UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Mass changes during hydrothermal alteration, Silver Queen epithermal deposit, Owen Lake, central British.. 1995

You don't seem to have a PDF reader installed, try download the pdf

Item Metadata

Download

Media
ubc_1995-059340.pdf [ 8.59MB ]
ubc_1995-059340.pdf
Metadata
JSON: 1.0052489.json
JSON-LD: 1.0052489+ld.json
RDF/XML (Pretty): 1.0052489.xml
RDF/JSON: 1.0052489+rdf.json
Turtle: 1.0052489+rdf-turtle.txt
N-Triples: 1.0052489+rdf-ntriples.txt
Citation
1.0052489.ris

Full Text

MASS CHANGES DURING HYDROTJIERMAL ALTERATION SILVER QUEEN EPITHERMAL DEPOSIT, OWEN LAKE, CENTRAL BRITISH COLUMBIA by XIAOLIN CUENG B.Eng., The China University of Geosciences (Wuhan), 1982 M.Sc., The China University of Geosciences (Wuhan), 1985 A THESIS SUBMITFED IN PARTIAL FULFILLMENT OF TUE REQUIREMENTS FOR TUE DEGREE OF DOCTOR OF PHILOSOPHY in TIlE FACULTY OF GRADUATE STUDIES (Department of Geological Sciences) We accept this thesis as conforming THE UNIVERSITY OF BRITISH COLUMBIA October 1995 © Xiaolin Cheng, 1995 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. (Signature) ______________________________ Department of óe.iic.cA Sc4’v2-i The University of British Columbia Vancouver, Canada Date Oct- 9 , DE-6 (2/88) ABSTRACT A procedure for determining metasomatic norms is developed in this thesis to quantitatively and objectively estimate mineral abundances from lithogeochemical data, The norm calculations use the same principles as do other norms such as CIPW, but the different mineral phases present in alteration systems are used as the normative standard minerals. Another distinctive difference between a metasomatic and a conventional norm is that the calculation procedure proposed for a metasomatic norm does not proceed along such a fixed hierarchical path as in the case of an igneous norm. A particular useful approach to the application of the norm concept to metasomatic rocks is to constrain the calculated normative mineralogy by apriori knowledge of existing minerals (i.e. to approximate the mode as closely as possible). Where an immobile component can be recognized the metasomatic norms for protoliths and altered rocks, as well as the chemical constituents lost or gained, can be further recast into the absolute amounts ofminerals and chemical constituents relative to a given mass of parent rock. Known errors within lithogeochemical data studied can be propagated to the final results of all norm calculations. As a result, a chemico mineralogical model for material exchange, including absolute losses and gains of chemical constituents, normative minerals in extensive units, as well as the corresponding propagated errors, is formulated in this work as follows: Mineral.ent rock ± error + Constituent gained from solution ± error = iVlineralafted rock ± error + Constituent lost from wall rock ± error (I) Equation I is particularly useful because it is quantitative and easily applied: information that can be obtained from the equation includes the mineralogy of the initial and final rocks, absolute gains and losses of specific chemical constituents as well as the uncertainties on each estimate at a specified confidence level. 11 The methodology for this approach is a natural extension of the use ofPearce element ratio (PER) diagrams for the study ofmetasomatic rocks. The metasomatic norm recovers the same quantitative information as do Pearce element ratio diagrams. The common principles are (i) correction for closure, that provides true relative lithogeochemical and mineralogical variations between parent and daughter rocks, and (ii) an effort to explain chemical variability in terms ofmineralogical variability. The strategy of a PER diagram is to test whether chemical changes in different rocks can be explained purely by the variation(s) of certain mineral(s), as demonstrated by disposition of the binary plotted points along predefined trends (slopes). Metasomatic norms are displayed more effectively as equations or profiles showing the spatial distributions of normative mineral assemblage, as well as the absolute losses and gains of chemical constituents based on comprehensive mass balance relationships. The approach described in the first part of this thesis is applied to a hydrothermal alteration study of the Silver Queen mine in central British Columbia. Hydrothermal alteration at the Silver Queen mine was derived from a multiple precursor system. However, local, individual alteration profiles exhibit the attributes of a single precursor system. Six types of hydrothermal alteration at Silver Queen mine have been described: viz. propylitization, sericitization, argillization, silicification, pyritization and carbonatization. In general, the wall rock alteration in the study area is composed of a widespread regional propylitic alteration with superimposed carbonatization. Regional alteration gives way, as the vein is approached, to an outer envelope of sericitic and argillic alteration + carbonatization and an inner envelope of silicification and pyritization + sericitic or argillic alteration + carbonatization. Thus, the sequence of alteration development is (i) widespread regional propylitic alteration, (ii) sericitic and argillic outer envelope, and (iii) silicification and pyritization inner envelope. Most of the hydrothermally altered samples in alteration envelopes at the Silver Queen mine have gained mass during hydrothermal alteration. In contrast, samples from 111 the profile of the northern segment of the No. 3 vein have lost mass. Other spatial variations of hydrothermal alteration from the southern segment to the northern segment of the No. 3 vein and from different levels (from 2600-foot level to 2880-foot level) have been recognized. In brief, the wall rock alteration is most intense in the alteration envelope at the central segment of the No. 3 vein and mildest at the northern segment of the No. 3 vein. The total mass change of each altered sample is largely the result of depletion of CaO andNa20, and addition of Si02,K2O,H20 and CO2. iv TABLE OF CONTENTS Abstract II Table of Contents V List of Tables xlii Acknowledgement X Chapter 1. Background and Objectives 1 1. 1. Introduction 1 1. 2. Current Quantitative Approaches to the Study ofHydrothermal Alteration 4 1.2.1 The Closure Effect 5 1.2.2 Comparison ofVarious Techniques Used to Remove the Closure Effect 7 1.3. Two Requirements for Loss and Gain Calculation 10 1.4. Pearce Element Ratios (PER) and Their Application to Hydrothermal Alteration 16 1.5. Additional Problems 23 Chapter 2. Metasomatic Norms: AMethod ofNorm Calculation Adapted to Hydrothermally Altered Rocks 26 2.1. Introduction 26 2.2. The Principle ofMetasomatic Norms 28 2.3. A Set of Standard Normative Minerals for Metasomatic Systems 32 2.4. A Manual Procedure for Metasomatic Norm Calculation 33 2.5. A Quantitative Model ofMetasomatic Systems 41 2,6. Case Histories: Application ofMetasomatic Norms 43 2.6.1. Sigma Mine, Abitibi, Quebec 43 2.6.2. Erickson Gold Mine, Northern British Columbia 47 2.7. Conclusions 55 V Chapter 3. Quality Control/Assessment ofLithogeochemical Data 57 3.1. Introduction 57 3.2. Strategies of Sampling and Sample Preparation 58 3.3. Quality Assessment ofAnalytical Measurements Based on a Small Set ofDuplicates 64 3.4. Propagation ofErrors in Lithogeochemical Calculations 71 Chapter 4. Geology of the Silver Queen mine, Owen Lake area, Central British Columbia 76 4.1. Introduction 76 4.2. Regional Geological Setting 77 4.3. Geology of the Study Area 80 4.4. Lithogeochemical Characters and Two Series of Igneous and Volcanic Rocks 92 4.5. Veins: Character and Correlation 96 4.6. Structures and the Interpretations 99 4.7. Summary 106 Chapter 5. Hydrothermal Alteration Associated with Epithermal, Base- and Precious-Metal Veins at Silver Queen Mine: Petrographic Variations 108 5.1. Introduction 108 5.2. Petrography ofHydrothermal Alteration Types 109 5.3. The Spatial Zonation ofHydrothermal Alteration 115 5.4. Paragenetic Sequence ofHydrothermal Alteration 125 5.5. Discussion and Conclusions 130 Chapter 6. A Quantitative Evaluation ofHydrothermal Alteration at Silver Queen Mine, Central British Columbia 133 6.1. Introduction 133 6.2. Sampling and Sample Preparation 134 vi 6.3. Errors inherent in Lithogeochemical Data 140 6.4. Lithogeochemical Data ofAltered Rock and Determination of immobile components 142 6.5. Calculation ofAbsolute Losses and Gains of Chemical Constituents and their Spatial Variations 144 6.6. Application ofPER Diagram to the Interpretation ofHydrothermal Alteration 149 6.7, Application ofMetasomatic NormMethodology 158 6.8. Propagated Error Analysis and Confidence Level of the Quantitative Evaluations 167 6.9. A Comprehensive Model ofHydrothermal Alteration 169 Chapter 7. Conclusions and Recommendations 172 Bibliography 183 Appendix A. Megascopic Description ofAltered Sample, Silver Queen Mine 196 Appendix B. Lithogeochemical Duplicate Analyses, Silver Queen Mine 201 Appendix C. Use of “Quattro Pro for DOS 5.0” to Calculate Metasomatic Norms 205 Appendix D. Diagrams of Alteration Evaluation, Silver Queen Mine 246 Appendix E. Tables ofAlteration Evaluation, Silver Queen Mine 268 vii LIST OF TABLES Table 1-1. A Summary of Quantitative Techniques Devised to Remove the Closure Effect and Evaluate Mass Transfer Process 8 Table 1-2. Eight Possible Cases ofPERDiagram 13 Table 2-1. A List of Standard Normative Minerals for Metasomatic Volcanic Rocks Associated with Epithermal Ore Deposits 34 Table 2-2. Variations in Major Element Oxide Concentration (in wt%) in the Profile 2103 across Alteration Envelope Around Tension Vein, Sigma Mine, Quebec 44 Table 2-3. The Calculation Results ofMetasomatic Norms (in wt%) in the Profile 2103 across Alteration envelope around Tension Vein, Sigma Mine, Quebec 44 Table 2-4. Summary of Characteristics ofAlteration Zones ofEnclosing Gold-Bearing Quartz Veins and the McDame Dolomite Vein, Total Erickson Mine 48 Table 2-5. Chemical Analyses of Jennie Vein Alteration Profile, Erickson Gold Mine 50 Table 2-6. Metasomatic Norms of Jennie Vein Alteration Profile, Erickson Gold Mine 50 Table 2-7. Metasomatic Norms Corrected for Closure and Absolute Losses and Gains of Components from Profile 80-88-JH across the Jennie Vein, Erickson Mine, Northern British Columbia 52 Table 3-1. The Classification ofMajor Variations ofLithogeochemical Data Generated by Different Processes 57 Table 4-1. Table ofFormations, Owen Lake Area 83 Table 4-2. Lithgeochemical Data ofVarious Types ofRock at Owen Lake Area, Central British Columbia 94 Table 5-1. Estimated Modes of Alteration Minerals in Hydrothermally Altered Rock around the No. 3 Vein, Silver Queen Mine, Central British Columbia 120 viii Table 5-2. Paragenetic Sequence ofMineral Assemblages, Silver Queen Mine 129 Table 6-1. Estimation of Optimal Sample Size by Using Binomial Function 136 Table 6-2. Estimated Optimal Fineness of Subsample by Using Binomial Function 138 Table 6-3. Error ofLithgeochemical Data Estimated by Using Sample Duplicates 141 Table 6-4. Error ofLithogeochemical Data Estimated by Using Measurement Duplicates 141 Table 6-7. Metasomatic Norms Corrected for Closure and Absolute Losses and Gains of Components (in Moles) around the No. 3 Vein, Silver Queen Mine, Owen Lake, Central British Columbia 160 Table 6-8. Metasomatic Norms Corrected for Closure and Absolute Losses and Gains of Components (in Grams) around the No. 3 Vein, Silver Queen Mine, Owen Lake, Central British Columbia 161 Table 6-9. Propagated Errors ofMetasomatic Norms Corrected for Closure and Absolute Losses and Gains of Components in Grams at the 68% Confidence Level, the No. 3 Vein, Silver Queen Mine, Central British Columbia 168 ix ACKNOWLEDGMENTS In the course of completing my thesis, several individuals and agencies have provided much appreciated assistance, without which the thesis would have been an impossibility. I am especially indebted to Dr. Alastair J. Sinclair for offering me the opportunity to work on the Owen Lake Project as a Ph. D. graduate student under his supervision, and for his constructive criticism, insights, and extraordinary patience that allowed me to complete this work. Dr. Gerry Carlson, Dr. Craig Leitch and Dr. Margaret Thomson provided much needed assistance in deciphering the geological story behind the Silver Queen precious- and base-metal vein deposit and greatly supplemented the evolution of this thesis with their own work. My thanks also go out to my coworkers Christopher T. S. Hood, Zophia Radlowski and Asger Bentzen for their suggestions, discussions and assistances. Pacific Houston Resources Inc. and New Nadina Explorations Ltd. are thanked for allowing access to the Silver Queen workings and for financial assistance in and out of the field. J. Hutter and W. W. Cummings provided helpful discussions on the mine area during my stay at Silver Queen mine. Dr. L. A. Groat and K. N. Nicholson are thanked for the advice and assistance with the X-ray diffraction operation; Dr. W.K. Fletcher and S. Horsky for the guidance on the XRF analytical measurement. I am also grateful to Dr. T. J. Barrett, Dr. T. H. Brown, Dr. R. L. Chase, Dr. G. M. Dipple, Dr. C.I. Godwin, Dr. J. K. Russell, Dr. C. R. Stanley and Dr. Mm Sun for providing instruction and discussion. This work was supported by Pacific Houston Resources Inc., New Nadina Explorations Ltd. and by a grant from the Natural Science and Engineering Research Council of Canada to Dr. A.J. Sinclair. x Chapter 1. Background and Objectives 1.1. Introduction Bates and Jackson (1987) define alteration as: “ ... any change in the mineralogical composition of a rock brought about by physical or chemical means, especially, by the action of hydrothermal solutions . . .“It is one of the most important topics studied by economic geologists because in many hydrothermal ore deposits the changes in composition, mineralogy and/or texture ofwall rocks, etc., that enclose the ore deposit are more extensive and more obvious than the ore deposit itself. Hydrothermally altered wall- rock is thus a “fossil” of a hydrothermal system; many parameters of the depositional environment of ore are interpretable from the assemblages of alteration minerals. Consequently, wall-rock hydrothermal alteration has been used widely as a guide during exploration of hydrothermal ore deposits and as a clue to the properties of the hydrothermal solution from which ores precipitated. However, hydrothermally altered wall rock can be the product of the reaction between wall rock and ore-bearing hydrothermal solution either before, during or after the precipitation of ore minerals from hydrothermal solutions. To understand the relation between ore and associated hydrothermally alteration is a challenging task. Uncertainties can lead to errors or complexities in using wallrock alteration as a guide to exploration of hydrothermal ore deposits if different types of alteration are confused. Appleyard and Guha (1991) review such practical uses of hydrothermal alteration and state: Wall-rock alteration was generally accorded little signficance as an exploration focus. Dunbar (1948), for example, notedwith reference to the ores of the Porcupine district that moderate bleaching of the chloritic host rock was considered to be a conditionfavorablefor ore occurrence but such evidence can only be utilized in a very general way. Conversely, hefound strong bleaching to be a poor indicator ofmineralization andwrote that it cannot be said that the ore 1 occurs where its effect (that ofhydrothermal alteration) is most intense. Since those days, technical improvements have been at the heart of the advancement of the state ofknowledge we have seen rather than the appearance ofnew paradigms. Lithogeochemistry, isotope geochemistry, fluid inclusion studies, statistical applications, and geochemical modeling are all areas where great advances in technique and important observations have been achieved. In recent years, research into hydrothermal alteration associated with precious- metal ore deposits has accelerated appreciably with increasing interest in understanding water/rock interactions, mass losses and gains, the geometry of alteration zones relative to the associated mineral deposit, and assemblages of alteration minerals. This information leads to the development of comprehensive models of alteration systems and provides a basis for designing mineral exploration guidelines, particularly as they relate to the use of lithogeochemical data and their integration into deposit model definition as an exploration tool. The general aim of this thesis is to improve quantitative methods of evaluating hydrothermal alteration associated with precious- and base-metal vein deposit in volcanic sequences. This goal will be approached through a particular case study of alteration at the Silver Queen mine, central British Columbia. This study is preceded by a brief review of the current status of the study in the field of quantitative losses/gains to wallrock during hydrothermal alteration. The basic aims ofmany alteration studies involve such questions as: (1) What are the changes in mineralogical assemblage of the rock during the alteration process? (2) What variations in chemical compositions of the rock arise from the alteration process? (3) What are the sequences, distribution patterns and spatial extents of alteration? 2 (4) What are the conditions of formation of alteration minerals and the properties of hydrothermal solution? (5) What are the mechanisms of hydrothermal alteration? and (6) What is the relationship between hydrothermal alteration and ore deposition? To answer such questions commonly involves two complementary approaches, mineralogical and lithogeochemical; both can be directed to the quantitative estimation. The basic tasks of these two approaches as applied to the evaluation ofmaterial exchange during hydrothermal alteration are: (i) determination ofmineral assemblages of altered and parent rocks, and (ii) calculations of the losses and gains of chemical components as a result of hydrothermal alteration. The mineralogy of altered rocks has been particularly important as a means of classification, such mineral-dependent terms as phyllic, sericitic, argillic, propylitic, etc., are entrenched in the literature. One reason for this is that a mineral assemblage contains information both about the chemical composition and the formation environment of the rock. Such information contributes to answering question 1 to 3, above, and less significantly to questions 4 to 6. Unfortunately, fine grain size, absence of easily identifiable optical features, and mixtures of non-ideal structures of alteration products can obscure mineralogy and/or make mineral abundances impractical to estimate with confidence. Consequently, the use of a mineralogical approach to study and classification of hydrothermally altered rocks, while essential, is limited. A lithogeochemical approach to the study of altered rock complements and has some advantages over the mineralogical approach. The large samples commonly used for chemical analysis can be more representative than, say, small areas of a thin section; thus, more accurate and consistent quantitative data can be obtained. A lithogeochemical approach to the study of hydrothermal alteration commonly is directed toward quantifying the loss or gain of each component during the alteration process and thus provide an 3 objective and quantitative chemical classification scheme. Elliott-Meadows and Appleyard (1991) state: the outer limits ofalteration can be detected more sensitively by their geochemical signatures than by their mineralogical expression, as can alteration zone boundaries. Lithogeochemical data provide information on the chemical compositions of rock. Rocks with similar chemical composition will have different mineral assemblages under different physical conditions. Therefore, a simple lithogeochemical analysis can provide definitive answers to question 2, and partial ones to question 3, 5 and 6, above, but can not give any answers to questions 1 and 4. Mineralogical- and lithogeochemical-based methodologies utilize different types of data. However, the two are related through the compositions and amounts of individual minerals. These two approaches are complementary; many researchers have integrated them in different ways (e.g. Gresens, 1967; Meyer and Hemley, 1967; Giggenbach, 1984; MacLean and Barrett, 1993; Barrett et al., 1993; Madeisky and Stanley, 1993). A review of the various approaches used to quantitatively evaluate hydrothermal alteration is given in the following sections. 1. 2. Current Quantitative Approaches to the Study of hydrothermal Alteration The quantitative evaluation ofmaterial exchange during hydrothermal alteration relies on lithogeochemical data. With the development ofX-ray fluorescence (XRF), atomic absorption spectrometry (AA), inductively coupled plasma-atomic emission spectrometry (ICP) and other advanced analytical techniques, the availability of high quality, sensitive, precise, and inexpensive analyses for a long list of elements has come about. It is probably fair to say, however, that the use of these data in exploration has to date been largely limited to empirical procedures including: (i) the identification and 4 distribution of pathfinder elements (e.g., Descarreaux, 1973; Boyle, 1979; Fyon and Crocket, 1982; Davies et al., 1982; Kishida and Kerrich, 1987), and (ii) the application of a varieties of empirical indices, such as an alteration index (A.I. = 100 x (MgO + K20)/(Na +K20+ CaO + MgO)) proposed by Ishikawa et al. (1976), and many others includingFe3/(Fe+MgO),A1203/Na,(Fe+MgO)/(FeMgO+CaO+NaO), K20/(Na+K),K20/Na,MgO/CaO,Na20/(Na +K20+CaO),K20/(Na + K20+ CaO) and CaO/(Na20+K20+CaO) (Hashiguchi and Usui, 1975; Spitz and Darling, 1978; Saeki and Date, 1980). A thorough review of these indices has been made by Stanley and Madeisky (1993). Depletion or enrichment anomalies, especially of silica, alkalis, and some metals, have been regarded as favorable signs in conjunction with the more conventional positive anomalies. In some cases, however, where subjective interpretation procedures have been used, these depletion or enrichment anomalies have been misconstrued as to whether or not they are absolutely depleted/enriched or relatively diluted/concentrated by the enrichment/depletions of other components. For example, silica depletion anomalies have been confused with Al or Mg enrichment effects (Appleyard and Guha, 1991). This confusion of enrichment and/or depletion is a product of the closure effect of lithogeochemical data. 1.2.1. The Closure Effect In attempting to deal quantitatively with the material exchange during alteration using lithogeochemical data, a common problem arises, the closure effect. In a multicomponents system closure refers to the fact that all components must total 100 percent. Thus, if a single component is changed, say 5i02 is added, the relative abundance of all other components decrease even though their absolute amounts are unchanged. This is the problem of the closure effect. Lithogeochemical analyses of altered rocks superficially can provide a distorted view of losses and gains of components. The matter 5 can be evaluated quantitatively as follows. Assume an original, simple system S0 consisting of three components X, Y and Z. S0 = X0 + + = 100(gram) (1-1) (upper case letters are used for weights) During an alteration process, components change by the absolute amounts dx, dY and dZ respectively. The total change of the system (in grams) will be: dS=dX+dY+dZ (1-2) In practice, the values ofX0+dX,Y0+dY andZ0+dZ are not accessible directly because chemical analytical data are conventionally presented as percentage, that is, s=x+y+z=100% (1-3) (lower case letters are used for percentages) where x, y and z, the concentrations of components can be further described in the following form: 100(X+dX)I(SdS) (1-4) y =100(Y+dY)I(SdS) (1-5) z=100(Z+dZ)/(SdS) (1-6) Equations 1-4 to 1-6 indicate that the difference in the concentration of a particular component between the unaltered parent and the altered product is affected not only by the absolute change of individual component (dx, dY or dZ), but also by the total absolute change of all components (dS). With regard to the impact of the closure effect on different constituents, Stanley and Madeisky (1993) indicate: Closure will most affect those constituents that occur in large concentrations in a system andwhich are added to or removedfrom the system in an incomplete way. Conversely, it will least affect those elements that have been added to or removed from the system in more complete ways. In essence, the larger the concentration of a constituent in a rock relative to the amount ofmaterial transfer that constituent 6 has undergone, the more closure will obscure our ability to understand the material transfers using the constituent concentrations. As a result, the closure effect should be removed before a meaningful interpretation of geochemical data proceeds. 1.2.2. Comparison of Various Techniques Used to Remove the Closure Effect The closure effect has long been recognized and researchers working in related fields have devised various techniques to deal with this problem. The earliest paper dealing with this issue has been traced back almost a hundred years. Geochemists working with weathered rock, calculated losses and gains of constituents by assuming the amount of alumina to have remained constant during the weathering process (e.g., Merrill, 1897; Golditch, 1938; Krauskopf, 1967). Later researchers in the field ofmetasomatic alteration and igneous fractionation developed their own techniques to remove the closure effect from lithogeochemical data (e.g., Gresens, 1967; Pearce, 1968; Winchester and Floyd, 1977; Floyd and Winchester, 1978; Finlow-Bates and Stumpfl, 1981; Grant, 1986; MacLean and Kranidiotis, 1987, MacLean and Barret, 1993). A summary of their principal contributions is presented in Table 1-1. The formulae of Table 1-1 are presented with standardized symbols to emphasize the degree of similarity of proposals by various authors. Among these techniques, Gresens’ equation (Gresens, 1967) and its modification (Grant, 1986) have been widely used by economic geologists to quantify the losses and gains of constituents during hydrothermal alteration processes (e.g., Babcock, 1973; Appleyard, 1980; Morton and Nebel, 1984; Robert and Brown, 1986; MacLean and Kranidiotis, 1987; Leitch and Day, 1990, Leitch and Lentz, 1994; Marquis et al., 1990; Sketchley and Sinclair, 1987, 1991; MacLean, 1990; Richards et al., 1991; Bernier and MacLean, 1989; Barrett and MacLean, 1991, Barrett el al., 1993). 7 Table 1-1. A Summary of Quantitative Techniques Devised to Remove the Closure Effect and Evaluate Mass Transfer Process Study Year Formula Application Notes Merrill, G. P. 1897 . = (ZP) — weathering z A1203and assumed to be immobile Zd f can be assumed to be one or Gresens, R. L. 1967 dK = — p metasomatism determined by assuming one p component is immobile so f =PpXp/j. Pearce, T.H. 1968 dX — Xd — x, igneous x can be a combination of — — fractionation several components, Z is Z, Za Zp immobile. Winchester et al. 1977 Za Xd metabasalt Both z and x are immobile. Floyd et al. 1978 — = — classification zp xp Grant, 3. A. 1986 P Metasomatic p / .D = Za / Z,Xa = — (x +) alterationD MacLean, W. H. 1993 . = — Metasomatic z = immobile elements -“ alteration such as Zr, Ti, Al, Nb, Y. Za Notes: where: P- mass of parent rock; D- mass of daughter or altered rock; dX - the mass gains or losses of component x from 100 grams parental rock; x. - weight or molar fraction of component x in parent rock; Xd - weight or molar fraction of component x in daughter or altered rock; z - weight or molar fraction of immobile component z in parent rock; 2d - weight or molar fraction of immobile component z in daughter or altered rock; p - specific gravity of parent rock; Pd - specific gravity of daughter or altered rock; and - volume factor = vd / v. 8 Pearce element ratio (PER) diagrams, devised by Pearce (1968) for examining material exchange during the process of fractional crystallization, recently have been extended by Stanley and Madeisky (1994) to metasomatic rocks. PER diagrams have been used in the past to examine chemical variations caused by igneous differentiation (Russell and Stanley 1990). More recent applications are to hydrothermal alteration, in particular, that associated with volcanogenetic massive sulfide deposits (Stanley and Madeisky, 1993). In brief, this method converts the weight units of raw chemical analytical data into molar units, then uses a conserved/immobile element as a reference scale to remove the closure effect, and finally, utilizes various diagrams designed in the light of the stoichiometries of the relevant minerals, to test various causes of the lithogeochemical variations in terms ofmineralogical variation(s). Gresen& equation and Pearce element ratio diagrams are superficially different but they are used to solve similar problems. Cheng and Sinclair (1991), and Stanley and Madeisky (1993) show that these two techniques, although having different starting points, are fundamentally similar in principle — that is, they both remove the closure effect in order to decipher the true chemical variations during alteration. Even though an independent solution exists for Gresens’ equation where the volume factor is known and the specific gravities have been measured, in practice, the volume factor can not be estimated except through the use of either an immobile component or an assumption such as constant volume during the hydrothermal alteration process. The concept of immobile element is defined by Stanley and Madeisky (1993) as an element that is neither signficantly added nor removedfrom a rock during metasomatism because of its low solubility in aqueousfluids (the stabilities of aqeuous complexes that contain it are signflcantly lower than the stabilities of minerals that contain it).’ The procedure of removing the effect of closure by using an immobile component is illustrated as follows. Given that a component Z is immobile (i.e. dZ = 0) then we have: 9 z = 100ZJ(S+&) (1-7) The use of this immobile component to remove the effect of closure involves using the immobile component as a divisor (standard reference) for other components as follows: x xo 100(Xo+dK)/(So+&) X0dX 18 Z Zo 100Z/(S+d ) Z0 1, The final result dX/Z0 in equation 1-8 can also be treated as the absolute change of element x with the reference unit of conserved or immobile component z0 because 4, = z0 if the original system is assumed to be 100 gram. Rearranging equation 1-8 produces Grant’s version of Gresens’ equation: dX=—x0—X (19) In summary, these various techniques of dealing with closure are all based on the same fundamental principle, an immobile component that allows the calculation of the true variations in rock compositions caused by material exchange. Applications of these techniques rely on a knowledge of either the change in rock volume during hydrothermal alteration (e.g. Robert and Brown, 1986), or the recognition of immobile component(s) in the rocks (e.g. MacLean and Kranidiotis, 1987). 1. 3. Two Requirements for Loss and Gain Calculations Before applying these quantitative techniques for estimating losses and gains in a metasomatic system, two requirements must be met. First, the available analytical data must be shown to contain immobile components; second, a suite of samples for which loss/gain variations are to be evaluated, must be the alteration products of either: (i) a common parent rock characterized by chemical and mineralogical homogeneity (single precursor system), or (ii) a suite of rocks with determinable pre-alteration chemical composition (multiple precursor system). 10 In order to examine whether a set of lithogeochemical data meets the first requirement, Nicholls (1988) summarizes three ways of recognizing a conserved element for the study of igneous differentiation: (1) The petrologic behavior of the element can be used to select conserved elements. They are usually the incompatible elements. (2) The ratio of two conserved elements will be constant in a comagmatic suite. (3) An element ratio diagram that is not constructedwith a set ofconserved element in the denominator will have a trendwith a near zero intercept. The geochemical behavior of elements is helpful to infer which elements might be conserved or immobile, particularly under certain circumstances where they are incompatible with the known mass transfer process. For example, the elements P, K and Ti are commonly thought to be incompatible with the main minerals that crystallize in a basaltic system, such as olivine, pyroxene and plagioclase (Pearce: 1968,1987; Nicholls, 1988; Russell, 1986; Russell and Nicholls, 1987; Russell and Stanley, 1989, 1990a, 1990b). For hydrothermal alteration the assumption ofZr, Ti and/or Al immobility has been used widely because of the relative insolubilities of these components in hydrothermal solutions. An objective method is needed to test these assumptions. In practice, ratios of immobile components remain constant regardless of the nature of alteration. This is an objective criterion for the recognition of immobile or conserved elements, and it can be easily proven as follows. Given that both dX and dZ equal to zero (i.e. both X and Z are immobile), then we have equation 1-4 divided by equation 1-6: x 100X(S+d ) — (1-10) — 100Z/(S+d ) — Zo Thus, a bivariate plot of two immobile components from altered samples with a common parent will define a linear trend that extends through the origin. The concept of equation 1-10 for determining whether certain elements have been immobile in 11 metasomatism and hydrothermal alteration has been discussed and applied by Gresens (1967), Babcock (1973), Finlow-Bates and Stumpfl (1981), Grant (1986), Kranidiotis and MacLean (1987), MacLean (1988, 1990), Elliott-Meadows and Appleyard (1991), and MacLean and Barrett (1993). For example, Al, Ti, Zr, Nb, Yb and Lu commonly are shown to be immobile in hydrothermal alteration zones formed in homogeneous volcanic rock units (single precursor systems) at the Phelps Dodge deposit (MacLean and Kranidiotis, 1987), at Atik Lake (Bernier and MacLean, 1989), and at other mines in the Noranda district (Cattalani et al., 1989). Some problems arise with the application ofNicholls’ (1988) third criterion for immobility. First, let us see theoretically how many possible patterns can be present in a PER diagram based on simple ratios. The linear relation for any two points on x/z versus. y/z diagram can be described by the following equation: (1-11) the general form of the slope will be: m_-=z_11z2 zdY—ydZ (1-12) d(x/z) dX/z—xdZ/z2 zdX—xdZ the general form of intercept will be: ydX-xdY (1-13) z z z (zdX — xdZ)z zdX — xdZ If the slope and intercept of each individual pair ofpoints in a data set are equal, then all points will plot as a straight line on a PER diagram. Otherwise, a data set may show a scattered distribution pattern to various extents on a PER diagram. Eight possible cases are summarized in Table 1-2. According to Table 1-2, we see that Nicholl’s third criterion for recognizing immobility is correct only under certain constrained conditions: (i) where elements in both 12 numerators are conserved (case 5), or (ii) dY << dz (case 4), then the intercept (dY/dz) will be close to zero. Other possibilities also exist for a trend going through the origin but with a conserved or immobile component as the denominator. For example, in case 2, where ydX - xdY = 0, then its slope dX/dY = X/Y and its intercept is equal to zero. The Table 1-2. Eight possible cases of PER diagram* case dX dY dZ slope intercept distributed pattern infinite lines or 1 < >0 < >0 < >0 zdY — ydZ ydX - xdY randomly zdX — xdZ zdX — xdZ distributed 2 < >0 < >0 =0 dY ydX - xdY dX zdX 3 <>0 =0 <0 —ydZ ydX zdX - xdZ zdX - xdZ 4 =0 < >0 < >0 zdY - ydZ dY -xdZ dZ infinite lines 5 0 0 < >0 y/x 0 through the origin 6 =0 < >0 0 {x/z = xdzo} cc a line// y/z axis 7 < >0 0 =0 0 {y/z y0/z} a line II x/z axis 8 =0 =0 =0 undefined undefined a point * After Russell and Stanley, 1990 physical meaning of this example is that components x and y are highly correlated to each other (i.e. both of them may exist in the same mineral phase concerned and have very similar geochemical properties). When this mineral phase is removed from the current system, either depletion by crystal fractionation or by hydrothermal alteration, the contents of these components may change in the same proportion as their initial ratio. As a result, there is also a trend with a near zero intercept on the PER diagram. In addition, an 13 element ratio diagram that is not constructed with a set of conserved element in the denominator could be randomly distributed rather than having a well defined trend with a near zero intercept, as in cases 1, 3 and 4 according to Table 1-2. In summary, it is reasonable to infer some possible conserved or immobile components on the basis ofunderstanding the behaviors of these components and the geological processes in which they are involved. Nevertheless, it is risky to accept such assumptions without objective tests. It is efficient and rational to demonstrate immobility in the available data set on the basis of the theorem that the ratios of conserved or immobile components remain constant. Moreover, a re-examination of all possible candidates for immobility is warranted to demonstrate that they are not mineralogically or geochemically compatible with each other during the hydrothermal alteration process. The concepts ofmobile/immobile and compatible/incompatible are used frequently in the literature. These terms share many features in common, but it is necessary to clarify their specific implications in the context of hydrothermal alteration. The concepts of mobile/immobile are used to indicate whether or not a component has mass loss or gain during a hydrothermal alteration process. The terms incompatible and conserved have been used to describe certain elements not involved in a primary differentiation processes. Here the terms compatible/incompatible are used to describe whether or not the geochemical relationship among a particular group of components/elements are sufficiently correlated that they may have mass loss or gain in proportion to their initial ratio during a hydrothermal alteration process. Therefore, a pair of possible immobile components, determined from their constant ratio or highly correlated linear trend passing through the origin of the binary plot, also should be incompatible with each other. To emphasize the point, consider a pair ofmobile components such as K and Rb which are also highly compatible with each other and which in a hydrothermal alteration system may display a highly correlated linear trend passing through the origin of the binary plot. 14 In reality, there is no perfectly constant ratio of a pair of immobile components. The reason for this is that apparent variability in ratios is a combination of geological variation, sampling and analytical error. Theoretically, the immobile component has not been involved in chemical transfer processes so the mass of the immobile component remains constant in a single precursor system. In reality, samples may not have been absolutely identical to each other before hydrothermal alteration in terms of immobile components, but if this inherent geological variation of a component is sufficiently small, this component can be treated as immobile. So immobility is a concept that depends on a high degree of homogeneity in the parent system prior to hydrothermal alteration. Analytical error is another major source of apparent variation of ratios of immobile constituents. Considering the influence of analytical error, Russell and Stanley (1 990a, 1990b) suggest that one could test for immobile/conserved components with a Pearce Element Ratio diagram accompanied by the propagated analytical error. If the dispersion or standard deviation of the ratio of two immobile or conserved candidates is less than or equal to the propagated analytical error, the dispersion can be interpreted to result entirely from analytical error. In such a case, the two candidates may be used as immobile or conserved components. This rule has been used in the study of basalt systems by Russell and Stanley (1989, 1990a, 1990b). The rule should be used cautiously. If the PER ratio is constructed with one of the components having a large geological variation and the other having poor analytical precision, then the latter component will contribute more to the final propagated error of the ratio, especially where it is used as the denominator of the ratio. As a result, mobility of the former component might be obscured and the plot might lead to the correct conclusion that both numerator and denominator are immobile. Therefore, ‘immobile’ components of relatively high analytical quality should be accepted in preference to those with poor analytical precision. 15 The second requirement for the removing of closure from lithogeochemical data can be met conventionally through the careful investigation of field and petrographic relationships in the study area. Rock derivatives altered to various degrees from a common homogeneous parent rock commonly are in close spatial proximity and may show gradational contacts between each other. Primary textural and structural features may remain identifiable in least-altered to more intensely altered derivatives. To examine these types ofvariations rigorously it is recommended that samples be collected systematically along alteration profiles from the strongly altered rock adjacent to or within a mineralized zone, to the least altered rock far from the ore deposit itself. Such sampling should be done after a careful field investigation of the profile. Even though the altered rocks are of main concern, careful attention should be paid to the least altered or unaltered rocks. They provide important information about the parent rocks that preceded hydrothermal alteration and give insight into the occurrence of single precursor or multiple precursor systems. For a multiple precursor system, the sequential relationships between different volcanic or intrusive events and their phase variations should be determined as clearly as possible. An efficient way of defining a single precursor system versus a multiple precursor system is to examine lithogeochemical plots, especially those constructed with immobile components such as Zr, Ti andAl203(MacLean, 1990). A single precursor system will present a trend that extends through the origin on the plot. The plot pattern for multiple precursor system will be more scattered but generally convergent toward the origin. If the numbers of least altered or unaltered samples collected and analyzed are sufficient, their plots may present a well defined trend either going through or cutting tangentially the region where the altered samples plot, as in the case of a sequence of volcanic precursors related through fractional crystallization from a common magma. 16 1. 4. Pearce Element Ratios (PER) and their Application to Hydrothermal Alteration The PER approach to examining metasomatic systems has an advantage over other procedures in not only removing the closure effect of lithogeochemical data but also: (i) explaining the corrected chemical variations in terms ofmineralogical variation(s), and (ii) testing for a multiprecursor system (Stanley and Madeisky, 1993). PER diagrams have been widely applied to the interpretation of igneous fractionation (Russell and Nicholls, 1987, Russell and Stanley, 1989, 1990a, 1990b). Commonly, igneous crystal fractionation can be interpreted by the addition or subtraction of one or a few minerals. Thus, a specific PER diagram can be designed to illustrate this crystal fractionation trend according to the known stoichiometries of the relevant mineral phases. For example, the compositional variations of a suite of samples which are subjected only to olivine fractionation must be related to the stoichiometry of olivine [(Fe,Mg)2SiO4],e.g., one mole Si gain or loss along with two moles ofFe and Mg; thus the appropriate combinations (e.g., axes coefficients) of numerator elements for the axes ofPER diagram are SiI(conserved element) as x-axis and 0. 5(Fe+Mg)/(conserved element) as y-axis. Finally, the hypothesis of olivine fractionation can be tested according to whether the plots of data are consistent with the model trend that has a predesigned slope of one on the binary plot SiI(conserved element) versus O.5(Fe+Mg)/(conserved element). Recently, Madeisky and Stanley (1993) applied PER analysis to lithogeochemical data for altered rhyolites collected from the volcanic hosted massive sulfide (VHIvIS) deposit at Rio Tinto, Spain. Their work revealed that quartz, potassium-feldspar and plagioclase fractionation and crystal sorting contribute to geochemical variations of the unaltered rhyolite. The fractionation trend is clearly shown on a PER diagram constructed with Al/Zr as abscissa and (2Ca+Na+K)/Zr as ordinate. In addition, metasomatism (alkali depletion) disperses data on such a plot, toward the abscissa, away from the fractionation trend on the same PER diagram. Metasomatic additions and losses of elements have been 17 recognized up to 3 km from the centre of the mineralization system (Cerro Colorado open pit). Madeisky and Stanley (1993) also indicate that the rhyolite directly underlying the mineralization is a highly evolved melt and only the most evolved portions of this rhyolite are metasomatized, suggesting a genetic link between these highly evolved rhyolites and the associated VITIVIS mineralization. Recent advances in dealing with metasomatic system have not dealt quantitatively with mineral abundances ofboth parent and altered rocks. Nor have there been enough efforts to integrate mineralogical variations with chemical exchange in a quantitative way. A specific PER diagram can be used to test the hypotheses that chemical variations are due to variations of particular mineral(s), but the amount of these minerals have not been determined explicitly. The methodology of designing such a specific PER diagram for the purpose of testing an hypothesis is based on a simple matrix equation (Stanley and Russell, 1990; Stanley and Madeisky, 1993, 1994). CxA=P (1-14) where C is a phase composition matrix (with minerals down the side and elements across the top), A is an axes coefficient matrix (with elements down the side and axes across the top) and P is a phase displacement matrix (with minerals down the side and axes across the top). The phase composition matrix contains the formulas ofminerals whose mass transfer effects are to be considered on the diagram. The axes coefficient matrix contains the coefficients for the linear combinations for each axis of the PER numerator. The phase displacement matrix depicts the displacement that mass transfer due to specific mineral losses or gains will have on each axis. A number ofPER diagrams with known axes coefficients have been designed for specific petrological material transfer hypothesis (e.g., Russell and Stanley, 1990a; Stanley and Madeisky, 1994). They can be used to test real data sets for particular mineralogical variations as explanation of chemical variations. However, in attempting to design a 18 diagram, without knowing the PER numerator linear combination coefficients, a more difficult set of procedures must be followed. These rely on the fact that a number of constraints, both mineralogical and geometric on the PER diagram being designed, can be assigned. This information allows determination of the entries in the ‘phase displacement matrix’. Thus, with knowledge of the mineral formulae, the ‘axes coefficient matrix’ may be calculated using the approach of Stanley and Madeisky (1993). If C is a square and non- singular matrix, the unique solution for A can be found by: A=C’xP (1-15) If C is a non-square matrix but CTxC is a non-singular matrix, the possible solution for A can be obtained through: A=(CT xC’xCTxP (1-16) The following example is used to illustrate the procedure of designing a specific PER diagram, given a host rock of andesite in which feldspar and clinopyroxene are dominant. Propylitic, sericitic, argillic and silicic alterations and carbonatization are thought to be major causes of secondary lithogeochemical variations. Specifically, the replacement of primary feldspar (about 60%) by muscovite or kaolinite and quartz, and the replacement of primary mafic minerals (mainly augite and hornblende, about 5% and 3%, respectively) by epidote, chlorite and carbonates are the major contributors to lithogeochemical variations. Thus a composition matrix (C) could be composed of fourteen mineral phases (anorthite, albite, orthoclase, augite, hornblende, epidote, chamosite, clinochiore, calcite, siderite, magnesite, kaolinite, muscovite and quartz) and seven constituents (Si, Al, K, Na, Ca, Fe and Mg). This composition matrix C is then used as a simplified system to test the hypothesis. The displacement vectors of primary minerals such as anorthite, albite, K-feldspar and augite are defined to have slopes equal to one. The displacement vectors of alteration minerals are designed to have their slopes different from one, such as kaolinite and muscovite have slopes equal to 1/4 and 7/6, respectively, on this specific PER diagram. Then the x-axis and y-axis of this specific PER 19 diagram can be determined by using equations 1-15 and 1-16. The detailed procedure of this calculation is as follows. An 2 2 0 1 0 0 0 x. y 2 2 An Ab 3 1 0 0 0 1 0 x 3 3 Ab Or 3 1 1 0 0 0 0 AL YAK 3 Or Aug 2 0 0 1 0 0.5 0.5 K YK 2 2 Aug 117Qtz 1 0 0 0 0 0 0 X Ya 1 0 Qtz - Kao22000 0 0 XNaYNa 20.5Kao Mus 3 3 1 0 0 0 0 Xpe YFe 3 35 Mus Ep 32020 1 0 XMgYMg 3 4 Ep C x A =P Multiply the right side matrix (P) of equation 1-17 by the inverse matrix C to produce X, Ysz 0 0 0.29 0 0.43 0.29 —0.29 0 2 1 0 XAI YAL 0 0 —0.36 0 —0.29 0.14 0.36 0 0 0.25 XK YK 0 0 0.36 0 —0.71 —0.14 0.64 0 0 2.75 XCa YCa = 1 0 0.14 0 —0.29 —0.86 —0.14 0 x = 0 1.5 (1-18) XNa YNa 0 1 —0.5 0 —1 —1 0.5 0 o”s 0 2.75 XFe YF6 —2 0 —0.43 0 —0.14 0.57 0.43 1 3 3:5 0 0.5 x 0 0 —1 2 —1 0 1 —1 0 0.5Mg .1Mg A = (CTxC)4xCT x P = x y The results of this calculation show that this specific PER diagram has a SiI(immobile component) as its x-axis and [1/4A1+ 1 1/4(Na+K)+3/2Ca+1/2(Fe+Mg)j/(immobile component) as its y-axis. The physical implications of this PER diagram can be understood through the stoichiometries of relevant minerals. For example, the decrease or increase in molar units of augite can be decomposed into two vectors (i.e., a one mole decrease or increase ofboth Ca and Fe and/or Mg (along the y-axis) will cause a corresponding two mole decrease or increase of Si (along the x-axis) on this specific PER diagram because of the stoichiometry of augite [Ca(Fe, Mg)Si206].As a result, the plots of different samples whose lithogeochemical variation is caused by the fractionation of augite only, will display 20 a trend with a slope of one on this particular PER diagram. The vector directions of other relevant mineral phases including hornblende, chlorite (chamosite and clinochlore) and carbonate (calcite, siderite, magnesite) then be projected on this PER diagram by using equation 1-14. Fe—Cl 3 2 0 0 0 5 0 1 0 Mg—C13200005 33 Ca 0001000 X_01.5 Sd OOoOolOxX,,1_OOS - Ma 0000001 00.5 Hb 7201022 00:5 ‘ C x A =P The expected mineralogical variation paths on this PER diagram are illustrated in Figure 1 for various hydrothermal products commonly associated with precious- and base- metal vein mineralization in volcanic sequences. A detailed description about this PER diagram is given as follows: (1) If all lithogeochemical variations are restricted by mineralogical variations of feldspar, augite and chlorite, then this set of lithogeochemical data will plot along a trend of slope equal to one and an intersection of zero. (2) Where quartz exists and has not been involved in mass change, the trend above will be shifted toward the right. (3) If the wall rock has suffered propylitic alteration (i.e. augite is replaced by chlorite, and primary feldspars are partially replaced by sericite through the addition ofvolatile components), the ‘loss’ of primary minerals can be pictured as moving from the precursor composition (P) to a1 down along the trend of slope equal to one and the ‘addition’ of alteration minerals can then be viewed as moving from P to a2 along the trend of slope equal to one (the replacement of primary mineral and 21 a2 C A / /d / at / / / / ! / / / / / ,I // + e , ( 1 ,, I / / .