls normal fractures, and in pull-aparts in plagioclase feldspar (Fig. 50). Garnet Crystals vary from l-5mm in diameter, are moderately to very poikiloblastic and define shapes between idioblastic and xenoblastic. Most garnets contain inclusion trails parallel to Ss and also deflect this surface, indicating probable syn-Ds growth (Fig. 73). / 134 Figure 73. Photomicrograph of garnet in metavolcanic rocks at station 84-622-5 (map unit am). Ss schistosity is included in, and deflected by garnet Cross polarized light Width of photo is about 3.8 mm. / 135 Epidote Ms epidote is fine to medium grained, yellowish in thin section, xenoblastic and commonly glomeroblastic. Crystals often lie parallel to, and deflect Ss foliation (Fig. 74, contrast with magmatic epidote in Fig. 69); M3 epidote occurs as an unoriented alteration phase of plagioclase. Biotite In mafic to intermediate metavolcanic rocks biotite is fine to medium grained and oriented parallel to Ss foliation. Laths occur in pressure shadows adjacent to porphyroblasts and porphyroclasts and are also spatially associated with amphibole (Figs. 48, 53), which they often appear to replace. In highly strained (mylonitic) rocks biotite has been observed in pulled apart amphiboles (Fig. 75). Quartz Quartz occurs as ribbon grains parallel to Ss (mylonitic) foliation, and in highest grade samples as a fine to very fine grained, relatively unstrained matrix phase (annealed, commonly lacking undulatory extinction). Quartz is also present in pressure shadows adjacent to porphyroblasts/porphyroclasts. 5.2.2. Metapelitic Rocks Metsedimentary rocks of pelitic composition are interlayered with quartzofeldspathic and amphibolitic rocks west of Whitesand Lake (unit Jmsp) and occur in a small (metre-scale) pendant in the midst of a mylonite tonalite orthogneiss body (LKogl; Plate 1). On the basis of textural relationships primarily observed in thin section, metamorphic minerals in these rocks crystallized mainly during Ds deformation, which has been dated as Eocene in age (Sees. 4.1.3., 4.1.4). These / 136 Figure 74. Photomicrographs of Ms epidote in metavolcanic rocks at station 84-726-4. Ss schistosity is deflected by epidote. A. Plane polarized light; B. Cross polarized light Field of view is 0.6 x 0.9 mm. / 137 Figure 75. Ms biotite and opaque in pulled-apart and necked amphibole, map unit Jmvl, station 84-621-4. A. Plane polarized light; B. Cross polarized light Field of view is 0.6 x 0.9 mm. METAMORPHISM / 138 relationships do not rule out the possibility that an earlier foliation developed, (accompanied by mica growth), and was nearly completely overprinted by pervasive Ds fabrics. Three metamorphic zones are defined by the presence or absence of Ms chlorite, biotite, garnet, staurolite, kyanite and sillimanite. These zones are: chlorite-biotite, garnet-staurolite and garnet-staurolite-kyanite-sillimanite with increasing structural depth (south to north in the Whitesand Lake area, Plate 6). The transition between the chlorite-biotite and garnet-staurolite-kyanite-sillimanite zone occurs across a maximum structural thickness of 300 m, located within a zone of high Ds ductile/brittle strain which straddles the metasedimentary(Jmsp)/metavolcanic(Jmvl) contact zone. The garnet-staurolite zone occupies this 300 m thickness (no kyanite or sillimanite yet identified) and is abruptly overlain by chlorite-biotite zone metapelites interlayered with quartzofeldspathic and metavolcanic rocks in the Jmsp/Jmv contact zone. As discussed in section 5.3, this metamorphic discontinuity is best explained as a late-Ds, mylonitic foliation-parallel, normal, ductile/brittle fault Refer to the metamorphic mineral growth vs. deformation diagram (Fig. 76) throughout the following descriptions of Ms minerals in pelitic rocks. Quartz Quartz occurs as ribbon grains parallel to Ss (mylonitic) foliation, (Fig. 77) and in highest grade samples as a fine to very fine grained, relatively unstrained matrix phase (annealed, commonly lacking undulatory extinction). Quartz is also present in pressure shadows adjacent to porphyroclasts/porphyroclasts. Biotite Biotite is fine to medium grained, lepidoblastic and defines the Ss schistosity. It MINERAL Ds D3 PRE SYN POST SYN POST QUARTZ BIOTITE MUSCOVITE PLAGIOCLASE GARNET STAUROLITE KYANITE SILLIMANITE ANDALUSITE — CHLORITOID -CHLORITE V B V B V B V B V B V B V B V B V B VB — EPIDOTE v v V V V V V V V V V V V V V V V V V V VV CALCITE V V V V V V V V V V V V V V V V V V VV OBSERVED CHLORITE-BIOTITE ZONE ROCKS ONLY INFERRED VBVB VEIN AND AFTER BIOTITE, GARNET v v w VEIN Figure 77. Quartz ribbon grains in metapelitic rocks, station 85-611-2. A. Plane polarized light; B. Cross polarized light Field of view is about 2.4 x 3.6 mm. METAMORPHISM / 141 has also been observed in pressure shadows and as coronas (85-610) around slightly resorbed garnets (Fig. 79). In rocks higher than biotite-chlorite grade, Ss fabric and early biotite are often folded (Fs microfolds) and cut by axial planar biotite defining the Ss2 crenulation cleavage (Fig. 83C). Unoriented biotite laths crosscutting both Ss and Ss2 have also been observed. These textural relationships indicate that biotite growth was synchronous with and locally outlasted Ds deformation. Pre-Ds growth cannot be ruled out Muscovite Muscovite is commonly fine to medium grained however coarse grains have been observed in very muscovite-rich samples. Lepidoblastic muscovite is interleaved with biotite and helps to define Ss and Ss2 foliations. In one muscovite-rich sample (84-622-4) Ss has been nearly completely transposed into parallelism with Ss2 (Fig. 79). Unoriented muscovite laths grow across all previous surfaces. The similar textural relationships of muscovite and biotite indicates that their growth was synchronous. Chlorite Chlorite is green with light green to light yellow pleochroism and anomalous blue birefringence. It is observed as a prograde (syn-Ds) phase only in chlorite-biotite zone rocks where it is parallel to and helps define the Ss foliation (Fig. 80). M3 chlorite, common in higher grade metapelites, is discussed in Section 5.3. Chloritoid Chloritoid has been identified in one sample (85-68-3), located in the garnet-staurolite-kyanite-sillimanite zone. It occurs as fine to medium grained, olive drab coloured (in thin section), ragged, poikiloblastic crystals which include Ss schistosity (Fig. 81). They are confined to 3 mm. thick biotite rich compositional layers or / 142 • Figure 78. Biotite fringing garnet in metapelitic schist, map unit Jmsp, station 85-610— 1. Plane polarized light; Field of view is about 6 x 9 mm. / 143 Figure 79. Mica in isoclinally folded garnet-staurolite-kyanite schist, map unit Jmsp, station 85-622-4. Cross polarized light; Field of view is about 2.4 x 3.6 mm. / 144 Figure 80. Ms chlorite in CHL-BI grade metapelitic rocks from station 85-612-2. Plane polarized light; Field of view is about 2.4 x 3.6 mm. / 145 Figure 81. Early Ms chloritoid in GT-STAUR-KY-SILL grade metapelitic rocks from station 85-68-3. Biotite appears to be growing at the expense of chloritoid. A. Plane polarized light; B. Cross polarized light; Field of view is about 2.4 x 3.6 mm. / 146 domains. Textural relationships indicate that biotite, staurolite and possibly sillimanite grew at the expense of chloritoid. The growth of chloritoid is interpreted to have occurred during the early portions of Ds deformation. Plagioclase Plagioclase is fine grained, idioblastic or equant, and finely twinned. It occurs as a matrix mineral with quartz and mica. Electron microprobe analyses indicate compositions of An 2 0- 3o in garnet-staurolite-kyanite-sillimanite zone rocks west of Whitesand Lake and An 3 8_ 4 0 in the pelitic pendant Garnet Garnet is dark red, varies from 1 to 10 mm in diameter, and often possess texturally recognizable cores and rims. Cores are often helicitic or rolled, containing a swirled internal foliation (interpreted as Ss) defined by inclusion trails of quartz and opaques. Rims are relatively poor in quartz inclusions, overgrow mica schistosity (recognized by opaque inclusions) and possess idioblastic morphologies. Rims also slightly deflect external schistosity (Ss and/or Ss2) and are therefore not post-kinematic (Fig. 82). In some samples core/rim morphologies have not been observed. Garnets in these rocks resemble either rolled, quartz inclusion rich cores (Fig. 82), or inclusion poor xenoblastic rims (Fig. 78). Textures described above indicate two periods of intra-Ds garnet growth or varying local relative timings of crystal growth with respect to strain. Partial garnet resorbtion has been observed, in one sample affecting both rims and cores. The replacement assemblage includes quartz, aluminosilicate, biotite, muscovite and later chlorite. In another sample (85-610) containing inclusion poor, xenoblastic garnets, minor resorbtion has occured with the development of biotite rich coronas / 147 Figure 82. Rotated garnet in GT-STAUR-KY-SILL zone metapelitic schist in map unit Jmsp. A. Station 85-67-1; B. Station 85-68-3. Plane polarized light and 2.4 x 3.6 mm field of view for both photos. METAMORPHISM / 148 (Fig. 78). Staurolite Staurolite is fine to medium grained, and pale yellow in thin section. Crystals are helicitic, overgrowing Ss foliation defined by quartz and opaque inclusion trails. The appearance of grains and their relationship to external foliation is variable, ranging from idioblastic with little or no deflection of external Ss schistosity (Fig. 83A), to ragged and pulled apart with significant deflection of this surface (Fig. 83B). In rocks of the garnet-staurolite zone staurolite is intergrown with, and parallel to biotite which defines Ss2 (Fig. 83C). Pulled apart grains become more common approaching the garnet-staurolite/chlorite-biotite zone boundary. The minerals quartz, biotite, muscovite and chlorite have been observed in pull-aparts. In one sample (85-68-3) a fringe composed of predominantly staurolite, and minor biotite and quartz has been observed adjacent to garnet (Fig. 83D). Kyanite Kyanite is fine to rarely medium grained, and colourless in thin section. It has a similar relationship to deformation as staurolite. Crystals commonly are helicitic, including opaque inclusion trails interpreted as Ss. External Ss and/or Ss2 schistosity is commonly but not always deflected around grains. Crystals vary from ragged and kinked to idioblastic (Fig. 84). Texturally early kyanite is very rare in the Whitesand lake area. Kyanite is most commonly observed with biotite, garnet and staurolite, adjacent to resorbed garnets, but also overgrows muscovite-rich compositional layers. Sillimanite Sillimanite is fine grained and occurs as both fibrolitic needles and well formed crystals. It comprises an estimated 15-20% (by volume) of the mineral assemblage in Figure 83. Ms staurolite in metapelitic schist, map unit Jmsp. A. Staurolite growing across Ss schistosity at station 85-610-1. Fs microfold can be seen above the staurolite crystal. B. Pulled-apart staurolite at station 85-68-3. Biotite, muscovite and quartz occur in the pull-aparts. Plane polarized light and 2.4 x 3.6 mm field of view for both photos. / 150 Figure 83. Continued. Ms staurolite in metapelitic schist, map unit Jmsp. C. Staurolite oriented parallel to Ss2 schistosity at station 85-612-1 (GT-STAUR zone). Field of view is 2.4 x 3.6 mm. D. Staurolite fringing garnet at station 85-68-3. Field of view is about 6 x 9 mm. Plane polarized light for both photos. METAMORPHISM / 151 Figure 84. Ms kyanite in metapelitic schist, map unit Jmsp. A. Kyanite growing across Ss schistosity at station 84-622-4. Plane polarized light; Field of view is about 0.6 x 0.9 mm B. Bent kyanite at station 84-622-4. Cross polarized light; note the variable extinction of bent crystal. Field of view is about 2.4 x 3.6 mm. / 152 the pelitic pendant in the northwestern part of the map area and is only a trace constituent in the Whitesand Lake area. In the latter area it is always found adjacent to garnet, sometimes nucleating on nearby biotite (Fig. 88A). Slightly kinked crystals have been observed in this area, suggesting that crystallization is not post-kinematic. Unoriented sillimanite in this area has only been observed in pressure shadows around garnet In the pelitic pendant sillimanite clearly post-dates kyanite and is parallel to Ls. It occurs as bundles which are intergrown with biotite, and is rarely texturally associated with garnet (Fig. 88B). Andalusite Andalusite has been rarely observed in the Whitesand Lake area as fine to very fine grained blocky crystals adjacent to partially resorbed garnets (Fig. 86). It has grown late during Ds deformation (Fig. 76). 5.2.3. Ms Metamorphism: Mineral Reactions Possible mineral reactions have been deduced for metapelitic rocks of the DSA, based on mineralogical and textural criteria. Some of these equilibria have been modeled in the KFASH, KMASH or K.FMASH systems (Sec. 5.2.4., Figs. 88, 90 and appendix 7). General mineral formulae and abbreviations are listed in Table 9. Late, M3 minerals are not included in assemblages listed below. CHLORITE-BIOTITE ZONE Assemblage: QZ, MS, BI, AB, CHL, EP, OP + SPH, AP, CC, ZI. Metamorphic reactions in chlorite-biotite bearing rocks cannot be suggested on the basis of textural relationships, however a biotite producing reaction (or reactions) can be inferred simply due to the presence of this mica. An example of such a / 153 Figure 85. Ms sillimanite in TLMC metapelitic schist A. Fine grained sillimanite, map unit Jmsp, station 85-610-1. Field of view is about 0.6 x 0.9 mm. B. Sillimanite intergrown wth biotite in pelitic pendant station 85-76-3. Cross polarized light Field of view is about 2.4 x 3.6 mm. Both photos taken in plane polarized light Figure 86. Fine grained andalusite, map unit Jmsp, station 85-68-3. Plane polarized light Field of view are about 0.6 x 0.9 mm. METAMORPHISM / 155 biotite forming reaction is listed below: 1) 8PHENG + CHL = 3BI + 5MS + 7QZ + 4H 20 (Hyndman, 1972), Phengite has not been identified in these rocks and could have served as a limiting reactant, being completely consumed in the reaction 1. METAMORPHISM / 156 GARNET-STAUROLITE ZONE Assemblage: QZ, MS, BI, PL, GT, STAUR, OP ± TOUR, AP, ZI. Staurolite is intergrown with and parallel to Ss2 biotite, and has clearly grown across Ss muscovite in rocks of the garnet-staurolite zone (Fig 81C, 85-612-2). These relationships suggest that Ss2 biotite and staurolite grew synchronously, and may have been products of a reaction such as: 2) 31CHL + 41MS = 8STAUR + 41BI + 33QZ + 108H2O (Garwin, 1987, modified from Hoscheck, 1969; Thompson and Norton, 1968). Prograde chlorite is not present in these rocks and may have been the limiting phase which was completely consumed in reaction 2. Garnet is inferred to have also formed as the product of a rection which consumed chlorite and muscovite such as: 3) 3CHL + IMS + 3QZ = 4GT + 1BI + 12H 20 (modified from Thompson and Norton, 1968). There is strong textural evidence indicating that garnets in these rocks were rotated during growth (and Ss development; Fig. 85A, 85B), and do not simply overgrow Fs microfolds. If this is the case, then garnet growth in these rocks predates (but may continue during) the crystallization of staurolite, which includes Ss foliation (Fig. 86). METAMORPHISM / 157 GARNET-STAUROLITE-SILLIMANITE-KYANITE ZONE Assemblage: QZ, MS, BI, OLIG-ANDES, GT, STAUR, SILL, OP + KY, ANDAL, CTD, SPH, AP, ZI. As in the garnet-staurolite zone, chlorite-muscovite consuming reactions (reactions 2 and 3) are inferred to be responsible for the production of garnet and staurolite in these rocks. A similar reaction is compatible with the formation of syn-Ds kyanite, which overgrows muscovite-rich compositional layers parallel to Ss (Fig. 84, 84-622-4): 4) 5MS + 3CHL = 8KY + 5BI + 1QZ + 12H 20 (Thompson and Norton, 1968). Chloritoid has been identified in one sample and may have participated in reactions producing garnet, staurolite and kyanite. Textures that support this contention have been observed in the case of staurolite and biotite (Fig. 79, 85-68-3). These chloritoid consuming reactions are listed below: 5) 1CTD + 1CHL + 2QZ = 2GT + 5H 20 6) 31CTD + 5MS = 4STAUR + 5BI + QZ + 23H 20 7) 3CTD + MS + QZ = 4K.Y + BI + 3H 20 (modified from Thompson and Norton, 1968) 8) 23CTD + 7QZ = 2STAUR + 5GT + 19H 20 (modified from Hyndman, 1972). Reactions 5, 6 and 8 may also be important in the garnet-staurolite zone, although chloritoid has not been identified in this area. In garnet-staurolite-kyanite-sillimanite zone rocks of the Whitesand Lake area partially resorbed garnets and associated replacement minerals provide evidence for the occurrence of reactions that consume garnet (Fig. 87, 84-622-4). Biotite, muscovite, / 158 Figure 87. Kyanite, biotite and quartz replacing partially resorbed garnet, map unit Jmsp, station 84-622-4. Plane polarized light Field of view is about 2.4 x 3.6 mm. METAMORPHISM / 159 quartz and the three Al 2Si0 5 polymorphs replace, or lie directly adjacent to partially resorbed garnets. Sillimanite and andalusite occur exclusively in this context. The following reaction is compatible with the above textural and mineralogical observations: 9) 1GT + IMS = 1BI + Al 2 S i 0 5 + 1QZ. Reaction 9, which produces A l 2 S i 0 5 in response to depressurization, (D. McMullin, personal communication, 1988), is thought to be responsible for the formation of late-Ds sillimanite and andalusite in the Whitesand Lake area. It is not possible to quantitatively evaluate the relative importance of reactions 4, 7 and 9 for the production of kyanite in this area. In sample 85-68-3 staurolite, biotite and quartz forming fringes on garnet (Fig. 86, 85-68-3) provides textural evidence for the following reaction: 10) 115MS + 69CHL + 32GT = 24STAUR + 115BI + 123QZ + 228H 20 (modified from Garwin, 1987 and Thompson and Norton, 1968). In the pelitic pendant (northwestern part of the map area, Plate 1; Fig. 85), abundant sillimanite primarily occurs as foliation-parallel bundles intergrown with biotite (not just nucleating on it), and is rarely in contact with garnet Potassium feldspar is not present muscovite is rare, and staurolite occurs as remnant xenoblastic grains commonly fringed with sillimanite. These relationships are compatible with the following reaction: 11) 6STAUR + 8MS + 17QZ = 62SILL + 8BI + 12H20 (modified from Thompson and Norton, 1968). Garnets in these rocks are interpreted to be pre-tectonic in relative age because they deflect Ss foliation and do not include i t They appear to have grown statically during the intrusion of the surrounding pluton. METAMORPHISM / 160 5.2.4. Ms Metamorphism: Conditions of Metamorphism Temperature-pressure (T-P) conditions experienced by metapelitic rocks of the DSA have been estimated with several thermobarometric systems, and by modeling some of the mineral reactions discussed above in section 5.2.3. These two approaches are discussed below. MINERAL EQUILIBRIA Some of the mineral reactions thought to be important in pelitic schist of the DSA have been modeled in P-T space with the computer program P-T SYSTEM (Perkins et al., 1986). This modeling involved themodynamic data derived from experimental penological studies, and required knowledge or estimates of activities for all phases considered. Reactions in the systems KASH, KFASH, KM ASH and KFMASH, which include the phases clinochlore, Mg- and Fe-chloritoid, muscovite, pyrope, almandine, phlogopite, annite, quartz, potassium feldspar, kyanite, sillimanite, staurolite and water, were investigated in this study (see Appendix 7 for details). Activities of pyrope, almandine, phlogopite and annite were derived from garnet and biotite electron microprobe analytical data. Activities of all other phases were estimated. Activities have been varied through calculated ranges for pyrope, almandine, phlogopite and annite and through geologically reasonable ranges for estimated phases in order to monitor the effect on the positions of investigated equilibria. Figure 88 is a plot of the equilibria modeled with preferred activity values. This net must be considered qualitative to semi-quantitative at best, due to the uncertainies associated with estimated activities. Appendix 7 contains listings of investigated equilibria (Table 15), activities used to generate the net in Fig. 88 (Table METAMORPHISM / 161 200 300 400 500 600 700 800 900 REACTION LIST Assemblages on the l e f t are s t a b l e on the: h igh s i d e of the Y - a x i s v a r i a b l e , or the h igh s i d e of the X - a x i s v a r i a b l e for v e r t i c a l r e a c t i o n s Temperature (C) 3) 4) 5) 6) 7A) 7B) 8) 10) 11) 12) 12 H20 + 4 PYROP • PHLOG = 3 CLN + MS + 3 QZ 3 CLN + 5 MS = 12 H20 » QZ • 6 PHLOG + 8 KY 5 H20 • 2 PYROP = MGCTD • CLN • 2 QZ 5 MS = 23 H20 + 4 STAUR + QZ + 5 ANN ANN + 4 KY + 3 H20 PHLOG • 3 H20 2 STAUR + 5 ALM 115 MS = 228 H20 • 24 STAUR + 123 QZ + 115 PHLOG 6 STAUR = 12 H20 • 62 SILL + 8 ANN • SILL + H20 31 FECTD QZ + MS + 3 FECTD QZ • MS + 3 MGCTD = 4 KY 23 FECTD * 7 QZ = 19 H20 32 ALM • 69 CLN 8 MS • 17 QZ QZ • MS = KSP Figure 88. Phase equilibria, in P-T space, which constrain Ms conditions of metamorphism. Reactions were chosen on the basis of mineralogical and textural evidence and calculated with the computer data base PT-SYSTEM as discussed in text METAMORPHISM / 162 16) and discussions of criteria involved in choosing preferred activities. The numbering scheme for reactions used in section 5.2.3. (above) is retained in Appendix 7 and below. Refer to Figure 88 during the following discussion of modeled equilibria. Reactions 3, 5, 6 and 8 mark the transition between the CHL-BI and GT-STAUR zones in the Whitesand Lake area. These reactions, that consume clinochlore and/or chloritoid and produce garnet and/or staurolite, occur in the temperature range of about 375-475 C up to 6 kb pressure. Reactions 4, 7A and 7B consume chloritoid or clinochlore and produce kyanite. At, pressures of 5-8 kb (in the stability field of kyanite) they span the temperature range of 510-590 C. The phases chlorite and chloritoid in these equilibria may have been largely consumed in reactions of the CHL-BI GT-STAUR transition zone. Equilibrium 10 is a garnet-clinochlore consuming, staurolite-biotite producing reaction proposed on the basis of textural criteria; staurolite, biotite and quartz fringing garnet in GT-STAUR-KY-SILL zone metapelites. Due to the rarity of this textural relationship reaction 10 is considered relatively unimportant in the study area. As in the case of kyanite forming reactions 4, 7A and 7B, chlorite may have been the limiting reactant Equilibrium 11 involves the breakdown of staurolite and formation of sillimanite and biotite. It provides a minimum temperature estimate for sillimanite rich rocks in the pelitic pendant (northwestern portion of the field area), and an upper limit for pelitic schist in the Whitesand Lake area. Sillimanite is very rare in these latter rocks, and as discussed in section 5.2.3, is thought to have formed as a product of reaction 9, which occurred during depressurization. The reaction: 12) IMS + 1QZ = 1SILL + 1KSP + 1H 20 METAMORPHISM / 163 (Guidotti, 1963; Evans and Guidotti, 1966) has not occurred in the pelitic pendant and may define maximum temperatures for these rocks. Failure to observe this reaction may also be due to the bulk composition of these rocks. THERMOBAROMETRY Pressures and/or temperatures have been calculated for six samples in the DSA employing various thermobarometric techniques. The precise mineral compositions required for these calculations were determined with an automated Cameca SX50 electron microprobe at UBC. Analytical techniques and mineral composition data are listed in Appendix 6, Table 13. Temperatures for pelitic and gamet-hornblende-biotite bearing samples were calculated with the garnet-biotite geothermometer, which is based on the exchange of Mg and Fe between garnet and biotite: 13) 1ANN + 1PYROP = 1PHLOG + 1ALM. For comparative purposes three sets of temperatures have been reported (Appendix 6, Table 14) for each analysed garnet-biotite pair, all using the Ferry Spear (1978) experimental calibration. In one calculation ideal mixing is assumed for garnet, while the latter two employ the mixing models of Newton and Haselton (1981; Fe, Mg and Ca mixing) and Ganguly and Saxena (1984; Fe, Mg, Ca and Mn mixing), respectively. When geobarometric calculations were not not possible, these three sets of temperatures were calculated; at 4, 5, 6 and 7 kb for each garnet-biotite pair. Temperatures reported below are mean values for samples at given pressures. Uncertainties of ±50 C (error on experimental calibration of Ferry and Spear, 1978) are reported for all samples with l a errors less than ± 50 C. Except for those from sample 84-76-3A, garnet-biotite temperatures reported in the text and plotted on Figure 90 were calculated with pyrope and grossular activities derived with the Newton METAMORPHISM / 164 and Haselton (1981) mixing model. Quoted temperatures for sample 84-76-7A, which contains garnet with subequal pyrope and spessartine components (Table 13, 14), were calculated with pyrope and almandine activities derived with the Ganguly and Saxena (1984) mixing model. Pressures in pelitic samples containing an Al 2Si0 5 phase (or phases) were calculated with the garnet-plagioclase-Al2Si05-quartz geobarometer. This method is based on the equilibrium: 14) GROS + 2Al 2SiOj + QZ = 3AN The calibration for reaction 14 which was used in this study is from the work of Lang and Rice (1985). Their P-T equation was derived with linear programming techniques, and is based on the experimental calibrations of reaction 14 (Hays, 1966; Hariya and Kennedy, 1968; Goldsmith, 1980). Grossular and anorthite activities used in pressure calculations were determined with the mixing models of Newton and Haselton (1981). Errors of +3 kb, derived mainly from calibration uncertainties (Lang and Rice, 1985; Hodges and McKenna, 1987), are reported for all samples. When both garnet-biotite and garnet-plagioclase-Al2SiOj-quartz methods were employed, T-P values reported in the text represent the intersection of calculated Kd curves for reactions 13 and 14. Three T-P sets, corresponding to the three garnet-biotite temperatures calculated for each garnet-biotite, garnet-plagioclase analysis, are listed in Table 14 (Appendix 6). An assumption implicit in the simultaneous solution of T-P conditions is that redistribution of Mg and Fe between neighbouring garnet and biotite and Ca between garnet and plagioclase had become negligible or had ceased simultaneously. Even in simple cases (disregarding the complicating effects of retrogression) it is unlikely that this assumption can be met because volume diffusion of Fe, Mg between garnet and METAMORPHISM / 165 biotite occurs more readily (and continues to lower temperatures) than Ca between garnet and plagioclase (Freer, 1981, Thompson and England, 1984) As shown on Figure 89, calculated garnet-biotite, garnet-plagioclase-Al2SiOs-quartz T-P esimates may not necessarily record peak metamorphic temperatures or pressures; in some cases they may not even intersect the T-P path of a rock. Therefore interpretation of thermobarometric data (discussed below) is approached cautiously, on a sample by sample basis. Crystallization pressures in hornblende-bearing intrusive rocks were calculated with an empirical geobarometer based on the concentration of aluminum in hornblende (Hammarstrom and Zen, 1986; Hollister et al., 1987). The latter workers have suggested that this geobarometer is governed by the pressure-sensitive reaction: 15) 2QZ + 2AN + 1BI = 1TSCH + 1KSP They have further stated that the empirical relationship between Al concentration in hornblende and pressure only holds for rocks containing the mineral assemblage quartz-plagioclase-biotite-potassium feldspar. Low activities of potassium feldspar appear to favour increased Al (TSCH) in hornblende (Hollister et al. 1987 and this study, see below). A preliminary experimental study of Al in hornblende at 10 kb (Rutter and Wyllie, 1988) agrees with the empirically derived curve, and also indicates that the minerals quartz-plagioclase-biotite-potassium feldspar must be present for the relationship between Al in hornblende and pressure to hold. Because this method is thought to record crystallization pressures or depths, pressure-time coordinates potentially can be determined for rocks of known crystallization age. Unfortunately this geobarometer could not be widely used in this study because most hornblende-bearing plutons within the map area contain negligible amounts of potassium feldspar. METAMORPHISM / 166 • T Figure 89. Hypothetical T-P path and GT -BI , GT-PL-Al 2Si0 5-QZ thermobarometric determinations. This figure graphically emphsizes that the T and P simultaneously calculated using thermobarometric techniques which are not set at the same time does not necessarily record the peak metamorphic conditions experienced by a rock. Stippled area is the simultaneously calculated T-P with associated errors. Thermobarometry discussed in text; For analytical techniques and data see Appendix 6. METAMORPHISM / 167 Thermobarometric results are discussed on a sample by sample basis in the following paragraphs. Temperatures and pressures are plotted on Figure 90, and fully reported in Table 14 (Appendix 6). 84- 76-3A This sample was collected east of Whitesand Lake, outside of the main area of pelitic schist (unit Jmsp, Plate 1), and contains the minerals garnet, biotite, hornblende, oligoclase, quartz, and epidote. It is therefore above the albite/oligoclase transition (Winkler, 1976), and is probably of similar grade as garnet-staurolite zone metapelites. Biotite is fresh, oriented parallel to Ss schistosity and concentrated near rotated garnet porphyroblasts. The temperature reported below, and Kd curve plotted on Figure 90A were calculated with the Ganguly and Saxena (1984) mixing model, due to the subequal concentrations of Mn and Mg in garnet (6-8 wt.% Mn, 5-7 wL% Mg), which exceed the 1:3 Mn/Mg ratio suggested by Newton and Haselton (1981) as the "safe" limit for usage of their mixing model. The mean Ganguly and Saxena (1984) modified temperature has been calculated as 497 ±50 C at 4 kb, about 20 C lower than the Newton and Haselton (1981) modified value. Aluminosilicate phases (K.Y, SILL, ANDAL) are lacking in this sample and as shown on Figure 90A, pressure is poorly constrained. 85- 610-1 This is a muscovite-rich schist from high in the garnet-staurolite-kyanite-sillimanite zone (Whitesand Lake area). It contains the minerals quartz, muscovite, biotite, garnet, staurolite, plagioclase and sillimanite. Biotite is- fresh and occurs as late-Ds coronas around slightly resorbed, inclusion-poor, idioblastic late-Ds garnets (Fig. 78). METAMORPHISM / 168 200 300 400 500 600 700 800 900 Temperature (C) Figure 90. Thermobarometric data from rocks of the DSA plotted over modeled reaction net of Figure 88. Bold, nearly vertical lines and enveloping stippled areas are mean calculated GT-BI Kd curves ±50 C. GT-QZ-PL-AliSiOs curves are labeled on these plots where they are relevant The positions of modeled reactions are approximate. See Section 5.2.4, Figure 88 and Appendix 7 for discussions of, and data associated with computer modeling of equilibria. See text for discussions of individual samples shown on Figure 90A-E A. Sample 84-76-7A, from east of Whitesand Lake; pressure constrains have not been determined. METAMORPHISM / 200 300 400 500 600 700 800 900 Temperature (C) Figure 90. Continued. B. Sample 85-610-1; from GT- STAUR- K.Y- SILL zone of pelitic schist west of Whitesand Lake. SILL-ANDAL and STAUR-out reaction curves define the limits of suggested T-P conditions at low pressure. Figure 90. Continued. C. Sample 85-622-4; from GT-STAUR-KY-SILL-ZONE of pelitic schist west of Whitesand Lake. Simultaneously calculated T-P Kd curves plotted. METAMORPHISM / 171 200 300 400 500 600 700 800 900 Temperature (C) Figure 90. Continued. D. Sample 85-67-1; from the GT-STAUR-KY-SILL zone of pelitic schist west of Whitesand Lake. Suggested conditions at low pressure and high temperature are constrained by the STAUR-out reaction (#11). METAMORPHISM / 172 200 300 400 500 600 700 800 900 Temperature (C) Figure 90. Continued. E. Sample 85-76-3; from the pelitic pendant in the northwestern part of the study area. Garnet core-inclusion T-P conditions are further constrained by modeled STAUR-out (#11) and SILL+KSP-in (#12) reactions METAMORPHISM / 173 Sillimanite, which is locally kinked, has been observed as a trace phase adjacent to garnet (Fig. 85). On the basis of textural relationships, biotite used for temperature calculations, and sillimanite appear to be co-crystallizing phases; both forming, to some extent, at the expense of garnet (reaction 9). The mean garnet-biotite temperature of 541+50 C, at 4 kb, (Appendix 6, Table 14), overlaps the sillimanite stability field (Fig. 90B), and is consistent with the observed mineral assemblage. It was not possible to calculate pressures for this sample due to a lack of plagioclase in contact with garnet Peak pressures above the KY-SILL reaction curve cannot be ruled out due to the presence of kyanite at nearby localities. 84-622-4 This is a muscovite-rich sample from high in the garnet-staurolite-kyanite-sillimanite zone (Whitesand Lake area). It contains garnets with rotated cores, and rims that overgrow muscovite schistosity. Both cores and rims have been partially resorbed. Kyanite and staurolite are of late-Ds relative age; they include and deflect Ss schistosity. Fibrolitic sillimanite is rare and appears to occur as part of the resorbed garnet replacement assemblage. Biotite and plagioclase are moderately fresh but are not abundant, and are rarely in contact with garnet Mean T-P conditions of 523±50 C and 8±3 kb (in the KY stability field) were simultaneously calculated with equilbria 14 and -15 (Fig. 90C; KY used in pressure calculation). This implies closure of garnet and plagioclase with respect to Ca diffusion prior to the growth of sillimanite, and is consistent with sillimanite forming during depressurization, via reacton 9 (discussed in section 5.2.2). Even if the garnet-biotite thermometer has not recorded peak temperature conditions, pressure estimates remain in the kyanite stability field (Fig. 90C). METAMORPHISM / 174 85-67-1 _ This sample is a quartz-mica schist from deep in the garnet-staurolite-kyanite-sillimanite zone west of Whitesand Lake. It contains the minerals quartz, garnet, biotite, muscovite, staurolite, plagioclase + sillimanite. Kyanite has not been observed in this section, but has been identifed in samples from nearby localities. Garnet is xenoblastic, contains quartz and opaque inclusions, and sometimes occurs as 3-5 cm long glomeroporphyroblasts which are confined to 1-2 mm thick, Ss-parallel compositional layers. Staurolite and sillimanite are very rare and have not been observed in the probe section. Biotite is often partially replaced by chlorite, but some fresh grains do occur in contact with garnet. A mean garnet-biotite temperature of 645+50 C has been calculated for this sample. Due to a lack of sillimanite in analysed domains, calculated pressures of greater than 10 kb (using Newton and Haselton (1981) modified temperatures) is regarded as an absolute maximum value (Fig. 90D; Table 14, Appendix 6). As in the case of sample 85-610-1, a lack of kyanite in the analysed section cannot rule out peak metamorphic pressures above the KY-SILL reaction curve, because kyanite has been observed at nearby localities. The staurolite out and SILL-AND AL reaction curves limit T-P conditions at low pressure (Fig 90D). 