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Alteration and infiltration : documenting controls on skarn formation at Mineral Hill, Sechelt, southwestern.. McConaghy, Katharine R. 2001

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A L T E R A T I O N AND INFILTRATION: DOCUMENTING C O N T R O L S ON SKARN FORMATION A T MINERAL HILL, SECHELT, S O U T H W E S T E R N BRITISH C O L U M B I A by K A T H A R I N E R. M C C O N A G H Y B.A. Western State College of Colorado, 1998  A THESIS SUBMITTED IN PARTIAL F U L F I L L M E N T OF T H E REQUIREMENTS FOR T H E D E G R E E OF M A S T E R OF SCIENCE in T H E F A C U L T Y OF G R A D U A T E STUDIES (Department of Earth and Ocean Sciences)  We accept this thesis as conforming to the required standard  T H E UNIVERSITY OF BRITISH C O L U M B I A July, 2001 © Katharine R. McConaghy, 2001  UBC Special Collections - Thesis Authorisation Form  http://www.library.ubc.ca/spcoll/thesauth.html  In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f the r e q u i r e m e n t s f o r an advanced degree a t the U n i v e r s i t y o f B r i t i s h Columbia, I agree t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y purposes may be g r a n t e d by the head o f my department o r by h i s o r her r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t copying or p u b l i c a t i o n of t h i s thesis for f i n a n c i a l gain s h a l l not be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n .  Department The U n i v e r s i t y o f B r i t i s h Columbia Vancouver, Canada  1 of 1  25/07/01 1:34 PM  ABSTRACT  The Mineral Hill wollastonite deposit is hosted by a north-west trending calcareous roof pendant enclosed within Late Jurassic plutons of the southwestern Coast Plutonic Complex. The study area consists of calcite marble, other meta-sediments and skarn in contact with a dioritic component of the Crowston Lake Pluton. The area is cross-cut by two Cretaceous-aged dike generations (D2 and D3). Detailed mapping, petrography, petrology and O and C stable isotope analyses has led to the interpretation of a complex infiltration history of the study area. High temperature mineral 18  production (i.e. wollastonite), skarn  16  0/  O ratios, and extensive SiC>2 metasomatism indicate  magmatic volatiles infiltrated and exchanged with the roof pendant during Late Jurassic pluton emplacement creating spatially extensive wollastonite and garnet skarn. Homogeneously depleted marble 0 values near the wollastonite skarn boundary require interaction with a low 18  8 0 fluid (meteoric) at high temperatures. Because very low 5 0 values (< 5 permil) for marble 18  18  are spatially associated with the pluton, and because both D2 and D3 dikes preserve textures that indicate a cold crust at the time of emplacement, a high temperature meteroic fluid must have 18  infiltrated pre- to syn- skarn formation during the Late Jurassic. Finally, low 5 O values io  preserved in D2 and D3, require at least one low 8 O fluid interaction event either during Cretaceous syn-dike emplacement (D2 and D3, or D3) as a response to thermal activity or during a post-Cretaceous high temperature event. This study also documents the nature and evolution of permeability at the wollastonite skarn/marble boundary within a 450 m by 150-200 m map area. Because syn-metamorphic permeability is destroyed by compaction, I used reaction transport theory to deduce paleo-fluid flow geometry. The distribution of multiple tracers (i.e. SiO*2, degraphitization, and 0 / 0 ) are 18  16  used in order to distinguish between infiltration sides in which flow is parallel to the alteration  Ill  boundary and infiltration fronts in which flow is perpendicular to interface geometry. At Mineral Hill, a dominance of infiltration sides and field observations support an irregular and interfingering contact between wollastonite skarn and marble. This geometry may be controlled by reaction infiltration instabilities (RII) at the reaction front which are derived from positive feedback coupling between infiltration and reaction [Ortoleva et al, 1987]. RII requires dissolution at the reaction front which allows fluid to focus into areas of high permeability.  T A B L E OF CONTENTS  ABSTRACT  .ii  T A B L E OF CONTENTS  iv  LIST O F T A B L E S  viii  LIST O F FIGURES  ix  LIST O F P L A T E S  xiv  ACKNOWLEDGEMENTS  xv  C H A P T E R 1: O V E R V I E W  .'.  1  1.1 Introduction  1  1.2 Regional Geology  4  1.3 Local Geology  6  1.3.1 Introduction  6  1.3.2 Structure  8  1.3.3 Prograde Skarn Episodes  15  1.3.4 Summary of results: overview  21  C H A P T E R 2: R O C K UNIT DESCRIPTIONS  23  2.1 Intrusive rocks  23  2.1.1 Crowston Lake Pluton  23  2.1.2 Monzonite  25  2.1.3 DI: Gabbroic dikes and sills-first generation  25  2.1.4 D2: Tonalitic dikes and sills-second generation  28  2.1.5 D3: Basaltic dikes-third generation  29  2.2 Meta-sedimentary and Skarn Units 2.2.1 Marble Green Marble  31 31 31  Grey and Bleached Marble  40  2.2.2 Quartzite  41  2.2.3 Skarnoid  45  2.2.4 Skarn  45  Wollastonite skarn Clinopyroxene skarn Garnet-wollastonite skarn Garnet skarn Garnetite  46 48 48 51 53  C H A P T E R 3: W H O L E - R O C K C H E M I S T R Y - I N F I L T R A T I O N A N D P R O T O L I T H CONTROLS ON SKARN FORMATION 56  3.1 Introduction  56  3.2 Method of Investigation  56  3.2.1 Inter-laboratory comparison  82  3.3 Intrusive rocks  82  3.4 Meta-sedimentary and skarn units  95  3.4.1 Meta-sedimentary Rock Compositions Vassalboro/ Sangerville Formation Waterville Formation Giles Mountain and Waits River Formations Roof Pendant at Hope Valley, CA 3.4.2 Geochemical trends in Meta-sedimentary Rocks Vassalboro/ Sangerville Formation Waterville Formation Giles Mountain and Waits River Formations Roof Pendant at Hope Valley, CA 3.4.3 Meta-sedimentary and Skarn rock compositions at Mineral Hill Marble Skarn  97 97 98 98 100 100 100 101 101 103 104 104 105  Wollastonite skarn Clinopyroxene skarn Garnet-wollastonite skarn Garnet skarn Garnetite  Calc-Silicate Skarnoid  105 106 106 107 107  108  Quartzite  108  3.5 Discussion  108  3.6 Distribution of Minerals in Calcic Exoskarn at Mineral Hill  Ill  3.6.1 Introduction  Ill  3.6.2 Skarn Zonation  112  Garnet zone Clinopyroxene zone Wollastonite zone Hydrothermally altered skarn  113 119 119 119  3.7 Marble to Wollastonite Skarn Transformation-Quantification of transient synmetamorphic permeability 120  3.7.1 Introduction  120  3.7.2 Mass Balance  122  Background  122  3.7.3 Results  126  Element Ratios  126  Fluid-rock ratios and time-integrated fluid fluxes for silica metasomatism Rare Earth Element patterns  130 150  3.7.4 Discussion  158  C H A P T E R 4: S T A B L E ISOTOPIC A N D P E T R O L O G I C E V I D E N C E F O R P E R M E A B I L I T Y E V O L U T I O N A N D T I M I N G O F I N F I L T R A T I O N EVENTS..161 4.1 Introduction  161  4.2 Method of Investigation  164  4.3 Carbonates  169  4.4 Silicates  177  4.4.1 Intrusive rocks  179  4.4.2 Skarn  179  Wollastonite skarn Garnet-wollastonite  skarn  179 183  Garnetite  184  Clinopyroxene skarn  184  4.4.3 Skarnoid  184  4.4.4. Quartzite  184  4.4.5 Clinozoisite Augen (in Black Marble)  184  4.5 Wollastonite skarn-marble interface  185  4.6 5 O variation of wollastonite skarn and marble  194  4.7 Discussion  196  4.8 Infiltration History  197  l s  4.8.1 Magmatic fluid event  198  4.8.2 Meteoric fluid event(s)  198  Prograde meteoric fluid event. Evidence from low 8 0 signatures in marble Timing of hi-T meteoric fluid event 18  Retrograde meteoric fluid event(s) Evidence from low 8 0 signatures in igneous and skarn units Timing of retrograde meteoric fluid event(s) I 8  4.9 Nature and evolution of syn-metamorphic permeability  198 198 200  202 202 205  .....206  4.9.1 Introduction  206  4.9.2 Background  206  4.9.3 Reaction Transport Theory: One-dimensional distribution of multiple reaction fronts 208 4.9.4 Reaction-infiltration instabilities at the skarn front: implications on flow geometry 215 4.10 Conclusions  216  REFERENCES  218  A P P E N D I X 1: S T R U C T U R A L M E A S U R E M E N T S  225  Vlll  LIST O F T A B L E S Table  Page  1.1  Notation for minerals and rocks  3  2.1  Mineral assemblages of intrusive rocks at Mineral Hill  24  2.2  Mineral assemblages of meta-sedimentary and skarn samples at Mineral Hill  32  2:3  Peak mineral assemblage for meta-sedimentary and skarn samples from Mineral Hill  36  3.1  Whole-rock chemical analyses from Mineral Hill (McGill University)  58  3.2  Whole-rock chemical analyses from Mineral Hill (ALS Chemex)  60  3.3  Selected igneous major-element whole-rock analyses from Mineral Hill from Ray and KUby [\996\ 63  3.4  Chemical compositions of common sedimentary rocks  81  3.5  End member chemical formulas for selected minerals  83  3.6  Mean variability of compared inter-laboratory elements and corresponding standard deviation 86  3.7  Mineral evolution of Giles Mountain and Waits River sediments  99  3.8  Skarn mineralogy- common minerals, mineral groups and compositions  114  3.9  Notation for equations in Chapter 3  124  3.10  Geochemistry of type A skarn, type B skarn, and marble  131  3.11a  Mass factors and volume factors for average compositions  136  3.11b  Mass factors for the transformation of average marble to wollastonite skarn based on immobility of A 1 0 and V 137 2  3  3.12  Gains/losses of components  139  3.13  Fluid-rock ratios and time-integrated fluid flux calculations over duration of silica metasomatism  148  3.14  R E E concentrations in marble and wollastonite skarn samples normalized to chondrite values . 1 5 1  ix  4.1  Notation for oxygen and carbon isotopes  163  4.2  O and C stable isotope data for samples from Mineral Hill  165  4.3  Mean and l o for blind duplicate analyses 5 C and 8 0 compositions  168  13  18  LIST O F F I G U R E S Figure  Page  1.1  Location of study area  2  1.2  Geologic map of Mineral Hill  7  1.3  Contoured stereonet of compositional layering structural measurements for Middle Bench, Upper Bench, Top Bench and Upper Marble Quarry locations  9  1.4  Detail map of Upper Bench, Top Bench and Upper Marble Quarry and structure localities 10  1.5  Detail map of Middle Bench and Lower Bench and structure localities  1.6  Contoured stereonet of compositional layering structural measurements for Marble Hill and igneous rocks 12  1.7  Structural Map of Marble Hill and sample localities  13  1.8  Detail map of Middle Bench and Lower Bench and sample localities  14  1.9  2 meter by 2 meter grid map #1  16  1.10  2 meter by 2 meter grid map #2  17  1.11  2 meter by 2 meter grid map #3  18  1.12  Detail map of Upper Bench, Top Bench and Upper Marble Quarry and sample localities 20  2.1  Detail map of North-east Extension and Marble Hill and sample localities  26  2.2  Schematic of metasomatic vs. thermal production of wollastonite  42  2.3  Schematic of wollastonite skarn and marble boundary types seen in Mineral Hill samples  43  Sketch from field notebook of quartzite outcrop, cut by irregular mafic dike with inclusions of quartzite  44  3.1  A S C ternary diagram (all iron in compiled data converted to Fe203)  65  3.2  ASF ternary diagram (all iron in compiled data converted to Fe203)  67  3.3  SFC ternary diagram (all iron in compiled data converted to Fe203)  69  3.4  A C F ternary diagram (all iron in compiled data converted to Fe203)  71  2.4  11  3.5  A S C ternary diagram (all iron in compiled data converted to FeO)  73  3.6  ASF ternary diagram (all iron in compiled data converted to FeO)  75  3.7  SFC ternary diagram (all iron in compiled data converted to FeO)  77  3.8  A C F ternary diagram (all iron in compiled data converted to FeO)  79  3.9  Inter-laboratory comparison of absolute abundances  84  3.10  Inter-laboratory comparison relative to detection limit  84  3.11  Inter-laboratory comparison of relative abundances  85  3.12  A S C ternary projections for samples submitted to McGill University and ALS Chemex  87  ASF ternary projections for samples submitted to McGill University and ALS Chemex  88  A C F ternary projections for samples submitted to McGill University and ALS Chemex  89  3.13  3.14  3.15  SFC ternary projections for samples submitted to McGill University and ALS Chemex  90  3.16  Chemical classification of Crowston Lake Pluton and D1  92  3.17  Metaluminous compositions of Crowston Lake Pluton and D1  93  3.18  Chemical classification of D2 and D3  94  3.19  Metaluminous compositions of D2 and D3  96  3.20  Geologic map of study area with zonation patterns  115  3.21  Schematic illustrating rock history of a marble infiltrated by magmatic fluid carrying aqueous Fe, A l and Si02 116  3.22  Time vs. distance schematic of reaction transport of two fronts with different propagation rates 118  3.23a Element Ratio plot of T i 0 vs. A 1 0 2  2  3  127  3.23b Element Ratio plot of Zr vs. AI2O3  127  3.23c Element Ratio plot of V vs. AI2O3  128  3.23d Element Ratio plot of Yb vs. A 1 0 2  3.23e Element Ratio plot of Y vs. A1 0 2  3  3  128 129  3.24a R E E pattern for marble samples  155  3.24b R E E pattern for wollastonite skarn type A and B samples  155  3.24c R E E pattern for garnet skarn samples  156  3.25a R E E concentrations of marble samples compared to wollastonite skarn B  157  3.25b R E E concentrations of marble samples compared to wollastonite skarn A  157  3.26  R E E pattern for marble, wollastonite skarn A and wollastonite skarn B samples  159  4.1  Detail map of Upper Bench, Top Bench and Upper Marble Quarry and O, C stable isotope values and locality  170  Detail map of Middle Bench and Lower Bench and O, C stable isotope values and locality  171  4.2  4.3  Detail map of North-east Extension and Marble Hill and O, C stable isotope values and locality 172  4.4  Structural Map of Marble Hill and O, C stable isotope values and locality  173  4.5  5 0 vs. powder type for marble samples from Mineral Hill  174  4.6  8 C vs. powder type for marble samples from Mineral Hill  174  4.7  5 0 compositions of Mineral Hill samples  175  4.8  5 0 isotopic differences between spatially related grey and bleached marble and wollastonite skarn and marble  176  4.9  8 C compositions of Mineral Hill marble samples  178  4.10  Silicate 8 0 compositions of meta-sedimentary and skarn rock samples  180  4.11  8 0-values of important geological reservoirs  181  4.12  5 0 compositions vs. alteration index for igneous rocks from Mineral Hill  182  4.13a  Centimeter-scale oxygen isotopic shifts in grid map sample GMla(U)  186  4.13b  Centimeter-scale oxygen isotopic shifts in grid map sample GMla(L)  187  18  1 3  18  18  1 3  1 8  18  18  xiii  4.13c  Centimeter-scale oxygen isotopic shifts in grid map sample GMle(L)  188  4.13d  Centimeter-scale oxygen isotopic shifts in grid map sample GMle(R)  189  4.13e  Centimeter-scale oxygen isotopic shifts in grid map sample G M l f  190  4.13 f  Centimeter-scale oxygen isotopic shifts in grid map sample GM1 g  191  4.13g  Centimeter-scale oxygen isotopic shifts in grid map sample GMla(UR)  192  4.13h  Centimeter-scale oxygen isotopic shifts in sample BM-1 from the Middle Bench  193  4.14  8 0 isotopic compositions for all samples collected at Mineral Hill  199  4.15  5 0 (cc-H 0) vs. temperature plot  201  4.16  Schematic showing spatial distribution of low 8 0-values in marble in reference to a lobate front and implications for timing of fluid event 203  4.17  Fluid history associated with igneous activity at Mineral Hill  204  4.18  Schematic of lobate vs. planar fronts  207  4.19  8 0 vs. distance plot relative to wollastonite skarn-marble contact  210  4.20  8 0 vs. distance plot with range of 10 centimeters outboard and inboard of the wollastonite skarn-marble boundary  212  8 C vs. distance plot of marble samples relative to the wollastonite skarn-marble contact  214  4.21  18  18  2  18  18  18  I3  LIST O F P L A T E S Plate 2.1  Page Rigidly boudinaged gabbroic sill within compositional layered garnet skarn  27  2.2  D2 tonalitic sill fractures infilled with epidote  27  2.3  Ductile boudinaged tonalitic sill cross cut by later basaltic dike  30  2.4  Reaction skarn on the margin of a D3 basaltic dike  30  2.5  Green marble within garnetite  39  2.6  Skarnoid cliff exposure  39  2.7  Grid map locality showing interfingering relationship of wollastonite skarn and marble boundary 47  2.8  Classic 'augen' within banded grey and bleached marble  47  2.9  Microphotograph of garnet infilling late-porosity around clinopyroxene grains  49  2.10  Compositionally-layered garnet-wollastonite skarn  50  2.11  Microphotograph of garnet-wollastonite skarn  50  2.12  Compositionally-layered garnet skarn  52  2.13  Ductile deformation of wollastonite veins within garnetite  54  2.14  Brittle deformation of wollastonite veins within garnetite  54  XV  ACKNOWLEDGMENTS  Foremost, I would like to thank my supervisor Greg Dipple for remaining enthusiastic about this project. His candid personality made him a joy to work with and I thank him for his great perspective and patience. He is not only a great advisor, but a brilliant and encouraging teacher for whom I hold in the highest regards. I would also like to thank Mati Raudsepp and Steve Rowins for being on my committee. Thanks to Rudy Riepe and his family for not only allowing me to study skarn on their property, but for also sharing their home. I thank Rudy Riepe for always being energetic, generous and sharing his vast knowledge of geology, Greg Riepe for being an excellent and hard-working field assistant, and Connie Riepe for opening her heart to a stranger in a way that should truly be commended. I am grateful to the office and technical staff in the Department of Earth and Ocean Sciences. Beyond doubt, they are the most important and helpful people in the building. Without them, I would have run circles around myself and what took three years to complete would have taken five. Finally, I'd like to give a shout out to all my homies in the house: yo homies! In particular, I'd like to thank my boyz Slinky K and Brudda Is for starting it all off and keeping me sane (by comparison). I have never met such polar opposites who kept me so enthralled by their mere presence. I owe much more to these two than I can express. I leave with this thought: as sculptor Henry Moore once declared to poet Donald Hall, "The secret to life is to have a task, something you devote your entire life to, something you bring everything to, every minute of the day for your whole life. And the most important thing is~ it must be something you cannot possibly do."  1 C H A P T E R 1: O V E R V I E W 1.1 Introduction  The Mineral Hill property is located approximately 60 kilometers due west-north-west of Vancouver and 5.5 kilometers north of Sechelt on the Sechelt Peninsula of British Columbia. The Sechelt Peninsula is located at the south-western end of the Coast Plutonic Complex (CPC), a north-west-trending concentration of Late Jurassic to Tertiary plutonic rocks, and is comprised of elongated and deformed calcareous roof pendants. The majority of these roof pendants are tentatively correlated to carbonates of the Upper Triassic Quatsino Formation [Ditson, 1987; Ray and Kilby, 1996]. At Mineral Hill, a north-west-trending pendant is completely enclosed by the Late Jurassic Crowston Lake and Snake Bay Plutons. These intrusions vary in composition from gabbro to quartz-diorite and quartz-diorite to granodiorite, respectively, and are likely responsible for altering the host sediments to calcite and dolomite marbles and calcic exoskarn (i.e. sedimentary protolith). The study area at Mineral Hill is located in a 450 meter by -200 meter south-eastern portion of the pendant (see Fig. 1.1). The study area consists of calcite marble, other metasediments and skarn in contact with a dioritic component of the Crowston Lake Pluton. Late dike phases (D2 and D3) crosscut marble and skarn units. Chapter Two of this thesis documents the rock units sampled within the study area at Mineral Hill in terms of field, textural and petrographic descriptions. Intact samples (I) were taken directly from outcrop as well as fall rock (FR) collected from loose material usually located below outcrops of similar lithology. Petrographic descriptions of units are provided in terms of mineral assemblages (prograde and retrograde), peak-metamorphic equilibrium phases, and macro- and micro textures observed in the field and using optical and scanning electron microscopy (SEM) (Notation defined in Table 1.1). Chapter Three describes rock units in terms of their whole-rock geochemistry, interprets  2  1 *3 3 ft  c  c o  Table 1.1. Notation for minerals and rocks Minerals  apatite chlorite biotite zeolite ttn titanite pyr pyrite ser sericite apo apophyllite grossular gr gnt garnet plagioclase feldspar pl ksp potassium feldspar graphite gph phi phlogopite muse muscovite ent enstatite elz clinozoisite woll wollastonite CC calcite opq opaques apa  chl bt zeo  ank alb qtz rut par ilm olig amph St ky an pyr spe andr hed di  Rocks  g-w skarn woll skarn gnt skarn gr marble cpx skarn qtz vein bk marble g-b marble  garnet-wollastonite skarn wollastonite skarn garnet skarn green marble clinopyroxene skarn quartz vein black marble grey and bleached marble  ankerite albite quartz rutile paragonite ilmenite oligoclase amphibole staurolite kyanite anorthite pyrope spessartine andradite hedenbergite diopside  geochemical controls of skarn zonation, estimates volume change caused by reaction of marble to form wollastonite skarn, fluid-rock ratios and time-integrated fluid fluxes over the duration of skarn formation. Whole-rock compositions of all meta-sedimentary and skarn units within the study area are plotted in A-S-C-F ternary space and graphically compared to seven metasedimentary units documented in the literature, twelve common sedimentary rocks, and endmember chemical compositions of eleven minerals. Igneous whole-rock chemistry from this study were augmented with data from Ray and KUby [1996] and classified using five NEWPET plots. Petrographic and petrologic data and observations are used to estimate volume changes caused by reaction from marble to wollastonite skarn, through graphical passive enrichment of immobile elements (element ratios) and calculations using Grant's [1986] mass balance approaches. Moreover, reaction transport theory is used to interpret geochemical controls (infiltration vs. protolith) on zonation of skarn in the study area. Chapter Four describes the stable isotope geochemistry of all units in respect to common oxygen and carbon reservoirs. The nature and evolution of permeability during skarn formation is delineated by the spatial extent of multiple reactions (alteration fronts): SiO*2, degraphitization, and 0 / 0 . The distinction 18  16  between infiltration sides and infiltration fronts due to the distribution of multiple tracers allows us to image the flow geometry at the wollastonite skarn/marble interface. Finally, the complex fluid history in the field area recorded by oxygen isotope alteration in skarn, marble and igneous units is interpreted.  1.2 Regional Geology The Coast Plutonic Complex (CPC), a northwest trending belt approximately 1700 km long and 50-175 km wide, is the largest single concentration of plutonic rock on the western North American margin [Friedman et al, 1995]. It is composed of Jurassic- to Tertiary-aged plutonic rocks which represent a suite of subduction-related magmatic intrusions which conceal  5  the contact between the morphogeological Insular and Intermontane belts of the Canadian Cordillera [Friedman et al, 1995; Cui and Russell, 1995]. The CPC makes up a substantial part of the Coast Belt which Journey and Freidman [1993] subdivided into eastern, central, and western structural and lithological domains. Moreover, the CPC has been subdivided into northern and southern isotopic domains. Nd and Sr isotopic data for plutonic rocks from the northern CPC show dominantly Late Cretaceous-Tertiary intrusions to have been contaminated by juvenile material and "old, recycled crustal material" [Samson et.al., 1991]. On the basis of Nd, Sr, and Pb radiogenic isotope characteristics, Cui and Russell [1995] concluded that Late Jurassic to Late Cretaceous intrusions in the southern CPC are juvenile in origin and resulted from partial melting of mantle-derived materials with little to no interaction with old continental crust. However, these intrusions may have had chemical interaction with older, isotopically primitive terranes (e.g. Wrangellia). Friedman et al. [1995] concluded that the Coast Plutonic Complex in the southwestern portion of the southern Coast Belt was generated in an isotopically juvenile magmatic arc. Here, the CPC intrudes the Wrangellian terrane, currently preserved primarily as deformed roof pendants [Friedman et al, 1995]. The Wrangellia terrane is primarily comprised of rocks of oceanic and volcanic arc affinity, which are dominated by juvenile isotopic values. The Mineral Hill property lies in the Caron Mountain Range, specifically within the Crowston Lake and Snake Bay Plutons of the southern CPC, southwestern British Columbia. The plutons at Mineral Hill were mapped as an early Coast Plutonic suite of granitic rock. Earlier authors associate pluton emplacement in the Late Jurassic inferred through correlation with similar intrusive bodies that have been dated by isotopic methods [Ray and Kilby, 1996]. They intrude amphibolites, marble and meta-volcanics correlated with Wrangellian strata [Roddick and Woodsworth, 1979; Friedman and Armstrong, 1995]. The meta-sediments studied at Mineral Hill are part of a roof pendant preserved within the Crowston Lake Pluton, which ranges in  6  composition from gabbro to quartz diorite [Ray and KUby, 1996]. The roof pendant at Mineral Hill is a discontinuous, elongate, northwestwardly trending belt. Various stages of intense deformation are observed within the pendant including isoclinal folding of metasediments and skarn and boudinaged early and late igneous sill phases (DI and D2). Although the pendant has not been dated, it is believed to be comprised of Upper Triassic Vancouver Island Group sediments. Units of layered to massive, fine to medium grained mafic metatuffs and metabasalts located in the northern portion of the roof pendant at Mineral Hill may be members of the Triassic Karmutsen Formation or the Jurassic Bowen Island Group metavolcanic sequence [Ray and KUby, 1996]. The calcic to dolomitic meta-sediments are tentatively correlated with the Triassic Quatsino Formation [Goldsmith and Kallock, 1988; Ray and KUby, 1996]. The unaltered Quatsino Formation of Vancouver Island is generally comprised of a gradational sequence between lower and upper limestone members. The lower member is a massive to poorly bedded, pure to cherty limestone. The cherty inclusions are dark-grey to brown-grey and occur at many levels within the member [Eastwood, 1968; Muller et al, 191 A; Jeletzky, 1976]. The upper member is predominantly medium to thinly well-bedded argillaceous limestones, which commonly contain nodules and laminations of brown-grey, dark-grey and black chert [Eastwood, 1968; Muller, et al, 1974; Jeletzky, 1976]. In the study area, the roof pendant is comprised of similar calcic sediments. No pre-Jurassic volcanic rocks are observed.  1.3 Local Geology 1.3.1 Introduction The study area at Mineral Hill is located in a 450 meter by -200 meter southeastern area of the northwest-trending pendant (see Fig. 1.1). The study area consists of calcite marble, other meta-sediments and skarn in contact with a dioritic component of the Late Jurassic Crowston Lake Pluton (Fig. 1.2). The intrusion is likely responsible for thermal and metasomatic alteration  7  Igneous Units Crowston Lake pluton  ^ Q  I I I I ri 1  1  1  1  1  1  l  L  •  Gabbro dikes and sills Monzonite  §§|  Tonalite dikes and sills  Si  Basalt dikes and sills  Units Marble Garnet-wollastonite skarn Wollastonite skarn  •  Garnet skarn Hydrothermallyaltered skarn Skarnoid Zone Marble Eg  Wollastonite zone  |||  Garnet zone Inferred pluton  \  Compositional layering Dike orientation  —  Contact  \  Inferred contact ****** Fault  Fig. 1.2. Geologic map of Mineral Hill. Locations of Upper Bench, Top Bench, Middle Bench, Lower Bench, Upper Marble Quarry, North-east extension, and Marble Hill are labelled. Map and sample locations shown in greater detail in Figs. 1.12, 1.7, 1.8, and 2.1. Other areas (central area on map) were mapped by Goldsmith and Kallock [1988] and compiled here. General structure of the area included. Marble Hill inset in Fig. 1.7.  sap- "  7  Igneous Units •j ™  Crowston Lake pluton Gabbro dikes and sills  T  T  5  Monzonite Tonalite dikes and sills Basalt dikes and sills  D3  Units Marble Garnet-wollastonite skarn  •  Wollastonite skarn Garnet skarn Hydrothermallyaltered skarn Skamoid  Zone  Marble Wollastonite zone Garnet zone Inferred pluton J? \ \  Compositional layering Dike orientation Contact Inferred contact Fault  F i g . 1.2. G e o l o g i c m a p o f M i n e r a l H i l l . L o c a t i o n s o f Upper Bench, Top Bench, Middle Bench, Lower B e n c h , U p p e r M a r b l e Q u a r r y , North-east e x t e n s i o n , and M a r b l e H i l l are l a b e l l e d . M a p a n d s a m p l e l o c a t i o n s s h o w n i n greater detail i n F i g s . 1 . 1 2 , 1 . 7 , 1.8, a n d 2.1. O t h e r areas (central area o n m a p ) w e r e m a p p e d b y Goldsmith and Kallock [1988] a n d c o m p i l e d here. G e n e r a l structure o f the area i n c l u d e d M a r b l e H i l l inset i n F i g . 1.7.  METRES  8  of host sediments to calcite marble and calcic exoskarn. Tonalitic and basaltic dike phases, D2 and D3, respectively, crosscut marble and skarn units, whereas gabbroic and tonalitic sill phases, DI and D2, conform with compositional layering defined by meta-sedimentary and skarn units.  1.3.2 Structure Skarn and meta-sediment units within the field area are intensely deformed. Goldsmith and Kallock [1988] mapped and diamond-drilled within the study area. They noted that primary bedding/compositional layering was accentuated by banded skarn assemblages (i.e. garnet skarn) and that the original limestone bedding had been transposed during plastic deformation. They also defined the structure of the area which was confirmed by structural measurements taken during detailed quarry mapping in this study (App. 1). The structure defined by compositional layering suggests a regional fold in the central portion of the map area (Fig. 1.2). Structure measurements taken during field mapping (this study) reveal compositional layering in the Top Bench, Upper Bench and Upper Marble Quarry generally trends north-east/south-west and dips near vertical to the northwest (Figs. 1.3b and 1.4). Although, there is a greater degree of variation in compositional layering possibly due to a fault and/or proximity to the Crowston Lake Pluton, structure in the middle bench is similar (Figs. 1.3a and 1.5). Compositional layering at Marble Hill, north of the aforementioned map areas, generally trends north-west/ south-east, and dips near vertical, confirming a change in strike direction and suggest the existence of a regional fold (Figs. 1.6 and 1.7). Dikes D2 and D3 are localized in the fold axis. These dikes strike predominantly to the east and dip near vertical (Figs. 1.6b and 1.5). D2 sills within the axis have ductile boudinage structures. Some DI dikes have the same trend, however, three DI structures strike north-west/south-east and have a shallower dip (Fig. 1.6b). Compositional layering of marble and skarn units proximal to the Crowston Lake Pluton generally strike parallel-tosubparallel to the contact (Figs. 1.8 and 1.7).  9  B) •'  /"' "  '  m  \  •  V  +8S m  1  \  +6S  1  !  i  •  *  • \ • ...  \  \  \  r  ^  / _  —  •  m  \  /  v  A  +4S •2S ~ E  —  Fig. 1.3. A) Contoured stereonet of compositional layering measurements from Middle Bench suggest NE-SW strike direction and near vertical dip direction although variation exists (see Fig. 1.6). B) Contoured stereonet of compositional layering measurements from Upper Bench, Top Bench, and Upper Marble Quarry suggest NE-SW strike direction and near vertical dip direction (see Fig. 1.4).  10  II  A)  •  \  1 1  i l l  • 1  II  — +2S  N =  n  N i  ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^  B) I /*  •  *  |  1  !  1  1  •  \  • \ ^  ••  •  • •  |  1  1  /  . y  N»40  Fig. 1.6. A) Contoured stereonet of compositional layering measurements from Marble Hill suggest NW-SE strike direction and near vertical dip direction (see Fig. 1.8). B) Stereonet of structural measurements of igneous dikes and sills. Red= DI, orange= D2, green= D3. Generally all dike generations strike east with a near vertical dip. Three DI strike to the N W with an average dip of -60 degrees (see Fiff. 1.2).  13  ,MN  20  o \  Compositional layering Contact Inferred contact  ****** Fault  Fig. 1.7. Structural map of Marble Hill (H) [inset; Fig. 1.2 and Fig. 2.1] and sample localities. See Fig. 1.9 for grid map #1 sample localities /s3  14  Brittle deformation is observed as faults within meta-sediments, skarn, and all igneous units (including D3) (Figs. 1.4, 1.5 and 1.7). Retrograde skarn assemblages are observed primarily in the proximity of brittle faults and pluton contacts. Two main faults have been mapped on the Mineral Hill property by previous workers outside of the study area: the northnorthwesterly trending and near vertical (80-90 degree) Wormy Lake Fault (WLF) and the more east-west trending steeply dipping Snake Creek Fault (SCF) [Ray and KUby, 1996; Murphy, 1999] (Fig. 1.1). The WLF is parallel to the regional northwest trend and has approximately 800 meters of sinistral movement. The SCF cross cuts and displaces the WLF approximately 2 kilometers to the west by dextral movement. Murphy [1999] contends that dextral movement cut off, ductily deformed and drag folded skarn. Extension on the eastern side of the roof pendant resulted in brittle tension fractures (intruded by later dike phases). On the western boundary, shortening is observed by compressional crenulation folds. Moreover, dextral displacement along the SCF shifted a large portion of the Crowston Lake Pluton to the west [Murphy, 1999].  