- 1 2 F ig ur e 1- 1. P E R di ag ra m sp ec if ic al ly de si gn ed to di sc ri m in at e pr im ar y fr ac ti on at io n an d hy dr ot he rm al al te ra ti on ty pe s co m m on ly as so ci at ed w it h pr ec io us - an d ba se -m et al de po si ts in vo lc an ic se qu en ce s. q tz . Q tz - qu ar tz , C ar b - ca rb on at es , K ao - ka ol in ite , A n - an or th it e, A b - al bi te , O r, K -f el ds pa r, C hi - ch lo ri te , A ug - au gi te , M us - m us co vi te , E p - ep id ot e. Se e te xt s fo r ce ta il ed ex pl an at io n. c53 + c”1 ÷ + + ‘I + L eg en d A lt er at io n pa th er ro r E p 2 1. 8 1. 6 1. 4- 1. 2- 1- 0. 8- 0. 6- 0. 4- 0. 2- 0- C ar b A b, O r, C hl K ao Q tz S i/ T iO 6 formations of alteration mineral happen in the meantime, but it is convenient to analyze a metasomatic process as two superimposed processes on this PER diagram). As a result, propylitically altered samples will plot roughly around their primary precursor’s position (P) on this diagram. (4) Where the wall rock has altered into a bleached alteration envelope around the epithermal precious- and base-metal vein, in general, all primary mafic minerals and feldspar are completely replaced by alteration minerals (from P to b1). (5) If carbonates and pyritization are the dominante alteration products which replace the primary minerals (i.e. intense carbonatization plus pyritization), samples will plot along a vertical trend shown on the left side of the primary fractionation trend of slope equal to one (from b to c). (6) If muscovite or sericite is the dominante alteration product (i.e. intense sericitization), samples will plot around a trend of slope equal to 7/6, which is close to the primary fractionation trend but slightly shifted toward the left (from b to d). (7) If kaolinite is the dominante alteration product (i.e. intense argillization), samples will plot toward a trend of slope equal to 1/4 (from b to e). (8) If quartz is the dominante alteration product (i.e. intense silicification), samples will plot around a trend parallel to x-axis (from b to f). In brief, some of the alteration types commonly associated with precious- and base-metal vein mineralization in volcanic sequences are expected to be discriminated in a preliminary fashion on the PER diagram ofFigure 1 by the relative displacements of altered samples from the primary feldspar and augite fractionation trend (slope = 1). 1. 6. Additional Problems Mineral assemblages commonly occurring in alteration envelopes or zones can be identified routinely with the aid of various conventional and advanced modern instruments. However, still lacking is an objective and efficient way to assess the 23 abundances of each alteration mineral with confidence. This arises because hydrothermally altered rock commonly is characterized by a very fine-grained nature and/or intimate intermixing ofmineral species. The technique of point counting, useful for medium to coarse grained rocks (especially igneous and metamorphic rocks) is limited in applications to products of hydrothermal alteration. In addition, serious sampling problems commonly arise in using thin sections for quantitative modal analysis. The losses and gains of chemical components during the hydrothermal alteration process can be calculated with the aid of immobile components. This leads to an appreciation of possible reactions between primary minerals and altered minerals. However, the results of such calculations are not linked routinely in a quantitative way with the mineralogical changes that arise during hydrothermal alteration. To make such quantitative links immobile constituents must be identified and the precursor must be known; such needs are relatively difficult to provide in hydrothermally altered rocks that are products of open systems. PER diagrams are superior to other quantitative approaches for the evaluation of hydrothermal alteration by not only removing the closure of lithogeochemical data, but also by linking the lithogeochemical variations to the mineralogical variations. However, the PER diagram approach still has some limitations in a quantitative evaluation of hydrothermal alteration. As demonstrated above, the PER diagram can be used to test hypotheses that chemical variations are due to variations of particular mineral(s). But the amount of these minerals can not be determined explicitly when a complicated multivariable system is dealt with because the total displacement on a PER diagram commonly is the sum of the displacements of different minerals. The length and slope of a displacement vector on a PER diagram may be the combination of various displacement vectors (i.e., various types of alteration). Briefly, the ambiguity about the relationship between lithogeochemical variations and mineralogical variations may arise where too many variables are squeezed into a two dimensional space. It is one of the goals of this 24 thesis to develop the idea of linking the lithogeochemical variations to the mineralogical variations and overcoming this limitation ofPER diagrams. The following study consists of two parts: (i) a theoretical documentation about a quantitative approach extended from the PER diagram to hydrothermal alteration systems; and (ii) a detailed, quantitative case history of the alteration system associated with the Silver Queen polymetallic epithermal vein deposit in central British Columbia. 25 Chapter 2. Metasomatic Norms: A Method of Norm Calculation Adapted to Hydrothermal Altered Rocks 2.1. Introduction Modeling a hydrothermal system quantitatively using either only mineralogical or only lithogeochemical data limits our knowledge of the system. We commonly limit our quantitative understanding of chemical losses and gains in a system if hydrothermal alteration minerals are the extent of our study. Conversely, if only chemical gains and losses are determined from lithogeochemical data (cf. Gresens, 1967) important mineralogical features are commonly minimized. Clearly, a procedure that takes account ofboth mineralogy and chemistry of altered rocks is desirable. lVlineralogy and chemistry of rocks are intimately linked through mineral abundances and the compositions of individual minerals. One way of combining mineralogical and lithogeochemical approaches to the study of altered rocks is to compute mineral abundances from the lithogeochemical data. It is easy to calculate an ideal mineral composition or norm. But it is not possible, in general, to calculate modal abundances without additional information because: (i) the minerals so-generated are idealized, or are end members of complex mineral families, and (ii) certain minerals or combinations ofminerals are chemically equivalent, for example, (Fe,Mg)2SiO4+ Si02 = 2(Fe, Mg)Si03.However, where sufficient mineralogical and chemical controls are available, the norm can be made to approximate closely or even coincide with a mode. A norm is a’ ... theoretical mineral composition of a rock expressed in terms of standard mineral molecules that have been determined by specific chemical analysis....’ (Margaret, et al., 1972). Norms are used to standardize rock description and classification and to provide insight into some aspects of genesis. The concept, applied widely to igneous rocks, has had limited application to other rock types. Applications to metasomatized rocks 26 are hindered by the wide range of chemical changes involved and the complexity ofmany mineral compositions and mineral assemblages. Various researchers have attempted to derive mineralogical information from lithogeochemical compositions for rocks other than igneous rocks. A particularly informative work by Brown and Skinner (1974) and Capitani and Brown (1987) use thermodynamic constraints and mass balance relations to calculate the weights of the minerals in the equilibrium mineral assemblages. Their results compare remarkably closely with modes. Davis and Ferry (1993) use mass balance relations to calculate the model protolith mineral abundances by assuming that a simple mineral assemblage (including calcite, dolomite/ankerite, quartz, albite, K-feldspar, muscovite and rutile (e.g., Rice, 1977; Ferry, 1985 a, 198 5b) suffers isochemical metamorphism. MacLean and Barrett (1993) recommend the Niggli-Barth cation normative calculation procedure (Barth, 1962) for metasomatic rocks for the purpose of approximating modes of altered rocks. The above techniques share the use ofmass balance relations between bulk rock composition and mineral abundances. They differ in the method used to select a reasonable mineral assemblage with which to partition the lithogeochemical data. Brown and Skinner (1974) and Capitani and Brown (1987) determine the mineral assemblage based on whether or not the minerals are stable under specific thermodynamic circumstance. Barth (1962), Rice (1977), Ferry (1985a, 1985b), Davis and Ferry (1993), MacLean and Barrett (1993) and many others choose the mineral assemblage according to petrographic observation and/or their experience. An important difference between the ‘thermodynamic and ‘petrographic approaches, above, is in the interpretation of the residuals of constituents. Ideally, there should be a perfect match between the analyzed bulk rock composition and the corresponding estimated normative mineral abundances. In reality, such is not the case. Some norm calculations leave some chemical components unused (residuals), such residuals should be in the range of analytical error. In general, the smaller the residuals are, the better is the quality ofmass balance. Brown and Skinner (1974), Capitani and Brown (1987) and 27 Davis and Ferry (1993) explain residuals as the mass losses or gains of corresponding constituents. The assumption of a stable equilibrium relation in a hydrothermal system is often questionable, whereas petrographic examination can provide the actual mineral assemblage. Normative approaches originally designed principally for igneous rocks are rigid in their application, and in general, do not accomodate important alteration minerals. In particular, volatile components are essential constituents ofmany metasomatic rocks but are not involved directly in determining normative minerals either by the CIPW norm or Niggli-Barth norm procedures. A different approach to the determination of norms of hydrothermally altered rocks by combining petrographic and lithogeochemical data warrants investigation. 2.2. The Principle ofMetasomatic Norms A possible approach to the application of the norm concept to metasomatic rocks is to constrain the calculated normative mineralogy by apriori knowledge of existing minerals (i.e., to approximate the mode as closely as possible). The methodology for this approach is a natural extension of the use ofPER (Pearce element ratio) diagrams for the study of metasomatic rocks (e.g., Stanley and Madeisky, 1993, 1994). Metasomatic norm calculation uses the same principles as the calculation of CIPW norms (e.g., Cross et al., 1903; Cox et al., 1979; Hughes, 1982; Philpotts, 1990). However, a wide range of possible mineral products is necessary for the determination of metasomatic norms that represent hydrothermal alteration systems. Moreover, the calculation of a metasomatic norm needs to take volatile components into account. Another distinctive difference between a metasomatic and a conventional igneous norm is that the calculation of a metasomatic norm can not proceed along as fixed a hierarchical path as is the case of an igneous norm. More flexibility is necessary because of the wide range in both rock and mineral compositions. In some cases, where constrained by known 28 mineralogy, the calculations must iterate back and forth using various abundance of normative minerals in order to eventually balance or best fit a calculated mineral assemblage with the fixed chemical composition of an altered rock (i.e., to make the chemical masses and the mineral masses balance). In addition, the calculation of a metasomatic norm must take into account possible incompatible mineral pairs in hydrothermal system, for example, kaolinite and feldspar are not stable in the presence of quartz. The mathematical relationship between lithogeochemical data and metasomatic norms is discussed by Cheng and Sinclair (1994) as follows: a rock mass, P, is comprised of the masses of a set ofminerals (mj): (2-1) For practical purposes, this equation can be extended in terms of the measurable items (in weight units) as follows: P x = (m x f,)) (2-2) i=1 1=1 j=1 for i= 1, 2, ..., q; and j1, 2, ..., p. where -q is the number of components analyzed; -p is the number of involved mineral phases; -wi is the weight fraction of component i of the rock sample (Zwi 1); -mj is the weight percent ofmineralj of the rock sample in grams; -fij is the weight fraction of component i in mineral phase j; The relation between the weight fraction of component i in mineral phase j and corresponding molar amounts can be expressed as follows: 29 (2-3) for i = 1, 2, ..., q, andj = 1, 2, ..., p, where nij is the number ofmoles of component un mineral phase j, a is the molar weight of component i, and bJ is the molar weight ofmineral phasej. The reference weight P can be assigned any value, for example, 100 grams, and equation 2-2 can be converted into molar units as follows: 100 x(w1/a)=((m/b1)xn) (2-4) 1=1 1=1 j=i In equation 2-4 the weight fraction of each chemical constituent of the rock (Wi) is measurable through whole rock chemical analysis; a and b hold the constant molar weights for each chemical constituent i and each mineral phase j; f1 and nij are either measurable through an analysis of mineral separates or referenced from the standard stoichiometry of corresponding minerals; mj, the remaining unknowns, are to be determined. Since 1/2a and 1/b can be converted into a diagonal matrix [l/aijlpxq and [l/b]pxq (for ij, 1/aij = 0 and 1/bij = 0), the relationship can also be expressed in matrix form as: 1/a.. 0.. 0 o :::: o o :: o }*;q flu ... fllj ... flip 1/b1 •. 0 •. 0 rni o :::: o (2-5) flqi...flqj...flqp o::o::i ,, or AxW=NxBxM (2-6) 30 where A [l/ajjlpxq (for ij, lIa1 = 0), W = [wjlq, B = [l/bijlpxq (for ij, 1/b = 0), N = [njjlpxq and M = [m]. Generally, there is a larger number of unknowns than equations in the linear set of equations 2-5 or 2-6. The values q and p are related to the number of analytical items and the number ofmineral phases considered, respectively. Usually, the composition of a rock sample is composed of only about a dozen major and minor components (q). In contrast, the mineral phases considered may be over twenty or more (p). Therefore, in general, matrix N is not square. Consequently, this set of linear equations cannot be solved explicitly. Some constraints are needed to reduce the number of independent variable m3s through either: (i) thermodynamic calculations (e.g., Brown and Skinner, 1974) to decide what are the stable mineral assemblages, or (ii) observation of the assemblage comprising the rock in question. It is essential that p is equal to or less than q in order that a unique solution is possible. In some cases the matrix might be singular or overdetermined. These problems may be caused by analytical errors and/or discrepancies between the compositions of real mineral phases of the rock sample and standard normative mineral phases used in matrix N. Thus, such set of linear equations needs to be solved using a fitting procedure, such as minimizing the sum of squares, R2 (e.g. Wright and Doherty, 1970; Stout and Nicholls, 1977). The principle of the technique is to search for the solution which produces the least R2 value (R2),where R2 (sum of squares of residual) is given by: R2 =>(w/a->(m x))2 (2-7) The least squares technique can provide either the best fit solution or the best fit approximations. In brief, the calculation of metasomatic norms as introduced here rests on the suppositions that lithogeochemical data are of adequate quality, and that the principal 31 alteration minerals have been identified. Norms determined in the foregoing manner are objective and quantitative. They are representative of the processes being modeled and can closely approximate modes of the altered rocks under study if appropriate constraints are available. 2.3. A Set of Standard Normative Mineral Components for a Metasomatic System The metasomatic process ofwall rock alteration, in most cases, can be described as the additions ofvolatile components (H20, C02, S, etc.) and ionic components (K, Si, etc.) from hydrothermal fluid to wall rock and a corresponding depletion of some ionic components of the wallrock (Na, Ca, Mg etc., extracted from the wall rock and contributed to hydrothermal fluid). This process of chemical exchange can also be described partly in terms ofmineral transformations. For example, anhydrous silicates such as olivine, pyroxene and feldspars, alter to (i) phyllosilicates such as chlorite, muscovite, kaolinite, chlorite, (ii) carbonates such as calcite, magnesite, siderite, rhodochrosite, dolomite, ankerite, etc., and, (iii) sulfides such as pyrite. Volatile components clearly are an essential part of a hydrothermal alteration system and cannot be omitted as in the case of C]PW normative calculations. The selection of a set of standard minerals for metasomatic norm calculation should be based on geological observations. Rock-forming minerals which account for most of the chemical components clearly have priority. In most cases for hydrothermally altered rock systems the major components are composed of: Si02,Al203,Fe203,FeO, MgO, CaO, Na20,K20,H20 and CO2. The standard minerals for metasomatic norms must include hydrous phases, carbonates and sulfides as well as anhydrous minerals. Ivlinerals found to be appropriate for metasomatic systems can be classed into nine categories: (1) anhydrous cafemic silicates such as olivine and pyroxene (Fe, Mg, Ca-silicates); (2) anhydrous calc-alkali aluminous silicate such as K-feldspar, albite and anorthite; 32 (3) hydrous caic-ferric aluminous silicate such as epidote; (4) hydrous mafic aluminous silicate such as chlorite; (5) hydrous alkaline aluminous silicate such as muscovite; (6) hydrous aluminous silicate such as kaolinite; (7) carbonate such as calcite, magnesite, siderite; (8) sulfide such as pyrite; and (9) oxides such as quartz, magnetite and hematite. The minor components contained in accessory minerals such asP205 (apatite), Ti02 (ilmenite or rutile), are less important to make the masses balance. The abundances of such accessory minerals generally do not exceed a few weight percent; however, in certain cases these normally minor minerals or trace minerals can be relatively abundant and can have strong impact on the norm calculation. For example, S can be dealt with as a minor component in most cases, but if a sample has more than a few weight percent of pyrite then S becomes an important component. A set of standard normative minerals based on the autho?s experience in treating metasomatism associated with precious- and base-metal deposits in volcanic sequences is listed in Table 2-1. This list is not exhaustive. It can be extended by the addition of new standard normative mineral(s) or substituted by other identified mineral species in order to meet specific requirements. 2.4. A Manual Procedure ofMetasomatic Norm Calculation Practically, the calculation ofmetasomatic norms is completed using a computer, but it is essential to understand the conceptual nature of the calculations. A manual procedure has been developed patterned after the CIPW procedure. These calculations must balance the available components (analytical data for an altered rock) with the amounts of a particular group ofminerals of known or assumed compositions. By using alteration minerals presented in the altered rock as members of the starting group of 33 Table 2-1. A List of standard normative mineral components for metasomatic volcanic rocks associated with epithermal ore deposits Normative Symbol Formula Molecular mineral weight Fayalite Fa Fe2SiO4 203.79 Forsterite Fo MgSiO 140.71 Ferrosilite Fs FeSiO3 131.94 Enstatite En MgSiO3 100.4 Wollastonite Wo CaSiO3 116.17 Rhodonite Rn MnSiO3 131.03 Orthoclase Or KA1SiO8 278.34 Albite Ab NaAlSi3Og 262.24 Anorthite An CaA12Si8 278.22 Epidote Ep aFeAli12(OH) 483.24 Chamosite Fe-Cl e5A1Si30(OH)g 713.48 Clinochlore Mg-Cl Mgl2i1(OH)g 555.78 Muscovite Mu KA1Si0(OH) 398.3 Paragonite Pa NaA13i1(OH) 382.2 Kaolinite Ka A12Si5(OH)4 258.14 Quartz Qz Si02 60.09 Calcite Ca CaCO3 100.09 Magnesite Ma MgCO3 84.32 Siderite Sd FeCO3 115.86 Rhodochrosite Rc MnCO3 114.95 Pyrite Py FeS2 119.97 Ilmenite Tm TiFeO3 151.75 Rutile Ru TiO2 79.9 Hematite He Fe203 159.7 Magnetite Mt Fe304 231.55 Apatite Ap Ca5(P0)OH) 502.21 standard minerals, a metasomatic norm is expected to approximate the mode of the hydrothermally altered rock. The extent to which this end can be achieved depends on how close the true mineralogy is reflected in the norm and whether appropriate mineral compositions have been used in the calculations. In principle, the calculation scheme is designed to allot cations to various normative minerals and to add in as many anions as required. Hence, the difference in value between calculated cations and the corresponding analyzed cations is generally equal to zero. To illustrate the procedure ofmetasomatic norm calculation, equation 2-3 or 2-4 is expanded by using the standard normative minerals listed in Table 3-1 and a set of equations results as follows. wax3map/bap (2-8a) w=a5x2m,/b (2-8b) 34 WTj (2-9a) WMil ax(mm/b+mrc/brc) (2-9b) WNa= aNax(maIjbabt mpa “bpa) (2-9c) WK= aKx(mo/bor+ mmu/bmu) (2-9d) WMg= aMgx(2mfo/bfo+men/ben+5Mgcl/ Mgcl+ mma/bmj (2-9e) WCa= acax(mwo/bwo+mjb+2ep/ ep+mca/bca+5apf ap) (2-9f) WFe+3 aFe+3x(mep/bep+mhjbha mj (2-9g) WFe+2 aFe+2x(mfa/bfa+e’bfe+5mFeC/bFeC1 +mSd/’bSd+m3/b13,+m/b) (2-9h) w1 aMx(mO/bor+mabfbab+aflfbep/ epFec1/bFec1 +2mMgcl/bMgcl+3mu mu aThpa+2mkaka) (2-1Oa) asix(mf.a/bfa+mf.o/bfo+mfe/bfe+mefl/befl+mwo/bwo +n+3mo/bof+3mab/bab+2mafl/bafl+3mep/bl, +3mFec1/bFe.C1+Mgc1/bMgcIfl.u/ mu.pa/bpa 2mkabka+mdb) (2-lOb) w03=acox(m/b+m.a/bma+mJbsd+ml.Jbfc) (2-11 a) WOH aoHY(meJbl,+8mMgcl/bMgcl8flIrcFeC1/bFe1 +2m/b+2mp/b+4Imjbka+map/bap) (2-i ib) WTO1 = Wet.j1s (2-lie) where w represents the weight percent of the certain constituent indicated by subscript, a represents the molar weight value of the constituent denoted by subscript, m is the weight fraction of the mineral indicated by subscript, and b is the molar weight value of the mineral indicated by subscript. A general procedure to be followed in determining a metasomatic norm has been developed patterned after the procedure used in igneous norm calculation. Significant changes arise in the “metasomatic procedure mainly due to the necessity of accounting for volatile components. A detailed procedure for establishing a metasomatic norm follows. 35 1. Recast the oxide weight percentage values to cation amounts, obtained by dividing the weights percent of oxides by their respective molecular weight, multiplying by the number of cations in the oxide formula. For example, if a sample has 12 wt% AJ203,then A13 = (12.00x2)/(26.98x2+16x3) = 0.2354 2. Use all P (and necessary Ca) to make apatite [Ca5(P04)3OH)]. A unique solution exists for equation 2-8a because apatite is the only mineral in the set of standard normative minerals containing P. 3. Use all S (and necessary Fe) to make pyrite (FeS2). There is a unique solution for equation 2-8b because pyrite is the only sulfide considered in the current set of standard normative minerals. 4. Use all Ti (and necessary Fe) to make provisional ilmenite (FeTiO3)and temporarily assign the value Ofmrjtjle equal zero (equation 2-9a). 5. Use all Mn to make provisional rhodonite (MnSiO3)and assign the value of mrhodocosjte equal zero temporarily (equation 2-9b). 6. Use all Na to make provisional albite (NaA1S13O8)and let the value Of1pagomte equal zero temporarily (equation 2-9c). 7. All K is provisionally allotted to K-feldspar (KAISi3O8)and the value of is set to zero temporarily (equation 2-9d). 8. There are 3 independent variables in equation 2-9e. Use all Mg to make provisional Mg-end member pyroxene, enstatite (MgSiO3),and leave the values of other Mg-bearing minerals as zero temporarily. 9. There are five mineral phases in equation 2-9f the value of m tite has been calculated previously with equation 2-8a. If the composition of plagioclase is known (i.e., the ratio of Ca:Na in plagioclase can be set) then an appropriate amount of Ca can be allotted provisionally to anorthite (CaA12SiO8)by assigning all Na to albite. In other words, is dependent on malbite. Finally, use the remaining Ca to make provisional Ca end member of pyroxene, wollastonite (CaSiO3)and set the values of mepjdote and mcalcjte 36 to zero. 10. There are three mineral variables in equation 2-9g; the value of mepjdote has been set provisionally in equation 2-9f above. Use all Fe3 and corresponding amount of ferrous iron to make provisional magnetite (Fe2O3FeO) and leave the values of mhematjteto be zero temporally. 11. The values ofm.te and mmagnetjte have been determined by previous equations so there are four items unknown in equation 2-9h. Use the remaining Fe2 to make provisional Fe-end member ofpyroxene, ferrosilite (FeSiO3)and leave the values of the remaining ferrous iron bearing minerals in equation 2-9h at zero. 12. Even though equation 2-lOa has 9 items, all of them but mkaolte have been determined by previous equations. As a result, the remaining excess Al is used to make provisional kaoliriite [A12SiO5(OH)4].However, the rock may already have a deficit ofA13 at this stage. In this eventuality the variable mkao1te in equation 2-1 Oa disappears and equation 2-lOa becomes a constraint for the previous equations. To eliminate a deficit ofAt3 the independent variables of certain minerals containing less A13 are used to substitute for some or all of the provisional minerals in previous equations. 13. All of the items but mqu in equation 2-lOb have been determined by previous equations. As a result, any excess Si is used to make provisional quartz (5i02). Of course, Si4 may already be in deficit at this step, in which case equation 2-lOb becomes a constraint for the previous equations. This deficiency can be accounted for by using as independent variables, certain minerals containing less Si4 relative to the provisional minerals estimated in previous equations. For example, convert pyroxene [(Fe,Mg)2SiO6]to provisional olivine [(Fe,Mg)2SiO4]to the extent necessary to rectify the deficiency. 14. All items in equation 2-1 la have been determined by previous equations. Therefore, it is a constraint equation. If the sum of the provisional values on the right side of the equation is not equal to the measured value on the left side, adjustments are required to 37 make the mass ofCO;2 balance. Usually, the value on the left side is greater than that on right side of the equation at this step because the provisional allotments set the values of all carbonates to be zero. Therefore, more carbonate(s) should be allotted to balance the equation. 15. There are no unknown items in equation 2-1 lb. As a result, it is another constraint equation. If the sum of the provisional values on the right side of the equation is not equal to the measured value on the left side, adjustments are required to balance the equation. If the measured value on the left side is greater than that on the right side of the equation, the independent variables ofminerals containing more hydroxyls are required and provisional amounts of anhydrous mineral must be reduced. Conversely, in other cases it may be necessary to reduce the amounts of hydroxyl-bearing minerals. 16. Equation 2-11 c is a general constraint related to the mass balance of 02. If the two sides of this equation are not balanced, the preceding allotments of standard mineral abundances are somewhere in error. To this point in the calculation, there are two equations with unique solutions (2-8a and 2-8b), eight equations having 14 independent variables in total (2-9a, 2-9b, 2-9c, 2-9d, 2-9e, 2-9f, 2-9g, 2-9h), two equations having single dependent variable (2-lOa and 2-lob), and three constraint equations (2-11 a, 2-1 lb and 2-11 c). There are more unknowns than available equations so far. More constraints are needed to achieve a satisfactory solution. 17. The first simplification for the calculation of a metasomatic norm is that olivine is not compatible with quartz. In other words, the following reactions move to the right until one of the components on the left side of the reactions is used up. Fe2SiO4+ Si02 2FeSiO3 (2-l2a) Fa Qz Fs Mg2SiO4+ Si02 = 2MgSiO3 (2-12b) Fo Qz En 18. The second simplification is that kaolinite is not compatible with feldspar and 38 pyroxene under the condition that quartz exists. In other words, the following equilibria proceed to the right until either kaolinite or anhydrous silicates on the left side of the reactions are used up. A12SiO5(OH)4+KA1Si3O8+2CaA1SiO8+Fe304+ 2CaSiO3 (2-1 2c) Ka Or An Mt Wo =KA13SiO10(OH)2+Si02 +2CaFeA1Si3O12(OH)+ FeSiO3 Mu Qz Ep Fs A12SiO5(OH)4+NaA1Si3O8+2CaA1SiO8+Fe304+ 2CaSiO3 (2-12d) Ka Ab An Mt Wo =NaA13SiO10(OH)2+Si02 +2CaFeAlSi3O12(OH)+ FeSiO3 Pa Qz Ep Fs M(OH)+Si4/9CaA1i1/9FeFeS O (2-12e) Ka Or An Mt Fs =KA13Si30 0( H)+2/9CaFeAIi2OH)+2/9Fe5823/ SiO Mu Ep Fe- Cl Qz 2i(0H)+NaMSi4/9Mh FeFeSi0 (2-12f) Ka Ab An Mt Fs =NaA13Si(OH)+2/9CaFe 12OH)+2/9Fe123/ SiO Pa Ep Fe-Cl Qz Mi5(OH)+KISi84/9CaA11/9FeMgSiO3 (2-12g) Ka Or An Mt En =KA13 0( H)+2/9CaFe I2OH)+ /9Mg23/ SiO Mu Ep Mg-Cl Qz 12Si(OH)+NaAlSi4/9CaAl1/9Fe3O4+MgSiO3 (2-12h) Ka Ab An Mt En =NaA13 i00(OH)+2/9CaFe 12OH)+ /9Mg3/9Si02 Pa Ep Mg-Cl Qz This simplification is supported by geological observation and thermodynamic relations. For example, according to the copper porphyry model, a phyllic or sericitic zone separates a potassic alteration zone from an argiffic alteration zone. On log (JQ/Hj versus log(H4SiO)activity-activity diagram, the stable region ofK-feldspar is 39 separated from that of kaolinite by muscovite in the presence of quartz. 19. Some additional practical constraints can be set on a normative calculation. For example, the composition of plagioclase (k) is easily measured, thus, the relation between anorthite and albite can be expressed as follows: k = malbite /(mote+ma1bjte) (2-13) A similar relationship can be applied to the end members of other solid solution minerals. As a result, more constraints can be established. In addition, a set of constraints can be established limiting the values of calculated norms as never less than zero. In summary, there are 14 independent variables after initial allotments, three constraints related to the mass balance equations ofOH-, C0;2 and total, and eight constraints derived from two simplifications. In most cases, the bulk chemical composition of the rock studied can be explained by about a dozen minerals within this set of standard normative minerals. The final result is that a particular sample represents a system that is simpler than that initially assumed. In other words, a realistic system generally has substantially less than 14 independent variables. Therefore, a satisfactory solution can commonly be achieved by using the above approach. A complex system, such as a weakly altered rock in which significant amount of primary minerals coexist with secondary alteration minerals, may have even more independent variables. Therefore, additional constraints are needed. Modern analytical techniques can provide the required knowledge-based constraints. The general procedural scheme for metasomatic norm calculation has been introduced. The procedure, however, is grossly inefficient for manual calculation. Consequently, a computer-based procedure using Quattro Pro 5.0, a sophisticated and readily available spread sheet program, has been devised to process norm calculations. It can be easily converted to other spread sheet software (Appendix C). The procedure involves the use of a built-in module (the ‘Optimizer’) in the software. The general 40 procedures of using Optimizer is to (i) decide the solution destination such asW0 - W mineral = 0, (ii) choose the variables (standard minerals) to be included in the calculation, and (iii) set up the constraints indicated at the end of the forgoing section. Then the Optimizer module can adjust the amounts of the variables and adhere to the constraints to provide a final best fit solution. Unlike other ‘black box’ types of software, this calculation model is transparent. Users can easily adjust and develop it according to their own purposes. 2.5. A Quantitative Model ofMetasomatic Systems The central goal of this work is to develop the concept ofmetasomatic norms and to apply the technique. One important outcome is the likelihood that with appropriate petrographic constraints the norm and mode can be made to coincide. With the recognition of an immobile component and a set of lithogeochemical compositions that includes both least altered parent rock (Zr) and altered daughter rock (Zd), the metasomatic norms and chemical constituents of an altered rock (xd) can be fhrther recast into the absolute amounts of minerals and chemical constituents (x+dx) for a given mass of parent rock (xe) by using the following equation to remove the closure effect (e.g., Merrill, 1897; Gresens, 1967; Pearce, 1968; Grant, 1986; MacLean and Kranidioties, 1987; MacLean and Barrett, 1993; Cheng and Sinclair, 1991): z XP+dXEXd (2-14) Consequently, the contribution of each mineral to the chemical variations of bulk rock, the absolute loss or gain of individual chemical constituents during hydrothermal alteration process can be stated explicitly as follows: Mineralent rock + Constituent gained from solution = Minerala1tered rock + Constituent lost from wall rock (2-15) 41 where all items have extensive units (e.g. grams). Such an equation is comprehensive, quantitative, and provides an easily understood chemico-mineralogical model; it illustrates and interprets a hydrothermal alteration system in terms of initial and final normative mineral assemblages (corrected for the closure) plus absolute losses and gains of chemical constituents. The model can be applied without the constraints of closed system and equilibrium assemblages. The value of such a model is that it provides useful, quantitative information about the hydrothermal system. If the altered rock is the product of a simple and unique hydrothermal alteration process, the model may reveal the properties ofhydrothermal solutions associated with metasomatic events. In reality, the reaction used may more likely represent the final result of a series of sequential and/or superimposed processes. That is, the model incorporated in the equation is an ‘end member’ model. Specifically, the model includes starting and ending rock mineralogies that may be evident in the field, as well as documenting gains and losses of specific chemical constituents. This model is quantitative in the same way as Pearce element ratio diagrams. The common principle is the correction for closure that provides true relative lithogeochemical and mineralogical variations between parent and daughter rocks. The normative approach is a useful supplement to PER analysis; the two procedures have much in common and contain much the same information presented in different ways. The sequence of developing a PER diagram is to: (1) remove the closure effect of lithogeochemical data to calculate the absolute chemical changes of elements by using an conserved or immobile element, and (2) interpret these absolute chemical variations in terms of specific mineral or mineral assemblage on a binary plot. In contrast, the technique ofmetasomatic norm is to: (1) allot the chemical analytical data of bulk rock into an assemblage of normative minerals (that in certain cases will approximate the mode), and 42 (2) remove the closure effect of the norms and use the difference between norms (modes) ofparent and metasomatized rocks and elemental losses and gains to develop a combined chemico-mineralogical model of the metasomatic process. The strategy of a PER diagram is to test whether chemical changes between two rocks can be explained purely by changes in amounts of one or a few minerals as demonstrated by the distribution of points along predefined trends (slopes). Metasomatic norms are displayed more explicitly as equations (models) or profiles showing the spatial distributions of normative mineral assemblage as well as the absolute losses and gains of chemical constituents based on the comprehensive mass balance relationships. 2.6. Case Histories: Application ofMetasomatic Norms 2.6.1. Sigma Mine, Abitibi, Quebec Mesothermal gold-quartz veins of the Sigma mine are enveloped by well defined, if narrow, walirock alteration zones (Robert and Brown, 1984, 1986). An outer cryptic alteration zone is succeeded by a visible alteration zone immediately adjacent to the vein. The semiquantitative mineral variations across the alteration envelope are illustrated in Figure 2-1. Unaltered rocks are composed of a greenschist mineral assemblage: albite chiorite-epidote-white mica-biotite-quartz with minor carbonate and accessory apatite, ilmenite, and pyrite. The cryptic alteration is characterized by the variable replacement of epidote by carbonate; the zone ofvisible alteration is marked by an abrupt outer transition (2-3 mm wide) parallel to vein margins, a carbonate-white mica outer subzone and a carbonate-albite inner subzone immediately adjacent to the vein. The salient mineralogical feature of visible alteration is the complete destruction of chlorite and biotite originally present in the parent volcanic rocks. A reassessment of the overall process of hydrothermal alteration at Sigma mine can be made by applying the technique ofmetasomatic norms using the lithogeochemical data presented in Table 2-2. The results of such a calculation (Table 2-3 and Figure 2-2) 43 Table 2-2. Variations in major element oxide concentration (in wt%) in the profile 2103 across alteration envelope around tension veins, Sigma mine, Quebec Sample_id 2103-14 2103-13e - 2103-13d 2103-13c 2103-13b 2103-13a Alteration u ch-cb-mi cb-mi cb-ab cb-ab cb-ab Si02 61.28 59.19 50.04 49.59 40.75 33.79 A1203 15.66 16.33 11.73 13 .04 10.52 9.22 Ti02 0.66 0.7 2.23 1 .33 1.27 1.62 FeO 5.39 5.16 1.96 2.8 9 8.63 12.8 MnO 0.14 0.12 0.27 0.18 0.17 0.17 MgO 2.65 2.56 0.66 0.63 0.62 0.59 CaO 5.03 4.65 14.76 13.4 2 14.52 14.1 Na20 4.34 4.12 6.56 7.35 5.38 4.6 K20 0.67 1.57 0.02 0.03 0.02 0.03 P205 0.23 0.23 0.54 0 .49 0.65 0.78 H20 1.98 2.05 0.13 0 0 0 C02 2.1 2.94 10.43 9.67 10.76 10.63 S 0.12 0.86 0.8 1.81 6.2 10.31 Total 100.25 100.48 100.13 100.43 99.49 98.64 Density 2.74 2.74 2.71 2.7 4 2.84 2.98 Profile 2103 is in feldspar porphyry. Alteration facies: U=unaltered rock, CH-CB-MI=carbon ate-chlorite-white mica, CB-MI = carbonate-white mica, CB-AB=carbonate-albite nd = not detected Data source: Robert & Brown 1986. Table 2-3. The calculation results of metasomatic norms (in wt%) in the profile 2103 across alteration envelope around tension veins, Sigma m ine, Quebec Sample_id 2103-14 2103-13e 2103-13d 2103-13c 2103-13b 2103-13a Alteration u ch-cb-mi eb-mi cb-ab cb-ab cb-ab Calcite 0.000 0.133 23.118 21.690 22.769 21.749 Epidote 20.367 18.323 0.000 -0.00 0 -0.000 -0.000 Ca.pyx* 0.000 0.041 2.270 0.249 0.000 0 .000 Anorthite 0.000 0.000 0.000 2.48 9 4.497 4.401 Mg-carb 3.543 5.355 -0.000 0.000 0.000 1.078 Mg-chl 2.637 0.000 0.300 0.000 0.000 0.008 Mg-pyx 0.000 0.000 1.373 1.569 1.544 0.178 Siderite 0.730 1.611 -0.000 0.000 1.621 0.956 Fe-chl 3.524 0.939 -0.000 0.000 0.000 0.007 Fe-pyx 0.000 0.000 0.000 1.583 0.738 0.000 Muscovite 5.667 13.279 0.169 0.000 0.000 0.003 K-feldspar 0.000 0.000 0.000 0.1 77 0.118 0.175 Na-mica 3.973 1.254 2.775 0.016 0.000 0.003 Albite 33.999 34.003 53.607 62.185 45.526 38.924 Ilmenite 0.000 0.000 2.246 0 .000 0.582 1.375 Rutile 0.660 0.700 1.047 1.330 0.963 0.896 Kaolinite -0.000 0.300 0.198 0.00 0 0.000 0.009 Quartz 24.126 21.980 9.618 3.856 6.175 4.901 Mn-carb 0.227 0.194 0.438 0.29 2 0.275 0.275 Apatite 0.543 0.543 1.274 1.156 1.533 1.840 Pyrite 0.225 1.609 1.497 3.3 87 11.600 19.290 Hemtite 0.000 0.000 0.000 0.000 0.000 0.000 total 100.220 100.265 99.930 99.978 97.943 96.067 * pyx - pyroxene; carb - carbonate; chl - chlorite. 44 II C D CD CD II 0 o t -t 1 . 0 C D t o 0 II -i C 0 ( o CD - - CD CD 0 II C D - C D C D . SD C D C D b C CD CD 0 C -I CD CD CD CD D - t o D CD < -t c L . CD o o CD 0 CD CD -t 0 C CD C CD C) ) 0 0 C CD I. w t% vo l.% () 1 agree qualitatively with the results reported by Robert and Brown (Figure 2-1), but a few quantitative differences arise. One is that the norm profile shows no significant difference between unaltered rock and cryptic alteration zone in contrast to the claim that rocks in the cryptic zone have a marked decrease in epidote (from about 10 % to zero) and carbonate increase (from 1 % to more than 10 %) relative to unaltered rock (Robert and Brown, 1984). Moreover, in all three alteration profiles for which chemical data are published by Robert and Brown (1986) it is clear that the CO2 content of the cryptic zone is indistinguishable from the CO2 content ofunaltered rock (the contents ofCO2 in unaltered samples versus cryptic altered samples in profile 2103-10, profile 2103-13 and profile 2209-01 are 2.61 versus 2.74, 1.98 versus 2.05 and 0.89 versus 1.08, respectively); this is true for any reasonable level of analytical error. The second obvious difference between the profiles of published modes and the normative calculations reported here is the existence of abundant pyrite in an inner subzone of visible alteration zone. Even though Robert and Brown (1984) describe the existence of pyrite, they did not estimate its abundance. Up to 10.6 % of S has been measured, equivalent to about 10 wt.% pyrite or other sulfides. The third difference between the profile of norms and generalized modes is in the estimation of albite abundance. The reported modes indicate no change in the abundance of albite between the unaltered rock and the cryptic alteration zone (about 50 volume % in both) and an obvious increase in the amount of albite in the visible alteration zone (up to 55 %). In contrast, metasomatic norm calculations indicate the presence of about 35 wt.% albite in both the unaltered and cryptic alteration zone, with a marked increase to about 60 wt. % in the outer subzone of the visible alteration zone and a decrease to about 40 % in the inner subzone immediately adjacent to the vein. The differences noted above emphasize how important quantitative changes can be overlooked where semiqualitative modes are reported. A more objective procedure, 46 illustrated here by the metasomatic norm calculation, clearly avoids ambiguity in measuring mineralogical changes. 