85-76-3 This sample was collected from a foliated pelitic pendant located in the northwestern part of the study area. It occurs as a low, rounded exposure surrounded on all sides by a foliated (locally mylonitic) tonalitic pluton (LKogl) dated as 71 ±2 Ma (no contacts exposed). Observed minerals include garnet, biotite, sillimanite, plagioclase, quartz + muscovite, kyanite and staurolite. Garnets, which vary from 1-7 mm in diameter, are METAMORPHISM / 175 poikiloblastic, xenoblastic and moderately to highly fractured and embayed. Fractures and embayments are filled with biotite, quartz, sericite and chlorite. In some garnets it is difficult to disinguish whether medium grained biotite occurs in inclusions or embayments in the two-dimensional perspective of a thin section. Foliation (interpreted as Ss) is deflected around these garnets and opaque inclusions are non-oriented, suggesting that garnet growth was pre-tectonic in relative age. Overgrowths, which occur on some garnets, are visibly identified as inclusion-poor areas separated from the rest of the crystal by a narrow zone rich in fine grained silicate inclusions (quartz, biotite and plagioclase). Sillimanite bundles oriented parallel to Ss texturally overprint kyanite and staurolite grains. Garnet in the pelitic pendant is zoned from core to rim with respect to Ca, Mg and Fe (Ca, Mg increasing, Fe decreasing from core to rim). Mean calculated T-P from biotite and plagioclase inclusions in garnet cores are 655+50 C and 5.3 ±3 kb is thought to be a reliable indicator of metamorphic conditions in this sample. These conditions are associated with intrusion of the surrounding tonalitic rocks of map unit LKogl. Garnet growth appears to have been pre-tectonic in relative age, as discussed above. Ca-rich rims, with up to 11% grossular, have been recognized in this sample. They sometimes occur as texturally discernable overgrowths. Rim pressures calculated with adjacent matrix plagioclase are about 3 kb higher than core values, at a given temperature. This apparent core to rim pressure increase is considered to be geologically significant, as discussed in section 5.5.1. Calculated rim and embayment GT-BI temperatures (Newton and Haselton (1981) modified values), vary from about 750 to greater than 1000 C; these are probably not be indicative of temperatures actually attained during metamorphism. It is METAMORPHISM / 176 likely that adjacent rim garnet and matrix biotite which yielded high temperatures were not in equilibrium with each other. As stated above, garnet appears to be pre-tectonic in relative age, while biotite is intergrown with sillimanite, parallel to Ss foliation and is clearly syn-tectonic. This biotite is thought to have been chiefly produced in the reaction: 6STAUR + 8MS + 17QZ = 62SILL + 8BI + 12H 20 (reaction 11), and could have inherited high Fe/Fe+Mg ratios from staurolite (staurolite was not analysed in this study, but Pigage and Greenwood (1982) have shown that Fe/Fe + Mg ratios in coexisting garnet and staurolite are often similar). Relatively Fe-rich biotite grains (relative to inclusion biotite), which had equilibrated with neighbouring garnet to different extents could account for the very high, variable calculated rim temperatures. In addition, the presence and sense of zoning of garnet from the pelitic pendant casts doubt on the geological significance of calculated rim GT-BI temperatures. Numerical modeling (Lasaga, 1983), and studies of natural metamorphic garnets (Tracy et al., 1976) indicate that zoning is easily homogenized, and rarely preserved in high grade metamorphic rocks (temperatures greater than about 650 C). Zoning that has been recognized in garnet from high grade metamorphic rocks is thought to be the result of post-growth retrogression (Tracy et al, 1976, Tracy 1982). This chemical variation is however, opposite to the sense of zoning in pelitic pendant garnets. Inclusion-garnet core T-P estimates are plotted on Figure 90E. These conditions are further constrained by modeled equilibria 11 (STAUR-out) and 12 (SILL+KSP-in). The positions of these modeled reactions are, however, approximate and cannot be treated as defined T-P bounds. METAMORPHISM / 177 84-76-2 This is a foliated to mylonitic tonalite orthogneiss body (LKogl, Plate 1) containing the major minerals plagioclase, hornblende, biotite, quartz and potassium feldspar. A crystallization pressure of 7.2 ± 1.4 kb, based on the total Aluminum content of hornblende, was calculated using the empirical formula of Hollister et al. (1987). This rock has also been U-Pb zircon dated as 71 ±2 Ma, which is interpreted as its crystallization age. Pressure and age determinations together indicate that this body crystallized at 71±2 Ma and 7.2± 1.4 kb. This pressure overlaps both core and rim values calculated with the garnet-plagioclase-Al2Si05-quartz geobarometer in the nearby pelitic pendant (85-76-3, discussed above). 5.3. M3 METAMORPHISM A low-grade retrograde metamorphism, (termed M3), which is largely synchronous with and/or postdates D3 deformation has been recognized throughout the entire lower plate of the TLMC. The composite M3 mineral assemblage includes the phases chlorite, epidote, sphene, calcite and albite. These minerals fill fractures and replace both Mc and Ms phases. In the gneissic core all phases of the M3 composite assemblage have been identified filling fractures of various orientations. These fractures are most commonly oriented normal to F3 fold axes (interpreted as A-C fractures), but have been rarely observed cutting these folds (Fig. 47). They are therefore interpreted as both syn- and post-D3 in relative age. In the matrix of gneissic country rocks, anomalous blue, length-slow chlorite partially or completely replaces biotite and hornblende parallel to Sic. Epidote and sphene occur as unoriented grains and glomeroblasts overprinting earlier fabric. M3 METAMORPHISM / 178 epidote is distinguished from epidote of magmatic origin by the absence of features such as sharp internal zoning patterns and straight, clean contacts with biotite, which have been observed in the latter (Fig. 69). The effects of M3 metamorphism are more difficult to identify in the rocks of the DSA than in those of the gneissic core. This is especially the case for greenschist grade, mafic to intermediate metavolcanic rocks (unit Jmvl), whose peak (Ds) mineral assemblage is nearly identical to that of the M3 assemblage. This unit contains the most well developed mineral-filled fractures in the study area, which are invariably oriented perpendicular to the Ls lineation direction, suggesting a temporal association with Ds rather than D3 deformation. The saussuritization of large plagioclase porphyroblasts is also very common in this unit This replacement/alteration is dated as Ds and/or D3 in age. M3 metamorphic minerals are clearly distinguished from Ms phases in amphibolite grade metasedimentary rocks. These rocks are however commonly fresh and M3 minerals are relatively rare. The most common M3 association in these rocks is chlorite after biotite (Fig. 91). In some metapelites unoriented masses of anomalous brown, length-fast chlorite have been observed partially replacing garnets. In one sample (84-622-4) it appears that chlorite dominantly replaces Ds biotite after garnet rather than the garnet itself (Fig. 91). As discussed in Sec 5.2.3, biotite is one of the main products of a garnet consuming reaction (#10, Sec. 5.2.3) thought to be important in these rocks. The M3 mineral assemblage of chlorite, epidote, quartz, sphene and calcite is noncritical, but is probably of subgreenschist (most likely prehnite-pumpellyite) grade. / 179 Figure 91. M3 chlorite in pelitic schist A. Chlorite after biotite in GT-STAUR-KY-SILL zone rock from station 85-610-1; Cross polarized light B. Chlorite as a late replacement mineral in partially resorbed garnet at station 84-622-4. This chlorite is after biotite, part of the original replacement assemblage for partially resorbed garnets at this locality. Plane polarized light; 2.4 x 3.6 mm fields of view for both photos. METAMORPHISM / 180 5.4. M E T A M O R P H I S M IN T H E UPPER PLATE Rocks of the TLMC upper plate have suffered low-grade (subgreenschist to lowest greenschist grade) metamorphism and lack penetrative deformational fabrics. The effects of metamorphism in the upper plate are only clearly displayed in greenstones of unit Jv, which are described below. The composite metamorphic mineral assemblage observed in volcanic and sedimentary rocks of unit Jv include chlorite + epidote + sericite + calcite + albite. The former three minerals replace plagioclase phenocrysts in volcanic rocks to varying degrees, and also occur in their fine grained groundmass. Massive volcaniclastic siltstone exposed on Little Meadow Mountain (Plate 1, southeastern part of the study area) contains the mineral assemblage epidote + calcite + sericite + albite. Epidote sometimes partially replaces plagioclase, but often comprises the whole of grains (Fig. 92), which may be either metamorphic or detrital in origin. Microfractures filled with epidote + sericite + calcite have also been observed in these rocks. TLMC upper plate greenstones do not exceed lower greenschist grade. The composite mineral assemblage chlorite + epidote + sericite + calcite + albite is non-critical, but probably indicates subgreenschist (prehnite-pumpellyite) conditions. The timing of metamorphism in the upper plate is not well known due to uncertainties in the age of 1MB volcanic rocks, and the lack of deformational fabrics which may be correlated with those in the lower plate. Metamorphism must postdate the volcanic age of these rocks (thought to be Jurassic), and predate ther age of overlying unmetamorphosed volcanic flows (lithologically correlated with the Eocene Ootsa Lake volcanics). Figure 92. Nonfoliated massive siltstone from map unit Jvs, station 84-72-12, in the upper plate. A. Plane polarized light; B. Cross polarized light Fields of view are 2.4 x 3.6 mm. METAMORPHISM / 182 5.5. SUMMARY AND DISCUSSION 5.5.1. Summary Amphibolite grade metamorphism of Cretaceous (to as late as) Eocene age (Mc) affected rocks of the TLMC gneissic core. The Cretaceous metamorphism (Mlc) was coeval with the development of regional gneissic foliation (Sic), which has been bracketed in time between 108 and 78 Ma, based on U-Pb dating of igneous (One Eye tonalite) and meta-igneous (tonalite orthogneiss) rocks (data summarized below is shown on Fig. 93, generalized metamorphic grade of the TLMC and 94, T-P-t diagram). Magmatic epidote in hornblende-bearing granoblastic gneiss indicates pre- to syn-Dlc pressures of >8 kb in the gneissic core (Zen and Hammarstrom, 1984, 1986; Zen, 1985). Post-Sic pegmatitic clots, interpreted as crystallized partial melts, indicate (post-Die) temperatures in excess of 650 C. Eocene hornblende and biotite K-Ar dates record the final cooling of core gneissic rocks below the 550 C and 350 C closure temperatures of these minerals. Greenschist and amphibolite grade metamorphic rocks occur in the DSA, increasing in grade with structural depth. Textures observed primarily in thin section indicate that the growth of metamorphic minerals in these rocks was largely coincident with the development of regional mylonitic foliation (Ss), which formed (at least in part) between 55 and 47 Ma. The pre-Eocene metamorphic history of DSA metapelitic rocks is obscure. Penetrative Eocene fabrics observed in these rocks appear to have overprinted any earlier foliations. It is possible, however, that some rotated garnets interpreted as Eocene in age may have grown during Cretaceous Mlc metamorphism. In this scenario internal schistosity in these rotated garnets is a relict Cretacous fabric (coeval with Sic METAMORPHISM / 183 in the gneissic core) that is not preserved elsewhere in the DSA. Evidence discussed below suggests that DSA rocks in the northwestern part of the study area were at elevated temperature and pressure by Latest Cretaceous time (71 Ma). Metamorphic minerals in DSA rocks of pelitic and intermdiate to mafic compositions were useful in qualitatively evaluating metamorphic grade across the study area. Pelitic schist increases from chlorite-biotite to garnet-staurolite-kyanite-sillimanite grade with structural depth in the Whitesand Lake area. There the transition from chlorite-biotite to kyanite-sillimanite bearing metapelitic rocks and albite to oligoclase in mafic to intermediate metavolcanic schist occurs within a 300 m thick zone of relatively highly strained rocks adjacent to the metavolcanic/metasedimentary contact Assuming a 30° to 35° southerly regional dip of metamorphic layering, kyanite-sillimanite bearing pelitic schist is presently no more than 4 structural km below subgreenschist grade Jurassic volcanic rocks across the southern Core/Cover fault (Plates 1. 5). Garnet-biotite temperatures from mainly metapelitic rocks near Whitesand Lake increase from 497+50 C to to 645+50 C with increasing structural depth. Pelitic schist in the garnet-staurolite-kyanite-sillimanite zone west of Whitesand Lake has yielded a GT-PL-Al 2Si0 5-QZ pressure of 8±3 kb. Porphyroblasts analysed are syn-Ds in relative age based on textural relationships, so that these T-P calculations reflect Eocene metamorphic conditions (possible Cretaceous rolled garnet cores were not used). A T-P of 655 ±50 C and 5.3 ±3 kb from a pelitic pendant in the northwestern part of the study area is thought to record metamorphic conditions during intrusion of the surrounding pluton. A crystallization age and pressure of 71 ±2 Ma (U-Pb) and 7.2± 1.4 kb (total A l in hornblende) has been determined for this body. A relative pressure increase of about 3 kb in analysed garnet rims and plagioclase of METAMORPHISM / 184 the pelitic pendant may be correlated with tectonic crustal thickening (syn-Dlc? burial beneath thrust sheets; Sec. 5.5.2). Mineral reactions in TLMC metapelitic rocks, which were deduced on the basis of texture and mineralogy, have been numerically modeled using P-T SYSTEM, a computer program by Perkins et al. (1986). The resulting reaction net (Fig. 88) is consistent with calculated mineral thermobarometry (Fig. 90). Hornblende and biotite K-Ar dates for the gneissic core and DSA record the final cooling of the TLMC during Eocene (Ds and D3) time. A mild retrograde metamorphism of probable prehnite-pumpellyite grade (M3) affected rocks of the TLMC lower plate during (to possibly slightly after) D3 deformation. 5.5.2. Discussion T-P-t data for the TLMC (Fig. 94) indicate that rocks of the gneissic core and amphibolite grade DSA rocks (from the northwestern part of the study area) were at elevated temperatures and pressures by Late Cretaceous time (gneissic core >79 Ma; DSA >71 Ma). Figure 94 shows a hypothetical prograde T-P path involving (Mid- to Late Cretaceous) crustal thickening. This crustal thickening is broadly coeval with compressional deformation recognized in the TLMC gneissic core and shortening in a northwest-trending east-vergent thrust belt exposed to the west of the Yalakom fault (Tipper, 1969B; Rusmore and Woodsworth, 1988). Burial of TLMC rocks may be temporally and spatially related to this compressional tectonic setting. Continued (pre?-Ds) thrust loading may also account for the 3 kb pressure increase recorded in minerals of the pelitic pendant in the northwestern portion of the DSA (Sec. 5.2.4, 5.5.1). METAMORPHISM / 185 Figure 93. Generalized metamorphic grade of the TLMC. Grade of stippled area is above, and ruled area is below the albite-oligoclase transition for rocks of mafic and intermediate composition. Metapelitic rocks in the stippled area are at or above garnet-staurolite grade and in the ruled area are at chlorite-biotite grade. Unpattemed area is at subgreenschist grade. Ruled/stippled boundary approximates the greenschist/amphibolite facies boundary. The data from which this map is derived are plotted on Plate 5. METAMORPHISM / 186 1 -Whitesand Lake Pelitic Rocks Syn -Ds T - P A Jur««ste?X ( ProtoMth ) V Depoiltton J _ l l 200 DSA: Pelitic Pendant P r e ? - D s T - P _ Gneissic Core : P r e - " to S y n - D 1 c P Magmatic Epidote > 79 Ma, P o s t - D 1 c T Pegmatitic C lo ts < 79 Ma DSA:AI in HB P r e ? - D s P DSA:Pel i t ic Pendant P r e - D s T - P -400 600 800 1000 Temperature C Figure 94. T-P-t path for rocks of the TLMC. Labeled boxes represent T and/or P data and associated errors; dashed portions indicate qualitative control; circles give age constraints: K.-Ar, HB: hornblende, BI: biotite;. Large arrows indicate T-P path suggested by data. Prograde portion of path (dashed arrow) is hypothetical. See text for details. METAMORPHISM / 187 Syn-Ds (circa 55-47 Ma) T-P conditions of 500 C to 650 C and 8±3 kb for metapelites in the Whitesand Lake area, and post-Dlc±D2c pegmatitic clots in the gneissic core indicate that the TLMC was still deeply buried during Eocene time (Fig. 94). Elevated Eocene T-P conditions and K-Ar cooling dates require rapid Eocene uplift of the TLMC as shown on Figure 94. These data, coupled with the lower over higher metamorphic grade of the TLMC and vicinity suggest that much of the uplift occured along a syn-Ds ductile/brittle normal fault system (Chapter 7, Fig. 99). During ductile Ds deformation mylonitic foliation (Ss) developed and strain is thought to have been distributed throughout the DSA. Later Ds strain was probably accomodated within more discrete ductile/brittle normal fault zones such as the one recognized near the metavolcanic/metasedimentary contact There the occurrence of a steep, lower over higher metamorphic grade (attenuated or truncated isograds) is consistent with late-Ds normal motion. Late-Ds strain in this zone can also account for the preservation of texturally late syn-Ds porphyroblasts (garnet, staurolite and especially kyante) which locally grow across early Ss foliation in underlying pelitc schist These porphyroblasts are difficult to explain in the context of a shoaling ductile/brittle fault zone. 6. GEOCHEMISTRY A suite of igneous and meta- igneous rocks from across the TLMC were chosen for major and trace element analysis by X-ray fluoresence (see Plate 4 for sample locations). Major element analyses were carried out on ground glass pellets using a Philips PW 1410 spectrometer located in the Department of Geological Sciences and trace element analyses (Ba, Cr, Nb, Ni, Rb, Sr, V, Y, and Zr) on pressed powder pellets using an automated model 1400 spectrometer in the Department of Oceanography. These analyses complete the description of major rock units and provide clues to the tectonic setting of multiple magmatic episodes. Sample preparation procedures are outlined in Appendix 4.4. Appendix 8 contains analytical precision (Table 17) and accuracy (Table 18) data, as well as major and trace element analyses of TLMC rocks (Table 19). Plutonic samples range from quartz diorite through granodiorite on a modal quartz-alkali feldspar-plagioclase feldspar diagram (Streckeisen, 1976) as shown on Figure 95. Fine-grained hypabyssal samples are dacitic to rhyolitic in composition based on the normative classification scheme proposed by Irvine and Baragar (1971). 6.1. CLASSIFICATION AND TECTONIC SETTING On plot of total alkalis vs silica (Fig. 96) samples plot within the subalkaline field of Irvine and Baragar (1971) and MacDonald and Katsura (1964). On the AFM diagram shown in Figure 97 all samples plot in the calc-alkaline field of Irvine and Baragar (1971). Samples are both low- and medium-K, based on the classification system of Irvine and Baragar (1971; normative AB-AN-OR plot). The relatively K-rich (medium-K) samples are predominantly Eocene U-Pb dated or structurally late rocks. 188 GEOCHEMISTRY / 189 Figure 95. Modes of geochemically analysed samples plotted on IUGS plutonic rock diagram of Streckeisen (1976). Q: quartz; A F : alkali feldspar; P F : plagioclase feldspar; QD: quartz diorite; T: tonalite; G: granodiorite. GEOCHEMISTRY / 190 Figure 96. Chemically analysed samples plotted on alkali vs silica diagram All samples occur in the subalkaline field. GEOCHEMISTRY / Figure 97. Chemically analysed samples plotted on AFM diagram. All samples occur the calc-alkaline field. GEOCHEMISTRY / 192 Trace element data are plotted on a bulk earth normalized diagram (BEND) in Figure 98, along with reference low- (triangles) and medium-K (squares) calc-alkaline volcanic rocks (from Gill, 1981). Bulk earth abundances are from Sun (1980), Armstrong (1981), and Thompson et al. (1984). Normalization factors are listed in Table 20. BEND patterns for TLMC samples are internally consistent and quite similar to those of the reference calc-alkaline rocks. The notable differences are a lesser Nb depletion and a more pronounced Ti depletion for TLMC samples. Overall, BEND patterns provide independent evidence for the calc-alkaline nature of TLMC rocks. Figure 99 is a plot of Rb vs Y + Nb, which has been used by Pearce et al. (1984) as a trace element tectonic setting discriminant diagram for granitic rocks. All TLMC samples plot in the volcanic arc granite field on this diagram. Major and trace element data suggest that TLMC igneous rocks were generated in a calc-alkaline volcanic arc, and are probably subduction related. The samples analysed range from Late Jurassic through Late Eocene in age, which leads to the conclusion that the TLMC has been the site of volcano-plutonic arc magmatism, probably related to subduction from at least Late Jurassic through Late Eocene time. GEOCHEMISTRY / 193 Figure 98. Bulk earth normalized diagram (BEND) which plots TLMC (solid lines) and reference calc-alkaline (dashed lines and triangles: low-K.; squares: medium-K.; Gill, 1981) trace element data. Bulk earth abundances are from Sun (1980), Armstrong (1981), and Thompson et al. (1984). Normalization factors are listed in Table 20. i GEOCHEMISTRY / 194 Y + Nb (ppm) Figure 99. Chemically analysed samples plotted on Rb vs Y + Nb tectonic setting dicriminant diagram for granitic rocks of Pearce et al. (1984) Circles: granitic rocks; Triangles: hypabyssal rocks; VAG: volcanic arc granite; ORG: ocean ridge granite; WPG: within plate granite; SCG: syn-collision granite. All samples occur in the volcanic arc granite field. 7. GEOLOGIC EVOLUTION AND TECTONIC MODELS FOR THE TLMC The following chapter is divided into three sections. First, results from structural, metamorphic, geochemical and geochronometric studies of the TLMC are summarized. The geologic evolution of the area, which has been derived from these data is then presented. Finally, the TLMC is viewed in a regional perspective and tectonic models most consistent with both local and regional constraints are discussed. 7.1. SUMMARY OF RESULTS WHICH BEAR ON THE GEOLOGIC EVOLUTION OF THE TLMC 7.1.1. Mapping and Structure Three major lithotectonic assemblages have been identified in the Tatla Lake study area: a gneissic and migmatitic core, overlain by a several km thick assemblage of mylonitic and ductilely sheared metamorphic rocks, which lie structurally below undeformed rocks of the 1MB. The transitions between assemblages are abrupt and have been interpreted as faults. This overall structural sequence matches those described for Cordilleran metamorphic core complexes (Coney, 1979; Armstrong, 1982). In this context the Gneissic Core and Ductilely Sheared Assemblage (DSA) of the TLMC comprise a lower plate and the 1MB cover rocks an upper plate. The DSA is a major crustal ductile shear zone. It involves rocks of increasing structural depth towards the northwest and is therefore inferred to have originally dipped towards the northwest or west These rocks possess a regional, gently dipping mylonitic foliation which contains a mineral elongation (stretching) lineation that trends towards 280° (110°)+20° (Fig. 31, Plate 2). Kinematic indicators in DSA rocks not deformed by syn-shear Fs folds (mostly mylonitic orthogneiss) overwhelmingly suggest a 195 SUMMARY / 196 top-to-the-west sense of shear (Section 3.2.2., Table 3). Map and outcrop scale, open to normal F3 folds deform both gneissic layering (Sic; Fig. 40) and mylonitic foliation (Ss; Plates 2, 7). Faults separating the DSA from 1MB cover rocks of the Upper Plate cut F3 folds in the northeastern part of study area are parallel in strike to folded mylonitic foliation in the southern part of the area (Plate 1). The Yalakom fault is the southwestern boundary of the TLMC. Because it cuts all foliations, the latest movement within this fault zone must postdate Ds deformation. 7.1.2. Metamorphism Metamorphic grade increases with depth in the TLMC (Fig. 93); rocks of the DSA increase from greenschist to amphibolite grade, and gneissic core rocks are of amphibolite grade. Metamorphism accompanied the development of gneissic layering in the gneissic core (Mlc, Sic; Cretaceous, circa 108-79 Ma) and mylonitic foliation in the DSA (Ms, Ss; Eocene, circa 55-47 Ma). Upper plate rocks are of subgreenschist grade. Magmatic epidote in hornblende bearing granoblastic gneiss indicates pre- to syn-Dlc pressures of >8 kb in the gneissic core (Zen and Hammarstrom, 1984, 1986; Zen, 1985). Post-Sic pegmatitic clots, interpreted as crystallized partial melts, indicate (post-Die) temperatures in excess of 650 C. DSA pelitic schist in the Whitesand Lake area increases from chlorite-biotite to garnet-staurolite-kyanite-sillimanite grade with structural depth. There the transition from chlorite-biotite to kyanite-sillimanite bearing metapelitic rocks and albite to oligoclase in mafic to intermediate metavolcanic schist occurs within a 300 m thick zone of relatively highly strained rocks adjacent to the metavolcanic/metasedimentary SUMMARY / 197 contact (Fig. 93). Assuming a 30° to 35° southerly regional dip of metamorphic layering, kyanite-sillmanite bearing pelitic schist is presently no more than 4 structural km below subgreenschist grade Jurassic volcanic rocks across the southern Core/Cover fault (Plates 1, 5). Garnet-biotite temperatures from mainly metapelitic rocks near Whitesand Lake increase from 497+50 C to to 645+50 C with increasing structural depth. Pelitic schist in the garnet-staurolite-kyanite-sillimanite zone west of Whitesand Lake has yeilded a GT-PL-Al 2Si0 5-QZ pressure of 8+3 kb. Porphyroblasts analysed are syn-Ds in relative age based on textural relationships, so that these T-P calculations reflect Eocene metamorphic conditions. A T-P of 655 ±50 C and 5.3 ±3 kb from a pelitic pendant in the northwestern part of the study area is thought to record metamorphic conditions during intrusion of the surrounding pluton. A crystallization age and pressure of 71 ±2 Ma (U-Pb) and 7.2± 1.4 kb (total Al in hornblende) has been determined for this body. T-P-t data for the TLMC (Fig. 94) indicate that rocks of the gneissic core and amphibolite grade DSA rocks (from the northwestern part of the study area) were at elevated temperatures and pressures by Late Cretaceous time (gneissic core >79 Ma; DSA >71 Ma). A hypothetical prograde T-P path involving magmatic heating followed by (Mid- to Late Cretaceous) crustal thickening is proposed. This crustal thickening is broadly coeval with compressional deformation recognized in the TLMC gneissic core and shortening in a northwest-trending east-vergent thrust belt exposed to the west of the Yalakom fault (Tipper, 1969B; Rusmore and Woodsworth, 1988). Burial of TLMC rocks may be temporally and spatially related to this compressional tectonic setting. Syn-Ds (circa 55-47 Ma) T-P conditions of 500 C to 650 C and 8±3 kb for metapelites in the Whitesand Lake area, and post-Die ±D2c pegmatitic clots in the SUMMARY / 198 gneissic core indicate that the TLMC was still deeply buried during Eocene time (Fig. 94). Elevated Eocene T-P conditions and K-Ar cooling dates require rapid Eocene uplift of the TLMC as shown on Figure 94. These data, coupled with the well defined, possibly discontinuous increase in metamorphic grade of the TLMC and vicinity wth structural depth, suggest that much of the uplift occured along a syn-Ds ductile/brittle normal fault system (Fig. 100). During ductile Ds deformation mylonitic Ss foliation developed and strain is thought to have been distributed throughout the DSA. Later Ds strain was probably accomodated within more discrete ductile/brittle normal fault zones such as the one recognized near the metavolcanic/metasedimentary contact There the occurrence of a steep metamorphic zones (increasng with structural depth, attenuated or truncated isograds) supports late-Ds normal motion. Late-Ds strain in this zone can also account for the preservation of texturally late syn-Ds porphyroblasts (garnet staurolite and especially kyante) in underlying pelitc schist which are difficult to explain in the context of a shoaling ductile/brittle fault zone. A mild retrograde metamorphism of probable prehnite-pumpellyite grade (M3) affected rocks of the TLMC lower plate during (to possibly slightly after) D3 deformation. 7.1.3. Geochemistry Major and trace element chemistry of intermediate through felsic plutonic and hypabyssal rocks from across the TLMC indicate that all samples are subalkaline (Fig. 96), calc-alkaline (Figs. 97, 98), volcanic arc granites (Fig. 99) and as such are probably related to subduction in their larger tectonic setting. SUMMARY / 199 7.1.4. Dating of TLMC Magmatism, Structural Fabric/Metamorphism, and Cooling/Uplift U-Pb Zircon Magmatism occurred in the study area from Late Jurassic through Eocene time, based on zircon dates from igneous rocks. These dates are rather evenly spaced between 157+3 Ma and 47+1.5 Ma (Sec. 4.1.3., Figs. 58-61, 63; Table 4). Any magmatic lulls which may have occurred in the area between 157 and 47 Ma cannot be recognized due to the meager quantity of data generated. The formation of gneissic foliation (Sic, and associated Dlc/Mlc) in the Gneissic Core occurred between 107 ±3 Ma and 79+6 Ma. In contrast to this, mylonitic fabrics in the DSA (Ss, Ls and associated Ds/Ms) largely developed during Eocene time. Pre- or syn-Ds igneous rocks have been dated as 55+3 Ma, and a post-Ds granodioritic stock as 47 ± 1.5 Ma. Cretaceous fabrics have not been identified in the DSA because of the pervasive Eocene overprint there. The penetrative nature of Ds fabrics and their geometric concordance with Cretaceous fabrics in the gneissic core (Plate 2) render core-DSA correlations indeterminate on the basis of structural criteria. Some garnets from DSA metapelites, with discordant internal schistosity, may be interpreted as either Cretaceous or Eocene in age. K-Ar Conventional K-Ar dates record the Eocene (53-45 Ma) cooling of gneissic core and DSA rocks through the hornblende (550 C) and biotite (300 C) closure temperatures (Sec. 4.2.1., Fig. 64; Table 6). These data indicate that uplift and cooling of the TLMC lower plate is closely associated with ductile-brittle deformation (Ds extension) in the DSA. Jurassic K-Ar dates from rocks of the 1MB upper plate, and west of the Yalakom fault, indicate a very different thermal history than that of the lower plate rocks (Fig. 64). SUMMARY / 200 7.2. THE GEOLOGICAL EVOLUTION OF THE TLMC The sequence of events affecting the TLMC metamorphic core and adjacent part of the 1MB are outlined below. 1. Late Paleozoic to Jurassic deposition/extrusion of stratified rocks which comprise 1MB upper plate volcanic rocks (Jv) and protoliths of metasedimentary/metavolcanic rocks of the TLMC metamorphic core (Jms, Jmv; Plate 1). 2. Late Jurassic (157 Ma) through Eocene (47 Ma) calc-alkaline (subduction-related) arc plutonism. 3. Cretaceous (107 Ma to 78 Ma) metamorphism (Mlc) and deformation (Die) affecting rocks of the TLMC gneissic core. Sic layering (+ F2c folds) formed during this time interval. 4. Lower to Middle Eocene (55 Ma to 47 Ma) Ds shear zone activity (normal, top-to-the-west sense of motion) and Ms metamorphism, associated with uplift, and closely followed by cooling of the entire TLMC lower plate. Ds deformation includes the development of mylonitic fabrics (Ss, Ls), Fs folds and brittle/ductile motion along the normal (detachment) fault which is the southern boundary of the lower plate. Deformation and reorientation of structures in the core may have continued at this time. 5. The formation of F3 map-scale folds, possibly in response to dextral transpression along the Yalakom fault This is associated with continued uplift of the TLMC. Steep, north-south trending fractures and dykes are also related to D3 deformation (post-47 Ma). 6. Post-D3 down-to-the-east motion along the eastern and northeastern segments of the 1MB upper plate/TLMC lower plate boundary and continued dextral motion along the Yalakom fault GEOLOGICAL EVOLUTION / 201 7.2.1. Pre-Eocene compression Pre-Eocene deformation and metamorphism (Dlc/Mlc) recorded in rocks of the gneissic core are temporally associated with deep burial of Jurassic supracrustal rocks of the DSA. A Late Jurassic to Eocene time window for burial of metapelites to pressures of 8±3 kb is bracketed by their depositional age (pre-Late Jurassic) and the Eocene age of metamorphic minerals used to calulate pressures. Pelite burial, and extreme Die flattening of structurally deeper core gneiss, are coeval with shortening recognized in a northwest-trending, east-vergent fold thrust belt exposed to the west of the Yalakom fault (Tipper, 1969B; Rusmore and Woodsworth, 1988). Burial of DSA supracrustal rocks may be related to the emplacement of a thrust sheet which has subsequendy been removed during Eocene extension (discussed below). 7.2.2. Eocene tectonic development of the TLMC The Eocene tectonic development of the TLMC is depicted in a series of schematic east-west cross sections in Figure 100. The dominant operative structural element in the TLMC during Ds deformation (55-47.5 Ma) was a gently westward dipping ductile and brittle normal fault zone (Fig. 100A). Mylonitic rocks of the DSA developed at deeper levels in the active top-to-the-west normal shear zone. The transport of mylonitic rocks to shallower crustal levels within this ductile/brittle fault zone accounts for structural and metamorphic omission (or attenuation of metamorphic zones) documented along the southern Core/Cover fault and in adjacent metavolcanic and metasedimentary rocks. The presence of texturally late porphyroblasts in DSA pelitic schist from the southern part of the lower plate (garnet, staurolite and especially kyanite;) is difficult to explain in the context of a shoaling ductile/brittle fault zone. A reasonable GEOLOGICAL EVOLUTION / 202 B o r 5 -1 0 -15 -Yalakom Fault Uplifted Inactive Ductile Shear Zone Breakaway Zone (covered) Figure 100. Schematic east-west cross section depicting the Early to Middle Eocene and later Tertiary tectonic development of the TLMC. Dashed pattern represents mylonitic and ductilely sheared metamorphic rocks. See text for details. 