MINOR ELEMENTS IN PYRITES FROM THE SMITHERS MAP AREA, AND-EXPLORATION APPLICATIONS OF MINOR ELEMENT STUDIES by BARRY JAMES PRICE B.Sc. (1965) U.B.C. A thesis submitted in partial fulfillment of the requirements, for the degree of Master of Science in the DEPARTMENT OF GEOLOGY We accept this thesis as conforming to the required standard TEE UNIVERSITY OF BRITISH. COLUMBIA April 1972 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, 1 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 representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of The University of British Columbia Vancouver 8, Canada i MINOR ELEMENTS IN PYRITES FROM THE SMITHERS MAP AREA, B.C. AND EXPLORATION APPLICATIONS OF MINOR ELEMENT STUDIES • ABSTRACT This study was undertaken to determine minor element geo• chemistry of pyrite and the applicability of pyrite minor-element research to exploration for mineral deposits. Previous studies show that Co, Ni, and Cu are the most prevalent cations substituting for Fe in the pyrite lattice; significant amounts of As and Se can substitute for S. Other elements substitute less commonly and in smaller amounts within the lattice, in interstitial sites, or within discrete mechanically-admixed phases. Mode of substitution is determined most effectively with the electron microprobe. 2+ Cation substitution for Fe is favored by transition elements with non-bonding "d" electrons .in low-spin configurations, an octa• hedral covalent radius similar to that of Fe (1.23 and high electronegativity. Anion substitution for S is favored by chalcogeri and pnigogen elements with a tetrahedral coordination radius close to 1.04 and high electronegativity. Statistical tests performed on several hundred pyrite analyses compiled from the literature and stored on computer cards support: (l) log-normal frequency distributions of minor elements in hydrothermal pyrite; (2) redistribution of minor elements in pyrite by metamorphism; (3) statistical differentiation of hydro- thermal, volcanic-exhalative, and syngenetic pyrites on the basis of Co and Ni concentrations and ratios; (4) relationship of minor element "spectra" and concentrations in disseminated pyrite to those in adjacent rocks; and (5) relationship of minor-element concentra• tions in hydrothermal pyrites to major ore-forming elements present. Forty pyrite samples from several distinct types of mineral deposits in the Smithers area, B.C. were analyzed for Co, Ni, Mn, Cu, Pb, and Zn using atomic-absorption spectrophotometry. Co concentrations are highest in pyrites from volcanic rocks, massive sulphide deposits and a breccia pipe. Ni and Mn concentrations are uniformly lo*r. High contents of Cu, Fb, and Zn are caused by inclusions of common sulphides. Calculation of correlation coeffi• cients for minor elements revealed that contamination does not significantly affect Co or Ni concentrations. Minor element data from the Smithers pyrites provides evidence for genetic relationships between several different mineral deposits, the presence of "metallogenetic" sub-provinces, and minor-element zonation in mineral deposits. Research into minor-element geochemistry of pyrite can be useful in exploration for mineral deposits; most effective use is during secondary stages of exploration. Most useful elements for exploration applications are Co, Ni, Cu, Au, Ag, Hg, Tl, Sn, As, and Se. ACKNOWLEDGMENTS I would like to thank Dr. A.J. Sinclair, who suggested the field of study, provided financial assistance for the •computer-based.statistical studies, and who offered much constructive criticism and many helpful suggestions during preparation of the thesis. Field work was carried out while the writer was employed by Manex -Mining Ltd., who provided transportation and financial assistance for the project. Dr. W.K. Fletcher provided facilities for analytical work, developed techniques for sample solution and elimination of analytical interferences. Much technical assistance was provided during sample preparation and analysis by Mr. A. Bentzen and Mr. A. Dhillon. Facilities for rock-crushing were provided by the Mineral Engineering Department and Bondar- Clegg Ltd. (Assayers). Finally I would like to thank Alexis Clague for typing the thesis. iv TABLE OP CONTENTS Page. , ABSTRACT i ACKNOWLEDGMENTS iii .TABLE OF CONTENTS iv LIST OF TABLES viii LIST OF FIGURES xii INTRODUCTION 1 CHAPTER I PYRITE CRYSTAL CHEMISTRY 3. A. The Pyrite Group and Related Groups 3 1. The Pyrite Group 3 2. Marcasite and Other Structural Groups 5 B. The Relationship of Crystal-Field Theory 9 to Pyrite Group Minerals C. The Co-Ni-Fe-S2 System 22 1. Natural and Synthetic Phases 22 2. Variation of Properties with Composition 25 a. Unit-cell Dimensions 26 b. Color, Reflectivity and Hardness 26 c. Anisotropism 33 d. Thermoelectric Effect 35 CHAPTER II MINOR ELEMENTS' CONTAINED IN PYRITE 37 A. General Discussion 37 TABLE OF CONTENTS (Continued) Page