2.6.2. Erickson Gold Mine, Northern British Columbia The Erickson gold-bearing deposits are quartz veins that cut Mesozoic basalts in the Cassiar area of northern British Columbia (Sketchley and Sinclair, 1991). These veins are surrounded by extensive alteration envelopes (Sketchley and Sinclair, 1987) that can be divided megascopically into 6 distinctive zones (Table 2-4). A semiquantitative cumulative volume percentage of the mode of each mineral is also estimated (Figure 2-3). Quantitative gains and losses during the alteration process have been calculated using Gresens equation and the assumption that Zr, Ti02and A1203were immobile (Sketchley and Sinclair, 1987, 1991). The parent rock at the Erickson mine is noncarbonated basalt that has been regionally metamorphosed to the upper greenschist faces. Sketchley and Sinclair (1991) concluded that the major chemical changes that took place during the development of the carbonate alteration envelope are: (i) volatile components increase progressively from unaltered rock toward the vein, (ii)K20 is added throughout an alteration envelope but is most pronounced near the vein, (iii) Na20 is depleted throughout an envelope, (iv) Si02 is increased throughout an envelope, particularly where a quartz vein is present, (v) CaO is depleted in the outer part of an envelope and added to the inner part, and (vi) MgO and Fe203are depleted throughout an envelope except where quartz veinlets are present ( depletion is greater near the vein than in the outer portion of an alteration halo). They further qualitatively interpreted these variations as follows: 47 variations in mineralogy as afunction ofhost-rock composition and losses andgains ofcomponents. Minerals noted in the carbonated basalt are ankerite, siderite, quartz, muscovite, kaolinite, titanium oxides, andpyrite. The presence of carbonates, hydrous aluminum silicates, andpyrite implies that the volatile (LOl) include, at least, CU2,H20, and S. An increase in volatile content corresponds to a volume increase. Table 2-4. Summary of Characteristics of Alteration Zones of Enclosing Gold Bearing Ouartz Veins and the McDame Dolomite Vein, Total Erickson Mine Zone Thickness Occurrence Color Mineralogy (m) B-Noncarbonated Host Pale to dark green p1, chl, act, epi, aug, calc(trace), basalt ti-oxides, ±py±qtz±hem±mt 2C-outer < 1 very pale green to buff p1, chl, ank, sid, qtz, ser, ti-oxide, carbonate common and pale gray ±kao±dol±py±carbon±calc±epi± aug±act 2B-intermediate < 10 very buff to pale gray ank, sid, qtz, ser, ti-oxides±kao±dol carbonate common ±py±carbon 2A-inner <4 common buff to pale gray ank, qtz, ser, py, ti-oxides±sid± carbonate with minor green carbon±arsenopy±pl mottling lB-outer carbon < 1 uncommon buff to black ank, qtz, ser, py, ti-oxides, carbon± sid±arsenopy lA-inner carbon < 3 uncommon black ank, qtz, ser, py, ti-oxides, carbon± sid±arsenopy Note: pl-plagioclase, chl-chlorite, act-actinolite, epi-epidote, aug-augite, calc-calcite, py-pyrite, qtz quartz, hem-hematite, mt-magnetite, ank-ankerite, sid-siderite, ser-sericite, kao-kaolinite, dol dolomite, arsenopy-arsenopyrite. Data source: Sketchley and Sinclair (1991) Even though the chemical data (Sketchley and Sinclair, 1991; listed in Table 2-5) contain LOT rather than measurements of F120 and C02, it is still possible to allot cation to carbonates and hydrous minerals in such a way that theH20plus CO2 comprising LOT can be balanced. Normative calculations ofminerals comprising the alteration envelope at Erickson gold mine involve such a partitioning and results are in good agreement with estimated modes (Table 2-6, and compare Figures 2-3 and 2-4). Zone B (unaltered basalt) 48 has a mineral assemblage consisting of primary minerals such as plagioclase, pyroxene, etc., with a significant amounts of epidote and minor amounts of carbonate, ilmenite and apatite, that is, a greensehist facies assemblage. Zone 2C is characterized by kaolinite and more quartz. Zone 2A is composed of abundant carbonates, sericite, quartz etc. The distribution pattern of chlorite, the main difference between the normative and modal (petrographic) estimates, may arise due to an underestimation ofLOl (particularly C02) since there is obvious difference between 100% and the reported analytical total (about 95%). More CO2 than reported will reduce the abundances of chlorite and K- feldspar and form more carbonate, sericite and quartz according to the following reaction. (Fe,Mg)5A12Si3O10(OH8+KA1Si3O85C02 CM Or = 5(Fe, Mg)C03+KAIi3SiO10(OH)23SiO2+ 3H20 (2-16) Fe-Mg carbonate Mu Qz This reaction also indicates the importance of accurate measurements of H20, CO2 and S in order to reduce errors that are carried through the calculation of a metasomatic norm. Another possible cause for the difference between the two chlorite profiles may arise from the calculation of sericite abundance. In reality, sericite may not be pure muscovite; instead it may be a non-ideal mixture of, for example, muscovite, paragonite, phlogopite and biotite, etc. Several pairs of chemical constituents (e.g. Zr, Ti02A1203,totalFe203)show a linear trend through the origin of a binary plot (Figure 2-5); these pairs of components or elements are incompatible and they are interpreted as having been immobile during the alteration process. Metasomatic normative minerals can be divided by an immobile component/element, such as Zr, to correct for closure (as in the case ofPER diagrams) and produce a quantitative model ofmineralogical changes during alteration. Figure 2-6 shows the result of such calculation for a ‘typical’ Erickson alteration profile, by treating the percentage values of components of parent rock as the mass values in grams. It 49 T ab le 2- 5. C he m ic al A na ly se s of Je nn ie V ei n A lt er at io n Pr of ile , E ri ck so n G ol d M in e U ’ C Sa m pl e_ id 80 -8 8- 31 1- 80 -8 8- JH - 80 -8 8- JH - 80 -8 8- il l- 80 -8 8- 31 1- 80 -8 8- .J H - 80 -8 8- il l- 80 -8 8- 1H - 80 -8 8- 31 1- A lt er at io n 2A 2A 2A 2A 2A 2C 2C B B (w t % ) S i0 2 38 .8 4 38 .9 5 39 .5 5 40 .0 4 41 .8 2 48 .1 9 52 .6 0 46 .8 1 47 .9 0 A 12 03 11 .4 0 11 .4 6 12 .0 7 12 .0 6 10 .0 2 15 .1 5 13 .4 3 13 .5 2 14 .1 4 T i0 2 1. 00 1. 01 1. 02 1. 04 0. 86 1. 40 1. 27 1. 24 1. 32 F e2 03 8. 69 8. 46 8. 93 8. 97 8. 97 10 .6 1 10 .3 8 10 .8 7 11 .3 3 M nO 0. 15 0. 15 0. 15 0. 15 0. 18 0. 16 0. 19 0. 17 0. 16 M gO 5. 87 5. 83 5. 60 5. 61 5. 98 5. 58 5. 83 7. 14 7. 31 C aO 11 .2 1 11 .2 1 10 .4 0 10 .1 4 10 .4 3 6. 23 4. 36 11 .1 9 10 .4 0 N a2 0 0. 30 0. 28 0. 28 0. 29 0. 10 0. 01 0. 01 1. 40 2. 11 1( 20 2. 78 2. 81 3. 12 3. 20 2. 25 0. 17 0. 58 0. 13 0. 11 P 20 5 0. 12 0. 11 0. 07 0. 07 0. 07 0. 10 0. 10 0. 10 0. 10 LO T 17 .2 8 17 .2 8 15 .2 2 15 .2 2 13 .7 0 7. 60 7. 44 4. 14 2. 96 T ot al 96 .7 7 96 .7 0 95 .5 2 95 .8 9 93 .4 8 94 .1 4 95 .1 5 95 .6 2 96 .7 0 Z r pp m 73 .8 9 73 .0 2 70 .7 5 71 .6 5 64 .9 2 88 .6 8 81 .4 1 83 .0 6 87 .5 8 D at a So ur ce : Sk et ch le y, D .A . an d Si nc la ir ,A .J . 19 91 , E co n. G eo l.v ol . 86 , pp .5 70 -5 87 T ab le 2- 6. M et as om at ic N or m s of Je nn ie V ei n A lt er at io n Pr of ile , E ri ck so n G ol d M in e Sa m pl e_ id 80 -8 8- IN - 80 -8 8- 31 1- 80 -8 8- il l- 80 -8 8- il l- 80 -8 8- il l- 80 -8 8- JH - 80 -8 8- JH - 80 -8 8- 31 1- 80 -8 8- il l- A lt er at io n 2A 2A 2A 2A 2A 2C 2C B B C ar bo na te 34 .4 8 34 .4 7 28 .7 3 27 .3 7 23 .0 3 3. 40 4. 03 5. 59 3. 44 E pi do te 0. 00 0. 00 0. 00 0. 00 0. 00 18 .6 9 8. 74 22 .4 0 18 .6 8 S er ic it e 21 .0 3 21 .6 3 19 .1 2 18 .9 4 12 .4 2 0. 78 4. 91 18 .3 7 17 .0 0 K ao li ni te 0. 00 0. 00 0. 00 0. 00 0. 07 15 .8 1 12 .0 9 0. 10 0. 00 C hl or it e 13 .4 9 12 .9 9 18 .7 2 19 .8 1 25 .5 2 27 .5 2 29 .7 8 0. 22 0. 00 P yr ox en e 0. 00 0. 00 0. 00 0. 00 0. 00 0. 00 0. 23 31 .7 7 35 .8 7 K -f el ds pa r 4. 32 3. 91 7. 50 8. 18 5. 48 0. 50 0. 00 0. 00 0. 00 Pl ag io cl as e 0. 00 0. 00 0. 00 0. 00 0. 00 0. 05 0. 09 3. 77 12 .5 1 P yr it e 0. 00 0. 00 0. 00 0. 00 0. 00 0. 00 0. 00 0. 00 0. 00 Q ua rt z 22 .0 8 22 .3 5 20 .1 4 20 .3 9 25 .1 7 25 .0 9 32 .6 3 10 .8 1 6. 46 ot he rs 1. 37 1. 36 1. 31 1. 21 1. 80 2. 30 2. 65 2. 59 2. 74 T ot al 96 .7 7 9 6 .7 0 95 .5 2 95 .8 9 93 .4 8 94 .1 4 95 .1 5 95 .6 2 96 .7 0 0 > ____ _ a) -o 0 2A 2A 2A 2A ZA 2C ZC Inner carboante zone outer carbonate zone Y’’sericite I* kaolintie fl I pyroxene vein quartz Ti-oxide chlorite Figure 2-3 Generalized distribution of mineral species throughout carbonate alteratio n envelopes enclosing gold-bearing veins, white quartz veins and carbon veins. Simplified from Sketchley and Sinclair (199 1) ‘ %- % S. S. S. S - : - Vein Zone LI I lo1ate epidote sericite kaolinite pyroxcne V//j plagioclase K-f eldspar r I quartz Figure 2-4. Metasomatic norms profile Je nnie vein, Erickson gold mine, northern British Columbia : 70 .--.--- , , , , / / , ., / , / / — ‘ - - . - ---:- ‘ . ‘. ‘. . .. ‘. ‘. . ‘. ‘ . ‘. ‘. ‘. , //////// .. ‘ttt’ fl ‘ .‘ . ‘. ‘. ‘. ‘ ‘. ‘ ‘. \ ‘. ‘. ‘.. ‘ S. ‘. ‘‘S.. ‘ ,,,,—,/—,,,,,,,,,, , ‘.S.S.S.S. S. \S.’. ‘. S. \‘.S.S.’.S. 5.5.5. , /,,,,/,.,/, , ,, / // / ...-. S.5.S.S.\5.S.5.5.’.5.’.S.5. 5.5.S.’.S.5.\S. n •--•--- .. 5.5. -... .‘-.-.- 5.5.5.5.5.5.S.S.S.5.S.S.5.S.S.5 .5.S.5.5.5.’.5.5.5.5. -‘--:- 40 ::::.: ,metabasalt epidote tY/’/i plagio clase 80 70 60 50 40 30 20 10 0 (2A Jennie 2A 2A 2A Inner Carbonate Zone 2A 20 2C Outer carbonate Metabasalt 51 Table 2-7a. Metasomatic norms corrected for closure and absolute losses and gains of components from profile 80-88-JET across the Jennie vein, Erickson mine, north ern British Columbia Sample_id 8O-88-JH-1 80-88-JH-la 80-88-JH-2 80-88-JH-2a 8O-88-JH-3 80—88-JH-4 80-88-JH-5 80-88-JH-6 80-88-JH-7 Alteration 2A 2A 2A 2A 2A 2C 2C B B mole Calcite 0.234 0.237 0.228 0.219 0.249 0.03 1 0.040 -0.000 0.000 Mg-carb 0.029 0.033 0.000 0.061 0.0 34 0.000 0.000 0.000 0.000 Fe-carb 0.128 0.126 0.108 0.052 0.025 0.000 0.000 0.000 0.000 Mn-carb 0.003 0.003 0.003 0.003 0.00 3 0.002 0.003 0.003 0.002 Mg-chl 0.029 0.028 0.034 0.022 0.033 0.027 0.031 0.037 0.022 Fe-chi 0.000 0.000 0.006 0.017 0.022 0.017 0.021 0.009 0.004 Muscovite 0.052 0.055 0.049 0.047 0.038 0.002 0.013 0.000 0.000 Na-mica 0.011 0.011 0.011 0.011 0.00 4 0.000 0.000 0.001 0.007 Kaolinite 0.000 0.000 -0.000 0.000 0.000 0.06 1 0.050 0.000 0.000 quartz 0.435 0.446 0.415 0.415 0.565 0.412 0.584 0.225 0.127 Epidote 0.000 0.000 -0.000 0.000 0.000 0.038 0.019 0.053 0.050 K-spar 0.018 0.017 0.033 0.036 0.027 0.002 0.000 0.003 0.002 Anorthite 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.014 0.020 Aibite 0.000 -0.000 0.000 0.000 0.000 0 .000 0.000 0.047 0.061 Ca-pyx 0.000 0.000 0.000 0.000 0.000 0 .000 0.001 0.044 0.031 Mg-pyx 0.000 -0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.035 Fe-pyx 0.000 0.000 0.000 0.000 0.000 0 .000 0.000 0.015 0.028 ilmenite 0.001 0.001 0.002 0.000 0.015 0.009 0.017 0.016 0.017 rutile 0.013 0.014 0.014 0.016 0.000 0.00 8 0.000 0.000 0.000 apatite 0.001 0.001 0.000 0.000 0.000 0 .000 0.001 0.000 0.000 total 0.954 0.970 0.902 0.900 1.016 0 .610 0.781 0.468 0.408 dSiO2* 0.031 0.020 -0.018 -0.017 -0.142 0.005 -0.145 -0.024 0.000 dAl+3 0.012 0.008 -0.016 -0.012 0.012 -0.01 6 -0.006 -0.002 0.000 dTi±4 0.002 0.001 0.001 0.001 0.002 -0.00 1 -0.001 0.000 0.000 dFe+2 0.013 0.015 0.003 0.005 -0.010 0.0 11 0.002 -0.002 0.000 dMn+2 -0.000 -0.000 -0.000 -0.000 -0.001 0.0 00 -0.001 -0.000 0.000 dMg+2 0.009 0.008 0.009 0.011 -0.019 0.0 45 0.026 -0.005 0.000 dCa+2 -0.05 1 -0.054 -0.044 -0.036 -0.065 0.0 76 0.102 -0.025 / 0.000 dNa+ 0.057 0.057 0.057 0.057 0.064 0.06 8 0.068 0.020 0.000 dK+ -0.068 -0.069 -0.080 -0.081 -0.062 -0.001 -0.011 -0.001 0.000 dP+5 -0.001 -0.000 0.000 0.000 0.000 0.00 0 -0.000 -0.000 0.000 Sum 0= -0.015 -0.025 -0.065 -0.048 -0.072 0.139 0.147 -0.026 0.000 dH2O -0.042 -0.041 -0.084 -0.077 -0.129 -0.182 -0.194 -0.076 0.000 dCO2 -0.390 -0.396 -0.336 -0.333 -0.309 -0.03 1 -0.041 -0.000 0.000 dS 0.000 0.000 0.000 0.000 0.000 0. 000 0.000 0.000 0.000 dTotal -0.444 -0.477 -0.571 -0.531 -0.731 0.1 11 -0.054 -0.141 0.000 dH2O’ -0.026 -0.017 -0.019 -0.029 -0.057 -0 .321 -0.341 -0.051 0.000 dCO2’ -0.360 -0.347 -0.206 -0.237 -0.166 - 0.308 -0.334 0.000 0.000 dOH- 0.000 0.000 0.000 0.000 0.000 0.0 00 0.000 -0.05 1 0.000 dCO3= 0.000 0.000 0.000 0.000 0.000 0.0 00 0.000 0.000 0.000 dHCO3- -0.030 -0.049 -0.129 -0.096 -0.143 0.277 0.294 -0.000 0.000 * prefixe d stands for the absolute difference of corresponding constituent b etween the least altered and altered rocks 52 Table 2-7h. Metasoniatjc norms corrected for closure and absolute losses and gains of components from profile 80-88-Ill across the Jennie vein, Erickson mine, northern British Columbia Sample_id 80-88-JH-1 8O-8-JH-1a 80-88-JH-2 80-88-JH-2a 80-88-JH-3 80-88-JH-4 8O-88-JH-5 80-88-111-6 80—88--IH-7 Alteration 2A 2A 2A 2A 2A 2C 2C B B gram Calcite 23.38 23.69 22.77 21.92 24.89 3.10 4.01 -0.00 0.00 Mg-carb 2.43 2.81 0.00 5.16 2.91 0.00 0.00 0.00 0.00 Fe-carb 14.78 14.56 12.49 6.08 2.87 0.00 0.00 0.00 0.00 Mn-carb 0.29 0.29 0.30 0.30 0.39 0.26 0.33 0.29 0.26 Mg-chl 15.99 15.58 19.12 12.10 18.41 15.20 17.29 20.76 12.31 Fe-chl 0.00 0.00 4.06 12.10 16.01 11.98 14.74 6.26 2.76 Muscovite 20.54 21.80 19.39 18.78 15.09 0.71 5.28 0.00 0.00 Na-mica 4.39 4.14 4.27 4.37 1.66 0.06 0.00 0.38 254 Kaolinite 0.00 0.00 -0.00 0.00 0.09 15.62 13.01 0.11 0.10 quartz 26.17 26.81 24.93 24.92 33.95 24.78 35.11 13.52 7.62 Epidote 0.00 0.00 -0.00 0.00 0.00 18.45 9.40 25.48 24.16 K-spar 5.13 4.69 9.28 10.00 7.39 0.49 0.00 0.81 0.65 Anorthite 0.00 0.00 0.00 0.00 0.00 0.01 0.01 3.98 5.68 Albite 0.00 -0.00 0.00 0.00 0.00 0.04 0.09 12.23 16.12 Ca-pyx 0.00 0.00 0.00 0.00 0.00 0.00 0.25 10.24 7.28 Mg-pyx 0.00 -0.00 0.00 0.00 0.00 0.00 0.00 0.00 7.09 Fe-pyx 0.00 0.00 0.00 0.00 0.00 0.00 0.00 4.04 7.40 ilmenite 0.22 0.22 0.33 0.00 2.20 1.38 2.59 2.48 2.51 rutile 1.07 1.10 1.09 1.27 0.00 0.66 0.00 0.00 0.00 apatite 0.34 0.31 0.20 0.20 0.22 0.23 0.25 0.25 0.24 total 114.70 115.98 118.24 117.21 126.11 92.97 102.36 100.82 96.71 dSiO2* 1.86 1.18 -1.06 -1.04 -8.52 0.31 -8.69 -1.46 0.00 dAl+3 0.33 0.21 -0.42 -0.32 0.33 -0.44 -0.16 -0.06 0.00 dTi+4 0.08 0.07 0.03 0.03 0.10 -0.04 -0.03 0.01 0.00 dFe+2 0.72 0.83 0.19 0.26 -054 0.60 0.11 -0.09 0.00 dMn+2 -0.01 -0.02 -0.02 -0.02 -0.06 0.00 -0.03 -0.01 0.00 dMg+2 0.21 0.19 0.23 0.27 -0.46 1.09 0.63 -0.13 0.00 dCa+2 -2.06 -2.18 -1.77 -1.43 -2.62 3.04 4.08 -1.00 / 0.00 dNa+ 1.30 1.32 1.31 1.30 1.47 1.56 1.56 0.47 0.00 dK+ -2.64 -2.71 -3.11 -3.16 -2.43 -0.05 -0.43 -0.02 0.00 dP+5 -0.02 -0.01 0.01 0.01 0.00 0.00 -0.00 -0.00 0.00 dH2O -0.75 -0.74 -1.51 -1.39 -2.32 -3.28 -3.50 -1.37 0.00 dCO2 -17.17 -17.42 -14.77 -14.66 -13.60 -1.36 -1.79 -0.01 0.00 dS 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 dTotal -18.39 -19.68 -21.93 -20.91 -29.81 3.64 -5.90 -4.10 0.00 Residual -0.40 -0.40 -0.40 -0.40 -0.40 -0.09 -0.24 0.02 0.00 dH2O’ -0.48 -0.30 -0.34 -0.52 -1.03 -5.77 -6.14 -0.91 0.00 dCO2’ -15.83 -15.25 -9.08 -10.42 -7.29 -13.56 -14.72 0.00 0.00 dOll- 0.00 0.00 0.00 0.00 0.00 0.00 0.00 -0.87 0.00 dCO3= 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 dHCO3- -1.86 -3.01 -7.90 -5.87 -8.75 16.91 17.93 -0.02 0.00 53 15 c 0ca C’] LI Q I— • 0 0. 0. • Ti02 * A1203 C Fe203 Figure 2-5. Immobile components scatter plot, Erickson gold mine, northerm British Columbia 2 0) inner carbonate zone outer carbonate zone metabasalt vein 11111111 carbonate sericite chlorite pyroxene I:: quartz epidote kaolinite plagioclase K-feldspar mDis Figure 2-6. Metasomatic norm profile after closure effect removed, Erickson gold mine, northern British Columbia Zr ppm 54 provides a clear and quantitative appreciation ofmineralogical differences between parent and daughter rock. The metasomatic norms corrected for closure can be integrated with the results of the absolute loss or gain of each chemical component to illustrate the total chemico/mineralogic effect of the hydrothermal alteration process in equation form (Table 2-7a and 2-7b). For example, the hydrothermal alteration of parent rock (sample 80-8 8- JH-7) to altered rock (sample 80-88-JH- 1) at Erickson gold mine can be illustrated in a simplified balanced equation as follows: 0.O02Carbonate + 0.O5Epidote + 0.026CM + O.O94Pyroxene + O.081P1 + 0.O07Sericite + 0.l27Qtz 0.26 g 24.16 g 15.07 g 21.76 g 21.8 g 2.54 g 7.63 g +0.Ol7llmenite+ Apatite+ 0.05 1Ca2+0.068K++2p+5+0.0261120+ 0.36C020.03HC03 2.51 g 0.24 g 2.06 g 2.64 g 0.01 g 0.02 g 0.48 g 15.83 g 1.86 g = 0.394Carbonate + 0.O29Chlorite + 0.O92Sericite + 0.018K-spar + 0.435Qtz+0.Ol3Rutile 40.87 g 15.99 g 24.92 g 5.13 g 26.17 g 1.07 g +0.00 lllmenite+0.OolApatite+0.03 lSiO2+0.012A1+ 0.OO2Ti +0.013Fe2 0.22 g 0.34 g 1.86 g 0.33 g 0.08 g 0.72 g +0.009Mg2+0.057Na (2-17) 0.21 g 1.30 g This equation explicitly indicates which minerals are destroyed, which minerals are formed and which components are gained and lost during the hydrothermal alteration process. 2.7. Conclusions A metasomatic norm, particularly if constrained to approximate a mode, provides a useful tool to quantify the combined mineralogical and lithogeochemical changes affected during walirock alteration associated with hydrothermal mineral deposits. Advantages of both mineralogical and lithogeochemical approaches to the study of such systems are inherent in the procedure, Where modes can be approximated by norms the normative procedure generally will provide results more efficiently and more optimally because of 55 the better representative of samples collected for lithogeochemical analysis relative to those generally used for modal analysis. Moreover, lithogeochemical analytical data generally are more objective and reproducible than are modal data. In summary, metasomatic norms: (i) lead to high quality estimates ofmineral abundances, and thus, provide accurate mineral distribution profiles across alteration envelopes, (ii) provide an objective and quantitative basis for a mineralogical classification of hydrothermally altered rock, (iii) give an interpretation of lithogeochemical variations in terms ofmineralogical variations which are more compatible with field observations than are interpretations quantifying lithogeochemical losses and gains only, (iv) with the recognition of an immobile component, can be recast into the absolute masses (not percentages) ofminerals relative to a specified amount of the parent rock (e.g. about 100 grams), and (v) can be combined with the results of calculated absolute losses and gains of lithogeochemical constituents to form comprehensive mass balanced equations (model) for a hydrothermal alteration system no matter whether it is closed or open, or in equilibrium or disequilibrium. 56 Chapter 3 Quality Control/Assessment of Lithogeochemical Data 3.1. Introduction In a quantitative evaluation of hydrothermal alteration, it is essential to know the quality of data so that conclusions can be derived with confidence. Thus, it is important to understand all sources of lithogeochemical variations and know how to separate the variation(s) generated by geological process(es) of interest from those generated artificially. The major causes for the variations of lithogeochemical data are listed in Table 3.1. Table 3.1. The classification of variations of lithogeochemical data generated by different processes Primary causes Secondary causes Artificial causes Fractionation metamorphism sampling and sample preparation Mixing hydrothermal alteration analytical measurement Assimilation weathering closure effect Ideally, variations generated by artificial processes should be eliminated. In practice, they can only be minimized through quality control, such as the estimation of the optimum sample size and the necessary fineness of the ground particle size. These variations should be evaluated by quality assessment in terms of precision, accuracy and detection limit. Among the artificial causes, closure effect has already been discussed in the foregoing chapter. Consequently, this chapter focuses on: (i) strategies of field sampling and sample preparation (i.e., estimation of an optimal sample size and the fineness of grain size of prepared subsample); (ii) determination of precision and detection limit by using a small set of duplicates, and (iii) the propagation of error through data evaluation procedures. 57 3.2. Strategies of sampling and sample preparation Variation caused by improper strategies of sampling and sample preparation has been discussed thoroughly among analysts (Shaw, 1961; Wickman, 1962; Wilson, 1964; Kleeman, 1967; Maxwell, 1968; Ondrick and Suhr, 1969; Ingamells and Switzer, 1973; Ingamells, 1 974a, 1 974b, 1981; Potts, 1987) who generally agree that the error caused by sampling and sample preparation may be so large that the meaning of lithogeochemical data can be seriously distorted or obscurred. The object of lithogeochemical sampling and sample preparation is to use a small amount of sample or subsample to represent a much larger geological entity. However, silicate rocks, with few exceptions, contain two or more mineral species with various grain sizes; rock powders prepared from them are heterogeneous to some extent. Consequently, it is possible that artificial variations which could significantly obscure lithogeochemical variations could arise from improper procedures of sampling and sample preparation. The concepts of homogeneity and heterogeneity of certain elements in a sample or subsample are relative and depend on the following factors: (i) sample size, (ii) grain size of the mineral(s) containing the element of interest, and (iii) abundance(s) of the mineral(s) containing the element of interest. With the variation of one of these three factors the homogeneity or heterogeneity of the element of interest in different samples can change correspondingly. From the perspective of sampling and sample preparation, the abundance of the mineral(s) containing the element of interest is an objective constant or nearly so. However, the sample size is adjustable at the sampling stage and the particle sizes of subsamples are definable at the stage of sample preparation to make the sample or subsample more representative. Heterogeneity between the samples from the same site or subsamples from the same sample could be reduced to a minimum degree if the size (mass) of sample is large enough or the particle size of a subsample is fine enough. In general, the coarser the grain size of a 58 rock, the larger the sample size needed to be representative. The smaller the size (mass) of a subsample, the finer the sample must be ground in order to obtain the subsample. Regardless of the approaches of increasing the sample mass or grinding to a finer particle size prior to subsampling, the effects are the same (i.e., increasing the number of grains or particle (n) of the sample or subsample). To estimate the optimum mass for a sample or the necessary fineness of the particle size for subsampling, the concept of a ‘two-mineral mixture of uniform grain size’ is helpful (e.g., Wilson, 1964; Kleeman, 1967; Ingamells and Switzer, 1973; Ingamells, 1974a, 1974b; 1981). This concept can be described through the following simplifications: (i) a hypothetical mixture contains only two minerals, one is rich in the element of interest and the other is poor in the element of interest; (ii) all the particles in a sample are of uniform volume; (iii) each particle consists of one mineral species only; and (iv) the chemical composition of each mineral species has uniform composition throughout the bulk specimen. In reality, a sample or subsample may consist ofmore than two minerals and the distribution of the element of interest can be more complicated than in the simplified system above. However, the main concerns here are: (i) whether the element of interest is homogeneously distributed in the sample or subsample, and (ii) to what extent the homogeneity of the sample or subsample can be achieved. The distribution of the element of interest in a natural and complicated system is generally more homogeneous than in a simplified ‘two-mineral mixture ofuniform size’ system. For example, to analyze a rock consisting of quartz, K-feldspar and plagioclase as phenocrysts by using ‘two-mineral mixture ofuniform size’ model, plagioclase will be treated as the only mineral phase containing sodium and calcium, K-feldspar as the only mineral having potassium and quartz phenocryst as the main contributor to the 59 heterogeneity of Si02. As we know, plagioclase also can contain a minor amount of potassium, K-feldspar, similarly, can contain small amount of sodium and calcium too. Both feldspars contain significant amounts of silica. Therefore, the homogeneity ofvarious elements as described in the simplified system is adequate in place of the more complicated real system. In brief, the simplified system is adequate for our discussion; use of real, more complicated systems may be more complicated than necessary in most cases and too complicated to deal with practically, in other cases. With regard to the simplification of uniform grain size, the mineral rich in the element of interest contributes to both the total concentration of the element of interest and the error in determining concentration. Therefore, the grain size of the mineral rich in the element of interest is usually used as the reference ofuniform grain size. The rest of the grains containing a low content of the element of interest are treated as the matrix. In reality, the grain or particle size of a sample or subsample is not commonly uniform. The assumption of a uniform grain size is acceptable ifwe either: (i) imagine that a coarse grain ofmineral containing a negligible content of the element of interest is the equivalent of a number of grains as fine as the mineral enriched in the element of interest, or (ii) treat a few finer grains of minerals containing a negligible content of the element of interest as the equivalent of a coarser grain of the mineral enriched in the element of interest. In brief the concept of uniform grain size always uses the grain size of the mineral rich in the element of interest as the reference. With the above simplifications, a binomial distribution function can be used to simulate the distribution ofmajor and trace elements during sampling and subsampling processes because: (i) each sample or subsample consists of n identical grains; (ii) each grain results in one of two outcomes, the grain is rich in the element of interest or it is poor in the element of interest; 60 (iii) the probability of getting a grain rich in the element of interest on a single trial is equal to p and remains the same from grain to grain, and the probability of getting a grain poor in the element of interest is equal to q = (1 - p); (iv) the grains are independent; (v) the random variable of interest is x, the number of the grains rich in the element of interest among the n grains. For a binomial distribution we have P(x)= n! pxqn_x (3-1) x’(n—x)! where n is the total number of equant grains; x is the number of equant grains rich in the element of interest; p is the volume percentage of the grain rich in the element of interest; (1 -p) is the volume percentage of the grains with negligible concentration of the element of interest. Thus, the expectation (p.) of the binomial distribution is ,u=np (3-2) and its variance (a2) j o2 =np(l—p)=npq (3-3) and its coefficient ofvariation (Rg) is (34) Equation (3-4) given by Kleeman (1967) illustrates the relationship between the number of grains (n) of the sample or subsample and the coefficient of variation of the grain distribution (Rg) generated by sampling or stages of sample preparation. Engels and Ingamells (1970) improved Kleeman’s equation through converting the coefficient of variation (Rg) generated by sampling the non-representative grain distributions to the coefficient of variation generated by lithogeochemical inhomogeneity (RE). The reason for doing this is to take into account the minor contribution of the grains which are poor in the element of interest to the total concentration in the sample of the element of interest. 61 p+q=1 (3-5) where p and q are the weight fractions of the minerals rich and poor in the element of interest, respectively. The relationship between the volume proportions and the weight proportions of the two minerals in the mixture is: qqd (3-6) P PWdL where dH and dL are the densities of the minerals rich and poor in the element of interest respectively. E=Hp+Lq (3-7) where E represents the concentration of the element of interest in sample; H is the concentration of the element of interest in the grain population with p fraction; L is the concentration of the element of interest in the grain population with q fraction. From Kleeman’s equation R=./i (3-8) RL=lJi (39) where RH is the relative error due to sampling the mineral rich in the element of interest; RL is the relative error due to sampling the mineral poor in the element of interest. The total sampling error, EREi5 not a statistical addition of the two components LRL and HRH because these are not independent: as p increases, q decreases and E approaches H. The exact relation is: (ERE)2=(PWHRH —qLR)2 (3-10) The physical implication of equation (3-10) is that the distribution of the element of interest will become more and more homogeneous if the contributions from both populations of grains to the total concentration of the element of interest become closer and closer to each other; thus the error from sampling and sample preparation will become 62 less and less significant. Furthermore, substitution of equation (3-6) in (3-8) and (3-9), and then substituting (3-8) and (3-9) in (3-10), gives R = I x Hdff — LdL (3-il)E 1fndHdL E Next, the relationship between the weight of the sample or subsample (w) and the coefficient of variation is derived as follows: = + wq = w (PWdL +qd) (312) dffv dLv dHdLv where v is the grain or particle volume in cubic millimeters; w is the weight in gram of a sample or a subsample. Substitution of equation (3-12) and (3-7) in equation (3-11) gives: (Hdff—LdL)2 (3-13) R(pWdL + qd) (Hp +Lq)2 Rearranging equation (3-13) gives: = wR(p,(,d +qdff) (Hp,, +Lq) 2 (3-14) (HdH — LdL)2 In equations (3-13) and (3-14) the value ofRE can be predefined; the values ofH, L, dH and dL are known when the ‘two minerals’ are determined, the values ofp and q, can be reasonably estimated by examining the hand specimen. Consequently, equation (3-13) can be used to calculate the optimum weight of the sample after the value ofv is estimated through examining the grain size of the mineral containing the element of interest. For the purpose of determining the necessary fineness of the subsample, equation (3-14) can be used after the subsample weight has been defined by the analytical measuring technique. Applications of equation 3-13 and 3-14 to Silver Queen lithogeochemical data are described in Chapter 6. It is helpful to understand the significances of equation 3-13 and 3- 14 by following the calculation of a realistic example. 63 3.3. Quality assessment of analytical measurements based on a small set of duplicates The discussion in the foregoing section has been aimed at the improvement in quality of lithogeochemical data at the stages of sampling and sample preparation. Next, it is important to focus on the quality assessment of lithogeochemical data at the stage of analytical measurement. A similar concept, quality control, has been commonly used by chemical analysts. However, the quality of lithogeochemical data in terms of analytical precision is not in all cases under the control of the geologist, but the quality of lithogeochemical data can be assessed through the examination of different types of duplicates. All analytical measurements are subject to error. There are two types of errors: (1) random errors arising from the variations inherent to any sampling or measurement process, and (2) non-random errors causing systematic negative or positive deviations from the true result. Bias can be recognized through repeated measurement of standards and is not considered here. Errors are assessed in terms of either precision or accuracy. Precision is a measure of analytical repeatability. A precise analysis is one where a set of replicate analyses forms a tight cluster around the average. The degree of precision is normally measured by the standard deviation of the analyses or by the relative error (coefficient ofvariation). Accuracy is a measure of how close the analyzed data lie to the ‘true’ composition of the sample. One of the difficulties in silicate rock analysis is that the true composition, even in reference material, is in some cases poorly known (Potts, 1987). From a practical viewpoint adequate accuracy can be considered to have been achieved where different analytical methods give essentially identical results (Fletcher, 1981). Further discussion on this issue is beyond the scope of this thesis. Of practical concern is the issue of how to determine the precision by using a small set of duplicate analyses. 64 Thompson and Howarth (1976, 1978) demonstrate that errors in analytical determinations can vary significantly and systematically over a wide range of concentrations. Therefore, a single value of standard deviation calculated from a set of duplicates of one sample cannot properly describe the analytical precision of a particular set of geochemical data over a wide range of concentrations. Instead, quantification of the systematic relation of error to concentration is desirable. This approach leads to realistic error estimates in contrast to the usual assumption of either a constant absolute error (by using the standard deviation), or a constant relative error (by using the coefficient of variation). Thompson and Howarth (1976, 1978) approximate the variation of error as a standard deviation (Se) as a linear function of the concentration (C): S=S0+kC (3-15) The parameters S0 (intercept) and k (slope) can be used to quantif,’ the precision (Pc) at the 95% confIdence level and at concentration C, by means of: P=2SJC (3-16) Substitution for S in equation (4-16) gives: = (2S0/C + 2k) (3-17) In addition, the practical detection limit Cd (when P = 1.0) can also be estimated from equation (3-17) as follows: Cd = 2S0 /(1-2k) (3-18) Equation (3-18) indicates that the detection limit Cdis proportional to S0 and k, but the value of k should not be equal to or larger than 0.5, otherwise the detection limit C will be infinite or negative and meaningless in the present context. To calculate the precision (Pa) of a particular component in a sample at a specific concentration (C), it is necessary to know the values ofS0 and k. There are two procedures utilizing duplicate analyses to estimate these values (Thompson and Howarth, 1976, 1978). Procedure 1 needs 50 or more duplicates which cover the whole range of concentration of interest in a relatively uniform pattern. These duplicates are further 65 divided into five or more groups (concentration ranges) with equal number of duplicates in each group; this is done easily with a data set ordered using average concentrations of pairs [(X1+2)/2]. The mean of the concentration [(X1+2)/2] and the median of the difference (1X-21)for each group is then calculated. A linear regression of these values of[(X1+2)/2] and (1X-21)for each group is calculated or obtained graphically. The regression parameters (intercept and slope) are multiplied by a coefficient (e.g. 1.048 at 50th percentile because median values rather than mean values as the y-coordinate) to give S0 (intercept) and k (slope) of the error model (cf. Fletcher, 1981). Procedure 2 requires only 10 to 50 duplicates. This is normally the range of lithogeochemical duplicates for a study ofhydrothermally altered rocks. Therefore, a detailed discussion will be given herewith. The basic idea of this procedure is to test the available duplicate data against an empirical standard of precision to see whether the analytical duplicates can be accepted at a specific precision. The empirical equations given by Thompson and Howarth, (1976, 1978) are listed below: d90 = 2.326(S0+ kC) (3-19) d99 = 3.643(S0+ kC) (3-20) The equations above are derived from equation (3-15) and the specific constants (2.326 and 3.643) represent specific percentiles of a one-sided normal distribution (i.e. d99 and d90 represent the 99th and 90th percentiles respectively of the absolute difference 1X-2 between pairs of duplicate analyses (X1,X2)). These absolute difference are estimators of the standard deviation (Se) at composition C where C = (X1+2)/2. Consider an example to illustrate this procedure. Figure 3-1 is constructed with (X1+2)/2 as x-axis and 1X-2 as y-axis; eighteen pairs ofAl203duplicate data are plotted. Then assuming S0 = 0, two percentile lines (90th 99th respectively) are drawn on this diagram according to equation 3-17 to test whether the precision ofAl203in this set of lithogeochemical data is better than 2 % (Pc = 0.02). If the duplicate analytical data comply with the specification, on average 90% of the points will fall below the A90 line and 99 % of the points below the 66 A99 line. If in Figure 3-lA, the precision is worse than that tested, then the value of k should be raised, a poorer precision will result. In this example, a satisfactory result is achieved by raising the value ofprecision to 4.2%. As a result, around 90% of the plotted points fall below the 90th percentile line and 99 % of the plotted points below the 99th percentile line in Figure 3-lB. For general geochemical purposes a control chart (for 10% precision, i.e. with percentile lines drawn for the specification S=0.05C on logarithmic axes) devised by Thompson and Howarth (1976,1978) has been widely used. Difficulties in the use of this control chart arise where the concentrations of some duplicates are close to the detection limit, that is, where the precision is near 100%. For example, an alteration profile cross cutting a propylitic alteration halo and a sericitic/argillic alteration envelope are usually characterized by a high concentration ofNa20 in propylitically altered rock, but an almost complete depletion ofNa20occurs within the sericitic/argillic alteration envelope. Using the control chart, above, the precision ofNa2Omeasurement tends to be largely overestimated because only the k value of the linear equations 3-19 and 3-20 is adjustable to meet the plotting requirements imposed by the 99th and 90th percentile lines (i.e. there is no point above the 99th percentile line and there are less than or equal to 10% of points above the 90th percentile line). There is an obvious discrepancy between the calculated precision and the deviation represented by the duplicates of high concentration (Figure 3- 2A). The cause of this problem is that the detection limit has not been taken into account. This problem may not appear where all duplicates have concentrations far removed from the detection limit. There is a substantial disparity between procedure 1 and 2. Procedure 1 defines error as a linear flinction of concentration, procedure 2 assumes a constant relative error. It seems that procedure 2 might be improved for some situations involving fewer than 50 pairs of duplicates, where data are sufficiently precise that both S0 and k can be estimated, even if not as rigorously as in procedure 1. 67 >< C\4 >< >< Figure 3.-I. Schematic illustration of Thompson and Howarth’s procedure 2 (see text ) for the precision estimation of a set of lithogeochemical data. (A) The duplicate data do not comply with the 2% error test percentile lines. There are more than 10% and 1% of plots fall above the 90th and 99th percentile lines respectively. This means that th e precision ofA1203in this set of data is higher than 2%. (B) After raising the prec ision to 4.2%, only 2 out of 18 duplicates plot between the 90th and 99th percentiles. The refore, this precision is acceptable. (Xl +X2)/2 0 5 10 15 20 25 (Xl +X2)/2 68 0.8 99t 0.7 th Na20 50 _ _ _ _ _ _ _ _ 0.6 So = 0.00 k = 0.8 Pc = 1.6 c4 0.4 >< 0.3 0.2 0.1• CD CD 0--a p I I I — 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 (Xl +X2)/2 0.8 0.7 Na20 0.6 So = 0.09 ::z— CD 50th 0.1 _________ _ _ _ _ _ _ _ _______________ _____ ID 0- I 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 (Xl +X2)/2 Figure 3-2. Comparison of the methods of precision estim ation of lithogeochemical data by using: (A) constant precision and variable standard dev iation for whole range of the concentration, and (B) variable precision and variab le standard deviation. See text for detailed explanation. 69 One way of dealing with this problem is the introduction of the detection limit (Cd) of the element of interest to the construction of the corresponding control chart. Commonly, the values ofdetection limits of each analytical technique for different constituents are provided by the analyst. With the known value of detection limit (Cd), equation (3-18) can be rearranged as follows: S0= Cd (0.5-k) (3-2 1) substitution of equation (3-21) in (3-19) and (3-20) gives: d90 =2.326(O.5Cd+ k(C-Cd)) (3-22) d99 =3.643(O.SCd + k(C-Cd)) (3-23) Now only one variable (k) remains in equation (3-22) and (3-23). Following the same procedure as Thompson and Howarth (1976, 1978) one increases the value of k and moves the 99th and the 90th percentile lines up until no plotted point lies above the 99th percentile line and less than or equal to 10% of the plotted duplicates lie above the 90th percentile line. The value (k) can then be estimated. Thus, the value S0 can be calculated by using equation (3-2 1). Where the information about detection limits is not available, there is another way to deal with this problem, that is, the estimation of S0 and k based on the analytical duplicates. A recommended procedure is as follows: (1) Introduce one more empirical precision equation to set one more constraint for taking one more variable (S0) into account, d50 0.954(S + kC) (3-24) (2) Initially assume S 0; (3) Gradually increase the value of k starting from zero in equations (3-20) until no point is above the d99 line (since 99% of points for a small set of duplicates 10 to 49 pair of duplicates means that all points should be below the 99th percentile line); (4) Construct the d90 line with the current values of S0 and k derived from the previous step and check whether 90% of the points are below the d90 line. If not, continue to 70 increment of k until only 10% of the points are above the d90 line; (5) Construct the d50 line with the current values of S0 and k derived from previous steps and check whether about 50%, or the maximum amount between 10 to 50% of the points, are above the d50 line. If the points above the d50 line are less than 50% or the maximum amount value between 10 to 50% of the total plotting points, then reject the initial assumption of S0; (6) Reassign the initial value of S0 by a small increment; (7) Repeat the steps (2) to (6) until the requirement for all three lines are satisfied; i.e., with certain values of S0 and k, no point is above the d99 line, no more than 10% of the points are above the d90 line and about 50% or the maximum amount between 10 to 50% of the points are above the d50 line (Figure 3-2B). In brief, this approach helps obtaining reasonable estimates of S0 and k. Consequently, the precisions of a particular set of lithogeochemical data with wide ranges of concentrations can be estimated in a form consistent with the case for more abundant paired data (i.e., duplicate pairs> 50). 3.4. Propagation of Errors in Calculation ofMetasomatic Norms Lithogeochemical data always incorporate some component of random error. Quantitative estimates of losses and gains of components during hydrothermal alteration are limited by the magnitude of these errors. Errors in analyses of individual components commonly are known. An important concern is the effect these known errors have on various calculated quantities, that is, the propagation of errors (Le Maitre, 1982; Cheng and Sinclair, 1994). In mathematical terms, if the calculated result, z, is a ffinction of a set ofmeasured variables: x1, x2, . . z=f(x1,x2...x) (3-25) 71 The quantity z will be in error by an amount dz as a consequence of the errors in each of the measured quantities x1, x2, . . .x. Then the error dz (as a variable) can be estimated using the approximation (e.g. Kendall, 1943): = --Js. + )s (3-26) where x1 and Xj are the ith component and thejth component respectively, S is the analytical error calculated through equation (3-15) by using corresponding S0 and k values; and S, is the value of covariance between the ith andjth variable. It is reasonable to treat the error of lithogeochemical data as independent since the analytical error of one element has no obvious link to the error of the other element. Therefore, a simplified equation used to calculate error propagation is as follow: 2 = (3-27) Substitution of equation (3-15) in (3-27) gives: 2 = (St,. +k1x)2 (3-28) Since the value of S)q is one standard deviation of a normal distribution, the value of error propagation (Si) derived from it is at the 68% confidence level. Equation 3-27 is commonly used for calculating the variance of a function. As indicated by Le Maitre (1982), with closed data of the constant sum type, not all the covariances can be zero, and their sum must be negative. This means that if the covariance terms in equation 3-27 are ignored, the absence of their overall negative contribution will tend to give an overestimate of the variance. As this is generally more acceptable than an underestimate of the variance, the use of equation 3-27 for closed data would, therefore, seem reasonable as a first approximation. 72 For the calculation of loss or gain of a specific component in a single precursor system the following equation is used: z dX=tXdxp (3-29) where dx is the value of absolute loss or gain of a component x during the hydrothermal alteration process, Z is immobile during the alteration process, x., and Xd are the mobile element concentrations in the least altered parent rock and altered daughter rock respectively. In equation (3-29) the calculation result (dx) is derived from four analytical measurement values (i.e. Zd, Z,, Xd and x.). Each of these four values has its own uncertainty. The value of dx contains the combination of the errors derived from all former dependent variables. Thus, the error propagation can be evaluated as follows: = +kZ)2+[_)(S0 +kzZd)2 2 2 (3-30) (S0 +kXxd)2+[._] (S +kx)2 ,- iZxi = (Se, +kZ)2+ ) (S0 + kzZd )2 z 2 (3-31) (S0 + kXxd)2+(S0 + By using an error determined from equation (3-31) the calculated absolute losses and gains of chemical constituents can be evaluated at an appropriate confidence level. For the calculation of the propagated error of an specific normative mineral, it is first necessary to find the functional relationship between the amount of a specific normative mineral and related chemical constituents allotted to it. A specific normative mineral can be treated as the summation of certain portions of relevant chemical 73 constituents from the whole rock compositions. Therefore, the functional relationship between the percentage of normative mineral and concentration of different components used to construct it can be presented as follows: (3-32) where z is the percentage value of the normative mineral, a is the proportion of the ith component used to make the normative mineral from the bulk rock compositions, and x1 is the concentration value of ith component in the rock. Substituting equation (3-3 2) in (3- 28), we have: S =a(S0+k1x)2 (3-33) By using equation (3-3 3) the uncertainty of a metasomatic norm calculation can be estimated through error propagation at the 68 % confidence level. There are two fundamental assumptions for the calculation of propagated errors as outlined above: (i) the errors of lithogeochemical data are assumed to be independent of each other because the error of certain chemical constituent of the whole rock sample has no obvious link to the errors of other chemical constituents of the same rock sample; (ii) the error contributed by a chemical constituent is assumed to be allotted to a normative mineral in the same proportion as the chemical constituent is allotted to the normative mineral. It is hard to prove these assumptions. Their use may lead to small overestimates of the propagated errors, and thus they provide a conservative approach. Furthermore, the propagated errors calculated through equation (3-31) and (3-3 3) can be integrated with the results of the absolute losses and gains of chemical constituents, as well as the normative minerals corrected for the closure to be presented as a comprehensive mass balance equation introduced in the previous chapter. We have: 74 M1neraI,eflt rock ±error + Constituent gained from solution±error =4ineralalted rk±0r + Constituent lost from wall rock±error (3-34) Propagated errors provide a basis for screening data for inclusion in the chemico mineralogic model. Abundances less than twice the propagated error are not significantly different from zero and can be ignored. 75 Chapter 4. Geology of the Silver Queen Mine, Owen Lake Area, Central British Columbia 4.1. Introduction The Silver Queen (also known as Nadina or Bradina) mine is near Owen Lake, 35 kilometres southeast ofHouston, and 100 kilometres southeast of Smithers in the Bulkley Valley region of central British Columbia (Figure 4-1). The deposit has had a long history of exploration since its discovery in 1912. It has produced 3160 oz Au, 168,000 oz Ag, 893,000 lbs Cu, 1.55 million lbs Pb, 11.1 million lbs Zn and 34,800 lbs Cd from 210,185 short tons of ore during a brief period from 1972 to 1973. Mine closure was due to overdesign of the mill and complex metallurgy (Cummings, 1987; Dawson, 1985). Geological reserves of the No. 3 vein at the Silver Queen mine presently stand at approximately 500,000 short tons grading 3 g/t Au, 200 glt Ag, 0.23% Cu, 0.92% Pb and 6.20% Zn (Nowak, 1991). Equity Silver mine (total reserves plus production of approximately 30 million tonnes of 0.4% Cu, 110 g/t Ag, and 1 g/t Au) lies 30 km to the east-northeast. Geological mapping of the 20 square kilometre area surrounding the deposit suggests that the stratified rocks (the Upper Cretaceous Tip Top Hill Formation: Church, 1971) hosting this epithermal gold-silver-zinc-lead-copper vein deposit may be correlated with rocks hosting the Equity Silver deposit (Wetherell et al., 1979; Cyr et al., 1984); they are lithologically similar to Kasalka Group rocks of late Early to early Late Cretaceous age (Leitch et al., 1990). Two series of igneous and volcanic rocks have been recognized by their distinctive lithogeochemical characters and K-Ar dating ages. The Silver Queen mine is hosted in the older series of igneous and volcanic rocks and is cut by dikes belonging to the younger series. Therefore, mineralization at the Silver Queen mine occurred during the period after the older series of igneous and volcanic activity, but before the younger one. 76 4.2. Regional Geological Setting The study area lies within the Stikine terrane, which includes submarine calc alkaline to alkaline immature volcanic island-arc rocks of the Late Triassic Takla Group; subaerial to submarine caic-alkaline volcanic, pyroclastic and sedimentary rocks of the Early to Middle Jurassic Hazelton Group; successor basin sedimentary rocks of the Late Jurassic and Early Cretaceous Bowser Lake, Skeena and Sustut groups; and Late Cretaceous to Tertiary calc-alkaline continental volcanic arc rocks of the Kasalka, Ootsa Lake and Endako groups (Maclntyre and Desjardins, 1988). The younger volcanic rocks occur sporadically throughout the terrane, mainly in down-thrown fault blocks and grabens. Plutonic rocks of Jurassic, Cretaceous and Tertiary ages form distinct intrusive belts (Carter, 1981), with which porphyry copper, stockwork molybdenum and mesothermal and epithermal base-precious metal veins are associated. The Silver Queen mine lies on the caldera rim or perimeter of the Buck Creek basin, which is delineated roughly by a series of rhyolite outliers and a semicircular alignment ofUpper Cretaceous and Eocene volcanic centres scattered between Francois Lake, Houston, and Burns Lake (Figure 4-1; see also Fig. 59 of Church 1985). The Buck Creek basin has been interpreted as a resurgent caldera, with the important Equity Silver mine located within a window eroded into the central uplifted area (Church, 1985; Church and Barakso, 1990). A prominent 30 km long lineament, trending east-northeasterly from the Silver Queen mine towards the central uplift hosting the Equity mine, appears to be a radial fracture coinciding with the eruptive axis of the Tip Top Hill volcanics and a line of syenomonzonite stocks and feeder dikes to an assemblage of Tertiary ‘moat volcanics’ (Church, 1985). Block faulting is common in the basin, locally juxtaposing volcanic rocks of various ages. Within the basin, a Mesozoic volcanic assemblage is overlain by a Tertiary volcanic succession. The oldest rocks exposed within the basin are at the Equity Silver mine and 77 540 540 Figure 4-1. General geology of central British Columbia, showing the regional setting of the study area (after Maclntyre, 1985). Tpb - Tertiary plateau basalt; Eg - Eocene granite; KTo - Ootsa Lake Group; Kg - Cretaceous granite; Kk - Kasalka Group; Ks - Skeena Group; Jg - Jurassic granite; Th - Ha.zelton Group. 