1.3.3 Prograde Skarn Episodes Ray and KUby [1996] identified three prograde skarn episodes associated with igneous activity at Mineral Hill. The first skarn episode is the most spatially extensive and accompanied the intrusion of the Late Jurassic Crowston Lake Pluton and associated gabbroic dikes and sills (DI). Skarn is characterized by garnet-wollastonite-pyroxene mineral assemblages. Ductile deformation includes intense flow folding (isoclinal) as well as boudinaged DI sills. The first skarn episode is the main focus of this study and was mapped within a 450m by ~200m area. The interface of the skarn front and marble pendant was mapped within 2m by 2m map areas (Fig 1.9, 1.10, and 1.11) in order to document the skarn geometry and alteration outboard the skarn front. The interface occurs as wollastonite skarn in contact with proximal bleached marble to distal grey marble (see Fig. 1.11). Bleached marble rarely extends more than a few centimeters  Grid Map1 (GM1)  fine-grained wollastonite s k a r n  grey marble  c o a r s e - g r a i n e d wollastonite s k a r n  quartz v e i n  garnet-bearing wollastonite s k a r n  outcrop c o v e r e d  b l e a c h e d marble  calcite v e i n grid orientation 032/66NE  Fig. 1.9. Grid Map 1. Scale is 2 meters by 2 meters. Sample localities in black boxes and labeled according to sample designation (i.e. sample GMla(U), came from locality a(li)). Stable isotope values for each area presented in Table 4.1. Petrography presented in Table 2.2. Geochemistry presented in Table 3.2.  17  Grid Map 2 (GM2)  1  J —  fine-grained wollastonite s k a r n  outcrop c o v e r e d  b l e a c h e d marble  grid orientation 290/55NE grey marble  Fig. 1.10. Grid Map 2 is located directly above (in outcrop) GM1 (see Fig. 1.9) at Marble Ffill. Scale is 2 meters by 2 meters. No samples were collected from GM2.  18  Grid Map 3 (GM3)  | grey marble  Fig. 1.11. Grid Map 3 is located in the Upper Marble Quarry. Scale is 2 meters by 2 meters. No samples collectedfromGM3.  19  outboard of wollastonite skarn. Moreover, the interface does not represent a planar boundary, but occurs as fingering lobes of wollastonite skarn extending irregularly into marble (see Figs. 1.9 and 1.10). This geometry suggests fluid infiltration into pervious rocks, where fluid is not restricted to structural conduits. Mechanisms allowing fluid infiltration into rocks undergoing metamorphism in which permeability is essentially destroyed by compaction is described later in this thesis. Porphyritic tonalitic dikes and sills (D2), the second pulse of igneous activity, intrude skarn and marble. Ray and KUby [1996] observed D2 crosscutting the Crowston Lake Pluton. Garnet-epidote reaction skarn is observed along the margins of D2 but is not observed to exceed two centimeters in width. Reaction skarn differs from the first skarn-forming event since the introduction of exotic components outside the sedimentary section is not required even though metasomatic zoning is displayed. Reaction skarn often forms due to the local exchange of fluid (bimetasomatism) by diffusive mass transfer in which fluid travels no more than a few centimeters [Einaudi and Burt, 1982]. Boudinaged D2 sills are fractured parallel to stretching. These fractures are infilled with epidote. D2 are altered proximal to the fractures, observed as color change from dark to light green in hand sample and greater plagioclase abundance in thin section. Emplacement of basaltic dikes (D3) cross-cutting boudinaged D2 sills represent the final pulse of igneous activity in the field area. These dikes predominantly strike east and in places show brittle deformation features (e.g. Upper Marble Quarry; see Fig. 1.12). Reaction skarn occurs along the margins of D3, but is not observed to exceed four centimeters in width. Reaction skarn occurs as proximal garnet and distal wollastonite were D3 intrudes bleached and grey marble [Ray and KUby, 1996].  21  1.3.4 Summary of results: overview The following section gives an overview of the main conclusions of this thesis within the context of an overall geologic history of skarn formation at Mineral Hill. A calcareous roof pendant tentatively correlated with the Quatsino Formation of the Vancouver Island Group was enclosed within the Late Jurassic Crowston Lake Pluton, which was probably emplaced near surface and comprises a juvenile portion of the southern CPC. Meteoric fluid infiltrated and isotopically (oxygen) altered marble near pluton and to a lesser extent distal marble (relative to pluton contact). Magmatic volatiles exsolved off of the pluton pervasively altering the roof pendant creating calcic exoskarn. Spatial extent of wollastonite skarn represents the spatial extent of the geochemical  Si02 front. Large scale zonation patterns  within skarn are partially controlled by infiltration of magmatic fluid and protolith composition. Positive feedback coupling between infiltration and reaction may have resulted in heterogeneous permeability within marble and focused flow into areas of high permeability producing a skarn/marble boundary that is highly irregular and fingered. Laminated and nodule-rich marble interleaved-with pure marble gave rise to two geochemically different wollastonite skarns: A and B. The former is generally higher in concentrations of immobile elements (i.e. Al, Ti, Zr, V , Yb, Y and HREEs). Rare earth element patterns suggest mobility of LREEs. Passive enrichment of immobiles support a calculation of ~ 20% volume loss associated with the formation of wollastonite skarn B from average pure marble samples from the field area. This may have created transient syn-metamorphic porosity at the reaction front. Intrusion of D2 and D3 events, correlated to Early Cretaceous extension, cross cut skarn and marble units. Reaction skarn occurs along the margins of both dike phases, as garnet-epidote and garnet-wollastonite, respectively. This indicates preservation of high temperature alteration although porphyritic and aphanitic textures within D2 and D3 reflect a cold crust at the time of emplacement. Low 8 0 alteration preserved in D2 and D3 suggest high temperature meteoric 18  22  fluid infiltration either syn-Cretaceous as a response to thermal perturbations or a post-D3 low 1 8  0 fluid event.  23  C H A P T E R 2: R O C K UNIT DESCRIPTIONS  2.1 Intrusive rocks  Intrusive igneous rocks identified within the map area at Mineral Hill include the Crowston Lake Pluton and associated gabbroic dikes and sills, monzonite, tonalitic dikes and sills , and basaltic dikes. They were classified by mineral content and rock texture. Mineral assemblages were identified in polished thin section using a petrographic microscope and, in some samples where petrographic examination was difficult, scanning electron microscope (SEM). Mineral assemblages for intrusive rocks are presented in Table 2.1.  2.1.1 Crowston Lake Pluton The mafic Crowston Lake Pluton outcrops along the eastern portion of the map area (Fig. 1.8). It is typically dioritic-to-gabbroic in composition and locally pegmatitic. The pluton is a black and white spotted, fine-to-medium grained (0.5-2 millimeters) and equigranular. Pegmatitic phases are coarser-grained (> 1 millimeter), often more felsic, and contain biotite. Near the contact with meta-sedimentary wall rocks, the pluton is foliated and contains late-stage quartz veins parallel to foliation. The dominant mineralogy is plagioclase, orthopyroxene, and hornblende. Isolated cores of clinopyroxene within hornblende are observed in sample L B l c . Apatite is present as an accessory mineral. Rims of orthopyroxene and hornblende are altered to hornblende and chlorite, respectively, indicating at least two pulses of retrograde alteration. Subsolidus hornblende growth is evident in foliated samples as randomly oriented hornblende grains overgrowing preexisting hornblende with a preferred orientation. Sample M B la was collected near the plutonwall rock contact and displays a weak alignment of plagioclase in thin section. Samples M B lb and L B Id were collected further from the pluton-wall rock contact; neither displays a grainshape preferred orientation although deformation microstructures (e.g. deformation twins in  24  W3S1  s a d o j o s i atqejsl  ("2 'A '3S 'C02JO) S90BJM  If  1  g 1  •6  zeo,  s a s e q d jaq»ol  chl( R,V)  c chl( R) bt  ^  apa,i  <  «  3 >  sanbedoj  ajopjdg Of X  apuaiqiuoH  X X  ejiuojSBiio/vy  zyenq  X  JEdS->i/BB|d  X £  X  *.  X  o > auaxojAdoijuol  auaxojAdounoj  UOj)EJ3)|M  uoipas ujijiJ  CC  uampads pued  E  (0  ">  -6 o  cc  2 — « 2 9 c = o ra S E  =  8I S B S3 oST S  O  CQ  ss  •6 1  a? 1  B B S 2'j D C O ~ O O O O > (2 ^ C CD £ C O - ~ .9 n JI sz s: -s o <2 ra E -o -D M ^ '5 £ .9, O O O O < -c •1 . cr co -5, o. CL CL a.  e- e- e- e-  -c ™  .ti  TJ TJ T3 TJ 0)0)0) j) j  £ 3Sg  2 * co ' *  o  to  a> w S E•  ra  A ? ? f O S . X ce > >  S -  +  5  25  plagioclase) were observed for all samples. Late mineralization includes Fe, Ti, A l , Cr, and Mnbearing opaques (identified by SEM) and epidote veins.  2.1.2 Monzonite Black and white spotted, medium-grained (1-2 millimeters) equigranular monzonite outcrops west of Marble Hill (Fig. 2.1). The dominant mineralogy is plagioclase/ K-feldspar, quartz, hornblende, and biotite. Retrograde minerals include biotite and chlorite, replacing hornblende and biotite, respectively. Late mineralization includes epidote and opaques. No foliation or alignment of minerals is evident macro- or microscopically. However, in thin section, plagioclase displays deformation twins and plagioclase and quartz display undulose extinction. Monzonite is interpreted as a pegmatitic phase of the Crowston Lake Pluton, since it is more felsic and contains a hydrous phase. The outcrop has been oxidized to a rusty color.  2.1.3 D I : Gabbroic dikes and sills- first generation The oldest dikes and sills (DI) in the map area are generally gabbroic in composition. They were interpreted by Ray and KUby [1996] as spatially and temporally related to the Crowston Lake Pluton. There are two phases of the first dike generation distinguished primarily by texture, but related geochemically and mineralogically. The first phase is black and white, fine-to-medium (0.5-3 millimeters) equigranular, and is clearly foliated with proximity to the wall rocks. Sills of this phase are boudinaged (Plate 2.1). Mineralogy includes pyroxenes (possibly one phase; pigeonite), plagioclase, and +/- hornblende and K-feldspar. Plagioclase and K-feldspar show undulose extinction and plagioclase shows deformation twinning. Replacement reactions include chlorite replacing pyroxene, and hornblende overgrowing pre-existing hornblende. Late mineralization includes epidote, pyrite, and other opaques. Sample M B d l a has quartz and epidote veins.  Plate 2.2. D2 tonalitic sill fractures infilled with epidote. Dike and sills are altered to a pale green color resulting from the increase in plagioclase content adjacent to epidote veins.  28 The second phase (samples MBdlb and TBdlf) is porphyritic with a blue-green finegrained matrix. The phenocrysts in this phase is coarse-grained euhedral hornblende and pyroxene (2-10 millimeters), and fine-to-medium grained plagioclase (0.5-2 millimeters ). The groundmass consists of very-fine grained (< 1 millimeter) randomly oriented plagioclase. Retrograde alteration minerals include chlorite, zeolite, epidote and pyrite. Zeolite occurs in vein in sample TBdlf. This second phase appears to be an intermediate between first phase gabbroic/dioritic dikes and sills and tonalitic dikes and sills on the basis of geochemistry (see Whole-rock chemistry), grain size and, on the basis of texture, cooling history.  2.1.4 D2: Tonalitic dikes and sills- second generation The second generation dikes and sills are tonalitic in composition and contain white feldspar phenocrysts set in an aphanitic groundmass. The groundmass is typically altered and green in handle sample but rarely is unaltered and black. D2 dikes and sills are located primarily in the center of the map area (Fig. 1.2 and 1.8). Altered and unaltered dikes were sampled. Sample MBFRd2 is black and porphyritic with lmillimeter plagioclase and >1 centimeter hornblende phenocrysts in an aphanitic plagioclase and hornblende matrix. Accessory minerals include apatite and titanite. Late mineralization includes Fe and Ti-bearing opaques, epidote veins and K-feldspar veins. Altered second generation dikes and sills (Samples MBd2a, MBd2b, Ubd2c, and UBFRd2) are porphyritic with plagioclase, and +/- hornblende and pyroxene phenocrysts in an green aphanitic plagioclase, hornblende, and +/- K-feldspar matrix which has been altered to randomly oriented chlorite. Phenocrysts range from 0.5-2 millimeters with the exception of sample UBFRd2 which has 5-8 millimeter hornblende phenocrysts. Plagioclase phenocrysts in these samples typically show deformation twins. Sills are boudinaged and are fractured perpendicular to stretching infilled with epidote. Adjacent to epidote veins, the sills have been  29 altered to a pale green color resulting from the increase in plagioclase content in the matrix material (Plate 2.2). Quartz and chlorite veins also occur. Late mineralization includes opaques and epidote. Garnet-epidote reaction skarn occurs along the margins of these tonalitic dikes and sills where in contact with marble. Reaction skarn has not been observed to exceed two centimeters in width.  2.1.5 D3: Basaltic dikes-third generation The final generation of dikes does not display ductile deformation textures or structures although, in places, brittle deformation is observed. Moreover, no sills are observed for this intrusive generation. It appears clear that the third generation dikes are not chemically, temporally, or genetically related to the two earlier dike episodes. These dikes intruded after the tonalitic dikes and sills indicated from cross-cutting relationships (Plate 2.3). The third generation dikes are dark green and very fine-grained (< 1 millimeter) to aphanitic with light green alteration rims. Mineralogy includes primarily plagioclase (>80 percent), clinopyroxene, and +/- hornblende and K-feldspar. Titanite occurs as an accessory mineral. Retrograde chlorite, hornblende, and zeolite is present. Late Pb, Zn, and Fe-bearing opaque minerals are observed (SEM) in sample UBd3a. There is no grain shape preferred orientation within the matrix. Compositionally and texturally these dikes are basaltic and are not related to the first or second dike generation [Ray and KUby, 1996; Chapter 3, this study]. Reaction skarn occurs along the margins of D3 basalt dikes as proximal garnet and distal wollastonite, where adjacent to marble (Plate 2.4). Reaction skarn has not been observed to exceed four centimeters in width.  30  Plate 2.4. Reaction skarn on the margin of a D3 basaltic dike occurs as proximal garnet (brown) and distal wollastonite (white) where adjacent to marble (grey).  31  2.2 Meta-sedimentary and S k a r n Units  Nine meta-sedimentary and/or skarn units were distinguished in the map area. Metasedimentary and skarn units at Mineral Hill were subdivided based on their appearance in the field (e.g. color and texture) and peak mineral assemblage (i.e. equilibrium phases). Peak mineral assemblages were identified in polished thin section using a petrographic microscope and, in some samples where petrographic examination was difficult, scanning electron microscope (SEM). Mineral assemblages are presented in Table 2.2. Peak mineral assemblages are presented in Table 2.3. Some thin sections were cut across skarn boundaries, and therefore represent more than one rock unit as determined by changes in peak mineral assemblages or changes in dominant mineral.  2.2.1 M a r b l e Two marble units were identified at Mineral Hill: green marble, and grey and bleached marble. There are no significant geochemical differences between the marbles. Mineralogically, marbles are similar however, grey marble contains graphite.  Green Marble On outcrop scale, green marble is bluish-green, medium-to-coarse grained (1-6 millimeters), and often massive. Green marble is distinguished by green color and limited occurrence within the map area. In places, green marble occurs as lenses within garnet zone skarn units. In these cases, it is unclear if green marble is derived from vein or marble that has been boudinaged and pinched-out during transposed bedding (Plate 2.5). Peak mineralogy is  32  W3S sadojosi a i q e i s  10  M S80BJ1  SJO[e|/\| sasegdjai|)0  O O  a. a. ra ra  sanbedo  a. a. a. a.  cc tr  a.  CE Hi  or ct0:0:0:0:  anuopotia  3  stopida  apuaiqujoH  ^x  ajpiBQ  X X  aj|uojsB||o/VA  XX  XXX  X  >< X ~  X XXX  X >  co > >  E  X  X XXX X  > X  X X X X XX X X X XX X X X X  jeds-x/6e|d  X xxx  }aiueg  X X X X Xx x  X  r x &J  E  X  X  E  X  auaxojAdoiflJO E  auaxojAdouno  X  o. E E X  uonejaiiv  uoijoas u | M l  co co co Q. a. a.  Q. Q. Q. OJ  E E E E •=  E  E E ?  X X x  co co co co co  a. 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Ct DC LL LL IL u_ CQ EQ C O QQ 3 3 33  oi •) ai q 1  O * - O) -C N N (v| N  E 5 SS ]  a ct cc a. ; u_ u- u_ u. : CQ CQ  3 3  m m 3  ?  was sado;os|  ra oi 5 E  aiqejs saoBJi  + +  sasEijd J8i|t0  O)  +  + + + +  Ol  sanbedo  a»!Uopoi|y ajopida apueiqujOH  o  8JPIB0  a> (0 == >* == o> _ra2(0 cu ©  a»!UO>SB||OM  x x x x X X X X XX X X X XX X X X X X X X X XX X X X XX X X X X  x x x x X XXX X  X XXX X  X XX X  X X ox x X XXX X  zjiBno  jeds-x/Beid  JSUJBQ  7>  x  X  X  X X X °8  auaxojAdounJO  X X 1z X X  X X X X XX X X  auaxojAdouno  X XX X  uoi>Eja)|v  uojjoas umx  a aaa  Q.  a. o_ o_ o_ oJ  Q. O. Q. QJ  uauipads PUBH  -O  -Q -Q - p  ro ra ro CD  E E E TJ  J3 CD  TJ  T3  TJ  JD  JD  J3  ca ca E £ £ E CD  E E E E  TJ TJ TJ  J3  CD  TJ TJ TJ TJ  TJ C  D)  (D  QJ  CD  TJ TJ TJ TJ C C C C  D I D> O i l  aa,  CD  T3 C  TJ H 73 IZ  CZ  TJ  CZ  CD  CD  CD  "  TJ TJ TJ TJ  TJ  c ccc c  OJ Ol Ol O) OilO l  HI 111 U J X X z z ^ g Q  SI.a .a  CO  CD  CD J2  CD CD  CD  <D (D  J3  X ) J 3 X>  CO  CD  © a>-Q  J3 .  -Q  CD  J3  CO ( 0  CD  E E E E E E E ECD CD E E TJ TJ T J TJ T J TJ TJ TJ TJ TJ E E CD CD CD CD CD CD CD CD CD CD J Z J Z J Z J Z J Z TJ TJ CD CD O O O O O O O O O OS € CD CD  JZ JZ JZ JZ cou oa o o JOZ JOZ JZ o JCD O O Z JCD Z CD CD CD CD CO o o o oCD a> a> a> Q) ai a) a) _ J3 I ! H £1 u J 2 J 2 J 2 J 3 XI J 3 J 3 £ » J 3 (D JZ  J5 .a  C  a) a> _Q) X> CO  J2 J 2  J2  J3  TJ TJ TJ TJ  J3  TJ  TJ TJ TJ TJ TJ  C  JD C  C  IZ  CZ CD  J3  J3  J3  CZ CZ C C CD CD CD  J3  CD  -Q TJ TJ  C  C  CZ CO >*  E E  cu  CD  QJ 5to C€O  J3 '  TJ C CO >. > J  -P t:ra"2ra.9-  Jj) JU j ;  ta tji co tz I E E Ii E ? ? *  c c  '5 '5 £ £. £.  P E E  >>>>>>•>> >A  O l D ) O) 0)j0 ) 0 ) 0 ) 0 )  P)  ^  IO ( O  o oo o o oo o  o>  Oil O lO lO) O l Oil  J  ^  f-  CM  —I —I =3 to n ?T PT ^ 0£ Ql c«raco 3 3  O)  o> o> o>|  CM CO  i § » f i d r  o3 3 s ' 0? 0? 0? E ) s S m m2t ^ mm 5 o m s s co S m i- i - 31 3  u  0) CL  _CU CL  E  CD CO  o  g  c o E  o cu w  o c  E  CO 10  O o \  I TO  I  T3  cu x: to o GL I  to  ^—  CM  1  Q.  CD  c  CD (0 CD  cz cu Q_ E cu "ra \— o _ro CU g  CL  E  i  i  X  c o i  a:  c cu co cu  cu  c o T3 CO CO  g  'E l  >  +  of-*  o E co cu o CO  CO o  CL  CO  l_  cu •o o E  c cu to cu  ro 0 to cu  t=  CD i  c o E co cu  c 0 to cu  £=  E  cu  c E  T3 O  E O)  t-  to TJ O CL T-  36  Table 2.3. Peak mineral assemblage for meta-sedimentary and skarn samples from Mineral Hill Peak A s s e m b l a g e M i n e r a l o g y  o  O  MB UB UB MB UB MB H H H H  I  UB MB MB H MB UB GM UMQ NE GM GM GM GM GM GM MB  I I I I I I I FR I I I I I I I I  TB MB UB TB TB H GM GM GM GM  I FR I I I I I I I  I I FR  GM1h 00UMQ-1 00UMQ-3 TB4f 00UMQ-2  UB MB UB NE H H H GM GM GM UMQ UMQ TB UMQ  FRW1a TB14e 00H11 q2  UMQ TB H GM  FR  UBFRM2f 00H14 00H15 00H16 00NE-3a FRW1d(m) 00H4 00H6  UMQ H H H NE UMQ  FR I I  H  FR I I  00H4  H  I  MB2b UB2c UB2d MB3a UBSd WG3b 00H5 00H7 00H8 00H3  1 0  1 1  1 4  X X X X X X X X X X  7  I I I I I I I I I  X X X X X X X X X X  g-w skarn g-w skarn g-w skarn g-w skarn g-w skarn g-w skarn woll skarn woll skarn woll skarn woll skarn  V V V  C.l< C.I C.I  C.I  s.f w.f m.f." m-s.f. 5  3  1,3  2) WG5b-2 MB4b MBSb  00H10 WG3a  WGSd a2(L) UBFRM2d 00NE-1 a3(L) a4(U) URa1 e(R)-3 e(R)-4  fl MBM1b  1 3  1 6  , S  X Ti-gr X X X X X X X X X X X X X X  8  X X X 3 X X X X(V) X X(V) X mn (V) X(pods) X X X X X X X X(pods) X X X X(pods) X X X X X X X 6  ?  9  apa?  g-w skarn g-w skarn g-w skarn woll skarn g-w skarn g-w skarn marble marble marble marble marble marble marble marble marble marble  C.I C.I  w-m.f. cl.  1,2,3  s.f.  1  s.f. s.f. s.f. w-m.f. s.f. s.f. s.f.  1,2 1,2?,3 1 1,3 1 1,3  3) TB4f MB9b WGSe TB13a TB13b 00H2 a4(U) e(R)-1 a5(U) q1  1 2  I  X X X X X X-mn X mn X X  X X gr X-80 X-80 X X X X X  X X X X X X X X X X  mn X X X X X X X X X X X X X  X X X X X X X X X mn mn X X Ti & gr  X X X X X X X X X X X X X X  V V V V V  gnt skarn g-w skarn gnt skarn garnetite garnetite woll skarn woll skarn woll skarn woll skarn woll skarn  X X X X X X X X X X X X X X  g-w skarn g-w skarn marble marble marble marble marble marble marble marble marble marble gr marble augen  V  cl cl. m-s.f. n.f. n.f. n.f. m-s.f. 2  1,2?,3  4) WGSb-1 MB5c UBFRM2C 00NE-3b2 00H3 00H4b  00H10 e(R)-2  gz  I I  I I I I I I I I I  ?(apa)  cl m.f. m.f. s.f s.f. s.f. m.f. s.f.  1,3 1,3 1,2,3 1 1,3 1,3  5) I  I I  X X X mn  X X X X  V  woll skarn woll skarn woll skarn woll skarn  X X X X X X X X  X X X X X X X X  X X X X X X X X  marble marble marble marble marble marble marble marble  m.f. m-s.f.  1,3  X  V  woll skarn  m.f.  1,3  n.f cl.  3  n.f.  1,3  6)  H  I I  ?  s.f. s.f. s.f. m.f.  7)  37  Peak A s s e m b l a g e M i n e r a l o g y  o 00H1 a1(L) URa2 e(L)-1 e(R)-3 fl GM1h FRW1d(w) 00H6 00H13  H GM GM GM GM GM GM UMQ  FRW1b FRW1c 00H4b a3(L) 00NE-2a 00H9 00H13 a1(L) URa2 e(L)-1  UMQ UMQ  C2-1 CZ-2  MB MB  I  TB9a UB5e TB14b  TB UB TB  I I I  X X X  UMQ UMQ MB  I FR I  X X X  MB MB  I I  UMQ NE NE  FR I I  UB NE  I I  MB  I  H  I  UB  I  H H  I I I  I I I I FR I I  X X X X X X X X X X  V V V V V V V V  X X X X X X X X X X  X X X X X X X X X X  woll skarn woll skarn woll skarn woll skarn woll skarn woll skarn woll skarn woll skarn woll skarn woll skarn  m-s.f. n.f. m.f. n.f. n.f. n.f. m.f. w.f w.f. m.f.  woll skarn woll skarn woll skarn woll skarn marble marble marble marble marble marble  n.f m.f w.f n.f. s.f. s.f. s.f. s.f. s.f. s.f.  1,3 1,3 1,2,3 1,3 1,3 1,3  1,3  8)  3)  H  GM NE H H GM GM GM  FR FR I I I I I  ?  I I I  X  X  skarnoid skarnoid  X X X  X X X  X X X  g-w skarn gnt skarn skarnoid  X gr X  X X X  X X X  X  X  2 1,3 1,2  1,3 1,3 1,3 1,2,3  10)  cl  11) UBMIa UBFRM2b MB3b 12) MB7a MB7c 13) UBFRM2g 00NE-2b 00NE-3b2 14) UB4e(w) 00NE-2b 1S) MB11a 16) 00H7 17) UB5e 18) MB4a MB4c UB4e(m) 00UMQ-2 UBFRM2e UBFRM2I) 19) UB14a UB14c 20) CZ-3 UB14d 21) TB4e UBFRM2a 22) 00H12 TB4e 23) BM-1 24) BM-1  MB MB UB UMQ UMQ UMQ  I  MB UB  I I  TB UMQ  FR  I  I  TB  I I  MB  I  MB  I  H  marble marble cpx skarn  X X X X X  ?  X X  X X X  X X X  X X  X X  X  X X Ti-Mg-Fe gr X X X X  X X  X  ?  V  V? V?  woll skarn auqen  n.f  quartzite  V?  qtz vein  X  cpx skarn  X ksp X X X X  apa?  X X  gr marble gr marble gr marble marble marble marble skarnoid skarnoid  X X  X X  skarnoid skarnoid  X X  apa  X X ent?  1,2,3  marble marble auqen opq  X X X X  quartzite quartzite  X X X  X X  FR FR  UB UB  X X X  gnt skarn marble marble qr marble  X  X  X  apa  Mq.Fe, Ti-qr  X  X  clz  phi  bk. marble auqen  alignment  1  2  3  c.l.-compositionally layered n.f.-non-foliated w.f.-weakly-foliated  4  m.f.-moderately foliated  5  s.f.-strongly foliated  6  mn-minor amounts  7  l-intact sample  8  FR-fall rock sample  9  ?-unsure identification  1 0  MB-middle bench  1 1  UB-upper bench  1 2  TB-top bench  1 3  GM-grid map 1 sample  1 4  H-Marble Hill  1  NE-northeast extension UMQ-upper marble quarry  boundary type: 1  samples with wollastonite grains in marble far from boundary / cc + qtz = woll + C 0  2  samples with area near boundary containing cc and woll indicating presence of reactants and products resulting from the reaction cc + Si0 (aq) = woll + C 0 2  3  2  samples with sharp boundary between marble and wollastonite skarn  2  Plate 2.6. Skarnoid cliff exposure  40  calcite and +/- wollastonite, garnet, calcic-clinopyroxene and plagioclase/K-feldspar with or without trace amounts of apatite. Late opaque minerals are observed.  Grey and Bleached Marble Grey and bleached marble is located in the Upper Marble Quarry (Fig. 1.12) and extends north-eastward to Marble Hill (Figs. 2.1 and 1.7). On outcrop scale, grey and bleached marble is grey and white, medium-to-coarse grained (1-10 millimeters), and thinly-to-medium layered (115 centimeters). Layering is defined by compositional differences between grey and bleached marble (i.e. disappearance of graphite in bleached marble). This layering may represent transposed bedding. A magnesium-rich (black) marble outcrops in the east central portion (Fig. 1.8; sample BM-1) of the map area, adjacent to a fault and the pluton-wall-rock contact. Peak mineralogy is calcite and +/- wollastonite, and calcic-clinopyroxene with or without minor-to-trace amounts of garnet, quartz, plagioclase/K-feldspar, apatite, titanite and graphite. Black marble (BM-1) contains phlogopite in addition. In places the marble unit contains black augens composed of one or more of calcic-clinopyroxene, garnet, K-feldspar, apatite, calcite, quartz and wollastonite, however no augen contains the entire assemblage. Minerals in augen vary in abundance. Augen in black marble (BM-1) contains garnet, calcite, and clinozoisite. Late opaque and epidote mineralization are observed in marble and augen. All marbles analyzed from Marble Hill and the northern extension of Mineral Hill are moderately-to-strongly foliated. The foliation is defined by grain-shape preferred orientation of calcite. In the Marble Hill samples (H), the foliation appears parallel-to-subparallel to the pluton contact. This observation is consistent with the pendant/pluton contact in the entire study area (see Fig. 1.8). This foliation may have resulted from contact metamorphism associated with pluton emplacement, or movement along Wormy-Lake fault. Generally, marbles in the Upper Marble Quarry of Mineral Hill are not foliated.  41  All marble samples examined contain wollastonite well away (> 2.5 mm) from the wollastonite-marble boundary in equilibrium with calcite (Table 2.3, (1)). The presence of wollastonite within marble is attributed to the presence of quartz within protolith limestone, formed by the reaction, calcite + SiO"2 (qtz) = wollastonite + CO2 (see Fig. 2.2). Wollastonite skarn commonly contains calcite, however the boundary between marble and wollastonite skarn is marked by a large increase in wollastonite abundance (in skarn). Two boundary types are observed in thin sections that display the wollastonite-marble contact (Fig. 2.3): Samples with a sharp boundary (<0.5 mm) between marble and wollastonite skarn (3) and samples in which calcite and wollastonite coexist over a scale > 0.5 mm (2). This latter occurrence indicates the presence of reactants and products from the reaction, calcite + SiG"2 (aq) = wollastonite + CO2. Boundary types are tabulated as (3) and (2), respectively, in Table 2.3. Most samples show a sharp boundary between marble and wollastonite skarn. However, samples FRW lb, H10, a3(L), a4(U)?, e(L)-l, and UBFRM2b, contain areas of reactant and product phases.  2.2.2 Quartzite Epidote-bearing quartzite was identified in the middle bench of the map area interspersed with garnet skarn. In outcrop, quartzite is white and green, fine-to-medium grained (1-2 millimeters) and massive. It is brecciated and intruded by small (< 6 inches wide), irregular, discontinuous, mafic dikes (Fig. 2.4). This unit may represent, highly silicified alterations of dike or skarn material, vein material or silica infiltration into brecciated garnet skarn. Peak mineralogy is quartz and epidote. Retrograde alteration is not observed. Late disseminated mineralization includes opaques.  42  Metasomatic vs. Thermal production of Wollastonite  Wollastonite skarn-Marble boundary  Two reactions: A) CaC03 + S i 0 (aq) = CaSiOs + CO2 2  B) C a C 0 + SiO-2 (qtz) = CaSiOs + CO2 3  Fig. 2.2. Schematic of metasomatic vs. thermal production of wollastonite  43  o + o U  44  Fig 2.4. Sketch from field notebook of quartzite outcrop, cut by irregular mafic dike with inclusions of quartzite. Q= quartz, E=epidote, hash lines= mafic dike.  45  2.2.3 Skarnoid Skarnoid is located within and interbedded with the main skarn body at Mineral Hill, and is best developed where extensively intruded by D2 and D3 (Fig. 1.8). On outcrop scale, skarnoid is a white-to-greenish, highly silicified, fine-to-medium grained unit (1-2 millimeters) and is resistant to weathering (often exposed as cliffs) (Plate 2.6). Skarnoid is located within the garnet zone due to field observations of garnet within this unit, and is interpreted to have had a silty-argillitic protolith on the basis of the abundance of feldspar in the peak mineral assemblage. Skarnoid typically contains clinopyroxene, feldspar (plagioclase and/or alkali-feldspar), quartz, wollastonite, garnet and minor biotite, however no sample contains all of these minerals. Moreover, mineral abundance is highly variable. Retrograde chlorite is observed in some samples with late opaque and epidote mineralization. Altered skarnoid, especially in proximity to dikes, contains hornblende. Skarnoid is distinguished mostly on the basis of high plagioclase content in equilibrium with other calc-silicates (i.e. wollastonite, calcic-clinopyroxene, garnet). Alignment of acicular minerals is observed.  2.2.4 Skarn Five skarn units were identified at Mineral Hill: wollastonite skarn, clinopyroxene skarn, garnet-wollastonite skarn, garnet skarn, and garnetite. Skarn units were subdivided based on mineral content and color. Some skarn units may derive from alteration of other pre-existing skarn assemblages or meta-sedimentary units. Garnet skarn is located proximal to the plutonskarn contact. Garnet skarn is interlayered with garnetite, garnet-wollastonite skarn, and green marble. Both garnet and garnet-wollastonite skarn are compositionally layered, however only garnet skarn, especially in places where garnet exceeds 80 percent (garnetite), is texturally massive. Wollastonite skarn is distal to the pluton. It is the interface of wollastonite skarn and marble that denotes the periphery of the skarn body. This marble-wollastonite contact is sharp  46  within the quarry, however in other localities (Marble Hill; see Fig. 1.9) wollastonite skarn clearly interfingers with grey and bleached marble (indicating replacement of calcite by an infiltrating S i 0 front) (Plate 2.7). 2  Wollastonite skarn Wollastonite skarn appears along the periphery of the skarn body adjacent to marble (Fig. 1.2). Wollastonite skarn is a white, fine-to-coarse grained (0.5-10 millimeters) unit. In places, it appears to be compositionally layered (1-15 centimeters) with calcite and/or quartz, however the calcite and quartz may reflect transposed calcite and quartz veins. Both of these vein types are observed cross-cutting wollastonite skarn. Wollastonite skarn is distinguished from all units by white color due to dominant wollastonite content. Peak mineralogy is wollastonite, +/- calcite, calcic-clinopyroxene and garnet. Sample UB4e(w) contains quartz . Generally, no retrograde alteration of peak minerals is observed, however there is late opaque minerals and apophyllite veins. Some samples have opticallyunidentifiable fine-grained alteration alteration along cleavage planes (e.g. sample GMlg-W) Sample 00H7 contains late epidote mineralization. Wollastonite skarn ranges from non-foliated to strongly- foliated, due to the mineral alignment of wollastonite, in the samples examined petrographically. However, wollastonite alignment is not always in the same direction as the marble foliation. Marble is often seen wrapping around wollastonite pods (few cm to ten's of cm) or augens (Plate 2.8). Both wollastonite skarn and wollastonite pods contain calcite veins. See Grey and bleached marble section (above) and Table 2.3 for boundary description.  Plate 2.8. Classic 'augen' within banded grey and bleached marble.  48  Clinopyroxene skarn One sample, MB3b, was identified as clinopyroxene skarn on an outcrop scale. It appears as a green and white, medium-grained (~2 millimeters), compositionally layered unit. It is distinguished from other skarn units by minor garnet and green coloration. MB3b differs from calc-silicate skarnoid by greater clinopyroxene and quartz content and less plagioclase. However, they are very similar in grain size and location within the map area. Sample UB5e reveals clinopyroxene skarn assemblages within compositional layering. The clinopyroxene in sample UB5e is coarser-grained than in sample MB3b and skarnoid samples. Peak mineralogy for clinopyroxene skarn is calcic-clinopyroxene, quartz, plagioclase/Kfeldspar, and wollastonite with or without garnet. Late mineralization includes opaques. A microphotograph of sample UB5e shows garnet infilling late-porosity around clinopyroxene grains (Plate 2.9). This suggests the possible existence of a magnesium front producing clinopyroxene prior to the iron front that produced garnet.  