B. Anion Substitution in Pyrite - 40 C. Cation Substitution in Pyrite 42 D. The Incorporation of Minor Elements in Pyrite 45 E. Distribution of Minor Elements within a Single Crystal 49 F. Specific Minor Elements Contained in Pyrite 53 1. The Copper Content of Pyrite 53 2. The Gold Content of Pyrite 57 3. The Silver Content of Pyrite 62 4. Platinum Group Elements in Pyrite 63 5c The Uranium Content of Pyrite 64 6. Thallium Content of Pyrite 67 7. The Mercury Content of Pyrite 69 8. Manganese Content of Pyrite 71 9. Tin Content of Pyrite 71 10. The Selenium Content of Pyrite 72 CHAPTER III THE GEOCHEMISTRY OF COBALT AND NICKEL IN ROCKS 77 A. Igneous Rocks 77 B. Sedimentary Rocks 83 C. Metamorphic Rocks 90 vi TABLE OF CONTENTS (Continued) Page CHAPTER IV STATISTICAL STUDIES OF MINOR ELEMENTS IN PYRITE . 95 A. Introduction 95 B. Frequency Distributions of Minor Elements 97 C. Sedimentary Pyrite 101 D. Massive-Sulphide - Volcanic-Exhalative Pyrite 110 E. Effects of Metamorphism on Pyrite 112 F. Hydrothermal Pyrite 124 1. Porphyry-Cu-Mo Deposits 124 2. Normal Vein and Replacement Deposits 129 G. Minor Elements in Pyrite and Silica Content of Associated Igneous Rocks 137 CHAPTER V MINOR ELEMENTS IN PYRITE FROM THE SMITHERS AREA, B.C. • 141 A. Introduction 141 B. General Geology of the Thesis Area 143 1. Stratigraphy ' 143 2. Structure 143 3. Igneous Rocks 144 4. Mineral Deposits 144 C. Analytical Method and Results 146 D. Discussion of Results 149 1. Dome Mountain Area 151 TABLE OF CONTENTS (Continued) Page 2. Grouse Mountain Area 152 a. Molymine Deposits 152 b. Other Deposits .162 3. Exploration Applications in the Snithers Area 164 CHAPTER VI SUMMARY AND CONCLUSIONS - 166 APPENDICES I. PROPERTY DESCRIPTIONS 191 II. • SAMPLE PREPARATION,. ANALYSIS, AND PRECISION CALCULATIONS . 211 III. EXPLANATION OF DATA FILING SYSTEM . " 221: IV. APPLICATION OF MINOR ELEMENT STUDIES -.• • TO EXPLORATION FOR MINERAL DEPOSITS 223 LIST OF TABLES Table Page 1. Pyrite Group - Minerals and properties 6 2. Electronic configurations of the elements of the first transition series 11 3. Electronic configurations and crystal-field stabilization energies of transition metal ions in octahedral coordination 12 4. The number of non-bonding d-electrons in -\": dianionic compounds - 16 5. Minerals with 6, 7, or 8 non-bonding "d"-electrons 16 6. Chalcogenides and pnictides of transition „ elements 17 7. Reflectivity and hardness values for the zoned bravoite crystal in relation to composition 30 8. Reflectivities, effective number of free electrons and electronic configuration of cations in the pyrite type disulphides 32 9. Results of the quantitative determination of trace elements by the electron microprobe on the two types of pyrite 34 10. Physicochemical parameters of anions 40 11. Physical parameters of cations 43-44 12. Ionization potentials, electronegativities, and ionic radii for divalent and trivalent cations 47 "13. Comparison of minor element content of pyrite crystal cores and margins, Belukhinskoye and Bukhinskoye deposits, U.S.S.R. 52 14. Uranium content of pyrite samples from uranium deposits 66 LIST OF TABLES (Continued) Table Page 15. Selenium content of pyrites from some 76 Canadian ore deposits • 16. Variation of cobalt and nickel with rock types 78 17. Average Co and Ki contents and Co/Ni. ratios of sediments 83 18. Average Co, Ni contents and Co/Ni ratios of syngenetic copper deposit sediments 84 19. Zero order correlations for Mn-Fe-Co-Ni in sediments from various environments 89 20. Comparison of minor element content of medium and high-grade metamorphic rocks, Adirondack Mountains, New York 91 21. Comparison of minor element content of low, medium and high-grade metamorphic rocks, New Hampshire 91 22. Comparison of means, standard deviations and t-test values for "syngenetic',' "hydrothermal" and "massive sulphide" pyrites 107 23. Comparison of means, standard deviations, and t-test values for minor elements in medium- grade and high-grade metamorphic pyrites 116 24. Comparison of means, standard deviations, and t-test values for minor elements in pyrites from the Berg and Endako "porphyry" deposits 126-127 25. Minor element data - "porphyry" pyrites 130 26. Minor element data - hydrothermal vein and replacement pyrite 131 27. Comparison of means, standard deviations, and t-test values for minor elements in pyrites from mineral deposits of different major metals 133-134 28. Relationship of maximum Ni content and Ni/Co ratio of sulphides to composition of adjacent igneous rocks 138 LIST OF TABLES (Continued) Table Page 29. Mineral deposits of the Done Mountain-Grouse Mountain area, Smithers, B.C. 145 30. Pyrite analyses from Smithers. map area, B.C. 147 31. Comparison of Dome Mountain and Dome Babine pyrites 154 32. Comparison of means, standard deviations and., t-test values for pyrites from Dome Mountain and Grouse Mountain mineral deposits 155 33.