128° 126° 55° 550 0 25 50 K I 0n e t r e s 78 the Silver Queen mine. The sequence at the Equity mine has been characterized by Church (1984) as the Lower Jurassic Telkwa Formation of the Hazelton Group, overlain with angular unconformity by Lower Cretaceous Skeena Group sedimentary rocks. However, Wojdak and Sinclair (1984) correlate the sequence hosting the Equity mine with the Lower Cretaceous Skeena Group sediments, and Wetherell et al. (1979) and Cyr et al. (1984) correlate it with the Lower to Upper Cretaceous Kasalka Group. The Kasalka Group is considered to be a late Early Cretaceous (Armstrong, 1988) or early Late Cretaceous (Maclntyre, 1985; Leitch et al., 1991) continental volcanic succession that is predominantly porphyritic andesite and associated pyroclastic rocks. It is well exposed in the Kasalka Range type section near Tahtsa Lake. Upper Cretaceous rocks with similarities to the Kasalka Group are exposed westwards from the Equity mine to the Owen Lake area, where they host the Silver Queen deposit (Church, 1984). These rocks, which have been dated at 75 to 80 Ma by K-Ar whole rock (Church, 1973; Leitch et a!., 1991) consist of a lower felsic volcanic unit overlain by andesites and dacites of the Tip Top Hill volcanics (Church, 1984). This subdivision is based on ‘rhyolitic volcanic rocks below the Tip Top Hill Formation in the Owen Lake area in extensive drill holes in the vicinity of the Silver Queen min& (Church, 1973), which he considers to be ‘lateral equivalents of quartz porphyry intrusions exposed nearby on Okusyelda Hill’ (Figure 4-2). Recent mapping indicates that the lower volcanic unit exposed in the drill holes may, in part, be a strongly altered equivalent of the Tip Top Hill volcanics (Leitch et a!., 1991). The quartz porphyry of Okusyelda Hill could correlate with dacitic quartz porphyry sills, dikes and laccoliths common within the type Kasalka Group section in the Tahtsa Lake area. Late quartz-feldspar porphyry dikes are also found at the Equity mine (Cyr et a!., 1984; Church, 1985), although these are dated at 50 Ma and thus belong to the younger Ootsa Lake Group. The Upper Cretaceous rocks are overlain by Eocene Ootsa Lake Group rocks, which include the Goosly Lake and Buck Creek formations of Church (1984). The Goosly 79 Lake andesitic to trachyandesitic volcanic rocks are dated at 48.8 ± 1.8 Ma by K-Ar on whole rock, and this is supported by similar dates of 49.6 ± 3.0 to 50.2 ± 1.5 Ma for related syenomonzonite to gabbro stocks with distinctive bladed plagioclase crystals at Goosly and Parrot Lakes between Equity and Silver Queen (Church, 1973). Andesitic to dacitic volcanic rocks of the Buck Creek formation, which directly overlie the Goosly Lake Formation, are dated at 48.1 ± 1.6 Ma by K-Ar on whole rock (Church, 1973). The Goosly Lake and Buck Creek formations correlate with Ootsa Lake Group rocks in the Whitesail Lake area south of Tahtsa Lake dated at 49.1± 1.7 Ma by K-Ar on biotite (Diakow and Koyanagi, 1988), but are slightly younger than dacite immediately north of Ootsa Lake, dated at 55.6 ± 2.5 Ma by K-Ar on whole rock (Woodsworth, 1982). Basalts of the upper part of the Buck Creek formation (Swans Lake Member: Church, 1984) may correlate with the Endako Group ofEocene-Oligocene age. These rocks give dates of4l.7 ± 1.5 to 31.3 ± 1.2 Ma by K-Ar on whole rock samples from the adjacent Whitesail Lake map-area (Diakow and Koyanagi, 1988; cf. the range of 45-40 Ma reported by Woodsworth, 1982). The youngest rocks in the Buck Creek basin are cappings of columnar olivine basalt ofMiocene age, called the Poplar Buttes Formation by Church (1984). These have been dated at 21.4 ± 1.1 Ma by K-Ar on whole rock (Church, 1973) and are correlated with the Chilcotin Group. 4.3. Geology of the study area The preliminary geology of the study area immediately surrounding the Silver Queen mine, as determined by fieldwork and petrological studies completed in 1989-1990, is shown in Figure 4-2 (units are defined in Table 4-1). Relationships between the map units are shown diagrammatically in Figure 4-3. The succession is strikingly similar to that observed in the Kasalka Range (Maclntyre 1985) and on Mount Cronin (Maclntyre and Desjardins, 1988). 80 Okusyelda I-lilt Sb 4 5b 1’. 4 76 2 70 _••_ Emil ‘ 4 2 George \ b 3, ‘ i-1& 0 \ .5 4 George Copper Veja \ Lake — Lake 26/ BartteVebt\ *1-47 i ‘k. oleVetri System c Sear Veki/ ‘ 3 No. 2 Vein / 2sf \ 7I / / 76 Lead Ve No.1 2 Vein7\26 n5George Lake 0 4 •[;- CLIneament Vein0, 78 NG 6 Ven S --... .. / 70 2 ci 60 Mine Q- 5 No. 5 6 -. • -.,tfll 85 5 . :---v N A \eo. \ CF Camp V ns . . •. , 08 £ 11O 2 .25 Sw(tchback .-. 2 ,, Veki No. Ruby Vein . ... 5 Vein S V — 5a NG 3 Vein 3 \. 5 -.-.-.- V •,,, 5a 60\Cttuci 2 .: \3 :° “,>. 2 holm Veins 2 ________________________ 4 t,5c \0. 7e1 Figure 4-2. Detailed property geology of the Silver Queen mine, Owen Lake area, west- central British Columbia (from Leitch et al., 1990). Units are defined in Table 4-1. 0 200 400 eoo Boo 1000 metres • . — 0 1000 2000 3000 f€et 81 XZfl v %7<LJV 4 t — : Figure 4-3. Schematic diagram of stratigraphic and intrusive relationships, Owen Lake area, west-central British Columbia. Units are defined in Table 4-1 (after Leitch e t al., 1990). I, Esv :E5E:EEEEEEEESJ7’8 7a V V V V V V K : ÷ V V V V V V V V 82 Table 4-1. Table of formations, Owen Lake area* Period Epoch Age Formation Symbol Unit Lithology 4a ) Tertiary Miocene 21 Poplar Buttes MPBV Olivine basalt Eocene- 45- Endako Group EOEV 8 Basalt diabase dike Oligocene 30 Eocene 56- Ootsa Lake E 7a Trachyandesite basalt 47 Group 7 Bladed feldspar porphyry dike Mineralization veins Cretaceous 6 Amygdular dikes (Late) “Okusyelda” uKqp 5b Quartz-eye rhyolite stock, dike uKp 5a Intrusive porphyry sills, stocks uKud 5 “Mine Hill” microdiorite 4a Feldspar-biotite porphyry dike 85- “Tip Top Hill’ uKfp 4 “Tip Top Hill” andesite 75 formation uKb 3 Medium to coarse tuff-breccia uKt 2 Crystal tuff, local lapilli tuff 2a Fine ash tuff uKc 1 Polymictic basal conglomerate, sandstone and shale interbeds *p.fter Leitch et al., 1990 The rocks of the study area have been subdivided into five major units plus three dike types; Table 4-1 lists the map units defined to date. A basal reddish purple polymictic conglomerate (Unit 1) is overlain by fragmental rocks ranging from thick crystal tuff (Unit 2) to coarse lapilli tuff and breccia (Unit 3), and this is succeeded upwards by a thick feldspar porphyritic andesite flow unit (Unit 4), commonly grading into and locally intruded by microdiorite sills and other small intrusions (Unit 5). The stratified rocks form a gently northwest-dipping succession, with the oldest rocks exposed near Riddeck Creek to the south and the youngest exposed in Emil Creek to the north. All the units are cut by dikes that can be divided into three groups: amygdaloidal dikes (Unit 6), bladed feldspar porphyry dikes (Unit 7), and diabase dikes (Unit 8). The succession is unconformably overlain by basaltic to possibly trachyandesitic volcanics that crop out in Riddeck Creek and further south. These volcanics may be correlative with the Goosly Lake Formation 83 (Church, 1973). The units are described below in detail, to facilitate comparison with other possibly correlative rocks. Basal Polymictic Conglomerate (Unit 1) The basal member of the succession is a reddish to purple, heterolithic, poorly sorted pebble conglomerate that contains rounded to subangular small white quartz and gray-brown to less commonly maroon tuff and porphyry clasts. Local interbeds of purplish sandstone with graded bedding are found within the unit, as are rare black shaly partings. The matrix is composed of fine sand, cemented by quartz, sericite and iron oxides. The best exposure is found in a roadcut at the southern tip ofOwen Lake, where the unit is about 10 m thick and dips 25° to the northwest. The base is not exposed and the unit is in presumed fault contact with the younger volcanic rocks of the Ootsa Lake Group (Goosly Lake Formation; Unit 7) exposed at higher elevations farther south along the road. In drill holes farther north, near the centre of the property, the upper contact of the conglomerate with overlying porphyry is sharp and appears conformable, but the porphyry may be an intrusion rather than a flow. Crystal-Lithic Tuff (Unit 2) In outcrop, the next major unit is a sequence ofmainly fragmental rocks that are mostly fine crystal tuffs with thin interbeds of laminated tuff, ash tuff, lapilli tuff and less abundant breccia. The unit may be as much as 100 m thick. The most widespread rock type is a massive, gray to white, strongly quartz-sericite-pyrite altered, fine crystal tuff that grades imperceptibly into a porphyry of similar appearance and composition; the latter may be partly flow, intrusive sill, or even a welded tuff. Only the presence ofbroken phenocrysts and rare interbeds of laminated or coarsely fragmental material suggest that the bulk of this unit is tuffaceous. In thin section, the rock is seen to be made up of 1 to 2 mm broken, altered plagioclase relics and 0.5 mm anhedral quartz grains (that may be 84 partly to entirely secondary) in a fine matrix of secondary sericite, carbonate, pyrite and quartz. Drill core exposures show that the basal contact ofUnit 2 with the underlying conglomerate is commonly occupied by the porphyry rather than the tuff. The best exposures ofUnit 2 are in the area of Cole Creek and the Chisholm vein, where thin (10 cm) interbedded laminated tuff bands occur, many with variable dips to near-vertical, although coarser lapilli tuff lenses, up to 1 m thick, display gentle northerly dips. In drill core, sections of laminated tuffs with faint but discernible layering on a cm scale, may be up to 10 m thick; angles with the core axis suggest a gentle dip for the banding. Outcrops on the northeast side of the George Lake fault have rare interbeds of a very fine, uniform “ash tuff’ that are up to several m thick (Unit 2a). Typically they are dark gray to medium gray-green and have a siliceous appearance. Locally they contain angular fragments of either mixed origins (heterolithic clasts) or of larger blocks that are only barely distinguishable from the matrix (monolithic clasts). Coarse Fragmental Unit (Unit 3) A distinctive coarse fragmental unit overlies, or in some places is interlayered with, the upper part ofUnit 2. It is composed of blocks and bombs(?) (cf. Maclntyre, 1985) of feldspar-porphyritic rock similar in appearance to both the underlying porphyry and the overlying porphyritic andesite. The clasts are mostly angular to subangular and about 2 to 5 cm in diameter, but some are much larger (up to 0.5 m); the matrix makes up a widely variable percentage of the rock, from almost 0 to 90 per cent. In places the rock has the appearance of an intrusive breccia with little or no rotation of fragments. In other places the fragments are clearly unrelated and “accidental” or unrelated clasts of chert or fine tuff are common, although still volumetrically minor; this has the appearance of a lahar. In outcrop near the Cole veins, this breccia unit forms discontinuous lenses generally less than 10 m thick, with a suggestion of gentle northerly dips. The lenses appear to be conformable with the underlying or enclosing tuffs. In drill core, two 85 distinctly different modes of occurrence are noted for this unit: in one, it appears to be conformably overlain by Unit 4 porphyritic andesites (the total thickness of the breccia unit is up to 30 m); in the other, it appears to have subvertical contacts, implying it is an intrusive breccia. Good examples of the latter distribution are found in the Cole Lake area, the Camp vein system and around the southern end ofNumber 3 vein (Leitch et al., 1991). There is thus a general correlation between the subvertical breccia bodies and mineralized areas, just as there is between the microdiorite and mineralized areas. In thin section, the clasts of the breccia are seen to be composed of highly altered andesite, fine tuff and quartz or quartzofeldspathic rocks, enclosed in a fine tuffaceous matrix. Alteration in the mine area is usually carbonate-sericite-quartz-pyrite. Andesite (Unit 4) The fragmental rocks appear to be conformably overlain by a thick, massive unit of porphyritic andesite that outcrops over much ofMine Hill and is best developed north of Wrinch Creek. This unit is equivalent to the Tip Top Hill volcanics of Church (1970), although in most places on the property the andesite is coarser and contains sparser phenocrysts than the exposures on Tip Top Hill. At exposures in Wrinch Creek canyon, a distinct flow lamination is developed by trachytic alignment of phenocrysts, best seen on weathered surfaces. This suggests that these andesites are mostly flows, with gentle northerly to northwesterly dips. However, some of the coarsest material probably forms intrusive sills and stocks [cf. the type sections ofMaclntyre and Desjardins (1988) and Maclntyre (1985)1 and in many places the andesite grades into intrusive microdiorite. Parts of this unit, particularly in Emil Creek, west ofEmil Lake, and on Tip Top Hill itself, may actually be crystal tuff. In these exposures, the feldspar phenocrysts are smaller, much more crowded and in places broken, and rare lithic fragments are visible. Unit 4 has a Late Cretaceous K-Ar whole-rock date of 78.3 ± 2.7 Ma and 77.1 ± 2.7 Ma reported by Leitch et al. (1992) and Church (1973), respectively. Rhyolite from 86 Tsalit Mountain on the west side of Owen Creek valley, 10 kilometres northwest of the Silver Queen mine, gives a very similar isotopic date of 77.8 ± 3.0 Ma, also by K-Ar on whole rock. This rhyolite is correlated with the Okusye1da1’quartz porphyry by (Church, 1973). In thin section, the andesite is seen to contain abundant 2 to 3 mm euhedral crystals of andesine. Oscillatory zoning is present, but with little overall change in composition within a given specimen, from An45 to An35.Mafic minerals include roughly equal amounts (about 5% each) of 1-2 mm clinopyroxene and hornblende, and euhedral 1 to 2 mm biotite phenocrysts. The groundmass is an aphanitic mesh of intergrown feldspar with minor opaque grains; primary magnetite is abundant in the fresh specimens. Biotite-feldspar porphyry dikes (Unit 4a) Rare thin (1 m or less) dikes, similar in composition and appearance to the flows of unit 4, probably represent feeders to flows ofunit 4. They are distinguished by prominent scattered books of black biotite up to 3 mm across, as well as abundant, 1-2 mm, plagioclase phenocrysts. These dikes have only been recognized near the north end of Cole Lake and on the highway at the north end of Owen Lake, but they could be more extensive (they are difficult to distinguish because of their similarity to unit 4). They are dated by K-Ar on whole rock at 70.3 ± 2.5 Ma, indicating a possible 7-8 Ma span of Tip Top Hill volcanic activity (Leitch et al., 1992). Microdiorite (Unit 5) Microdiorite forms subvolcanic sills, dikes, and possibly, small irregular stocks on the Silver Queen mine property. These intrusions are centrally located in the two main mineralized areas of the property, the No. 3 Vein and Cole vein areas. Contacts with the andesite are indistinct or gradational. Typically the microdiorite is a medium to fine grained, dark greenish gray equigranular to porphyritic rock characterized by small (1 mm, 87 but locally glomeratic to 4 mm) plagioclase phenocrysts and 0.5 mm mafic relics in a phaneritic pink feldspathic groundmass. Primary magnetite is found in the less altered specimens. It is distinguished in outcrop by its relatively fine-grained, even-weathering texture and lacks the flow structure of the andesite. Because of the gradational relationship to the andesite, distinction is difficult in places. In thin section, the plagioclase is the same as in the andesite (oscillatory zoned andesine,An45_30), and euhedral clinopyroxene phenocrysts, partly altered to carbonate, are the most abundant mafic. Apparent hornblende relics are completely altered to chlorite. No biotite is seen, but rare scattered quartz phenocrysts, displaying late-stage overgrowths of quartz, are observable ranging up to 1 mm in size (these are not visible in hand specimen). The groundmass is composed of fine (0.1 mm) quartz, plagioclase and potassium feldspar. The microdiorite has a K-Ar whole rock age of 78.7 ± 2.7 Ma and 75.3 ± 2.0 Ma reported by Leitch et al. (1992) and Church (1973), respectively. The age of the microdiorite is indistinguishable from the age ofunit 4 andesite, in agreement with the gradational contacts between these two rocks. Porphyry (Unit 5a) Large bodies up to 1000 m across of a coarse feldspar porphyritic rock crop out in the vicinity of Cole Creek and are also found in drill core from the south end of the No. 3 vein system, where the porphyry body usually occurs between Unit 1 and Unit 3. The rock is composed of roughly 50% plagioclase phenocrysts of up to 5 mm diameter and 10 to 20% smaller mafic minerals in a fine feldspathic groundmass. The porphyry is distinguished from the andesite, Unit 4, by its coarser texture and by the absence of flow textures. It probably represents subvolcanic or high-level intrusive bodies that were emplaced below or postdate the extrusive andesite, but are related to the same magmatic event that produced the andesite. Such subvolcanic intrusive bodies, with identical mineralogy to the extrusive porphyritic andesites, have also been noted in the Kasalka 88 Group near Tahtsa Lake (Maclntyre, 1985). No K-Ar whole rock age data is determined for this rock unit because no fresh sample can be found (the outcrops of this unit of rock are always variably saussuritized or sericitized). Quartz-feldspar Porphyry (Unit Sb) Quartz-feldspar porphyry, which appears to be part of a subvolcanic intrusive stock, crops out along Emil Creek and on Okusyelda Hill to the north of the creek. This unit was called “Okusyeld&’ dacite (rhyolite) by Church (1970). Although its contact relation is uncertain, it appears to intrude Unit 4 (Tip Top Hill volcanics; Leitch et al., 1992). Church (1984) correlates the quartz porphyry intrusions on Okusyelda Hill with felsic volcanic rocks in the Tchesinkut Lake and Bulkley Lake areas, and possibly with the Tsalit Mountain rhyolite of 77.8 Ma. However, in the Kasalka Range, Maclntyre (1985) found sills and dikes of quartz-porphyritic dacite and rhyolitic quartz ‘eye’ porphyry, commonly associated with mineralization, that cut stocks dated at approximately 76 Ma (Carter, 1981). However, the quartz porphyry cannot be significantly younger than the microdiorite-feldspar porphyry in the Owen Lake area; the 84.6 ± 0.2 Ma U-Pb date on zircon shows that it is the same age or older. It is cut by thick calcite veins and quartz sericite-pyrite alteration on the extension of the George Lake vein and so is probably pre mineralization. Thin sections show the quartz porphyry consists of 10 to 15% 2 mm quartz phenocrysts and slightly smaller euhedral andesine plagioclase crystals, plus smaller relic mafic grains, in a microgranular groundmass of roughly equal amounts of quartz, plagioclase and potash feldspar. Quartz, and to a lesser extent, plagioclase also occur as angular fragments. 89 Amygdaloidal Dikes (Unit 6) Units 1 to 5 are cut by a series ofvariably amygdaloidal dikes that are concentrated in the two main areas ofmineralization (No. 3 vein and Cole vein areas). They generally trend northwesterly parallel to the mineralized veins, but north, east and northeast-trending examples are known. Dips are either subvertical to steep, or else gentle (as low as 200). These dikes are irregular and anastamosing in some parts of the property, for example between the Camp and Switchback vein systems. Highly altered examples are commonly found adjacent to and parallel to veins; elsewhere veins cut through these dikes. These dikes have been referred to previously as ‘pulaskite’ at both the Silver Queen and Equity, but this is an inappropriate term, implying an alkali-rich mineralogy including soda orthoclase, alkali pyroxene or amphibole, and feldspathoids. In underground exposures the dikes range from dark gray-green where fresh, to pale green or creamy-buffwhere strongly altered in underground exposures; they are purplish in weathered surface outcrops. They are typically fine grained and are characterized by amygdules filled by calcite, or less commonly, iron oxides, particularly at their chilled margins (dikes less than 1-2 m wide commonly lack amygdules), Flow orientations, generally parallel to the walls, provide an indication of attitude in surface outcrops.In the larger dikes (up to 10 m thick) the flow orientations are random. In thin section, the most striking feature of this dike is the abundance of fine, trachytic-textured feldspar microlites that average about 0.25 mm long. Alteration to carbonate and sericite is extensive, but the texture is generally preserved. This dike has an Eocene K-Ar whole rock age ofSl± 1.8 Ma that almost certainly reflects alteration, thus establishing a maximum but likely age ofmineralization. Bladed Feldspar Porphyry Dikes (Unit 7) A set of trachytic-textured porphyry dikes, 1 to 5 m wide and characterized by coarse (up to 1 cm long) bladed plagioclase phenocrysts, cut and slightly offset the 90 amygdaloidal dikes. The complete lack of alteration in the bladed feldspar porphyry dikes, and the fact that they distinctly crosscut mineralized veins (for example, the Bear Vein, Cole Lake area), indicates that they postdate mineralization. The K-Ar whole rock age of these dikes is 51.9 ± 1.8 Ma, indistinguishable from the K-Ar whole rock isotopic age of the amygdular dikes (Unit 6). Their spatial distribution is also similar to that of the amygdaloidal dikes, with concentrations in the two main mineralized areas; orientations are similar too, but with subvertical dips only. The similarity of these post-mineral bladed feldspar porphyries to the Goosly and Parrot Lake syenomonzonite stocks, and bladed feldspar andesite dikes at Equity dated at 50.7 ± 1.8 Ma by K-Ar on whole rock, suggests that there is a genetic relation among them. In thin section, the bladed feldspar porphyry dikes are composed of large (4-10 mm) plagioclase phenocrysts and rare to locally abundant clinopyroxene crystals up to 5 mm across, set in a dark purplish groundmass of feathery interlocking plagioclase microlites with interstitial quartz, alkali feldspar, opaque and skeletal rutile. The plagioclase forms strongly zoned, oscillatory crystals that range from cores of andesine (An50) to rims of oligoclase (An15). The pyroxene has a strong green color and is probably iron-rich. Diabase Dikes (Unit 8) Black fine-grained dikes of basaltic composition cut all other units on the property. They are much more limited in distribution than the older dikes, with subvertical dips and northwest or east-west strikes. In thin section, they lack olivine and are composed of diabasic-textured plagioclase set in clinopyroxene, with accessory opaque.minerals The K-Ar whole rock isotopic age of these dikes is 50.4 ± 1.8 Ma, only slightly younger than the dikes ofUnit 6 and Unit 7. It is likely that Unit 8 dikes are related to the basaltic Buck Creek Formation (48.1 ± 1.6 Ma; Church, 1973). 91 4.4 Lithogeochemical characters and two series of igneous and volcanic rocks The various types of igneous and volcanic rocks at Owen Lake area and its peripheral region can be classified into two series according to lithogeochemical features and K-Ar ages. The first series consists of igneous and volcanic units from intermediate to felsic composition, and is characterized by having relatively low contents ofTi02 (from 0.36 to 0.8 wt%), MgO (from 0.65 to 4.18 wt%), total iron (from 1.73 to 6.5 wt%) and P205 (from 0.09 to 0.42 wt%) as well as the older K-Ar ages (from 78.8 to 57.2 Ma). In contrast, the second series consists of the igneous and volcanic units from intermediate to mafic composition, and has higher contents of TiO2 (from 0.95 to 1.27 wt%), MgO (from 2.11 to 7.81 wt%), total iron (from 5.14 to 8.98 wt%) andP205 (from 0.49 to 0.67 wt%) as well as younger K-Ar ages (from 48.7 to 21.4 Ma; Table 4-2). The former series predates and hosts the mineralization; the latter is post-mineralization. These two series of igneous and volcanic rocks can be distinguished by using a Zr-Ti02binary plot (Figure 4- 4). In Figure 4-4, the amygdaloidal dike composition plots in the middle of the older series of igneous and volcanic rock but has a young age (51.3 Ma). The tentative explanation for this apparent anomaly is that where sampled amygdaloidal dikes were ‘younge& by later hydrothermal activity. It may also be noted that samples of porphyry (Unit 5a) and tuff (Unit 2) plot somewhat off the main trend of the series. These may also arise because of the effects ofhydrothermal alteration; dated samples of both of these rock units were not as fresh as the others plotted in Figure 4-4. Lithogeochemical data used to construct Figure 4-4 are selected from relatively unaltered rocks and listed in Table 4-2. Two lithogeochemical analyses with the corresponding K-Ar age known from Church and Barasko (1990) are listed in Table 4-2 to complete the illustration of the relation between the lithogeochemical compositions and the timing of igneous and volcanic activities. 92 0 0 V 1. 50 [. 0 0 - 0. 50 L eg en d D ia ba se di ke A nd es it ic fl ow S y n er rn zo n it e R hy ol ite G ra ni te A rn yg da lO id al di ke A sh tu ft M ic ro di or ite A nd es it e P or ph yr y • 1 S e r i e s I e s I I S er ie s I 0. 00 — I 0 10 0. 00 20 0 30 0. 00 Z rp p m F ig ur e 4- 4. A Z r- T i0 2 bi na ry pl ot di st in gu is hs tw o se ri es o f ig ne ou s an d vo lc an ic ro ck s in O w en L ak e ar ea an d it s pe ri ph er al re gi on . S er ie s I ha s K -A r ag e fr om 78 -5 1 M a an d ho st s th e S il ve r Q ue en ve in m in er al iz at io n. S er ie s II ha s K -A r ag e o f 50 M a or yo un ge r an d ov er li es or cu ts th e ve in s. X LC 2 9 /0 9 /9 6 T ab le 4- 2. L it ho ch em ic al d at a of va ri ou s ty pe s of ro ck at O w en L ak e ar ea , ce nt ra l B ri ti sh C ol um bi a S am pl eI D C hu rc h- v1 8 S9 1- 9 SQ -S O S9 1- 4 SQ -1 13 S9 1- 1A S9 1- 3 S9 1- 10 C hu rc h- i4 D A 48 -1 3 x ll -l b x4 -4 Sy en - A m yg da R oc k N am e B as al t N ad in a di ke D ia ba se di ke A nd es ite A nd es ite m on zo ni te R hy ol ite G ra ni te G ra ni te lo id al di ke M ic ro di or ite A nd es ite L oc at io n Po pl ar N ad in a M t. W re tc h E. R id ge of R id di ch N . E qu ity N E qu ity N ad in a M t. E qu ity m in e C ol e L ak e Ja ck ve in N . se gm en t B ut te s C re ek O w en L ak e C re ek of N o. 3 ve in w t% S i0 2 44 00 49 .6 4 55 .2 0 57 .2 6 60 .3 9 61 .3 8 72 .1 1 68 .0 3 67 .0 0 56 .0 5 57 .0 5 57 .8 6 T i0 2 30 1 1. 27 1. 24 1. 08 1. 06 0. 95 0. 36 0. 50 0. 67 0. 70 0. 69 0. 65 A 12 03 15 .1 1 15 .1 5 15 .5 9 15 .7 3 15 .4 0 15 .3 8 13 .7 8 14 .2 0 16 .2 0 15 .1 4 15 .7 7 15 .6 1 Fe 2O 3 5. 11 3. 34 3. 45 6. 57 4. 73 3. 57 1. 21 1. 04 2. 18 2. 13 2. 73 3. 09 Fe O 7. 90 5. 64 4. 33 0. 99 1. 26 1. 57 0. 52 1. 87 1. 58 2. 86 3. 77 2. 89 M nO 0. 18 0. 31 0. 12 0. 14 0. 11 0. 06 0. 05 0. 08 0. 04 0. 09 0. 22 0. 34 M gO 8. 62 7. 81 4. 85 2. 62 3. 15 2. 11 0. 65 1. 76 1. 30 2. 72 4. 18 2. 94 C aO 9. 86 6. 58 6. 65 5. 31 4. 20 4. 11 1. 27 2. 45 3. 30 4. 15 5. 78 6. 07 N a2 0 4. 48 2. 96 3. 38 3. 71 4. 26 3. 96 4. 15 3. 75 4. 32 2. 53 3. 76 3. 65 K 20 1. 73 1. 53 1. 94 3. 29 3. 16 3. 21 4. 41 4. 68 3. 69 3. 39 2. 97 3. 09 P 20 5 0. 58 0. 56 0. 59 0. 63 0. 67 0. 49 0. 09 0. 22 0. 28 0. 29 0. 42 0. 38 H 2O 3. 63 1. 95 0. 35 0. 35 0. 35 0. 60 0. 25 0. 25 1. 69 0. 91 0. 97 C O 2 0. 01 2. 88 1. 89 2. 03 0. 90 1. 36 0. 48 0. 36 0. 08 1. 25 2. 03 L O l 9. 33 T O T A L 10 4. 22 99 .6 2 99 .5 8 99 .7 1 99 .6 4 98 .7 5 99 .3 3 99 .1 9 10 2. 33 99 .3 8 99 .5 0 99 .5 7 pp m S 30 86 5 33 Zr 18 4. 40 21 3. 90 24 3. 34 22 4. 29 30 5. 64 29 4. 32 22 0. 68 17 9. 31 16 6. 44 19 1, 07 Y 26 .4 7 20 .8 0 27 .7 4 29 .1 9 25 .7 1 26 .5 1 32 .6 9 12 .8 4 30 .7 5 27 .9 5 R b 99 .1 0 54 .1 7 10 0. 61 79 .5 4 92 .0 2 13 7. 16 20 1. 25 12 2. 20 92 .0 4 10 0. 28 Sr 73 3. 87 92 2. 48 11 87 .5 7 11 48 .2 4 90 1. 97 31 3. 80 42 3. 86 40 9. 23 63 0. 05 59 2. 72 A ge (M a) * 21 .4 50 .4 48 .8 48 .7 57 .2 51 .3 78 .7 78 .3 * K -A r da ti ng ag e w it h ab ou t 2 M a er ro r on av er ag e. X LC 2 9 /0 9 /9 5 T ab le 5- 2. L it ho ch em ic al d at a of va ri ou s ty pe s of ro ck at O w en L ak e ar ea , ce nt ra l B ri ti sh C ol um bi a (C on ti nu ou s) Sa m pl e ID xl O -6 xl O -6 D D A 63 -1 S Q -1 19 x5 -6 x2 -5 x 3 3 x3 -6 x3 -7 SQ -7 7 S9 1- 15 R oc k N am e M ic ro di or it e M ic ro di or ite M ic ro di or it e A nd es ite A nd es ite A nd es ite A nd es ite A nd es ite A nd es ite A sh tu ft’ po rp hy ry L oc at io n C . se gm en t C . se gm en t Sw itc h B ac k N . O w en So ut h se gm en t N . se gm en t N . se gm en t N . se gm en t N . se gm en t SW C ol e hi ll D uc k L ak e of N o. 3 ve in of N o. 3 ve in ve in L ak e of N o. 3 ve in of N o. 3 ve in of N o. 3 ve in of N o. 3 ve in of N o. 3 ve in w t% Si O 2 61 .2 5 59 .0 0 57 .9 9 56 .0 5 56 .5 8 57 .2 9 57 .7 5 57 .2 0 57 .9 7 61 .1 6 63 .2 2 T i0 2 0. 58 0. 59 0. 71 0. 80 0. 67 0. 66 0. 66 0. 66 0. 65 0. 61 0. 55 A 12 03 15 .1 1 15 .9 8 16 .5 3 16 .0 9 16 .0 4 15 .7 0 15 .8 5 16 .0 3 15 .8 7 15 .5 3 14 .8 1 F e2 03 2. 30 2. 52 2. 22 4. 45 2. 36 3. 08 3. 02 3. 12 2. 86 1. 07 3. 00 F eO 2. 86 2. 85 3. 76 1. 74 3. 38 2. 92 2. 86 2. 70 3. 05 4. 76 1. 82 M nO 0. 14 0. 18 0. 16 0. 13 0. 22 0. 25 0. 31 0. 23 0, 20 0. 15 0. 12 M gO 2. 78 2. 18 2. 63 2. 78 2. 50 3. 33 2. 87 2. 61 2. 64 2. 71 3. 40 C aO 4. 92 5. 16 6. 25 7. 45 5. 11 5. 67 5. 75 5. 97 5. 66 5. 29 3. 03 N a2 0 3. 93 3. 63 3. 43 3. 22 3. 05 3. 39 3. 96 3. 55 4. 09 3. 81 4. 20 K 2 0 3. 14 3. 09 3. 16 1. 80 3. 19 3. 15 3. 02 3. 04 2. 92 2. 61 2. 62 P 20 5 0. 26 0. 34 0. 43 0. 27 0. 28 0. 37 0. 39 0. 40 0. 38 0. 33 0. 28 H 2 0 1. 39 1. 22 0. 93 2. 35 2. 16 1. 04 1. 14 2. 18 1. 27 C 0 2 1. 85 2. 40 1. 34 2. 93 4. 35 2. 75 1. 92 2. 34 2. 14 L O l 1. 32 2. 45 T O T A L 10 0. 51 99 .1 4 99 .5 4 10 0. 06 99 .8 9 99 .6 0 99 .5 0 10 0. 03 99 .7 0 99 .3 5 99 .5 0 pp m S 12 7 15 3. 00 12 2. 00 21 71 1 31 18 0 16 0 18 0 44 5 Z r 17 2. 67 16 9. 80 15 8, 38 12 4. 27 16 8. 02 17 8. 64 18 5. 22 18 8. 35 19 2. 04 14 0. 62 12 6. 03 Y 24 .2 9 24 .8 9 25 .7 5 18 .0 2 29 .6 5 33 .0 5 31 .9 1 28 .4 9 30 .3 6 24 .5 8 18 .3 6 R b 11 9. 76 11 8. 77 92 .6 5 77 ,9 4 10 8. 22 12 1. 40 10 3. 70 12 2. 52 10 8. 45 75 .7 4 77 .1 3 Sr 62 0. 61 47 2. 32 60 8. 28 58 7. 77 10 71 .4 4 57 3. 45 59 7. 08 56 6. 67 60 7. 36 52 4. 71 56 2. 36 A ge (M a) * 4.5. Veins: Character and Correlation Mineralization on the property is mainly restricted to 0.1 to 2 m thick quartz carbonate-barite-specular hematite veins that contain disseminated to locally massive pyrite, sphalerite, galena, chalcopyrite, tennantite and argentian tetrahedrite. Locally, in chalcopyrite-rich samples, there is a diverse suite ofCu-Pb-Bi-Ag sulfosalts such as aikinite, matildite (in myrmekitic intergrowth with galena), pearcite-arsenopolybasite, and possibly schirmerite (Hood, 1991). Berryite (Harris and Owens, 1973), guettardite and meneghinite (Weir, 1973), boulangerite (Marsden, 1985) and seligmannite and pyrargyrite (Bernstein, 1987) have also been reported but not yet confirmed. All the Au and much of the Ag are in the form of 60-70 fine electrum, as grains generally less than 50 microns in diameter and hosted in galena that is associated with fine grained pyrite (Hood, 1991). Paragenetically, the mineralization is divided into four distinct stages: Stage I is characterized by fine grained pyrite, quartz and hematite in the central segment of the No. 3 vein. Barite, svanbergite, and binsdalite become abundant towards the south end of the No. 3 vein, with marcasite more abundant towards the north. Stage II is dominated by the presence ofmassive sphalerite and layered carbonate (calcite in the south, manganoan carbonates in the north). Stage III, however, is more complex. Mineralization consists of chalcopyrite, galena, fahlores (tetrahedrite-tennantite), electrum, quartz and sulfosalts. Included in the sulfosalt assemblage are the unusual Pb-Bi-Cu-Ag species berryite, matildite, gustavite and aikinite. Stage IV is volumetrically minor and is dominated by fine grained quartz, pyrobitumen and calcite (Hood, 1991) The veins cut the amygdaloidal, fine-grained plagioclase-rich dikes (Unit 6), and are cut by the series of dikes with bladed plagioclase crystals (Unit 7). Both these dike types are possibly correlative with the Ootsa Lake Group Goosiy Lake volcanics of 96 Eocene (approximately 50 Ma) age, although chemically the amygdaloidal dikes appear older. The bladed feldspar porphyry dikes cut the amygdaloidal dikes, and both are cut by the diabase dikes that may correlate with Endako Group volcanism ofEocene-Oligocene (approximately 40 to 30 Ma) age. The major veins are concentrated into two main areas on the property centered on the Mine Hill and Cole Lake areas, with an apparently less mineralized area between in which only the George Lake vein has been found to date. However, this intervening area is heavily covered by overburden and more veins may remain to be discovered here (the relatively minor Jack and Axel veins, not shown on Figure 4-2, are located west of the George Lake vein). The most important known vein on the property, both in terms of length and tonnage potential, is the No. 3 which outcrops for over 1000 m on Mine Hill. Its extension to the north appears to taper and die out, but significant potential may exist on faulted extensions to the south where exploration has been hampered by heavy overburden cover. South ofRiddeck Creek post-mineralization volcanic cover may preclude further exploration. The predominant strike direction for the main veins is northwesterly, with moderate to steep northeasterly dips. The relatively minor Church, Chisholm and Owl veins also have the dominant northwesterly trend. However, strikes in the Cole Lake, Camp, No. 5 and Switchback vein areas are more variable (see structural analysis below). Dikes and faults on the property have orientations similar to those of the veins, although one major difference is the presence of gently west-dipping dikes; no veins of this orientation are seen. The veins are highly variable in character, ranging from simple massive or banded gangue-rich veins with well-defined walls through irregular massive sulfide veins to ill defined stockwork zones. Note how the No. 3 vein divides into two in its upper part; further division into several sub-parallel thin veins or stringers is common, making correlation difficult even between closely spaced drill holes. In places, the vein pinches 97 out, with the zone of pinching (which correlates with flattening of the vein) raking moderately east in the plane of the vein. Post-mineral shearing is common along the veins, further complicating correlations by attenuating or removing (faulting out) the mineralized section. A strong bleaching alteration envelope (quartz-sericite/kaolinite-carbonate-pyrite alteration) generally accompanies the veining. True thickness of the mineralized structure is also an aid to correlation if the total thickness (e.g. of all the vein strands) is compared from hole to hole. However, the strong lateral and vertical variations make this a less useful tool over longer distances between sections. In general, the tenor ofmineralization, as measured by assay composites, is the most reliable correlation tool. Although the assays are necessarily a reflection ofvein mineralogy, and mineralogy is useful for correlation, the silver and gold values that have proved to be the most important correlations, cannot be seen visually. Correlation is made more difficult by the presence of one or more hangingwall or footwall veins that are found discontinuously along the length of the major vein structures. The presence of these subsidiary structures has been well established during underground development for exploration of the No. 3 vein; however, in drill core it is difficult to be sure if a given intersection is of a hanging/footwall structure or an en echelon shift of the main vein. In fact, some of the ‘hangingwall’ and ‘footwalP veins are probably en echelon portions of the No. 3 vein; in other places they may be splays off the No. 3 vein (Fig. 4-2). One of the most difficult problems in making correlations is the en echelon character ofmany of the veins, both along strike and down dip. Resolution of this problem is important because of the implications it has for physical continuity of the vein, and consequently, for tonnage and grade estimations. For example, intersections ofveins in the No. 3 vein, George Lake, Camp and Cole Lake areas can be interpreted either as simple tabular bodies or as en echelon lenses (see sections in Fig. 4-5 to 4-9); there may be no vein, or an attenuated vein, in the locations predicted by the simple tabular model. 98 Potential problems are: (1) an increased, non-quantifiable error in tonnage estimation, and (2) disregard for possible different grade character of two en echelon vein segments. 4.6. Structures and the Interpretations The structure of the Silver Queen mine area is dominated by a gently west to northwest-dipping homocline. There is no folding apparent at the scale mapped; the sequence appears to have been tilted 200 to 300 from the horizontal by block faulting. The average bedding plane is 032/25°NW and the most prominent joint set dips steeply, roughly perpendicular to the bedding at 057/77°SE (Leitch et al., 1991). Two prominent sets of faults displace this homoclinal sequence, cutting it into a series of fault panels: a northwest-trending (NW) set and a northeast-trending (NE) set (Fig. 4-2). The former predates or is contemporaneous with mineralization, whereas the latter is mainly post-mineral (a few veins trend east-northeast). The NW faults dip 60° to 80° to the northeast (average 315/75°NE), and the ‘cross’ or NE set appears to be subvertical (070/90°). There are subsidiary trends indicated at 295/85°NE and 085/90°, and a few flat-dipping faults possibly roughly parallel to bedding planes. Most of the mineralized veins and the dikes follow the northwest faults, and in places veins are cut off and displaced by the northeast set. The sense of motion on the northwest faults is such that each successive panel to the east is upthrown, leading to successively deeper levels of exposure to the east. Thus, in the panel between the George Lake and the Emil Lake faults (Fig. 4-2), there is considerably more of the lower fragmental rocks (Unit 2 and Unit 3) exposed than in the next panel to the west, between the Owen Lake and the George Lake faults. There does not seem to be much displacement across the No. 3 vein fault; slickensides seen underground on this structure suggest a reverse sense of last movement with indeterminable horizontal component. 99 2500 2400 C C 0 2300 2200 2100 2000 Figure 4-5. Cross-section of Camp vein shows gently dipping dike approximately perpendicular to the steeply dipping vein system. Horizontal scale equals vertical scale. Numbers represent the geological units which are defined in Table 4-1. Thick solid line - vein, thin solid line - geological contact, ripple line - fault, dash line - drill, circle - drill site. SW 2600 0 0 wz 00 00 OC C., 1% q \O NE //b 100 2600 2500 2400 z 0 > w 2300 -J Ui 2200 2100 Figure 4-6. Cross-section of the southern segment of the No. 3 vein at 21000 E cBU-1 16) to show branching and en echelon character of the vein. Horizontal scale equals vertical scale. Numbers represent the geological units which are defined in Table 4-1. Thick solid line - vein, thin solid line - geological contact, dash line - drill, circle - drill site. 5 EEJUT2.8U116 5 4 101 3000 22500N SW 2900 2800 - 2700 2600 2500 2400 2300 2200 200 Figure 4-7. Cross-section of the southern segment of the No. 3 vein at 20,000 E (S-88-3 1) shows branching and en echelon character of the vein. Horizontal scale equals vertical scale. Numbers represent the geological units which are defined in Table 4-1. Thick solid line - vein, thin solid line - geological contact, dash line - drill, circle - drill site. 2 NE 2 44 b. i 3 U88-06 I 4 U88-075 102 N E z 0 > Ui -J Ui SW 3 2 0 0 3 1 0 0 3 0 0 0 2 9 0 0 2 8 0 0 2 0 0 Fi gu re 4- 8. C ro ss -s ec tio n of C ol e ve in sh ow s ge nt ly di pp in g di ke of un it 6 cu tb y la te r di ke s of U ni ts 7 an d U ni t 8. H or iz on ta l sc al e eq ua ls ve rt ic al sc al e. N um be rs re pr es en tt he ge ol og ic al un its w hi ch ar e de fi ne d in T ab le 4- 1. T hi ck so lid lin e - ve in , th in so lid lin e - ge ol og ic al co nt ac t, da sh lin e - dr ill , ci rc le - dr ill si te . C 0z 0 I > LU -J LU SW Figure 4-9. Cross-section of George vein at the 2600 foot level of the Bulkley cross-cu t, with the available intersections interpreted as part of an en echelon system. Horizontal scale equals vertical scale. Numbers represent the geological units which are defined in Table 4-1. Thick solid line - vein, thin solid line - geological contact, dash line - drill, cir cle — drill site. NE 4 4 2900 2800 2700 2600 2500 2400 2600 Lev& X-Cut 4 4 104 The sense of motion on the northeast faults appears to be south side down, with a small component of sinistral shear. Offsets of No. 1 and 2 veins across the fault along Wrinch Creek (Fig. 4-2) suggest a few m of left-lateral displacement, but the displacement of an amygdaloidal dike near the portals of the 2880 level suggests the south side must have dropped as well. The boundaries of this fault zone, and its dip, are not well constrained; in outcrops in Wrinch Creek, it appears as a vaguely defmed zone up to 10 m wide, with segments that have possible shallow southerly to moderate northerly dips. The Cole Creek fault is not well exposed at surface; a splay from it may cause the change in orientation of the No. 3 vein to the Ruby vein (Fig. 4-2). A considerable left-lateral offset of as much as 200 m is suggested by drill-hole intersections of the NG3 vein, which may be a faulted extension of the No. 3 vein south of the Cole Creek fault. Underground, this fault is exposed at the southernmost extent of drifting as a northeast-trending gouge zone 1 to 2 m thick. Other examples of minor northeast faults are seen underground. Most of the dikes show similar orientations to the veins (310-325160-85°NE), with the pre-mineral amygdaloidal dikes commonly found parallel and adjacent to the veins. Along the No. 3 vein, one such major dike causes significant dilution problems due to the incompetent nature of some of these soft, strongly clay-altered dikes near the veins. There is one major exception to this northwest trend: a prominent gently west- dipping (323/33°SW) set of Unit 6 (pre-mineralization amygdaloidal dikes) is well developed in both the No. 3 vein, Camp and Cole Lake areas (Fig. 4-5, 4-7, 4-8 and 4- 9). This gently-dipping set is roughly orthogonal to the main, steeply northeast dipping dikes and veins, and also roughly parallel to the general gentle westerly dip of the host stratigraphy. A similar orthogonal fracture pattern, with steeply dipping fractures better mineralized and with stronger alteration surrounding them than the gently dipping fractures, is also observed in outcrops in Wrinch Creek. 105 4.7. SUMMARY The sequence of rocks exposed in the Silver Queen mine area, mapped as Tip Top Hill Formation (Church, 1984) is petrographically and stratigraphically similar to the Kasalka Group as defined in the Tahtsa Lake area by Maclntyre (1985) and the Mount Cronin area by Maclntyre and Desjardins (1988). The section in all three areas comprises a sequence from a basal, reddish purple heterolithic conglomerate upwards through a sequence of fragmental volcanic rocks, to a widespread, partly intrusive porphyritic andesite, all intruded by a distinctive microdiorite. However, K-Ar dating suggests that the rocks in the Silver Queen mine area are ofLate Cretaceous age; both porphyritic andesite volcanics and microdiorite are about 78 Ma. This is younger than the Kasalka Group rocks in the type section near Tahtsa Lake, which give dates of 108 to 107 Ma near the base, and are cut by intrusions dated at 87 to 84 Ma (Maclntyre, 1985). These dates actually straddle the Early to Late Cretaceous boundary (Harland et al., 1989). Thus, there may be two episodes, with the later one as young as 78 Ma (Leitch et al., 1991). Possibly the magmatic front associated with mid- to Late Cretaceous volcanic activity took longer to arrive further inland (i.e. 65 kilometres in 30 Ma gives a rate of advance of 0.22 cm per year, comparable to the rate of 0.25 cm annually suggested by Godwin, 1975; cf. Armstrong, 1988 and Leitch, 1989). Mineralization in epithermal veins at the Silver Queen mine occurred after the time of deposition of the Late Cretaceous Kasalka Group and before the intrusion ofEarly Tertiary post-mineral dikes dated at about 50 Ma. Some of these dikes may correlate to the Goosly Lake trachyandesite volcanics (49 Ma) of the Ootsa Lake Group and syenomonzonite stocks (50 Ma) found at Equity Silver mine and Parrot Lakes (Church, 1973). Another dike is diabase (50 Ma), which also cuts the vein. It may correlate with the Buck Creek basaltic volcanics, dated at 48 Ma (Church, 1973). Although the main outcrop areas ofKasalka anclesite and microdiorite correlate with the main areas of mineralization, and a genetic link has been postulated between two (Church, 1970), the 106 Late Cretaceous Kasalka andesite and microdiorite must have preceded mineralization by at least 25 Ma. So far there is no evidence at Silver Queen that the Early Tertiary dikes have remobilized older mineralization. Recognition of the fact that significant mineralization at Equity and Silver Queen is Early Tertiary in age, but is found in regionally correlative Upper Cretaceous rocks has important implications for metallogeny of the area. Since no significant mineralization has been found to date in the Early Tertiary rocks, it may be postulated that the Upper Cretaceous rocks represent a regional metallotect for base- and precious-metal mineralization. More significantly, it is possible that only the older (Cretaceous) rocks were sufficiently structurally prepared for ore deposition during a period ofwidespread magmatism during the Early Tertiary (Leitch et al,, 1991). 107 Chapter 5. Hydrothermal Alteration at the Silver Queen mine: Field and Petrographic Characters 5.1. Introduction The aim of this chapter is to describe petrographically the various hydrothermal alteration types, the spatial zonation of alteration associated with precious- and base-metal veins in volcanic sequences and the paragenetic sequences of the alteration mineral assemblage at the Silver Queen mine. Hydrothermal alteration at the Silver Queen mine has been examined in a preliminarily way by other workers. Most of the previous work focused mainly on the alteration types and only briefly discussed the spatial zonation of alteration. Fyles (1984) stated that clay with or without sericite is common at the Silver Queen mine, the principal clay mineral is kaolinite and the principal carbonate is siderite. Bernstein (1987) reported that alteration envelopes associated with Zn-Pb-Cu-Au-Ag sulfide-rich veins at the Silver Queen mine are characterized by silicification and argillic alteration. Church and Pettipas (1990) noted that the veins at the Silver Queen mine are commonly in an argillic envelope within a broader aureole of propylitic alteration. Cheng et al. (1991) presented field descriptions and a preliminary petrographic study of the hydrothermal alteration envelopes. Emphasis in the present chapter is given to the qualitative identification of the alteration mineral assemblages, their spatial zonation in the wall rock, specifically andesite (Unit 4) and microdiorite (Unit 5) of the vein and their paragenetic sequences. Results are based on 20 km2 field mapping, drill core logging, 72 whole rock sampling, 140 thin section examination and X-ray diffraction analysis. These investigations have defined a specific succession of related alteration and mineralization events at the Silver Queen mine and contribute to the development of a genetic model for this type ofmineralization system. 