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Carbon sequestration in chrysotile mine tailings 2006

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C A R B O N S E Q U E S T R A T I O N IN C H R Y S O T I L E M I N E T A I L I N G S by S I O B H A N A L E X A N D R A W I L S O N B . S c , McMaster University, 2003 A THESIS S U B M I T T E D I N P A R T I A L F U L F I L M E N T O F T H E R E Q U I R E M E N T S F O R T H E D E G R E E O F M A S T E R O F S C I E N C E in T H E F A C U L T Y OF G R A D U A T E STUDIES Geological Sciences T H E U N I V E R S I T Y OF B R I T I S H C O L U M B I A November 2005 © Siobhan Alexandra Wilson, 2005 A B S T R A C T ABSTRACT Active sequestration of atmospheric carbon dioxide (CO2) is occurring in chrysotile mine tailings at Clinton Creek, Yukon and Cassiar, British Columbia. Hydrated magnesium carbonate minerals develop in mine tailings as a natural consequence of the weathering process within the residues. Magnesium, leached from silicate minerals, reacts with dissolved CO2 and bicarbonate in rainwater, precipitating carbonates at the surface of tailings upon evaporation of pore fluids and in near-surface environments with possible mediation by photosynthetic microbes. Increased reaction rates are observed in the tailings environment due to fine grain size resulting from mineral processing. Mine tailings may therefore represent the optimal environment in which to pursue mineral sequestration. Stable carbon and oxygen isotopes and radiogenic carbon are used to confirm an atmospheric source for CO2 in recently-precipitated carbonate efflorescences in mine tailings. X-ray powder-diffraction studies demonstrate that CO2 is crystallographically bound within the hydrated magnesium carbonate minerals nesquehonite [ M g C C V 3 H 2 0 ] , dypingite [Mg5(C0 3)4(OH)2-5H 20], hydromagnesite [Mg5(C0 3)4(OH)2-4H 20], and lansfordite [ M g C 0 3 - 5 H 2 0 ] . Quantitative phase analysis with the Rietveld method for X - ray powder-diffraction is used to determine the modal abundance of hydrated magnesium carbonates in mine tailings. Isotopic-fingerprinting and the Rietveld method are an effective verification protocol for carbon sequestration in mine tailings. i i T A B L E O F C O N T E N T S TABLE OF CONTENTS Abstract i i Table of Contents i i i List o f Tables v List o f Figures v i List o f Abbreviations ix List o f Symbols x Preface x i i Acknowledgements x iv C H A P T E R I: Introduction : 1 1.1 Introduction and Motivation for Study 1 1.2 References 5 C H A P T E R II: Mineralogical characterization of magnesium-carbonate precipitates in chrysotile mine tailings 6 2.1 Introduction 6 2.2 Characterization of Tailings Material 7 2.2.1 Field Localities 7 2.2.2 Sampling Methodology 11 2.3 Experimental Techniques for Characterization of Tailings 13 2.3.1 Qualitative X-ray Powder Diffraction 13 2.3.2 Scanning Electron Microscopy 14 2.3.3 Grain Size Analysis 15 2.3.4 Bulk Geochemistry 16 2.4 Results of Bulk Tailings Characterization 16 2.4.1 Bulk Mineralogy .16 2.4.2 Asbestos Mineral Content : 18 2.4.3 Carbonate Precipitate in Bulk Tailings Samples 19 2.4.4 Grain Size Analysis 21 2.5 Hydrated Magnesium Carbonate Mineralogy 23 2.6 Modes of Occurrence and Mechanisms of Formation 30 i i i T A B L E O F C O N T E N T S 2.7 Interpretation of Experimental Results 38 2.8 References 44 C H A P T E R III: Isotopic Characterization of Magnesium-Carbonate Precipitates 49 3.1 Introduction 49 3.2 Experimental Method 49 3.2.1 Light Stable Isotopes 49 3.2.2 Radiogenic Carbon Fingerprinting 50 3.2.3 Surface Area Analysis 51 3.3 Results of Isotopic Investigation 51 3.3.1 Stable Carbon and Oxygen Isotopes 51 3.3.2 Radiogenic Carbon 54 3.4 Determination of the Source of Carbon 56 3.5 The Source for Cations 63 3.6 References 67 C H A P T E R IV: Verifying and quantifying carbon fixation in minerals from serpentine-rich mine tailings using the Rietveld method with X-ray powder diffraction data 70 4.1 Introduction 70 4.1.1 Sample Localities 75 4.2 Experimental Methods 77 4.2.1 Sample Preparation and Data Collection 77 4.2.2 Motivation for Using the Rietveld Method 82 4.2.3 Rietveld Refinement and Quantitative Phase Analysis 86 4.3 Results and Discussion 91 4.3.1 Synthetic Mine Tailings 91 4.3.2 Natural Mine Tailings 100 4.4 References 111 C H A P T E R V : Conclusions 119 Appendix A : Whole Rock Geochemistry for Clinton Creek and Cassiar 122 Appendix B : X-ray Powder Diffraction Data for Qualitative Analysis 125 Appendix C: Sieving Data 197 iv LIST O F T A B L E S L I S T O F T A B L E S T A B L E 2.1: Empirical formulae for hydrated magnesium carbonate minerals 29 T A B L E 2.2: Mineralogy and mode of carbonate occurrence 31 T A B L E 3.1: Mineralogical and isotopic data for carbonate samples 52 T A B L E 3.2: Estimates for surface area of mineral phases in bulk tailings samples 66 T A B L E 4.1: Compositions of synthetic serpentinite mine tailings renormalized to exclude fluorite spike 79 T A B L E 4.2: Sources of crystal structure data for Rietveld refinement 87 T A B L E 4.3: Results of quantitative phase analysis of synthetic serpentinite mine tailings 92 T A B L E 4.4: Results o f quantitative phase analysis o f natural serpentinite mine tailings renormalized to exclude 10% fluorite spike 101 T A B L E 4.5: Estimated amounts of atmospheric CO2 crystallographically bound in serpentinite mine tailings 109 LIST O F F I G U R E S L I S T O F F I G U R E S F I G U R E 1.1: Location of Clinton Creek, Y T , and Cassiar, B C 3 F I G U R E 2.1: Location of Clinton Creek, Y T , and Cassiar, B C 8 F I G U R E 2.2: Collapse of the northern lobe of the Wolverine tailings pile at Clinton Creek 9 F I G U R E 2.3: Modes of carbonate occurrence at Clinton Creek and Cassiar 12 F I G U R E 2.4: Back-scattered electron image of actinolite grains in sample 04CA0401 20 F I G U R E 2.5: Results of grain size analysis for two typical samples of tailings 22 F I G U R E 2.6: Mass fractions of fibrous and non-fibrous tailings materials for each size fraction used in wet-sieving for sample 04CC1401 24 F I G U R E 2.7: Percent of tailings to pass through each sieve for sample 04CC1401 25 F I G U R E 2.8: Pi20-MgO-C02 compositional ternary for the hydrated magnesium carbonate minerals 28 F I G U R E 2.9: Variation in habit and intensity of backscattered electrons between nesquehonite and dypingite/hydromagnesite phases in vertical crust sample 04CC0201B 33 F I G U R E 2.10: Distinguishing between hydromagnesite/dypingite and nesquehonite in thin section with E D S 34 F I G U R E 2.11: Secondary electron (SE) and Back-scattered electron (BSE) images of spire samples 04CC0702 and 04CC0902 and vertical crusts 04CC0201B and 04CC0703 35 F I G U R E 2.12: Secondary electron (SE) and Back-scattered electron (BSE) images of spire samples 04CC0702 and 04CC0902 and vertical crust 04CC0106 36 v i LIST OF F I G U R E S F I G U R E 2.13: Zonation of hydrated magnesium carbonate minerals in crusts and spires 39 F I G U R E 2.14: Best-case scenario model for hydrated magnesium carbonate formation in mine tailings 41 F I G U R E 2.15: Mechanisms of formation for the four modes of occurrence 43 F I G U R E 3.1: Stable oxygen and carbon isotope data by mode of carbonate occurrence and mineralogy 53 F I G U R E 3.2: Worst-case scenario for carbonate stability in mine tailings 60 F I G U R E 3.3: Best-case scenario model for hydrated magnesium carbonate formation in mine tailings 61 F I G U R E 3.4: Variation of 8 1 3 C with F 1 4 C for seven samples from Cassiar and Clinton Creek 62 F I G U R E 4.1: Locations of Clinton Creek, Yukon, Cassiar, British Columbia, and At l in , British Columbia 72 F I G U R E 4.2: Modes in which hydrated magnesium carbonate minerals have been identified at Clinton Creek, Yukon and Cassiar, British Columbia 76 F I G U R E 4.3: Abundance of serpentine from Rietveld refinement versus nominal abundance for three different concentrations of the fluorite spike (9, 10, and l l % C a F 2 ) 90 F I G U R E 4.4: Rietveld refinement plot, A C M L X 7 0 94 F I G U R E 4.5: Modal abundances from Rietveld refinement versus nominal abundances in synthetic serpentinites 95 F I G U R E 4.6: Absolute (wt.%) error in estimates for al l minerals versus the abundance of that mineral in a sample 96 F I G U R E 4.7: Relative and absolute (wt.%) error in Rietveld estimates of hydromagnesite abundance for all synthetic samples 97 F I G U R E 4.8: Refinement results used to determine the percent magnesite contamination in the "pure" hydromagnesite sample 99 v i i LIST O F F I G U R E S F I G U R E 4.9: Rietveld refinement plot of a chrysotile mine residue from Clinton Creek, Y T (04CC0703) 103 F I G U R E 4.10: Detailed mineralogy for modal occurrences of hydrated magnesium carbonate crusts in serpentine-rich mine tailings 105 F I G U R E 4.11: Evolution of magnesium-carbonate mineral phases and bound carbon per mole cation ( M g 2 + ) during dehydration in a mine-tailings carbon-disposal site 108 v i i i LIST OF A B B R E V I A T I O N S L I S T O F A B B R E V I A T I O N S A M S Accelerator Mass Spectrometry B P Before Present B S E Back-Scattered Electron E D S Energy-Dispersive Spectrometry or Energy-Dispersive Spectrum P C I G R Pacific Centre for Isotopic and Geochemical Research S E Secondary Electron S E M Scanning Electron Microscope or Scanning Electron Microscopy V P D B Vienna Pee Dee Belemnite V S M O V Vienna Standard Mean Ocean Water X R D X-ray Diffractometer or X-ray Diffractometry X R P D X-ray Powder Diffractometer or X-ray Powder Diffractometry y B P Years Before Present IX LIST OF S Y M B O L S L I S T O F S Y M B O L S Non-Greek 1 4 C Carbon-14 A Amount of amorphous phase C a Calcium CO2 Carbon dioxide \F\ Refined structure factor \Fcalculate^ Calculated structure factor FI4C Fraction Modern Carbon i Index for intensity measurements / Intensity of scattered X-rays M Mass of formula unit M g Magnesium r index for mineral phases Rs Amount of spike, s, determined by Rietveld refinement s Spike phase S Rietveld scale factor Sy Least-squares residual for Rietveld fit t Number of mineral phases in a refined sample V Volume of unit cell x LIST O F S Y M B O L S wt Weight on least squares residual, Sy ws Weighed amount of spike, s Wr Relative weight fraction of phase r wt.% Weight-percent yci Calculated intensity at the i'h step in an X-ray diffractogram v, Measured intensity at the ith step in an X-ray diffractogram Z Number of formula units per cell Greek SI3C Delta Carbon-13 S,80 Delta Oxygen-18 0 Scattering angle for X-rays x i P R E F A C E P R E F A C E This work is composed of three body chapters, one of which has been accepted for publication pending minor revisions, and two of which are in preparation for publication. Chapter II outlines the detailed characterization of mineral assemblages, grain size, and mode of carbonate occurrence in the mine tailings from Clinton Creek and Cassiar. Samples for the 2003 field season were collected by Gregory M . Dipple, R . G . Anderson, and M . Mihalynuk. Dry-sieving was done by Elizabeth Castle. Wet-sieving on two samples was done with the assistance of James Thorn and Joanne Woodhouse. Chapter III is a discussion of isotope data for carbonate precipitates from chrysotile mine tailings. A method for fingerprinting the source of carbon dioxide tapped in the precipitation of calcium and magnesium-carbonates is given. Stable isotope analyses and radiocarbon dating were performed by Janet Gabites and Beta Analytic Radiocarbon Dating Laboratory, respectively. Surface area analysis using the B E T N - gas adsorption isotherm technique was done by James Thorn. Chapter IV has been accepted for publication in the American Mineralogist, pending minor revisions, under the title "Verifying and quantifying carbon fixation in minerals from serpentine-rich mine tailings using the Rietveld method with X-ray powder diffraction data". It is co-authored by Drs. Mati Raudsepp and Gregory M . Dipple. This chapter describes a new technique, for use with the Rietveld method for X - ray powder diffraction data, which overcomes the previously unresolved barriers to x i i P R E F A C E quantitative phase analysis in samples containing disordered minerals. This new approach to the Rietveld method allows CC^-sequestration in mineral carbonates to be quantified in serpentine-rich mine tailings. M . Raudsepp provided valuable technical advice and suggestions. G . M . Dipple, who initiated the project, provided oversight on applications and general concepts. Drs. Gregory M . Dipple and Mat i Raudsepp initiated this line of research, secured funding, and supervised this project. xni A C K N O W L E D G E M E N T S A C K N O W L E D G E M E N T S This research was funded by Natural Sciences and Engineering Research Council of Canada Discovery Grants held by G . M . Dipple and M . Raudsepp, by the Y u k o n Geological Survey, and the British Columbia Ministry of Energy, Mines and Petroleum Resources. I would like to thank Grant Abbott from the Yukon Geological Survey and Hugh Copland from the Yukon Department of Energy, Mines, and Resources for their interest in this project. Bob Anderson from the Geological Survey of Canada provided samples from Clinton Creek and valuable advice. Mi tch Mihalynuk from the British Columbia Ministry of Energy, Mines and Petroleum Resources provided samples from Cassiar. Ernie Hatzl of Cassiar Jade Contracting Inc. provided access and accommodations at Cassiar during the 2003 and 2004 field seasons. Arnt Kern supplied invaluable advice pertaining to the use of the Pawley method. Thanks to Marcia Y u and Andrea De Souza for training in Raman microspectroscopy and to Michael Blades for granting access to his laboratory facilities. Thanks to James Thorn for advice and for grain size and surface area data. Lyle Hansen shared his programming expertise in Matlab. Joanne Woodhouse and Elizabeth Castle provided expert laboratory assistance. Thanks to Gordon Southam and Ian Power for discussion and advice regarding the geomicrobiological aspects of this study. I would like to thank Elisabetta Pani for providing me with training in the use of the X-ray diffractometer and scanning electron microscope and for being an example xiv A C K N O W L E D G E M E N T S of stoicism and grace under pressure. Thanks to U l i Mayer for advice, constructive criticism, and for serving on my advisory committee. Thanks to Dominique Weis for serving on my examination committee and for sharing her expertise in the field of isotope geochemistry. Many thanks to Greg Dipple and Mati Raudsepp for guidance, for getting me involved in such a fascinating project, and for helping me to become a better scientist. Thanks to Greg for teaching me to always keep the "big picture" in mind and to Mat i for impressing upon me the importance of precision and detail in research. Thanks to Gareth Chalmers, Sarah Gordee, Lyle Hansen, Steve Johnston, Cathy Lovekin, Diana Moscu, Kirsten Parker, Daniel Ross, Swati Singh, Reza Tafti, James Thorn, Stuart Sutherland, and all the graduate students in the Department of Earth and Ocean Sciences at U B C for tea, sympathy, and excellent times. M y gratitude goes to F .D . Spike for inspiration. Thanks especially to Jesse, my parents, and M i n for their patience and for everything else. xv C H A P T E R I C H A P T E R I : Introduction 1.1 I N T R O D U C T I O N A N D M O T I V A T I O N F O R S T U D Y The combustion of fossil fuels currently accounts for greater than 80% of global energy use (Goldberg et al. 2001). Although alternative energy sources such