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U-PB geochronometry and regional ecology of the southern Okanagan Valley, British Columbia : the western.. Parkinson, David Lamon 1985

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U-PB GEOCHRONOMETRY AND REGIONAL GEOLOGY OF THE SOUTHERN OKANAGAN VALLEY, BRITISH COLUMBIA: THE WESTERN BOUNDARY OF A METAMORPHIC CORE COMPLEX by DAVID LAMON PARKINSON BA. UNIVERSITY OF CALIFORNIA, SANTA BARBARA, 1981 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES Geological Sciences We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA August, 1985 David Lamon Parkinson In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the 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. Geological Sciences The University of British Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 Date: August. 1985 ABSTRACT The Okanagan Valley is the boundary between the Okanagan Metamorphic and Plutonic Complex of the Omenica Belt to the east and the Intermontane Belt to the west. The Okanagan Metamorphic and Plutonic Complex consists of greenschist to amphibolite grade paragneiss and large areas of massive, gneissic, and mylonitic granitic rock. The Intermontane Belt consists of tectonically scrambled late Paleozoic to Triassic eugeosynclinal rocks, intruded by large Jurassic plutons and locally by plutons of mid-Cretaceous age. These are overlain by Eocene non-marine volcanic and sedimentary rocks, capped by fanglomerate breccias and gravity slide megabreccias. The thesis area contains all of these elements. In particular, the mid-Jurassic Oliver pluton is composed of three separate intrusive phases. The oldest phase is a heterogeneous biotite-hornblende diorite, which was intruded by the most extensive phase: a porphyritic biotite granite. The youngest phase is a garnet-muscovite granite. The intrusion of this last phase created the porphyritic biotite granite from an originally more mafic, hornblende bearing granodiorite. The mineralogy of the garnet-muscovite granite suggests that it might be of S-type. Several geochemical plots contradict this and suggests it is a highly evolved I-type magma. Previous geochronometry indicates that the tectonic boundary between the Okanagan Metamorphic and Plutonic Complex and the Intermontane Belt separates: 1) gneisses on the east that consistently yield K-Ar dates of 40-60 Ma, typically 51 Ma for hornblende and 48-50 Ma for biotite, from 2) intrusive rocks on the west that yield Jurassic K-Ar and Rb-Sr dates and Eocene volcanic rocks, erupted largely between 53 and 45 Ma. U-Pb dating of zircons indicates the presence of early Jurassic to mid-Jurassic plutons both east (granite of Anarchist Mtn., 160Ma; gneiss of Osoyoos, 201Ma; ii deformed) and west (Similkameen granodiorite, 170Ma; Olalla Syenite, 18O-190Ma; undeformed) of the Okanagan Valley. East of the Okanagan Valley there are also mylonitic gneisses of Cretaceous age (gneiss of Skaha Lake, 105-120Ma; gneissic sill of Vaseaux Lake, 97Ma), as well as metamorphosed and deformed Eocene intrusives (Rhomb Porphyry, 51Ma). The interpretation is thaL although there are Jurassic plutons and early Mesozoic deformation in both the Okanagan Metamorphic and Plutonic Complex and the Intermontane Belt, there are also Cretaceous and Tertiary intrusive bodies within the Okanagan Metamorphic and Plutonic Complex that have been highly deformed in late Cretaceous to early Tertiary time. Regional geochronometry summarized on time versus blocking temperature graphs emphasizes the large (10 km) and rapid (1-4 mm/yr) unroofing needed to bring the gneisses east of the Okanagan Valley to near surface temperatures in Eocene time. Field evidence for a low angle west dipping detachment fault (Okanagan Valley fault) which juxtaposes brittle disrupted Eocene and older rocks against unannealed mylonitic rocks with Eocene K-Ar dates justifies comparison of the Okanagan Metamorphic and Plutonic Complex with other Cordilleran metamorphic core complexes. iii Table or Contents LIST OF FIGURES AND PLATES vi LIST OF TABLES viiI. INTRODUCTION . . .. 1 Location of Study Area 1 Previous Field Work 3 Acknowledgements 5 II. REGIONAL GEOLOGIC SETTING 6 Okanagan Metamorphic and Plutonic Complex 6 Eugeosynclinal Formations of the Okanagan Valley Region 12 Plutonic Rocks West of the Okanagan Valley .. 6 Tertiary Formations . 18 III. DESCRIPTION OF MAP UNTTS/STRATIGRAPHY 22 PCLFCl£1%dSS€S H«4 MWMM 1M»WH* WM»»*»M«mtMMMHWttW»«««««t»M»»— #»«»««»>«»»» Leucogneiss 25 Cretaceous or Jurassic gniessic granitic rocks .. 28 Late Paleozoic- Triassic Eugeosynclinal Rocks 2Oliver Ptuton .™_...™.„..........„m....„.._™...........„....„ 9 Porphyritic Biotite Granite . 33 Garnet-Muscovite Granite 3Discussion of Geochemistry 41 EOCCftC Stf@t& wmw«n«MWMWmmMW»ww.tn»»w«tw.w.»wmiMWM*HWW«WM mtmtwwwwmi — — •»—••« 54" IV. GEOCHRONOMETRY 6Geochronometry - Previous Work ... 61 Geochronometry - This Study . 78 West of the Okanagan Valley .. 7Samples from the Okanagan Metamorphic and Plutonic Complex 82 Summary of Geochronometry !. 89 Discussion 90 V. STRUCTURE ; 94 Upper Plate . 9Okanagan Valley Fault and Related Fault Rocks 8 Lower Plate  102 Timing of Brittle and Ductile Deformation 10Discussion and Regional Implications , 109 Conclusions 111 VI. GEOLOGIC HISTORY OF THE SOUTHERN OKANAGAN REGION 113 REFERENCES CITED 116 APPENDIX A - WHOLE ROCK SAMPLE LOCALITIES AND DESCRIPTIONS ....127 APPENDIX B - U-PB ANALYTICAL PROCEDURE AND DATA 128 APPENDIX C - RB/SR ANALYTICAL TECHNIQUES 149 v 11ST OF FIGURES AND PLATES Figure 1: Location Map 2 Figure 2: Geologic Map and Legend 7 Figure 3: Outcrop of gneisses 9 Figure 4: Stereonet of poles to fractures 19 Figure 5: Mylonitic gneisses 21 Figure 6: Foliated leucogneiss 4 Figure 7: Photomicrographs of leucogneiss 27 Figure 8: Isoclinal fold in lPz-Tr 30 Figure 9: Boudins in lPz-TrFigure 10: Agmatite 32 Figure 11: Contact between Jpgr and Jgr 3Figure 12: Diorite 4 Figure 13: Pegmatitic Diorite 3Figure 14: Photomicrograph of Diorite 35 Figure 15: General character of JpgrFigure 16: Photomicrograph of Jpgr 7 Figure 17: Photomicrograph of JpgrFigure 18: Photomicrograph of Jpgr 38 Figure 19: Photomicrograph of JgrFigure 20: Photomicrograph of Jgr 40 Figure 21: Major element variation diagram 42 Figure 22: AFM diagram 43 Figure 23: Normative Q-Or-Plag diagram 4 Figure 24: MgO vs CaO 5 Figure 25: Sr and Rb vs SiO„ 7 Figure 26: Zr and Ba vs SiO 50 Figure 27,: Normative Q-Ab-Or 2 Figure 28: C and Di vs SiO . . . 3 Figure 29: Molar Al^/(CaO+Na20+K20) vs Rb/Sr 56 Figure 30: Skaha Formation 57 Figure 31: Photomicrograph of Eocene dike 5Figure 32: Photomicrograph of Eocene dike 9 Figure 33: Foliated, lineated rhomb porphyryFigure 34: Photomicrographs of rhomb porphyry 60 Figure 35: Location map for previous K-Ar dates 2 Figure 36: White Lake Basin Chronology 66 Figure 37: K-Ar histograms 67 Figure 38': Rb-Sr diagram for Osoyoos area plutons... 68 Figure 39: Rb-Sr diagram for leucogneiss .' 69 Figure 40: U-Pb location Map 70 Figure 41: Concordia diagram: 150-225 Ma 84 Figure 42: Photomicrograph of gneissic sill of Vaseaux Lake 85 Figure 43: Concordia diagram: 25-150 Ma 7 Figure 44: U-Pb sample locality for gneiss of Skaha Lake 85 vi Figure 45: Closure temperature vs time 91 Figure 46: Approximate uplift rates 2 Figure 47: Fractured Oliver pluton ....95 Figure 48: Stereonet of poles to fractures and dikes 96 Figure 49: Low angle faults and fractures.. 97 Figure 50: Map of Mahoney Lake area... 9 Figure 51: Photomicrographs of mylonitic pgn. 101 Figure 52: Photomicrographs of brecciated mylonite 103 Figure 53: Photomicrographs of mylonites.. 104 Figure 54: Asymmetric fabric in rhomb porphyry 105 Figure 55: Stereonet of poles to foliations 7 Figure 56: Lineations in leucogneiss 10Figure 57: Stereonet of lineations 110 Figure 58: Cross Section White Lake - Vaseaux Lake area 112 PLATE 1 ia=poeket Se vii I-1ST OF TABLES Table 1: Vaseaux Formation 11 Table 2: Structural succession from Ryan (1973) ....13 Table 3: Eugeosynclinal Formations 15 Table 4: Stratigraphy of White Lake Basin 17 Table 5: Whole Rock Chemistry 48 Table 6: Previous K-Ar data 63 Table 7: Previous and present study Rb-Sr data 72 Table 8: Previous U-Pb data 79 Table 9: U-Pb data 80 Table 10: Structural elements in the Vaseaux Formation 106 viii I. INTRODUCTION This study focuses on the boundary between the Intermontane and Omineca Belts of the Canadian Cordillera. In southern British Columbia this boundary is coincident with the Okanagan Valley, east of which is the Okanagan Metamorphic and Plutonic Complex (Okulitch et al., 1977; Okulitch, 1984) of the Omineca Belt, and west of which are Carboniferous to Triassic eugeosynclinal formations, Jurassic intrusives and Eocene volcanic and sedimentary rocks of the Intermontane Belt The Okanagan Valley and adjacent uplands have been under geologic study for more than a century, and most recently the site of many University of British Columbia Ph.D. theses (Church, 1967; Okulitch, 1969; Christie, 1973; and Ryan, 1973). The purpose of the present study has been to map an area connecting these four thesis maps (Fig. 1), to study the Oliver pluton with its mixed S- and I-type characteristics, and to carry out a regional U-Pb geochronologic reconnaissance. The result is a geologic synthesis of the southern Okanagan Valley region. Several conventions will be used throughout, these are: a) the time scale used is that of Palmer (1983); b) decay constants used for age calculations are from Steiger and Jage'f (1977); c) plutonic rock names are from Strekeisen (1976). Location of Study Area One reason for the continued geologic work in the Okanagan Valley is its accessibility. Highway 97 runs the length of the valley and is connected to Vancouver by Highway 3 at its southern end, near the U.S.-Canada border (Fig. 1), and by Highway 1 at its northern end, near Vernon. Within the study area there are many secondary or lower class roads. 1 0 2 H Little. 1961 119 30' 119 SCALE Figure 1: Location map of the study area; also shown are areas mapped for Ph.D. theses and by the G.S.C.. 3 An area of 80 km2 extending 12 km north, and 4 km east' and west, of the town of Oliver (latitude 49° 11', longitude 119° 3T) was mapped from June to August 1983. Mapping was done on 1:16,000 scale topographic maps enlarged from 1:50,000 NTS maps 82E/1,2,5,6 sheets, supplemented by air photographs (series 7580-82,7602 B.C. Ministry of Environment) and 1:5,000 scale topographic maps of series 72-6T (B.C. Ministry of Environment). Field observations were compiled onto a final 1:25,000 scale base (Plate 1). Previous Field Work Field work in the Okanagan Valley began in the 1860's with a reconnaissance by G.M. Dawson (1877). This work was followed by the International Boundary Survey (Daly, 1906 and 1912), and then by Brock (1934), who studied the metamorphic rocks of the southern Okanagan. The first systematic detailed mapping of the southern Okanagan Valley was done by Bostock from 1927-1930 (Maps 341A, 1940; 627A, 1941a; 628A, 1941b), and Cairnes in 1934 (Maps 37-21, 1937; 538A, 1947) for the Geological Survey of Canada. This work was revised and incorporated by H.W. Little in 1958-1959 in his map of the west half of the Kettle River Sheet (Map 15-1961) (Fig. 1). A new Geological Survey of Canada 1:250,000 scale map of the Penticton Sheet was begun in 1983 by D. Templeman-KluiL Metamorphic and plutonic rocks east of the Okanagan Valley were studied by J.V. Ross and his students (Ross, 1973, 1974, 1981; Ryan, 1973; Christie, 1973; Medford, 1975, 1973; Ross and Christie, 1979). The abundant granitic rock in the Okanagan area was noted by Daly (1906), and by Brock (1934), who attributed metamorphism of the Shuswap rocks to the emplacement of these granitic bodies. Waters and Krauskropfs (1941) study of the Colville batholith, just south of the U.S.-Canada border, is the classic on protoclastic 4 borders of granitic plutons. The Colville batholith has since been restudied and reinterpreted by Snook (1965), Fox et al. (1976), and Cheney (1980). Hibbard (1971) mapped a large area in northern Washington state, primarily within the plutonic granitic rocks of the Okanogan Range. Work on granitic rocks north of the border has been directed to the west of Okanagan Valley. Petb (1973 and 1979) and Petb and Armstrong (1976) published papers on the petrology and geochronology of the Pennask Batholith. The Oliver pluton has been the subject of many U.B.C. B.Sc. theses because of its proximity to the U.B.C. field camp, and to its petrologie diversity (Matsen, 1960; Lammle, 1962; Cannon, 1966; Richards, 1968; Moore, 1970; Holtby, 1972). These were supervised by W.H. White and AJ. Sinclair and some results have been published (White et al., 1968; Sinclair, et al., 1983). The Intermontane Belt lower grade rocks of Carboniferous-Permian to Triassic age have been the subject of two theses (Okulitch, 1969; Milford, 1984) (Fig. 1). Other work on these rocks include those by Ross and Barnes (1972), Barnes and Ross (1975) and Read and Okulitch (1977). The Tertiary sedimentary and volcanic rocks of the White Lake Basin were studied by Church (1967) (Fig. 1). He has continued to work on these and other Tertiary outliers in and around the Okanagan Valley (Church, 1972, 1973, 1975, 1977, 1978, 1979a, 1979b, 1980a, 1980b, 1980c, 1980d, 1980e, 1981a, 1981b, 1982, 1985; Church and Johnson, 1978; Church et al., 1983). W.H. Mathews has investigated the relationship between the Tertiary volcanics and the underlying metamorphic rocks (Mathews, 1981). 5 Acknowledgements The author would like to thank R. L. Armstrong, thesis supervisor, for providing support, supervision, advice and enthusiasm throughout the project Thanks are also due to R. Parrish for suggesting the map area and for continued guidance, insight, and enthusiasm. P. Van der Heyden, K. Scott and S. Horsky provided laboratory assistance. J. Mortensen is thanked for his guidance, and healthy dose of paranoia, in U-Pb techniques and interpretation. Assistance from members of the staff at the Department of Geology, University of British Columbia, most notably E. Montgomery, also merits recognition. This study benefited greatly from discussions with R. Parrish, J. Mortensen, W. H. Mathews, J. Monger, D. Templeman-Kluit, J. Montgomery, J. Fillipone, J. Logan, I. Moffat, M. Bloodgood, L. Erdman, K. McColl, and R. Friedman. Finally the writer would like to thank J. Rublee for patience and encouragement, and M. Stockton, F. Borah and M. Honer for unique insights, postcards and financing his education. Natural Sciences and Engineering Research Council of Canada grant number 67-8841 to R. L. Armstrong provided support throughout the project II. REGIONAL GEOLOGIC SETTING The rocks in the Southern Okanagan can be divided into four "packages": The Okanagan Metamorphic and Plutonic Complex, which is mainly east of the Okanagan Valley; late Paleozoic to Triassic eugeosynclinal formations found both east and west of the Okanagan Valley; undeformed Jurassic (and a few Cretaceous) plutons which occur mainly west of the Okanagan Valley; and finally Eocene sedimentary and volcanic rocks of White Lake Basin, also largely west of the Okanagan Valley (Fig. 2). Okanagan Metamorphic and Plutonic Complex The Okanagan Metamorphic and Plutonic Complex, in the southern Okanagan, consists primarily of granitic orthogneiss (K-Jg on Fig. 2); only locally does amphibolite-grade paragneiss predominate (pgn on Fig. 2). The best exposures of paragneiss are around Vaseaux Lake where they comprise the Vaseaux Formation defined by Bostock (1941a). These feldspathic gneisses, with minor mica schist, calc-silicate rocks and amphibolite, crop out over an area of 200 km2. Throughout the Vaseaux Formation there are also voluminous discordant to concordant foliated granitic bodies (Fig. 3). The Vaseaux Formation is in fault contact everywhere along its northwest, west and southwest limits with rocks of the Intermontane Belt To the northeast, east and southeast, the Vaseaux is in intrusive(?) contact with gneissic granites (Christie, 1973; Little, 1961). Christie (1973) defined five paragneiss units within the Vaseaux Formation, (Table 1) from structurally lowest numbered 1, to highest numbered 5. In addition he defined two intrusive units, designated A and B. (A sample of Christie's unit A, leucogneiss of this study, was collected for U-Pb analysis). 6 7 Figure 2: Geologic map and legend of the southern Okanagan area. 8 LEGEND Tertiary late Paleozoic. -Triassic Qal Alluvium eTs Eocene sediments; non-marine ss & shales eTcgl Eocene conglomerate eTbr Eocene breccia eTv Eocene volcanic rocks; trachyte, dacite trachyandesite, andesite, basaltic andesite lPz-Tr late Paleozoic-Triassic; greenstones, chert limestone, argillites, minor greywacke; includes: Old Tom, Shoemaker, Kobau, Anarchist, and Nicola formations © o c —I 3 0) o> (0 • Tertiary Cretaceous Jurassic -lgn eTi Kg K-Jg • • Jgrd,Jgr,Jd ejg paragneiss; amphibolite, feldspathic gneiss, semipelitic gneiss, calc-silicates, marble, schist; locally with up to and more than 50% granitic injections leucogneiss; concordant with foliation in surrounding pgn, possible J-K age Eocene intrusive; syenitic to granitic Cretaceous intrusives; gneissic granodiorite of Skaha Lake, and possibly Fairview grano diorite Cretaceous or Jurassic (?) granodioritic to granitic gneiss; most highly deformed adjacent to Okanagan Valley Jurassic hb granodiorite (Similkameen batho-lith and probable satellites);Jurassic granite, foliated east of Okanagan Valley;Jurassic hb-bi diorite Early Jurassic granodioritic gneiss Fault; known, assumed; hachure on upper plate Contact; known, assumed 9 Figure 3: Photograph of outcrop of gneisses in roadcut on east shore of Vaseaux Lake, showing xenoliths of Vaseaux paragneiss in foliated granitic gneiss. 10 Christie identified and described five phases of deformation. He interpreted the first three to be pre-mid-Pennsylvanian by structural correlation with the Kobau Formation (Okulitch, 1973). Unit A was interpreted by Christie to have been intruded during phase 2 deformation, and unit B during or prior to phase 3. He considered phases 4 and 5, namely very broad warping on two trends and vertical joints, to be of Tertiary age. The protolith for the Vaseaux Formation was inferred to be a sequence of greywacke, argillite, minor ultramafic rock, mafic volcanic rock, and minor limestone (Christie, 1973). To the south, and east of Osoyoos Lake, Ryan (1973) studied paragneisses (Table 2) which he mapped as high-grade equivalents of, and traceable into, the Anarchist Group of the eugeosynclinal package east of the Okanagan Valley. Ryan also mapped five intrusive bodies, which display varying degrees of deformation. Five phases of deformation were identified, the first 3 interpreted as pre-mid-Pennsylvanian, based on structural correlation with Old Tom and Shoemaker formations (Ross and Barnes, 1972; Read and Okulitch, 1977), and the latter two as Tertiary. The earliest intrusive body (gneiss of Osoyoos; collected for U-Pb analysis) was interpreted by Ryan as being either pre- or syn-phase 1 deformation. Two of the remaining four intrusives were interpreted as post-phase 2 but pre-phase 3, a relatively late one as syn-phase 3 (Anarchist Mtn. granite; collected for U-Pb analysis) and the latest (the Oliver pluton; 152 Ma by U-Pb by R.L. Armstrong and B. Ryan, unpublished) as post-phase 3. Ryan's Rb-Sr work indicated that most intermediate and late intrusives were of Jurassic age. The Anarchist Group consists of greywacke, argillite, chert, mafic volcanic, and minor limestone; it contains lenses of ultramafic rock (Rinehart and Fox, 1972; Ryan, 1973). Krauskopf (1941) identified mid-Permian fossils from the middle and upper divisions of the Anarchist Group, as mapped in northern Washington (which continues north into Ryan's thesis area). Ryan chose to disregard the fossil and Rb-Sr data to reach his conclusions on the ages of the deformation based on structural 11 Table 1 - Description of Vaseaux Formation (from Christie, 1973) Unit B Unit A Unit 5 Foliated and unfoliated syn-, to post-F^ granitic intrusives Syn-F2 leucocratic granitic intrusive. Biotite granulite; Hornblende granulites; Amphibolite layers common. Unit 4b- Laminated and massive amphibo1ites Unit 4a Sheared Contact Sheared Contact Laminated amphibo1ites; Basal granulites; Minor impure quartzite, ca1c-silicate and marble Sheared Contact Unit 3 - Semi-pelitic granulites, hornblende greater than biotite; thin biotite schist layers. Sheared Contact Unit 2 - Biotite-muscovite schists with interlayered semi-pelitic granulite; Minor marble, ca1c-silicate, quartzite. Sheared Contact Unit 1 - Biotite semi-pelitic granulite; Biotite schist layers characteristic's with associated ultramafic lenses. 