108 5.2. Petrography ofHydrothermal Alteration Types Six types of hydrothermal alteration have been recognized at the Silver Queen mine, viz. (i) propylitization, (ii) carbonatization, (iii) sericitization, (iv) argillization, (v) silicification and (vi) pyritization. They are fhrther classified into three zones on which carbonatization is superimposed to various degrees: propylitic alteration halo, sericitic argillic alteration outer envelope, and silicic-pyritic alteration inner envelope. Detailed descriptions of these hydrothermal alteration types at the Silver Queen mine are given below. Propylitic alteration is typically a weak alteration (Cheng, et al., 1991). Propylitically altered andesite is black or dark green in color, dense and hard. A strong magnetic character that can be tested easily in the field with a hand magnet indicates the presence of relatively abundant magnetite. The propylitically altered andesite is typical of those with porphyritic texture. A common mineral assemblage for the propylitically altered andesite is: aphanitic groundmass (about 40%), plagioclase (3 5-40%), clinopyroxene (0-6%), hornblende (0- 4%), biotite (0-2%), epidote (0-4%), chlorite (4-8%), carbonates (1-15%), sericite (1- 8%), and accessory magnetite and ilmenite (about 5%) and apatite and zircon (trace). Of these, plagioclase, biotite, augite and hornblende are replaced by epidote, chlorite, carbonate and sericite to various degrees. Pseudomorphs of epidote, chlorite and carbonate after clinopyroxene and hornblende are commonly well preserved. The remaining minerals are not obviously affected by hydrothermal alteration (Figure 5-1). Propylitically altered microdiorite has features roughly equivalent to those of propylitically altered andesite, except that it is paler in color and ofgranular or porphyroid texture. A common mineral assemblage for the propylitically altered microdiorite is: unidentified fine grain minerals (about 10%), plagioclase (25-35%), augite (0-6%), hornblende (0-4%), K-feldspar (about 10%), quartz (about 10%), epidote (0-2%), chlorite 109 Figure 5-1. Photomicrograph (crossed nicols) of propylitically altered andesite with superimposed carbonatization (SQ-44: surface outcrop sample from the southern segment of the No. 3 vein). Plagioclase (P1) phenocrysts are partially replaced by sericite (Ser) and carbonate (Carb). Augite phenocrysts are completely replaced by epidote (Ep), chlorite (Chi), carbonate and magnetite (mt). I •“ $- *I$ fr 4W I - r.. ‘— ‘--: i V - 0.2 mm roui d -n j S S C).2 mm 110 (3-10%), carbonate (5-15%), sericite (2-8%), and accessory magnetite and ilmenite (about 5%) and apatite and zircon (trace). The grain sizes of plagioclase, augite and hornblende are relatively coarser. They are commonly replaced by: epidote, chlorite, carbonate and sericite to various degrees (Figure 5-2). Sericitic-argillic alteration commonly appears as a bleached outer envelope around a vein. This type of alteration is called as ‘moderate’ and is more intense than propylitic alteration. Microdiorite and andesite having this type of alteration are softer and paler than their propylitic alteration equivalent. Magnetite is altered to hematite or pyrite. Biotite is unstable in this type of alteration and is progressively replaced by muscovite. Pseudomorphs of primary minerals, especially plagioclase, are remarkably well preserved. Recrystallization, especially of quartz, is obvious in the groundmass. Sericite, kaolinite and carbonates are the major dominant mineral phases and are commonly present with very fine grain size (Figure 5-3). An approximate mode of this type of altered rock is: unidentified fine grain minerals (about 25%), sericite (16-42%), kaolinite (0-28%), quartz (15-20), hematite (2-6%), pyrite (0-5%), siderite and dolomite (4-10%) as well as trace amount of apatite, rutile and zircon. Silicic and pyritic alteration is the most intense alteration type at the Silver Queen mine in terms of the variations ofmineral composition and rock texture. It can develop particularly intensely altered zones of hard, pale apple green rock where fresh and orange-yellow on weathered surfaces. No magnetite is present. A distinctive feature of this type of alteration zone is that pseudomorphs of primary minerals are not preserved as well as they are in sericitic and argillic alteration zones. The texture of the silicification and pyritization alteration zone is mosaic or polygonal (Figure 5-4). The rock is characterized by having a simple mineral assemblage. For example, unidentified fine grain minerals (about 20%), quartz (26-30%), sericite (10-28%), kaolinite (0-24%), carbonates (10- 15%) and pyrite (10-15%) as well as trace amount of apatite, rutile and zircon. 111 Figure 5-2. Photomicrograph (crossed nicols) of propylitically altered microdiorite with superimposed intense carbonatization (SQ-85: surface outcrop sample from the Cole lake segment). Note rock has an unequal-granular texture. Pseudomorph of carbonate after augite and some plagioclase (P1) crystals partially replaced by carbonate (carb) and sericite (ser) are relatively coarse grained. Compare to Figure 5-1. Primary augite phenocryst is completely replaced by carbonate instead of by epidote, chlorite and carbonate. • 4- k I 0.5 mm 112 Figure 5-3. Photomicrograph (crossed nicols) of sericitized-argillized andesite (X5-3: underground sample from the southern segment of the No. 3 vein). Note pseudomorph of sericite (Ser), kaolinite (Kao) and quartz (Qtz) after plagioclase; pseudomorph of sericite and carbonate (Carb) after mafic phenocryst. 0.2 mm Ser— Kao CO LI fl d mass Qtz Cia LI n d rn ass 113 Figure 5-4. Photomicrograph (crossed nicols) of silicified-pyritized microdiorite (X5-1O: underground sample from the southern segment of the No. 3 vein). Note the replacement of sericite (Ser) by abundant quartz (Qtz) and the formation of abundant pyrite (Py). The pseudomorph of sericite and kaolinite (Kao) after plagioclase is not preserved as well as those in the outer sericitic-argillic alteration envelope. 0.2 mm 114 Carbonatization superposed on propylitically altered rock is characterized by the further replacements of epidote, chlorite and plagioclase by carbonates. Where the rock is intensively carbonatized, epidote and chlorite are completely replaced by carbonates which become pervasive in the rock (Figure 5-2). Of the carbonates calcite is an abundant species characterized by reacting with diluted acid fiercely. Carbonatization is also observed in the visible alteration envelope (sericitic and argillic alteration, and silicification and pyritization envelope as described below) as replacements of calcite and chlorite by Fe- and Mg-carbonates such as siderite and dolomite. 5.3. The Spatial Distribution ofHydrothermal Alteration In general, the zonation of hydrothermally altered rocks in the Silver Queen mine district consists of a broad propylitic alteration halo which gives way as the polymetallic vein is approached to a broad bleached outer sericitic-argillic alteration envelope, which in turn gradates into a narrow inner silicic-pyritic alteration envelope (Figure 5-5). All rocks within the study area, that are older than mineralization, have affected some degree of propylitic alteration. That is, an early stage of propylitic alteration appears to be regional in extent (>20 km2). The least propylitized andesite and microdiorite are characterized by only slight alteration of plagioclase by sericite and partial replacement of mafic minerals (clinopyroxene and hornblende) by epidote and chlorite with very minor carbonate. A propylitically altered rock with superimposed carbonatization has been recognized at the Silver Queen mine through the examination of a total of 140 thin sections from various successive profiles cross-cutting the No. 3 vein throughout its length and rock samples altered to various degrees from different parts of the Owen Lake area. The spatial distribution of propylitically altered rocks with superimposed carbonatization is controlled by a complicated structure system, rather than by being restricted to the vein and associated mineralized structures. Samples collected a few hundred metres away from a vein commonly have intense propylitic alteration with superimposed carbonatization, 115 1 8 0 0 0 E 1 9 0 0 0 E 2 0 0 0 0 E 2 1 0 0 0 E 12 6 °4 4 - - - I I I o + + + + + + \ 4- -I- + . + + + + -I- — ‘ ‘ , , / ‘ / , / / / / , / / / / / / / / / / + + + + + + + \ + + + -J -- + + + + + 0 + + + + + + + + + + + + + - 2 + + + + + ÷ + + + + + + + + + + + + + + + + + + + + + + 4- + + + + P ro p y li ti c a n d e si te + + + + + + \ + + ÷ . + + — + ÷ ÷ + + \ ÷ P ro p y li ti c m ic ro d io ri te ÷ ÷ + + \ + ÷ + — + + \ + \ + ÷ ÷ ÷ + + + + \ + P y ro c la st ic ro c k Z + + + \ + + \ + + S — , , / , , / / / / / + + / + G ra d a ti o n a l c o n ta c t + + ‘- f\ + + 4- + + (5 ) + + - 4- + ‘ + + — + + + + + \ + .. . + S h a rp c o n ta c t + + + + + + - “ ‘ I , , + + + + + + ‘ ‘ I , , + + + + + + \— v ei n (N o rt h er n 4 - + • / + + \ / \ + ‘ \ + \÷ + + + + ( I S il ic ic /p y ri ti c in n e r - / / / / ‘ + + _ — - ÷ i ÷ + - + + + [ j a lt e ra ti o n en v el o p e / / “ / / + -4 + ÷ ‘ - + + + C • . _ / / / / / / / _ _ _ _ / . - 4- + + + + + N - ÷ ± U n d e rg ro u n d w o rk in g + + + + \+ + “ + + + / / , ‘ i , •1- + + + \ + + + + 4- + + ÷ 4- + ‘ 7 7 7 9 9 9 •+ + + \÷ \ 7 7 7 7 9 7 V , V V 7 7 7 7 V / 7 7 7 7 7 7 V V .’ V V 9 V V 7 7 ‘7 , , , , , , , , , , , , i i i , , , , , V 9 9 V V 7 V 7 _ / / / / / / / / / / / / / / / / / / / , •• •. z •• • / / / / / / / / / / / / / / / / / / / 1 / S Z V ‘7 9 ‘7 ‘7 V ‘7 7 9 — -. - , . r) 7 7 7 V v - c’ i / / / / / / / / / / / / / / / / / / / / / / / / A . m _ - N -. ,k ? < 4 \, 8 // /V V / I \ I / / / / / / / / / / / / / / / / / / / / / / / / 7 / , - . - - Fi gu re 5- 5. Sc he m at ic pl an of hy dr ot he rm al al te ra tio n on th e 26 00 -f oo t le ve l, Si lv er Q ue en m in e (m od if ie d fr om C he ng Ct al ,, 19 91 ). similar to or even stronger than those collected only a few metres from the bleached alteration envelope around the vein. In contrast, there is a tendency for the intensity of carbonatization in propylitically altered rocks at the southern segment of the No. 3 vein to be stronger than that at the northern segment of the No. 3 vein (Figures 5-6 and 5-7). The bleached alteration envelope is characterized by having remarkable zonations both parallel and perpendicular to the vein. Three representative alteration profiles cross cutting the No. 3 vein at the 2600 foot level of the southern, the central, and the northern segments are illustrated in Figures 5-8a, 5-8b and 5-8c. In general, all alteration profiles have the following zonation parallel to the vein: (1) An outer sericitic and argillic alteration envelope commonly has a relative ‘sharp contact’ that grades from a bleached envelope into a dark colored propylitic wall rock within a few centimetres (Figure 5-9). (2) An inner silicification and pyritization envelope immediately adjacent to the vein has a gradational contact with the outer sericitic and argillic alteration envelope (Figure 5-10). Zonation of alteration envelopes perpendicular to the veins are also presented. In detail, the silicic and pyritic inner envelope is almost absent at the northern segment of the No. 3 vein. Also, the alteration envelope is more argillic at the northern segment compared with the southern segment of the No. 3 vein which has more sericite than kaolinite. Silicification and pyritization are more intense at both the central and southern segments than at the northern segment of the No. 3 vein. In addition, the width of the alteration envelope is narrower along the northern segment ofNo. 3 vein (total width about 7 m wide) than adjacent to the central and southern segments of the No. 3 vein (total width up to 130 m wide). Some alteration envelopes around veins are distributed asymmetrically. For example, the widths of the alteration envelopes at the northern and central cross-cuts of 117 Figure 5-6. Photomicrograph (crossed nicols) of least propylitically altered andesite in the northern segment of the No. 3 vein (X3-7: underground sample from the northern segment of the No. 3 vein). Note primary phenocrysts (augite and plagioclase) are slightly altered along their margin and cleavages. Aug - augite; P1 - plagioclase, Mt - magnetite. - :\ ;;:;: F ‘ 118 -4 Figure 5-7. Photomicrograph (crossed nicols) of propylitically altered andesite with superimposed carbonatization in the southern segment of the No. 3 vein (SQ-44: surface outcrop sample from the southern segment fo the No. 3 vein). Note pseudomorph of chlorite (Chi) and carbonate (carb) after augite, partial replacement of plagioclase (P1) by carbonate and sericite (ser). Ap - apatite Crossed nicols. I. 0.2 mm C ra u n d rn ass GroUnd in ass C roUnd in ass 119 Tabel 5-la. Estimated modes of alteration minerals in hydrother mally altered wall rock at the northern segment of the No. 3 vein, Silver Queen mine, central British Colu mbia Mode Propylitically altered andesite S ericitic and argillic alteration envelope (Volume %) with superimposed carbonatization Distance(m) 10 9 8 7 6 5 4 3 2 1 0.5 0 unknown* 40 40 40 40 40 25 25 25 25 25 20 20 augite&Hb 7 9 10 7 5 0 0 0 0 0 0 0 Epidote 1 2 2 1 0 0 0 0 0 0 0 0 Chlorite 5 4 2 7 7 0 0 0 0 0 0 0 Carbonate 4 3 1 3 6 4 4 4 4 5 5 6 Magnetite 5 5 5 4 4 0 0 0 0 0 0 0 Pyrite 0 0 0 0 0 4 4 3’ 3 3 4 5 feldspar 35 36 39 35 35 0 0 0 0 0 0 0 Muscovite 3 1 1 3 3 27 27 22 22 18 18 16 Kaolinite 0 0 0 0 0 25 2 5- 26 26 27 28 28 Quartz 0 0 0 0 0 15 15 20 20 22 25 25 Total 100 100 100 100 100 100 100 100 100 100 100 100 Figure 5-8a. Estimated mode of alteration minerals in hydrothermal alterati on profile at northern segment of the No. 3 vein at the Silver Queen mine. Unknown - unidentifiab le material including groundmass and extremely fme-grain mineral aggregates. 100 90 80 70 60 - 50 40 30 20 10 0 i:i Quartz I Kaolinite Muscovite till Feldspar Magnetite Caibonate Chloiite / Epidote P3’X & Fib D unknown Distance from the vei:(m) ________ ___ ________ ________ __ propylitic alteration halo . . .sencitic & argillic with superimposed alteration envelope carbonatization 120 C 0 ’ q CD CD C 0 g E C D i - z - 0 0 0 $ - - t < a 0 0 C D CD CD I4 ) L f CD H i q c o CD CD D CD o _ B .. C D 0 - - :: :: C D fl H CD - CD II ECD CD— CD 0. I r ! f 1 — ;. I N c cv -1 0 c,— CDCD t’ J . 0 . C 0 U C 0 tJ C L l -a t’3u 0 0 0 0 0 0 0 J1 V . _ ) ) C C C C C O O 00 CD C C 0 0 0 _ - ) C I — ‘ . ) CD c C C O O C C 0 C D 0 0 0 C C L ’ . 00 0 0 0 0 0 . C D l ( • ) CD — — 0 0 0 Q C C ‘ C, 0 0 . CD CD CD CD T 1 CD CD 0 C D (g 0 F ’ C p D CD C D C D In 0 CD CD 0 CD 0 E; . H CD CD rn I 0 CD 0 I M od e vo l. % — .) W U . C 0 0 C ’ C o c o c 0 0 0 0 0 0 ) C D — i . CD N N Q 0 O 0 CD 1 CD CD 0 = 0 t) 0 0 U ) 0 \ 00 . 0 U ) C ’ C ’ U ) 0 0 0 00 0 0 U ) C . 0 U ) 0 0 U ) 0 0 0 C ’ U ) U . U . 0 0 0 U . L ) U ) 0 CD “ CD U ) 0 U ) 0 if ru 0 0 U ) C U ) 0 0 0 0 U ) 0 U ) 0 0 0 J 0 0 0 0 0 0 J 0 0 0 0 0 0 J 0 0 0 C) I. 0 0 0 0 0 0 U ) C ’ C ’ 0 0 0 0 0 Figure 5-9. The relatively sharp contact between propylitic alteration and a bleached alteration envelope (Bulkley cross-cut, 2600 foot level underground working). 123 Figure 5-10. Outcrop of the southern segment of the No. 3 vein and its bleached alteration envelope. 124 the No. 3 vein are greater on the footwall than on the hanging-wall. At the cross cuts of the Jack and George veins the situation is reversed (Figure 5-5). These asymmetrical features can be explained by en echelon geometry of individual veins within mineralized zones (Leitch et a!., 1991). The reason for these is that the alteration envelope is developed around the structure zone centering the en echelon veins. Therefore, the alteration envelope may appear in different asymmetrical patterns depending upon where the cross-section cuts the upper or lower part of an individual vein (see Figure 5- 11). This explanation may help exploration for hydrothermal veins developed in en echelon structural patterns. 5.4. Paragenetic Sequence ofHydrothermal Alteration Propylitization, carbonatization, sericitization, argillization and silicification as well as pyritization, have all taken place in the host rock at the Silver Queen mine. Consistent, systematic sequences of alteration minerals and specific zoned distributions are observed in the host rocks. Many other textures and features in vein-wall-rock profiles strongly support the concept of a consistent sequence in the development of the hydrothermal mineral assemblages at the Silver Queen mine. The distribution of broad propylitic alteration halos suggests that this type of alteration is the product of regional, pre-mineralization hydrothermal activity. Carbonatization controlled by the complicated fracture system developed subsequent to regional propylitic alteration and was superimposed on the propylitically altered rocks. The distribution of bleached alteration envelopes around mineralized structures suggests that the bleached alteration envelopes developed subsequent to, and superimposed on, the broad propylitic alterations referred to above. A series of schematic profiles are constructed to illustrate the spatial distribution pattern and timing sequences of these alteration types (Figure 5-12). 125 SW N E L ev el I Le ve l II Fi gu re 5- 1 I Sc he m at ic pr of ile ill us tr at es th e as ym m et ri ca l re la tio ns hi p be tw ee n en ec he lo n ve in s an d hy dr ot he rm al al te ra tio n en ve lo pe s, Si lv er Q ue en m in e. SW NE Figure 5-12. A series of schematic profiles illustrate the spatial zonation and sequence of development of various types of alteration at Silver Queen mine. Propylitic alteration Stage I: A regional broad pre-mineralization propylitic alteration Ckrbonatization Stage H: Carbonatization superposed on the propylitically altered rocks is controlled by fractures Stage III: Bleached alteration envelopes (sericitic-argillic outer envelopes and silicic pyritic inner envelopes) VCIfl around the main vein (a NW mineralized fracture zone). 127 The general sequences of formation of alteration minerals has been established by the replacement relationship between mineral pairs. Microscopic observations indicate the following alteration sequences. Propylitically altered samples show that mafic minerals such as augite and hornblende and plagioclase are initially altered to epidote, chlorite, calcite and sericite along margins and cleavages (Figures 5-1, 5-2, 5-3, 5-6 and 5-7). These replacements are completed where propylitic alteration is intense with superimposed carbonatization; in such cases pseuclomorphs of carbonate, mainly calcite, after primary mafic mineral occur. Early epidote and chlorite are replaced by carbonate (Figure 5-2). Biotite, magnetite, apatite and zircon remain unchanged in the propylitic alteration halo. Quartz is not significantly changed in the propylitic alteration halo. In the bleached alteration envelope near the propylitic alteration halo, primary minerals are completely altered. In particular, plagioclase is completely replaced by sericite and kaolinite along with quartz. Clinopyroxene and hornblende are totally altered to carbonate. No epidote or chlorite pseudomorphs after primary minerals are present in the bleached alteration envelope. Therefore, it appears that epidote, chlorite and calcite pseudomorphs after primary mafic mineral, as well as biotite, are further altered to sericite and siderite. Magnetite is totally altered to hematite and pyrite. Apatite and zircon retain their euhedral forms. Quartz increases in the outer alteration envelope largely due to the decomposition of plagioclase (Figure 5-3). Silicification in the inner envelope is characterized by the progressive replacement of sericite by quartz; eventually sericite occurs as inclusions in pervasive quartz (up to about 30 wt%). Siderite and other carbonates are abundant (up to 10 wt%). Pyrite is disseminated and locally, densely disseminated (content up to about 15 wt%) in the inner alteration envelope. Recrystallization and silicification of the matrix are intense in the inner alteration envelope (Figure 5-4). 128 T ab le 5- 2. P ar ag en et ic S eq ue nc e of M in er al A ss em bl ag es , S il ve r Q ue en m in e, O w en L ak e A re a M in er al s M ag ne ti te /i lm en it e A pa ti te Z ir co n A ug it e H or nb le nd e P la gi oc la se K -f el ds pa r B io ti te Q ua rt z E pi do te C hl or it e C al ci te S id er it e/ do lo m it e K ao li ni te M us co vi te P yr it e H em at it e R ut il e S er ic it iz at io n N ot e: Th e so lid lin e an d its th ic kn es s re pr es en tt he fo rm at io n of a m in er al an d its se m iq ua nt ita tiv e ab un da nc e. Th e da sh lin e m ea ns th at th e m in er al s re m ai n st ab le at ce rt ai n al te ra tio n st ag es . Combining all the relationships described above leads to a general paragenetic sequence for the alteration around veins at the Silver Queen mine. This sequence is summarized and illustrated in Table 5-2. 5.5 Discussion and Conclusions Hydrothermal alteration patterns, similar to those described above, have been reported in many other deposits [e.g., Waite Amulet (Price and Bancroft, 1948), Creed and Summitville (Hayba Ct al., 1985), Sigma (Robert and Brown, 1984, 1986), Round Mountain (Sander and Einaudi, 1990), Erickson (Sketchley and Sinclair, 1991), Porgera Richards et al., 1991)1. In comparison with the alteration patterns reported by Robert and Brown (1984, 1986) and Sketchley and Sinclair (1991), the propylitic alteration with superimposed carbonatization at the Silver Queen mine shares many similar features with the cryptic alteration at Sigma mine and the carbonate envelope at Erickson mine in terms of alteration mineral assemblages and the mineral paragenetic sequence. For example, primary mafic minerals initially replaced by epidote and chlorite are subsequently replaced by carbonate. However, there are significant differences in the spatial distribution patterns between the propylitic alteration with superimposed carbonatization at the Silver Queen mine and the cryptic alteration reported at the Sigma mine. The width of the cryptic alteration zone is up to 2 m into the walls of the veins at the Sigma mine (Robert and Brown, 1984). The spatial distribution of propylitically altered rock with superimposed carbonatization at the Silver Queen mine is much more widespread than the Sigma example (Figure 5-5). Propylitic rocks with intense carbonatization have also been found at Goose Lake, about 10 kilometres southwest of the Silver Queen mine, but no vein mineralization was found nearby. In short, the distribution pattern of the propylitic alteration with superimposed carbonatization at the Silver Queen mine is a wide irregular halo, unlike a restricted envelope that locally parallels the veins. In contrast, the intensity 130 of carbonatization, more precisely the completeness of the replacement of epidote and chlorite by carbonate, is weak in the northern segment of the No. 3 vein and stronger to the south. In brief, the distribution pattern of propylitic alteration with superimposed carbonatization at the Silver Queen mine is likely controlled by a complicated fracture system rather than by the mineralized structure zone only. It is suggested that the propylitic alteration at the Silver Queen mine might be related to the hydrothermal activities that immediately followed the volcanic eruption and intrusion of the early Late Cretaceous Kasalka Group equivalent rocks. Carbonatization superimposed on the early propylitic alteration halo may be the product of a CO2 degassing process. This might be related to the hydrothermal activity associated with mineralization and controlled by a complicated fracture system. Even though the propylitic alteration with superimposed carbonatization at the Silver Queen mine is not an alteration envelope, the distribution pattern of propylitic alteration with superimposed carbonatization does indicate a broad CO2 degassing halo that may be used to delineate the hydrothermal alteration anomaly associated with mineralization. In summary, the following conclusions about hydrothermal alteration at the Silver Queen mine can be deduced based on observations above: (1) Regional propylitic alteration is characterized by replacement ofmainly primary mafic minerals initially by epidote and chlorite as well as minor amount of carbonate and the partial replacement of plagioclase replaced by carbonate and sericite. This type of alteration is interpreted to be the product of hydrothermal activity followed by the initial stage ofvolcanism, which predates the mineralization. (2) Carbonatization superimposed on the early propylitic alteration halo may be the product of a CO2 degassing process, which might be related to the hydrothermal activity associated with mineralization; it is controlled by a complicated fracture 131 system. With increasing intensity of superimposed carbonatization on propylitic alteration at Silver Queen, more complete replacement of epidote and chlorite by abundant carbonates occurs. (3) Hydrothermal activity associated with mineralization forms the outer alteration envelopes marked by complete replacement of plagioclase by sericite and kaolinite, chlorite by siderite and magnetite by pyrite or hematite. (4) Inner alteration envelopes are interpreted as maximum stage hydrothermal alteration superimposed on the sericitic and argillic outer alteration envelope; it is marked by the replacement of sericite by quartz and direct precipitation of quartz, sulfide and carbonate. The close association between mineralization and the inner silicification envelope indicates that the ore-forming metals are transported as Si, S and C complexes, and that the precipitation of quartz, sulfide and carbonate through reaction with wall rock and hydrothermal solution might trigger ore deposition. 132 Chapter 6. Quantitative Model of lEydrothermal Alteration, Silver Queen Mine, Central British Columbia 6.1 Introduction The Silver Queen mine is an ideal locality to study hydrothermal alteration for the following reasons: (1) The major types of the rocks that host the vein at the Silver Queen mine are andesite and diorite; these are typical wall rocks in many other ore deposits of similar type. (2) The petrographic and timing relations among various rock types and mineralization at the Silver Queen mine are well understood through contact relations, thin section study and isotopic dating. (3) The young ages and short interval between the formation ofwall rock and mineralization event (about 78 Ma for the wall rock and 50 Ma for mineralization, respectively) as well as the simple deformation history in the study area exclude the complexities caused by other processes superimposed, but unrelated to, deposit genesis. (4) The uniformity of composition of both the andesite flows and the microdiorite dome, the two host units for veins, is favorable in terms of having a single precursor. (5) Abundant trenches, drill cores and underground workings provide good access for the study of alteration and its spatial relationship to veins. Silver Queen mine, thus, provides an excellent opportunity to evaluate the quantitative effects of hydrothermal alteration spatially associated with precious- and base metal vein mineralization in volcanic sequences. This chapter discusses a quantitative evaluation of the hydrothermal alteration at the Silver Queen mine, Owen Lake area, central British Columbia by applying the approaches described in previous chapters. I specifically address: 133 (i) optimal sampling and sample preparation method, (ii) estimation of the precisions of lithogeochemical data, (iii) determination of immobile components, and the calculation of absolute losses and gains of chemical constituents during the hydrothermal alteration, (iv) interpretation of the lithogeochemical variations in terms ofmineral variations through the use ofPER diagrams, (v) calculation ofmetasomatic norms, (vi) calculation of the propagated errors for the quantitative evaluations of lithogeochemical data, and (vii) integration of the mineralogical variations corrected for closure with the absolute losses and gains of chemical components and the errors at specific confidence levels to provide a quantitative chemico-mineralogic model of hydrothermal alteration. 6.2 Sampling and Sample Preparation The collection and preparation of samples is an often overlooked aspect of data gathering that impacts strongly on the quantitative interpretation of losses/gains in hydrothermal systems. Many published papers related to lithogeochemistry do not document sampling and sample preparation methods in detail. For example, small chips collected from limited drill core may not be of sufficient size to represent the geological unit being sampled; a small sample may not be representative of coarse grained units. As shown in Chapter 3, the larger the sample mass and the finer the sample is ground, the more homogeneous and representative the sample can be made for subsampling. However, for economic reasons it is not desirable to collect too large a sample nor to grind a subsample finer than needed. In order to minimize the artificial sampling and sample preparation errors, equations 3-13 and 3-14 have been applied to samples used to study hydrothermal alteration at the Silver Queen mine. 134 Rock types in study area are massive and porphyritic volcanic flows and high level intrusive rocks. Therefore, the main sources of inhomogeneities at the sampling stage are: (i) the presence of phenocrysts such as plagioclase and augite, and (ii) accessory minerals such as rutile (rich in Ti02)and zircon (rich in Zr). The results of calculated optimal sample sizes based on equations in Chapter 3 are presented in Table 6-1. These calculations indicate that the optimal sample size depends on the coarseness of phenocrysts and inhomogeneities of the constituents of interest among the minerals. For instance, plagioclase and augite phenocrysts are the important minerals which determine the size of a field sample because they are the coarsest minerals (v (mm3)= 8 and 1.73 respectively); albite and enstatite, as end members of these two mineral series, are rich in Na20 and MgO relative to the rest of the rock (the values OfHNa2O and HM of these two end member mineral phases are 0.24 and 0.40 respectively, whereas the value ofLN2oand LMgO for the rest of rock are 0.00 and 0.01, respectively). Therefore, they are the biggest contributors to inhomogeneity of the sample, and nearly 500 grams of sample is needed to reduce the sampling error to about one percent at the 68% confidence level. In contrast, another relatively coarse mineral, quartz (v (nun3)= 3.38), has a high value ofH502 ( 1) but also a high value ofL502(0.4) for the rest of the rock. This means that Si02 is distributed more homogeneously in the rock thanNa20orMgO. According to the calculation using equation 3-13 and by treating the rest ofbulk rock as the equivalent of ultramafic rock or mafic rock, only 15 grams of sample are necessary to provide an adequately homogeneous sample for analysis of Si02. Accessory minerals, such as apatite, may have a high value ofH (=1) and the rest part of rock has the low value of L ( 0), but commonly accessory minerals such as apatite have much finer grain size (e.g. 0.0005 mm3). So if the sample size is just a few grams the homogeneity ofP205 in the sample will be adequate. Therefore, 500 grams is considered the optimal sample size to provide adequate homogeneity for all components of the samples. This size results in a sampling error of less than or equal to 1% (RE) at the 68% confidence level. 135 Table 6-1. Estimation of Optimal Sample Size by Using Binomial Function Component Si02 TiO’, FeO MgO Na20 P205 Zr Mineral Quartz Rutile Pyrite Enstatite Albite Apatite Zircon v (nun3) 3.375 0.064 0.125 1.728 8.000 0.0005 0.0003 H 1.000 1.000 0.470 0.402 0.240 0.424 0.498 L 0.400 0.001 0.010 0.010 0.000 0.000 0.000 d(gIcm3) 2.648 4.245 5.011 3.210 2.620 3.180 4.669 dL (g/cm3) 2.87 2.87 2.87 2.87 2.87 2.87 2.87 Pw 0.150 0.005 0.050 0.050 0.300 0.005 0.0003 qw 0.850 0.995 0.950 0.950 0.700 0.995 0.9997 RE 0.01 0.01 0.01 0.01 0.01 0.01 0.01 (HdH-LdL)2 2.250 17.996 5.413 1.588 0.395 1.818 5.406 1p+Lq2 2.40x10’ 3.59x10 1.09x103 8.75x104 5.18x103 4.49x106 2,28x108 w (g) 15.0 376.2 60.2 466.7 475.5 3.2 38.9 Note: the notations used are defined in Chapter 3. The detailed descriptions of sampling strategy including: sampling locations, the length of the profile that sample represented, rock and alteration type, as well as sample size are listed in Appendix A. An example of sampling strategy along a typical profile is illustrated in Figure 6-1. The samples are collected continuously in the intensely altered zone adjacent to the vein, and discontinuously in the broad moderately and weakly altered zones away from the vein. Using equation 3-14, the optimal fineness of subsamples have been calculated and are listed in Table 6-2. This table shows various components, their principal minerals and 136 Q) ‘i i -d S am p le ID d c’ co co u) cc ) C O N C D O I I I I I I I I I I I I I I I I • Q 0 0 0 0 0 0 0 - — - 1 — ,— 1 — - r- .1 0 — I — - — > < > > ‘< < > M > >< >< < S am p le si te / f + + + G eo lo g ic al + + + + + + + + + + + + + + + + \ _ / + \ + + + + + + + \ - + + + f + + - + + + + + + p ro fi le o u te r en v el o p e in n er en v el o p e v e i n in n er en v el o p e o u te r en v el o p e m ic ro d io ri te se ri c it ic /a rg il ii c si li c ic /p y ri ti c N o 3 si li c ic /p y ri ti c se ri c it ic /a rg il li c p ro p y li ti c p ro p y li ti c se ri c it ic /a rg il li c L eg en d [\ v ei n [+ m ic ro d io ri te .1o u te r en v el o p e 0 5 10 m si li c ic /p y ri ti c D is c o n ti n o u s c o n ti n u o u s I in n e r en v el o p e V ch ip sa m p le I ch ip sa m p le F ig ur e 6- 1. A ty pi ca l sa m pl in g pr of ile ac ro ss th e al te ra tio n en ve lo pe in th e ce nt ra l se gm en t of th e N o. 3 ve in , Si lv er Q ue en m in e. Table 6.2. Estimated Optimal Fineness of Subsample by Using Binomial Function the proportional abundance of each component in the principal mineral (H) and the remainder of the rock (L), as well as the weight proportion of the mineral rich in the constituent of interest (P). These are the key factors in determination of the optimal fineness of a subsample. For instance, the fineness of passing through 80 mesh (i.e. the diameter of grain 177 microns) can provide adequate homogeneity of the major components: FeO, MgO andNa20. It gives a subsampling error of less than or equal to 1% (RE) at the 68% confidence level. In contrast, the homogeneities ofminor constituents Component Si02 TiO, FeO MgO Na20 P205 Zr Mineral Quartz Rutile Pyrite Enstatite Albite Apatite Zircon H 1.000 1.000 0.470 0.402 0.240 0.424 0.498 L 0.400 0.001 0.010 0.010 0.000 0.000 0.000 dH (g/cm3) 2.648 4.245 5.011 3.210 2.620 3.180 4.669 dL (g/cm3) 2.87 2.87 2.87 2.87 2.87 2.87 2.87 Pw 0.150 0.005 0.050 0.050 0.300 0.005 0.0003 qw 0.850 0.995 0.950 0.950 0.700 0.995 0.9997 RE 0.01 0.01 0.01 0.01 0.01 0.01 0.04 (HdH-LdL)2 2.250 17.996 5.413 1.588 0.395 1.818 5.406 (Hp+Lq)2 2.40x10 3.59x10 1.09x103 8.75x104 5.18x103 4.49x106 2.28x108 w (g) 4.00 4.00 4.00 4.00 4.00 4.00 4.00 v (mm3) 0.89765 0.00068 0.00831 0.01481 0.06730 0.00063 0.00041 d (micron) 964.65 87.96 202.54 245.58 406.77 85.81 74.37 Sieve Size (mesh) < 12 < 140 < 60 < 60 < 40 < 140 < 200 Note: Common sieve size Micron Conimon sieve size Micron 12 1680 80 177 20 841 140 105 40 420 200 74 60 250 400 37 138 such as Ti02 andP205 require the fineness ofmaterial to be subsampled to pass through 200 mesh (i.e. the diameter of the grains are 74 microns). This provides a subsampling error of less than 1% (RE) at the 68% confidence level. Zircon has the lowest concentration (about 0.0003 wt%) among the minerals listed in Table 6.2. It is the only common mineral containing Zr (i.e. L = 0), so even a subsample that has been ground to pass through 200 mesh will have a subsampling error four time larger than those of other constituents at the same confidence level. The detailed procedure of subsample preparation is documented below: (1) wash and saw off the mud, veinlets and weathering surface; (2) preserve hand specimen and select a block for thin section; (3) weigh the remaining sample (generally from 480 to 3000 grams); (4) crush sample to grains equal to, or less than, 4 mm by passing through ajaw crusher; (5) homogenize sample thoroughly on rag paper and randomly scoop out a 300 grams subsample; (6) grind this subsample in a swing mill to a particle size less than 75 microns; (7) check the fineness by randomly scooping out a portion of subsample and passing it through a nylon sieve (200 mesh); if not fine enough, randomly scoop out about 100 grams of sample and regrind it until all fines pass the check; and (8) clean the equipment to minimize carryover contamination. In summary, the procedure outlined above minimizes the effects of artificial error arising from improper sampling and sample preparation. It is of a special significance for the determination of immobile components of interest in this study. As indicated in Table 6.1., if the size of a field sample is less than 200 grams (equivalent of a sample from a half drill core with diameter of 4 cm and length of 12 cm), the sampling error for Ti02 could be doubled relative to the current sample size (equal to or greater than 500 g). Similarly, 139 if the weight of subsample is reduced from 4 gram to 2 gram, the subsampling error for Zr will increase by (i.e. from RE = 4% to RE 4%xl.414 = 5.7%). Consequently, the difficulty of recognizing and using these potentially immobile components corresponding would be increased significantly. 6.3. Errors in Lithogeochemical Data The lithogeochemical determinations of: Si02,Ti02,A1203,TotalFe203,MgO, MnO, CaO, Na20,K20,P205, S, Rb, Sr, Y and Zr reported here were obtained by X-ray fluorescence (XRF) using 4 gram pressed rock powder pellets. This technique is suitable for the purpose here because there is neither the sample dilution problem inherent in borate bead preparation, not the problem of incomplete solution in acid digestion methods (MacLean and Barrett, 1993). In the analytical scheme ofXRF the oxidation state of iron (i.e. ferrous and ferric) cannot be distinguished. Thus, the XRF data have been supplemented by determinations for ferrous iron based on titrimetry (Potts, 1987). The determinations of structural water and carbon dioxide were conducted separately by the ignition method (Shapiro and Brannock, 1955, 1962). The quality of lithogeochemical data is a function ofvarious factors including the strategy of the sampling and sample preparation scheme, the skill and experience of the researcher and instrument operator, the operating condition of the instrument, the standards used to calibrate the counting values, the method of converting the counting values to meaningful lithogeochemical data and the concentrations of components/elements. Therefore, the quality of each set of lithogeochemical data should be assessed individually through the use of duplicates that are representative of the range of composition. The duplicates selected for this study were obtained at two different stages. One was at the field sampling stage and other was at the analytical measurement stage. There are 18 sample duplicates and 20 measurement duplicates for major components analyzed 140 by XRF, 10 duplicates for ferrous iron, 10 duplicates for structural water, 10 duplicates for carbon dioxide, 20 duplicates for sulfur and 22 duplicates for trace elements analyzed by methods previously mentioned. The general procedure for assessing errors is presented in Appendix D (Figures 6-2a, 6-2b, 6-2c, 6-2d, 6-3a and 6-3b). The final results of error analysis of lithogeochemical data are listed in Tables 6-3 and 6-4. With the determination of the values of S0 and k for each component or element, the standard deviation (Se) and the precision (Pc) for each component or element at specific concentration can be calculated by using equation 3-15 and 3-16 introduced in Chapter 3. Table 6-3. Error of lithoeochemical data estimated by usina sample duplicates Si09 TiO, A1,O Fe,O FeO MgO MnO CaO Na,O So 0.01 0.006 0.01 0.06 0.045 0.074 0.022 0.08 0.09 k 0.012 0.008 0.021 0.018 0.018 0.03 0.007 0.011 0.013 Cd 0.02 0.012 0.021 0.124 0.093 0.157 0.045 0.164 0.185 K,O P,Oç CO, 11,0 S Zr Y Rb Sr So 0.02 0.02 0.01 0.04 18 0.01 0.3 2.00 5.00 k 0.018 0.015 0.12 0.13 0.07 0.032 0.09 0.035 0.019 Cd 0.041 0.041 0.026 0.108 41.86 0.021 0.732 4.301 10.395 Table 6-4. Error of lithogeochemical data estimated by using measurement duplicates SiO, TiO, A1,O. The MgO MnO CaO Na,O K,O P,Oç So 0.001 0.006 0.001 0.042 0.07 0.007 0.028 0.02 0.005 0.001 k 0.002 0.008 0.007 0.025 0.008 0.01 0.012 0.003 0.009 0.04 Cd 0.002 0.012 0.002 0.088 0.142 0.014 0.057 0.04 0.01 0.002 Analytical precision for all components can be seen to be much less than field sampling precision. The reason for this is that the duplicates at the field sampling stage 141 contain more sources of variability, including the artificial errors caused by insufficient sample size, inhomogeneity of subsamples and inconsistent analytical measurements. On the other hand, measurement duplicates reveal only the error caused by inconsistent analytical measurements. The purpose of lithogeochemical data is to reveal lithogeochemical variations at scales larger than sample size. Therefore, the sum of all sources ofvariability of the samples should be known for interpretation purposes. 6.4. Lithogeochemical Data of Altered Rock and Determination of Immobile Components The analytical results of the whole rock samples collected from four representative alteration profiles at the Silver Queen mine are listed in Appendix E (Table 6-5). A Ti02 versus Zr binary plot (Figure 6-4) is constructed with these data and the lithogeochemical data are listed in Table 4-2. The two distinctive series ofvolcanic and intrusive rocks around Owen Lake area (Chapter 4) are evident in Figure 6-4. Compositions of altered rocks from four alteration profiles form linear patterns which converge toward the origin. These patterns indicate that the hydrothermally altered samples were derived from a multiple precursor system along the fractionation trend of the older series of igneous rocks at Owen Lake area. Therefore, Ti02and Zr are likely immobile in the hydrothermal alteration system at the Silver Queen mine. The lithogeochemical data indicate that hydrothermally altered rocks are related to a multiple precursor system on the scale of the entire property. However, samples from each local hydrothermal alteration profile exhibit the attribute of a single precursor system that is a linear trend going through the origin of the Ti02-Zr binary plot. This linear pattern results from dilution or concentration ofTi02 and Zr in proportion to the gain or loss of the total mass of the sample during the hydrothermal alteration (Figure 6-4). In other words, before wall-rock hydrothermal alteration at the Silver Queen mine, rocks that are hundreds ofmetres apart from each other have significant differences in their 142 1. 50 H L eg en d Z r pp m P os tm in er al iz at io n ig ne ou s se ri es Pr e m in er al iz at io n ig ne ou s se ri es 30 0 1. 00 — U na lt er ed ro ck no rt h N o. 3 ve in ce nt ra l N o. 3 ve in so ut h N o. 3 ve in 0 Sw itc h B ac k ve in er ro r 0. 50 — 0. 00 0 10 0 20 0 40 0 F ig ur e 6- 4. Im m ob il e co m po ne nt /e 1e m en ts ca tt er pl ot , S il ve r Q ue en m in e, ce nt ra l B ri ti sh C ol um bi a. lithogeochemical compositions, but those within a few tens ofmetres from each other are not significantly different in composition. Therefore, each individual hydrothermal alteration profile can be treated as a single precursor system. Furthermore, Ti02 and Zr are mineralogically and geochemically incompatible, hence both are used as immobile constituents with which to quantifj the mobilities of other components. Theoretically, there should be no significant difference in the recognition ofmobile components using both immobile components (Ti02 and Zr). In reality, this is not so. Thus, the question is, which should be used to correct for closure to provide the most accurate quantification of losses and gains? The sampling (+analytical) variability for Ti02 ranges from 3 to 5.6% at 95% confidence level in the abundance range of interest (0,3 to 0.9 wt% Ti02). Comparable variability for Zr is 6.4% or more at 95% confidence level in the abundance range of interest (120 to 220 ppm Zr). It therefore is reasonable to deduce that Zr has contributed more to the dispersion of the immobile linear trend for each profile than has Ti02. This conclusion is also consistent with what is expected based on the calculations of the optimal sample size and the optimal fineness of subsample (Tables 6-1 and 6-2). As a result, Ti02 is chosen to be the preferred immobile component. It is used to remove the closure of lithogeochemical data in this study. 6.5. Calculation ofAbsolute Losses and Gains of Chemical Constituents and Their Spatial Variations The total mass change of each sample can be visually and qualitatively evaluated from the Ti02-Zr plot (Figure 6-4) after knowing the composition of the precursor. Most of the hydrothermally altered samples at the Silver Queen mine plot between the primary Late Cretaceous fractionation trend and the origin of the plot. This means that these hydrothermally altered rocks have gained mass during alteration, so that the immobile constituents Ti02 and Zr are diluted proportionally. For example, most of the hydrothermally altered samples from the southern and central profiles of the No. 3 vein, 144 and Switch Back vein plot in this fashion. In contrast, the samples that plot further from the origin reflect loss of the mass and thereby proportional concentration of the immobile constituents Ti02 and Zr. The specific amounts lost and gained remain to be determined. Equation 1-9 is used to calculate the absolute losses and gains of individual chemical constituents. The mass ofprecursor is assumed to be around 100 grams and the mass loss or gain is also presented in an extensive unit (grams), which are the absolute mass change relative to the mass of the precursor (100 grams). The results are listed in Appendix E (Table 6-6). Moreover, to see what lithogeochemical variation is significant and what variation is caused by error propagation, equation 3-31 is applied to calculate the propagated error. If the variation of a constituent between two samples is obviously larger than its propagated error, then this variation is thought to be significant; otherwise, it is not significant. A selected example of these calculations are combined with the previous calculation result are present in Figure 6-5a and rest of the results in Appendix D (Figures 6-5b, -5c, -5d, -5e, -5f, -5g, -5h, -5i, -5j, -5k, -51, -5m, -5n, -5o, -5p). The absolute losses and gains of chemical constituents indicated by the samples from different hydrothermal alteration profiles at the Silver Queen mine have many features in common and show some systematic variations from the southern segment to the northern segment of the No. 3 vein and from different levels (from 2600-foot level to 2880-foot level). The general feature shared by all profiles may represent the common attributes of ore-forming hydrothermal solutions in this district. Whereas the differences from place to place may illustrate the spatial variations of the properties of ore-forming hydrothermal solutions. Both are important in the study of ore deposits, but the latter is of specific significance to exploration. The systematic variation in fluid/rock interaction may help to interpret the migration direction of ore-bearing hydrothermal fluid. Therefore, both the general features and the spatial variation of absolute losses and gains of each chemical constituents in various hydrothermal alteration profiles at the Silver Queen mine are described below. 145 -6 0 x4 -4 x3 -6 x3 -4 x3 -2 x3 -3 d x2 -5 x3 -7 x3 -5 x3 -1 x3 -2 x3 -3 pr op yl iti c an d es it e\ \ al te ra tio n en ve lo pe \ pr op yl iti c an de si te ve in b c 8 0 _ — . - - — .