Garnet-wollastonite skarn Garnet-wollastonite skarn is white and greenish-brown and medium-to-coarse grained (13 millimeters), except sample UB2d which contains coarse-grained (up to 20 millimeters) wollastonite. It is typically compositionally layered on a scale of 1-5 centimeters (Plate 2.10). Compositional layering is defined by garnet dominant and wollastonite dominant alternating layers. Garnet-wollastonite skarn outcrops primarily within the garnet zone of the map area. Peak mineralogy is wollastonite, garnet, and -/+ calcic-clinopyroxene and calcite. It is distinguished from garnet skarn on the basis of having wollastonite content greater than garnet (Plate 2.11). Calcite occurs as part of the peak assemblage and in veins (e.g. WG3a and WG5d). In some samples (e.g. MB2b, UB2d, MB3a, and MB5b), wollastonite content is less than 50 percent due to the presence of other minerals. In other cases, wollastonite content can reach up to  Plate 2.9. Microphotograph of garnet (isotropic) infilling late-porosity around clinopyroxene grains (cross-polarized light). L.d. is 1.25 mm (lOx).  Plate 2.11. Microphotograph of garnet-wollastonite skarn. Garnet is isotopic and wollastonite has first-order birefringence in cross-polarized light. L.d. is 1.25mm (lOx).  51  80 percent by volume (e.g. UB2c, MB5c, and MB4b). Apatite is present as an accessory mineral in MB4b. Some samples within this unit display clear and distinct compositional layering (e.g. UB2d, MB3a, and MB5b), while in others, compositional layering is not so clear on a macroscale, but observed petrographically (e.g. MB5c, MB2b, UB5d, MB4b, MB9b, and TB9a). UB2c is the only sample of garnet-wollastonite skarn that does not display compositional layering in hand sample nor petrographically. In most garnet-wollastonite skarn samples, retrograde alteration is not observed, although sericite and rhodonite are identified in trace amounts in sample MB2b. Late mineralization in some samples includes pyrite, other opaques, epidote, and apophyllite (i.e. WG3a).  Garnetskarn Garnet skarn is dark red-brown and green in outcrop, medium grained (1-3 millimeters) and often displays brown, green, and grey compositional layering on a 2-10 centimeter scale (Plate 2.12). Garnet skarn is rarely massive and in places is brecciated by coarse crystalline quartz veins. Garnet skarn is exclusively located within the garnet zone of the map area. Garnet skarn is distinguished from garnet-wollastonite skarn on the basis on having a garnet content greater than wollastonite and the presence of calcic-clinopyroxene. Peak mineralogy is garnet, wollastonite, calcic-clinopyroxene, -/+ quartz (UB5e), and +/calcite (TB4e). Calcite occurs as vein material in sample WG5e. TB4e was the only sample in which no wollastonite was identified. In some cases where garnet content reaches 75 percent, wollastonite does not exceed 10 percent volumetrically. Garnet skarn is especially evident on outcrop scale by the striking brown hue to the rock. Compositional layering of garnet, wollastonite, and calcic-clinopyroxene is common in this unit (e.g. UB5e, MB9b, and TB4f) and may be controlled in part by protolith composition. Retrograde alteration is not observed in garnet skarn, however late opaque mineralization and apophyllite veins are present.  Plate 2.12. Compositionally-layered garnet skarn.  53  Garnetite Garnetite is a massive brown unit with wollastonite and quartz veinlets or stringers (Plates 2.13 and 2.14). Lenses of green marble are seen within this unit and may be (i) veins of calcite or (ii) representative protolith for garnetite (Plate 2.5). The latter interpretation implies that garnetite was formed by metasomatic alteration of marble. Garnetite occurs within the garnet zone of the map area and is only observed adjacent to garnet skarn (e.g. samples 13a and 13b; see Fig. 1.12). Peak mineralogy is garnet, calcic-clinopyroxene, and wollastonite. Garnetite is distinguished from garnet skarn on the basis of garnet content exceeding 80 percent, although calcic-clinopyroxene and wollastonite are seen in equilibrium with garnet petrographically. No late or alteration minerals are observed in garnetite.  Plate 2.14. Brittle deformation of wollastonite veins within garnetite.  55  BLANK PAGE  56  C H A P T E R 3: W H O L E - R O C K C H E M I S T R Y - I N F I L T R A T I O N A N D P R O T O L I T H CONTROLS ON SKARN ZONATION  3.1 Introduction  Whole-rock geochemistry of representative samples of all units sampled at Mineral Hill, coupled with petrographical analyses, allows further and more accurate identification of igneous, meta-sedimentary and skarn rocks. By projecting geochemistry in SACF ternary space (defined in section 3.2) and comparing samples from Mineral Hill with meta-sedimentary rocks from Ferry [1988, 1989, and 1994] that formed at or near to isochemical condition and with chemical compositions of common sedimentary rocks compiled by Brownlow [1996], we can deduce either a protolith or a metasomatic origin for the units. Furthermore, based on the distribution of minerals in skarn at Mineral Hill, the aforementioned geochemical observations, and basic principles of one-dimensional reactiontransport theory, we interpret controls on skarn zonation as either being primarily controlled by protolith composition or infiltration and interaction with external material (e.g. magmatic volatiles). Because interaction with fluid affects the hydrodynamics of the system, we would expect to see a volume change at the reaction front (i.e. marble-wollastonite skarn boundary). Petrographic and petrologic data and observations are used to estimate volume changes caused by reaction at this interface, through graphical trends of immobile elements (element ratios) and calculations using Grant's [1986] mass balance approaches.  3.2 Method of Investigation  Samples collected at Mineral Hill were cut into -8-10 cm rock slabs with a water saw 3  from the freshest part of each sample. Slabs were cleaned in an ultrasound bath of deionized distilled water and initially crushed to a size fraction less than 1.6 cm (pebble size) with a steel-  57  faced mechanical jaw crusher. Crushed samples were further ground to a powder in a tungsten carbide ring-mill. Powders were mixed and quartered in order to ensure sample homogeneity. A few grid map (GM) samples were too large to be cut with the water saw without destroying the integrity of the sample for detailed isotopic study described later in this thesis. These samples were initially cut with an oil saw, trimmed down to ~6 cm slabs with a water saw, submersed in 3  a Neutrad ultrasound bath, followed by an ultrasound bath in deionized water, ground, resubmersed in an ultrasound bath of deionized water, and crushed and powdered as described above. Chemical analysis of thirty-one samples for ten major elements plus four trace elements, Cr203, Sc, V , and Zn, by X-ray fluorescence (XRF) were done by Geochemical Laboratories at McGill University. Reported data is presented in Table 3.1. Chemical analysis of forty-two samples for eleven major elements by X R F plus thirty-six trace elements by inductively coupled plasma mass spectrometry (ICP-MS) were done by A L S Chemex in North Vancouver, British Columbia. Reported data is presented in Table 3.2. Eleven igneous rocks were analyzed including gabbro (N=6), tonalite (N 3), and basalt =  (N=2). Oxide and element abundances were converted to molar quantities, normalized to 100 percent, and plotted using NEWPET graphical software. All Fe203 was recalculated to FeO for igneous samples to circumvent the effects of 'variable oxidation'. This underestimates the degree of oxidation and favors calculation of amphibole, pyroxene and biotite. These analyses were plotted with and compared to correlating data from Ray and KUby [1996]. Partial data from Ray and KUby [1996] is presented in Table 3.3. Sixty-two meta-sedimentary and skarn samples were analyzed including marble (N=29), wollastonite skarn (N=22), garnet-wollastonite skarn (N=3), clinopyroxene skarn (N=l), garnetite (N=l), garnet skarn (N=2), calc-silicate skarnoid (N=3), and quartzite (N=l). Oxide and element abundances were converted to molar quantities. 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U-  6° ^  64 A 1 0 , F e 0 , MnO, MgO, CaO, N a 0 , K 0 and P 0 . Nine major oxides (minus T i 0 ) were 2  3  2  3  2  2  2  5  2  reduced to a four component system to allow visual analysis of bulk compositional trends. Silica was projected from alkali feldspar (Na 0 and K 0 ) , aluminium and ferric iron were projected 2  2  from alkali feldspar, calcium was projected from apatite, and ferrous iron, magnesium and manganese were combined. These were calculated by S'= [Si0 ] -3/2([Na 0]+[K 0]) 2  2  2  A'=[Al 0 ]+[Fe 0 ] -([Na 0]+[K 0]) 2  3  2  3  2  2  C'= [CaO] -3.3[P 0 ] 2  5  F'= [MgO] + [FeO] + [MnO]  and projected onto the A S C , ASF, A C F , and SFC ternary diagrams [Winkler, 1976 ; Bucher and Frey, 1994]. All meta-sedimentary and skarn samples were calculated for total iron as F e 0 (Fe 0 T, 2  3  2  3  large symbols; Figs. 3.1-3.8) and total iron as FeO (FeOx, small symbols; Figs. 3.1-3.8). Total iron calculated as F e 0 increases abundance of andradite garnet and epidote, whereas total iron 2  3  calculated as FeO overpredicts almandine garnet and calcic-clinopyroxene abundance. Rocks from Mineral Hill probably contain a combination of FeO and F e 0 mineral compositions and 2  3  therefore realistically fall along a line between the two extremes (Fe 0 T and FeOx). The data 2  3  was normalized and plotted using Sigma Plot [SPSSInc., 1997]. Major element whole-rock analyses of the seventy-three samples are presented in Table 3.1 and 3.2. In order to interpret possible protolith compositions for the meta-sedimentary and skarn rocks, the data are compared to the compositions of seven meta-sedimentary rock types from the literature [Ferry,\9%%, 1989 and 1994]. These are discussed in a later section. The chemical compositions of twelve common sedimentary rocks from Brownlow [1996] were also included. These are presented in Table 3.4. Moreover, end-member chemical compositions of six minerals were projected. These include garnet (grossular, andradite, spessartine, pyrope, and  65  Fig 3.1. A S C ternary diagrams for a) meta-sedimentary rocks (compiled data converted to Fe203). Possible protolith fields were constructed from whole-rock analyses from sandstone, pelite, limestone/marble, and calcareous hornfels from Ferry [1988, 1989, 1994]. Light green= micaceous, carbonate-bearing sandstones from the Vassalboro/ Sangerville Formation [Ferry, 1988]; bright green= calcareous hornfels from roof pendants at Hope Valley, C A [Ferry, 1989], orange= marble from roof pendants at Hope Valley, C A [Ferry, 1989]; light pink= limestone from Giles Mountain Formation and Waits River Formation [Ferry, 1994], light blue= sandstone from Giles Mountain Formation and Waits River Formation [Ferry, 1994], red= pelites from Giles Mountain Formation and Waits River Formation [Ferry, 1994], light purple= metacarbonate rocks from the Waterville Formation [Ferry, 1994]. Common sedimentary rock compositions from Brownlow [1996] denoted by blue circles; 1. Orthoquartzite, 2. Arkose, 3. Graywacke, 4. Sub-graywacke, 5. Lithographic limestone, 6. Fossiliferous limestone, 7. Oolitic limestone, 8. Dolomite, 9. Si-shale, 10. K-shale, 11. Calcareous shale, 12. Carbonaceous shale, b) Marble samples (FeOx and Fe203j) denoted by blue triangles (small) and blue triangles (large), respectively, c) Skarn samples (FeOj and Fe203i). Wollastonite skarn denoted as yellow triangles (Iarge-Fe203) and blue triangles (small- FeO); Garnet-wollastonite skarn denoted as red triangles (Iarge-Fe203; small-FeO); Garnet skarn denoted as red circles (large-Fe 0 ; smallFeO); Garnetite denoted as red squares (Iarge-Fe203; small-FeO); Clinopyroxene skarn denoted as green circles (Iarge-Fe203; small-FeO). d) Skarnoid and quartzite samples (FeOj and Fe203j). Skarnoid denoted as green hexagons (Iarge-Fe20 ; small-FeO); Quartzite denoted as yellow circle (Iarge-Fe203) and blue circle (small-FeO). Small black circles for all ternaries represent end-member mineral compositions; an= anorthite, qtz= quartz, cc=calcite, woll= wollastonite, pyr= pyrope garnet, alm= almandine garnet, spe= spessartine garnet, andr= andradite garnet, gross= grossular, hed= hedenbergite, di= diopside. 2  3  3  66  Fig 3.1. A S C ternary diagram (all iron in compiled data converted to Fe203)  66  C O — C O i—  •g  o  CM  i—  0)  rz  03  O OJ O  <p a) <c  U ^ L L _ L L  iili  CD T3 C  03  CO CCTOCO  CD  to  0)  o-  cr  CO r >  t  CO CO  d> o  to  CO CO JB  •—  1eo 1 o- 1  —  & CM UL C CB 0) ai  _ £  O  S  CD CD C  C  O tr  c ,a> co  CO c  0)  c  >= LL LL CD CU  »11 III C  C  C  oo  § 5 5 3 co « to = ~ s oiDicnaooioo  U  CD  CO  Fig 3.1. A S C ternary diagram (all iron in compiled data converted to Fe203)  67  Fig 3.2. ASF ternary diagrams for a) meta-sedimentary rocks (compiled data converted to Fe203). Possible protolith fields were constructed from whole-rock analyses from sandstone, pelite, limestone/marble, and calcareous hornfels from Ferry [1988, 1989, 1994]. Light green= micaceous, carbonate-bearing sandstones from the Vassalboro/ Sangerville Formation [Ferry, 1988]; bright green= calcareous hornfels from roof pendants at Hope Valley, C A [Ferry, 1989], orange= marble from roof pendants at Hope Valley, C A [Ferry, 1989]; light pink= limestone from Giles Mountain Formation and Waits River Formation [Ferry, 1994], light blue= sandstone from Giles Mountain Formation and Waits River Formation [Ferry, 1994], red= pelites from Giles Mountain Formation and Waits River Formation [Ferry, 1994], light purple= metacarbonate rocks from the Waterville Formation [Ferry, 1994]. Common sedimentary rock compositions from Brownlow [1996] denoted by blue circles; 1. Orthoquartzite, 2. Arkose, 3. Graywacke, 4. Sub-graywacke, 5. Lithographic limestone, 6. Fossiliferous limestone, 7. Oolitic limestone, 8. Dolomite, 9. Si-shale, 10. K-shale, 11. Calcareous shale, 12. Carbonaceous shale, b) Marble samples (FeOx and Fe203x) denoted by blue triangles (small) and blue triangles (large), respectively, c) Skarn samples (FeOx and Fe203x). Wollastonite skarn denoted as yellow triangles (large-Fe 0 ) and blue triangles (small- FeO); Garnet-wollastonite skarn denoted as red triangles (Iarge-Fe203; small-FeO); Garnet skarn denoted as red circles (Iarge-Fe20 ; smallFeO); Garnetite denoted as red squares (Iarge-Fe20 ; small-FeO); Clinopyroxene skarn denoted as green circles (Iarge-Fe203; small-FeO). d) Skarnoid and quartzite samples (FeOx and Fe20 x). Skarnoid denoted as green hexagons (Iarge-Fe203; small-FeO); Quartzite denoted as yellow circle (Iarge-Fe203) and blue circle (small-FeO). Small black circles for all ternaries represent end-member mineral compositions; an= anorthite, qtz= quartz, cc=calcite, woll= wollastonite, pyr= pyrope garnet, alm= almandine garnet, spe= spessartine garnet, andr= andradite garnet, gross= grossular, hed= hedenbergite, di= diopside. 2  3  3  3  3  68  so c i—  CO  iZ CO  n — ro -—.  o*-o N  O  N  t O  tu a> a> ®  LL_U-  LI-  'S-a a) a>  c  111?  CD  it: 3 3 to co cr cr  CO <0 (0 © CD i |  cn _  T3  co  CD CO W <C  « 5  « § o o o > S To  C C  ul O tr <n <n O CD CD c . * * c c  "—' O J  <-ILII $ t j * ' X X Co  2  i_  ffi s ®  CD © CD C L C L 1  g o Jo  0)0 0)00  — — c  c c c o 0 i b i c c CD CO CC ~  —  Fig 3.2. A S F ternary diagram (all iron in compiled data converted to Fe203)  69  Fig 3.3. SFC ternary diagrams for a) meta-sedimentary rocks (compiled data converted to Fe2<J3). Possible protolith fields were constructed from whole-rock analyses from sandstone, pelite, limestone/marble, and calcareous hornfels from Ferry [1988, 1989, 1994]. Light green= micaceous, carbonate-bearing sandstones from the Vassalboro/ Sangerville Formation [Ferry, 1988]; bright green= calcareous hornfels from roof pendants at Hope Valley, C A [Ferry, 1989], orange= marble from roof pendants at Hope Valley, C A [Ferry, 1989]; light pink= limestone from Giles Mountain Formation and Waits River Formation [Ferry, 1994], light blue= sandstone from Giles Mountain Formation and Waits River Formation [Ferry, 1994], red= pelites from Giles Mountain Formation and Waits River Formation [Ferry, 1994], light purple= metacarbonate rocks from the Waterville Formation [Ferry, 1994]. Common sedimentary rock compositions from Brownlow [1996] denoted by blue circles; 1. Orthoquartzite, 2. Arkose, 3. Graywacke, 4. Sub-graywacke, 5. Lithographic limestone, 6. Fossiliferous limestone, 7. Oolitic limestone, 8. Dolomite, 9. Si-shale, 10. K-shale, 11. Calcareous shale, 12. Carbonaceous shale, b) Marble samples (FeOx and Fe203x) denoted by blue triangles (small) and blue triangles (large), respectively, c) Skarn samples (FeOx and Fe203x). Wollastonite skarn denoted as yellow triangles (Iarge-Fe203) and blue triangles (small- FeO); Garnet-wollastonite skarn denoted as red triangles (Iarge-Fe203; small-FeO); Garnet skarn denoted as red circles (Iarge-Fe203; smallFeO); Garnetite denoted as red squares (Iarge-Fe203; small-FeO); Clinopyroxene skarn denoted as green circles (Iarge-Fe203; small-FeO). d) Skarnoid and quartzite samples (FeOx and Fe203x). Skarnoid denoted as green hexagons (Iarge-Fe20 ; small-FeO); Quartzite denoted as yellow circle (Iarge-Fe203) and blue circle (small-FeO). Small black circles for all ternaries represent end-member mineral compositions; an= anorthite, qtz= quartz, cc=calcite, woll= wollastonite, pyr= pyrope garnet, alm= almandine garnet, spe= spessartine garnet, andr= andradite garnet, gross= grossular, hed= hedenbergite, di= diopside. 3  70  CO  p oi O  f~*  8c?  tl  <5  tg © © LL LL CO CO © CD CO — C C fi CM CO CO " C C CD CD CC CO O O LL LL O fc- CO CO ~ ^ " O J O CD CD C C CD CD C C CO CO CO CO J= •= LL LL CD CD c CD CD .2 iS Tn " S CD CD O O CO CO «— ^ E i _ !  p  c O tC •c ^£ ^  ^ ^ a .  5o o *?  © C  © C  c c O-oJ oc co :=  ©  1  ©  C »- i CO CO CO CO ~ 010)010)0  0  Fig 3.3. S F C ternary diagram (all iron in compiled data converted to Fe203)  71  Fig 3.4. A C F ternary diagrams for a) meta-sedimentary rocks (compiled data converted to Fe2C>3). Possible protolith fields were constructed from whole-rock analyses from sandstone, pelite, limestone/marble, and calcareous hornfels from Ferry [1988, 1989, 1994]. Light green= micaceous, carbonate-bearing sandstones from the Vassalboro/ Sangerville Formation [Ferry, 1988]; bright green= calcareous hornfels from roof pendants at Hope Valley, C A [Ferry, 1989], orange= marble from roof pendants at Hope Valley, C A [Ferry, 1989]; light pink= limestone from Giles Mountain Formation and Waits River Formation [Ferry, 1994], light blue= sandstone from Giles Mountain Formation and Waits River Formation [Ferry, 1994], red= pelites from Giles Mountain Formation and Waits River Formation [Ferry, 1994], light purple= metacarbonate rocks from the Waterville Formation [Ferry, 1994]. Common sedimentary rock compositions from Brownlow [1996] denoted by blue circles; 1. Orthoquartzite, 2. Arkose, 3. Graywacke, 4. Sub-graywacke, 5. Lithographic limestone, 6. Fossiliferous limestone, 7. Oolitic limestone, 8. Dolomite, 9. Si-shale, 10. K-shale, 11. Calcareous shale, 12. Carbonaceous shale, b) Marble samples (FeOj and Fe203r) denoted by blue triangles (small) and blue triangles (large), respectively, c) Skarn samples (FeOj and Fe 03r). Wollastonite skarn denoted as yellow triangles (Iarge-Fe20 ) and blue triangles (small- FeO); Garnet-wollastonite skarn denoted as red triangles (Iarge-Fe20 ; small-FeO); Garnet skarn denoted as red circles (Iarge-Fe203; smallFeO); Garnetite denoted as red squares (Iarge-Fe203; small-FeO); Clinopyroxene skarn denoted as green circles (Iarge-Fe203; small-FeO). d) Skarnoid and quartzite samples (FeOj and Fe 03T). Skarnoid denoted as green hexagons (Iarge-Fe203; small-FeO); Quartzite denoted as yellow circle (Iarge-Fe20 ) and blue circle (small-FeO). Small black circles for all ternaries represent end-member mineral compositions; an= anorthite, qtz= quartz, cc=calcite, woll= wollastonite, pyr= pyrope garnet, alm= almandine garnet, spe= spessartine garnet, andr= andradite garnet, gross= grossular, hed= hedenbergite, di= diopside. 2  3  3  2  3  72  CO  00  Pp EE O fc <o to LL O r— CO CO O OIL ^CNJ Q CD CD C ,« <D C C CD135—05_ " C"= LL LL CD CD  CB  CO  CO  CO  CD c c o o  tr) Io  11  0)  c e o CO  CO  «  X  X  "io S ® 2 2 © CD © = E >.>.] c c c CD CD CD 0 . 0 . 1 C C C O o' CO CC CO O O) COcnCOo — D) D> O)C co cj ~ V-  4_  1_  Fig 3.4. A C F ternary diagram (all iron in compiled data converted to Fe203)  73  Fig 3.5. A S C ternary diagrams for a) meta-sedimentary rocks (compiled data converted to FeO). Possible protolith fields were constructed from whole-rock analyses from sandstone, pelite, limestone/marble, and calcareous hornfels from Ferry [1988, 1989, 1994]. Light green= micaceous, carbonate-bearing sandstones from the Vassalboro/ Sangerville Formation [Ferry, 1988]; bright green= calcareous hornfels from roof pendants at Hope Valley, C A [Ferry, 1989], orange= marble from roof pendants at Hope Valley, C A [Ferry, 1989]; light pink= limestone from Giles Mountain Formation and Waits River Formation [Ferry, 1994], light blue= sandstone from Giles Mountain Formation and Waits River Formation [Ferry, 1994], red= pelites from Giles Mountain Formation and Waits River Formation [Ferry, 1994], light purple= metacarbonate rocks from the Waterville Formation [Ferry, 1994]. Common sedimentary rock compositions from Brownlow [1996] denoted by blue circles; 1. Orthoquartzite, 2. Arkose, 3. Graywacke, 4. Sub-graywacke, 5. Lithographic limestone, 6. Fossiliferous limestone, 7. Oolitic limestone, 8. Dolomite, 9. Si-shale, 10. K-shale, 11. Calcareous shale, 12. Carbonaceous shale, b) Marble samples (FeOx and Fe203x) denoted by blue triangles (small) and blue triangles (large), respectively, c) Skarn samples (FeOx and Fe203x). Wollastonite skarn denoted as yellow triangles (Iarge-Fe203) and blue triangles (small- FeO); Garnet-wollastonite skarn denoted as red triangles (Iarge-Fe203; small-FeO); Garnet skarn denoted as red circles (Iarge-Fe20 ; smallFeO); Garnetite denoted as red squares (Iarge-Fe203; small-FeO); Clinopyroxene skarn denoted as green circles (Iarge-Fe203; small-FeO). d) Skarnoid and quartzite samples (FeOx and Fe203x). Skarnoid denoted as green hexagons (Iarge-Fe203; small-FeO); Quartzite denoted as yellow circle (Iarge-Fe20 ) and blue circle (small-FeO). Small black circles for all ternaries represent end-member mineral compositions; an= anorthite, qtz= quartz, cc=calcite, woll= wollastonite, pyr= pyrope garnet, alm= almandine garnet, spe= spessartine garnet, andr= andradite garnet, gross= grossular, hed= hedenbergite, di= diopside. 3  3  74  Fig 3.5. A S C ternary diagram (all iron in compiled data converted to FeO)  75  Fig 3.6. ASF ternary diagrams for a) meta-sedimentary rocks (compiled data converted to FeO). Possible protolith fields were constructed from whole-rock analyses from sandstone, pelite, limestone/marble, and calcareous hornfels from Ferry [1988, 1989, 1994]. Light green= micaceous, carbonate-bearing sandstones from the Vassalboro/ Sangerville Formation [Ferry, 1988]; bright green= calcareous hornfels from roof pendants at Hope Valley, C A [Ferry, 1989], orange= marble from roof pendants at Hope Valley, C A [Ferry, 1989]; light pink= limestone from Giles Mountain Formation and Waits River Formation [Ferry, 1994], light blue= sandstone from Giles Mountain Formation and Waits River Formation [Ferry, 1994], red= pelites from Giles Mountain Formation and Waits River Formation [Ferry, 1994], light purple= metacarbonate rocks from the Waterville Formation [Ferry, 1994]. Common sedimentary rock compositions from Brownlow [1996] denoted by blue circles; 1. Orthoquartzite, 2. Arkose, 3. Graywacke, 4. Sub-gray wacke, 5. Lithographic limestone, 6. Fossiliferous limestone, 7. Oolitic limestone, 8. Dolomite, 9. Si-shale, 10. K-shale, 11. Calcareous shale, 12. Carbonaceous shale, b) Marble samples (FeOr and Fe203j) denoted by blue triangles (small) and blue triangles (large), respectively, c) Skarn samples (FeOj and Fe203x). Wollastonite skarn denoted as yellow triangles (large-Fe2C>3) and blue triangles (small- FeO); Garnet-wollastonite skarn denoted as red triangles (Iarge-Fe203; small-FeO); Garnet skarn denoted as red circles (Iarge-Fe203; smallFeO); Garnetite denoted as red squares (Iarge-Fe203; small-FeO); Clinopyroxene skarn denoted as green circles (Iarge-Fe203; small-FeO). d) Skarnoid and quartzite samples (FeOj and Fe203i). Skarnoid denoted as green hexagons (Iarge-Fe203; small-FeO); Quartzite denoted as yellow circle (Iarge-Fe203) and blue circle (small-FeO). Small black circles for all ternaries represent end-member mineral compositions; an= anorthite, qtz= quartz, cc=calcite, woll= wollastonite, pyr= pyrope garnet, alm= almandine garnet, spe= spessartine garnet, andr= andradite garnet, gross= grossular, hed= hedenbergite, di= diopside.  76  •g  fhco—co  o  c  OJ  cc  O oi O  CB 0) CD CD LL.U_LL.L1.  co  co r—• H cfl 00 ,—.  JC  CD  co co S J C .2 co co a> «5 co  JC  I  £  O £ £ £  CO CO  c CO JC CO CD  c CO JC CO CD  c c X X CD CD  o o  CO  Fig 3.6. A S F ternary diagram (all iron in compiled data converted to FeO)  77  Fig 3.7. SFC ternary diagrams for a) meta-sedimentary rocks (compiled data converted to FeO). Possible protolith fields were constructed from whole-rock analyses from sandstone, pelite, limestone/marble, and calcareous hornfels from Ferry [1988, 1989, 1994]. Light green= micaceous, carbonate-bearing sandstones from the Vassalboro/ Sangerville Formation [Ferry, 1988]; bright green= calcareous hornfels from roof pendants at Hope Valley, C A [Ferry, 1989], orange= marble from roof pendants at Hope Valley, C A [Ferry, 1989]; light pink= limestone from Giles Mountain Formation and Waits River Formation [Ferry, 1994], light blue= sandstone from Giles Mountain Formation and Waits River Formation [Ferry, 1994], red= pelites from Giles Mountain Formation and Waits River Formation [Ferry, 1994], light purple= metacarbonate rocks from the Waterville Formation [Ferry, 1994]. Common sedimentary rock compositions from Brownlow [1996] denoted by blue circles; 1. Orthoquartzite, 2. Arkose, 3. Graywacke, 4. Sub-graywacke, 5. Lithographic limestone, 6. Fossiliferous limestone, 7. Oolitic limestone, 8. Dolomite, 9. Si-shale, 10. K-shale, 11. Calcareous shale, 12. Carbonaceous shale, b) Marble samples (FeOj and Fe203x) denoted by blue triangles (small) and blue triangles (large), respectively, c) Skarn samples (FeOx and Fe203j). Wollastonite skarn denoted as yellow triangles (Iarge-Fe203) and blue triangles (small- FeO); Garnet-wollastonite skarn denoted as red triangles (Iarge-Fe203; small-FeO); Garnet skarn denoted as red circles (Iarge-Fe203; smallFeO); Garnetite denoted as red squares (Iarge-Fe203; small-FeO); Clinopyroxene skarn denoted as green circles (Iarge-Fe203; small-FeO). d) Skarnoid and quartzite samples (FeOx and Fe203x). Skarnoid denoted as green hexagons (Iarge-Fe203; small-FeO); Quartzite denoted as yellow circle (Iarge-Fe203) and blue circle (small-FeO). Small black circles for all ternaries represent end-member mineral compositions; an= anorthite, qtz= quartz, cc=calcite, woll= wollastonite, pyr= pyrope garnet, alm= almandine garnet, spe= spessartine garnet, andr= andradite garnet, gross= grossular, hed= hedenbergite, di= diopside.  78  q  o"  Fig 3.7. S F C ternary diagram (all iron in compiled data converted to FeO)  79  Fig 3.8. A C F ternary diagrams for a) meta-sedimentary rocks (compiled data converted to FeO). Possible protolith fields were constructed from whole-rock analyses from sandstone, pelite, limestone/marble, and calcareous hornfels from Ferry [1988, 1989, 1994]. Light greenmicaceous, carbonate-bearing sandstones from the Vassalboro/ Sangerville Formation [Ferry, 1988]; bright green= calcareous hornfels from roof pendants at Hope Valley, C A [Ferry, 1989], orange= marble from roof pendants at Hope Valley, C A [Ferry, 1989]; light pink= limestone from Giles Mountain Formation and Waits River Formation [Ferry, 1994], light blue= sandstone from Giles Mountain Formation and Waits River Formation [Ferry, 1994], red= pelites from Giles Mountain Formation and Waits River Formation [Ferry, 1994], light purple= metacarbonate rocks from the Waterville Formation [Ferry, 1994]. Common sedimentary rock compositions from Brownlow [1996] denoted by blue circles; 1. Orthoquartzite, 2. Arkose, 3. Graywacke, 4. Sub-graywacke, 5. Lithographic limestone, 6. Fossiliferous limestone, 7. Oolitic limestone, 8. Dolomite, 9. Si-shale, 10. K-shale, 11. Calcareous shale, 12. Carbonaceous shale, b) Marble samples (FeOy and Fe203x) denoted by blue triangles (small) and blue triangles (large), respectively, c) Skarn samples (FeOj and Fe203x). Wollastonite skarn denoted as yellow triangles (Iarge-Fe203) and blue triangles (small- FeO); Garnet-wollastonite skarn denoted as red triangles (Iarge-Fe203; small-FeO); Garnet skarn denoted as red circles (Iarge-Fe203; smallFeO); Garnetite denoted as red squares (Iarge-Fe203; small-FeO); Clinopyroxene skarn denoted as green circles (Iarge-Fe203; small-FeO). d) Skarnoid and quartzite samples (FeOx and F e 0 3 T ) . Skarnoid denoted as green hexagons (Iarge-Fe203; small-FeO); Quartzite denoted as yellow circle (Iarge-Fe203) and blue circle (small-FeO). Small black circles for all ternaries represent end-member mineral compositions; an= anorthite, qtz= quartz, cc=calcite, woll= wollastonite, pyr= pyrope garnet, alm= almandine garnet, spe= spessartine garnet, andr= andradite garnet, gross= grossular, hed= hedenbergite, di= diopside. 2  80  Fig 3.8. A C F ternary diagram (all iron in compiled data converted to FeO)  CO  T-  CO CM 00  2  . CO CO  TT CO  Q  °  a• Ol  CD  o cb  r~-  CM O CN1  T—  -  CO CD  T CD  C\i  o  O) CO  E  CM  r~ r~ co  co  o o o  IO r-  d  CO O  CO  ci  e\i co  ^ co d  ci cri  2  t  co»  O  o  CN Oi CM tCO  r- 2  o o co o  ^ - CO  oo m ci oi CM CM  o  CO M " CM CD  ci ci ci  CM IO O  M-  O  CD | T  CO C O |  o  5  CM  CM  d  d  CO  CO  r-  d  1  _  ^_ ^ O  d °  .  CO CM  d  CO „, . O  [2 d  s a s £ ° 2 o d  h».2 CD  Q Q co h-  d  CM  00  CM CM CM  d d d  o d  IO O  d  oq  CD CM  d m  •* cn  CM CD  d  CD IO CO  T_  r-  d  CM  T-  CO 00 CM 00 CM CO  CO CO CM  CO CO CO CO CM  CM CO CO  T-  00 00 CO  CM O  d  CM CO o , M CO CM • O d d CO t—i  m d  x_  d  CD  m •cr eo d d d  CO 00 CO M" o CO d CM  co 0 ) o T" d d  o o o o o o O o o o o CM CO w CD c u> co — ~ CM CM o o < £  u- 5 2 O  CM  I  O CO  82 almandine), calcic-clinopyroxene (diopside and hedenbergite), wollastonite, anorthite, calcite, and quartz. End-member compositions are listed i n Table 3.5.  3.2.1 Inter-laboratory comparison Thirty-one rock powders were sent to Geochemical Laboratories at M c G i l l University and forty-two rock powders were sent to A L S Chemex in North Vancouver, British Columbia for whole-rock geochemical analysis. Repeated analyses o f blind samples were submitted to A L S Chemex i n order to compare the results reported by each laboratory. These samples included two marble samples, W l d ( m b ) and U B M I a , and five wollastonite skarn samples, W l a , W l b , W l c , Wld(w), andUB4e. Inter-laboratory comparisons o f absolute abundances, relative abundances and relative abundances in respect to the detection limit between A L S Chemex and M c G i l l University were examined. A L S Chemex gives systematically lower abundances o f TiC«2, Fe2C>3, M n O , and M g O and systematically higher abundances o f AI2O3 and V than M c G i l l University (Figs. 3.9-3.11). M e a n variability and standard deviation o f each comparable element is presented i n Table 3.6. The evaluations reveal that analyses between labs should not be compared when looking at element ratios because inter-laboratory variation would introduce significant error, especially since relatively immobile elements (i.e. T i 0 2 and AI2O3) occur in such l o w abundance. O n the other hand, these variable element oxides are low enough i n abundance that analyses between labs can be compared i n ternary projections in order to distinguish between the geochemistry o f different unit types (Figs. 3.12-3.15).  3.3 Intrusive rocks The chemical components o f eleven samples o f intrusive rocks were examined i n order to classify their composition. Three rock powders from the Crowston Lake Pluton were analyzed  Table 3.5. E n d member chemical formulas for selected minerals  Garnet Group grossular andradite  Ca Al Si 0i2 Ca Fe Si 0i2  pyrope almandine spessartine  Mg Al Si 0i2 Fe Al Si 0i Mn Al Si 0i2  3  2  3  3  2  3  3  2  3  3  2  3  3  2  2  3  Calcic-clinopyroxene diopside hedenbergite  CaMgSi 0 CaFeSi 0 2  2  6  Other minerals wollastonite anorthite calcite quartz  CaSi0 CaAlSi 0 CaC0 Si0 3  2  3  2  8  6  84  Inter-lab comparison (absolute) 1-2 1  -1.3  •  1  Fig 3.9. Inter-laboratory comparison of absolute abundances from data reported by McGill University and A L S Chemex. Red lines denote wollastonite skarn; blue lines denote marble.  Inter-lab comparison (relative to detection limit) 150 i  1  -150  Fig 3.10. Inter-laboratory comparison of relative abundances in respect to detection limit from data analyzed by McGill University and A L S Chemex. Red lines denote wollastonite skarn; blue lines denote marble.  