12 correlations of the three early deformation episodes (using attitude, style, and ages assigned elsewhere by other workers). Studies on granitic rocks within the Okanagan Metamorphic and Plutonic Complex generally have been related to structural geometry (Christie,- 1973; Ryan, 1973; Medford, 1973). Little (1961) distinguished two major phases: Nelson type - generally more mafic and petrographically similar to the Nelson Batholith to the east, and Valhalla type - more felsic and younger than the Nelson intrusives. Recent work, east of the study area, in the Valhalla Dome (Parrish, 1984; Parrish et al., 1985) has shown that in the type area for the Valhalla Intrusives identified by Little, the rocks are in part Eocene in age. This suggests that regional petrologic correlations may be misleading. Eugeosynclinal Formations of the Okanagan Valley Region The eugeosynclinal rocks (lPz-Tr on Fig. 2) adjacent to the Okanagan Valley have various formation and group names (Table 3). Because of structural complexity, poor exposure, scarcity of fossils, and lack of distinctive stratigraphic horizons, no complete, or consistent stratigraphic picture has emerged. Okulitch (1973) interpreted the highly deformed Kobau Formation to be pre-mid-Pennsylvanian on structural correlations with metamorphic rocks of the Okanagan Metamorphic and Plutonic Complex to the east, and on its relationship to the undeformed Blind Creek limestone to the north. The Blind Creek limestone was originally interpreted to be Upper Mississippian to Lower Permian in age (Barnes and Ross, 1975) but has since been reinterpreted as Late Triassic in age (Read and Okulitch, 1977). Ryan (1973) interpreted the Anarchist Group to be older than the Kobau and equivalent to the Vaseaux Formation on structural grounds. Both of these correlations disregard mid-Permian fossils identified from the Anarchist Group in Table 2 Description of Structural Succession from an area east of Osoyoos (B. Ryan, 1973) Unit IX - Oliver pluton (unfoliated) post-F^ Unit VIII - Garnet-biotite granite, syn-F.; (Anarchist Mtn. granite of this study). Unit VII - Mu scov it e-b io t it e granite. Unit VI - Biotite granite. Unit V - Biotite-hornblende (Osoyoos gneiss of granodiorite, syn-, this study) . Unit IV - Amphibo1i t e. Unit III - Pelite - argillit e, phyllite, schist. Unit II - Quartzite - probable metachert. Unit I - Amphibolite - high grade area; greenstone - low grade area. 14 northern Washington (Krauskopf, 1941). Rinehart and Fox, (1972), and Fox et al. (1977) have mapped both Anarchist and Kobau equivalents in northern Washington and have also concluded that the Anarchist Group is older and the Kobau Formation lies unconformably or disconformably upon Anarchist Peatfield (1978) attempted to correlate eugeosynclinal formations between Rossland B.C. on the east and the Okanagan area. His correlations, at least those pertaining to the Okanagan area, follow Okulitch (1973). Read and Okulitch (1977) documented a regional Triassic unconformity and also attempted a correlation of eugeosynclinal formations. This unconformity is exposed near Olalla, 20 km northwest of the study area. Read and Okulitch (1977) recognized there a pre-Late Triassic deformation that affected late Paleozoic rocks (Old Tom and Shoemaker Formations of Little, 1961). This deformed eugeosynclinal sequence (limestone pods, greenstone, ultramafic lenses, ribbon chert, and argillite) is overlain by relatively undeformed Upper Triassic Nicola Group equivalents (chert pebble conglomerate, bedded limestone, and siltstone). Milford (1984) has found fossils that show the Apex Mountain Group (formerly Old Tom and Shoemaker Formations) ranges in age from mid-Carboniferous on the east near Olalla to mid-Triassic on the west This sequence was intruded by the Olalla Syenite, a zoned mafic alkalic complex (Sturdevant, 1963) (collected for U-Pb analysis by R.L. Armstrong), and Similkameen batholith to the south (Fox et al., 1977; collected for U-Pb analysis). The lithologic similarity of these different formations (Kobau Formation, Anarchist Group, Apex Mountain Group) is noteworthy and, with the exception of intermediate volcanic rocks and greywackes in the Anarchist, they appear to be nearly identical. On this basis, and on lack of contradictory fossil evidence, these formations are, in the present report, lumped together as a single mid-Carboniferous to Triassic eugeosynclinal package. They represent a complex of marine basin environments (either ocean floor or interarc or back arc basin; Monger, 1977) that was deformed in Triassic time, then eroded, and subsequently overlain by the Late Triassic Nicola 15 Table 3 - Eugeosynclinal Formations Nicola Group at Olalla (Read and Okulitch, 1977) -massive limestone -chert granule limestone -chert breccia -minor sandstone -shale, limestone Apex Mtn. Group Kobau Formation Anarchist Group (Milford, 1984) (Okulitch, 1973) (Fox et al., 1977) Formerly Old Tom and Shoemaker format ions. -chert -greenstone -chert conglomerate -arg ill it e -1imestone -chert -greenstone -argillite -1imestone -greenstone -chert conglomerate -chert -argillite -greywacke -1imestone 16 Group (Read and Okulitch, 1977). This is admittedly a broad interpretation but based on existing data, or its inadequacy, little more can be said. Plutonic Rocks West of the Okanagan Valley Since the pioneering study of Daly (1912), petrologic work on granitic rocks in the southern Okanagan, north of the U.S.-Canada border, has been restricted to study of the Jurassic Pennask batholith (Jgrd on Fig. 2) between Princeton, Penticton and Kelowna (Peto, 1973, 1973a, 1974, and 1979; Peto and Armstrong, 1976). The Pennask batholith is zoned with mafic intrusives at the border and younger felsic intrusives more abundant towards the center. Peto argues, on chemical grounds, that the felsic intrusives could be derived from the mafic intrusives through magmatic differentiation (Petb, 1973) and that the chemical data is consistent with the interpretation that the mafic (and felsic differentiates) could be derived from partial fusion of the Triassic Nicola Group basalts (Peto, 1979). He argues against the batholith being derived from Shuswap gneisses of the Okanagan Metamorphic and Plutonic Complex to the east of Okanagan Lake on the basis of higher 87Sr/86Sr ratios in the gneisses (Petb and Armstrong, 1976). The wide range in ages makes a single magmatic series unlikely. The other major batholith in the Southern Okanagan is the Similkameen (Jgrd on Fig. 2). Rinehart and Fox (1972) and Fox et al. (1976, 1977) have studied this complex in some detail in Washington. It is zoned from an older, mafic and alkalic border phase (Kruger Complex) to a more felsic core (Fox et al., 1977). K-Ar dates on Similkameen biotite and hornblende are discordant but the oldest K-Ar dates of 171 and 177 Ma are inferred to be the intrusive age (Engels et al., 1976). 17 Table 4 - Stratigraphy of White Lake Basin (Church, 1973) SHAHA FORMATION Upper Member: Fanglomerate. Lower Member: Slide breccias, some intercalated conglomerate and tephrite (augite porphyry) WHITE LAKE FORMATION Upper Member: Pyroclastic rocks, volcanic breccia, sedimentary rocks and tephrite. Lower and Middle Members: Volcanic sandstone, conglom erate and some coal; feldspar porphyry lavas, lahars, pyroclasitc rocks. MARAMA FORMATION Rhyolite, rhyodacite, pyroclastics, basal conglomerate. MARRON FORMATION Nimp it Lake Member: Trachyte and tra chyandesite lavas. Kearns Creek Member: Pyroxene rich v esicular basaltic and e s it e lava . Kitley Lake Member: Trachyte and tra chyandesite lavas. Yellow Lake Member : Anorthoclase lav a, augite porphyry lavas , and pyroclastic rocks. SPRINGBROOK FORMATION Bould er conglomerate. 18 Tertiary Formations The largest and best studied section of Tertiary rocks is the White Lake Basin section (Fig. 2). Church (1973) divided this section into five formations (Table 4). The following summary is taken from Church, (1973). The maximum thickness of this section is 2400 m. Volcanic rocks comprise most of the lower half, and volcaniclastic to coarse clastic sediments comprise the upper half of the section. A relatively thin (0-60 m) conglomerate (Springbrook Formation) is the basal unit This is followed by voluminous basaltic, andesitic, and trachyandesitic Marron Formation, deposited with slight angular unconformity upon the conglomerate. A second slight angular unconformity marks the base of the Marama Formation, composed of rhyodacite, rhyolite lava and pyroclastic rock and a basal conglomerate. The first significant angular unconformity marks the base of the White Lake Formation comprised of volcaniclastic to arkosic sediments, pyroclastic rocks, and rare lavas. The Skaha Formation overlies a second major angular unconformity. The Lower Skaha is mainly coarse conglomerate (fanglomerate) and megabreccias. These megabreccias include large (1 km2), intact "rafted slabs" of Old Tom Formation, Shoemaker Formation, and granite - probably Oliver pluton (Church, 1973). The upper Skaha Formation is a poorly-bedded coarse conglomerate interpreted to be shed from a high terrain to the southeast The clasts within this conglomerate are chert, greenstone, granite, arkose, Tertiary augite porphyry, and phyllite. The rocks of White Lake Basin are folded, ruptured and ultimately become chaotic along the eastern boundary of the basin. Along the western border the lower units dip eastward only moderately (0-10°) but eastward and stratigraphically upward, the successive formations dip increasingly to the east In addition, all formation boundaries are at least slight angular unconformities, becoming increasingly angular for younger formations. Normal faulting appears to have been active throughout deposition 19 N Figure 4: Stereonet of poles to fractures/cleavages from the eastern border of White Lake Basin (from Church, 1973); contour intervals are >7%, 5-7%, 2-5%, 1-2%, 0.5-1.0% and <0.5%. 20 of the basin but especially at the time of deposition of White Lake sediments, and culminating during deposition of Skaha Formation. Along the eastern boundary, where the deformation is greatest, Church did a detailed study of slickenside, and fracture orientation (Fig. 4), which shows that the predominant fracture/cleavage orientation is NNE, dipping steeply both west and east The slickensides point to both normal -NW side down and slightly obliquely normal - NNW side down movement There are several known intrusives of Eocene age in' the southern Okanagan. A few were described and dated by Armstrong and Peto (1981) and Medford et al. (1983). The Shingle Creek porphyry (Bostock, 1966) was dated by K-Ar as 52.4 Ma (Church, 1979b). These intrusives are calc-alkaline to alkaline, potassic, rhyolite to syenite. They are probably related to rhyolite in the Marama Formation (Church, 1973). Figure 5: Photograph of outcrop of mylonitic gneisses on old railway cut west of Vaseaux Lake. III. DESCRIPTION OF MAP UNITS/STRATIGRAPHY Using the broad subdivision of rock types developed for the regional geology, the stratigraphy of the thesis area can be divided into four parts: metamorphic rocks of the Okanagan Metamorphic and Plutonic Complex (pgn and lgn); chert, limestone, minor argillite, greenstone, and greywacke of probable late Paleozoic to Triassic age (lPz-Tr); intrusive plutonic rocks of Jurassic age (Jgr, Jgrd, Jd); and Tertiary volcanic, sedimentary, and intrusive rocks (eTv, eTs, eTd). This section will deal with distribution, relationship to other units, lithology, chemical composition of the intrusive units, and finally age and correlations (Plate 1). Paragneisses (pgn) As mentioned in the previous chapter the paragneisses within the study area were named the Vaseaux Formation by Bostock (1941a). They were studied structurally by Christie (1973) who defined five lithologic units in a structural succession (Table 1). In the present study these were grouped into one unit - pgn. The area of pgn mapped extends from Mahoney Lake in the west to the cliffs west of Vaseaux Lake in the east, and from Covert Farms in the south to Green Lake in the north. Unit pgn has been intruded by unit lgn, but is in low-angle fault contact with all adjacent map units (lPz-Tr, eTv, eTs, Jd and Jpgr) to the west Within the study area the paragneisses are predominantly banded to massive amphibolite and biotite- or hornblende-plagioclase gneiss with minor mica schist and rare calc-silicate and diopside marble lenses. The amphibolites range in mineralogy from biotite-plagioclase-hornblende to plagioclase-hornblende amphibolites, both contain garnet The grain size is also variable 22 23 from fine (0.5-1 mm) to medium (2-4 mm). These rocks predominate in the mapped area of pgn and are more abundant in the western and northern half of pgn exposure. Schist is subordinate to amphibolite and tends to follow the outline of the leucogneiss (lgn) body which is interpreted by Christie (1973) as intruding the core of a phase 2 antiform. Minor and discontinuous pods of calc-silicate and diopside marble are found within the schist unit The schist consists predominantly of biotite, quartz, plagioclase, and garnet, but muscovite is commonly present "in highly sheared portions of the unit" (Christie, 1973). The schist is also interlayered with what Christie (1973) has called semi-pelitic granulite or simply biotite-quartz-feldspar gneiss. Gneissic granitic sheets or sills are common as lit-par-lit injections into the schist and amphibolite. Studying the metamorphic grade of these gneisses is, as stated by Christie, unrewarding, mainly because of lack of variation of mineral assemblages within the area. Most of the area is at the same metamorphic grade: middle to upper amphibolite facies. Christie (1973) states that sillimanite is only locally developed at the contacts with intrusive granitic bodies. The paragneisses have a well developed foliation which dips gently westward. Throughout the pgn unit variable shear is evident, with locally developed mylonitic fabrics (Fig. 5). The amount of mylonite within pgn generally increases structurally and topographically upward and is most intensely developed directly below eTv and eTs at Mahoney Lake. Also at this locality are exposures of very siliceous mylonites and banded quartzites (metachert?). At high structural and topographic levels (again in particular at Mahoney Lake but continuing southward from there to Meyers Flat) the paragneisses are increasingly altered to chlorite and epidote with very late pyrite. This chlorite alteration is both synchronous with the latest mylonites (epidote and chlorite deformed in highest level mylonites) as well as post-mylonite (pyrite cubes and chlorite breccias with mylonite clasts). These structurally highest zones of mylonite and Figure 6: Photograph of foliated leucogneiss, from north of Coven Farms. 25 associated chlorite alteration are spatially related to fault breccias, also chloritized , and faulted eTv and eTs. The contact between these Tertiary units and underlying mylonitic pgn has been mapped in the present study as a low-angle (10°-20°) west-dipping fault zone. The stratigraphy of the paragneisses is not distinctive enough to make any lithologic correlations. The age of the paragneisses is only known to be older than Jurassic (based on Rb-Sr data of Armstrong on lgn). The abundance of amphibolite, and associated metamorphosed ultramafics (and lack of quartzite or well bedded, continuous carbonate) suggests to the author that these gneisses can be correlated with the lower grade Anarchist Group, Kobau Group, and Apex Mountain Group found locally. Ryan (1973), working east of Osoyoos, traced greenschist grade Anarchist Group rocks northward into amphibolite grade paragneisses which are identical to, but not continuous with, paragneisses in the Vaseaux area. Whole-rock Rb-Sr dating of schists within the Vaseaux Formation, in contrast, suggests a Precambrian age (Ryan and Armstrong, unpublished). Leucogneiss (lgn) Within the pgn unit, and containing all but the earliest fabric present in the pgn, is a granitic intrusion: leucogneiss. At the southwestern end of exposure of lgn near Covert Farms it is easily demonstrated that the lgn/pgn contact is intrusive. This contact is commonly marked by leucocratic pegmatite and the intrusive body is here (Covert Farms area) relatively leucocratic (hence the name). This intrusion is now sill-like with respect to the foliation and compositional layering in pgn. The lgn unit can be easily traced on both sides of Vaseaux Lake and defines a broad, domal structure (phases 4 and 5 of Christie, 1973) within the metamorphic complex. Farther to the north and east across Okanagan Valley, this unit becomes richer in biotite. 26 The overall textural character of the lgn unit is variable and ranges from weak development of gneissic foliation (Fig. 6) to well developed horizons of lineated and foliated mylonite. Overall the body is a homogeneous biotite granite to granodiorite with lighter colored pegmatitic borders. The large volume of small granitic sills within the pgn unit are both texturally and lithologically similar to lgn, and apparently are injections from this intrusive. The lgn unit is a medium-grained equigranular biotite granodiorite. In thin section quartz is ubiquitously strained, variably recrystallized, and elongated parallel to the foliation. Plagioclase and K-feldspar are rounded and commonly broken due to deformation (Fig. 7). The plagioclase (An5_10) (all plagioclase compositions determined optically) is commonly zoned (normal to complex). The only mafic mineral is biotite (or chlorite after biotite) which defines the foliation and is generally intergranular to plagioclase and K-feldspar, rarely occuring as inclusions in K-feldspar. The pegmatitic and most leucocratic phases contain muscovite, gray quartz, white plagioclase, potassium feldspar, and red garnet At the structurally uppermost exposures of the leucogneiss it is commonly altered: chloritized biotite, minor epidote, and allanite. The age and correlation of lgn are debatable. U-Pb results are ambiguous. The interpretation, although not unique, is that the leucogneiss was intruded in the Jurassic and has since been subjected to a later event(s) of Cretaceous or younger age. Part of the reason for suggesting a Jurassic intrusive age is that there are no known older plutons in the southern Okanagan area. In addition a whole-rock Rb-Sr errorchron (Armstrong, unpublished) based on a fairly large sample suite is Jurassic - likely a maximum age. 27 Figure 7: Photomicrograph of leucogneiss showing extensive deformation. 