— 60 — - — - - - - - — — — . . . . . . . . — _ - . :: . . .j.: :z:: zzz hty f i c e T v F — 4( • . . . * C en tr al se gm en t of th e N o. 3 ve in -6 0 xi -8 sl -6 xl -4 xl -2 c1 al -i xl O -l xl l- 3x 10 -3 dx iO -4 dO -S cl O -6 x1 0- 6D xi -7 al -S D xi -3 xi -2 xb O -l xl O -2 ,c lO -3 x1 0- 3d xl O -4 xl O -5 xl O -6 x1 0- 6D al te ra ti o n o u te r\ \ 0 al te ra ti o n o u te r’ . p ro p y li ti c en v el o p e s al te ra io n in n er en v el o p e “ n si cr o d io ri te en v el o p e io u un ce rt ai nt y at 95 % co nf id en ce le ve l 80 — ab so lu te lo ss or ga in 6 0 . . . . * z S w it ch B ac k ve m -6 0 D A 63 -8 D A 63 -5 D D M 3 4 D A 63 -3 D D A 63 -3 D A 63 -1 D A 63 -6 D M 3- S D M 3 4 D A 63 -3 D D A 63 .I D al te ra ti o n o u te r e n v e lo p e ” \ p ro p y li ti c - n ii cr o d io ri te F ig ur e 6- 5 a. A bs ol ut e lo ss es an d ga in s of S i0 2 fr om fo ur al te ra tio n pr of ile s at th e Si lv er Q ue en m in e, ce nt ra lB ri tis h C ol um bi a. T he bl an k pa rt of ea ch ba r in cl ud es th e m ea n es tim at e (a ho ri zo nt al im ag in ar y lin e th ro ug h th e ce nt re of th e bl an k ba r) an d a ra ng e re pr es en ti ng ± 2 st an da rd de vi at io ns . u n ce rt ai n ty at 95 % co n fi d en ce le ve l ab so lu te lo ss or g ai n 4 o ) . * 2 0 - 2 : . . . . . . . !..L 40 * - N o rt h er n se gm en t of th e N o. 3 ve in 0 Ia lte ra tio n in n er ”\ en ve lo pe d i c- i 0 xS -1 x5 -3 x5 4 x5 -1 0 xS -2 xS -4 xS -5 x5 -6 x5 -6 d x5 -8 \v e in \ ‘\ al te ra tio n ou te r al te ra ti o n in n er en v el o p e en v el o p e ‘ \ p ro p y li ti c ” \ se ri ci ti c m ic ro d io ri te al te ra ti o n Si02: In general, this constituent is added from hydrothermal solution to wall rocks in all alteration envelopes discussed here, except in the alteration envelope of the northern segment of the No. 3 vein and in the outmost subzone of the alteration envelope at the central and southern segment of the No. 3 vein. The greatest addition of Si02 is at the 2600-foot level of central segment of the No. 3 vein, and the 2600-foot level of southern segment of the No. 3 vein. In turn, mildly intensive addition of Si02 occurs at the Switch Back vein. In contrast, a loss of Si02 occurs at the northern segment of the No. 3 vein and in the outmost subzone of the alteration envelope at the central and southern segments of the No. 3 vein (Figure 6-5a). A1203.In general, A1203 has a loss-gain pattern similar to that of Si02 but the changes are less obvious than are those of 5i02 (Appendix D, Figure 6-5b). Fe203:Ferric oxide is depleted or reduced to various extents in most portions of the alteration envelopes. A moderate increase in Fe203commonly occurs immediately adjacent to the veins, probably due to the occurrence of hematite veinlets (Appendix D, Figure 6-5c). FeO: Ferrous oxide is ‘added’ (probably by reduction of ferric iron) prominently in all alteration envelopes. This ‘addition’ is strongly intensified at the Switch Back vein and in the central segment of the No. 3 vein (Appendix D, Figure 6-5d). MnO: Manganese addition and depletion patterns are two-fold. Type one is characterized by a pervasive addition ofMnO to the wall rocks in the alteration envelopes at the northern segment of the No. 3 vein and the Switch Back vein. Type two involves the addition ofMnO to most portions of the alteration envelopes, but there is a narrow depletion ‘valley’ adjacent to the vein at the 2600-foot level of central segment and southern segment of the No. 3 vein (Appendix D, Figure 6-5e). MgO: Magnesium is moderately depleted in the alteration envelopes. There is no significant systematic addition and depletion pattern in the profiles (Appendix D, Figure 6- 5f). 147 Na20and CaO: Sodium and calcium depletions from the wall rocks are prominent and intense in all alteration envelopes. In particular, the depletion ofNa20 is almost complete in all alteration envelopes (Appendix D, Figures 6-5g, 6-5h). K20 and Rb: Potassium and rubidium additions to the wall rocks are prominent but variable in intensities from the southern segment to the northern segment of the No. 3 vein. Additions ofK20 and Rb are most intense in parts of the alteration envelopes at the 2600-foot level of the central and southern segment of the No. 3 vein, and moderately intense in the alteration envelope at the Switch Back vein. In contrast, only one sample shows a slight addition ofK20 and Rb, the rest indicate depletion or no significant mass change, ofK20 and Rb in the alteration envelope at the northern segment of the No. 3 vein. K20 and Rb depletions occur at the outmost parts of the alteration envelopes at the central and southern segments of the No. 3 vein (Appendix D, Figures 6-5i, 6-5j). H20, CO2and S: Volatile constituents are prominently added from hydrothermal solution to wall rocks in all alteration envelopes discussed here except the southern segment of the No. 3 vein. The spatial variation of addition ofH20, CO2and S are described as follows. The additions ofH20 and CO2are the most intense in the alteration envelopes at the Switch Back vein and the central segment of the No. 3 vein, the second most intense in the alteration envelope at the northern segment of the No. 3 vein. There is almost no significant addition ofH20 and CO2in the alteration envelope at the southern segment of the No. 3 vein. In contrast to the addition ofH20 and C02, the addition of sulfur reaches its peak in the alteration envelope about the southern segment of the No. 3 vein, as well as at the central segment of the No. 3 vein. The addition of sulfur is minor along the Switch Back vein profile. There is very little addition of sulfur in the alteration envelope at the northern segment of the No. 3 vein (Appendix D, Figures 6-5k, 6-51 and 6-5m). Sr: Strontium is depleted in the alteration envelopes in a pattern similar to those of Na20 and CaO but the intensity of depletions vary from profile to profile. It appears to be 148 more intense at the southern segment of the No. 3 vein than at the northern segment of the No. 3 vein. In addition, the subzone adjacent to the vein in the alteration envelope at the central segment of the No. 3 vein shows strong addition of Sr (Appendix D, Figure 6-5n). Y: Yttrium in the alteration envelope have gained a small amount ofmass from the hydrothermal solution, but lost its mass in part of the alteration inner envelope in the central and southern segment of the No. 3 vein. These changes may not be significant since yttrium has a large analytical error (Appendix D, Figure 6-5o). P205:Phosphorous is probably a locally immobile component during the hydrothermal alteration process because it has no significant loss or gain in the sericitic and argillic outer alteration envelope; its depletion is mild in the silicic and pyritic inner alteration envelopes at the Silver Queen mine (Appendix D, Figure 6-5p). In brief, wall rock alteration is most intense in the alteration envelope at the central segment ofNo. 3 vein and least intense at the northern segment ofNo. 3 vein in terms of absolute losses and gains of chemical constituents according to the lithogeochemical data from the current four profiles. The total mass change of each altered sample is largely the result of the depletions of CaO andNa20, and the addition of 5i02,K20, 1120 and CO2. 6.6. Application of PER Diagram to the Interpretation of Hydrothermal Alteration Knowing the absolute losses and gains of chemical constituents during the hydrothermal alteration process, we can infer corresponding mineralogical changes. For example, an addition ofK20 along with the depletion of CaO andNa20ofandesitic volcanic rock samples might be intuitively interpreted as the replacement of plagioclase or K-feldspar by muscovite. This can be illustrated by the following equations: 3CaA12SiO8+2K + 4H =2KA13SiO10(OH)+ 3Ca (6-1) Anorthite Muscovite 3NaAlSiO8+K+2W =KA13SiO10(OH)2+ 3Na + 6SiO2 (6-2) Albite Muscovite 149 3KAISiO8+2H =KA13SiO10(OH)2+2K + 6SiO2 (6-3) K-feldspar Muscovite In another case, the depletions ofK20, CaO andNa20along with no mass changes of Si02 might indicate the occurrence of argillic alteration. This can be represented as follows: CaAl2SiO8+ 2W +H20=A12Si05(OH4+Ca (6-4) Anorthite Kaolinite 2NaA1Si3O8+2W + 1120 =Al2Si5(0H4+ 2Na + 4Si02 (6-5) Albite Kaolimte 2KA1Si3O8+2W +1120 =A12Si5(OH)4+2K + 4Si02 (6-6) K-feldspar Kaolimte A previous petrographic examination documents the existences of propylitization, carbonatization, argillization, sericitization and silicification in the study area. These alteration processes lead to the replacement ofprimary minerals such as plagioclase, augite and hornblende by epidote, chlorite, carbonates, kaolinite and sericite, with the addition of quartz. These processes can be tested in detail for each analysis using PER diagrams (Russell and Stanley, 1990a; Stanley and Russell, 1989a, 1989b, 1989c, 1990). There are two preconditions that must be satisfied before applying this PER diagram to the interpretation of the lithogeochemical data. The first is that the chemical composition and mineral assemblage of parent rock or precursor of alteration derivatives must be known or predictedable. This has already been demonstrated in Figure 6-4 and the related discussion. The lithogeochemical composition and mineral assemblage of a propylitic rock can be treated as the precursor of the altered rocks in the superimposed alteration envelope. The second precondition is that the proportion ofprimary minerals converted into alteration product must be reasonably estimated. The microscope observations indicate that primary minerals are completely replaced by altered minerals including mainly sericite, kaolinite, quartz, carbonate and pyrite within the alteration envelope, and partially replaced by epidote, chlorite, carbonate and sericite in propylitic alteration halo. 150 The PER diagram designed previously (Figure 1) is used to test (i) whether feldspar and augite fractionations are still the main contributors to lithgeochemical variation among the propylitically altered rocks; (ii) whether either carbonatization, sericitization, argillization or siicification is the dominant alteration type at the Silver Queen mine. The propylitically altered samples on the PER diagram are characterized by a scattered trend with a slope approximately equal to one within the error range at the 95% confidence level. This implies that the total mass of corresponding chemical constituents used to construct this PER diagram have had no significant changes during the propylitic alteration process. In other words, primary feldspar and augite crystal fractionations may be still the major causes for the lithogeochemical variations of the corresponding chemical constituents among the propylitically altered samples (Figure 6-6a). However, it is not certain whether the unchanged mass means that the mass of each constituent is unchange or that the masses of corresponding constituents do change but the total mass remain unchange by compensation. In general, all the samples from the alteration envelope (not including propylitic alteration) plot far from the primary fractionation trends on this PER diagram. This implies that there are significant mass changes of the corresponding chemical constituents among these samples relative to the propylitically altered samples. Also, all the samples from the alteration envelope spread between sericitic trend and argillic trend rather than concentrating around one alteration trend, indicating that the lithogeochemical variation of altered rocks is not entirely controlled by either carbonates, sericite, kaolinite or quartz at the Silver Queen mine. Instead, the lithogeochemical variations among these samples have to be interpreted as due to the complete replacement of primary minerals as well as the ‘propylitic’ minerals by different proportions of sericite, kaolinite, carbonate, pyrite and quartz. According to petrographic observations one of the possible alteration paths is deduced as follows (Figure 6-6b): all primary minerals and propylitical minerals in the least 151 F ig ur e 6- 6a . P E R pl ot to di sc ri m in at e th e al te ra ti on ty pe s as so ci at ed w ith pr ec io us - an d ba se -m et al ve in m in er al iz at io n in vo lc an ic se qu en ce s at th e Si lv er Q ue en m in e. Q tz - qu ar tz , C ar b - ca rb on at es , K ao - ka ol in ite , A n - an or th ite , A b - al bi te , O r, K -f el ds pa r, C hl - ch lo ri te , A ug - au gi te , M us - m us co vi te , E p - ep id ot e, N . N o. 3 v. - th e no rt he rn se gm en t of th e N o. 3 ve in , SW B K v. - Sw itc h B ac k ve in , C . N o. 3 v. - ce nt ra l se gm en t of th e N o. 3 ve in , S N o. 3 v. - so ut he rn se gm en t of th e N o. 3 ve in , se e te xt fo r de ta ile d di sc us si on . 1. 8 1. 6 1. 4 1. 2 L eg en d r.J C 0. 8 er ro r un al te re d 0. 6 0. 4 0. 2 + N . N o. 3 v. * SW B K v. x C . N o. 3 v. A S .N o. 3 v. S i! T iO 2 2r3 C 1 .8 1. 4 1. 2 1 0. 8 a2 ,/ P / / b4 L eg en d A lte ra tio n pa th er ro r E p b 5 b3 I— I — — I 0. 4 b2 ,/ /1 ,/ ,/ t A b, O r, C hl C ar b K ao 1 2 3 4 S i/ T i0 2 F ig ur e 6- 6b . O ne of th e po ss ib le al te ra ti on pa th s on P E R di ag ra m de si gn ed to di sc ri m in at e th e al te ra ti on ty pe s as so ci at ed w it h pr ec io us - an d ba se -m et al ve in m in er al iz at io n in vo lc an ic se qu en ce s at th e Si lv er Q ue en m in e. Q tz - qu ar tz , C ar b - ca rb on at es , K ao - ka ol in ite , A n - an or th ite , A b - al bi te , O r, K -f el ds pa r, C hi - ch lo ri te , A ug - au gi te , M us - m us co vi te , E p - ep id ot e. or propylitically altered wall rocks are completely replaced (from P to b 1) by carbonatization (from b 1 to b2), argillization (from b2 to b3, sericitization (from b3 to b4) and silicification (from b4 to b5). Another PER diagram is used to further test alteration types at the Silver Queen mine. This PER diagram has a A1/Ti02 as x-axis and (2Ca+Na+K)/Ti0 as y axis (Stanley and Madeisky, 1993). The displacement vectors of primary minerals (feldspar and hornblende) are defined to have slopes equal to one, the displacement vectors of carbonates are vertical, that of kaolinite horizontal, that ofmuscovite has a slope equal to 1/3, and that of quartz is perpendicular to the paper (Figure 6-6c). The alteration samples of Silver Queen mine on this PER diagram show again that least or propylitically altered samples plot along the fractionation trend of slope equal to one within the error range (at the 95% confidence level). This means that lithgeochemical variation of least or propylitically altered wall rock is caused mainly by feldspar. The displacement vector of augite is vertical on this PER diagram (Figure 6-6d). Compared to the previous PER diagram, this PER diagram shows a more understandable dispersion of plotted points; the alteration patterns are more distinguishable because the effect of quartz has been removed and only carbonates, muscovite and kaolinite alteration are presented on this PER diagram. In addition, a bubble plot superimposed on this PER diagram is used to investigate the effect of silicification (Figure 6-6e). With regard to the alteration intensity relative to the spatial distribution, the plots of the samples from the alteration envelopes of the northern segment of the No. 3 vein, the Switch Back vein, the southern segment of the No. 3 vein and the central segment of the No. 3 vein are presented in turn from the lowest left portion to the highest right portion of this PER diagram. This plotting pattern indicates that samples from the alteration envelope of the central segment of the No. 3 vein are affected by the most intense alteration including sericitization, carbonatization, pyritization and silicification. In contrast, the alteration intensity of the samples from alteration envelope of 154 F ig ur e 6- 6c . P E R di ag ra m de si gn ed to di sc ri m in at e th e al te ra ti on ty pe s w it ho ut co ns id er in g th e ef fe ct of qu ar tz . Q tz - qu ar tz , C ar b - ca rb on at es , K ao - ka ol in ite , A n - an or th ite , A b - al bi te , O r, K -f el ds pa r, C hi - ch lo ri te , A ug - au gi te , M us - m us co vi te , E p - ep id ot e. P - pr ot ol it h; au gi te re pl ac ed (a l) by ca rb on at es (a 2) ; pr im ar y m in er al s ar e co m pl et el y re pl ac ed (b ) by ca rb on at es (c ), m us co vi te (d ) or ka ol in ite (e ). 0. 9 0. 8- L eg en d + C + z + Ce 0 I I 0 0. 2 0. 4 0. 6 0. 8 1 1. 2 A 1 /T i0 2 L I U I 1. 4 + z + L) L eg en d er ro r un al te re d + N . N o. 3 V . SW B K V . x C . N o. 3 v. A S .N o, 3 v. 0 0. 2 0. 4 0. 6 0. 8 1 1. 2 1. 4 A l/ T iO a F ig ur e 6- 6d . P E R pl ot to di sc ri m in at e th e al te ra ti on ty pe s as so ci at ed w ith pr ec io us - an d ba se -m et al ve in m in er al iz at io n in vo lc an ic se qu en ce s at th e Si lv er Q ue en m in e (t he di sp la ce m en t ve co to r of qu ar tz is pe rp en di cu la r to th e pa pe r) . q tz . Q tz - qu ar tz , C ar b - ca rb on at es , K ao - ka ol in ite , A n - an or th ite , A b - al bi te , O r, K -f el ds pa r, C hl - ch lo ri te , A ug - au gi te , M us - m us co vi te , E p - ep id ot e, N . N o. 3 v. - th e no rt he rn se gm en t of th e N o. 3 ve in , SW B K v. - Sw itc h B ac k ve in , C . N o. 3 v. - ce nt ra l se gm en t of th e N o. 3 ve in , S N o. 3 v. - so ut he rn se gm en t of th e N o. 3 ve in , se e te xt fo r de ta ile d di sc us si on . + z + L) Fi gu re 6- 6e . P E R di ag ra m su pe ri m po se d by Si /( im m ob ile el em en t) bu bb le pl ot . T he si ze of bu bb le re pr es en ts th e re la tiv e m ol ar am ou nt of Si co rr ec te d fo r cl os ur e. A 1/ T iO 2 L I the northern segment of the No. 3 vein is the mildest relative to others. Its alteration types are mainly carbonatization and argillization plus sericitization. All these are consistent with the conclusions drawn from the calculations of absolute losses and gains of chemical constituents in the previous section. 6.7. Application ofMetasomatic Norm Methodology For the purpose of a general examination of the types and intensities of hydrothermal alteration associated with precious- and base-metal vein deposit in volcanic sequence by using the lithogeochemical data, the PER diagram, described above, is a useful tool. However, projections ofmulticomponents systems can be ambiguous and may not involve all variables, partly because of its 2-dimensional limitation. For example, an altered sample plotted on the PER diagram, above, could be interpreted as either the combined product of argillization, carbonatization, sericitization and silicification or simply the product of carbonatization plus intense silicification. A more complicated system has to be taken into account to reduce the ambiguities or to test other hypotheses. In the example mentioned above, the product of carbonatization plus intense silicification will lead to the content of CO2 in the bulk rock composition being more abundant than in the case of silicification, argillization and sericitization. In contrast, the combined product of silicification, argillization, carbonatization and sericitization will contain more 1120 in the bulk rock composition than in the product of carbonatization plus intense siliciflcation. One means of reducing these ambiguities is through use of the methodology described by Cheng and Sinclair (1994) and in Chapter 2. The lithogeochemical data of four hydrothermal alteration profiles at the Silver Queen mine have been processed by applying the approach ofmetasomatic norm calculation. The minerals listed in Table 2-1 are chosen to be the standard normative minerals for the metasomatic norm calculation. These mineral occurrences are based on the petrographic observations and XRD examination of the samples (Cheng et al., 1991). 158 Finally, all the calculated metasomatic norm values have been corrected for closure by using Ti02as an immobile component and equation 1-9. The metasomatic norms corrected for the closure and the absolute loss and gain values of chemical constituents of the northern segment of the No. 3 vein profiles as the selected examples are presented in units ofmole and gram in Tables 6-7a and 6-8a, respectively. The calculations of other profiles are listed in Appendix E, Table 6-7b, 6-7c and 6-7d and Tables 6-8b, 6-8c and 6- 8d, respectively. Residuals have been used to monitor how closely the masses of parent-daughter losses and gains balance. A residual is defined as metasomatic normftered rock - ( metasomatic normprecsor rock + zMass change). The residuals ofmetasomatic norm calculation after the correction for the closure range from 0.16 to -0.49 gram relative to the mass of precursor rock (about 100 gram). This indicates that the mineral assemblages chosen here represent the bulk rock composition well. The data listed in Tables 6-8a, 6-8b, 6-8c and 6-8d are illustrated in Figures 6-7a, 6-7b, 6-7c and 6-7d. For the purpose of comparison, the scales ofy-axes are uniform in Figures 6-7a, 6-7b, 6-7c and 6-7d. Thus, the type and intensity ofwall-rock hydrothermal alteration in different profiles can be quantitatively evaluated and objectively compared. The propylitic altered rock is characterized by a metasomatic normative mineral assemblage composed mainly of plagioclase, K-feldspar, pyroxene, quartz, epidote, chlorite and carbonate. There is no systematic spatial variation of the abundances of these minerals relative to the vein. This attribute is convincing evidence that propylitic alteration is related to pre-mineralization volcanic activity rather than the ore-fluid. The carbonatization is relatively intense in hydrothermal alteration envelopes and is indicated by the increase in the content of carbonate from 5.6 gram on average in the propylitic alteration halo to about 15 gram on average in the bleached alteration envelope. Of the four profiles the alteration envelope of the Switch Back vein is the most strongly 159 Table 6-7a. Metasornatjc norms corrected for closure and absolute losses and gains of components (in moles) at northern segment of the No. 3 vein, Silver Queen mine, Ow en Lake, central BC SmpIeJd x4-4 x3-7 x3-6 x3-5 x3-4 x3-1 x3-2 x3-2 x3-3d x3-3 x2-5 Afteration w-alt w-alt w-alt rn-alt ms-alt ms-alt rn-alt rn-alt w-alt w-alt w-alt mole Pyroxene 0.02 0.00 0.00 0.00 0.00 0.00 0.0 0 0.00 0.01 0.02 0.02 Plagioclas 0.14 0.16 0.10 0.00 0.00 0.00 0.0 0 0.00 0.11 0.15 0.15 K-feldspar 0.07 0.06 0.06 0.00 0.00 0.00 0.00 0.00 0.07 0.06 0.07 Quartz 0.20 0.22 0.26 0.46 0.68 0.59 0.58 0.58 0.23 0.19 0.24 Carbonate 0.05 0.05 0.05 0.09 0.16 0.13 0.1 0 0.10 0.04 0.05 0.06 Epidote 0.04 0.02 0.02 0.00 0.00 0.00 0.00 0.00 0.03 0.03 0.01 Chlorite 0.00 0.01 0.02 0.00 0.00 0.00 0.0 0 ,‘O.OO 0.02 0.01 0.01 Sericite 0.00 0.00 0.02 0.04 0.11 0.06 0.0 7 0.07 0.01 0.00 0.00 Kaolinite 0.00 -0.00 0.01 0.06 0.02 0.07 0.05 0.05 -0.00 0.00 0.00 Pyrite 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Hematite 0.00 0.01 0.01 0.00 0.01 0.01 0.01 0.01 0.00 0.00 0.01 Magnetite 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Ilinenite 0.00 0.01 0.00 0.00 0.00 0.00 0.0 0 0.00 0.00 0.00 0.00 Rutile 0.01 0.00 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 Apatite 0.00 0.00 0.00 0.00 0.00 0.00 0.0 0 0.00 0.00 0.00 0.00 Total 0.53 0.55 0.56 0.67 1.00 0.87 0.83 0.82 0.52 0.52 0.58 dSiO2 0.00 0.00 -0.03 -0.24 0.11 -0.04 -0.05 -0.06 -0.00 -0.02 -0.02 dAl+3 0.00 0.01 0.00 -0.04 0.08 0.03 0.02 0.02 0.00 -0.00 -0.00 dTi+4 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 dEe +3 0.00 -0.00 -0.00 -0.03 -0.02 -0.02 -0.01 -0.01 -0.00 -0.00 -0.00 dFe+2 0.00 0.00 -0.00 -0.00 0.05 0.04 0.01 0.01 0.00 -0.00 -0.00 dMn+2 0.00 -0.00 -0.00 0.01 0.02 0.02 0.00 0.00 0.00 -0.00 -0.00 dMg+2 0.00 -0.01 -0.01 -0.06 -0.04 -0.05 -0.05 -0.05 0.00 -0.00 0.01 dCa+2 0.00 -0.01 -0.00 -0.07 -0.09 -0.10 -0.08 -0.08 -0.01 -0.01 / -0.01 dNa+ 0.00 0.01 -0.00 -0.11 -0.10 -0.11 -0.11 -0.11 0.00 0.01 -0.01 dK+ 0.00 -0.00 -0.00 -0.03 0.03 -0.01 -0.00 -0.00 0.00 -0.00 0.00 dP+5 0.00 0.00 0.00 -0.00 -0.00 -0.00 -0.00 -0.00 0.00 0.00 -0.00 Sum 0= 0.00 -0.01 -0.02 -0.30 -0.01 -0.15 -0.17 -0.17 -0.00 -0.01 -0.01 dH2O 0.00 0.02 0.07 0.13 0.12 0.16 0.1 5 0.14 0.05 0.01 0.00 dCO2 0.00 0.00 0.01 0.04 0.11 0.08 0.04 0.04 -0.01 -0.00 0.02 dS 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 -0.00 dTotal 0.00 0.01 0.01 -0.69 0.26 -0.15 -0.25 -0.27 0.04 -0.03 -0.03 160 Table 6-8a. Metasomatic norms corrected for closure and absolute los ses and gains of components (in grams) at northern segment of the No. 3 vein, Silver Queen mine, Owen Lake, central BC Sample Id x4-4 x3-7 x3-6 x3-5 x3-4 x3-1. x3-2 x3-2 x3-3d x3-3 x2-5 AIteraon w-alt w-alt w-alt rn-alt ms-alt ms-alt rn-alt rn-alt w-alt w-alt w-alt gram Pyroxene 5.11 1.22 0.90 0.00 0.00 0.00 0.00 0.00 1.80 4.33 33 Plagioclase 36.01 41.63 26.19 0.25 1.12 0.53 0.89 0.08 28.51 39.58 40.72 K-feldspar 18.26 17.26 16.00 0.00 0.00 0.0 0 0.00 0.08 18.50 17.58 18.34 Quartz 12.02 13.40 15.88 27.38 40.90 35.35 34.72 34.76 13.87 11.17 14.21 Carbonate 4.86 5.85 5.35 9.81 17.14 14.14 10.25 10.21 3.98 5.10 5.53 Epidote 18.70 9.79 11.07 1.78 0.00 0.00 0.00 0.00 15.49 13.55 3.89 Chlorite 3.05 7.28 11.35 0.00 0.00 0.00 0.00 ,.0.00 11.71 4.16 7.65 Sericite 0.00 0.02 7.39 17.28 44.29 25.43 28.75 29.59 3.96 0.00 0.00 Kaolinite 0.00 -0.00 1.56 16.28 6.06 17.77 13.92 12.95 -0.00 0.17 0.01 Pyrite 0.02 0.03 0.03 0.04 0.27 0.13 0.10 0.09 0.05 0.03 0.01 Hematite 0.00 1.24 1.24 0.65 1.44 1.21 2.00 2.10 0.25 0.74 2.39 Magnetite 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Ilmenite 0.00 1.20 0.00 0.00 0.00 0.43 0.00 0.00 0.00 0.08 0.01 Rutile 0.65 0.02 0.65 0.65 0.65 0.42 0.65 0.65 0.65 0.61 0.64 Apatite 0.90 0.90 0.93 0.48 0.51 0.46 0.56 0.55 0.92 0.91 0.86 Total 99.58 99.83 98.53 74.60 112.38 95.86 91.83 91.06 99.69 98.01 98.09 dSiO2 0.00 0.11 -1.53 -14.19 6.76 -2.32 -2.99 -3.50 -0.27 -0.99 -1.44 dAI+3 0.00 0.14 0.09 -1.10 2.16 0.70 0.61 0.51 0.10 -0.00 -0.08 dTi+4 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 dFe+3 0.00 -0.16 -0.01 -1.50 -1.16 -1.31 -0.77 -0.69 -0.20 -0.08 -0.04 dFe+2 0.00 0.12 -0.18 -0.10 2.88 2.14 0.35 0.31 0.15 -0.06 -0.01 dMn+2 0.00 -0.11 -0.09 0.51 1.19 0.92 0.16 0.16 0.01 -0.03 -0.07 dMg+2 0.00 -0.18 -0.22 -1.37 -0.98 -1.14 -1.24 -1.23 0.08 -0.07 0.20 dCa+2 0.00 -0.29 -0.14 -2.90 -3.74 -3.83 -3.23 -3.22 -0.33 -0.29 . -0.35 dNa+ 0.00 0.33 -0.11 -2.54 -2.34 -2.50 -2.47 -2.48 0.03 0.19 -0.23 dK+ 0,00 -0.14 -0.08 -1.11 1.34 -0.33 -0.00 -0.01 0.03 -0.10 0.01 dP+5 0.00 0.00 0.01 -0.08 -0.07 -0.08 -0.06 -0.06 0.00 0.00 -0.01 Sum 0= 0.00 -0.10 -0.25 -4.78 -0.21 -2.40 -2.70 -2.76 -0.01 -0.17 -0.20 dH2O 0.00 0.30 1.18 2.31 2.10 2.82 2.63 2.58 0.87 0.16 0.05 dCQ2 0.00 0.11 0.27 1.86 4.70 3.55 1.91 1.85 -0.38 -0.14 0.68 dS 0.00 0.00 0.00 0.01 0.13 0.06 0.04 0.03 0.01 0.00 -0.01 dTotal 0.00 0.14 -1.05 -24.98 12.76 -3.73 -7.76 -8.52 0.10 1.57 -1.49 Residual 0.00 0.11 -0.00 0.00 0.03 0.01 0.01 0.01 0.00 0.00 -0.00 161 •0 - . 0 — , c C c o 0 . 0 C) C) C) C) 1 • c9 . C) -t gr am gr am S Pt S Q’j’ B Pt B Pt B 00 -i - 0 — CD , 0 ( -t CD II . 0 0 < CD CD CD CD gr am li I gr am C t ijc j fi1 B B Pt i1 o o s 0 :t . 0 0 . 0 0 -t CD CD 0 CD CD . < CD L CD • • 0 CD — Pt -t = 0 CD CD B o CD 0 ii gr am gr am wjii .I B Pt B Pt (I, Pt Pt Pt B S 5’ B Pt B 5’ Pt Pt 1ii jfl1 B Pt C’ , 5’ Pt 5’ Pt 5’ B Pt B 5’ B Pt B 5’ 5’ 5’ (1C O I j C- CC — 0 0 p J CC 0 — j o 0 -C 0 - 0 CD 0 CD CM -t CD CD — CM o CM CD O CD CD • 0 , II I gr am gr am CM (C CM I o 1! CM (C C - carbonatized. The carbonatization of the alteration envelope at the southern segment of the No. 3 vein is the mildest. Argillization is extensively developed in the narrow alteration envelope at the northern segment of the No. 3 vein. The alteration envelope of the Switch Back vein is characterized by an inner extensive argillic subzone. The broad alteration envelope at the central segment of the No. 3 vein has an inner argillic subzone similar to that of the Switch Back vein but much narrower than that of the Switch Back vein. There is also an argillic alteration outer subzone adjacent to the boundary between the alteration envelope and propylitic halo at the central segment of the No. 3 vein. A similar outermost argillic subzone is present in the alteration envelope of the southern segment of the No. 3 vein too. Sericitization is extensive in all four alteration envelopes but is strongest in the alteration envelope of the southern segment of the No. 3 vein (the content of sericite is up to about 61 gram relative to 48 gram on average). In contrast, the content of sericite in the alteration envelope of the northern segment of the No. 3 vein is relatively low (up to 44 gram and 29 gram on average, respectively). Potassic alteration is indicated by the presence of normative K-feldspar in the alteration envelopes of the central and southern segments of the No. 3 vein. In contrast, there is no normative K-feldspar present in the alteration envelopes of the Switch Back vein and the northern segment of the No. 3 vein. Silicification is strong in the alteration envelopes of the central and southern segments of the No. 3 vein. It is weakest in the alteration envelopes of the northern segment of the No. 3 vein and the Switch Back vein. In brief, the results of the metasomatic norm calculations of four alteration profiles provide a comprehensive, quantitative view ofmass and mineralogical changes that are associated with hydrothermal alteration at the Silver Queen mine. The ambiguities of the interpretation have been largely reduced by considering all constituents of the geochemical 166 system, and by using mass balance and known minerals as constraints. The metasomatic norm profiles documented in this section link the lithogeochemical variations with the mineralogical variations. They present the hydrothermal alteration associated with precious- and base-metal vein mineralization in an easily understood way. 6.8. Propagated Error Analysis and Confidence Level of the Quantitative Evaluations To decide which chemical and mineralogical variations discussed in the previous sections are significant, the propagated errors are calculated using equations 3-31 and 3- 33 and the values of S0 and k of each chemical constituent (derived from the duplicate analyses, cf. Table 6-3). The propagated error calculation of the northern profile of the No. 3 vein are listed in Tables 6-9a as a selected example. The calculation results of other three profiles are listed in Appendix E, Table 6-9b, 6-9c and 6-9d. Only the chemical or mineralogical variations that are larger than the corresponding propagated errors can be safely considered as significant. Smaller apparent variations may be caused entirely by artificial factors. By using this technique the words ‘significant’ and ‘insignificant’ are used to describe the variations according to an objective criterion. Based on the calculation of propagated error, the four alteration profiles can be interpreted with respect to significant chemical variations. For example, the propylitic altered samples from the alteration profile at the northern segment of the No. 3 vein have absolute losses and gains of Si02 ranging from -0.11 to 1.53 gram, and the propagated errors of Si02 for these samples range from ± 1.76 to ±1.80 gram at 68% confidence level. Thus, Si02 mobility in the propylitically altered rock is not significant. In contrast, the altered samples x3-5 and x3-4 in the alteration envelope have absolute losses and gains of Si02 equal to -14.19 and 6.76 gram respectively. These changes in Si02 contents are much greater than their propagated errors (±1.38 and ±2.03 gram at the 68% confidence level, respectively). The other three samples (x3 -1, x3 -2 and x3 -3d) in the alteration 167 Table 6-9a. Propagated errors of metasomatic norms corrected for closure and absolute losses/gains of components in grams at the 68% confidence level, the northern segment of the No. 3 vein, Silver Queen mine, central BC San,pleid x4-4 x3-7 x3-6 x3-5 x3-4 x3-1 x3-2 x3-2 x3-3d x3-3 x2-5 AlteTation w-alt w-alt w-alt rn-alt ms-alt m s-alt rn-alt rn-alt w-alt w-alt w-alt gram Pyroxene 0.17 0.04 0.03 0.00 0.00 0.00 0.00 0.00 0.16 0.19 0.28 Plagioclase 0.95 1.10 0.69 0.01 0.04 0.02 0.04 0.00 0.75 1.04 1.08 K-feldspar 0.48 0.45 0.42 0.00 0.00 0.00 0.00 0.00 0.49 0.46 0.48 Quartz 0.33 0.36 0.43 0.71 1.15 0.96 0.93 0.93 0.38 0.30 0.39 Carbonate 0.40 0.36 0.34 0.60 1.05 0.86 0.65 0.65 0.24 0.34 0.40 Epidote 0.50 0.26 0.29 0.05 0.00 0.00 0.00 0.00 0.41 0.36 0.10 Chlorite 0.11 0.28 0.41 0.00 0.00 0.00 0.00 0.00 0.42 0.15 0.27 Serjcite 0.00 0.00 0.20 0.47 1.26 0.71 0.79 0.82 0.11 0.00 0.00 Kaolinite 0.00 0.00 0.05 0.51 0.21 0.58 0.45 0.42 0.00 0.01 0.00 Pyrite 0.00 0.00 0.00 0.00 0.01 0.01 0.01 0.01 0.00 0.00 0.00 Hematite 0.00 0.06 0.06 0.04 0.10 0.09 0.10 0.10 0.01 0.03 0.11 Magnetite 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Ilmenite 0.00 0.04 0.00 0.00 0.00 0.01 0.00 0.00 0.00 0.00 0.00 Rutile 0.02 0.00 0,02 0.02 0.02 0.01 0.02 0.02 0.02 0.02 0.02 Apatite 0.04 0.04 0.04 0.02 0.05 0.04 0.03 0.03 0.04 0.04 0.03 Total 2.99 2.99 2.98 2.44 3.89 3.29 3.01 2.98 3.04 2.94 3.16 dSiO2* 1.73 1.73 1.68 1.33 1.95 1.66 1.63 1. 61 1.72 1.70 1.69 ciAl+3 0.32 0.32 0.32 0.28 0.38 0.33 0.33 0.32 0.32 0.31 0.31 dTi+4 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 dFe+3 0.13 0.12 0.13 0.09 0.11 0.10 0.11 0.11 0.12 0.12 0.12 dFe+2 0.12 0.12 0.12 0.11 0.20 0.17 0.13 0.12 0.12 0.12 0.12 dMn+2 0.03 0.03 0.03 0.03 0.05 0.04 0.03 0.03 0.03 0.03 0.03 dMg+2 0.14 0.14 0.14 0.11 0.12 - 0.12 0.11 0.11 0.15 0.14 0.15 dCa+2 0.18 0.18 0.18 0.12 0.13 0.12 0.13 0.13 0.18 0.18 0.17 dNa+ 0.16 0.16 0.16 0.11 0.13 0.12 0.12 0.12 0.16 0.16 0.15 dK+ 0.11 0.11 0.11 0.08 0.15 0.10 0.11 0.11 0.11 0.11 0.11 dP+5 0.02 0.02 0.02 0.01 0.02 0.01 0.01 0.01 0.02 0.02 / 0.02 Sum 0= 0.65 0.65 0.65 0.53 0.70 0.62 0.60 0.60 0.65 0.65 0.65 dH2O 0.24 0.27 0.36 0.49 0.48 0.56 0.54 0.53 0.33 0.25 0.24 dCO2 0.36 0.37 0.39 0.54 0.87 0.74 0.55 0.55 0.33 0.35 0.43 dS 0.00 0.00 0.00 0.00 0.01 0.01 0.01 0.01 0.00 0.00 0.00 dTotal 4.19 4.23 4.28 3.87 5.31 4.72 4.41 4.37 4.25 4.15 4.20 * prefixe d stands for the absolute difference of corresponding constituent betwee n the least altered and altered rocks. 168 envelope have gained Si02 ranging from 2.32 to 3.5 gram, respectively. This is close to their propagated errors of Si02 ranging from ±1.68 to ± 1.73 gram at the 68% confidence level and is almost equal to the propagated error at the 95% confidence level (from ±3.36 to ± 3.46 gram). Therefore, the gains of Si02at the sites where these three sample were collected are very small. Similar examination of the other chemical and mineralogical variations can be carried on by comparing the data listed in Tables 6-8a, with the corresponding propagated errors listed in Tables 6-9a. 6.9. A Comprehensive Model ofHydrothermal Alteration A comprehensive model is suggested here to illustrate the process of hydrothermal alteration at the Silver Queen mine. A set of comprehensive, mass balanced reaction equations can be constructed by combining the data listed in Tables 6-7a, 6-8a, and 6-9a. For instance, if sample x4-4 is the precursor rock of sample x3 -5, the hydrothermal alteration of sample x3-5 can be interpreted as follows. The primary minerals such as pyroxene (0.023 mole or 5.11±0. 17 gram), plagioclase (0.136 mole or 36.01± 0.95 gram) and K-feldspar (0.066 mole or 18.26±0.48 gram) as well as some of propylitic altered minerals including chlorite (0.004 mole or 3.05±0.11 gram) and epidote (0.039 mole or 18.7±0.5 gram) are mainly replaced by sericite (0.044 mole or 17.28±0.47 gram), kaolinite (0.063 mole or 16.28±0.5 1 gram), carbonate (increased from 0.053 mole or 4.86±0.34 gram to 0.093 mole or 9.81±0.6 gram) and quartz (increased from 0.2 mole or 12.02±0.3 3 gram to 0.456 mole or 27.3 8±0.71 gram). These replacements are accompanied by the mass losses of Si02 (-0.236 mole or -14.19±1.38 gram),A13(-0.041 mole or -1.1±0.22 gram),Fe3(-0.027 mole or -1.5±0.04 gram), Mg2 (-0.056 mole or -1.37±0.03 gram), Ca2(-0.072 mole or 2.9±0.07 gram), Na (-0.110 mole or -2.54±0.04 gram), K(-0.029 mole or -1.11±0.06 gram) from wall rock to hydrothermal solution and the mass gains of H20 (0.129 mole or 2.31±0.1 gram) andC02(0.042 mole or 1.86±0.12 gram). All these exchanges can be presented as a comprehensive reaction equation as follows: 169 Primary 0.O23pyroxene +0. l36plagioclase + 0.066K-feldspar + 0.2quartz minerals 5.11±0.17 g 36.01± 0.95 g 18.26±0.48 g 12.02±0.33 g Propylitic + 0.O04chlorite + 0.O39epidote + 0.O53carbonate alteration 3.05±0.11 g 18.7±0.5 g 4.86±0.34 g mass - 0.236SiO - 0.04 1A13 - 0.027Fe3 - 0.056Mg2 - 0.072Ca2- 0.11Na - 0.029K losses -14.19±1.38 g -1.1±0.22 g -1.5±0.04 g -1.37±0.03 g -2.9±0.07 g -2.54±0.04 g -1.11±0.06 g mass + 0. 129H + 0.042C02 gains 2.31±0.1 g 1.86±0.12 g sericitic, argillic, = 0.O44sericite + 0.O63kaolimte + 0.O93carbonate + 0.456quartz carbonatized, 17.28±0.47 g 16.28±0.51 g 9.81±0.6 g 27.38±0.71 g silicified alteration The chemical constituents have been converted from oxides into ionic species. There are two reasons for these conversions. One is to correct for the effect of sulfur on the value of the total weight of the sample. Analytical measurements provide the results of most constituents in the form of oxides but report sulfur in elemental form. In reality, however, sulfur is in the form of an anion combined principally with Fe. Thus, Fe2 may not combine with oxygen anion entirely as an oxide but may combines partly with sulfur anion as a sulfide, such as FeS2. As a result, the total weight of the sample may be exaggerated when abundant sulfides exist in the sample and their cations are analytically reported as oxides. In contrast, calculations of a metasomatic norm allot cations to critical minerals and take corresponding required amounts of necessary anions to form each normative mineral according to the stoichiometries of the mineral. Consequently, the total value of normative minerals will not be balanced with the total value of analytical constituents when sulfur is present in an analysis. The extra oxygen will be easily taken out during the conversion of oxides to ionic species. The other reason for converting oxides to ionic species except Si02 is that a mass balanced equation is commonly presented in the forms of solid mineral phases and soluble ionic species or complexes rather than oxides. Si02 is an exception because it exists both in a solid form as quartz and as an aqueous species. It is also possible that these species can 170 be further converted to any probable form of aqueous complex such as HC02,Al(OH)2, etc., if there is sufficient evidence to support the existences of these complexes in the hydrothermal fluid. 171 Chapter 7 Conclusions and Recommendations The aim of this thesis is to extend quantitative methods in the evaluation of material exchanges during hydrothermal alteration associated with precious- and base- metal vein deposit in volcanic sequences. Of the methods currently used, Gresen& equation and Pearce element ratio diagrams are the most popular and most useful. Gresens’ equation and Pearce element ratio diagrams are superficially different but are fundamentally similar in principle. That is, they both remove the closure effect in order to decipher the true chemical variations during alteration. Gresens’ procedure emphasizes chemistry. Pearce element ratios provide the ability to discuss losses and gains mineralogically. The first requirement of applying these quantitative techniques to the estimation of absolute losses and gains in a metasomatic system is to determine immobile components from lithogeochemical data. The determination of immobile components is recommended through a two-fold consideration of: (i) the ratio of two immobile components remains constant in a single precursor system regardless of the nature of the alteration, and (ii) two immobile components must not be mineralogically or geochemically compatible with each other during the hydrothermal alteration process. In reality, there is no perfectly constant ratio of a pair of immobile components. Minor variation in ratios may result from improper sampling and sample preparation procedure as well as analytical error. Analytical error can be quantified to provide a basis for recognizing significant variation, such as ratio variability that is too large to be attributed to analytical error (thus, too large to accept the two components of the ratio as being immobile). This rule is to be used cautiously. If a PER ratio is constructed with one of the components being mobile and the other having poor analytical precision, then the latter component will contribute more to the final propagated error of the ratio, especially 172 where it is used as the denominator of the ratio. As a result, mobility of the former component might be obscured and the plot might lead to the incorrect conclusion that both numerator and denominator are immobile. Therefore, ‘immobil& components of relatively high analytical quality should be accepted in preference to those with poor analytical precision. The second requirement of applying these quantitative techniques for estimating losses and gains in metasomatic system is that a suite of samples for which loss/gain variations are to be evaluated, must be the alteration products of either: (i) a single parent rock characterized by chemical and mineralogical homogeneity (single precursor system), or (ii) a suite of rocks with determinable pre-alteration chemical compositions (multiple precursor system). This requirement can be met conventionally through the careful investigation of the field and petrographic relationships in the study area. Rock derivatives altered to various degrees from a common homogeneous parent rock commonly are in close spatial proximity and may show gradational contacts between each other. Primary textural and structural features may remain identifiable in least-altered to more intensively altered derivatives. To examine these types ofvariations rigorously it is recommended that samples be collected systematically along alteration profiles from the strongly altered rock adjacent to, or within, a mineralized zone, to the least altered rock far from the ore deposit itself. Such sampling should be done after a careful field investigation of the profile. Even though the altered rocks are our main concern, equal attention should be paid to the least altered or unaltered rocks because they provide important information about the parent rocks before hydrothermal alteration. This gives insight into the possibilities of a single precursor system versus a multiple precursor system. The PER approach to examining a metasomatic system has an advantage over other procedures in not only removing the closure effect of lithogeochemical data by using immobile components, but also by explaining the corrected chemical variations in terms of mineralogical variation. Two specific PER diagrams have been designed to discriminate 173 the hydrothermal alteration types commonly associated with epithermal vein deposits in volcanic sequences. The first one is constructed with Si/(immobile component) as its x axis and [l/4A1 +1 1/4(Na+K)+3/2Ca+1/2(Fe+Mg)J/(immobile component) as its y-axis. The displacement vectors of primary minerals such as augite, anorthite, albite and K- feldspar, and alteration mineral chlorite are defined to have slopes equal to one, the displacement vectors of carbonates and pyrite are parallel to the y-axis, the slope of muscovite is 7/6, the slope of kaolinite is 1/4 and the slope of quartz is zero. Therefore lithogeochemical variations cuased by either primary feldspar and augite fractionation, intense carbonatization, argillization, sericitization or silicification can be discriminated if either of them is the dominant contributor to the lithogeochemical variation. The second PER diagram is designed to deal with more complicated types of alteration. It has A1/(immobile component) as its x-axis and (2Ca+Na+K)/(immobile component) as its y axis. The displacement vector of quartz is designed to be perpendicular to the diagram. As a result, the discriminations of carbonatization, argillization and sericitization from primary crystal fractionations are relatively easier on this PER diagram These specifically designed PER diagrams can be used to test the hypotheses that chemical variations are due to variations in amounts of a particular set ofminerals, but the amount of each mineral can not be determined explicitly because the total displacement on a PER diagram commonly is the sum of the displacements of different minerals when a complicated multiple variable system is considered. In other words, ambiguity arises where too many variables are summarized in two dimensional space. A metasomatic norm approach has been developed in this thesis to quantitatively and objectively evaluate material exchange in complicated hydrothermal alteration systems associated with precious- and base-metal vein deposits in volcanic sequences. A metasomatic norm is a quantitative and objective approach to estimating mineral abundances from the lithogeochemical data since the mineralogy and chemistry of a rock are intimately linked through mineral abundances and the compositions of individual 174 minerals. The normative approaches, originally designed principally for igneous rocks, are rigid in their application and in general, do not utilize important alteration minerals. The different approach here, to the determination of norms of hydrothermally altered rocks combines petrographic and lithogeochemical data. Metasomatic norm calculation uses the same principles as the calculation of CIPW norms, but different mineral phases including volatile component-bearing minerals are used as the normative standard minerals that represent hydrothermal alteration systems. Another distinctive difference between a metasomatic and a conventional igneous norm is that the calculation of a metasomatic norm does not proceed along as fixed a hierarchical path as in the case of an igneous norm. More flexibility is necessary because of the wide range in both rock and mineral compositions. In some cases, where constrained by known mineralogy, the calculations must alternate back and forth following a loosely defined sequence in order to eventually balance or best fit a calculated mineral assemblage with the fixed chemical composition of an altered rock (i.e., to make the chemical masses and the mineral masses balance). In addition, the calculation of a metasomatic norm take into account possible incompatible mineral pairs in a hydrothermal system. A possible approach to the application of the norm concept to metasomatic rocks is to constrain the calculated normative mineralogy by a priori knowledge of existing minerals (i.e. to approximate the mode as closely as possible). The selection of a set of standard minerals for metasomatic norm calculation is based on geological observations. A set of standard normative minerals based on the author’s experience are given in this thesis. This set of normative minerals should not be considered exhaustive. It can be extended by the addition of new standard normative mineral(s). Other identified mineral species can be substituted to meet specific requirements. The general procedural scheme for metasomatic norm calculation is inefficient for manual calculation. Consequently, a computer-based procedure using Quattro Pro 5.0, a 175 sophisticated and readily available spread sheet program, has been devised to process norm calculations. It can be easily converted to other spread sheet software (Appendix C). The procedure involves the use of a built-in module— Optimizer in the software. The general procedure ofusing Optimizer is to decide on the solution destination, choose the variables (standard minerals) to be included in the calculation, and set up the constraints. Then the Optimizer module can adjust the amounts of the variables and adhere to the constraints to provide a final best-fit solution. Unlike other black box’ types of software, this calculation model is transparent. Users can easily adjust and develop it according to their own purposes. With the recognition of an immobile component, the metasomatic norms for precursor and altered rocks, and the constituents lost or gained, can be further recast into the absolute amounts of minerals and chemical constituents relative to a given mass of parent rock by using Gresens’ equation. Consequently, the calculated results can be used to construct a comprehensive mass balanced and easily understood chemico-mineralogical model to interpret a hydrothermal alteration system in terms of initial and final normative mineral assemblages (corrected for closure) plus absolute losses and gains of chemical constituents. It does not matter whether the system is closed or open, or whether it represent equilibrium or disequilibrium assemblages. All lithogeochemical data contain errors. Therefore, errors have been propagated in this thesis to the final results of all calculations of absolute losses and gains, including metasomatic norm in intensive units (percentage) and metasomatic norm in extensive units (grams relative to a specific amount of precursor rock) after correction for closure. Such propagated errors also have been integrated with the results of the chemico-mineralogic model for material exchange (including absolute losses and gains of chemical constituents as well as the normative minerals) formulated in this work as follows: Mineralparent rocic ± error + Constituent gained from so1uon± error Mineralaiterk± error + Constituent lost from wall rock± error (7-1) 176 The value of such an equation is that it provides useful, quantitative information about the hydrothermal system and limits the properties of the hydrothermal solution that effected the metasomatism, provided the equation represents a simple and