85  -250  Si02  Ti02  AI203 Fe203 MnO  MgO  CaO  P205  V  Fig. 3.11. A) Inter-laboratory comparison of relative abundances from data reported by McGill University and A L S Chemex. Red lines denote wollastonite skarn; blue lines denote marble. B) Inter-laboratory comparison of relative abundances from data reported by McGill University and A L S Chemex. Red lines denote wollastonite skarn; blue lines denote marble.  T— Y— T O O O  o'  o  T  -  -  O  o  d  O  O  CO  q  q  %  O  CM g  CN  TO  CN O O O  CN O  d o d o  8 f=  5  o  5  Q_  9 V d  CN  O OS  O CD O  CO CC  g> o  00 CO  CO  a 9 S 5g  a  9 f? 9 CO O  S O  CO CO O O  d o d o '  o  CM  O  d  o  <j  O  O  O  d  d  d  co  co  !G  O  CO  cp  .  9 <V So CO O  d  N O  S O  d  d  d  >fi  CO  §  o  83 9 °?  CN  cu u_  •  Tt O  d d  LO  r- £_ £  o°- •* 52 <° O  O  O  O  d  d o  5 9  T  d  5 S g §  O  o CO  CO T f d d  T>  CD Tt  d  d  O  -r-  CM CO  T  d  0  0 ) 0 0  87  LL  u  co 9) O JE L L  p a o  £ _ x  Ills € €  <o to  E  E  5 5  o CO  +-»  T3  U BO  ca  u  •6 GO  C  o  c o .2  • ?»*  o  C  "E cc a  £  E  o  o 13  (0 —I  cn  0«'33 to  o  !ru C °M <  cc O  I <• -c  m  o  o  • CD C50 M  89  £ o U  1 (9  O >  a  o  I o  O r  O S  I "_. ? J  1 E E ! 9 JS J? Si  -a u  JO 3  e  - n o -  a  o  1  g I« a  _* o  90  o o  p  O  o  91 for major element oxides plus C r 0 , Sc, V , and Zn by XRF. Whole rock analyses are 2  3  graphically represented by plots created in NEWPET. The data collected in the course of this study (open symbols) is augmented with the data of Ray and KUby [1996] (closed symbols). Their data is tabulated in Table 3.3. The Crowston Lake Pluton is calc-alkaline (with the exception of sample M B lb) and sub-alkaline (Fig. 3.16(a,b)). The Crowston Lake Pluton is a gabbro (Fig. 3.16c), however data from Ray and KUby [1996] indicate a variation from gabbro to quartz diorite. The samples analyzed by Ray and KUby [1996] derive, in part, from localities outside of the map area and therefore may be more representative of the pluton as a whole. This study sampled no further than 20 meters from the pluton-wall rock contact, and might represent a mafic part of the pluton. The mafic character of pluton rocks within the study area might reflect an early phase of crystallization or interaction with carbonate wall rocks [cf. Westphal et al., 1999]. The pluton is metaluminous (Fig. 3.17), thus K 0 +Na 0 < A 1 0 < K 0 +Na 0 + CaO 2  2  2  3  2  2  [Hess, 1989]. The first dike and sill generation (DI), which is temporally and genetically related to the Crowston Lake Pluton [Ray and KUby, 1996] is gabbro in composition (Fig. 3.16c). It has a similar composition to the Crowston Lake Pluton, however is slightly enriched in Si0 , N a 0 , 2  2  and K 0 and is slightly depleted in A1 0 , F e 0 , MgO, and CaO. 2  2  3  2  3  The second dike and sill generation (D2) is dominant in the axis of a regional fold interpreted as a result of field mapping (Fig. 1.8). The second dike and sill generation is chemically, mineralogically and texturally distinct from the gabbroic dikes and sills related to the Crowston Lake Pluton, however it is uncertain if the two are related as no isotopic dating has been done on the intrusives at Mineral Hill. Three rock powders were analyzed for ten major element oxides plus C r 0 , Sc, V , Zn by XRF. Whole-rock analyses are graphically represented 2  3  by plots created in NEWPET. The D2 dikes and sills are calc-alkaline and sub-alkaline (Fig. 3.18(a, b)). Compositionally, the D2 dikes and sills are tonalitic and metaluminous (Figs. 3.18c  92  b)  a)  FeO  I O  + r° I  85  Alkaline  6 4 2 0 MgO  SubAlkaline 35  40  I  ^—i—i  1  1  1  50  55  60  I  I  65  70  75  L_  80  85  Si02 (wt%)  d) 15  45  I  400  1  •  \ p h  "a  U3/ F  o  T \U2  / S3  o •a z  Ul  r i  /  •o Pc 35  300  CJ  \  \  ••  \  »  Ol  03  02  55  65  Si02 (wt%)  [1996] This study  \  a  B  45  Ray and KUby  200  R  • o O  1>  75  -400  -300  -200  -100  0  100  200  300  P = K - (Na + Ca)  Crowston Lake Pluton  J  Gabbro dike and sill  Fig. 3.16. a) A F M diagram for Crowston Lake pluton and gabbroic dike and sill compositions after Irvine and Baragar [1971]. b)Alkali vs. Silica for Crowston Lake pluton and gabbroic dike and sill compositions after Irvine and Baragar [1971]. c) N a 2 0 vs. S i 0 2 composition diagram for Crowston Lake pluton and gabbroic dikes and sills after Le Maitre [1989]; Rock Compositions: F= foidite, Pc= picrobasalt, B = basalt, 0 1 = basaltic andesite, 0 2 = andesite, 0 3 = dacite, R = rhyolite, S l = trachybasalt, S2= basaltic trachyandesite, S3= trachyandesite, T= trachyte, U l = tephrite basanite, U2= phonotephrite, U3= tephriphonolite, Ph= phonolite. D) Q vs. P composition diagram for Crowston Lake pluton and gabbroic dikes and sills after Debon andLe Fort [1983]; Rock compositions: 1. Granite, 2. Adamellite, 3. Granodiorite 4. Tonalite, 5. Quartz syenite, 6. Quartz monzonite, 7. Quartz monzodiorite, 8. Quartz diorite, 9. Syenite, 10. Monzonite, 11. Monzogabbro, 12. Gabbro.  93  o  <N  +  o  cd  g, o  < CN  1 A1203/(CaO + Na20 + K 2 0 )  Ray and Kilby [1996] This study  j_ } ^  Q  r  o  w  s  t  o  n  p] t u  o n  Gabbro dike and sill  Fig. 3.17. Metaluminous compositions for Crowston Lake pluton and gabbroic dikes after Maniar & Piccoli [1989].  94  RayandKilby  [1996]  (  A  I  •  Tonalitic dikes and sills Basaltic dikes  A  ^  •D  J  This study  F i g . 3.18. a) A F M diagram for tonalitic and basaltic dike compositions after Irvine and Bar agar [1971]. b) A l k a l i vs. Silica for tonalitic and basaltic dike compositions after Irvine and Bar agar [1971]. C ) N a 2 0 vs. S i 0 2 composition diagram for tonalitic and basaltic dikes after Le Maitre [1989]; Rock Compositions: F= foidite, Pc= picrobasalt, B = basalt, 0 1 = basaltic andesite, 0 2 = andesite, 0 3 = dacite, R = rhyolite, S l = trachybasalt, S2= basaltic trachyandesite, S3= trachyandesite, T= trachyte, U l = tephrite basanite, U2= phonotephrite, U 3 = tephriphonolite, Ph= phonolite. d) Q vs. P composition diagram for tonalitic and basaltic dikes after Debon and Le Fort [1983]; Rock compositions: 1. granite, 2. adamellite, 3. granodiorite 4. Tonalite, 5. quartz syenite, 6. quartz monzonite, 7. quartz monzodiorite, 8. quartz diorite, 9. syenite, 10. monzonite, 11. monzogabbro, 12. gabbro.  and 3.19). The data suggests that the tonalitic dikes and sills could be silica enriched counterparts to the gabbroic dikes and sills. However, because their temporal relationship is unclear, their genetic relationship cannot be definitely determined. Likewise, the third generation dikes (D3) are dominant in the axis of a regional fold interpreted as a result of field mapping (Fig. 1.8). D3 are calc-alkaline and sub-alkaline (Fig. 3.18 (a, b)) and vary from basalt to basaltic-andesites (Fig. 3.18c). The basalt dikes are metaluminous, however are enriched in AI2O3 as compared to the tonalitic dikes and sills (Fig. 3.19).  3.4 Meta-sedimentary and skarn units Skarn samples (N=l 1), including garnet-wollastonite skarn, garnetite, clinopyroxene skarn and wollastonite skarn; marble (N=7); calc-silicate skarnoid (N=l) and quartzite (vein?) (N=l) sample(s) were analyzed by X R F at Geochemical Laboratories at McGill University. Additional samples (N=42) were analyzed by XRF and ICP-MS at A L S Chemex Ltd., including marble (N=22), wollastonite skarn (N=16), garnet skarn (N=2), and calc-silicate skarnoid (N=2) samples. Oxide and element abundances were converted to molar quantities, calculated for S', A ' , C', and F', normalized to 100 percent, and projected onto ternary diagrams. All geochemical data was plotted using total iron as Fe203i (large symbols) and FeOx (small symbols) in Figs. 3.1-3.8. Seven meta-sedimentary rocks from geochemical analyses from the literature [Ferry, 1988, 1989, and 1994], were also projected onto A S C , ASF, A C F , and SFC ternary diagrams as graphical comparisons to the meta-sedimentary and skarn samples analyzed at Mineral Hill. These fields represent micaceous, carbonate-bearing sandstones from the Sangerville Formation [Ferry, 1988], meta-carbonate rocks from the Waterville Formation [Ferry, 1994], limestone, sandstone, pelites and their metamorphic equivalents from Giles Mountain and Waits River  1  1  1  1  -Metaluminous  .  •  i  1  i  1  1  1  •  1  1  1  Peraluminous  • •  4 A  i  i  i  •  i  i  i  i  i  •  i  •  •  1  2  A1203/(CaO + Na20 + K20)  Ray and KUby r 19961 L  J  ( i I  A M  Tonalitic dikes and sills Basaltic dikes  A •  ^ > This study J  Fig. 3.19. Metaluminous compositions for tonalitic and basaltic dikes after Maniar & Piccoli [1989].  97 Formations [Ferry, 1994], and calcareous hornfels and marbles from roof pendants at Hope Valley, C A [Ferry, 1989]. Chemical compositions for all meta-sedimentary units were converted to molar quantities, normalized to 100 percent, and projected onto A S C , ASF, A C F , and SFC ternary diagrams (as described in Method of Investigation). The range of composition for each type of meta-sediment is represented by a field in Figs. 3.1-3.8. Chemical compositions from twelve common sedimentary rock types compiled by Brownlow [1996] were also projected onto the ternary diagrams representing literature fields. These analyses were not added to the plots that project data from Mineral Hill in order to avoid clutter. Finally, end-member chemical compositions of grossular, andradite, spessartine, pyrope, almandine, diopside, hedenbergite, wollastonite, anorthite, calcite and quartz were projected onto all constructed ternary diagrams. The following section is two-fold: (1) to describe the geologic setting and mineralogy of each meta-sedimentary field from the literature and significant geochemical trends, and (2) to discuss geochemical trends of meta-sedimentary and skarn units from Mineral Hill observed in ternary diagrams as well as any distinguishing geochemical characteristics between units (as classified petrographically), and relationship to literature fields.  3.4.1 Meta-sedimentary Rock Compositions Vassalboro/ Sangerville  Formation  Chemical compositions for micaceous, carbonate-bearing sandstones from the Silurian Sangerville (formerly Vassalboro) Formation, south-central Maine are tabulated in Ferry [1988, p. 6 ]. The meta-sediments are isoclinally folded by deformation that preceded the peak of metamorphism, both which occurred during the Acadian Orogeny [Osberg, 1979, Dallmeyer and Van Breeman, 1981; Ferry, 1988]. The sandstones are classified under four mineral assemblages which correspond to metamorphism in the amphibolite facies at peak conditions:  98  Assemblage A: calcite + ankerite + muscovite + quartz + albite +/- chlorite Assemblage B: biotite + quartz + plagioclase +/- ankerite +/- calcite +/- chlorite +/- muscovite Assemblage C: calcic-amphibole + biotite + chlorite + calcite + quartz + plagioclase Assemblage D: clinozoisite + diopside + calcic-amphibole + calcite + quartz + plagioclase +/garnet +/- microcline  Waterville Formation Chemical compositions o f meta-carbonate rocks o f the Silurian Waterville Formation, south-central Maine are tabulated in Ferry [1994, p. 928]. The meta-sediments were isoclinally folded i n the same deformation event as the Sangerville Formation and regionally metamorphosed during the Acadian Orogeny. Two limestones were differentiated and analyzed in the Waterville Formation; folded limestones and thin limestones (interbedded with a sandy-topelitic package). The mineralogy o f the folded limestones includes muscovite, biotite, chlorite, ankerite, calcite, plagioclase, quartz, rutile, pyrrohotite, and chalcopyrite. The thin limestones show mineral evolution with increasing metamorphic grade. Zones are based on mineral assemblages in pelites and correspond to greenschist-amphibolite facies conditions:  chlorite zone: muscovite + ankerite + albite + quartz + rutile + accessory sulfides + chlorite or calcite (but not both) biotite zone: muscovite + biotite + chlorite + calcite + plagioclase + quartz + ilmenite + accessory sulfides +/- ankerite garnet zone: biotite + chlorite + calcite + plagioclase + quartz + garnet + ilmenite + accessory sulfides +/- calcic-amphibole staurolite-andalusite zone: calcic-amphibole + chlorite + calcite + plagioclase (calcic) + quartz + garnet + ilmenite + accessory sulfides +/- biotite  Giles Mountain and Waits River Formations Chemical compositions for limestone, sandstone, and pelitic units o f the Siluro-Devonian Giles Mountain and Waits River Formations, east-central Vermont are tabulated i n Ferry [1994, p.930-931]. Stratigraphically, the Waits River Formation is overlain by the Giles Mountain Formation. Similarly to the sediments studied i n south-central Maine, these rocks were folded  and regionally metamorphosed during the Acadian Orogeny. Because analogous rock types are found in the Giles Mountain and Waits River Formation, their geochemical analyses were grouped together to represent three fields; limestone, sandstone, and pelite. The Giles Mountain Formation is composed of interbedded pelites, micaceous sandstones, and minor micaceous carbonate rocks (limestones). The Waits River Formation is composed of interbedded micaceous limestone and pelites (and their metamorphic equivalents). All packages within the Giles Mountain and Waits River Formation show mineral evolution with increasing metamorphic grade. For simplicity, these are compiled in Table 3.7.  Table 3.7. Mineral evolution of Giles Mountain (GM) and Waits River (WR) sediments Formation Rock type Chlorite zone  GM limestones muse, ank, cc, alb, qtz, rut, sulfides  Biotite zone  muse, ank, cc, qtz, sulfides +/ (rut or ilm), +/- (alb or olig) muse, gnt, ank, cc, pi, qtz, sulfides, rut a/o ilm, +/-bt muse, gnt, ank, cc, pi, qtz, sulfides, chi, rut a/o ilm, +/- bt  Garnet zone  Kyanite zone  WR limestones muse, par, ank, cc, alb, qtz, rut, sulfides +/chi muse, ank, cc, olig, qtz, rut, sulfides +/chi  GM pelite muse, chi, ank, alb, qtz, rut, sulfides, +/- siderite  WR pelite muse, chi, ank, pi, qtz, rut, +/- ilm, +/- par  GM sandstone muse, ank, alb, qtz, rut, sulfides, (chi or cc)  muse, chi, bt, ilm, olig, qtz, rut, ank, sulfides  n/a  muse, bt, ilm, ank, olig, qtz, rut, sulfides, (chi or cc)  muse, ank, cc, olig, qtz, rut, sulfides +/chi  muse, bt, chi, gnt, pi, qtz, ilm, sulfides, +/- rut  muse, bt, chi, gnt, ank, pi, qtz, ilm, sulfides  muse, bt, chi, gnt, pi, qtz, ilm, sulfides, (ank or cc), +/-rut  muse, bt, chi, ank, cc, pi, qtz, rut, sulfides, +/ calc-amph (replacing muse)  n/a  muse, bt, chi, gnt, pi, qtz, ilm, sulfides, rut, cc, st, ky, elz  muse, bt, chi, gnt, pi, qtz, ilm, sulfides, elz a/o calcamph, (ank or cc), +/- rut  100  Roof pendant at Hope Valley, CA Chemical compositions for the calcareous hornfels and marble from a Mesozoic roof pendant at Hope Valley, California are tabulated in Ferry [1989, p. 407]. Although the rocks at Hope Valley were originally interbedded limestones, marls, sandstones, tuffs, and other volcanics, the study focused on the carbonate rocks which were contact metamorphosed in the Cretaceous with the emplacement of the calc-alkaline Sierra Nevada batholith. Two fields were created and projected onto ternary diagrams; calcareous hornfels and marble. The mineralogy for both calcareous hornfels and marble includes calcite + K-feldspar + quartz + sphene +/- diopside +/- plagioclase +/- scapolite +/- clinozoisite. Moreover, rocks on one side a fault contain variable amounts of biotite, amphibole, and muscovite while those on the other side contain variable amounts of grossular, wollastonite, and axinite.  3.4.2 Geochemical trends in Meta-sedimentary Rocks Geochemical analyses from each formation was projected onto the A S C , ASF, A C F , and SFC diagrams and fields were constructed separately for geochemical data calculated and projected using total iron as Fe203 and FeO (e.g. Fig. 3.1a vs. Fig. 3.5a). Because all rocks will contain a mix of Fe203 and FeO, these two projections serve as end-members that bound rock composition. For clarity, geochemical trends for the literature are noted below in tabulated format followed by brief descriptions.  Vassalboro/Sangerville Formation iron  3  S' 64-95% 62-93%  ASC A' 2-9% 5-11%  C 1-32% 3-34%  S' 80-90% 82-92%  ASF A' 2-10% 4-12%  3  A' 10-30% 15-50%  ACF C variable variable  F* variable variable  F' 8-11% 3-8%  SFC S' variable variable  FeO Fe 0 2  FeO Fe 0 2  lithology F' 7-11%  sandstone  2-8%  sandstone  C* variable variable  sandstone sandstone  The chemical composition of the Vassalboro/Sangerville sandstone is controlled primarily by Si02 and to a lesser extent CaO. Therefore the Vassalboro/Sangerville field plots near the S' apex with variable CaO (< 34 percent). In projections where the Si02 component is not represented, the field ranges between the C and F' apex with no more than 50 percent [AI2O3 + Fe203], controlled by Fe203 in mineral compositions (Fig. 3.4). Where CaO is not represented (Fig. 3.2, 3.6), the Vassalboro/Sangerville field strongly is restricted and plots near the S' apex.  Waterville Formation iron FeO Fe 0 2  3  FeO Fe 0 2  3  S' variable  ASC A' 0-9%  C* variable  S' 60-90%  ASF A' 0-11%  F* 6-33%  variable  1-11%  variable  62-92%  1-18%  4-24%  A' 0-20%  ACF C variable  F' variable  F' 2-20%  SFC S' variable  C variable  variable  variable  5-30%  1-17%  variable  variable  lithology m etacarbonate m etacarbonate  metacarbonate m etacarbonate  The chemical composition of the Waterville meta-carbonate is dominated by Si02, CaO, and to a lesser extent FeO and Fe203. In ternary projections where both the primary components (Si02 and CaO) are represented (Figs. 3.1, 3.3, 3.5, and 3.7), the Waterville field trends linearly between the S' and C apexes. In projections where one of the primary components is missing (Fig. 3.2, 3.6, 3.4, 3.8) the field trends toward the F' apex.  Giles Mountain and Waits River Formation 1. limestone iron FeO Fe 0 2  3  S* variable variable  ASC A* 0-7% 1-8%  C variable variable  S' 67-94% 70-95%  ASF A' 0-7% 1-12%  lithology F' 7-28% 3-19%  limestone limestone  102  FeO Fe 0 2  3  A' 0-13% 1-24%  ACF C 58-93% 63-94%  F' 7-32% 5-19%  F* 2-17% 1-12%  SFC S' variable variable  C variable variable  limestone limestone  The Giles Mountain and Waits River limestone is consists predominantly of Si02 and CaO and to a lesser extent FeO or Fe203 and mimics the Waterville trend. The Giles Mountain and Waits River limestone fields are smaller, but this probably reflects a smaller number of analyzed samples.  1.  sandstone iron FeO Fe 0 2  3  FeO Fe.Oj  S' 72-93% 69-92%  ASC A' 5-11% 5-14%  C 4-20% 5-19%  S' 72-91% 2-10%  ASF A' 4-11% 75-93%  F' 5-18% 5-15%  sandstone sandstone  A' 19-30% 35-45%  ACF C 28-45% 30-50%  F' 38-45% 16-27%  F' 5-18% 2-10%  SFC S' 67-92% 76-96%  C 2-27% 2-19%  sandstone sandstone  lithology  The chemical composition of the Giles Mountain and Waits River sandstone is controlled primarily by Si02 and to a lesser degree CaO and mimics the Vassalboro/Sangerville trend.  2. pelite iron FeO Fe 0 2  3  S' 69-92% 66-91%  ASC A' 6-35% 7-28%  C 0-11% 0-9%  S' 60-83% 62-87%  ASF A' 7-21% 10-28%  F' 7-20% 2-10%  pelite pelite  F' variable 20-39%  F' 6-23% 4-14%  SFC S' 70-92% 80-97%  C 0-10% 0-11%  pelite pelite  ACF FeO Fe 0 2  3  A' variable 52-78%  C* 1-24% 1-28%  lithology  The chemical composition of the Giles Mountain and Waits River pelite is controlled primarily by Si02, AI2O3, and to a lesser extent FeO or Fe203. In projections where all three of the  103  aforementioned components are represented, the pelite field strongly favors the S' apex. This trend also holds for projections that do not represent the A ' apex.  Roof pendant at Hope Valley, CA 1. calcareous  hornfels  iron FeO Fe 0 2  3  FeO Fe 0 2  3  S'  ASC A'  C  S'  ASF A'  F*  65-85%  2-7%  12-30%  80-90%  2-8%  7-16%  calcareous hornfels  73-83%  5-9%  11-21%  80-94%  4-10%  2-10%  calcareous hornfels  A'  ACF C  F'  F'  SFC S'  C  1-24%  52-66%  21-31%  7-12%  60-82%  12-27%  calcareous hornfels  15-31%  56-69%  9-19%  1-8%  65-85%  12-29%o  calcareous hornfels  lithology  The chemical composition of the calcareous hornfels at Hope Valley is controlled primarily by SiC>2 and to a lesser extent CaO. Calcareous hornfels falls within the Vassalboro/Sangerville field.  2.  marble iron FeO Fe 0 2  3  FeO Fe 0 2  3  S'  ASC A'  C  S'  ASF A'  F'  3-20%  0-2%  79-96%  3-21%  0-2%  79-97%  70-85%  5-7%  10-23%  marble  72-86%  5-10%  9-17%  marble  A'  ACF C  F'  F'  SFC S'  0-2%  C  93-99%  1-5%  1-3%  3-21%  88-96%  marble  0-2%  95-99%  0-3%  0-3%  4-21%  88-96%  marble  lithology  The chemical composition of marble at Hope Valley is controlled primarily by CaO and to a lesser extent Si02. The marble field plots near the C apex. In projections that represent Si02, the  104  marble field plots more toward the S' apex, however never exceeds 21 percent S', except where CaO is not projected (Fig. 3.2, 3.6).  3.4.3 Meta-sedimentary and Skarn rock compositions at Mineral Hill Marble Marble outcrops throughout the map area. Twenty-nine samples were analyzed for whole rock chemical composition by XRF (Tables 3.1 and 3.2), including green marble (N=3) from within the main skarn body, grey and bleached marble (N=8) from the upper marble quarry, grey and bleached marble (N=4) from the northern extension, grey and bleached marble (N=12) from Marble Hill and black marble (N=l) (Fig. 1.2). Most marbles are chemically similar with the notable exception of B M - l - M , a black phlogopite-bearing marble, which plots toward the F' apex due to high magnesium content (10.72 percent; Figs. 3.2b, 3.6b, 3.3b, 3.7b, 3.4b, and 3.8b). Moreover, B M - l - M , is drawn toward the chemical composition of dolomite (8). All other marble analyses plot near the C apex due to the dominance of CaO content. Some marbles are influenced by a higher  Si02 content  coupled with small increases in FeO and MgO, which pull marble composition towards the S' and F' apex, respectively. In general, Mineral Hill marble compositions coincide most closely with the roof pendant marble composition from Hope Valley, CA. In a few samples, compositions are closer to the fields representing the Waterville meta-carbonates and Giles Mountain/Waits River limestone. Most marble analyses resemble those of fossiliferous, lithographic, and oolitic limestone (5, 6, 7) from Brownlow [1996], but are more siliceous (e.g. Fig. 3.2b).  105  Skarn Geochemical analyses of twenty-nine skarn samples including wollastonite skarn (N=22), clinopyroxene skarn (N=l), garnet-wollastonite skarn (N=3), garnet skarn (N=2), and garnetite (N=l) are presented in Tables 3.1 and 3.2.  Wollastonite skarn Not suprisingly, the composition of wollastonite skarn is primarily controlled by CaO and Si02 (Figs. 3.1c, 3.5c, 3.3c, and 3.7c). As a consequence, wollastonite skarn analyses plot along the line between the S' and C apexes (average 50:50). Wollastonite skarn contains very little iron. In the A C F ternary diagram (Figs. 3.4c and 3.8c), projected partially from Si02, wollastonite skarn plots near the C apex illustrating the strong influence of CaO within the mineral assemblage. Likewise, in the ASF ternary diagram (Figs. 3.2c and 3.6c), wollastonite skarn plots near the S' apex. One clear exception is sample W l b which has an anomolously high magnesium content. Wollastonite skarn is poor in AI2O3, (< 2.2 wt. %). Wollastonite skarn samples do not consistently plot near any single meta-sedimentary protolith field. In general, wollastonite skarn samples coincide mostly closely with Waterville meta-carbonate and Giles Mountain/Waits River limestone, except in ternary diagrams projected from either S' or C (Figs. 3.2c, 3.6c, 3.4c, and 3.8c). In this case, wollastonite skarn plots within the fields for roof pendant marble from Hope Valley, CA. In those ternary diagrams which include both primary components (i.e. CaO and Si02; Figs. 3.1c, 3.5c, 3.3c, and 3.7c), wollastonite skarn compositions most commonly resemble a calcareous shale (11) from Brownlow [1996].  106  Clinopyroxene  skarn  The chemical composition of one sample of clinopyroxene skarn is dominated by Si02, AI2O3,  and CaO with lesser iron (Fe203 and FeO) and MgO. Clinopyroxene skarn is chemically  distinctive from all other skarn types due to very high (-70 percent) Si02 content. Clinopyroxene skam plots within (or near to) compositions of the Vassalboro sandstone and calcareous hornfels from Hope Valley, C A (Figs. 3.1-3.8) and most closely resembles a subgraywacke (4) from Brownlow [1996].  Garnet-wollastonite  skarn  The chemical composition of garnet-wollastonite skarn is dominated by CaO, S-O2, AI2O3,  iron (Fe203 and FeO), and to a lesser extent MgO. Samples fall on a line between Fe203  and FeO end-members. Garnet-wollastonite skarn plots near garnetite and garnet skarn compositions although typically (except sample UB2c) with lesser [AI2O3 + Fe203] and greater S.O2 content (see below)( e.g. Figs. 3.2c and 3.6c). They are differentiated from wollastonite skarn by greater  [AI2O3  + Fe203] even among plots where total iron is FeO (e.g. Figs. 3.4c and  3.8c). UB2c has the highest percentages of Si02,  AI2O3,  (Fe203 or FeO), and MgO at the expense  of CaO, driving this sample farthest from the C apex (Figs. 3.1c, 3.5c, 3.3c, 3.7c, 3.4c, and 3.8c). Garnet-wollastonite skarn compositions plot near the Waterville meta-carbonate and Giles Mountain/ Waits River limestone. One exception is sample UB2c which also plots near to the Vassalboro sandstone and calcareous hornfels from Hope Valley, C A , especially if the mineral composition of garnet dominantly fixed by FeO (e.g. Fig. 3.4c). Garnet-wollastonite skarn compositions most closely resemble that of calcareous shale (11) from Brownlow [1996].  107  Garnet skarn The chemical composition of garnet skarn is dominated by CaO, S i 0 , A l 0 , iron (Fe 0 2  2  3  2  3  and FeO) and to a lesser extent MgO. Because of the prevalence of grandite garnet, samples fall on a line between Fe20 and FeO end-members. Garnet skarn plots in a similar field as garnet3  wollastonite skarn and garnetite samples, however is differentiated by greater [A1 0 + Fe20 ] 2  3  3  contents. In general, garnet skarn compositions coincide most closely with the Waterville metacarbonate and Giles Mountain/Waits River limestone, although garnet skarn at Mineral Hill has greater [A1 0 + F e 0 j content (Figs. 3. lc, 3.5c, 3.2c, 3.6c, 3.4c, and 3.8c). In the A C F 2  3  2  3  projection (Figs. 3.4c and 3.8c), garnet skarn plots near the compositions of the Vassalboro/Sangerville sandstone and calcareous hornfels from Hope Valley, CA. Garnet skarn does not consistently plot near any common sedimentary rock type.  Garnetite Garnetite consists of < 80 wt % andraditic garnet and its composition therefore plots near this end-member composition. If garnetite was FeO-rich the bulk composition (FeOi) would plot near pyrope/almandine end-member compositions. The composition of garnetite is primarily controlled by CaO, Si0 , iron (Fe 0 Q FeO), and Al20 . Garnetite plots near garnet-wollastonite 2  2  3  3  skarn and garnet skarn and is differentiated from garnet-wollastonite skarn by the higher [Al20  3  +Fe 0 ] content in garnet pulling the composition toward the A ' (Figs. 3.1c, 3.5c, 3.2c, 3.6c, 2  3  3.4c, and 3.8c). In general, the Mineral Hill garnetite sample lies spatially close to the Waterville metacarbonate and Giles Mountain/Waits River limestone fields, however the garnetite always plots closer to the A ' apex (Figs. 3.1c, 3.5c, 3.2c, 3.6c, 3.4c, and 3.8c). As with garnet skarn, garnetite does not consistently plot near any common sedimentary rock type.  108  Calc-silicate Skarnoid Three skarnoid samples were analyzed by XRF for whole rock chemical composition. The compositions of two of the samples (CZ-3  and UB14c) are primarily controlled by Si0 , 2  AI2O3, CaO and N a 0 with lesser iron (Fe 0 and FeO), MgO and K 0 . The greater percentage 2  2  3  2  of N a 0 and K 0 reflect the presence of feldspar and distinguishes these skarnoid samples from 2  2  all other meta-sedimentary and skarn units at Mineral Hill. The alkali content of these rocks is not reflected in the ternary diagrams which are projected from the alkali feldspars. Samples CZ-1 and UB14c plot near clinopyroxene skarn (cf. Fig. 3.1c and 3.Id). Skarnoid sample CZ-1 is very rich in S i 0 (94.86 wt %) and plots near the S' apex in all ternary projection except A C F (Fig. 2  3.4d and 3.8d), where it plots near the A ' apex. Skarnoid most closely resembles the chemical composition of a sub-graywacke  (CZ-3  and UB14c) (4) and orthoquartzite (CZ-1) (1) from Brownlow [1996]. Skarnoid does not plot near any single meta-sedimentary rock type.  Quartzite The chemical composition of a single sample of quartzite is dominated by Si0 , AI2O3, 2  and CaO. The rock is of unknown origin and consists predominantly of quartz and epidote. Quartzite plots near the compositions of the Vassalboro sandstone and calcareous hornfels from Hope Valley, C A and closely resembles the chemical composition of a subgraywacke (4) from Brownlow [1996].  3.5 Discussion By observing geochemical trends of meta-sedimentary rocks formed at or near isochemical conditions [Ferry, 1988, 1989, and 1994], and whole-rock geochemistry of common sedimentary rocks [Brownlow, 1996] and comparing whole-rock geochemistry of meta-  109  sedimentary and skarn rocks from Mineral Hill, we can deduce to a certain degree the origin of each unit. In particular, by comparing each in SACF ternary space, whether the chemical composition of the rock unit is primarily controlled by protolith composition or interaction with external material (discussed later) can be inferred. Both garnet-wollastonite skarn and wollastonite skarn plot near fields for the Waterville meta-carbonate and Giles Mountain/Waits River limestone, however do not fall consistently within these fields. Moreover, garnet-wollastonite plots closer to the A ' apex than wollastonite skarn, due to higher concentrations of AI2O3, probably reflecting the greater garnet abundance. Both garnet-wollastonite skarn and wollastonite skarn also most closely resemble a calcareous shale (11, from Brownlow, 1996). It is unlikely that wollastonite skarn formed isochemically from a calcareous shale since it would reflect higher concentrations of AI2O3. Wollastonite skarn on average has < 1.5 wt % AI2O3. Instead, it is likely that wollastonite skarn formed from marble due to the interaction with aqueous silica by the reaction: CaC03 + Si0 (aq) = CaSi0 + C 0 . 2  3  2  (Rl)  This is supported by wollastonite skarn compositions consistently plotting on average 50:50 between the S' and C apex. Moreover, in the field, wollastonite skarn is often proximal to and in contact with marble units. Even though garnet-wollastonite skarn most closely resembles the chemical composition of a calcareous shale, all samples do not consistently plot near it (e.g. Figs. 3.1, 3.2, 3.3, and 3.4). Instead, it varies in having a greater SiCh, CaO and AI2O3 abundance than calcareous shale. This probably reflects the varying garnet and wollastonite content in garnet-wollastonite skarn. Therefore, garnet-wollastonite skarn was probably derived from protolith interaction with external material. Meinert [1992] argues that a garnet skarn derived from a limestone protolith would be relatively wollastonite-rich (discussed later). Based on his assertion and the proximity  110  of many garnet-wollastonite skarn sample to green marble in the field, it is probable that this unit derived from a limestone or marble protolith (possibly interbedded with variable amounts of argillaceous or marl material) and external Si02 and possibly AI2O3. Garnet skarn and garnetite plot most closely to meta-sedimentary fields of the Waterville meta-carbonate and Giles Mountain/Waits River limestone however elevated in [AI2O3 + Fe203] consistently plotting closer to the A' apex. They do not resemble any singular common sedimentary rock [from Brownlow, 1996]. Therefore, garnet skarn and garnetite probably originated from a protolith that interacted with an external source. Because of the dominance of grandite garnet (Ca), in garnet skarn mineral assemblage and relative lack of wollastonite (to garnet-wollastonite skarn), garnet skarn (and clinopyroxene skarn?) probably formed from a mixed sequence of calc-argillaceous, marl and marble material or intensive infiltration of FeO, MgO, AI2O3, and Si02. Although we see evidence of infiltration of these elements by the existence of a garnet zone in the study area (zonation discussed later), it is more probable that a mixture of these scenarios produced garnet skarn. However, it should be noted that no calc-silicate protolith is preserved within the field area. Because garnetite contains >80 percent andraditic garnet, a metasomatic origin from marble is likely due to higher AI2O3 content from that of marble and garnet skarn geochemistry. In the field, garnetite is observed to be spatially associated with green marble. Skarnoid is highly variable geochemically. Skarnoid most closely resembles a subgraywacke and orthoquartzite. This reflects the high Si02 content in these samples. However, it is unlikely that skarnoid derived from similar sediments because they resemble no members within the Quatsino sequence, and skarnoid outcrops in a large portion of the map area. Skarnoid generally crops out within in an area that is intruded extensively by dikes and likely represents a unit with a complex origin, possibly involving several metasomatic events.  