28 Cretaceous or Jurassic gneissic granitic rocks (K-Jgr) Foliated and lineated granitic rocks were mapped on the southeastern margin of the study area. Christie (1973) mapped this as his unit B, and Ryan (1973) as his units VI and VII. Little (1961) mapped this unit as continuous with much of the granitic rocks to the east This unit is in the footwall of the Okanagan Valley fault which is its western boundary. K-Jgr comprises only a minor portion of the study area and therefore was not examined in any detail. Its composition is biotite granodiorite to quartz monzonite. The presence or absence of K-feldspar porphyroclasts is the main variation within this unit Both Christie and Ryan interpreted this unit to have intruded post F2 and pre- or syn-F3, although the trend of the lineations for both of these phases is coaxial. Little correlated, on the basis of petrology, the K-Jgr with Valhalla intrusives to the east The only age determination on this unit is a K-Ar biotite date of 56 Ma (Armstrong and Mathews, unpublished), which more than likely represents thermal resetting. iMte Paleozoic-Triassic Eugeosynclinal Rocks (lPz-Tr) Exposures of lPz-Tr are restricted to south and north of the Oliver pluton along the western margin of the field area. This unit is in fault contact to the north with the Tertiary White Lake Basin sequence (Bostock, 1941a; Little, 1961) and in partial fault contact with dioritic rocks of the northern Oliver pluton. The southern contact of the Oliver pluton is intrusive into the Kobau Formation, and at the upper reaches of Orofino Creek the Oliver pluton again appears to have intruded lPz-Tr. Because this unit is sporadically exposed, as well as lacking any distinctive or continuous stratigraphy, only the bounding structures were mapped. No attempt was 29 made to decipher its internal structure, although this is known to be complex (Fig. 8; Okulitch, 1973). This unit is composed of chert or metachert, greenstone, carbonate, and minor greywacke. The metachert ranges from 90 to 98 percent quartz with very rare plagioclase, and rare to common biotite, white mica, and chlorite. The texture of the quartz is also variable, with the development of both 120° and sutured grain boundaries. The grain size is generally fine (0.5 mm or less) but ranges to medium (0.5-1 mm). Carbonates are discontinuous along strike and are commonly found as pods: 10 meters or less in strike length and, 5 meters or less in thickness. Locally these carbonate pods are metamorphosed to calc-silicates adjacent to the Oliver pluton, and show extensive deformation (Fig. 9). The greywacke is restricted to the northeasternmost exposures of the map area. It is fault bounded. The greywacke is an immature, medium grained, well-sorted sediment with angular clasts of mono-crystalline quartz, plagioclase, and K-feldspar. Oliver Pluton (Jd, Jpgr, Jgr) The Oliver pluton is a composite, very heterogeneous intrusive body. The heterogeneity is defined by both compositional differences and textural variations between three distinct phases. The northern third of the pluton is predominantly diorite, becoming agmatitic southward towards the contact with the main body of porphyritic biotite granite. This biotite granite is in turn intruded by a garnet-muscovite granite. The pluton is not neatly concentrically zoned but there is a mafic outer zone and a felsic core. Three distinct magmatic intrusive episodes are inferred but they are not necessarily separated by long time periods. The outer contact relationships of the Oliver pluton vary considerably. As stated in the previous section intrusive contacts into lPz-Tr unit are found on the southern 30 Figure 9: Photograph of calc- silicate boudins in IPz-Tr unit 31 border of the Oliver. Contacts to the north with lPz-Tr, to the northeast with pgn, and to the east with gneissic granite have all been mapped as faults. Nowhere can the Oliver pluton be seen to intrude the metamorphic rocks to the east The internal contacts between the three phases vary from a broad agmatitic zone between Jd and Jpgr (Fig. 10) to a knife sharp contact between Jpgr and Jgr (Fig. 11). The three phases (Jd, Jpgr, Jgr) will be described in order of decreasing relative age. Diorite (Jd) The dioritic phase of the northern third of the Oliver pluton is also exposed on the western edge of the map area, west of Burnell Lake (Plate 1). The diorite is observed in various stages of disaggregation and assimilation (Fig. 12) in a broad agmatitic zone at the contact with the porphyritic biotite granite. This assimilation is the cause for the porphyritic biotite granite being more mafic adjacent to and within this agmatite zone. There are various types of agmatite: angular, rounded, and sheared; mostly diorite, or mostly granitic. Near its northern contact the diorite becomes increasingly foliated. Just north of Orofino Creek highly deformed, mylonitic, metasediments of lPz-Tr are exposed. Northward in the metasediments this deformation decreases. These observations suggest that this contact is a fault, dipping gently (<30°) to the north. The presence of a large inclusion of lPz-Tr within the diorite is evidence that the _ diorite does in fact intrude the metasediments. Supporting evidence is the development of higher-grade calc-silicates adjacent to the diorite in the northwestern part of the area. Internally the diorite is extremely heterogeneous. It is difficult to discern how much of this heterogeneity is original and how much is superimposed by the later 32 Figure 11: Photograph of sharp contact between Jpgr (on right) and Jgr (on left). 33 intrusion of Jpgr and Jgr. Texturally the diorite ranges from agmatite to gneiss. Within a single outcrop grain size ranges from fine and medium to pegmatitic (Fig. 13). Hornblende diorite is the most comon composition but can change within meters, to biotite diorite. This heterogeneity may be original or superimposed. In thin section the diorite is variably but ubiquitously altered with the development of chlorite, epidote, and sericite. Hornblende is invariably euhedral, plagioclase (An35-«) ranges from euhedral, in plagioclase rich samples, to anhedral and interstitial in rocks which contain 80 percent or more hornblende (Fig. 14). Biotite content ranges from zero to generally about 10 percent and rarely reaches 40 percent Opaques are common and are in part secondary pyrite. The age, based on field relationships, is well bracketed between Triassic (youngest age of lPz-Tr unit that it intrudes) and mid-Jurassic (age of Jgr that intrudes it). The origin and correlation is more of a problem. It may be an intrusive equivalent to Late Triassic Nicola volcanic rocks. More likely, it represents an early mafic phase of the Early to Mid-Jurassic intrusions. Porphyritic Biotite Granite (Jpgr) The main phase of the Oliver pluton is a porphyritic K-feldspar granite (Fig. 15). This phase clearly intruded the diorite. The Jpgr also intruded lPz-Tr along the southern border of the pluton and is itself intruded by Jgr in the central part of the map area, northwest of the town of Oliver. A west-dipping low angle fault is the contact between the gneissic granites of the Okanagan Metamorphic and Plutonic Complex, to the east, and Jpgr. The mineralogy of the Jpgr is consistently biotite-plagioclase (An20) - quartz- porhyritic K-feldspar (1 cm). Biotite is the main mafic mineral and, for most of the area, the only original one present The southern border of the Jpgr, the only Figure 13: Photograph of pegmatite Jd 35 Figure 15: Photograph showing the general character of Jpgr unit 36 area where hornblende is identified as a component (Fig. 16), is more mafic. In addition the biotites display a deep brown pleochroism and striking pleochroic haloes (Fig. 17). Elsewhere in the Jpgr the biotites are green and show very small or no pleochroic haloes (Fig. 18). In the southern exposures plagioclase (25 percent, An25) is euhedral to subhedral and lath shaped; K-feldspar (25 percent, microcline microperthite) is not as porphyritic as elsewhere in this unit but is still coarse (0.5 cm); quartz (25 percent) is anhedral and strained but not recrystallized - as it very commonly is elsewhere in the unit Sphene, zircon, and apatite are accessory minerals, the latter two being responsible for the well-developed pleochroic haloes in biotite. This mineralogy puts the southern part of the Jpgr unit (in Strekeisens, 1976 IUGS classification) on the border between granodiorite and granite. The alteration in the southern Jpgr is limited to minor saussurite development in plagioclase, minor chlorite and epidote. The majority of Jpgr exposures lack hornblende and contain chlorite, epidote, saussurite/white mica+calcite as common alteration products - locally making up to 5-10 percent of the rock. The rocks with green biotite + alteration products are interpreted to be an altered equivalent of the hornblende-biotite granite exposed in the southern part of the Jpgr. This alteration is spatially related to the later intruding Jgr, which is more felsic, potassic and sodic. Another explanation for the mafic character of the southern border of the Oliver was proposed by Richards (1968). He called on the assimilation of Kobau formation as the cause. Lack of Kobau Formation inclusions along this contact and the unsuitable composition of the Kobau (chert, limestone, and rare greenstone) argue against this hypothesis. For the Jpgr unit as a whole, it appears that alteration of an original hornblende-biotite granite/granodiorite to a biotite granite by the later intruding Jgr is the most satisfactory explanation for the limited preservation of hornblende. Figure 17: Photomicrograph of brown biotite from southern Jpgr, with pleochroic haloes. 39 The Jpgr unit is older than Jgr unit, which gives a 152 Ma concordant U-Pb zircon date (Ryan and Armstrong, unpublished), and younger than the lPz-Tr unit which it intrudes. Garnet- Muscovite Granite (Jgr) The youngest phase of the Oliver pluton is a leucocratic garnet-muscovite granite. Sharp intrusive contacts are observed with the Jpgr unit. The Jgr is the least voluminous of the three phases. It is restricted to an exposure with the shape of a large half circle, northwest of the town of Oliver. The only other exposures are small circular outcrops, two of which are of mappable scale. The field exposures, and contact relationships suggest a very viscous, nearly solid intrusion. The highly felsic nature of this unit supports this interpretation. The only rocks that cut the Jgr are Eocene rhomb porphyry and lamprophere dikes. The Jgr unit is extremely homogeneous. It does not change texturally or lithologically across its exposure. The only variability is amount of manganese stain along fractures. The mineralogy of the granite is plagioclase (Ano.2) = quartz = K-feldspar (microcline, with minor microperthite) > muscovite > garnet (Fig. 19). The quartz, plagioclase, and K-feldspar are equigranular and. give the unit its characteristic gray-white color. The muscovite is magmatic, and euhedral (Fig. 19) (Best et al, 1974; Anderson and Rowley, 1981; Miller et al., 1981) The garnet is red in hand specimen and commonly 0.2 mm in size. Garnets range from nearly euhedral with minor alteration or reaction rims to completely replaced by white mica pseudomorphs (Fig. 20). This unit has given a concordant U-Pb zircon date of 152+3 Ma and a Rb-Sr whole rock date of 157±8 Ma (Armstrong and Ryan, unpublished). Figure 20: Photomicrograph from Jgr showing partly altered garnets (top) and unaltered and completely altered garnets (bottom). 41 Discussion of Geochemistry Whole rock XRF major element analyses, using pressed powder pellet technique of Van der Heyden, Horsky and Fletcher (1982), were done on a total of 26 samples. Two analyses were duplicated. Trace elements were measured on 11 samples, and Rb and Sr concentrations on 20 samples. The results are given in Table 5. The discussion of the whole rock chemistry will be broken into three parts 1) general characteristics, 2) differences between Jpgr and Jgr and, 3) investigation of S- and 1-type classifications. It should be stated, however, that because some samples are both intrusive and altered, in some cases highly altered, the data should only be used for discerning general trends and associations and should not be used for detailed petrogenetic models and calculations. 1) General Characteristics General characteristics are: A - the scattered nature of the diorites on the Harker diagram and AFM plot (Fig. 21 and 22) which confirms the textural and lithologic heterogeneity seen in the field and thin section. B - the highly felsic nature of the Jgr unit - 75 to 78 percent Si02 and virtually no iron or magnesium, and C - the spread in Jpgr samples from moderate to higher silica values and lower Fe, Mg and Ca. On an AFM diagram (Fig. 22) the three units, in particular Jpgr and Jgr, plot within the trend for calc- alkaline rocks (Kuno, 1968; Irvine and Baragar, 1971). On a normative Q-Or-Plag diagram (Fig. 23) the Jpgr straddles the granodiorite/granite fields and Jgr plots mostly within the granite field. 2) Geochemical Comparison of Jpgr and Jgr. The spread in values in the Jpgr is interpreted to be due to alteration affects caused by the intrusion of Jgr. The samples of Jpgr which are at the lower silica end of this trend are the least altered in thin section. Those samples with values approaching Jgr are increasingly altered - as well as spatially closer to Jgr. On a 42 wt. % 2 _ • • A Jpgr • Jd • Jgr • leucogneiss Ti02 1 _ 0 • T A Al203 14 -1 0 • • A • • • Fe203 8 -r\ A A 0 — 8 -• A A • CaO 4 -n rri A MgO 8 -0 • • A • • Na20 4 -o • A A • • K20 4 -0 • • • A A • • • I I I I I I I I 40 50 60 70 80 Si02 wt- * Figure 21: Major element variation diagram for different phases of Oliver pluton. Also shown are two analyses from the leucogneiss. 43 Figure 22: AFM diagram for samlpes from Oliver pluton; note symbol change for Jpgr unit Also plotted are U-Pb samples. 44 Q Normative Figure 23: Q-Or-Plag diagram showing most Jgr plotting in the granite field, most Jpgr plotting on boundary between granite and granodiorite fields. 45 MgO 3-1 2-J H Jpgr Jgr CaO 4 wt. % Figure 24: Mgo vs CaO plot for Jpgr and Jgr samples. 46 MgO vs CaO diagram (Fig. 24) these two units plot even more distinctly apart with only two Jpgr values close to the Jgr cluster. These two samples are again the most highly altered. This separation of units on geochemical characteristics also can be seen on trace element plots (Fig. 25 and 26) (Sr, Rb, Ba, and Zr vs Si02). Of these Zr and Sr seem to show the most distinct separation. The interpretation of this, as suggested above, is that the Jpgr values which plot away from Jgr represent the original composition of this unit (that of a Hb-Bi granodiorite), which was altered when the Jgr unit intruded. These two units are not an in situ differentation sequence and may have separate origins. In support of this is the normative Q-Ab-Or projection (Fig. 27; "Petrogeny's Residua System") on which the Jpgr and Jgr plot in or approaching the thermal trough at the experimentally determined minima for low pressure conditions (Turtle and Bowen, 1958). Taking normative An into account would shift the minimum towards Q, for a particular Pt (Strong, 1979; Hyndman, 1984). In general the Jpgr samples plot to the Ab side of the fractionation curve which separates liquids which become more potassic as cooling continues from those which become more sodic with continued cooling (Carmichael et al., 1974). The Jgr samples generally plot on the Or side of this fractionation line. This, from petrographic evidence, is to be expected. Plagioclase was clearly a liquidus mineral for the Jpgr unit and alkali-feldspar is euhedral to sub-hedral in Jgr samples, suggesting it was a liquidus mineral. 3) Comparison with S- and I-Type Granites In recent years work on granites has focused on whether the source rock was of sedimentary (S) or igneous (I) origin (Chappell and White, 1974). The Jgr unit (containing both garnet and muscovite, as well as having very high silica composition) appears to fit into the S category. In an effort to substantiate the petrographic observations several plots were made which demonstrate the S or I character of a granitic rock. These plots show: A - degree of alumina saturation with respect to 47 Sr 500J 400 300 200J 100 J E a 0^ Rb 300-1 250J 200. 150H 100-1 50 J • Jpgr • Jgr • • • ' iiir-48 52 56 60 64 68 SiCL 72 76 80 wt. % Figure 25: Sr and Rb vs Si02 for Jpgr and Jgr samples. Table 5 (See Appendix A for procedures and error estimates). WHOLE ROCK DATA FOR PORHYRITIC BIOTITE GRANITE SAMPLE* 227 205 275.1 275.2 205 203 71 245 S102 73 .74 72 87 69 .45 66 66 72 .74 70 05 74 .64 67 .47 T102 0 . 10 0 .25 0 28 0 39 0 . 27 0 31 0 .07 0 46 A 1203 13 . 18 12 .97 13 .90 13 73 13 .02 14 35 12 83 14 49 Fe203 1 38 2 67 2 95 4 37 3 .05 3 18 1 .31 4 45 MnO 0 . 17 0. 16 0 17 0. 18 0 .06 0 06 0 12 0 17 MgO 0 69 1 44 1 83 2. 88 1 .38 1 35 0 ,47 2 . 25 CaO 1 37 2 15 2 .74 3 22 2 27 2 51 1 .37 3 27 Na20 4 59 3 64 4 15 4 24 3 19 3 43 4 .43 2 85 K20 3 77 3 26 3. 23 2 99 3 38 4 04 3 97 3 93 P205 0 07 0. 10 0. 1 1 0. 16 0 14 0. 16 0. 06 0, 20 H20 0 93 0. 49 1 . 19 1 . 19 0 49 0. 56 • 0 73 0. 46 WHOLE ROCK DATA FOR DIORITE SAMPLE* 207 178 261.1 261.2 140 S102 46 .97 49 .86 56 .29 45 .90 41 17 T102 1 . 70 1 . 10 0 .78 0 .91 2 .08 A1203 15 .04 18 .43 13 70 12 .91 13 65 Fe203 14 .25 10 88 8 93 12 .44 13 .45 MnO 0 17 0 .20 0 18 0 28 0 . 16 MgO 7 .79 5 17 8. 92 15. 94 16 55 CaO 9 07 7 . 36 5 66 7. 36 9. 39 Na20 1 90 3 .09 2. 53 1 44 1 44 K20 1 05 1 38 2 49 2 67 1 . 39 P205 O 93 0 68 0. 14 0 15 0. 22 H20 1 13 1 . 86 1 . 10 1 50 1 . 20 CATION NORMS CATION NORMS 0 27 . 40 32 .66 23 51 18 .56 30 91 25 87 28 87 23 68 OR 22 51 20 39 19 36 17 .90 19 57 24 25 23 . 7 1 23 .66 AB 41 . 73 29 .30 38 . 1 1 38 .88 33 28 31 32 40 28 26 . 12 AN 4 .24 10 .57 9 .76 9 .58 9 54 1 1 .59 3 41 15 .20 DI 1 .74 2 65 4 .44 0 51 2. 46 HY 1 06 4 . 18 4. 1 1 7 77 3 79 4 12 0. 08 8 . 10 MT 0 19 1 88 1 . .87 1 98 1 82 1 91 0 14 2 08 IL 0. 14 0 38 0 40 0 55 0 35 0. .44 0 10 0. 65 HM 0. 84 O. 02 0. 83 AP 0. 15 0. 30 0. 23 0 34 0. 21 0. 34 0. 13 0 43 C O. 35 o. 16 o 08 0 0 39 4 .67 OR 6 .45 a .41 14 .78 15 .58 8 . 17 AB 17 . 78 28 . 73 23 .07 9 48 1 .33 AN 30 .55 33 . 10 18 .64 20 .51 26 .49 OL 1 84 36 62 35 .83 DI 7 93 6 92 1 1 68 14 . 76 HY 27 77 23 48 28 . 17 NE 2 . 1 1 7 .00 MT 3 18 2 75 2 .37 2 .46 3 .07 IL 2 46 1 58 1 09 1 . 25 2 88 HM AP 2 02 1 . 47 0 29 0. 31 0. 46 C 0. 09 TRACE ELEMENTS (ppm) Rb Sr Ba Nb Y Zn Zr 150 212 146 348 670 12 17 126 163 365 154 396 150 347 592 15 12 47 126 180 389 817 14 11 47 1 18 135 294 204 462 TRACE ELEMENTS (ppm) Rb Sr Ba Nb Y Zn Zr 37 821 34 756 924 14 23 133 1 1 1 131 380 479 15 26 62 138 294 557 1 1 31 51 52 489 611 1 1 25 46 oo WHOLE ROCK DATA FOR GARNET MUSCOVITE GRANITE WHOLE ROCK DATA FDR U-PB SAMPLES SAMPLE* 234 209. 