7A. West dipping normal ductile and brittle fault zone active during Ds deformation (55-47.5 Ma). Rocks of the DSA were deformed in the active ductile shear zone shown in this section. B. Uplifted inactive shear zone folded by F3 folds during the late stages of D3 deformation (Post-47 Ma) synchronous with early movement on the Yalakom Fault 7C. Post-D3 movement along the eastern/northeastern Core/Cover Fault along which upper and lower plate rocks are juxtaposed; Yalakom Fault present but amount of movement undefined. GEOLOGICAL EVOLUTION / 203 hypothesis is that strain largely abated in these porphyroblast-bearing rocks prior to the end of Ds deformation; during the later stages of Ds deformation strain was concentrated in narrow anastamosing shear zones around lenticular bodies, such as the areas sampled, where earlier fabrics are preserved. While normal motion within the ductile/brittle fault depicted in Figure 100A accounts for most of the structure of the TLMC lower plate and part of its uplift, final uplift and exhumation of these rocks is thought to postdate activity along that system. Post-47.5 Ma K-Ar cooling dates (Table 6) indicate that uplift and cooling occured after deformation ceased in the TLMC shear zone; part of the uplift may be related to D3 deformation. D3 deformation is hypothesized to be the result of transpression at a restraining bend along the dextral transcurrent Yalakom fault This is based on the geometry of map-scale F3 folds as shown on the map on Plate 1 and the schematic diagram in Figure 101. These folds curve into parallelism with the trace of the Yalakom fault and are best developed adjacent to i t Transpressive crustal thickening and consequent uplift would be predicted to increase towards the Yalakom fault Figure 100B is a schematic east-west cross section set at the end of D3 deformation. The then inactive ductile shear zone had been deformed by F3 folds and was at high crustal levels and perhaps exposed to erosion. Figure 100C shows the TLMC when the eastern-northeastern Core/Cover fault was active. The topology of this cross section is similar structures observed today. Upper and lower plate rocks are juxtaposed along the eastern/northeastern Core/Cover and Yalakom faults. GEOLOGICAL EVOLUTION / 204 Figure 101. Schematic diagram depicting Ds transpression localized at a minor restraining bend in the Yalakom Fault (post-47.5 Ma). D3 deformation is thought to be responsible for final uplift and cooling of the lower plate. GEOLOGICAL EVOLUTION / 205 7.3. REGIONAL PERSPECTIVES AND TECTONIC MODELS 7.3.1. Regional Cretaceous Compression The following brief discussion of Cretaceous compression in the central segment of the western North American Cordillera is included to emphasize that 107 Ma to 77 Ma shortening documented in the TLMC gneissic core was part of a widespread regional pattern. Cretaceous compression, which may be broadly related to convergence between the North American and oceanic/microcontinental plates, has been widely documented in the western Cordillera of North America (references cited below). In the central Canadian Cordillera at the latitude of B.C. Early to Mid-Cretaceous shortening occurred in a convergent Andean style magmatic arc which developed after the accretion of superterranes I (Eastern Assemblage of Monger, 1977; Quesnellia and Stikinia; Mid-Jurassic) and II (Insular superterrane; Wrangellia, Alexander etc.; Late Jurassic). Early and/or Mid-Cretaceous compression has been documented (structures geochronometrically and/or stratigraphically dated) in the western North Cascades (Brown, 1987; Vance et al., 1980) and San Juan Islands (Whetten et al., 1978) of northwestern Washington, the Hope and Ashcroft map sheets of southern interior B.C. (Greig, 1988; Monger, 1986; 1985; Travers, 1982), the southern Canadian Rocky Mountains (Price, 1981), the central Coastal Plutonic Complex (van der Heyden, 1982; Crawford and Hollister, 1982), and Tyaughton-Methow Basins (Rusmore and Woodsworth, 1988; Glover and Schiarizza, 1987; Ray, 1986). Evidence from a number of areas (western North Cascades; Brown, 1987; Hope and Ashcroft Sheets, southern interior B.C.; Monger, 1985; Central and Northern B.C.; Gabrielse, 1985) indicate that a switch from dominant compressive to transcurrent (including transpression and TECTONIC MODELS / 206 transtension) tectonics occurred during Late Cretaceous time. This may correlate with a change from normal to oblique covergence between the North American and oceanic (Farallon and Kula) plates (Engebretson et al., 1985). 7.3.2. Eocene extensional deformation in southern B.C. and the northwestern U.S. Early to Middle Eocene crustal extension and rapid uplift/cooling of deeper crustal metamorphic rocks has been documented in Cordilleran metamorphic core complexes in southeastern B.C., northeastern Washington and northern Idaho (Cheney, 1980; Armstrong, 1982; Parrish, 1984; Can, 1985; Parkinson, 1985; Rhodes, 1986; Carr et al., 1987, Parrish et al., 1988). Structural studies indicate an approximate east-west extension direction throughout these core complexes and top-to-the-west sense of shear along their westernmost sides (Armstrong, 1982; Parkinson, 1985; Wust, 1986). Eocene ductile deformation with near-horizontal intermediate and maximum elongation axes has been observed in the Bridge River Terrane of southwestern B.C. where deformed igneous rocks have been dated as 41 Ma u> 45 Ma (Potter, 1986; U-Pb zircon dates of J. Monger and P. van der Heyden). Farther south, in the North Cascades of Washington and B.C., U-Pb (45 Ma; Haugerud et al., 1988) and Rb-Sr data (whole rock isochron, 45 Ma; Babcock et al., 1985) from ductilely deformed rocks of the Ross Lake Shear Zone indicate an Eocene time of movement within this structural zone (including differential uplift; Haugerud, 1985). Eocene K-Ar and Rb-Sr mica dates tightly clustered at 45 to 50 Ma give the time of uplift and final cooling for southern B.C. and northwestern U.S. Cordilleran metamorphic core complexes (Armstrong, 1974, 1975, 1976, 1988; Ross, 1974; Medford, 1975; Miller and Engels, 1975; Fox et al., 1977; Mathews, 1981, Parrish et al., 1988), the Nicola Batholith (Preto et al., 1979; Ewing, 1980), the North Cascades (Misch, 1964; Engels et al., TECTONIC MODELS / 207 1976) and Bridge River areas (Armstrong, unpublished data; Potter, 1983). 7.3.3. The TLMC and Eocene regional tectonics of southern B.C. and northern Washington Overthickened, thermally weakened crust and a change of plate motions in the northeastern Pacific region have been cited as general causes of Eocene extensional deformation in southeastern B.C. and northern Washington (Parrish et al., 1988, following the general extensional model of Sonder et al., 1987). Similar argurments may also apply to coeval extension documented in the TLMC. There, thermal weakening of the crust was probably primarily related to Eocene magmatism, as it was situated in the central portion of a wide and vigorous magmatic belt (Figs. 102, 103; Armstrong, 1988). Tectonic thickening may have also played a role in thermally weakening the crust and in creating the potential for later extension in the TLMC area. An easterly-verging Cretaceous fold thust system located near the Coast Belt-1MB boundary (Tipper, 1969B; Rusmore and Woodsworth, 1988; van der Heyden, 1982; Glover and Schiarizza, 1987) could have caused or been related to this thickening. High level thrusts in this system are presently exposed directly to the west of the study area. High level thrusts that may have overlain the TLMC at the time of Die and D2c deformation could have been removed during Eocene Ds and D3 deformation, uplift, and erosion. Moreover, Cretaceous crustal shortening occurred throughout the Intermontane Belt, as shown by deformed Cretaceous rocks of the Methow-Tyaughton (Kleinspehn, 1985; Ray, 1986), Bowser and Sustut (Eisbacher, 1974; Moffat, 1985; Evenchick, 1987, 1988;) basins, and K-Ar dating of deformed Hazelton and Bowser Lake Group volcanic and sedimentary rocks (Alldrick et al., 1987; Devlin, 1987). The external cause of Eocene extension listed above, a change in plate motions TECTONIC MODELS / 208 in the northeastern Pacific region, is thought to have resulted in oblique northward motion of the Farallon Plate relative to North America (Londsdale, 1988; Engebretson et al., 1985). This external tectonic change could have been responsible for a reduction in stress exerted normal to the North American Plate, which when coupled with magmatic weakening of thickened crust, could have resulted in widespread extension in southwestern Canada and the northwestern U.S. A more specific kinematic model for Eocene extension in southeastern B.C. has been proposed by Price (1979) and Price and Carmichael (1986). They envisaged Eocene crustal stretching in the southern 1MB occurring in a right step from the Fraser-Straight Creek (F-Sc) to the Northern Rocky Mountain Trench-Tintina (NRMT-T) dextral fault systems. This model can geometrically explain extension in large areas of southern B.C., but as shown on Figure 102, the region between the en echelon Fraser and NRMT-T fault systems is not large enough to account for Eocene ductile extension documented in all the Eocene metamorphic core complexes of the northwestern U.S., or those west of the Fraser fault In addition to the geometrical problem discussed above, the time of motion along the F-Sc fault system largely postdates ductile extensional deformation in the TLMC and other Pacific Northwest core complexes. Deformed granitic dykes dated as 45 Ma (U-Pb zircon, xenotime; unpublished data, P. van der Heyden, 1987; Haugerud et al., 1988) provide the minimum age of ductile deformation in the Ross Lake Shear Zone and a maximum age for motion along the cross cutting brittle F-Sc fault system. Two reverse faults which are interpreted as splays of the Fraser fault have also been assigned Middle or Late Eocene maximum ages. The Phair Creek fault located southwest of Lillooet (Fig. 2), places upper Triassic rocks over a Middle Eocene igneous body (U-Pb zircon date of 47 Ma; Monger, 1982, 1985). Farther TECTONIC MODELS / 209 Figure 102. Map of southwestern Canada and the northwestern U.S. showing the distribution of Eocene metamorphic core complexes and the areal extent of the Paleogene magmatic arc. Eocene metamorphic core complexes: wavy ruled pattern; magmatic arc: "v" pattern, bounded by dot-dashed lines; area in' right step between dextral NRMT and F-Sc Fault systems where extension (transtension) would be predicted (Price and Carmichael, 1986): stipple pattern; Tertiary rocks of Washington and Oregon Coast Ranges and southernmost Vancouver Island, and post-Eocene cover: diagonal ruled lines; H: Hozameen Fault; NRMT: Northern Rocky Mountain Trench Fault; RL: Ross Lake shear zone; SC: Straight Creek Fault; Y: Yalakom Fault; Two apparently separate magmatic belts are shown; the minor western belt occurs on Vancouver Island and in the western foothils of the North Cascade Mountains. The western boundary of the main magmatic belt has been offset by the Straight Creek Fault TECTONIC MODELS / 210 north, between the Yalakom and Fraser faults (Fig. 2), motion along the Hungry Valley fault must postdate the Middle Eocene age of strata which it cuts (Mathews and Rouse, 1984). A 35 Ma minimum age of motion along the F-Sc system is provided by the oldest dated phase of the Chilliwack Batholith (Silver Creek Stock; Richards and McTaggart, 1976), which. intrudes the fault zone. The general model for extension discussed above, which involves thermal weakening of the crust as a result of magmatism in areas that had previously undergone tectonic thickening, coupled with external tectonic change, is perhaps the most satisfactory explanation for Eocene extensional deformation. Thermal weakening of the crust is supported by the observation that exposures of Eocene ductilely stretched rocks in B.C. and the northwestern U.S. lie within the coeval volcano-plutonic arc (Fig. 102) and that most core complexes occur in areas that were tectonically thickened during Cretaceous and Paleocene compressional deformation. This leads to the hypothesis that a regional ductile shear zone (presently largely unexposed), formed within the crust of the southern 1MB during Early to Middle Eocene time. This idea is illustrated in a crustal cross section containing the TLMC and southeastern B.C. core complexes (Fig. 103, discussed below). At the time of ductile stretching, before displacement on the Fraser fault system, the TLMC would have been opposite the central part of the Shuswap Metamorphic Complex. Its reconstructed position is the basis for Figure 103, not its present position north of the Intermontane and Omineca Belt areas most affected by Eocene crustal extension. The similar fabrics, stretching direction, sense of shear, and age of the TLMC and structures along the western side of the Omineca Belt invite the hypothesis that both are related parts of a regional ductile stretching zone. As shown in the section in Figure 103, the TLMC shear zone roots into a regional TECTONIC MODELS / 211 Figure 103. Eocene Cordilleran cross-section through the TLMC, circa 55-47.5 Ma, restoring approximately 100 km of dextral motion along the Fraser fault system (with apologies to Monger et al. 1985). Dashed pattern: North American continental basement; Crossed pattern: Mesozoic plutonic rocks; TLMC: Tatla Lake Metamorphic Complex; Bold and fine arrows denote Eocene and Mesozoic movement directions respectively. TECTONIC MODELS / 212 ductile shear zone which extends eastward across the 1MB (the width of the Early to Middle Eocene magmatic arc), connecting with structures that emerge along the west side of the Omineca Belt Although this regional shear zone is hypothetical, it is subject to future testing. If an Eocene ductile shear zone underlies the southern 1MB, then mylonitic foliated and tectonically banded rock may be observed across the entire 1MB on deep seismic reflection profiles. In the U.S. Cordillera many seismic profiles in the hinterland of the Mesozoic foreland fold and thrust belt show gently dipping reflectors (expressing a layered lower crust) that have been interpreted to be mylonite or tectonically interlayered rocks along low-angle normal structures related to crustal extension (Smithson et al., 1979; Allmendinger et al., 1983; Fountain et a l , 1984; Potter et al., 1986; Allmendinger et al., 1987). Subhorizontal, discontinuous reflectors at middle to lower crustal levels across the Basin and Range Province (Allmendinger, et al., 1983; Klemperer et al., 1986) and the Okanogan region of northern Washington (Potter et al., 1986) have been inferred to be Cenozoic compositionally or tectonically banded rocks formed as a result of crustal stretching at depth. Friedman and Armstrong (in press) predict that LITHOPROBE transects connecting the subduction zone imaged on Vancouver Island (Yorath et al., 1985) with the core complex to Rocky Mountains fold and thrust belt line of southeastern B.C. (Cook et al., 1988), may likewise observe similar fabrics/structures (an extensive shear zone) in the lower crust beneath the southern 1MB. The significance of the TLMC is that it affords access to rocks that may representative of those present at depth in the be mid- to lower-crust, so that the nature and ages of those reflectors can be directly examined rather than inferred. REFERENCES CITED Alldrick, D.J., DA. Brown, J.E. Harakal, J.K. Mortensen, and R.L. Armstrong, 1987, Geochronology of the Stewart mining camp (104B/1), in Geological Research 1986: British Columbia Ministry of Energy, Mines and Resources, Paper 1987-1, p. 81-92. Allmendinger, R.W., Nelson, K.D., Potter, C.J., Barazangi, M., Brown, L.D., and Oliver, J.E., 1987, Deep seismic reflection characteristics of the continental crust, Geology, v. 15, p. 304-310. Allmendinger, R.W., Sharp, J.W., von Tish, D., Serpa, L., Brown, L., Kaufman, S., Oliver, J., and Smith, R.B., 1983, Cenozoic and Mesozoic structure of the eastern Basin and Range province, Utah, from COCORP seismic-reflection data: Geology, v. 11, p. 532-536. Armstrong, R.L., 1968, A model for the evolution of strontium and lead isotopes in a dynamic earth: Reviews of Geophysics, v. 6, p. 175-199. Armstrong, R.L., 1974, Geochronometry of the Eocene volcanic-plutonic episode in Idaho: Northwest Geology, v. 3, p. 1-15. Armstrong, R.L., 1975, The geochronometry of Idaho: Isochron/West, no. 14, p. 1-50. Armstrong, R.L., 1976, The geochronometry of Idaho: Isochron/West, no. 15, p. 1-33. Armstrong, R.L., 1981, Radiogenic isotopes: the case for crustal recycling on a near-steady-state no-continental-growth earth: Philosophical Transactions of the Royal Society of London Series A, v. 301, p. 443-472. Armstrong, R.L., 1982, Cordilleran metamorphic core complexes-From Arizona to southern Canada: Annual Review of Earth and Planetary Sciences, v. 10, p. 129-154. Armstrong, R.L, 1988, Mesozoic and early Cenozoic magmatic evolution of the Canadian Cordillera: Geological Society of America Special Paper 218, p. 55-91. 213 REFERENCES / 214 Ashworth, J.R, 1985, Introduction, in Ashworth, J.R., ed., Migmatites: Blackie & Son Limited, Glasgow and London, p. 1-35. Babcock, R.S., Armstrong, R.L., Misch, P., 1985, Isotopic constraints on the age and origin of the Skagit Metamorphic Suite and related rocks: Geological Society of America Abstracts with Programs, v. 17, p. 339. Baer, A.J., 1973, Bella Coola - Laredo Sound Map-Areas, British Columbia: Geological Survey of Canada Memoir 372, 122 p. Becke, F, 1908, Uber Myrmekit: Schweiz. Min. Pet Mitt, v. 27, p. 377-390. Bell, T.H., 1978, Progressive deformation and reorientation of fold axes in a ductile mylonite zone: Tectonophysics, v. 44, p.285-320. Bell, T.H. and Hammond, R.L., 1984, On the internal geometry of mylonite zones: Journal of Geology, v. 92, p. 667-686. Berthe, D., Choukroune, P. and Jegouzo, P., 1979, Orthogneiss, mylonite and non coaxial deformation of granites: the example of the South Amorican Shear-Zone: Journal of Structural Geology, v. 1, p. 31-42. Bevier, M.L., 1983, Regional stratigraphy and age of the Chilcotin Group basalts, south-central British Columbia: Canadian Journal of Earth Science, v. 20, p. 515-524. Brewer, M.S., 1969, Excess radiogenic argon in metamorphic micas from the eastern Alps, Austria: Earth and Planetary Science Letters, v. 6, p.47-55. Brown, E.H., 1980, Structural geology and accretionary history of the Northwest Cascade system, Washington and British Columbia: Geological Society of America Bulletin, v. 99, p. 201-214. Brown, W.L., Macaudiere, J. and Ohnenstetter, M., 1980, Ductile shear zones in a meta-anorthosite from Harris, Scotland: textural and compositional changes in plagioclase: Journal of Structural Geology, v. 2, p. 281-287. Burg, J.P., 1986, Quartz shape fabric variations and c-axis fabrics in a ribbon-mylonite: arguments for an oscillating foliation: Journal of Structural REFERENCES / 215 Geology, v. 8, p. 123-131. Can, S.D., 1985, Ductile shearing and brittle faulting in Valhalla gneiss complex, southeastern British Columbia: Current Research, Part A, Geological Survey of Canada Paper 85-1 A, p. 89-96. Can, S.D., Parrish, R.R. and Brown, R.L., 1987, Eocene structural development of the Valhalla Complex, Southeastern British Columbia: Tectonics, v. 6, p. 175-196. Chen, J.H. and Moore, J.G., 1982, U-Pb isotopic ages from the Sierra Nevada Batholith, California: Journal of Geophysical Research, v. 87, p. 4761-4784. Cheney, E.S., 1980, Kettle dome and related structures in northeastern Washington, in Crittenden, M.J., Jr., Coney, P.J., and Davis, G.H., eds., Cordilleran metamorphic core complexes: Geological Society of America Memoir 153, p. 463-483. Christie, J.M., 1963, The Moine Thrust zone in the Assynt region, northwest Scotland: California University, Publications in Geological Sciences, v. 40, p. 245-319. Coney, P.J., 1980, Cordilleran metamorphic core complexes: An overview, in Crittenden, M.D., Jr., Coney, P.J., and Davis, G.H., eds., Cordilleran metamorphic core complexes: Geological Society of America Memoir 153, p. 7-31. Cook, F.A., A.G. Green, P.S. Simony, R.A. Price, R.R. Parrish, B. Milkereit, P.L. Gordy, R.L. Brown, K G Coflin, and C. Patenaude, 1988, Lithoprobe seismic reflection structure of the southeastern Canadian cordillera: Initial results: Tectonics, v. 7, p. 157-180. Crawford, M.L. and Hollister, L.S., 1982, Contrast of metamorphic and structural histories across the Work Channel Lineament, Coast Plutonic Complex, British Columbia: Journal of Geophysical Research, v. 87, p. 3849-3860. Davies, O.L., ed., 1961, Statistical Methods in Research and Production: Hafner Publishing Company, New York, 396 p. Dawson, G.M., 1876, Report on explorations in British Columbia, in Geological Survey REFERENCES / 216 of Canada Report of Progress 1875-1876, p. 233-265. Devlin, B.D., 1987, Geology and genesis of the Dolly Varden silver camp, Alice Arm area, northwestern British Columbia: M.Sc. thesis, University of British Columbia, Vancouver, British Columbia, 131 p. Dodson, M.H., 1979, Theory of cooling ages, in J'ager, E. and Hunziker, J.C., eds., Lectures in isotope geology: Springer-Verlag, New york, New York, p. 195-202. Dolmage, V., 1926, Tatla-Bella Coola area, Coast District, British Columbia: Geological Survey of Canada Summary Report, 1925, Part A, p. 155-163. Eisbacher, G.H., 1970, Deformation mechanisms of mylonitic rocks and fractured granites in Cobequid Mountains, Nova Scotia, Canada: Geological Society of America Bulletin, v. 81, p. 2009-2020. Eisbacher, G.H., 1974, Deltiac sedimentation in the northeastern Bowser basin, British Columbia: Geological Survey of Canada, Paper 73-33, 13 p. Engebretson, D.C, Cox, A. and Gordon, R.G., 1985, Relative motions between oceanic and continental plates in the Pacific Basin: Geological Society of America Special Paper 206, 59 p. Engels, J.C., Tabor, R.C., Miller, F.K. and Obradovich, J.D., 1976, Summary of K-Ar, Rb-Sr, U-Pb, Pbo, and Fission-Track ages of rocks from Washington State prior to 1975: United States Geological Survey Miscellaneous Field Study Map MF-710. Etchecopar, A., 1974, Simulation par ordinateur du la deformation progressive d'un aggregat polycrystallin. Etude du development de structures orientees par ecrasement et cisaillement: Ph.D. thesis, University of Nantes, Nantes, France, 134 p. Etchecopar, A., 1977, A plane kinematic model of progressive deformation in a polycrystalline aggregate: Tectonophysics, v. 39, p. 121-139. Evans, B.W. and Guidotti, C.V., 1966, The sillimanite-potash feldspar isograd in western Maine, U.S.A.: Contributions to Mineralogy and Petrology, v. 12, p. 25-62. REFERENCES / 217 Evenchick, C.A., 1987, Stratigraphy and structure of the northeast margin of the Bowser basin, Spatsizi map area, north-central British Columbia: Current Research, Part A, Geological Survey of Canada, Paper 87-1 A, p. 719-726. Evenchick, C.A., 1988, Structural style and stratigraphy in northeast Bowser and Sustut basins, north-central British Columbia: Current Research, Part E, Geological Survey of Canada, Paper 88-IE, p. 91-95. Ewing, T.E., 1980, Paleogene tectonic evolution of the Pacific northwest: Journal of Geology, v. 88, p. 619-638. Faure, G., 1977, Principles of Isotope Geology: John Wiley and Sons, New York, 464 p. Ferry, J.M. and Spear, F.S., 1978, Experimental calibration of the partitioning of Fe and Mg between biotite and garnet: Contributions to Mineralogy and Petrology, v. 66, p. 113-117. Fountain, D.M., Hurich, CA. and Smithson, S.B., 1984, Seismic reflectivity of mylonite zones in the crust: Geology, v. 12, p. 195-198. Fox, K.F., Rinehart, CD. and Engels, J.C, 1977, Plutonism and orogeny in north-central Washington-timing and regional context: United States Geological Survey Professional Paper 989, 27 p. Freer, R., 1981, Diffision in silicate minerals and glasses: a data digest and guide to the literature: Contributions to Mineralogy and Petrology, v. 76, p. 440-454. Gabites, J.E., 1985, Geology and geochronometry of the Cogburn Creek-Settler Creek area, northeast of Harrison Lake, British Columbia: M.Sc. thesis, University of British Columbia, Vancouver, British Columbia, 153 p. Gabrielse, H., 1985, Major dextral transcurrent displacements along the Northern Rocky Mountain Trench and related lineaments in north-central British Columbia: Geological Society of America Bulletin, v. 96, p. 1-14. Ganguly, J. and Saxena, S.K., 1984, Mixing properties of aluminosilicate garnets: constraints from natural and experimental data, and applications to REFERENCES / 218 geomermo-barornetry: American Mineralogist, v. 69, p. 88-97. Garwin, S.L., 1987, Structure and metamorphism in the Niagra Peak area, western Cariboo Mountains, British Columbia: M.Sc. thesis, University of British Columbia, Vancouver, British Columbia, 177 p. Gebaur, D. and Grunenfelder, M., 1979, U-Th-Pb dating of minerals, in Jager, E. and Hunziker, J.C., eds., Lectures in isotope geology: Springer-Verlag, New York, New York, p. 105-131. Ghosh, S.K. and Ramberg, H., 1976, Reorientation of inclusions by combination of pure shear and simple shear: Tectonophysics, v. 34, p. 1-70. Gill, J.B., 1981, Orogenic andesites and plate tectonics: Springer-Verlag, Berlin, 390 p. Glover, J.K. and Schiarizza, P., 1987, Geology and mineral potential of the Warner Pass map sheet (920/3), in British Columbia Ministry of Energy, Mines and Petroleum Resources, Geological Research 1986, Paper 1987-1, p. 157-169. Goldsmith, J.R., 1980, The melting and breakdown reactions of anorthite at high pressures and temperatures: American Mineralogist, v. 65, p. 272-284. Greig, C.J., 1988, Geology and geochronometry of the Eagle Plutonic Complex, Hope map-area, southwestern British Columbia: Current Research, Part A, Geological Survey of Canada Paper 88-IE, p. 177-183. Guidotti, C.V., 1963, Metamorphism of the pelitic schists in the Bryant Pond quadrangle, Maine: American Mineralogist, v. 48, p. 772-791. Hammarstrom, J.M. and Zen, E-an, 1983, Aluminum in hornblende: an empirical igneous geobarometer: American Mineralogist, v. 71, p. 1297-1313. Hansen, E, 1971, Strain Fades: Springer-Verlag, New York, New York, 207 p. Hariya, Y. and Kennedy, G.C., 1968, Equilibrium study of anorthite under high pressure and temperature: American Journal of Science, v. 266, p. 193— 203. REFERENCES / 219 Harrison, T.M., 1981, Diffusion of 4 0Ar in hornblende: Contributions to Mineralogy and Petrology, v. 78, p. 324-331. Harrison, T.M. and McDougall, I., 1980, Investigations of an intrusive contact, northwest Nelson, New Zealand-1. Thermal, chronological and isotopic constraints: Geochimica et Cosmochimica Acta, v. 44, p. 1985-2003. Haugerud, R.A., 1985, Geology of the Hozameen Group and the Ross Lake Shear Zone, Maselpanik area, North Cascades, southwest British Columbia: Ph.D. thesis, University of Washington, Seattle, Washington, 263 p. Haugerud, R.A., Tabor, R.W., Stacey, J. and van der Heyden, P., 1988, What is the core of the North Cascades?: Geological Society of America Abstracts with Programs, v. 20, p. 168. Hays, J.F., 1966, Lime-alumina-silica: Yearbook of the Carnegie Institution of Washington, v. 65, p. 234-239. Hodges, K.V. and McKenna, L.W., 1987, Realistic propagation of uncertainties in geologic thermobarometry: American Mineralogist, v. 72, p. 671-680. Hollister, L.S., Grissom, G.C., Peters, E.K., Stowell, H.H. and Sisson, V.B., 1987, Confirmation of the empirical correlation of Al in hornblende with pressure of solidification of calc-alkaline plutons: American Mineralogist, v. 72, p. 231-239. Hoschek, G., 1969, The stability of staurolite and chloritoid and their significance in metamorphism of pelitic rocks: Contributions to Mineralogy and Petrology, v. 22, p. 208-232. Hyndman, D.W,, 1972, Petrology of igneous and metamorphic rocks, McGraw-Hill Company, 533 p. Irvine, T.N. and Baragar, R.A., 1971, A guide to the classification of the common volcanic rocks: Canadian Journal of Earth Science, v. 8, p. 523-548. Jeletzky, J.A. and Tipper, H.W., 1968, Upper Jurassic and Cretaceous rocks of the Taseko Lakes map-area and their bearing on the geological history of southwestern British Columbia: Geological Survey of Canada Paper 67-54, 218 p. REFERENCES / 220 Johannes, W, 1984, Beginning of melting in the granite system Qz-Or-Ab-An-H 20: Contributions to Mineralogy and Petrology, v. 72, p. 264-273. Johannes, W., 1985, The significance of experimental studies, in Ashworth, J.R., ed., Migmatites: Blackie & Sons Limited, p. 36-85. Kleinspehn, K.L., 1985, Cretaceous sedimentation and tectonics, Tyaughton-Methow basin, southwestern British Columbia: Canadian Journal of Earth Science, v. 22, p. 154-174. Klemperer, S.L., Hague, T.A., Hauser, E.C., Oliver, J.E., and Potter, C.J., 1986, The Moho in the northern Basin and Range privince, Nevada, along the COCORP 40° N seismic-reflection transect, Geological Society of America Bulletin, v. 97, p. 603-618. Krogh, T.E., 1973, A low contamination method for hydrothermal decomposition of zircon and extraction of U and Pb for isotopic age determinations: Geochimica et Cosmochimica Acta, v. 37, p. 485-494. Lang, H.M. and Rice, J.M., 1985, Geothermometry, geobarometry and T-X(Fe-Mg) relations in metapelites, Snow Peak, northern Idaho: Journal of Petrology, v. 26, p. 889-924. Lasaga, A.C, Geospeedometry: an extension of geothermometry, in Saxena, S.K., ed., Kinetics and Equilibrium in Mineral Reactions, Springer-Verlag, New York, New York, p. 81-114. Lister, G.S. and Snoke, A.W., 1984, S-C mylonites: Journal of Structural Geology, v. 6, p. 617-638. Londsdale, P., 1988, Paleogene history of the Kula plate: Offshore evidence and onshore implications: Geological Society of America Bulletin, v. 100, p. 733-754. Luth, W.C., Jahns, R.H., and Tuttle, O.F., 1964, The granite system at pressures of 4 to 10 kilobars: Journal of Geophysical Research, v. 69, p. 759-773. MacDonald, G.A. and Katsura, T., 1964, Chemical composition of Hawaiian lavas: Journal of Petrology, v. 5, p. 82-133. REFERENCES / 221 Mathews, W.H., 1981, Early Cenozoic resetting of patassium-argon dates and geothermal history of the northern Okanagan area, British Columbia: Canadian Journal of Earth Science, v. 18, p. 1310-1319. Mathews, W.H. and G.E. Rouse, 1984, The Gang Ranch - Big Bar area, south-central British Columbia: stratigraphy, geochronology, and palynology of the Tertiary beds and their relationship to the Fraser fault: Canadian Journal of Earth Science, v. 21, p. 1132-1144. Medford, G.A., 1975, K-Ar and fission track geochronometry of an Eocene thermal event in the Kettle River (west half) map-area, southern British Columbia: Canadian Journal of Earth Science, v. 12, p. 836-843. Miller, F.K. and Engels, J.C., 1975, Distribution and trends of discordant ages of the plutonic rocks of northwestern Washington and northern Idaho: Geological Society of America Bulletin, v. 86, p. 517-528. Miller, M.G., 1986, Deformation near the Yalakom fault, Lillooet, British Columbia: Structures incompatible with dextral slip: Geological Society of America Abstracts with Programs, v. 18, p. 158. Misch, P., 1964, Age determinations on crystalline rocks of the Northern Cascade Mountains, Washington, in, Kulp, J.L., et al, eds., Investigations in isotopic geochemistry: United States Atomic Energy Commission, Publication, NYO-7243, Appendix D, p.1-15, Pallisades, New York, Columbia University, Lamont Geological Observatory. Moffat, I., 1985, The nature and timing of deformational events and organic and inorganic metamorphism in the northern Groundhog coalfield: implications for the tectonic history of the Bowser basin: Ph.D. thesis, University of British Columbia, Vancouver, British Columbia, 205 p. Monger, J.W.H., 1977, Upper Paleozoic rocks of the Canadian Cordillera and threir bearing on Cordilleran evolution: Canadian Journal of Earth Science, v. 14, p. 1832-1859. Monger, J.W.H., 1982, Geology of Ashcroft map area, southwestern British Columbia: Current Research, Part A: Geological Survey of Canada Paper 82-IA, p. 293-297. Monger, J.W.H., 1985, Structural evolution of the southwestern Intermontane Belt, REFERENCES / 222 Ashcroft and Hope map areas, British Columbia: Current Research, Part A, Geological Survey of Canada Paper 85- 1A, p. 349-358. Monger, J.W.H., 1986, Geology between Harrison Lake and, the Fraser River, Hope map area (92H), southwestern British Columbia: Current Research, Part B, Geological Survey of Canada Paper 85-IB, p. 699-706. Monger, J.W.H. and Berg, H.C., 1984, Lithotectonic terrane map of western Canada and southeastern Alaska: United States Geological Survey Open-File Report 84-0523. Monger, J.W.H., R.M. Clowes, R.A. Price, P.S. Simony, R.P. Riddihough, and GJ. Woodsworth, 1985, Juan de Fuca Plate to Alberta plains: Geological Society of America Continent/Ocean Transect no. 7. Monger, J.W.H. and Huchison, W.W., 1971, Metamorphic map of the Canadian Cordillera: Geological Survey of Canada Paper 70-33, 61 p. Morrison, G.W., Godwin, C.L, and Armstrong, R.L, 1979, Interpretation of isotopic ages and 8 7Sr/ 8 6Sr initial ratios for plutonic rocks in the Whitehorse map area, Yukon: Canadian Journal of Earth Science, v. 16, p. 1988-1997. Newton, R.C. and Haselton, 1981, Thermodynamics of the garnet-plagioclase-Al 2Si05-quartz geobarometer, in Newton, R.C., Navrotsky, A. and Wood, B.J., eds., Thermodynamics of Minerals and Melts: New York, New York, Springer-Verlag, p. 131-147. Nicolas, A. and Poirier, J.P., 1976, Crystalline Plasticity and Solid State Flow in Metamorphic Rocks: Wiley Interscience, New York, 444 p. Ohmoto, H. and Kerrick, D.M., 1977, Devolatilization equilibria in graphitic systems: American Journal of Science, v. 277, p. 1013-1044. Parkinson, D.L., 1985, U-Pb geochronometry and regional geology of the southern Okanagan valley, British Columbia: western boundary of a metamorphic core complex: M.Sc. thesis, University of British Columbia, Vancouver, British Columbia, 149 p. Parrish, R.R., 1984, Slocan Lake Fault: A low angle fault zone bounding the Valhalla gneiss complex, Nelson map-area, southern British Columbia: Current REFERENCES / 223 Research, Part A, Geological Survey of Canada Paper 84-1 A, p. 323-330. Parrish, R.R., Carr, S.D., and Parkinson, D.L., 1988, Eocene extensional tectonics and geochronology of the southern Omineca Belt, southern British Columbia and Washington: Tectonics, v. 7, p. 181-212. Passchier, C.W. and Simpson, G, 1986, Porphyroclast systems as kinematic indicators: Journal of Structural Geology, v. 8, p. 831-843. Pearce, J.A., Harris, N.B.W. and Tindle, A.G., 1984, Trace discrimination diagrams for the tectonic interpretation of granitic rocks: Journal of Petrology, v. 25, p. 956-983. Perkins, E.H., Brown, T.H. and Berman, R.G., 1986, PT-SYSTEM, TX-SYSTEM, PX-SYSTEM: 3 programs which calculate PTX phase diagrams: Computers and Geoscience, v. 12, p. 749-755. Phillips, E.R., 1980, On polygenetic mymekite: Geological Magazine, v. 117, p. 29-36. Pigage, L.C. and Greenwood, H.J., 1982, Internally consistent estimates of pressure and temperature: the staurolite problem: American Journal of Science, v. 282, p. 943-969. Piwinskii, A.J., 1968, Experimental studies of igneous rock series: Central Sierra Nevada batholith, California: Journal of Geology, v. 76, p. 548-570. Piwinskii, A.J., 1973, Experimental studies of granitoids from the Central and Southern Coast Ranges, California: Tschermaks Mineralogische und Petrographische Mitteilungen, v. 20, p. 107-130. Piwinskii, A.J. and Wyllie, P.J., 1968, Experimental studies of igneous rock series: a zoned pluton in the Walllowa batholith, Oregon: Journal of Geology, v. 76, p. 205-234. Potter, C.J., 1983, Geology of the Bridge River Complex, southern Shulaps Range, British Columbia: Ph.D. thesis, University of Washington, Seattle, Washington, 192 p. REFERENCES / 224 Potter, C.J., 1986, Origin, accretion, and postaccretionary evolution of the Bridge River Terrane, southwest British Columbia: Tectonics, v. 5, p. 1027-1041. Potter, C.J., W.E. Sanford, T.R. Yoos, E.I. Prussen, R.W. Keach, II, J.E. Oliver, S. Kaufman, and L.D. Brown, 1986, COCORP Deep seismic reflection traverse of the interior of the North American Cordillera, Washington and Idaho: Implications for orogenic evolution: Tectonics, v. 5, p. 1007-1025. Preto, V.A., Osatenko, W.J., McMillan, W.J. and Armstrong, R.L., 1979, Isotopic dates and strontium isotopic ratios for plutonic and volcanic rocks in the Quesnel Trough and Nicola Belt, south-central British Columbia: Canadian Journal of Earth Science, v. 16, p. 1658-1672. Price, R.A., 1979, Intracontinental ductile crustal spreading linking the Fraser River and northern Rocky Mountain trench transform fault zones, south-central British Columbia and northeast Washington: Geological Society of America Abstracts with Programs, v. 11, p. 499. Price, R.A., 1981, The Cordilleran foreland thrust belt in the southern Canadian Rocky Mountains, in Price, N.J., ed., Thrust and Nappe Tectonics: Geological Society of London Special Publication, no. 9, p. 427-448. Price R.A. and Carmichael, D.M., 1986, Geometric test of Late Cretceous-Paleogene intracontinental transform faulting in the Canadian Cordillera: Geology, v. 14, p. 468-471. Ramsay, J.G., 1967, Folding and fracturing of rocks: McGraw-Hill, New York, 568 p. Ray, G.E., 1986, The Hozameen fault system and related Coquihalla serpentine belt of southwestern British Columbia: Canadian Journal of Earth Science, v. 23, p. 1022-1041. Rhodes, B.P., 1986, Metamorphism of the Spokane dome mylonitic zone, Priest River Complex: constraints on the tectonic evolution of northeastern Washington and northern Idaho: Journal of Geology, v. 94, p. 539-556. Richards, T.A., and K.C. McTaggart, 1976, Granitic rocks of the southern Coast Plutonic Complex and the northern Cascades of British Columbia: Geolological Society of America Bulletin, v. 87, p. 935-953. REFERENCES / 225 Ross, J.V., 1974, A Tertiary thermal event in south-central British Columbia: Canadian Journal of Earth Science, v. 11, p. 1116-1122. Rusmore, M.E., 1985, Geology and tectonic significance of the Upper Triassic Cadwallader Group and its bounding faults, southwestern British Columbia: Ph.D. thesis, University of Washington, Seattle, Washington, 174 p. Rusmore, M.E. and Woodsworth, G.J., 1988, Eastern margin of the Coast Plutonic Complex, Mount Waddington map area (92N), British Columbia: Current Resaerch, Part E, Geological Survey of Canada Paper 88-IE, p. 185-190. Rutter, M.J. and Wyllie, P.J., 1988, Experimental calibration of hornblende as a proposed empirical geobarometer: EOS, Transactions of the American Geophysical Union, v. 69, p. 86-87. Saleeby, J.B., 1982, Polygenetic ophiolite belt of the California Sierra Nevada: geochronological and tectonostratigraphic development: Journal of Geophysical Reaearch, v. 87, p. 1803-1824. Schmid, S.M., 1986, Microfabric studies as indicators of deformation mechanisms and flow laws operative in mountain building, in Hsu, K.J., ed., Mountain Building Processes: Academic Press, London, p. 95-110. Schoneveld, C, 1979, The geometry and significance of inclusion pattern in syntectonic porphyroclasts: Ph.D. thesis, University of Leiden, Leiden, Netherlands. Simpson, C. and Schmid, S.M., 1983, An evaluation of criteria to deduce the sense of movement in sheared rocks: Geological Society of America Bulletin, v. 94, p 1281-1288. Smith, D.L. and Evans, B., 1984, Diffusional crack healing in quartz: Journal of Geophysical Research, v. 89, p. 4125-4135. Smithson, S.B., Brewer, J.A., Kaufman, S., Oliver, J.E. and Hurich, C.A., 1979, Structure of the Wind River uplift, Wyoming, from COCORP deep reflection data and gravity data: Journal of Geophysical Research, v. 84, p. 5955-5972. REFERENCES / 226 Sonder, L.J., England, P.C., Wernicke, B.P., and Christiansen, R.L., 1987, A physical model for Cenozoic extension of western North America: Special Publication of the Geological Society of London, no. 28, p. 187-201. Souther, J.G., 1977, Volcanism and tectonic environments in the Canadian Cordillera- a second look, in Baragar, W.R.A., Coleman, L.C. and Hall, J.M., eds., Volcanic Regimes in Canada: Geological Association of Canada Special Publication, no. 16, p. 3-24. Spry, A., 1969, Metamorphic textures: Pergamon Press, 352 p. Stacey, J.S., and J.D. Kramers, 1975, Approximation of terrestrial lead isotope evolution by a two-stage model: Earth and Planetary Science Letters, v. 26, p. 207-221. Streckeisen, A., 1976, To each plutonic rock its proper name: Earth Science Reviews, v. 12, p. 1-33. Sun, S.