as nuclear fission, wind, and solar power are available, it is unlikely that increased reliability on these methods of energy production w i l l significantly reduce greenhouse gas emissions in the near future. A s national dependence on fossil fuels is unlikely to diminish in the next fifty years, the sequestration of anthropogenic carbon dioxide (CO2) may be required to meet Canada's commitment to the Kyoto Protocols. Several methods of CO2 sequestration including storage in coal seams, in oi l and gas reservoirs, in the ocean and saline aquifers, and in mineral carbonates have been proposed (Office of Fossil Energy 2004). O f these schemes, mineral carbonation provides the most stable and environmentally benign means of fixing anthropogenic CO2 (Lackner et al. 1995; Lackner 2003). Mineral carbonation is a process by which kaolinite-serpentine minerals and olivine are artificially altered to carbonate minerals as a means of binding carbon dioxide in mineral form (Lackner et al. 1995). Carbon dioxide bound in carbonates is potentially trapped within the crystal structure of these minerals on a geologic timescale. A large- scale industrial process for mineral carbonation has been under development by the 1 C H A P T E R I Mineral Sequestration Working Group affiliated with the U .S . Department of Energy (Goldberg et al. 2001). Carbonation of kaolinite-serpentine group minerals in ultramafic mine tailings has only recently been recognized as a natural analogue of the industrial process (Huot et al. 2003). Furthermore, enhanced carbonation in mine tailings may provide a potential implementation of the mineral carbonation process. The primary goals of this research project have been to document the mineralogy and the modes in which carbonation occurs in mine tailings, to identify the environmental controls upon natural carbonation, to determine the sources for carbon dioxide and magnesium tapped during carbonate formation, and to establish whether net sequestration is occurring in the tailings from two abandoned chrysotile mines at Clinton Creek, Yukon and Cassiar, British Columbia (Fig. 1.1). The outcomes of this study include a first detailed description of low-temperature carbonate alteration in ultramafic mine tailings, a method for X-ray powder diffraction data that allows for the quantification of carbon dioxide sequestration with mineral carbonation, and a means by which to fingerprint the source of carbon tapped in the precipitation of modern carbonates using stable and radiogenic isotopes of carbon. Chapter II provides a detailed account of the mineralogy, modes of occurrence, and methods of formation for carbonate alteration in mine tailings. The hydrated magnesium carbonate minerals lansfordite, nesquehonite, dypingite, and hydromagnesite and the calcium carbonate minerals calcite and aragonite are determined to be developing in situ in the ultramafic mine tailings. Five distinct modes of carbonate mineralization 2 C H A P T E R I F I G U R E 1.1: Location of Clinton Creek, Y T , and Cassiar, B C (A). The tailings pile at Clinton Creek is shown in B (trees for scale) and the tailings at Cassiar in C (road for scale). 3 C H A P T E R I are documented: Efflorescences or "crusts" on vertical surfaces, spire-like structures on horizontal surfaces, coatings on cobbles, disseminated cements, and linings in runoff streams. Chapter III discusses the use of stable and radiogenic isotope geochemistry to identify the sources for carbon and cations tapped in the precipitation of carbonates in mine tailings environments. Using stable isotope data for carbon and oxygen and radiogenic carbon dating, an atmospheric source for carbon is identified for the hydrated magnesium carbonates, while the calcium carbonates are determined to have reprecipitated from bedrock. Chapter IV has been accepted for publication by the American Mineralogist, pending minor revisions. This chapter describes a quantitative method for determining the amount of carbon dioxide that has been crystallographically bound in mineral carbonates in serpentine-rich mine tailings. This procedure employs a variant of the Rietveld method for X-ray powder diffraction data, in which kaolinite-serpentine group minerals are modeled as amorphous phases to account for structural disorder. This method is developed and optimized for a series of synthetic chrysotile and antigorite mine tailings and later implemented on a number of natural mine tailings samples from Clinton Creek and Cassiar. A discussion of the implications of the results presented in Chapters II, III, and TV is given in Chapter V . 4 C H A P T E R I 1.2 REFERENCES Goldberg, P., Chen, Z . - Y . , O'Connor, W. , Walters, R., and Ziock, H . (2001) C 0 2 Mineral Sequestration Studies in U S . In the Proceedings of the First National Conference on Carbon Sequestration. Retrieved in 2004 from the National Energy Technology Laboratory of the U .S . Department of Energy Website: http://www.netl.doe.gov/ publications/proceedings/01/carbon_seq/6cl.pdf. Huot, F., Beaudoin, G . , Hebert, R. Constantin, M . , Bonin, G . , and Dipple, G . (2003) Evaluation of Southern Quebec asbestos residues for C 0 2 sequestration by mineral carbonation; preliminary results. Joint Annual Meeting of the Geological and Mineralogical Associations of Canada. Lackner, K . S . (2003) Climate change: A guide to C 0 2 sequestration. Science, 300, 1677- 1678. Lackner, K . S . , Wendt, C . H . , Butt, D.P. , Joyce, G .L . , and Sharp, D . H . (1995) Carbon dioxide disposal in carbonate minerals. Energy, 20, 1153-1170. Office of Fossil Energy. (2005, June 1) Carbon Sequestration R & D . Retrieved October 22, 2005 from the U .S . Department of Energy: http://www.fossil.energy.gov/ programs/sequestration/index.html. 5 C H A P T E R II C H A P T E R II : Mineralogical characterization of magnesium-carbonate precipitates in chrysotile mine tailings 2.1 I N T R O D U C T I O N The carbonation of kaolinite-serpentine group minerals in ultramafic mine tailings is one potential implementation of the mineral carbonation process (Huot et al. 2003). Carbonation of historical mine residues could provide the dual benefit o f destroying the fine fibre content of tailings and binding atmospheric greenhouse gases in the process. CO2 futures or credit trading could also provide a revenue stream for implementing the industrial process. Futures of CO2 sequestration currently trade for about U S $ 2.50 per tonne ($/tC0 2 ) at the Chicago Climate Exchange (2005), while long- term forecasts approach US$ 100/tCO 2 (Ciorba et al. 2001). On October 25, 2003, a system for emissions trading between member nations came into effect in the E U , under the auspices of Directive 2003/87/EC. Limitations on production of greenhouse gases within the E U were implemented January 1, 2005. Polluters that exceed set emissions caps are fined €40 per tonne of excess CO2. This fine w i l l increase to €100/tCO 2 in 2008. E U emissions allowances currently trade for about €23/tC02 through Carbon Pool Europe (Climate Corporation 2005). The discovery that some chrysotile mine residues are spontaneously carbonating presents an opportunity to study a natural analogue to the industrial carbonation process that is currently under development by the Mineral 6 C H A P T E R II Sequestration Working Group affiliated with the U .S . Department of Energy (Goldberg et al. 2001). Additionally, in situ acceleration of mineral carbonation in the tailings environment could render large mining operations CCVneutral . A thorough investigation of the mineralogy of carbonate alteration in serpentinite tailings piles is a necessary first step toward understanding and accelerating uptake of CO2 in mine tailings. In this chapter, we identify the mineral phases precipitating in these tailings environments and describe the mechanisms by which they form. 2.2 C H A R A C T E R I Z A T I O N O F T A I L I N G S M A T E R I A L 2.2.1 F ie ld Localit ies The Clinton Creek chrysotile deposit is a partially carbonate-altered serpentinized peridotite (Htoon 1979). The Clinton Creek Mine, situated near Dawson City, Y u k o n Territory (Fig. 2.1), operated from 1967 to 1978 (Htoon 1979). A total of 16 M t of chrysotile ore were extracted from the four open pit mines at Clinton Creek during this eleven year period. In addition to the ore, 60 M t of waste rock and 10 M t of tailings were produced as a by-product of the mining process ( E M A N - N o r t h 2003). The tailings pile, situated on a topographic high overlooking Wolverine Creek, slumped into the creek in two stages: The southern lobe of the pile dammed the creek in the early 1970s followed by the northern lobe which destabilized in 1986 (Fig. 2.2). Because most of the 7 C H A P T E R II F I G U R E 2.1: Location of Clinton Creek, Y T , and Cassiar, B C (A). The tailings pile at Clinton Creek is shown in B (trees for scale) and the tailings at Cassiar in C (road for scale). 8 C H A P T E R II F I G U R E 2.2: Collapse of the northern lobe of the Wolverine tailings pile at Clinton Creek. The southern lobe of the tailings pile (left-most lobe in all photos) has already dammed Wolverine Creek by 1976 (A). The northern lobe (right-most lobe) of the tailings pile slumps into the creek in 1986 (B). Terracing features and roads on the tailings surface, added in the 1990s, have not changed from 1999 to 2003 (C and D). N o new large-scale slumping features have developed since 1999. (Photographs courtesy of the Yukon Geological Survey.) 9 C H A P T E R II sampling done at Clinton Creek was carried out on the surface of these two lobes, it allows us to constrain the age of carbonate alteration at the surface of the tailings pile. Carbonates that have developed on the southern lobe must have formed later than 1974, after the first episode of slope instability, while carbonates on the northern lobe must have formed later than 1986. In an effort to mitigate instability in the tailings pile, the lower sections of the northern and southern lobes were reworked into a series of terraces. Carbonates that have developed on these terrace structures are likely to have formed no earlier than the 1990s when the terraces were initially constructed. Tailings at Clinton Creek are characterized by short-fibre chrysotile and serpentinite cobbles containing massive serpentine and minor amounts of magnetite, calcite, dolomite, magnesite, quartz, clinochlore, and pyroaurite. The chrysotile deposit at Cassiar, British Columbia, forms part of a serpentinized harzburgite tectonite (Wicks and O'Hanley 1988). Cassiar is located approximately 130 k m north of Dease Lake, B C (Fig. 2.1). During the 39-year operational lifetime of the mine, from 1953 to 1992, 17 M t of mine tailings were produced. These tailings were stored outdoors in an elongate pile. Beginning in 1993, the mine underwent a six-year process of renovation and revitalization. B y January 2000 commercial production of chrysotile had been renewed. Mining proceeded until December 25, 2000 when the mi l l was severely damaged by fire ( M I N F I L E 2005). Tailings are composed primarily of short-fibre chrysotile and cobbles of massive serpentine with minor magnetite, clinochlore, and occasional quartz and carbonates. 10 C H A P T E R II Hydrated magnesium carbonate and calcium carbonate minerals occur in five distinct modes in the mine tailings at Clinton Creek and Cassiar: 1) as crusts on vertical surfaces, 2) as carbonate spires on horizontal tailings surfaces, 3) as thin crusts (< 1 m m in thickness) on serpentinite cobbles, 4) as a fine-grained disseminated cement between tailings grains, and 5) as precipitates lining the beds of ephemeral runoff streams (Fig. 2.3). Vertical carbonate crusts, spires, coated cobbles, and cements composed of hydrated magnesium carbonates are abundant at Clinton Creek. Vertical hydrated magnesium carbonate crusts, calcium-carbonate cobble-coatings, and stream linings have been observed at Cassiar. Hydrated magnesium carbonate mineralization is easily recognised by its off-white colour, coloform habit, and reactivity with dilute hydrochloric acid (10% HCI). Calcium-carbonate cobble-coatings and stream-bed precipitates are also recognizable by their off-white colour and reactivity with dilute HCI . 2.2.2 Sampling Methodology The samples under study were collected during the 2003 and 2004 summer field seasons. In 2003, 23 samples were taken from Clinton Creek at the surface of the tailings pile by R. Anderson. Forty samples from Cassiar were taken at depths varying from 0 to 1.7 m below the surface of the tailings pile. Sampling at Cassiar was done by M . Mihalynuk, G . Dipple, and R. Anderson. These samples can be characterized as crust- like material, loose tailings, or bulk samples, collected by shovel or auger. Having set 11 C H A P T E R II F I G U R E 2.3: Modes of carbonate occurrence at Clinton Creek and Cassiar. A ) Crusts on vertical surfaces, B) thin coatings on cobbles, C) spires on horizontal surfaces, and D) disseminated carbonate cement. 12 C H A P T E R II some early constraints on the appearance and occurrence of hydrated magnesium carbonate minerals in mine tailings, the goal of the 2004 field season was to find and sample carbonate-rich crusts. During this season, 19 samples of surface tailings and 11 samples from the waste rock pile were collected from Clinton Creek. Fourteen samples were collected from the surface of the tailings pile and one sample was collected from the waste rock pile at Cassiar. 2.3 EXPERIMENTAL TECHNIQUES FOR CHARATERIZATION OF TAILNGS 2.3.1 Qualitative X-ray Powder Diffraction Mineral phases were identified with X-ray powder diffraction ( X R P D ) . Finely- ground aliquots of sample were smear-mounted onto petrographic slides with ethanol and allowed to dry at room temperature. X R P D data for mineral identification were collected with a scanning step of 0.04° 20 and counting time of 2s/step on a Siemens D5000 0-20 diffractometer over a range of 3-70° 20 with each scan taking 55 minutes. Constituent mineral phases were identified with reference to the I C D D PDF-4 database using D I F F R A C ' " 1 E V A (Bruker A X S 2004a). The normal-focus C u X-ray tube was operated at 40 k V and 40 m A . Samples from the 2003 field season were scanned for amphibole asbestos to a detection limit o f less than 0.2 wt.%. A scanning step of 0.02° 20 and a counting time of 10 s/step over a range of 9-11° 20 were used, taking approximately 17 13 C H A P T E R II minutes. In order to detect hydrated magnesium carbonate minerals at low abundance, a scanning step of 0.04° 29 and a counting time of 40 s/step over a range of 12-17° 20 were used, giving a scan time of 1 hour and 24 minutes. 2.3.2 Scanning Electron Microscopy Characterization of carbonate crust habits and textural relations between carbonate phases was carried out using the Philips X L - 3 0 Scanning Electron Microscope (SEM) , equipped with a Princeton Gamma-Tech Energy Dispersive X-ray Spectrometer (EDS) system, in the Department of Earth and Ocean Sciences at U B C . Secondary electron imaging was used to observe the surface morphology of carbonate crusts while back-scattered electron imaging was used to observe textural relations in thin section. Energy dispersive X-ray spectroscopy (EDS) was used for the identification of minerals and to distinguish between magnesium carbonate phases. Two samples of vertical crusts (04CC0201B and 04CC0703) and two carbonate spires (04CC0702 and 04CC0901) from Clinton Creek were impregnated with epoxy and thin-sectioned for petrographic analysis. Additionally, small segments of carbonate crusts and coatings were mounted on aluminum stubs for imaging mineral habit with the S E M . 