1 209 .2 263 1B2 9 263 SAMPLE* 156 95 179 246 90 300 S102 73 .63 76 67 78 13 76 22 75 .34 75 . 15 75 .49 S102 74 30 74 .25 66 43 68 .22 74 . 1 1 53. 77 T102 0 OS 0. 03 0. 03 0 .04 0 08 0 08 0 .04 T102 0 04 0. 14 0 32 0 30 0. 14 0.84 A 1203 13 75 12 . 45 1 1 78 12 .73 13 .40 13 .33 12 77 A1203 13 89 13 19 14 97 13 .83 14 .33 17.OO Fe203 1 , ,00 O. 88 1 . 04 1 .08 1 09 1 .39 0 91 Fe203 0. 38 1 .66 3 21 3 .44 1 .46 6.50 MnO 0 17 0. 10 0 03 0 .02 0 .03 0 .04 0 .07 MnO O 12 0 17 0 18 0 . 17 0 02 0.11 MgO 0 36 0. 21 0 07 0 .09 0 .27 0 .26 0 37 MgO 0. 24 O 67 0 95 1 57 0.45 5. 29 CaO 0 17 0. 75 0 .79 1 .09 0 .92 1 . 11 1 03 CaO 2 32 1 59 5 12 3 68 2 79 5 02 Na20 6 88 4 . 30 3 42 3 20 3 64 3 68 3, 91 Na20 5 92 3 77 6 . 28 5 08 4.61 4 . 74 K20 3 .04 4 . 25 4 37 5 10 4 76 4 71 4 95 K20 2 . 41 4 14 2 . 18 3 21 2 .06 5.03 P205 0. 04 O. 03 0. 01 0. 02 0. 03 0 03 0 04. P205 0 05 0 07 0 18 0 19 0.02 1 OO H20 0 92 0. 33 0. 03 0. 42 0. 44 0 .23 0. .42 H20 0 33 0. 33 0 19 0 29 0.20 0. 26 CATION NORMS CATION NORMS 0 20 . 24 31 .61 37 .46 33 .60 31 .62 30 .96 29 .55 0 24 83 30 38 12 17 17 32 30 82 29 . 36 OR 17 .83 25 .33 26 .29 30 .65 28 48 28 . 14 29 .53 OR 14 16 24 76 12 77 18 98 12 22 30 36 AB 56 .56 39 .01 31 . 32 29 .29 33 . 15 33 .47 35 .52 AB 52 91 34 27 55 97 45 7 1 4 1 71 9 96 AN 2 10 3 93 5 .31 4 . 26 5 25 2 .67 AN 4 17 6 93 6 13 5 43 12 31 10 58 DI 0 .50 1 . . 16 1 78 01 3 44 0 48 10 26 9 28 0 84 HY 1 . 64 0 20 0 25 0. . 76 0. . 73 0. 14 HY 1 63 0 59 0 83 7 22 MT 0 17 0 .01 0. 08 MT 0 20 0 16 1 . 88 1 88 2 40 IL 0 04 O. 04 0 04 0 03 0. .05 0. 06 0. 06 IL 0. 06 0. 20 O 44 O 42 0 03 1 16 HM 0. 50 0 73 0 . 77 0. .77 0. 98 0. 59 HM 0. 13 1 05 1 02 AP 0. 08 0. 06 0 02 0 .04 0. 06 0. 06 0. 08 AP 0. 10 0. 15 O 37 O 40 O .04 2 07 C 0. 03 0. 78 0. 03 C SP 0. .04 0. 10 0. 07 ACMITE 2.76 -NAMETASILO.53 - - - - - -TRACE ELEMENTS (ppm) Rb 63 151 44 125 51 141 TRACE ELEMENTS (ppm) Sr 409 350 1004 640 787 3313 Ba 1362 3492 Rb 312 136 136 141 221 213 141 Nb 6 90 Sr 45 181 181 201 209 185 201 Y 9 27 Ba 684 254 401 349 Zr 57 4 12 Nb 14 4 12 14 Y 8 3 12 16 Zn 17 18 24 36 Zr 60 69 65 64 • Jpgr • Jgr • Jd 150-Zr 100-• • • E a • A A a. A 800- • Ba 600- A A • • 400-A • • • 40 1 1 50 60 70 80 Si02 Figure 26: Zr and Ba vs Si02 for Jpgr and Jgr samples. 51 normative corundum or diopside, versus Si02 (Fig. 28); and B - molar Al203/(CaO + Na20 + K20) versus Rb/Sr ratio (Fig. 29). Rocks with normative corundum and molar Al203/(CaO + Na20 + K20) > 1.1 are considered typical S-type granites. Both Jpgr and Jgr units have samples which contain (<1 percent) normative corundum. Otherwise the samples are scattered mainly with low to moderate normative Di. On the molar Al203/(CaO + Na20 + K20) vs Rb/Sr the most striking characteristic is again the separation (in Rb/Sr values) between these two units. In terms of S and I classification the Jgr samples are all (except one) below 1.1, suggesting a highly evolved I-type magma. The Jpgr unit straddles this dividing line at 1.1, with several values up to 1.2 molar Al203/(CaO + Na20 + K20). Petrographically the Jpgr unit is not of S-type character. An alternate explanation for the slightly aluminous character of this unit and very likely considering the mineralogy, is amphibole fractionation causing alumina enrichment (Cawthorn and Brown 1976, Cawthorn et al, 1976). In summary it appears that neither of these granitic bodies is truly of S-type. The Jpgr unit has high molar Al203/(CaO + Na20 + K20) values due possibly to amphibole fractionation and the Jgr unit which has S-type petrographic characteristics, does not plot neatly in S-type granite fields on either C-Di or molar Al203/(CaO + Na20 + K20) scales. Jgr may be a highly differentiated I-type magma or it could be the result of fusion of eugeosyclinal or lower crust rocks rather than pelitic schists and therefore does not clearly display S-type geochemistry. 52 Q Normative wt. % Figure 27: Q-Ab-Or for Jpgr, Jgr, and Jd samples. Boundary curves and temperature contours for water saturated liquids at P = 1.0 kb, from Carmichael et al. (1974). 5 -i 4H Jpgr Jgr Di 3H 2-4 1 H l-type S-type 1 H 68 70 72 74 SiO. 76 78 Figure 28: C and Di vs Si02 for Jpgr and Jgr samples. 54 Eocene Strata (eTv, eTs,) Eocene volcanic rocks and coarse clastic sediments are exposed in the northwestern part of the area. They represent a small part of this study area but were examined in detail by Church (1973) and therefore the internal stratigraphy is well defined. The volcanic rocks within the study area include the Matron Formation and local occurrences of rhyodacite and pyroclastic rocks of the Marama Formation. Clastic sediments present are the Skaha Formation. In the area studied the volcanic rocks are found at lower stratigraphic, structural and topographic levels than the sediments. The contact between the volcanics and overlying sediments has been mapped (Church, 1979b, and the present study) as a fault directly north and northwest of Mahoney Lake, but elsewhere in the White Lake Basin Church has demonstrated this contact to be an angular unconformity. The contact between the volcanics and lPz-Tr to the south is also a fault, as is the contact between the Eocene rocks and the Vaseaux gneisses to the east The volcanic flows exposed west of Mahoney Lake are extremely altered, fractured, and faulted. They can be related to Church's detailed stratigraphy only on the basis of texture (relict "Clot Porphyry", Church, 1973). The phenocrysts, except for feldspars, are invariably altered beyond recognition. These volcanics are andesite to trachyandesite in composition; the groundmass is a mosaic of quartz and feldspar. The alteration consists of calcite, quartz, and opaques (oxidized pyrite, and fracture-filling iron oxides). The Skaha sediments are coarse conglomerates, and form the youngest unit in White Lake Basin. Church describes them as fanglomerate, shed from highlands which lay to the southeast The predominant clasts are chert, greenstone, and unfoliated granite. Church (1973) reports phyllite clasts which he interprets as coming from Vaseaux Formation. The Vaseaux Formation is not seen at such a low metamorphic 55 grade, therefore the phyllite is interpreted to come from Kobau Formation to the south, or an equivalent unit of lPz-Tr age. Church reports the presence of Vaseaux clasts but this could not be confirmed in the present study. Various highly strained rocks from the lPz-Tr formations make up the greatest percentage of clasts within the Skaha. At Green Lake this unit is faulted and fractured. The clasts, in a sand matrix, are pebble to boulder (1 m) size (Fig. 30). Bedding or stratification is not evident at this locality but from the east side of the Okanagan valley, looking west, large-scale bedding can be discerned, dipping 25° to the east The White Lake volcanic rocks, which include both andesitic and alkali- trachyandesitic compositions can be correlated with other Eocene volcanics in B.C., Washington, and Montana. Andesitic rocks have been well studied further north near Kamloops by Ewing (1981a) and alkaline volcanics are known from south central B.C. and north-central Washington as well as from Montana (Church, 1973). Eocene Dikes Tertiary dikes are the most conspicuous in the Oliver pluton. This is partly due to exposure and a marked color contrast but also because of truly greater frequency. The dikes are 1-2 m wide and can be followed for no more than 50-100 m along strike. They occur locally in swarms, particulary near Madden Lake. They invariably are fractured and commonly altered. Mineralogically these dikes are identical to the lower volcanic units within the Marron Formation. Rhombehedral zoned anorthoclase is common, as is zoned clinopyroxene (Fig. 31). These dikes generally are altered but a few unaltered ones were observed. These show in thin section delicate pyroxene zoning and unaltered or slightly altered olivine (Fig. 32). These dikes were apparently feeders to the basal flows of the Marron Formation. 56 O 1.3 -J CM + O 1.2 H CM CO + o CO o CO CM 1.1 0.99 H « 0.98 -| O • Jpgr • Jgr + 234 S-type l-type 0.4 0.5 0.6 "1 r~ 0.7 0.8 Rb/Sr 0.9 1.0 1.1 Figure 29: Molar Al203/(CaO + Na20 + K20) vs Rb/Sr for Jpgr and Jgr samples. 57 Figure 30: Photograph of fractured outcrop of Skaha Formation, west of Green Lake. Figure 31: Photomicrographs of Eocene rhomb porphyry dike. 58 The number of dikes found in the pgn and lgn units is low considering their proximity to the White Lake Basin. A metamorphosed and deformed dike bearing rhomb-shaped anorthoclase phenocrysts in the pgn and lgn just north of Covert Farms (Plate 1) has for many years been suspected to be an equivalent to the basal rhomb porphyry of the Marron (Ross, 1974). This dike cuts the compositional layering and foliation in the pgn and lgn at a very low angle and is itself strongly foliated and lineated (Fig. 33). Metamorphism is expressed as garnet and biotite growth in pull-aparts of anorthoclase and clinopyroxene, as well as in the matrix (Fig. 34). Clinopyroxene appears to be reacting to form hornblende; the matrix is a recrystallized mosaic of quartz, feldspar, biotite and chlorite. A U-Pb date on zircon from this sill gives a concordant date of 51 Ma (this study). Ross (1974) has reported several other dikes/sills of similar composition and texture within the pgn and lgn units. The number of dikes or sills within the metamorphic rocks is probably not anomalously low but many have been overlooked because the metamorphism and deformation has rendered them almost indistinguishable from the pgn, except where well exposed. Only undeformed dikes are rare in the metamorphic rocks. Figure 33: Photograph of foliated and lineated rhomb porphyry from within the pgn unit, north of Covert Farms area. Figure 34: Photomicrographs of metamorphosed and deformed rhomb porphyry' showing garnet and biotite growth in pullaparts of pyroxene (top) and feldspar (bottom). IV. GEOCHR ONOMFXR Y In the Shuswap Metamorphic Complex of southern B.C. an extensive area of largely pre-Eocene plutonic and metamorphic rocks yields K-Ar dates of 45-55 Ma. Many authors have observed and discussed this regionally extensive pattern of reset dates (Armstrong, 1974, 1982, 1983, 1985; Ross, 1974; Medford, 1975; Miller and Engels, 1975; Fox et al., 1977; Mathews, 1981, 1983; Parrish, 1979; Okulitch, 1984; Price, 1985; Price, et al., 1981; Archibald et al., 1984). The explanations include high heat flow and tectonic unroofing. One purpose of the present study was to determine the geologic nature (abrupt or transitional) of the western boundary of this reset terrane. Another was to use the U-Pb method to obtain original ages for pre-, syn-, and post-kinematic granitic rocks to ascertain the time(s) of deformation within the metamorphic complex. Geochronometry - Previous Work Geochronometric studies in the Okanagan region began with reconnaisance K-Ar work on Cenozoic volcanic rocks (Mathews, 1964). Since that time both K-Ar and Rb-Sr studies have been done for a number of theses and research projects. This section summarizes the results of those studies (Fig. 35; Table 6). The early K-Ar work done by Mathews (1964), Baadsgard et al. (1961) and White et al. (1968) established that volcanic rocks equivalent to those in White Lake Basin are Eocene, about 50 Ma old, and that intrusive rocks west of the Okanagan Valley are Mesozoic. Geochronology of the White Lake Basin was reported by Church (1970, 1973, and 1980d), and is summarized in Figure 36. Church (1975, and 1979a), Ewing (1981a, and 1981b) and Mathews (1981) have documented other Eocene volcanic 61 62 119 30' KNA-1004 KNA-1315 KNA-1348 3-20 JR-1 3-10 3-22 Inkaneep *1 80-55 Inkaneep +2 ^Anarchist phyllite| 78-84 78-85 SCALE Figure 35: Location map of previous K-Ar analyses. 63 Table 6 - Previous K-Ar Data Data from 49°-49°50'; 119°10'-120° Sample // Rock Type Mineral Date Ma* Latitude Longitude G.S.C. analyses (Wanless et al., 1979; Stevens et al ., 1982) 76-1 gneiss Hb 48.4 49°39'50M 119°36'10" 78-82 gneiss Bi 47.8 49°17.5' 119°30' 78-83 gneiss Ms 45.5 1! II 78-84 gneiss Bi 45.6 49°00'40" 119°24'15" 78-85 gneiss Hb 63.5 it II 80-54 gneiss Hb 48.8 49°39'50" 119°36'10" 80-55 gneiss Ms 59.4 49°09'45" 119°30,15" Analyses done for B.C.M.E. M.P.R. by U.B.C.; except * done by Geochron Labs (Church, 1970, 1979, 1980, 1982; Church et al., 1983). *Kitley trachyte Bi 52.9 49°20.6' 119°44.3' BNC-78-1 breccia Bi 52.5 49°18.5 119°37.5' KNA-1004 dacite WR 44.2 49°54.75' 119°39.5' BNC-78-2 porphyry Bi 52.4 49°28.52' 119°38.83' BNC-70-5 tephrite WR 48.4 49°18.75' 119°37' KNA-1315 dacite(?) Bi 52.9 49°49.65' 119°44.4' KNA-1348 rhyolite Mica 47.7 49°48.45' 119°43.40' SUM-1006 dacite WR 47.9 4 9°35' 119°40' OK-12 trachyte Bi 52.7 49°33' 119°52' LYN-001 syenite Bi 53.0 49°23' 119°20.4' Analyses from Medford, 1975. 1-50 dike WR 48.2 49°36.7' 119°34.6' 1-148 gneiss Hb 49.3 49°43.9' 119°31.3' 1-150 gneiss Hb 50.7 49°44.5' 119°31.0' 1-160 dike WR 49.8 49°39.2' 119°33.8* 1-178 gneiss Hb 51.8 49°42.6' 119°36.0' 3-3 diorite Bi 188 49°25.2' 119°47.2' 3-7 Kruger syenite Hb 173 49°03.5' 119°38.5' 3-10 paragneiss Hb 61.0 49°16.5' 119°31.2' 3-13 gneiss Hb 53.3 49°26.6' 119 34.5' 3-18 diorite Bi 168 49°36.6* 119°47.8' 3-20 grd. Bi 135 49°42.5' 119°48.8' 3-21 gneiss Bi 52.7 49°42.8' 119°16.5' 3-22 grd. Bi 52.7 49°15' 119°10.5' cont inued *A11 dates corrected to decay constants recommended by Steiger and Jager (1977). 64 Table 6 (con't) Analyses from Read and Okulitch, 1977. HP-1 dike Hb 153 49°18*31" 119°47'39" HP-2 dike Hb 172 49°18'09" 119°47'48" Olalla Gd . grd. Bi 155 49°18'43" 119048'34" Analyses from Ross, 1974. JR-1 rhomb por. WR 42.4 49°16.7' 119°29.0' JR-1 rhomb por. Bi 45.3 rl It JR-1 rhomb por. Hb 48.4 it It JR-2A Marron Fm. WR 42.2 49°18.0' 119°36.6' JR-1 A Marron Fm. WR 44.3 49°17.7' 119°35.2' M-15 pegmatite Ms 48.9 49°15.9' 119°32.8' Analyses from White et al. , 1968, and Sinclair et al., 1984. W-65-1 syenite Px-Hb 154 49°3.2' 119°41.7' W-65-2 grd. Bi 113 49°12' 119°38.2' W-65-3 granite Bi 120 49°12' 119°35.9' W-65-4 granite Bi 84 49°12.2' 119°35.4' W-65-5 granite Bi 104 49°12.1' 119°34.85' W-65-6 granite Ms 141 49° 1.1.4' 119°33.3' W-65-7 alterat ion Ser 138 49°11.8* 119°33.5' W-66-2 dike Bi 53.8 49°11.8' 119°33.6' W-66-5 granite Ms 146 49°11.5' 119°35.5' W-66-7 granite Bi 101 49°10' 119°35' W-67-1 alteration Ser 115 49°13.0' 119°35.9' Unpublished analyses from U.B.C. (1-3, collected by Mathews and Armstrong; 4 collected by Mathews; 5 and 6 collected by Soregaroli and Christopher). Inkaneep #1 granite Inkaneep #1 " Inkaneep #2 gneiss Anar. Mtn. S74-6-12.3 S74-7-3.1 phyllite qtz. monzo. grd. Bi Ms Bi WR Hb Bi 87 146 56.4 53.6 171 112 49 10'35" 49 09'50" 49°0r45" 49°06' 49°01' 119 29'30" 119 29'50" 119°2r20" 119°48' 119°55' K-Ar reported by: Okulitch et al., 1977: Olalla syenite Hb 184 49°16.5* 119°50' Fox et al., 1975 and 1977: Osoyoos #2 gneiss L-704 grd. south of 49°: L-618 grd. L-618 grd. L-301 alkalic L-301 border Bi Hb Hb Bi Hb Bi 50. 118. 181 73 175 72 49 01.4' 49°3.0* 119 22.5* 119°44.2' Similkameen batholith 65 basins and erosion remnants, north and. east of the southern Okanagan Valley. Engels et al. (1976) dated equivalent rocks south of 49° as Eocene as well. K-Ar studies by White et al. (1968), Roddick et al. (1972), Medford (1975), and Fox et al., (1976) dated the extensive granitic rocks west of the Okanagan Valley as Jurassic and mid-Cretaceous. This duality of dates (Fig. 37) is in contrast to unimodal Eocene K-Ar and fission track dates for dikes, pegmatites and gneissic granites (Ross, 1974; Medford, 1975) east of Okanagan Valley, from within the Okanagan Metamorphic and Plutonic Complex. Several Geological Survey of Canada K-Ar analyses (Table 6) on gneisses from east of both Osoyoos and Vaseaux Lake, also show this pervasive Eocene event (Wanless et al., 1979; Stevens et al., 1982). These dates on metamorphosed plutonic rocks have been interpreted to be thermal reset ages, and not the intrusive age. Published Rb-Sr data of Peto and Armstrong (1976) and Medford et al. (1983) documented Jurassic (and possible Paleozoic) intrusives to the west of Okanagan Valley with 87Sr/"Sr initial ratios below 0.705. Armstrong and Petb (1981) as well as Medford et al. (1983) demonstrated the presence of both Eocene (Shingle Creek, Trout Creek, and Siwash Creek porphyries) and Paleocene (Whiteman Creek stock) high level intrusives west of Okanagan Lake. A wealth of unpublished Rb-Sr data (Table 7) exists for the southern Okanagan, and by far the majority of this data is on orthogneiss, paragneiss and schist from the Okanagan Metamorphic and Plutonic Complex. Much of this work was done by Ryan (Ph.D. thesis, 1973) at U.B.C. and in recent years R.L. Armstrong has supplemented this. The results from this ongoing study are varied. Armstrong (unpublished) has obtained a 157+8 Ma whole rock date on the Oliver pluton, on the west side of the Okanagan Valley. In addition three variably deformed intrusive bodies, mapped by Ryan (1973) northeast of Osoyoos from within the Okanagan Metamorphic and Plutonic Complex, yield Jurassic isochrons with large errors (Fig. 38). 66 Skaha Formation fanglomerate, slide breccias White Lake Formation sediments, pyroclastic rocks Marama Formation rhyolite, rhyodacite Marron Formation andesite, trachyandesite basaltic andesite, anorthoclase, augite porphyry flows Springbrook Formation conglomerate upper lower upper mid-lower Park Rill Member Nimpit Lake Member Kearns Cr Member Kitley Lake Member Yellow Lake Member K-Ar Date (Ma) 48.4 52.5 47.9 52.7 52.9 52.9 Figure 36: K-Ar chronology for White Lake Basin. 67 K-Ar dates from the Okanagan Metamorphic and Plutonic Complex Data from LAT 49°- 49°50' LONG 119° 10' - 120° K-Ar dates from west of the Okanagan Valley Volcanic Rocks Plutonic Rocks 20 80 100 J~l n 120 140 160 180 I 200Ma Figure 37: Histograms of K-Ar dates from plutonic rocks and volcanic rocks west of the Okanagan Valley, and metamorphic rocks east of the Okanagan Valley. 68 Osoyoos Area Plutons A UNIT VII A UNIT VI Figure 38: Rb-Sr diagram for four gneissic granitic units of Ryan (1973), east of Osoyoos. 69 Leucogneiss 0.707 -\ . WHOLE ROCK A FELDSPARS FROM L2 0.704H 0.2 0.4 87 86 Rb Sr 0.6 0.8 1.0 Figure 39: Rb-Sr diagram for leucogneiss. 70 DP300, rhomb porphyry Ol-Sy, Olalla Syenite DP246, Similkameen batholith SCALE Figure 40: U-Pb sample locality map for both previous work and the present study. 