unique alteration process. In reality, this type of reaction equation may more likely represent the final result of a series of sequential and/or superimposed processes. Nevertheless, the form of the equation is particularly useful because it is both quantitative and easily comprehensible. Specifically, the equation includes starting and ending rock mineralogies that may be partly evident in the field. It documents gains and losses of specific chemical constituents in space. Also it includes the uncertainties of each item at certain confidence level, which indicate what variations are significant. In brief, this chemico-mineralogical model: (i) provides an objective and quantitative basis for a mineralogical classification of hydrothermally altered rock; (ii) maps spatial distribution of normative minerals from lithogeochemical data; (iii) interprets lithogeochemical variations in terms ofmineralogical variations (iv) recasts norms to mass units relative to a specified amount of the parent rock (v) then combines norms with the absolute losses and gains of lithogeochemical constituents to form a comprehensive mass balanced equation; (vi) integrates the propagated errors to indicate what variation is significant. The methodology for this approach is a natural extension of the use ofPearce element ratio (PER) diagrams for the study ofmetasomatic rocks. The metasomatic norm approach is quantitative in the same way as Pearce element ratio diagrams. The common principle is the correction for closure that provides true relative lithogeochemical and mineralogical variations between parent and daughter rocks. The normative approach is a useful supplement to PER analysis; the two procedures have much in common and contain much the same information presented in different ways. The strategy of a PER diagram is 177 to test whether chemical changes between two rocks can be explained purely by the variation(s) of certain mineral(s) as demonstrated by disposition of plotted points along predefined trends (slopes) according to the partial mass balance relationship. Metasomatic norms are displayed more explicitly as equations or profiles showing the spatial distributions of normative mineral assemblages, as well as the absolute losses and gains of chemical constituents based on comprehensive mass balance relationships. In brief, metasomatic norms solve the problems ofmultiple variables in multiple dimensional space. In a quantitative evaluation of hydrothermal alteration, it is essential to know the quality of data so that conclusions can be derived with confidence. The major causes for the variations of lithogeochemical data are classified as primary causes (such as crystal fractionation, mixing and assimilation), secondary causes (such as metamorphism, hydrothermal alteration and weathering) and artificial causes (insufficient sample size, improper sample preparation, analytical error, etc.). Ideally, variations generated by artificial processes should be eliminated. In practice, however, they can only be minimized through quality control, such as the estimation of the optimum sample size, the necessary fineness of the ground grain size, and quality assessment of analytical results in terms of precision, accuracy and detection limit. To estimate the optimum size for a sample or the necessary fineness of the particle size for a subsample, the model of’two-mineral mixture ofuniform grain size’ and binomial distribution function are used in this thesis to simulate the distribution ofmajor and compatible trace elements during sampling and subsampling processes. Because the rock types in the study area (Silver Queen mine) are massive and porphyritic volcanic flows and high level intrusive rocks, the inhomogeneities ofvarious constituents at the sampling stage are mainly caused by phenocrysts, such as plagioclase and augite. Calculations indicate that the optimal sample size depends on the coarseness of phenocryst and homogeneities of the constituents of interest in the rock; 500 grams of sample are needed to reduce the sampling error to around one percent at the 68% confidence level. The 178 optimal particle fineness of the subsample depends on the variable being considered: both the abundance of an element in a mineral of interest and the amount of the mineral are important parameters. The quality of lithogeochemical data is a function ofvarious factors including: (i) strategy of sampling, (ii) the sample preparation scheme, (iii) the skill and experience of the researcher and/or instrument operator, (iv) the operating condition of the instrument, (v) the standards used to calibrate the counting values and (vi) the method of converting the counting values to meaningful lithogeochemical data as well as (vii) the concentrations of components/elements. Therefore, the quality of each set of lithogeochemical data must be assessed individually through the use of duplicates. To assess the quality of lithogeochemical data the method ofThompson and Howarth (1976, 1978) has been used to treat precision as a function of concentration; the method has been modified slightly to deal with small sets of duplicate lithogeochemical data. Duplicates selected for the Silver Queen study are arranged at two different stages. One is at the field sample stage and the other at the analytical measurement stage. Analytical errors are consistently much lower than field sampling variability. The reason for this is that the duplicates arranged at the field sampling stage contain more sources of errors and include the artificial errors caused by insufficient sample size, inhomogeneity of subsample and inconsistent analytical measurements. Because the purpose of using lithogeochemical data is to reveal real geochemical variations it is essential to include sampling variability (i.e. using duplicates samples) as a basis for recognizing meaningful variation. The application of the approach described in the first part of this thesis to the study of the Silver Queen mine reveals that there are two distinctive series ofvolcanic and intrusive rocks in Owen Lake area. The first series consists of igneous and volcanic units from intermediate to felsic composition. They are characterized by having the lower content ofTi02,MgO, total iron andP205as well as the older K-Ar dating ages (range 179 from 78.8 to 57.2 Ma). The second series consist of igneous and volcanic units from intermediate to mafic composition. They have higher contents ofTi02,MgO, total iron andP205 as well as the younger K-Ar dating ages (range from 48.7 to 21.4 Ma). The former predates and hosts the mineralization. The latter is post-mineralization. The hydrothermally altered samples at the Silver Queen mine derive from a multiple precursor system defined by the fractionation trend of the older series of igneous rocks of the Owen Lake area. However, each local, individual hydrothermal alteration profile exhibits the attributes of a single precursor system. These are characterized by a linear trend going through the origin of a Ti02-Zr binary plot. Furthermore, the mineralogical and geochemical incompatibility of these two potentially immobile constituents are examined to eliminate any possibility that Ti02 and Zr could be mobile. Of these two immobile components, Ti02 is used to remove the closure of lithogeochemical data because its lithgeochemical error is smaller than that ofZr. Six types of hydrothermal alteration at the Silver Queen mine have been described. They are propylitic alteration, sericitic and argillic alteration, silicification, pyritization and carbonatization. In general, the wall rock alteration in the study area is composed of a widespread regional propylitic alteration which gives way as the vein is approached to an outer envelope of sericitic and argillic alteration + carbonatization and an inner envelope of silicification and pyritization + sericitic or argillic alteration + carbonatization. Widespread regional propylitic and carbonatic alteration, sericitic and argillic outer envelope and silicification and pyritization inner envelope developed sequentially in that order. Most of the hydrothermally altered samples in alteration envelopes at the Silver Queen mine have gained mass during the hydrothermal alteration. In contrast, samples from the profile of the northern segment of the No. 3 vein have lost mass. Other spatial variations of hydrothermal alteration from the southern segment to the northern segment of the No. 3 vein and from different levels (from 2600-foot level to 2880-foot level) have 180 been recognized. In brief, the wall rock alteration is most intense in the alteration envelope at the central segment of the No. 3 vein and mildest at the northern segment of the No. 3 vein. The total mass change of each altered sample is largely the result of depletions of CaO andNa20, and additions of Si02,K20, 1120 and CO2. In addition, the width of the alteration envelope is very much narrower along the northern segment of the No. 3 vein (total width about 7 m wide) compared to the central and southern segments of the No. 3 vein (total width up to 130 m wide). In some places, alteration envelopes around veins are distributed asymmetrically, principally because of the presence of other veins and because the No. 3 vein is, in reality, an en echelon vein zone. In brief, the hydrothermal alteration at the Silver Queen mine can be summarized as follows: (1) The regional propylitic alteration is characterized by the replacement ofmainly primary mafic mineral initially by epidote and chlorite as well as minor amount of carbonate and the partial replacement of plagioclase replaced by carbonate and sericite. This type of alteration is interpreted to be the product of hydrothermal activity that followed the initial stage of volcanism and predates the mineralization. (2) Carbonatization superimposed on the early propylitic alteration may be the product of a CO2 degassing process, which might be related to the hydrothermal activity associated with mineralization, and is controlled by complicated fracture systems. With increasing intensity of superimposed carbonatization on propylitic alteration, more complete replacements of epidote and chlorite by abundant carbonates occur. (3) The hydrothermal activity associated with mineralization leads to the complete replacement ofplagioclase by sericite and kaolinite, chlorite by siderite and magnetite by pyrite or hematite to form the outer alteration envelope. (4) The inner alteration envelope is interpreted as the product of the process superimposed on sericitic and argillic alteration outer envelope at a maximum stage 181 of ore-forming hydrothermal activity. This is marked by the replacement of sericite by quartz and by the direct precipitation of quartz, sulfide and carbonate from the hydrothermal solution. The close association between mineralization and the inner silicification envelope is clear. This implies that ore-forming metals are transported as Si, 5, C complexes, and that the precipitation of quartz, sulfide and carbonate by the reaction between wall rock and hydrothermal solutions might trigger ore deposition. Many questions dealing with material exchange in hydrothermal systems remain unanswered. A great deal ofwork is required to adapt what is known to a workable system that can be used by explorationists. Further insight is required into optimizing sampling procedure. Methods such as Pearce element ratio diagrams and metasomatic norms need to be extended to a wide range ofgeological environments so that the methodologies can be extended and their advantages and limitations more fully appreciated. 182 Bibliography Albarede, F., and Provost, A. (1977): Petrological and geochemical mass-balance equations; an algorithm for least-square fitting and general error analysis, Computers & Geoscience, 3, pp. 309-326. Appleyard, B.C. (1980) Mass balance computations in metasomatism; metagabbro /nepheline syenite pegmatite interacton in northern Norway. Contributions to Mineralogy and Petrology, 73, (2), pp.13 1-144. Appleyard, E.C. and J. Guha (1991) A special issue on application of hydrothermal alteration studies to mineral exploration, Preface. Economic Geology, 86, (3), pp. 461-465. Armstrong, R.L. (1988): Mesozoic and Early Cenozoic Magmatic Evolution of the Canadian Cordillera; Geological Society ofAmerica, Special Paper 218, pp. 55- 91. Babcock, R.S. (1973) Computational Models ofMstasomatic Processes. Lithos, 6, pp. 279-290. Barrett, T.J., MacLean, W.H. (1994) Chemostratigraphy and hydrothermal alteration in exploration for VIIMS deposits in Greenstones and younger volcanic rocks. in Lentz, D.R., ed., Alteration and alteration processes associated with ore-forming systems: Geological Association ofCanada, Short Course Notes, 11, pp. 433- 467. Barrett, T.J. and MacLean, W.H. (1991): Chemical, mass, and oxygen isotope changes during extreme hydrothermal alteration of an Archean rhyolite, Noranda, Quebec. Economic Geology, 86, (2), pp. 406-414. Barrett, T. J., MacLean, W. H. and Cattalani, S. (1993) Massive sulfide deposits of the Noranda area, Quebec. V. The Corbet mine: Canadian Journal ofEarth Sciences, 30, pp. 1934-1954. Barth, T.F.W., (1959) Principles of classification and norm calculations ofmetamorphic rocks. Journal of Geology, 67: pp.135-52. Barth, T. F. W. (1962) Theoretical Petrology. Wiley, New York, 416 p. Bates, R. L. and Jackson, J. A, editors (1987): Glossary of Geology. American Geological Institute, 749 p. Bernier, L. R. and MacLean, W. H. (1989): Auriferous chert, banded iron formation, and related volcanogenic hydrothermal alteration, Atik Lake, Manitoba. Canadian Journal ofEarth Sciences, 26, (12), pp. 2676-2690. Bernstein, L.R. (1987) Mineralogy and petrography of some ore samples from the Silver Queen mine, near Houston, British Columbia. Unpub. report to Pacific Houston 183 Resources Inc. by Mineral Search, 380 Willow Road, Menlo Park, California 94025, Aug. 1, 1987, 13 p. Billings, M. P. and C. J. Roy (1933) Weathering of the Medford Diabase - Pre- or Postglacial? A discussion. Journal of Geology, XII, pp. 654-666. Boyle, R. W., (1979) The geochemistry of gold and its deposits (together with a chapter on geochemical prospecting for the element): Geological Survey Canada Bull. 280, 584 p. Bodnar, R. J., Reynolds, T. 3. and Kuehn, C. A. (1985) Fluid-inclusion systematics in epithermal systems; in Berger, B. R., and Bethke, P. M. (ed.), Geology and Geochemistry ofEpithermal Systems: Society ofEconomic Geologists, Reviews in Economic Geology, 2, pp. 73-98. Brown, T.H. and Skinner, B.J., (1974) Theoretical prediction of equilibrium phase assemblages in multicomponent systems, American Journal of Science, 274, pp. 961-986. Capitani, C. and Brown, T.H. (1987) The computation of chemical equilibrium in complex systems containing non-ideal solutions. Geochimica et Cosmochimica Acta, 51, pp. 263 9-2652. Carter, N.C. (1981): Porphyry Copper and Molybdenum Deposits West-central British Columbia; B. C. Ministry ofEnergy, Mines and Petroleum Resources, Bulletin 64, iSO p. Cattalani, S., Barrett, T. J., MacLean, W.H., Hoy, L. Hubert, C. and Fox, J.S. (1989): The Home massive sulfide deposit, Noranda, Quebec. Steam, Cohn W. Geological Association of Canada, Mineralogical Association of Canada; annual meeting; program with abstracts, 14. p. 33-34 Cheng, X. and Sinclair, A.J. (1994) Optimizing norm calculations ofmetasomatic rocks. in Chung, C. F. (ed.) Proceedings, 1994 International Association for Mathematical Geology Annual Conference, pp. 8 1-86. Cheng, X. and Sinclair, A.J. (1991) Recognition of immobile/conserved components and its application to hydrothermal altered rocks. Exploration Geochemistry, 1990, ed. F. Mrna, Prague, 1991, pp. 137-143. Cheng, X., Sinclair, A.J., Thomson, M.L., and Zhang, Y. (1991) Hydrothermal alteration associated with Silver Queen polymetallic veins at Owen Lake, central B.C. (93L/2). B.C. Ministry ofEnergy, Mines and Petroleum Resources, Geological Fieldwork 1990, Paper 1991-1, pp. 179-183. Church, B.N. (1970): Nadina (Silver Queen). B. C. Ministry ofMines, Energy and Petroleum Resources, Geology, Exploration and Mining 1969, pp. 126-13 9. 184 Church, B.N. (1971) Geology of the Owen Lake, Parrot Lakes, and Goosly Lake Area. B. C. lVlinistry ofEnergy, Mines and Petroleum Resources, Geology, Exploration and Mining 1970, pp. 119-127. Church, B.N. (1973): Geology of the Buck Creek Area; B. C. Ministry ofEnergy, Mines and Petroleum Resources, Geology, Exploration and Mining, 1972, pp. 353- 363. Church, B.N. (1984): Geology of the Buck Creek Tertiary Outlier; B.C. Ministry of Energy, Mines and Petroleum Resources, unpublished 1:100 000 scale map. Church, B.N. (1985): Update on the Geology and Mineralization in the Buck Creek Area - the Equity Silver Mine Revisited (93L/1W); B.C. Ministry ofEnergy, Mines and Petroleum Resources, Geological Fieldwork, 1984, Paper, 198 5-1, pp. 175- 187. Church, B.N. and Barakso, J.J. (1990): Geology, lithogeochemistry and mineralization in the Buck Creek area, British Columbia. Paper Ministry ofEnergy, Mines and Petroleum Resources. 95 p. Church, B.N. and Pettipas, A.R. (1990) Interpretation of second derivative aeromagnetic maps at the Silver Queen and Equity Silver mines, Houston, BC. Canadian Mining Metallurgy Bull., 83, no. 934, pp.69-76. Cox, K.G., Bell, J. D. and Pankhurst, R. J., (1979) The interpretation of igneous rocks. George Allen & Unwin Ltd. London, 450 p. Cross, W., Iddings, J.P., Pirsson, L. V. and Washington, H.S., (1903) Quantitative classification of igneous rocks. University of Chicago Press. Cross, W., Iddings, J.P., Pirsson, L. V. and Washington, H.S., (1902) A quantitative chemico-mineralogical classification and nomenclature of igneous rocks. Journal of Geology, 10: pp. 555-690. Cummings, W.W. (1987) Report on the Silver Queen Mine, Omineca Mining Division, British Columbia. Unpub. report for Houston Metals Corporation, March, 1987, 17 p. Cyr, J.B., Pease, R.B., and Schroeter, T.G. (1984) Geology and mineralization at the Equity Silver Mine. Economic Geology, 79, pp. 947-968. Davies, J. F., Whitehead, R. E. S., Cameron, R. A., and Duff, D. (1982) Regional and local patterns ofC02-K-Rb-As alteration: A guide to gold in the Timmins area: Canadian Inst. Mining Metallurgy Spec., 24, pp. 130-143. Davis, S.R. and Ferry, J.M. (1993): Fluid infiltration during contact metamorphism of interbedded marble and calc-silicate hornfels, Twin Lakes area, central Sierra Nevada, California. Journal ofMetamorphic Geology, 11. (1). pp. 7 1-88. 185 Dawson, J.M. (1985) Report on the Owen Lake Property, Omineca IVlining Division, British Columbia, for Bulkley Silver Resources Ltd. Unpub. report by Dawson Geological Consultants Ltd., Kamloops, B.C., August 1985, 30 p. Descarreaux, J. (1973) A petrochemical study of the Abitibi volcanic belt and its bearing on the occurrence ofmassive suiphide ores: Canadian Mining Metallurgy Bull., 66, (730), pp. 61-69. Diakow, L.J. and Koyanagi, V. (1988) Stratigraphy and mineral occurrences of Chikamin Mountain and Whitesail Reach Map areas (93E/06, 10). B.C. Ministry ofEnergy, Mines and Petroleum Resources, Geological Fieldwork 1987, Paper 1988-1, pp. 155-168. Dipple, G. M., Winstch, R.P., Andrews, M.S. (1990) Identification of the scales of differential element mobility in a ductile fault zone. Journal ofMetamorphic Geology, 8, pp. 646-661. Dunbar, W.R. (1948) Structural relations of the Porcupine ore deposits, in Structural geology of Canadian ore deposits: Montreal, Canadian Inst. Mining Metallurgy, Geology Div. Spec. Pub., pp. 442-456. Duffell, S. (1959): Whitesail Lake Map-area, British Columbia. Geological Survey of Canada, Memoir 299. Elliott-Meadows, S.R. and Appleyard, E. C. (1991): The alteration geochemistry and petrology of the Lar Cu-Zn deposit, Lynn Lake area, Manitoba, Canada. Economic Geology, 86. (3). pp. 486-505. Engels, J. C. and Ingamells, C. 0. (1970) Effect of sample inhomogeneity in K-Ar dating. Geochimica et Cosmochimica Acta, 34, pp. 1007-1017. Ferry, J.M.(1985a): Hydrothermal alteration ofTertiary igneous rocks from the Isle of Skye, Northwest Scotland; 1, Gabbros. Contributions to Mineralogy and Petrology, 91. (3). pp. 264-282. Ferry, J.M. (1985b): Hydrothermal alteration of Tertiary igneous rocks from the Isle of Skye, Northwest Scotland; 2, Granites. Contributions to Mineralogy and Petrology, 91. (3). pp. 283-304. Finlow-Bates and Stumpfl (1981) The behavior of so-called immobile elements in hydrothermally altered rocks associated with volcanogenic submarine-exhalative ore deposits. Mineralium Deposita, 16, pp. 319-328. Field, C. W., and Fifarek, R. H. (1985) Light stable-isotope systematics in the epithermal environment; in Berger, B. R., and Bethke, P. M. (ed.), Geology and Geochemistry ofEpithermal Systems: Society ofEconomic Geologists, Reviews in Economic Geology, 2, pp. 99-128. 186 Fletcher, W.K. (1981) Analytical methods in geochemical prospecting. handbook of exploration geochemistry, editor: Govett, G. J. S. Handbook of exploration geochemistry. 1. 262 p. Floyd, P. A. and Winchester, J.A. (1978) Identification and discrimination of altered and metamorphosed volcanic rocks using immobile elements. Chemical Geology, 21, pp. 29 1-306. Fyles, J.T., (1984) Report on notes on thin sections ofNew Nadina DDH 84-15. unpublished report to Mr. G. Stewart. 2 p. Fyon, J. A., and Crocket, J. H., (1982) Gold exploration in the Timmins district using field and lithogeochemical characteristics of carbonate alteration zones: Canada Inst. Mining Metallurgy Spec., 24, pp. 113-129. Giggenbach, W. F. (1984) Mass transfer in hydrothermal alteration systems—A conceptual approach. Geochimica et Cosmochimica Acta, 48. pp. 2693-2711. Godwin, CI. (1975): Imbricate Subduction Zones and their Relationship with Upper Cretaceous to Tertiary Porphyry Deposits in the Canadian Cordillera; Canadian Journal ofEarth Sciences, 12, pp. 1362-1378. Golditch, S.S. (1938) A study in rock weathering, Journal of Geology, 46, pp. 17-58. Grant, I. A. (1986) The isocon diagram - A simple solution to Gresen& equation for metasomatic alteration. Economic Geology, 81, pp. 1976-1982. Gresens, R. L. (1967) Composition-volume relationships ofmetasomatism: Chemical Geology, 2, pp. 47-65. Guilbert, J. M. and Park, C. F. Jr. (1986): The geology of ore deposits. W.H. Freeman and Company I New York, 985 p. Hanor, J.S., and K. C. Duchac (1990): Isovolumetric silicification of early Archean komatiites; geochemical mass balances and constraints on origin, Journal of Geology, 98, pp. 863-877. Harland, W.B., Armstrong, R.L., Cox, A.V., Craig, L.E., Smith, A.G. and Smith, D.G. (1989): A Geologic Time Scale, 1989; Cambridge University Press, 1st Edition July, 1989. Harris, D.C., and Owens, D.R. (1973). Berryite, a Canadian occurrence. Canadian Mineralogist, 11, (5), pp. 1016-1018. Hashiguchi, H. and Usui, H. (1975) An approach to delimiting targets for prospecting of the Kuroko ore deposits: on the sulphur and magnetic susceptibility haloes: Mining Geology, 25, pp. 293-301. 187 Hayba, D. 0. (1983) A compilation of fluid-inclusion and stable-isotope data on selected precious- and base-metal epithermal deposits: U.S. Geological Survey, Open-File Report 83-450, 24 p. Hayba, D. 0., Bethke, P. M. Heald, P. and Foley, N. K. (1985) Geologic, mineralogic, and geochemical characteristics ofvolcanic-hosted epithermal precious-metal deposits; in Berger, B. R., and Bethke, P. M. (ed.), Geology and Geochemistry of Epithermal Systems: Society ofEconomic Geologists, Reviews in Economic Geology, 2, pp. 129-168. Helgeson, H. C. (1979) Mass transfer among minerals and hydrothermal solutions, In Geochemistry of hydrothermal ore deposits. edited by H. L. Barnes, John Wiley & Sons, Inc., New York, NY, pp. 568-610. Hood, C.H.B. (1991) Mineralogy, paragensis, and mineralogic zonation fo the Silver Queen vein system Owen Lake, central British Columbia, Unpublished M. Sc. thesis, The University ofBritish Columbia, 273 p. Hughes, C. 3., (1982) Developments in petrology 7, Igneous petrology, Elsevier Scientific Publishing Company, 551 p. Ingamells, C.O. and Switzer, P. (1973) A proposed sampling constant for use in geochemical analysis. Talanta, 20, pp. 547-568. Ingamells, C.O. (1974a) New approaches to geochemical analysis and sampling. Talanta, 21, pp.141-55. Ingamells, CO. (1974b) Control of geochemical error through sampling and subsampling diagrams. Geochmica et Cosmochimca Acta, 38, pp. 1225-1237. Ingamells, C.O. (1981) Evaluation of skewed exploration data— the nugget effect. Geochimica et Cosmochimica Acta, 45, pp. 1209-1216. Ishikawa Y., Sawaguchi, T., Iwaya, S. and Horiuchi, M. (1976) Delineation of prospecting targets for Kuroko deposits based on modes of volcanism of underlying dacite and alteration haloes. Mining Geology, 26, pp. 105-117. Kamilli, R. 3., and Ohmoto, H. (1977) Paragensis, zoning, fluid-inclusion, and isotopic study of the Finlandia vein, Colqui district, Central Peru: Economic Geology, 72, pp. 950-982. Ke, Peiwen (1992): A new approach to mass balance modeling: Applications to igneous petrology, M. Sc. thesis, University ofBritish Columbia, 153 p. Kendall, M.G. (1943) The advanced theory of statistics. vol. 1, Griffin & Co., London, 457 p. 188 Kishida, A., and Kerrich, R. (1987) Hydrothermal alteration zoning and gold concentration at the Kerr-Addison Archean lode gold deposit, Kirkland Lake, Ontario: Economic Geology, 82, pp. 649-690. Kleeman, A.W. (1967) Sampling error in the chemical analysis of rocks. Journal of Geological Society ofAustralia, 14, pp. 43-47. Kranidiotis, P. and MacLean, W. H. (1987): Systematics of chlorite alteration at the Phelps Dodge massive sulfide deposit, Matagami, Quebec. Economic Geology, 82. (7). pp. 1898-1911. Krauskof, K. B. (1967) Chemical weathering, chapter 4, Introduction to Geochemistry, McGraw-Hill, Inc. 721 p. Kwong, Y. T. J., Brown, T. H. and Greenwood, H. J. (1982) A thermodynamic approach to the understanding of the supergene alteration at the Afton copper mine, south- central British Columbia: Canadian Journal ofEarth Sciences, 19, pp. 2378-2386. Le Maitre, P. W. (1982) Numerical Petrology - Statistical Interpretation of Geochemical Data. Developements in Petrology 8, Elsevier Scientific Publishing Company Inc. 281 p. Leitch, C.H.B. (1989): Geology, Walirock Alteration, and Characteristics of the Ore Fluids at the Bralorne Mesothermal Gold Quartz Vein Deposit, Southwestern British Columbia; unpublished Ph.D. thesis, The University ofBritish Columbia, Vancouver, 483 p. Leitch, C.H.B. and Day, S.J. (1990) Newgres: a Turbo Pascal program to solve a modified version ofGresens’ hydrothermal alteration equation: Computers & Geoscience, 16, pp. 925-932. Leitch, C.H.B. and Lentz, D. R. (1994) The Gresens approach to mass balance constriants of alteration systems: Methods, Pitfalls, Examples. in Lentz, D.R., ed., Alteration and alteration processes associated with ore-forming systems: Geological Association of Canada, Short Course Notes, 11, pp. 161-192. Leitch, C.H.B., Hood, C.T., Cheng, X. and Sinclair, A.J. (1990) Geology of the Silver Queen mine area, Owen Lake, central British Columbia. B.C. IVlinistry ofEnergy, lVlines and Petroleum Resources, Geological Fieldwork 1989, Paper 1990-1, pp. 287-295. Leitch, C. H. B., Cheng, X., Hood, C. T., Sinclair, A.J. (1991) Structural character of en echelon polymetallic veins at the Silver Queen mine, British Columbia. CIM Bulletin, 84, (955), pp. 57-66. Leitch, C.H.B., Hood, C.T., Cheng, X. and Sinclair, A.J. (1992) Tip Top Hill unit: Upper Cretaceous volcanic rocks hosting Eocene epithermal base- and precious-metal veins 189 at Owen Lake, central British Columbia.Canadian Journal ofEarth Sciences, 29, pp. 854-864. Lindgren, W., (1933): Mineral Deposits. 4th ed. New York: McGraw-Hill, 930 p. Maclntyre, D.G. (1985): Geology and Mineral Deposits of the Tahtsa Lake District, West-central British Columbia; B.C. Ministry ofEnergy, Mines and Petroleum Resources, Bulletin 75, 82 p. Maclntyre, D.G. and Desjardins, P. (1988): Babine Project (93L/15); B.C. Ministry of Energy, Mines and Petroleum Resources, Geological Fieldwork, 1987, Paper, 1988-1, pp. 181-193. MacLean, W.H. (1988) Rare earth elements mobility at constant inter-REE ratios in the alteration zone at the Phelps Dodge massive suiphide deposit, Matagami, Quebec. Mineralium Deposita, 23, pp. 231-238. MacLean, W.H. (1990): Mass change calculations in altered rock series. Mineralium Deposita. 25. (1). pp. 44-49. MacLean, W.H. and Barrett, T.J., (1993) Lithochemical techniques using immobile elements, Journal of Geochemical Exploration, 48, pp. 109-133. MacLean, W.H. and Kranidiotis, P. (1987): Immobile elements as monitors ofmass transfer in hydrothermal alteration; Phelps Dodge massive sulfide deposit, Matagami, Quebec. Economic Geology, 82. (4). pp. 951-962. Madeisky, H. E. and Stanley, C. R. (1993): Tdentifjing metasomatic zones associated with volcanic-hosted massive sulfide deposits using Pearce Element Ratio analysis, Lithogeochemical exploration for VMS deposits. The Gangue, GAC- Mineral Deposits Division Newsletter, issue 41, Jan. 1993, pp. 5-7. Margaret, G., McAfee, Jr., R., and Wolf, C. L.,(1972) (eds.) Glossary of Geology; Amer. Geol. Inst., Washington, D. C., 805 p. plus appendix. Marquis, P., A. C. Brown, C. Hubert and D. M. Rigg (1990) Progressive alteration associated with auriferous massive sulfide bodies at the Dumagami mine, Abitibi greenstone belt, Quebec. Economic Geology, 85, pp. 746-764. Marsden, H.W. (1985): Some Aspects of the Geology, Mineralization and Wallrock Alteration of the Nadina Zn-Cu-Pb-Ag-Au Vein Deposit, North-central B.C.; Unpublished B.Sc. thesis, The University ofBritish Columbia, 90 p. Maxwell, J.A. (1968) Rock and mineral analysis. Wiley-Interscience, new York. Merrill, G.P. (1897) Rock, Rock-Weathering, and Soil. New York, Macmillan Co., 218 p. Meyer, C., and Hemley, J.J. (1967) Wall rock alteration, in Geochemistry of hydrothermal ore deposits, ed. Barnes, H. L. : New York, Holt, Rinehart and Winston, Inc., pp. 166-23 5. 190 Myers, J. D., and C. L. Angevine (1986): Mass balance calculations with end member compositional variability: application to petrologic problems, EOS Trans. AGU, 67, p. 404. Myers, J. D., C. D. Frost and C. L. Angevine (1986): A test of a quartz eclogite source for parental Aleutian magmas: a mass balance approach, Journal of Geology, 94, pp. 811-828. Myers, J. D., and C. L. Angevine and C. D. Frost (1987): Mass balance calculations with end member compositional variability: application to petrologic problems, Earth Planet. Sci. Lett., 81, pp.212-20. Morton, R.L. and Nebel, M.L. (1984): Hydrothermal alteration of felsic volcanic rocks at the Helen siderite deposit, Wawa, Ontario. Economic Geology, 79, pp. 1319- 1333. Nicholls, J. (1988) The statistics ofPearce element diagrams and the Chayes closure problem. Contributions to Mineralogy and Petrology. 99, pp. 11-24. Niggli, P., (1954) Rocks and mineral deposits. San Francisco: W. H. Freeman. Nowak, M. (1991) Ore reserve estimation, Silver Queen vein, Owen Lake, British Columbia; Unpubl. M.A.Sc. thesis, The University ofBritish Columbia, 204 p. Ondrick, C. W. and Suhr, N. H. (1969) Error and the spectrographic analysis of greywacke samples. Chemical Geology, 4, pp. 429-437. Pearce, T. H, (1968) A contribution to the theory of variation diagrams. Contributions to Mineralogy and Petrology, 19, pp. 142-157. Pearce, T.H. (1987): The identification and assessment of spurious trends in Pearce-type ratio variation diagrams; a discussion of some statistical arguments. Contributions to Mineralogy and Petrology, 97, (4), pp. 529-534. Philpotts, A. R. (1990) Principles of igneous and metamorphic petrology. Prentice Hall, Englewood Cliffs, New Jersey, 498 p. Potts, P.J.(1987) A handbook of silicate rock analysis, Blackie & Son Limited. Press, W. H., B. P. Flattery, S. A. Teukolsky, and W. T. Vetterling (1987): Numerical Recipes in C, Cambridge University Press, 818 p. Price, P., and Bancroft, W. L. (1948) Waite Amulet mine—Waite section, in Structural geology of Canadian ore deposits: Montreal, Canadian Inst. Mining metallurgy, Geology Div., Spec. Pub., pp. 748-756. Ribbe, P.H. (1983) Chemistry, structure and nomenclature of feldspars, Feldspar Mineralogy, ed. Ribbe, P. H., Reviews in Mineralogy, 2, Mineralogical Society of America. pp. 1-20. 191 Rice, AR. (1977): Solute banding; a possible indicator of turbulent thermal convection in magmas and a possible precursor to rollover in stratified magmas with attendent explosive volcanism. EOS (Am. Geophys. Union, Trans.). 58. (12). p. 1249 Richards, J. P. McCulloch, M. T. Bruce, W. C. and Kerrich, R. (1991) Sources ofmetals in the Porgera gold deposit, Papua new Guinea: Evidence from alteration, isotope, and noble metal geochemistry. Geochimica et Cosmochimica Acta, 55, pp. 565- 580. Rittmann, A., (1973) Stable mineral assemblages of igneous rocks, A method of calculation, Springer-Verlag, 262 p. Robert, F. and Brown, A. C. (1984): Progressive alteration associated with gold-quartz tourmaline veins at the Sigma mine, Abitibi greenstone belt, Quebec; Economic Geology, 79, pp. 393-399. Robert, F. and Brown, A. C. (1986): Archean gold-bearing quartz veins at the Sigma mine, Abitibi Greenstone belt, Quebec: Part II. vein paragenesis and hydrothermal alteration, Economic Geology, 81. pp. 593-616. Rose, A. W. and Burt, D. M. (1979) Hydrothermal alteration, in Geochemistry of hydrothermal ore deposits, 2ed., ed. Barnes, H.L. New York, John Wiley and Sons, pp. 173-235 Russell, J. K. (1986) A Fortran-77 computer program for the least squares analysis of chemical data in Pearce variation diagrams. Computers & Geosciences, 12, pp. 327-338. Russell, J. K. and Nicholls, J. (1987) Early crystallization history of alkali olivine basalts, Diamond Craters, Oregon. Geochimica et Cosmochimica. Acta. 51, pp. 143-154. Russell, J. K. and Stanley, C.R. (1989) Differentiation of the 1954-1960 lavas ofKilauea volcano. Pacific N.W. Amer. Geoph. Union, program with abstr., 1, p. 10. Russell, 3. K. and C. R. Stanley (1990a) Theory and application ofPearce Element Ratios to geochemical data analysis. Geological Association of Canada Short Course #8, 1989, 315 p. Russell, 3. K. and Stanley, C. R.(1990b): Origins of the 1954-1960 lavas ofKilauea Volcano; constraints on shallow reservoir magmatic processes. Continental magmatism; abstracts. Bulletin New Mexico Bureau ofMines and Mineral Resources. 131. p. 230 Saeki, Y. and Date, J. (1980) Computer application of the alteration data for the footwall dacite lava at the Ezuri Kuroko deposits, Akita Prefectrue, Mining Geology, 30, pp. 241-250. 192 Sander, M. V. and Einaudi, M. T. (1990) Epithermal deposition ofgold during transition from propylitic to potassic alteration at Round Mountain, Nevada. Economic Geology, 85, pp. 285-3 11. Shapiro, L. and W.W. Brannock (1955) Rapid determination ofwater in silicate rocks. Analytical Chemistry. 27, pp. 560-562. Shapiro, L. and W.W. Brannock (1962) Rapid analysis of silicate, carbonate and phosphate rocks. US Geological Survey Bull. 1144-A. Shaw, D. M. (1961) Manipulative errors in geochemistry: a preliminary study. Trans. Roy. Soc. Can. LV, pp. 4 1-55. Sketchley, D.A. and Sinclair, A. J., (1987) Gains and losses of elements resulting from wall-rock alteration— a quantitative basis for evaluating lithogeochemical samples: British Columbia Ministry Energy Mines Petroleum Resources Rept. 1987-1, pp.57-63. Sketchley, D. A. and A. J. Sinclair (1991) Carbonate alteration in basalt, Total Erickson Gold Mine, Cassiar, Northern British Columbia, Canada, Economic Geology, 86, pp. 570-587. Spitz, G. and Darling, R. (1978) Major and minor element lithogeochemical anomolies surrounding the Louvem copper deposit, Val d’Or, Quebec. Canadian Journal of Earth Science, 15, pp. 1161-1169. Stanley, C.R. and H. E. Madeisky (1993) Pearce element ratio analysis: Applications in lithochemical exploration, MDRU short course notes: SC-13, Dept. of Geological Sciences, University ofBritish Columbia, 542 p. Stanley, C.R. and H. E. Madeisky (1994) Lithogeochemical exploration for hydrothermal ore deposits using Pearce element ratio analysis. in Lentz, D.R., ed., Alteration and alteration processes associated with ore-forming systems: Geological Association ofCanada, Short Course Notes, 11, pp. 193-211. Stanley, C. R. and Russell, J.K. (1989a)PEARCE,PLOT: Interactive Graphics-Supported Software for testing petrologic hypotheses with Pearce Element Ratios. American Mineraloist, 74, pp. 317-320. Stanley, C. R. and Russell, J.K. (1989b) PEARCE.PLOT: A Turbo-Pascal Program for the analysis of rock compositions with Pearce Element Ratios. Computers & Geosciences, 15, pp. 950-926. Stanley, C. R. and Russell, J.K. (1989c): Petrologic hypothesis testing with Pearce element ratio diagrams; derivation of diagram axes. Contributions to Mineralogy and Petrology. 103. (1). pp. 78-89. 193 Stanley, C. R. and Russell, J.K. (1990): Derivation of axis coefficients for Pearce element ratio diagrams. Continental magmatism; abstracts. Bulletin New Mexico Bureau ofMines and Mineral Resources, 131. p. 252 Stormer, J.C., and J. Nicholls (1978): XLFRAC: a program for the interactive testing of magmatic differentiation models, Computers & Geosciences, 4, pp. 143-159. Stout, M.Z and Nicholls, J. (1977): Mineralogy and petrology ofQuaternary lavas from the Snake River plain, Idaho. Canadian Journal ofEarth Science, 14. (9). pp. 2 140-2156. Streckeisen, A.L. (1967): Classification and Nomenclature of Igneous Rocks; Neues Jahrbuch Mineralogie, Abhandlung, 107, pp. 144-214. Sutherland Brown, A. (1960): Geology of the Rocher Deboule Range; B.C. Ministry of Energy, Mines and Petroleum Resources, Bulletin 43, 78 p. Thompson, M. and Howarth, R.J., (1976) Duplicate analysis in geochemical practice, 1. Theoretical approach and estimation of analytical reproducibility. Analyst, 101: pp. 690-698. Thompson, M. and Howarth, R.J., (1978) A new approach to the estimation of analytical precision. Journal of Geochemical Exploration, 9: pp. 23-30. Tipper, H.,W. and Richards, T.A. (1976): Jurassic Stratigraphy and History ofNorth- central British Columbia; Geological Survey of Canada, Bulletin 270, 73 p. Weir, B. (1973). A mineralogical and milling study of the Nadina mine. Unpub. term report for Geology 409, Univ. ofBritish Columbia, April 1973, 31 p. Wetherell, D.G., (1979), Geology and ore genesis of the Sam Goosly copper-silver- antimony deposit, British Columbia. Unpub. M.Sc. thesis, Univ. ofBritish Columbia, Vancouver, 208 p. Wetherell, D.G., Sinclair, A.J. and Schroeter, T.G. (1979): Preliminary Report on the Sam Goosly copper-silver Deposit; B.C. Ministry ofEnergy, Mines, and Petroleum Resources, Geological Fieldwork, 1978, pp. 132-137. Wickman, F. E. (1962) The amount ofmaterial needed for a trace element analysis. Ark. Mineral. Geol. 3, (6), pp. 131-139. Wilson, A.D. (1964) The sampling of silicate rock powders for chemical analysis. Analyst, 89, pp. 18-30. Wisser, E. (1951) Tectonic analysis of a mining district —Pachuca, Hidalgo: Economic Geology, 46, pp. 459-477. Winchester, T.A. and Floyd, P.A. (1977) Geochemical discrimination of different magma series and their differentiation products using immobile elements. Chemical Geology, 20, pp. 325-347. 194 Wojdak, P.J. and Sinclair, A.J. (1984): Equity Ag-Cu-Au Deposit: Alteration and Fluid Inclusion Study; Economic Geology, 79, pp. 969-990. Woods, T. L, Bethke, P. M., and Roedder, E. (1982) Fluid-inclusion data at Creede, Colorado in relation to mineral paragenesis: U. S. Geological Survey, Open-File Report 82-3 13, 61 p. Woodsworth, G.J. (1982): Age Determinations and Geological Studies, K-Ar Isotopic Ages, Report 15; Geological Survey ofCanada, Paper 81-2, pp. 8-9. Wright, T.L. and P.C. Doherty (1970) A linear programming and least square computer method for solving petrologic mixing problems, Geol. Soc. America. Bull., 81, pp. 1995-2008. 195 Appendix A. Megascopic Description of Altered Samples, Silver Queen Mine 196 Table A-i. Megascopic Description of Altered Samples, Silver Queen Mine Sample Description Weight* No. (g) X1-1 the main cross-cut (also named Bulkley cross-cut) of 2600 foot level of 610 underground working; 0-0.3 m from the footwall of the No. 3 vein (1.2 m wide, 325fNEL47°) to walirock; strongly silicffied and pyrilized microdiorite; pale apple green, not magnetic, fine grain porphyroid texture, quartz, clay minerals and abundant disseminated pyrite. X1-2 same location as above; 0.3-0.6 m from the footwall of the No. 3 vein to wallrock; 1260 strongly silicified and pyritized microdkrite; petrographic features are same as above except containing less pyrite. X1-2d same location as above; 0.6-0.8 m from the footwall of the No. 3 vein to wallrock; 645 moderately silicffied microdionte, petrographic features are same as above. X1-3 same location as above; 0.8-1.6 m from the footwall of the No. 3 vein to wallrock; 1196 sericitic-argillic altered nricrodiorite, it is getting away from the vein, the intensity of alteration seems weaker than above samples; the color of the rock looks pale white to grey white or yellowish grey, the rock has more clay (can be tasted) and less_quartz_and pyrite than the_above_samples. X1-4 same location as above; 1.6 - 2.4 m from the footwall of the No. 3 vein to 1085 walirock; sericitic-argillic altered microdiorite; its petrographic features are similar to the above sample. X1-5. same location as above; 2.4- 3.2 m from the footwall of the No. 3 vein to wallrock; 1522 sericitic-argillic altered microdiorite; its petrographic features are similar to the above sample. X1-6. same location as above; 5-7 m from the footwall of the No. 3 vein to wallrock 2143 (inaccessible for sampling between 3.2-Sm); sericitic-argillic altered microdiorite; its petrographic features are similar to the above sample. X1-7. same location as above; 7-14 m from the footwall of the No. 3 vein to walirock; 2216 sericitic-argillic microdiorite; it seems having more sericitic and less clays. Primary textrue is well preserved. X1-8. same location as above; 14-27 m from the footwall of the No. 3 vein to wallrock; 3051 moderate sericitic-argillic microdiorite; the alteration intensity looks obviously weaker than the samples above; ther is a post-mineralization structure zone at the place of 27 m. 197 X2-1 the northern cross-cut of 2600 foot level underground working; 6.4-8.9 m from 880 the hanging-wall of the No. 1 vein to wall-rock (at the footwall side of the No. 2 vein), propylitic andesite, black or dark grey, massive and dense, detectable magnetism, reacting with diluted acid, porphyritic and flow texture, feldspar, hornblende and augite are identifiable phenocrysts, their sizes range from 0.5 to 2 mm,_there are about 40% of aphanitic grounchnass. X3 -1 the northern cross-cut of 2600 foot level underground working; 1 m of horse rock 920 between two veins (belong to No. 2 vein system), strong sericitic-argillic andesite; pale green, no magnetic, not reacts with diluted acide, alteration is relatively strong characterized by intensed fracture and poorly preserved primary texture; disseminated pyrite and other sphalerite are oberserved; all primary minerals are altered to_clay minerals_(stick tongue). X3-2 same location as above; 0-2.5 m from the footwall of the No. 2 vein to wall rock; 580 moderate sericitic-argillic andesite; petrographic features are similar to the above sample. X3-2d same location as above; 2.5-6 m from the footwall of the No. 2 vein to wall rock; 840 moderate sericitic-argillic andesite; .pale white or grey white, no magnetic, no reaction with diluted acide, primary porphyritic and flow texture is well preserved, primary minerals such as feldspar, hornblende and augite are all altered to clay minerals. X3-3 same location as above; 6-8 m from the footwall of the No. 2 vein to wallrock; 1380 propylitic andesite, its petrographic features are similar to those of sample X2-1. X3-3d same location as above; 8-16 m from the footwall of the No. 2 vein to wallrock; 995 propylitic andesite, its petrographic features are similar to those of sample X2-1. X3-4. same location as above; 0-0.4 m from the hanging-wall of the No. 2 vein to 990 wallrock; strong sericitic-argillic andesite; its petrographic features are similar to sample X3-l. X3-5. same location as above; 0.4-1.4 m from the hanging-wall of the No. 2 vein to 770 wallrock; moderate sericitic-argillic andesite. Its petrographic features are similar to X3-2d. X3-6. same location as above; 1.4 - 4.4 m from the hanging-wall of the No. 2 vein to 860 wallrock; propylitic andesite. Its petrographic features are similar to X3-2d. X3-7. same location as above; 4.4-15 m from the hanging-wall of the No. 2 vein to 967 wallrock; propylitic andesite. Its petrographic features are similar to X2-1. 198 X4-4 same location as above; 3-12 m from the footwall of the No. 3 vein to wall rock, 980 propylitica andesite. Its petrographic features are similar to X2-1. X5-1 the southern cross-cut of 2600 foot level underground working; 0-0.3 m from the 1350 hanging-wall of the No. 3 vein to walirock, silicic and pyritic andesite. It is intensely fractured and altered. X5-2. same location as above; 0.3-1.1 m from the hanging-wall of the No. 3 vein to wall 1320 rock, moderate silicic and pyritic andesite, similar to the sample above but less intensely fractrued. X5-3. same location as above; 1.1-1.6 m from the hanging-wall of the No. 3 vein to 1110 walirock, sericitic and argillic andesite, pale brown, massive, primary texture well preserved, no magnetic and no reaction with diluted acide. X5-4. same location as above; 1.6-3.1 m from the hanging-wall of the No. 3 vein to 1615 wallrock, sericitic and argillic andesite, X5-5. same location as above; 3.1-14 m from the hanging-wall of the No. 3 vein to 1058 wallrock, sericitic and argillic andesite. X5-5d same location as above; 14-33 m from the hanging-wall of the No. 3 vein to 908 wallrock, sericitic and argillic andesite. X5-6. same location as above; 33-36 m.from the hanging-wall of the No. 3 vein to 893 wallrock, propylitic andesite. X5-6d. same location as above; 36-38 m.from the hanging-wall of the No. 3 vein to 860 walirock,_propylitic_andesite. X5-7. same location as above; 38-56 m from the hanging-wall of the No. 3 vein to wall- 956 rock, sericitic and argillic andesite. This alteration envelope may be related to a non-mineralized breccia zone (see the description below). X5-8 same location as above; 56-70 m from the hanging-wall of the No. 3 vein to wall- 1512 rock, sericitic and argillic andesite. The rock at the working face (70 m) is intensely fractured_(breccia_zone). X5-9 same location as above; 0-0.5 m from the hanging-wall of the Footwall vein to 1528 wall-rock, silicic and pyritic andesite, pale apple green, abundant disseminated pyrite. X5-10 same location as above; 0.5-6.5 m from the hanging-wall of the Footwall vein to 1715 the footwall of the No. 3 vein, silicic and pyritic andesite, similar to the sample above but less abundant disseminated pyrite. 199 X10-1 the main cross-cut (also named Bulkley cross cut) of 2600 foot level of 487 underground working; 0-1.2 m from the hanging-wall of the No. 3 vein to wall rock, silicic and pyritic niicrodiorite, pale apple green, abundant hematite veinlets cut pyrite veinlets and altered wallrock with abundant disseminated pyrite. It is also intensely fractured. X10-2 same location as above; 1.2-4 m from the hanging-wall of the No. 3 vein to wall- 950 rock, moderate silicic and argillic microdiorite. Its petrographic features are similar to the above but less adundent of veinlets, disseminated pyrite and not intensely fractured. X10-3 same location as above; 4-5.5 m from the hanging-wall of the No. 3 vein to wall- 830 rock, sericitic and argillic microdiorite. Its petrographic features are similar to above but there_is_much_less veinlets_than above_sample. X10-3d same location as above; 5.5-7.5 m from the hanging-wall of the No. 3 vein to 815 wall-rock, sericitic and argillic microdiorite, buffer brown. There is no veinlets. X10-4. same location as above; 7.5-20 m from the hanging-wall of the No. 3 vein to wall- 803 rock, sericitic and argillic microdiorite, similar to the sample above. Xl0-5. same location as above; 20-38 m from the hanging-wall of the No. 3 vein to wall- 847 rock, moderate sericitic and argillic microdiorite, similar to the sample above. X10-6 same location as above; 38-44 m from the hanging-wall of the No. 3 vein to wall- 651 rock, propylitic microdiorite, black, dark grey, magnetic. It has a ‘sharp contact’ (gradational contact in the range of 2 cm) with the sample above. X10-6d same location as above; 44-56 m from the hanging-wall of the No. 3 vein to wall- 545 rock, propylitic microdiorite, similar to the sample above. DA63-1 Switch back vein, 32-44 ft of drill 87-S-04, propylitic andesite contacts with a 488 post-mineralization dike (DA63-2). DA63-3 same location as above, 460-469 ft of drill 87-S-04, sericitic and argillic andesite 720 DA63 -4 same location as above, 472-496 ft of drill 87-S-04, sencitic and argillic andesite, 610 DA63 -5 same location as above, 497-499 ft of drill 87-S-)4, silicic andesite 620 DA63-6 same location as above, 500-504 ft of drill 87-S-04, silicic andesite. There is 720 hanging-wall sphalerite-galena-pyrite-barite vein (DA63-7) between sample DA63-6 and DA63-8. DA63-8 same location as above, 506-514 ft of drill 87-S-04, silicic andesite contacs the 770 hanging-wall of the main vein at 514 ft. * sample weight after sawing out the weathering surface and veinlets. 