14 C H A P T E R II 2.3.3 Grain Size Analysis Grain size analysis was performed by dry-sieving, on 40 samples from Cassiar and 20 samples from Clinton Creek, collected during the 2003 field season. Standard sieve sizes ranging from 16 mm to 0.053 mm were used. Chrysotile-rich samples do not give particularly accurate grain size data due to the fibrous nature of the mineral. Long fibres do not pass easily through sieves and as such are generally included in larger size fractions which do not reflect the size and higher surface area associated with fibres. A separate method of wet sieving, developed by James Thorn at the Department of Earth and Ocean Sciences at U B C , was used to determine the "fibre fraction" of one bulk sample from each locality. Accounting for the fibre fraction allows for improved quantification of grain size and surface area within chrysotile-rich samples. Improved estimates for surface area allow for better estimates of the available cross-section for chemical reaction of the serpentine minerals. For each locality, the bulk sample was dry- sieved and bundles of fibres were hand-picked from the larger size fractions. The remaining, predominantly non-fibrous material was washed in deionised water in an ultrasonic bath and mechanically stirred to disaggregate small fibres. The fibre-rich water was decanted from the bath and passed through filter-cloth to collect the fine fibre fraction. Tailings from individual size fractions and the filtered fibres were placed under a drying hood for 96 hours and weighed on an electronic balance once dry. 15 C H A P T E R II 2.3.4 Bulk Geochemistry Bulk geochemical analysis of 22 samples from Clinton Creek and Cassiar was done by M c G i l l Geochemical Laboratories. Samples were analysed for major element oxides, N i , V , Z n and volatiles (Appendix A ) . Analyses were done by X-ray fluorescence using a Philips PW2440 spectrometer with a 60 k V rhodium end-window X-ray tube. Bulk geochemical data do not distinguish bedrock carbonate from carbonate efflorescences. 2.4 R E S U L T S O F B U L K TAILINGS C H A R A C T E R I Z A T I O N 2.4.1 Bulk Mineralogy Samples from the tailings pile at Clinton Creek are characterized by kaolinite- serpentine group minerals, chrysotile in particular, with minor magnetite, calcite, dolomite, magnesite, quartz, clinochlore, and pyroaurite (refer to Appendix B for complete mineralogical data). Carbonate crusts, spires, and cobble coatings which were analysed separately from the underlying tailings material generally contain hydrated magnesium carbonate phases. Nesquehonite, dypingite, and hydromagnesite, with occasional lansfordite, have been identified at Clinton Creek. The presence of nesquehonite and dypingite has been documented at Cassiar. Samples taken at water level from the artificial lake in the waste rock pile were found to contain the hydrated 16 C H A P T E R II sulphate minerals epsomite and hexahydrite. Hexahydrite was also observed in two vertical carbonate crusts in the tailings pile. The most likely source of the sulphur in these minerals is the pyrite present in the carbonaceous argillite that underlies the Clinton Creek valley (Htoon 1979). Calcite, dolomite, magnesite, and pyroaurite are abundant in the bedrock at Clinton Creek. The presence of pyroaurite [a hydrotalcite group mineral which can be produced in association with the infiltration of serpentinites by a C C V r i c h fluid (Grguric et al. 2001)], and evidence for acid intrusion during the Latest Cretaceous to Earliest Ternary documented by Htoon (1979), seem to indicate that the tailings from Cassiar and Clinton Creek are mineralogically distinct. Furthermore, silica-carbonate veining has replaced cryptocrystalline serpentine and fibrous chrysotile along fractures (Htoon 1979). Based on Htoon's (1979) observations of talc-magnesite-silica alteration of serpentinite at Clinton Creek, some of the bedrock has undergone post- serpentinization alteration to listwanite. Tailings at Cassiar are composed primarily of kaolinite-serpentine group minerals (predominantly chrysotile) with minor magnetite, clinochlore, and occasional quartz and carbonates (mostly dolomite). Thin coatings of aragonite ± calcite have been found on serpentinite cobbles in both the tailings and the waste rock. In one instance, a thin fi lm of calcite + aragonite was found lining the periphery of a small stream flowing through the waste rock pile. 17 CHAPTER II 2.4.2 Asbestos Mineral Content During the past two decades, research into the carcinogenic properties of asbestiform minerals has shown that exposure to amphibole asbestos poses a greater health hazard than exposure to chrysotile (Langer 2001). Prolonged exposure to high doses of both chrysotile and amphibole asbestos (e.g., tremolite-actinolite, grunerite, riebeckite, and anthophyllite) is known to cause mesothelioma, asbestosis, and lung cancer in humans (Langer 2001). Pulmonary tissues retain chrysotile asbestos to a much lesser degree than amphibole asbestos, completely independent of the degree of exposure. The Mg-ions in chrysotile are easily leached from the surface of fibres under the slightly acidic conditions found in lung fluids. Mg-depleted fibres have a higher solubility and can be cleared from the lungs at an increased rate, accounting for the relatively short-lived biopersistence of chrysotile (Johnson and Mossman 2001). A recent study shows that the typical amphibole content of chrysotile ore from the Jeffrey Mine, Asbestos, Quebec is less than 2.5 wt.% (Williams-Jones et al. 2001). Despite the low amphibole content of the ore, the same study showed an average distribution of 72 wt.% fibrous tremolite and 26 wt.% chrysotile in the lungs of miners and millers from this locality (Williams-Jones et al. 2001). Previous studies at other chrysotile mines and in laboratory mammals have found similar results (e.g., Johnson and Mossman 2001; Williams-Jones et al. 2001). Since amphibole asbestos fibres have a residence half-life in lung tissue on the order of years, compared to months for chrysotile, the length of in vivo exposure to the pathogen is significantly longer (Johnson and 18 C H A P T E R II Mossman 2001). Thus, exposure to amphibole asbestos is likely to pose a greater health risk than exposure to chrysotile. Four of the fifty-seven samples analysed for amphibole asbestos from Cassiar were found to contain an amphibole mineral when analysed with X R P D . N o amphibole phases were detected in Clinton Creek samples to a detection limit of approximately 0.2 wt.%. Grains of the amphibole mineral were analysed using energy dispersion spectroscopy (EDS) on the scanning electron microscope (SEM) . E D S revealed that the amphibole in question is non-fibrous actinolite [Ca2(Mg,Fe)5Sig022(OH)2], which is consistent with the presence of nephrite jade at the Cassiar mine (Fig. 2.4). The absence of fibrous amphiboles implies that the likelihood of serious illness resulting from working with Cassiar tailings is greatly reduced in comparison to tailings with amphibole-asbestos content. 2.4.3 Carbonate Precipitate in Bulk Tailings Samples X R P D scans of bulk tailings samples have identified the hydrated magnesium carbonate minerals nesquehonite, dypingite, and hydromagnesite at Clinton Creek and Cassiar by X R P D . Detailed mineralogical data are given in Appendix B . The high- sensitivity X R D scans performed on bulk tailings samples from the 2003 field season do not allow for the determination of hydromagnesite versus dypingite because both minerals share several major peaks and the intensities of their characteristic reflections 19 C H A P T E R II F I G U R E 2.4: Back-scattered electron image of actinolite grains in sample 04CA0401. Actinolite grains detected by X R P D in several samples from Cassiar have been determined by back-scattered S E M imaging to be non-fibrous. A - Actinolite. 20 C H A P T E R II are typically below detection. As such, these minerals are identified as "either/or" in the 2003 samples (Appendix B) , except for the occasional case in which sufficient carbonate material was available for separate analysis or for particularly carbonate-rich samples of bulk tailings. Samples from the 2004 field season were selected for carbonate abundance rather than bulk determination of tailings mineralogy. Wi th more carbonate material available for analysis, carbonate phases are readily identified; dypingite and hydromagnesite become distinguishable and low abundances of lansfordite can be detected. 2.4.4 G r a i n Size Analysis Twenty bulk samples from Clinton Creek and 40 from Cassiar were analyzed for grain size using standard sieve techniques (refer to Appendix C for detailed results). The conclusions of this analysis are threefold: 1) Although the samples were heterogeneous, they were generally composed of sand to cobble-sized grains (Udden-Wentworth scale) at both localities; 2) no significant difference in grain size between crust-like materials at the surface of the tailings pile and loose or bulk materials was observed (Fig. 2.5), which implies that carbonate precipitation is not solely a function of grain size, and 3) the medium to fine sand fraction of most samples from Cassiar comprises approximately 10 wt.%. A t Clinton Creek, the fine sand to silt fraction represents the finest 10 wt.% of most samples. 21 C H A P T E R II Grain Size Analysis for Loose Tailings Sample 03CA0802 100 90 80 70 c a eo Q. £ 50 O) g 40 30 20 10 0 - % Passing -Weight % >16.0 >9.51 >4.76 >2.00 >0.850 >0.425 >0.212 >0.180 >0.150 >0.106 >0.075 >0.053 <0.053 Sieve Size (mm) Grain Size Analysis for Crust Sample 03CC0201A >16.0 >9.51 >4.76 >2.00 >0.850 >0.425 >0.212 >0.180 >0.150 >0.106 >0.075 >0.053 <0.053 Sieve Size (mm) F I G U R E 2.5: Results o f grain size analysis for two typical samples of tailings. N o significant difference in grain size distribution is observed between carbonate-free 03CA0802 (A) and the carbonate-rich tailings sample 03CCO2O1A (B). 22 C H A P T E R II Wet-sieving was done for sample 04CC1401 - a bulk tailings sample from Clinton Creek. The fine fibres from each size fraction were decanted, dried, and weighed, yielding the result that 6.8 ± 0.3 wt.% of the bulk sample consisted of fine fibres of chrysotile. The breakdown for each size fraction, by weight, is shown in Figure 2.6. What is most notable about the results of wet-sieving is that over 50 wt.% of the fine fibres in the sample were decanted from the coarse sand to cobble size fractions (Fig. 2.7). These fibres were loosely adhered to the surfaces of cobbles and cemented between grains of sand. The fine fibres from the bulk tailings sample from Cassiar (03CA1601) constituted 10.9 wt.% of the bulk sample, 56.9% of which fibres were decanted from the coarse sand to cobble size fractions (J. Thorn, pers. comm.). 2.5 H Y D R A T E D M A G N E S I U M C A R B O N A T E M I N E R A L O G Y The efficiency of the natural carbonation of serpentine minerals to produce hydrated magnesium carbonates is an important aspect of this study, as it has implications for CO2 sequestration within mine tailings. Carbonate mineral species differ in terms of thermodynamic stability and sequestration potential. Lansfordite, nesquehonite, dypingite, hydromagnesite, and aragonite have been identified at Clinton Creek and nesquehonite, dypingite, aragonite, and calcite have been observed at Cassiar. There is a possibility that other magnesium carbonate species with varying states of hydration are occurring at both sites in amounts below detection by X R P D . 23 CHAPTER II 900 800 700 600 h Fibrous and Non-fibrous Fractions for all Sieve Sizes " i 1 1 1 1 r~ 1 T" 3 V) w ro 500 400 300 200 100 n I Non-fibrous I Fibrous J3L JE3L >9.51 >1.68 >1.41 >0.840 >0.595 >0.350 >0.212 >0.180 >0.106 >0.053 <0.053 Sieve Size (mm) FIGURE 2.6: Mass fractions of fibrous and non-fibrous tailings materials for each size fraction used in wet-sieving for sample 04CC1401. 24 C H A P T E R II % Passing for Fibrous and Non-fibrous Fractions >9.51 >1.68 >1.41 >0.840 >0.595 >0.350 >0.212 >0.180 >0.106 >0.053 <0.053 Sieve Size (mm) F I G U R E 2.7: Percent of tailings to pass through each sieve for sample 04CC1401. More than 50 wt.% of the fine chrysotile fibres are found in the coarse sand to cobble fractions. 25 C H A P T E R II The hydrated magnesium carbonate minerals can be organized into three groups based on their chemical formulae (after Canterford et al. 1984): 1) M g C 0 3 - x H 2 0 , for integral values of x greater than zero. The first group consists of those minerals whose formulae are composed of magnesite ( M g C 0 3 ) with variable waters of hydration. Three such minerals are known to occur in nature: Barringtonite is M g C 0 3 - 2 H 2 0 (Nashar 1965), nesquehonite is M g C 0 3 - 3 H 2 0 (Stephan and MacGil lavry 1972), and lansfordite is M g C 0 3 - 5 H 2 0 (Hi l l et al. 1982). Stability of these minerals tends to decrease with increasing H 2 0 (e.g., Langmuir 1965; H i l l et al. 1982; Garvie 2003). 2) M g 2 ( C 0 3 ) ( O H ) 2 - x H 2 0 , for integral values of x greater than zero. The second group of hydrated magnesium carbonate minerals is distinguished from the first by the addition of hydroxyl groups or a brucite-like formula component, M g ( O H ) 2 . Artinite [ M g 2 ( C 0 3 ) ( O H ) 2 - 3 H 2 0 ] is the only known member o f this group (Canterford et al. 1984). 3) M g 5 ( C 0 4 ) ( O H ) 2 - x H 2 0 , for integral values of x in the range of 4 to 11. Five minerals have been identified as belonging to this group, four of which have been confirmed to occur in nature: Hydromagnesite with x - 4 (Akao and Iwai 1977), dypingite with x = 5 (Raade 1970), giorgiosite with x = 6 (Canterford et al. 1984), and yoshikawaite with x - 8 (Suzuki and Ito 1973). Protohydromagnesite, characterized by x — 11, has only been identified in synthetic samples (Davies and Bubula 1973). 26 C H A P T E R II The values for waters of hydration, x, have been drawn from the most recent formula determinations from oxide weight-percent data by Canterford et al. (1984). The formation of the magnesium carbonate minerals barringtonite, nesquehonite, lansfordite, and magnesite optimizes the sequestration of atmospheric CO2. This can be demonstrated by inspection of the H 2 0 - M g O - C 0 2 compositional ternary for hydrated magnesium carbonates (Fig. 2.8) or simply by inspection of the general formulae for the three mineral groups (Table 2.1). The ratio of CO2 to M g per formula unit of the Group 2 and 3 minerals is always less than 1 (i.e., C C ^ / M g < 1), while that for the Group 1 minerals is equal to 1 (i.e., C C V M g = 1). The carbon dioxide to cation ratio for calcite and aragonite is also unity (i.e., C C V C a = 1 ) , implying similarly high capacity for sequestration as the Group 1 minerals. In terms of the amount of dissolved cation required, Group 1 minerals, calcite, and aragonite are more efficient hosts for CO2. Lansfordite is unstable at atmospheric pressure above 10 °C (Langmuir 1965), at which temperature it dehydrates to nesquehonite. Nesquehonite decomposes to hydromagnesite via a series of metastable intermediate phases above 55 °C (e.g., De l l and Weller 1959; Kazakov et al. 1959; Langmuir 1965; Davies and Bubela 1973). Dypingite is the most commonly observed intermediate phase in the decomposition of nesquehonite to hydromagnesite in nature and in the laboratory (e.g., Davies and Bubela 1973; Canterford et al. 1984; Inaba et al. 1985). Canterford et al. (1984) have speculated that the decomposition of nesquehonite may proceed via several pathways dependent upon differing environmental controls. Mineralogy of observed intermediate phases varies between decomposition experiments and between site localities in the literature. 