71 One of these (granite of Anarchist Mtn.) was collected for zircons in the present study. The other orthogneiss (Unit V) from Ryan's Ph.D. area did not yield an interpretable whole rock isochron. Mineral-whole rock isochrons from these same orthogneisses yield mostly Paleocene-Eocene dates. The leucogneiss body north of Covert Farms, within the present study area (and sampled for zircons), gives a Jurassic Rb-Sr errorchron (Fig. 39; Armstrong, unpublished). Rb-Sr data for paragneiss from the Okanagan Metamorphic and Plutonic Complex do not produce whole rock isochrons, but all the mineral-whole rock pairs yield Paleocene-Eocene dates. Some paragneiss samples have highly radiogenic strontium, supporting the interpretation that the protolith is Precambrian in age (Ryan, 1973; and Armstrong, unpublished). Previous U-Pb work (Table 8; Fig. 40) in the Okanagan has been done on the Oliver pluton (152+3; Armstrong and Ryan, unpublished), and on a gneissic granite from Medford's Ph.D. thesis (1973) area south of Kelowna (3 fractions concordant at 68 ±2 Ma; analaysis by Geological Survey of Canada). Fox et al. (1976) reported a late Cretaceous U-Pb date from the Okanogan Dome in north-central Washington, 50 km south of the present study area. Table 7 Previous Rb-Sr Analytical Data*  Sample Description Latitude Longitude  Sample Suite: Paragneiss, Covert Farms (Armstrong) SH L paragneiss 49°15.13' 119°32.92' SH M amphibolite 49°15.14' 119°33.16' SH R paragneiss 49°15.0' 119°33.0' SH S paragneiss 49°15.14' 119°33.25' SH U hb granulite 49°15.20' 119°33.27' SH W paragneiss 49°15.14' 119°33.16' SH K paragneiss 49 15.11' 119°32.73' SH C hb diorite 49°15.19' 119°32.27' SH D hb diorite 49°15.20' 119°32.25' SH E hb diorite 49°15.25' 119°32.22' SH A paragneiss 49°15.08' 119°32.33' SH T paragneiss 49°15.17' 119°33.25' Sample Suite: Paragneiss, Covert Farms (Ryan, 1973) S9 schist, Vaseaux 49°15'10" 119°33,25" Formation SIO SmlO muscovite " " Sample Suite: Paragneiss, Vaseaux Lake roadcut (Armstrong) VL 1 gneiss 49°16.7' 119°31.0' VL 2 gneiss " " VL 3 gneissVL 5 gneiss " " VL 6 gneissVL 7 gneiss " " 310 150 1.400 0.7209 211 22.8 0.312 0.7066 106 84.3 3.69 0.7273 292 78.7 0.78 0.7228 704 99.4 0.409 0.7073 193 64.4 0.968 0.7185 328 51.8 0.457 0.7201 913 71.3 0.226 0.7073 763 83.2 0.315 0.7079 647 99.9 0.447 0.7083 476 108 0.659 0.7218 393 109 0.805 0.7145 166 116 2.039 0.7673 117 149 3.683 0.7467 38.9 310 23.21 0.7640 608 43.7 0.208 0.7045 667 41.9 0.182 0.7051 1021 47.5 0.135 0.7055 683 57.7 0.245 0.7062 534 61.3 0.332 0.7065 793 20.0 0.073 0.7062 Sample // Description Previous Rb-Sr Analytical Data  Lat ltude Longitude  ppm Sr Sample Suite: Plutonic Rocks; Vaseaux Lake area (Ryan, 1973) Gl Gbl P2 Pm2 Pml2 Synkinematic Qtz-monzonlte sill biotite pegmat ite muscovite muscovite 49 18'0' 49 04' 53' 49°515' 119 29*40" 119 27*57" 119 28.5 * 777 .3 262.2 519.6 139.3 17.98 Sample Suite: Leucogneiss, Cover Farms (Armstrong) SHI garnet leuco gneiss SH3 " SH5 " SH6 " SHF SHG " SHN " SHO " SHP mylonite SHQ mylonite Leucol granod. gneiss Leuco2 it Leuco2--I heavy feldspar Leuco2--IV light feldspar Leuco2--M muscovite Leuco2--B biotite + chlorite 49 15.45' 49 15.43' 49°15. 49°15. 49°15. 49°15. 49°15, 49°15. 49°15. 49°15. 49°15. 49°15. .41' .40' .40' .40' .43' .44' ,60' .60' .40' .42' 119 33.35' 119 33.35' 119°33.40' 119°33.40* 119°32.28' 119°32.29' 119°33.41' 119°33.42' 119°33.48' 119°33.48' 119°32.36' 119°33.35' 609 647 519 521 693 594 662 657 1275 680 623 616 320 790 43.0 104 Sample Suite: Rhomb Porphyry, Covert Farms (Armstrong) Rhomb P anorthoclase augen 49°14.97' 119°33.00' gneiss 3402 28.9 0.1075 0.7044 256. 2 2.825 0.7058 34. 0 0.1892 0.7082 232. 0 4.819 0.7106 462. 2 74.7 0.7511 27. 5 0.130 0.7048 55. 7 0.249 0.7055 78. 1 0.436 0.7055 83. 3 0.463 0.7056 31. 3 0.131 0.70515 47. 8 0.233 0.7048 27. 6 0.121 0.7046 79. 8 0.351 0.70585 38. 1 0.086 0.70475 66. 1 0.281 0.7051 23. 2 0.107 0.7042 39. 0 0.183 0.7053 5. 2 0.047 0.7050 167 0.611 0.7057 124 8.33 0.7120 267 7.41 0.7098 151 0.129 0.7061 Previous Rb-Sr Analytical Data Sample // Description Latitude Longitude  Sample Suite: Anarchist Pelite (Unit III of Ryan, 1973) 51 pelite 49°04'59" 119°28'07" Sbl biotite " Sml muscovite " " 52 pelite 49°04'57" 119°28'00" Sb2 biotite " " 55 pelite 49°04'10" 119°25'17" Sb5 biotite S4 pelite 49°05'12" 119°25'42" Sb4 biotite Sm4 muscovite " " 56 pelite 49O02'15" 119°22'55" 57 pelite 49°or45" 119°20'53" Sb7 biotite 58 pelite 49°or40" 119°20'40" Sample Suite: Anarchist Amphibolite (Unit I of Ryan, 1973) Al greenschist facies 49°0r00" 119°20'20" A2 amphibolite facies 49°03'15" 119°25'13" A3 " 49°05,17" 119°28,26M A4  49°06'35" 119°30158" „, 87„ ,86„ 87 ,86 ppm Sr ppm Rb Rr/ Sr Sr/ Sr 109.4 145.6 3.354 0.7156 8.05 568.1 207.1 0.8577 63.0 293.0 13.45 0.7206 270.0 122.0 1.308 0.7139 21.14 416.2 57.15 0.7413 182.1 54.2 0.861 0.7115 13.74 223.0 47.08 0.7287 86.7 126.9 4.356 0.7250 8.70 550.0 184.4 0.7937 41.38 247.0 17.31 0.7335 273.1 142.3 1.511 0.7278 164.3 80.4 1.416 0.7131 66.34 233.8 10.21 0.7177 122.4 89.1 2.107 0.7136 165 4.9 0.086 0.7058 181 7.7 0.123 0.7060 309 41.0 0.384 0.7088 166 22.0 0.384 0.7071 Sample // De script Ion Previous Rb-Sr Analytical Data  Latitude Longitude  „L 87^ .86„ 87„ ,86„ ppm Sr ppm Rb Rb/ Sr Sr/ Sr Sample Suite: gneiss of Osoyoos (Unit V of Ryan, 1973; *analysed by Armstrong) bi granod gneiss Fl F2 F3 F4 F5 F6 F7 F8 F9 *BDRgn *BDRap II II separate body ti gneiss def. aplite 49 00'40" 49°0r53" 49°0r33" 49° 04'37" 49°04'34" 49° 04'50" 49°05'45" 49°08'40" 49°09'20" 49°0.65* 49°0.65' 119 20*43" 119°23'00" 119°24,50" 119°25'15" 119°27'20" 119°29'20" 119°3r04" 119°26'50" 119°26,55" 119°24.0' 119°24.0' Sample Suite: quartz monzonite (Unit VI of Ryan, 1973) qtz. monzonite El E2 Eb2 Em2 E3 E4 ,o, 49 08'15" 49°02'44" 119 30'40' 119°23'53' biotite muscovite separate body alaskite 49 04'55" 49°02'48" 119 28'40* 119°20'38' Sample Suite: quartz monzonite (Unit VII of Ryan, 1973) DI Dml D2 Dm2 D3 D4 D5 qtz. monzonite muscovite qtz. monzonite muscovite qtz. monzonite 4 9° 08'20" 119°26,35* 49 08'15" 119 26'25" 49 08'10" 49°07'50" 49°07'40" 119°26'17" 119°2r35" 119°21'30" 487.3 63.2 0.376 0.7074 459.8 74.4 0.468 0.7054 549.3 56.3 0.296 0.7050 536.2 69.1 0.373 0.7066 458.9 63.7 0.401 0.7045 442.8 71.1 0.487 0.7054 455.3 74.6 0.474 0.7048 459.7 76.9 0.484 0.7070 616.5 54.7 0.257 0.7045 515 68.4 0.384 0.7045 119 239.0 5.82 0.7158 637.8 103.8 0.471 0.7081 310.1 281.5 2.63 0.7128 192.0 840.0 12.69 0.7220 223.0 658.3 8.55 0.7182 740.2 79.0 0.309 0.7088 5.72 344.1 181.8 1.166 101.0 175.1 5.022 0.7186 36.38 615.8 49.23 0.7622 99.77 180.5 5.238 0.7168 42.09 596.6 41.2 0.7562 133.8 160.6 3.474 0.7134 257.7 92.72 1.041 0.7083 243.5 100.0 1.188 0.7079 Ul Sample // Description Previous Rb-Sr Analytical Data  Latitude Longitude  ppm Sr ppm Rb 87Rb/86Sr 87Sr/86Sr Sample Suite: late quartz monzonite (Unit VIII of Ryan, 1973) Cl Cbl C2 C3 qtz. monzonite biotite altered, saussur-itized, fractured qtz. monzonite 49 11'35" 49 11 '02' 49 12'10" Sample Suite: Oliver pluton (Armstrong) 01 granite 490H'29" 01-m muscovite " W-65-7 muscovite from 49°ir45" Gypo mine 119 28'00' 119 27'30" 119 26'30" 119 33'07" 119 33* 31' Sample Suite: Olalla area plutons (Armstrong) „o. „ . .. .. n HP2 hb andesite HPl porph hb andesite Gd-Olalla granodiorite Horn Silver hb monzonite 49 18*09" 49°18'31" 49°18'43" 49°03.4' 119 47*48" 119°47'39" 119°48'34" 119°41.5' 194 1. 0 449.4 456.0 1003.0 10.6 4.1 12.9 555 510 533 1638 51.1 804.0 151.7 66.4 0.142 5.181 0.963 0.192 314 87.56 1199 1057.0 1813 448.0 29.3 29.5 125 142 0.158 0.167 0.679 0.251 0.7070 0.7169 0.7092 0.7119 0.9014 3.253 1.744 0.7071 0.7058 0.7059 0.7045 —i Sample // Description Rb-Sr Analytical Data  from this study Lat itude Longitude Sample Suite: Oliver pluton (Jpgr) DP275.1 DP275.2 DP245.2 hb-bi granod. 49 12.11 119 31.2 49 11.6' 119 34.0' ppm Sr ppm Rb 87Rb/86Sr 87Sr/86Sr 395 154 1.127 0.7094 365 163 1.293 0.7098 462 204 1.276 0.7091 Sample Suite: U-Pb samples DP156 plag« gneiss gneissic sill of Vaseaux Lake DP95 gar-bi granite granite of Anarchist Mtn. 49°18.0' 49°03.5' 119 31.5' 119 21.1' 409 350 63 0.446 151 1.246 0.704 6 6 0.7106 DP179 hb granod. gneiss 49 24.5' gneiss of Skaha Lake DP246 hb granodiorite 49°02.0' Similkameen batholith 119 34.0' 119 41.5' 1004 640 44 0.129 125 0.564 0.7095 0.7056 DP90 bi gneiss leucogneiss 49 18.5' 119 30.2' 772 51 0.190 0.7061 (See Appendix C for procedures and error estimates). —i -J 78 Geochronometry - This Study Detailed mapping done west of the Okanagan Valley by Bostock (1940, 1941a, 1941b) and east of the Okanagan Valley by Ryan (1973), and Christie (1973), along with the regional map of Little (1961) provided a basis for the U-Pb study undertaken (Fig. 40). Two samples from west of the Okanagan Valley fault and six samples from the Okanagan Metamorphic and Plutonic Complex east of the fault were dated using analytical procedures given in Appendix B. A summary of analytical data and dates is given in Table 9, with complete analytical data and rock descriptions in Appendix B. All U-Pb errors stated are at a 2 a level (95% confidence limit). West of the Okanagan Valley Similkameen batholith (DP246) The Similkameen batholith is a mesozonal hornblende granodiorite (Fig. 2). It crosscuts structures in the lPz-Tr unit and is itself undeformed (Bostock, 1941a; Fox et al, 1977). Fox et al. (1977) published K-Ar dates of 171 and 177 Ma for hornblendes of the Similkameen batholith. To confirm this a sample for U-Pb analysis was collected from the northern border of this batholith, southeast of Keremeos (Fig. 40). Two zircon fractions (Table 9) were analysed (Fig. 41). The coarse nonmagnetic fraction is concordant at 170 ± 2 . Ma, and the fine magnetic fraction is slightly discordant at 169±2 Ma. The zircons appear to be magmatic, and are colorless to slightly pink, euhedral with occasional opaque inclusions. The discordance, which can be attributed to minor low temperature lead loss, is not considered significant because at the 95% confidence level the ages for the two fractions overlap. The U-Pb date of 170+2 Ma confirms the K-Ar date and represents the crystallization age of the 79 Table 8 Previous U-Pb Geochronometry Sample # Fraction Dates Ma 206Pb/238u 207Pb/235u 207Pb/2°6Pb Source CAa76-3 foliated hb granod. very coarse coarse nonmag. 68.3 68.5 73.4 67.8 68.0 72.0 G.S.C. Wanless and Loveridge (unpublished; Okulitch, pers. comm.) fine magnetic 67.2 67.1 64.4 0-176E 87.3 100.0 Fox et al.,1976 Oliver pluton 151.9 +/- 2 152.1 +/- 3 156.2 +/- 15 Ryan and Armstrong, unpublished. Table 9 U-Pb isotopic data Isotopic abundance^ Measured Dates (Ma) +/- 2o error2,3 size <u) weight (mg) U (ppm) rad. Pb (ppm) Pb 206 = 100 206Pb 206Pb 207Pb 2°7Pb 207 208 204 204pb 238u 235u 206Pb DP156; gneissic sill of Vaseaux Lake 45-75 M 37.4 1474 20. 5 4. 8808 3 .0853 0. 0002 38,426 95. 7±1 .0 97. 3+1 .0 137. 3±8.2 45-75 NM 0.3 3594 49. 4 4. 8454 1 .7174 0. 0085 2,005 95. 8±1 .2 94. 4±1 .8 59. 7±38 75-150 NM 38.5 1272 17. 4 4. 8855 1 .7445 0. 0006 20,105 95. 6+1 .0 97. 3+1 .0 136. 9±5.8 >150 NM 3.9 1620 22. 6 4. 9296 1 .8944 0. 0028 17,459 97. 2 + 1 .0 99. 0+1 .2 142. 3±12.: Oso; gneiss of Osoyoos 45-75 M 37.6 4 64 14. 2 5. 07 94 7 .6381 0. 0016 19,421 200. 2+2 .2 201. 8±2 .0 220. 7±8.4 45-75 NM 0.6 891 27. 8 5. 2043 8 .6363 0. 0105 5,384 201. 7+2 .2 203. 0±2 .8 218. 2±22. 75-150 NM 27.5 476 14. 5 5. 0651 7 .1205 0. 0005 19,468 200. 5±2 .2 202. 2±2 .0 221. 9±6.0 DP95; granite of Anarchist Mtn. 45-75 M 31.9 7852 185 4. 9749 4 .2912 0. 0015 36,116 159. 7±1 .8 160. 6±1 .6 172. 9+5.8 75-150 NM 39.0 3983 94. 6 4. 9660 4 .2654 0. 0003 34,856 160. 9±1 .8 162. 0±1 .6 176. 9±4.8 DP246; Similkameen batholith 45-75 M 36.4 633 17. 3 5. 4754 13 .7505 0. 0338 2,555 168. 6±1 .8 169. 7±1 .8 185. 3+13. 75-150 NM 35.2 488 13. 6 5. 9722 13 .4675 0.0700 1,000 169. 9±1 .8 169. 8±2 .0 168. 6±17.l DP90; leucogneiss 45-75 M 31.6 1111 18. 5 5. 3178 4.4765 0. 0032 11,877 112. 9±1 .2 122. 6+1 .2 316. 3±6.4 45-75 M 14.9 1132 18. 8 5. 4198 4 .3973 0. 0017 21,819 m. 6+1 .? ]±] 368. 6+6.0 45-75 NM 16.4 1080 18. 33 5. 3411 4 .5535 0. 0032 12,864 114. 7±l .2 125. 1±1 .2 326. 1±5.8 75-150 NM 16.4 954 17. 4 5. 5007 5 .0930 0. 0032 11,107 122. 2 + 1 .4 136. 5+1 .4 393. 1+5.6 >150 NM 9.5 845 15. 5 5. 1965 1 .6540 0. 0091 6,774 120. 7±1 .4 125. 8±1 .2 223.8±7.0 U-Pb Isotopic data Isotopic abundance Pb 206 = 100 Measured Dates (Ma) +/- 2o error 2,3 206 size (u) weight (mg) U rad. Pb (ppm) (ppm) Pb 206 Pb 207. Pb 207 208 204 204 Pb 238. 235, 207 Pb 206. Pb DP179; gneiss of Skaha Lake 45-75 M 34.2 308 4.7 4.9393 10.0325 0.0064 5,885 98.7+1.0 99.7±1.2 121.6+13.2 75-150 NM 33.0 381 6.1 4.9574 9.4778 0.0064 4,233 104.3+1.2 105.4±1.2 130.1+16.0 DP300; rhomb porhyry 45-75 75-150 NM 1.6 1.4 1100 1923 9.5 5.8566 18.0336 0.0658 799 51.5+0.6 53.4±0.8 142.2+25 16.1 5.6498 15.7190 0.0661 617 50.9+0.6 50.6+1.8 36.7+40 Olalla Syenite 45-75 NM 6.7 1341 51.2 5.1738 46.3786 0.0060 9,279 185.612.0 189.2±1.8 234.6±6.2 ,c c/ 206„, ,204^, 15.54; Pb/ Pb: 17.75. ^rrected for blank with composition = 208Pb/204Pb: 37.00; 207Pb/204Pb: 2 207 206 Isotopic composition of common Pb is based on Pb/ Pb age and is derived from the growth curve of Stacey and Kramers (1975). 238 = 0. 155125 x 10 Vyr; X 235 -9 ?T8 0.98485 x 10 /yr; U/ U = 137.88. M = Magnetic fraction, (magnetic at 1.5A and 0.5 side tilt on Franz); NM = Nonmagnetic. 82 intrusive. Olalla Syenite (Ql- Sy) A sample of the Olalla Syenite Complex (Sturdevant, 1963) was collected by R.L. Armstrong, and dated in this study (Fig. 41). More work is required, but one fraction (fine) from this rock is slightly discordant at 185-189 Ma. This supports a K-Ar hornblende date on this body of 184 Ma from Queens University reported by Okulitch et al. (1977). Samples from the Okanagan Metamorphic and Plutonic Complex Two samples were collected from B. Ryan's Ph.D. thesis area (his Units V and VIII). One (the gneiss of Osoyoos, unit V) is exposed at the lookout above Osoyoos on Highway 3. Ryan interpreted it to be possibly syn-Fi, but definitely pre-F2, and the oldest granitic unit in the succession. gneiss of Osoyoos (Oso) Three zircon fractions (Table 9) were analysed. All three are very slightly discordant at 201.5 Ma (Table 9 and Fig. 41.) the 207Pb/206Pb dates are 219±20Ma. The zircons appear to be magmatic, and are transparent, pink, generally euhedral with common cloudy cores. The intrusive age is interpreted to be 201.5 ±2.2 Ma (Early Jurassic). The discordance, though slight, may be ascribed to inheritance, or to slight lead loss from a latest Triassic pluton. A geologic maximum age limit for this pluton is mid-Permian to early Triassic, the age of the Anarchist Group which is intruded by the body. A minimum age is 150 Ma, provided by a Rb-Sr whole rock date on an aplite from the Osoyoos lookout (Table 7; Armstrong, unpublished). Both K-Ar and Rb-Sr mineral dates from this gneiss are Eocene. 83 granite of Anarchist Mtn, (PP95) The other unit from Ryan's thesis area is a slightly foliated garnet-biotite granite (Unit VIII of Ryan, 1973). This unit is interpreted by Ryan to have been emplaced late in the deformation (post F2 and pre- or syn-F3). Two fractions of zircon (Table 9) were analysed and plot very near (within two sigma error) concordia at 160.2±1.8 Ma and 161.4±1.8 Ma. The 207Pb/206Pb ages are 173 Ma and 177 Ma, and probably represent an upper age limit (Fig. 41). The zircons, interpreted to be magmatic, are generally euhedral but highly fractured, and cloudy. The discordance, though very slight, is probably attributable to inheritance, particularly with the hint of S-type character of the intrusive. The interpretation is that 160.512 Ma represents a minimum crystallization age. Three samples were collected from Christie's thesis area at Vaseaux Lake: 1) A crosscutting, but foliated, intrusive sill (gneissic sill of Vaseaux Lake); 2) The leucogneiss body north of Covert Farms; 3) the rhomb porphyry sill at Covert Farms. The latter two are also within the area mapped for this study. 1) gneissic sill of Vaseaux Lake (PP156^ This gneissic sill (Fig. 42) was collected 0.5 km east of Vaseaux Lake where it crosscuts the paragneiss but is itself foliated and lineated. Four zircon fractions (Table 9) from this rock plot between 95.5 and 97.21 1.2 (206Pb/238U ages). The 207Pb/206Pb dates for the fine magnetic, coarse nonmagnetic, and very coarse fractions are all approximately 140110 Ma. The fine nonmagnetic handpicked fraction (0.3 mg) is essentially concordant, although slightly above concordia, at 95.811.2 Ma (206Pb/238U age; Fig. 43). The zircons are transparent, slightly pink, euhedral, with no visible cores; they are interpreted to be magmatic. The minimal spread of these analyses, with large variation in uranium and lead content, suggests that lead loss is probably not significant (not > 5 percent) and that the intrusive age for this gneissic sill is Figure 41: Enlargement of 150-225 Ma section of U-Pb concordia diagram. Figure 44: U-Pb sample locality for gneiss of Skaha Lake, note deformed mafic dikes(?). 86 probably on the Early-Late Cretaceous boundary. 2) leucogneiss (PP9Q) The leucogneiss north of Covert Farms has not yielded an interpretable zircon array after analysing five fractions. The zircons are clear, euhedral, with common cloudy cores and apparent overgrowths. The points are all discordant and scatter between 112 Ma and 135 Ma (Fig. 43). Unlike most discordant zircons, these do not lie along a single line but instead plot in a cluster. A probable interpretation (there are an infinite number of interpretations) is that the leucogneiss body was intruded in the Jurassic, based on the Rb-Sr errochron (Fig. 39; Armstrong, unpublished), and was subjected to later metamorphism. This would have to have occured in post-Aptian time based on the discordance pattern of the zircons. The problem is compounded by a small inherited component and possible later low temperature lead loss. 3) rhomb porphyry (DP3QQ) The rhomb porphyry body (as described in Chapter 3) was collected from the north edge of Covert Farms (Plate 1). At this locality the rhomb porphyry can be followed for 1 km as it cuts through the paragneiss and leucogneiss. It is deformed and metamorphosed. Two zircon fractions (both very small amounts) were analysed. The zircons are slightly to deeply pink colored, equant, and barrel shaped. They are interpreted to be magmatic. The fine zircon fraction from this rock plots very nearly concordant at 52 ± 1 Ma, a second (coarser) fraction is concordant at 51 ± 1 Ma (Fig. 43). The slightly discordant point probably indicates traces of xenocrystic zircon, and the concordant date of 51+1 Ma is interpreted to be the crystallization age. The deformed rhomb porphyry is therefore equivalent in age to the basal rhomb porphyry flows of the Marron Formation, as has long been inferred but never proven, and in accord with U-Pb ages of Coryell syenites dated by Parrish (pers. comm., 1985). oo 88 gneiss of Skaha Lake (PPP9) The other unit sampled east of the Okanagan Valley, but not in Ryan or Christie's thesis areas, is a large gneissic granodiorite mapped by Little (1961) as crosscutting the paragneiss but itself foliated and lineated. The outcrop sampled (Fig. 44) is on Skaha Lake, 5.5 km south of Penticton. Two zircon fractions were analysed, both are slightly discordant: the fine magnetic fraction discordant at 99.5±1.2 Ma (207Pb/J06Pb age = 122± 12 Ma), the coarse nonmagnetic discordant at 104.5+1.2 Ma (207Pb/206Pb age = 130+16 Ma) (Fig. 43). There are no cores visible in the zircons, which are clear, and generally euhedral. This is interpreted as a Cretaceous intrusive that was subsequently metamorphosed. The discordance could be due to lead loss, in which case the Cretaceous dates represent a minimum age for the intrusive. If lead loss was significant then this intrusive could be as old as Jurassic. The discordance of zircons from the leucogneiss north of Covert Farms (in addition to an inherited component), the gneissic sill of Vaseaux Lake, and the gneiss of Skaha Lake, is inferred to be due to metamorphism and deformation. During the metamorphic event the zircons either lost lead or overgrowths of new zircon developed (or both). The latter interpretation is favoured based on the nonmetamict character of the zircons and work done by Martinson (1972, and 1978) and Williams et al. (1984). Either interpretation is viable however, given the present data. The lead loss or zircon growth episode would have to be in post-middle Cenomanian time. 89 Summary of Geochronometry The K-Ai woik in the southern Okanagan demonstrates that the volcanic rocks of White Lake Basin, and equivalents, are Eocene and that the intrusive age for plutonic rocks west of the Okanagan Valley is generally Jurassic. The gneisses of the Okanagan Metamorphic and Plutonic Complex have had an Eocene thermal overprint however, and therefore their original ages are not obtainable by K-Ar techniques. The Rb-Sr work done in the Okanagan has documented Jurassic and Paleocene- Eocene intrusives to the west of the valley. In addition unpublished data of Armstrong and Ryan indicate Jurassic intrusives both east and west of the Southern Okanagan Valley. This data also shows that, like K-Ar, the Rb-Sr mineral dates on the Okanagan Metamorphic and Plutonic Complex are Paleocene and Eocene. The results of the U-Pb geochronometry reveal: -Early Jurassic or Late Triassic intrusive within the Okanagan Metamorphic and Plutonic Complex (gneiss of Osoyoos). -Middle to Late Jurassic intrusives both east (granite of Anarchist Mtn., deformed) and west (Oliver pluton, Similkameen batholith, and Olalla Syenite, all undeformed) of the Okanagan Valley. -Jurassic or Cretaceous intrusives (leucogneiss north of Covert Farms, gneiss of Skaha Lake, gneissic sill of Vaseaux Lake, all deformed) within the Okanagan Metamorphic and Plutonic Complex. -Eocene intrusive (rhomb porphyry, deformed) within the Okanagan Metamorphic and Plutonic Complex. 