Ill The distribution of minerals in skarn units at Mineral Hill denote a typical zonation pattern found in skarn formed adjacent to plutons. Skarn zonation within the field area and controls of protolith and fluid infiltration are discussed in further detail in the next section.  3.6 Distribution of Minerals in Calcic Exoskarn at Mineral Hill  3.6.1 Introduction No skarn unit identified at Mineral Hill falls within a typical geochemical field for metacarbonate rocks formed at or near to isochemical conditions [from Ferry, 1988, 1989, and 1994], nor do they correspond consistently with an chemical composition for common sedimentary rocks [from Brownlow, 1996]. Although some protolith control within skarn is evident, metamorphism could not have been purely isochemical to produce the geochemistry and volume loss we see in skarn units. The distribution of map units at Mineral Hill is attributed to: (1) changes in protolith host rock and (2) the variation in style and intensity of alteration which reflects the propagation rates of alteration fronts, and overprinting of multiple fluid events. Skarn units (wollastonite and garnet-wollastonite) which most likely formed from marble (1) plot outside of the field for marbles and limestone compositions, more Si02-and Al 03-rich, 2  respectively. (2) Garnet-wollastonite skarn does not plot within approximately constant ratios with marble compositions from Mineral Hill, implying either different protolith or different reactions to produce skarn. In other skarn units (garnet and clinopyroxene), the protolith composition is uncertain although their percent mineralogy suggests either a mixed parent lithology (such as calcargillite), or intensive infiltration of FeO, MgO , AI2O3, and Si02- Although mobility of these elements is likely, it is more probable that a mixture of these scenarios occurred to form skarn.  112  Interleaves of garnet and garnet-wollastonite skarn are observed within the main skarn body proximal to the pluton contact. This occurrence suggests that the sedimentary pendant prior to metamorphism was an interbedded limestone, dirty limestone and/or calc-argillitic sequence. This is consistent with descriptions outlined in the Quatsino sequence. Both garnet and garnetwollastonite skarn are compositionally layered. Garnet infilling clinopyroxene grain boundary porosity suggests that MgO front occurred producing a clinopyroxene zone prior to garnet formation. Most evidence of a clinopyroxene zone has been overprinted by garnet. All units in which brown, greenish-brown and dark red garnets are observed are defined as garnet zone. The extent of garnet zone reaches the contact of wollastonite skarn. Even though some wollastonite skarn contains garnet, these rocks are predominantly monomineralic and garnet presence is attributed to greater concentrations of AI2O3 and Ti02 in the protolith composition. It can also be suggested that if garnet-wollastonite was produced from a similar protolith, some of the garnet could be controlled by protolith composition, however not all due to lack of abundant AI2O3 and Ti02 in marble compositions.  3.6.2 Skarn Zonation Zonation at Mineral Hill is observed within a 450 m by 150 m area on the south-eastern flank of a roof pendant enclosed by a dioritic component of the Crowston Lake Pluton (Fig. 3.20). Zones were interpreted on the basis of the presence of minerals dominant in skarn development; garnet, pyroxene, and wollastonite. The deposit is zoned over -65 m from garnet skarn (with interleaved garnet-wollastonite skarn and garnetite) proximal to the Crowston Lake Pluton, through wollastonite skarn to distal calcite marble. As with most skarn systems, garnet and pyroxene are the dominant minerals and represent the first products of water-rock reactions [Einaudi and Burt, 1982]. Zoning during the early stages of skarn formation commonly occurs as garnet-pyroxene-(wollastonite)-marble, proximal to distal from the pluton, respectively [Einaudi  113  and Burt, 1982]. Grossular-andradite solid solutions are common garnet phases in calcic exoskarn [Zharikov, 1970] with less than 15 mole percent spessartine + almandine [Einaudi and Burt, 1982]. Pyroxene phases range within the diopside-hedenbergite and hedenbergitejohannsenite solid solution series, with a notable absence of diopside-johannsenite compositions [Einaudi and Burt, 1982]. Other common skarn minerals (calc-silicates) are wollastonite, rhodonite, vesuvianite, epidote, scapolite, plagioclase, and potassium feldspar (Table 3.8). Accessory minerals are titanite and apatite; rare minerals are monticellite, merwinite, spurrite, melinites, cuspidine, and bustamite.  Garnet zone The Mineral Hill skarn deposit has similar zoning characteristics as most skarn systems, however most evidence of a pyroxene zone has now been overprinted. Garnet skarn, garnetwollastonite skarn, garnetite, and some outcrops of skarnoid are attributed to the garnet zone of the map area based on the presence of garnet (Fig. 3.20). Garnet zone extends at most ~50 m outboard of the Crowston Lake Pluton. Relative mineral abundance differences between skarn units within the garnet zone can be partially attributed to controls of protolith composition. Although the protolith is not always preserved in skarns, the composition of the protolith often defines skarn mineralogy and zonation. For instance, Meinert [1992] showed that a garnet skarn derived from a limestone protolith would be wollastonite-rich (approximately >75-80 percent) whereas garnet skarn derived from marl will be relatively wollastonite-poor (< 20 percent), and will be dominated by garnet and clinopyroxene (Fig. 3.21). On this basis, garnet skarn at Mineral Hill is proposed to have been altered from an argillitic or marl sequence and garnet-wollastonite skarn from marble or calcite veins interbedded within the argillite or marl. Extensive isoclinal deformation precludes identification of the calcitic protolith of garnet-wollastonite skarn. The calcitic unit could be interbeds of pinched out marble due to isoclinal folding or boudinaged  114 Table 3.8. Skarn mineralogy- common minerals, mineral groups and compositions [after Meinert,1992]. Minerals identified in Mineral Hill skarn (bold). General Group  End Members  Composition  Garnet  grossular andradite  Ca Al (Si0 )3 Ca Fe (Si04)3  spessartine almandine pyrope  Mn Al (Si0 )3 Fe Al (Si0 )3 Mg3Al (Si0 )  diopside  CaMgSi 0  hedenbergite johannsenite fassaite  CaFeSi 0 CaMnSi 0 Ca(Mg, Fe, Al)(Si, A1) 0  larnite forsterite fayalite tephroite  Ca Si0 Mg Si0 Fe Si0 Mn Si0  ferrosilite rhodonite  FeSi0 MnSi0  3  wollastonite  CaSi0  3  tremolite ferroactinolite manganese actinolite hornblende  Ca Mg Si 0 (OH) Ca Fe5Sis0 (OH) Ca MnsSi80 (OH) Ca (Mg, Fe)4Al Si 0 2(OH)  pargasite cummingtonite dannemorite grunerite  NaCa (Mg, Fe)4Al Si 022(OH) Mg (Mg, Fe) Si 0 2(OH)2 Mn (Fe, Mg)5Si 0 (OH) Fe (Fe, Mg) Si 0 2(OH)  piemontite allanite  Ca (Mn, Fe, Al) (Si0 ) (OH) (Ca, REE) (Fe,Al) (Si0 ) (OH)  epidote clinozoisite  Ca (Fe, Al) (Si0 ) (OH) Ca Al (Si0 ) (OH)  Plagioclase  anorthite  CaAl Si O  Scapolite  marialite meionite  Na4Al Si 02 (Cl, C 0 , OH, S0 ) C a A l S i 0 ( C 0 , CI, OH, S0 )  Pyroxene  Olivine  Pyroxenoid  Amphibole  Epidote  Axinite Other  3  2  3  2  3  3  4  2  4  2  4  2  4  2  2  3  6  6  2  6  2  2  6  4  2  2  4  4  2  4  3  2  5  8  22  2  2  22  2  2  22  2  2  2  7  2  2  3  2  5  g  8  5  8  2  22  2  4  2  3  3  2  3  2  4  2  3  4  9  6  6  2  2  3  2  2  2  2  2  2  6  4  3  4  3  3  3  s  4  24  3  4  3  4  (Ca, Mn, Fe, Mg) Al BSi Oi (OH) 3  vesuvianite prehnite  2  4  5  Ca,o(Mg, Fe, M n ) A l S i 0 ( O H , CI, F ) Ca Al Si Oio(OH) 2  2  2  3  2  4  9  34  4  115  Igneous Units Crowston Lake pluton  Marble Hill  Gabbro dikes and sills Monzonite D2  Tonalite dikes and sills  D3  Basalt dikes and sills  Unit  Protolith v  Marble  •  J Limestone Garnet-wollastonite > or skarn Wollastonite skarn Garnet skarn Hydrothermally altered skarn Skarnoid  Zone Marble Wollastonite zone Garnet zone Inferred pluton  Fig. 3.20. Geologic map of study area with zonation from garnet skarn proximal to the pluton contact to distal wollastonite skarn. Late D2 and D3 events cross-cut map area.  116  Fig. 3.21. Schematic illustrating the rock history of a marble infiltrated by magmatic fluid carrying aqueous Fe, A l and SiCh. At t = 0, marble; t = n, Si02 has reacted with marble to form wollastonite skarn; at t = n+1, Fe and A l have reacted to form garnet.  117  calcite vein material within garnet skarn and garnetite units. The protolith was probably contaminated with clastic sediment due to garnet abundance up to but not exceeding 35 percent. Due to its green color, the calcite marble spatially associated to garnet-wollastonite skarn is differentiated from other marble units. Although protolith composition can partially control the mineralogy and zonation in skarn, infiltration of reactive fluid can also define spatial distribution of skarn mineralogy and zoning; often both controls work in tandem. Fluid composition influences reactions producing skarn. If an exotic fluid is out of equilibrium with the rock it infiltrates, reaction will occur in order to maintain chemical equilibrium. As reaction continues, the composition of the rock and fluid changes. Several studies have determined that different reactions propagate at different rates [Korzhinskii,  1970; Bickle andBaker,\990;  Dipple and Gerdes, 1998]. They observed that  although the reactions may start at the same interface, the reaction fronts spread farther apart as infiltration continues (Fig. 3.22). Such geometries are distinctive of infiltration-driven reaction and allow mapping of fluid flow paths. This sort of phenomena could have partial control over mineral zone distribution in skarn. Moreover, reaction caused by infiltration of fluid can have a tremendous impact on skarn development due to reaction-infiltration feedback (discussed later). Parts of skarnoid is attributed to the garnet zone due to the presence of garnet observed in field and identified petrographically in samples TB14B, CZ-1, and CZ-2. However, skarnoid is distinguished from typical skarn since this unit appears to have a complex origin, probably involving multiple metasomatic events and/or overprinting of skarn-like assemblages onto a hornfels or reaction skarn. This is inferred due to high SiC<2 content and spatial relationships with extensive tonalite and basalt diking events. Quartzite outcrops within the garnet zone, however no garnet is present in these samples. This unit might represent altered dike or skarn material, vein or SiC^ infiltration into brecciated  118  Distance  Fig. 3.22. Time versus distance schematic showing that two reactions that start at the same interface (t=0), propagate at different rates. The result is a spatial distribution or zoning of metasomatized sediments in respect to the magmatic fluid source (i.e. pluton) from distal marble to wollastonite skarn to proximal garnet-wollastonite skarn. Cross section A A ' illustrates fluid migration of mobile elements at t =n.  119 garnet skarn related or emplaced with the skarn forming event, but was not altered by it (with the possible exception of late epidotization).  Clinopyroxene  zone  One sample MB3b is identified as a clinopyroxene skarn, however no other clinopyroxene skarn samples were observed. Some garnet skarn samples do show compositionally layering with mineralogy from high garnet abundance to zones of high clinopyroxene abundance. Nevertheless, evidence of a clinopyroxene zone is preserved as garnet infilling porosity around clinopyroxene grains, although no 'classic' clinopyroxene zone exists in the map area.  Wollastonite  zone  Wollastonite skarn is attributed to the wollastonite zone. Where exposed, wollastonite skarn interfingers into grey and bleached marble (Plate 2.8, Figs. 1.9-1.11). This boundary marks the extent of aqueous silica infiltration. Even though garnet is present in many samples, wollastonite skarn is essentially monomineralic. Garnet production in these samples cannot be exclusively contributed to the infiltration of an elemental front (metasomatism) since the marble protolith probably varies in AI2O3 and T i 0 2 (i.e. type A skarn). Moreover, wollastonite skarn does not plot near the A' or F' apex in ternary diagrams, therefore the composition is not primarily controlled by the presence of grossular or andradite.  Hydrothermally  altered skarn  Often zoning will occur due to overprinting of the initial skarn event by either a single fluid event or multiple fluid events. Since calcic exoskarn is dominated by mostly anhydrous  120 minerals (e.g. garnet, pyroxene and wollastonite phases) formed by infiltration of magmatic fluids, it represents the highest temperature metasomatic alteration, which often introduces silica, iron and alumina while removing large amounts of volatiles from the system [Barton et ah, 1991]. This is often the first skarn forming event, especially when the alteration is related to the emplacement of a pluton. It is not uncommon, however, that subsequent lower temperature hydrothermal activity will result in production of hydrous calc-silicates (e.g. epidote), and deposition of oxides and sulfides referred to as hydrous skarn or retrograde skarn [Barton et al., 1991]. This fluid event can overprint anhydrous skarn, and the anhydrous phases may retrograde to their lower temperature equivalents. At Mineral Hill, hydrous skarn overprinting is observed within garnet zone and wollastonite zone units. Extensive hydrous skarn is always spatially related to late brittle faults and/or the pluton contact. The areas of intense retrograde mineralization are shown as hydrothermally altered garnet skarn on the map (Fig. 1.2) and are characterized by the abundance of chlorite, epidote and sulfide minerals overprinting anhydrous assemblages (e.g. garnet and pyroxene). However, in places where the hydrous alteration occurs near the pluton is not always clear if the outcrop is hydrothermally altered garnet skarn or hydrothermally altered pluton. Less extensive hydrous alteration occurs throughout the map area in all units to some extent (sometimes in trace amounts) typically as epidote or pyrite mineralization.  3.7 Marble to Wollastonite Skarn Transformation- Quantification of transient synmetamorphic permeability  3.7.1 Introduction Early researchers recognized skarn formation as a dynamic process [Lindgren, Barred, 1902; Lawson, 1914; Korzhinskii,  1902;  1936]. Since, it has been shown that metasomatism is  121  a much more complex process to quantify than isochemical metamorphism. In general, metasomatism can be defined as a type of metamorphism that occurs when the chemical composition of a rock changes due to the introduction of material from an external source. Although the primary control on the chemical composition of a metamorphic rock is the composition of the protolith, often fluid dynamics during metamorphism drive reaction causing changes in composition and can produce infiltration skarn. This type of skarn formation generally occurs at high temperature by metasomatic reaction with magmatic fluids where advective mass transfer is the main mechanism driving the alteration event. Although fluid composition controls much of the reaction producing skarn mineralogy and zoning, many factors are integral in influencing and driving reaction (e.g. permeability and fluid pressure gradients). Moreover, when quantifying a skarn system , there are several assumptions that must be evaluated based on geologic field and analytical evidence. First, the alteration event must be defined as open or closed. A n open system involves the exchange of mass and energy between the system and surroundings whereas if the system remained closed the exchange of energy can occur but no mass change between the system and surroundings. Therefore, if gain and losses of species accompanies alteration, the geologic process must be defined as a geochemically open. Once the skarn system is defined, other assumptions must be considered: (1) volume change, (2) immobile components, and (3) protolith. It is not necessary to make all of these assumptions simultaneously as one assumption may lead the researcher to conclusions about the others. Nevertheless, an accurate initial assumption when attempting to quantify skarn formation is essential. Textural relationships can often reveal the nature of volume change during an alteration event. On the outcrop scale, drastic volume losses (e.g. -60-70 percent) may be seen in the field as extensive collapse features and vuggy textures. However, often these textures are not observed especially when volume losses are only on the scale of-10 percent. Constant volume has been observed by measuring beds between protolith and altered rock and finding no  122 difference in thickness [Lindgren, 1924]. However, thickness differences usually cannot be measured due to extensive deformation and/or lack of protolith. Likewise, immobility of one or more element can be an unreliable assumption. Many studies have assumed the immobility of A1 0 and/or T i 0 [Ague, 1994; Lentz, 1995; this study]. 2  3  2  However, other authors contend that few to no elements remain immobile during this scale of metasomatic alteration in skarn [Rae et. al, 1996; Lentz, 2000]. Moreover, protolith assumptions can be difficult in cases where no true (unaltered) protolith is preserved. This is especially evident in some roof pendants in the Coast Plutonic Complex of British Columbia (e.g. Mineral Hill) especially when reaction between units effectively creates a "new" rock type. Furthermore, metamorphism is frequently accompanied by deformation. Consequently, there may be tectonic interleaving of different protolith compositions, which gives rise to a metamorphic rock of mixed parentage. The following section integrates geochemistry (e.g. XRF, ICP-MS) and mass balance to attempt to quantify complex geologic processes forming the Mineral Hill skarn deposit. In particular, volume change due to the reaction of marble to form wollastonite skarn is assessed.  3.7.2 Mass Balance  Background Because changes in modes of minerals and bulk chemical composition is the essence of metasomatism, mass balance approaches were used to quantify gains and losses of components during wollastonite skarn petrogenesis at Mineral Hill. Gresens' [1967] introduced compositionvolume relationships that calculate gains and losses using the chemical compositions and specific gravities of unaltered and metasomatically altered rocks or minerals. For the reaction: 100 grams of rock A + added species = X grams of rock B + removed species  (R2)  123 he derived a set of equations to assess gains or losses of species in solution denoted as x„ (in grams): 1 0 0 [ f ( g / g ) C „ - C „ ] = x„ B  A  B  (1)  A  v  where f is the volume factor, g /g B  v  A  is the ratio of specific gravity of rock B to rock A, C„ is the B  weight fraction of chemical species in rock B, C „ is the weight fraction of chemical species in A  rock A (notation is also defined in Table 3.9). To use Gresens' equations when comparing two rocks, it is necessary to know the chemical composition of the protolith (sometimes the "least-altered" sample is considered), and either the nature of volume change (reference frame) or the mobility/immobility of at least one component [Gresens, 1967; Grant, 1986]. Gresens' [1967] argued that some components will be immobile during alteration, therefore they can be used to define the volume change. Assuming that this volume factor is common to all components in the system, gains and losses of each component can be calculated. Grant [1986] simplified Gresens' equations to mass relationships rather than volume and derived the equation: AM„ = [ ( M / M ) C „ - C „ ] M B  A  B  A  (2)  A  where M„ is the mass of component n in rock A , M  A  is the total mass o f r o c k A ( M = 100  grams, dictated by eq. 1), M is the total mass in rock B, C  A  B  A n  is M „ / M and C„ is M „ / M . If A  A  B  B  B  the mass factor, f , is known ( M / M ) then a simple solution to the equation: B  A  m  M [ C „ f - C „ ] = AM„ A  B  (3)  A  m  will yield gains and losses of each component in the metasomatic system. However, if f is unknown, as is common in most metasomatic systems, then AM„ = 0 for m  known or inferred immobile components. In this case, the mass factor can be resolved by: f =f (g /g ) = C „ / C „ B  m  v  A  A  B  (4)  124  Table 3.9. Notation for equations in Chapter 3. Definition Superscript for unaltered sample Superscript for altered sample Subscript for component (species) Specific gravity Volume factor Mass factor Mass of sample Mass of component n Gain or loss of component relative To reference mass Gain or loss of component relative To reference volume Concentration of species n time-integrated fluid flux time-integrated molar flux distance coordinate fluid-rock ratio  Symbol A B n g fv  fm M M„ AM„ x„ C q q z F/R n  v  m  125  if n = an immobile element. The mass factor can be graphically estimated by plotting C „ against A  C„ . The concentration ratios of the immobile elements create an "isocon" through the origin that B  represents a linear array ( M / M ) . This slope is taken as the mass factor value (considered a B  A  constant for the whole chemical system), consequently the volume change due to alteration. If f„, = 1 then there was no mass change; f > 1 a gain in mass; f < 1 a loss in mass [Gresens, 1967; m  m  Grant, 1986]. Moreover, the relative gains and losses for the mobile elements are graphically displayed above and below this isocon, respectively. It is crucial to note that the validity of an isocon choice increases when it is based on several geochemically unrelated species [Grant, 1986]. Grant's method was not used in this study even though it is easy to implement, since it is only convenient for small sample populations. In this study, element ratio diagrams were utilized to assess immobile components since they easily accommodate large sample sets. This method plots the concentration of two immobile elements against each other (e.g. AI2O3 vs. T1O2). The samples should plot along a straight line (or close to) that intercepts at the origin. The sample population experiencing a mass gain plots on the line below (closer to the origin) protolith samples; those experiencing a mass loss plot on the line above the protolith samples [Russell and Nicholls, 1988; Russell and Stanley, 1990]. In order to accurately evaluate mass transport in this method (as with any of the aforementioned methods), multiple analyses of altered and unaltered rocks were included in order to evaluate the uncertainties associated with analytical procedures and the degree of variation within the sample population. Moreover, it is important to note that when using a massbalance approach to quantify a metasomatic process, the gains and losses calculated address only time-integrated effects, not changes at any moment in time [Baumgartner and Olsen, 1995]. Few studies have been done that use Gresens' approach to mass balance calculations in order to quantify skarn-forming processes. Most studies have compared unaltered mineralogy and microprobe data to altered equivalents [Lindgren, 1924; James, 1976; Kwak, 1978; Kwak  126  andAskin,  1981]. There is uncertainty in their results where no assumptions on volume change  or immobility were made. Since detailed field mapping showing skarn mineral phases and their distribution, combined with geochemistry, can provide much of the information in order to make the appropriate assumptions involved in mass balance calculation, the gains and losses of components in a specific skarn can be quantified.  3.7.3 Results Element Ratios Element ratio diagrams were constructed in order to identify immobile components during skarn formation at Mineral Hill. Inter-laboratory comparisons revealed that geochemical analyses between A L S Chemex and McGill labs should not be compared when looking at element ratios because inter-laboratory variation would introduce significant error (see section 3.2.1). Therefore, only geochemical analyses from A L S Chemex were examined for the following reasons: (1) A more extensive suite of elements was analyzed, and (2) abundant spatially related wollastonite skarn and marbles were analyzed. Approximately constant ratios between A l , Ti, Zr, V , Yb, and Y in marble and wollastonite skarn suggest that they were relatively immobile during skarn formation (Fig. 3.23). Marble whole rock major, minor and trace element abundances are relatively homogeneous. Most marble compositions fall within fields for marble from Hope Valley, C A and common limestone chemical compositions. However, wollastonite skarn whole rock compositions vary markedly. Wollastonite skarn samples have been divided into two groups based on the abundance of A l , Ti, Zr, V , Yb, and Y. Although there is some overlap, in type B skarn these components are slightly elevated over those in the marble while in type A skarn these elements are much more abundant. However, there are no obvious, systematic textural or mineralogical  127  0.16  BM1-M  • marble X wollastonite skarn B O wollastonite skarn A  GM1a(L)-G 2  3  4  AI203 (Wt%)  B)  0.009  0.008  0.007  a ft  0.006 • marble  N  X wollastonite skarn B  0.005 0.004  O wollastonite skarn A  0.003  • BM1-M GM1a(L)-G 2  3  AI203 (Wt%) Fig 3.23. A) Element Ratio plot of T i 0 vs. AI2O3. B) Element Ratio plot of Zr vs. AI2O3. Ovals represent fields for type A skarn or type B skarn based on concentrations of AI2O3 greater (A) or less than (B) ~1 wt%. 2  128  C)  o. 07  0.06  0.05  0.04  • marble X wollastonite skarn B O wollastonite skarn A  0.03  GM1a(L)-G 0.02  X  GD  0.01  BM1-M  2  D)  AI203  (wt%)  0.00014  0.00012  B ft fe  o  0.0001  0.00008  0.00006  • marble  X  HZ X 0.00004  BM1-M  ->m<im<.Q-  X wollastonite skarn B Owollastonite skarn A  o GM1a(L)-G  0.00002  2  AI203 (Wt%)  Fig 3.23. C) Element Ratio plot of V vs. A1203. D) Element Ratio plot of Yb vs. A1203. Relatively constant ratios suggest immobility during wollastonite skarn formation.  129  E)  0.002  0.0018  0.0016  0.0014 CM  >  0.0012  0.001  -X-  • marble  X  X wollastonite skarn B  BM1-M  O wollastonite skarn A  0.0008  0.0006  o  GM1a(L)-G  0.0004  0.0002  0 2  3  4  5  A I 2 0 3 (Wt%)  Fig. 3.23. E) Element Ratio plot of Y vs. A1203. Relatively constant ratios suggest immobility during wollastonite skarn formation.  130  differences between skarn types. Geochemistry of type A skarn, type B skarn, and marble are presented in Table 3.10. Elemental differences between type A and type B skarn can be interpreted in one of two ways: (1) the two wollastonite skarn types developed from different protoliths, or (2) they shared a common protolith but developed by different reactions. The volume change from marble samples to type A skarn and from marble to type B skarn was calculated from eq. 4, chemical analyses, and densities of calcite and wollastonite (Table 3.11). Since A M =0 for inferred immobile components (i.e. AI2O3), then the mass factor n  can be resolved by f = C / C . Volume losses of -50-70% were calculated for the formation of A  m  n  B  n  type A skarn from marble (Table 3.11). Volume losses of -20% were calculated for the formation of skarn B from marbles (Table 3.11). Volume losses of 50-70 % are considered unlikely along the delicately fingered skarn-marble interface because of the lack of collapse features to accommodate a large volume change. Therefore, it is suggested that the two wollastonite skarn types developed from different protoliths, since Type A skarn probably formed by reaction between limestone and other rock types that contained these elements in greater abundance. Type A skarn also contains greater abundances of Ni, La, Lu, and Fe2C>3 although constant ratios are not observed among these elements insinuating their possible mobility. Type B skarn appears to have formed by reaction of calcite marble with SiO^-bearing, HbO-rich fluids. The large volume loss (-20%) associated with this reaction must have led to a substantial local increase in permeability.  Fluid-rock ratios and time-integratedfluid fluxes for silica metasomatism Gains and losses of species from average marble to wollastonite type B, type A , and type ? (borderline A or B) were calculated assuming the immobility of AI2O3 and V , and respective mass factors (Table 3.1 la, b). These values are presented in Table 3.12. Wollastonite skarn at  131 Table 3.10.  Geochemistry of type A skarn (A), type B skarn (B), and marble. All analyses from ALS Chemex  Sample lithology Ba Ce Cs Co Cu Dy  ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS  W1d (w) A  UB4e(w) A  00-H8-W A  6.5 4.5  16.5 8  <0.1 8 30 1  <0.1 17  16.5 8 <0.1 10 <5 1.7  Er Eu Gd Ga Hf  ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS  Ho La Pb Lu  ICP-MS ICP-MS ICP-MS ICP-MS  Nd Ni Nb Pr  ICP-MS ICP-MS ICP-MS ICP-MS  3.5 10 1 1  Rb Sm  ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS  0.2 0.7 <1 69.1 <0.5  Th  ICP-MS ICP-MS ICP-MS  Tm  0.8 0.2 0.9 2 <1 0.2 4.5 <5 0.1  5 1.5 1 0.3 1.8 3 <1 0.3 8.5 <5 0.1  <1 0.4 9.5 5 0.2  W1b B  W1c B 201 5 <0.1 6 5 0.8 0.7  4.5 2.5  4.5 2  2.5 2  <0.1 3 5 0.8 0.7 0.2 0.7 2 1 0.1  <0.1 13 5 0.5  <0.1 12  2.5 5  2.5 <5 <0.1 2 25 <1 0.5 0.4  <0.1  0.5 0.1 0.7 1 <1 0.1  5 0.5 0.4 0.1 0.5 1 <1 0.1 2 10 <0.1  00H13-W 00H1-W B B 23 2  12.5 21.5  <0.1 4  <0.1 14  5 0.7 0.5 0.1 0.9 1 <1  5 0.8 0.5 0.2 0.9 1 <1  0.1 2.5 5  0.1 22 <5  <5 <1  <0.1 2.5 5 <1  0.9 6.2 0.6 <1  0.5 0.8 0.5 <1  <0.1 6.5 <5 1 2  33 <0.5 0.1 <0.5 <1  68.5 <0.5 0.1 <0.5 <1  <0.1 <1 29 12.5 70 0.5 9.5 25  <0.1 <1 40 4.5 160 0.4  4 0.53 44.98  3 0.63 46.24  0.45 45.85  <0.01  <0.01  <0.01  0.37 0.02  0.26 0.04 0.21  0.1 0.9 1 <1 0.2 5 <5 <0.1 4  1.8 2.2 1.5 2 102.5 <0.5  7.5 25 1 1.8 1.2  2.5 <5 1 0.6 1  1.3 <1 99.4 <0.5  0.6 <1 44.4  0.1 <0.5 <1  0.2 <0.5 <1  0.3 <0.5 <1  <0.5 0.1 <0.5 1  ICP-MS  0.1  0.1  0.1  <0.1  Sn W U V Yb Y  ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS  <1 70 16  <1 66 6.5 150  <1 35 25.5 45 0.5 9.5  Zn Zr AI203 CaO  ICP-MS ICP-MS XRF XRF  <1 21 6.5 150 0.8 11.5 95 13.5 1.17 45.48  150 21 1.21 45.32  Cr203 Fe203  XRF  <0.01  <0.01  1.04  0.23  0.01  0.97 0.02  0.6  K20  XRF XRF  0.05  0.02  0.02  0.03  0.31 0.22  MgO  XRF  0.44  0.46  0.43  0.23  0.86  4.31  0.98  0.28  MnO  XRF XRF  0.1 <0.01  0.06  Na20 P205  0.11 <0.01 0.14  0.15 0.18 <0.01 <0.01  0.18 <0.01  0.11 <0.01  0.05  49.34  50.51  <0.01 1.05 45.52  0.1 <0.01  0.16 0.03 44.34 51.17  0.25 51.52  0.1 46.87  0.06 1.41  0.09 0.41  0.08 4.29  0.03 0.16  0.04  Ag Sr Ta Tb Tl  Si02  XRF XRF  Ti02  XRF  LOI  XRF  8 50 4  1.3 0.4 1.8 1  00-H11-W M1hA A?  650 1.1 14.5  0.25  1.2 19 70 14.5 1.25 45.83 <0.01  1.5 <5 <1 0.4  0.5 <1 92.2 <0.5  0.6 0.4 <1 94.5 <0.5  0.1 <0.5 <1  <0.1 <0.5 <1  <0.1 <1 135 5 205 0.4  <0.1 <1 69 1.5  7  115 0.3 6 125  25 87.5 1.7 45.36  55 5 5.5 0.95 0.51 45.53 37.57  <0.01  <0.01 <0.01 0.33 1.57  50.66 0.02 0.83  0.04  0.01  6.83  3.8  8.5 275  4.56  1.4 0.9 <1 104 0.5 0.1 <0.5 <1 <0.1 <1 75 5 75 0.3 7.5 30 2  0.13 <0.01 0.15 51.1 0.02 0.85  I  132  Table 3.10.  Sample lithology Ba Ce Cs Co  ICP-MS ICP-MS ICP-MS ICP-MS  Cu Dy Er  ICP-MS  Eu Gd Ga Hf Ho La Pb Lu Nd Ni Nb Pr Rb Sm  ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS  Ag Sr  ICP-MS ICP-MS ICP-MS  Ta Tb TI  ICP-MS ICP-MS ICP-MS  Th Tm Sn W U V  ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS  Yb Y Zn Zr  00H7-W B  00H4-W B  00H3-W B  00-H2-W B  9.5 5 <0.1  20.5 1.5 <0.1 4 5  5 2 <0.1 5  3 4 <0.1  6 10 0.7 0.5 0.1  0.6 0.5 <0.1  0.8 <1 <1  0.6 <1 <1  0.1 5 <5 <0.1 5 <5 <1  0.1 2 <5 <0.1 2 <5 <1 0.4 0.2 0.4 <1  1.1 1.6 1 <1 207  5 0.5  5 15  W1a B?  2 3 <0.1 5 <5  6 5 <0.1 9 15 0.4 0.4  0.5 0.1 0.7 <1 <1  0.8 0.6 0.1 0.8 <1 <1  0.7 0.6 0.1  0.1  0.2  2.5 <5 <0.1 2 15 <1  3.5 <5 <0.1 3.5 <5 <1  0.1 1.5 <5 <0.1 2.5 30 <1  0.5 0.6 0.4 4  0.8 0.4  0.8 1 <1  0.5 <0.2 0.5 <1  0.1 0.7 1 <1 0.1 5.5 <5 <0.1 4 <5 <1 1 1.2 0.7 <1  56 1.5  479 <0.5 <0.1 <0.5 <1 <0.1 <1 37 4  80 0.5  25 0.3  1.5 60 0.4  ICP-MS  7.5  7  8  ICP-MS  225  20  20  25  35  35  ICP-MS XRF  0.5 0.47  1.5 0.46  0.5 0.67  8 0.8  45.8  45.85 <0.01 0.57  0.5 0.1 <0.5 <1 <0.1 <1  228 <0.5 0.1 <0.5 <1 <0.1 <1 57  0.7 <1 54.7  00H10-W W1d (mb B? marble  <0.1 9 10  0.8 0.7 0.1  0.5 0.4 0.1  10 0.4 0.3 0.1  0.7 1 <1 0.2  0.6 <1 <1  0.5 <1 <1  0.1 5  0.1 4 <5 <0.1 2.5 <5 <1 0.7  2.5 <5 <0.1 2.5 5 <1 0.6 0.8 0.5 11 55.4  55.1 <0.5 <0.1 <0.5 <1  60 0.4  90 0.4  <0.5 0.1 <0.5 <1 0.1 1 53 10.5 85 0.5  10  9  6  10.5  CaO Cr203 Fe203  XRF  47.55  XRF XRF  <0.01 0.28  46.19 <0.01 0.12  1.5 0.29 46.02  <0.01 0.22  O.01 0.22  <0.1 <1 41 7  UBM1a marble  4 2 <0.1 13 5  47.3 <0.5 0.1 <0.5 <1 <0.1 <1 57 1.5 105 0.6  0.5 0.1 <0.5 <1 <0.1 <1 57 4  4.5 0.48 47.41  AI203  1a(u B  8 4  <5 <0.1 4 <5 <1 1.2 0.2 0.5 <1 790 <0.5 <0.1 <0.5 <1 <0.1 <1 25 1 55 0.3  7 4 <0.1 7  3 0.5 <1 340 <0.5 <0.1 <0.5 <1 <0.1 <1 14 4 55  6.5  0.3 4.5  25  25  5  4.5 0.79 45.57  8.5 0.39 53.68  9 0.49 54.95  <0.01 0.46  <0.01 0.27  <0.01 0.27  K20  XRF  0.05  0.03  0.03  0.04  O.01 0.46 0.03  0.02  0.02  0.03  0.03  MgO  XRF  0.26  0.22  0.27  0.31  0.33  0.38  0.24  0.25  0.27  MnO Na20 P205  XRF XRF XRF XRF  0.05 <0.01 0.04  0.09 <0.01 0.01  0.13 <0.01 0.15  38.71  51.38  0.11 <0.01 0.04 50.94  0.1 <0.01 0.22 50.94  0.17 <0.01 0.34 47.87  0.03 <0.01 0.01  38.05  0.15 <0.01 0.15 50.54  XRF  0.03 12.61  0.01 1.23  0.01 11.86  0.03 0.6  0.03 0.7  0.03 0.18  0.03  9.86 0.01  0.03 <0.01 0.09 1.65  3.77  34.71  Si02 Ti02 LOI  XRF  0.03 41.41  Table 3.10.  