200 Appendix B. Lithogeochemical Duplicate Analyses, Silver Queen Mine 201 T ab le B -i S am pl e D up li ca te s of M aj or C om po ne nt s at S il ve r Q ue en m in e, ce nt ra l B ri ti sh C ol um bi a SA M PL E ID R O C K T Y PE A L T E R A T IO N L O C A T IO N S 10 2 A 12 03 F e2 0 3 F eO M gO C aO N a2 0 K 20 T 10 2 M nO P 2 0 5 xl O -6 d rn . di .* w -a lt m ai n x- cu t 59 .0 5 15 .4 3 2. 64 2. 89 2. 69 5. 10 3. 70 3. 15 0. 59 0. 18 0. 28 D A 63 -3 rn . di . rn -a lt Sw tc h bk V . 87 -S -4 51 .1 9 16 .2 4 0. 66 11 .2 4 1. 35 1. 25 0. 25 4. 27 0. 58 0. 98 0. 28 D A 8- 3 an d. s- al t C am p v. 88 -S -2 9 58 .1 1 15 .6 9 2. 73 3. 49 0. 38 1, 00 0. 03 3. 57 0. 54 4. 09 0. 30 D A 63 -5 m d i. s- al t S w tc h b k v .8 7 -S -4 54 .4 1 15 .3 4 2. 15 9. 14 0. 80 1. 24 0. 04 3. 34 0. 45 0. 69 0. 31 D A 63 -1 m . di . w -a lt S w tc h bk v. 87 -S -4 57 .9 9 16 .5 3 2. 22 3, 76 2. 63 6, 25 3. 43 3. 16 0. 71 0. 16 0. 43 D A 48 -2 m d i. rn -a lt C o le lk v .8 8 -S -5 52 .6 8 18 ,8 8 0. 81 6. 43 1. 16 2. 16 0. 14 6. 39 0. 61 1, 16 0. 32 S 91 -1 5D po rp hy ry w m -a lt D uc k la ke 60 .0 5 15 .3 4 2. 59 2. 42 2. 76 5, 02 3. 83 2. 37 0. 59 0. 41 0. 29 D A 48 -5 m . dl . w m -a lt C ol e 1k v. 88 -S -5 54 ,7 1 16 .8 1 2, 46 3. 20 2. 14 5. 67 2. 66 4. 34 0. 58 0. 21 0. 41 D A 48 -4 m . dl . rn -a lt C ol e 1k v. 88 -S -5 52 ,7 7 21 .9 4 2. 02 3. 60 0. 92 4. 95 0. 13 3. 05 0. 51 0. 31 0. 31 x3 -3 an d. w -a lt N N o3 v. x- cu t 57 .7 5 15 .8 5 3, 02 2. 86 2. 87 5. 75 3. 96 3. 02 0. 66 0. 31 0. 39 x ll -1 m d i. w -a lt F W Ja ck v , 57 .0 1 15 .7 0 2. 69 3. 77 4. 29 5. 80 3. 76 2. 98 0. 66 0. 21 0, 42 S 91 -9 N ac ii an dk w -a lt N ad ln aM t. E .s lo 49 .6 4 15 .1 5 3. 34 5. 64 7. 81 6. 58 2. 96 1. 53 1. 27 0. 31 0. 56 S 91 -1 0 N d g ra n lt e w -a lt N ad ln aM t. E .s lo 68 ,0 3 14 ,2 0 1. 04 1. 87 1. 76 2. 45 3. 75 4. 68 0. 50 0. 08 0. 22 xl O -6 rn .d i. w -a lt m al n x -c u t 61 .2 0 15 .0 6 2. 36 2. 86 2. 81 4. 90 3. 96 3. 15 0. 58 0. 14 0. 27 xl O -3 d m .d i. rn -a lt m ai n x -c u t 63 .2 7 17 .7 6 0. 99 3. 11 1. 05 1. 60 0. 32 4. 98 0. 40 0. 49 0. 13 xl -1 m . di . s- al t m aI n x- cu t 59 .1 0 14 .6 7 0. 51 9. 11 0. 85 0. 66 0. 05 2. 75 0. 34 1. 08 0. 17 x l- 9 0 m .d l. w -a lt m al n x -c u t 61 .8 9 15 .3 3 1. 99 2. 44 2. 25 4. 09 3. 52 3. 69 0. 43 0. 16 0. 23 x l- 5 m .d l. rn -a lt m ai n x -c u t 63 .8 5 16 .1 5 1. 33 3. 33 1. 22 1. 56 0. 31 4, 55 0, 41 1. 06 0. 12 xl O -6 D m .d i. w -a lt m al n x -c u t 59 .0 0 15 .9 8 2. 52 2. 85 2. 18 5. 16 3 6 3 3. 09 0. 56 0, 18 0, 34 D A 63 -3 D m . dl . rn -a lt S w tc h bk v. 87 -S -4 51 .6 8 16 .2 0 0. 41 11 .2 4 1. 34 1. 24 0, 03 4. 24 0. 56 0. 98 0, 25 D A 8- 3D an d, s- al t C ar n p v .8 8 -S -2 9 55 .6 9 16 .4 3 2. 81 3. 49 0. 39 1. 55 0. 05 3. 78 0. 55 4. 27 0. 30 D A 63 -5 D m . di . s- al t S w tc h bk v. 87 -S -4 54 .5 9 14 .9 5 2. 02 9. 13 0. 87 1. 04 0. 02 3. 29 0. 46 0. 63 0. 29 D A 63 -1 D m .d l, w -a lt S w tc h b k v .8 7 -S -4 57 .7 2 16 .6 3 2. 32 3. 76 2. 62 6. 45 3. 28 3. 26 0. 72 0. 16 0. 43 D A 48 -2 D m .d l. rn -a lt C o le lk v .8 8 -S -5 52 .6 3 18 .9 5 0. 81 6. 43 1. 16 2. 04 0. 14 6. 37 0. 60 1. 18 0, 32 S 9 1 -l 5 D d po rp hy ry w rn -a lt D uc k la ke 60 .6 4 15 ,2 4 2. 54 2. 42 2. 62 4. 98 3. 90 2. 36 0, 59 0. 36 0. 29 D A 4B -5 D m d l. w rn -a lt C o le lk v .8 8 -S -5 54 .2 0 17 .0 5 2. 41 3, 20 2. 15 5. 68 2. 59 4. 42 0. 57 0. 21 0. 41 D A 48 -4 D m . dl . rn -a lt C ol e 1k v. 88 -S -5 53 .8 2 20 .7 5 2. 02 3, 60 0. 84 4. 65 0. 16 3. 05 0. 53 0. 31 0. 33 x3 -3 d an d, w -a lt N N o3 v. x- cu t 57 .5 9 15 .8 0 2. 81 3. 08 3 ,0 7 5. 61 3. 69 3. 13 0. 65 0. 35 0. 39 x ll -l b m d l. w -a lt F W Ja ck v . 57 .0 5 15 .7 7 2. 73 3. 77 4. 18 5. 78 3. 76 2. 97 0. 69 0. 22 0. 42 S 91 -9 D N ad ia n d k w -a lt N ad ln aM t. E .s lo 49 .8 2 15 .0 3 3. 23 5, 64 7. 64 6. 50 2. 98 1. 51 1. 26 0. 31 0. 56 S9 1- 1O D N d gr an it e w -a lt N ad in a M t. E. sb 67 .4 6 14 .2 8 1. 05 1. 87 1. 86 2. 44 3. 83 4. 69 0. 51 0. 08 0. 21 xl O -6 d m . dl . w -a lt m ai n x- cu t 59 .0 0 15 .9 8 2. 52 2. 85 2. 18 5. 16 3. 63 3. 09 0. 56 0. 18 0. 34 xl O -3 D m d l. rn -a lt rn al nx -c ut 63 .5 2 17 ,9 9 1. 02 3. 11 1. 06 1. 62 0. 32 5. 03 0. 40 0. 49 0. 14 X 1- 1D m d l. s- al t m al n x -c u t 59 .2 0 14 .2 9 0. 67 9. 17 0. 83 0. 68 0. 07 2. 78 0. 35 1. 06 0. 17 xl -9 0d m . dl . w -a lt m aI n x- cu t 61 .8 7 15 .0 2 1, 83 2. 61 2. 47 3. 97 3, 54 3. 72 0, 43 0. 19 0. 22 X 1- 5D m . dl . rn -a lt m ai n x- cu t 64 .5 1 15 .1 5 1. 52 3. 19 0. 86 1. 81 0. 00 4. 19 0. 44 1. 14 0. 20 m d i. - m ic ro d io ri te ; an d . - an d es it e; w -a lt . - w ea kl y al te re d ; rn -a lt . - m o d er at el y al te re d ; s- al t. - st ro n g ly al te re d ; x -c u t - C rO S S cu t; 1K - la K e; V . - v ei n . C T ab le B -2 . M ea su re m en t D up li ca te s of M aj or C om po ne nt s at S il ve r Q ue en m in e, ce nt ra l B ri ti sh C ol um bi a SA M PL E ID R O C K T Y PE A L T E R A T IO N L O C A T IO N - S 10 2 A 12 03 F e2 0 3 F eO M gO C aO N a2 0 K 20 T i0 2 M nO P 2 0 5 x5 -9 an d. s- al t S N o 3 v .x -c u t 64 .1 0 16 .0 0 2. 23 3, 35 1. 10 0. 35 0. 33 4. 73 0. 45 0. 08 0. 19 S 91 -1 5 po rp hy ry w m -a lt D uc k la ke 63 .2 2 14 .8 1 3. 00 1. 82 3. 40 3. 03 4. 20 2. 62 0. 55 0. 12 0. 28 xI O -3 m .d i. rn -a lt m ai n x -c u t 63 .2 7 17 .4 1 0. 88 3. 52 1. 01 0. 66 0. 31 5. 67 0. 39 0. 95 0. 12 xl O -2 m d i. s- al t m al n x -c u t 60 .4 3 15 .7 1 2. 45 5. 40 1. 28 0. 63 0. 29 4. 45 0. 39 1. 41 0. 10 xl O -5 m , di . rn -a lt m ai n x- cu t 59 .7 1 18 .1 6 1. 43 3. 43 1. 48 2. 71 0. 31 3. 34 0 5 8 0. 31 0. 19 xl O -4 m d i, rn -a lt m ai n x -c u t 64 ,1 9 17 .0 8 1. 22 2. 75 1, 25 1. 60 0. 28 4. 36 0. 46 0. 36 0. 15 xl -3 m . di . s- al t m ai n x- cu t 64 .2 3 15 .5 0 1. 35 4. 70 0. 92 0. 95 0. 14 4. 02 0. 39 0, 81 0. 15 D A 48 -5 m . di . w m -a lt C ol e 1k v. 88 -5 -5 54 ,6 1 16 .7 7 2. 41 3. 20 2. 12 5. 73 2. 69 4. 31 0. 58 0. 21 0. 42 D A 48 -4 D m . di . rn -a lt C ol e 1k v. 88 -S -S 53 .8 2 20 .7 5 2. 02 3. 60 0. 84 4. 65 0. 16 3. 05 0. 53 0. 31 0. 33 D A 63 -4 m d i. rn -a lt S w tc h b k v .8 7 -S - 48 .4 0 18 .1 6 0. 86 12 .7 9 1. 21 1. 02 0. 06 4. 04 0. 59 0. 90 0. 29 D A G 3- 3D m . di . rn -a lt S w tc h bk v. 87 -S - 51 .6 8 16 .2 0 0. 41 11 ,2 4 1. 34 1. 24 0. 03 4. 24 0. 56 0. 98 0. 25 x5 -5 d an d, rn -a lt S N o3 v. x- cu t 53 .5 3 16 .5 8 1. 81 3. 60 1. 93 6, 42 0. 81 3. 93 0. 69 0. 47 0. 28 xS -5 an d. rn -a lt S N o 3 v .x -c u t 55 .2 4 17 .5 1 1. 57 4. 26 1. 71 4. 34 0. 33 3. 58 0, 78 0, 67 0. 26 x5 -6 d an d. w -a lt S .N o3 v. x- cu t 56 .6 8 15 .3 4 2. 22 3. 58 3. 42 4. 56 4. 19 2, 70 0, 64 0. 19 0. 26 x5 -6 an d. w -a lt S N o3 v x- cu t 56 .5 4 15 .9 4 2. 40 3. 38 2. 49 5. 31 3, 00 3. 15 0. 67 0. 22 0. 25 x5 -4 an d. rn -a lt S N o 3 v .x -c u t 66 ,3 0 15 .9 0 1. 48 2. 62 1. 26 0. 66 0. 33 4. 56 0. 51 0. 37 0. 20 x2 -5 an d. w -a lt N N o3 v. x- cu t 57 .1 8 15 .7 6 3. 09 2. 92 3. 23 5. 91 3. 36 3. 09 0. 66 0. 26 0. 37 xl O -6 m d i. w -a lt m ai n x -c u t 61 .2 5 15 .1 1 2. 30 2. 86 2. 78 4. 92 3. 93 3. 14 0. 58 0. 14 0. 26 x3 -7 an d. w -a lt . N N o3 V . x- cu t 57 .9 1 15 .8 2 2. 89 3. 05 2. 57 5. 85 4. 10 2. 83 0. 65 0. 20 0. 38 x3 -2 an d. rn -a lt N N o3 V . x- cu t 59 .9 4 18 .3 0 2. 18 3. 65 0. 97 1. 70 0. 35 3. 37 0. 71 0, 59 0. 26 x5 -9 an d. s- al t S N o 3 v .x -c u t 64 .3 1 16 .0 9 2, 20 3. 35 1. 14 0. 35 0. 35 4. 69 0. 44 0. 08 0. 19 S 91 -1 5 po rp hy ry w m -a lt D uc k la ke 63 .0 0 14 .8 9 3. 01 1. 82 3. 40 3. 07 4. 26 2. 64 0. 56 0. 12 0. 28 xl O -3 m d i. rn -a lt m ai n x -c u t 63 .3 9 17 .3 7 0. 85 3. 52 1. 00 0. 67 0. 31 5. 61 0. 39 0. 96 0. 11 xl O -2 m .d i. s- al t m ai n x -c u t 59 ,1 9 16 .3 5 2. 93 4. 20 0. 93 0. 70 0. 03 1. 29 0. 41 1. 66 0, 19 xl O -5 m .d l. rn -a lt m al n x -c u t 59 .9 0 17 .8 7 1. 44 3, 43 1. 47 2. 72 0 .2 9 3. 38 0. 58 0. 30 0. 19 xl O -4 m .d i. rn -a lt m al n x -c u t 64 .2 7 17 .0 7 1. 19 2. 75 1. 25 1. 60 0. 27 4. 37 0. 45 0. 37 0. 14 x l- 3 m . di . s- al t m ai n x- cu t 64 .1 4 15 .6 8 1. 24 4. 68 0, 78 1. 00 0. 20 3. 96 0. 4G 0, 83 0. 19 D A 48 -5 m . dl . w m -a lt C ol e 1k v. 88 -S -S 54 .7 1 16 .8 1 2. 46 3. 20 2. 14 5. 67 2. 66 4. 34 0. 58 0. 21 0, 41 D A 48 -4 D m . di . rn -a lt C ol e 1k V . 88 -S -S 53 .4 4 20 .8 1 2. 09 3. 60 0. 85 4. 69 0. 15 3. 06 0. 54 0. 31 0. 34 D A 63 -4 m .d i. rn -a lt S w tc h b k v .8 7 -S - 48 .4 3 18 .0 7 1. 01 12 .6 8 1. 21 1. 02 0. 06 4. 05 0. 59 0. 90 0. 29 D A 63 -3 D m d i. rn -a lt S w tc h b k v .8 7 -S - 51 .3 6 16 .2 9 0. 59 11 .2 4 1. 36 1. 24 0. 05 4. 26 0. 57 0. 98 0. 26 x5 -5 d an d. rn -a lt S N o 3 v .x -c u t 53 .6 3 16 .8 7 1. 85 3. 60 2, 13 6. 23 0. 82 3. 94 0, 69 0. 48 0. 28 x5 -5 an d. rn -a lt S N o 3 v .x -c u t 55 .4 0 17 .5 0 1. 86 4. 00 1. 86 4. 38 0. 33 3. 62 0. 78 0. 69 0. 26 x5 -6 d an d. w -a lt S N o3 V . x- cu t 56 .6 4 15 .4 2 2. 23 3. 58 3. 43 4. 44 4. 22 2 7 5 0. 64 0. 19 0. 30 x5 -6 an d. w -a lt S N o 3 v .x -c u t 56 .5 8 16 .0 4 2. 36 3. 38 2. 50 5. 11 3. 05 3. 19 0. 67 0. 22 0. 28 x5 -4 an d. rn -a lt S N o3 V . x- cu t 66 .4 3 16 .0 5 1, 49 2. 62 1. 24 0. 66 0. 34 4. 69 0. 51 0. 36 0, 20 x2 -5 an d. w -a lt N N o3 V . x- cu t 57 .2 9 15 .7 0 3. 08 2, 92 3. 33 5. 67 3. 39 3. 15 0. 66 0. 25 0. 37 xl O -6 m .d i. w -a lt m al n x -c u t 61 ,2 0 15 .0 6 2. 36 2. 86 2. 81 4. 90 3. 96 3. 15 0. 58 0. 14 0, 27 x3 -7 . an d. w -a lt N N o3 v. x- cu t 57 .9 7 15 .8 7 2. 86 3. 05 2. 64 5. 66 4. 09 2. 92 0. 65 0 2 0 0. 38 x3 -2 an d. rn -a lt N N o3 V . x- cu t 60 .2 1 18 .3 5 2. 33 3. 65 0. 99 1. 73 0. 34 3. 41 0. 72 0. 60 0. 26 C Table 8-3. Duplicates of C02, H20 & S at Silver Queen mine, central British Columbia SAMPLE ID C02 H20 S (ppm) SAMPLE ID C02 H20 S (ppm) xlO-2 3.64 898 x10-2 4.69 867 xl-2 3.75 1.95 800 xl-2d 3.26 ‘1.9 0 732 xl-90 2.35 128 xl-90d 2.40 124 xlO-3 4.15 1.86 458 xlO-3d 4.04 2.27 659 xlO-6 1.85 1.39 127 xlO-6d 2.40 1.22 154 xlO-4 421 x10-4 423 xlO-5 357 xlO-5 349 x5-4 3.30 2.12 1635 x5-4 3,40 2.02 1610 x5-5 7 51 x5-5 720 xll-1 0.90 970 xll-lb 0.91 865 x3-3 1.92 1.14 181 x3-3d 1.85 1.64 250 xS-6 4.35 2.16 711 x5-6d 4.15 1.28 1056 S91-10 0.25 0.36 S91-1OD 0.35 0.58 391-9 2.88 S91-9D 3.19 SQ-119 2.93 21 SQ119D 3.19 5 xl-2 8 00 xl-2 768 x3-2 5 59 x3-2 504 Table 8-4. Duplicates of Trace Elements at Silve r Queen mine, central British Columbia SAMPLE ID ZR V RB SR SAMPLE ID ZR V RB SR DA48-4D 127 29 116 2 17 DA48-4D 145 30 116 220 xl-1 133 20 110 35 xl-1 131 20 105 42 xl-2 135 18 148 2 01 xl-2d 159 21 165 219 xl-20 159 22 166 2 20 xl-2d 159 21 165 216 xl-3 158 21 172 2 08 xl-3 162 26 169 209 xlO-2 150 19 199 69 xlO-2 155 21 204 79 xlO-3 177 26 206 1 79 xlO-3d 178 27 177 172 xlO-3D 178 26 206 179 xlO-3d 178 27 177 172 xlO-6 172 24 120 511 xlO-6d 172 27 121 462 xlO-6D 170 25 119 4 72 xlO-6d 172 27 ‘121 462 x3-2 198 27 123 376 x3-2 198 27 123 376 S91-l5Dd 125 17 82 397 S91-15D 116 17 77 398 DA48-2D 135 30 260 196 DA48-2 142 31 265 200 DA48-4D 127 30 116 220 DA48-4 127 30 116 220 DA48-5D 124 28 179 4 46 DA48-5 138 28 188 454 DA63-ID 165 25 104 636 DA63-1 158 26 93 608 DA63-3D 112 24 179 143 DA63-3 114 25 173 141 DA63-5D 99 20 120 87 DA63-5 91 21 123 74 DA8-2D 152 31 177 23 DA8-2 152 31 177 23 DAB-3D 163 31 127 1 82 DA8-3 164 30 121 176 X1-1D 133 18 113 32 xl-1 132 19 110 32 xl-2D 159 22 166 2 20 xl-2 135 18 148 201 X1-5D 156 24 177 1 11 xl-5 160 25 179 114 xl-9Oci 167 21 136 4 21 xl-90 165 24 135 422 xll-lb 166 31 92 630 xll-1 166 2 8 90 595 x3-3d 180 24 117 606 x3-3 185 3 2 104 597 S91-9D 182 25 99 732 S91-9 184 2 6 99 734 SQ119D 124 18 71 557 SQ-119 145 18 78 588 204 Appendix C Metasomatic Norm Calculation Using Quattro Pro for DOS 5.0 205 Instruction of using Quattro Pro for DOS 5.0 to calculate metasomatic norm Page A. This is the title page ofmetasomatic norm calculation using Quattro Pro for DOS 5.0 Page B. The first block of this page contains lithogeochemical raw data. For example, the block B: B3..126 contains the raw data in following page. The second block of page B converts the lithogeochemical raw data into their corresponding molar amounts. For example, the content of Si02 of sample x4-4 in cell C7, 57.86, divided by the molar weight of Si02, 60.09 g/mole in cell A32 gives its molar amount of 0.962889 in cell C32. Page C. Absolute losses and gains of lithogeochemical constituents are calculated in the first notebook block of this page using Ti02 as immobile component and sample x4-4 as equivalent of least altered parent rock. For example, the value in cell C :D6 is calculated by Gresen& equation (cf. equation 1-9. in chapter 1): dXX0 (C1) In detail, dX is the value of absolute loss or gain of Si02 of sample x3-5, z0 is the immobile component Ti02 of sample x3-5 (B:E9), z the immobile component Ti02 of sample x4-4 (B:C9), x0 (B:E7) and x (B:C7) are Si02wt.% of the altered sample x3-5 and the least altered sample x4-4 respectively. 206 The second block ofpage C presents lithogeochemical data corrected for closure using the equation as follows: X=--x0 (C-2) Clearly, the equation above is derived from equation (C-i). It converts the intensive value ofx0 (wt.%) to X with an extensive unit (such as gram). Page D and E Page D and E contain the formulas to calculate metasomatic norms using Optimizer, oneof the powerful tools provided in Quattro Pro for DOS 5.0. In general, Optimizer can (i) evaluate more than one formula; (ii) solve sets of linear and nonlinear equations and inequalities; (iii) find a minimum or maximum solution instead of an exact target; (iv) find values that satisfy limits. To use Optimizer, a notebook model is created. It contains the realistic estimates and define the elements ofmetasomatic norm calculation as follows: 1. The results of calculated metasomatic norms, which are given on page E. The formulas in this notebook block are based on equations introduced in Chapter 2; 2. A set of variables Optimizer can change to produce the results above, which is listed in the block ofAdjust Factor Matrix on page D; and 3. The constraints, or limitations, the solution must accommodate, which are listed in the block of Constraint Matrix on pageD. For example, dTotal = 0, dH2O < 0.3 and >-0.3, dCO2 <0.3 and >-0.3 etc. All formulas in these notebook blocks are based on the equations introduced in Chapter 2 and attached on the pages following page D and E. After the problem is properly defined, Optimizer can adjust the variables, recalculates the notebook, and then, based on the new results, continues these adjustments until it finds a solution that meets the requirements. 207 Page F This page contains the notebook blocks calculating propagated error. The formulas in each notebook blocks on this page are based on the equations introduced in Chapter 3 and attached on the pages following page F for reference. Page G This is the last notebook page of this program. It presents the final results of metasomatic norm calculation in units ofmole and gram respectively. A set of comprehensive, mass balanced reaction equations can be constructed by combining the results listed on page F and G. For example, sample x4-4 is the least altered precursor rock of altered sample x3 -5, the hydrothermal alteration of sample x3 -5 can be presented as follows: Primary 0.O23pyroxene + 0. l36plagioclase + 0.066K-feldspar + 0.2quartz minerals 5.11±0.17 g 36.01± 0.95 g 18.26±0.48 g 12.02±0.33 g Propylitic + 0.O04chlorite + 0.03 9epidote + 0.O53carbonate alteration 3.05±0.11 g 18.7±0.5 g 4.86±0.34 g mass - 0.236SiO - 0.041Al3 - 0.027Fe3 - 0.056Mg2 - 0.072Ca2- O.11Na - 0.029K losses -14.19±1.38 g -1.1±0.22 g -1.5±0.04 g -1.37±0.03 g -2.9±0.07 g -2.54±0.04 g -1.11±0.06 g mass + 0. 129H + 0.042C02 gains 2.31±0.1 g 1.86±0.12 g sericitic, argillic, = 0.O44sericite + 0.O63kaolinite + 0.O93carbonate + 0.456quartz carbonatized, 17.28±0.47 g 16.28±0.5 1 g 9.8 1±0.6 g 27.38±0.7 1 g silicified alteration Unlike other ‘black box’ types of software, this Quattro Pro program is transparent. User can easily adjust and develop it according to his own purpose, such as add or replace some standard norm minerals, set different constrains. In addition, user should keep in mind when using Optimizer that calculations ofmetasomatic norms are complex nonlinear problems and could have many different solutions. Depending on the values user start 208 with, Optimizer’s recommended solutions vary. User should use his knowledge to well constrain the problem and treat his negative results as a case that his hypothesis is rejected and his positive results as the case that his hypothesis is not rejected rather than approved. 209 Notebook page A. METASOMATIC NORM By Xiaolin Cheng and A. J. Sinclair Dept. of Geological Sciences University of British Columbia 1995 210 Notebook page B. Al B CI DIEt Fl G 1 H I Lithogeochemical Raw Data 2 Sample_id x4-4 x3-7 x3-5 x3-4 x3-1 x3.3d x2-5 3 Alteration w-alt w-alt ni-alt nis-alt ms-alt w-alt w -alt 4 rock and. and. and. and. and, and. and . 5 location N No3 v. x N No3 v. x N No3 v. x N No3 V. x N No3 v. x N No3 v. x N No 3 v. x 6 Si02 57.86 57.97 58.45 56.67 57.25 57.59 57.29 7 A1203 15.61 15.87 18.11 17.27 17.45 15.80 15.70 8 Ti02 0.65 0.65 0.87 0.57 0.67 0.65 0.66 9 Fe203 3.09 2.86 1.26 1.26 1.25 2.81 3.08 1 0 FeO 2.89 3.05 3.69 5.78 5.82 3.08 2.92 11 MnO 0.34 0.20 1.34 1.65 1.57 0.35 0.25 12 MgO 2.94 2.64 0.90 1.15 1.09 3.07 3 .33 13 CaO 6.07 5.66 2.69 0.73 0.73 5.61 5.67 14 Na20 3.65 4.09 0.31 0.44 0.29 3.69 3.39 15 1(20 3.09 2.92 2.34 4.12 2.77 3.13 3 .15 16 P205 0.38 0.38 0.27 0.19 0.20 0.39 0.37 17 H20 0.97 1.27 4.39 2.69 3.9 1.84 1.04 18 C02 2.03 2.14 5.2 5.9 5.75 1.65 2.75 19 S 0.013 0.018 0.029 0.127 0.073 0.025 0.0 03 20 LOl 3.01 3.43 9.62 8.72 9.72 3.52 3.79 21 Total 99.58 99.72 99.85 98.55 98.81 99.69 99.60 22 Zr 191 192 220 163 188 180.19 178.6 4 23 Y 28 30 32 12 23 23.62 33.05 24 Rb 100 108 96 172 114 117.16 121.40 25 Sr 593 607 238 231 630 605.75 573.45 26 27 28 Conversion of wt% to molar amount Sample_id x4-4 x3-7 x3-5 x3-4 x3-1 x3-3d x2-5 30 Molar wt Alteration w-alt w.alt rn-alt ms-alt ms-alt w-alt w-alt 31 60.09 Si 0.962889 0.96472 0.972708 0.943085 0.952738 0.958396 0.953403 32 101.96 Al 0.306199 0.311299 0.355237 0.33876 0.342291 0.309925 0.3 07964 33 79.90 Ti 0.008135 0.008135 0.010889 0.007134 0.008385 0.008135 0.0 0826 34 159.70 Fe+3 0.038698 0.035817 0.01578 0.01578 0.015654 0.035191 0.038572 35 71.85 Fe+2 0.040223 0.04245 0.051357 0.080445 0.081002 0.042867 0.04064 36 70.94 Mn 0.004793 0.002819 0.018889 0.023259 0.022131 0.00493 4 0.003524 37 40.31 Mg 0.072935 0.065492 0.022327 0.028529 0.02704 0.0 7616 0.08261 38 56.08 Ca 0.108238 0.100927 0.047967 0.013017 0.013017 0.100036 0.101106 39 61.98 Na 0.11778 0.131978 0.010003 0.014198 0.009358 0.11907 1 0.10939 40 94.18 K 0.065619 0.062009 0.049692 0.087492 0.058824 0.066468 0.066893 41 141 .94 P 0.005354 0.005354 0.003804 0.002677 0.002818 0.00549 5 0.005213 42 18.00 OH- 0.107411 0.141111 0.487778 0.298889 0.4.33333 0.204444 0.115211 43 44.01 C03= 0.046126 0.048625 0.118155 0.13406 0.130652 0.03749 1 0.062486 44 32.06 S 0.000415 0.000549 0.000895 0.003949 0.002283 0.00 0780 0.000097 45 90.03 Zr 2.122293 2.133067 2.445851 1.813284 2.086082 2.001444 1.984227 46 211 Notebook page C. AIBICDIEI FIGI H Absolute loss or gain calculation 2 (by using Gresens’s/MacLean’s Equation) 3 Sample_id x4-4 x3-7 x3-5 x3-4 x3-1 x3-3d x2-5 4 Alteration w-alt w-alt rn-alt ms-alt ms-alt w-alt w-alt 5 dSiO2 0.00 0.11 -14.19 6.76 -2.32 -0.27 -1.44 6 dA12O3 0.00 0.26 -2.08 4 .08 1.32 0.19 -0.15 7 dTiO2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 8 dFe2O3 0.00 -0.23 -2.15 -1.65 -1.88 -0.28 -0.06 9 dFeO 0.00 0.16 .0.13 3.70 2.76 0.19 -0.01 10 dMnO 0.00 -0.14 0.66 1.54 1.18 0.01 -0.09 11 dMgO 0.00 -0.30 -2.27 -1.63 -1.88 0.13 0.34 12 dCaO 0.00 -0.41 -4.06 -5.24 -5.36 -0.46 -0.49 13 dNa2O 0.00 0.44 -3.42 -3.15 -3.37 0.04 -0.31 14 dK2O 0.00 -0.17 -1.34 1.61 -0.40 0.04 0.01 15 dP2O5 0.00 0.00 -0.18 -0.16 -0.19 0.01 -0.02 16 dH2O 0.00 0.30 2.31 2.10 2.82 0.87 0.05 17 dCO2 0.00 0.11 1.86 4.70 3.55 -0.38 0.68 18 dS 0.00 0.00 0.01 0.13 0.06 0.01 -0.01 19 dLOI 0.00 0.42 4.18 6.93 6.42 0.51 0.72 20 dTotal 0.00 0.14 -24.98 12.80 -3.72 0.11 -1.49 21 dZr 0.00 0.97 -26.55 -4.91 -8.87 -10.88 -15.14 22 dY 0.00 2.41 -3.88 -14.29 - 5.69 -4.33 4.60 23 dRb 0.00 8.17 -28.33 95.59 10.33 16.88 19.28 24 dSr 0.00 14.64 -414.58 -328.93 18.37 13.03 -27.96 25 26 Lithogeochemical Data Corrected for Closure Sample_id x4-4 c3-7 x3-5 x3-4 x3-1 x3-3d x2-5 28 Alteration w-alt w-alt rn-alt ms-alt m s-alt w-alt w-alt 29 dSiO2 57.86 57.97 43.67 64.62 55.54 57.59 56.42 30 dAl2O3 15.61 15.87 13.53 19.69 1 6.93 15.80 15.46 31 dTiO2 0.65 0.65 0.65 0.65 0 .65 0.65 0.65 32 dFe2O3 3.09 2.86 0.94 1.44 1.21 2.81 3.03 33 dFeO 2.89 3.05 2.76 6.59 5.65 3.08 2.88 34 dMnO 0.34 0.20 1.00 1.88 1.52 0.35 0.25 35 dMgO 2.94 2.64 0.67 1.31 1.06 3.07 3.28 36 dCaO 6.07 5.66 2.01 0.83 0.71 5.61 5.58 37 dNa2O 3.65 4.09 0.23 0.50 0.28 3.69 3.34 38 dK2O 3.09 2.92 1.75 4.70 2.69 3.13 3.10 39 dP2O5 0.38 0.38 0.20 0.22 0.19 0.39 0.36 40 dH2O 0.97 1.27 3.28 3.07 3.78 1.84 1.02 41 dCO2 2.03 2.14 3.89 6.73 5.58 1.65 2.71 42 dS 0.01 0.02 0.02 0.14 0.07 0.03 0.00 43 dLOI 3.01 3.43 7.19 9.94 9.43 3.52 3.73 44 dTotal 99.58 99.72 74.60 112.38 95.86 99.69 98.09 45 dZr 191.07 192.04 164.52 186.16 182.20 180.19 175.93 46 dY 27.95 30.36 24.07 13.66 22.26 23.62 32.55 47 dRb 100.28 108.45 71.95 195.87 110.61 117.16 119.56 48 dSr 592.72 607.36 178.14 263.79 611.09 605.75 564.76 49 212 Notebook page D. Al 81 ci Dl El Fl Gi H — 2 x3-1 x3-3d x2-S 3 ms-alt w-ak w-alt 4 1.000 0.149 0.271 5 0.000 1.000 0.339 6 0.000 0.000 0.000 0.000 0.535 0.805 8 0.000 0.000 0.195 9 0.000 1.000 1.000 10 0.000 0.000 0.416 11 0.221 0.913 1.000 12 0.349 0.000 0.011 13 0.000 0.171 0.522 14 0.000 0.000 0.000 15 0 / 1 0.339311 16 0 0.535345 1 17 18 19 x3-1 x3-3d x2-5 20 ms-alt w-ait w-alt 21 0.00000 0.00000 0.00000 22 0.00000 0.00000 0.00000 23 0.00000 0.00000 0.00000 24 0.00000 0.00000 0.00000 25 0.00000 0.00000 0.00000 26 0.00000 0.00000 0.00000 27 0.00000 0.00000 0.00000 28 0.00000 0.00000 0.00000 29 0.00000 0.00000 0.00000 30 0.00000 0.00000 0.00000 31 0.00000 0.00000 0.00000 32 33 34 0.148 -0.076 0.073 35 -0.166 0.069 -0.075 36 0.000 0.000 0.000 0.018 0.007 0.001 38 0.000 0.000 0.000 39 14.570 3.981 5.615 40 0.000 15.489 3.952 41 26.216 3.961 0.000 42 18.313 -0.000 0.008 43 0.000 11.711 7.771 44 0.000 1.802 3.884 45 0.000 18.501 18.619 46 0.542 28.508 41.346 - 47 0.137 0.047 0.006 48 36.433 13.867 14.434 49 Adjust factor matrix Sample_id x4-4 x3-7 x3-5 x3-4 Alteration w-alt w-alt rn-alt ms-alt Calcite 0.043 0.393 0.763 1.000 Mg-chl 0.000 1.000 0.000 0.000 Mg-pyx 0.472 0.000 0.000 0.000 Fe-chl 0.535 0.000 0.000 0.000 Fe-pyx 0.312 0.270 0.000 0.000 Or 1.000 1.000 0.000 0.000 An 0.156 0.191 0.000 0.000 Ab 1.000 1.000 0.127 0.265 ilmenite 0.000 0.969 0.000 0.000 Ca-pyx 0.000 0.000 0.000 0.000 magnetite 0.000 0.000 0.000 0.000 Mg-chI4-p 0.472389 1 0.000479 0 Fe-chl+py 0.846492 0.270079 0 0 Residual Matrix Sample_id x4-4 x3-7 3.5 x3-4 Alteration w-alt w-alt rn-alt ms-alt dSiO2 0.00000 0.00000 0.00000 0.00000 dAl2O3 0.00000 0.00000 0.00000 0.00000 dTiO2 0.00000 0.00000 0.00000 0.00000 dFe2O3 0.00000 0.00000 0.00000 0.00000 dFeO 0.00000 0.00000 0.00000 0.00000 dMnO 0.00000 0.00000 0.00000 0.00000 dMgO 0.00000 0.00000 0.00000 0.00000 dCaO 0.00000 0.00000 0.00000 0.00000 dNa2O 0.00000 0.00000 0.00000 0.00000 dK2O 0.00000 0.00000 0.00000 0.00000 dP2O5 0.00000 0.00000 0.00000 0.00000 Constraint matrix dH2O 0.294 0.128 0.244 0.178 dCO2 -0.299 -0.240 -0.251 -0.209 dS 0.000 0.000 0.000 0.000 dLOI 0.004 0.112 0.007 0.032 dTotal 0.001 0.108 0.000 0.000 Carbnate 4.857 5.850 13.129 15.027 Epidote 18.700 9.787 2.388 0.000 Sericite 0.000 0.016 23.128 38.839 KaoI 0.000 -0.000 21.789 5.318 ChI 3.052 7.280 0.001 0.000 Pyx 5.106 1.222 0.000 0.000 Or 18.264 17.260 0.000 0.000 P1 36.013 41.628 0.334 0.985 Pyrite 0.025 0.033 0.054 0.237 Qtz 12.017 13.395 36.654 35.863 213 Notebook page E. A B I CJ DIE I FIG I Hill Metasomatic Norms (closed) Sample_id x4-4 x3-7 x3-5 x3-4 x3-1 x3-3d x2-5 Molar wt Alteration w-alt w-alt rn-al t ms-alt ms-alt w-alt w-alt 100.09 Calcite 0.350 2.626 3.177 0.856 0.833 1.127 0.608 483.24 Epidote 18.700 9.787 2.388 0.000 0.000 15.489 3.952 232.34 Ca-pyx 0.000 0.000 0.000 0.000 0.000 1.802 2.844 278.22 An 5.126 7.029 0.000 0.000 0.000 0.000 12.659 84.32 Mg-carb 3.245 0.000 1.882 2.406 2.280 0.000 4.602 555.78 Mg-chl 0.000 7.280 0.001 0.000 0.000 8.466 3.116 200.80 Mg-pyx 3.459 0.000 0.000 0.000 0.000 0.000 0.000 115.86 Fe-carb 0.712 2.900 5.898 9.092 8.913 2.287 -0.000 713.48 Fe-chl 3.052 0.000 0.000 0.000 0.000 3.245 4.656 263.88 Fe-pyx 1.647 1.222 0.000 0.000 0.000 0.000 1.039 398.30 Muscovite 0.000 0.000 19.792 34.848 23.429 0.000 0.000 278.34 Or 18.264 17.260 0.000 0.000 0.000 18.501 18.619 382.20 Na-mica 0.000 0.016 3.336 3.991 2.786 3.961 0.000 262.24 Ab 30.887 34.599 0.334 0.985 0.542 28.508 28.686 151.75 ilmenite 0.000 1.196 0.000 0.000 0.444 0.000 0.013 79.90 rutile 0.650 0.020 0.870 0.570 0.436 0.650 0.653 258.14 Kaol 0.000 -0.000 21.789 5318 18.313 -0.000 0.008 60.09 qtz 12.017 13.395 36.654 35.863 36.433 13.867 14.434 114.95 Mn-carb 0.551 0.324 2.171 2 .674 2.544 0.567 0.405 502.21 apatite 0.896 0.896 0.637 0.448 0.472 0.920 0.873 119.97 pyrite 0.025 0.033 0.054 0.237 0.137 0.047 0.006 159.70 hemtite 0.000 1.243 0.865 1 .260 1.250 0.251 2.427 231.55 magnetite 0.000 0.000 0.000 0 .000 0.000 0.000 0.000 total 99.581 99.825 99.849 98.547 98 .813 99.685 99.600 Final Metasomatic Norms (Closed) Sample_id x4-4 x3-7 x3-5 x3-4 x3-1 x3-3d x2-5 Alteration w-alt w-alt rn-alt ms-alt ms-alt w-alt w-alt apatite 0.896 0.896 0.637 0.448 0.472 0.920 0.873 ilmenite 0.000 1.196 0.000 0.000 0.444 0.000 0.013 magnetite 0.000 0.000 0.000 0.0 00 0.000 0.000 0.000 pyroxene 5.106 1.222 0.000 0 .000 0.000 1.802 3.884 plagioclase 36.013 41 .628 0.334 0 .985 0.542 28.508 41 .346 orthoclase 18.264 17.260 0.000 0 .000 0.000 18.501 18.619 quart 12.017 13.395 36.654 35.863 36.433 13.867 14434 epidote 18.700 9.787 2.388 0.000 0.000 15.489 3.952 chlorite 3.052 7.280 0.001 0.000 0.000 11.711 7.771 sericite 0.000 0.016 23.128 38.839 26.216 3.961 0.000 kaolinite 0.000 -0.000 21.789 5.318 18.313 -0.000 0.008 carbonate 4.857 5.850 13.129 15.027 14.570 3.981 5.615 rutile 0.650 0.020 0.870 0.570 0.436 0.650 0.653 hemtite 0.000 1.243 0.865 1.260 1.250 0.251 2.427 pyrite 0.025 0.033 0.054 0.237 0.137 0.047 0.006 total 99.581 99.825 99.849 98.547 98.813 99.685 99.600 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 214 A lB I C DI El F G I HI — Error Propagation 2 So k Cd So k Cd 3 S102 0.010 0.012 0.020 K20 0.020 0.018 0.041 4 AL203 0.012 0.020 0.025 P205 0.020 0.015 0.041 5 T102 0.006 0.008 0.012 H20 0.040 0.130 0.108 6 FE203 0.060 0.018 0.124 C02 0.010 0.120 0.026 7 FEO 0.045 0.018 0.093 S 0.002 0.070 0.004 8 MNO 0.022 0.007 0.045 Zr(ppm) 0.010 0.032 0.021 9 MGO 0.074 0.030 0.157 Y(ppm) 0.300 0.090 0.732 10 CAO 0.080 0.011 0.164 Rb(ppm) 2.000 0.035 4.301 11 NA2O 0.090 0.013 0.185 Sr(ppm) 5.000 0.019 1.395 12 Standard Deviation at 68% confidence level 13 Sample_id x4-4 x3-7 x3-5 x3-4 x3-1 x3-3d x2-5 14 Calcite 0.0000 0.1706 0.2657 0.1037 0.1008 0.0784 0.0416 15 Epidote 0.0025 0.2544 0.0358 0.0000 0.0000 0.3735 0.0952 16 Ca-pyx 0.0937 0.0000 0.0061 0.0000 0.0000 0.0333 0.0524 17 An 0.2666 0.1186 0.0013 0.0000 0.0000 0.0000 0.2270 15 Mg-carb 0.4208 0.0000 0.2144 0.2613 0.2516 0.0000 0.4119 19 Mg-chl 0.1024 0.3620 0.0000 0.0000 0.0000 0.3982 0.1512 20 Mg-pyx 0.0000 0.0000 0.0034 0.0000 0.0000 0.0000 0.0000 21 Fe-carb 0.0039 0.1864 0.3591 0.5657 0.5544 0.1557 -0.0000 22 Fe-chi 0.0000 0.0000 0.0000 0.0000 0.0000 0.1226 0.1857 23 Fe-pyx 0.0821 0.0323 0.0094 0.0000 0.0000 0.0000 0.0247 24 Muscovite 0.0000 0.0000 0.3479 0.6067 0.4095 0.0000 0.0000 25 Or 0.2891 0.2742 0.0000 0.0000 0.0000 0.2926 0.2943 26 Na-mica 0.0174 0.0003 0.1516 0.1316 0.1152 0.0740 0.0000 27 Ab 0.5104 0.5722 0.0000 0.0375 0.0274 0.4796 0.4899 28 ilmenite 0.0153 0.0296 0.0000 0.0000 0.0094 0.0000 0.0003 29 rutile 0.0057 0.0003 0.0130 0.0106 0.0074 0.0112 0.0112 30 Kaol 0.0113 -0.0000 0.7336 0.1811 0.6116 -0.0000 0.0003 31 qtz 0.1607 0.1611 0.4456 0.4367 0.4436 0.1688 0.1757 32 Mn-carb 0.0507 0.0389 0.1327 0.1581 0.1516 0.0518 0.0429 33 apatite 0.0406 0.0409 0.0401 0.0542 0.0559 0.0413 0.0404 34 pyrite 0.0005 0.0006 0.0010 0.0037 0.0021 0.0009 0.0001 35 hemtite 0.0589 0.0438 0.0704 0.0827 0.0825 0.0099 0.0910 36 magnetite 0.0788 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 37 Sc_SiO2 0.704 0.706 0.711 0.690 0.697 0.701 0.697 38 Sc_A1203 0.324 0.329 0.374 0.357 0.361 0.328 0.326 39 Sc_Ti02 0.011 0.011 0.013 0.011 0.011 0.011 0.011 40 Sc_Fe2O3 0.116 0.111 0.083 0.083 0.083 0.111 0.115 41 Sc_FeO 0.097 0.100 0.111 0.149 0.150 0.100 0.098 42 Sc_MnO 0.024 0.023 0.031 0.034 0.033 0.024 0.024 43 Sc_MgO 0.162 0.153 0.101 0.109 0.107 0.166 0.174 44 Sc_CaO 0.147 0.142 0.110 0.088 0.088 0.142 0.142 45 Sc_Na20 0.137 0.143 0.094 0.096 0.094 0.138 0.134 46 Sc_K2O 0.076 0.073 0.062 0.094 0.070 0.076 0.077 47 Sc_P205 0.026 0.026 0.024 0.023 0.023 0.026 0.026 45 Sc_H20 0.166 0.205 0.611 0.390 0.547 0.279 0.175 49 Sc_C02 0.254 0.267 0.634 0.718 0.700 0.208 0.340 50 Sc_S 0.003 0.003 0.004 0.011 0.007 0.004 0.002 51 Sc_Zr 6.124 6.155 7.056 5.234 6.020 5.776 5.726 52 215 Notebook page F. Al B jc I DIE I FjG I H I Table 7- Error propagation of norms c orrected for closure in grani(SD at 68% c onfidence level) 54 at northern segment of No.3 vein, Silver Qu een mine, Owen Lake, central BC 55 Samplejd x4-4 x3-7 x3-5 x3-4 x3-1 x3-3d x2-5 56 Calcite 0.025 0.192 0.189 0.121 0.100 0.083 0.043 57 Epidote 0.638 0.336 0. 070 0.000 0.000 0.531 0.133 58 Ca-pyx 0000 0.000 0. 000 0.000 0.000 0.055 0.085 59 An 0.155 0.213 0. 000 0.000 0.000 0.000 0.376 60 Mg-carb 0.307 0.000 0. 168 0.306 0.250 0.000 0.420 61 Mg.chl 0.000 0.403 0. 000 0.000 0.000 0.448 0.167 62 Mg-pyx 0.132 0.000 0.000 0.000 0.000 0.000 0.000 63 Fe-carb 0.052 0.209 0.3 04 0.696 0.577 0.165 0.000 64 Fe-chl 0.144 0.000 0.000 0.000 0.000 0.146 0.214 65 Fe-pyx 0.056 0.041 0.0 00 0.000 0.000 0.000 0.035 66 Muscovite 0.000 0.000 0 .425 1.220 0.678 0.000 0.000 67 Or 0.531 0.502 0.000 0.000 0.000 0.537 0.531 68 Na-mica 0.000 0.000 0. 114 0.189 0.129 0.122 0.000 69 Ab 0.915 1.019 0.01 3 0.051 0.029 0.844 0 .838 70 ilmenite 0.000 0.041 0.000 0.000 0.014 0.000 0.000 71 rutile 0.019 0.001 0.018 0.020 0.012 0.019 0.019 72 Kaol 0.000 0.000 0.656 0.257 0.732 0.000 0.000 73 qtz 0.327 0.365 0.707 1.148 0.957 0.378 0.386 74 Mn-carb 0.052 0.040 0.106 0.196 0.159 0.054 0.043 75 apatite 0.046 0.046 0.032 0.063 0.055 0.047 0.045 76 pyrite 0.001 0.001 0.001 0.008 0.004 0.001 0.000 77 bemtite 0.000 0.057 0.045 0.101 0.085 0.012 0.107 78 magnetite 0.000 0.000 0.000 0.000 0.000 0.000 0.000 79 Total 3.4013 3.4662 2.8480 4.3782 3.7823 3.4430 3.4443 80 81 Table 7- . Error propagation of absolute lo sses & gains in gram (SD at 68% confiden ce level) 82 at northern segment of No.3 vein, Silver Queen mine. Owen Lake, central BC 83 Sample_id x4-4 x3-7 x3-5 x3.4 x3.1 x3-3d x2-5 84 dSiO2 1.726 1.729 1.330 1.946 1.660 1.720 1.686 1.000 85 dAl+3 0.315 0.319 0.279 0.381 0.333 0.318 0.313 0.529 86 dTi+2 0.013 0.013 0.013 0.014 0.013 0.013 0.013 0.599 87 dFe+3 0.126 0.122 0.0 93 0.107 0.100 0.122 0.12 5 0.699 88 dFe+2 0.120 0.123 0.111 0.200 0.172 0.123 0.119 0.777 89 dMn+2 0.027 0.026 0.03 2 0.051 0.042 0.028 0.027 0.774 90 dMg+2 0.145 0.140 0. 108 0.125 0.117 0.147 0.150 0.603 91 dCa+2 0.182 0.176 0.1 24 0.128 0.122 0.176 0 .174 0.715 92 dNa+ 0.159 0.165 0.1 15 0.131 0.122 0.159 0.154 0.742 93 dK+ 0.109 0.105 0.0 81 0.147 0.100 0.109 0.109 0.830 94 dP+5 0.016 0.016 0.014 0.016 0.015 0.016 0.016 0.436 95 dH2O 0.235 0.265 0.49 1 0.481 0.563 0.328 0.240 1.000 96 dCO2 0.362 0.372 0.545 0.874 0.737 0.330 0.425 1.000 97 dS 0.004 0.004 0.00 4 0.013 0.007 0.005 0.003 1.000 98 dO= 0.652 0.650 0.53 3 0.696 0.618 0.653 0.647 1.000 99 216 Notebook page G. AIBICIDIEIFIG1H Table 7a. Metasomatic norms corrected for closure & absolute losses and gains 2 at northern segment of No. 3 vein, Silver Queen min e. Owen Lake, central BC 3 S.nip4ld x4.4 x3-7 x3-S x3-4 x3-l x3-3d x2-5 4 øjwiaion w-alt w-alt rn-alt ms-a lt ms-alt w-alt w-alt 5 mole 6 Calcite 0.0035 0.0262 0.0237 0.0098 0.0081 0.0113 0.0060 7 Epidote 0.0387 0.0203 0.0037 0.0 000 0.0000 0.0321 0.0081 8 Ca-pyi 0.0000 0.0000 0.0000 0.0000 0.0000 0.0078 0.01 21 9 Au 0.0184 0.0253 0.0000 0.0000 0.0000 0.0000 0.0448 10 Mg-carb 0.0385 0.0000 0.01 67 0.0325 0.0262 0.0000 0.0538 11 Mg-chl 0.0000 0.0131 0.0000 0.0000 0.0000 0.0152 0.0055 12 Mg-pyx 0.01 72 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 13 Fe-carl, 0.0061 0.0250 0.0380 0.0895 0.0746 0.0197 -0.0000 14 Fe-cht 0.0043 0.0000 0.0000 0.0000 0.0000 0.0045’ 0.0064 15 Fe-pyx 0.0062 0.0046 0.0000 0.000 0 0.0000 0.0000 0.0039 16 Muscovite 0.0000 0.0000 0.037 1 0.0998 0.0571 0.0000 0.000 0 17 Or 0.0656 0.0620 0.0000 0.0000 0.0000 0.0665 0.0659 18 Na-mica 0.0000 0.0000 0.0065 0.0119 0.0071 0.0104 0.0000 19 Ab 0.1178 0.1319 0.0010 0.0043 0.0020 0.1087 0.1077 20 ilmenite 0.0000 0.0079 0.0000 0.0000 0.0026 0.0000 0.0001 21 nitile 0.0081 0.0003 0.0081 0 .0081 0.0053 0.0081 0.0080 22 KaoL 0.0000 -0.0000 0.0631 0.0235 0.0688 -0.0000 0.0000 23 qtz 0.2000 0.2229 0.4557 0.6806 0.5882 0.2308 0.2366 24 Mn-carb 0.0048 0.0028 0.0141 0.0265 0.0215 0.0049 0.0035 25 apatite 0.0018 0.0018 0.0009 0.0010 0.0009 0.0018 0.0017 26 pyrite 0.0002 0.0003 0.0003 0 .0023 0.0011 0.0004 0.0000 27 bemtite 0.0000 0.0078 0.0040 0.0090 0.0076 0.0016 0.01 50 28 magnetite 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 29 Total 0.5313 0.5522 0.6731 0 .9987 0.8713 0.5238 0.5790 30 dSiO2 0.0000 0.0018 -0.2362 0.1126 -0.0386 -0.0045 -0.0239 31 dAI+3 0.0000 0.0051 -0.0408 0.0 801 0.0259 0.0037 -0.0029 32 dTi+4 0.0000 0.0000 0.0000 0 .0000 0.0000 0.0000 0.0000 33 dFe+3 0.0000 -0.0029 -0.0269 - 0.0207 -0.0235 -0.0035 -0.0007 34 dFe+2 0.0000 0.0022 -0.0019 0.0515 0.0384 0.0026 -0.0002 35 dMn+2 0.0000 -0.0020 0.0093 0.0217 0.0167 0.0001 -0.0013 36 dMg+2 0.0000 -0.0074 -0.0563 -0.0404 -0.0467 0.0032 0.0084 37 dCa+2 0.0000 -0.0073 -0.0724 -0.0934 -0.0956 -0.0082 -0.0087 38 dNa+ 0.0000 0.0142 -0.1103 -0.1016 -0.1087 0.0013 -0.0100 39 dK+ 0.0000 -0.0036 -0.0285 0.0342 -0.0086 0.0008 0.0003 40 dP+5 0.0000 0.0000 -0.0025 -0.0023 -0.0026 0.0001 -0.0002 41 Sum 0= 0.000 -0.006 -0.29 9 -0.013 -0.150 -0.001 -0.012 42 dH2O 0.000 0.017 0.129 0.117 0.156 0.049 0.003 43 dCO2 0.000 0.002 0.042 0.107 0.081 -0.009 0.015 44 dS 0.000 0.000 0. 000 0.004 0.002 0.000 -0 .000 45 dTotal 0.000 0.014 -0.694 0.256 -0.154 0.035 -0.034 46 47 48 49 217 Notebook page G. AB)CIDJEIFG IH 50 Table 7b. Metasomatic norms corrected for closure & absolute losses and gains 51 at northern segment of No. 3 vein, Silver Queen mine. Owen Lake. central BC 52 sarnp4.W x4-4 x3-7 y3-5 x3-4 x3-1 x3-3d x2-5 53 Ajt.ratton w-alt w-alt rn-alt ms-a lt ms-alt w-alt w-alL 54 gram 55 Calcite 0.3499 2.6257 2.3738 0.9765 0.8079 1.1 268 0.5989 56 Epidote 18.6998 9.7869 1.7840 0.0000 0.0000 15.4890 3.8918 57 Ca-pyx 0.0000 0.0000 0.0000 0.0000 0.0000 1.8023 2.8013 58 Au 5.1 260 7.0290 0.0000 0.0000 0.0000 0.0000 1 2.4674 59 Mg-carb 3.2447 0.0000 1.4059 2.7432 2.2120 0.0000 4.5324 60 Mg.chl 0.0000 7.2799 0.0009 0.0000 0.0000 8.4656 3.0685 61 Mg-pyx 3.4591 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 62 Fe-carb 0.7117 2.9001 4.4068 10.3677 8.6472 2.2868 .0.0000 63 Fe-chl 3.0522 0.0000 0.0000 0.0000 0.0000 3.2449 4.5852 64 Fe-pyx 1.6470 1.2220 0.0000 0.0000 0.0000 0.0000 1.0237 65 Muscovite 0.0000 0.0000 14.787 4 39.7390 22.7300 0.0000 0.0000 66 Or 18.2644 17.2596 0.0000 0 .0000 0.0000 18.5008 18.3369 67 Na-mica 0.0000 0.0156 2.4924 4 .5513 2.7033 3.9605 0.0000 68 Ab 30.8866 34.5992 0.2498 1 .1231 0.5259 28.5076 28.2518 69 ilmenite 0.0000 1.1961 0.0000 0.00 00 0.4312 0.0000 0.0130 70 rutile 0.6500 0.0202 0.6500 0.6 500 0.4230 0.6500 0.6432 71 Kaol 0.0002 -0.0001 16.2790 6.0 642 17.7660 -0.0004 0.0078 72 qtz 12.0169 13.3950 27.3848 40.8 959 35.3457 13.8670 14.2150 73 Mn-carb 0.5509 0.3241 1.6222 3 .0489 2.4681 0.5671 0.3990 74 apatite 0.8963 0.8963 0.4758 0.51 11 0.4577 0.9199 0.8595 75 pynce 0.0249 0.0329 0.0401 0.27 01 0.1329 0.0468 0.0057 76 hemtite 0.0001 1.2428 0.6466 1.43 68 1.2127 0.2506 2.3903 77 magnetite 0.0000 0.0000 0.0000 0. 0000 0.0000 0.0000 0.0000 78 total 99.5809 99.8254 74.5996 112.37 77 95.8636 99.6854 98.0914 79 dSiO2 0.0000 0.1100 -14.1905 6 .7637 -2.3190 -0.2700 -1.4380 80 dAl+3 0.0000 0.1376 -1.1005 2.16 13 0.6981 0.1006 -0.0783 81 dTi+4 0.0000 0.0000 0.0000 0. 0000 0.0000 0.0000 0.0000 82 dFe+3 0.0000 -0.1609 -1.5028 -1.1 563 -1.3131 -0.1958 -0.0396 83 dFe+2 0.0000 0.1244 -0.1035 2. 8770 2.1425 0.1477 .0.0111 84 dMn+2 0.0000 -0.1084 0.5120 1 .1939 0.9163 0.0077 -0.0726 85 dMg+2 0.0000 .0.1809 -1.3675 -0.9 822 -1.1353 0.0784 0.2048 86 dCa+2 0.0000 -0.2930 -2.9018 -3.7432 -3.8320 -0.3288 -0.3473 87 dNa+ 0.0000 0.3264 -2.5359 -2 .3355 -2.4990 0.0297 -0.2310 88 dK+ 0.0000 -0.1411 -1.1138 1.3350 -0.3343 0.0332 0.0102 89 dP+5 0.0000 0.0000 -0.0778 -0.0713 -0.0812 0.0044 -0.0068 90 Sum 0= 0.000 -0.095 -4.777 -0.207 -2.397 -0.010 -0.199 91 dH2O 0.000 0.303 2.313 2.101 2.817 0.873 0.054 92 dCO2 0.000 0.110 1.855 4.698 3.548 -0.380 0.678 93 dS 0.000 0.004 0.008 0.131 0.058 0.012 -0.010 94 dTotal 0.000 0.137 -24.982 12.765 -3.731 0.102 -1.487 95 Residual 0.000 0.108 0.00 1 0.032 0.014 0.002 -0.003 96 97 98 218 D :B 4 : C o n st ra in t m at ri x D :A 35 : “d H 2 O Q :B 35 : (F 3) @ A O U N D (B :C l8 -B :$ A $ 1 8 (E :C 6 /E :$ A $ 6 + E ;C 1 O ’ 8 / E ; $ A $ 1 O + E : C 1 3 t8 / E ; $ A $ 1 3 + E : G 1 5t2 /E :$ A $ 1 5 + E :C 1 7 ’2 /E :$ A $ 1 7 + E :C 2 1 ’4 /E :$ A $ 2 1 ÷ E :0 24 /E :$ A $2 4) /2 S ) D :C 35 : (F 3) + E :D 24 1E :$ A $2 4) 12 5) D D 3 5 : (F 3) @ R U N D (B :E 1 B :$ A $ 1 8 (E :E 6 /E :$ A $ 6 + E :E 1 O * 8 /E $ A $ 1 O ÷ E :E 1 3 8 /E :$ A $ 1 3 + E :E 1 5 2 /E :$ A $ 1 5 + E ;E j7 ’2 /E :$ A $ 1 7 + E :E 2 1 t4 / E : $ A $ 2 1 + E :E 2 4 )E :$ A $ 2 4 )/ 2 6 ) D :E 35 : (F 3) ÷ E F 2 4 IE :$ A $ 2 4 )/ 2 5 ) D :F 35 : (P 3) @ R O U N D (B :G 1 8 B :$ A $ 1 8 * (E :G 6 /E :$ A $ 6 ÷ E :G IO * 8 /E :$ A $ 1 O + E :G 1 3 * 8 /E :$ A $ 1 3 + E :G 1 5 e2 /E :$ A $ 1 6 + E :G 1 7 * 2 /E :$ A $ 1 7 + E :G 2 1 * 4 /E :$ A $ 2 1 + E :G 2 4 /E :$ A $ 2 4 )/ 2 5 ) D :G 35 : (F 3) + E :I -Q 4 /E :$ A $ 2 4 )/ 2 5 ) D :H 35 : (P 3) @ R O U N D (B :I 1 8 B :$ A $ 1 9 (E :l 6 /E :$ A $ 6 + E :I 1 O * 8 /E :$ A $ 1 O + E :I l 3* 81 E :$ A $1 3+ E :1 15 *2 /E ;$ A $l 5+ E :I 1 7 2 /E :$ A $ 1 7 + E :I 2 l t4 / E : $ A $ 2 1 + E ;I 41 E :$ A $2 4) 12 5) D :A 36 : “d C O 2 D :B 36 : (F 3) @ R O U N D (B :C 9 B :$ A $ 1 9 * (E :C 5 /E :$ A $ 5 + E :C 9 /E :$ A $ 9 + E :C 1 2 /E :$ A $ 1 2 + E :C 2 3 /E :$ A $ 2 3 ), 5 ) D :C 36 : (F 3) @ R O U N D (B :D 1 9- B ;$ A $1 9 (E :D S /E :$ A $ 5 + E :D 9/ E :$ A $S + E: D 1 2 /E :$ A $ l 2 -t -E :D 2 3 /E :$ A $ 2 3 )5 ) D :D 36 : (F 3) @ R O U N D (9 ’: E 1 9 -S $ A $ 9 ’( E :E 5 /E :$ A $ 5 -i -E :E 9 /E ;$ A $ 9 + E :E 1 2 /E :$ A $ t2 + E E 2 3 )E $ A 2 3 )5 ) D :E 36 : (F 3) D :F 36 : (F 3) @ R O U N D (B :G 1 9 -B :$ A $ 1 9 (E :G 5 /E :$ A $ 5 + E :G 9 /E :$ A $ 9 + E :G 1 2 /E $ A $ l 2 ÷ E :G 2 3 /E :$ A $ 2 3 )5 ) D :G 36 : (F 3) @ R O U N D (B :H 1 9 .B :$ A $ 1 9 * (E :I t5 /E :$ A $ 5 + E :H 9 JE :$ A $ 9 + E :H 1 2 /E :$ A $ 1 2 + E :H 2 3 /E :$ A $ 2 3 )S ) D :H 36 : (F 3) @ R O U N D (B :I I9 -B :$ A $ 1 9 (E :I 5 /E :$ A $ 5 + E :I 9 /E :$ A $ 9 4 -E :I 1 2 /E :$ A $ 1 2 + E :I 2 3 /E :$ A $ 2 3 ), 5 ) D :A 37 ; “ d S D :B 37 : (F 3) @ R O U N D (B :C 20 -B :$ A $2 0 E :C 2 5 ’2 /E :$ A $ 2 5 6 ) D :C 37 : (F 3) @ R O U N D (B : 0 2 0 -B :$ A $ 2 0 t E ;D 2 5 ’2 /E :$ A $ 2 5 5 ) D :0 37 : (F 3) 0 R O U N D (B : E 20 -B :$ A $2 0’ E: E 2 5 * 2 /E ;$ A $ 2 5 5 ) D :E 37 : (P 3) @ R O U N D (B :F 2 O B :$ A $ 2 O * E :F 2 5 2 /E :$ A $ 2 5 5 ) D :F 37 : (F 3) 0 R O U N D (B :G 20 .B :$ A $2 0* E :G 2 5 ’2 /E :S A $ 2 6 5 ) D :G 37 : (P 3) R O U N D (B :I O B :$ A $2 O * E :F -5 ’2 /E :$ A $ 2 5 5 ) D :H 37 (F 3) 0 A O U N D (B :1 20 =B :$ A $2 0* E : 1 2 5 t2 /E :$ A $ 2 5 5 ) D :A 39 : “d L O I D ;B 38 : (P 3) + B :C 2 1 -S U M (B C 1 B C 2 O )- @ S U M (B 3 5 .B 3 7 ) D :C 38 : (F 3) ÷ B :D 21 -@ S U M (B :D 18 .D 20 )- @ S U M (C 35 ,,C 37 ) D :D 38 : (F 3) + B :E 2 1 -@ S U (B :E 1 8 .. E 2 O )- @ S U M (D 3 5 ,, D 3 7 ) D :E 38 : (F 3) + B :F 21 -@ S U M (B :F 18 ..F 20 )- @ S U M (E 35 ..E 37 ) D :F 3 : (F 3) + B :G 21 -@ S U M (B :G 1 8 .G 2 0 )- @ S U M (F 3 5 F 3 7 ) D :G 38 : (F 3) -i- 9: H 21 -g S U M (B :H 1 8. i- O )- @ S U M (G 35 .,G 37 ) D :H 38 : (F 3) + B :I 21 ..@ S U M (8 :1 8, i2 O )- @ S U M (H 35 .H 37 ) D :A 39 : “d T ol aI D :B 39 : (F 3) @ A B S (+ B :C 22 -E :C 28 ) D :C 39 : (F 3) @ A B S (+ B :D 22 -E :D 28 ) D :D 39 : (F 3) @ A B S (+ B :E 22 -E :E 28 ) D :E 39 : (F 3) @ A B S (+ B :F 22 -E :F 28 ) D :F 39 : (F 3) @ A B S (+ B :G 22 -E :G 28 ) D :G 39 : (F 3) @ A B S (+ 8: I- 22 -E :H 28 ) D :H 39 : (F 3) @ A B S( +B :1 22 -E :1 28 ) D :A 40 : “ C a rb n a t D :B 40 : (F 3) + E :C 5+ E :C 9+ E :C 1 2+ E :C 23 D :0 40 : (F 3) + E :D 5+ E :D 9+ E :D 12 + E :D 23 D :D -4 O : (F 3) + E :E 5+ E :E 9+ E :E 12 + E :E 23 D :E 40 : (F 3) + E :F 5 + E :F 9 + E :F 1 2 + E F 2 3 D :F 40 : (F 3) + E :G S + E :G 9+ E :G 1 2+ E :G 23 D :G 40 : (F 3) + E :- + E :H 9 + E :H 1 2 + E :H 2 3 D :H 40 : (F 3) + E :1 5+ E :1 9+ E :1 12 + E :1 23 D :A 41 : “E p Ic 1 o t D :B 41 : (F 3) + E :C 6 D :C 41 : (F 3) + E :D 6 D :D 41 : (F 3) + E :E 6 D :E 4 : (F 3) + E :F 6 D :F 41 : (F 3) + E :G 6 0 :6 4 1 : (F 3) + E :H 6 D :H 41 : (F 3) +E :1 6 D :A 42 : (F 3) “ S rl c It e 0: 84 2: (F 3) + E :C 15 + E :C 17 D :C 42 : (F 3) + E :D 15 + E :D 17 D :D 42 (F 3) + E :E 15 + E :E 17 D :E 42 : (F 3) + E :F 16 + E :F 17 D :F 42 : (F 3) + E :G 1S + E :G 17 0 :6 4 2 : (F 3) + E :H 15 + E :H 17 D :H 42 : (F 3) + E :1 15 + E :1 17 D :A 43 : K a o I D :B 43 : (F 3) + E :C 21 D :C 43 : (F 3) + E :D 21 D :D 43 : (F 3) + E :E 21 D :E 43 : (F 3) + E :F 21 D :F 43 : (F 3) + E :6 21 D :G 43 : (F 3) + E :- 1 0: 1- 44 3: (F 3) +E :1 21 D :A 44 : ‘C h I D :8 44 : (F 3) + E :C 1O ÷ E :C 13 0: C 44 : (F 3) + E :D 1O + E :0 13 D :D 44 : (F 3) + E :E 1O + E :E 13 D :E 44 : (F 3) ÷ E :F 1O + E :F 13 D :F 44 : (F 3) + E :G 1O + E :G 13 0 :6 4 4 : (F 3) -t -E :H 1O +E :H 13 D :H 44 : (F 3) + E :I lO + E :1 13 D :A 45 : ‘P y x 0 :8 4 5 : (F 3) + E :C 7+ E :C 11 + E :C 14 D :C 45 : (F 3) + E :D 7+ E :D 11 + E :D 14 0 :0 4 5 : (F 3) + E :E 7+ E :E 11 + E :E 14 D :E 45 : (F 3) + E :F 7 + E :F 1 I+ E :F 1 4 D :F 45 : F 3 ) + E :G 7+ E :G 1 1 + E :G 14 D :G 45 : (F 3) ÷ E :H 7+ E :H l1 + E :H 14 D :H 45 : (F 3) + 5: 17 + 5: 11 1 +E :1 14 D :A 46 : “O r D :8 48 : (F 3) + E :C 16 D :C 46 : (F 3) + E :D 16 D :0 46 : (F 3) + 5 :5 1 6 0: E 46 : (F 3) + E :F 16 D :F 46 : (F 3) + 5 :6 1 6 D :G 46 : (F 3) + E :H 16 D :H 46 : (F 3) + 5: 11 6 D :A 47 : “P 1 D :8 47 : (F 3) + E :C 8+ E :C 18 D :C 47 : (F 3) + E :D 8+ E :D 18 D :D 47 : (F 3) + E :E 8+ E :E 18 D :E 47 : (F 3) + E :F 8+ E :F 18 D :F 47 : (F 3) + E :G 8+ E :G 18 D :G 47 : (F 3) + E :H 8+ E :H 18 D :H 47 : (F 3) + E :1 8+ E :1 18 D :A 48 : “P y ri te D :B 48 : (F 3) + E :C 25 D :C 48 : (F 3) + 5 :0 2 5 0 :0 4 8 : (F 3) + E :E 25 D :E 48 : (F 3) + E :F 25 D :F 48 : (F 3) + 5 :6 2 5 D :G 48 : (R 3) + E :H 26 0: 1- 14 8: (F 3) + 5: 12 5 D :A 49 : “Q tz 0: 84 9: (F 3) + 5 :0 2 2 D :C 49 : (F 3) + E :D 22 0 :0 4 9 : (F 3) + 5 :5 2 2 D :E 49 : (F 3) + E :F 22 D :F 49 : (F 3) + 5 :6 2 2 D :G 49 : (F 3) ÷ E :I -2 D :H 49 : (F 3) +E :1 22 k ) C E :C 2: M el as o rn at ic N cm s (d o se d ) 0 :9 3 . [W l0 ] “ S a m p le _ Id 0 :0 3 : (P 0) U “x 4 -4 0 0 3 : (F 0) U “x 3 -7 0 :0 3 : (P 0) 14 “x 3 -S E :F 3 :( F 0 )U “x 3 -4 0 :3 3 : (P 0) 14 “ x 3 -l E :H 3: (P 0) U x 3 -3 d 0: 13 : (P 0) U x2 -5 E :A 4: M ol ar w t% E :B 4: [W I0 ) “A lt er at io n 0 :0 4 . (P 0) U “w -a Il 0 :0 4 (P 0) U “ w -a lt 0 0 4 (P 0) U m al l E :F 4 (F 0 )U “m s- al l 0: 04 (P 0) U “m s- al l E. H 4. (P 0) U “ w -a lt 0. 14 : (P 0) U w -a ll 0: A 5: (F 2) 4 0 .0 8 + 12 01 + 16 *3 E :8 5: (W 10 ] “C at d te 0 :0 5 : (F 3) + 0 :8 5 (B :C 39 C 7* 2/ $A $7 .C 8) $A $8 .C 24 *5 /S A $2 4) *$ A $5 0 :0 5 : (P 3) + D :C 5 * (B :D 3 9 D 7 * 2 )$ A $ 7 .0 9 /A $ 8 .0 2 4 * 5 f$ A $ 2 4 )* $ A $ 5 0: 05 : (P 3) + D :D 5* (B :E 39 .E 7* 2/ $A $7 .E 8/ $A $8 E 24 *5 /$ A $2 4) *$ A $S E :F 5: (P 3) + 0: E S * (8 :P 39 .F 7 * 2 f$ A $ 7 P 8 /A $ 8 .F 2 4 * S /$ A $ 2 4 )* * A $ S E :G S: (P 3) + 0: F 5* (8 :0 39 .0 7* 21 $A L 7. G 8/ $A $e .0 24 *6 /$ A S 24 )* $A $5 0: 1- IS : (P 3) + 0 :3 5 * (8 :H 3 9 .H 7 * 2 /$ A $ 7 il 8 I$ A $ 8 H 2 4 * 5 f$ A $ 2 4 )* S A $ 5 E: 15 : (F 3) + 0: H 5* (B :l 39 l7 *2 /$ A $7 le ,$ A S 8. l2 4* S /S A S 24 )* S A $5 E :A 6: (P 2) 4 0 .0 8 * 2 + 5 5 .8 5 + 2 6 .9 8 * 2 + 2 8 .0 9 * 3 + 1 6 * 1 2 + 1 7 0: 86 : IW 1O ) “E p id o te 0 :0 6 : (P 3) (1 0 :B 5 )* (B :C 3 9 .C 7 * 2 /$ A $ 7 .C 8 f$ A $ 8 .C 2 4 * 5 /S A $ 2 4 )* $ A 6 /2 E :0 6: (P 3) (1 .0 C 5 )* (8 0 3 9 .0 7 * 2 1 $ A $ 7 .D 9 /$ A $ 8 .0 2 4 * 5 4 A $ 2 4 )* $ A $ 6 /2 0: 06 : (F 3) (1 0 :D 5 )* (B :E 3 9 .E 7 * 2 fA S 7 E 8 J$ A S 8 .E 2 4 * 5 /A $ 2 4 )* $ A $ 6 /2 E :P 6: (F 3) (I .D :E 5 )* (G :F 3 9 F 7 * 2 /$ A $ 7 .F 8 f$ A S 8 F 2 4 * 5 /$ A $ 2 4 )* A S 6 /2 E :0 6 : (P 3) (1 .0 :F 5 )* (B :3 3 9 .0 7 * 2 /$ A $ 7 .G 8 /$ A $ 8 .0 2 4 * 5 /$ A $ 2 4 )* $ A S 6 /2 E :H 6: (P 3) (1 .0 .0 5) *( 8: H 39 .H 7* 2/ S A S 7t 18 /t ,A L 8. H 24 *5 /$ A S 24 )* $A $6 /2 0: 16 : (P 3) (l .D :H 5 )* (9 :l 3 9 l7 * 2 /S A $ 7 t8 f$ A $ 8 .t 2 4 * 5 /$ A $ 2 4 )* S A $ 6 /2 E :A 7: (F 2) 4 0 .0 8 * 2 + 2 8 .0 9 * 2 + 1 6 * 6 0: 87 : W 1 0 ] “C a- p y x E :C 7: (P 3) + 0 :8 1 4 * (B :0 3 9 C 8 f$ A $ 8 C 2 4 * 5 f$ A $ 2 4 )* S A $ 7 /2 0 :0 7 : (P 3) + 0: C 1 4 * (B :0 3 9 D 8 /$ A $ 8 0 2 4 * S /$ A $ 2 4 )* $ A $ 7 /2 0: 07 (P 3) + 0: 01 4* (B :E 39 .E 8/ S A $8 .E 24 *5 4A S 24 )* S A $7 )2 E :F 7: (P 3) + 0: 01 4* (B .F 3 9 .P B ,$ A S 8 .F 2 4 * 5 /A $ 2 4 )* A $ 7 ,2 0 :3 7 : (P 3) + D :F 1 4 (8 :G 3 9 .G 8 /$ A $ 8 G 2 4 * 5 /$ A $ 2 4 )* $ A $ 7 /2 E :H 7 (P 3) + 0 3 1 4 * (8 :H 39 H 8f $A $8 .H 24 *5 f$ A $2 4) *$ A S 7/ 2 0. 17 : (P 3) + D :H 1 4 * (8 l3 9 I8 /S A 8 l2 4 * 5 /$ A $ 2 4 )* S A $ 7 )2 E :A 8: (P 2) 4 0 0 8 + 2 6 .9 8 * 2 + 2 8 .0 9 * 2 + 1 6 * 8 0: 98 . (W I0 ) “ A n 0 :0 8 : (P 3) + 0 :8 i* G .C 4 0 * $ A $ 8 E :0 8: (P 3) + 0 :C 1 1 * 8 :0 4 0 * $ A 6 8 E :E 8: (P 3) + 0 :0 l1 * 8 :E 4 0 * $ A $ 8 E :F 8: (P 3) ÷ 0 :E ll * B :F 4 0 * S A $ 8 0 :3 8 (P 3) + 0 :F ll * B :0 4 0 * S A $ 8 E :H 8: (P 3) + 0 :3 1 l* B .l l4 0* S A $8 E: 18 : (P 3) + D :H ll * 8 1 4 0 * $ A $ 8 E :A 9: (P 2) 2 4 .3 1 + 6 0 .0 1 0: 89 : (W l0 ) “M q -c ar b 0 :0 9 : (F 3) (t .0 .8 6 .0 :8 7 )* B .C 3 0 * $ A $ 9 0 :0 9 : (P 3) (1 .D :C 6D :C 7) *B :0 88 *$ A $9 0: 09 : (P 3) (1 .D :0 6 0 :D 7 )* 8 E 3 8 * S A S 9 E :P 9: (P 3) (1 0 :E 6 0 :E 7 )* B :F 3 8 * $ A $ 9 E :3 9: (P 3) (l .0 :P 6 0 :P 7 )* 9 :Q 3 8 * S A S 9 E :H 9: (P 3) (1 .0 3 6 .0 3 7 )* B H 3 8 * $ A $ 9 I— ’) - 4 0: 19 : (P 3) (I .D :H 6. D :H 7) *9 :1 38 *$ A $9 E :A I0 : (P 2) 2 4 .3 1 * 5 + 2 6 .9 8 * 2 + 2 8 ,0 9 * 3 + 1 6 * lO + 17 *8 0: 81 0: [W iG ) M g .c h I 0 :0 1 0 : (P 3) + 0 :B 6 * 0 :C 3 8 /s * $ A $ IO 0 :0 1 0 : (P 3) + D :C 6* 8: 03 8/ S *$ A $i O E :E i0 : (F 3) + D :D 6* B :E 38 15 *$ A $1 0 E :P i0 : (P 3) + 0 :E 6 * 8 :F 3 8 /6 * $ A $ lO 0 :0 1 0 : (P 3) + D :F 6* 0: 03 8/ 5* $A f. iO 0: H I0 : (P 3) ÷ D :0 6* 8: H 38 /S *$ A $i O 0: 11 0: (P 3) + 0: H 6* 8: 13 8/ 5* $A $l O E :A il : (P 2) 2 4 .3 1 * 2 + 2 8 .0 9 * 2 + 1 6 * 6 E :8 l1 : W i0 ] “M g .p y x 0 :0 1 1 : (F 3) + 0 :8 7 * 8 :C 3 8 1 2 * $ A $ 1 i 0 :0 1 1 : (P 3) + 0 .C 7 * 8 :0 3 8 /2 * $ A $ li 0: 01 1: (P 3) + D ;D 7* B :0 38 12 *S A $i i E :F I1 ’ (P 3) + D :E 7 * 8 :P 3 8 /2 * S A $ ii 0 :0 1 1 : (P 3) + D :F 7 * 9 :G 3 8 /2 * S A $ il E :H 11 : (P 3) + D :0 7 * 8 :H 3 8 /2 * $ A $ ii 0: 11 1: (P 3) + D :H 7* 9: 13 8/ 2* $A $1 1 E :A 12 : (P 2) 5 5 .8 5 + 6 0 .0 1 0: 81 2: W l0 ) F e -c a rb 0 :0 1 2 : (P 3) (1 .D :9 8 .0 :9 9 )* (B :C 3 6 .C i 9/ S A S I 9 .C 2 5 /$ A $ 2 5 .0 2 7 /$ A $ 2 7 )* $ A S I2 0 :0 1 2 : (P 3) (1 -0 :C 8 -D :C 9 )( B :0 3 6 .D i 9 /S A Il 9 .0 2 5 /$ A 5 2 5 .0 2 7 /$ A $ 2 7 )* $ A $ 1 2 0: 01 2: (F 3) (1 .D :0 8 .0 :D 9 )* (B :0 3 5 .E i 9 /$ A $1 9. E 25 /$ A $2 5. 02 71 $A $2 7) *$ A $i 2 0: P i 2: (P 3) (1 -D :E 8 -D :0 9 )( B :P 3 6 .F I 9 /S A $ 1 9 .F 2 5 /$ A 5 2 5 -F 2 7 /$ A 5 2 7 )’ $ A 5 i2 0 :0 1 2 : (P 3) (I -D :F 8. 0: P 9) ’( B :0 36 -G 1 9 /S A Il 9. G 25 /$ A 52 5. 02 7/ 5A 12 7) *$ A $ 12 E :H 12 : (F 3) (1 .D G 9 .O G 9 )* (8 H 3 6 H 1 9 /$ A 5 1 9 .H 2 5 ,S A $ 2 5 .H 2 7 /$ A $ 2 7 )* $ A 5 j 2 E :l i 2: (P 3) (1 .D :H 8. 0: H 9) *( 9: 13 6. Il 9 /S A Il 9. 12 5/ $A $2 6. 12 7/ $A 52 7) *$ A $l 2 E: A 1 3: (P 2) 5 5 .8 5 * 5 + 2 6 .9 8 * 2 + 2 8 .0 9 * 3 + 1 6 * 1 0 + 1 7 * 8 0: 81 3: [W iG ) P e- ch i 0 :0 1 3 : (P 3) + D :9 8 * (9 :0 3 6 .0 l 9 /S A Il 9 -C 2 5 /I A S 2 5 .C 2 7 /5 A $ 2 7 )/ 5 $ A $ 1 3 0 :0 1 3 : (P 3) + D :C 8 * (8 :0 3 6 .0 i 9 /S A Il 9 .0 2 5 /$ A $ 2 5 .D 2 7 /$ A $ 2 7 )/ 5 * S A $ i 3 0: 01 3: (P 3) + D :D 8* (B :E 36 .E 1 9 /S A Il 9. E 25 /$ A $2 5. E 27 /$ A $2 7) /5 *$ A S 1 3 0: P l 3: (P 3) + D :E 8* (9 :F 36 .P 1 9 /S A Il 9. P 25 /$ A $2 5. P 27 /$ A 52 7) 15 *$ A $1 3 0 :0 1 3 : (P 3) + D :P 8