90 Discussion A plot of closure temperature versus age (cooling curve) has been constructed for the gneisses east of the Okanagan Valley using K-Ar, fission track, and Rb-Sr muscovite data (Medford, 1975; Armstrong, unpublished) (Fig. 45). Also plotted are zircon ages and closure temperatures from the rhomb porphyry, gneissic sill of Vaseaux Lake, and gneiss of Skaha Lake. Closure temperatures for K-Ar and fission track dates are from Harrison (1981) and Harrison and McDougall (1980, and 1982). (For an alternate assessment of the K-Ar closure temperature concept in amphiboles, see Deutsch and Steiger, 1985). For zircons, estimates of closure temperatures are from Parrish and Roddick (1985), and Mattinson (1978). Rb-Sr muscovite-whole rock closure temperatures are estimated at 550° ± 50° C (Wagner et al., 1977). A Rb-Sr muscovite-whole rock date of 58 Ma from the leucogneiss north of Covert Farms indicates that the gneisses were below approximately 600° C by this time. The K-Ar hornblende dates (with closure temperature of approximately 530° C) cluster with minimal spread around 51 Ma. Both the K-Ar biotite and fission track sphene dates have considerable spread, both in age and error; the fission track apatite is well constrained (closure temperature = 105° C) between 44 and 48 Ma. This data alone dictates that the gneisses of the Okanagan Metamorphic and Plutonic Complex cooled through 400° C in 3-10 Ma. Assuming a geothermal gradient it is possible to calculate the depth of the gneisses at 51 Ma, and at 45-48 Ma (Fig. 46), and thereby estimate uplift rates during that time interval. Using 50° C/km, the gneisses would have been uplifted from 11 km (at 51 Ma) to 2 km (at 45-48 Ma); this implies a 2-4 mm/yr uplift and erosion rate. Using 30°C/km, a more reasonable estimate (being the present-day Basin and Range geothermal gradient according to Eaton, 1982), the gneisses would have been uplifted from 18 km (at 51 Ma) to 3 km (at 45-48 Ma); this implies a 3-5 91 Closure Temperature vs Time Data from Lat 49°- 49°50' Long 119°10' - 120° T i i i I I 1 U-Pb Zircon T T -1 1 I II I II T TTTT ' n • •••• i ii 11111 X I 11 I Rb-Sr Muscovite I I T, | U. 1 ± K-Ar Hb TT T T F.T. Sph»n» K-Ar BI •~i5S-5- F.T. Apatite I I I I I I I I P-0 20 40 60 80 Time Ma Figure 45: K-Ar, fission track, and muscovite Rb-Sr mineral dates versus their respective blocking temperature for gneisses of the Okanagan Metamorphic and Plutonic Complex; sources: Ryan (1973), Medford (1975), and Armstrong (unpublished). Approximate Uplift Rates Geothermal Gradient Depth of Gneisses at 51 Ma Uplift Rate a) for 3Ma interval b) for 5Ma interval c) for 10Ma interval 50 C/km 11 km a) 3 mm/yr b) 1.8 mm/yr c) 0.9 mm/yr 30 C/km 18 km a) 5 mm/yr b) 3 mm/yr c) 1.5 mm/yr Figure 46: Uplift rates for the gneisses of the Okanagan Metamorphic and Plutonic Complex using assumed geothermal gradients. 93 mm/yr uplift and erosion rate. In contrast the granitic rocks west of the Okanagan Valley were well below the blocking temperature for hornblende and biotite by 100 Ma, indicating a depth of only 2 to 3 km. Recent work on uplift of the Himalaya reports rates not much higher than 1 mm/yr and generally much less (Zeitler, 1985). Bradbury and Nolen-Hoeksema, (1985) calculate uplift rates for the Lepontine Alps of between 1 and 2 mm/yr. Taken at face value the Okanagan data require either exceptional erosion rates (filling unknown basins), exceedingly high geothermal gradients, or a tectonic explanation. V. STRUCTURE The most important structural feature within the study area is a low-angle (10-20°) west-dipping fault (named the Okanagan Valley fault by DJ. Templeman-Kluit, 1984). In the upper plate of this fault the rocks were deformed in a brittle fashion whereas in the lower plate the rocks were deformed ducuiy, and show a complex overprint of metamorphic fabrics. This chapter will be divided into four parts 1) upper plate structure; 2) Okanagan Valley fault and related fault rocks; 3) lower plate structure; and 4) timing of deformation. Upper Plate The late Paleozoic to Triassic formations were isoclinally folded (Fig. 8) prior to the deposition of the Upper Triassic Nicola Group (Read and Okulitch, 1977). Within the study area this deformation predates the Oliver pluton which is itself unfoliated. Other than the results of this Triassic deformation the predominant structure seen in the upper plate rocks is brittle fracturing. Within the study area, this is best observed in the Oliver pluton, and to the north in the Eocene volcanic and sedimentary rocks of White Lake Basin. Fractures are. pervasively developed within the Oliver pluton (Fig. 47). In addition there are distinctive topographic lineaments which contain fault gouge but, in the absence of identifiable markers, any sense and amount of offset is uncertain. Tertiary dikes within the Oliver pluton commonly intrude a fracture system (trend N40E, dip 60-90NW; Fig. 48) and are themselves fractured. Fracturing and faulting in the Oliver pluton is more intense approaching the Okanagan Valley fault; in addition, fractures become predominantly low angle (Fig. 49). Ultimately this intense fracturing produces a monolithologic breccia (Fig. 47). A highly fractured 94 Figure 47: Photographs of fractured and brecciated Oliver pluton. 96 Figure 48: Stereonet of poles to fractures and Eocene dikes in upper plate of Okanagan Valley Fault. Triangles=dikes; dots=fractures. Figure 49: Photographs of low angle faults and fractures in Oliver pluton. 98 and faulted section has been documented by Church (1973) in the southeastern White Lake Basin. In addition to the pervasive northeast-trending northwest-dipping fracture and fault set there are less abundant but possibly large westnorthwest- trending, north-dipping faults in the upper plate. The largest one in the map area is in Orofino Creek and can be followed for several kilometers to the westnorthwest It separates the Oliver pluton from lPz-Tr rocks. Another north-dipping fault, just north of the map area, separates lPz-Tr from White Lake Basin volcanic rocks. These faults are not well understood, but are restricted to the upper plate. They have normal displacement, and may be partly responsible for the large megabreccias/landslide blocks of lPz-Tr and Oliver pluton in the Skaha Formation. Okanagan Valley Fault and Related Fault Rocks The Okanagan Valley fault can be traced from Green Lake where it enters the map area from the north, to southeast of Oliver, where it leaves the map area. It is exposed only locally east of Oliver and at Mahoney Lake, (Fig. 50) where the map pattern shows it to be low angle (10°-20°), and west dipping. The fault is, in these exposures, marked by underlying mylonitic pgn, orthogneiss, or ultramylonite (Fig. 51), which grades upward into microfaulted mylonite, brecciated mylonite and ultimately brecciated, chloritized, and silicified upper plate rocks (Fig. 52). This fault everywhere juxtaposes intensely fractured rocks against ductiley deformed rocks. The fault itself was presumably ductile at depth (represented by mylonitic pgn) and brittle at shallow levels (represented by abrupt truncation of the brecciated upper plate). The overprinting of contrasting strain types is seen in brecciated mylonite. In this interpretation the fault embraces a brittle-ductile transition, and now juxtaposes rocks from contrasting strain environments. ° Is 1 ^ Hi* H ** 1 CP c> IP o to a 0 100 101 Figure 51: Photomicrographs of mylonitic pgn at Mahoney Lake. 102 Sense of shear indicators (Simpson and Schmid, 1983) (Fig. 53) from mylonitic rocks at Mahoney Lake are not everywhere unambiguous (Ross, 1973, and 1981) but are interpreted to be consistent with westward movement of the upper plate. This same sense of shear can be seen in asymmetric fabrics (Bell and Etheridge, 1973; Berthe et al., 1980; White et al., 1980; Lister and Snoke, 1984) parallel to the stretching lineation in rhomb porphyry 1 km east of Willowbrook (Fig. 54) and in gneiss east of the Okanagan Valley (Bardoux, 1985; Parrish et al., 1985). Lower Plate Rocks structurally beneath the Okanagan Valley fault have been deformed at temperatures of at least 400°-500° C. The structural geometry of these gneisses has been well documented (Christie, 1973; and Ross and Christie, 1979), and is summarized in Table 10. The predominant fabric within the gneisses is the foliation (Fig. 55) (F2 of Christie) which consistently dips gently westward. The leucogneiss body (lgn) has been demonstrated to crosscut the earliest fabric (FO but contains the F2 foliation. This foliation is generally defined by compositional layering and is commonly mylonitic. This mylonitic foliation becomes more common, and more strongly developed structurally upward and towards the west Within the mylonites there is a consistent stretching lineation, outlined by elongated quartz and pulled apart feldspars (Fig. 56), which trends N65W, 10SW (Fig. 57). F2 fold axes parallel this stretching lineation (Christie, 1973), and are interpreted to be rotated into parallelism by progressive simple shear (Bell, 1978; Bell and Hammond, 1984). The rhomb porphyry (dated at 51 Ma) can be shown to locally crosscut this mylonitic fabric but is "also foliated and lineated parallel to F2. The post-51 Ma deformation must have been at temperatures higher than 450° -500° C (Harrison, 1981), because of garnet and biotite growth in pullaparts of feldspar and pyroxene in the rhomb porphyry, and 51 Ma hornblende dates on the Figure 52: Photomicrographs of brecciated mylonite from Mahoney Lake. 1 mm Figure 53: Photomicrographs of mylonites showing sense of shear of top to the west Looking north. 105 106 Table 10 Summary of the Structural Elements In the Vaseaux Formation (Christie, 1973) isoclinal rootless folds; fold axes and penetrative lineations plunging variably N and S. tight often rootless folds; fold axes and penetrative lineations gently plunging NW and SE; open to tight folds; SSW and NNE gently inclined axial surfaces; fold axes and penetrative lineations plunging gently WNW and ESE. open folds; steeply dipping NE fractures; rare fold axes gently plunging N and S. open folds; steeply dipping W to NNW fractures; minor fold axes gently plunging NW and SE. Figure 56: Photograph of lineations in lgn unit 108 gneisses. Temperatures could not have exceeded 500° -600° C (Wagner et al., 1977), because of only partially reset 58 Ma Rb-Sr date on muscovite from the leucogneiss. This ductile fabric is overprinted by several sets of minor warps (F3, F4, FJ( of Christie, 1973) which interfere to produce a foliation dome evident in the topography. Possible interpretations for the rhomb porphyry both cutting and containing an apparent F2 fabric, are: 1) That it was intruded late in a single protracted mylonitic event, and crosscut some mylonitic zones but was caught up in continuing deformation; 2) that the rhomb porphyry crosscuts an earlier fabric (syn-, or post-intrusion of lgn) which was reactivated after 51 Ma. In either case, the deformation responsible for the fabric in the rhomb porphyry is also responsible for bringing the gneisses to the surface. In summary, the lower plate shows ductile strain. The overwhelming fabric is a gently west dipping foliation (F2). This fabric affects all rocks within the lower plate, except the rhomb porphyry which apparently both contains and crosscuts it This deformation was either one protracted event or was reactivated after the intrusion of the rhomb porphyry. The interpretation is that the deformation seen in the rhomb porphyry is responsible for much of the mylonite which becomes increasingly pervasive structurally upwards (towards the west). This mylonitization represents mid-crustal movement related to the Okanagan Valley fault These mylonitic rocks were then overprinted by the chlorite breccia as they approached the surface. Timing of Brittle and Ductile Deformation The brittle deformation in the upper plate is known to be as young as Eocene because it affects White Lake 'Basin rocks. There are several angular unconformities in the upper parts of White Lake Basin, with associated conglomerates and megabreccias, deposited in active-fault bounded basins. The lower half of White Lake Basin shows 109 little evidence of syn-depositional faulting. Extensive tectonism appears to have affected White Lake Basin only after deposition of the Marron Formation at approximately 50 Ma. The age of structures in the lower plate is not well constrained. In a relative order there is a fabric (foliation, early isoclinal folds) within the paragneiss which is older than the intrusion of the leucogneiss body. The second, predominant fabric overprints the lgn body. Apparently this fabric also affects the rhomb porphyry. The best absolute age relationship is that the fabric in the rhomb porphyry is younger than 51 Ma. The earliest fabric (pre-lgn) is pre-Jurassic, and may be as old as Precambrian. The main F2 event is post-Early Jurassic to possibly post-Aptian. A strong argument that the mylonites in the lower plate are Eocene is that they are not annealed even though, from geochronometric evidence, the gneisses must have been at relatively high temperatures at this time. The deformation of the rhomb porphyry, and presumably formation of the mylonites, is coincident in time with the Eocene extensional deformation in the upper plate. Discussion and Regional Implications In recent years the literature on crustal extension has blossomed (McKenzie, 1978; Frost and Martin, 1982; Wernicke, 1981, 1985; Wernicke and Burchfiel, 1982; Wernicke et al., 1982; Wernicke et al., 1985; Allmendinger et al., 1983; Miller, 1983; Miller et al., 1983). Quantitative evaluation of the amount of extension and diplacement on known faults has been the focus of much of this work. Because no units or structures can be matched across the Okanagan Valley fault, reconstruction to a pre-extension configuration is not possible. However, an estimate for structural omission across the Okanagan Valley fault can be derived using geochronometric data presented in the previous chapter. 110 Granitic rocks west of the fault give Jurassic and Cretaceous K-Ar hornblende and biotite dates. Gneisses immediately in the footwall of the Okanagan Valley fault give K-Ar hornblende dates averaging 51 Ma. Using assumed geothermal gradients of 50° C/km and 30° C/km implies between 9 and 15 km structural omission across this fault Combining this with a simplified fault geometry implies displacements between 10 and 60 kilometers. These estimates are meant to show: a) the extremes in possible displacement due to fault geometry (listric versus planar; Wernicke and Burchfiel, 1982), and b) that displacement must be on the order of 10's of kilometers. Figure 57: Stereonet of mylonitic lineations. Ill Conclusions Although there is evidence for early structures (pre-Late Triassic) in both the upper and lower plates, the latest, and locally pervasive structures are interpreted to be Eocene. This includes both the brittle deformation of the upper plate and some ductile deformation and mylonitization in the lower plate. The explanation for these late structures is a low angle normal fault regime (Fig. 58) as described by many workers in the Basin and Range area of the western U.S. (Armstrong 1972, 1982; Crittenden et al., 1980; Coney, 1980; Coney and Harms, 1984; Davis, 1983; Davis and Coney, 1979; Wernicke, 1981; Wernicke, et al., 1985). The resulting interpretation is that the Okanagan Valley fault is responsible for the tectonic unroofing and rapid cooling of the Okanagan Metamorphic and Plutonic Complex. This idea is compatible with both structural and geochronometric evidence, and implies 10's of kilometers displacement on the Okanagan Valley fault Geologic Cross Section White Lake - Vaseaux Lake Area 0 1 2 Miles Scale Figure 58: Cross-section through White Lake and Vaseaux Lake area (see Figure 2 for location and legend); unit symbols: eTv=Eocene volcanic rocks; eTs=Eocene sedimentary rocks; lPz-Tr=late Paleozoic to Triassic eugeosynclinal formations; lgn=leucogneiss; pgn=paragneiss of Vaseaux Formation; K-Jg=Cretaceous or Jurassic gneissic granitic intrusives. Elevations in feeL Modified from Christie (1973), and Church (1973). VI. GEOLOGIC HISTORY OF THF. SOUTHERN OKANAGAN REGION The pre-late Paleozoic history of the southern Okanagan region can be, at present, only inferred. The age of the Vaseaux Formation protoliths is unknown. Highly radiogenic Sr from these gneisses suggests that they could be Precambrian in age. This Precambrian component is not evident in the U-Pb work. (Except possibly the leucogneiss discordance). Deposition of the eugeosynclinal formations (Apex Mountain, Kobau, Anarchist; Milford, 1984; Okulitch, 1973; Read and Okulitch, 1977; Monger, 1977) began in the mid-Carboniferous and continued through the early Triassic. This sequence (ultramafic, greenstone, chert, limestone, argillite) represents an ocean floor, interarc, or back arc basin. By late Triassic time these eugeosynclinal formations had been intensely folded and deeply eroded (Read and Okulitch, 1977). This pre-Late Triassic deformation probably represents telescoping of this basin before the beginning of the Nicola-Rossland volcanic arc environment (Monger and Price, 1979). Following this deformation the Late Triassic Nicola Group equivalents at Olalla Creek were deposited (Read and Okulitch, 1977). The Nicola Group represents a Late Triassic to Early Jurassic island arc sequence. The gneiss of Osoyoos is time correlative with the Guichon Batholith and other early Jurassic intrusives associated with Nicola Group. An important observation in the history of the rocks west of the Okanagan Valley is that the Late Triassic rocks are only mildly deformed (tilted and faulted) and unmetamorphosed except near Jurassic or younger plutons. Jurassic time in the southern Okanagan was marked by abundant plutonism. This began