-S., 1980, Lead isotopic study of young volcanic rocks from mid-ocean ridges, ocean islands and island arcs: Philosophical Transactions of the Royal Society of London Series A, v. 297, p. 409-445. Thompson, A.B. and England, P.C., 1984, Pressure-temperature-time paths of regional metamorphism II. Their inference and interpretation using mineral assemblages in metamorphic rocks: Journal of Petrology, v. 25, p. 929-955. Thompson, J.B., Jr. and Norton, S.A., 1968, Paleozoic regional metamorphism in New England and adjacent areas, in Zen, E-an, White, W.S. and Hadley, J.B., eds., Studies of Appalachian Geology: Northern and Maritime: Interscience Publishers, John Wiley and sons, New York, New York, p. 319-327. Thompson, R.N., Morrison, M.A., Hendry, G.L., and Parry, S.J., 1984, An assesment of the relative roles of the crust and mantle in magma genesis: an elemental approach: Philosophical Transactions of the Royal Society of London Series A, v. 310, p. 549-590. Tipper, H.W., 1969A, Anahim Lake map-area (93C): Geological Survey of Canada Map 1202A. REFERENCES / 227 Tipper, H.W., 1969B, Mesozoic and Cenozoic geology of the northeastern part of the Mount Waddington map-area (92N), Coast District, British Columbia: Geological Survey of Canada Paper 68-33, 103 p. Tipper, H.W., Woodsworth, G.J. and Gabrielse, H., 1981, Tectonic assemblage map of the Canadian Cordillera and adjacent parts of the United States of America: Geological Survey of Canada Map 1505A. Tracy, R.J., 1982, Compositional zoning and inclusions in metamorphic minerals, in Ferry, J.M., ed., Characterization of Metamorphism through Mineral Equilibria: Mineralogical Society of America Reviews in Mineralogy, v. 10, p. 355-397: Tracy, R.J., Robinson, P. and Thompson, A.B., 1976, Garnet composition and zoning in the determination of temperature and pressure metamorphism, central Massachusetts: American Mineralogist, v. 61, p. 762-775. Travers, W.B., 1982, Possible large scale overthrusting near Ashcroft, British Columbia: Implications for petroleum prospecting: Bulletin of Canadian Petroleum Geology, v. 30, p. 1-8. Turner, F.J. and Verhoogen, J., 1960, Igneous and metamorphic petrology, second edition: McGraw-Hill, New York, 694 p. Turtle, O.F., and Bowen, N.L., 1958, Origin of granite in the light of experimental studies in the system NaAlSi 3 0g-KAlSi308-Si0 2 -H 20: Geological Society of America Memoir 74, 153 p. Vance, J.A., Dugan, M.A., Blanchard, D.P. and Rhodes, J.M., 1980, Tectonic setting and trace element geochemistry of Mesozoic ophiolitic rocks in western Washington: American Journal of Science, v. 280-A, p. 359-388. van der Heyden, P., 1982, Tectonic and stratigraphic relations between the Coast Plutonic Complex and Intermontane Belt, west-central British Columbia: M.Sc. thesis, University of British Columbia, Vancouver, British Columbia, 172 p. Wanamaker, B.J. and Evans, B., 1985, Experimental diffusional crack healing in olivine in, Schock, R.N., ed., Point Defects in Minerals: American Geophysical Union geophysical monograph, no. 31, p. 194-210. REFERENCES / 228 Wanless, R.K., Stevens, R.D., Lachance, G.R., and Delabio, R.N., 1979, Age determinations and geological studies: K-Ar isotopic ages, Report 14: Geological Survey of Canada Paper 79-2, 67 p. Wetherill, G.W., 1956, Discordant uranium-lead ages: Transactions of the American Geophysical Union, v. 37, p. 320-326. Wheeler, J.O. and McFeely, P, 1987, Tectonic assemblage map of the Canadian Cordillera and adjacent parts of the United States of America: Geological Survey of Canada Open File Map OF1565. Whetten, J.T., Jones, D.L., Cowan, D.S. and Zartman, R.E., 1977, Ages of Mesozoic terranes in the San Juan Islands, Washington, in Howell, D.G. and McDougall, K.A., eds., Mesozoic Paleogeography of the Western United States: Pacific Coast Paleogeography Symposium 2, Pacific Section, Society of Economic Paleontologists and Mineralogists, p. 117-132. White, S.H., 1977, Geological significance of recovery and recrystallization processes in quartz: Tectonophysics, v. 39, p. 143-170. White, W.H., G.P. Erickson, K.E. Northcote, G.E. Dirom, and J.E. Harakal, 1967, Isotopic dating of the Guichon Batholith, B.C.: Canadian Journal of Earth Science, v. 4, p. 677-690. Winkler, H.G.F., 1976, Petrogensis of metamorphic rocks: Springer-Verlag, Berlin, 334 P-Wust, S.L., 1986, Regional correlation of extension directions in Cordilleran metamorphic core complexes: Geology, v. 14, p. 828-830. Yorath, C.J., A.G. Green, R.M. Clowes, A. Sutherland Brown, M.T. Brandon, E.R. Kanasewich, R.D. Hyndman, and C. Spencer, 1985, Lithoprobe, southern Vancouver Island: Seismic reflection sees through Wrangellia to the Juan de Fuca plate: Geology, v. 13, p. 759-762. York, D., 1967, The best isochron: Earth and Planetary Science Letters, v. 2, p. 479-482. Zen, E-an, 1985, Implications of magmatic epidote-bearing plutons on crustal evolution in the accreted terranes of northwestern North America: Geology, v. 13, REFERENCES / 229 p. 266-269. Zen, E-an, and Hammarstrom, J.M., 1984, Magmatic epidote and its petrologic significance: Geology, v. 12, p. 515-518. Zen, E-an, and Hammarstrom, J.M., 1986, Reply, in Comments and reply on "Implications of magmatic epidote-bearing plutons on the crustal evolution of northwestern North America" and "Magmatic epidote and its petrologic significance": Geology, v. 14, p. 186-189. APPENDICES 1. APPENDIX 1. LIST OF CHEMICAL, ISOTOPIC AND MICROSTRUCTURAL SAMPLES FROM THE TLMC Table 2 is a listing of analytical tecniques employed on samples from this study. It plots sample number against the following modes of analyses: isotopic (U-Pb, K-Ar and Rb-Sr), chemical (XRF:whole rock and electron probe: mineral) and microstructural. The locations of these samples are shown on Plate 5. Locations of some isotopically dated samples are also plotted on Plate 1 (U-Pb, K-Ar) and Figure 64 (K-Ar). In Table 2, which directly follows, a plus sign ( + ) indicates that a particular technique was employed and a minus sign (-) signifies that it was not 230 TABLE 2. E x p l a n a t i o n of samples p l o t t e d on sample l o c a t i o n map and d i s c u s s e d i n t e x t SAMPLE U-PB ZIRCON K-AR RB-SR MAJOR AND TRACE MICROPROBE ORIENTED NUMBER SAMPLE ELEMENT ANALYSIS SAMPLE SECTION 8 4 - 7 1 - 7 + - + + - -84-71 1-2 + + + + - + 8 4 - 7 1 4 - 1 0 + + - - - -8 4 - 7 2 6 - 5 + - + + - -8 4 - 8 2 - 2 + - + + - -8 4 - 8 7 - 2 + - + + - -8 4 - 8 9 - 1 + + + + - -8 4 - 8 1 2 - 2 + - + + - -8 4 - 7 1 4 - 3 + + + + - -85-7 17-7 + - + + - -8 5 - 8 1 2 - 2 + - + + - + 8 5 - 8 1 7 - 2 + - + + - -8 4 - 6 1 4 - 1 0 - + + + - -8 4 - 6 1 7 - 3 A - - + - -8 4 - 6 1 7 - 3 B - - + + - -8 4 - 7 1 3 - 8 - - + + - -8 4 - 8 3 - 5 - - + - - -84-817-1 - - + + - + 8 4 - 8 3 0 - 5 - - + + - -85-71 1-3 - - + - - -8 4 - 7 2 3 - 3 - + - - - -8 4 - 7 2 5 - 4 - + - - - -8 5 - 7 1 2 - 7 - + - - - -8 5 - 7 2 5 - 3 - + - - -Cont i n u e . . . • M a j o r e lement a n a l y s i s o n l y . ' S a m p l e not l o c a t e d w i t h i n bounds of P l a t e 4. 3 Two o r i e n t e d t h i n s e c t i o n s from t h i s l o c a l i t y . T a b l e 2. C o n t i n u e d SAMPLE U-PB ZIRCON K-AR RB-SR MAJOR AND TRACE MICROPROBE ORIENTED NUMBER SAMPLE ELEMENT ANALYSIS SAMPLE SECTION P Y P - 1 1 + - - -C P C - 1 ! + - - -GSC78-G0 + - - -8 4 - G 2 2 - 4 - - + -8 4 - 6 2 6 - 3 - - - -8 4 - 7 6 - 7 A - - + -8 4 - 7 1 4 - 1 3 - - - + 85 -67 -1 - - + + 85-610-1 - - + + 8 5 - 7 6 - 2 - - + + 8 5 - 7 6 - 3 - - + -8 5 - 7 1 3 - 4 - - - + J 85-714-1 - - - -8 5 - 7 2 0 - 3 - - - -85-724-1 - - - -8 5 - 7 2 7 - 7 - - - -8 4 - 6 1 5 - 2 - - - + 8 4 - 6 2 1 - 2 - - - + 8 4 - 6 2 1 - 4 - - - + 8 4 - 7 7 - 3 - - - + 8 4 - 7 8 - 3 - - - + > 8 4 - 7 1 9 - 5 - - - + 8 4 - 8 2 - 3 - - - + 8 5 - 6 7 - 3 - - - + Cont i nue . . . ' M a j o r e l ement a n a l y s i s o n l y . ' S a m p l e not l o c a t e d w i t h i n bounds of P l a t e 4 . 'Two o r i e n t e d t h i n s e c t i o n s f rom t h i s l o c a l i t y . T a b l e 2. C o n t i n u e d SAMPLE U-PB ZIRCON K-AR RB-SR MAJOR AND TRACE MICROPROBE ORIENTED NUMBER SAMPLE ELEMENT ANALYSIS SAMPLE SECTION 8 5 - 6 7 - 4 - - - - - + 8 5 - 6 7 - 5 - - - + 8 5 - 6 8 - 2 - + 8 5 - 6 8 - 3 - _ _ + 8 5 - 6 1 1 - 2 - - - - - + 85 -612 -1 - - - • - - + 8 5 - 7 2 1 - 4 - + 8 5 - 7 2 1 - 5 - - - - - + 8 5 - 7 2 4 - 6 - _ - + 3 8 5 - 7 2 4 - 8 - + 8 5 - 7 2 6 - 4 - + 85 -810 -1 - - - - - + 8 5 - 6 1 8 - 2 * + + - -8 5 - 6 2 0 - 2 ' - + 8 5 - 6 2 0 - 3 ' - _ _ + 3 8 5 - 6 2 5 - 8 ' + -8 5 - 6 2 8 - 3 ' - + 8 5 - 6 2 8 - 4 ' - + 8 5 - 6 2 8 - 8 ' - + + ' M a j o r e lement a n a l y s i s o n l y . ' S a m p l e not l o c a t e d w i t h i n bounds o f P l a t e 4. 'Two o r i e n t e d t h i n s e c t i o n s f rom t h i s l o c a l i t y . APPENDICES / 234 2. APPENDIX 2. MICROSTRUCTURAL DATA FROM THE DSA Table 3 is a listing of kinematic indicators observed in oriented thin sections from rocks of the ductilely sheared assemblage. All sections were cut parallel to the Ls lineation and perpendicular to the Ss foliation (see Table 1 for explanation of structural terminology). The microstructures included in this table are: asymmetric pressure shadows, S-C surfaces, shear bands, mica fish (retort shaped mica), shape fabric in recrystallized quartz ribbons and microfaulted porphyroclasts. In Table, the letters W or E indicate that a westerly or easterly sense of vorticity was determined with a particular category of microstructure. A plus sign ( + ) indicates that the microsructure was present but yeilded a neutral or conflicting sense of shear. A minus sign (-) signifies that the microstructure was not observed in the thin section. TABLE 3. SENSE OF SHEAR INDICATORS IN ORIENTED X -Z SECTIONS. TLMC DUCTILELY SHEARED ROCKS SAMPLE NUMBER PRESSURE SHADOWS S-C SURFACES SHEAR BANDS MICA ' F I S H ' SHAPE FABRIC IN RIBBON QUARTZ ' F A U L T E D ' PORPHYROCLASTS 8 4 - 6 1 5 - 2 W - - - - -8 4 - 6 2 1 - 2 - - - + - + 8 4 - 7 7 - 3 A - - W - - + 8 4 - 7 8 - 3 A - E - - + 8 5 - 6 7 - 3 - - w + + -8 5 - 6 7 - 4 - - w + - -8 5 - 6 7 - 5 W W w - - -8 5 - 6 8 - 2 - W - w - -8 5 - 6 8 - 3 w w w - - -85-610-1 w w - w - -85-61 1-2 - w - w W -85-612-1 w - w w - -85 -67 -1 - - - w - -8 5 - 7 6 - 2 + - w - - + 8 5 - 7 1 3 - 4 w - - - - -8 5 - 7 1 3 - 4 w w w - - -85-72 1 -4 w - w - - -8 5 - 7 2 1 - 5 w - - w w -8 5 - 7 2 4 - 6 w w w - - -8 5 - 7 2 4 - 6 w w - w -8 5 - 7 2 4 - 8 w - - E - W 8 5 - 7 2 6 - 4 - - w - - -84-7 19-5 - w w - w -Cont i nue. T a b l e 3. C o n t i n u e d SAMPLE 1 PRESSURE S-C SURFACES SHEAR BANDS MICA ' F I S H ' SHAPE FABRIC IN ' F A U L T E D ' NUMBER SHADOWS RIBBON QUARTZ PORPHYROCLASTS 8 4 - 8 2 - 3 8 4 - 7 1 1 - 2 8 4 - 62 1-4 8 5 - 810-1 8 5 - 8 1 2 - 2 8 4 - 7 8 - 3 A 84 -817 -1 8 4 - 7 13- 14 8 5 - 6 2 0 - 2 1 8 5 - 6 2 0 - 3 ( 1 ) 8 5 - 6 2 0 - 3 ( 2 ) 1 8 5 - 6 2 8 - 4 ' 8 5 - 6 2 8 - 3 ' 8 5 - 6 2 8 - 8 1 W W w w w w w w w W: T o p - t o - t h e - w e s t s e n s e of s h e a r . E: T o p - t o - t h e - e a s t s e n s e of s h e a r . +: M i c r o s t r u c t u r e p r e s e n t but I n d i c a t e s c o n f l i c t i n g or n e u t r a l sense of s h e a r . - : M i c r o s t r u c t u r e not o b s e r v e d in s e c t i o n . ' O u t s i d e the bounds of P l a t e 1, i n Render Mt. a r e a . APPENDICES / 237 3. APPENDLX 3. GEOCHRONOMETRIC DATA Sample and/or analytical data for U-Pb zircon (Tables 4 and 5), K-Ar (Table 6) and Rb-Sr (Tables 7 and 8) dating techniques. T a b l e 4 . U-Pb z i r c o n i s o t o p i c d a t e s f rom the T a t l a Lake Metamorph ic Complex S A M P L E , ' WEIGHT U P b 3 Pb ISOTOPIC ABUNDANCE * OBSERVED 5 ' " P b / " ^ ' ' ° ' P b / I l s U * ° ' P b / ' ° 6 P b FRACTION" (mg) (ppm) (ppm) ! 0 « P b = 1 O O " " P b / ! 0 , P b DATE (Ma)" DATE (Ma) DATE (Ma) 208 207 204 RATIO ATOMIC RATIO ATOMIC RATIO ATOMIC RATIO 85 -817 -2 F , ABR, N T / 1 . 5 A FF N 1 0 ' / 1 - 5 A M T / 1 - 5 A 5 .0 2447.0 16.97 5.255 4 .917 0 .0129 5680 10.6 3640.5 26 .43 7.653 5 .830 0 .0726 1340 46 .9 + 0 . 6 0 . 0 0 7 3 0 ± 1 0 47.1 1 0 .8 0 .00734112 47 .2 ± 0 . 6 0 . 0 4 7 6 ± 6 47 .7 ± 0 . 6 0.0481+8 62 .8 + 12.8 0 .04727126 7 9 . 5 1 10.2 0 .04760120 85 -812 -2 C ABR, N T / 1 - 5 A FF N 1 0 ' / 1 A M r / 1 -3A 7.7 4 7 3 . 0 4 . 1 0 13.812 5.286 0 .0364 7 .3 5 7 3 . 0 4 .97 17.598 5 .056 0 .0217 1399 2150 54 .2 1 O .6 0 .00844110 5 2 . 6 1 0 . 6 0 .00819110 54 .8 + 1 .O 0 .0555110 5 2 . 9 1 1.0 0.0535+10 8 4 . 7 1 31 .8 0 .04771134 6 7 . 5 1 37 .0 0 .04736174 8 4 - 7 1 4 - 10 F .ABR, N 1 ' / 2A FF N 5* / 1A M 1 ' / 1 . 5 A 5.4 514.4 4.41 10.027 4 .870 0 .0093 4 . 5 651 .9 5 .89 14.379 5.082 0 .0257 3291 1946 55 .6 1 0 . 6 O.00866+10 56 .2 ± 0 . 8 0.00875+12 55 .8 1 1.2 O.0565+12 56.1 1 1.4 O.0568+14 6 5 . 7 1 4 1 . 6 0.04733+82 51.1 ± 53 .8 0 .047041106 84 -711 -2A C N 0 . 5 * / 2 . 2 A F N 1 ' / 1 . 8 A M 0 . 5 ' / 2 . 2 A F* N 1 * / 1 .8A M 0 . 5 ' / 2 . 2 A 1.2 454 .9 3.92 9 .033 5.031 0.0391 1.8 275 .0 2 .29 11.288 5 .550 0 .0398 1.3 624 .9 5.41 12.112 5.903 0 .0798 907 609 586 55 .8 1 0 . 8 0.00869+12 52 .7 1 0 . 6 O.00821110 53 .9 + 0 .4 0 .00840114 55'. 9 1 1.6 0.0566+16 55 .5 1 2 . 0 0 .0562120 54 . 1 1 0 . 8 0 .0547112 6 1 . 7 ± 58 .2 0.0472511 16 178.3 + 79 .0 0 .049641168 62 .2 + 30 .8 0.04726162 Cont i n u e d . T a b l e 4 . C o n t i n u e d SAMPLE, 1 WEIGHT U P b 3 Pb ISOTOPIC ABUNDANCE' OBSERVED 5 ' " P b / ^ ' U 1 " > ' P b / ! 3 5 U 2 ° 7 P b / ' ° 6 P b FRACTION' (mg) (ppm) (ppm) * 0 S P b = 1 O O ' ° 6 P b / ! ° ' P b DATE (Ma)" DATE (Ma) DATE (Ma) 208 207 204 RATIO ATOMIC RATIO ATOMIC RATIO ATOMIC RATIO 8 5 - 7 1 7 - 7 C A B R , N 0 . 5 ' / 2 . 2 A F . A B R , N 0 . 5 ' / 2 . 2 A F N 5" / 1 • 5A M T / 2 . 2 A FF N 5" / 1 . 5A M T / 2 . 2 A 1.3 632 .5 6 .69 7.937 4 .949 0 .0147 1.1 369.2 3 .29 9.912 5.183 0.0201 1.3 1325.1 9 .97 9.192 5.037 0 .0195 1.2 1285.4 9 .75 8.558 5.192 O.0312 2036 1393 2294 2436 69 . 6 1 1.0 O.01085114 57 .6 + 0 . 8 0 .00898112 4 9 . 0 1 0 . 6 0.00763+10 49 . 5 ± 0 . 6 O.00770110 69 . 5 + 1.0 0 .0708110 59 .6 1 2 0 .0605120 49 .5 1 0 0.0500+8 49 .8 1 1 0 .0503114 0 8 6 5 . 5 1 15. 0 .04732132 141.8 1 70 . 0 .048871148 7 4 . 0 1 2 3 . 0 .04749146 6 5 . 5 + 56 . 0.04732+112 8 5 - 7 1 4 - 3 C C , A B R , N 0 . 5 ' / 2 A C N 5 ' / 0 . 8 A M 0 . 5 ' / 1 5 A 6 . 9 253.6 3 .12 21.317 6.124 0 .0885 7 .8 216.7 2 .53 17.571 5.072 0 .0225 674 1 125 70 .7 1 0 .8 0 .01103112 70 .6 1 0 . 8 0.01101+12 71 .9 1 1.2 0 .0733114 70 .6 1 1.0 0 .0720110 109.5 1 36 .4 0 .04821174 7 0 . O 1 2 5 . 5 0.04741+50 84 -812 -2 CC N 0 . 5 " / 2 . 2 A C * N 0 . 5 ' / 1 . 9 A M 0 . 5 ' / 2 . 2 A F N 5' / 1 A M O. 5' / 1 . 9A 8 .3 173.5 2 .15 16.200 5.183 0 .0277 5 .0 195.3 2 .55 19.420 6 .136 0 .0910 3 .8 247.3 3.12 18.980 4 .853 0 .0093 1896 847 1316 75 .7 1 1.0 0 .01182116 76.1 + 0 . 6 0 .01187108 75 .5 1 1.2 0 .01178118 76.1 + 1.0 0.0778+10 76 .7 1 0 .8 O.0785110 74 .9 1 2 . 0 0 .0766122 86 .4 1 12 .0 0 .04774124 9 7 . 3 1 19.3 0 .04796140 57 . 1 1 56 . 4 0 .04 7 16+112 Cont i n u e d . T a b l e 4 . C o n t i n u e d S A M P L E , ' WEIGHT U P b 3 Pb ISOTOPIC ABUNDANCE" OBSERVED 5 * o 5 p b / * 3 . y s ' " ' P b / ' ^ U " " P b / ' » ' P b FRACTION' (mg) (ppm) (ppm) * ° « P b = 1 0 0 * < " P b / ! 0 4 P b DATE (Ma)" DATE (Ma) DATE (Ma) 208 207 204 RATIO ATOMIC RATIO ATOMIC RATIO ATOMIC RATIO 8 4 - 8 7 - 2 CC N 0 . 5 ' / 2 . 2 A C C * , A B R , N 0 . 5 * / 2 . 2 A C * N O . 5 ' / 1 . 9 A M 0 . 5 ' / 2 . 2 A 10.5 166.0 2 .22 17.640 5.178 0 .0262 0 . 9 221 .0 3.11 21.664 5 .279 0 .0316 4 . 9 202.2 2 .67 17.811 5.001 0.0142 2413 646 2488 8 0 . 5 ± 1.0 0 .01256116 8 1 . 9 1 0 .8 0 .01279112 79 .9 1 0 . 6 0 .01248110 8 1 . 0 1 1.0 0.0830+12 8 2 . 8 ± 2 .2 0 .0849124 80 .4 + 0 .8 0 .0824108 95 .4 1 15.4 0.04792+32 106.1 1 59 .2 0 .048141120 9 5 . 6 1 11.6 0 .04792124 8 4 - 8 9 - 1 C C , A B R , N 0 . 5 ' / 1 . 5 A F N 5" /1A M 0 . 5 ' / 1 . 9 A FF N 5 ' / 1 A M 0 . 5 ' / 1 . 9 A 7.2 238.2 3.86 6 .729 4 .868 0.0012 6 .3 305.3 4 .98 7.321 5.031 0.0131 1.0 398.9 6 .43 7.401 5.031 0.0131 4788 2989 1521 107.9 + 1.4 0 .01688122 107.7 + 1.2 0 .01685118 106.3 1 1.4 0 .01661122 108.6 + 1.2 O.1129114 108.3 + 1.8 0.1126+20 106.8 + 2 .2 O.1108124 123.7 1 9 .4 0 .04850120 121.9 + 32 .8 0.04846+68 117.6 + 37 .8 0 .04837178 8 4 - 8 2 - 2 CC N 0 . 5 ' / 2 . 2 A 10.4 241.0 4 .05 8 .966 5.044 0.0144 F N 1 0 ' / 0 . 5 A M T / 1 . 9 A 3 .5 261.2 4 .28 9 .270 5.059 0.0156 3640 2192 109.2 + 1.4 0 .01709122 106.2 1 1.4 0.01662+20 109.5 1 1.4 0 .1139116 106.5 1 1.6 0 .1106118 115.0 + 16.2 0 .04832134 113.2 1 26 .3 0 .04828154 Cont i n u e d . T a b l e 4. C o n t i n u e d SAMPLE, 1 WEIGHT U P b 3 Pb ISOTOPIC ABUNDANCE 4 OBSERVED 5 2 ° 6 P b / 2 3 a U 6 2 ° ' P b / 2 3 5 U 2 ° ' P b / 2 0 6 P b FRACTION 2 (mg) (ppm) (ppm) 2 0 6 P b = 1 0 0 2 ° « P b / 2 ° « P b DATE (Ma)" DATE (Ma) DATE (Ma) 208 207 204 RATIO ATOMIC RATIO ATOMIC RATIO ATOMIC RATIO 8 4 - 7 2 6 - 5 F ,ABR, 2. 1 279.5 5.55 7.225 5 .068 0 .0117 3312 131.0 1 1 . 6 131.8 1 2 .6 145.9 1 40 .8 N 1 ' / 1 . 5 A 0.02052+26 0 .1385130 0 .04896186 FF.BM 0 . 7 363.2 7.22 7 .686 5.094 0. .0153 1509 130.4 ± 1 .8 130.6 1 4 .0 132.6 1 66 .4 0.02041+28 0 .1370146 0.04868+138 8 4 - 7 1 - 7 C ,ABR, 12.7 214.7 5 . 34 1 1.701 5. 158 0. 0143 2791 157.0 1 3. 4 157.8 1 3 . 2 170.2 1 10. 9 N 1' /1 . 5A 0.02466156 0 .1682138 0.04947124 FF N 5 ' / 1 A 3 .7 382.7 9 . 26 10.692 5.062 0. 0068 3274 154.6 ± 1. 6 156.0 1 2. . 2 176.9 + 24. 1 M T / 1 . 5 A 0.02428126 0.1661+24 0.04961152 ' S e e P l a t e s 1 and 4 f o r sample l o c a t i o n s . L a t i t u d e s (N) and Long i t u d e s (W) of s a m p l e s : 8 5 - 8 1 7 - 2 : T a t l a Lake G r a n o d i o r i t e ( E t l ) 5 2 ' 0 1 . 0 ' N , 124*23 .1 'W; 8 5 - 8 1 2 - 2 : E a g l e Lake T o n a l i t e ( E e l ) 5 1 * 5 2 . 6 ' N , 1 2 4 ' 1 8 . 2 ' W ; 8 4 - 7 1 4 - 1 0 : E a g l e Lake T o n a l i t e ( E e l ) 5 1 * 5 3 . 3 ' N , 124 '17 .6 'W; 8 4 - 7 1 1 - 2 A : m e t a d a c i t e s i l l ( E d s i ) 5 1 * 5 5 . 9 ' N , 1 2 4 ' 1 8 . 7 ' W ; 8 5 - 7 1 7 - 7 : g r a n o d i o r i t e s i l l / d y k e of S u c k e r Creek 5 2 * 0 3 . 8 ' N , 124*44 .8 'W; 8 4 - 7 1 4 - 3 : m y l o n i t i c t o n a l i t e o r t h o g n e i s s ( L K o g 1 ) 5 2 ' 0 3 . 7 ' N , 124*53 .O 'W; 8 4 - 8 1 2 - 2 : One Eye T o n a l i t e ( L K o e ) 5 1 * 5 6 . 7 ' N , 124*46 .5 'W; 8 4 - 8 7 - 2 : One Eye T o n a l i t e ( L K o e ) 5 1 * 5 6 . 3 ' N , 124*45 .1 'W; 8 4 - 8 9 - 1 C : g r a n o b l a s t i c t o n a l i t e o r t h o g n e i s s ( E K g g l ) 5 1 * 5 5 . 6 ' N , 1 2 4 * 4 4 . 9 ' W ; 8 4 - 8 2 - 2 : f o l i a t e d q u a r t z d i o r i t e s tock(MKqd) 5 1 * 5 9 . 2 ' N , 124*53.O'W; 8 4 - 7 2 6 - 5 : m y l o n i t i c t o n a l i t e o r t h o g n e i s s o f M a r t i n M o u n t a i n ( J K o g 2 ) 5 1 * 5 7 . 2 ' N , 124*40 .7 'W; 8 4 - 7 1 - 7 : m y l o n i t i c t o n a l i t e o r t h o g n e i s s o f S p l i n t e r Hi 11(Ldog4) 5 1 * 5 1 . 1 ' N , 124*23 .O 'W; ' A b b r e v i a t i o n s f o r z i r c o n f r a c t i o n c h a r a c t e r i s t i c s . G r a i n s i z e : CC : 212- 1 SO^m; C : 1 5 0 - 7 5 < / m ; F : 7 5 - 4 5 < / m ; FF:<45 < / m. M a g n e t i c p r o p e r t i e s : M,N : m a g n e t i c and n o n - m a g n e t i c f r a c t i o n s a t i n d i c a t e d s i d e t i l t a n g l e and amperage o f F r a n z i s o d y n a m i c s e p a r a t o r ; f r o n t t i l t or s l o p e was se t at 1 0 ' . BM: bu lk m a g n e t i c f r a c t i o n . ABR: a b r a d e d f r a c t i o n . * S t a r r e d f r a c t i o n s : U and Pb c o n c e n t r a t i o n s d e t e r m i n e d u s i n g a mixed 2 0 5 P b / 2 3 5 U s p i k e ; f o r a l l o t h e r f r a c t i o n s a mixed 2 0 8 P b / 2 3 S U s p i k e was u s e d . ' R a d i o g e n i c and common Pb. ' R a d i o g e n i c and common Pb, c o r r e c t e d f o r 0.15% per AMU f r a c t i o n a t i o n and f o r 150150 pg to 400+150 pg b l a n k Pb w i t h the c o m p o s i t i o n 2 0 8 : 2 0 7 : 2 0 6 : 2 0 4 = 3 7 . 3 0 : 1 5 . 5 0 : 1 7 . 7 5 : 1 . 0 0 . C o r r e c t e d f o r 0.15% per AMU f r a c t i o n a t i o n . 6 2 o e r r o r s r e p o r t e d f o r a l l d a t e s ; Decay c o n s t a n t s : Xz3.=0.155125x10"3a"1, kz1 -,=0.98485x10"8a"1; r a t i o s a r e c o r r e c t e d f o r U and Pb f r a c t i o n a t i o n (0.15% per AMU), b lank and common Pb . I s o t o p i c c o m p o s i t i o n s o f Pb used f o r common Pb c o r r e c t i o n s f rom S t a c e y and Kramers (1975) growth c u r v e at i n f e r r e d age o f e a c h s a m p l e . T a b l e 5. Dominant c h a r a c t e r i s t i c s of z i r c o n p o p u l a t i o n s Sample Shape , e x t e r n a l f e a t u r e s ' C o l o u r , t r a n s p a r e n c y I n t e r n a l f e a t u r e s 8 5 - 8 1 7 - 2 ; T a t l a Lake G r a n o d i o r i t e ( E t l ) E u h e d r a 1 , l o n g - p r i s m a t i c ( l / w = 3 - 6 ) C o l o u r l e s s , t r a n s p a r e n t Homogenous, i nc1 us i ons r a r e b l a c k 8 5 - 8 1 2 - 2 ; E a g i e Lake T o n a l 1 t e ( E e l ) E u h e d r a l , 1ong-pr i smat i c ( l / w = 3-5) C o l o u r l e s s to p a l e p i n k , t r a n s p a r e n t Homogenous r o d - s h a p e d w i t h o v a l cav i t i es and 8 4 - 7 1 4 - 1 0 ; E a g l e Lake T o n a l i t e ( E e l ) E u h e d r a l , 1ong-pr imat i c ( 1 / w = 3-5) C o l o u r l e s s to p i n k , t r a n s p a r e n t Homogenous cav i t i es w i t h r o d - shaped 8 4 - 7 1 1 - 2 A ; M e t a d a c i t e s i 1 1 ( E d s i ) E u h e d r a l to s u b h e d r a l , l o n g - p r i s m a t i c ( l / w = 3 - 6 ) C o l o u r l e s s , t r a n s p a r e n t ; minor p ink to b r o w n , t r a n s 1ucent to t u r b i d in c o a r s e r f r a c t i o n s . Homogenous cav i t i es w i t h r o d - shaped 8 5 - 7 1 7 - 7 ; G r a n o d i o r i t e s i 1 1 / d y k e o f S u c k e r C r e e k E u h e d r a l , 1 o n g - p r 1 s m a t 1 c ( l / w = 3 - 6 ) ; Minor s u b h e d r a l to a n h e d r a l , s h o r t - p r i s m a t i c to equant ( l /w=1-3 ) i n c o a r s e r f r a c t i o n s C l e a r to p i n k , t r a n s p a r e n t ; Minor t r a n s l u c e n t to t u r b i d Homogenous, i nc1 us i o n - f r e e 8 4 - 7 1 4 - 3 ; M y l o n i t i c t o n a 1 i te o r t h o g n e i s s ( L K o g 1 ) E u h e d r a l , p r i s m a t i c ( 1 / w = 2 - 4 ), f r a g m e n t s common P i n k , t r a n s p a r e n t to t r a n s 1u c e n t Homogenous, ova 1 -shaped minor cav i t i es 8 4 - 8 1 2 - 2 ; One Eye T o n a l i t e ( L K o e ) E u h e d r a l , 1ong-pr i smat i c ( 1 / w = 3-6) C l e a r to p a l e p i n k , t r a n s p a r e n t to t r a n s l u c e n t Homogenous cav i t i es w i t h o v a l - s h a p e d Cont i n u e . . . ' 1 /w ( l e n g t h / w i d t h ) r a t i o s a r e v i s u a l e s t i m a t e s . co T a b l e 5. C o n t i n u e d Sample Shape , e x t e r n a l f e a t u r e s ' C o l o u r , t r a n s p a r e n c y I n t e r n a l f e a t u r e s 8 4 - 8 7 - 2 ; One Eye T o n a l i t e ( L K o e ) E u h e d r a l , l o n g - p r i s m a t i c ( l /w=3-6 ) C l e a r to p a l e p i n k , t r a n s p a r e n t to t r a n s l u c e n t Homogenous w i t h o v a l - s h a p e d c a v 1 t 1 e s 8 4 - 8 9 - 1C t o n a l i t e o r t h o g n e 1 s s ( E K g g l ) G r a n o b l a s t i c E u h e d r a l to subrounded p r i s m a t i c to s h o r t - p r i s m a t i c ( l / w = 2 - 4 ) P i n k , t r a n s p a r e n t to t r a n s 1ucent Homogenous, i n c l u s i o n - f r e e 8 4 - 8 2 - 2 ; F o l i a t e d q u a r t z d i o r i t e s t o c k ( M K q d ) E u h e d r a l to s u b r o u n d e d , p r i s m a t i c to equant ( l /w=1-3 ) C o l o u r l e s s to p i n k ( r a r e l y brown) , t r a n s l u c e n t to t u r b i d Homogenous, i n c l u s i o n - f r e e 8 4 - 7 2 6 - 5 ; M y l o n i t i c t o n a l i t e o r t h o g n e i s s o f M a r t i n Mounta in (UKog2) E u h e d r a l , l o n g - p r i s m a t i c ( l / w = 3 - 6 ) C o l o u r l e s s to p a l e p i n k , t r a n s p a r e n t Homogenous, o v a l - s h a p e d cav i t i es 8 4 - 7 1 - 7 ; M y l o n i t i c t o n a l i t e o r t h o g n e i s s o f S p l i n t e r Hi 11 (LJog4) E u h e d r a l to s u b h e d r a l , p r i s m a t i c to equant (1 /w=1-4 ) P i n k , t r a n s l u c e n t to t u r b i d Homogenous, i n c l u s i o n - f r e e 1/w ( l e n g t h / w i d t h ) r a t i o s a r e v i s u a l e s t i m a t e s . >fc> T a b l e G . K-Ar- D a t e s from the T a t l a Lake Metamorphic Complex and v i c i n i t y SAMPLE' NAME MATERIAL %K "/.RADIOGENIC RADIOGENIC 4 °Ar DATE (Ma) 2 NUMBER ANALYSED x10-' s c c / g m 8 4 - G 1 4 - 10 GRANODIORITIC S ILL BIOTITE 7 .46 79 .4 13. . 384 45 .6 + 1 .6 8 4 - 7 2 5 - 4 METAVOLCANIC HORNBLENDE 0 .424 49 . 9 0 . 766 45 .9 + 1 .6 8 4 - 8 9 - 1 C GRANOBLASTIC GNEISS HORNBLENDE 0 .655 76 . 3 1 . . 197 46 . 4 + 1 .6 8 4 - 7 1 1 - 2 A METADACITIC S ILL BIOTITE 7 . 1 1 9 0 . 6 13 . 254 47 . 3 + 1 . 7 8 4 - 7 1 4 - 1 0 EAGLE LAKE TONALITE BIOTITE 7 . 59 9 1 . 5 14 . 210 47 . 5 + 1 . 7 8 4 - 7 2 3 - 3 GRANOBLASTIC GNEISS HORNBLENDE 0 . 776 49 .0 1 . .470 48 . 1 + 1 . 7 GSC 78-60" GRANOBLASTIC GNEISS BIOTITE 7 . 77 8 0 . 6 15 . 28 49 .9 + 2 .4 8 5 - 6 2 5 - 8 ' TONALITIC ORTHOGNEISS HORNBLENDE 1 . .02 69 .4 2 . 076 51 . 6 + 1 . 7 8 5 - 7 1 2 - 7 GRANOBLASTIC GNEISS HORNBLENDE 0. .483 45 . 2 1 . 017 53 . 4 + 1 .8 8 5 - 7 1 4 - 3 ORTHOGNEISS HORNBLENDE 0. .414 54 . 8 0. 998 61 . .0 + 2 .0 PYP- 1 ' VOLCANIC WHOLE ROCK 0. 228 63 . 3 0. 6 12 67 . 8 + 2 . 7 8 5 - 7 2 5 - 3 QUARTZ DIORITE HORNBLENDE 0. 478 90 . 1 3 . 038 157 . 0 + 5 .0 C P C - 1 QUARTZ DIORITE HORNBLENDE 0. 298 88 . 3 2 . 231 190. 0 + 7 .0 ' S e e P l a t e s 1, 4 and F i g u r e 64 f o r sample l o c a t i o n s . *^0 e r r o r s r e p o r t e d f o r a l l d a t e s . ' O u t s i d e the bounds o f P l a t e s 1, 4 and F i g u r e 64. ' F r o m Wan less e t a l . (1979) . L a t i t u d e s ( N ) and L o n g i t u d e s ( W ) of s a m p l e s : 8 4 - 6 1 4 - 1 0 : 5 1 ' 5 1 . 8 ' N , 1 2 4 ' 3 4 . 3 ' W ; 8 4 - 7 2 5 - 4 : 5 1 ' 5 7 . 4 ' N , 124*40 .5 'W; 8 4 - 8 9 -1C: 5 1 ' 5 5 . 6 ' N , 1 2 4 ' 4 4 . 9 ' W ; 8 4 - 7 1 1 - 2 A : 5 1 * 5 5 . 9 ' N , 124*18.7 'W; 8 4 - 7 1 4 - 1 0 : 5 1 * 5 3 . 3 ' N , 124*17 .6 'W; 8 4 - 7 2 3 - 3 : 5 1 * 5 8 . 9 ' N . 124*33 .1 'W; GSC 7 8 - 6 0 : 5 1 * 5 5 . 7 ' N , 124*45 .6 'W; 8 5 - 6 2 5 - 8 : 5 2 ' 1 9 . 6 ' N . 1 2 5 ' 0 4 . 5 ' W ; 8 5 - 7 1 2 - 7 : 5 2 ' 0 0 . 6 ' N , 124*50 .3 'W; 8 5 -7 1 4 - 3 : 5 2 * 0 3 . 7 ' N , 124*53.O'W; P Y P - 1 : 5 2 * 0 4 . 2 ' N , 124*08.4 'W; 8 5 - 7 2 5 - 3 : 5 2 * 0 2 . 7 ' N , 124*33 .8 'W; C P C - 1 : 5 1 * 4 9 . 7 ' N , 124' 4 2 . O ' W . T a b l e 7. R b - S r a n a l y t i c a l d a t a f o r the T a t l a Lake Metamorphic Complex SAMPLE Sr (ppm) Rb (ppm) R b / S r ' ' R b / • 6 S r MEASURED INITIAL ZIRCON NUMBER ±5% ±5% ±2% RATIO 8 ' S r / ' 6 S r " ' S r / « 6 S r DATE RATIO RATIO (Ma) ± 0 . 0 0 0 1 8 4 - 8 9 - 1 C 450. 20.8 0 .046 0 . 134 0 .7036 0 . 70340 107 8 4 - 8 7 - 2 1093 . 10. 7 0 .010 0 .028 0 .7035 0 . 70347 82 84 -812 -2 1019. 16.6 0 .016 0.047 0.7034 0 .70335 76 8 5 - 8 1 2 - 2 1076. 55 . 1 0 .05 1 0. 148 0.704 1 0 .70399 54 8 4 - 7 2 6 - 5 621 . 16.8 0 .027 0 .078 0 .7035 0 .70335 131 8 5 - 8 1 7 - 2 457 . 90 .8 0. 198 0.574 0 .7039 0 . 70352 47 8 5 - 7 1 4 - 3 854 . 36 .6 0 .043 0 . 124 0 .7035 0 . 70337 71 8 4 - 7 1 - 7 324. 48 . 2 0. 149 0 .430 0 .7045 0 . 70354 157 8 4 - 8 2 - 2 47 1 . 13.1 0 .028 0.081 0 .7035 0 .70338 108 84-71 1-2A 636 . 97 .6 0. 153 0.444 0 .7045 0 .70415 55 8 5 - 7 1 7 - 7 591 . 77 .4 0.131 0 . 379 0 .7038 0 .70354 49 84-817-1 330. 98 .9 0. 300 0 .868 0 .704 1 8 5 - 6 1 8 - 2 929 . 32 .7 0 .035 0 . 102 0 .7036 8 4 - 8 3 0 - 5 407 . 9 . 1 0 .022 0 .065 0 .7036 8 4 - 6 1 7 - 3 A 1611. 3 1 . 0 0 .019 0 .056 0 .7037 8 4 - 6 1 7 - 3 B 196 . 19.6 0. 100 0 . 290 0 .7043 8 4 - 6 1 4 - 1 0 1338. 35 .8 0 .027 0 .077 0 .7036 8 4 - 7 1 3 - 8 231 . 35 .6 0. 154 0 .446 0 .7049 85 -711 -3A 909. 2 . 7 0 .003 0 .009 0.7034 85 -711 -3B 1 166 . 7 . 7 0 .007 0 .019 0 .7035 8 5 - 7 1 1 - 3 C 1021 . 20 .6 0 .020 0.058 0 .7034 85-71 1-3D 1033 . 16 . 2 0 .016 0 .045 0 .7034 8 4 - 8 3 - 5 A 1255. 27 . 7 0 .022 0.064 0 .7035 8 4 - 8 3 - 5 B 961 . 20 .0 0.02 1 0 .060 0 .7035 84 -83 -5D 703 . 14.1 0 .020 0 .058 0 .7035 8 4 - 8 3 - 5 E 304 . 18.2 0 .060 0 . 173 0.704 1 8 4 - 8 3 - 5 F 791 . 6 . 4 0 .008 0 .023 0.7034 8 4 - 8 3 - 5 H 354. 21 .7 0.061 0 . 177 0 .7040 T a b l e 8. R b - S r sample l o c a t i o n s and d e s c r i p t i o n s SAMPLE LATITUDE (N) LONGITUDE (W) SAMPLE DESCRIPTION NUMBER 84 - 8 9 - 1C 51' 55 6 ' 124'44 9 ' G r a n o b l a s t i c b i o t i t e h o r n b l e n d e t o n a l i t e o r t h o g n e i s s 84 - 8 7 - 2 51 56 3 ' 124'45 1 ' B i o t i t e h o r n b l e n d e t o n a l i t e 84 - 812 -2 51' 56 7 ' 124'46 5' B i o t i t e h o r n b l e n d e t o n a l i t e 85 - 812 -2 51' 52 6 ' 124' 18 2' F o l i a t e d and l i n e a t e d b i o t i t e t o n a l i t e 84 - 7 2 G - 5 51' 57 2' 124 '40 7 ' F o l i a t e d and l i n e a t e d b i o t i t e t o n a l i t e 85 - 817 -2 52' 01 0 ' 124'23 1 ' N o n f o l i a t e d b i o t i t e g r a n o d i o r i t e 85 - 7 1 4 - 3 52' 03 7 ' 124'53 0 ' B i o t i t e h o r n b l e n d e t o n a l i t e 84 - 7 1 - 7 51' 51 1 ' 124'23 0 ' F o l i a t e d and l i n e a t e d t o n a l i t e o r t h o g n e i s s 84 - 8 2 - 2 51" 59 2 ' 124'53 2' F o l i a t e d q u a r t z d i o r i t e 84 -711 -2A 51" 55 9 ' 124' 18 7' F o l i a t e d and l i n e a t e d p o r p h y r i t i c d a c i t e s i l l 84 -817-1 51" 56 4 ' 124' 29 3' N o n f o l i a t e d p o r p h y r i t i c r h y o l i t e dyke 85 - 618 -2 52' 22 7 ' 125' 06 4 ' L i n e a t e d g r a n o d i o r i t e o r t h o g n e i s s 84 - 8 3 0 - 5 51' 55 9 ' 124'45 9 ' Ap1i t i c c l o t 84 -617 -3A 51' 56 4 ' 124 '20 0 ' F i n e g r a i n e d n o n f o l i a t e d g r a n o d i o r i t e s i l l 84 - 6 1 7 - 3 B 51' 56 3 ' 124'20 0 ' A p l i te s i l l 85 - 7 1 7 - 7 52' 03 8 ' 124' 44 8' N o n f o l i a t e d b i o t i t e g r a n o d i o r i t e s i l l / d y k e 84 - 6 1 4 - 1 0 51' 51 8' 124'34 3' F o l i a t e d g r a n o d i o r i t e s i l l 84 - 7 1 3 - 8 51' 55 3 ' 124' 18 0 ' F o l i a t e d m u s c o v i t e g r a n o d i o r i t e 85 -711 -3A 52' 01 5 ' 124'50 9 ' G r a n o b l a s t i c g n e i s s : l e u c o c r a t i c l a y e r 85 -711 -3B 52" 01 5 ' 124'50 9 ' G r a n o b l a s t i c g n e i s s : m e l a n o c r a t i c l a y e r 85 -711 -3C 52' 01 5 ' 124 '50 9 ' G r a n o b l a s t i c g n e i s s : i n t e r m e d i a t e l a y e r 85 -711-3D 52' 01 5' 124 '50 9 ' G r a n o b l a s t i c g n e i s s : i n t e r m e d i a t e l a y e r 84 -83 -5A 51' 59 7 ' 124'51 0 ' G r a n o b l a s t i c g n e i s s : i n t e r m e d i a t e l a y e r 84 -83 -5B 51' 59 7 ' 124"51 0 ' G r a n o b l a s t i c g n e i s s : i n t e r m e d i a t e l a y e r 84 - 8 3 - 5 C 51' 59 7 ' 124'51 0 ' G r a n o b l a s t i c g n e i s s : m e l a n o c r a t i c l a y e r 84 - 8 3 - 5 E 51' 59 7 ' 124'51 0 ' G r a n o b l a s t i c g n e i s s : m e l a n o c r a t i c l a y e r 84 - 8 3 - 5 F 51" 59 7 ' 124'51 0 ' G r a n o b l a s t i c g n e i s s : l e u c o c r a t i c l a y e r 84 -83 -5H 51' 59 7 ' 124'51 0 ' G r a n o b l a s t i c g n e i s s : l e u c o c r a t i c l a y e r APPENDICES / 248 4. APPENDIX 4. GEOCHRONOMETRIC AND GEOCHEMICAL SAMPLE PREPARATION AND ANALYTICAL TECHNIQUES 4.1. U-Pb sample preparation and analytical techniques Samples of 30 to 50 kg were broken into clean, fist-sized pieces in the field. At UBC these were reduced to to finer than 80 mesh (about 200um) with jaw crusher and disc mill. Heavy mineral concentrates were obtained by running crushed samples over a wilfley table, and purified with heavy liquids (methylene iodide ± bromoform) and magnetic separator apparatus (Franz isodynamic separator). Where pyrite was present heavy silicates were further isolated using a high voltage electrostatic separator. Fractions of single zircon populations were selected using coventional procedures (nylon mesh sieve and Franz isodynamic separator) followed by handpicking to virtually 100% purity. Sample dissolution and chemistry were carried out using a procedure modified from Krogh (1973). U and Pb concentrations were determined using mixed 2 0 8Pb / 2 3 5 U (pre-1987) and 2 0 5Pb / 2 3 5 U spikes. Purified U and Pb were loaded on Re filaments using H 3P0 4-silica gel technique. Mass spectrometric analysis was carried out using a Vacuum-Generators Isomass 54R solid source mass spectrometer in single collector mode (Faraday cup). Precisions for 2 0 7Pb/ 2 0 6Pb and 2 0 8Pb/ 2 0 6Pb were better than 0.2% and for 2 0 4Pb/ 2 0 7Pb were better than 3%. Pb /U, and Pb/Pb errors for individual zircon fractions were obtained by individually propagating all calibration and analytical uncertainties through the entire date calculation program and summing the individual contributions to the total variance. 