Sample lithology  00H3-M marble Ba Ce Cs Co Cu Dy Er Eu Gd Ga Hf Ho La Pb Lu Nd Ni Nb Pr Rb Sm  17 3  13 2  21 4  42.5 7  ICP-MS ICP-MS ICP-MS  <0.1 3  <0.1 3 5 0.3  <0.1 3 10  <0.1 2  10 0.4  0.1 2 5 0.2  0.5 0.1 0.6 <1 <1  0.2 <0.1 0.3 <1 <1  0.2 <0.1 0.4 <1 <1  ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS  0.1 9 5 <0.1 4 <5 <1 1.1 1.2  ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS  <0.5 <0.1 <0.5 <1 <0.1 <1 14 3.5  ICP-MS ICP-MS ICP-MS  60 0.3 6  Zn  ICP-MS  125  Zr AI203  ICP-MS XRF  CaO  XRF XRF  3 0.25 54.68  U V Yb Y  Cr203 Fe203 K20 MgO MnO Na20 P205 Si02 Ti02 LOI  00UMQ-2-M 0UMQ-1marble marble  12 7  0.6 <1 696  Tm Sn W  0-NE-2-M marble  ICP-MS ICP-MS  ICP-MS ICP-MS ICP-MS  Ag Sr Ta Tb Tl Th  00NE-3amarble  <0.1 3.5 <5 <0.1 1.5 <5 <1 0.5 3 0.3 <1 240 <0.5 <0.1 <0.5 <1  0.1 7 <5  <0.1 2.5 <5 <1 0.6 1 0.3 <1 361 <0.5 <0.1 <0.5 <1  <0.1 3 <5 <1 0.8 3.4 0.4 <1 369 <0.5 <0.1 <0.5 <1 <0.1 <1 7  '  0.1 0.5 <1 <1  0.1 0.6 <1  <0.1 3.5 5 <0.1 2 <5 <1 0.5 0.6  0.1 3.5 <5  <1  <0.1 3 <5 <1 0.6 0.2  3  70 0.2 4  60 0.3 4.5  50 0.1 3.5  105  25  5  <5  15  3 0.27  <0.5 0.29  3 0.42  7  54.72  55.22  0.28 55.16  <0.5 0.24 54.91  0.32 53.79  <0.01 0.09  <0.01  <0.01  <0.01  <0.01  1.18 0.03  0.31 0.03  0.03 0.03  0.23 0.02  0.31  0.28  0.21  0.32  0.06 O.01 0.07 1.61  0.05 <0.01 0.03 1.19  0.01 <0.01 0.07 1.04  0.03 <0.01  <0.01 42.72  0.01 39.56  3.5  0.1 0.04  XRF  0.16 0.01  0.23  <0.01 40.41  <0.1 4 <5  0.1  <0.1 3 10 0.4 0.4  55 0.2 4  0.05 0.03  XRF  0.3 0.1 0.5 <1 <1  10 3  9 3  3 55 0.1  <0.01  XRF XRF  1.8 0.3 <1 302  2.5 <0.1 3 5 0.2  00H10marble  <0.1 <1 5 5  <0.1 <1 10  XRF XRF  <0.01 0.13 3.45  1.5 <5 <1 0.4  259  5 0.3  0.1 0.4 <1 <1  marble  0.3 <1 356 <0.5 <0.1 <0.5 <1 <0.1 <1 12 3  55.08 <0.01  XRF XRF XRF  <0.1 2.5 5 <0.1  0.3 0.2  00H4-M  0.01 <0.01 0.05  <0.5 <0.1 <0.5 <1 <0.1 <1  0.03 0.22 0.01  0.89  <0.01 0.06 0.89  <0.01 42.54  <0.01  0.03  <0.01  42.83  40.11  41.99  0.6 <1 402 <0.5 <0.1 <0.5 <1 <0.1 <1 16 2.5 70 0.3 5.5 125 4  0.08 4.91  134 Table 3.10.  00H6-M marble Ba Ce  ICP-MS ICP-MS  ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS  0.1 0.5 <1 <1  <0.1 5 <5  <0.1 2 <5 <0.1  0.1 3.5 <5 <0.1  1.5 <5 <1 0.4  2.5 25 <1 0.6 <0.2 0.4 <1 454  544  531 <0.5 <0.1 <0.5 <1  ICP-MS  35  Zr  ICP-MS  AI203  XRF XRF  <0.5 0.21  Fe203 K20  XRF XRF  MgO MnO  XRF XRF XRF  Na20 P205 Si02 Ti02 LOI  XRF XRF XRF XRF  <0.1 3 <5 0.2 0.3  <0.1 0.2 <1 <1  <0.5 <0.1 <0.5 <1 <0.1 <1 14 2 45 0.1 4  XRF  <0.1 3 5 0.3  0.1 0.4 <1 <1  ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS  CaO Cr203  0.1 4  5 <0.1 0.1  <0.1 2.5 <5 <1 0.7 <0.2 0.4 <1  Yb Y Zn  19 2.5  3 20 0.4 0.3  ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS  Ta Tb TI Th Tm Sn W U V  12.5 3  4.5 <0.1  Eu  Ag Sr  11 4.5  13  3 <0.1 2  ICP-MS ICP-MS ICP-MS  Lu Nd Ni Nb Pr Rb Sm  00H15-M marble  24  <0.1 3 5 0.2 0.3  La Pb  0UMQ-3marble  8.5  ICP-MS ICP-MS  Ho  GM1h-M marble  4.5  Cs Co Cu Dy Er Gd Ga Hf  00NE-1marble  2.6 0.2 <1  10 0.7 0.5 0.2 0.9 <1 <1 0.1 4.5 <5 <0.1 4 5 1 0.9 0.6 0.7 <1  00NE-3bmarble  00H12marble  00H9-M marble  11.5 4.5 <0.1  10 4.5 <0.1  4 25 0.4 0.3  3 15 0.3 0.4  0.1 0.4 <1 <1  0.1 0.5 <1  0.1 0.7 <1  <1  <1  0.1 3 <5 <0.1  <0.1 2.5 <5 <0.1  2 <5 <1 0.5 0.4 0.3 <1  1.5 <5 <1 0.4  <0.1 2.5 <5 <0.1 2 15 <1 0.5 1.4 0.4 <1 369  0.1 3.5 <5 <0.1 3 <5 <1 0.6 1 0.5 <1  0.3 0.1 0.5 <1 <1  316  357  0.8 0.3 25 253  <0.5 0.1 <0.5 <1  <0.5 <0.1 <0.5 <1  <0.5 <0.1 <0.5 <1  <0.5 <0.1 <0.5 <1  <0.5 <0.1 <0.5 <1  <0.1 <1  <0.5 <0.1 <0.5 <1 <0.1 <1  <0.1 <1  <0.1 <1  <0.1 <1  <0.1 <1  8 2  9 2  8 2  145 0.3 5.5  8.5  3.5  16 3 45 0.4 4.5  9 2  40 <0.1 2  18 5 80 0.4  <0.1 <1 13 2 90 0.3 4.5  5  25  20  25  35  10  <0.5  3.5 0.32  6  1.5  0.5  0.35  <0.5 0.34  3  0.6  0.72  0.39  53.92  52.45  52.68  <0.01  <0.01 1.18  <0.01 0.09  0.03 2.93 0.06  0.03  0.1 0.05  1.46 0.06  0.24 0.01  <0.01  <0.01 0.07  <0.01  55.59  0.29 54.49  <0.01 0.01  <0.01 0.01  0.01 0.17  0.09 0.23 0.01  0.19 0.02 0.36 0.03  0.01 <0.01 0.07  <0.01 0.04  <0.01 0.06  1.92  2.89  <0.01 41.21  <0.01 41.08  7.37 <0.01 36.99  0.09 1.51 0.03 40.22  5.47 0.01 39.05  60 0.2  54.85 <0.01  0.03 1.54 0.02 42.17  457  75 0.4 6.5 285  53.11  53.6  <0.01 0.21  <0.01 0.22  0.07 0.46 0.04  0.05 0.28 0.02  <0.01 0.07  <0.01  4.29 0.03 40.28  4.3 0.01 40.27  0.08  Table 3.10.  Sample lithology Ba Ce  ICP-MS  Cs  ICP-MS ICP-MS ICP-MS  Co Cu Dy Er Eu Gd Ga Hf Ho La Pb Lu Nd Ni Nb Pr Rb Sm  ICP-MS  ICP-MS  00H13-M marble  BM-1-M marble  00H14-M marble  15 4  88.5  14.5  10.5 1.1  4.5 <0.1  10 5  4 5  1.2 0.7  0.3  3 15 0.4  0.3 0.1 0.4 <1 <1  0.4 0.2 0.8 <1 <1  0.1  0.1 5 <5 <0.1  <0.1 2 <5 0.4  ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS  0.3  ICP-MS ICP-MS ICP-MS ICP-MS  0.1  ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS  0.1 0.6 <1 <1 3 <5 <0.1 2 <5 <1 0.5 0.6 0.4 <1  0.4 1.4 3 <1 0.2 5 <5 0.1 6  2.5 <5 <0.1 2 <5 <1  ICP-MS  416  15 3 1.3 10.8 1.2 <1 264  Ta Tb Tl Th Tm Sn W  ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS  <0.5 <0.1 <0.5 <1  <0.5 0.2 <0.5 <1  <0.5 <0.1 <0.5 <1  <0.1 <1 8  <0.1 <1 16  U V  ICP-MS ICP-MS ICP-MS ICP-MS  3 50 0.2  0.1 <1 13 14.5  Ag Sr  Yb Y  ICP-MS  5 25  AI203  ICP-MS XRF  <0.5 0.29  CaO  XRF  54.25  Cr203  XRF XRF XRF XRF  Zn Zr  60 0.6 9.5  0.5 <0.2 0.4 <1 348  1.5 40 0.1 4.5  14.5 6 <0.1  3.5 20 <1 0.9 <0.2 0.6 <1 474 <0.5 <0.1 <0.5 <1 <0.1 <1 9 3.5 115 0.3 5  10 16.5  1.5  3.83 40.14  0.19 54.91  <0.01 1.68 0.53 10.72  <0.01 0.07 0.02  XRF  <0.01 0.09 0.05 0.18 0.03 O.01 0.11 5.55 0.01  <0.01 0.16 11.81 0.15  <0.01 0.08 1.75  <0.01 0.1 6.17  Ti02  XRF XRF XRF XRF  <0.01  LOI  XRF  38.78  29.86  41.83  0.01 38.37  Fe203 K20 MgO MnO Na20 P205 Si02  0.03  10  GM1e(R) marble  0.53 0.02  80 1.5 0.37 53.81 <0.01 0.13 0.03 0.24 0.03  136  T a b l e 3 . 1 1 a . M a s s f a c t o r s a n d v o l u m e factors m a s s factor  AI2Q3  Ti02  Y  V  Zr  Yb  a v e r a g e m a r b l e to t y p e B s k a r n  0.840  0.471  0.598  0.846  1.105  0.584  a v e r a g e m a r b l e to t y p e A s k a r n  0.314  0.176  0.356  0.283  0.083  0.267  a v e r a g e m a r b l e to ? S k a r n  0.495  0.330  0.619  0.557  0.484  0.554  a v e r a g e m a r b l e to type B s k a r n  0.799  0.448  0.569  0.804  1.051  0.555  a v e r a g e m a r b l e to t y p e A s k a r n  0.299  0.167  0.338  0.269  0.079  0.254  a v e r a g e m a r b l e to ? S k a r n  0.471  0.314  0.589  0.529  0.460  0.527  v o l u m e factor  137  b < T3  Qi  £  IE  T-  (O  CO CO -D CO 0)  ro  CQ  Q.  ZS rz i ro  E  CO to c  i  CO to  CD h-  co  c> b  CO hCD CD  b  b  -3-  co  T-  CO  1_  05 (/) 0)  > CQ CM rz X  -4—'  o o  'rz o to TO  ro  w CQ  "5  CO  CD  X  o  T-  o o  •+-»  OJ X.  CD  1  03  X o  E  CD  ro i_  o  rz o  X  E  ro E  o  to  CD CM CO CO O CM  > ro  > T3 C  en ro c ro co  O  OJ O ^  >-  o  =  > -Q  2 £ o  X o o  o  o  E  JQ ro  H  ro to  ro  CO CQ  —  co *NT O)  CD  b  b  CD  b  b  CD T I- o s  ro to  o  <  _cu  b  CQ  to ±=  CO  rz  CO rz \  " J! 2  b  CQ  •§< CO CU _Z1 ro  h~ CO CO 00  ro to  b  T-  CM T 00 CD  b co O CM <  b  138  X  ^  9 -S  00 00 LO CO  o  d  CM CO LO No  -C  ^ CD  C  ro  o  •RT O O  o  o  «  LO rCM LO  8 « CO 1  o o  c  ra  ci  -c-  oo  ci  o  w  LO  -r00 -r-  3 (/>  o  ci  00  CM •>  <  139  Table 3.12.  Ba Ce Cs Co Cu Dy Er Eu Gd Ga Hf Ho La Pb Lu Nd Ni Nb Pr Rb Sm Ag Sr Ta Tb Tl Th Tm Sn W U V Yb Y Zn Zr AI203 CaO Cr203 Fe203 K20 MgO MnO Na20 P205 Si02 Ti02 LOI  Gains/losses of components from average marble to skarn B based on the immobility of AI2Q3  ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%)  W1b W1c -24.95 131.90 -2.51 -0.20 -0.01 -0.01 6.41 1.29 -3.64 -3.80 0.07 0.29 0.01 0.24 -0.01 -0.02 -0.12 0.18 0.72 0.69 0.00 0.00 0.02 0.10 -2.38 -0.07 7.47 -0.75 0.00 0.00 -1.34 0.59 -3.50 -3.50 -0.05 -0.05 -0.33 0.06 -0.60 3.81 -0.11 0.04 -1.25 -125 -340.71 -392.26 0.00 0.00 -0.01 0.07 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 44.69 10.93 -1.67 6.98 23.98 -15.16 0.01 0.16 0.08 2.66 52.95 -29.99 1.69 0.34 0.00 0.00 -23.37 -18.68 0.00 0.00 1.05 0.00 -0.01 0.14 3.06 0.29 0.12 0.11 0.00 0.00 -0.05 0.13 38.59 37.28 0.00 0.01 -37.13 -40.12  00H13-W -11.70 -2.82 -0.01 -0.79 -4.42 0.13 0.02 -0.03 0.07 0.57 0.00 0.01 -2.36 2.58 0.00 -0.91 -0.17 -0.05 -0.32 -0.56 -0.10 -1.25 -372.79 0.00 0.06 0.00 0.00 0.00 0.00 14.60 0.09 35.91 0.03 0.80 133.15 -0.83 0.00 -23.49 0.00 0.00 -0.02 -0.29 0.04 0.00 -0.01 27.72 0.02 -37.22  00H1-W -15.36 15.87 -0.01 9.59 -3.09 0.40 0.15 0.09 0.31 0.83 0.00 . 0.03 16.46 -0.75 0.00 3.48 -3.50 0.88 1.21 0.21 0.40 -1.25 -321.51 0.47 0.08 0.00 0.00 0.00 0.00 57.83 1.76 -0.67 0.04 2.13 -21.82 -0.96 0.00 -11.55 0.00 0.00 0.00 -0.28 0.09 0.00 0.07 44.13 0.01 -39.46  00H7-W -18.71 0.21 -0.01 1.79 0.98 0.27 0.12 -0.01 0.17 -0.10 0.00 0.03 0.34 -0.75 0.00 1.79 -3.50 -0.05 0.31 0.31 0.44 -1.25 -237.66 0.44 0.08 0.00 0.00 0.00 0.00 36.88 -1.59 -0.67 0.20 1.70 146.66 1.10 0.00 -12.86 0.00 0.00 0.01 -0.25 0.02 0.00 -0.04 29.76 0.02 -29.24  Table 3.12.  Ba Ce Cs Co Cu Dy Er Eu Gd Ga Hf Ho La Pb Lu Nd Ni Nb Pr Rb Sm Ag Sr Ta Tb TI Th Tm Sn W U V Yb Y Zn Zr AI203 CaO Cr203 Fe203 K20 MgO MnO Na20 P205 Si02 Ti02 LOI  ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%)  00H4-W 00H3-W -8.72 -22.45 -2.81 -2.33 -0.01 -0.01 0.12 1.10 -3.29 -3.20 0.19 0.12 0.13 . 0.14 -0.10 0.00 0.00 0.11 -0.10 -0.10 0.00 0.00 0.03 0.03 -2.24 -1.75 -0.75 -0.75 0.00 0.00 -0.79 -0.75 -3.50 10.16 -0.05 -0.05 -0.30 -0.20 -0.91 -0.54 -0.08 -0.07 -1.25 2.39 8.67 -210.67 0.00 0.00 -0.01 0.08 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 20.99 39.92 0.67 -1.53 -48.21 -15.85 0.03 0.12 1.39 2.44 -31.92 -31.53 -2.38 -1.46 0.00 0.00 -13.06 -10.93 0.00 0.00 -0.13 -0.04 -0.01 -0.01 -0.28 -0.23 0.11 0.05 0.00 0.00 0.06 -0.06 41.60 31.81 0.00 0.00 -39.15 -29.45  00-H2-W -22.67 1.63 -0.01 3.77 13.92 0.82 0.55 0.05 0.63 -0.10 0.00 0.23 1.03 -0.75 0.00 2.48 -3.50 -0.05 0.50 -0.51 0.58 -1.25 -339.32 0.72 0.13 0.00 0.00 0.00 0.00 70.36 2.88 16.19 0.34 9.60 -13.63 -0.66 0.00 12.25 0.00 0.08 0.02 -0.03 0.16 0.00 0.14 70.78 0.03 -39.38  GM1a(u)-W ave skarn B -25.75 -2.27 -0.01 -0.32 -7.75 0.10 0.06 -0.03 -0.03 0.53 0.00 0.00 -3.09 -0.75 0.00 -1.01 15.26 -0.05 -0.34 -1.09 -0.12 -1.25 -388.77 0.00 0.05 0.00 0.00 0.00 0.00 23.65 -1.96 -4.84 0.14 0.78 -27.86 -2.51 0.00 -25.60 0.00 0.05 -0.02 -0.27 0.04 0.00 -0.05 28.40 0.01 -39.81  -0.96 0.14 -0.01 2.24 -2.62 0.23 0.13 -0.01 0.11 0.37 0.00 0.04 0.27 0.65 0.00 0.18 1.17 0.04 0.01 0.01 0.07 -0.88 -295.54 0.14 0.06 0.00 0.00 0.00 0.00 32.51 0.46 -0.51 0.11 1.96 23.04 -0.68 0.00 -16.20 0.00 0.11 0.01 0.19 0.08 0.00 0.01 36.70 0.01 -36.85  141  Table 3.12.  Ba Ce Cs Co Cu Dy Er Eu Gd Ga Hf Ho La Pb Lu Nd Ni Nb Pr Rb Sm Ag Sr Ta Tb Tl Th Tm Sn W U V Yb Y Zn Zr AI203 CaO Cr203 Fe203 K20 MgO MnO Na20 P205 Si02 Ti02 LOI  Gains/losses of components from average marble to skarn A based on the immobility of AI2Q3  ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%)  W1d (W011) -24.67 -2.54 -0.01 -0.59 2.99 0.02 -0.03 -0.02 -0.21 0.62 0.00 0.01 -2.41 -0.75 0.04 -1.32 0.08 0.31 -0.30 -1.02 -0.18 -1.25 -393.60 0.00 0.03 0.00 0.00 0.04 0.00 -4.48 -0.57 -16.78 0.05 -0.73 -15.73 2.01 0.00 -37.95 0.00 0.13 -0.03 -0.32 0.01 0.00 -0.02 14.22 0.01 -39.74  UB4e(w) -21.29 -1.38 -0.01 2.44 -6.02 0.18 0.03 0.01 0.09 0.94 0.00 0.04 -1.08 -0.75 0.03 0.20 13.81 1.34 -0.03 -0.33 0.08 -0.56 -382.86 0.00 0.06 0.00 0.00 0.03 0.00 12.24 2.64 154.58 0.14 0.17 2.19 4.45 0.00 -38.55 0.00 0.09 -0.03 -0.32 0.01 0.00 0.01 14.04 0.02 -40.11  00-H8-W -21.47 -1.47 -0.01 -0.10 -7.75 0.23 0.12 0.04 0.07 0.24 0.00 0.07 -0.84 0.93 0.07 -0.06 4.88 0.29 -0.05 -0.69 0.00 -1.25 -385.03 0.00 0.09 0.00 0.00 0.03 0.00 10.12 -0.72 -20.22 0.16 1.52 -26.29 2.04 0.00 -38.88 0.00 -0.04 -0.02 -0.34 -0.01 0.00 0.28 11.81 0.02 -38.81  00-H11-W ave skarn -25.89 -23.54 -3.53 -2.34 -0.01 -0.01 -2.71 -0.46 -6.52 -4.61 -0.14 0.05 -0.14 -0.02 -0.05 -0.01 -0.36 -0.12 0.39 0.53 0.25 0.08 -0.04 0.02 -3.41 -2.06 0.48 0.04 0.00 0.03 -1.96 -0.88 -3.50 3.18 0.20 0.50 -0.51 -0.25 -0.84 -0.73 -0.29 -0.11 -1.25 -1.09 -407.41 -393.56 0.00 0.00 0.01 0.05 0.00 0.00 0.25 0.08 0.00 0.02 0.00 0.00 -3.37 3.09 3.39 1.38 -59.41 7.72 -0.12 0.04 -2.51 -0.57 -43.59 -23.02 18.74 7.91 0.00 0.00 -43.06 -39.93 0.00 0.00 -0.18 -0.02 -0.03 -0.03 -0.42 -0.36 0.00 0.00 0.00 0.00 -0.06 0.04 9.03 11.96 -0.01 0.01 -40.04 -39.70  Table 3.12.  Ba Ce Cs Co Cu Dy Er Eu Gd Ga Hf Ho La Pb Lu Nd Ni Nb Pr Rb Sm Ag Sr Ta Tb TI Th Tm Sn W U V Yb Y Zn Zr AI203 CaO Cr203 Fe203 K20 MgO MnO Na20 P205 Si02 Ti02 LOI  G a i n s / l o s s e s of components from average marble to skarn ? b a s e d on the immobility of AI2Q3  ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%)  GM1h-W -25.02 -3.27 -0.01 2.28 -5.54 -0.12 -0.09 -0.05 -0.22 0.34 0.00 -0.02 -2.92 -0.75 0.00 -1.69 7.53 -0.05 -0.43 -0.91 -0.21 -1.25 -377.68 0.00 0.03 0.00 0.00 0.00 0.00 47.54 -0.69 19.92 -0.06 -1.76 -25.49 -0.62 0.00 -34.16 0.00 -0.10 -0.03 -0.10 0.04 0.00 0.00 16.10 0.01 -37.24  W1a -23.86 -1.53 -0.01 1.26 0.11 -0.13 -0.11 -0.04 -0.16 0.42 0.00 -0.01 -1.14 -0.75 0.00 -0.48 -3.50 -0.05 -0.13 -0.46 -0.07 -1.25 -389.49 0.00 -0.01 0.00 0.00 0.00 0.00 9.47 0.77 -23.36 -0.03 -1.71 -31.42 1.37 0.00 -30.23 0.00 0.06 -0.03 -0.28 0.02 0.00 0.04 23.23 0.00 -40.15  0 0 H 1 0 - W ave skarn -24.88 -24.61 -3.09 -2.67 -0.01 -0.01 3.44 2.32 -5.10 -3.63 0.08 -0.06 0.06 -0.05 -0.04 -0.05 -0.16 -0.18 0.43 0.39 0.00 0.00 0.05 0.01 -2.70 -2.29 -0.75 -0.75 0.00 0.00 -1.25 -1.17 -0.85 1.45 -0.05 -0.05 -0.34 -0.31 -0.67 -0.69 -0.17 -0.15 4.58 0.56 -388.97 -384.91 0.00 0.00 0.04 0.02 0.00 0.00 0.00 0.00 0.05 0.02 0.53 0.16 16.11 25.78 2.67 0.81 -25.42 -7.81 0.03 -0.03 0.72 -0.97 -36.49 -30.78 -0.44 0.06 0.00 0.00 -30.07 -31.65 0.00 0.00 0.00 -0.02 -0.03 -0.03 -0.35 -0.24 0.06 0.04 0.00 0.00 0.11 0.05 21.94 20.16 0.00 0.01 -38.25 -38.47  143 Table 3.12.  Ba Ce Cs Co Cu Dy Er Eu Gd Ga Hf Ho La Pb Lu Nd Ni Nb Pr Rb Sm Ag Sr Ta Tb Tl Th Tm Sn W U V Yb Y Zn Zr AI203 CaO Cr203 Fe203 K20 MgO MnO Na20 P205 Si02 Ti02 LOI  Gains/losses of components from average marble to skarn B based on the immobility of V  ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%)  W1b -25.47 -2.92 -0.01 3.91 -4.68 -0.03 -0.07 -0.03 -0.22 0.51 0.00 0.00 -2.80 5.38 0.00 -1.66 -3.50 -0.05 -0.41 -0.72 -0.19 -1.25 -360.42 0.00 -0.01 0.00 0.00 0.00 0.00 30.30 -1.98 0.00 -0.06 -1.17 26.88 0.55 -0.11 -31.21 0.00 0.72 -0.02 2.16 0.08 0.00 -0.05 27.92 0.00 -37.92  W1c 175.44 0.89 -0.01 2.59 -2.71 0.47 0.39 0.01 0.38 0.91 0.00 0.14 1.01 -0.75 0.00 1.45 -3.50 -0.05 0.25 5.15 0.17 -1.25 -385.11 0.00 0.09 0.00 0.00 0.00 0.00 17.21 9.69 0.00 0.26 4.72 -24.57 1.20 0.11 -8.94 0.00 0.07 0.19 0.51 0.15 0.00 0.18 48.44 0.02 -40.09  00H13-W -16.87 -3.27 -0.01 -1.69 -5.55 -0.03 -0.09 -0.05 -0.13 0.34 0.00 -0.02 -2.92 1.45 0.00 -1.47 -1.30 -0.05 -0.43 -0.74 -0.21 -1.25 -388.17 0.00 0.03 0.00 0.00 0.00 0.00 5.63 -0.92 0.00 -0.06 -1.10 71.42 -1.50 -0.14 -33.87 0.00 -0.08 -0.03 -0.36 0.02 0.00 -0.03 17.20 0.01 -38.24  00H1-W -15.25 16.06 -0.01 9.71 -3.05 0.41 0.16 0.09 0.32 0.84 0.00 0.03 16.66 -0.75 0.00 3.54 -3.50 0.89 1.23 0.23 0.41 -1.25 -320.59 0.47 0.08 0.00 0.00 0.00 0.00 58.50 1.80 0.00 0.04 2.20 -21:55 -0.95 0.00 -11.14 0.00 0.00 0.00 -0.28 0.09 0.00 0.07 44.58 0.01 -39.45  00H7-W -18.63 0.26 -0.01 1.84 1.06 0.28 0.13 -0.01 0.18 -0.10 0.00 0.03 0.38 -0.75 0.00 1.83 -3.50 -0.05 0.31 0.32 0.45 -1.25 -235.93 0.44 0.08 0.00 0.00 0.00 0.00 37.35 -1.58 0.00 0.20 .1.76 148.53 1.14 0.00 -12.46 0.00 0.01 0.01 -0.25 0.02 0.00 -0.04 30.08 0.02 -29.14  00H4-W 30.81 0.08 -0.01 7.83 6.35 1.35 1.10 -0.10 1.16 -0.10 0.00 0.22 1.62 -0.75 0.00 3.07 -3.50 -0.05 0.47 -0.53 0.69 -1.25 932.43 0.00 -0.01 0.00 0.00 0.00 0.00 92.34 8.38 0.00 0.61 14.89 6.65 -1.42 0.91 76.01 0.00 0.10 0.05 0.14 0.39 0.00 0.35 139.07 0.02 -36.78  Table 3.12.  Ba Ce Cs Co Cu Dy Er Eu Gd Ga Hf Ho La Pb Lu Nd Ni Nb Pr Rb Sm Ag Sr Ta Tb TI Th Tm Sn W U V Yb Y Zn Zr AI203 CaO Cr203 Fe203 K20 MgO MnO Na20 P205 Si02 Ti02 LOI  ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%)  00H3-W -21.13 -1.80 -0.01 2.43 -1.88 0.25 0.27 0.02 0.29 -0.10 0.00 0.06 -1.09 -0.75 0.00 -0.23 14.13 -0.05 -0.07 -0.39 0.04 3.45 -150.45 0.00 0.11 0.00 0.00 0.00 0.00 54.98 -1.14 0.00 0.23 4.55 -26.25 -1.06 0.12 1.63 0.00 0.02 0.00 -0.16 0.08 0.00 -0.06 42.03 0.00 -26.31  00-H2-W -23.48 0.55 -0.01 2.43 9.88 0.60 0.39 0.02 0.41 -0.10 0.00 0.18 0.09 -0.75 0.00 1.54 -3.50 -0.05 0.29 -0.62 0.39 -1.25 -354.08 0.59 0.11 0.00 0.00 0.00 0.00 54.98 1.80 0.00 0.23 6.90 -20.38 -1.06 -0.08 -0.17 0.00 0.02 0.01 -0.12 0.12 0.00 0.10 56.92 0.02 -39.54  GM1a(u)-W ave skarn B -25.66 -0.77 -2.14 0.17 -0.01 -0.01 -0.09 2.28 -7.75 -2.58 0.13 0.23 0.09 0.14 -0.03 -0.01 0.01 0.12 0.57 0.37 0.00 0.00 0.01 0.04 -3.02 0.30 -0.75 0.66 0.00 0.00 -0.90 0.20 16.64 1.20 -0.05 0.04 -0.32 0.01 -1.09 0.02 0.07 -0.10 -1.25 -0.87 -386.59 -294.65 0.00 0.14 0.06 0.06 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 26.27 32.84 -1.89 0.48 0.00 0.00 0.16 0.11 1.19 2.01 -26.25 23.57 -2.49 -0.66 0.03 0.00 -23.49 -15.93 0.00 0.00 0.07 0.12 -0.02 0.01 -0.26 0.19 0.05 0.08 0.00 0.00 -0.05 0.01 30.75 36.99 0.01 0.01 -39.78 -36.83  145  Table 3.12.  Ba Ce Cs Co Cu Dy Er Eu Gd Ga Hf Ho La Pb Lu Nd Ni Nb Pr Rb Sm Ag Sr Ta Tb Tl Th Tm Sn W U V Yb Y Zn Zr AI203 CaO Cr203 Fe203 K20 MgO MnO Na20 P205 Si02 Ti02 LOI  Gains/losses of components from average marble to skarn A based on the immobility of V  ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%)  W1d (W011) -23.95 -2.04 -0.01 0.31 6.35 0.13 0.06 0.00 -0.11 0.84 0.00 0.03 -1.91 -0.75 0.05 -0.93 1.20 0.42 -0.19 -1.00 -0.11 -1.25 -385.87 0.00 0.04 0.00 0.00 0.05 0.00 -2.13 0.16 0.00 0.14 0.56 -5.10 3.52 0.13 -32.87 0.00 0.25 -0.03 -0.27 0.02 0.00 -0.01 19.74 0.02 -39.59  UB4e(w) -25.21 -3.28 -0.01 -1.61 -7.21 -0.18 -0.21 -0.06 -0.33 0.23 0.00 -0.03 -3.10 -0.75 0.01 -1.71 1.92 0.38 -0.46 -0.85 -0.27 -1.03 -407.23 0.00 0.01 0.00 0.00 0.01 0.00 -4.41 -1.16 0.00 -0.12 -3.28 -33.48 -0.55 -0.29 -49.33 0.00 -0.14 -0.03 -0.43 -0.02 0.00 -0.05 2.03 0.00 -40.20  00-H8-W -19.25 -0.39 -0.01 1.25 -7.75 0.46 0.30 0.09 0.32 0.37 0.00 0.13 0.44 1.60 0.09 0.95 8.25 0.42 0.19 -0.53 0.18 -1.25 -371.63 0.00 0.13 0.00 0.00 0.05 0.00 19.02 0.16 0.00 0.32 4.08 -16.85 3.99 0.17 -32.70 0.00 0.04 -0.01 -0.28 0.00 0.00 0.42 17.94 0.03 -38.23  00-H11-W ave skarn< -19.95 -23.88 -0.23 -2.52 -0.01 -0.01 1.25 -0.76 0.08 -4.92 0.91 0.01 0.78 -0.05 0.22 -0.02 0.57 -0.16 3.03 0.47 1.57 0.07 0.10 0.01 -0.11 -2.25 7.08 -0.04 0.00 0.03 1.34 -1.05 -3.50 2.52 1.52 0.45 0.29 -0.29 0.48 -0.76 0.51 -0.14 -1.25 -1.11 -348.79 -396.00 0.00 0.00 0.15 0.04 0.00 0.00 1.57 0.07 0.00 0.02 0.00 0.00 42.83 1.60 37.05 0.96 0.00 0.00 0.54 0.02 10.03 -0.99 -10.58 -25.66 134.26 6.85 2.24 -0.04 16.82 -41.35 0.00 0.00 0.12 -0.04 0.00 -0.03 -0.12 -0.37 0.13 0.00 0.00 0.00 0.01 0.03 75.91 10.44 0.02 0.01 -38.95 -39.76  146 Table 3.12.  Ba Ce Cs Co Cu Dy Er Eu Gd Ga Hf Ho La Pb Lu Nd Ni Nb Pr Rb Sm Ag Sr Ta Tb TI Th Tm Sn W U V Yb Y Zn Zr AI203 CaO Cr203 Fe203 K20 MgO MnO Na20 P205 Si02 Ti02 LOI  Gains/losses of components from average marble to skarn ? based on the immobility of V  ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%) XRF(%)  GM1h-W W1a -25.45 -22.30 -3.46 -0.23 -0.01 -0.01 1.02 3.60 -6.03 4.00 -0.17 -0.03 -0.14 0.00 -0.06 -0.02 -0.29 0.02 0.24 0.68 0.00 0.00 -0.03 0.02 -3.17 0.28 -0.75 -0.75 0.00 0.00 -1.89 0.56 5.10 -3.50 -0.05 -0.05 -0.48 0.13 -0.95 -0.15 -0.26 0.11 -1.25 -1.25 -386.64 -375.19 0.00 0.00 0.02 -0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 34.43 20.12 -1.18 2.58 0.00 0.00 -0.10 0.07 -2.44 -0.15 -30.84 -22.33 -1.11 3.44 -0.09 0.21 -38.58 -18.33 0.00 0.00 -0.13 0.21 -0.03 -0.02 -0.18 -0.18 0.02 0.05 0.00 0.00 -0.02 0.10 11.80 36.45 0.00 0.01 -37.90 -40.11  00H10-W av e skarn -23.68 -24.31 -2.49 -2.48 -0.01 -0.01 7.33 3.04 -3.60 -3.11 0.32 -0.02 0.27 -0.02 -0.01 -0.04 0.05 -0.14 0.73 0.46 0.00 0.00 0.01 0.11 -1.95 -2.08 -0.75 -0.75 0.00 0.00 -0.50 -1.00 0.65 2.07 -0.05 -0.05 -0.16 -0.27 -0.43 -0.64 -0.02 -0.12 7.87 0.79 -372.40 -380.74 0.00 0.00 0.07 0.03 0.00 0.00 0.00 0.00 0.08 0.02 0.83 0.19 31.96 30.49 5.81 1.27 0.00 0.00 0.17 0.00 3.86 -0.49 -29.01 -28.41 0.91 0.42 0.24 0.05 -16.44 -28.83 0.00 0.00 0.14 0.01 -0.02 -0.02 -0.28 -0.21 0.11 0.05 0.00 0.00 0.21 0.06 36.25 23.11 0.01 0.01 -37.12 -38.25  147  M i n e r a l H i l l p r o b a b l y f o r m e d b y R l b y the i n f l u x o f an H 0 - r i c h , S i 0 - b e a r i n g f l u i d . R e a c t i o n 2  2  transport theory c a n be used to assess the time-integrated f l u i d f l u x ( T I F F ) o v e r a m a x i m u m w o l l a s t o n i t e skarn extent o f 65 meters at M i n e r a l H i l l . Three scenarios were evaluated: (1) TIFF(  m a x  ) required to f o r m wollastonite skarn type B f r o m average marble c o m p o s i t i o n s , (2)  TIFF(max) r e q u i r e d to f o r m wollastonite skarn type A f r o m average m a r b l e c o m p o s i t i o n s , and (3) TIFF(  m a x  ) r e q u i r e d to f o r m borderline w o l l a s t o n i t e skarn type ? ( A or B ) f r o m average m a r b l e  c o m p o s i t i o n s . T h e values and parameters for f l u i d / r o c k ratios and T I F F are presented i n T a b l e 3.13. N o t a t i o n is presented i n T a b l e 3.9. R 2 dictates s i l i c a a d d i t i o n to calcite m a r b l e to f o r m w o l l a s t o n i t e skarn. O n average w o l l a s t o n i t e skarn B f o r m e d f r o m the a d d i t i o n o f 37 grams o f S 1 O 2 to m a r b l e . A m a x i m u m o f 2.4 grams o f S i 0 2 can be added to the system f r o m each k i l o g r a m o f H2O that infiltrates under c o n d i t i o n s o f 5 5 0 ° C , 1 kbar [from Dipple and Gerdes, 1998]. These P - T c o n d i t i o n s are reasonable for w o l l a s t o n i t e skarn f o r m a t i o n at M i n e r a l H i l l . C a l c u l a t i o n s result i n a f l u i d / r o c k ratio o f - 4 1 3 to 4 1 7 and a T I F F o f - 2 . 7 x 1 0 c m / c m for (1) (Table 3.13a,b). O n average 6  3  2  w o l l a s t o n i t e skarn A f o r m e d f r o m the a d d i t i o n o f 10 to 12 grams o f Si02 to m a r b l e . A f l u i d / r o c k ratio o f ~ 1 1 8 to 135 and a T I F F o f - 7 . 6 x 1 0 to 8.7 x 1 0 c m / c m w a s c a l c u l a t e d for (2) ( T a b l e 5  5  3  2  3.13c,d). A v e r a g e transitional wollastonite skarn ? f o r m e d f r o m the a d d i t i o n o f 20 to 23 grams o f Si0  to m a r b l e . C a l c u l a t i o n s result i n a f l u i d / r o c k ratio o f 2 2 7 to 2 6 0 and a T I F F o f 1.5 x 1 0 to 5  2  1.7 x 1 0 c m / c m (Table 3.13e,f). 5  3  2  F o r a m o l a r v o l u m e o f H20= 22 c m , the D a r c y f l u x can be related to a m o l a r f l u x (q ) o f 3  OT  -10  4  - 1 0 m o l e s / c m (Table 3.13). T h i s time-integrated m o l a r f l u x is consistent w i t h fluxes 5  2  integrated o v e r the duration o f contact and r e g i o n a l m e t a m o r p h i c events interpreted f r o m measured reaction progress [Dipple and Ferry, 1992]. M o r e o v e r , this v a l u e is c o m p a r a b l e to fluxes c a l c u l a t e d for m e t a s o m a t i s m i n ductile fault zones [Dipple and Ferry, 1992].  148  <°  CO  + LU  oo  CO CD  o  CM  + LU  LO  cri  CO CD un o O o  + LU  + LU  OO CD T— CO CO CN  cn CD  CD LO  ^ ~ c ^o °+O+ co LU  CO  CO  L_  ^  ^ CM CN 03 1CN l  5  I*-  co  „ CO  Oi  CM  oS  CD  LO  + LU  + UJ  O  CO CN CO  c o  co  O  CN  ^  o * w S  S  g  S  co  CM CM CD  LU UJ CM  «•) o i  L  CO P U  CD  ro o ro o x  TJ '3 5=  +  +  CM 5: ^  LO °  +  LU  00  x  c zX m o CD e _ ^ ^E "~-  CO  {-  -K  CD  o  o o  o  CO  E  o O °o  "r^  «  o  O CO CO g  |  to — — E CO  c o  TS (D (0  co  CM  E o  O  I  0)  o  oi co  CO ^X  N  CO  CT  E  cr  1 0  CO  fe  8 - 8? O  ii.  CD  £ ^  u >  §  co CM  -  -  c^^S  ?!  CO CD  00  O —  + LU CD  CD  ^ <^ " LO CD  co  00  CM  io  CN  cf'  s:  0  ro  ivJ CN  CM  ^  LO CD  "CT  cn c o  _o ro o x  o 00  co co8 ? 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CN CD  CM  10  OJ  (O  o  ><  ro Q-l D? E CO  O  X to  LO CO CD o •q- O O + +  ro  E  O O  CN  ro o OT c x 'ro cj: o>l 73  CD  CM  c V.o  U  h CD  LO CD  ro  "=  CD  O + LU  CD OT  o o ro CO  LU  r-  CD  0)  T3 OT C  T3  LO CO  S  5 E  CN O O  LU  1 0  CD  •^r CN  +  CM CD  m  ^  c o 3  LU  CD > TO  00 X  00  o +  r~ co  OT  O O  O  i2 £ co P M  o t; u- E co "fe o  = cu .-^ ~  E c o i_ cn  o r or v  c  N  p  5  o  o>01 X CO  CT  o  E,  E cr  150  Rare Earth Element patterns Forty samples were analyzed for rare-earth elements (REE) by A L S Chemex. REE's have atomic numbers (Z) from 57 to 71 and decrease in radius with increasing atomic number. Elements with Z = 57 to 62 (i.e. La, Ce, Pr, Nd, and Sm) are referred to as light rare earth elements (LREE); elements with Z> 63 (europium) (i.e. Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu)are the heavy rare-earth elements (HREE) [Brownlow, 1996]. To study R E E distribution, we calculated a chondrite-normalized ratio in which the concentration of R E E in the samples were divided by chondrite values; representatives of unfractionated original solar system meteorites [Brownlow, 1996]. R E E plots were constructed for marble, wollastonite skarn type A , wollastonite skarn type B and garnet skarn to observe if their respective concentrations produce distinguishable trends. R E E normalized to chondrite values [Table 3.14; McDonough and Sun, 1995] show a negative Ce anomaly indicative of seawater deposition of marble (Fig. 3.24a). A negative Eu anomaly in seawater may reflect either aolian or hydrothermal input [Whitney and Olmsted, 1998; Boulais et al., 2000]. Generally, the marble trend is enriched in LREE's and depleted in HREE's. Although there is some overlap, wollastonite skarn shows a similar but slightly elevated R E E pattern (Fig. 3.24b and Fig. 3.25). This is consistent with other studies in which R E E concentrations in skarn are enriched over protolith concentrations due to isotopic equilibration with magmatic volatiles from adjacent igneous intrusions [Vander Auwera and Andre, 1991]. Moreover, the patterns suggest that some LREEs may be mobile (i.e. enrichment in La; Fig. 3.24b). Several authors contend that R E E systematics are not significantly affected unless intense infiltration metasomatism has occurred [Bau, 1991; Whitney and Olmsted, 1998; Boulais et al., 2000.] Garnet skarn is enriched in HREE's indicating garnet take-up of the REE's [Whitney and Olmsted, 1998] but still reflects a negative Eu anomaly (Fig. 3.24c).  151  00  JO  00  N- oo co O  o  CD co  U0  t  CN CN  co  O  OO  O  CO  o  uo CN  o  00  o  o  o  o  O  o  T  o  o  o  d  CO C O 00  o o o  co cn T— IT) CO CD c o O O CN UO o T O O £ CO CM CD or - CN CO 0 0 oo LO O 5 ro CO UO CN oo c \ i =) E CN 1 o CO CO CM O o o T -  CM  O 3 o o  a)  U0  co  o  <b  N" UO  C O UN O C N"  -Q  cb  1—  C M o CM  co  o  1--;  o  CM  o o o o  o  o  CM oo CN o  —  m  o C No co o  o U0  CN  o o o d  o  CM oo CO  d  CN •flCN  o o o o  CO o C N O O O o o o o CN o CO 0 0 0 0 C NO O CN o UO o CN CN O O O O CN o CN o CN oo 00 C CO M O CN d d d d  ro a> cn 00 LU ro c? S Z  E  LO  X  o o  rcn  rv!  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Q 3 C O L U O H - Q X L U H ^ - I  155  Fig 3.24. A) R E E pattern for marble samples (red diamonds) and B) wollastonite skarn A (black triangles) and wollastonite skarn B (blue circles) samples. Generally, wollastonite skarn A is enriched in HREEs relative to wollastonite skarn B. All patterns are in log scale and show negative Ce and Eu anomalies and L R E E enrichment. Values below detection limit were not included.  156  Fig 3.24. C) R E E pattern for garnet skarn samples (black squares). Enriched pattern suggests garnet takeup of HREEs. All patterns are in log scale.  Fig 3.25. A) R E E concentrations of marble samples (red) compared to wollastonite skarn B samples (blue). Reveals that marble and skam B have similar R E E concentrations. B) R E E concentrations of marble samples (red) compared to wollastonite skarn A (black). Wollastonite skarn A has higher concentrations of REEs than marble. All patterns are in log scale; values below detection limit were not included.  158  Two marble protoliths for wollastonite skarn are delineated from R E E and element ratios for wollastonite skarn consistent with whole rock major, minor and trace interpretations. Type B skarn is likely derived from a relatively pure marble since its R E E distribution pattern is similar yet slightly elevated (Fig. 3.25a). However type A skarn appears to have been derived from a marble protolith enriched in REE's, since the R E E distribution pattern mimics that of pure marble samples but it elevated over Type B skarn ( Fig. 3.25b and Fig. 3.26a, b). These patterns are especially evident in H R E E concentrations.  3.7.4 Discussion Element ratios between marble and wollastonite skarn suggest two skarn types. It is improbable that the divergent elemental abundances in type A and type B skarn were produced by different reactions; instead they probably reflect variances in protolith composition. It is plausible that both wollastonite skarn types have a marble precursor, however that which proceeded type A skarn had greater abundance of A l , Ti, Zr, V , Yb, and Y. Moreover, type A skarn has greater abundance of HREE's. If type A skarn formed from a different protolith, Gresen's [1967] mass balance (gains and losses of species) calculations for wollastonite skarn A formed from average marble compositions have no physical relevance. However, in this case, gains and losses calculated for type B skarn formed from average marble are still valid. A volume loss of ~20% estimated from the conversion of marble to type B skarn must have led to a substantial local increase in permeability and may have resulted in reaction-flow focusing. Wollastonite skarn at Mineral Hill probably formed by R l by the influx of an HaO-rich, Si02-bearing fluid. Mass balance calculations support large increases of SiG^ to produce wollastonite skarn. Type B skarn has the largest SiC>2 addition probably facilitated by the associated volume loss. Type A skarn and borderline (?) skarn gained less silica indicating more calcite dissolution associated with skarn formation, although this cannot be confidently  159  100  La  Ce  Pr  Nd  Sm  Eu  Gd  Tb  Dy  Ho  Er  Tm  Yb  Lu  Marble Wollastonite skarn A  Wollastonite skarn B  Fig. 3.26. R E E pattern for marble, wollastonite skarn B, and wollastonite skarn A samples showing passive enrichment of HREEs in wollastonite skam A and B over marble H R E E concentrations. All patterns are in log scale; values below detection limit are not included.  160 determined since it is improbable that skarn B derived from a relatively pure marble. That is, volume losses on the order o f 50-70 % estimated during skarn A formation are not supported by major collapse features as evidence o f a large porosity gain. Time-integrated molar fluxes between 3 x 10 and 1 x 10 moles/cm are calculated over 4  5  2  the duration o f wollastonite skarn formation. However, the lower flux (i.e. ~3 x 10  4  moles/cm ) 2  assessed for skarn A and borderline ? skarn formation are probably misleading i f their respective mass balance calculations are invalid. R E E patterns suggest L R E E mobility during the alteration event. Large time-integrated molar fluxes, such as those calculated for Mineral H i l l samples, might have facilitated not only spatially extensive skarn formation but L R E E systematics [Bau, 1991; Whitney and Olmsted, 1998; Boulais et al, 2000].  161  C H A P T E R 4: S T A B L E ISOTOPIC A N D P E T R O L O G I C E V I D E N C E F O R P E R M E A B I L I T Y E V O L U T I O N AND TIMING O F INFILTRATION E V E N T S  4.1 Introduction It is well established that the oxygen isotopic composition of igneous rocks is distinctly different from that of sedimentary rocks. As such, studies of the isotope variations around intrusive contacts allow the role of fluids interacting with rocks around cooling plutons to be investigated. Although this study area is not a classic "aureole", but rather a raft of metasedimentary rock enclosed in a pluton, the system can be defined in one of two ways : (1) a "closed" aureole where fluids are derived internal to the defined system (i.e. pluton or the wallrock) or (2) an "open" aureole which part of the metamorphic history involves infiltration by fluids external to the defined system [Nabelek, 1991]. The first scenario will be dominated by magmatic or metamorphic fluids, whereas the isotopically "open" system are dominated by surface-derived fluids [Hoefs, 1997]. Combined petrologic and isotope studies in many contact aureoles have provided evidence that fluids were primarily locally derived. For example, several studies have concluded that oxygen isotope composition of calc-silicates from various contact aureoles approach those of the respective intrusions. They conclude that magmatic fluids are often dominant during contact metamorphism [Taylor and O'Neil, 1977; Nabelek et al, 1984; Bowman, 1985; Valley, 1986]. Moreover, stable isotopic studies have been important in documenting the multiple fluids present in skarn systems [e.g. Taylor and O'Neil, 1977]. Although it is suggested magmatic fluids controlled skarn formation at Mineral Hill, we see isotopic signatures in skarn and marble that are indicative of exchange with externally-derived fluids (i.e. meteoric). We conclude therefore that skarn genesis occurred within an open system. Oxygen isotope data have been used in mineral deposit studies where the distribution of mineral alteration is irregular and where mineral assemblages have been obliterated by  162  subsequent metamorphism [Beaty and Taylor, 1982; Green et al, 1983; in Hoefs, 1997]. Moreover, spatial correlation between low 8 0-values (see Table 4.1 for 5-notation) and 18  economic mineralization have been documented [Criss et al, 1985,  1991]. Consequently, regions  18  that show anomalously low  O contents may be a valuable analytical tool for exploration o f  hydrothermal ore deposits. Interaction between water and rock or mineral may result in a shift o f the oxygen isotope ratios o f the rock and/or the water away from their initial values. Three possible exchange mechanisms for water/rock interaction are discussed by Hoefs [1997]. These include: (1) Solution-precipitation where larger grains grow at the expense o f smaller grains, decreasing the surface area and lowering the surface energy o f the system. Isotopic exchange with the fluid occurs while the material is in solution. (2) Chemical reaction occurs when the chemical activity of one component o f both fluid and solid is out o f equilibrium i n the two phases. The breakdown of the original crystal and the formation o f new crystals is inferred as they form at or near isotopic equilibrium with the fluid. (3) During diffusion, isotopic exchange occurs along grain boundaries between the crystal and the fluid with little to no change i n shape o f the reactant grains. The driving force is the random thermal motion o f the ions with net movement along an activity gradient [Hoefs, 1997]. In this chapter mineralogic and isotopic alteration i n Mineral H i l l samples are examined in order to evaluate the nature o f fluid flow during the first and most spatially extensive skarnforming event. The timing and source o f fluid infiltration can be constrained from the extent and type o f alteration o f peak mineral assemblages. In order to interpret flow geometiy based on mineralogic and isotopic data we must first answer two questions: (1) What is the timing o f isotopic alteration? (2) In which samples can isotopic shifts be attributed to devolatilization reactions? This chapter not only documents isotopic alteration in Mineral H i l l samples, but interprets the timing o f isotopic alteration i n these from mineralogic evidence, especially those  Table 4.1. Notation for oxygen and carbon isotopes. Standard  Ratio  SMOW  18,  PDB  13,  Notation  measurement (ratio)  oro  permil  'c/ c  permil  12  Superscripts (i.e. 18, 16 in O) represent mass numbers (A). A= proton number (Z) - neutron number (N). (A)variation results in fractionation during geologic processes.  