27 C H A P T E R II MgO F I G U R E 2.8: H 2 0 - M g O - C 0 2 compositional ternary for the hydrated magnesium carbonate minerals, after Canterford et al. (1984). 28 C H A P T E R II T A B L E 2.1: Empirical formulae for hydrated magnesium carbonate minerals. M I N E R A L SPECIES C H E M I C A L F O R M U L A Group 1 M g C 0 3 x H 2 0 Barringtonite M g C 0 3 - 2 H 2 0 Nesquehonite M g C 0 3 - 3 H 2 0 Lansfordite M g C 0 3 - 5 H 2 0 Group 2 M g 2 ( C 0 3 ) ( O H ) 2 x H 2 0 Artinite M g 2 ( C 0 3 ) ( O H ) 2 - 3 H 2 0 Group 3 M g 5 ( C 0 3 ) 4 ( O H ) 2 - x H 2 0 Hydromagnesite M g 5 ( C 0 3 ) 4 ( O H ) 2 - 4 H 2 0 Dypingite M g 5 ( C 0 3 ) 4 ( O H ) 2 - 5 H 2 0 Giorgiosite M g 5 ( C 0 3 ) 4 ( O H ) 2 - 6 H 2 0 or M g 5 ( C 0 3 ) 4 ( O H ) 2 - 5 H 2 0 Yoshikawaite M g 5 ( C 0 3 ) 4 ( O H ) 2 - 8 H 2 0 Protohydromagnesite M g 5 ( C 0 3 ) 4 ( O H ) 2 - l l H 2 0 29 C H A P T E R II 2.6 MODES OF OCCURRENCE AND MECHANISMS OF FORMATION Nesquehoni te , dypingi te, and hydromagnesite are abundant at C l i n t o n C reek wh i l e lansfordite remains scarce. Nesquehoni te and dypingi te have been ident i f ied i n tai l ings mater ials f rom Cass iar . Aragoni te precipitates are found at both local i t ies as th in crusts on the surface o f cobbles. A corre lat ion between mode o f carbonate occurrence and carbonate species has been ident i f ied f rom X R D data (Table 2.2). Carbonate crusts and spires general ly conta in nesquehonite, dypingi te, and hydromagnesite. Lansford i te has been found to occur i n some ver t ica l crusts. Crusts vary i n compos i t ion f rom most ly nesquehonite w i t h m ino r dypingi te ± hydromagnesite to dypingite ± nesquehonite ± hydromagnesi te. The nesquehonite ± dypingi te ± hydromagnesite crusts are more c o m m o n . C o b b l e coat ings are a lmost exc lus ive ly dypingi te or aragonite ± calc i te w i th one case o f dypingi te + hydromagnesi te f r om C l i n t o n Creek. D isseminated carbonate cements are composed ent i rely o f hydromagnesi te. The bed o f one ephemeral runof f stream in the waste rock p i le at Cass iar was found to be l ined by a coat ing o f calc i te + aragonite. Zona t ion o f carbonate phases i n spires and ver t ica l crusts is readi ly observed i n th in sect ion w i t h back-scattered S E M imaging. In th in sect ion, nesquehonite can be dif ferent iated f rom dypingi te and hydromagnesite by habit, s l ight var ia t ion in the intensity o f backscattered electrons (i.e., nesquehonite appears darker as a result o f its 30 CHAPTER II TABLE 2.2: Mineralogy and mode of carbonate occurrence. MODE OF OCCURRENCE CARBONATE MINERALOGY Magnesium Carbonates Calcium Carbonates Vertical Crusts Nesquehonite ± Dypingite ± Hydromagnesite Horizontal Spires Nesquehonite ± Dypingite ± Hydromagnesite Cobble Coatings Dypingite ± Hydromagnesite Aragonite ± Calcite Disseminated Cements Hydromagnesite Stream Linings Aragonite ± Calcite 31 C H A P T E R II lower density), and a small but detectable increase in the ratio of the intensities of the C to M g K a X-ray peaks in energy dispersion spectra (Fig. 2.9 for habit and "colour" and Fig . 2.10 for EDS) . A s a result of their similar chemical composition, density, and habit, dypingite and hydromagnesite are indistinguishable with S E M . Back-scattered electron (BSE) images of spire samples 04CC0702 and 04CC0902 and vertical crusts 04CC0201B and 04CC0703 in thin section reveal the zonation of hydrated magnesium carbonate phases which cannot be seen in secondary electron (SE) images of the surfaces of crusts and spires (Figs. 2.11 and 2.12). Dypingite and/or hydromagnesite are abundant at depth within vertical crust and spire samples. Fine- grained, radiating crystals of dypingite and/or hydromagnesite have nucleated on the surfaces of serpentinite grains, forming a cement between them (Fig. 2.11 A ) . Because nesquehonite is the primary phase at the surface of crust and spire samples, it is not usually possible to observe the habit and topography of dypingite and hydromagnesite crystals using secondary electrons; but similar habits have been observed in dypingite coating serpentinite cobbles. Dypingite commonly forms rosette-like structures at the surface of cobbles at Clinton Creek (Fig. 2.1 IB) . The fine-grained dypingite/hydromagnesite observed in thin section can be interpreted as a cross-section though rosettes which have formed at depth rather than at the surface of a cobble. Grains of hydrated magnesium carbonate minerals are frequently observed infilling fissures in serpentinite grains (Fig. 2.1 IC) . This appears to be the result of silicate dissolution, as the pieces of these grains cannot be reassembled without obvious loss of material. Fracture patterns which do not reflect dissolution are also common (Fig. 2.1 ID). The 32 C H A P T E R II F I G U R E 2.9: Variation in habit and intensity of backscattered electrons between nesquehonite and dypingite/hydromagnesite phases in vertical crust sample 04CC0201B. N - characteristic bladed crystals of nesquehonite. D / H - finely crystalline rosette-like masses of dypingite and/or hydromagnesite. S - serpentine grains. 33 C H A P T E R II F I G U R E 2.10: Distinguishing between hydromagnesite/dypingite (A) and nesquehonite (B) in thin section with E D S . The lower density of nesquehonite and the slightly higher ratio of the C : M g peaks can be used to distinguish it from other hydrated magnesium carbonates. Spectra were collected in semi-quantitative mode for 180 s. X s mark the points at which E D S were taken. C H A P T E R II mem Try '^""^^"' F I G U R E 2.11: Secondary electron (SE) and back-scattered electron (BSE) images o f spire sample 04CC0702, vertical crust 04CC0201B, and cobble 04CC0601B-CB. A ) B S E image of cross-section through dypingite/hydromagnesite rosettes on surfaces o f serpentinite grains at depth in 04CC0201B. B) Dypingite rosettes in S E as seen on the surface of cobble sample 04CC0601B-CB. C) Nesquehonite infilling dissolution fissures in a serpentinite grain near the spire surface in 04CC0702 (BSE). D) Formation o f nesquehonite may subject serpentinite grains to a type of freeze-thaw action which could lead to the type of Assuring seen in here in 04CC0702 (BSE) . N - nesquehonite. D / H - dypingite and/or hydromagnesite. D - dypingite. S - serpentine grains. M - magnetite. 35 C H A P T E R II F I G U R E 2.12: Secondary electron (SE) and back-scattered electron (BSE) images o f spire samples 04CC0702 and 04CC0902 and vertical crust 04CC0106. A ) Interface between nesquehonite and dypingite/hydromagnesite phases in 04CC0902 (BSE). The circled region may be evidence of a dehydration front. B ) View of a nesquehonite- dypingite contact in 04CC0106 (SE). C) B S E image of nesquehonite at the surface o f sample 04CC0702. Boxed region is shown in D) Dypingite/hydromagnesite rosettes nucleating on serpentinite grains at depth. N - nesquehonite. D / H - dypingite and/or hydromagnesite. D - dypingite. S - serpentine grains. M - magnetite. 36 C H A P T E R II latter textures could be indicative of a type of freeze-thaw action occurring within serpentinite grains, by which lansfordite or nesquehonite precipitate at low temperatures, causing serpentinite grains to fracture. There are few intact interfaces between the nesquehonite caps at the surfaces of the crusts and spires and the dypingite/hydromagnesite at depth. Some interfaces are continuous (e.g., Fig . 2.12A), but most are broken by gaps ranging from 100 to 500 um between the nesquehonite caps and the rosette-covered serpentinite grains. This effect may simply have resulted during the manufacture of the thin sections; else, it may be indicative of a volume loss within the sample. Volume could have been lost from either the evaporation of adsorbed water in chrysotile fibres or from dehydration of nesquehonite. The region circled in Figure 2.12A is suggestive of a dehydration front, but most continuous interfaces between the nesquehonite and dypingite/hydromagnesite do not show evidence of replacement textures. Contacts between the mineral species can occasionally be seen outside of thin sections in vertical crusts (Fig. 2.12B), but the textural relationships do not provide definitive support for a particular interpretation. Regardless of the formational relationship between the magnesium carbonate phases, the zonation is consistent in crusts and spires with nesquehonite at the surface (Fig. 2.12C) and dypingite and/or hydromagnesite at depth (Figs. 2.12C and D). It is possible that a differential in pore-water evaporation or chemistry may be the cause of zonation within carbonate crusts and spires. Qualitative X R P D results for other samples of vertical crusts and spires indicate that they often contain all o f nesquehonite, dypingite, and hydromagnesite. Dypingite is a metastable mineral phase, which can be 37 C H A P T E R II created as nesquehonite transforms to hydromagnesite (Davies and Bubela 1973; Canterford et al. 1984; Inaba et al. 1985). Hydromagnesite in the tailings at Clinton Creek may be a product of the decomposition of nesquehonite forming in contact with the atmosphere. If so, decomposition of nesquehonite in mine tailings would not appear to be a function of humidity, but rather a function of age, with the metastable minerals forming at the interface between the tailings and the atmosphere, and the older carbonate precipitates decomposing to increasingly stable mineral phases at depth (Fig. 2.13). The S E M data are inconclusive, and may suggest that the zonation of minerals within carbonate crusts and spires is controlled by water chemistry and temperature or progressive decomposition of nesquehonite to dypingite and hydromagnesite. 2.7 I N T E R P R E T A T I O N O F E X P E R I M E N T A L R E S U L T S Observations of the occurrence patterns of the hydrated magnesium carbonate minerals at Clinton Creek and Cassiar imply that they have developed in situ, rather than having been inherited from bedrock through the mining process. The precipitation of carbonate crusts is a surface phenomenon, which is most likely driven by evaporation and/or freeze-out. The development of disseminated carbonate cements may be a near- surface pedogenic process. Marked differences in the mineralogy of the modes of occurrence indicate that there may be several reaction pathways by which mineral 38 C H A P T E R II F I G U R E 2.13: Zonation of hydrated magnesium carbonate minerals in crusts and spires. A ) Carbonate spire capped by nesquehonite with dypingite + hydromagnesite at depth, B) serpentinite cobble with coating of dypingite, and C) vertical crust with nesquehonite at the surface and dypingite + hydromagnesite at depth. 39 C H A P T E R II sequestration is occurring in the residues. A s such, it is likely that there are multiple routes by which the rate of precipitation could be increased for enhanced carbonation. The most likely means by which hydrated magnesium carbonate crusts are developing in the mine residues at Clinton Creek and Cassiar is outlined in Figure 2.14. Carbon dioxide and bicarbonate, dissolved in rain water, come into contact with mine residues. Magnesium is leached from the tailings and carried, in aqueous solution by evaporation and upward flow, to the surface of the tailings piles, where carbonates are precipitated through evaporation and/or freeze-out. Carbonation is much less abundant at Cassiar than at Clinton Creek due to comparatively less favourable hydrological conditions within the tailings pile. A t Clinton Creek, pore waters may be channelled through regions of higher permeability within the tailings. It is possible that fine-grained tailings materials retain moisture, essentially trapping it in place until solar heat induces evaporation and/or wicking to the surface of the pile. Carbonation is limited at Cassiar, because the tailings are contained within a steeply-sloping, compact pile. The core of the tailings pile is frozen year round (Ernie Hatzl, pers. comm.), hastening the run-off of rainwater through the pile and limiting dissolution of magnesium to the upper few metres of material. Regular, steeply- sloping sides shorten the residence time of pore waters in the tailings pile at Cassiar, providing little chance for silicate weathering and precipitation of carbonate at the surface. The bulk sample from Clinton Creek (04CC1401) was taken from the base of the tailings pile near the water table. Pore waters flowing through the sampled surface are rich in dissolved M g 2 + , HCO3", and CO3 2", having passed through 40 C H A P T E R II C H A P T E R II much of the hummocky terrain that has been produced by slumping in the tailings pile. A s a result, tailings from this sampling location are rich in Mg-carbonate cement. The development of magnesium carbonate crusts within mine tailings may be structurally controlled by the positions of relatively more permeable horizons within the tailings. Where flux of M g 2 + and H C C V ion-rich pore waters is high at vertical outlets in a tailings pile, vertical crusts are more likely to develop by evaporation or freeze-out of these fluids (Fig. 2.15). Regions with high moisture retention capacity, high pore water residence time, and higher Mg-concentration are also potential controls on precipitation. Pore waters, flowing through permeable horizons near the tailings surface, are subject to wicking by chrysotile fibres. Redirection of pore water to horizontal surfaces by wicking leads to the development of carbonate spires. Carbonate crusts on cobbles may form by local dissolution of serpentine and direct reprecipitation of Mg-carbonates onto the cobble surface or by nucleation of mineral precipitates from the out-flowing tailings waters. Cobble coatings, when observed on a single grain surface, are frequently on the underside, suggesting long contact with moisture from the tailings pile. A s cobbles are dislodged from their original sites of deposition, the previously uncoated surfaces receive increased exposure to surface water, also developing coatings. Disseminated hydromagnesite cements likely form in regions of the tailings pile characterized by fine grain size and high pore-water residence times. 42 C H A P T E R II F I G U R E 2.15: Mechanisms of formation for the four modes of occurrence: 1) Vertical crusts, 2) carbonate spires, 3) cobble coatings, and 4) disseminated cement. C H A P T E R II A n alternate explanation for the simultaneous occurrence of multiple hydrated magnesium carbonate phases may be the direct precipitation of separate phases without having to invoke decomposition as a mechanism of formation. Possible cyanobacterially-mediated precipitation of magnesite has been observed in the laboratory by Thompson and Ferris (1990); however, direct precipitation of magnesite is thought to be kinetically inhibited in most lacustrine environments (refer to Zedef et al. 2000 for a brief review). Zedef et al. (2000) and Renaut and Long (1989) have observed direct precipitation of hydromagnesite in playa environments. It has been proposed by Renaut and Long (1989) that salinity and the M g / C a ionic ratio of lake water control which magnesium carbonate phases precipitate from solution. Similar controls may be active in the mine tailings environment. Precipitation of specific mineral species may be seasonally variable based on water chemistry or temperature. 