2a errors are reported for all dates. The decay constants used are: X 2 3 8 = 0.155125xl0-9a-1, X 2 3 3 = 0.98485x10"'a1; APPENDICES / 249 4.2. K-Ar sample preparation and analytical techniques Approximately 1-3 kg samples were crushed and ground in jaw crusher and disc mill and 40- 80 mesh (425 to about 200M m) size fractions were obtained using metal sieves. Biotite and hornblende separates were concentrated employing heavy liquids, wet and/or dry shaker tables and magnetic separation techniques in various combinations. K was determined in duplicate by atomic absorption using a Techtron AA4 spectrophotometer and Ar by isotope dilution using an AEI MS-10 mass spectrometer, high purity 3 8Ar spike, and conventional gas extraction and purification procedures (White et al., 1967). The constants used are: X 4 0Ke = 0.581x10" "a" 1, X40K/» =4.962x10""a"1, 4 0K/K = 0.01167 atom%. Analyses by K. Scott (potassium) and J. Harakal (argon) at the Department of Geological Sciences, University of British Columbia. APPENDICES / 250 4.3. Rb-Sr sample preparation and analytical techniques Approximately 1 kg samples were collected in the field and reduced to < 1 cm3 with a standard jaw crusher. The material was run through a disc mill and further reduced to < 40 mesh (about 425M m). Finally, representative 10-20 g samples were ground to < 200 mesh (75M m) with an agate mortar and pestle. Rb and Sr concentrations were determined by replicate analyses of pressed powder pellets employing the X-ray fluorescence technique. U.S. Geological Survey rock standards were used for calibration; mass absorption coefficients were obtained from Mo K alpha Compton scattering measurments. Rb/Sr ratios have a precision of 2% (one sigma) where both concentrations exede 50 ppm. If either concentration is below 50 ppm the ratio uncertainty is based on an uncertainty in the concentration measurment of 1 ppm. Concentrations have a precision of 5% or 1 ppm, whichever is greater. Sr isotopic composition was measured on unspiked samples prepared using standard ion exchange techniques. Sr measurments were made on a Vacuum-Generators Isomass 54R mass spectrometer automated with a Hewlett-Packard HP85 computer. Measured ratios have been normalized to a 8 6Sr/ 8 8Sr ratio of 0.1194 and adjusted so that the National Bureau of Standards standard SrCo3 (SRM 987) gives a 8 7Sr/ 8 6Sr ratio of 0.71020 + 0.00002 and the Eimer and Amend Sr standard a ratio of 0.70800 ± 0.00002. The precision of a single 8 7Sr/ 8 6Sr ratio is < 0.0001 (one sigma). Rb-Sr dates are based on a Rb decay constant of 1.42 x 10_ 1 1a_ l. The regressions were calculated according to the technique of York (1967). APPENDICES / 251 4.4. XRF sample preparation Representative, fresh, fist sized samples were reduced to about 5 mm pieces in a i standard jawcrusher. A sample splitter was used to separate representative 20-30 gram samples. These were further reduced to finer than 200 mesh (about 75M m) by grinding about 5 minutes in a W-C (tungsten-carbide) ringmill. Pressed powder pellets for trace element (and Rb-Sr) analases were made with 4.00 grams of rock powder, 3-4 drops of dilute poly vinyl acetate solution (PVA) as a binding agent, and about 1 Tablespoon of boric acid as a pellet backing medium. Pressed ground glass pellets were used for major element analyses. 1.000 gram of rock powder was mixed with 2.000 grams of Lithium tetraborate, placed in graphite crucibles and fused in a 1000 C oven for about 10 minutes. After cooling, glass beads were crushed for about 5 minutes in a ringmill to finer than 200 mesh (about 75jum). Ground glass samples were pressed into pellets using 4-5 drops of PVA as a binding agent and boric acid as a backing medium. APPENDICES / 252 5. APPENDIX 5. PETROGRAPHIC DATA FROM THE TLMC Mineral abbreviations used in this section and in the text of the thesis are listed in Table 9, along with their general chemical formulae. Petrographic data from the gneissic core and ductilely sheared assemblage/upper plate appear in Tables 10 and 11, respectively. Brief descriptions of some typical mineral occurrences are listed below. Departures from these common characteristics are noted in Tables 10 and 11. Plus signs ( + ) indicate typical form of mineral is present. Gneissic Core: Plagioclase: Poikiloblastic, with rounded inclusions of quartz, apatite and hornblende. Both albite and pericline twins are observed. Compositions vary between A N 3 0 and AN 3 5 . Quartz: Undulose extinction, kink bands and subgrains are commonly observed. Quartz also occurs as inclusions in hornblende and plagioclase Hornblende: Poikiloblastic, subhedral to euhedral; usually occurs as glomeroporphyroblasts with biotite. Quartz, plagioclase and apatite inclusions are common. Biotite: Occurs as glomeroporphyroblasts with hornblende. Alkali Feldspar: Commonly untwinned. Chlorite: Commonly replaces biotite. Apatite: Occurs as inclusions in plagioclase, quartz, hornblende and biotite. Ductilely sheared assemblage: Mineral descriptions are provided in sections 3.2.2, 5.2.1 and 5.2.2 and a few explanatory notes are listed below. Quartz: Commonly fine to very fine grained. In quartz-feldspathic rocks ribbon grains APPENDICES / 253 (ribgrs in Table 11) have been recrystallized and are composed of fine grained quartz. Plagioclase: Occurs as medium to coarse grained porphyroclasts and fine grained idioblastic crystals. Compositions commonly occur in the AN2 0-4o range. Albitic compositions from map unit Jmvl are noted in Table 11. Mica: Biotite and muscovite commonly occur parallel to the Ss foliation plane. Mineral zones are listed for samples of DSA pelitic schist from the Whitesand Lake area (unit Jmsp). Abbreviations other than minerals listed in Table 9: poikiloblastic=poik; inclusions=incls; euhedral = euhed; subhedral = subhed; anhedral = armed; kinkbands=kink; magmatic=magma; glomeroporphyroblastic=glom; fractures=fracts; ribbon grains=ribgrs; trace=tr; porphyroclasts=pclasts; sausseritized = sauss; undulatory extinction=und; See Table 1 for structural terminology. Table 9: M i n e r a l a b b r e v i a t i o n s and formulae 254 M i n e r a l Name A b b r e v i a t i o n General Formulae a l b i t e AB NaAlSi 3 0 8 almandine ALM F e 3 A l 2 S i 3 0 , 2 a n d a l u s i t e ANDAL A l 2 S i 0 5 andesine ANDES (Na,Ca)Si 30 8{AB 7oAN3 0-AB 5 0AN 5 0} an n i t e ANN K F e 3 A l S i 3 0 , o ( O H ) 2 a n o r t h i t e AN C a A l S i 2 0 8 K ( F e , M g ) 3 A l S i 3 0 1 0 ( O H ) 2 b i o t i t e BI c a l c i t e CC CaC0 3 ( F e r M g ) 5 A l 2 S i 3 0 , 0 ( O H ) a c h l o r i t e CHL c l i n o c h l o r e CLN M g 5 A l 2 S i 3 0 1 0 ( O H ) 8 c h l o r i t o i d CTD (Fe,Mg) 2Al < 1Si 20 1 0(OH)» F e - c h l o r i t o i d FECTD F e A l 2 S i 0 5 ( O H ) 2 M g - c h l o r i t o i d MGCTD M g A l 2 S i 0 5 ( O H ) 2 epidote EP C a 2 F e A l 2 S i 30, 2(OH) garnet GT (Fe,Mg,Mn,Ca) 3Al 2Si 30, 2 g r o s s u l a r GROS C a 3 A l 2 S i 30! 2 hornblende HB (Na,K) 0.,Ca 2 (Mg,Fe* 2 , F e + 3 , A l ) 5 [ S i s . , A l 2 . , 0 2 2 ] (OH,F) 2 k y a n i t e KY A l 2 S i 0 5 muscovite MS K A l 3 S i 3 0 1 0 ( O H ) 2 opaques OP o l i g o c l a s e OLIG ( C a N a ) A l S i 3 0 8 { A B 9 0 A N 1 0 -AB 7 0AN 3 0} phengite PHENG K A l 3 S i 3 0 1 0 ( O H ) 2 p h l o g o p i t e PHLOG K M g 3 A l S i 3 0 1 0 ( O H ) 2 p l a g i o c l a s e PL (Na,Ca)AlSi 3 0 8 potassium f e l d s p a r KSP K A l S i 3 0 8 pyrope PYROP M g 3 A l 2 S i 3 0 , 2 quartz QZ S i 0 2 r u t i l e RU T i 0 2 s e r i c i t e SER K A l 3 S i 3 0 1 0 ( O H . ) 2 s i l l i m a n i t e SILL A l 2 S i 0 5 s p e s s a r t i n e SPES Mn 3Al 2Si 30, 2 sphene SPH CaTiSiO,(OH) s t a u r o l i t e STAUR (FeMg) SA1, 8Si 7 s0, a(OH), F e - s t a u r o l i t e FESTAUR F e t t A l 1 8 S i 7 sOq^OH),, C a 2 ( F e , M g ) 3 A l a S i 6 0 2 2 ( O H ) 2 tchermakite TSCH Fe-tourmaline TOUR N a ( F e , M n ) 3 A l 6 B 3 S i 6 0 2 7 (OH) 2 z i r c o n ZI ZrSiO» Table 1 0 . Petrographic data from the gneissic core of the TLMC. Descriptions of typical mineral occurrances are listed below. Departures from these common characteristics are noted in the table. Plus signs (+) indicate typical form of mineral is present. Plagioclase: Poikiloblastic, with rounded inclusions of quartz, apatite and hornblende. Both albite and pericline twins are observed. Compositions vary between ANi« and ANis. Quartz: Undulose extinction, kink bands and subgrains are commonly observed. Quartz also occurs as inclusions in hornblende and plagioclase Hornblende: Poikiloblastic, subhedral to euhedral; usually occurs as glomeroporphyroblasts with biotite. Quartz, plagioclase and apatite inclusions are common. Biotite: Occurs as glomeroporphyroblasts with hornblende. Alkali Feldspar: Commonly untwinned. Chlorite: Commonly replaces biotite. Apatite: Occurs as inclusions in plagioclase, quartz, hornblende and biotite. Abbreviations:Poiki1 obiastic=poik; Inclusions=inc1s; Euhedra1=euhed; Subhedral=subhed; Anhedra1=anhed; Kinkbands = kink; Magmatic=magma; GIomeroporphyroblastic=glom; Fractures=fracts; Ribbon Grains=ribgrs; Trace=tr. See Table 9 for mineral abbreviations. LTI T a b l e 10. P e t r o g r a p g i c d a t a from the g n e i s s i c c o r e of the TLMC SAMPLE, MAP UNIT PLAGIOCLASE QUARTZ HORNBLENDE BIOTITE K S P GARNET 84-89-1 991 absent absent 84-89-1B g g l absent absent 84-89-1C EKggl ragged c r y s t a l s absent absent 84-812-2 LKoe some ragged g r a i n s ; twinned absent absent 84-87-2 LKoe absent absent 84-812-4 991 k i n k , f r e s h absent absent Cont i nue. T a b l e 10. C o n t i n u e d : c o r e g n e i s s i c r ocks SAMPLE, 1 MAP UNIT CHLORITE EPIDOTE SPHENE APATITE ZIRCON MAGNETITE 84-89-1A g g i a f t e r BI v e i n 8> assoc/w HB, magma 84-89-1B gg i a f t e r BI v e i n & assoc/w v e i n & i n c l s i n HB. magma HB. magma 84-89-1C EKggl a f t e r BI t r , magma t r , assoc/w PL, HB 84-812-2 LKoe t r . a f t e r BI t r , magma absent 34-87-2 LKoe a f t e r BI t r , subhed, magma absent 84-812-4 gg i t r , a f t e r BI t r , magma subhed, t r Cont1nue. to cn —1 Table 10. Continued: core g n e i s s i c rocks SAMPLE, MAP UNIT PLAGIOCLASE QUARTZ HORNBLENDE BIOTITE KSP GARNET 84-84-5 ggi very poik, sutured edges absent f i n e grained absent subhed, QZ, PL as i n c l s 85-720-3A ggi sutured edges absent t r , f i ne gra i ned absent smal1, i nc1s-f ree 85-720-3B ggi poik & in GT f r a c t s f i n e grained in GT f r a c t s GT f r a c t s & groundmass GT f r a c t s & t r . in groundmass absent large, f r a c t s 84-724- 1A ggi =ANi 5 anhed f i n e grained t r EP, QZ as i n c l s 84-724-3 ggi =AN* absent f i n e grained untwinned, assoc/w myrmek i te absent 84-724-8 ggi(am) t r euhed to subhed f i n e grained t r ? absent Cont i nue. Ln co T a b l e 10. C o n t i n u e d : c o r e g n e i s s i c r ocks SAMPLE, 1 MAP UNIT CHLORITE EPIDOTE SPHENE APATITE ZIRCON MAGNETITE 84-84-5 a f t e r BI absent absent 85-720-3A gg i a f t e r BI and i n G f r a c t s absent absent 85-720-3B 991 a f t e r BI t r i n G f r a c t s absent 84-724-1A gg i a f t e r BI i n c l s i n G glom assoc/w HB, BI 84-724-3 g g i a f t e r BI absent subhed 84-724-8 gg1(am) t r , a f t e r BI absent subhed Cont i nue. T a b l e 10. C o n t i n u e d : c o r e g n e i s s i c r o c k s SAMPLE, MAP UNIT PLAGIOCLASE QUARTZ HORNBLENDE BIOTITE KSP GARNET 84-82-8 9 9 1 subhed, f r e s h f r e s h absent absent 84-84-6 991 f r e s h absent absent 84-88-2 991 t r a f t e r HB? absent absent 84-7 19-6 992 = AN 1 s absent absent 84-723-1 992 = AN* t r assoc/w mymek i t e absent Cont i nue. T a b l e 10. C o n t i n u e d : c o r e g n e i s s i c r ocks SAMPLE,' MAP UNIT CHLORITE EPIDOTE SPHENE APATITE ZIRCON MAGNETITE 84-82-8 991 A f t e r BI absent subhed, i n c l s i n HB 84-84-6 9 9 1 t r A f t e r BI subhed, magma absent 84-88-2 9 9 1 t r a f t e r BI t r assoc/w HB t r , i n c l s i n HB 84-719-6 992 t r , a f t e r BI assoc/w BI, assoc/w BI, magma 84-723-1 992 absent subhed, HB i n c l s ; magma 8> as i n c l s i n PL absent Cont i nue. T a b l e 1 0 . C o n t i n u e d : c o r e g n e i s s i c r o c k s S A M P L E , P L A G I O C L A S E Q U A R T Z H O R N B L E N D E B I O T I T E K S P G A R N E T M A P U N I T 8 4 - 7 2 3 - 3 = A N ; s a b s e n t a b s e n t f i n e g r a i n e d + a b s e n t g g 2 8 4 - 7 2 1 - 1 0 f i n e g r a i n e d , + a b s e n t f i n e g r a i n e d u n t w i n n e d a n d a b s e n t g g 2 ( s i l l ? ) = A N * o t a r t a n t w i n s ; m i c r o c l 1 n e , a s s o c / w m y r m e k i t e C o n t i n u e . . . N J N J Table 10. Continued: core gneissic rocks SAMPLE,1 CHLORITE EPIDOTE SPHENE APATITE ZIRCON MAGNETITE MAP UNIT 84-723-3 after BI tr, magma + absent absent absent 992 84-721-10 tr, after BI SUB, magma absent + + absent gg2(si11?) T a b l e 11. P e t r o g r a p h i c d a t a from the d u c t i l e l y s heared assemblage of the TLMC: m e t a p e l i t i c r o c k s SAMPLE, QUARTZ BIOTITE MUSCOVITE PLAGIOCLASE GARNET STAUROLITE MAP UNIT 85-76-3 + + t r AN,,-,! p r e - D s , f r a c t s t r pel 11 ic pendant 85-67-1 Jmsp: GT-STAUR-KY-SILL zone AN, t r 85-67-3A Jmsp: GT-STAUR-KY-SILL zone absent 85-68-3 Jmsp: GT-STAUR-KY-SILL zone AN ; ro11ed 85-610-1 Jmsp: GT-STAUR-KY-SILL zone f r i n g e s GT t r 84-89-1 Jmsp: GT-STAUR-KY-SILL zone t r r o l 1 e d absent Cont i nue. . . to T a b l e 11. C o n t i n u e d : m e t a p e l i t i c rocks SAMPLE, 1 KYANITE SILLIMANITE ANDALUSITE CHLORITE TOURMALINE OTHER TRACES MAP UNIT 84-76-3 pe1i t i c pendant ear l y . t r syn-Ds.abundant absent GT f r a c t s ABSENT EP.SPH.RU.AP.OP 85-67-1 Jmsp: GT-STAUR-KY-SILL zone absent t r absent tr:GT f r a c t absent EP.AP,OP 85-67-3A Jmsp: GT-STAUR-KY-SILL zone absent absent absent a f t e r EI absent AP.OP.CC 85-68-3 Jmsp: GT-STAUR-KY-SILL zone t r l a t e - Ds t r : l a t e a f t e r BI t r CTD,AP,OP 85-610-1 Jmsp: GT-STAUR-KY-SILL zone absent t r absent a f t e r BI + AP.OP,ZI 85-89-1 Jmsp: GT-STAUR-KY-SILL zone absent absent absent a f t e r BI,GT f r a c t t r OP , CC Cont i nue. . . to Ln T a b l e 11. C o n t i n u e d : m e t a p e l i t i c r o c k s SAMPLE. QUARTZ BIOTITE MUSCOVITE PLAGIOCLASE GARNET STAUROLITE MAP UNIT 85-612-1 r i b g r s + + t r r o l l e d l a t e - D s Jmsp:GT-STAUR zone 84-622-4 Jmsp: GT-STAUR-KY-SILL zone r i bgrs 84-76-7B Jmsq AN; r o l 1 e d c o r e s / l a t e - D s r i ms l a t e - D s t r Up t o 5mm;po i k;ro11ed absent 85-611-2 r i b g r s + + n e u t r a l r e l i e f absent absent Jmsp:CHL-BI zone 85-611-3 r i b g r s + mica f i s h n e u t r a l r e l i e f absent absent Jmsp:CHL-BI zone Cont i nue. .. T a b l e 11. C o n t i n u e d : m e t a p e l i t i c r ocks SAMPLE, 1 KYANITE SILLIMANITE ANDALUSITE CHLORITE TOURMALINE OTHER TRACES MAP UNIT 85-612-1 absent absent absent i n v e i n s + AP.OP.ZI Jmsp:GT-STAUR zone 84-622-4 late-Ds t r : l a te-Ds absent a f t e r BI + SPH,AP.OP.ZI Jmsp : GT-STAUR-KY-SILL zone 84-76-7B absent absent absent a f t e r BI absent EP,AP.OP.ZI Jmsq 84-611-2 absent absent absent Ds & a f t e r BI absent EP.OP.CC.ZI Jmsp:CHL-BI zone 85-611-3 absent absent absent syn-Ds absent EP.OP.CC.ZI Jmsp:CHL-BI zone Cont i nue. . . cn T a b l e 11. C o n t i n u e d : q u a r t z o f e l d s p a t h i c rocks SAMPLE, MAP UNIT PLAGIOCLASE QUARTZ BIOTITE MUSCOVITE GARNET AMPHIBOLE 84-614-10 Jmsq absent absent absent 84-626-31 Jmsq t r : l a t e absent 84-626-2W Jmsq tr absent 84-819-5 Jmsq pr e - or syn-Ds;BI,CHL,EP i nc 1 s absent 84-78-3A Jmsq:my1 p c 1 a s t s / s a u s s wel1 developed r i b g r s f i n e g r a i n e d f i n e g r a i n e d 1 a t e Ds/f ine gra i ned absent 84-714-13 Jmsq:my 1 p c l a s t s / s a u s s wel1 developed r1bgrs f i n e g r a i n e d f i n e g r a i n e d l a t e D s / f i n e gra i ned absent Cont i nue. to CO T a b l e 11. C o n t i n u e d : q u a r t z o f e l d s p a t h i c r ocks SAMPLE, KSP CHLOHITE EPIDOTE CARBONATE SPHENE OTHER TRACES MAP UNIT 84-614-10 Umsq t r ? t r : a f t e r BI l a t e absent t r TOUR,ZI 84-626-31 Jmsq absent a f t e r BI t r : 1 a t e absent absent OP,AP,ZI 84-626-2W Jmsq tr : u n t w i n n e d a f t e r BI.GT t r : i n PL t r absent OP.AP.ZI 84-819-5 Jmsq absent a f t e r BI l a t e 1 a t e absent OP,AP,RU,ZI 84-78-3A Jmsq:my1 absent a f t e r BI a f t e r PL t r : l a t e l a t e OP.AP.ZI 84-714-13 Jmsq:my1 absent a f t e r BI a f t e r PL absent l a t e OP.AP.ZI Cont i nue. . . to O T a b l e 11. C o n t i n u e d : q u a r t z o f e l d s p a t h i c r o c k s SAMPLE, MAP UNIT PLAGIOCLASE QUARTZ BIOTITE MUSCOVITE GARNET AMPHIBOLE 84-617-3 Jmsq:fe1s i c metavo 1 can 1 c. f i ne gra i ned r i bgrs absent f i n e g r a i n e d , syn-Ds, QZ i nc 1 s absent 84-67-4 Jmsq absent absent 84-68-2 Jmsq r i bgrs absent absent 84-610-1 Jmsq r i bgrs absent 84-727-7 Jmsq absen t t r absent 84-71-5 Jmsq absent absent C o n t i n u e . . . to -J O T a b l e 11. C o n t i n u e d : q u a r t z o f e l d s p a t h i c r o c k s SAMPLE, MAP UNIT KSP CHLOHITE EPIDOTE CARBONATE SPHENE OTHER TRACES 8 4 - 6 1 7 - 3 J m s q : f e l s i c m e t a v o l c a n i c t r ? t r : a f t e r B I a f t e r GT l a t e a b s e n t OP.AP.TOUR.ZI 8 5 - 6 7 - 4 J m s q a b s e n t a f t e r B I , i n GT f r a c t s t r : 1 a t e a b s e n t a b s e n t OP.AP.RU.ZI 8 4 - 6 8 - 2 J m s q a b s e n t a f t e r BI t r t r : i n f r a c t s a b s e n t O P , A P . Z I 8 4 - 6 1 0 - 1 J m s q a b s e n t a b s e n t a b s e n t i n v e i n s OP,AP,TOUR,ZI 8 4 - 7 2 7 - 7 Jmsq t r a f t e r BI a b s e n t a b s e n t a b s e n t O P . A P . Z I 8 4 - 7 1 - 5 J m s q a b s e n t a f t e r BI t r : a f t e r PL a f t e r PL a b s e n t O P . A P . Z I C o n t i n u e . T a b l e 11. C o n t i n u e d : q u a r t z o f e l d s p a t h i c rocks SAMPLE, PLAGIOCLASE QUARTZ BIOTITE MUSCOVITE GARNET AMPHIBOLE MAP UNIT 84- 614-10 + r i b g r s absent l a t e , i n PL absent absent Lkgs i : f r a c t s g r a n o d i o i t i c s i l l 85- 810-1 sauss w e l l developed + + - absent absent s i l l i n Jmsq r i b g r s 84-711-2B + f i n e g r a i n e d + + t r absent f e l s i c s i l l i n Jmsq 84-621-2 sauss r i b g r s t r + absent absent s i l l i n Jmsq 84-77-3A + + + + absent absent JKog2 84-77-5 + + + + absent absent JKog2 Cont i nue. . . NJ - J NJ T a b l e 11. C o n t i n u e d : q u a r t z o f e l d s p a t h i c r o c k s SAMPLE, KSP CHLOHITE EPIDOTE CARBONATE SPHENE OTHER TRACES MAP UNIT 84- 614-10 untwinned t r : a f t e r BI absent absent t r : l a t e O P . A P . Z I LKgs i : granod1 o r i t i c s i l l 85 - 810-1 1n p u l l e d - a f t e r B I , i n GT l a t e absent a b s e n t O P . A P . Z I s i l l i n Jmsq a p a r t s 8> t a i l s f r a c t s a s s o c / w PL 84 -711 -2B untwinned a f t e r BI f i n e g r a i n e d i n t r a b s e n t O P . Z I fe1 s i c s i 11 PL i n Jmsq 84 -621 -2 s i l l i n Jmsq i n p u l 1 - a p a r t s & t a i l s a s s o c w/PL a f t e r BI & p u 1 1 - a p a r t s PL I n i n t r t r : l a t e in v e i n s O P . A P . Z I 8 4 - 7 7 - 3 A i n p u l l - a p a r t s a f t e r BI l a t e absent + O P . A P . Z I JKog2 & t a i l s a s s o c w/PL 8 4 - 7 7 - 5 JKog2 untwi nned t r : a f t e r BI t r absent a b s e n t O P , A P , Z I Cont i nue . NJ T a b l e 11. C o n t i n u e d : q u a r t z o f e l d s p a t h i c rocks SAMPLE, MAP UNIT PLAGIOCLASE QUARTZ BIOTITE MUSCOVITE GARNET AMPHIBOLE 84-711-2A E d s i : metadac i t i c s i l l i n Jmsq f i n e g r a i n e d absent l a t e , i n PL f r a c t s absent absent 84-724-8 Umv:fels i c f i n e g r a i n e d t r absent absent 84-724-6 og3:my1 p e l a s t s r 1bgrs absent absent absent 84-729-7 f e l s i c myl s i l l i n JKog2 n e u t r a l r e l i e f r i b g r s . k i n k t r absent absent 84-817-3 JKog2:my 1 wel1 developed r i b g r s t r absent 85-812-2 Eel:my1 t o n a l i t e medium g r a i n e d , sauss r i bgrs F i n e & medium g r a i n e d , kink t r : i n PL absent absent Cont i nue. to T a b l e 11. C o n t i n u e d : q u a r t z o f e l d s p a t h i c rocks SAMPLE. MAP UNIT KSP CHLOHITE EPIDOTE CARBONATE SPHENE OTHER TRACES 84-711-2A E d s i : metadac i t i c s i l l i n Jmsq untwinned t r : a f t e r BI i n PL & groundmass t r t r OP.AP.ZI 84-724-8 J m v : f e l s i c metavolcan i c t r i n f r a c t s f i n e g r a i n e d absent f i n e g r a i n e d OP,AP,ZI 84-724-6 og3:my 1 i n p u l l - a p a r t s a f t e r BI & in A l l a n i t e c o r e s & t a i l s assoc/w v e i n s PL absent absent OP.AP.ZI 85-729-7 f e l s i c myl s i l l i n JKog2 absent a f t e r BI absent absent absent OP,AP.ZI 84-817-3 JKog2:my 1 t r ? a f t e r BI & GT i n PL absent 1 a t e : t r OP.AP.ZI 84-812-2 Eel:my1 to n a 1 i te absent a f t e r BI t r absent euhed,magma OP.AP.ZI Cont i nue. to Ln T a b l e C o n t i n u e d : q u a r t z o f e l d s p a t h i c rocks SAMPLE, MAP UNIT PLAGIOCLASE QUARTZ BIOTITE MUSCOVITE GARNET AMPHIBOLE 84-710-7 Eel:my1 t o n a 1 i te f i n e g r a i n e d , r i b g r s f i n e g r a i n e d & p e l a s t s i n PL 8. BI p u l 1 - a p a r t s absent absent 84-714-10 Eel:myl t o n a l i t e k i nked,und p e l a s t s t r absent absent 84-726-5 JKog2:myl t o n a l i te r i bgrs f i n e g r a i n e d f i n e g r a i n e d absent 84-721-5 UKog2:myl t o n a l i t e bent 1ame11ae i n p c l a s t s r i bgrs absent- absent absent 85-817-2 JKog2 p o l y g o n i z e d absent t r a b sent 84-82-3 JKog2:myl t o n a 1 i te pc1 a s t s we 11 deve1 oped r i bgrs f i n e g r a i n e d absent absent absent Cont i nue. T a b l e 11. C o n t i n u e d : q u a r t z o f e l d s p a t h i c rocks SAMPLE, MAP UNIT KSP CHLOHITE EPIDOTE CARBONATE SPHENE OTHER TRACES 84-710-7 Eel:myl t o n a l i te absent t r : a f t e r BI in PL absent euhed,magma OP.AP.ZI 84-714- 10 Eel:my1 to n a 1 i t e absent t r A11ani te c o r e s absent euhed,magma OP.AP.ZI 84-726-5 <JKog2 : myl t o n a l i t e t r : i n pul 1 -a p a r t s & t a i l s assoc/w PL a f t e r BI & i n GT f r a c t s t r absent absent OP,AP,ZI 85-721-5 JKog2:myl t o n a 1 i te t r : i n pul 1 -a p a r t s & t a i l s assoc/w PL a f t e r BI i n PL absent absent OP,AP,ZI 84-817-2 JKog2 untwinned, assoc/w myrmek i t e a f t e r BI l a t e absent absent OP.AP.ZI 84-82-3 JKog2:myl t o n a l i te in pu11-aparts S t a i1s assoc/w PL;myrmek i t e a f t e r BI absent absent absent OP.AP.ZI Cont i nue. . . to -J T a b l e 11. C o n t i n u e d : q u a r t z o f e l d s p a t h i c r ocks SAMPLE, PLAGIOCLASE QUARTZ BIOTITE MUSCOVITE GARNET AMPHIBOLE MAP UNIT 84-71-7 + r i b g r s + + absent absent UKog4:myl t o n a l i t e 84-818-8 p c l a s t s , s a u s s kinked, und, + + absent absent JKog4:myl r i b g r s t o n a 1 i t e 84-67-3 + r i b g r s + + absent absent iJKog4 : my 1 t o n a l i t e 85-713-8 ver y sauss r i b g r s t r syn-Ds S l a t e absent absent J K o g 4 : a l t e r e d i n PL myl t o n a l i t e 85-76-2 p c l a s t s p o l y g o n i z e d o c c u r s w/HB absent absent HB:occurs w/BI LKogl:myl hornb1ende t o n a 1 i t e 85-713-4 p c l a s t s f i n e g r a i n e d o c c u r s w/HB HB:occurs w/BI absent absent LKog1:my1 horn b l e n d e t o n a 1 i te Cont i nue.. . 00 T a b l e C o n t i n u e d : q u a r t z o f e l d s p a t h i c r o c k s SAMPLE , MAP UNIT KSP CHLOHITE EPIDOTE CARBONATE SPHENE OTHER TRACES 84-71-7 Ldog4:my1 t o n a l i t e t r t r : a f t e r BI l a t e gloms t r i n PL t r OP.AP.ZI 84-818-8 LJog4:my1 t o n a 1 i t e Minor p e r t h i t e a f t e r BI & i n PL f r a c t s l a t e gloms t r l a t e gloms OP.AP.ZI 85-67-3 Ldog4:my1 t o n a 1 i t e 1n p u l 1 - a p a r t s & t a i 1 s assoc/w PL a f t e r BI & i n ve i ns l a t e i n PL l a t e i n PL t r OP.AP.ZI 85-713-8 t r ? t r a f t e r BI l a t e i n PL l a t e l a t e gloms OP.AP.ZI L d o g 4 : a l t e r e d myl t o n a l i t e 84-76-2 LKogl:myl hornb1ende t o n a 1 1 t e tr:untw i nned, assoc/w myrmek i t e a f t e r EI 8. f r a c t s t r : i n c I s i n HB absent l a t e gloms OP.AP.ZI 84-713-4 LKog1:my1 h o r n b l e n d e t o n a l 1te i n p u l 1 - a p a r t s & t a i l s assoc/w PL;myrmek i t e a f t e r BI & f r a c t s l a t e , f i n e g r a i n e d i n matr i x absent OP,AP,ZI Cont i nue. . . Table 11. Continued: quartzofeldspathic rocks SAMPLE. PLAGIOCLASE QUARTZ BIOTITE MUSCOVITE GARNET AMPHIBOLE MAP UNIT 85-76-2 + kink.und absent absent absent ' HB:fine grained s i l l in LKog1 84-82-2 + und.polygonized assoc/w absent absent HB:poik, QZ MKqd:foliated (after?)HB incls quartz diorite 85-724-3 AB ribgrs absent tr absent absent og3:brecc i ated myl metavolcanic 85-725-5 AB ribgrs absent tr absent absent og3:myl Cont i nue. . . to oo o T a b l e 11. C o n t i n u e d : q u a r t z o f e l d s p a t h i c rocks SAMPLE, KSP CHLOHITE EPIDOTE CARBONATE SPHENE OTHER TRACES MAP UNIT 84-76-2 t r ? i n f r a c t s t r S absent i n f r a c t s OP.AP.ZI s i l l i n LKogl 84-82-2 absent t r a f t e r BI t r absent absent OP.AP.ZI M K q d : f o l i a t e d q u a r t z d i o r i t e 85-724-3 absent syn-Ds & i n syn-Ds ft i n absent + OP.ZI o g 3 : b r e c c i a t e d v e i n s v e i n s myl m e t a v o l c a n i c 85-725-5 t r ? syn-Ds & v e i n p re- or syn-Ds syn-Ds t r OP.AP.ZI og3:myl Cont i nue. . . M CO T a b l e 11. Co n t i n u e d : mafic to i n t e r m e d i a t e m e t a v o l c a n i c rocks and a m p h i b o l i t e s SAMPLE, PLAGIOCLASE QUARTZ BIOTITE MUSCOVITE GARNET AMPHIBOLE MAP UNIT 85-68-1 OLIG r i b g r s + absent medium A c t i n o l i t i c HB a m p h i b o l i t e i n grained,QZ Jmsp i n c I s 84-78-7A t r ? r i b g r s + absent r o l l e d . E P i n c l s A c t i n o l i t i c HB amp h i b o l i te i n Umsq 84-615-2 OLIG kink,und syn-Ds absent + A c t i n o l i t i c a m p h i b o l i t e i n HB:poik/QZ Jmsq i n c l s 84-614-10 OLIG kink,und syn-Ds & i n GT absent + A c t i n o l i t i c a m p h i b o l i t e In f r a c t s HB:poik QZ Jmsq " i n c l s 84-620-4 OLIG f i n e g r a i n e d syn-Ds & i n absent absent A c t i n o l i t i c HB a m p h i b o l i t e i n f r a c t s Jmsq 84-626-6 OLIG + amphi b o l 1 t e i n Jmsq Cont i nue. . . syn-Ds absent absent Act i no 1i t i c HB:poik QZ i n c l s M 00 M T a b l e 11. C o n t i n u e d : m a f i c t o i n t e r m e d i a t e m e t a v o l c a n i c r o c k s and a m p h i b o l i t e s SAMPLE, KSP CHLOHITE EPIDOTE CARBONATE SPHENE OTHER TRACES MAP UNIT 85-68-1 absent t r : a f t e r BI & absent l a t e absent OP.AP.ZI? a m p h i b o l i t e i n i n f r a c t s Jmsp 84-76-7A absent a f t e r BI l a t e l a t e absent OP.AP.ZI? a m p h i b o l i t e i n Jmsq 84-615-2 absent a f t e r BI & i n n o n - o r i e n t e d absent t r OP, AP a m p h i b o l i t e i n v e i n s Jmsq 84-614-10 absent a f t e r BI t r l a t e t r l a t e + OP.AP? a m p h i b o l i t e i n Jmsq 84-620-4 absent a f t e r BI abundant:1 a t e t r t r OP.AP.ZI a m p h i b o l i t e i n Jmsq 84-626-6 absent a f t e r GI abundant:1 a t e absent absent OP.AP amph i b o l i t e i n Jmsq Cont i nue. . . to CO LU T a b l e 11. C o n t i n u e d : m a f i c to i n t e r m e d i a t e m e t a v o l c a n i c rocks and a m p h i b o l i t e s SAMPLE, PLAGIOCLASE QUARTZ BIOTITE MUSCOVITE GARNET AMPHIBOLE MAP UNIT 84-614-5 OLIG f i n e g r a i n e d syn-Ds & i n GT absent medium A c t i n o l i t i c HB a m p h i b o l i t e i n f r a c t grained,QZ Jmsp i n c l s 84-71-5 OLIG f i n e g r a i n e d + absent f i n e g r a i n e d A c t i n o l i t i c a m p h i b o l i t e i n HB:QZ i n c l s Jmsq 84-622-5 OLIG/ANDES f i n e g r a i n e d syn-Ds absent medium g r a i n e d , A c t i n o l i t i c HB a m p h i b o l i t e i n Very poik:QZ Jmsp i n c l s 84-725-4 Jmv2 : metavolcan 1c ANDES:AN3 r i bgrs absent absent absent A c t i n o l i t i c HB:f i ne gra i ned, p a r a 1 l e i to Ls 84-728-11 OLIG/ANDES:fine f i n e g r a i n e d syn-Ds & i n absent absent A c t i n o l i t i c HB Jmv2: g r a i n e d ; l a r g e f r a c t s m e t a v o l c a n i c p c l a s t s r e p l a c e d by EP 84-721-4 OLIG/ANDES:sauss amph1 bo 1 i t e i n JKog2 Cont i nue. . . to oo r i b g r s t r : a f t e r absent absent A c t i n o l i t i c amphibole? HB:syn-Ds T a b l e 11. C o n t i n u e d : m a f i c to i n t e r m e d i a t e m e t a v o l c a n i c rocks and a m p h i b o l i t e s SAMPLE, KSP CHLOHITE EPIDOTE CARBONATE SPHENE OTHER TRACES MAP UNIT 85-614-5 absent t r : a f t e r BI S absent l a t e gloms OP.AP.ZI? a m p h i b o l i t e i n assos/w GT Jmsp 84-71-5 absent t r : a f t e r BI f i n e g r a i n e d , absent absent OP.AP.ZI? a m p h i b o l i t e i n e v e n l y Jmsq d i s t r i b u t e d 84-622-5 absent a f t e r BI, i n GT t r ? absent t r ? OP.AP a m p h i b o l i t e i n f r a c t s & HB Jmsp p u l l - a p a r t s 84-725-4 absent a f t e r BI & i n g l o m s : l a t e t r l a t e absent OP.AP? Jrnv2: v e i n s metavolcan i c 84-728-11 absent a f t e r BI & in a f t e r P L : l a t e t r : v e i n absent OP.AP Jmv2: v e i n s metavolcan i c 84-721-4 absent a f t e r BI a f t e r P L : l a t e absent absent OP.AP amph i b o l i t e i n JKog2 Cont i nue. . . M CO LTI T a b l e 11. C o n t i n u e d : m a f i c to Inte r m e d i a t e m e t a v o l c a n i c rocks and a m p h i b o l i t e s SAMPLE, PLAGIOCLASE QUARTZ BIOTITE MUSCOVITE GARNET AMPHIBOLE MAP UNIT 84-821-3 OLIG/ANDES kink,und syn-Ds absent absent A c t i n o l i t i c Jmv2: HB:po1k, QZ m e t a v o l c a n i c i n c l s 84-714-13 v e r y f i n e f i n e g r a i n e d & t r abundant f i n e A c t i n o l i t e : a m p h i b o l i t e g r a i n e d f r e s h & r i b g r s g r a i n e d : s y n - D s syn-Ds w i t h i n Jmsq a l t e r e d p c l a s t s 84-73-10 A N 4 , s a u s s und,kinked absent syn-Ds absent absent Jmvl : meta v o l c a n i c 84-72-12 A N J , s a u s s f i n e g r a i n e d t r i n P L absent absent Jmvl : m e t a v o l c a n i c 85-67-5 A N 3 - 5 , f i n e r i b g r s t r i n P L absent A c t i n o l i t e : Jmvl: g r a i n e d , sauss syn-Ds m e t a v o l c a n i c p c l a s t s 85-621-4 AB r i b g r s t r i n P L absent A c t i n o l i t e : Jmv1: syn-Ds metavo1 can i c Cont i nue. . . NJ 00 CTi T a b l e 11. C o n t i n u e d : m a f i c t o i n t e r m e d i a t e m e t a v o l c a n i c r o c k s and a m p h i b o l i t e s SAMPLE, KSP CHLOHITE EPIDOTE CARBONATE SPHENE OTHER TRACES MAP UNIT 84-821-3 absent a f t e r BI + absent absent OP.AP.ZI? Jmv2 : m e t a v o l c a n i c 84-714-13 absent syn-Ds & a f t e r syn- & post Ds t r i n v e i n s t r ? OP.AP.ZI? amph i bo 1i t e 1 n BI Jmsq 84-73-10 absent syn-Ds syn-Ds absent + OP.AP Umv1 : m e t a v o l c a n i c 84-72-12 absent syn-Ds syn-Ds i n m a t r i x & + OP.AP <Jmv1: v e i n s : s y n - & m e t a v o l c a n i c p o s t Ds 84- 67-5 absent syn-Ds, a f t e r syn-Ds & a f t e r t r : v e i n + OP.AP dmvl: BI & i n v e i n s PL m e t a v o l c a n i c 85- 621-4 absent syn-Ds, a f t e r syn-Ds & a f t e r absent t r OP.AP <Jmv1: BI 8 i n v e i n s PL m e t a v o l c a n i c Cont i nue. . . IV) CO T a b l e 1 1 . C o n t i n u e d : mafic to i n t e r m e d i a t e m e t a v o l c a n i c rocks and a m p h i b o l i t e s SAMPLE, PLAGIOCLASE QUARTZ BIOTITE MUSCOVITE GARNET AMPHIBOLE MAP UNIT 8 4 - 7 2 4 - 6 AB,sauss r i b g r s syn-Ds t r ? absent A c t i n o l i t e : Jmvl: syn-Ds m e t a v o l c a n i c 8 4 - 7 2 6 - 4 AB,sauss r i b g r s t r absent absent A c t i n o l i t e : Jmv1: syn-Ds m e t a v o l c a n i c 8 4 - 8 1 7 - 1 AB r i b g r s syn-Ds absent absent A c t i n o l i t e : Jmvl: syn-Ds metavo1 can i c 8 5 - 8 1 6 - 1 t r ? f i n e g r a i n e d absent absent absent absent Jmv 1 : metavo1 can i c 8 4 - 8 2 4 - 3 A A N s - i , s a u s s Very f i n e syn-Ds absent absent absent Jmsq: p c l a s t s g r a i n e d metavolcan i c Cont i nue. . . to 00 00 T a b l e 11. C o n t i n u e d : m a f i c to i n t e r m e d i a t e m e t a v o l c a n i c rocks and a m p h i b o l i t e s SAMPLE, KSP CHLOHITE EPIDOTE CARBONATE SPHENE OTHER TRACES MAP UNIT 84-724-6 absent t r syn- & post-Ds absent t r OP.AP.ZI Jmv 1 : metavolcan i c 84-726-4 absent syn-Ds & a f t e r syn- & post Ds absent + OP.AP Jmvl: BI m e t a v o l c a n i c 84- 817-1 absent a f t e r BI syn -& post-Ds absent t r OP.AP Jmv 1 : metavo1cani c 85- 816-1 absent syn-Ds syn-Ds syn-Ds syn-Ds:gloms OP.AP Jmv 1 : metavolcan i c 84-824-3A absent syn-Ds l a t e gloms l a t e absent OP.AP Jmsq: metavolcan i c to co APPENDICES / 290 6. APPENDIX 6. ELECTRON MICROPROBE ANALYTICAL PROCEDURES, MINERAL ANALYSES AND CALCULATED THERMOBAROMETRY 6.1. Electron microprobe analytical procedures A four channel automated Cameca SX-50 electron microprobe was used to determine the chemical compositions of garnet-biotite and garnet-plagioclase pairs in metapelitic rocks and hornblende from metaplutonic rocks of the TLMC Ductilely Sheared Assemblage. Analyses were performed on polished, carbon coated thin sections. All chosen garnet-biotite and garnet-plagioclase pairs were in physical contact with each other and 10-30 of each type were analysed within a sample when sufficient fresh material was present Most of these garnet analyses were performed on rims, however there were some biotite or plagioclase inclusion and adjacent garnet core determinations made for sample 85- 76- 3A. Additional core analyses for selected garnet and plagioclase grains were performed to determine core-rim chemical zonation. The microprobe operating conditions were, a specimen current of 49-50 nanoamps, an acceleration potential of 15 kv and a beam diameter of 3-Sum. Counting times were 10 seconds, except for Si, Al, Fe, Mg, Mn and Na in hornblende where 15 second counting times were used. 6.2. Mineral analytical data Standards used in calibration schemes for mineral analyses are reported in Table 12. Mineral analyses of garnet biotite, plagioclase and hornblende from the TLMC are listed in Table 13. T a b l e 12: M i c r o p r o b e s t a n d a r d s f o r m i n e r a l a n a l y s e s E1ement St a n d a r d ID Number Source GARNET S1,Al,Mg,Ca g a r n e t 278 South A f r i c a Fe f a y a l 1 t e 250 s y n t h e t I c Mn . pyroxmangi te 245 Japan T i h ornblende 229 New Z e a l a n d BIOTITE S i , T i , C a hornblende 229 New Z e a l a n d A l ,K o r t h o c l a s e 96 New York, U.S.A. Mg f o r s t e r 1 t e 275 A r i z o n a , U.S.A. Fe f a y a l 1 t e 250 s y n t h e t i c Mn pyroxmang i t e 245 Japan Na a n o r t h o c l a s e 365 l o c a t i o n unknown PLAGIOCLASE S i ,K m l c r o c l i n e 276 l o c a t i o n unknown Al ,Ca a n o r t h i t e 369 Japan Fe f a y a l i t e 250 s y n t h e t i c Na a n o r t h o c l a s e 365 l o c a t i o n unknown HORNBLENDE Si,Mg,Ca pyroxene 378 New Mex i c o , U.S.A. A l o r t h o c l a s e 96 New York, U.S.A. T i,Na,K hornblende 229 New Z e a l a n d Fe f a y a l i t e 250 s y n t h e t i c Mn pyroxmangi te 245 Japan NJ t-1 Table 13: Electron microprobe analytical data from the TLMC Garnet! 84~76"~7A G23 G22 103 104 105 Si 37.129 37.171 37.017 Al 20.843 21.145 21.160 Fe 30.499 31.153 31.697 Fe 0.000 0.000 0.000 Mg 1.529 1.540 1.456 Mn 2.811 2.945 3.295 Ca 6.986 6.680 6.459 Ti 0.090 0.095 0.087 99.887 100.730 101.171 G21 G20 G19 G18 616 Q15 G14 G13 FM AL PY SP GR 106 37.430 21.081 30.874 0.000 1.434 3.056 6.771 0.198 100.845 107 36.463 21.206 30.741 0.000 1.656 2.652 6.953 0.013 99.685 108 36.690 21.022 30.848 0.000 1.525 2.841 7.014 0.117 109 37.126 21.098 30.861 0.000 1.615 2.634 6.926 0.125 Si 5.9S4 5.952 5.924 5.979 Al 3.959 1 3.991 3.991 3.969 Fe 4.111 4.172 4.242 4.124 Fe 0.000 0.000 0.000 0.000 Mg 0.367. 0.368 0.347 0.341 Mn 0.384 i 0.399 0,447 0.414 Ca 1.206 1.146 1.107 1.159 Ti 0.011 0.011 0.010 0.024 16.023 16.039 16.068 16.010 Number of 5.900 4.044 4.160 0.000 0.400 0.363 1.205 0.002 16.074 100.058 100.386 Ions on the 5.921 3.998 4.163 0.000 0.367 0.388 1.213 0.014 16.064 5.955 3.989 4.140 0.000 0.386 0.358 1.190 0.015 16.033 End members 92.446 67.816 6.059 6.331 19.632 92.556 68.636 6.049 6.573 18.575 93.104 69.120 5.658 7.278 17.790 93.001 68.466 5.669 6.865 18.644 91.885 67.890 6.529 5.933 19.633 92.539 67.995 5.993 6.342 19.461 92.094 68.256 6.366 5.901 19.253 110 37.015 21.302 30.301 0.000 1.582 2.950 7.353 0.035 100.539 bas 1 s 5,929 4.021 4.059 0.000 0,378 0.400 1.262 0.004 16.054 (%) 92.192 66.580 6.195 6.566 20.596 111 36.626 21.240 31.514 0.000 1.501 3.046 6.457 0.073 100.457 Of 24 5.899 4.032 4.245 0.000 0.360 0.416 1.114 0.009 16.074 92.825 69.250 5.877 6.780 17.962   G12 G11 G10 G9 112 113 114 115 120 121 122 123 37.067 37.062 37.167 37.411 37.473 36.970 37.026 37.244 21.132 21.213 21.109 21,338 .. 