Example: The isotopic ratio in qtz: R ^Oqtz  =  Oqtz/ Oqtz  are reported relative to Standard Mean Ocean Water (SMOW), as: 5  1 8  0  = [(R O 1 8  /R O 1 8  q t z  s t d  ) - l ] x 1000  These values are reported in permil which is already a ratio, therefore compositions can be directly compared.  164  with low  18 16 0/ O ratios. In order to determine if oxygen isotopic shifts are solely a result of  fractionation due to devolatilization reactions, 8 0 variation of wollastonite skarn and marble 18  samples is evaluated. Those samples in which changes in 8 0 can be attributed entirely to 18  devolitilization reactions are excluded from further consideration. From this suite:, we can confidently image flow geometry and interpret an infiltration history for the study area.  4.2 Method of Investigation One hundred and twelve rock powders from Mineral Hill were analyzed for 5 0 at I 8  Queen's University Geochemistry Lab (Dr. T.K. Kyser, dir.) (Table 4.2). Silicate whole rock powders (N=53) were analyzed using BrFs procedure described in Clayton andMayeda [1963]. Carbonates (N=59) were also analyzed for 8 C and 8 0 using the techniques outlined in 13  18  McCrea [1950] for liberation of C O 2 by reaction with H 3 P O 4 . Values are reported relative to V S M O W ( S 0 ) and VPDB(8 C). Analyzed samples include green marble, bleached marble, 18  I3  grey marble, black marble, augen material, calcite vein material, wollastonite skarn, clinopyroxene skarn, calc-silicate skarnoid, quartzite, garnet-wollastonite skarn, garnetite, diorite, tonalite, and basalt. Blind duplicate analyses yielded a l o of 0.07 permil for 8 0 and 18  8 C (Table 4.3). 8 0 and 8 C data are listed in Table 4.2. 13  I8  I3  Forty-six whole-rock silicate and twenty-seven whole-rock carbonate analyses derive from the same powders that were used for whole-rock chemical analyses (see Chapter 3). An additional seven silicate analyses of wollastonite pods were crushed and powdered from ~3cm  3  slabs in a steel mortar and pestle. Thirty-two additional carbonate powders were drilled from slabs using a diamond-impregnated drill bit in a Dremel tool. Powders constituted no more than 4mm of sample material.  165  Table 4.2. O and C stable isotope data (in permil) for samples from Mineral Hill, Distance measurements are relative to the wollastonite skarn/marble interface where the contact = 0 cm.  Sample  lithology  KM-MB4c KM-UB4e(mb) KM-TB4e KM-TB4f KM-Wld(mb) GMla(U)-B GMla(U)-B2 GMla(L)-Bl GMla(L)-B2 GMla(L)-B3 GMla(UR)-B GMle(L)-Bl GMlf-B BM-l-B MH5a-B KM-UBMla KM-FRM2C GM lh-M 00H3-M 00H4-M 00H5-M 00H6-M 00H9-M 00H10-M 00H12-M 00H13-M 00H14-M 00H15-M 00H16-M 00NE-1-M 00NE-2-M 00NE-3a-M 00NE-3b-M OOUMQ-1-M OOUMQ-2-M OOUMQ-3-M GMle(R)-G GMla(L)-G GMla(U)-G GMla(L)-Gl GMla(L)-G2 GMla(L)-G3 GMla(UR)-G GMle(L)-Gl GMle(L)-G2 GMle(L)-G3  green marble green marble green marble green marble bleached marble bleached marble bleached marble bleached marble bleached marble bleached marble bleached marble bleached marble bleached marble bleached marble bleached marble grey marble grey marble grey marble grey marble grey marble grey marble grey marble grey marble grey marble grey marble grey marble grey marble grey marble grey marble grey marble grey marble grey marble grey marble grey marble grey marble grey marble grey marble grey marble grey marble grey marble grey marble grey marble grey marble grey marble grey marble grey marble  del 180 (SMOW) del 13C (PDB) 15.6 2.3 4 2.8 3 3.8 3.4 3.3 3.1 3.1 3.5 2.7 2.9 12.4 4.2 15.9 12.3 3 3.9 6.5 4.7 3.6 3.4 3.6 4.2 2.9 3.6 3.1 3.4 6.2 8.5 9.6 8.9 13 12.2 10 3 3.2 3.6 3.4 3.3 3.3 3.4 3.7 3.2 3  0.3 -5 -4.6 -2.6 -4.2 -2.9 -2.5 -2.5 -3.2 -2 -2.3 -3.4 -3.5 -1.9 -0.8 -0.2 -2 -3.5 -1.3 -3.1 -6.2 -0.6 -2.6 -1.9 -1.1 -1.6 -0.9 -1 -1.6 0.2 -4.7 -3.1 -5.1 -1.1 -1.1 -2.1 -3.2 -3.6 -2.6 -2.7 -3.1 -1.4 -2.7 -3.1 -3.4 -3.4  distance (cm)  1.13 0.53 0.39 6.09 1.16 0.36 0.62 3.05  600  100 200 300 200 200 200 100 400 400 1000 500 5500 5700 3500 3500 1000 1000 1000  1.65 2.13 5.61 1.45 3.91 3.55 1.68 0.44  Sample  lithology  GMle(L)-G4  grey marble  3.2  GMle(R)-Gl GMle(R)-G2  grey marble grey marble grey marble  3.7 3.5 3.4  grey marble grey marble  3 10.7 4.1  GMlf-Gl GMlf-G2 BM-1-G1 MH5a-G BM-l-M BM-1-D1 BM-1-D2 BM-1-D3 GMlg-Vl GMlg-V2 KM-Wld(w) KM-Wla KM-Wlc KM-UB4e(w) KM-Wlb 00NE-2-WP 00NE-3a-WP 00UMQ-2-WP GM-lh-W 00H1-W 00H2-W 00H3-W 00H4-WP OOH5-WP 00H7-W 00H8-W 00H10-W 00H11-W 00H13-W 00H14-WP 00H16-WP GMla(UR)-W GMle(L)-W GMle(R)-W MH5a-W GMla(L)-Wl GMla(L)-W3 GMla(U)-Wl GMla(U)-W2 GMlg-W 00H4-W GMla(U)-W GMlf-W KM-TB9a KM-UB2c KM-MB5b KM-MB4b KM-TB13a  grey marble grey marble black marble black marble black marble calcite vein calcite vein woll skarn woll skarn woll skarn woll skarn woll skarn woll skarn woll skarn woll skarn woll skarn woll skarn woll skarn woll skarn woll skarn woll skarn woll skarn woll skarn woll skarn woll skarn woll skarn woll skarn woll skarn woll skarn woll skarn woll skarn woll skarn woll skarn woll skarn woll skarn woll skarn woll skarn woll skarn woll skarn woll skarn g-w skarn g-w skarn g-w skarn g-w skarn garnetite  del 180 (SMOW) del 13C (PDB) -3.3 -3.5 -2.9 -3.2 -4  ' 1.24 4.47 1.38 0.77 2.59  -2.9 -0.6 -2.2 -3.6 -3.7 -1.3 -4.1  14.4 12.1 12 16.3 2.1 2.4 3.6 6.1 10.2 6.4 7.1 12.1 19.8 9.6  -3.1  17.5 12 11.5 11.3 7.6 10.1 17.4  -300 -200  -50 -100  18.6 9.4  -100  7.6 17.7 10.8 8 13.5 10.6 6 8.4 9 12.9 6.6 8.9 3.3 12.8 13.9 9.2 1.5 1 9.4 8.4 0.6  distance (cm)  -0.89 -1.33 .-1.03 -0.97 -1.45 -0.60 -5.85  -0.77  •  Sample  lithology  KM-MB3b KM-UB14c BM-l-A KM-MB7a KM-LBld KM-MBla KM-MBlb KM-dla KM-dlb KM-dlf KM-d2a KM-UBFRd2 KM-MBFRd2 KM-UBd3a KM-FRd3a  cpx skarn skarnoid augen quartzite diorite diorite diorite diorite dike diorite dike diorite dike tonalitic dike tonalitic dike tonalitic dike basaltic dike basaltic dike  del 180 (SMOW) del 13C (PDB) 1.9 2.6 7.1 3.1 4.3 1.1 5.4 1.4 3.1 2.3 2.9 4.7 3.5 1.8 0.8  distance (cm)  168  O  CO  on  CO  •6  CO  CO  o o  o Q.  E o  o  1  ean  CO  O  d-1  o  T3  E  00  Ca  W)  c=  CO  o  lyses  •  w  LO CD CO  CD  r-~  CO  CO  CO  o  CD  •o  "O  0.07  d-13C  uplicate  ro  CO  c  O  CO XJ  C(P DB) mea  1  TD  ard dev tion  s o M—  TJ  CO  CO  co  c  ro  to  LO CJ)  cz  CN  •a  cCO tz  ro 0 CO X) CD X!  ro  1—  XI  E E  zCQ C zO  169  4.3 Carbonates Carbonates analyzed for 5 0 and 5 C included green marble (N=4), bleached marble 18  13  (N=l 1), grey marble (N=17), grey and bleached marble (N=22), black marble (N=3), and calcite vein (N=2). Localities and values presented in Fig. 4.1, 4.2, 4.3, and 4.4. Fig. 4.5 plots 8 0 of carbonate versus sampling method (bulk vs. micro drill). The 18  similar spread for both sampling methods suggests that the two data sets can be directly compared. A similar analysis for 8 C (Fig. 4.6) illustrates that drilled samples have a more I3  restricted range in composition than bulk crushed samples. Below, these trends are analyzed as a function of the rock type sampled. 5 0 isotope compositions for all marbles range from 2.3 to 16.3 permil and are depleted 18  relative to marine limestone even though S 0 values for limestone vary through geologic time 18  (-27 to 35 permil in Upper Triassic)[Veizer et al., 1999]. These compositions therefore likely *  18  record the interaction between marble and a low  O fluid such as meteoric and/or magmatic  water. Marble from Mineral Hill is also depleted in 0 relative to the Waterville limestone I 8  (8 0=18.2 to 19.8 permil) [Bickle et al, 1997]. 8 0-values for green marble range between 2.3 18  18  to 15.6 permil, bleached marble range between 2.7 to 12.4 permil, grey marble range between 2.9 to 15.9 permil, black marble range between 12.0 to 16.3 permil and calcite vein range between 2.1 to 2.4 permil (Fig. 4.7). Among spatially related grey and bleached marble samples (i.e. grid map samples from Marble Hill), bleached marble tends to have between 0.1 to 0.5 permil lower 18  0-content(Fig.4.8). Marbles from Mineral Hill are depleted relative to 8 C-values for Upper Triassic marine l3  carbonates (2 to 4 permil) [Veizer et al., 1999]. S C-values for green marble range between -5.0 13  to 0.3 permil, bleached marble range between -4.2 to -0.8 permil, grey marble range between 6.2 to 0.2 permil, black marble range between -3.7 to -1.3 permil and calcite vein range between  170  171  N  co LU LU  c<U CCJ  CQ  y  C  CS  ll  1>  tu  > \  pp <p cn  IS« •—|  —  -a c C3 —J J2  S D cn  cn CD  C  3 ta o  3 c £ U  c3  cn cu  •«  cn  _  i  PL.  53  O  E3  0  E o  T3  + —  cu cn  a  M r£  1*  C3  CC  T3  E  '5 M  GO  O  C OJO  o  3  f  O  o o" d d  —-  § J2 c2  —  S— E  C3 C o cn TS, c "33 « 9 e'•-s a cn O 3 .s cn • o s U o c s c  A  11  So'-J •si 1 Q W  fe  2  CD 53  172  173  rMN  20  J§ \  • N  Compositional layering Contact Inferred contact  ****** Fault [O]  I8  0 / 0 in calc-silicate/skarn 16  [O, C] 0 / 0 , C / C in carbonate 1 8  1 6  1 3  1 2  .Grid map #1  Fig. 4.4. Structural map of Marble Hill [inset; Fig. 1.2 and Fig. 4.3] and O, C stable isotope values and locality. See Table 4.1 for O, C stable isotope values and Fig. 1.9 for locality for grid map #1 samples.  174  CO  •S3  Bulk Fig.4.5.  0  Drilled  0 vs. powder type for marble samples from Mineral Hill.  to  Bulk  Drilled  Fig. 4.6. C vs. powder type for marble samples from Mineral Hill. Closed symbols from Marble Hill samples; open symbols from Upper Marble Quarry and North-east extension. 0  5\18 0  O-values for samples from Mineral Hill  Fig. 4.7.  0  O compositions of Mineral Hill samples.  176  G M = grey marble B M = bleached marble M = marble WS= wollastonite skarn  •^GM-BM= ^ G M - ^ B M  •^WS-M= ^WS -  A  A  AA1AANA  JtAAJtA  .  A  *  A  A  l  T  -4  -2  0  2  4  6  8  10  12  14  16  A in permil  5vl 8  Fig. 4.8. O isotopic differences between spatially related grey and bleached marble (solid circles) and wollastonite skarn and marble (solid triangles). Differences in grey and bleached marble were derived from ^ G M - B M = ^ G M - ^ B M . Differences in wollastonite skarn and marble (both G M and B M ) were derived from A\VS-M= ^ws - ^ M . Note the dominance of positive values (see text for explanation). 0  177 -4.1 to -3.1 permil (Fig. 4.9). The variation in 5 C values in calcite could be due to progressive 13  reaction of magmatic fluids with carbonate wall rocks. The S C-values for powders derived I3  from drilled samples have a more restricted range than bulk samples (Fig. 4.6). Samples MB4c, U B M l a , and NE-1 have higher 13C-content (0.3 to -0.2 permil) than drilled samples. No powders from these samples where derived from drilling. Higher values might reflect bulk sampling methodology, differences in lithology (i.e. green marble; sample MB4c) or geographic location (i.e. no samples from Marble Hill). Samples NE-2, NE-3b, 00H5, TB4e, Wlb, and 13  UB4e have lower  C-content (-4.2 to -6.2 permil) than drilled samples. Lower values might also  reflect bulk sampling methodology, differences in lithology (i.e. green marble; sample TB4e and UB4e) or geographic location (i.e. only one sample from Marble Hill). The lowest value (-6.2 permil; sample H5) occurs in close proximity to the Crowston Lake Pluton at Marble Hill, however, other samples near this sample locality have 5 C values that range between -0.6 to -3.6 I3  permil, suggesting heterogeneity in carbon isotopic alteration on outcrop scale. To conclude, there is no direct evidence to suggest that sampling by microdrill contaminates the isotopic composition of carbonate rocks. The only systematic differences between bulk samples and drilled samples is in 5 C , but the drilled samples show a more 13  restricted range of composition; a trend opposite of what would be expected through contamination. The observed variation in 8 C likely reflects heterogeneous 8 C compositions I3  13  between various rock types and on an outcrop scale. 4.4 Silicates Analyzed silicates powders derive from diorite, tonalite, basalt, wollastonite skarn, garnet-wollastonite skarn, garnetite, clinopyroxene skarn, calc-silicate skarnoid, clinozoisite augen (in black marble), and quartzite. Values are reported relative to V S M O W . 8 0 18  Fig. 4.9.  0  C compositions of Mineral Hill marble samples.  179  compositions for all samples from Mineral Hill are compared in Fig 4.10. Localities and values are presented in Figs. 4.1, 4.2, and 4.4.  4.4.1 Intrusive rocks Igneous rocks from Mineral Hill analyzed for 0 content include diorite (N=3), DI l 8  diorite dike (N=3), D2 tonalite dike (N=3) and D3 basalt dike CN==2). Values reported for diorite ranges between 1.1 to 5.4 permil, DI ranges between 1.4 to 3.1 permil, D2 ranges between 2.9 to 4.7 permil and D3 ranges between 0.8 to 1.8 permil. The data indicate that the igneous rocks are depleted in 0-content compared to standard 0-values reported for mafic igneous rocks (Fig. 18  18  4.11). Igneous rocks must have also interacted with an isotopically light oxygen reservoir. A n alteration index for diorite, D2 and D3, based on petrographical observation and estimation of alteration minerals, was developed in order to determine whether isotopically low oxygen values decreased relative to alteration of the sample (Fig. 4.12). Generally, the least altered samples 18  have higher  O compositions than the most altered samples, however there is significant  overlap. Overall, retrograde minerals and textures are observed in igneous samples (see Chapter 18 2). Therefore, it is likely that depleted  O-values are a result of subsolidus isotopic exchange of  dike rocks with a low 8 0 fluid (e.g. meteoric water). I8  4.4.2 Skarn Wollastonite skarn Wollastonite skarn from the Upper Marble Quarry (N=5), the North-east Extension (N=2), Marble Hill (N=l) and in green marble (N=l) range in 8 0 composition from 3.6 to 19.8 18  permil. Wollastonite skarn (N=24) was also sampled on a centimeter scale at Marble Hill along the wollastonite skarn-marble contact as a part of a detailed isotopic study. 5 0 values range 18  25.0  20.0  15.0  10.0  g M CO  cn  CD  O  '3 O  CD  S3 1)  X  o •>»  cd  o  OH  o  o  CL)  i o  Fig. 4.10. Silicate  -a 'o  0J  5\18 0  e  M  1  CD tjfj CCJ  CD  ccj 3  o to  I  O N O  u  O compositions of meta-sedimentary and skarn rock samples.  181  Meteoric waters Ocean water Sedimentary rocks Metamorphic rocks Granitic rocks Basaltic rocks  40  30  20  10  0  -10  -20 -30  -40 -50 -60 -70  8 0 in permil 18  Fig. 4.11. 8 O-values of important geological reservoirs [modified from Hoefs, 1997].  182  O diorite | + D2 XD3  Alteration index Least altered  Most altered  5 O compositions vs. alteration index for igneous rocks from Mineral H i l l . 1. Least * . -r. altered, 2. Moderately altered, 3. Most altered. Alteration index based on petrographical observation and estimation o f alteration minerals. 18  i f e  183  between 3.3 to 18.6 permil. The 5 0 compositions of wollastonite skarn along this contact and 18  in wollastonite pods within grey and bleached marble are systematically higher than 8 0 18  compositions reported for marble (Fig 4.7). Trace amounts of late opaque mineralization and calcite veins were observed in thin section for samples with reported 8 0 compositions less than 18  5 permil. This carbonate was removed by reaction with HC1 prior to 8 0 analysis, but the veins 18  may record incursion of exotic fluids that altered skarn after skarn formation. Two wollastonite skarn samples, which yield a 8 0-value less than 5 permil, include G M l g - W and Wld(w), at 18  3.3 and 3.6 permil, respectively. Upon petrographic examination, G M l g - W ranges from nonfoliated to strongly foliated, has optically-unidentifiable fine-grained alteration along cleavage planes (-15% by volume) whereas most wollastonite skarn samples examined show minor to no alteration. Calcite veins are common at Mineral Hill: In contrast, W l d (w) is weakly foliated and shows no retrograde alteration of peak minerals (woll) although trace amounts of opaque minerals are present. However, many wollastonite samples that contain opaque minerals yield magmatic 8 0 signatures. 18  Garnet-wollastonite  skarn  Garnet-wollastonite skarn (N=4) was sampled in the Upper Bench and Middle Bench. The 8 0 values range between 1.0 to 9.4 permil. Late opaque and epidote mineralization, veins 18  and moderately-altered skarn minerals were observed in samples with 8 0 compositions less 18  than 5 permil. The alteration and depleted isotopic signatures probably reflect interaction with a I  low  o  O fluid after skarn formation.  184  Garnetite A sample o f garnetite from the Top Bench has a 8 0 value o f 0.6 permil. In thin section, 1 8  extensive wollastonite, quartz and calcite veins are observed within garnetite.  Clinopyroxene skarn One sample o f clinopyroxene skarn from the Middle Bench has a 5 O -value o f 1.9 l s  permil. Late opaque and epidote mineralization, veins and moderately-altered skarn minerals are present i n thin section.  4.4.3 Skarnoid One sample o f calc-silicate skarnoid from the Upper Bench has a 5 0 value o f 2.6 1 8  permil. Late opaque and epidote mineralization, veins and moderately-altered skarn minerals are present in thin section.  4.4.4 Quartzite A sample o f quartzite from the Middle Bench has a 5 0 value o f 3.1 permil. The 1 8  sample contains very high amounts o f moderately-altered epidote, some late opaque mineralization, and veins.  4.4.5 Clinozoisite Augen (in Black Marble) A sample o f an augen ( B M - 1 ; see Table 2.2) from a black marble from the M i d d l e Bench has a S 0 value o f 7.1 permil. This value is lower than the 8 0 values reported from the 1 8  adjacent black marble, grey marble and bleached marble.  I 8  185  4.5 Wollastonite skarn-marble interface Variation in 8 0 across skarn-marble contacts was examined closely in seven places I8  (centimeter-scale). Six contacts between wollastonite skarn and marble were in samples collected from Grid Map #1 (Fig. 1.9) at Marble Hill (Fig. 4.13 a-g). In general, there are sharp isotopic shifts (< 2 centimeters) across the contact from marble to wollastonite skarn. Moreover, 1S  wollastonite skarn samples are enriched in  O relative to marble samples, ranging from 6 to 13.9  permil, indicating 0 exchange equilibrium with the pluton. Calcite marble is observed directly 18  outboard of wollastonite skarn as proximal bleached marble to distal grey marble (Fig. 1.9). Bleached marble has depleted 8 0 compositions that range between 2.7 and 3.8 permil. 18  Generally, grey marble is slightly higher in 0 and ranges between 3 to 3.7 permil. Only grey 18  marble in sample GMla(U) has a lower 8 0 composition than the spatially related bleached 18  marble (Fig. 4.13a). One wollastonite skarn sample (GMlg-W) has a significantly lower signature ( 8 0 = 3.3 permil), however this sample is in very close proximity to large calcite I8  veins with 8 0 compositions of 2.1 and 2.4 (Fig. 4.13f). Because of the presence of veins in this 18  sample, the isotope alteration in sample G M l g - W is probably due to influx of exotic fluids that equilibrated with skarn after skarn formation. In the last sample (BM-1), I examined isotopic variations between black marble, grey marble, bleached marble, and a clinozoisite augen (Fig. 4.13h). In sample BM-1, the 8 0 I 8  compositions in marbles are significantly higher than those in the previous contacts, grey marble has the lowest 0-content (10.7 permil), bleached marble has 12.4 permil, and black marble 18  ranges between 12 to 16.3 permil. Spatially, sample BM-1 is located proximal to the Crowston Lake Pluton and unlike other marble samples does not seem to have equilibrated with a meteoric fluid. However, marble is depleted from "pristine" values for marble (-20-25 permil), and likely  186  GMla(U)  1U  W2 •  9 (permil)  8  O  oc "3 X)  Wl •  7 6 5 4  GB  3  B2 •  2 1 0 4  5  6  7  8  9  10  11  12  13  distance (cm)  15 cm  Fig. 4.13. a) Centimeter-scale oxygen isotopic shifts in grid map sample G M l a ( U ) . A l l analyses derive from drilled powders from slabs (photo). G= grey marble, B = bleached marble, W = wollastonite skarn; numbers indicate sample number (see Table 4.1).  GMla (L)  Fig. 4.13. b) Centimeter-scale oxygen isotopic shifts in grid map sample GMla(L). All analyses derive from drilled powders from slabs (photo). G= grey marble, B= bleached marble, W= wollastonite skarn; numbers indicate sample number (see Table 4.1).  Fig. 4.13. c) Centimeter-scale oxygen isotopic shifts in grid map sample GMle(L). All analyses derive from drilled powders from slabs (photo). G= grey marble, B= bleached marble, W= wollastonite skarn; numbers indicate sample number (see Table 4.1).  GMle(R)  Fig. 4.13. d) Centimeter-scale oxygen isotopic shifts in grid map sample GMle(R). All analyses derive from drilled powders from slabs (photo). G= grey marble, B= bleached marble, W= wollastonite skarn; numbers indicate sample number (see Table 4.1).  GMlf  Fig. 4.13. e) Centimeter-scale oxygen isotopic shifts in grid map sample G M l f . All analyses derive from drilled powders from slabs (photo). G= grey marble, B = bleached marble, W= wollastonite skarn; numbers indicate sample number (see Table 4.1).  191  Fig. 4.13. f) Centimeter-scale oxygen isotopic shifts in grid map sample G M l g . All analyses derive from drilled powders from slabs (photo). V= calcite vein, W= wollastonite skarn; numbers indicate sample number (see Table 4.1).  192  GMla(UR)  5.5  6  6.5 7  7.5 8  9.5  distance (cm)  16 cm  Fig. 4.13. g) Centimeter-scale oxygen isotopic shifts in grid map sample GMla(UR). All analyses derive from drilled powders from slabs (photo). G= grey marble, B= bleached marble, W= wollastonite skarn (see Table 4.1).  193  Fig. 4.13. h) Centimeter-scale oxygen isotopic shifts in sample BM-1 from the Middle Bench. All analyses derive from drilled powders from slabs (photo). D= black marble, G= grey marble, B= bleached marble, A= clinozoisite augen; numbers indicate sample number (see Table 4.1).  194 equilibrated with magmatic volatiles. This is supported by the 8 0 value (7.1 permil) of a 18  clinozoisite augen within sample BM-1. This composition is consistent with values of mafic igneous rocks, suggesting interaction with magmatic volatiles.  4.6 8iiO_v_ariaiiojnj)jf^ All analyzed samples have depleted 8 0 values relative to inferred protoliths (igneous I8  and sedimentary), suggesting that all examined rocks in the study area exchanged 0 with an 1 8  isotopically light fluid. The shift toward lower carbon and oxygen isotopic values within the roof pendant at Mineral Hill can be the result of a number of different processes. Samples with isotopic compositions lower than the unmetamorphosed equivalents (i.e. marble to wollastonite skarn) are often considered to have been altered by fluid-rock interaction [Valley, 1986]. However, metamorphic reactions can occur that release volatiles ( H 2 O and C O 2 ) as reaction products. These reactions (devolatilization) fractionate carbon and oxygen isotopes between the host rock and volatile phase, and, as a result, the 8 C and 8 0 values of the host rock are 13  18  lowered [Rumble, 1982; Valley, 1986]. Hence, fractionation due to devolatilization reactions could account for some of the observed isotopic depletion. Therefore, to evaluate the nature of the fluid infiltration, any samples whose isotopic shifts can solely be attributed to devolatilization reactions must be withdrawn [Roselle et al, 1999]. The 8 0 values of wollastonite skarn decrease from 19.8 to as low as 3.3 permil, and the 18  8 C values of the marbles fraction from 0.3 to -6.2 permil. Increases in temperature drive 13  decarbonation reactions in calc-silicate rocks. The effects of devolatilization in relation to natural processes fall between two extremes; batch and Rayleigh devolatilization. Valley [1986] gives an excellent overview of the derivations for isotopic shifts for these end-members. Batch devolatilization implies a closed system in which fluid escapes in a single episode. However, in  195  reality, the large volume increase that accompanies volatilization requires a gradual escape of fluid. Therefore, batch processes set a minimum value for isotopic shifts due to devolatilization reactions. On the other hand, Rayleigh devolatilization implies an open system where a continuous release of fluid occurs in small increments. Using the devolatilization reaction, C a C 0 + Si0 tz) = CaSi0 + C 0 3  2(q  3  R3  2  we can evaluate the largest possible devolatilization effects to produce wollastonite skarn. The mole fraction of oxygen remaining in the rock (F(  0X  y en)) g  after all the fluid has left the system is  dictated by the stoichiometry of this reaction. R3 has an F( yg )-value of 0.6. For values of 0X  F(oxygen)  en  ^ 0.6 (known as the 'calc-silicate' limit) the amount of 0 depletion by Rayleigh 18  distillation is very similar to that of a batch process. Figure 1 in Valley [1986], illustrates the range of isotopic depletion due to decarbonation reactions. It shows that 8 0 depletion is 18  restricted by the calc-silicate limit (F(  0X  ygen)  ^ 0.6), and therefore, only small differences (at most  2 permil) are seen between Rayleigh and batch calculations. Carbon isotopes are much more susceptible to change by devolatilization and F(  car  bon)  can  approach zero. Figure 7 in Nabelek et al. [1984] illustrates as F—> 0, isotopic shifts in 8 C 13  values for marble can be as large as 12 permil. Thus, large depletion in C in carbonate rocks 1 3  can occur as reaction reaches completion and nearly all carbon is converted to C 0  2  [Valley,  1986]. As such, we contend that the change in 8 C values in marble down to -6.2 permil can be 13  attributed solely to decarbonation reactions. However, the amount of C 0 released (in the 2  extreme example given by R3) cannot produce 5 0 shifts of > 3 permil recorded in wollastonite I8  skarn samples. Therefore, we reject total oxygen isotopic shifts as a function of devolatilization reactions.  196  Fractionation of 0 between calcite and wollastonite dictates that they will have different 1 8  8 0 values at equilibrium. This equilibrium fractionation factor, A n-cc, is temperature I 8  wo  dependent and ranges from -5.0 permil at 400°C to -3.4 permil at 600°C [Zheng, 1993a], where ^woll-cc  —  8\voll " Sec1  Mineral Hill and Marble Hill wollastonite skarn tends to have greater  o  O-content than  spatially related marble resulting in values ranging from -2.6 to 14.8 permil for A u wo  cc  (Fig. 4.8).  Because A ii-cc -values do not range between -5.0 and -3.4 permil [Zheng, 1993 a], calcite and WO  wollastonite could not have been in equilibrium at 400°C to 600°C at Mineral Hill. To conclude, it is likely that 8 0 was lowered by infiltration and exchange of externally 18  derived fluids out of equilibrium with the host rocks, however 8 C isotopic shifts could have I 3  resulted from devolatilization reactions and/or the exchange with graphite or organic matter. Graphite is observed in grey marbles at Mineral Hill. 8 0 values of marbles and silicates less than 5 permil indicate exchange with 18  meteoric/and or seawater. Other 8 0 values of marbles and silicates between 19.8 and 8.0 18  permil suggest exchange with magmatic water.  4.7 Discussion Although powders were taken from the freshest part of each sample, there were samples in which veining and alteration was so extensive within skarn that contamination is likely. A l l igneous samples show retrograde alteration. Moreover, depleted 0 values (1.8 to 0.8 permil) in 1 8  the latest diking event (D3) require interaction with a low  O fluid. Therefore, it is likely that  igneous rocks were depleted after the first skarn formation event. Even though igneous rocks at Mineral Hill exchanged with a late isotopically light oxygen reservoir, these samples are not excluded from the suite as they hold evidence to the timing of this low  18 O fluid event. However,  197  their 5 0 values are not used to directly determine the nature of fluid flow during skarn 18  formation. Some highly veined skarn samples include TBI3a (garnetite) and MB3b (clinopyroxene skarn). In other samples a moderate amount of veins were observed in thin section. Although most powders are relatively vein-free, some contamination is expected, especially for analyzed powders taken from whole rock. Moreover, petrographic examination of low 8 0 silicates (< 5 18  permil) indicates on average moderate alteration of peak mineral grains. In all of these samples, opaque minerals were observed, although not exclusive to samples with 5 0 < 5 permil. 18  Because retrograde alteration and veining is apparent in these low 8 0 units (garnetite, garnet18  wollastonite skarn, and clinopyroxene skarn) they have been excluded in the interpretation of infiltration history involved in anhydrous skarn genesis at Mineral Hill. Likewise, two wollastonite skarn samples yield 8 0 values less than 5 permil; G M l g - W I8  and Wld(w), at 3.3 and 3.6 permil, respectively. These wollastonite skarns could have been altered to meteoric oxygen signatures by late meteoric infiltration, or could have formed from pre-existing low 5 0 marbles. Late alteration of G M l g - W is considered likely because of the 18  alteration and proximity to large calcite veins. The low 5 0 content of Wld(w) may reflect the 18  1 8  0 composition of skarn at high temperature, however, because it is only one of thirty-three  skarn samples, this interpretation cannot be made with confidence. This thesis will focus on the majority of skarn samples which record 8 0 > 5 permil. 18  4.8 Infiltration History Because devolatilization reactions cannot account for the 8 0 isotopic shifts observed in 18  wollastonite skarn and marble, the study area must have been infiltrated by externally derived fluids. As discussed above, all samples from Mineral Hill record exchange with an isotopically  198 light oxygen reservoir. The following section interprets the timing and source of fluid(s) responsible for the S 0 alteration in context to skarn formation and igneous activity. l 8  4.8.1 Magmatic fluid event Spatially extensive high temperature wollastonite production is prevalent in Mineral Hill skarns. Wollastonite formed from a relatively pure marble requires a source for Si02-bearing, H20-rich fluids. Moreover, magmatic volatiles must have infiltrated the roof pendant as evidenced by some skarn in O exchange equilibrium with the pluton. Because the roof pendant l s  is essentially a xenolith or wedge of country rock preserved within the Crowston Lake Pluton, it is likely that the intrusion is the source of magmatic fluid. Therefore, the spatially extensive skarn formation event at Mineral Hill likely occurred in the Late Jurassic.  4.8.2 Meteoric fluid event(s) Meteoric  1 8  0 isotopic signatures (5 0 < 5permil) occur within every unit sampled at 18  Mineral Hill (Fig. 4.14). Almost all 8 0 alteration to values < 5 permil can be attributed to 1 8  moderate temperature alteration mineral assemblages. We have identified at least two temporally separate high to moderate temperature meteoric fluid events at Mineral Hill: a prograde and retrograde event(s), respectively. This section discusses each separately, including evidence for high temperature meteoric alteration and timing of these events.  Prograde meteoric fluid event Evidence from low tf 0 signatures in marble 8  In order to deplete a marble or limestone with an initial 8 0 signature of ~20 permil to 1 8  ~0 permil, exchange and equilibrium with a very low  1 8  0 fluid (i.e. meteoric/seawater) at high  199  5vl 8 0  O-values for samples from Mineral Hill  Pristine Marble  Depleted with respect to magmatic volatiles  O  u  u  Fig. 4.14.  