with the intrusion of the granodioritic gneiss of Osoyoos (eJ) into deformed Anarchist Formation, followed by the Olalla Syenite and Similkameen granodioritic batholith (mJ) intruding deformed Apex Mountain, and Kobau strata. The 113 114 Late Jurassic was marked by more felsic intrusions (Miller and Bradfish, 1980) of the Oliver pluton (garnet-muscovite phase) and the granite of Anarchist Mountain (garnet-biotite). This Jurassic intrusive event has correlatives farther east with Kuskanax (Miller, 1978; Parrish and Wheeler, 1983; Olalla, Similkameen), Nelson (granite of Anarchist Mountain), and Galena Bay Stock (Oliver Granite), both in time and sequence of composition (Gabrielse and Reesor, 1974). Within the Okanagan Metamorphic and Plutonic Complex several plutons were emplaced in either Jurassic or Cretaceous time which have since been highly deformed and metamorphosed (leucogneiss, gneiss of Skaha Lake, and gneissic sill of Vaseaux Lake). The Kettle (Cheney, 1980; Rhodes and Cheney, 1981), Okanogan (Fox et al., 1976; Goodge and Hansen, 1983) and Valhalla (Parrish, 1984; Parrish et al., 1985; Carr, 1985) gneissic culminations all contain deformed Cretaceous and Cretaceous(?) intrusives. This observation may be the key to explaining the later evolution of these domes. Cretaceous time in southeastern B.C. is marked by crustal melts indicating large amounts of crustal thickening (Monger et al., 1982; Armstrong, 1983). A scenario of crustal thickening prior to and spatially related to later crustal extension fits the model of Coney and Harms (1984) for the development of metamorphic core complexes. The Paleocene was a time of relative quiescence with only a few known intrusives of this age (Medford et al., 1983; Parrish, 1984), which probably represent the beginning of the magmatic episode that culminated in Early Eocene time. The Eocene begins with a regionally developed basal conglomerate (Springbrook and Kettle River Formations) followed by the voluminous mafic alkaline Marron Formation. This volcanic sequence then evolved with time into a more felsic and calc-alkaline composition (Church, 1973). The higher parts of this Eocene basin are highly disrupted by syn-depositional normal faulting. The entire Eocene section appears to have been deposited in 4-10 Ma. This basin development and subsequent extensional deformation in the upper plate of the Okanagan Valley fault is coincident with intrusion, 115 deformation and metamorphism of the rhomb porphyry in the lower plate, and development of extensive mylonites responsible for tectonic unroofing of the Okanagan Metamorphic and Plutonic Complex. A similar pattern of deformation, but with opposite sense of movement, has been documented for the Valhalla Dome to the east (Parrish et al., 1985; Carr, 1985). A highly extended Eocene section has also been documented at Midway (Monger, 1968), between the Okanagan and the Valhalla area. The implication is that a large area of southern B.C. has undergone crustal extension (Parrish, 1985). The geochronometric evidence shows this to have taken place very rapidly beginning at approximately 51 Ma. This might possibly be tied to interaction of the North American plate and the Kula/Farallon plates offshore (Ewing, 1980). Plate motions and velocities for these plates (Engebretson et al., 1984) indicates that for most of Paleocene time the motion between North America and Kula/Farallon plates was at a low velocity with oblique, nearly strike slip, convergence. The Eocene is marked by very rapid plate velocities and more orthogonal convergence (Engebretson et al., 1984). This apparently set up an intense arc-back arc volcanic regime which may have brought about mantle upwelling. The initial mafic alkaline magmatism can be interpreted as mantle melting, signaling the onset of this aesthenospheric upwelling. As this thermal pulse moved upward into the crust the volcanism changed to a calc-alkaline, felsic composition. 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Williams, I.S., Compston, W., Black, L.P., Ireland, T.R., and Foster, J.J., 1984, Unsupported radiogenic Pb in zircon: a cause of anomalously high Pb-Pb, U-Pb and Th-Pb ages: Contribution to Mineralogy and Petrology v. 88, p. 322-327. Zeitler, P., 1985, Cooling history of the northwest Himalaya, Pakistan: Tectonics v. 4, p. 127-151. APPENDIX A - WHOLE ROCK SAMPLE LOCALITIES AND DESCRIPTIONS Sample // Description Latitude and Longitude Diorite samples (Jd): 207 biotite-hornblende diorite 49°13.3'N, 119034.2'W 178 biotite-hornblende diorite 49° 119° . 'W 261.1 hornblende-biotite diorite 49°14.2'N, 119°35.0'W 261.2 hornblende diorite 49°14.2'N, 119°35.0'W 140 biotite-hornblende diorite 49°13.55'N, 119°35.4'W Porphyritic biotite granite samples (Jpgr): 275.1 porphyritic biotite granite 49°12.2'N, 119°31.2'W 275.2 porphyritic biotite granite 49°12.2'N, 119°31.2'W 245.2 hornblende-biotie granodiorite' 49°11.5'N, 119°35.0'W 227 porphyritic biotite granite 49°12.4'N, 119°35.4'W 205 porphyritic biotite granite 49°13.1'N, 119°34.7'W 203 porphyritic biotite granite 49013.1'N, 119°34.8'W 71 porphyritic biotite granite (altered) 49°13.2N, 119°35.0'W Garnet-Muscovite granite samples (Jgr) : 234 garnet-muscovite granite 49°11.75'N, 119°33.8'W 209.1 garnet-muscovite granite 49013.1'N, 119°34.3'W 209.2 garnet-muscovite granite 49°13.1'N, 119°34.3'W 263 garnet-muscovite granite 49°12.5'N, 119°34.4'W 182 garnet-muscovite granite 49°13.3'N, 119°37.4'W 9 garnet-muscovite granite 49°13.2'N, 119°37.35'W Whole rock data was derived from XRF analyses of pressed powder pellets using an automated Phillips X-ray spectrometer in the Oceanography Department of U.B.C. Results are oxidized, anhydrous, and normalized to 100 percent totals. Trace element analyses of the same pellets were done using the same equipment Major and tracre element concentrations are based on comparison with U.S.G.S. and other widely analysed igneous rock standards. Mass absorption coefficients are calculated from major element compositions. 127 APPENDIX B - U-PB ANALYTIC AT, PROCEDURE AND DATA Mineral Separation Zircon concentrates were separated from 20-40 kg samples using standard Wilfley table, heavy liquid, and magnetic techniques. The procedure is summarized below. 1. samples were broken into fist-sized pieces at the collecting site, and stored in separate pails for shipment Only the freshest available material with the cleanest surfaces was collected. 2. the surfaces of the sample were wire-brushed and all loose matter was removed using a high-pressure air nozzle. 3. samples were reduced to very fine sand size or smaller using a jaw crusher and a disk mill. The crushing equipment was completely dismantled and cleaned, and all crushing surfaces wire-brushed and blown clean between samples. 4. the heavy mineral concentrate was separated from the sample using a Wilfley table. The concentrates were washed with acetone and then dried. 5. metal filings and magnetite were removed using a strong hand magnet 6. the light minerals were removed using tetrabromoethane (S.G.=2.89). 7. the samples were washed in warm 6N HCI for 15 minutes to remove iron oxide coatings on the grains. 8. samples were passed through methylene iodide (S.G. = 3.32) to remove apatite and other impurities. 9. the final heavy mineral concentrates were washed for 15 minutes in warm 8N HN03 and then for 15 minutes in warm 6N HCI to remove sulfides and any remaining iron oxide coatings. 10. samples were cleaned using a Franz magnetic separator (25° forward tilt, 2° side tilt, 1.7 amps magnet current). 128 129 This procedure usually produced a 99% pure zircon separate. Preparation of Fractions and Sample Dissolution Desired magnetic fractions were separated using the Franz. Each of these samples was then separated into a coarse (100-200 mesh) and fine (200-325 mesh) fraction. Several samples yielded very coarse (70-100 mesh) fractions. Individual fractions were then weighed and hand-picked to greater than 90% purity under a binocular microscope. These hand-picked fractions were carefully weighed, then put into pre-cleaned Teflon dissolution capsules, given a final acid wash (15 minutes in 7N HN03, 15 minutes 6N HCI, 15 minutes 2B H20 on a hot plate at 120° C). After pipetting off the rinse water, 0.75 to 1.0 ml of concentrated 2B HF was added to the samples along with 3-4 drops of concentrated 2B HN03. The capsules were then sealed in steel jackets, and placed in a 200°-210° C oven for one week. In all cases dissolution was complete in 7 days. After one week, the samples were removed from the oven, and capsules opened. The contents (HF plus fluorides) were evaporated to dryness overnight on a 120° hotplate. The capsules were then placed back in the ovens at 200° -210° C overnight, after adding 0.5 ml of 3.1 N HCI. They were then removed and the sample was aliquoted, one half of the 3.1N HCI solution to be analysed for the isotopic composition (IC), the other half to be mixed with a 20!Pb/235U spike for determination of U and Pb concentrations using isotope dilution (ID). The IC and ID splits were carefully weighed and the ID placed on the hotplate overnight to equilibrate the spike and sample. Then both IC and ID were ready for column chemistry. 130 Ion Exchange Column Chemistry All chemical processing of samples was carried out in a laminar flow hood. Separation of the U and Pb from the dissolved samples was carried out using 0.5 and 0. 15 ml Teflon columns. These were stored in 8N HN03 between use. They were removed from storage, rinsed in 2B H20, then loaded with pre-cleaned anion exchange resin, (Dowex AG1-X8, 100-200 mesh chloride form, in 2B H20). The resin was then washed as follows. 1. 2 column volumes (c.v.) IX H20 2. 2 c.v. 6N HCI 3. 2 c.v. 2B H20 4. 2 c.v. 6N HCI 5. 2 c.v. 2B H20 The resin was then equilibrated with 3-4 c.v. of 3.1N HCI. The samples (dissolved hr 3.1N HCI) were then carefully pipetted onto the columns and allowed to drip through. The sample was then washed and Pb and U collected as follows. 1. add 1 drop 3.1N HCI and allow to drip through 2. repeat step (1) five times 3. add 100 lambda 3.1N HCI 4. add 150 lambda 3.1N HCI 5. take off Pb with 6 c.v. of 6N HCI 6. take off U with 6 c.v. of 2B H20 After the Pb and U have been taken off the columns, the resin is removed and the columns are rinsed in IX H20 and stored in 8N HN03. The resin is discarded. Cleaning of Dissolution Capsules and Beakers 131 Teflon dissolution capsules and beakers were cleaned after use as follows: 1. wash in warm soapy water; rinse in IX H20. 2. 2 days in warm aqua regia; " 3. 2 days in warm 8N HN03; " 4. 2 days in warm 6N HCI; " 5. 2 days in cold IN HBr; " 6. 2 days in warm IX H20; " 7. remove, drain, and store in IX H20 in a clean plastic container. Reagants and Blanks IX H20 was obtained from a pyrex-vycor still in K. Fletcher's lab, or from a quartz still in K. Scott's lab. Using IX H20, 2B H20 was prepared by a sub-boiling teflon bottle still described by Martinson (1970). All other reagents were purified starting with reagent grade stock. IX HCI and HN03 were obtained by distillation in pyrex; 2B HCI, HN03, and HF were then prepared by sub-boiling still. Total procedural blanks, run with every batch of zircons processed, range from 0.1 ng to 1.0 ng Pb, and generally were 0.5 ng or less. Mass Spectrometry U and Pb isotopic ratios were measured on a V.G. Isomass 54 R which has data aquisition digitized and automated using a HP. 85 computer. Pb was loaded using the phosphoric acid-silica gel method on a single rhenium filament, U was run as an oxide using tantalum oxide-nitric acid-phosphoric acid method on a single rhenium filament U was also loaded using the phosphoric acid-silica gel method and found to 132 be more stable and gave longer runs. Precision on all measured ratios were normally better than 0.1%, and commonly better than 0.05%. Pb and U ratios were corrected for instrumental mass fractionation on the basis of replicate analyses of National Bureau of Standards SRM-981, and 983 for Pb and U-500 for U. Data reduction and error calculation U-Pb date errors (2a) are obtained by individually propagating all calibration and analytical uncertainties through the entire date calculation program and summing all the individual contributions to the total variance. Data reduction and automation are done on a dedicated Hewlett-Packard HP-85 computer. U decay constants and isotope ratios are: 238UX = 0.155125 x 10-9 a-1  23iUA =0.98485 x 10-9 a"1  238U/235U = 137.88 All published dates cited in the text have been recalculated, if necessary, to conform to these constants. 133 U_Dh • Mineral analysis • O • Concordia interpretation • Mineral or rock isochron Sample Number(s) and Reference(s)  Lab No: £>P/S&  (NTS Ref: Ckrisrit; /US f&D. Record No:  Suite No:  Sample Name: rif/s&Z SJ/I g-f VasetkuX Lake decay constant • old: 0.1537/0.9722/0.0499/137.8 Qtfew: 0.155125/0.98A85/0.049475/137.88 • other: • not reported Upper Intercept 2a error Computed Q Assumed • + Ma Lower Intercept 2o error Computed• Assumed • + Ma 238IT 206DV J U- Pb date + Ma 235 207 U-Pb date + Ma 207Pb/206Pb date + Ma 232Th-208Pb date + Ma Number of Points: n= Latitude: Longitude: (X V Z" or X Y.Y1) ° 'OO" N, //? °3/ <30" W (± ); Elevation: /«3 SB E N; Province: C C'. UMT Zone Sec. , T (NTS Co., State Per* f/c So/l Map Area (1:250,000) Location: frm MIB of )/as<?a.L>x: LOLUP ^ g g-f c/j-fb cleave °j*ivel rd. Source Type:  Rock Types: f eocaa^j ,~c a Uc - ^ r j- - [<-s^c^- n\Wni+rc y^-eUsi^. sUI Geologic Unit: f>teiss/C sit/of ^asea^r L«ke. . ' Geologic Setting: /negates. Vassal* A.rA^/SAeJi Material Analysed: Zircon  Comment on Analyses: Interpretation: Collected by: Dated by:_ JL far forts on Date of listing: Sample Name or Number: ptt?'^ Sheet • Split-Mineral ppm U ppm Pb 206 207 208 2Ct Meas. 206 Mole % Blank Pb Rad. Pb Rad+ComPt Common Pb Aqe Fin e <p /V7V 20,5" o. oooa. /.ooa 266 207 Pb ratio + 207 Pb „. o + 206 Pb . 207 Pb da te + 207 Pb j ate + R 218 U - 215 U 206 Pb rau 238 U date - 235 U da 206 Pb d o./ooG> to.ooay O. oY*7P to-oeaog- 9S-.7 - AO ?7. 3 t Ao (37.3 ±£f Split-Mineral ppm U ppm Pb 206 207 208 20l| Meas. ™L 20T Mole * Blank Pb Rad. Pb Rad+ComPt Common Pb Aqe fine MntAfAo /OO y'f/sy 6- Oo8£~ 3. S% o. rrV -33STn, 2tjb 207 Pb ratio + 207 Pb o + 206 Pb j , . 207 Pb da te + 207 Pb j ate + K 2l8 U ,<Jl'" - 215 U 206 Pb rati 238 U - 215 U da 206 Pb d 0. o/V?7 -6.000/0 Oo97y - O.oo/e 9YY - Ae 0 7/ " 3?.o Spli t-Mlneral ppm U ppm Pb 206 207 208 20*1 „„c 206 Meas. —r-20T Mole % Blank Pb Rad. Pb Rad+ComPt Common Pb Aqe jr. 5~m<> /<2 73. /7 y / 7W5' PC} /OS /.OO -&oonf 20b Pb u, . 2lFTTratio t 207 Pb ... 215 U rat'°t 207 Pb „, A 206-Pb rat'° i 206 Pb j . 238 U date -207 Pb j , , 2i5 li -207 Pb j . 2o5-pb date i £>. /ooS ±0. oooST oo-Yg77 -0°°o6C ^ 6 -/a AO /si.? -i:/ % Split-Mineral ppm U ppm Pb 206 207 208 20^ Meas- m Mole % Blank Pb Rad. Pb Rad+ComPt Common Pb Aqe Very Course 3.9^9 / OO (7^VS? 0.3% o.m /VC m pb . 2~T8-irr ° t 267 Pb . 215 U rat!° * 207 Pb ,. ^ loTTb rati° i 206 Pb J . . nmrdate i 207 Pb j t , 215 U d3te *-207 Pb . . A IbTTb date t O.o/Sjo -aooocf o./o£<( taoooc, aofssff ±0.ooo/3 ff.o * AJ °& Spli t-Mineral ppm U ppm Pb 206 207 208 20*i Meas. ™L 20T Mole % Blank Pb Rad. Pb Rad+ComPb Common Pb Aqe 206 Pb f, ^ 207 Pb ... 215 U rat'°± 207 Pb . loTTb ratio t 206 Pb . . A 207 Pb j . 215 U d3te i 207 Pb j . 206-pb datC i TA + + + + + + Statement of Uncertainties: errors 3x/£ _£__P— lov- Jo^.i,,' / _g~ £re: isefop/'t faAiaS. Isotopic composition of blank: [Is-K Modern Pb (6A:l8.7, 7/^: l|flWi?®h :38.63) or 0Other (6/'i:/77/7/'i/j:i'78/'i:J700 ) Isotopic composition of common Pb based on S-K growth curve: 6/l»»i 1Vl'5?T 7/^=12.998, 0?T=31.23 at 3-7Ga with 238U/20'iPb=9.7'i, 232Th/20'tPb=37.19; decay constants 0.155125, 0.981(85, 137-88; or [JJ Other (G/'t: J/U: 8/l» : ) 4^ 135 U—DK D Mineral analysis ~» O •Concordia interpretation D Mineral or rock isochron Sample Number(s) and Reference(s)  Lab No: 7>P /77  (NTS cfj. e/s Ref: L,rf/f Mm /6~-Record No:  Suite No:  Sample Name: / skaka. Ukt. decay constant • oldj 0. 1537/0.9722/0.0499/137.8 0^: 0. 155125/0.98485/0.049475/137.88 • other: Qnot reported Upper Intercept Computed• Assumed D + 2a error Ma Lower Intercept Computed• Assumed • + 2a error Ma 238,, 206o, , ^ U- Pb date + Ma 235U-207Pb date + Ma 207Pb/206Pb date + Ma 232Th-208Pb date + Ma Number of Points: : n= • a Latitude: Longitude: (X° Y' Z" or X° Y.Y') (V? °JY'2S'" N, //? °3Y ' OS~" W (± ); Elevation: ///O ' Province: <—-UMT Zone Sec. , T (NTS N; ,R. Co., State_ _Map Area (1:250,000) Location: S~-/ km SovrA ok Pe^rv'c/c^ —on ^^cst*- s/orct S/^g/a. -4g/f> Source Type: roa.ct'<Lvr~ Rock Types: 9*e>/'5<,/V Mb £>sa>roe//or/£r  Geologic Unit: a*e;sj> s6*Aa. Zaitp Geologic Setting: / /yi£uff(es Vasea.uK fats q-.H/e, JlGf) Material Analysed: g/Vcon Comment on Analyses: Interpretation: Collected by: J). 7%,/HS>0*>? Dated by: 3 - 7*' Date of listing: Sample Name or Number: ^t^e/sS °f SAaric ^-A^C Sheet | ] Statement of Uncertainties: arc a. a- £^ A&4,> jra. Spli t-Hlneral ppm U ppm Pb 206 207 208 20*1 Meas. 20T Mole % Blank Pb Rad. Pb Rad+ComPt Common Pb Aqe Fj*e Mat 3oS y-7 /oo 4. ?3?3 /O.033.S to. oo(></ O. (=% o. ??£ 2t)6 Pb „. _,_ mrrrat'° -207 Pb „. ^ 235 U rat'° ± 207 Pb tI ^ 206-pb rat'° * 206 Pb j . TWIT date ± 207 Pb . . A 235 U date t 207 Pb j . 20S~Pb * R O.0'S*/y t o.eooof O./03/ -o.oooC fr.7 - / o • ??. 7 - / 2. % Split-' Mineral ppm U ppm Pb 206 207 208 20A Meas. 206 IoT Mole * Blank Pb Rad. Pb Rad+ComPl Common Pb Aqe C^aars e Mr* Mey 33 Or»f G./a. /OO A/.?S7Y coo fey VJ33 o. 9% O. ? 96 . /oS 20b Pb . 2wrrrat,° t 207 Pb ... 2v;u rat'°± 207 Pb t. ^ 206-Tb rat,° t 206 Pb , . . 2WTT date t 207 Pb . . • 235 U date t 207 Pb j , 206~Pb date t R C>/63o to.ooooj O./0 93 ±00007 /o</. 3 /o£~. Y t /• SL % Spl1t-Mi neral ppm U ppm Pb 206 207 208 20(t Meas. 206 IoT Mole % Blank Pb Rad. Pb Rad+ComPt Common Pb Aqe 206 20TPb ratio + 20J Pb rati o + 20& Pb 207 Pb da te + 207 Pb , ate + 218 U — - 235 U 206 Pb ratl 238 u date - 235 U aa 206 Pb d + + + + + + Split-Mineral ppm U ppm Pb 206 207 208 20lf Meas. 22* 20T Mole % Blank Pb Rad. Pb Rad+ComPt Common Pb Aqe 206 Pb „. 2T8~rrra t 207 Pb ... 215 U rat'°± 207 Pb ,. ^ I06-Pb rat'° t 206 Pb . „ ^ MT date i 207 Pb , . . 215 U date t 207 Pb . . A loTTb date t + + + + + + Split-Mineral ppm U ppm Pb 206 207 208 Meas. 206 20T Mole % Blank Pb Rad. Pb Rad+ComPb Common Pb Aqe 206 Pb . 2Wratio t 207 Pb . 2,su rat.o. 207 Pb ¥. loTTb ratio i 206 Pb , . ^ TTiTTT date t 207 Pb J . , 235 U date ± 207 Pb j . 206-Tb datC t + + + + + + Isotopic composition of blank: f~]s-K Modern Pb (6/l»:l8.7, 7/^:1$J63', l/A: 38.63) or pTother (6/A J7- 7fl/k :Ai'S78/U : 37°* ) Isotopic composition of common Pb based on S-K growth curve: 6/A-11'. 152,'' 7/A=12.998, 57V=31.23 at 3.7Ga with 238U/20APb=9.7't, 232Th/20'tPb=37.19; decay constants 0.155125, 0.98A85, 137-88; or Other (6/^: J/k: %/k : ) 137 U— Dh D Mineral analysis • O Q Concordia interpretation D Mineral or rock isochron (NTS Sample Number(s) and Reference(s) Lab No: gFJ^O  __ Record No: Suite No: Upper Intercept Computed D Sample Name: decay constant • old: 0.1537/0.9722/0.0A99/137.8 • other: • not reported 2a error Assumed D + . Ma Lower Intercept Computed • Assumed • + 2a error Ma 238IT 206.,, . U- Pb date + Ma 235.. 207_, . ^ U- Pb date + Ma 207D. ,206-. , Pb/ Pb date + Ma 232_ 208,,, , Th- Pb date + Ma Number of Points: n= =5 Latitude: Longitude: (X Y' Z" or X Y.Y') (V? ° " N, //? 