2.8 R E F E R E N C E S Akao, M . and Iwai, S. (1977) The hydrogen bonding of hydromagnesite. Acta Crystallographica, Section B : Structural Crystallography and Crystal Chemistry, B33, 1273-1275. B R U K E R A X S (2004a) E V A V . 10.0: Release 2004 - User's Manual. Bruker A X S , Karlsruhe, Germany. 44 C H A P T E R II Canterford, J .H. , Tsambourakis, G . , and Lambert, B . (1984) Some observations on the properties of dypingite, M g 5 ( C 0 3 ) 4 ( O H ) 2 - 5 H 2 0 , and related minerals. Mineralogical Magazine, 48, 437-442. Chicago Climate Exchange (2005) Chicago Climate Exchange Market Data. Retrieved September 2005 from the Chicago Climate Exchange Website: http://vvww.chicagoclimateexchange.com/trading/marketData.html. Ciorba, U . , Lanza, A . , and Pauli, F. (2001) Kyoto Protocol and emission trading: does the U S make a difference? Fondazione Eni Enrico Mattei, Mi lan . Climate Corporation (2005) C 0 2 Climate Pool: The E U ETS: Facts and Figures. Retrieved September 2005 from the Climate Corporation Website: http://www.climatecorp.com. Davies, P.J. and Bubela, B . (1973) The transformation of nesquehonite into hydromagnesite: Chemical Geology, 12, 289-300. Del l , R . M . and Weller, S.W. (1959) The thermal decomposition o f nesquehonite, M g C C V 3 H 2 0 , and magnesium ammonium carbonate, MgC03 (NH4 ) 2 CCV4H 2 0 . Transactions of the Faraday Society, 55, 2203-2220. E M A N - N o r t h . (2003) Northern Contaminants Program: Local Contaminants Sources (Yukon): Clinton Creek Mine. Retrieved in 2004 from the Ecological Monitoring and Assessment Network for Northern Canada Website, Government of Canada: http://www.emannorth.ca/ic/ds014/clinton.cfm. Garvie, L . A . J . (2003) Decay-induced biomineralization of the saguaro cactus (Carnegiea gigantean). American Mineralogist, 88, 1879-1888. 45 C H A P T E R II Goldberg, P., Chen, Z . - Y . , O'Connor, W. , Walters, R., and Ziock, H . (2001) C 0 2 Mineral Sequestration Studies in U S . In the Proceedings of the First National Conference on Carbon Sequestration. Retrieved in 2004 from the National Energy Technology Laboratory of the U .S . Department of Energy Website: http://www.netl.doe.gov/ publications/proceedings/01 /carbon_seq/6c 1 .pdf. Grguric, B . A . , Madsen, I.C., and Pring, A . (2001) Woodallite, a new chromium analogue of iowaite from the Mount Keith nickel deposit, Western Australia. Mineralogical Magazine, 65, 427-435. H i l l , R.J . , Canterford, J .H. , and Moyle, F.J . (1982) N e w : data for lansfordite. Mineralogical Magazine, 46, 453-457. Htoon, M . (1979) Geology of the Clinton Creek asbestos deposit, Yukon Territory. M . S c . Thesis, University of British Columbia, Vancouver, British Columbia. Huot, F. , Beaudoin, G . , Hebert, R. Constantin, M . , Bonin, G . , and Dipple, G . (2003) Evaluation of Southern Quebec asbestos residues for C 0 2 sequestration by mineral carbonation; preliminary results. Joint Annual Meeting of the Geological and Mineralogical Associations of Canada. Inaba, S., Minakawa, T., and Noto, Shigetoshi. (1985) Nesquehonite and dypingite from Shiraki, M i e Prefecture, Japan, 34, 281-287. Johnson, N . F . and Mossman, B .T . (2001) Dose, dimension, durability and biopersistence of chrysotile asbestos. In The Health Effects of Chrysotile Asbestos: Contribution of Science to Risk-Management Decisions, Canadian Mineralogist Special Publications, 145-154. 46 CHAPTER II Kazakov, A . V . , Tikhomirova, M . M . , and Plotonkova, V.I. (1959) The system of carbonate equilibria. International Geology Review, 1, 1-39. Langer, A . M . (2001) Health experience of some U.S. and Canadian workers exposed to asbestos: foundation for risk assessment. In The Health Effects of Chrysotile Asbestos: Contribution of Science to Risk-Management Decisions, Canadian Mineralogist Special Publication 5, 9-20. Langmuir, D. (1965) Stability of carbonates in the system MgO-C02-H20. Journal of Geology, 73, 730-754. MINFILE (2005) Cassiar, 104P005. Retrieved April 2005 from the BC Ministry of Energy and Mines MINFILE Digital Data Website: http://www.em.gov.bc.ca/ cf/minfile/search/search.cfm?mode=capbib&minfilno=104P%20%20005. Nashar, B. (1965) Barringtonite, a new hydrous MgCCh from Barrington Tops, New South Wales, Australia. Mineralogical Magazine, 34, 370-372. Raade, G. (1970) Dypingite, a new hydrous basic carbonate of magnesium, from Norway. American Mineralogist, 55, 1457-1465. Renaut, R.W. and Long, P.R. (1989) Sedimentology of the saline lakes of the Cariboo Plateau, Interior British Columbia, Canada. Sedimetnary Geology, 64, 239-264. Stephan, G.W. and MacGillavry, C H . (1972) The crystal structure of nesquehonite, M g C 0 3 3 H 2 0 . Acta Crystallographica, B28, 1031-1033. Suzuki, J. and Ito, M . (1973) New magnesium carbonate hydrate mineral Mg 5(C03)4(OH) 2-8H 20, from Yoshikawa, Aichi Prefecture, Japan. Ganseki Kobutsu Kosho Gakkaishi, 68, 353-361. 47 C H A P T E R II Wicks , F.J . and O'Hanley, D.S. (1988) Serpentine Minerals: Structures and Petrology. In Hydrous Phyllosilicates (Exclusive of Micas), edited by S.W. Bailey, Reviews in Mineralogy, V o l . 19 (Mineralogical Society of America), 91-167. Williams-Jones, A . E . , Normand, C , Clark, J.R., V a l i , H . , Martin, R.F. , Dufresne, A . , and Nayebzadeh, A . (2001) Controls of amphibole formation in chrysotile deposits: evidence from the Jeffrey Mine, Asbestos, Quebec. In The Health Effects of Chrysotile Asbestos: Contribution of Science to Risk-Management Decisions, Canadian Mineralogist Special Publication 5, 89-104. Zedef, V . , Russell, M . J . , Fallick, A . E . , and Hal l , A . J . (2000) Genesis of vein stockwork and sedimentary magnesite and hydromagnesite deposits in the ultramafic terranes of Southwestern Turkey: A stable isotope study. Economic Geology, 95, 429-446. 48 C H A P T E R III C H A P T E R III : Isotopic characterization of magnesium-carbonate precipitates 3.1 I N T R O D U C T I O N The source of CO2 tapped in the formation of carbonate minerals can be determined using stable and radiogenic isotope techniques. In this chapter, isotope data for samples from the abandoned chrysotile mines at Clinton Creek, Yukon, and Cassiar, British Columbia are used to determine the sources for carbon and cations accessed in the precipitation of carbonates. Isotopic characterization of carbonate precipitates provides confirmation of net sequestration of carbon. The results of this analysis can be used with quantitative phase analysis (Chapter 4; Wilson et al. 2006) to give an initial estimate for the sequestration capacity of ultramafic mine tailings. 3.2 E X P E R I M E N T A L M E T H O D 3.2.1 L i g h t Stable Isotopes The fractionation of light stable isotopes in minerals can be used to identify the reservoir or reservoirs from which the constituent elements were drawn. 5 , J C and 5 ' ° 0 data (Craig 1959) for carbonate minerals can be used to identify the source of carbon 49 C H A P T E R III tapped during their precipitation (eg., Kral ik et al. 1989; Zedef et al. 2000; Deines 2004). A s such, the fractionation of carbon and oxygen in hydrated magnesium carbonates and calcium carbonates can be used to determine whether atmospheric CO2 is being crystallographically trapped in mine tailings. Stable carbon and oxygen isotope compositions were determined for 41 samples from Clinton Creek and Cassiar by J. Gabites using a Thermo Finnigan DeltaPlus X L L S - I R M S at the Pacific Centre for Isotopic and Geochemical Research (PCIGR), U B C . Carbonate samples (weighing from 10 to 100 mg) were treated with phosphoric acid in sealed gas exetainers after having been flushed with helium. The CO2 produced in the reaction was carried by continuous flow of helium into the mass spectrometer. Carbon dioxide gas and calcite of known isotopic composition were run with the samples as reference standards to correct for machine fractionation. Raw values for 8 1 8 0 / 8 1 6 0 were corrected for fractionation between phosphoric acid and calcite or phosphoric acid and magnesite (for all M g - carbonates). Replicate analyses were done on five samples to assess the reproducibility of the data. Measurement errors were determined from the averages of multiple analyses of N B S standards 18 and 19. 3.2.2 Radiogenic Carbon Fingerpr int ing Radiogenic carbon dates for five Mg-carbonate crust samples from Clinton Creek and Cassiar, three Ca-carbonate crusts from Cassiar were obtained with Accelerator Mass 50 C H A P T E R III Spectrometric ( A M S ) dating by Beta Analytic Radiocarbon Dating Laboratory in M i a m i , Florida. Samples underwent no laboratory pre-treatment prior to analysis. 3.2.3 Surface A r e a Analysis Surface-area analysis was done on A65-grade chrysotile from Cassiar with the B E T N-gas adsorption isotherm technique using a Micromeritics A S A P 2010 surface area analyser in the Department of Earth and Ocean Sciences, at U B C . 3.3 R E S U L T S O F I S O T O P I C I N V E S T I G A T I O N 3.3.1 Stable Ca rbon and Oxygen Isotopes The 5 1 3 C results for carbonate samples from Clinton Creek and Cassiar (Table 3.1 and Fig. 3.1) vary from -8%o to 1596o ( V P D B ) , with 5 1 8 0 values ranging from 12% 0 to 29%o ( V S M O W ) . A relationship between mineralogy, mode of carbonate occurrence, and 8 1 3 C is observed in the isotope data. Bedrock carbonate-rich samples from both sites yield 8 1 3 C values in the range of-8.0%o to 0.7%o ( V P D B ) and 5 1 8 0 values between 12% 0 and 16%o. These samples are mostly bedrock dolomite from Cassiar and magnesite from Clinton Creek. It is notable that the aragonite and calcite cobble coatings and streambed precipitates plot in the same region of 8 1 8 0-8 1 3 C-space as the bedrock carbonates. Bulk 51 C H A P T E R III T A B L E 3.1: Mineralogical and isotopic data for carbonate samples. SAMPLE MODE MAJOR PHASE T MINOR PHASES 1 5 I 5C 2a5"c 8'»0 2a6"o F 1 4 C or 1 4 C * DATE 03CC01A Bulk* Dyp/Hymag Dol, Mags, Pyro 3.322 0.128 19.854 0.094 03CC01B Crust Nesq Dyp, Cal, Mags, Pyro 14.528 0.092 25.699 0.063 1.114 ± 0 . 0 0 6 03CC01C Bulk* Dyp Mags, Pyro -0.025 0.137 17.568 0.098 03CC0201A Bulk* Hymag Dol, Mags, Pyro -2.159 0.277 16.280 0.207 03CC0401B Cobble Dyp Mags, Pyro 8.638 0.173 18.176 0.126 03CC0601B Bulk Dyp/Hymag Mags, Pyro 4.306 0.204 19.522 0.124 03CC0701A Bulk* Nesq Dol, Mags, Pyro -5.141 0.482 15.518 0.342 03CC1001A Bulk* Dyp/Hymag Cal, Dol, Mags, Pyro 3.871 0.147 20.493 0.141 04CC0104 Bedrock Mags Pyro -7.994 0.070 15.066 0.104 > 46 kyBP 04CC0105 Cobble Dyp, Hymag, Pyro -1.617 0.208 19.021 0.132 1.026 ±0 .005 04CC0106 Crust Nesq Dyp 7.489 0.139 20.820 0.143 04CC0107-CA Cobble Arag 0.022 0.107 15.605 0.143 04CC0108-CA Cobble Arag Pyro 0.687 0.108 15.123 0.159 04CC0109 Cobble Dyp Pyro 1.957 0.191 20.754 0.289 04CC0111 Crust Not detected -3.200 0.324 13.136 0.374 04CC0201A Crust Nesq Dyp, Lans, Pyro 10.369 0.236 25.215 0.196 04CC0202A Crust Dyp 9.828 0.227 27.711 0.135 04CC0301 Bedrock Mags Dol -6.809 0.170 15.837 0.119 04CC0401-CA Cobble Dyp Mags, Pyro -1.454 0.076 17.419 0.103 04CC0601A Crust Dyp Mags, Pyro 4.431 0.147 20.693 0.120 1.156 ± 0 . 0 0 6 04CC0601B-CA Cobble Hymag, Dyp? Pyro 2.074 0J92 22.966 0.220 04CC0601B-CB Cobble Dyp 6.610 0.107 20.969 0.106 04CC0701 Crust Nesq Dyp, Hymag, Pyro 10.447 0.077 22.114 0.060 04CC0701 Crust Nesq Dyp, Hymag, Pyro 10.062 0.086 22.024 0.164 04CC0702 Spire Nesq Dyp, Hymag 7.799 0.172 23.502 0.145 04CC0703 Crust Nesq Dyp, Hymag 13.185 0.296 23.896 0.214 04CC0703 Crust Nesq Dyp, Hymag 13.597 0.146 23.772 0.087 04CC0703-nesq Crust Nesq Dyp, Hymag 13.320 0.098 22.574 0.103 04CC0703-hymag Crust Hymag Dyp, Nesq 4.330 0.066 18.302 0.096 04CC0901 Crust Dyp, Pyro 6.678 0.181 28.495 0.171 04CC1001 Crust Nesq Dyp/Hymag, Mags 11.256 0.276 24.821 0.208 04CC1101 Crust Nesq Dyp/Hymag 12.530 0.146 23.991 0.116 04CC1201 Crust Dyp, Hymag Mags 3.481 0.264 22.537 0.253 04CC1301 Bedrock Mags Dol -4.481 0.109 15.664 0.046 04CC1301 Bedrock Mags Dol -4.344 0.069 15.448 0.061 04CC1401 Bulk Hymag Mags/Pyro -5.565 0.102 16.180 0.130 03CA1601 Bulk Cal/Dol -2.119 0.233 18.847 0.301 04CA0I01 Crust Arag -7.017 0.515 12.842 0.658 2790 ± 40 yBP 04CA0202-CA Cobble Cal/Dol 1560 ± 4 0 yBP 04CA0202-CB Cobble Cal/Arag -0.509 0.134 13.875 0.133 04CA0202-CC Cobble Cal/Dol 0.474 0.477 15.057 0.326 04CA0202-CC Cobble Cal/Dol 0.736 0.252 15.530 0.180 04CA0202-CD Cobble Cal/Arag 0.351 0.318 14.889 0.310 04CA0202-CD Cobble Cal/Arag 0.720 0.080 15.799 0.111 04CA0301-CA Cobble Cal MC -5.576 0.188 12.098 0.179 04CA0601 Crust Nesq Dyp 8.429 0.137 26.519 0.191 1.072 ±0 .005 04CA1001 Stream Cal Arag -3.543 0.168 12.636 0.180 9840 ± 40 yBP * Denotes major contamination by bedrock carbonates due to extremely low concentration of hydrated magnesium carbonate material t Arag - Aragonite, Cal - Calcite, Dol - Dolomite, Dyp - Dypingite, Hymag - Hydromagnesite, Lans - Lansfordite, Mags - Magnesite, M C - Monohydrocalcite, Nesq - Nesquehonite, Pyro - Pyroaurite. 5 2 C H A P T E R III 8 1 8 0 vs. 8 1 3 C for Clinton Creek and Cassiar 3 0 25 o oo O oo 2 0 15 10 mixing or respiration/ t • evaporation o bedrock • • n A ' 0 0 Oo v 00 <0 ^ atmospheric n—i—I 30C 20C 5C OC ^ Nesquehonite-rich Crust A Nesquehonite-rich Spire ^ Crust (Contaminated) • Dypingite/Hymag Crust • Dypingite/Hymag Cobble • Cobble (Contaminated) O Bedrock Carbonates • Aragonite Cobble/Stream -Cr Cement (Contaminated) - 1 0 1 0 1 5 8 1 3 C ( V P D B ) F I G U R E 3.1: Stable oxygen and carbon isotope data by mode of carbonate occurrence and mineralogy. Temperature effect for fractionation of carbon is calculated after the method of Deines (2004) for magnesite. The scale for temperature fractionation is given for the typical range of non-freezing temperatures at Clinton Creek and Cassiar. The symbols marked with asterisks represent data collected for the nesquehonite and dypingite/hydromagnesite zones in sample 04CC0703. 2a measurement errors are smaller than the symbols employed. 53 C H A P T E R III tailings containing hydromagnesite cement or minor hydrated Mg-carbonates from Clinton Creek tend to plot in this region as well . These samples all contain a significant amount of pyroaurite ± magnesite contamination which could lead to a reduction in 8 1 3 C . Generally, dypingite cobble coatings and vertical crusts are isotopically heavier than bedrock carbonates, being characterized by -2.1%o < 8 1 3 C < 6.7%o and 16%o < 8 1 8 0 < 28%o. Nesquehonite-rich spires and vertical crusts are further-enriched in both 8 I 3 C and 8 1 8 0 , falling in the range of 4.3%o < 8 I 3 C < 1596o and 24%o < 8 1 8 0 < 29%o). 