21.206 21.209 21.289 21.174 31.216 31.087 31.580 31.401 . 30.587 30.869 31.004 30.938 0,000 0.000 0.000 0.000 0.000 0.000 0.000 0,000 1,474 1.496 1.532 1.656 1.504 1.438 1.474 1.608 3.001 3.091 3.114 2.775 3.202 3.534 3.254 2.901 6.880 7.259 6.726 6.582 6,870 6.564 6.396 6.995 0.065 0.032 0.077 0.038 0.112 0.098 0.073 0.125 100.834101.290 101.306 101.202 100.953 100.682 100.515 100.985 (O) 5.938 5,915 5.934 5.556 5.975 5.932 5.942 5.945 3.990 3,990 3,972 4.004 3.985 4.011 4.027 3.984 4.182 4.149 4.216 4.181 4.079 4.142 4.161 4.130 0.000 0.000 0.000 0.000 0.000 0.000 0,000 0.000 0.352 0.356 0.365 0.393 0.357 0,344 0.353 0.383 0,407 0.418 0.421 0.374 0,433 0.480 0.442 0.392 1.181 1.241 1.151 1.123 . 1.174 1.128 1.100 1.196 0.008 0.010 0.009 0.005 0.013 0.012 0.009 0.015 16.057 16.07? 16.063 16.035 16.016 16.049 16,033 16,045 92.877 92.773 92.711 92.056 92.658 93.077 92.885 92.198 68.363 67.375 68.591 68.898 67.591 68.042 68.772 67.791 5.754 5.777 5,931 6.479 5.923 5.648 5.828 6.281 6.656 6.786 6.852 6.167 7.167 7.890 7.311 6.433 19.112 19.918 18.492 18.389 19.118 19,244 17.957 19.267 Oxides: S1»S10i: A1=A1,OJ; Fe=FeO; Mg=MgO; Mn=MnO; Ca=CaO: T1=T10> FM=(FeO+MnO/FeO+MnO+MgO)* 100 to Table 13: Electron microprobe analytical data: continued Qametl 84~76~7A Q7 G6 G5 G4 G3 G2 G1 124 125 126 127 128 129 130 Si 37,306 36.885 36.630 36.579 36.675 36.506 36.540 Al 21.276 21.030 21.191 21.162 21.215 21.047 20.983 Fe 30.331 30.559 31.173 31.655 31.114 31.155 30.934 0.000 0.000 0.000 0.000 0.000 0.000 0.000 Mg 1.501 1.414 1.466 1.529 1.583 1.542 1.454 Mn 2.997 2.881 3.111 3.047 2.945 2.894 3.126 Ca 7.237 7.274 6.680 6.692 6.915 6.477 6.918 Ti 0.060 0.128 0.065 0.155 0.112 0.167 0.117 100.707 100.171 100.315 100.819 100.560 99.788 100.072 Number of Ions on the basis of 24 (O) Si 5.960 5.939 5.905 5.879 5,895 5.911 5.907 Al 4.006 3.991 4.026 4.009 4.019 4.016 3.998 Fe 4.052 4.115 4.202 4.255 4.182 4.218 4,182 Fe 0.000 0.000 0.000 0.000 0.000 0.000 0.000 Mg 0.357 0.339 0.352 0.366 0.379 0.372 0.350 Mn 0.406 0.393 0.425 0.415 0.401 0.397 0.428 Ca 1.239 1.255 1.154 1.152 1.191 1.124 1.198 Ti 0.007 0.016 0.008 0.019 0.014 0.C20 0.014 16.027 16.047 16.072 16.095 16.080 16.058 16.077 End members (%) FM 92.579 92.997 92.927 92.727 92.355 92.538 92.936 AL 66.985 67.535 68.574 68.879 68.055 69.168 67.999 PY 5.907 5.571 5.747 5.929 6.173 6.102 5.697 SP 6.704 6.448 6.931 6.716 6\525 6.507 6.960 GR 20.298 20.215 18.633 18.202 19.048 17.924 19.136 Oxides: S1=S10>; Al=A1»Oi; Fe=FeO; Mg=MgO; Mn*MnO: Ca=CaO; T1=T10> FM=(FeO+MnO/FeO+MnO+MgO)*lOO Table 13: Electron microprobe analytical data: continued QamOt: 8 5 _ 6 1 0" 1 02 04 01 0 5 0 6 08 010 011 14 15 20 21 22 23 24 25 26 27 28 29 30 31 Si 37.482 37.445 37.800 37.411 37.287 36.737 36.714 37.304 37.328 37.347 37.229 37.150 37.047 37.206 Al 21.680 21.619 21.574 21.432 21.111 20.979 21.194 \ 21.255 21.096 21.438 21.200 21.285 21.194 21.614 „ Fe 33.092 33.844 33.316 32.888 33.539 33.480 33.806 33.398 33.349 33.376 33.529 32.768 33.117 33.385 g Fe 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0,000 0.000 0.000 0.000 x.Mg 3.192 3.225 3.205 3.024 2.761 2.699 3.195 2.993 3.053 2.882 2.918 3.131 3.220 3.276 ° Mn 0.284 0.216 0.185 0.227 0.226 0.287 0.239 0.289 0.309 0.252 0.260 0.220 0,241 0.333 Ca 5.440 5.129 5.152 5.439 5.721 5.719 5.103 5.366 5.085 5.787 5.615 5.419 5.015 4.750 Ti 0.033 0.062 0.083 0.045 0.103 0.037 0.062 0.067 0.062 0.028 0.062 0.042 0.000 0.045 101.203 101.541 101.315 100.467 100.749 99.938 100.312 100.672 100.280 101.110 100,813 100.013 99.835 100.609 Number of ions on the basis of 24 (0) Si 5.924 5.912 5.961 5.953 5.944 5.916 5.886 5.942 5.964 5,925 5.930 5.941 5.941 5.913 Al 4.038 4.023 4.010 4.019 3.966 3.982 4.004 3.990 3.973 4.009 3.980 4.012 4.006 4.052 Fe 4.374 4.469 4.393 4.376 4.471 4.509 4.532 4,448 4.456 4.428 4.466 4.382 4.442 4.441 Fe 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 Mg 0.752 0.759 0.753 0.717 0.656 0.648 0.763 0.711 0,727 0.631 0,693 0.746 0.770 0.777 Mn 0,038 0.029 0.025 0.031 0,031 0.039 0.032 0,03? 0.042 0.034 0.035 0.030 0.033 0.045 Ca " 0.921 0.863 0.870 0.927 0.977 0.987 0.876 0.916 0.370 0.984 0.958 0.929 0.862 0,310 Ti 0.004 0.007 0,010 0.005 0.012 0.004 0.007 0.008 0.007 0,003 0.00" 0.005 0.000 0.005 16.051 16,067 16.022 16.029 16.058 16.086 16.102 16.053 16.040 16.065 16.070 16,045 16,053 16.045 End members (%) FM 85.438 85.561 85.432 86.002 87.281 87.530 85.670 86.331 86.036 86.751 86,661 85.533 85.322 85.239 AL 71.907 73.020 72.788 72.357 72.970 72.959 73.098 72.819 73.160 72.235 72.646 72.032 72.744 73.174 PY 12.362 12.402 12.481 11.860 10.706 10.485 12.314 jn.631 11.936 11,126 11.270 12.266 12.607 12.800 SP 0.625 0.471 0.409 0.506 0.498 0.633 0.523 0,639 0.686 0.552 0.570 0.489 0.537 0.740 GR 15.048 14.000 14.175 15.197 15.645 15.858 13.957 14.794 14.109 15.977 15.497 15.139 14.113 13.207 Oxides: S1=S10.; Al*AliO>; Fe=FeO; Mg=MgO; Mn=MnO; Ca=CaO; T1=T10< FM=(FeO+MnO/FeO+MnO+MgO)* 100 to Table 13: Electron microprobe analytical data: continued QfimOt! 85—610*~T G22 025 G26 G27 G28 G29 73 74 78 79 81 86 88 89 90 91 92 93 94 95 Si 37.323 37.362 37.832 37.648 37.772 37.492 37.753 37,321 37.383 36.643 37.268 37.728 36.930 37.223 Al 21.767 21.618 21.865 21.808 22.003 21.408 21.833 21.013 21.049 20.835 20.947 21.304 20.920 20.886 Fe 33.426 33.193 33.081 33.097 33.123 33.416 33.116 33.111 33.678 33.314 33.493 32.746 34.650 34.423 Fe 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 Mg 2.888 3.167 3.135 3.086 3.101 3.116 3.072 3.000 2.792 2.880 2.872 2.756 2.252 2.306 Mn 0.146 0.292 0.265 0.294 0.252 0.272 0.234 0.241 0.297 0.189 0.235 0.243 0.500 0.465 Ca 5.257 5.201 5.227 5.178 5.141 5.041 5.211 5.199 5.563 5.367 5.314 5.425 5.005 4.971 Ti 0.062 0.037 0.070 0.132 0.050 0.008 • 0.017 0.095 0.070 0.128 0.103 0.070 0.053 0.058 100.869 100.869 101.477 101.244 101.441 100.754 101.236 99.981 100.833 99.357 100.232 100.270 100.314 100.333 Number of ions on the basis of 24 (O) Si 5.922 5.926 5.950 5.939 5.942 5.956 5.953 5.976 5.956 5.926 5.966 6.006 5.946 5.979 Al 4.071 4.041 4.053 4.055 4.079 4.008 4.058 3.965 3.952 3.972 3.952 3.997 3.970 3.954 Fe 4.436 4.403 4.351 4.366 4.357 4.439 4.367 4.434 4.487 4.506 4.484 4.360 4,665 4.624 Fe 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 Mg 0.683 0.749 0.735 0.726 0,727 0.738 0.722 0.716 0,66? 0.694 0.685 0.654 0.540 0,552 Mn 0.020 0.039 0.035 0.039 0.034 0.037 0.031 0.033 0.0*0 0.026 0.032 0.033 0.068 0.063 Ca 0.894 0.884 0.881 0.875 0.866 0.858 0.880 0.892 0,950 0.930 0.911 0.925 0.863 0.856 Ti 0.007 0.004 0.008 0.016 0.006 0.001 0.002 0.011 0.008 0.016 0.012 0.008 0.007 0.007 16.032 16.046 16.013 16.016 16,010 16.037 16,013 16.027 16.057 16.070 16.043 15.984 16.060 16.035 End members (54) FM 86.705 85.576 85.648 85.860 85.795 85.850 85,896 86.185 37.225 86.714 86.824 87.041 89.754 89.461 AL 73.587 72.511 72.550 72.807 72.855 73,121 72.789 73.073 73.141 73.305 73.446 73.067 76.069 75.918 PY 11.334 12.331 12.256 12\099 12.156 12.151 12,037 11.799 10.808 11.296 11.225 10.960 8.811 9.066 SP 0.325 0.646 0.588 0.656 0.561 0.604 0.520 0.540 0.653 0.420 0.522 0.549 1.111 1.038 GR 14.644 14.448 14.481 14.204 14.339 14.109 14.624 14.419 15.274 14.750 14.624 15.298 13.905 13.873 Oxides: S1=SiOr; A 1 = A 1 » O J ; Fe=FeO; Mg=MgO; Mn=MnO; Ca=CaO: Ti=TiO, FM=(FeO+MnO/FeO+MnO+MgO)* 1 0 0 to T a b l e 13: E l e c t r o n m i c r o p r o b e a n a l y t i c a l d a t a : c o n t i n u e d Gamott 85~610~1 Q12 Q13 Q14 Q15 50 52 53 54 55 56 57 58 59 Si 37.477 37.695 37.452 37.469 37.163 37.717 37.638 37.931 37.912 Al 21.716 21.861 21.850 21.808 21.895 21.602 21.648 21.757 21.525 Fe 33.425 33.051 33.565 32.654 33.247 33.523 33.196 32.595 33.388 Fe 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 Mq 3.122 2.827 2.822 2.701 2.761 2.711 2.809 j 2.822 2.749 Mn 0.216 0.275 0.225 0.225 0.198 0,235 0.284 ' 0.240 0.216 Ca 4.946 5.733 5.502 5.865 5.490 5.421 5.314 5.457 5.296 Ti 0.050 0.062 0.120 0.078 0.012 0.037 0.107 0.087 0.062 100.952 101.504 101.535 100.801 100.766 101.245 100.995 100.889 101.147 ! Number of Ions on the basis of Si 5.936 5.937 5.910 5.938 5.905 5,964 5.958 5.990 5.992 Al 4.054 4.058 4.064 4.074 4.101 4.026 4.039 4.049 4.009 Fe 4. d?7 4.353 4.42? 4,328 4,418 4,433 4.395 4.304 4.413 Fe 0.000 ' 0.000 0.000 0.009 0.000 0.000 0.000 0.000 0.000 Mq 0.737 0.664 0.664 0.638 0.654 0.639 0.663 0.664 0.648 Mn 0.029 0.037 0.030 0.030 0.027 0.0 3i 0.038 0.032 0.029 Ca 0.83? 0.967 0.330 0.996 0,?35 0.913 0.901 0.923 0.897 Ti 0.006 0.007 0.014 0.003 0.001 0,004 0.013 0.010 0.007 16.029 16.024 16.041 16.013 16.041 16,016 16,007 15.973 15.994 End members (%) FM 85.807 86.867 87.044 87.229 87.175 87.479 86.993 86.717 87.275 AL 73.432 72.353 73.276 72.294 73.238 73.647 73.376 72.736 73.772 PY 12.226 11.031 10.981 10.658 10.839 10.616 11.066 11.224 10.827 SP 0.480 0.610 0.497 0.504 0.441 0.523 0.636 0.543 0.483 GR 13.774 15.896 15.035 16.403 15.461 15.149 14.731 15.340 14.809 Q16 G18 G21 60 61 68 69 70 71 72 37.847 37.802 37.514 37.332 37.475 37.390 37,659 21.689 21.969 21.740 21.489 21.731 21.446 21.381 33.262 32.887 33.406 33.466 33.438 33.690 33.263 0.000 0.000 0.000 0.000 0.000 0.000 0.000 2.820 2.928 2.900 2.824 2.890 2.981 3.000 0.200 0.232 0.239 0.252 0.318 0.260 0.232 5.451 5.367 5.043 5.387 5.397 5.262 5.115 0.058 0.028 0.067 0.067 0.045 0.045 0.107 .01.329 101.215 100.908 100.816 101.293 101.073 100.758 24 (O) 5.969 5.956 5,945 5.935 5.926 5.933 5.975 4.032 4.080 4.061 4.027 4.050 4.011 3.998 4.387 4.333 4.427 4.450 4.422 4.470 4.414 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.663 0.638 0.685 0.669 0.681 0.705 0.709 0.027 0.031 0.032 0.034 0.043 0.035 0.031 0.921 0.906 0.856 0.918 0,914 0.895 0.870 0.007 0.003 0.008 0.008 0.005 0.005 0.013 16.006 15.998 16.014 16.041 16.041 16.054 16.010 86.940 96.388 86.684 87.013 86.762 86.468 86.237 73.192 72.754 73.839 73.358 73.007 73.264 73.362 11.062 11.546 11.425 11.032 11.247 11.555 11.791 0.446 0.521 0.535 0.559 0.702 0.572 0.519 15.196 15.128 14.082 14.932 14.964 14.530 14.137 Oxides: S1=S10»; Al°AlrOi; Fe=FeO; Mg=MgO; Mn=MnO; Ca=CaO; Ti=T10, FM=(FeO+MnO/FeO+MnO+MgO)* 100 NJ Table 13: Electron microprobe analytical data: continued QamOt! 84~622~4 01 03 04 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 Si 37.223 37.067 37.096 37.154 37.377 36.677 37.024 37.201 37.133 37.191 36.835 37.133 36.641 36.327 36.705 37.096 36.900 Al 21.491 21.482 21.720 21.619 21.516 21.364 21.548 21.561 21.653 21.542 21.563 21.485 21.030 21.236 21.225 21.361 21.537 Fe 33.802 33.686 33.273 33.345 32.874 32.082 31.966 32.755 32.535 32.100 31.992 30.261 30.959 29.439 31.033 32.319 32.831 Fe 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 Mq 2.905 3.036 2.351 2.834 2.054 3.880 3.780 2.683 2.333 2.031 1.698 1.471 1.516 1.436 1.723 1.801 2.315 Mn 0.183 0.178 0.147 0.186 0.182 0.068 0.062 0.121 0.125 0.142 1.450 2.629 2.629 3.062 2.318 0.626 0.147 Ca 5.122 4.991 6.190 5.567 6.786 5.316 5.481 5.965 6.541 7.571 6.573 7.407 7.041 7.498 7.038 7.104 6.372 Ti 0.033 0.097 0.025 0.022 0.025 0.050 0.067 0.000 0.092 0.067 0.092 0.142 0.125 0.133 0.060 0.082 0.098 100.760 100.516 100.803 100.728 100.814 99.437 99.927 100.286 100.417 100.643 100.203 100.528 99.940 99.631 100.101 100.388 100.250 Number of Ions on the basis of 24 (0) 5.885 5.902 5.936 5.921 5.923 5.913 5.936 5.918 5.940 5.910 5.938 5.905 4.040 4.048 4.054 4.069 4.044 4.080. 4.048 4.003 4.037 4.028 4.029 4.071 4.305 4.262 4.370 4.339 4.276 4.295 4.045 4.182 3.971 4.178 4.326 4.393 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 C.000 0.000 0.000 0.000 0.923 0.898 0.638 0-556 0.482 0.406 0.350 ' 0.365 0.345 0.413 0.430 0.552 0.009 0.008 0.016 0.017 0.019 0.197 0.356 0.360 0.418 0.316 CO?" O.OZ'O 0.314 0.936 1.020 1.128 1.292 1.131 1.269 1.219 1.296 1.214 1.218 1.092 0.006 0.008 0.000 0.011 0.008 0.011 0.017 0.015 0.016 0.007 0.010 0.012 16,087 16.063 16.035 16.030 16.044 16.033 16.021 16.062 16.023 16.067 16.035 16.045 End members (%) 82.298 82.619 87.303 88.685 89.905 91.706 92.625 92.563 92.708 91.576 91.125 88.881 69.971 69.867 72.304 72.043 70.505 71.316 67.308 68.378 65.956 68.301 71.470 72.608 15.083 14.727 10.555 9.227 7.952 6.746 5.831 5.966 5.734 6.758 7.098 9.124 0.151 0.137 0.271 0.281 0.316 3.274 5.923 5.881 6.947 5.167 1.403 0.330 14.706 15.151 16.870 18.284 21.108 18.498 20.684 19.551 21.120 19.668 19.883 17.762 Si 5.926 5.913 5.907 5.913 5.948 Al 4.033 4.039 4.076 4.055 4.035 Fe 4.500 4.491 4.430 4.438 4.375 Fe 0,000 0.000 0.000 0.000 0.000 Mg 0.689 0.722 0.558 0.672 0.487 Mn 0.025 0.024 0.020 0.025 0.025 Ca 0.874 0.853 1.056 0.949 1.157 Ti 0.004 0.012 0.003 0.003 0.003 16.051 16.053 16.050 16.055 16.029 FM 86.780 86.216 88.858 86.910 90.028 AL 73.948 73.829 73.079 72.956 72.408 PY 11.327 11.867 9.204 11.051 8r065 SP 0.406 0.396 0.327 0.412 0.406 GR 14.259 13.737 17.345 15.543 19.076 Oxides: SI'SIOi; A1=A1iOi; Fe=FeO: Mg=MgO: Mn=MnO; Ca=CaO; T1=T10; FM=(FeO+MnO/FeO+MnO+MgO ) * 100 VO Table 13: Electron microprobe analytical data: continued G&rFtGt! 8 4 _ 6 2 2 — 4 in 241 242 248 249 250 251 252 253 254 Si 37.550 37.501 37.062 37.030 37.488 37.302 37.484 36.887 37t069 Al 21.754 21.580 21.270 21.317 21.612 21.491 21.584 21.907 21.593 Fe 33.756 33.567 28.135 31.908 33.254 33.657 32.825 32.741 33.007 Fe 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 Ho 0,CXC 2.888 1.204 1.960 3.338 3.180 3.208 3.306 2.806 Mn 0.121 0.170 5.605 0.617 0.121 0.108 0.179 0.098 0.160 Ca 4.873 5.037 7.020 6.782 5.176 4.882 4.802 5.004 5.479 Ti 0.000 0.120 0.145 0.052 0.090 0.022 0.065 0.073 0.073 0 1 3 G16 G17 G18 Q19 021 255 256 257 258 259 260 261 37.208 37.129 37.236 37.407 37.497 37.439 37.195 21.360 21.797 21.536 21.602 21.693 21.808 21.680 32.819 33.841 33.462 33.458 32.874 33.689 33.780 0.000 0.000 0.000 0.000 0.000 0.000 0.000 « M  3.212 2.650 3.026 3.250 2.126 2.146 2.631 2.588 "" " " " " " 0.128 0.139 0.205 0.152 0.125 0.110 0.106 6.063 4.984 4.780 6.467 6.618 5.352 5.219 0.047 0.008 0.068 0.137 0.112 0.107 0.008 101.266 100.863 100.441 99.666 101.079 100.642 100.148 100.015 100.187 100.873 100.924 100.537 101.350 101.065 101.136 100.576 Number of Ions on the basis of 24 (0) 5.898 5.927 5.928 5.943 5.930 5.930 4.081 4.040 4.035 4.053 4.071 4.074 4.495 4.454 4.434 4.358 4.462 4.504 0.000 0.000 0.000 0.000 0.000 0.000 0.716 0.771 0.502 0.507 0.621 0.615 0.019 0.028 0.020 0.017 0.015 0.014 0.848 0.815 1.098 1.124 0.908 0.892 0.001 0.008 0.016 0.013 0.013 0.001 16.058 16.043 16.035 16.014 16.020 16.029 End members (%) FM 85.545 86.761 94.033 90.304 84.872 85.626 85.233 84.786 86.899 87.463 86.302 85.322 89.870 89.615 87.815 88.018 AL 73.627 74.137 62.698 71.402 72.435 73.683 73.200 72.589 73.105 72.267 73.958 73.463 73.352 72.659 74.385 74.763 PY 12.486 11.371 4.781 7.817 12.959 12.410 12.752 13.065 11.075 10.399 11.788 12.717 8.306 8.452 10.356 10.210 SP 0.263 0.381 12.652 1.399 '0.268 0.241 0.405 0.220 0.359 0.285 0.309 0.457 0.338 0.280 0.245 0.237; GR 13.619 13.896 19.607 19.288 14.180 13.629 13.524 13.994 15.329 ,16.966 13.931 13.242 17.761 18.408 14.822 14.774 • Si 5.932 5.950 5.948 5.955 5.928 5.935 5.967 5.887 5.922 5.901 Al 4.050 4.035 4.023 4.040 4.028 4.030 4.049 4.121 4.066 4.105 Fe 4.460 4.454 3.776 4.291 4.398 4.478 4.370 4.370 4.410 4.353 Fe 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 Mq 0.756 0.683 0.288 0.470 0.787 0.754 0.761 0.787 0.663 0.626 Mn 0.016 0.023 0.762 0.084 0.016 0.015 0.024 0.013 0.022 . 0.017 Ca 0.825 0.856 1.207 1.169 0.877 0.832 0.819 0.856 0.938 1.030 Ti 0.000 0.014 0.018 0.006 0.011 0.003 0.008 0.009 0.009 0.006 16.040 16.016 16.021 16.016 16.044 16.045 15.998 16.041 16.034 16.038 Oxides: S1-S10i: Al-AltOs; Fe~FeO; Mg=MgO; Mn-MnO; Ca-CaO: TI-TIOt FM"(FeO+MnO/FeO+MnO+MgO)*100 to vo 00 Table 13: Electron microprobe analytical data: continued Gam©t' 84—622—4 Q22 Q23 Q23B PQ1 PQ7 267 268 269 277 278 279 Si 36.549 36.637 36.463 37.357 36.992 37.357 Al 21.523 21.347 21.344 21.504 21.266 21.396 n Fe 33.155 33.361 33.125 33.353 33.545 32.405 t) Fe 0.000 0.000 0.000 0.000 0.000 0.000 X o Mg 2.738 3.213 2.915 3.197 3.303 3.460 Mn 0.129 0.186 0.199 0.132 0.110 0.127 Ca 5.705 5.107 5.503 4.774 4.927 5.251 Ti 0.052 0.000 0.000 0.008 0.105 0.038 99.850 99.851 99.549 100.326 100.247 100.035 Number of Ions on the basis of 24 (0) Si 5.876 5.888 5.882 5.952 5.915 5.953 Al 4.079 4.043 4.058 4.038 4.008 4.019 Fe 4.458 4.483 4.468 4.444 4.485 4.318 Fe 0,000 0.000 0.000 0.000 0.000 0.000 Mg 0.656 0.770 0.701 0.759 0.787 0.822 Mn 0.018 0.025 0.027 0.018 0.015 0.017 Ca 0.983 0.879 0.951 0.815 0.844 0.897 Ti 0.006 0.000 0.000 0.001 0.013 0.005 16.075 16.088 16.087 16.026 16.066 16.030 End members (%) FM 87.215 85.417 86.513 85.459 85.112 84.063 AL 72,955 72.808 72.686 73.633 73.244 71.363 PY 10.737 12.500 11.401 12.579 12.§54 13.583 SP 0.288 0.411 0.442 0.295 0.243 0.282 Gfi 15.929 14.281 15.471 13.479 13,473 14,703 Oxides: S1=S10.; AI'AliOi; Fe = FeO; Mg=MgO; Mn=MnO; Ca=CaO; T)=T107 FM = (FeO+MnO/FeO+MnO+MgO)* 100 vo Table 13: Electron microprobe analytical data: continued Gam0fc85~67~ 1 Q1 02 03 05 06 07 08 QIO Q11 Q12 Q15 PG1 140 141 142 143 144 145 146 1 149 159 160 161 163 164 165 291 Si 37.5S1 37.315 37.486 37.116 37.796 37.300 37.126 36.654 37.396 37.646 37.526 : 37.364 36.701 36.769 37.265 Al 21.772 21.650 21.710 21.665 21.601 21.625 21.344 21.421 21.504 21.349 21.551 21.319 21.200 21.066 21.240 in 0 Fe 31.625 31.567 31.215 31.861 32.397 31.614 31.855 31.884 32.584 31.929 32.057 31.969 31.370 31.392 30.670 Fe 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 "0 x Mg 4.202 3.535 3.892 3.860 3.324 3.815 3.930 4.168 3.308 3.298 3.482 3.331 3.910 3.759 3.580 o Mn 0.487 1,166 0,475 0.434 0.411 0.368 0,399 0.802 0.686 0.646 0.523 0.634 0.558 0.604 1.089 Ca 5.415 5.127 5.323 5.117 5.233 5.407 5.060 5.005 5.250 5.914 5.379 5.885 5.166 5.618 4.920 Ti 0.098 0.457 0.150 0.047 0.027 0.025 0.068 0.038 0.000 0.082 0.090 0.087 0.060 0.073 0.083 101.160 100.816 100.250 100.099 101.288 100.153 99.782 99.972 100.727 100.864 100.609 100.588 98.965 i99.282 98.847 Number of ions on the basis of 24 (O) Si 5.903 5.901 5.934 5.904 5.945 5.924 5.926 5.858 5.936 5.957 5.944 5.935 5.909 5.911 5.987 Al 4.033 4.035 4.051 4.062 4.004* 4.048 4.015 4.035 4.023 3.981 4.024 3.991 4.023 3.991 4.021 Fe 4.157 4.175 4.132 4.239 4.261 4.199 4.252 4.261 4.325 4.225 4.247 4.246 4.224 4.220 4.120 Fe 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 Mg 0.984 0.833 0.918 0.915 . 0,896 0.903 0.935 0.993 0.783 0.778 0.822 0.789 0.938 0.901 0.857 Mn 0.065 0.156 0.064 0.058 0.055 0.050 0.054 0.109 0.092 0.087 0.070 0.085 0.076 0.082 0.148 Ca 0.912 0.869 0.903 0.872 0.882 0.920 0.865 0.857 0.893 1.003 0.913 1.001 0.891 0.968 0.847 Ti 0.012 0.054 0.018 0.006 0.003 0.003 0.008 0.005 0.000 0.010 0.011 0.010 0.007 0.009 0,010 16.066 16.024 16.020 16.056 16.047 16,046 16.056 16.117 16.051 16.040 16.031 16.057 16.069 16.082 15.990 End members (%) FM 81.092 83.864 82.045 32.440 82.802 82.467 82.161 81.484 84.949 84.716 84.002 84.598 82.087 82.690 83.276 AL 68.023 69,576 68.799. 69.700 69.944 69.176 69.691 68.541 70.988 69.419 70.246 69.435 68.961 68.449 69.059 FY 16.108 13.887 15.288 15.051 14.714 14.880 15.323 15.972 12.845 12.780 13.600 12.896 15.319 14.609 14.367 SP 1.061 2.603 1.061 0.961 0.898 0.816 0.884 1.746 1.513 1.422 1.161 1.395 1.242 1.335 2.483 GR 14.637 13.118 14.584 14.204 14.397 15.084 13.980 13.674 14.654 16.236 14.834 . 16.123 14.371 15.478 ;13.939 Oxides: Si=S10,;.A1=A110,; Fe»FeO; Mg=MgO; Mn=MnO; Ca»CaO; Tf-TIO, fM"(FeO+MnO/FeO+MnO+MgO)* 100 o o \ T a b l e 13: E l e c t r o n m i c r o p r o b e a n a l y t i c a l d a t a : c o n t i n u e d G8!TI6t! 85—67—1 PQ2 PG6 PQ10 PQ11 292 296 297 298 299 Si 37.554 37.379 37.710 37.899 37.779 Al 21.344 21.631 21.510 21.704 21.740 S Fe 31.242 32.586 31.404 31.441 31.409 0.000 0.000 0.000 0.000 0.000 o Ha 4.246 4.064 3.814 3.780 3.824 Mn 0.430 0.288 0.684 0.496 0.52? Ca 5.149 4.960 5.103 5.574 5.451 Ti 0.062 0.000 0.027 0.000 0.052 100.027 100.908 100.252 100.895 100.784 Number of ions on the bas I s Si 5.958 5.907 5.974 5.964 5.952 Al 3.991 4.028 4.016 4.026 4.037 Fe 4.145 4.306 4.160 4.138 4.133 Fe 0.000 0.000 0,000 0.000 0.000 Mg 1.004 0.957 0,901 0.887 0.898 Mn 0.058 0.039 0.032 0.066 0.071 Ca 0.875 0.84fi 0.866 0,940 0.920 Ti 0.007 0.000 0.003 0.000 0.006 16.037 16.077 16.012 16.020 16.021 End members (%) FM 80.715 81,946 82.524 82.580 82.417 AL 68.199 70.113 69.144 63.613 63.704 PY 16.522 15.586 14.966 14.705 14r907 SP 0.951 0.629 1,526 1.096 1.173 GF. 14.219 13,674 14.316 15.586 15.125 Of 24 (O) Oxides: S1=S10*; Al=AliOi; Fe=FeO; Mg=MgO; Mn=MnO; Ca=CaO: T1=T(Oi FM=(FeO+MnO/FeO+MnO+MgO)* 100 W O I Table 13: Electron microprobe analytical data: continued Garnet: 85-76-3 G1 G2 GO G4 G6 G5 G7 G8 G10 172 173 174 175 176 177 180 181 182 183 135 201 202 203 204 205 206 Si 37.668 37.370 37.488 37.501 37.398 37.811 37.689 37.580 37.445 37.452 37.601 37.394 37.289 37.375 37.340 36.863 37.357 Al 22.096 22.035 21.937 21.924 21.893 22.077 21.875 21.978 21.746 21.712 21.763 21.619 21.729 21.472 21.841 21.686 21.761 in Fe 33.190 33.749 33.712 33.915 33.590 32.953 33.229 34.344 34,463 34.672 34.762 34.646 34.265 34.603 32.603 32.918 33.586 0 T> Fe 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0,000 0.000 0.000 0.000 0.000 0.000 X Q Ma 5.823 5.419 5.737 5.792 5.361 5.914 5.825 4.855 4.900 4.701 4.362 4.361 4.732 4,671 6.198 6.123 5.876 Mn 1.104 1.059 1.045 1.126 1.141 1.147 1.105 1.271 1.216 1.313 1.475 1.462 1.387 1.382 0.963 0.939 1.061 Ca 1.104 1.242 1.156 1.142 1.107 1.111 1.157 1.138 1.171 1.201 1.360 1.363 1.254 1.150 1.177 1.157 1.170 Ti 0.110 0.068 0.072 0.000 0.077 0.0P5 0.063 0.085 0.022 0.005 " 0.030 0,058 0.070 0.078 0.000 0.008 0.078 101.094 100.983 101.146 101.399 101.068 101.013 100.344 101.250 100.963 101.055 101.353 10P.901 100.726 100.731 100.122 99.695 100.890 Si 5.904 5.886 5.890 5.884 Al 4,081 4.090 4.062 4.055 Fe 4.350 4.445 4.430 4.450 Fe 0.000 0.000 0.000 0.000 Mo 1.360 1.272 1.344 1.355 Mn 0.147 0.147 0.139 0.150 Ca 0.185 0.210 0.195 0.192 Ti 0.013 0.008 0.008 0.000 16.040 16.058 16.068 16.086 Number of 5,881 4,058 4.417 0.000 1.374 0.152 0,186 0.009 16,078 Ions on 5.923 4.076 4.317 0.000 1.381 0.152 0,186 0,001 16.036 the basis of 24 5.919 4.049 4.364 0.000 1.364 0.147 0.195 0.007 16.046 5.918 4.079 4.523 0.000 1.140 0.169 0.192 0.010 16.030 5.921 4.052 4.557 0.000 1.155 0.163 0.198 0.003 16.048 (0) 5.325 4.043 4.587 0.000 1.108 0.176 0.203 0.001 16.048 049 589 000 1.027 0.197 0.230 0.004 5,932 4.042 4,596 0.000 1.031 0.196 0.232 0.007 5.913 4.061 4,544 0.000 1,119 0.186 0.213 0.008 5.935 4.018 4.595 0.000 1.105 0.186 0.196 0.009 5.900 4.067 4.308 0.000 1.460 0.129 0.199 0.000 5.368 4.068 4.382 0.000 1.453 0.127 0.197 0.001 5.886 4.041 4.425 0.000 1.380 0.142 0.197 0.009 16.033 16.037 16.045 16.044 16.064 16.095 16.081 End members (%) FM 76.773 78.306 77.274 77.251 76.883 76.393 76.790 80.459 80.343 81.121 AL 72.085 73.248 72.596 72.404 72.128 71.517 71.957 75.158 75.055 75.512 Pr 22.543 20.962 22.020 22.038 22.434 22.879 22.482 18.937 19.019 18.248 SF 2.429 2,416 2.278 2.435 2.483 2.521 2.424 2.816 2.683 2.897 2.750 3.255 2.980 3.123" 2.823 3.C5 3.025 2.938 3.204 3.335 82.341 75.970 16.993 3.264 3.720 82.294 75.955 17.040 3.246 3.655 80.876 75.023 18.467 3.075 3.310 81.219 75.620 18.194 3.058 2.989 75.245 70.671 23.946 2.115 3.268 75.629 71.157 23.593 2.055 3.180 76.794 72.036 22.480 2.307 2.990 Oxides: S 1 = S 1 0 , ; A 1 = A 1 . 0 , ; Fe=FeO; „Mg=MgO; Mn=MnO; Ca=CaO: T 1 = T 1 0 , FM=(FeO+MnO/FeO+MnO+MgO)* 100 o NJ Table 13: Electron microprobe analytical data: continued Garnet: 85-76-3 G13 PQ1 PQ2 Si Al Fe Fe Mg Mn Ca Ti 207 37.368 21.883 33.290 0.000 5.201 1.068 1.266 0.008 100.090 208 37.681 22.005 33.735 0,000 5.281 1.388 1.166 0.067 209 37.276 21.631 34.097 0.000 4.790 1.222 1.187 0.042 101.322 100.244 210 37.661 21.926 32.482 0.000 6.024 1.145 1.180 0.025 100.443 Si 5.927 5.915 5.931 5.926 Al 4.032 4.071 4.056 4.066 Fe 4.416 4.429 4.537 4.275 Fe 0.000 0.000 0.000 0.000 Mg 1.230 1.236 1.136 1.413 Mn 0.143 0.185 0.165 0.153 Ca 0.215 0.196 0.202 0.199 Ti 0.001 0.008 0.005 0.003 16.024 16.039 16.033 16.035 FM 78.757 78.873 80.539 75.806 AL 73.552 73.319 75.153 70.803 PY 20.484 20.458 18.819 23.404 SP 2.390 3.056 2.727 2.529 GR 3.560 3.050 3.227 3.221 211 37.434 21.672 32.402 0.000 5.943 1.007 1.226 0.055 93.793 Number 5.333 4.046 4.292 0.000 1.403 0.135, 0.2031 0.0071 16.023 75.935 71.128 23.851 2.239 3.284 280 37.869 21.710 32.549 0.000 5.459 0.946 2.639 0.008 281 37.790 21.635 32.972 282 37.796 21.772 32.599 0.000 6.125 0.923 1.599 0.000 4.702 1.183 2.838 0.000 101.180 101.124 100.815 of ions on the basi 5.935 5.948 4.014 4.340 0.000 1.103 233 37.642 21.808 32.832 0.000 5.706 0.394 1.485 0.008 100.475 s of 284 37.954 21.848 32.594 0.000 6.253 1.003 1.196 0.030 100.879 24 (O) 4.010 4.266 0.000 1.275 0.126 0.443 0.001 16.056 0.158 0.479 0.000 16.042 5.929 4.026 4.277 0.000 1.432 0.123 0.269 0.000 16.055 5.933 4.051. 4.328 0.000 1.340 0.133 0.251 0.001 16.037 End members 498 80.305 71.380 18.145 2.605 7.871 (%) 69.828 20.872 2.057 7.229 75.440 70.105 23.478 2.011 4.407 "] 76.892 J71.520 '•22.153 1 2.194 4.119 5.942 4.031 4.267 0.000 1.459 0.133 0.201 0.004 16.036 75,098 70.441 24.086 2.196 3.225 285 38.464 21.939 32.464 0.000 5.714 0.855 2.519 0.065 102.018 5.959 4.006 4.206 0.000 1.319 0.112 0.418 0.008 16.028 236 38.427 21.954 31.988 0.000 5.699 0.915 2.384 0.052 101.419 5.976 4.024 4.160 0.000 1.321 0.121 0.397 0.006 16,004 283 37.944 21.846 32.590 0.000 6.069 0.946 1.496 0.078 100.969 5.939 4.030 4.265 0.000 1.416 0.125 0.251 0.009 16.035 76.596 69.507 21.805 1.854 6.721 76.418 69.389 22.034 2.011 6.475 289 37.959 21.627 34.027 0.000 5.404 1.085 1.331 0.038 101.470 5.951 3.996 4.461 0.000 1.263 0.144 0.224 0.005 16,044 75.619 70.481 23.393 2.073 3.916 290 37.674 21.646 32.358 0.000 5,515 0,923 2.235 0.000 100.351 5.945 4.026 4.270 0.000 1.297 0.123 0.378 0.000 16.039 78.480 73.269 20.739 2.366 3.560 77.206 70.366 21.375 2.033 6.226 Oxides: Si=SiO*; Al=AliO>; Fe=FeO; Mg=MgO; Mn=MnO; Ca=CaO; Ti=TiO> FM=(FeO+MnO/FeO+MnO+MgO)* 100 T a b l e 13: E l e c t r o n m i c r o p r o b e a n a l y t i c a l d a t a : c o n t i n u e d Biotite: 84-76-7A B1 B2 B3 B4 B5 B6 B7 90 91 92 93 94 95 96 Si 35.501 35.130 35.218 35.862 35.864 36.089 36.256 Al 17.608 17.557 17.576 17.515 17.610 18.020 17.844 Ti 1.927 1.877 1.748 1.506 1.710 1.686 1.660 Mq 9.246 9.140 9.398 9,730 9.426 9.078 9.131 Fe 21.374 21.979 21.456 21.284 22.407 21.949 22.009 Mn 0.120 0.090 0,087 0.093 0.067 0.093 0.116 Ca 0.000 0,064 0.001 0.028 0.006 0.000 0.014 Na 0.135 0.080 0.081 0.124 0.106 0.059 0.113 K 8.967 8.356 8.703 8.861 8.931 9.305 9.019 H20 3.888 3.862 3.865 3.901 3,927 3.939 3.942 98.764 98.134 98.133 98,905 100.055 100.219 100.164 Number of Ions on the b a s i s Si 5.476 5.455 5.464 5.512 5.476 5.493 5.515 Al 3.201 3.213 3.214 3.173 3.169 3.233 3.199 Ti 0.223 0,219 0.204 0.174 0.196 0.193 0.190 Mg 2.126 2.115 2.173 2.229 2.145 2.060 2.084 Fe 2.757 2.854 2.784 2.736 2.861 2.794 2.800 Mr, 0.016 0.012 0.011 0.012 0.009 0.012 0.015 Ca 0.000 0.011 0.000 0.005 0.001 0.000 0.002 Na 0.040 0.024 0.024 0.037 0.032 0.018 0.033 K 1.764 1.655 1.723 1.737 1.740 1.807 1.750 15.603 15.559 15.598 15.615 15.629 15.60? 15.588 OH 4,000 4,000 4.000 4.000 4.000 4.000 4.000 FM 56.606 57.535 56.259 55.213 57.224 57.670 57.461 B9 B10 B11 B12 B13 B14 B15 B16 98 99 100 101 102 103 104 105 106 35.464 35.903 35.956 35.302 35.860 35.573 34.959 36.121 35.824 17.655 17.680 17.718 17.689 18.003 18.048 18.417 17.591 17.610 1.842 1.501 1.243 1.678 1.613 1.615 1.261 1.683 1.808 9.302 9.821 9.741 9.542 9.610 9.365 9.969 9.581 9.695 21.834 22.344 22.120 21.676 21.245 21.083 21.813 21.618 21.886 0.045 0.112 0.079 0.093 0.127 0.077 0.045 0.063 0.111 0.031 0.000 0.001 0.046 0.006 0.013 0.046 0.032 0.018 0.146 0.127 0.128 0.124 0.144 0.140 0.084 0.113 0.098 8.930 8.955 9,032 8.918 8.789 8.757 8.297 8.907 8.760 3.896 3.941 3.927 3.889 3.923 3.894 3.896 3.928 3.926 99.145 100.383 99.945 98.957 99.319 98.566 98.786 99.643 99.736 Of 24 (O, OH) 5.458 5.463 5.490 5.443 5.482 5.478 5.381 5.514 5.471 3.203 3.171 3.189 3.214 3.243 3.275 3.341 3.165 3.170 0.213 0.172 0.143 0-195 0.185 0.187 0.146 0.193 0.208 2.134 2.228 2.217 2.193 2.190 2.149 2.287 2.180 2.207 2.810 2.844 2.825 2.795 2.716 2.715 2.808 2.760 2.795 0.006 0.014 0.010 0.012 0.016 0.010 0.006 0.009 0.014 0.005 0.000 0.000 0.008 0.001 0.002 0.008 0.005 0.003 0.043 0.037 0.038 0.037 0.043 0.042 0.025 0.034 0.029 1.753 1.738 1.759 1-754 1.714 1.720 1.629 1.734 1.707 15.626 15.667 15.671 15.651 15.590 15.579 15.630 15.594 15.604 4.000 4.000 4.000 4.000 4.000 4.000 4.000 4.000 4.000 56.892 56.198 56.114 56.142 55.513 55.905 55.163 55.950 56.008 Oxides: S1=SiO* : A l = A 1 . 0 i ; Fe = FeO; Mg=MgO; Mn=MnO: Ca=CaO; Na=NaiO; K=KJO FM=(FeO+MnO/FeO+MnO+MgO)* 100 T a b l e 13: E l e c t r o n m i c r o p r o b e a n a l y t i c a l d a t a : c o n t i n u e d filotitO! 84~76~7A B18 B19 B20 B21 B22 B23 1 115 116 117 118 119 120 Si 34.225 34.717 34.765 36.192 35.462 35.631 Al 17.385 18.358 16.886 17.232 17.240 17.266 0.954 1.313 1.371 1.511 1.843 1.490 Mq 10.524 10.672 10.824 9.969 9.753 9.818 Fe 23.000 21.572 22.678 21.457 21.127 21.527 Mn 0.057 0.076 0.035 0.111 0.128 0.098 Ca 0.136 0.070 0.073 0.052 0.010 0.034 Na 0.080 0.081 0,053 0.105 0.088 0.085 K 7.447 7.409 7.889 8.963 9.000 9.020 H20 3.831 3.891 3.863 3.922 3.879 3.887 97.639 98.160 98.437 99.514 98.529 98.855 Number of 1ons .on...; the b a s i s . o f 24 (0\, Si 5.357 5.350 5.396 5.533 5.482 5.496 Al 3.207 3.334 ; 3.089 3.105 3.141 3.139 Ti 0.112 0.152 i 0.160 0.174 0.214 0.173 Mq 2.455 2.451 ! 2.504 2.272 2.247 2.257 Fe 3.011 2.730 2.944 2.744 2.731 2.777 Hr, 0.008 0.010 0.005 0.014 0.017 0.013 Ca 0.023 0.012 0.012 0.008 0.002 0.006 Na 0.024 0.024 0.016 0.031 0.026 0.025 K 1.487 1.457 1.562 1.748 1.775 1.775 15.683 15.571 15.688 15.630 15.634 15.661 OH 4.000 4.000 4.000 4.000 .4.000 4.000 FM 55.143 53.233 54.073 54.8J4 55.013 55.276 Si=S10!; Al>AliO>; Fe = FeO; Mg=MgO; Mn=MnO; Ca=CaO; Na=Na,0: K = K;0 FM=( FeO+MnO/FeO+MnO+MgO) * lOO T a b l e 13: E l e c t r o n mic roprobe a n a l y t i c a l d a t a : c o n t i n u e d BiOtltO: 85_610"~1 BI B2 B4 B5 B6 B8 5 6 7 8 9 11 Si 34.360 36.162 35.911 36.525 35.240 35.053 Al 21.002 21.587 21.098 20.548 21.268 21.510 Ti 0.442 0.734 0.425 0.597 0.239 0.280 Mq 12.477 11.446 12.368 12.058 11.438 11.118 Fe 18.695 17.884 17.790 17.846 18.874 18.084 Mn 0.093 0.074 0.062 0.074 0.058 0.062 Ca 0.046 0.004 0.034 0.049 0.029 0.025 Na 0.183 0.334 0.113 0.125 0.214 0.104 K 7.470 8.710 8.208 8.651 8.695 8.928 M20 3.974 4.076 4.048 4.059 4.010 3.983 98.743 101.011 100.057 100.533 100.064 99.148 Number of ions on the Si 5.184 5.320 5.320 5.396 5.270 5.278 Al 3.734 3.743 3.684 3.577 3.749 3.817 Ti 0.050 0.081 0.047 0.066 0.027 0.032 Mq 2.806 2.510 2.731 2.655 2.550 2.495 Fe 2.359 2.200 2.204 2.205 2.361 2.277 Mn 0.012 0.009 0.008 0.009 0.007 0.008 Ca 0.007 0.001 0.005 0.008 0.005 0.004 Na 0.054 0.095 0.033 0.036 0.062 0.030 y. 1.438 1.635 1.551 1.630 1.659 1.715 15.644 15.593 15.583 15.582 15.689 15.655 OH 4.000 4.000 4.000 4.000 4.000 4.000 FM 45.797 46.817 44.748 45.472 -48.154 47.804 B10 B11 B12 B13 B14 B15 B16 16 17 ' 18 31 32 33 34 35 36 38 35.762 34.976 35.034 35.789 36.048 36.230 36.594 35.436 36.085 35.800 20.896 21.631 21.313 20.603 20.709 21.325 20.386 20.040 20.758 21.395 0.677 0.182 i 0.425 0.616 0.697 0.257 0.155 0.435 0.217 0.475 10.035 10.832 12.320 11.768 12.345 12.685 13.137 12.875 12.384 12.318 19.433 17.938 18.366 17.988 17.297 17.141 17.306 17.688 16.925 16.758 0.018 0.077 0.076 0.039 0.058 0.075 0.050 0.022 0.000 0.027 0.000 0.056 0.056 0.066 0.027 0.014 0.000 0.038 0.004 0.018 0.360 0.090 0.243 0.127 0.295 0.303 0.225 0.108 0.124 . . 0.217 8.521 9.154 7.320 8.940 8.919 9.008 8.934 8.635 9.319 8.984 3.993 3.970 4.011 4.019 4.052 4.086 4.074 3.996 4.031 4.048 99.694 98.907 99.164 99.954 100.447 101.123 100.862 99.273 99.846 100.040 basis of 24 (O, OH) 5.371 5.283 5.238 5.340 5.334 5.317 5.386 5.318 5.368 5.304 3.699 3.850 3.756 3.623 3.612 3.688 3.536 3.544 3.640 3.736 0.076 0.021 ! 0.048 0.069 0.078 0.028 0.017 0.049 0.024 0.053 2.246 2.439 ' 2.746 2.617 2.723 2.775 2.882 2.880 2.746 2.720 2.441 2.266 2.297 2.245 2.141 2.104 2.130 2.220 2.106 2.076 0.002 0.010 0.010 0.005 0.007 0.009 0.006 0.003 0.000 0.003 0.000 0.009 0.009 0.011 0.004 0.002 0.000 0.006 0.001 0.003 0.105 0.026 0.070 0.037 0.085 0.086 0.064 0.031 0.036 0.062 1.632 1.764 1.396 1.702 1.684 1.686 1.677 1.653 1.769 .. 1.698 15.572' 15.667 15.569 15.648 15.666 15.697 15.700 15.703 15.690 15.655 4.000 4.000 4.000 4.000 4.000 4.000 4.000 4.000 4.000 4.000 52.097 48.271 45.651 46.223 44.098 43.233 42.572 43.560 43.401 43.329 Oxides: S1=SiOi; A 1 = A 1 . 0 > ; Fe=FeO; Mg = MgO; Mn=MnO: Ca=CaO; Na=Na,0; K=K;0 FM=(FeO+MnO/FeO+MnO+MgO)*iOO T a b l e 13: E l e c t r o n mic roprobe a n a l y t i c a l d a t a : c o n t i n u e d BiOtttB!85~610~ 1 B19 B21 B22 39 50 51 52 53 Si 35.978 36.063 34.018 37.860 36.472 Al 21.351 21.215 20.633 21.240 22.800 lT* 0.302 0.332 0.377 0.784 0.587 .19 12.137 11.947 10.182 9.373 10.383 SFe 17.225 16.979 21.068 14.751 15.695 X Mn: 0.022 0.087 0.000 0.030 0.026 ° Ca: 0.004 0.011 0.013 1.305 0,165 Na 0.329 0.301 0.142 1.498 0.200 K 9.101 8.974 8.190 7.178 9.225 H20 4.056 4.040 3.905 4.040 4.062 100.504 99.949 98.527 98.059 99.614 Number of Si 5.319 5.352 5.224 5.620 5.385 Al 3.721 3.711 3.735 3.716 3.967 Ti 0.034 0.037 0.044 0.088 0.065 Mg 2.675 2.643 2.331 2.074 2.235 Fe 2.130 2.107 2.706 1.831 1.938 Mn 0.003 0.011 0.000 0.004 0.003 Ca 0.001 0.002 0,002 0.208 0.026 Na 0.094 0.086 0.042 0.431 0.057 K 1.716 1.699 1.605 1.359 1.737 15.692 15.648 15.688 15,330 15.464 OH 4.000 4.000 4.000 4.000 4.000 FM 44.361 44.492 53.723 46.944 45.933 55 56 57 58 38.733 36.033 35.646 35.809 26.589 21.686 21.638 21.482 1.046 0.807 1.622 0.555 8.168 11,776 11.723 11,882 11.256 16.381 16.198 16.053 0.000 0.019 0.054 0.019 0.169 0.129 0.043 0.228 0.453 0.259 0.135 0.272 8.939 9.301 9,399 9.072 4.196 4.067 4.026 ; 4.031 99.549 100.457 99.486 J99.403 Ions on the b a s i s of 24 (O, OH) 5.535 5.313 5.309 5.327 4.478 3.768 3.798 3.767 0.112 0.090 0.070 0.062 1.740 2.588 2.602 2.635 1,345 2.020 2.018 1,997 0.000 0.002 0.007 0.092 0.026 0.020 0.007 0.036 0.125 0.074 0.039 0.079 1.630 1.749 1.786 1.722 14.991 15.625 15.635 15.627 B28 B29 59 64 65 66 67 68 35.772 35.387 37.155 36.979 35.819 36.545 22.099 22.371 19.823 21.051 20.750 20.293 0.275 0.302 0.899 0.992 0.590 1.269 12.031 12.058 12.171 11.733 11.962 11.710 15.700 15.457 15.931 16.667 16.996 16.261 0.067 0.008 0.030 0.041 0.010 0,027 0.017 0.001 0.021 0.000 0.028 0.022 0.483 0.348 0.368 0.352 0.361 0.373 8.633 8.984 8.473 8.590 8.563 8.791 4.038 4.027 4.036 4.099 4,010 4.032 99.116 98.944 98.951 100,543 99.090 99.324 5.312 5.269 5.526 5.423 5,357 5.434 3.869 3.926 3.472 3.638 3.657 3.557 0.031 0.034 0.100 0.109 0.066 0.142 2,663 2,676 2.695 2.575 2.666 2.595 1.950 1.925 1.980 2.044 2.126 2,022 0.008 0.001 0.0C4 0.005 0.001 0.003 0.003 0,000 0,003 0.000 0.004 0,004 0.139 0,100 0.106 0.100 0.105 0.108 1.636 1.706 1.606 1.607 1,634 1.668 15.610 15.638 15.493 15.502 15,617 15.533 4.000 4.000 4,000 4.000 4.000 4.000 42.375 41.948 42.390 44.310 44.374 43,536 O x i d e s : S1=S10>: A 1 = A 1 , O J ; Fe = FeO: Mg=MgO;' Mn=MnO; Ca=CaO: Na=Na,0; K = K,0 FM=(FeO+MnO/FeO+MnO+MgO)* 100 w O r Tab 1 e 13: Electron m 1 croprobe ana 1 y11 ca 1 data: cont 1 nued BlOtltO! 