0 3 3 ' & " W (± ); Elevation:_ B.C. UMT Zone Sec. , T (NTS _N; Province: Co., State Map Area (1:250,000) >e: fu -r^crep ' f Location  Source Typ  Rock Typ Geologi  Geologic Setting: T^i^urJe<i Material Analysed: Z/rrmsf c Unit: Xh***L '?»zA«ry <Jikc" " ' Comment on Analyses: Interpretation: Collected by: ,/), task/nSm^ Dated by: /a r f( Date of listing: Sample Name or Number Sheet • Split-Mineral ppm U ppm Pb 206 207 208 20*1 Meas. 206 20T Mole * Blank Pb Rad. Pb Rad+ComPt Common Pb Aqe •f.n € / C »<g //OO 9-5" 5". 'f /r.o32& 0.96/ S& ' 206 Pb .. . 2iru-rat,° t 207 Pb „. ^ 2« „ rat.o ± 207 Pb ^ 206-Tb rati° i 206 Pb . . t IWT date i 207 Pb , . A 235 U datC t 207 Pb _, . . 206" Pb date - R O.oS-Vf to-oooy sy.s -0.6 £~3. V * O. ? Mine 11-ral ppm U ppm Pb 206 207 208 20l| H„c 206 neas. —r-20T Mole 1 Blank Pb Rad. Pb Rad+ComPt Common Pb Aqe Coarse /9a 3 / /oo <o/7 C-6% a?t/) SO '206 Pb ^ 2WTTratl° ± 207 Pb ., . 235 U ratio± 207 Pb ., ^ 206-Tb rat,° t 206 Pb j . 238 U date i 207 Pb , . A 235 U date *-207 Pb j . 206- Pb date - R 0. eo 793 ±000005 0.oS~// toooof viftf. ? - £ ^o.& ± f-8 3^.7 % Split-Mi nera 1 ppm U ppm Pb 206 207 208 20^ Meas. 206 20TT Mole S Blank Pb Rad. Pb Rad+ComPt Common Pb Aqe 206 Pb 2TO-rat,° t 207 Pb ... 235 U rat'° ± 207 Pb ., . 206-Tb rati° t 206 Pb j 23TTTdate t 207 Pb , . ^ 235 U datC t 207 Pb j . 206" Pb date - R + + + + + + Split-Mineral ppm U ppm Pb 206 207 208 20*) Meas. 2?T^ 20¥ Mole % Blank Pb Rad. Pb Rad+ComPt Common Pb Aqe 206 Pb .. . 2WTrat,° t 207 Pb ... 235 U rat'°± 207 Pb ,. ^ 206-Tb rat'° t 206 Pb . „ 23TTT DATE ± 207 Pb . . A 235 U date -207 Pb j , 206" Pb datG -+ + + + + + bp 111-Mlneral ppm U ppm Pb 206 207 208 20A Meas. 206 20T Mole % Blank Pb Rad. Pb Rad+ComPb Common Pb Aqe 206 Pb „, ^ 207 Pb ... 235 U rat'°± 207 Pb , 206-Tb ratio i-206 Pb . . A 23TTT DATE ± 207 Pb . . 235 U date t 207 Pb j . 266" pb date i + + + + + + Statement of Uncertainties: efroKS CW^ cD CT <^^~^T^J /0~~ (hr /So/op. v'C rex //Q3 Isotopic composition of blank: [Is-K Modern Pb (6/^:18.7, 7/'t:ljj Isotopic composition of common Pb based on S-K growth curve: 6A' 238U/20'iPb=9.7't, 232Th/20'»Pb=37.19; decay constants 0.155125, 0.98485, 137-88) or [ [ Other !8A:38.63) or f^fo'ther {(>/UJTTiV/U-JL<:y78/k:37O0 ) 1'. 152,' 7/4=12.998, 87T= 31-23 at 3-7Ga with Ilk: 8/A : 139 U—Dh ©"Mineral analysis ""*v U Q Concordia interpretation • Mineral or rock isochron Sample Number(s) and Reference(s)  Lab No: Ref: £/-v't>tffWrL /f63 ~~ (NTS %c2 £ Record No:  Suite No:  Sample Name: decay constant • old: 0.1537/0.9722/0.0499/137.8 Qliew: 0.155125/0.98485/0.049475/137.88 • other: • not reported Upper Intercept 2o error Computed • Assumed • + Ma Lower Intercept 2a error Computed• Assumed • + Ma 238TT 206^ . U- Pb date + Ma 235.. 207,,, , „ U- Pb date + Ma 207D. ,206D, , „ Pb/ Pb date + Ma 232^ 208nv . Th- Pb date + Ma Number of Points: n= • / Latitude: Longitude: (X Y' Z" or X Y.Y') O" N, //?0V?.6< W (± ); Elevation: Province: UMT Zone Sec. (NTS N; _,R. Co., State _Map Area (1:250,000) Location: -/<?c*rW erf O/g/fa tCov\ rogJcok j^s~r SovM d Arto-isl  Source Type: oof crop ^ Rock Types: AfaA'f SyreuiH AnupltX Geologic Unit: g 'O/a//* SyfxJ/-tt  Geologic Setting: i A tr ucf e± 'Apr* Mou«A;« r^aop Material Analysed: ircevt  Comment on Analyses: Interpretation: Collected by: R- I. Ar*1S-/rtv19 Dated by: 2). Tar fail Sam  Date of listing: Sample Name or Number: Sheet • Spli t-Mlnera1 ppm U ppm Pb 206 207 208 20l| Meas. 206 20T Mole % Blank Pb Rad. Pb Rad+ComPt Common Pb Aqe Gin* /3V/ /oo S/73? • */C.17U O. OOQo 0.??7 DOG ' 206 Pb . . . 2irrrrat,° i 207 Pb „. A 215 U rat'° * 207 Pb .. A 206-pb rat,° ± *°6 Pb , . ^ 218 u date -207 Pb . „ ^ 215 U date ± 207 Pb j . loTTb date i R 0OSO8& ±QOO<x>7 /SS. C ±2-0 2. + /. Spl i t-Mlneral ppm U ppm Pb 206 207 208 201. Meas. 206 20T Mole % Blank Pb Rad. Pb Rad+ComPt Common Pb Aqe 206 Pb_.,„ A 207 Pb ratio + 207 Pb rati 0 + *°S Pb date + 207 Pb da te + 207 Pb . ate + R 218 u — - 215 U 206 Pb rati 218 u date - 215U da 206 Pb d + + + + + + Split-Mineral ppm U ppm Pb 206 207 208 20l) Meas. 106 Mole % Blank Pb Rad. Pb Rad+ComPt Common Pb Aqe 206 2l8 Pb h. A —ra 11 o + 207 Pb 215 U rat'° * 207 Pb ^ 206-pb rat'° *-206 Pb j , iinrdate -207 Pb j , 215 U date t 207 Pb j . 206 Pb date - R + + + + + + Split-Mineral ppm U ppm Pb 206 207 208 20<i Meas. 12^L 20T Mole % Blank Pb Rad. Pb Rad+ComPt Common Pb Aqe 206 Pb ,. ^ 2T8-u-rat,° ± 207 Pb ... 215 U rat'° ± loTTb ratl° t 206 Pb . . 2imrdate i 207 Pb , . . 215 U date - 2bTTb date t + + + + + + bp 111-Mineral ppm U ppm Pb 206 207 208 201) Meas. 2°6_ 20T Mole % Blank Pb Rad. Pb Rad+ComPb Common Pb Aqe 206 Pb . Mirratl° t 207 Pb . 215 U rat'°± 207 Pb . » . 20TTb ratio t 206 Pb 1^ , iTB-rrdate ± 207 Pb j . 215 U date t 207 Pb j . loTTb date t R + + + + + + rj_g~ r/*/eJ-( : ^ / <r~ Jtr*- /So /npic /-O.//0-S Statement of Uncertainties: -rrors are Isotopic composition of blank: £^]s-K Modern Pb (6/*4:18.7, 7A:15 Isotopic composition of common Pb based on S-K growth curve: 6/'t *3^M'»: 38.63) or 00ther {S/h:/7 rf/k:/S.S79>lk : 37-06 ) 1.152, 7/^=12.998, 87V=31.23 at 3-7Ga with isotopic compobiiion or common Dased on s-is growtn curve: D/M- //M=IZ.33O, O/H=JI.Z^ at j./ua witn 238U/20'iPb=9.7't, 232Th/20i4Pb=37.19; decay constants 0.155125, O.SSkSS, 137-88; or Q Other (6/l»: 7/k: 8/1) 141 U QL • Mineral analysis ™r D •Concordia interpretation • Mineral or rock isochron Sample Number(s) and Reference(s) Upper Intercept Lab No: Z>P ' Computed • (NTS Ref: ?-ax g/ g/ (977 Record No:  Suite No:  Sample Name: decay constant • old: 0.1537/0.9722/0.0499/137.8 •-new: 0.155125/0.98485/0.049475/137.88 • other: • not reported 2a error Assumed • + Ma Lower Intercept 2a error Computed• Assumed • + Ma 238IT 206o, , U- Pb date + Ma 235U-207Pb date + Ma 207Pb/206Pb date + Ma 232Th-208Pb date + Ma Number of Points: n= Latitude: Longitude: (X Y' Z" or X Y.Y') (f? ° 1 OO " N, //? ° V/ ' VJ" » w (± ); Elevation:, UMT Zone Sec. , T. (NTS N; Province: ,R. Co., State_ _) "Pe/i kic -kcrv1 _Map Area (1:250,000) Location: ^ km norski ok OS - Czr,g</^ ho^cker gV AVy 3," 31 je ok Kerc^^ Source Type: /W//gr5 k!od>jed -h-cn^ road Cv+- ' _ Rock Types: 6rrr.^orJ.or.ff Geologic Unit: S/m,'/Ko-'v?e™ 6^rha///li Geologic Setting: /nkkuefrs /ToAau for**a.-/>tn<] Material Analysed: ~P-;<con Comment on Analyses: Interpretation: Collected by: 7)- 7kr!< Dated by:_ Date of listing: Sample Name or Number: 'S//^///(ameir^ £>o//to/'Y~/\ Sheet | ) bp 1i t-Mlnera1 ppm U ppm Pb 206 207 208 201, M„t 206 MeaS- 20T Mole % Blank Pb Rad. Pb Rad+ComPt Common Pb Aqe fine. Mc^a ZC m<\ G2>2. 9 /7.3 /oo c 2% O. ?7 7 /7& 206 Pb_f!„ A 207 Pb rat io + 201 Pb rati 0 + 20° ^ date + 207 Pb da te + 207 Pb , ate + R 218 u — - 235 U 206 Pb raU 238 U date - 235 U da 206 Pb d o./8/f ±000// O.CV7 7? ±0.000/'/ /<**.£ * /.V ?. 7 - / r °$ bp 1i t-Mlnera1 ppm U ppm Pb 206 207 208 201) MCaS- 20? Mole % Blank Pb Rad. Pb Rad+ComPt Common Pb Aqe C rs A/0* Moy /3. 6 /oo 13. YC 7b C- 07 OO / COO ' / ty 0. 9S7 769 oo-Jo"*, 206 Pb ,. ^ 2wirratio i 207 Pb . 235 U rati° * 207 Pb „, ^ IbT-pb rat,° i 206 Pb j . 2lO- datC t 207 Pb . t ^ 235 U date t 207 Pb . . _,_ 206-pF date t R 0-0^.07/ ±0000,5 o./fJ-l ±0.00// 0. ov?yy t a 0001% 9. ? t J 0 Split-Mineral ppm ll ppm Pb 206 207 208 204 H„t 206 Meas. —Tr- Mole X Blank Pb Rad. Pb Rad+ComPt Common Pb Aqe 206 Pb A 2nnrrat,° ± 207 Pb ... 235 U rat'° -207 Pb t loTTb rat'° ± 206 Pb j . 23inrdate -207 Pb j , 235 U date i 207 Pb . . ^ 2oiTPb date i R + + + + + + Split-Mineral ppm U ppm Pb 206 207 208 201) Heas- m Mole % Blank Pb Rad. Pb Rad+ComPt Common Pb Aqe 206 Pb A 2T8-rrrat,°t 207 Pb ... 235 U rat'° ± 207 Pb , 206-pb rat'° ± 206 Pb , . ^ 230- d3te *-207 Pb . 235 U date ± 207 Pb . „ A loTTb date * + + + + + + bp 111-Mineral ppm U ppm Pb 206 207 208 201) Meas. 206 20T Mole % Blank Pb Rad. Pb Rad+ComPb Common Pb Aqe 206 Pb ^ 2iF__ratlo t 207 Pb . 235 u rat,°r 207 Pb ... 206-pb rat,° ± 206 Pb . h ^ 2Tinrdate ± 207 Pb , . . 235 U date t 207 Pb . „ ^ 206-pF date i TA + + + + + + Statement of Uncertainties: g/yor-s are. 2 a-— mm Isotopic composition of blank: Qs-K Modern Pb (6/4: 18.7, 7/4 : l£ 43 :38.63) or f^fother (6/4 :P 7Sj/lt: ,s.S7 8/4 :7- °0) Isotopic composition of common Pb based on S-K growth curve: 6/4-11'.'l527/4=12.998, 875=31-23 at 3-7Ga with 238U/204Pb=9-74, 232Th/204Pb=37- 19; decay constants 0.155125, 0.98485, 137-88; or fj Other (6/4: 7/4: 8/4: ) 143 U_DK Q-Mineral analysis r D •Concordia interpretation • Mineral or rock isochron Sample Number(s) and Reference(s)  Lab No: 2>P9e>  Ref: CAr-xA-c. /g-Zi-(NTS zaz/s /?o*s v- £77,*/?* /?7* ergs Record No:  Suite No: Sample Name: A foe o Q/te/sS decay constant • old: 0. 1537/0.9722/0.0499/137.8 Qfiew: 0.155125/0.98485/0.049475/137.88 • other: • not reported Upper Intercept 2a error Computed • Assumed O + Ma Lower Intercept 2a error Computed• Assumed • + Ma 238TI 206„. , U- Pb date + Ma 235.. 207_, , ^ U- Pb date + Ma 207Pb/206Pb date + Ma 232Th-208Pb date + Ma Number of Points: n= ^ Latitude: Longitude: (X Y* Z" or X Y.Y') {¥? ° /cf ' 30 " N, //? ° 36 < /O •' W (± ); Elevation: ^ SO E N; Province: 73. C UMT Zone Sec. , T. (NTS _,R. Co., State_ /e*>f/c -rz> Map Area (1:250,000) Location: ,2.3 k»* A/£ /V'W' */ Vtu Rock Types: A/nj Source Type: Qo/crap </~ /j-,/-'/* frTZjul.t-C Aar. Geologic Unit: A ^ rJ, ;<?_(//'73) \ /e*ceptriss /« M^Ainsovf C/ffS. Geologic Setting: /nAroc/fS " VasfiauX. /Tn Material Analysed: Comment on Analyses: Interpretation: Collected hy\ZE>.7nr'kl'n<&*i ¥ /• <4r/HS-fro x9 — , . "7^ T$ 7- 7 Date of listing: Dated by: . /& r/\<rt^er>] 6 -Sample Name or Number: /t? VCOCfZ/S^ Sheet Q] bp 1 i t-Mlneral ppm U ppm Pb 206 207 208 20A Heas. 206 Mole $ Blank Pb Rad. Pb Rad+ComPl Common Pb Aqe h»e '"lap 3/ & ~f /HI ZOO S~3/ 7? v y c. 0 oja O. 3% o.?rs> 76, 0 206 Pb ^ rnnrrat,° ± 207 Pb „. ^ 2„ „ rat.o + 207 Pb ^ 206-Tb rati° ± 206 Pb j . 238 u date - 207 Pb . . ^ 235 U date *- 207 Pb j . 206" Pb date - R e>.oi7(,(> to.oco/o //3.9 -/a. /22 c - /.a. 3/4.3 + 6/ °± bplit-Mlneral ppm U ppm Pb 206 207 208 20l» Meas. ™ 20T Mole * Blank Pb Rad. Pb Rad+ComPt: Common Pb Aqe r-,«r (H-P) //33 ^ /oo S. H/9c? y 3?Z3 0 001 7 <5V? 0-3% 6. ?7? 3 00 206 Pb -i j—ratio + 207 Pb .. . 235 U ratl°t 207 Pb ^ 206-pb ratio i 206 Pb j . 238 U date -207 Pb j . 235 U date -207 Pb A . 206 Pb d3te - R X&/76 3 ±0.0oo/o /3// ±ooot>-) O.CxS'Z9Y ±0oeoe>7 //S- 6 - / 3. /2S. / ± /: 3. ?* bp 1i t-Mineral ppm U ppm Pb 206 207 208 20(4 Meas. 206 20T Mole % Blank Pb Rad. Pb Rad+ComPt Common Pb Aqe f-Tne A/orttfay /(, Y~<> /o*o /f-33 /oo S-3V// 206 Pb .. . ITrjrrat.o + 207 Pb 235 U rat'° ± 207 Pb ., , 206-pb rati° ± 206 Pb j . mirdate -207 Pb j . 235 U date -207 Pb j . 206-pb date i R 0.017?C? ±0.000/0 0/3// ±0 0007 Oo£2>9y ±600007 //y 7 -A3. ps./ -/a 32 6./ Sp 1 i t-Mineral ppm U ppm Pb 206 207 208 20^ Mole % Blank Pb Rad. Pb Rad+ComPt Common Pb Aqe Coarse AJmMam /(,. V«f / ?S</ /oo s'.S'ooy //,'C7 0.3% 206 Pb „. ^ iwirraUo ± 207 Pb ... 235 U rat'° -207 Pb ., . loTTb rat'° ± 206 Pb . . 2W1T date ± 207 Pb , . . 235 U date -207 Pb j . 206-Tb date * 00/9/3 ±a.oo°/( O.ZY3? ± 0.0008 0.oS'YS3 ±o°o°o7 /<=2^?. Q ± /. y /J6.JT - /</ bp 1 i t-Mineral ppm U ppm Pb 206 207 208 20<4 M»=C 206 Meas. —,-20T Mole S Blank Pb Rad. Pb Rad+ComPb Common Pb Aqe SYS /oo 7 6 5y * OOO?/ o.S% o.??y ZOO b - roo^ 206 Pb „, ^ ?1Tnrrat,° ± 207 Pb ^ 235 U rat'°± 207 Pb ., . 206-Tb ratio ± 206 Pb . \ ^ nnrdate ± 207 Pb J . . 235 U date -207 Pb j . 206 Pb datC -O-O / &7o ± 6. ooo// 0/3/9 ±0.0007 O 0S0G3 ±0.0000$ /30.7 -/V Statement of Uncertainties: are. / cr ^rr- /i5'/ot>,x ra.Ac ~<2JL Isotopic composition of blank: [JjS-K Modern Pb (6A:l8.7, 1/U : 15 j63, flA : 38 .63) or P^f Other (6/'i:/?. ifl/h \ISS~1 Q/k -.TJ.oO ) Isotopic composition of common Pb based on S-K growth curve: 6A=11.152,' 7/^=12.998, 8/5=31.23 at 3-7Ga with 238U/20'(Pb=9.7'i, 232Th/20')Pb=37.19; decay constants 0.155125, Q.39>h^, 137-88; or Other (6/A: 1/k: 9,/k : ) 145 U—DK Q~Mineral analysis D • Concordia interpretation Q Mineral or rock isochron Sample Number(s) and Reference(s)  Lab No: 2>P?3~  (NTS &3L £/3 Ref: #yg^ ^tXTJeiCS Q„ /> V77T Record No: Suite No: Sample Name: decay constant • old: 0. 1537/0.9722/0.0499/137.8 •"new: 0.155125/0.98485/0.049475/137.88 • other: • not reported Upper Intercept Computed • Assumed • + 2a error Ma Lower Intercept Computed• Assumed • + 2a error Ma 238tI 206DV J U- Pb date + Ma 235.. 207_. , „ U- Pb date + Ma 207Pb/206Pb date + Ma 232Th-208Pb date + Ma Number of Points Latitude: Longitude: (X° Y' Z" or X° Y.Y') (V?°&3'^0" N, //?°<5/' " W (± ); Elevation: VjOO/Z. Province: & (-~-UMT Zone Sec. (NTS N; ,R. P^V /ic /on Co., State _Map Area (1:250,000) Location: JuarT.L'^/ /JAi - ~ 8 Km p/ Osoj/*ur. 3£' /ViV*f Source Type: A,,/rref 7 ^ Rock Types: awe f - As* /i/e QfnitC J. . . . Geologic Unit/ fj«i-/- 777/4/ ^/A^Cl973):ar^„if *f JmarchA/-f» X,A Geologic Setting: }*Aucl(><> _Jy&.rcJii±4- £*o<jp>. Material Analysed: jZ-irTetf  cm Comment on Analyses: Interpretation: Collected by:J?). /$W/>.-?^ f /?•/•• ds«<sA'0>r<> _ _ , . 7> / 7 Date of listing: Dated by: JJ. /%„Ain3*r*  6 -Sample Name or Number: /U/a'c/i&t prasi'Se Sheet Spl1t-M i nera1 ppm U ppm Pb 206 207 208 204 Meas. 206 20T Mole X Blank Pb Rad. Pb Rad+ComPt Common Pb Aqe J/. 9 ~? /?s~ 70 O Y?7f? Y39/2 O. oo/S~ o./% o.n? /60 206 Pb ., . 2lFl^^at,0 t 207 Pb .. ^ 235 U rat'° +-207 Pb „. ^ 206-p¥ rat'° * 206 Pb j , 238 U date -207 Pb . . ^ 235 U date ± 207 Pb j . 206-pb date ± R O. O2£~09 ±o. &oo/y C>./7/3 to.oaot O.oYfS'3 to.ooooC /ST. 7 - / * /60. £ -AC ?* bpli t-Mlneral ppm U ppm Pb 206 207 208 204 Meas. 206 20T Mole X Blank Pb Rad. Pb Rad+ComPt Common Pb Aqe 39.0*9 3? 83 /oo O.0003 3f 8SC / OO 206 Pb ,, , j^j-jj-ratlo + 207 Pb .. . 235 U rat'° ± 207 Pb ., . loTTb ratio i 206 Pb j . iwirdate ± 207 Pb j , ' , 235 U date ± 207 Pb j . 206-PF date t R 0./7J? ^O.ooof O.OY96/ ^O.ooccQ /7t>.? Spli t-Mineral ppm U ppm Pb 206 207 208 204 Meas. 206 20T Mole X Blank Pb Rad. Pb Rad+ComPt Common Pb Aqe 206 Pb .. 2lFTTratl° i 207 Pb ... 235 U rat'° * 207 Pb ., . WTb rati° t 206 Pb j . 2WTT date -207 Pb j ^ , 235 U datC -207 Pb j . 206-pb date t K + + + + + + Split-Mineral ppm U ppm Pb 206 207 208 204 Meas. 206 20T Mole X Blank Pb Rad. Pb Rad+ComPt Common Pb Aqe 206 Pb „. 2WTTrat,° t 207 Pb .. . 235 U rat'° ± 207 Pb ,. ^ loTTb rat'° t 206 Pb . . ^ i3inrdate i 207 Pb . . 235 U date -207 Pb j . 206-pb date t + + + + + + Spli t-Mi nera1 ppm U ppm Pb 206 207 208 204 H„c 206 Meas. —,-20T Mole % Blank Pb Rad. Pb Rad+ComPb Common Pb Aqe 206 Pb ., . 2irnrratl°^ 207 Pb ... 235 U rat'° t 207 Pb ... loTTb rat'° t 206 Pb . t ^ iTinrdate t 207 Pb j . 235 U date -207 Pb j . 206-Tb date t R + + + + + + - w Statement of Uncertainties: £trc.r-< aye 3 g- o/a-/rS' / <T /£r /So-fvp/c rii//oS Isotopic composition of blank: QS'K Modern Pb (6/4:18.7, 7/4 : 15 '63, 8/4 : 38.63) or f^jother (6/4 :/7 7J~7/4 :/SS 78/4 : 37.06 ) Isotopic composition of common Pb based on S-K growth curve: 6/4=11.152, 7/4=12.998, 8/4=31.23 at 3.7Ga with 238U/204Pb=9.74, 232Th/204Pb=37-19; decay constants 0.155125, 0.98485, 137-88; or Y~] Other (6/4: 7/4: 8/4: ) 147 U—.DK • Mineral analysis ~"rD •Concordia interpretation • Mineral or rock isochron Sample Number(s) and Reference(s)  Lab No: OsoynoS  Ref: /{ye* /f73 PL D rt^/l (NTS ^2 /?/3 T Record No:  Suite No: Sample Name: decay constant • old: 0.1537/0.9722/0.0499/137.8 Q-riew: 0.155125/0.98485/0.049475/137.88 • other: • not reported Upper Intercept 2a error Computed• Assumed • + Ma Lower Intercept 2a error Computed • Assumed • Ma 238,, 206DV , U- Pb date + Ma 235U-207Pb date + Ma 207Pb/206Pb date + Ma 232Th-208Pb date ' + Ma Number of Points : n= : 3 Latitude: Longitude: (X Y' Z" or X Y.Y') (V? °Or7.' /O " N, //f °JPS~'/0 " W (± ); Elevation:, UMT Zone Sec. , T (NTS N; Province: ,R. Co., State Pert//c/o^ OB S Map Area (1:250,000) Location: 3 JT/*I C/OIO«A>7/ /ro*, /oa/Coo/ o» ^t^y. 3j eai r* 0J Qsoy Source Type: roa-dcui- _ Rock Types: 9rt<?/Ss*~C 9rjttf»£//*r*'rif Geologic Unit7-: Unif 2i£ fiy4r?jil973)j G«e/L<.s eV (DSoyaoS in /^rA/rtScnT//?^ Geologic Setting: i«-bu<Je< 4*,a„,.l,L<+ ^QQJ> ' ' Material Analysed: JZ/'~e.at/l  Comment on Analyses: Interpretation: Collected by: R.L. 4r*HS-/rorl^  Dated bY: 2±L Park;nsnM Date of listing: Sample Name or Number: (j&oyooS y?e/SJ Sheet Split-Mineral ppm U ppm Pb 206 207 208 204 Meas. 2pF Mole % Blank Pb Rad. Pb Rad+ComPt Common Pb Aqe Fine Afa<?. 27 <c ~9 J /oo 7.6 3?/ 0 OOlCo 1/a.l o.a% J«o - '266 Pb . 2lB~U~rat,° ± 207 Pb _ 2V, U rat'° ± 207 Pb „. _ 206-Tb rat,° i 206 Pb . „ _ 238 u date -207 Pb . . _ 235 U date ± 207 Pb j . IbTTb datC * 003 ATS" -«O«D/7 300. a. - <__<2_ ao/.g ±20 JJQ 7 0 Split-Mineral ppm U ppm Pb 206 207 208 20k Meas. 206 2W Mole % Blank Pb Rad. Pb Rad+ComPt Common Pb Aqe pint A'»"/*f«^ O' (t r»f S7/ 3-7.7? /oo y. 6363 O. o/oS~ 0.7% O. 973 D3S~ 206 Pb ,, . 2l8-l^rat,0 ± 207 Pb _ 235 U rati°± 207 Pb „. _ IbTTb rat'° t 206 Pb _ _ . 238 U date -207 Pb , . _ 235 U date t 207 Pb j . IbTTb date i R OOSIlg tcxeoo/g ao/-7 -a.3. P03.0 - a.. % Spli t-Mlneral ppm U ppm Pb 206 207 208 Meas. 206 Mole % Blank Pb Rad. Pb Rad+ComPt Common Pb Aqe 3 7. S^f H7C 7. /3oS o. 000 5~ /% <Y(,S /.OO 3. ° 1 20b Pb . 2ifnrrat,° -207 Pb „. t  2„ „ ratio ± 207 Pb „, , loTTb raU° t 206 Pb j , 23TTT date -207 Pb . . _ 235 U date ± 207 Pb . „ _ loTTb date i R 0O3'f? to-ee./7 c-.Q3.o3 ±000/VL 0.05-o6"^ to.0O»'t- 3 00. S -bpli t-Mi nera1 ppm U ppm Pb 206 207 208 204 Meas. 20&L 20? Mole % Blank Pb Rad. Pb Rad+ComPt Common Pb Aqe 266 Pb . . 2TO-rat .ot 207 Pb . 2„ _ ratio + 207 Pb .. A loTTb rat,° * 206 Pb . . _ 2iinrdate i 207 Pb , . , 235 U date -207 Pb . . _ 206-Tb datC t + + + + + Split-Mineral ppm U ppm Pb 206 207 208 20*1 Meas. 206 20T Mole % Blank Pb Rad. Pb Rad+ComPt Common Pb Aqe 206 Pb „. _ 2nnrratio t 207 Pb „. _ 235 U rat'° ± 207 Pb , 206-Tb ratI° t 206 Pb . , _ iTinrdate t 207 Pb _ . , 235 U date -207 Pb . , _ IbTTb datG i + • + + + + -71 : :— Statement of Uncertainties: e^or^ ore 3- <r~ cia/Ts) I 0~~ -/o-y /So/pfi/C rezTitaS. _____ •.fc--V'4:.' Isotopic composition of blank: __JS-K Modern Pb (6/'4:l8.7, 1/h : 15,^3, 8/4 :38.63) or Hither (6/'(: /* 737/l( 7 8/4 J 7. OO ) Isotopic composition of common Pb based on S-K growth curve: 6/4=11.152,' 7/4=12.998, 8/4=31.23 at 3-7Ga with 238U/204Pb=9.7'i, 232Th/204Pb=37-19; decay constants 0.155125, 0.98485, 137.88; or ["J Other (6/4: 7/4: 8/4: ) 149 APPENDIX C - RB/SR ANALYTICAL TECHNIQUES Rb and Sr concentrations were determined by replicate analysis of pressed powder pellets using X-ray fluorescence. U.S. Geological Survey rock standards were used for calibration; mass absorption coefficients were obtained from Mo K-alpha Compton scattering measurements. Rb/Sr ratios have a precision of 2% (1 sigma) and concentrations a precision of 5% (1 sigma). Sr isotopic composition was measured on unspiked samples prepared using standard ion exchange techniques. The mass spectrometer, a V.G. Isomass 54 R, has data aquisition digitized and automated using a H.P. 85 computer. Experimental data have been normalized to a S6Sr/88Sr ratio of 0.1194 and adjusted so that the NBS standard SrC03 (SRM 987) gives a !7Sr/!6Sr ratio of 0.71020± 2 and the Eimer and Amend Sr a ratio of 0.7080012. The precision of a single 87Sr/86Sr ratio is better than 0.00010 (1 sigma). Rb-Sr dates are based on a Rb decay constant of 1.42 x 10" "y1. The regressions are calculated according to the technique of York (1967). 

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