3.3.2 Radiogenic Carbon Radiogenic l 4 C can be used as an indicator for modern precipitation of carbonate minerals. Due to the artificial enrichment of atmospheric 1 4 C caused by nuclear testing in the mid-twentieth century (the so-called "Bomb Effect"), minerals precipitated from atmospheric CO2 w i l l contain a greater proportion of 1 4 C than the 1950 A D reference standard (Reimer et al. 2004). Radiogenic carbon dating relies upon the relative proportion of radiogenic to stable isotopes in a sample to be less than or equal to the 1950 reference ratio in order to obtain ages. Values of this ratio in excess of the reference can only be expressed as a fraction of the modern value (i.e., the value for 1950). The level of bomb 1 4 C in the atmosphere reached a global equilibrium in the late 1960s (Telegadas 1971), significantly decreasing the difference between 1 4 C readings from distant sampling locations. The amount of 1 4 C in the atmosphere has been steadily decreasing due primarily to exchange with the Earth's oceans (Rafter and Fergusson 54 C H A P T E R III 1957) and by dilution from the Suess Effect (Suess 1955). A s such, younger carbonate precipitates w i l l have increasingly lower values of F 1 4 C (i.e., the Fraction Modern Carbon, as defined by Reimer et al. 2004). There is potential that more than one source of carbon is being tapped in the precipitation of modern carbonate minerals. For instance, a hydrated magnesium carbonate mineral may contain 95% atmospheric carbon and 5% carbon derived from the dissolution of bedrock carbonates. Most bedrock is older than 40 ka, containing 1 4 C below detection limits, and cannot be dated with radiocarbon techniques - as such it is considered to effectively contain zero 1 4 C . Because the amount of 1 4 C in the atmosphere has been decreasing over the past forty years, dilution of the 1 4 C content of a modern carbonate sample gives a lower value for F I 4 C and consequently a younger date of precipitation. Radiogenic 1 4 C analysis of hydrated magnesium carbonate samples from Clinton Creek and Cassiar provides values of F 1 4 C ranging from 1.02 to 1.15 for cobble coatings and vertical crusts. These results suggest a post-1950 (i.e., F 1 4 C > 1) date of formation for carbonate minerals and confirm that carbonate precipitation occurred after mining. Although analysis yields modern atmospheric signatures, minor dilution of modern 1 4 C by bedrock carbonate may be occurring in these samples. The negligible amount of l 4 C remaining in the magnesite sample from Clinton Creek (04CC0104) implies that it is bedrock carbonate, likely having formed from listwanite alteration of the serpentinite. The aragonite/calcite samples from Cassiar (04CA0101, 04CA0202-CA, and 04CA1001) give radiocarbon dates corresponding to 55 C H A P T E R III precipitation 2790 ± 40 years before present (yBP), 1560 ± 40 yBP , and 9840 ± 40 y B P , respectively. Despite the radiocarbon dates associated with the Ca-carbonate samples, field observations suggest that their formation was recent. 3.4 D E T E R M I N A T I O N O F T H E S O U R C E O F C A R B O N There exist three sources for carbon in mine tailings, one or more of which may have been tapped during mineral carbonation: 1) Bedrock carbon from mined carbonates; 2) Atmospheric carbon from meteoric precipitation, and 3) Organic carbon from mined organic sediments or microbial pathways. The fractionation of the stable isotopes of carbon and oxygen in carbonate minerals can be used to identify the source of CO2 tapped in the precipitation of these minerals. Negative values for 8 1 3C in the range of+l%o to -8%o with 8 1 80 between 10%o and 20%o often reflect the isotopic compositions of metamorphic (bedrock) magnesite (Kralik et al. 1989; Hansen 2005). Moderately high, positive values of 8 1 3C and 8 1 80 are typical of carbonates that have formed at low-temperature from atmosphere-derived CO2 (e.g., Kra l ik et al. 1989; Zedef et al. 2000). The temperature-dependence of the carbon fractionation effect in magnesium carbonates (Fig. 3.1) was calculated using the theoretical results of Deines (2004), using magnesite in equilibrium with the atmosphere (-8%o < 8 C < -7%o) as a proxy for the hydrated magnesium carbonates. Temperature- dependence of carbon fractionation covers the range of values from ~7%o to ~12%o for 0- 56 C H A P T E R III 30 °C (Fig. 3.1), spanning the typical range of non-freezing temperature conditions for Clinton Creek and Cassiar. Surface precipitates with abnormally low 8 l 3C-values in the range of 0%o to 5%o and with 8 I 80 between 18%o and 24%o have been documented by Knauth et al. (2003). Knauth et al. (2003) have described 8 1 3C-depletion in atmospherically-sourced caliche on basaltic lava flows in the San Francisco volcanic field, Arizona, U S A . In the course of their studies, Knauth et al. (2003) identified an isotopic distinction between pedogenic calcitic caliche that had developed in heavily weathered basaltic soils and subaerial calcitic caliche on recent (< 900 yBP) basaltic flows. Pedogenic caliche gave rise to values of -9%o < 8 1 3 C < -4%„ and 13%o < 8 I 80 < 32%0, while subaerial caliche was characterized by 4%o < 8 1 3 C < 15%o and 24%0 < 8 1 80 < 32%o. A positive correlation between 81 80 and 8 I 3 C is observed for caliche developed on basalts at three locations in Arizona. A correlation between 8 1 80 and 8 1 3 C data for pedogenic caliche has also been observed by Schlesinger et al. (1998), who argue that the isotopically heaviest samples formed when the soil horizon experienced the greatest exposure to atmospheric CO2 and during times of significant water loss due to evaporation. They suggested that covariation reflects a transition to soil atmospheres increasingly dominated by microbial CO2 at depth with soil waters that are less affected by evaporative enrichment in O. Knauth et al. (2003) speculate that the isotopically intermediate caliche developed within the soil horizon in contact with respired carbon and with less exposure 57 C H A P T E R III to the atmosphere than the subaerial caliche (which developed in an evaporative environment, drawing exclusively on the atmospheric carbon reservoir). From inspection of Figure 3.1, most nesquehonite-rich crust and spire samples can be interpreted as having an atmospheric source of CO2, based on enrichment in 8 1 3 C and 8 1 8 0 . Most data for nesquehonite-rich samples fall into the range of values explained by temperature-dependent fractionation. Samples for which the major carbonate phases include calcite, aragonite, dolomite, magnesite, and pyroaurite give typical bedrock to organic signatures. Crusts and cobble coatings contaminated by bedrock carbonate plot within or near the region populated by the bedrock carbonate samples. This result is consistent with the bedrock carbonate content observed in X-ray diffractograms for these samples. Uncontaminated dypingite ± hydromagnesite crusts and cobbles plot in a distinct region that could reflect either a mixing line between atmospheric carbon and bedrock carbon sources or an atmospheric source with an intermediate-caliche or soil-like signature. In the former case, dissolution of bedrock carbonates may play a role in the precipitation of dypingite. Under this interpretation, for each mole of bedrock carbonate consumed in reaction at low temperatures, one mole of atmospheric CO2 is required to precipitate new carbonate (Faure 1986). A s such, the relative scarcity of bedrock carbonate at Cassiar may be a contributing factor to the less- than vigorous rate of carbonation in the tailings pile. In the case that hydrated magnesium carbonate phases are being reprecipitated from dissolved bedrock carbonate, one mole of atmospheric CO2 would be required to precipitate one mole of hydrated magnesium carbonate. Wi th each cycle of dissolution and reprecipitation, the bedrock 58 C H A P T E R III carbon would be diluted by an additional 50% atmospheric carbon (Fig. 3.2). Although this model for precipitation has the potential to bind as much atmospheric carbon as the model for 100%>-atmospheric precipitation (Fig. 3.3), it does not lead to a net increase in mineralogically-bound CO2. Precipitation at the end of each dissolution cycle releases an amount of bedrock carbon equal to the amount of atmospheric carbon trapped. The ambiguity in the 8 C data for dypingite can be resolved using radiogenic 1 4 C . Fraction modern values above unity correspond distinctly to modern atmospheric CO2. A s a result, samples containing dissolved bedrock carbonate w i l l give F 1 4 C < 1. Sample data fall within two isotopically distinct fields when 8 1 3 C is plotted against F 1 4 C (Fig. 3.4). The first field is populated by bedrock carbon (with F 1 4 C = 0 and 8 1 3 C < 0) and aragonite/calcite precipitates (with F I 4 C < 0.5 and 8 1 3 C < 0). The second field contains two uncontaminated crusts of nesquehonite, one uncontaminated crust of dypingite, and one dypingite/hydromagnesite crust with minor pyroaurite contamination. Despite the wide spread in 8 C-values, these hydrated magnesium carbonate samples all have modern atmospheric 1 4C-signatures. N o clear trend between bedrock and hydrated magnesium carbonates is detectable, while a mixing line is clearly present between bedrock and Ca-carbonate precipitates. The lack of a mixing trend between the modern and bedrock populations suggests that precipitation of hydrated magnesium carbonate efflorescences is not driven by the dissolution of bedrock carbonate. Hydrated magnesium carbonate efflorescences have tapped the atmospheric carbon reservoir. 1 ^ Depletion in , J C is microbially mediated, giving rise to soil-like stable isotope signatures. The marked differences in mineralogy and isotopic signatures observed in Mg-carbonate 59 C H A P T E R III F I G U R E 3.2: Worst-case scenario for carbonate stability in mine tailings: Carbonate efflorescences may precipitate cyclically from dissolved bedrock carbonate minerals. Wi th each cycle, the original bedrock 1 4C-signature becomes increasingly enriched by addition o f atmospheric carbon. After six or seven cycles, such carbonate could be indistinguishable from carbonate precipitated directly from atmospheric carbon. 60 C H A P T E R III F I G U R E 3 . 3 : Best-case scenario model for hydrated magnesium carbonate formation in mine tailings. A n atmospheric source of carbon dioxide and a bedrock silicate source for magnesium guarantee sequestration o f carbon. 61 CHAPTER III Variation of 6 1 3 C with F 1 4 C 15 10 5 h o co ""To atmospheric 04CA0601 03CC01B mixing 04CC0601 bedrock 6 -10 - 04CA1001 • 04CA0101 04CC0104 04CC0105 O '•5 2 EL </) 0> t Nesquehonite-rich Crust • ^ Dypingite-rich Crust • Dypingite Cobble O Bedrock Carbonates • Aragonite Cobble/Stream 0.2 0.4 0.6 F 1 4 C 0.8 1.2 FIGURE 3.4: Variation of 8 1 3 C with F l 4 C for seven samples from Cassiar and Clinton Creek. No mixing line is present between the bedrock and atmospheric carbonate samples, indicating that the precipitation of hydrated magnesium carbonates is not driven by the dissolution of bedrock carbonate. 62 C H A P T E R III precipitates at Clinton Creek and Cassiar reflect at least two separate pathways for formation: A n abiotic, atmospheric pathway for lansfordite and nesquehonite and a microbially-mediated pathway for dypingite and hydromagnesite. Microbially-mediated precipitation of hydromagnesite and magnesite has been proposed by Renaut and Stead (1991) and Braithwaite and Zedef (1996). Power and Southam (2005) have shown that hydromagnesite and/or dypingite precipitate in association with cyanobacteria in Mg-r ich water, whereas under similar yet abiotic conditions, only nesquehonite forms. The high cost associated with radiocarbon dating precludes its regular use as a diagnostic tool. Ideally, stable carbon and oxygen isotope techniques can be calibrated to reflect the definitive results provided by radiocarbon dating for confirmation of an atmospheric source for carbon. In terms of calibrating stable isotope data for the identification of modern, atmospheric carbonate minerals, values for 8 1 3 C > 7%o with 8 1 8 0 > 20%o can be considered definitive evidence of an atmospheric origin for CO2, while values in the range of 2%o < 8 1 3 C < 7%o and 17%o < 8 1 8 0 < 20%o are very likely indicative of atmospheric carbon. Samples giving values of 8 1 3 C < 2%o with 8 1 8 0 < 17%o may be either bedrock or atmospheric carbonates contaminated by bedrock carbonate. 3.5 THE SOURCE FOR CATIONS Final confirmation that the dissolution of bedrock carbonate does not drive the precipitation of carbonate efflorescences must come from the identification of the cation 63 C H A P T E R III source. Should the cations be sourced from dissolved bedrock carbonate, one molecule of CO2 would be released during dissolution of bedrock carbonate for every molecule bound in the reprecipitated mineral. Although a carbonate that has been through several cycles of dissolution and reprecipitation could give an atmospheric carbon signature (Fig. 3.2), no additional sequestration occurs for a bedrock source of cations. The only available sources for the C a 2 + in calcium carbonate precipitates are bedrock dolomite and calcite. Calcium carbonate precipitates are isotopically distinct from the hydrated magnesium carbonates in 8 1 3 C , 8 1 8 0 , and F 1 4 C . These samples plot on a mixing line between bedrock and atmospheric populations (Fig. 3.4), defining the isotopic field for bedrock dissolution. Calcium-carbonate precipitates are strictly the result of the repreciptation of bedrock carbonate. Several bedrock sources exist for M g 2 + in hydrated magnesium carbonate precipitates: dolomite, magnesite, chrysotile, antigorite, and lizardite. Sequestration can only occur in magnesium carbonates for a silicate source of magnesium. Although silicate minerals typically dissolve more slowly than carbonates in mine tailings environments (e.g., Nesbitt and Jambor 1998), surface area, grain size, mineral content, porewater composition and pH, and deviation from equilibrium conditions have a significant effect on the total amount of dissolution. A simple model can be developed to estimate the order of magnitude difference in geometric surface area between magnesium-bearing carbonate grains and the surface area of the serpentine-group weight fraction in a bulk tailings sample. Geometric surface area is used to estimate an upper limit for reactive surface area, which is typically smaller 64 C H A P T E R III than geometric and B E T surface areas. Approximating tailings grains as cubes with perfectly smooth surfaces and assuming zero porosity (i.e., perfect packing), an approximation of the surface area per gram of material can be calculated for typical sieve-size fractions (as in Chapter 2). The median value for successive sieve sizes was used to approximate the grain size for the smaller of two size fractions. From this value, the surface area per gram of the tailings grains can be estimated (Table 3.2). B E T N-gas absorption isotherm grain size analysis of chrysotile fibres from Cassiar gives a surface area of 17.45 m /g (J. Thorn, pers. comm.). The fibres provide an increase in surface area of 4 orders of magnitude over the area calculated for grains of medium sand (Udden-Wentworth scale). The non-fibrous fraction of sample 04CC1401 from Clinton Creek (which was wet-sieved for grain size analysis in Chapter 2) has a surface area on the order of 1.8 x 10"3 m 2 /g. The non-fibrous fraction for sample 03CC1601 from Cassiar gives a surface area on the order of 2.4 x 10" m /g. The fibrous fraction of the same bulk samples has a surface area of 17.45 m7g - an increase of 4 orders of magnitude. Although the contribution of massive, non-fibrous serpentine generally outweighs that of chrysotile fibres by an order of magnitude, its contribution to surface area is comparatively small and can be neglected in further calculations. Assuming negligible microporosity in the carbonate grains in the tailings, and using the grain size distribution (Chapter 2) and mineral composition (Chapter 4, Wi lson et al. 2006) from 04CC1401 (Table 3.2), the average surface area per gram of magnesium carbonate in a typical sample of bulk tailings is in the range of 0.0020 g/cm . The surface area per gram of chrysotile fibres is 4 orders of magnitude larger than that 65 C H A P T E R III T A B L E 3.2: Estimates for surface area of mineral phases in bulk tailings samples. Size Fraction (mm) Fraction Mass (g) Mean Grain Size (mm) Surface