84""622™4 B1 B3 30 31 33 34 Si 36.923 46.869 36.572 37.631 Al 21.461 37.442 20.142 20.932 Ti 1.043 0.505 2.279 2.225 Mq 12.292 0.635 12.104 12.040 Fe 15.835 0.879 14.022 13.868 Mn 0.000 0.000 0.019 0.063 Ca 0.049 0.022 0.046 0.020 Na 0.314 1.371 0.286 0.321 K 7.949 8.204 8.389 8.527 H20 4.099 4.605 4.024 4.115 100.024 100.533 ; 97.883 99.742 Number of ions on Si 5.401 6.103 5.450 5.483 Al 3.700 5.746 3.537 3.595 Ti 0.U5 0.049 0.255 0.244 Mq . 2.680 0.123 2.688 2.615 Fe 1.944 0.096 1.747 1.690 Mn 0.000 0.000 0.002 0.008 Ca 0.008 0.003 0.007 0.003 Na 0.089 0.346 0.083 0.091 K 1.483 1.363 1.595 1.585 15.420 13.829 15.365 15.313 OH 4.000 4.000 4.000 -4.000 FM 42.048 43.704 39.426 39.368 B4 35 46 47 36.303 38.367 46.264 19.925 21.895 36.934 1.975 0.822 0.364 12.287 12.583 0.700 14.796 14.777 0.735 0.000 ... 0.028 0.000 0.063 0.011 0.000 0.262 0.301 1.206 8.184 8.550 8.775 4.008 4.186 4.546 97.801 101.521 99.523 he b a s l s j i f 24 (O,. OH) 5.432 5.496 6.102 3.514 3.697 5.742 0.222 0.089 0.036 2.740 2.687 0.138 1.852 1.770 0.081 O.OOC 0.003 0.000 0.010 0.002 0.000 0.076 0.083 0.309 1.562 1.562 1.477 15.408 15.390 13.884 4.000 4.000 4.000 40.323 39.765 37.069 Oxides: S1=S10i; A1=A1.0.; Fe=FeO; Mg=MgO; Mn=MnO; Ca=CaO: Na=NatO; K=K!0 FM<= (FeO+MnO/FeO+MnO+MgO)*10O Oxides 3 S ^ Z O at O J -n n —i n> to ro o# a» s» n> I J O M on co C O CO CO A M CJI CO -Cr. J > O H» O N H CO Ul to O OJ h* U 3 - N J OO O o i ro w o PO OO -Ck k£l CD cn oo ro -vJ "xj M CO OJ O lfl yj j-» N J 0 1 o - N J on -0. -vi cn 4 > C J O CO -C> CO -Ck COMCDoCDcDCDCDCnOn I O i k C O » - * 0 0 > - * M O r j l C ^ C O C D C O A O J O O M W O M O N i U 1 * . t - O O f t O f \ ) - s l M ( J , -vj C D M o o o cn o ro o 'H c o u i c u N O p j O c n f \ ) j > u l on C D t o ^ o i - » u ) u i \ j r o y 3 A i J i o c o x k A c o ^ c o c J i i j O N -©» »-* to M M ro co - O U l H ' O o O l - ' M O O J C n C O f r C O O O O ^ M M H i N j • - - - - - - - cri «J3 C D C O U I O O O C O U I H - C O U I k D O M M O O C O u i ^ M N J C O cn C D o t O N j o o r j ( \ ) i > - c r i u i « - c*^cD - v i r o c D J > r \ j j a n c n ' s o . 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TI cn -o -c» oo CD <CD J> cn • n CD cn C D - ^ j r o C D c D V - ' p>.;i i_n -xi »— oj M cn r>j CD IJD oj -.j >T* ro '-o J& M 1 o M j—- ro '-O to j> cn M o o o k- ro a >'0 (ji ' o ji, oo CD CD> CD u l M M M rri co CD u i cr, M o a 1 ^ ut K- • \j cu u i CD oo r>j CD CD on cn cn to CD ro CD o N J o o o fx* ' - O an -j ai r q w j> (-• o N J o H * CI-PO CD CO CO O co O v | i.r| ft r j l H r-.j C O ft CO C O O Ti v j t O CTi ' T l 0 OA 09 at a « a CD 03 ro 09 ro ro 09 ro CO 09 ro cn T a b l e 13: E l e c t r o n mic roprobe a n a l y t i c a l d a t a : c o n t i n u e d Biotite: 85_67"~1 B1 B2 B4 B5 B6 145 146 147 148 149 150 151 Si 35.71? 37.259 36.880 36.337 36.405 36.254 37.413 Al 20.163 19.858 19.696 19.874 19.233 18.382 20.397 Ti 1.583 1.678 1.638 0.796 1.313 1.615 1.413 Mg 10.249 12.068 12.113 12.132 11.952 11.967 12.320 Fe 17.786 16.847 16.898 17.543 17.783 17.312 16.017 Mn 0.090 0.046 0.075 0.068 0.050 0.065 0.080 Ca 0.035 0.010 0.000 0.008 0.017 0.006 0.007 Na 0.221 0.175 0.187 0.232 0.185 0.134 0.237 K 8.682 8.798 8.708 8.294 8.562 8.465 8.580 H20 3.965 4.090 4.062 4.016 4.011 3.992 4.103 98.496 100.830 100.257 99.300 99.512 98.850 100.568 B7 B8 B10 B11 B12 B15 152 153 154 164 165 166 167 163 169 170 171 36.756 36.085 31.968 35.984 36.658 36.059 34.615 36.714 36.771 36.545 34.884 20.051 20.270 20.752 19.596 20.459 20.129 19.715 20.762 20.202 20.365 19.668 1.611 0.499 0.504 1.274 1.526 1.523 1.183 1.550 0.967 1.713 1.450 12.124 12.180 13.238 11.267 11.119 9.882 11.630 11.171 11.643 11.021 7.024 16.351 18.289 21.371 18.658 17.656 19.862 18.692 15.762 16.894 16.870 24.387 0.046 0.057 0.108 0.076 0.071 0.152 0.058 0.054 0.028 0,065 0.099 0.011. 0.018 0.067 0.000 0.007 0.032 0.024 0.015 0.059 0.003 0.021 0.245 0.163 0.050 0.152 0.197 0.158 0.170 0,244 0.247 0.315 0.117 8,329 7.643 2.667 8.291 8.498 8.374 7.354 8.689 8.356 8.526 7.823 4.054 4.015 3.840 3.991 4.056 4.007 3.918 4.038 4.030 4.034 3.892 99.580 99.219 94.567 99.290 100.248 100.178 97.358 98.998 99.199 99.457 99.364 Number of Ions on the b a s i s of 24 (0, OH) 5.442 5.446 5.467 5.437 5.389 "4.992 " 5.406 5.420 5.397 5,297 5.452 5.471 5.432 5.375 3.388 3.361 3.513 3.496 3.568 3.819 3.470 3.565 3.551 3,556 3.634 3.543 3.568 3.571 0.148 0.182 0.155 0.179 0.056 0.059 0.144 0.170 0,171 0.136 0.173 0.108 0.191 0,168 2.663 2.679 2.683 2.673 2.711 3.081 2.523 2.450 2.205 2.653 2.473 2.582 2,442 1.613 2-223 2.175 1.957 2.023 2.284 2.791 2.344 2.183 2.486 2.392 1.958 2.102 2.097 3.142 0.006 0.008 0.010 0.006 0.007 0.014 0.010 0.009 0.019 0.008 0.007 0.004 0.008 0.013 0.003 0.001 0.001 0.002 0.003 0.011 0.000 0.001 0.005 0.004 0.002 0.009 0.000 0.003 0.054 0.057 0.067 0.070 0.047 0.015 0.044 0,056 0.046 0.050 0.070 0.071 0.091 0.035 1.633 1.622 1.600 1.572 1.456 0.531 1.589 1.603 1.599 1.436 1.646 1.586 1.617 1.537 15.559 15.531 15.454 15.457 15.522 15.313 15.531 15.457 15.479 15.532 15.416 15.477 15.446 15.458 OH 4.000 4.000 4.000 4.000 4.0X10 4,000 4.000 4.000 4.000 4.000 4.000 4.000 4.000 4.000 4.000 4,000 4.000 4.000 FM 49.462 43.992 44.018 44.888 45.571 44.397 42.302 43.146 45.803 47.656 48.267 47.217 53.194 47,496 44.273 44.919 46.298 66.172 Oxides: S 1 = S i O ! : A1-a 1,0.: Fe=FeO: Mg=MgO: Mn=MnO; Ca=CaO: Na=Na ,0 : K=K,0 FM= ( FeO+MnO/FeO+MnO+MgO)* 1 0 0 Si 5.401 5.463 5.444 5.426 Al 3.594 3.431 3.427 3.497 Ti 0.180 0.185 0.182 0,089 Mg 2.310 2,637 2.665 2.700 Fe 2.249 2.066 2.086 2.191 Mn 0.012 0.006 0.009 0.009 Ca 0.006 0.002 0.000 0.001 Na 0.065 0.050 0.054 0.067 K 1.675 1.646 1.640 1.580 15.492 15.484 15.507 15.560  T a b l e 13: E l e c t r o n m i c r o p r o b e a n a l y t i c a l d a t a : c o n t i n u e d Btottte: 85-76-3 B1 181 Si 35.826 Al 19.401 Ti 1.561 Mg 9.982 Fe 20,002 Mn 0.053 Ca! 0.000 Na 0.113 K 8.498 H20 3.965 99.402 Si 5.418 Al 3.458 Ti 0.178 Mg 2.250 Fe 2.530 Mn 0.007 Ca 0.000 Na 0.033 K 1.639 [15.512 B2 B3 B4 Be B5 183 184 185 186 187 35.616 36.025 36.589 36.301 36.296 20.102 20.348 19.781 19.157 19.082 2.307 2.621 1.715 2.215 2.067 9.916 9.672 12.230 11.875 11.807 19.141 18.706 17.379 17.437 18.544 0.063 0.080 0.034 0.052 0.071 0.000 0.029 0.000 0.000 0.001 0.146 0.147 0.291 0.272 0.212 8.292 8.318 8.071 8.173 8.273 3.993 4.022 4.060 4.023 4.036 99.576 99.967 100.150 93.506 100.389 67 68 188 189 190 36.444 36.472 34.878 18.897 19.057 18.957 1.977 2.190 2.207 11.632 11.393 9.358 18.655 18.600 20.150 0.074 0.049 0.048 0.000 0.000 0.022 0.191 0.220 0.316 8.257 8.085 8.333 4.026 4,031 3.901 100.153 100.097 98.201 Number of ions on the basis of 24 (0, OH) 5.348 5.371 5.404 5.410 5.392 5.428 5.426 5.362 3.558 3.575 3.443 3.365 3.341 3.317 3.341 3.435 0.261 0.294 0.190 0.248 0.231 0.221 0.245 0.255 2.219 2.149 2.692 2.638 2.615 2.582 2.526 2.144 2.404 2.332 2.147 2.174 2.304 2.324 2.314 2.591 0.008 0.010 0.004 0.007 0.009 0.009 0.006 0.006 0.000 0.005 0.000 0.000 0.000 0.G00 0.000 0.004 0.042 0.042 0.083 0.079 0.061 0.055 0.063 0.103 1.588 1.582 1.521 i 1.554 1.568 1,569 1.534 1.634 15.428 15.360 15.486 15.475 15.521 15.505 15.457 15.534 0 H 4.000 4.000 4,000 4.000 4.000 4.000 4.000 4.000 4.000 FM !'52.993 52.078 52.150 44.409 45.245 46.938 47.465 47.875 54.772 54.656 52.311 55.839 53.588 52.605 B10 B13 191 192 193 194 196 34.837 35,571 34.767 34.593 35.453 19.447 19.290 20,433 19.702 20.263 2.240 2.025 1.928 2.289 2.007 9.375 10.146 9,070 9.484 9.758 20.076 19.812 20.364 19.451 19.279 0.063 0.023 0.075 0.066 0.023 0.055 0.000 0.056 0.000 0,000 0.311 0.194 0.205 0.264 ! 0.200 8.276 8.338 7.495 8.170 ! 8.279 3.922 3.966 3,931 3,908 3.977 98.601 99.365 99.323 97.926 99.23? 5.327 5.378 5.304 5.308 5.346 3.505 3.437 3.674 3.563 3.601 0.258 0.230 0.221 0.264 0.223 2.137 2.286 2.062 2.169 2.193 2.567 2.505 2.599 2.496 2.431 C.008 0.003 0.010 0,009 0.003 0.009 0.000 0.009 0.000 0,000 0.092 0.057 0.061 0.079 0.058 1.614 1.60? 1.459 1.599 1.592 15.517 15.505 15.398 15.486 15.452 4.000 4.000 4.000 4.000 4.000 Oxides: SI-SIO.; Al«Al iO>; Fe=FeO; Mg=MgO; Mn=MnO; Ca=CaO; Na=Na,0; K=K,0 FM=(FeO+MnO/FeO+MnO+MgO)* Table 13: Electron microprobe analyt ica l data: continued PlagioCl&80: 85_67—1 PI P2 P3 P7 P10 P11 23 24 25 26 2 7 28 2 9 30 31 32 3 3 3 4 35 Na 8.212 8.122 8.258 9.416 8.285 8.395 9.395 9.313 9.389 8.968 8.906 8.689 8.324 K 0.105 0.094 0.105 0.094 0.082 0.095 0.112 0.108 0.140 0.119 0.125 0.425 0.094 Si 61.246 61.111 59.029 63.693 60.766 60.751 64.191 63.580 63.533 63.094 62.927 62.228 60.766 Al 24.839 24.448 24.163 22.821 24.427 24.529 23.173 22.959 22.944 23.551 23.380 23.972 24.446 Fe 0.005 0.060 0.342 0.131 0.120 0.090 0.118 0.037 0.075 0.000 0.033 0.098 0.117 Ca 6.059 6.145 6.392 4.115 6.110 6.211 4.080 4.017 4.059 4.680 4.720 4.568 6.127 100.465 99.980 98.288 100,270 99.790 100.072 101.070 100.015 100.139 100.412 100.092 99.980 99.874 Number of Ions on the b a s i s of 8 (0) Na 0.704 0.700 0.728 0.805 0.716 0.724 0.796 0.797 0.804 0.766 0.763 0.747 0.719 K 0.006 0.005 0.006 0,005 0.005 0.005 0.006 0.006 0.008 0.007 0.007 0.024 0.005 Si 2.708 2.716 2.683 2.808 2.709 2.703 2.806 2.807 2.804 2.779 2.781 2.758 2.707 Al 1.294 1.280 1.294 1.186 1.283 1.286 1.194 1.195 1.194 1.223 1.218 1.252 1.284 Fe 0.000 0.002 0.013 0.005 0.004 0.003 0.004 0.001 0.003 0.000 0.001 0.004 0.004 Ca 0.287 0.293 0.311 0.194 0.292 0.296 0.191 0.190 0.192 0.221 0.224 0.217 0.292 4.999 4.996 5.036 5.003 5.009 5.018 4.998 4.997 5.004 4.995 4.994 5.001 5.012 End members (%) AB 70.617 70.139 69.634 80.123 70.718 70.607 80.140 80.256 80.083 77.092 76.800 75.601 70.712 OR 0.593 0.534 0.581 0.526 0.460 0.527 0.629 0.615 0.784 0.674 0,711 2.434 0.525 AN 28.790 29.327 29.784 19.351 -28.822 23.967 19.232 19.130 19.133 22.233 22.490 21.965 28.763 Oxides: Na=Na !0: K=K,0; S1=S10>; A1=A1,0,: Table 13: Electron microprobe analyt ica l data: continued PfelQiOCl&S6: 84—87~2 53 54 Na 7.898 7.754 n 0 K 0.155 0.157 TJ Si 59.282 60.043 X o Al 25.304 25.198 Fe 0.136 0.080 Ca 6.768 6.948 99.543 100.180 Number of Na 0.687 0.669 K 0.009 0.009 Si 2.658 2.672 Al 1.337 1.322 Fe 0.005 0.003 Ca 0.325 0.331 5.021 5.006 AB 67.272 66.291 OR 0.871 0.881 m 31.857 32.829 55 56 57 8.193 8.178 7.816 0.136 0.146 0.113 59.335 60.413 59.538 24.988 24.869 25.285 0.096 0.078 0.144 6.455 6.492 7.030 99.204 100.177 99.926 1ons on the b a s i s 0.714 0.705 0.677 0.008 0.008 0.006 2.668 2.687 2.660 1.324 1.304 1.331 0.004 0.003 0.005 0.311 0.309 0.336 5.030 5.017 5.016 End members (%) 69.143 68.946 66.376 0.756 0.808 0.633 30.101 30.246 32.991 58 59 7.967 7.744 0.184 0.222 59.590 59.502 25.117 25.370 0.163 0.041 6.613 6.906 99,633 99.785 Of 8 (O) 0.692 0.671 0.011 0.013 2.668 2.660 1.326 1.337 0.006 0.002 0,317 0.331 5,019 5.013 67,847 66.152 1.033 1.246 31.121 32.602 O x i d e s : Na=NaiO: K=K.O; 51=SiO. : Al=Al»Oi; Fe=FeO; Ca=CaO OJ M OJ Table 13: Electron microprobe analyt ica l data: continued Plagioclase 8 5 - 7 6 - 3 8 4 - 6 2 2 - 4 P1 P2 P3 P7 7 8 9 10 11 12 13 14 15 16 « "7 1 ' Na 6.946 6.706 7.101 7.174 9.088 8.913 8.910 8.641 8.821 8.754 8.666 K 0.111 0.075 0.043 0.041 0.092 0.088 0.096 0.071 0.098 0.106 0.060 Si 58.599 57.564 57.876 58.034 62.722 62.272 62.009 61.500 61.237 60.929 60.843 Al 26.645 27.318 26.850 26.477 23.524 24.046 23.624 23.424 23.386 23.611 23.953 Fe 0.085 0.165 0.188 0.259 0.026 0.046 0.030 0.030 0.057 0.075 0.203 Ca 8.230 8.786 8.192 8.236 4.648 4.974 4.908 5.304 5.071 5.162 5.664 100.617 100.613 100.250 100.221 100.099 100.339 99.578 98.970 98.669 93.636 99,390 Number of fons on the bas 1 s of 8 (0) Na 0.599 0.579 0.615 0.622 0.779 0.763 0.769 0.751 0.769 0.764 0.752 K 0.006 0.004 0.002 0.002 0.005 0.005 0.005 0.004 0.006 0.C06 0.003 Si 2.604 2.565 2.586 2.595 2.774 2.750 2.759 2.756 2.753 2.742 2.723 Al 1.396 1.435 1.414 1.395 1.226 1.252 1.239 1.237 1.239 1.252 1.264 Fe 0.003 0.006 0.007 0.010 0.001 0.002 0.001 0.001 0.002 0.003 0.008 Ca 0.392 0.419 0.392 0.395 0.220 0.235 0.234 0.255 0.244 0.249 0.272 5.000 5.009 5.016 5.019 5.005 5.007 5.008 5.003 5.014 5.016 5.022 End members i%) i AB 60.051 57.761 60.919 61.045 77.564 76.052 76.247 74.369 75.476 74.973 73.220 OR 0.630 0.423 0.245 0.229 0.514 0.494 0.543 0.402 0.549 0.597 0.335 AN 39.319 41.816 38.837 38.726 21.922 23.455 23.211 25.229 23.975 24.429 26.445 Oxides: Na=Na.O; K=K.O: S1=S10»: A l = A l , O i ; Fe=FeO; Ca=CaO u> Table 13: Electron microprobe analyt ica l data: continued 84-82-2 85-76-2 61 62 63 64 65 66 57 68 Na 6.894 6.788 7.105 7.508 8.116 7.173 7.880 7.931 K 0.117 0.089 0.110 0.080 0.261 0.188 0.253 0.2S9 Si 56.879 56.714 57.502 58.002 59.707 57.082 59.286 59.917 Al 26.500 26.564 26.220 25.793 24.760 26.084 25.007 24.652 Fe 0.014 0.059 0.126 0.071 0.149 0.174 0.081 0.118 Ca 8.486 8.619 8.071 7.451 6.261 7.961 6.648 6.463 . 98.890 98.834 99.133 98.905 99.255 98.662 99.155 99.371 Number of ions on the b a s i s of 8 ( O ) Na 0.606 0.597 0.622 0.658 0.707 0.632 0.638 0,690 K 0.007 0.005 0.006 0.005 0.015 0.011 0.015 0.017 Si 2.573 2.573 2.598 2.622 2.632 2.594 2.663 2.688 Al 1.416 1.420 1.396 1.374 1.311 1.337 1.326 1,303 Fe 0.001 0.002 0.005 0.003 0.006 0.007 0.003 0,004 Ca 0.412 0.419 0.391 0.361 0.301 0.388 0.321 0.311 5.020 5.017 5.018 5.022 5.022 5.028 5.020 5,013 End members (%) AB 59.122 58.470 61.056 €4.295 69.084 61.326 67.237 67.830 OR 0.659 0.505 0.620 0.448 1.464 1.057 1.420 1.627 AN 40.219 41.024 38.324 35.257 29.452 37.616 31.343 30.543 O x i d e s : Na=Na*0: K=K,0; S1=S10*; A 1 = A l , O i ; Fe»FeO; Ca=CaO Table 13: Electron microprobe analyt ica l data: continued Hornblende: 84-87-2 3 9 10 11 13 14 15 IS 17 19 19 20 21 25 26 27 29 Na 1.694 1.618 1.492 1.671 1.729 1.765 1.849 1.777 1.821 1.816 1.829 1.518 1.696 1.661 1.702 1.581 1.665 K 0.600 0.617 0.514 0.628 0.607 0.655 0.601 0.641 0.640 0.690 0.648 0.577 0.658 0.583 0.612 0.606 0.678 Si 42.758 41.587 42.571 41.181 41.735 42.269 40.849 41.658 41.829 40.954 40.532 41.424 41.076 42.107 42.644 42.013 41.195 Al 13.136 13.245 12.514 13.852 13.328 13.614 14.458 13.799 13.293 13.891 13.982 13.011 13.742 12.822 13.485 13.901 14.054 Ti 0.877 0.351 0.759 0.877 0.886 0.892 0.889 0.924 0.912 0,906 0.874 0.854 0.874 0.842 0.894 0.861 0.944 Fe 17,404 17,365 16.826 17.401 17.198 17.127 17.148 17.369 17.694 ;17.795 17.639 17.185 17.543 17.077 17.355 17.513 17.698 Mn 0.399 0.405 0.323 0,333 0.427 0.421 0.434 0.386 0.358 0.429 0.385 0.336 0.372 0.380 0.394 0.403 0.381 Mq 10.517 16,620 11.206 10.463 10.703 10.622 10.270 10.488 10.353 10,091 9.934 10.803 10,197 10.658 10.728 10.295 10.143 Ca 11.192 11.429 11.699 11.556 11.318 11.226 11.187 11.065 11.196 11.135 11.320 11.676 11.482 11.254 11.180 11.250 11.620 H20 2.015 1.991 2.004 1.994 1.998 2.016 1.992 2.002 1.997 1.985 1.972 1.985 1.985 1.990 2.025 2.010 2.000 100.542 99.728 99.908 99.956 99.930 100.607 99.677 100.107 100.094 99.691 99.115 99.369 99.625 99.374 101.019 100.432 100.378 Number of Ions on the basis o f 24 (O, OH) Na 0.489 0.472 0.433 0.487 0.503 0.509 0.540 0,516 0.530 0.532 0.539 0.445 0.496 0.485 0.489 0.457 0.484 K 0.114' 0.118 0.098 0.120 0.116 0.124 0.115 0.122 0.122 0.133 0.126 0.111 0.127 0.112 0.116 0.115 0.130 Si 6.356 6.261 6.368 6.191 6.263 6.288 6.150 6.239 6.278 6.187 6.162 6.258 6.203 6.343 6.314 6.266 6.177 Al 2.304 2.350 2.206 2.454 2.358 2.337 2.565 2.436 2.351 2.473 2.505 2.317 2.446 2.276 2.353 2.444 2.484 Ti 0.098 0.096 0.085 0.099 0.100 0.100 0.101 0.104 0.103 0.103 0.100 0.097 0.099 0.095 0.100 0.097 0.106 Fe 2.166 2.186 2.105 2.188 2.159 2.131 2.159 2.175 2.221 2.248 2.243 2.171 2.215 2.151 2.149 2.185 2.219 Mn 0.050 0.052 0.041 0.042 0.054 0.053 0.055 0.049 0.045 0.055 0.050 0.043 0.048 0.048 0.049 0.051 0.048 Mq 2.333 2.383 2.498 2.344 2.394 2.355 2.305 2.341 2.316 2.272 2.251 2.433 2.295 2.393 2.368 2.289 2.267 Ca 1.785 1,844 1.875 1.861 1.820 1.789 1.804 1.776 1.801 1.802 1.844 1.890 1.858 1.816 1.774 1.798 1.867 15.695 15.763 15.709 15.787 15.768 15.736 15.795 15.758 15.769 15.806 15.818 15.764 15.787 15.722 15.712 15.701 15.782 OH 2.000 2.000 2.000 2.000 2.0TI0 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2,000 2.000 2.000 2.000 2.000 R-l 48.718 48.430 46.204 48.751 48.032 4g.U2 49.001 48.722 49,458 50.336 50.454 47.651 49.646 47,895 48.147 49.410 50.010 O x i d e s : Na=Na,0; K=K;O; S1=S10*; A1= A1 ,0 , : T1=T10,; Fe=FeO; Mn=MnO; Mg=MgO: Ca=CaO FM=(FeO+MnO/FeO+MnO+MgO )* 100 Table 13: Electron microprobe analyt ical data: continued Hornblende: 84-87—2 30 31 32 33 34 35 36 37 Na 1.863 1.805 1.662 1.595 1.700 1.732 1.620 1.545 K 0.657 0.649 0.665 0.632 0.661 0.625 0.630 0.624 Si 41.204 41.959 40.596 40.870 41.183 41.863 42.043 41.833 » Al 13.918 13.521 14.097 14.126 13.304 13.566 13.901 13.464 xj Ti 0.961 0.857 0.886 0.852 0.896 0.909 0.921 0.804 * Fe 17.473 17.051 17.513 17.171 17.440 17.467 17.274 17.254 Mn 0.400 0.402 0.340 0.336 0.376 0.349 0.349 0.378 Mq 10.194 10.585 10.012 10.126 10.012 10.488 10.114 10.260 Ca 11.247 11.075 11.724 11.683 11.419 11.192 11.416 11.577 H20 1.993 2.001 1.980 1.984 1.973 2.003 2.008 1.995 99.909 99.906 99.475 99.376 98.963 100,194 100.276 99.735 Number of Ions on the b a s i s of 24 ( O . OH) Na 0.543 0.524 0.488 0.467 0,501 0.503 0.469 0.450 K 0.126 0.124 0.128 0.122 0,128 0.119 0.120 0.120 Si 6.199 6.286 6.147 6.176 6.258 6.265 6.276 6.288 Ai 2.468 2.387 2.516 2.516 2.383 2.393 2.446 2.385 Ti C.109 0.097 0.101 0.097 0.102 0.102 0,103 0.091 Fe 2.198 2.136 2.218 2.170 2.216 2.186 2.157 2.169 Mn 0.051 0.051 0.044 0.043 0.048 0.044 0.044 0.048 Mq 2.286 2.364 2.260 2.281 2.268 2.339 2.251 2.293 Ca 1.813 1.778 1.902 1.892 1.859 1.795 1.826 1.864 15.79? 15.749 15.803 15.764 15.763 15.747 15.692 15.714 OH 2.000 2.000 2.000 2.000 2.0D0 2.000 2.000 2.000 Hi 49.598 48.062 50.019 49.246 49.967 48.806 49.439 49.097 O x i d e s : Na=Na*0; K = K . O ; S1=S10.; A l = A l » O i ; T1=T10i: Fe=FeO; Mn=MnO; Mg=MgO; Ca=CaO FM=(FeO+MnO/FeO+MnO+MgO)* 100 UI - J Table 13: Electron microprobe analyt ica l data: continued HOmblOnde: 84 —82—2 41 Na 1.508 K 0.372 Si 41.397 Al 15.482 Ti 0.325 Fe 17.226 Mn 0,460 Mg 9.135 Ca 11.198 H20 1.991 99.094 Na 0.440 K 0,071 Si 6.233 Al 2.747 Ti 0.037 Fe 2.169 Mn 0.059 Mg 2.050 Ca 1,306 15.613 OH 2,000 FM 52,077 43 44 1,297 1.095 0.473 0.334 40.742 42.845 14,426 12.278 0.480 0.677 17.565 16.448 0,416 0.424 9.388 10.914 11.787 11.707 1.968 1.983 98.542 98,710 Number 0.383 0.320 0.092 0.064 6,208 6.457 2.591 2.181 0.055 0.077 2.238 2.073 0.054 0.054 2.132 2.452 1.924 1,890 15.679 15.568 2.000 2.000 51.905 46.457 of 46 47 48 1.302 1.262 1.202 0.466 0.429 0.501 40.554 40.757 40.205 15.590 15.152 14.948 0.434 0.444 0.357 17.531 17.540 17.289 0.467 0.433 0.394 8.889 9.299 9.135 11.755 11.745 11.654 1.979 1.981 1.952 98.967 99.040 97.637 Ions on the b a s i s of 0.383 0.370 0.358 0.090 0.083 0.093 6.145 6.169 6.175 2.784 2.703 2.706 0.049 0.051 0.041 2.222 2.220 2.221 0.060 0.055 0.051 2.008 2.098 2.091 1.903 1.905 1.918 15.650 15.655 15.659 2.00?) 2.000 2.000 53.193 52.034 52.072 56 57 58 1.561 1.236 1.192 0.399 0.457 0.518 40.122 41.287 ; 40.746 15.857 13.062 ' 13.958 0.284 0.522 0.507 17.880 17.806 17.550 0.520 0.377 0.336 8.548 9.692 ' 9.271 11.359 11.962 12.023 1.965 1.961 1.956 98.493 98.362 98.057 24 (O, OH) 0.462 0.366 0.354 0.078 0.089 0.101 6.120 6.313 6.245 2.851 2.354 2.521 0.033 0.060 0.058 2.281 2.277 2.249 0.067 0.049 0.044 1.944 2.209 2.118 1.857 1.960 1.974 15.691 15,677 15.664 2.000 2.000 2.000 54.716 51.290 51.987 O x i d e s : Na=Na>0: K=K>0; S1=S10>: A l = A l i O i ; T i=T10r ; Fe=FeO; Mn = MnO: Mg=MgO: Ca = CaO FM=(FeO+MnO/FeO+MnO+MgO)* 100 Table 13: Electron microprobe analyt ica l data: continued H ornblende: 85-76-2 62 65 66 67 69 70 71 72 73 74 75 76 77 ' 78 Na 1.351 1.507 1.402 1.611 1.605 1.690 1.454 1.577 1.762 1.189 1.465 1.467 1.553 1.612 K 0.752 0.705 0.743 0.767 0.850 0.862 0.722 0.850 0.836 0.619 0.741 0.717 0.779 0.846 Si 42.323 42.197 41.966 41.743 41.397 41.754 43.298 41.553 41.645 43.942 42.922 42.184 41.743 40.783 Al 10.802 11.399 11.213 12.149 12.168 12.599 10.900 12.340 12.807 9.716 11.080 11.339 11.403 12.652 Ti 0.937 1.096 1.081 0.997 1.081 1.024 1.039 1.076 1.021 0.832 1.083 1.116 1.084 0.997 Fe 17.239 16.977 16.727 16.735 17.493 17.045 16.513 17.489 16.907 16.588 17.199 17.107 16.919 17.171 Hn 0.342 0.376 0.297 0.319 0.337 0.359 0.380 0.364 0.359 0.312 0.334 0.341 0.325 0.358 MS 10.708 10.539 10.579 10.625 9.987 10.425 11.312 10.257 10.418 11.418 10.688 10.449 10.524 10.151 Ca 11.808 11.644 11.802 11.591 11.497 11.557 11.700 11.781 11.392 11.871 11.637 11.760 11.573 11.702 H20 1.959 1.966 1.954 1.969 1.957 1.981 1.992 1.974 1.980 1.978 1.982 1.965 1.953 1.954 98.221 98.405 97.768 98.507 98.372 99.297 99.311 99.262 99.127 98.466 99.131 98.444 97.856 98.224 Number of Ions on the b a s i s of 24 (0 , OH) 0.464 0.517 0.349 0.430 0.434 0.462 0.480 ; 0.165 0.161 0.120 0.143 0.140 0.153 0.166 6.310 6.306 6.661 6.494 6.436 6.410 6.259 2.209 2.286 1.736 1.976 2.039 2.064 2.288 0.123 0.116 0.095 0.123 0.128 0.125 0.115 2.221 2.141 2.103 2.176 2.183 2.173 2.204 0.047 0.046 0.040 0.043 0.044 0.042 0.046 2.322 2.351 2.580 2.410 2.376 2.409 2.322 1.917 1.848 1.928 1.886 1.923 1.904 1.924 15.777 15.774 15.611 15.681 15.703 15.741 15.804 Ma 0.401 0.446 0.417 0.476 0.477 0.496 0.424 K 0.147 0.137 0.145 0.149 0.166 0.166 0.139 Si 6.478 6.436 6.440 6.357 6.341 6.318 6.516 Al 1.949 2.049 2.029 2.180 2.197 2.247 1.933 Ti 0.108 0.126 0.125 0.114 0.125 0.117 0.118 Fe 2.207 2.165 2.147 2.131 2.241 2.157 2.078 Mn 0.044 0.049 0.039 0.041 0.044 0.046 0.048 Mg 2.443 2.396 2.420 2.412 2.280 2.351 2.537 Ca 1.937 1.903 1.941 1.891 1.887 1.874 1.887 15.713 15.706 15.702 15.751 15.757 15.773 15.681 OH 2.000 . 2.000 2.000 2.000 2.000 2.000 2.000 FM 47.956 48.027 47.455 47.390 50.049 48.373 45.598 O x i d e s : Na=Na,0: K=K,0; S1=S10,; A1=A1,0 , ; T1=T10,; Fe=FeO: Mn=MnO; Mg=MgO; Ca = CaO FM=(FeO+MnO/FeO+MnO+MgO)* 100 w APPENDICES / 320 6.3. Calculated thermobarometric results Thermobarometric calculations employing mineral analytical data from Table 13 are listed in Table 14. Temperatures for pelitic and garnet-hornblende-biotite bearing samples were calculated with the garnet-biotite geothermometer. For comparative purposes three sets of temperatures have been reported for each analysed garnet-biotite pair, all using the Ferry and Spear (1978) experimental calibration. In one calculation (TI in Table 14) ideal mixing is assumed for garnet, while the latter two employ the mixing models of Newton and Haselton (1981; Fe, Mg and Ca mixing, T2 in Table 14) and Ganguly and Saxena (1984; Fe, Mg, Ca and Mn mixing, T3 in Table 14), respectively. When geobarometric calculations were not possible, these three sets of temperatures were calculated; at 4, 5, 6 and 7 kb for each garnet-biotite pair. Except for those from sample 84-76-3A, garnet-biotite temperatures quoted in the text and plotted on Figure 89 were calculated with pyrope and grossular activities derived with the Newton and Haselton (1981) mixing model. Quoted temperatures for sample 84- 76- 7A, with garnet that has subequal amounts of grossular and spessartine components (Table 13), were calculated with pyrope and almandine activities derived with the Ganguly and Saxena (1984) mixing model. Pressures in pelitic samples containing an Al 2SiO s phase (or phases) were calculated with the garnet-plagioclase-Al2Si05-quartz geobarometer which is based on the mass transfer reaction: GROS + 2Al 2Si0 5 + QZ = 3 AN The end-member calibration for this reaction comes from the work of Lang and Rice (1985). Their P-T equation was derived with linear programming techniques, and is APPENDICES / 321 based on the experimental calibrations of the above reaction 16 (Hays, 1966; Hariya and Kennedy, 1968; Goldsmith, 1980). Grossular and anorthite activities used in pressure calculations were determined with the mixing models of Newton and Haselton (1981). Errors of ±3 kb are reported for all calculated GT- STAUR- QZ- Al 2 S i 0 5 pressures. This error is due to the large extrapolation necessary to get the end-member experimentally calibrated reaction to compositional ranges of interest (Lang and Rice, 1985; Hodges and McKenna, 1987). Mole fractions of Fe and Mg in biotite (XFeBi and XMgBi), Fe, Mg, Ca, and Mn in garnet (XFeGt, XMgGt, XCaGt and XMnGt) and Ca in plagioclase (XCaPl) are listed for each calculated temperature or temperature-pressure pair. Compositional data from two garnet analyses are listed for each simultaneous T-P calculation. The upper values are from the garnet-biotite pair and the lower from the garnet plagioclase pair. K in Table 14 is Kd, the distribution coefficient T a b l e 14: Thermo-baromet r 1 c d a t a from the TLMC Q^ — yQ-.yf^ B1-G1 NO PLAGIOCLASE. XFeGt=0.679 XMgGt=0.057 XCaGt=0.195 X F e B i = 0 . 5 6 5 XMgBi=0.435 K=0.109 P (b ) T1 (C) T2(C) T3(C) 4000. 435. 508. 495. 5000. 438. 511. 498. 6000. 442. 514. 501. 7000. 4 15. 517. 504. XMnGt=0.070 B2-G2 NO PLAGIOCLASE. XFeGt=0 .690 XMgGt=0.061 XCaGt=0.184 XFeBi=0 .574 XMgBi=0.426 K=0.119 P (b ) T K C ) T2(C) T3(C) 4000. 458. 528. 514. 5000. 46 1. 531. 5 18. 6000. 464. 534. 52 1. 7000. 468. 537. 524. XMnGt=0.065 B3-G3 NO PLAGIOCLASE. XFeGt=0. 680 XMgGt = 0 .062 XCaGt =0.194 XFeBi=0 . 562 XMgBi = 0. 438 K =0. 1 16 P (b ) T K C ) T2(C) T3(C) 4000. 452 . 525 . 508 . 5000. 455 . 528 . 5 11. 6000. 458 . 531 . 5 15. 7000. 461 . 534 . 518 B4-G4 NO PLAGIOCLASE. XFeGt=0. 688 XMgGt = 0. 059 XCaGt =0.186 X F e B i ^ O . 551 XMgB 1 = 0. 449 K =0. 106 P (b ) T K C ) T2(C) T3(C) 4000. 429 . 498 . 485 . 5000. 432 . 501 . 488 . 6000. 435 . 504 . 491 . 7000. 438 . 507 . 494 . XMnGt=0.065 XMnGt=0.067 B5-G5 NO PLAGIOCLASE. XFeGt=0. 685 XMgGt = 0 .057 XCaGt =0.188 XFeB i =0. 572 XMgBi = 0 . 428 K =0. 1 12 P ( b ) T K C ) T2(C ) T3(C) 4000. 442 . 513 . 501 . 5000. 445 . 5 16 . 504 . 6000. 449 . 519 . 508 . 7000. 452 . 522 . 5 11. B6-G6 NO PLAGIOCLASE . XFeGt=0. 674 XMgGt = 0 .056 XCaGt =0.206 XFeB i =0. 576 XMgB i = 0 424 K =0. 1 12 P ( b ) T K C ) T2 (C) T3 (C) 4000. 442 . 520 . 504 . 5000. 445 . 523 . 507 . 6000. 449 . 526 . 510. 7000. 452 . 529 . 514 . B7-G7 NO PLAGIOCLASE. XFeGt=0. 669 XMgGt =o .059 XCaGt =0.205 X F e B i = 0 . 573 XMgB 1 = 0 . 427 K =0. 1 18 P ( b ) T K C ) T2 (C ) T3 (C) 4000. 456 . 534 . 517 . 5000. 460. 537 . 520. 6000 . 463 . 54 1 . 523 . 7000. 466 . 544 . 526 . B9-G9 NO PLAGIOCLASE. XFeGt=0. 687 XMgGt =0. 058 XCaGt =0.182 XFeB1=0. 568 XMgBi =0. 432 K =0. 1 12 P ( b ) T K C ) T2 (C ) T3(C) 4000. 442 . 511. 500. 5000. 445 . 514 . 503 . 6000 . 449 . 517. 507 . 7000. 452 . 520. 510. XMnGt=0.069 XMnGt=0.064 XMnGt=0.067 XMnGt=0 073 Cont i n u e . to NJ T a b l e 14: Thermo-baromet r 1 c d a t a : c o n t i n u e d 84—76 — 7A B10-G10 NO PLAGIOCLASE. XFeGt=0 .680 XMgGt=0.056 XCaGt=0.185 XMnGt=0.079 XFeB1=0.561 XMgBi=0.439 K=0.106 P (b ) T1 (C) T2(C) T3(C) 4000. 430. 499. 489. 5000. 433. 502. 492. 6000. 436. 505. 495. 7000. 439. 508. 499. B 1 1-G1 1 NO PLAGIOCLASE. XFeGt=0.675 XMgGt=0.059 XCaGt=0.194 XFeB1=0.560 XMgBi=0.440 K=0.112 P (b ) T K C ) T2(C) T3(C) 4000. 442. 515. 500. 5000. 445. 518. 503. 6000. 448 . 52 1. 507. 7000. 451 . 524. 5 10. XMnGt=0.072 B12-G12 NO PLAGIOCLASE. XFeGt=0.689 XMgGt=0.065 XCaGt=0.185 X F e B i = 0 . 5 6 0 XMgBi=0.440 K=0.120 P (b ) T1 (C) T2(C) T3(C) 4000. 459. 530. 513. 5000. 463. 533. 516. 6000. 466. 536. 5 19. 7000. 469. 539. 523. XMnGt=0.062 B13-G13 NO PLAGIOCLASE. XFeGt=0.673 XMgGt=0.058 XCaGt=0.201 XMnGt=0.068 XFeBi=0 .554 XMgBi=0.446 K=0.106 P(b) T1 (C) T2(C) T3(C) 4000. 43 1. 506. 489. 5000. 434. 509. 493. 6000. 4 37. 512. 496. 7000. 440. 515. 499. B14-G14 NO PLAGIOCLASE. XFeGt=0 .683 XMgGt=0.057 XCaGt=0.193 X F e B i = 0 . 5 5 8 XMgB1=0.442 K=0.106 P (b ) T 1 ( C ) T 2 ( C ) T3 (C) 4000. 43 1. 503 . 489 . 5000. 434. 506. 492. 6000. 437 . 509 . 495. 7000. 440. 512. 498. XMnGt=0.066 B15-G15 XFeGt=0 .692 XFeB1=0.551 P ( b ) 4000. 5000. 6000. 7000. B16-G16 XFeGt=0 .666 XFeB1=0.559 P ( b ) 4000. 5000. 6000. 7000. NO PLAGIOCLASE. XMgGt=0.059 XCaGt=0.182 XMnGt=0.068 XMgB i =0.449 K = 0. 104 T1 (C ) T2 (C ) T3(C) 426. 493. 482. 429 . 496. 485. 432. 499 . 488. 435 . 502 . 491. NO PLAGIOCLASE. XMgGt=0.062 XCaGt=0.207 XMgB1=0.441 K=0.118 T1(C ) T2(C ) T3 (C) 455 . 534. 513. 459 . 537. 516. 462. 540. 520. 465 . 543. 523. XMnGt=0.066 B18-G18 NO PLAGIOCLASE. XFeGt=0 .682 XMgGt=0.064 XCaGt=0.196 XFeB1=0.551 XMgB1=0.449 K=0.114 P ( b ) T1 (C ) T 2 ( C ) T3(C) 4000. 448. 522. 502. 5000. 45 1. 525 . 505. 6000. 454. 528. 508. 7000. 4 58 . 531 . 512. XMnGt=0.059 Cont1nue . T a b l e 14: T h e r m o - b a r o m e t r 1 c d a t a : c o n t i n u e d 8 4 - 7 6 - 7 A B19-G19 NO PLAGIOCLASE. XFeGt=0.679 XMgGt=0.060 XCaGt=0.198 XFeBi=0 .531 XMgB1=0.469 K=0.100 P (b ) T1 (C) T2(C) T3(C) 4000. 416. 490. 472. 5000. 420. 493. 475. 6000. 423 . 496. 478. 7000. 426. 498. 48 1. XMnGt^O.063 B20-G20 NO PLAGIOCLASE. XFeGt=0.679 XMgGt=0.065 XCaGt=0.197 XMnGt=0.059 X F e B i = 0 . 5 4 0 XMgBi=0.460 K=0.113 P(b) T K C ) T2(C) T3(C) 4000. 445. 519. 498. 5000. 448. 522. 501. 6000. 452. 525. 504. 7000. 455. 529. 507. B21-G21 NO PLAGIOCLASE . XFeGt=0. 683 XMgGt = 0. .056 XCaGt =0.192 XFeB i =0. 547 XMgB i =0 453 K=0. 100 P (b ) T K C ) T2(C) T3(C) 4000. 4 16. 487 . 474 . 5000. 4 19. 490. 477 . 6000. 422 . 493 . 480. 7000. 425 . 496 . 483 . B22-G22 NO PLAGIOCLASE. XFeGt=0. 686 XMgGt = 0. 060 XCaGt =0.188 XFeB i =0. 549 XMgB i =0. 451 K=0. 107 P (b ) T K C ) T2(C) T3(C) 4000. 432 . 503 . 488 . 5000. 436 . 506 . 491 . 6000. 4 39 . 509 . 494 . 7000. 442 . 512. 497 . XMnGt=0.069 XMnGt=0.066 B23-G23 NO PLAGIOCLASE. XFeGt=0.677 XMgGt=0.060 XCaGt=0.199 XFeB1=0.552 XMgBi=0.448 K=0.110 P ( b ) T K C ) T2 (C ) T3 (C ) 4000. 438. 5 13. 495 . 5000. 44 1. 516. 498. 6000. 445. 519 . 501 . 7000. 448. 522. 504. XMnGt=0.063 Cont i nue. . . M T a b l e 14: Thermo-baromet r i c d a t a : c o n t i n u e d 8 5 ~ 6 1 0 — 1 B1-G1 NO PLAGIOCLASE. XFeGt=0. 729 XMgGt =0 .105 XCaGt =0.160 XFeB i =0. 457 XMgBi =0 . 543 K =0. 12 1 P(b ) T K C ) T2(C) T3(C) 4000. 462 . 523 . 474 . 5000. 465 . 526 . 477 . 6000. 468 . 529 . 480. 7000. 47 1 . 532 . 484 . B2-G2 NO PLAGIOCLASE. XFeGt=0. 7 19 XMgGt =0. 124 XCaGt =0.151 XFeBi=0 . 467 XMgB i = 0. 533 K =0. 151 P ( b ) T K C ) T2(C) T3(C) 4000. 522 . 582 . 518. 5000. 526 . 586 . 521 . 6000. 529 . 589 . 525 . 7000. 533 . 593 . 528 . B4-G4 NO PLAGIOCLASE. XFeGt=0. 723 XMgGt = 0. 118 XCaGt =0.153 XFeBi=0 . 447 XMgBi =0. 553 K =0. 132 P (b ) T K C ) T2(C) T3(C) 4000. 485 . 545 . 485 . 5000. 489 . 548 . 489 . 6000. 492 . 551 . 492 . 7000. 495 . 554 . 495 . B5-G5 NO PLAGIOCLASE. XFeGt=0. 73 1 XMgGt =0. 119 XCaGt =0.143 XFeBi=0 . 454 XMgB 1 =0. 546 K =0. 135 P (b ) T K C ) T2(C) T3(C) 400O. 492 . 547 . 490. 5000. 495 . 551 . 494 . 6000. 499 . 554 . 497 . 7000. 502 . 557 . 501 . XMnGt=0.006 XMnGt=0.006 XMnGt=0.005 XMnGt=0.007 B6-G6 XFeGt=0 .726 XFeBi=0 .481 P ( b ) 4000. 5000. 6000 . 7000. B8-G8 XFeGt=0 .720 X F e B i =0.477 P ( b ) 4000. 500O. 6000. 7000 . B10-G10 XFeGt=0 .727 XFeBi=0 .521 P ( b ) 4000. 5000. 6000. 7000. B1 1-G11 XFeGt=0.731 XFeB1=0.482 P ( b ) 4000. 5000. 6000. 7000. NO PLAGIOCLASE. XMgGt=0.113 XCaGt=0.156 XMnGt=0.006 XMgB1=0.519 K=0.144 T1 (C ) T2 (C ) T3 (C) 508. 570 . 514. 512. 573 . 517. 515 . 576 . 521 . 519 . 580 . 524. XMnGt=0.005 NO PLAGIOCLASE. XMgGt=0.123 XCaGt=0.153 XMgBi=0.523 K=0.155 T1 (C ) T2 (C ) T3(C) 53 1 . 592 . 528. 535. 596 . 531. 539 . 599 . 535. 542 . 603 . 539 . NO PLAGIOCLASE. XMgGt=0.126 XCaGt=0.141 XMnGt=0.005 XMgBi=0.479 K=0.188 T1 (C) T2 (C ) T3 (C ) 595. 653 . 586. 599. 656 . 590. 602. 660 . 594. 606 . 664 . 598. NO PLAGIOCLASE. XMgGt=0.128 XCaGt=0.133 XMgB1=0.518 K=0.163 T 1 ( C ) T2 (C ) T3 (C ) 545. 599 . 535. 549. 602 . 539 . 553 . 606 . 542. 556. 610 . 546. XMnGt=0.007 Cont i nue . . . U) T a b l e 14: Thermo-baromet r 1 c d a t a : c o n t i n u e d 85~610 — 1 B12-G12 NO PLAGIOCLASE. B16-G1G NO PLAGIOCLASE. XFeGt=0.734 XMgGt=0. 122 XCaGt =0.139 XMnGt=0.005 XFeGt=0 .738 XMgGt=0. 114 XCaGt =0.143 XFeB1=0.440 XMgBi=0. 560 K=0. 13 1 XFeB1=0.434 XMgB1=0. 566 K=0. 1 19 P ( b ) T1(C) T2(C) T3(C) P ( b ) T K C ) T 2 ( C ) T3 (C) 4000. 482 . 536 . 478 . 4000. 457 . 511 . 460. 5000. 486 . 540. 481 . 5000. 460. 515 . 463 . 6000. 489 . 543 . 485 . 6000 . 464 . 5 18 . 466 . 7000 . 493 . 546 . 488 . 7000. 467 . 52 1 . 469 . B13-G13 NO PLAGIOCLASE. B19-G19 NO PLAGIOCLASE. XFeGt=0. 722 XMgGt =0 106 XCaGt =0.166 XMnGt = 0 .005 XFeGt=0 .733 XMgGt = 0 .110 XCaGt =0.15 1 XFeB i =0. 480 XMgB i =0. . 520 K = 0. 136 XFeB i =0.444 XMgB i =0 . 556 K = 0. 120 P ( b ) T K C ) T2(C ) T3(C) P ( b ) T K C ) T2 (C ) T3(C) 4000. 494 . 558 . 505 . 4 OOO. 459 . 517 . 466 . 5000. 497 . 562 . 509 . 5000 . 463 . 520 . 470. 6000. 500. 565 . 512 . 6000 . 466 . 524 . 473 . 7000. 504 . 568 . 5 16. 7000. 469 . 527 . 476 . B14-G14 NO PLAGIOCLASE. B2 1 -G21 NO PLAGIOCLASE. XFeGt=0. 732 XMgGt =0. 108 XCaGt =0.155 XMnGt = 0. 004 XFeGt=0 .733 XMgGt = 0. 118 XCaGt =0.144 XFeB1=0. 425 XMgB i =0 575 K = 0. 109 XFeB i =0.469 XMgB i = 0. 531 K =0. 142 P ( b ) T K C ) T2(C) T3(C) P ( b ) T K C ) T2 (C ) T3(C) 4000. 437 . 495 . 445 . 4000. 505 . 561 . 504 . 5000. 440. 498 . 449 . 5000. 508 . 565 . 508 . 6000. 4 44 . 502 . 452 . 6000. 512 . 568 . 5 11. 7000. 447 . 505 . 455. 7000. 515. 571 . 5 15. B15-G15 NO PLAGIOCLASE. B22-G22 NO PLAGIOCLASE. XFeGt=0. 733 XMgGt = 0. 111 XCaGt =0.150 XMnGt =0. 006 XFeGt=0 .735 XMgG^ = 0 . 113 XCaGt =0.148 XFeB1=0. 435 XMgBi =0. 565 K = 0. 1 16 XFeBt=0 .459 XMgB1' =0. 541 K : = 0. 131 P (b ) T K C ) T2(C) T3(C) P ( b ) T K C ) T2 (C ) T3 (C) 4000. 452 . 509 . 458 . 4000. 482 . 539 . 486 . 5000. 455 . 512. 462 . 5000. 485 . 542 . 489 . 6000. 458 . 515. 465 . 6000. 489 . 546 . 492 . 7000. 462 . 518. 468 . 7000. 492 . 549 . 496 . XMnGt=0.006 XMnGt=0.005 XMnGt=0.003 C o n t i n u e . U) T a b l e 14: T h e r m o - b a r o m e t r i c d a t a : c o n t i n u e d 85 — 6 1 0 — 1 B25-G25 NO PLAGIOCLASE. XFeGt=0 .730 XMgGt=0.118 XCaGt=0.147 XMnGt=0.005 XFeBi=0 .438 XMgBi=0.562 K=0.126 P (b ) T K C ) T2(C) T3(C) 4000. 472. 529. 472. 5000. 476. 532. 476. 6000. 479. 535. 479. 7000. 482. 539. 482. B29-G29 NO PLAGIOCLASE. XFeGt=0 .730 XMgGt=0.110 XCaGt=0.155 X F e B i = 0 . 4 1 8 XMgBi=0.582 K=0.108 P ( b ) T K C ) T2 (C ) T3(C) 4000 . 434 . 492 . 441 . 5000. 437 . 495 . 445. 6000 . 440 . 498 . 448. 7000. 443 . 501 . 451 . XMnGt=0.006 B26-G26 NO PLAGIOCLASE. XFeGt=0.731 XMgGt=0. 108 XCaGt =0.155 XFeB i =0.437 XMgBi=0. 563 K=0. 1 15 P ( b ) T1 (C) T2(C) T3(C) 4000. 448 . 507 . 457 . 5000. 452 . 510. 461 . 6000. 455 . 513 464 . 7000. 458 . 516. 467 . B27-G27 NO PLAGIOCLASE. XFeGt=0.732 XMgGt =0. 113 XCaGt =0.151 XFeBi=0 .431 XMgBi =0. 569 K=0. 1 17 P ( b ) T K C ) T2(C) T3(C) 4000. 453 . 510. 457 . 5000. 456 . 513. 46 1 . 6000. 459 . 517 . 464 . 7000. 463 . 520 . 467 . B28-G28 NO PLAGIOCLASE. XFeGt=0.734 XMgGt =0. 112 XCaGt =0.149 XFeBi=0 .423 XMgB i =0. 577 K=0. 1 12 P ( b ) T K C ) T2(C) T3(C) 4000. 442 . 499 . 447 . 5000. 446 . 502 . 451 . 6000. 449 . 505 . 454 . 7000. 452 . 508 . 457 . C o n t I n u e . u> to T a b l e 14: T h e r m o - b a r o m e t r i c d a t a : con t i nued 8 4 - 6 2 2 - 4 B1-G1 NO PLAGIOCLASE. XFeGt=0.739 XMgGt=0. 113 XCaGt =0.144 X F e B i = 0 . 4 2 0 XMgBi=0. 580 K = 0. 1 1 1 P (b ) T K C ) T2(C) T3(C) 4000. 44 1. 495 . 444 . 5000. 444 . 498 . 447 . 6000 . 447 . 501 . 450. 7000. 4 50. 504 . 454 . B3-G3 NO PLAGIOCLASE. XFeGt=0.698 XMgGt=0. 147 XCaGt =0.153 XFeB i =0.393 XMgBi=0. 607 K=0. 136 P (b ) T K C ) T2(C) T3(C) 4000. 493 . 553 . 468 . 5000. 497 . 556 . 472 . 6000. 500. 560. 475 . 7000. 504 . 563 . 479 . B4-G4 NO PLAGIOCLASE. XFeGt=0.723 XMgGt = 0. 106 XCaGt = 0 169 XFeB1=0.403 XMgB i =0. 597 K=0. 099 P (b ) T K C ) T2(C) T3(C) 4000. 4 14. 476 . 425 . 5000. 4 17. 479 . 428 . 6000. 420. 482 . 43 1 . 7000. 423 . 485 . 434 . B13-G13 NO PLAGIOCLASE. XFeGt=0.732 XMgGt=0. 127 XCaGt =0.137 XFeB1=0.420 XMgB1=0. 580 K=0. 126 P (b ) T K C ) T2(C) T3(C) 4000. 472 . 525 . 463 . 5000. 475 . 528 . 466 . 6000. 479 . 53 1 . 470. 7000. 482 . 534 . 473 . 1 B13-G13 P7-PG7 XFeGt=0 .732 XMgGt=0.127 XCaGt=0.137 XMnGt=0.004 X F e B i = 0 . 4 2 0 XMgB1=0.580 XCaPl=0 .265 K=0.126 XFeGt=0 .713 XMgGt=0.136 XMnGt=0.003 XCaGt=0.148 TEMPERATURE IN DEGREES C . PRESSURE IN BARS. T l ( F e r r y & Spear )= 482. P ( a t T1) = 6910. T2(Newton S H a s e l t o n ) = 539 . P l a t T2)= 8279. T 3 ( G a n g u l y & Saxena)= 472. P ( a t T3)= 6672. B16-G16 P3-PG1 XFeGt=0 .722 XMgGt=0.104 XFeBi=0 .424 XMgBi=0.576 XCaGt=0.171 XMnGt=0.003 XCaPl=0 .232 K=0.106 XFeGt=0 .736 XMgGt=0.126 XMnGt=0.003 XCaGt=0.135 TEMPERATURE IN DEGREES C , PRESSURE IN BARS. T K F e r r y S Spear )= 436. P ( a t T1)= 5976. T2(Newton & H a s e l t o n ) = 505. P (a t T2)= 7664. T 3 ( G a n g u l y & Saxena)= 450. P l a t T3)= 6325. B16-G16 XFeGt=0.722 X F e B i = 0 . 