O isotopic compositions for all samples collected at Mineral Hill. Grey hashed field  0  5vl 8  represents  0  O isotopic composition range for pristine marbles. Grey field represents samples  depleted in oxygen isotopes with respect to magmatic fluids (8 0 < ~ 6 permil). 18  200  temperatures (~400°-500°C) must have occurred (Fig. 4.15). Marble is pervasively altered on a large scale (up to 10 meters; see section 4.9.3) to values as low as 2.3 to 5 permil. Alteration over this length scale reflects fluid advection. Therefore, the new composition (2.3 to 5 permil) emulates the composition ofthe fluid source, after correcting for equilibrium fractionation. Isotope fractionation is temperature dependent. Fig. 4.15 illustrates what combinations of fluid composition and temperature can produce a marble near 0 permil. A fluid source of < 0 permil is not included (even though meteoric water can be < than 0 permil) since there is no evidence in vein or alteration compositions that reflect negative 8 0 exchange equilibrium. As such, we 18  conclude that high temperatures (> 400°C if fluid 5 0= 0 permil) must have accompanied the 18  meteoric fluid that equilibrated with marble at Mineral Hill.  Timing ofhi-T meteoric fluid event It is interpreted that low 5 0 signatures in marble occurred due to reaction with meteoric 18  fluid at high temperatures. However, the timing of this event must be evaluated. There are three possible scenarios for a high temperature event that would have allowed meteoric water to deplete marble to 8 0-values < 5 permil: (1) pre-pluton emplacement (Triassic to Mid18  Jurassic), (2) syn-pluton emplacement (Late Jurassic), and (3) post-pluton emplacement (Cretaceous). High temperature depletion of marbles could have occurred during the Triassic to MidJurassic period. Although this possibly cannot be completely ruled out, it is unlikely since the depleted marbles have such a strong spatial association with the Crowston Lake Pluton. Moreover, there is no evidence regionally for Triassic- mid-Jurassic large scale intrusive events. Therefore, marble depletion either occurred as a result of a syn-pluton, pre-skarn formation or post-pluton, post-skarn formation meteoric fluid event. A syn-pluton emplacement,  201  Fig. 4.15.  O J g 0  | g  O (cc-FhO) versus temperature plot. Dashed line indicates path of marble O-  5 18  xxx xx x x . ~ x x x . x ~ xxxxxx xxxxx, x , ~ w x x x x x x x x x x x x x w x x x , . ; xx x x v x x v x xx 0= 8 permil (magmatic). Solid line indicates path of marble 0-depletion with increasing temperture that has b  18  £18  been infiltrated by a fluid with a 0= 0 permil (conservative meteoric/seawater). Lines calculated by 0 (cc-fl)= A(10 /T ) + B, A=2.78; B=-2.89 [Friedman and O'Neill, 1977]. Fields show values of "pristine marble" and the lowest marble values at Mineral Hill. Intersection of lowest marble values (S 0 ~ 3) and the meteoric fluid line at ~ 450 °C, indicates that lowest marble at Mineral Hill must have exchanged and equilibrated with meteoric fluids at high temperature. 0  A l 8  6  2  18  202  pre-skarn formation depletion of marbles is supported by evidence and observations made within the study area at Mineral Hill. Spatially, low 8 0 values for marble are isolated near the 18  Crowston Lake Pluton (i.e. Marble Hill); marble samples collected distal to the pluton have higher 5 0 values (i.e. Upper Marble Quarry and N E extension). It is possible that the contact 18  between the pluton and the roof pendant could have been a conduit for meteoric water to depths typically unavailable to meteoric fluid. The proximity to the pluton would have provided the temperatures needed to deplete marble 5 0 isotope compositions. Moreover, the 18  homogeneously low isotopic signatures of marble in areas of convex and concave interfingering of wollastonite skarn suggest that high temperature depletion was not post pluton and skarn formation. First, it is unlikely that late meteoric fluids would mimic the irregular, lobate wollastonite skarn/marble contact. Secondly, if the fluid was post-pluton, then concave areas along the wollastonite skarn/ marble boundary would have been sheltered from exchange with meteoric water (Fig. 4.16). However, at Mineral Hill, detailed cm-scale sampling along this highly irregular lobate boundary (see Figs. 4.13a-g) suggest that no areas of marble were sheltered from depletion, except those distal (i.e.Upper Marble Quarry and North-east Extension) to the Crowston Lake Pluton. Therefore, it is most likely that the high temperature 8 0 marble 18  depletion was associated with Late Jurassic pluton emplacement and that skarn overprinted this low  O alteration event (Fig. 4.17). Furthermore, the porphyritic and fine-grained nature of dikes  D2 and D3 indicate that the region was cool during subsequent igneous activity.  Retrograde meteoric fluid event(s) Evidence from low S 0 signatures igneous and skarn units l8  1  Petrographic observations from rock with low  P.  O-values (< 5.4 permil) suggest that the  meteoric signatures in the Crowston Lake Pluton were attained during moderate temperature  203  -a a cd  I  3  3  O  o O  T J  -o > "5 * c2 . ,-...1  oo  S3  -f-»  ^ >  Illf If  cd  c ° i2 co  CU CO — i CX, .CO  mm  S ££ ^  O  l 7-1°.  svtftttm  cd cn r 3 5 e3 i s ,2 is O u co « c.  CO  > ^  I  o  -au  43 • —«  _!  CO  _9 co  o *<3 fi o o 3  'B :  3  y co  o -fi «  III m I  O  A  O  OO  III  <  I 1 1I  i  cd od  C(H  o cd CU  - M .3? 3 C L L cu  2 \_, > fi C  ^  .  cd  H  IB  .2 fi 3-2  cTj co co cd O cu cd  B 9 o 3tz, g> cd p cu cd  CQ > 3  •cu  > cd CJ  O  G c  "Id  CJ  >  CO  o cd 2 o 2 u 8 .2 OT  fi  -fi ^ -B  CJ  _C  cu  ^  T3  n-' c3 fi c cd .5 ^  2  .cd  C+H  fi  2 " S H '"5  cu  S ta  cu  ^2  4 - 1  CJ  "oG  X  o '5  EG cj  (U * C  c  o  CO  cod  «» ,9 -s  CU  cu eg  ^  l -2  E  *  -2  |  .DO  n £  cd  f  o  «" s  cu o  Jj  cd  8  as  >% ' t o cd ^  •B S 5  CO  o  (B  O  co  o -fi =5 g  o  I  c £ "§E  c  Cd  C+H  co TJ  cd cd  In CO  15  00  mmmim  3  '-O  2 O ,  rt  fi  O  M  cu > cd  cd  u c+-i S  s° S c  cd cu cu fi3 J3  c2  -2  > .fi  cd  204  INFILTRATION HISTORY  Magmatic  mwm  Hi-T Meteoric  i  Hi-T Meteoric Pluton/DI  Late Jurassic  i  D2  r Or j.  i  D3  Cretaceous  Post-D3  Tertiary?  Fig. 4.17. Fluid History associated with igneous activity at Mineral Hill. 1). The emplacement of the Late Jurassic Crowston Lake Pluton resulted in contact metasomatism of a Triassic roof pendant producing garnet and wollastonite skarn zones by infiltration of magmatic fluid. 2) High  6 18 O-values to < 5 permil  pre- to syn-skarn formation. A late high temperature meteoric event is supported by depleted isotopic signatures and retrograde alteration in all igneous units including Cretaceous-aged D 2 and D3 dikes and sills. Three models for late infiltration of meteoric water: a) meteoric fluid response to each thermal event (D2 and D3) and/or b) meteoric fluid event during D3 emplacement which altered all previous igneous units and/or c)all meteoric fluid could be postdike events (late) possibly during the Tertiary.  205 alteration (i.e.  1 8  0 alteration associated with chlorite, hornblende alteration). Moreover, depleted  values of 5 0 in the Cretaceous tonalitic (D2) and basaltic (D3) dikes of -5.0 -0.8 permil 18  indicate exchange with meteoric and/or seawater. Most garnet-wollastonite skarn, garnetite, clinopyroxene skarn, and quartzite samples 18  also have  O-values < 3.1 permil. Petrographic observations suggest that these meteoric  signatures were attained during moderate temperature alteration (i.e. chlorite and epidote alteration). It is concluded that this alteration event post-dated skarn formation (and pluton emplacement) because these retrograde minerals overprint skarn assemblages.  Timing of retrograde meteoricfluidevent(s) Several scenarios are possible for the timing of skarn and igneous 5 0 retrograde 18  meteoric alteration at Mineral Hill (Fig. 4.17). Meteoric fluid infiltration and exchange during Late Jurassic, post skarn formation could have depleted skarn samples. However, because Cretaceous-aged D2 and D3 rocks are also depleted in 8 0, it could not have been an isolated 18  retrograde meteoric fluid episode. Depletion of 5 0-values in D2 and D3 could have occurred as 18  a meteoric fluid response to thermal perturbations in the Cretaceous. Reaction with this fluid event could have altered all igneous and skarn rocks. Furthermore, alteration could be due to a post-Cretaceous meteoric fluid event(s) (Tertiary?). Even though any or all of these scenarios are possible, it should be noted that because D3 is depleted in 8 0, and is the last intrusive event 18  observed in the study area, a retrograde meteoric event had to occur either syn-D3 emplacement or by a post-D3 meteoric event. One retrograde meteoric fluid event could have depleted all igneous and skarn rocks, but is unlikely considering that meteoric fluid alteration seems prevalent in the history of the area (i.e. prograde and retrograde events).  206 4.9 Nature and evolution of svn-metamorphic permeability 4.9.1 Introduction  Igneous, meta-sedimentary and skarn units have 0-values that indicate exchange and I8  equilibrium not only with magmatic fluid (internal to the system), but also with a low 0 fluid 1 8  such as meteoric water (external to the system). Due to the proximity to the pluton, and preserved 8 0 signatures of wollastonite skarn, it is concluded that magmatic fluids were the 18  main control for mineralogy, geochemistry and stable isotope geochemistry in skarn genesis at Mineral Hill. This final section investigates the role of fluids during the most spatially extensive skarnforming event by interpreting petrographic and isotopic constraints on the system. In particular, we focus our discussion on the flow geometry and distribution of multiple reaction fronts at the periphery of skarn formation (wollastonite/marble interface) at Mineral Hill.  4.9.2 Background Mineral reaction may determine the pathways and rates of fluid flow by changing permeability and fluid pressure gradients during Darcian fluid flow. Permeability changes in the system result from volume change due to precipitation or dissolution of minerals. Dipple and Gerdes [1998] found that a decrease in permeability due to reaction closes the permeability networks in marble layers and focuses flow into regions of high permeability (Fig. 4.18a). Although the rate of skarn formation slows due to the lowered permeability of the entire system, these focused networks have the potential to serve as conduits for later ore-bearing fluids. On the other hand, an increase in permeability produces a small increase in the rate of formation since exhaust fluid must escape downstream through a permeable pathway [Dipple and Gerdes, 1998]. These fluid flow pathways can cause interfingering of wollastonite skarn and marble as seen at  207  CU X  o .| o  JJ  oo  \  \ c o  •  \  \ \  \  \  \  \  \  \  \  \  \  \  \  \  \  \  \  \  \  \  CL co cu  T  \  q o cu  IH O  \"  1 cd  acu  O '  £ "  so  IH  u  ^  0]  LL.  _c  s-  cd  1  o  e  £ O 3  (3  < < c o fi o cu cd OJ  IH  H  C cd u  X X  s-  c d  o cd  £  CU  X cu CO  cu  CU  r-  o  C  § I cu CQ IH  ,CU  T3  cu CJ  *  fi cu  a  s  cd O S X  fi  *  ed  OH  C/j  W> cd 00 >:  13  • H  —'  tJ  oo  •3  ra b  fi  cd  a  u  CO " °  ra X0  £  co  CO CU  >  X CU  fi 3 p  IH cd  ca,  cu  ocn)m« o P  CD 3 Tj  I <  £  s  —->  X  3  3  P  rvi  CO  CU  O  S3 co  cd  3  Ti  • H  £  cd  O  ^ £ _ai  ra I*  cd  no I H  cd o L^ co £ 5  o  u  —H X )  g  .22  »4H  O  _o o  cd  cd cu  i*  d  ^  CD  c  2 'Y >  X  . a£ ^3 S B efn  CN  O  60  ^1  N \  o  vo  O  fi o X CL rt a  IH  H co cd  X> 3 g  O  3  3  ^  ^ cBu P c3 CJJ  •S o  O  1  E  co z 3 c^ "2 "S  "leg  £ T3  \ • \ \ •  —'  111  _fi  W  ? o O  Cfl CU  |  T3 33  tfl ^  O  O  to »  fi o I  3 ..cu +j X 3  &  ~° 2 ?  • \  00  0 3  E O  o  N  >  cd  6 0  "•+-» +->  CD  c co o  "S'S 2 cd §  *•§ m  PH  cu  -2  3 -3  3  o  "2  E H  "2  <  Tcd j o o fi X S cd T3 X CD CD cd  CL  i-c  O  «  g £ M iCU c-u + > eg g X cd S3 X CD  H->  Bp _  rN  CO  1  £ * 1£ O  rtd O CO cu c  c c fi o O  C3.  O  u  £°  oo  CJ T J 3 cu  . I-H  CU  co  C+H  o  cu w ~ CU £j =1 CO  CU  fi o  oo  —  GO  2 2  -.•a  oo  £ "  ra  53  3 cu  2  <2 .  ra CSO  E  "3 ,_ CU  O  '"gcd CL cu oo X XO S tH  OO  o  I  g  fi 'oo"  c  bp  Cd  & tJb'jd cd i-f t i >_ o cu ~0 cd.9 0 0 . " c cd cu 3 " "3 •« *c< — *<— oo O  cd  +J  00  cd cu  2 .2 2S £ 1 2-• ao A < -a g cS O x2 o. o 2 r-j  CL '3 -5 < § C O X cr " 3  fi 00  C4-H  £cd ^ 00 ti  U o &,«  3  e o  C d  • fi "2  ^3  c2 C+H  "  SP,§  CU  " w  oo cd  ca o  I  o X  oo  o  i  cd fi "2 oo cd cu t i cd fi  T3 3  -1—t  X  cd  +-> "3  fl  00  208  M i n e r a l H i l l (discussed later). T h u s , propagation rates o f reaction, a n d p e r m e a b i l i t y c r e a t i o n or destruction not o n l y influence the size o f the skarn, but c a n also be used to pattern the geometry o f the f l u i d f l o w event.  4.9.3 Reaction Transport Theory: One-dimensional distribution of multiple reaction fronts B e c a u s e s y n - m e t a m o r p h i c p e r m e a b i l i t y is destroyed b y c o m p a c t i o n w e use r e a c t i o n transport theory to deduce p a l e o - f l u i d f l o w . T h e p r o p a g a t i o n rate (u) o f a r e a c t i o n front (e.g. Si0 , 2  , 0  0 / ' ° 0 ) c a n be related to the time-integrated f l u i d f l u x ( T I F F ) a n d the distance the front  has t r a v e l l e d :  u = AzJ q  v  where q is the time-integrated D a r c y f l u x a n d A z is the distance o f r e a c t i o n front p r o p a g a t i o n v  [Korzhinskii,  1970; Dipple and Gerdes, 1998]. A s briefly discussed i n C h a p t e r 3, several studies  have d o c u m e n t e d that different reactions w i l l propagate at different rates [Korzhinskii, 1 9 7 0 ; Bickle and Baker, 1990; Dipple and Gerdes, 1998]. T h i s o n e - d i m e n s i o n a l concept is illustrated i n F i g . 3.22. G e o c h e m i c a l fronts such as F e , A l , a n d S i 0 2 start at the same interface (t=0), but t h r o u g h t i m e spread apart. A t M i n e r a l H i l l , partial c o n t r o l o n skarn z o n a t i o n is attributed to the distance the F e , A l , M g ? , a n d S i 0 2 reaction front has travelled a n d is reflected i n m a p v i e w w i t h garnet s k a r n p r o x i m a l to the p l u t o n to distal w o l l a s t o n i t e skarn i n contact w i t h m a r b l e (see F i g . 3.20). T h e contact between w o l l a s t o n i t e skarn a n d marble m a r k s the extent o f aqueous s i l i c a infiltration. in  T h i s study uses m u l t i p l e tracers (i.e. S i 0 ,  1 /•  0 / O a n d d e g r a p h i t i z a t i o n alteration) i n  2  order to i m a g e f l u i d f l o w geometry at the w o l l a s t o n i t e skarn-marble interface. F i g . 4 . 1 8 b illustrates a o n e - d i m e n s i o n a l m a p v i e w S i 0 2 ,  1 8  0/  1 6  0 a n d degraphitization r e a c t i o n fronts (t=n)  at s u c h a n interface. B e c a u s e the Si02 front propagates at a s l o w e r v e l o c i t y ,  1 8  0/  l 6  0 and  d e g r a p h i t i z a t i o n reaction fronts are distributed outboard o f the w o l l a s t o n i t e s k a r n - m a r b l e contact.  209  M o r e o v e r , e a c h front occurs as a planar b o u n d a r y since o n e - d i m e n s i o n a l reaction-transport theory does not a c c o m m o d a t e heterogeneous p e r m e a b i l i t y d i s t r i b u t i o n ; f l u i d p e r v a s i v e l y f l o w s p e r p e n d i c u l a r across a l l alteration fronts (i.e. r e a c t i o n front). A t M i n e r a l H i l l , the d e g r a p h i t i z a t i o n front (denoted b y the disappearance o f graphite f r o m b l e a c h e d m a r b l e to grey m a r b l e ) appears to travel at a faster rate than the  18  0/ 0 16  front  since the graphite-out i s o g r a d occurs a f e w centimeters outboard o f the w o l l a s t o n i t e s k a r n m a r b l e contact (see F i g 4.18). T h i s distance is attributed to d i f f u s i o n mass transfer o f f l u i d s across the contact, h o w e v e r the s m a l l scale o b s e r v a t i o n o f the graphite-out i s o g r a d ahead o f the 18  0/ 0 l6  front p r o b a b l y m i m i c s the large scale scenario. T h e extent o f the SiC>2 front a n d the  graphite-out i s o g r a d is r e c o r d e d b y the spatial extent o f w o l l a s t o n i t e s k a r n and b l e a c h e d m a r b l e , r e s p e c t i v e l y . These alteration fronts are m a p p a b l e i n the f i e l d . M o r e o v e r , the  Si02 front  is noted  as the distinct c h e m i c a l change f r o m ~ 4 w t percent SiC>2 i n m a r b l e to ~ 5 0 w t % S1O2 i n w o l l a s t o n i t e skarn. In order to evaluate the extent o f the  1 8  0 / O front, the 8 0 i e  18  values o f w o l l a s t o n i t e s k a r n  a n d m a r b l e were p l o t t e d as a f u n c t i o n o f distance f r o m the skarn/marble b o u n d a r y o n c m - s c a l e ( F i g . 4.13a-f) a n d m - s c a l e ( F i g . 4.19a-d). 8 0 18  values o f m a r b l e and w o l l a s t o n i t e s k a r n differ  because m a g m a t i c v o l a t i l e s ( c a r r y i n g aqueous silica) f r o m a p l u t o n react w i t h m a r b l e s to create w o l l a s t o n i t e skarn. W o l l a s t o n i t e forms at or near i s o t o p i c e q u i l i b r i u m w i t h the f l u i d . I n other s k a r n systems it has been noted that s k a r n adopts a m a g m a t i c 5 0 18  signature w h i l e m a r b l e retains  i t ' s p r i m i t i v e signature (20-30 p e r m i l ) ( F i g . 4.20b) [e.g. Taylor and O'Neill, H i l l , s o m e w o l l a s t o n i t e s k a r n samples are at or near  18  1977]. A t M i n e r a l  0 exchange e q u i l i b r i u m w i t h m a g m a t i c  v o l a t i l e s . H o w e v e r , d i r e c t l y across the contact, m a r b l e 8 0 18  values are less than 5 p e r m i l , up to  - 1 0 m o u t b o a r d the w o l l a s t o n i t e skarn/marble b o u n d a r y , suggesting w i t h m e t e o r i c / seawater ( F i g . 4.19b). Therefore, the 8 0 18  18  0 exchange e q u i l i b r i u m  alteration front is s p a t i a l l y c o i n c i d e n t  210  15  25  35  45  55  distance (m) 20 i  B  A  18 -  A  16 14 2 °  to  A  12 -  A  10 8 -  A  6 4 2 -  o-5  -4  -3  -2  -1  1 0  1  A  ~i  2  3  i  1  4  5  r  6  7  8  9  10  distance (m)  *  i &  . -r. w .  v  5 180  v s . distance plot. D i s t a n c e = 0 at the w o l l a s t o n i t e skarn/marble b o u n d a r y .  R a n g e i n c l u d e s a l l samples i n the study area ( w o l l a s t o n i t e skarn-open triangles, b l e a c h e d m a r b l e squares, grey m a r b l e - c l o s e d triangles). B ) same p l o t as A ) w i t h range o f 10 meters o u t b o a r d w o l l a s t o n i t e skarn/marble b o u n d a r y .  211  -500  -400  -300  -200  -100  0  100  200  2  4  300  400  500  distance (cm)  D  20 18 16 14  O to  12  io  A A  A  8  A^  6 4 2 0 -10  -6  -2  0  10  distance (cm)  x x . 6  5 18O v s . distance  plot. D i s t a n c e = 0 at the w o l l a s t o n i t e skarn/marble b o u n d a r y .  R a n g e i n c l u d e s a l l samples 500 centimeters outboard o f the w o l l a s t o n i t e skarn/marble b o u n d a r y ( w o l l a s t o n i t e skarn-open triangles, b l e a c h e d marble-squares, grey m a r b l e - c l o s e d triangles). D ) same p l o t as C ) w i t h range o f 10 centimeters outboard w o l l a s t o n i t e skarn/marble b o u n d a r y . N o t e sharp i s o t o p i c v a r i a t i o n o f w o l l a s t o n i t e skarn a n d m a r b l e .  212  sio 5o  A Woll skarn  A) 20 -i  60  18 -  ®  16 -  •  • Bleached marble A Grey marble  2  18  Graph-out  50  14 -  40  12 -  <  A  10 -  o  8  30  &  A  ^—<  oo  to  6 -  A  O  20  A  4 2 o •10  -5  0  5  10  Distance (cm) B) 20  •• i i•ii•i i•i•iiIiiIiiiI i i i i i ii I  CO  io fe:  = MM =  MM =  MH =  MM =  EE llll WW HII = llll EE llll i -_ M uMn — — M MMM — — M mM i —_ MM IIII — -  I  •  •  •  •  •  •  • •  • •  = 1111 = 1111 = 1111 = HIM • = 1111 = 1111 = 1111 = 1111 = •  •  •  •  •  • •  •  •  • •  •  •  • •  •  •  • •  • •  i i i i i ii i i i i i ii i i II II •  •  •  •  •  •  •  •  •  •  •  •  •  •  Distance  Fig. 4.20. A) O vs. distance plot with range of 10 centimeters outboard and inboard of the wollastonite skarn/marble boundary denoted by the increase in SiQ2 from -4 wt % in marble to -50 wt % in wollastonite skarn. A sharp isotopic shift from wollastonite skarn in 180 exchange 0  518 O values  < 5 permil, indicate the 0/ O front overlaps the Si02 front. The graphite-out isograd, the extent of bleached marble outboard wollastonite skarn, generally does not exceed a few centimeters. This distance can be accommodated for by diffusional mass transfer across the skarn front. The spatial stacking of multiple tracers indicates that flow is parallel to the wollastonite skarn/marble boundary (reaction/infiltration side). B) Schematic of typical oxygen isotopic shifts between wollastonite skarn and marble due to infiltration of magmatic fluids. Wollastonite skarn adopts a magmatic oxygen isotopic signature (-10 permil) while marble more or less maintains it's primitive signature (20-25 permil), minus depletion due to devolatilization reactions.  v  ^  ^  ^  ,  ^  „.„x x„v* «x^vw &  •v.x^xxxw., . v  uvj.iv.vu  w  213  with the S1O2 front. Plots of 8 C versus distance from the wollastonite skarn/ marble interface 13  show no systematic variation in values (Fig. 4.21a,b). The graphite-out isograd was determined by the distance bleached marble extends outboard wollastonite skarn. Generally, bleached marble does not occur more than a few centimeters past the interface; a distance easily accommodated by diffusion or bi-metasomatism across this boundary. This spatial stacking of multiple tracers is not consistent with one-dimensional reaction transport theory in which tracers should be spread apart due to perpendicular flow across the reaction front. Instead, stacking of tracers suggests flow parallel to alteration fronts, known as reaction or infiltration sides [Dipple and Gerdes, 1998]. Moreover, based on a molar TIFF on the order of 10 moles/cm (see section 3.7.3), the 0 / 0 front should have moved approximately 5  2  1 8  1 6  12 kilometers [cf. Dipple and Ferry, 1992]. Samples record 0 / 0 alteration no farther than the 1 8  1 6  Si02 front (~65m). This is consistent with the interpretation of reaction sides documented in samples along the wollastonite skarn-marble interface. However, it is important to note that this analysis is predicated on the assumption that marble (5 0) was altered by meteoric fluids prior 18  to skarn formation. This assumption is justified in section 4.8.2. A n alternative explanation for the variations in 5 0 in the vicinity of the marble-skarn interface is that marble was depleted 18  through interaction with meteoric fluids after wollastonite skarn formation. In this scenario, the isotopic alteration of marble during skarn formation was obliterated by subsequent infiltration of meteoric water. Even in this instance, the interpretation that the sampled marble-skarn contacts are infiltration sides is still supported by the limited development of bleached marble. Furthermore, one-dimensional reaction transport theory cannot account for the observed wollastonite skarn-marble contact geometry. Detailed mapping at Mineral Hill reveals that the  214  -5  5  15  25  35  45  55  distance (m)  1  B  -7  H -5  1  1  1  -4  -3  -2  1  -1  1 0  1  1  1  1  1  1  1  1  1  1  2  3  4  5  6  7  8  9  1 10  distance (m)  F i g . 4.21. A ) 8  C v s . distance plot. D i s t a n c e = 0 at the w o l l a s t o n i t e skarn/marble  b o u n d a r y . R a n g e i n c l u d e s a l l m a r b l e samples i n the study area (bleached m a r b l e - squares, grey marble-triangles). B ) S a m e p l o t as A ) w i t h range o f 10 meters o u t b o a r d o f w o l l a s t o n i t e skarn/marble b o u n d a r y .  215 l i t h o l o g i c contact between w o l l a s t o n i t e skarn and m a r b l e (i.e. S 1 O 2 front) is not planar, but h i g h l y irregular a n d fingered ( F i g . 1.9).  4.9.4 Reaction-infiltration instabilities at the skarn front: Implications on flow geometry T h e m o r p h o l o g y o f the reaction front (e.g. planar versus lobate fronts) is c o n t r o l l e d b y the i n i t i a l p e r m e a b i l i t y structure o f the country r o c k s , reaction infiltration feedbacks a n d m e c h a n i c a l processes s u c h as c o m p a c t i o n [Balashov and Yardley, 1998; Dipple and  Gerdes,  1998]. I n fact, it is essential that the host r o c k s be c h e m i c a l l y reactive and p e r m e a b l e for skarn to be p r o d u c e d . T h e extent o f the  O front is observed to overlap the S i 0 2 front ( F i g . 4.20a). I f the t i m i n g  o f the m e t e o r i c exchange and e q u i l i b r i u m w i t h marble is pre-skarn f o r m a t i o n (see s e c t i o n 4.8.2), m o s t o f the w o l l a s t o n i t e skarn/marble b o u n d a r y samples represent a n i n f i l t r a t i o n or r e a c t i o n side and not a front. Therefore, d o m i n a n t f l o w (advection) is p a r a l l e l to the w o l l a s t o n i t e skarn/marble interface p r o b a b l y w i t h d i f f u s i o n a l exchange o c c u r r i n g across this b o u n d a r y . T h e i s o t o p i c e v i d e n c e o f m o s t l y reaction sides supports a lobate m o r p h o l o g y since a planar front w o u l d result i n m o s t l y r e a c t i o n fronts. T h e b l e a c h e d m a r b l e represents a graphite out i s o g r a d and occurs b y a r e a c t i o n s u c h as: 2 C + 2 H 0 = CFL, + C 0 2  2  [from Todd, 1990]  S i n c e this zone o n l y occurs w i t h i n centimeters between w o l l a s t o n i t e s k a r n and grey m a r b l e , the d e g r a p h i t i z a t i o n c a n be attributed to diffusive mass transfer o f an H2O- r i c h f l u i d a l o n g a n infiltration side [Todd, 1990]. I f the b l e a c h e d zone w a s extensive ( 1 0 0 ' s o f meters to k i l o m e t e r s ) then w e w o u l d be located a l o n g a n exhaust pipe o f a infiltration front or i n a g e o m e t r i c a l l y planar front ( F i g . 4.18). S o m e e x a m p l e s o f extensive b l e a c h e d marble zones outboard o f s k a r n are M a g i s t r a l , P e r u [Floyd, 2 0 0 1 ] , A n t a m i n a , P e r u [O'Connor, [Webster and Ray,  1990.]  2001] and T e x a d a I s l a n d , B . C  216 In a d d i t i o n , p e t r o l o g i c a l evidence shows that the reaction creating w o l l a s t o n i t e skarn f r o m m a r b l e ( R l ) resulted i n a v o l u m e loss o f - 2 0 percent. It has been d o c u m e n t e d that v o l u m e losses at the r e a c t i o n boundary focuses f l o w s u c h that the geometry o f the b o u n d a r y b e c o m e s lobate [Dipple and Gerdes, 1998]. O n the other hand, a v o l u m e g a i n (destruction o f p e r m e a b i l i t y n e t w o r k s ) w o u l d divert f l o w f r o m the reaction site a n d result i n a g e o m e t r i c a l l y planar front [Dipple and Gerdes, 1998].  4.10 Conclusions T h e e m p l a c e m e n t o f the L a t e Jurassic C r o w s t o n L a k e P l u t o n drove a c o n v e c t i o n c e l l o f m e t e o r i c f l u i d into T r i a s s i c sediments (preserved as a r o o f pendant). T h i s early h i g h temperature m e t e o r i c f l u i d event i s preserved i n l o w 8  1 8  0 marbles that are spatially c o i n c i d e n t w i t h the p l u t o n  contact. Farther f r o m the p l u t o n contact, the marbles are depleted to m a g m a t i c signatures ( - 1 5 to 9 permil). M a g m a i n the p l u t o n reached v o l a t i l e saturation a n d e x s o l v e d m a g m a t i c f l u i d s into the r o o f pendant r e s u l t i n g i n contact m e t a s o m a t i s m p r o d u c i n g the first s p a t i a l l y extensive garnet a n d w o l l a s t o n i t e skarns. T h e lobate or interfingering geometry o f the r e a c t i o n front at the w o l l a s t o n i t e skarn/marble interface at M i n e r a l H i l l is deduced f r o m 2 m b y 2 m g r i d m a p p i n g , c m scale b l e a c h e d m a r b l e z o n e , c a l c u l a t i o n o f v o l u m e loss, a n d s t a c k i n g o f g e o c h e m i c a l a n d i s o t o p i c fronts. P l a n a r fronts are l i m i t e d b y h o w permeable the host r o c k is p r i o r to i n f i l t r a t i o n . H o w e v e r , at M i n e r a l H i l l , w e c o n c l u d e that reaction drove i n f i l t r a t i o n a n d resulted i n v o l u m e loss a n d l o c a l increase i n p e r m e a b i l i t y (reaction-infiltration instabilities) f o c u s i n g f l u i d a l o n g the w o l l a s t o n i t e / m a r b l e b o u n d a r y t o w a r d a n d out t h r o u g h exhaust pipes at the r e a c t i o n front (unsampled). R e a c t i o n enhanced p e r m e a b i l i t y has several i m p l i c a t i o n s for skarn f o r m a t i o n . P o s i t i v e r e a c t i o n - i n f i l t r a t i o n feedback p r o v i d e s a t w o - d i m e n s i o n a l picture o f a transient aquifer. I f skarn r e a c t i o n creates porosity, a s m a l l increase i n rate o f f o r m a t i o n occurs w h i c h , i n turn, c a n  217  influence the size o f the skarn deposit. 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F . , 1976, Pedogenesis  of Metamorphic  Z h a r i k o v , V . A . , 1970, Skarns: International  Rocks, S p r i n g e r - V e r l a g , 3 3 4 pages.  Geology Review, v o l . 12, p p . 5 4 1 - 5 5 9 , 6 1 9 - 6 4 7 ,  760-775. Z h e n g , Y . F . , 1993a, C a l c u l a t i o n o f o x y g e n isotope fractionation i n S i 0 a n d A b S i O s p o l y m o r p h s : effect o f c r y s t a l structure: European Journal of Mineralogy, v o l . 5, p p . 6 5 1 658. 2  A P P E N D I X 1: STRUCTURAL MEASUREMENTS  A p p . 1. Structural measurments for Mineral Hill. Magnetic declination is 20 degrees. Corresponding localities found in Fig 1.4 (UB, T B , UMQ) and Fig 1.5 (MB, LB). cation strike dip location strike dip location strike 1 235 7 7 N W 12 240 8 5 N W 16b 215 220 8 4 N W 235 7 3 N W 204 240 8 4 N W 220 8 0 N W 15b 350 2 25 70SE 205 85W 300 55SE 35 211 70W 16c 220 21 86SE 215 64W 206 3 250 7 5 N W 73W 209 205 230 5 5 N W 71W 240 30 255 8 5 N W 222 71W 15c 295 4 250 8 0 N W 227 68W 296 290 8 0 N W 65W 17 225 255 255 90 73W 209 240 5 280 6 5 N W 315 65N 225 280 5 3 N W 325 70N 242 280 6 8 N W 324 64N 213 6 250 7 2 N W 337 74N 252 230 8 0 N W 304 70N 285 115 7 5 S W 337 45N 18a 277 7 255 7 5 N W 330 58N 295 250 90 352 53E 275 8 260 76N 13 255 7 6 N W 19 305 280 7 5 N W 75 85SE 25 258 80N 344 76E 260 9 240 71N 115 85SE 235 230 8 8 N W 126 69S 20 340 214 86N 325 87NE 18b 267 71N 218 185 E 21 200 212 69N 80SE 30 30 205 69N 330 70NE 195 10 255 25NE 14 302 84N 45 62E 168 110 85S 29 64E 160 112 85S 22 223 355 80NE 265 7 5 N W 170 11 182 72E 15a 300 7 6 N W 210 197 86E 275 8 8 N W 290 184 82E 270 7 9 N W 290 285 82N 23 235 104 86S 260 16a 240 7 0 N W 276 215 7 5 N W 265 34 87E 253 213 71W 24 265 205 7 5 N W 275 215 8 0 N W 25 323 16b 202 71W 321 205 8 0 N W 327 225  dip 71W 83W 90 86N 80NW 76W 80NW 60SE 85NE 90 75NW 75NW 90 66NW 82NW 81NW 80NW 71 N W 80NW 75NW 20NW 75E 80NW 90 75NE 70NE 90 84E 85E 88E 90 69NW 70SW 75W 71W 85NW 70NW 62NW 52N 55NW 58NW 76NW 80NW 64NW 79NW 75NW 85W  227  location 26  27  28  29  30  31  32  33  strike 225 250 22 245 245 230 245 245 260 260 265 225 230 245 235 50 85 285 75 290 40 40 210 200 240 275 235 260 285 205 270 225 270 280 225 245 225 235 225 219 244 235 20 200 264 225  dip 86SE 85NW 84SE 84NW 80NW 90 80NW 62NW 64NW 60NW 90 82NW 88NW 89NW 90 81SE 80SE 45NW 40NW 65NW 40SE 80SE 90 77W 42NW 60NW 60NW 60NW 85NW 70NW 64NW 80NW 65NW 72NW 88NW 75NW 70NW 82NW 84NW 20W 44NW 40W 89SE 80NW 25NW 64NW  location 32a 34  35 33 36  37  38 39  40  41  strike 20 277 300 289 285 298 291 326 298 330 249 250 190 210 285 246 50 228 237 230 135 242 235 245 56 242 230 74 270 48 198 35 45 30 35 40 30 140 45 212 214 214 214 36 222 280  dip  location  90 70N 63N 73N 55N 59N 51N 50NE 69N 80NE 70NW 34NW 23W 10W 90 80NW 83SW 74NW 38NW 66NW 80NE 84NW 65NW 90 89SE 89NW 75NW 85SE 76NW 63SE E 80SE 78SE 90 79SE 85SE 78SE 85SW 90 83NW 78NW 88W 89W 88E 64W 90  41 42  43  44  45  46 47  48 49  50  51  52  53  54 55  strike 302 299 265 185 70 58 102 94 94 64 250 260 250 230 255 42 70 62 265 290 245 260 244 68 270 255 90 235 235 234 254 250 62 54 64 240 65 70 62 76 82 255 225 73 260 82  dip 78N 83N 65NW 57W 10NW 68SE 86S 76S 52S 80SE 80NW 85NW 88NW 75NW 68NW 52SE 67SE 75SE 70NW 85NW 68NW 85NW 77NW 82SE 75NW 70SW 80SE 55NW 88NW 81NW 86NW 82NW 53SE 60SE 63SE 85NW 75SE 76SE 89SE 85SE 82SE 72NW 75NW 85SE 55NW 80SE  (APPROX)  U P P E R LIMB U P P E R LIMB U P P E R LIMB  (APPROX) (APPROX)  strike 250 255 265 160 268 280 282 275 250 250 265 240 295 272 266 50 242 262 60 230  dip 81 N W 75NW 68NW 70NW 60NW 69N 72N 87N 76NW 83NW 80NW 43NW 65NW 70N 72N 88SE 75NW 59NW 85SE 90  location  strike  H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H  155 180 175 195 344 150 175 225 245 160 158 275 255 170 155 140 175 200 165 150 125 155 330 145 315 325 325 325 325 310 325 315 330 295 290 315 300 120 345 0 120 315 110 110 335 100 320  dip 75 85 65 86 85 76 75 51 77 77 70 68 80 77 90 70 45 57 80 90 86 70 75 90 70 75 80 73 85 75 65 75 75 68 72 83 65 75 65 75 80 60 75 75 88 90 75  location H H H H H H H H H H H H H H H H Sheer zo  strike 110 305 160 310 155 300 305 305 280 280 5 225 140 235 180 180 120  dip 85 80 73 60 75 75 83 80 90 75 85 65 70 35 75 70 78  

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