Area per Grain (m2) Volume per Grain (m3) Grains per g of Tailings (g"') Area per Gram (m2/g) Area for Mg- Silicates (m2/g) Area for Carbonates (m2/g) Area for Other Phases (m2/g) Area per Size Fraction (m2) Total Area (m2) > 16.0 199.7 1.60xl0"2 8.04x10"" 2.14x10"" 1.67x10"' 1.34x10"" 2.34x10"2 6.85x10" 2.62xl0"3 2.67x10"2 11.3 >9.50 377.3 1.28 xlO"2 5 .11X10" 1 1.09x10" 3.29x10"' 1.68x10"" 5.56x10'2 1.62xl03 6.2x10"3 6.34x10" 2 >4.76 854.7 7.13 xlO"3 1.60x10"" 1.90x10"' 1.88 3.01x10"" 2.25x10"' 6.58xl0"3 2.52x10"2 2.57x10"' >2.00 953.7 3.38 xlO'3 3.59xl0"5 2.02x10"8 1.77x10' 6.34x10"" 5.30x10"' 1.55xl0"2 5.93x10"2 6.05x10"' s >0.850 758.5 1.43 xlO"3 6.38x10" 1.52x10"' 2.36xl02 1.50xl0"3 9.99x10"' 2.92x10'2 1.12x10"' 1.14 SO < >0.425 343.5 6.38 xlO"" 1.28x10" 1.36x10"'° 2.63xl0 3 3.36x10"3 1.01 2.96xl0"2 1.13x10"' 1.15 03 C  >0.212 256.7 3.19x10"" 3.19x10-' 1.69x10"" 2.11x10" 6.73x10"3 1.51 4.42xl0"2 1.69x10"' 1.73 >0.150 97.4 1.81x10-" 1.03x10-' 3.10xl0"12 1.15xl05 1.18xl0"2 1.01 2.95xl0"2 1.13x10"' 1.15 >0.106 93.7 1.28x10-" 5.15xl0"8 l.lOxlO"12 3.25xl05 1.67xl0"2 1.37 4.02xl02 1.54x10"' 1.57 >0.075 75.1 9.05x10"5 2.57x10"8 3.88xl0"13 9.20x105 2.37x10"2 1.56 4.55x10"2 1.74x10"' 1.78 >0.053 53.9 6.40xl0"5 1.29xl0"8 1.37xl0"'3 2.60x10" 3.35xl0'2 1.58 4.62xl0"2 1.77x10"' 1.80 <0.053 68.9 5.30xl0"5 8.82x10"' 7.79x10"'" 4.58x10" 4.04x10"2 2.44 7.13xl0"2 2.73x10"' 2.79 Fibre 17.45 8856 >9.51 255.8 9.5ixi0"3 2.84x10"" 4.50x10"7 7.93x10"' 2.25x10"" 5.09xl0"2 1.78xl0"J 4.93xl0"3 5.76x10-2 3.36 >1.68 807.1 5.60x10-' 9.83x10"5 9.17xl0"8 3.89 3.83x10"" 2.73x10"' 9.55x10'3 2.6xl0"2 3.09x10"' >1.41 107.3 1.55x10° 7.50x10* 1.93x10"' 1.85xl02 1.39xl0"3 1.31x10"' 4.60x10"3 1.27xl0"2 1.49x10"' >0.840 208.4 1.13x10° 3.98x10" 7.45x10""' 4.79x102 1.90xl0"3 3.51x10"' 1.23xl0"2 3.40x10"2 3.97x10"' >0.59S 132.1 7.18x10" 1.62x10"" 1.93x10"'° 1.85xl03 2.99x10"3 3.49x10"' 1.22xl0"2 3.38xl0"2 3.95x10"' s T >0.350 155.8 4.73x10"" 7.01 xlO"7 5.52x10" 6.47x10 3 4.54x10"3 6.24x10"' 2.18xl0"2 6.05x10"2 7.07x10"' IC C  >0.212 80.7 2.81x10"" 2.48x10"' 1.16x10" 3.07x10" 7.63x10"3 5.44x10"' 1.90xl0"2 5.27xl0"2 6.15x10"' © >0.180 10.5 1.96x10"" 1.21x10-' 3.94x10"'2 9.06x10" 1.09xl0"2 1.01x10"' 3.55xl0"3 9.83x10"3 1.15x10"' >0.106 22.6 1.43x10"" 6.42x10"8 1.53xl0"12 2.33x10s 1.50xl0"2 2.99x10"' 1.05xl0"2 2.90x10"2 3.39x10"' >0.053 7.6 7.95x10"' 1.99xl0"8 2.63xl0"13 1.36x10" 2.70x10"2 1.81x10"' 6.33x10"3 1.75xl0"2 2.05x10"' <0.053 1.9 5.30xl0"5 8.82x10"' 7.79x10"'" 4.58x10" 4.04x10"2 6.79x10"2 2.37xl0"3 6.58x10"3 7.68xl0"2 Fibre 17.45 2272 6 6 C H A P T E R III for the magnesium carbonates. The large surface area from which M g can be leached in chrysotile fibres and the distinct atmospheric signature in the 8 1 3 C and F 1 4 C data for hydrated magnesium carbonates indicate that chrysotile is the primary source for M g 2 + in magnesium carbonate precipitates. It can be concluded from the stable and radiogenic isotope data and the estimate for surface area that dissolution of bedrock carbonate does not drive the precipitation of hydrated magnesium carbonate minerals. Sequestration of atmospheric CO2 is occurring in chrysotile mine tailings at Clinton Creek and Cassiar. 3.6 R E F E R E N C E S Braithwaite, C.J.R. and Zedef, V . (1996) Hydromagnesite stromatolites and sediments in alkaline lake, Salda Golu, Turkey. Journal of Sedimentary Research, 66, 991- 1002. Craig, H . (1957) Isotopic standards for carbon and oxygen and correction factors for mass-spectrometric analysis of carbon dioxide. Geochimica et Cosmochimica Acta, 12, 133-149. Deines, P. (2004) Carbon isotope effects in carbonate systems. Geochimica et Cosmochimica Acta, 68, 2659-2679. Faure, G . (1986) Principles of isotope geology. New York, John Wiley & Sons, Inc. 67 C H A P T E R III Hansen, L . D . (2005) Geologic setting of listwanite, At l in , B . C . : Implications for carbon dioxide sequestration and lode-gold mineralization. M.Sc . Thesis, University of British Columbia, Vancouver, British Columbia. Knauth, L .P . , B r i l l i , M . , and Klonowski , S. (2003) Isotope Geochemistry of Caliche Developed on Basalt. Geochmicica et Cosmochimica Acta, 67(2), 185-195. Kral ik , M . , Aharon, P., Schroll, E . , and Zachmann, D . (1989) Carbon and oxygen isotope systematics of magnesites: a review. Monograph Series on Mineral Deposits (Ed. G . Friedrich), 28, 197-223. Melezhik, V . A . , Fallick, A . E . , Medvedev, P .V . , and Makarikhin, V . V . (2001) Palaeoproterozoic magnesite: lithological and isotopic evidence for playa/sabkha environments. Sedimentology, 48, 379-397. Nesbitt, H . W . and Jambor, J .L. (1998) Role of mafic minerals in neutralizing A R D , demonstrated using a chemical weathering methodology. In Modern Approaches to Ore and Environmental Mineralogy (Cabri, L . J . and Vaughan, D.J . , Eds.), Mineralogical Association of Canada Short Course Series, 27, 403-421. Power, I .M. and Southam, G . (2005) Carbon dioxide sequestration through enhanced weathering of chrysotile mine tailings and subsequent microbial precipitation of magnesium carbonates. Goldschmidt 2005, Moscow, Idaho. Rafter, T . A . and Fergusson, G.J . (1957) Atom bomb effect - recent increase in the carbon-14 content of the atmosphere, biosphere, and surface water of the oceans. New Zealand Journal of Science and Technology, Section A : Agricultural Research Section, 38, 871-883. 68 C H A P T E R III Reimer, P.J., Brown, T .A . , and Reimer, R . W . (2004) Discussion: Reporting and calibration of post-bomb 1 4 C data. Radiocarbon, 46, 1299-1304. Renaut, R . W . and Stead, D . (1991) Recent magnesite-hydromagnesite sedimentation in the playa basins of the Cariboo Plateau, British Columbia. Geological Fieldwork ( B C G S B ) , Paper 1991-1, 279-288. Schlesinger, W . H . , Mario, G . M . , and Fonteyn, P.J. (1998) Stable isotope ratios and dynamics of caliche in desert soils. In Stable Isotopes in Ecological Research (Rundel, P .W., Ehleringer, J.R., and Nagy, K . A . , Eds.), 307-317. Springer- Verlag, New York. Suess, H . E . (1955) Radiocarbon concentration in modern wood. Science, 122, 415-417. Telegadas, K . (1971) The seasonal atmospheric distribution and inventories of excess carbon-14 from March 1955 to July 1969. U .S . Atomic Energy Commission Report H A S L - 2 4 3 . Wilson, S.A., Raudsepp, M . , and Dipple, G . M . (2006) Verifying and quantifying carbon fixation in minerals from serpentine-rich mine tailings using the Rietveld method with X-ray powder diffraction data. American Mineralogist, In review. Zedef, V . , Russell, M . J . , Fallick, A . E . , and Hal l , A . J . (2000) Genesis of vein stockwork and sedimentary magnesite and hydromagnesite deposits in the ultramafic terranes of Southwestern Turkey: A stable isotope study. Economic Geology, 95, 429-446. 69 C H A P T E R IV C H A P T E R I V : Verifying and quantifying carbon fixation in minerals from serpentine-rich mine tailings using the Rietveld method with X-ray powder diffraction data 4.1 I N T R O D U C T I O N The release of anthropogenic greenhouse gases (e.g., CO2, CH4, N 2 0 , and S 0 2 ) into the atmosphere has been linked to environmental degradation and global climate change (IPCC 2001). Production of atmospheric pollutants, C 0 2 in particular, is associated with the combustion of fossil fuels - which accounts for as much as 90% of greenhouse gas emissions in the past 20 years (IPCC 2001). It is expected that development and implementation of new carbonless sources of energy w i l l require another 50 to 100 years (e.g., Lackner 2003; Pacala and Socolow 2004), during which time fossil fuels w i l l see continued widespread use (Lackner 2003). Current models require that atmospheric C 0 2 levels be stabilized on this timescale in order to curtail irreversible climate change (Pacala and Socolow 2004). Carbon dioxide sequestration or disposal is an essential component in the international effort to stabilize C 0 2 emissions. O f the proposed sequestration schemes, mineral sequestration represents the most geologically stable and environmentally benign method for carbon disposal (Lackner et al. 1995). Mineral sequestration mimics natural silicate weathering processes which bind C 0 2 in carbonate minerals. A n estimated 87% of the Earth's carbon, or 9 . 2 x l 0 1 6 tonnes, is bound in carbonate minerals (Sundquist 1985). Kump et al. (2000) have predicted 70 C H A P T E R IV that, given a timescale of 10 years, carbonate minerals w i l l be the ultimate sink for anthropogenic CO2. Mineral sequestration seeks to accelerate this natural process. Carbonate minerals in mine tailings are of general interest for their role in suppressing acid generation (e.g., Jambor and Blowes 1991; Blowes et al. 1998). Carbonate precipitates were observed in tailings from the K i d d Creek copper-zinc mine near Timmins, Ontario, Canada in 2000 ( A l et al. 2000). Similar carbonation phenomena have been observed in tailings from the Lower Will iams Lake uranium mine near Ell iot Lake, Ontario (Paktunc and Dave 2002), and in tailings from the chrysotile mines at Thetford, Quebec (Huot et al. 2003), Clinton Creek, Yukon (Wilson et al. 2003), and Cassiar, British Columbia (Wilson et al. 2005). The carbon bound in many tailings environments may not have an atmospheric origin, but the data presented in Chapter 3 indicate that the millions of tonnes of serpentinite tailings from the abandoned chrysotile mining operations at Clinton Creek, Yukon Territory, and Cassiar, British Columbia, Canada (Fig. 4.1) are actively fixing atmospheric CO2 in mineral carbonates. The magnesium-carbonate minerals dypingite, hydromagnesite, nesquehonite, and more rarely, lansfordite, are forming in situ at the surface of the tailings piles at these historical mine sites. The hydrated magnesium carbonate minerals found at Cassiar and Clinton Creek are of interest as they have potential for long-term storage of greenhouse gases (Lackner et al. 1995; Lackner 2003). In this chapter we discuss the mineralogy of magnesium carbonates at Clinton Creek and Cassiar and develop a quantitative method for carbonate 71 C H A P T E R I V C H A P T E R IV determination in serpentine-rich mine tailings. The isotopic data and implications for fingerprinting the source of carbon are discussed in Chapter 3. Carbonate crusts are observed in mine tailings within months of tailings deposition, indicating that mineral sequestration in chrysotile tailings can be a rapid process (Huot et al. 2003). The rapidity and extent of carbonate formation in mine tailings is almost certainly linked to the vast increases in silicate mineral surface area that are a direct result of mineral processing. Acceleration of the carbonation process in historical and active mining operations could be used to render large mining operations C02-neutral and may help to reduce the greenhouse gas content of the atmosphere on a global scale. Quantification of the amount of atmospheric carbon sequestered in geologic samples from Clinton Creek and Cassiar w i l l give an estimate for the sequestration capacity of ultramafic mine tailings in general and w i l l provide a framework for the development of standard policies related to the trading of CO2 emissions for enhanced mineral sequestration at mine sites. Standard bulk geochemical measures of CO2 abundance cannot be used to quantify mineral trapping as they cannot distinguish between carbonate phases, nor can they discriminate between the sources of carbon - bedrock, atmospheric, or industrial. Stable and radiogenic fingerprinting of carbon can be used to identify which carbonate minerals in a geological sample are the sinks for atmospheric, industrial, or bedrock carbon. Quantitative phase analysis using the Rietveld method provides a measure of the weight-percent contribution of each carbonate mineral in a sample. From this measure, the amount of CO2 stored in atmosphere- 73 C H A P T E R r v derived carbonate minerals can be determined. Quantitative phase analysis is therefore essential to verification and quantification of carbon disposal via mineral sequestration. In order to develop and test a practical method of quantitative phase analysis for serpentinites, a series of synthetic serpentinite mine tailings of typical and known composition were prepared by weighing and mixing pure mineral constituents. A t issue here is that kaolinite-serpentine group minerals generally exhibit planar disorder and thus cannot be fitted by diffraction patterns calculated from the ideal structures which is the basis of the Rietveld method (Rietveld 1967, 1969). A previous study made use of a combined reference intensity ratio and Rietveld method to measure serpentine abundance (Gualtieri and Art io l i 1995). If, however, the experimental pattern of the disordered phase can be fitted independently by some means and i f a known weight of a spike of an extraneous phase is added to the sample, the amount of serpentine in the sample could be measured as i f it were an amorphous phase. Spikes have been used successfully as internal standards for largely amorphous materials (e.g., Gualtieri 2000; De L a Torre et al. 2001; Orlhac et al. 2001), but have not been applied to disordered crystalline phases. We seek to develop a standardless method that is applicable to most geological samples containing a disordered mineral phase. For this study, we used annealed C a F 2 as a spike and fitted the diffraction pattern of the disordered kaolinite-serpentine group mineral with the Pawley method (Pawley 1981). This procedure was subsequently applied to samples of tailings from the mines at Cassiar and Clinton Creek. We propose that the Rietveld method with X-ray powder-diffraction data can be used to accurately quantify the amount of carbonation occurring in serpentinite mine tailings. 74 C H A P T E R TV 4.1.1 Sample Localities The Clinton Creek chrysotile deposit is a partially carbonate-altered serpentinized peridotite (Htoon 1979). The Clinton Creek Mine, situated near Dawson City, Y u k o n Territory, operated from 1967 to 1978 (Htoon 1979). A total of 16 M t of chrysotile ore were extracted from the four open pit mines at Clinton Creek during this eleven year period. In addition to the ore, 60 M t of waste rock and 10 M t of tailings were produced as a by-product of the mining process ( E M A N - N o r t h 2003). Tailings materials are characterized by short-fibre chrysotile and serpentinite cobbles containing massive serpentine and minor amounts of magnetite, calcite, dolomite, magnesite, quartz, clinochlore, and pyroaurite. Carbonate mineral formation occurs in four distinct modes at Clinton Creek: crusts on vertical surfaces (composed of nesquehonite, dypingite, hydromagnesite, and occasional lansfordite), carbonate spires on horizontal tailings surfaces (composed of nesquehonite, dypingite, and hydromagnesite and caused by wicking-up of pore fluids), as thin crusts of dypingite (< 1 mm in thickness) on serpentinite cobbles, and as a disseminated cement of hydromagnesite in bulk tailings (Fig. 4.2). Carbonate crusts are abundant and easily recognised by their off-white color, coloform habit, and reactivity with dilute hydrochloric acid (10 % HCI). The chrysotile deposit at Cassiar, British Columbia, forms part of a serpentinized harzburgite tectonite (Wicks and O'Hanley 1988). Cassiar is located approximately 130 k m north of Dease Lake, B C . During the 39-year operational lifetime of the mine, from 1953 to 1992, 17 M t of mine tailings were produced. These tailings were stored outdoors 75 C H A P T E R IV F I G U R E 4.2: Modes in which hydrated magnesium carbonate minerals have been identified at Clinton Creek, Yukon and Cassiar, British Columbia: A ) nesquehonite/dypingite crust from Cassiar, B) dypingite on cobble from Clinton Creek, C) nesquehonite/dypingite/hydromagnesite spires from Clinton Creek, and D) disseminated hydromagnesite cement from Clinton Creek. 