4 2 4 P ( b ) 4OO0. 5000. 6000 . 7000. XMgGt=0 T K C ) 4 30. 433 . 436 . 439 . NO 104 XMgBi=0.576 PLAGIOCLASE. XCaGt=0.17 1 K=0.106 XMnGt=0.003 T2 (C ) 494 . 497 . 500. 503 . T3 IC) 443 . 446 . 449 . 452 . B17-G17 NO PLAGIOCLASE. XFeGt=0 .740 XMgGt=0.118 XCaGt=0.140 X F e B i = 0 . 4 2 3 XMgBi=0.577 K=0.117 P ( b ) T1 (C) T2 (C) T3(C) 4000. 453. 506. 452. 5000. 457. 510. 456. 6000 . 460. 513 . 459. 7000. 463. 516. 462. XMnGt=0.003 C o n t 1 n u e . . . 0 0 T a b l e 14: Thermo-baromet r1c d a t a c o n t 1 n u e d 8 4 - 6 2 2 B17-G17 P3-PG1 XFeGt=0 .740 XMgGt=0.118 XCaGt=0.140 XMnGt=0.003 XFeB1=0.423 XMgB1=0.577 XCaPl=0.232 K=0.117 XFeGt=0.736 XMgGt=0.126 XMnGt=0.003 XCaGt=0.135 TEMPERATURE IN DEGREES C , PRESSURE IN BARS. T K F e r r y S Spear )= 462. P (a t T1) = 6609. T2(Newton & H a s e l t o n ) = 519. P (a t T2) = 8012. T 3 ( G a n g u l y & Saxena)= 46 1. P (a t T3) = 6584. B18-G18 NO PLAGIOCLASE. XFeGt=0. 734 XMgGt=0. 127 XCaGt =0.134 XFeB i =0. 4 13 XMgB i =0. 587 K = 0 . 122 P (b ) T K C ) T2(C ) T3(C) 4000 . 464 . 515. 455 . 5000 . 467 . 518. 458 . 6000. 470. 52 1 . 46 1 . 7000. 473 . 524 . 464 . B18-G18 P3-PG1 XFeGt=0.734 XMgGt=0127 XCaGt=0.134 XMnGt=0.005 XFeB1=0.413 XMgBi=0.587 XCaPl=0.232 K=0.122 XFeGt=0.736 XMgGt=0.126 XMnGt=0.003 XCaGt=0.135 TEMPERATURE IN DEGREES C , PRESSURE IN BARS. T K F e r r y & Spear )= 473. P ( a t T1)= 6880. T2(Newton & H a s e l t o n ) = 529. P ( a t T2)= 824 1. T 3 ( G a n g u l y & Saxena)= 463. P ( a t T3) = 664 1. B19-G19 NO PLAGIOCLASE. XFeGt=0.726 XMgGt=0. 084 XCaGt =0.187 XFeB i =0.419 XMgB i =0. 581 K=0. 084 P (b ) T K C ) T2(C) T3(C) 4000. 379 . 446. 407 . 5000. 382 . 449 . 410. 6000. 385 . 452 . 4 13. 7000. 388 . 455 . 4 16 . B21-G2 1 XFeGt=0.748 XFeB1=0.418 P ( b ) 4O0O. 5000 . 6000. 7000. B22-G22 XFeGt=0.734 XFeB1=0.457 P ( b ) 4000 . 5000. 6000. 7000 . NO PLAGIOCLASE. XMgGt=0.102 XCaGt=0.148 XMgBi=0.582 K=0.098 T 1 ( C ) T2 (C ) T3 (C) 412. 466. 424. 415. 469 . 427. 418 . 472. 430. 42 1. 475 . 433. NO PLAGIOCLASE. XMgGt=0.108 XCaGt=0.155 XMgB i =0.543 K=0. 124 T K C ) T 2 ( C ) T3 (C) 468 . 527. 476. 471 . 530. 480. 474. 533 . 483. 478 . 537 . 486. XMnGt=0.002 XMnGt=0.003 B23-G23 NO PLAGIOCLASE. XFeGt=0.728 XMgGt =0. 125 XCaGt =0.143 XFeB i=0 .495 XMgB i = 0 . 505 K=0. 168 P ( b ) T K C ) T2 (C ) T3(C) 4000. 557 . 614 . 549 . 5000. 560. 6 18 . 553 . 6000 . 564 . 62 1 . 557 . 7000. 568 . 625 . 56 1 . B25-G23B NO PLAGIOCLASE. XFeGt=0.727 XMgGt=0. 114 XCaGt =0.155 XFeB i =0.426 XMgBi=0. 574 K=0. 1 17 P ( b ) T1 (C) T2 (C ) T3 (C) 4000. 453 . 512 . 457 . 5000 . 456 . 515 . 460. 6000 . 459 . 5 18 . 463 . 7000. 463 . 521 . 466 . Cont1nue . T a b l e 14: T h e r m o - b a r o m e t r i c d a t a cont i nued 85-67 B1-G1 NO PLAGIOCLASE. XFeGt=0 .692 XMgGt =0. 138 XCaGt =0.144 XFeB i =0.493 XMgBi =0. 507 K=0. 194 P (b ) T K C ) T2(C) T3(C) 4000. 606 . 665 . 588 . 5000. 610. 669 . 592 . 6000. 6 14. 673 . 596 . 7000. 618 . 676. 600. B2-G2 NO PLAGIOCLASE. XFeGt=0.687 XMgGt =0. 153 XCaGt =0.150 X F e B i = 0 . 4 3 9 XMgB 1 = 0. 561 K=0. 174 P (b ) T K C ) T2(C ) T3(C) 4000. 567 . 628 . 536 . 5000. 571 . 632 . 540. 6000. 575 . 635 . 543 . 7000. 579 . 639 . 547 . B2-G2 P7-PG7 XFeGt=0.687 XMgGt = 0. 153 XCaGt =0.150 X F e B i = 0 . 4 3 9 XMgBi =0. 561 XCaPl=0.192 XFeGt=0.691 XMgGt =0. 150 XMnGt =0.015 XMnGt=0.026 XMnGt=0.011 XMnGt=0.011 K=0.174 XCaGt=0.144 TEMPERATURE IN DEGREES C , PRESSURE IN BARS. T K F e r r y 8. Spear )= 598. P (a t T1)= 12133. T2(Newton & H a s e l t o n ) = 664. P (a t T2)= 13899. T 3 ( G a n g u l y & Saxena)= 563. P (a t T3)= 11199. B2-G2 P10-PG10 XFeGt=0.687 XMgGt=0.153 XCaGt=0.150 XMnGt=0.011 X F e B i = 0 . 4 3 9 XMgBi=0.561 XCaPl=0.222 K=0.174 XFeGt=0.686 XMgGt=0.147 XMnGt=0.011 XCaGt=0. TEMPERATURE IN DEGREES C , PRESSURE IN BARS. T K F e r r y & Spear )= 596. P (a t T1 )= 1 1627. T2(Newton & H a s e l t o n ) = 662. P (a t T2)= 13356. T 3 ( G a n g u l y & Saxena)= 561 . P (a t T3)= 10713. 156 B2-G2 P1 1-PG11 XFeGt=0.687 XMgGt=0.153 XFeB1=0.439 XMgBi=0.561 XCaGt=0.150 XMnGt=0.011 XCaPl=0 .225 K=0.174 XFeGt=0.687 XMgGt=0.149 XMnGt=0.012 XCaGt=0.153 TEMPERATURE IN DEGREES C , PRESSURE IN BARS. T K F e r r y & Spear )= 595. P ( a t T1 )= 11467. T2(Newton & H a s e l t o n ) = 662. P ( a t T2)= 13183. T 3 ( G a n g u l y & Saxena)= 561 . P ( a t T3)= 10560. B1-G1 P7-PG7 XFeGt=0 .690 XMgGt=0.144 XCaGt=0.142 XMnGt=0.025 XFeB1=0.493 XMgBi=0.507 XCaPl=0 .192 K=0.203 XFeGt=0.691 XMgGt=0.150 XMnGt=0.015 XCaGt=0.144 TEMPERATURE IN DEGREES C , PRESSURE IN BARS. T K F e r r y S Spear )= 660 . P ( a t T1)= 13801. T2(Newton & H a s e l t o n ) = 724. P ( a t T2)= 15506. T 3 ( G a n g u l y & Saxena)= 634. P ( a t T3)= 13090. B1-G1 P10-PG10 XFeGt=0.591 XMgGt=0.123 XCaGt=0.265 XMnGt=0.021 XFeB1=0.493 XMgB1=0.507 XCaPl=0 .222 K=0.203 XFeGt=0.686 XMgGt=0.147 XMnGt=0.011 XCaGt=0.156 TEMPERATURE IN DEGREES C , PRESSURE IN BARS. T K F e r r y & Spear )= 658 . P ( a t T1 )= 13254. T2(Newton & H a s e l t o n ) = 777 . P ( a t T2)= 16371. T 3 ( G a n g u l y & Saxena)= 672 . P ( a t T3)= 13607. B1-G1 P1 1-PG1 1 XFeGt=0.591 XMgGt=0.123 XCaGt=0.265 XMnGt=0.021 XFeB1=0.502 XMgBi=0.498 XCaPl=0 .225 K=0.210 XFeGt=0.687 XMgGt=0.149 XMnGt=0.012 XCaGt=0.153 TEMPERATURE IN DEGREES C , PRESSURE IN BARS. T K F e r r y & Spear )= 673. P ( a t T1)= 13481. T2(Newton & H a s e l t o n ) = 793. P ( a t T2)= 16588. T 3 ( G a n g u l y & Saxena)= 687 . P ( a t T3)= 13837. Cont inue. co OJ O T a b l e 14: Thermo-baromet r i c d a t a : c o n t i n u e d 85~67 — 1 B4-G3 NO PLAGIOCLASE. XFeGt=0. 697 XMgGt = 0. 150 XCaGt=0.143 XMnGt =0.010 XFeBi=0 . 455 XMgB 1 =0. 545 K=0.180 P (b ) T1 (C) T2 (C) T3(C) 4000. 579 . 638. 548. 5000. 583 . 641 . 552. 6000. 587 . 645 . 556. 7000. 591 . 649 . 560. B4-G3 Pt -PG1 XFeGt=0. 697 XMgGt =0. 150 XCaGt=0.143 XMnGt =0.010 XFeBi =0. 455 XMgB i =0. 545 XCaPl=0.288 K=0 . 180 XFeGt=0. 690 XMgGt =0. 144 XMnGt=O.G25 XCaGt =0.142 TEMPERATURE IN DEGREES C T K F e r r y & Spear )= 603. T2(Newton & H a s e l t o n ) = PRESSURE IN BARS. P (a t T1)= 10135. 666. P (a t T2)= 11655 T 3 ( G a n g u l y & Saxena)= 569. P (a t T3)= 9318. B4-G3 P2-PG2 XFeGt=0.697 XMgGt=0.150 XCaGt=0.143 XMnGt=0.010 XFeB1=0.455 XMgBi=0.545 XCaPl=0.294 K=0.180 XFeGt=0.682 XMgGt=0.165 XMnGt=0.010 XCaGt=0.144 TEMPERATURE IN DEGREES C . PRESSURE IN BARS. T K F e r r y & Spear )= 603. P ( a t T1)= 10197. T2(Newton & H a s e l t o n ) = 666. P (a t T2)= 11706. T 3 ( G a n g u l y & Saxena)= 569. P (a t T3)= 9386. B5-G5 NO PLAGIOCLASE. XFeGt=0.699 XMgGt=0.147 XCaGt=0.145 XMnGt=0.009 XFeBi=0 .448 XMgBi=0.552 K=0.171 P(b ) T1(C) T2(C) T3(C) 4000. 561. 620. 534. 5000. 565. 623. 538. 6000. 569. 627. 542. 7000. 572. 630. 545. B5-G5 P1-PG1 XFeGt=0 .699 XMgGt=0.147 X F e B i = 0 . 4 4 8 XMgBi=0.552 XCaGt=0.145 XCaPl=0 .288 XMnGt=0.009 K=0.17 1 XFeGt=O.690 XMgGt=0.144 XMnGt=0.025 XCaGt=0.142 TEMPERATURE IN DEGREES C, PRESSURE IN BARS. T K F e r r y & Spear )= 582. P ( a t T1 )= 9645. T2(Newton & H a s e l t o n ) = 646 . P (a t T2)= 11167. T 3 ( G a n g u l y & Saxena)= 553. P ( a t T3)= 8932. B5-G5 P2-PG2 XFeGt=0 .703 XMgGt=0.148 XFeB1=0.448 XMgBi=0.552 XCaGt=0.140 XMnGt=0.009 XCaPl=0 .294 K=0.17 1 XFeGt=0 .682 XMgGt=0.165 XMnGt=0.010 XCaGt=0. TEMPERATURE IN DEGREES C . PRESSURE IN BARS. T K F e r r y & Spear )= 583. P ( a t T1)= 9711. T2(Newton & H a s e l t o n ) = 644. P ( a t T2)= 11170. T 3 ( G a n g u l y & Saxena)= 551. P ( a t T3)= 8967. 144 B6-G6 NO PLAGIOCLASE. XFeGt=0 .692 XMgGt=0.149 XCaGt=0.152 XFeB1=0.422 XMgBi=0.578 K=0.157 P ( b ) T1 (C ) T2 (C ) T3 (C) 4000 . 534. 595. 507. 5000. 538. 598. 511 . 6000 . 542. 602. 515. 7000. 545. 605. 518. XMnGt=0.008 C o n t 1 n u e . T a b l e 14: T h e r m o - b a r o m e t r i c d a t a : c o n t i n u e d 85—67"" 1 B6-G6 P1-PG1 XFeGt=0.692 XMgGt=0.149 XCaGt=0.152 XMnGt=0.008 XFeBi=0 .422 XMgBi=0.578 XCaPl=0.288 K=0.157 XFeGt=0 .690 XMgGt=0.144 XMnGt=0.025 XCaGt=0.142 TEMPERATURE IN DEGREES C , PRESSURE IN BARS. T K F e r r y S Spear )= 552. P (a t T1)= 8921. T2(Newton & H a s e l t o n ) = 618. P (a t T2)= 10493. T 3 ( G a n g u l y & Saxena)= 523. P l a t T3)= 8212. B6-G6 P2-PG2 XFeGt=0.692 XMgGt=0.149 XCaGt=0.152 XMnGt=0.008 XFeBi=0 .422 XMgBi=0.578 XCaP1=0.294 K=0.157 XFeGt=0.682 XMgGt=0.165 XMnGt=0.010 XCaGt=0.144 TEMPERATURE IN DEGREES C , PRESSURE IN BARS. T K F e r r y & Spear )= 552. P (a t T1 )= 8991. T2(Newton & H a s e l t o n ) = 618. P (a t T2)= 10552. T 3 ( G a n g u l y & Saxena)= 523. P (a t T3)= 8287. B7-G7 NO PLAGIOCLASE. XFeGt=0.696 XMgGt=0.153 XCaGt=0.142 XMnGt=0.009 XFeBi=0 .431 XMgBi=0.569 K=0.166 P (b ) T1(C) T2(C) T3(C) 4000. 553. 610. 520. 5000. 557. 6 14. 524. 6000. 560. 6 17. 528. 7000. 564. 621. 531. B7-G7 P1-PG1 XFeGt=0.696 XMgGt=0.153 XCaGt=0.142 XMnGt=0.009 XFeBi=0 .431 XMgBi=0.569 XCaPl=0.288 K=0.166 XFeGt=0 .690 XMgGt=0.144 XMnGt=0.025 XCaGt=0.142 TEMPERATURE IN DEGREES C , PRESSURE IN BARS. T K F e r r y & Spear )= 573. P (a t T1 )= 9422. T2(Newton & H a s e l t o n ) = 635. P l a t T2)= 10906. T 3 ( G a n g u l y S Saxena)= 537. P (a t T3)= 8559. B7-G7 P2-PG2 XFeGt=0 .696 XMgGt=0.153 XCaGt=0.142 XMnGt=0.009 XFeB1=0.431 XMgB1=0.569 XCaPl=0 .294 K=0.166 XFeGt=0 .682 XMgGt=0.165 XMnGt=0.010 XCaGt=0.144 TEMPERATURE IN DEGREES C . PRESSURE IN BARS. T K F e r r y & Spear )= 573 . P l a t T1 )= 9489. T2(Newton & H a s e l t o n ) = 635 . P ( a t T2)= 10962. T 3 ( G a n g u l y & Saxena)= 537. P ( a t T3)= 8632. B8-G8C NO PLAGIOCLASE. XFeGt=0 .685 XMgGt=0.160 XCaGt=0.138 XMnGt=0.018 X F e B i = 0 . 4 5 7 XMgBi=0.543 K=0.196 P ( b ) T1 (C) T2 (C ) T3 (C) 4000. 610. 666 . • 569 . 5000. 614. 670 . 573 . 6000 . 6 17. 674 . 577. 7000. 621 . 678 . 58 1. B8-G8C P1-PG1 XFeGt=0 .685 XMgGt=0.160 XCaGt=0.138 XMnGt=0.018 XFeB1=0.457 XMgBi=0.543 XCaPl=0 .288 K=0.196 XFeGt=0 .690 XMgGt=0.144 XMnGt=0.025 XCaGt=0.142 TEMPERATURE IN DEGREES C . PRESSURE IN BARS. T K F e r r y 8 Spear )= 637 . P ( a t T1)= 10964. T2(Newton 8. H a s e l t o n ) = 699 . P l a t T2)= 12443. T 3 ( G a n g u l y & Saxena)= 592 . P ( a t T3)= 9884. B8-G8C P2-PG2 XFeGt=0 .685 XMgGt=0.160 XCaGt=0.138 XMnGt=0.018 XFeB1=0.457 XMgB1=0.543 XCaPl=0 .294 K=0.196 XFeGt=0 .682 XMgGt=0.165 XMnGt=0.010 XCaGt=0.144 TEMPERATURE IN DEGREES C , PRESSURE IN BARS. T K F e r r y 5 Spear )= 637 . P ( a t T1)= 11020. T2(Newton & H a s e l t o n ) = 699 . P ( a t T2)= 12489. T 3 ( G a n g u l y & Saxena)= 593. P ( a t T3)= 9948. C o n t i n u e . OJ NJ T a b l e 14: T h e r m o - b a r o m e t r I c d a t a : c o n t i n u e d 85-67 B10-G10 NO PLAGIOCLASE. XFeGt=0 .710 XMgGt=0. 129 XCaGt =0.147 XFeBi =0.482 XMgBi=0. 518 K = 0. 168 P(b) T K C ) T2(C) T3(C) 4000. 556 . 615 . 547 . 5000. 560. 619. 55 1 . 6000. 564 . 623 . 555. 7000. 567 . 626 . 559 . B10-G10 P3-PG6 XFeGt=0 .710 XMgGt=0.129 XFeBi=0 .482 XMgBi=0.518 XCaGt=0.147 XMnGt=0.015 XCaPl=0.298 K = 0.168 XFeGt=0.701 XMgGt=0.156 XMnGt=0.006 XCaGt=0.137 TEMPERATURE IN DEGREES C. PRESSURE IN BARS. T K F e r r y & 5pear)= 576. P (a t T1)= 9281. T2(Newton 8. H a s e l t o n ) = 640. P (a t T2)= 10790. T 3 ( G a n g u l y & Saxena)= 566. P t a t T3) = 9053. B11-G1 1 NO PLAGIOCLASE. XFeGt=0.693 XMgGt=0. 128 XCaGt =0.165 XFeB1=0.47 1 XMgBi=0. 529 K = 0. 164 P(b) T K C ) T2(C) T3(C) 4000. 548 . 615. 542 . 5000. 552 . 618. 546 . 6000. 556 . 622 . 550. 7000. 559 . 625 . 553 . B11-G11 P3-PG6 XFeGt=0.693 XMgGt=0.128 XCaGt=0.165 XMnGt=0.014 XFeBi=0 .471 XMgBi=0.529 XCaPl=0.298 K=0.164 XFeGt=0.701 XMgGt=0.156 XMnGt=0.0GC XCaGt=0.137 TEMPERATURE IN DEGREES C , PRESSURE IN BARS. T K F e r r y & Spear )= 567. P (a t T1) = 9070. T2(Newton & H a s e l t o n ) = 639. P (a t T2) = 10759. T 3 ( G a n g u l y & Saxena)= 561. P (a t T3) = 8916. B12-G12 NO PLAGIOCLASE. XFeGt=0 .702 XMgGt=0. 136 XCaGt =0.151 XFeB i =0.530 XMgB1=0. 470 K=0. 2 18 P ( b ) T K C ) T2 (C ) T3 (C ) 4000. 650. 713 . 633 . 5000. 654 . 717 . 637 . 6000 . 658 . 72 1 . 64 1 . 7000. 662 . 725 . 645 . B12-G12 P3-PG6 XFeGt=0.702 XMgGt=0.136 XCaGt=0.151 XMnGt=0.012 X F e B i = 0 . 5 3 0 XMgBi=0.470 XCaPl=0 .298 K=0.218 XFeGt=0.701 XMgGt=0.156 XMnGt=0.006 XCaGt=0.137 TEMPERATURE IN DEGREES C , PRESSURE IN BARS. T K F e r r y S Spear )= 682 . P ( a t T1 )= 11793. T2(Newton & H a s e l t o n ) = 751 . P (a t T2)= 13404. T 3 ( G a n g u l y & Saxena)= 663. P ( a t T3)= 11342. B15-G15 NO PLAGIOCLASE. XFeGt=0.694 XMgGt=0. 129 XCaGt =0.164 X F e B i = 0 . 4 6 2 XMgB1=0. 538 K=0. 160 P ( b ) T K C ) T2 (C) T3 (C ) 4000. 540. 605 . 532 . 5000. 543 . 609 . 536 . 6000. 547 . 612 . 540. 7O0O. 551 . 616 . 543 . B15-G15 P3-PG6 XFeGt=0.694 XMgGt=0.129 XCaGt=0.164 XMnGt=0.014 XFeB1=0.462 XMgBi=0.538 XCaPl=0 .298 K=0.160 XFeGt=0.701 XMgGt=0.156 XMnGt=0.006 XCaGt=0.137 TEMPERATURE IN DEGREES C , PRESSURE IN BARS. T K F e r r y & Spear )= 557. P ( a t T1 )= 8839. T2(Newton 8 H a s e i t o n ) = 628 . P (a t T2)= 10509. T 3 ( G a n g u l y & Saxena)= 549. P (a t T3)= 8654. Cont i n u e . U) OJ OJ T a b l e 14: T h e r m o - b a r o m e t r i c d a t a : c o n t i n u e d 8 5 - 7 6 - 3 B4-G4 NO PLAGIOCLASE. XFeGt=0 .750 XMgGt=0.190 XCaGt=0.033 XFeB1=0.444 XMgBi=0.556 K=0.202 P ( b ) T K C ) T 2 t C ) T3(C) 4000. 620. 634. 536. 5000. 624. 638. 540. 6000. 628. 642. 544. 7000. 632. 646. 548. XMnGt=0.027 B6-G6 NO PLAGIOCLASE XFeGt=0. 755 XMgGt =0 182 XCaGt =0.033 XFeB i =0. 452 XMgBi =0. 548 K =0. 199 P (b ) T K C ) T2 (C) T3(C) 4000. 615 . 628 . 539 . 5000 . 6 19. 632 . 543 . 6000. 623 . 636 . 547 . 7000. 627 . 640 . 55 1 . B5-G5 NO PLAGIOCLASE. XFeGt=0. 759 XMgGt =0. 170 XCaGt =0.038 XFeB i =0. 468 XMgBi =0. 532 K = 0. 198 P (b ) T K C ) T2(C) T3(C) 4000. 6 12. 628 . 550. 5000. 6 16 . 632 . 554 . 6000. 620 . 636 . 558 . 7000. 624 . 640. 562 . XMnGt=0.029 XMnGt=0.032 B7-G7 NO PLAGIOCLASE. XFeGt=0 .750 XMgGt=0.185 XCaGt=0.035 XFeBi=0 .474 XMgBi=0.526 K=0.222 P ( b ) T K C ) T2(C) T3(C) 4000. 656. 671 . 576. 5000. 661. 675 . 580. 6000. 665. 679 . 584. 7000. 669. 683 . 588. XMnGt=0.031 B8-G8 NO PLAGIOCLASE. XFeGt=0 .756 XMgGt=0.182 XCaGt=0.032 XFeB1=0.478 XMgB1=0.522 K=0.220 P ( b ) T K C ) T 2 ( C ) T3 (C) 4000 . 654. 667 . 576. 5000 . 658 . 6 7 1 . 580. 6 0 0 0 . 662 . 676 . 584. 7000. 666. 680 . 588. XMnGt=0.031 B38A-G38A NO PLAGIOCLASE. XFeGt=0 .767 XMgGt=0.162 XCaGt=0.038 X F e B i = 0 . 4 8 9 XMgBi=0.511 K=0.202 P ( b ) T K C ) T2 (C) T3 (C) 4000. 62 1. 636 . 566. 5000. 625. 640 . 570. 6000 . 629 644. 574. 7000. 633 . 648 . 578. XMnGt=0.032 B38B-G38B NO PLAGIOCLASE. XFeGt=0.761 XMgGt=0.174 XCaGt=0.033 XFeB1=0.473 XMgBi=0.527 K=0.204 P ( b ) T K C ) T2 (C ) T3 (C ) 4000. 624. 638 . 557. 5000 . 628 . 642 . 561 . 6000 . 632. 646 . 565. 7000 . 636 . 650 . . 569 . XMnGt=0.032 Cont1nue . OJ T a b l e 14: Thermo-barometr i c d a t a : c o n t i n u e d 85 — 76 — 3 B4-G4 P1-PG1 XFeGt=0.750 XMgGt=0.190 XCaGt=0.033 XMnGt=0.027 XFeBi=0.444 XMgBi=0.556 XCaPl=0.393 K=0.202 XFeGt=0.701 XMgGt=0.235 XMnGt=0.020 XCaGt=0.044 TEMPERATURE IN DEGREES C, PRESSURE IN BARS. T K F e r r y & Spear)= 624. P ( a t T1 )= 4941. T2(Newton & H a s e l t o n ) = 639. P(at T2)= 5172. T3(Ganguly & Saxena)= 534. P(at T3)= 3502. B4-G4 P2-PG2 XFeGt=0.750 XMgGt=0.190 XCaGt=0.033 XMnGt=0.027 XFeBi=0.444 XMgBi=0.556 XCaP1=0.418 K=0.202 XFeGt=0.715 XMgGt=0.221 XMnGt=0.022 XCaGt=0.041 TEMPERATURE IN DEGREES C, PRESSURE IN BARS. T K F e r r y & Spear)= 622. P l a t T1)= 4410. T2(Newton & H a s e l t o n ) = 636. P l a t T2)= 4631. T3(Ganguly & Saxena)= 533. P l a t T3)= 3035. B4-G4 P7-PG9 XFeGt=0.750 XMgGt=0.190 XCaGt=0.033 XMnGt=0.027 XFeBi=0.444 XMgBi=0.556 XCaPl=0.383 K=0.202 XFeGt=0.695 XMgGt=0.242 XMnGt=0.018 XCaGt=0.044 TEMPERATURE IN DEGREES C, PRESSURE IN BARS. T K F e r r y & Spear)= 625. P l a t T1)= 5086. T2(Nev»ton & H a s e l t o n ) = 639. P l a t T2)= 5319. T3(Gangu1y & Saxena)= 535. P l a t T3)= 3631. B4-G4 P8-PG8 XFeGt=0.750 XMgGt=0.190 XCaGt=0.033 XMnGt=0.027 XFeBi=0.444 XMgBi=0.556 XCaPl=0.386 K=0.202 XFeGt-0.706 XMgGt=0.200 XMnGt=0.017 XCaGt=0.0/6 TEMPERATURE IN DEGREES C, PRESSURE IN BARS. T K F e r r y & Spear)= 634. P l a t T1 )= 7320. T2(Newton & H a s e l t o n ) = 648. P l a t T2)= 7594. T3(Ganguly & Saxena)= 543. P l a t T3)= 5604. B4-G4 P7-PG7 XFeGt=0.750 XMgGt=0.190 XCaGt=0.033 XMnGt=0.027 XFeBi=0.444 XMgBi=0.556 XCaPl=0.383 K=0.202 XFeGt=0.689 XMgGt=0.187 XMnGt=0.022 XCaGt=0.102 TEMPERATURE IN DEGREES C, PRESSURE IN BARS. T K F e r r y & Spear)= 639. P l a t T1 )= 8594. T2(Newton & Hase1ton)= 653. P l a t T2)= 8890. T3(Ganguly & Saxena)= 547. P l a t T3)= 6735. B4-G4 P4-PG4 XFeGt=0.750 XMgGt=0.190 XCaGt=0.033 XMnGt=0.027 XFeB1=0.444 XMgB1=0.556 XCaP1=0.393 K=0.202 XFeGt=0.702 XMgGt=0.192 XMnGt=0.025 XCaGt=0.081 TEMPERATURE IN DEGREES C, PRESSURE IN BARS. T K F e r r y & Spear)= 634. P l a t T1 )= 7463. T2(Newton & H a s e l t o n ) = 649. P l a t T2)= 7739. T3(Ganguly I Saxena)= 543. P l a t T3)= 5731. B4-G4 P6-PG6 XFeGt=0.750 XMgGt=0.190 XCaGt=0.033 XMnGt=0.027 XFeB1=0.444 XMgBi=0.556 XCaPl=0.394 K=0.202 XFeGt=0.713 XMgGt=0.173 XMnGt=0.033 XCaGt=0.081 TEMPERATURE IN DEGREES C, PRESSURE IN BARS. T K F e r r y & Spear)= 634. P l a t T1)= 7401. T2(Newton & H a s e l t o n ) = 648. P l a t T2)= 7679. T3(Ganguly & Saxena)= 543. P l a t T3)= 5659. B4-G4 P5-PG5 XFeGt=0.750 XMgGt=0.190 XCaGt=0.033 XMnGt=0.027 XFeB1=0.444 XMgB1=0.556 XCaPl=0.386 K=0.202 XFeGt=0.703 XMgGt=0.192 XMnGt=0.024 XCaGt=0.081 TEMPERATURE IN DEGREES C, PRESSURE IN BARS. T K F e r r y & Spear)= 635. P l a t T1 )= 7551. T2(Newton & H a s e l t o n ) = 649. P l a t T2)= 7829. T3(Gangu1y & Saxena)= 544. P l a t T3)= 5804. Cont i nue. OJ on T a b l e 14: Thermo-baromet r i c d a t a : c o n t i n u e d 85 — 76~ 3 B1-G1 NO PLAGIOCLASE. XFeGt=0.732 XMgGt=0.209 XCaGt=0.035 XMnGt=0.024 XFeB1=0.529 XMgBi=0.471 K=0.322 P (b ) T1(C) T2(C) T3(C) 4000. 837. 852. 709. 5000. 842. 857. 714. 6000. 847. 862. 719. 7000. 852. 867. 724. B10-G10 NO PLAGIOCLASE. XFeGt=0 .720 XMgGt=0.225 XCaGt=0.032 XMnGt=0.023 X F e B i = 0 . 5 2 3 XMgBi=0.477 K=0.342 P ( b ) T1 (C) T2 (C) T3 (C ) 4000. 873 . 887 . 721 . 5000. 878 . 892. 727 . 6000. 883 . 897. 732. 7000. 889 . 902 . 737. B2-G2 NO PLAGIOCLASE. XFeGt=0 721 XMgGt=0.224 XCaGt=0.030 XMnGt=0.025 X F e B i = 0 . 5 2 0 XMgBi=0.480 K=0.337 P (b ) T K C ) T2(C) T3(C) 4000. 865. 878. 715. 5000. 870 883. 720. 6000. 875. 888. 725. 7000. 880. 893. 730. B13-G13 NO PLAGIOCLASE. XFeGt=0 .708 XMgGt=0.234 XCaGt=0.033 XMnGt=0.025 XFeBi=0 .526 XMgBi=0.474 K=0.366 P ( b ) T K C ) T2(C) T3 (C) 4000 . 918. 932. 749 . 5000. 923 . 937. 754. 6000. 929 . 942. 759 . 7000. 934. 948. 765. NO PLAGIOCLASE. XFeGt=0 .7 19 XMgGt=0. 225 XCaGt =0.032 XFeB i =0 520 XMgB i =0. 480 K=0. 339 P ( b ) T K C ) T2(C) T3(C) 4000. 869 . 882 . 718. 5000. 874 . 887 . 723 . 6000. 879 . 892 . 728 . 7000. 884 . 898 . 733 . OJ Cn APPENDICES / 337 7. APPENDIX 7. COMPUTER MODELING OF METAMORPHIC REACTIONS Some metamorphic reactions which are thought to have occurred in metapelitic schist of the DSA have been modeled in P-T space with the computer program P-T SYSTEM (Perkins et al., 1986). Reactions investigated, in the systems KASH, KFASH, KMASH and K.FMASH, are listed in Table 15 (see Table 9, Appendix 5 for mineral abbreviations used). The phases involved in modeled reactions include clinochlore, Mg-and Fe-chloritoid, muscovite, pyrope, almandine, phlogopite, annite, quartz, potassium feldspar, kyanite, sillimanite, staurolite and water. The numbering scheme for reactions used in this appendix is the same as in sections 5.2.3 and 5.2.4. The activities of all involved phases are required to model reactions with P-T SYSTEM. The ranges of pyrope, almandine, phlogopite and annite activities have been calculated (assuming ideal behavior) with electron microprobe mineral analytical data. The activities for other phases have been estimated. Activities have been varied through calculated ranges for garnet and biotite components, and through geologically reasonable ranges for estimated phases in order to monitor the effect on the position of modeled equilibria. Activities which have been used to generate the reaction net in Figure 88 are listed in Table 16. Criteria used to choose these values are discussed below. In all applicable reactions, activities of 1.0 have been chosen for quartz, kyanite and sillimanite. These values are considered reasonable due to the pure nature of these phases. A preferred value of 0.8 was used for water, which was involved in all reactions investigated (Ohmoto and Kerrick, 1977; Pigage and Greenwood, 1982). A variation of ±0.2 offset equilibria by about ±20 C. An activity of 0.8 was also chosen for muscovite for all reactions in which it APPENDICES / 338 occurs. Variation between 0.75-0.95, reasonable values for metamorphic muscovite (assuming an ideal solution model), had a small effect on the positions of reactions. Variation of chloritoid activities (both Mg and Fe) caused significant shifts in the calculated placement of equilibria. The chosen activities for chloritoid (Table 16; MGCTD=0.35, FECTD=0.65) bring Fe and Mg end-member reactions 7A and 7B into close proximity (Fig. 88). Clinochlore activities were varied between 0.01 and 0.8, which shifted equilibria involving this phase more than 100 C. Larger activities moved reactions towards lower temperatures. A comprimise value of 0.1 was chosen for use in Figure 88. This value yielded reasonable temperatures and converts to midrange chlorite compositions (activity of Mg in chlorite equals the mole fraction of Mg in chlorite to the fifth power, assuming ideal behavior). Ranges of pyrope, almandine, phlogopite and annite activities were calculated from electron microprobe analytical data (activity equals mole fraction cubed, assuming ideal behavior; see Appendix 6, Tables 13 and 14 for probe data). Pyrope activities varied by nearly three orders of magnitude (0.00017-0.014), while calculated values for the other phases were much more restriced (ALM:0.21-0.45; PHLOG:0.075-0.22; ANN:0.06-0.19). Activities of these phases used to generate the net in Figure 88 were chosen as a function of metamorphic grade of reaction. Reactions of relatively low metamorphic grade (numbers 3, 5, 6 and 8, for example; see Tables 15 and 16), were assigned combinations of the following relative activity values: low pyrope, high almandine, high phlogopite low annite. These values were progressively flipped for higher grade equilibria such as reaction 11 ( higher annite, etc.). Staurolite Mg/Mg + Fe ratios were set equal to those of garnet from rocks of similar grade. Fe-staurolite activities were calculated with these Mg/Mg+Fe ratios APPENDICES / 339 (activity equals Mg/Mg + Fe to the fourth power; see Appendix 6, Tables 14 and 15 and Appendix 7, Table 16). T a b l e 15. Equ i 1 i b r i a which have been modeled i n p r e s s u r e - t e m p e r a t u r e s p a c e ' . RXN#* SYSTEM REACTION 3 KMASH 3CLN + 1MS + 3QZ = 12HiO + 4PYR0P + 1PHLOG 4 KMASH 3CLN + 5MS = 12H*0 + 1QZ + 5PHL0G + SKY 5 KMASH 1MGCTD + 1CLN + 20Z = 2PYR0P + 5H>0 6 KF ASH 31FECTD + 5MS = 23H;0 + 4STAUR + 1QZ + 5ANN 7A KFASH 1QZ + 1MS + 3FECTD = 1ANN + 4KY + 3H*0 7B KMASH 1QZ + 1MS + 3MGCTD = 4KY + 1PHL0G + 3H;0 8 KFASH 23FECTD + 7QZ = 19H*0 + 2STAUR + 5ALM 10 KMFASH 32ALM + 69CLN + 115MS = 228H*0 + 24STAUR + 123QZ + 115PHL0G 1 1 KFASH 8MS + 17QZ + 6STAUR = 12H.0 + 62SILL + 8ANN 12 KASH 1QZ + 1MS = 1KSP + 1SILL + 1H*0 • E q u i l i b r i a modeled w i t h P-T SYSTEM, a computer program by P e r k i n s e t a l . ( 1986 ) . See F i g u r e 88 f o r net g e n e r a t e d w i t h a c t i v i t i e s l i s t e d in T a b l e 16. ' R e a c t i o n number ing scheme u s e d i n S e c t i o n s 5 . 2 . 3 , 5 . 2 . 4 . o T a b l e 16. A c t i v i t i e s of phases u s e d to model e q u i l i b r i a shown i n F i g u r e 8 8 1 . RXN#* C L N 3 MGCTD FECTD MS PYROP ALM PHLOG ANN KY SILL STAUR KSP 3 0 . 1 0 - - 0 . 8 0 0 .0002 - 0 . 2 0 4 0 . 1 0 - - 0 .80 - - 0 . 15 - 1.0 5 0 . 1 0 0 .35 - - 0 .0004 - - - - - -6 - 0 .65 0 . 8 0 - 0 .075 - - 0 . 6 0 7A - - 0 . 65 0 . 8 0 - - - 0 .075 1.0 7B - 0 .35 - 0 .80 - - 0 .22 - 1.0 -8 - - 0 .65 - - 0 .35 - - - - 0 . 6 0 10 0 . 1 0 - - 0 . 8 0 - 0 . 3 0 0 .15 - 0 . 5 0 11 - - - 0 . 8 0 - - - 0 . 100 - 1.0 0 . 5 0 12 - - - 0 . 8 0 - - - - - 1.0 - 1.0 ' R e a c t i o n s modeled w i t h P-T SYSTEM ( P e r k i n s e t a l . , 1986) . ' E q u i l i b r i a l i s t e d by r e a c t i o n number (RXN#) i n T a b l e 15. Q u a r t z and water were i n v o l v e d i n a l l r e a c t i o n s and were a s s i g n e d the a c t i v i t i e s 1.0 and 0 . 8 0 , r e s p e c t i v e l y . 3 See T a b l e 9 f o r m i n e r a l a b b r e v i a t i o n s and f o r m u l a e . APPENDICES / 342 8. APPENDIX 8. GEOCHEMICAL ANALYSES AND ASSOCIATED PRECISION AND ACCURACY Precision estimates for major element chemical data (Table 17) are derived from duplicate analyses of 5 unknowns from the TLMC, using the method described in Davies (1961), section 3.35 and Table G - l . Major element analytical accuracy estimates are Used in Table 18. Major and trace element whole rock analyses for rocks from the TLMC appear in Table 19. Trace element precision is also included in Table 19. Normalization factors for trace element bulk earth normalized diagram (BEND; Fig. 97) are listed in Table 20. T a b l e 17. Major element a n a l y t i c a l p r e c i s i o n ' SAMPLE 84-87-2 84 -87-2 RANGE 84-I 312-2 84-I 312-2 RANGE 85-812-2 85-812-2 RANGE Wt. % (1) (2) (1) (2) (1) (2) SI02 60 .34 59 .55 0 . 79 62 . 46 62 . 70 0 .24 59.87 ' 60 .01 0.14 TI02 O .75 0 .76 0 .01 O .75 0 . 75 0 .OO 0.84 0 . 83 0.01 AL203 18 .66 18 .98 0 .32 17 .58 17 .42 O . 16 18 . 48 18 . 54 0.06 FE203 5 .49 6 .07 0 .58 5 . 19 5 .21 0 .02 5.48 5 . 39 0.09 MNO 0 .07 0 .07 0 .00 0 .08 0 .08 0 .00 0.05 0 .05 0.00 MGO 2 .41 2 .35 0 .06 2 .34 2 .32 0 .02 2.77 2 .77 0.00 CAO 6 .36 6 .25 0 . 11 5 .34 5 .39 0 .05 5.31 5 . 23 0.08 NA20 5 .06 5 .03 0 .03 4 . 97 4 .85 O . 12 4 . 94 5 .03 0.09 K20 O .71 0 .69 0 .02 1 .06 1 .07 O .01 1 . 96 1 . 96 O.OO P205 0 . 15 0 . 25 0 . 10 0 .23 0 .22 0 .01 0.30 0 . 17 0.13 SAMPLE 84-726-5 84-726-5 RANGE 84-617-3B 84-617-3B RANGE AVG RANGE STD D E V STD ERF Wt. % ( D (2) (1) (2) SIQ2 71 . 05 71 . 26 0. ,21 75 .25 75 .49 0. , 24 0.324 O, .29 0.4% TI02 0. 18 O. . 18 0. ,00 0, .20 0, .20 0. OO 0.004 0, .01 0. 7% AL203 16. 25 16. .07 0. 18 14. 59 14, 58 0. 01 0. 146 0. . 13 0.8% FE203 2. .43 2. ,35 0. 08 1 . 72 1 , .40 0. 32 0.218 0. , 19 4 . 7% MNO 0. 08 0. 08 0. 00 0. 01 0. ,01 0. 00 0.000 0. 00 0.0% MGO 0. 54 0. 53 0. 01 0. ,37 0. .35 0. 02 0.022 0. 02 1 .2% CAO 3. 00 3. 04 0. 04 1 . 79 1 . 79 0. 00 0.056 0. 05 1 . 1% NA20 5. 00 5. 01 0. 01 4 . 69 4. 80 0. 1 1 0.072 0. 06 1 .3% K20 1 . 37 1 . 38 0. 01 1 . 33 1 . 34 0. 01 0.010 O. 01 0. 7% P205 0. 1 1 0. 09 0. 02 0. 03 0. 03 0. OO 0.052 0. 05 28 . 8% • P r e c i s i o n e s t i m a t e s d e r i v e d from n o r m a l i z e d , anhydrous a n a l y s e s . 'Standard d e v i a t i o n (rounded v a l u e ) c a l c u l a t e d u s i n g ranges of d u p l i c a t e a n a l y s e s as o u t l i n e d i n D a v i e s (1961), S e c t i o n 3.35 and T a b l e G-1. 3 Thei average c o n c e n t r a t i o n (n=10) f o r each o x i d e i s used t o c o n v e r t s t a n d a r d d e v i a t i o n to s t a n d a r d e r r o r ( i n %) T a b l e 18. Major e lement a n a l y t i c a l a c c u r a c y SAMPLE QLO-1(REF ) 1 OLO- I (ANAL) DIFF(%DI FF) S C o - l ( R E F ) S C o - l ( A N A L ) DIF F(%DIFF) BHVO(REF) BHVO(ANAL) DIF F (%D IFF) Wt. % SIQ2 66 . 13 65 .62 0 . 5 1 ( 0 .78) 68 .63 68 .42 0 . 2 1 ( 0 31) 49 .61 49 . 65 0 . 0 4 ( 0 . 0 8 ) TI02 0 .62 0 .62 0 . 0 0 ( 0 . 0 0 ) 0 .67 0 .66 0 .01 (1 .49) 2 .67 2. 72 0 . 0 5 ( 1 . 8 4 ) AL203 16.42 16 .65 0 .23( 1 .40) 14. .83 14 .90 0 . 0 7 ( 0 • 47) 13 .77 13. 1 1 0 . 6 6 ( 5 . 0 3 ) FE203 4 . 3 0 4 .53 0 . 2 3 ( 5 .35) 5 .65 6 .02 0 . 3 7 ( 6 .55) 12 . 16 1 1 . 73 0 . 4 3 ( 3 . 7 0 ) MNO 0 . 0 9 0. .09 0 . 0 0 ( 0 .00) 0. .05 0 .05 0 . 0 0 ( 0 .00) 0 . 17 O. 15 0 . 0 2 ( 1 3 . 3 0 ) MGO 1 .04 1. .07 0 .03 (2 .88) 2. .99 2 .99 0 . 0 0 ( 0 .00) 7 .27 7 . 28 0 . 0 1 ( 0 . 1 4 ) CAO 3 .25 3. . 10 0 .15 (4 .62) 2. 86 2. .80 0 . 0 6 ( 2 . 10) 1 1 . 26 12 . 29 1 . 0 3 ( 8 . 3 8 ) NA20 4 .24 4. 43 0 . 1 9 ( 4 . 48) 1 . 03 0. 98 0 . 0 5 ( 4 .85) 2 .28 2. 26 0 . 0 2 ( 0 . 8 8 ) K20 3 .64 3. 63 0 . 0 1 ( 0 . .28) 3. .05 2 .95 0 . 1 0 ( 3 .28) 0 .54 0 . 52 0 . 0 2 ( 3 . 8 5 ) P205 0 . 2 6 0. 25 0 . 0 1 ( 4 . .00) 0. 24 0. 22 0 . 0 2 ( 8 . .33) 0 .28 0 . 29 0 . 0 1 ( 3 . 4 5 ) SUMMARY SAMPLE B C R - I ( R E F ) BCR-1(ANAL) BCR-1(ANAL) BCR-1(ANAL) STD ERR ! STD ERR 3 STD ERR" EST ERR Wt. % (1) (2) (3) SID2 54 .58 54. 39 54. ,24 54. 46 0. 4% 0. .5% 0. .4% 0. 5% TI02 2 .23 2. 32 2. 31 2. 29 3. 5% 2. .2% 0. .7% 2 % AL203 13.69 13. 19 13. . 12 13. 29 3. 6% 2. .7% 0, .8% 3 % FE203 13.52 14. 29 14. 56 14. 17 6. 2% 4. 8% 4. 7% 5 % MNO 0. 18 0. 18 0 . 18 0 . 17 3 . 2% 1 1 . 6% 0. 0% 10 % MGO 3 .46 3. 49 3. 50 3. 50 1 . 1% 0. 5% 1 . 2% 1 % CAO 6 .98 6. 93 6. 92 6. 88 1 . 1% 5. 0% 1 . 1% 1 t o 5% NA20 3 .28 3. 15 3 . 08 3. 17 4 . 6% 4 . 5% 1 . 3% 4 % K20 1 .70 1 . 71 1 . 71 1 . 69 0 . 6% 2 . 5% 0. 7% 1 t o 3% P205 0 . 37 0 . 37 0. 37 0 . 37 0 . 0% 5. 4% 28 . 8% 15 % ' A l l a n a l y s e s a r e anhydrous and n o r m a l I z e d to 100%. R e f e r e n c e v a l u e s f o r s t a n d a r d s f rom Abbey ( 1983) ' S t a n d a r d e r r o r e s t i m a t e s of a c c u r a c y f o r BCR-1 i n %. 3 Comb1ned s t a n d a r d e r r o r e s t i m a t e s o f a c c u r a c y f o r o t h e r s t a n d a r d s ; CaO e r r o r i s the mean o f % d i f f e r e n c e s . • S t a n d a r d e r r o r e s t i m a t e s of p r e c i s i o n ( s e e T a b l e 17) . " E s t i m a t e d a n a l y t i c a l e r r o r ( In %) i n c o r p o r a t i n g p r e c i s i o n and a c c u r a c y s t a n d a r d e r r o r e s t i m a t e s . OJ T a b l e 19 Ma jor and t r a c e e lement g e o c h e m i c a l d a t a f rom the T L M C SAMPLE 8 5 - 7 1 7 - 7 8 4 - 8 7 - 2 ' 8 4 - 8 1 2 - 2 ' 8 5 - 8 1 2 - 2 ' 84 -89-1 84-71-1 84-71 1-2 8 5 - 6 1 8 - 2 EST ERR 8 Wt % SI02 68 .60 59 .95 62 . 58 59 .94 65 .60 69 .46 68 .06 7 ° . 22 + 0. 5% TI02 0 .44 0 .76 0 .75 0 .84 0 .47 0 .47 0 .41 0 .25 + 2 % AL203 16 .20 18 .82 17 .50 18 .51 16 . 32 15 . 18 16 .68 16 . 29 + 3 % FE203 3 .44 5 .60 5 .20 5 .44 5 . 28 4 .05 2 .85 2 . 33 + 5 % MNO 0 .03 0 .07 0 .08 0 .05 0 . 10 0 .08 0 .03 0 .05 + 10 % MGO 1 .20 2 . 38 2 . 33 2 .77 2 .01 1 .21 1 . 15 0 . 72 + 1 % CAO 3 . 10 6 .31 5 . 37 5 . 27 • 4 .92 3 . 28 2 . 75 2 .72 ±1 to 5% NA20 4 .05 5 .05 4 .91 4 .99 4 . 1 1 4 .07 4 .69 5 .30 + 4 % K20 2 .85 0 .70 1 .07 1 .96 1 .01 2 .09 3 . 25 2 .04 ±1 to 3% P205 0 .09 0 .09 0 .23 0 .24 0 . 12 0 . 1 1 0 . 13 0 .09 + 15 % LOI 3 0 . 39 0 . 72 0 .48 0 .97 0 .53 1 .48 0 .68 0 .42 ppm STD DEV 7 Ba 1736 . 483 . 645 . 1018. 578. 825 . 1 144 . * 1069. + 7. Cr 10. 19 . 18 . 20. 12 . 7 . 18 . 1 1 . + 9. Nb 6 . 6. 6 . 6 . 5 . 8 . 5 . 10. + 1 . Ni 4 . 9 . 14 . 19. 5. 1 . 0 . 0 . + 4 . Rb 79 . 11 . 20 . 55 . 23 . 54 . 105 . 35 . + 2 . S r 594 . 1 127. 1067 . 1 1 9. 449 . 337 . 674 . 914 . + 2. V 52 . 75 . 78 . 94 . 46 . 45 . 39 . 19 . + 16 . Y 14 . 9 . 12 . 14. 18. 21 . 13 . 1 1 . + 4 . Zr 205. 178 . 178. 239. 132 . 156 . 182 . 161 . + 5 . ' A l l major e lement a n a l y s e s a r e anhydrous and n o r m a l i z e d to 100%. ' A v e r a g e o f two major e lement a n a l y s e s . 3 L 0 I d e t e r m i n e d on s e p a r a t e r e p r e s e n t a t i v e p o r t i o n s o f s a m p l e s . The LOI v a l u e f o r sample 8 4 - 6 1 7 - 3 B i s an a v e r a g e o f two d e t e r m i n a t i o n s ; a l l o t h e r s were o b t a i n e d from s i n g l e r u n s . ' A v e r a g e o f two t r a c e e lement a n a l y s e s . 5 N o t A n a l y s e d . " E s t i m a t e d major e lement a n a l y t i c a l e r r o r i n c o r p o r a t i n g p r e c i s i o n and a c c u r a c y s t a n d a r d e r r o r e s t i m a t e s . ' S t a n d a r d d e v i a t i o n e s t i m a t e s f o r t r a c e e lement p r e c i s i o n In ppm, b a s e d on s c a t t e r o f s t a n d a r d s about w o r k i n g c u r v e s . , . UJ £» T a b l e 19 C o n t i n u e d SAMPLE 84 -617 -3A 8 4 - 7 2 6 - 5 ' 84 -830 -5 8 4 - 6 1 7 - 3 B ' 84 -82 -2 84 -713 -8 84-817-1 8 4 - 7 1 4 - 3 EST ERR 6 Wt % SI02 60 .39 71 . 16 78 . 39 75 . 37 57 . 37 76 . 12 71 . 66 57 . 67 + 0 . 5% TI02 1 .05 0 . 18 0 . 14 0 .20 0 .85 0 .24 0 . 26 0 .96 + 2 % AL203 19 . 12 16 . 16 12 .36 14 .59 17 . 16 12 .67 14 . 98 19 .86 + 3 % FE203 4 .38 2 .39 1 .49 1 .56 8 .90 2 . 33 2 . 38 5 . 39 + 5 % MNO 0 .04 0 .08 0 .02 0 .01 0 . 15 0 .03 0 .02 0 .07 + 10 % MGO 1 .99 0 .54 0 .54 0 .36 3 .67 0 . 54 0 .63 2 .38 + 1 % CAO 4 .81 3 .02 2 .67 1 . 79 7 .60 1 .94 2 .09 6 . 18 ±1 to 5% NA20 6 .47 5 .01 3 .77 4 .75 3 . 35 4 . 75 3 .60 4 .93 + 4 % K20 1 .31 1 .38 0 .57 1 .34 0 .79 1 . 34 4 .29 2 .27 ± 1 t o 3% P205 0 .45 0 . 10 0 .05 0 .03 0 . 16 0 .05 0 .08 0 .30 + 15 % L O I 3 SNA 0 .63 0 . 26 0 .92 0 .70 1 .80 1 . 14 0 .77 ppm STD D E V Ba NA 629 . 424 . 999 . •331 . 705 . « 1284. 927 . + 7 . C r NA 13. 14 . 5. 10. 9 . 12 . 37 . + 9 . Nb NA 7. 6 . 7 . 4. 8 . 9 . 1 1 . + 1 . Ni NA 0. 0. 0. 9 . 0 . 1 . 21 . + 4 . Rb NA 19 . 1 1 . 25 . 14 . 41 . 101 . 34 . + 2 . Sr NA 622 . 424 . 201 . 468. 239 . 338 . 805 . + 2 . V NA 6 . 0 . 1 1 . 103. 12 . 21 . 105 . + 16. Y NA 12 . 1 1 . 19. 25 . 21 . 18 . 17 . + 4 . Z r NA 120. 90. 135. 99 . 1 15 . 171 . 230. + 5. ' A l l major e lement a n a l y s e s a r e anhydrous and n o r m a l i z e d to 100%. ' A v e r a g e of two major e lement a n a l y s e s . 3 L 0 I d e t e r m i n e d on s e p a r a t e r e p r e s e n t a t i v e p o r t i o n s of s a m p l e s . The LOI v a l u e f o r sample 84 -617 -3B i s an a v e r a g e o f two d e t e r m i n a t i o n s ; a l l o t h e r s were o b t a i n e d from s i n g l e r u n s . " A v e r a g e o f two t r a c e e lement a n a l y s e s . 5 N o t a n a l y s e d . 6 E s t i m a t e d major e lement a n a l y t i c a l e r r o r i n c o r p o r a t i n g p r e c i s i o n and a c c u r a c y s t a n d a r d e r r o r e s t i m a t e s . ' S t a n d a r d d e v i a t i o n e s t i m a t e s f o r t r a c e e lement p r e c i s i o n i n ppm, b a s e d on s c a t t e r o f s t a n d a r d s about w o r k i n g c u r v e s . , , LtJ J> T a b l e 19. C o n t i n u e d SAMPLE 8 4 - 6 1 4 - 1 0 8 5 - 8 1 7 - 2 EST ERR' Wt. % SI02 70 . 15 70 . 14 + 0. 5% TI02 0 .27 0 . 24 + 2 % AL203 16 .36 15 .90 + 3 % FE203 1 .92 2 .63 + 5 % MNO 0 .02 0 .05 + 10 % MGO 0 .57 0 .94 + 1 % CAO 2 .05 2 .80 + 1 to 5: NA20 5 . 45 4 .39 + 4 % K20 3 . 13 2 .82 ±1 to 3! P205 0 .08 0 .08 + 15 % L O I 1 0 .45 0 .53 ppm STD DEV Ba 1559. 1 147. + 7. Cr 9 . 1 1 . + 9. Nb 6. 9 . + 1 . Ni 0 . 0. + 4 . Rb 38 . 92 . + 2 . S r 1313 . 444 . + 2. V 27 . 24 . + 16 . Y 1 1 . 16. + 4. Zr 205. 122 . + 5 . ' A l l major e lement a n a l y s e s a r e anhydrous and n o r m a l i z e d to 100%. ' A v e r a g e o f two major e lement a n a l y s e s . 'LOI d e t e r m i n e d on s e p a r a t e r e p r e s e n t a t i v e p o r t i o n s o f s a m p l e s . The LOI v a l u e f o r sample 84 -617 -3B i s an a v e r a g e two d e t e r m i n a t i o n s ; a l l o t h e r s were o b t a i n e d f rom s i n g l e r u n s . ' A v e r a g e o f two t r a c e e lement a n a l y s e s . ' N o t a n a l y s e d . " E s t i m a t e d major e lement a n a l y t i c a l e r r o r i n c o r p o r a t i n g p r e c i s i o n and a c c u r a c y s t a n d a r d e r r o r e s t i m a t e s . ' S t a n d a r d d e v i a t i o n e s t i m a t e s f o r t r a c e e lement p r e c i s i o n i n ppm, b a s e d on s c a t t e r o f s t a n d a r d s about w o r k i n g c u r v e s . Table 20: Normalization factors for BEND1 348 5.6 620. 2.0 120. 0.35 11.8 3.8 0.21 1Trace element concentrations in parts per m i l l i o n are divided by respective values. 2Bulk earth abundances from Sun, 1980. 3Bulk earth abundances from Armstrong, 1981. "Bulk earth abundances from Thompson et a l . , 1984. 

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