7 6 C H A P T E R IV in an elongate pile. Beginning in 1993, the mine underwent a six-year process of renovation and revitalization. B y January 2000 commercial production of chrysotile had been renewed. Min ing proceeded until December 25, 2000 when the mi l l was severely damaged by fire ( M I N F I L E , 2005). Tailings are composed primarily of short-fibre chrysotile with cobbles of massive serpentine with minor magnetite, clinochlore, and occasional quartz and carbonates. The carbonate minerals nesquehonite and dypingite form crusts on vertical tailings surfaces at Cassiar. 4.2 E X P E R I M E N T A L M E T H O D 4.2.1 Sample Preparation and Data Collection Twenty-four mixtures of pure mineral samples were prepared to simulate serpentinite mine tailings. Minerals commonly found in the tailings at Clinton Creek and Cassiar were used: kaolinite-serpentine group (antigorite and chrysotile), magnetite, quartz, calcite, dolomite, magnesite, and hydromagnesite. Mixtures of pure mineral samples were prepared to simulate serpentinite mine tailings. Minerals commonly found in the tailings at Clinton Creek and Cassiar were used: kaolinite-serpentine group (antigorite and chrysotile), magnetite, quartz, calcite, dolomite, magnesite, and hydromagnesite. A s sufficient amounts of pure nesquehonite, dypingite, and lansfordite (also present in the mine tailings at Clinton Creek and Cassiar) 77 C H A P T E R TV were not available, and well-crystallized, synthetic hydrated magnesium carbonates are difficult to manufacture (Davies and Bubela 1973; Kloprogge et al. 2003), hydromagnesite was used in their place. Samples of the constituent minerals were checked for purity using X-ray powder diffraction. Kaolinite-serpentine group minerals were identified positively as chrysotile and antigorite using X-ray powder diffraction and dispersive Raman microspectroscopy according the method of Rinaudo et al. (2003). A l l components, with the exception of hydromagnesite, were greater than 99% pure. Rietveld analysis showed that the hydromagnesite had partially decomposed to 4.8 wt.% magnesite. Three identical stock mixtures ( A l , C l and A C 1 ) were prepared with the relevant phases exclusive of serpentine in the following abundances: magnetite (40 wt.%), quartz (20 wt.%), calcite (10 wt.%), dolomite (10 wt.%), magnesite (10 wt.%), and hydromagnesite (10 wt.%). Each mixture was ground under anhydrous ethanol with synthetic corundum grinding elements for 10 minutes in a McCrone micronising m i l l to reduce the mean grain size and to ensure homogenization. Stock mixtures were dried at room temperature under a fume hood and were disaggregated with an agate mortar and pestle when dry. From each of the identical 6-phase mineral mixtures, series of 5 synthetic serpentinite samples each were produced by adding serpentine as follows. Antigorite and chrysotile were added in amounts of 10, 30, 50, 70 and 90 wt.% to mixtures A l and C l , " A M I X " and " C M L X " series, respectively (Table 4.1). A third series ( " A C M I X " series) was prepared by adding both chrysotile and antigorite to mixture A C 1 in amounts 5, 15, 25, 35 and 45 wt.%. A spike of annealed C a F 2 was added 78 C H A P T E R IV T A B L E 4.1: Compositions of synthetic serpentinite mine tailings renormalized to exclude fluorite spike. Phase (wt.%) Stock Mix SERPMIX10 SERPM1X30 SERPMIX50 SERPMIX70 SERPMIX90 HM1XI HMIX2 HMIX3 HMIX4 HMIX5 HMIX6 HMIX7 HMIX8 HMIX9 Chrysotile 10.00 30.00 50.00 70.00 90.00 90.00 80.00 50.00 80.00 45.00 70.00 60.00 Magnetite 40.00 36.00 28.00 20.00 12.00 4.00 10.00 5.00 5.00 5.00 0.00 10.00 Quartz 20.00 18.00 14.00 10.00 6.00 2.00 5.00 5.00 49.67 40.00 Calcite 10.00 9.00 7.00 5.00 3.00 1.00 5.00 5.00 9.93 10.00 Dolomite 10.00 9.00 7.00 5.00 3.00 1.00 10.60 10.00 Magnesite 10.48 9.43 7.33 5.24 3.14 1.05 0.48 0.95 2.39 0.48 2.39 0.72 1.19 10.88 10.95 Hydromagnesite 9.52 8.57 6.67 4.76 2.86 0.95 9.52 19.05 47.62 9.52 47.62 14.28 23.81 18.92 19.05 Total 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 79 CHAPTER PV to each sample such that it constituted 10 wt.% of the renormalized weight. Although low abundances of antigorite or chrysotile are not found in serpentinite mine tailings, they were used in this study to define the limitations of the method. The synthetic samples were ground under anhydrous ethanol in the McCrone micronising mill for an additional 7 minutes to reduce the grain size of the serpentine phases and to homogenize the samples. The fourth, and final, series ("HMLX" series) consisted of 9 weighed mixtures, 7 of which represented more realistic mineral abundances and 2 of which contained no serpentine (Table 4.1). These samples were prepared individually, rather than from a stock mixture. As with the previous 15 samples, a 10 wt.% spike of CaF 2 was added to each HMLX sample. The HMLX series samples were ground for 10 minutes in the McCrone micronising mill. The grinding times were chosen to minimize the degradation of the serpentine structure while optimizing particle-size reduction. Samples were dried at room temperature and disaggregated with an agate mortar and pestle. In addition, two specimens of tailings from Cassiar and eight specimens from Clinton Creek were prepared to assess the method on real mine tailings. Two samples from a hydromagnesite playa in Atlin, BC were also included to demonstrate Rietveld refinements on carbonate-rich samples that lack serpentine. Samples were left in a drying hood for 48 hours and were then homogenized mechanically with a spatula. A five kilogram aliquot was taken from a bulk sample (weighing in excess of 20 kg) from each locality. These large aliquots were dried and homogenized prior to division into smaller, more workable aliquots for X-ray powder diffraction. An aliquot of each sample was powdered using a tungsten carbide ringmill. A 10 wt.% spike of annealed CaF 2 was 80 C H A P T E R IV added to 3.00 g of each sample of tailings and the mixture was ground under ethanol for 10 minutes in the micronising mi l l . Samples were mounted in a back-loading aluminum cavity holder of the design described by Raudsepp and Pani (2003). Preferred orientation of inequant crystallites was minimized by covering the top of the cavity with a sheet of ground glass and loading powdered samples against the roughened surface. To further inhibit preferred orientation of crystallites, particularly those of chrysotile, the surface of each sample was serrated with a razor blade along two axes: one parallel to the axis of the diffractometer goniometer and the second in the perpendicular direction. X-ray powder diffraction data were collected on a Siemens D5000 0-20 diffractometer with a step size of 0.04° 20 and counting time of ls/step over a range of 3-90° 20. The normal-focus C u X-ray tube was operated at 40 k V and 40 m A . Conventional quantitative modal analysis with X-ray powder diffraction data is performed through the integration of peak intensities and calibrated using internal standards. This is an awkward method due to the difficulty inherent in the preparation of standards displaying similar materials properties (i.e., crystallinity, composition, and microabsorption) to the minerals in a sample. The overlap of Bragg reflections in complex patterns, such as those for geological samples, makes it extremely difficult to locate peaks suitable for integration of intensity. Although deconvolution protocols can be used to account for peak overlap in modern whole-pattern profile fitting, the use of internal standards is still prerequisite. New imaging technology has brought about a renaissance in the field of point counting; however such methods are limited by grain 81 C H A P T E R TV size, time constraints, and the high cost of experimental accuracy. (Raudsepp and Pani 2003) Normative calculations depend upon assumptions made from ideal mineral assemblages based on mass-balance calculations, and as such are indirect and fairly inaccurate for minerals that do not preferentially partition trace to minor abundance elements (Dipple et al. 2002; Raudsepp and Pani 2003). 4.2.2 Motivation for Using the Rietveld Method The Rietveld method is a standardless, full-profile method for quantitative phase analysis which can be applied to diffraction patterns collected using conventional laboratory diffractometers (Rietveld 1967, 1969). Essentially, the Rietveld method is a least squares refinement which is carried out until a best fit is obtained between the entire experimental powder diffraction pattern and the entire calculated pattern for a mineral or mixture of minerals. What makes the Rietveld method so useful is that it provides feedback between an ever-improving model for crystal structure and the assignment of observed intensities for overlapping Bragg reflections (Young 1993). In all other quantitative refinement methodologies the assignment of Bragg reflections to observed intensities and the structure refinement depending on this assignment are non-interacting processes. The quantity to be minimized in the Rietveld least squares refinement is the 82 C H A P T E R IV least squares residual (for a best fit to all intensities, yh simultaneously): sy = X Wi(yi-ya)2 (4.1) where sy is the least squares residual for the least squares fit, w, = 1/yi is a weight on the residual, yt is the observed intensity at the fh step in the acquired X R P D pattern, and yci is the calculated intensity at the / t h step. (Young 1993) The relative masses of the constituent mineral phases in a specimen can be calculated using the relation: where Wr is the relative weight fraction of the r mineral phase in a mixture of f-many phases, S is the Rietveld scale factor, Z is the number of formula units per unit cell o f the mineral in question, M is the mass of the formula unit, and V is the volume of the unit cell (H i l l and Howard 1987). This relation holds for well-crystallized phases, but becomes less accurate for samples containing amorphous, nanocrystalline, or disordered phases. Structural models for crystalline materials, derived from the literature, are only directly applicable to simple structures and minerals for which the degree of solid solution is negligible (Gualtieri 2000). Complex minerals, such as clays and serpentines, Sr(ZMV)r (4.2) 83 C H A P T E R IV which are strongly affected by planar disorder, w i l l cause under or overestimates of the scale factor during a standard Rietveld refinement, leading to a misestimate of the mineral content in the sample. However, the addition of a known weight of a spike o f an extraneous phase (e.g., CaF2) and the use of structureless profile fitting of the serpentine pattern allows the measurement of the amount of serpentine in the sample as i f it were an amorphous phase. During refinement, amorphous and nanocrystalline components are usually included in the background model and subtracted out of the pattern (Raudsepp and Pani 2003). The crystalline phases are subsequently normalized to 100%. For a specimen to which a spike has been added, there w i l l be a discrepancy between the known weight percent of the spike and the amount calculated with the Rietveld method. This discrepancy can be used to determine the amount of amorphous material in the specimen with the relation: A = l~W'/R> - 1 0 4 % (4.3) 100-Wx where A (%) is the amount of amorphous phase in the specimen, Ws (%) is the weighed amount of spike, and Rs (%) is the amount o f spike determined by Rietveld analysis (Gualtieri 2000; De L a Torre et al. 2001). A n appropriate amount of spike must be chosen such that it contributes significantly to the overall pattern signal without dominating the other phases in the 84 C H A P T E R IV specimen. A recent study has shown that the relative error on the amorphous content of a specimen increases as the percent content of the spike decreases and that 10% spike gives a sufficiently high signal without drowning out the rest of the pattern (Gualtieri 2000). A spike of approximately 10% is typically recommended as a good compromise between resolution of intensities and accuracy of estimation for the amorphous phase (Bish and Post 1993; Gualtieri 2000). Structureless profile fitting with the Pawley method helps to provide an estimate of the amount of a disordered mineral phase in a specimen (Pawley 1981). The Pawley method is a variation on the standard Rietveld method. It differs in that the location of each Bragg reflection is held fixed, while the peak intensities are permitted to vary. The Pawley method resembles, yet should not be confused with, the Le Ba i l method for structureless profile fitting. The distinguishing feature of the Le Bai l method being the initial definition of the structure factors, \F\ (i.e., the sum of the scattering vectors for all atoms in a unit cell), assigned to the Bragg peaks for the hypothetical crystal structures used in the refinement. Iterations are begun with a set of arbitrarily identical values of \F\ rather than using the \FcaicuiateJ\ values used in the standard Rietveld method or the refinable peak heights used in the Pawley method (Le Ba i l 1988; Le Ba i l 2002). The Pawley and Le Ba i l methods constrain the positions of the Bragg reflections in an X-ray diffraction pattern according to crystal data for the relevant phases but do not use structural data to fit the peak intensities. Due to the effects of structural disorder and preferred orientation on Bragg intensities, it is necessary to use a method for structureless fitting to obtain a direct estimate of the amount of serpentine in a spiked specimen. 85 C H A P T E R I V Essent ia l ly , f i t t ing w i th the P a w l e y method a l lows the disordered phase to be subtracted f r om the pattern as a part o f the background curve. The wt .% abundance o f the disordered phase is then calculated as a funct ion o f the overestimate o f the spike phase us ing (4.3). 4.2.3 Rietveld Refinement and Quantitative Phase Analysis Rie t ve ld ref inements were done w i th R ie t ve ld ref inement software Topas V e r s i o n 3 (Bruker A X S 2004b) us ing the fundamental parameters approach (Cheary and C o e l h o 1992). Sources o f crystal structure data for the constituent phases are l is ted i n Tab le 4.2. T o avo id the unpredictable effect o f planar disorder on the d i f f ract ion patterns o f the serpentine minera ls , the P a w l e y method (Pawley 1981) was used to extract peak intensit ies independent ly o f atomic scattering f rom the powder d i f f ract ion patterns o f pure chrysot i le and antigorite. The extracted intensit ies w i th the appropriate space groups and ce l l d imens ions o f antigorite and chrysot i le were subsequently used to fit the serpentine component i n the powder d i f f ract ion patterns o f the mixtures as a peak phase us ing the P a w l e y method. A s the relat ive intensit ies o f peaks dur ing P a w l e y ref inement are not constrained b y atomic scattering, the relat ive intensit ies o f the peaks for the serpentine were in i t ia l ly he ld constant to avo id the interference o f serpentine peaks w i t h peaks f rom the other phases. A f te r the correct fitting o f these peaks, the relat ive intensit ies o f the serpentine peaks were ref ined. In order to prov ide an estimate o f the 86 C H A P T E R PV T A B L E 4.2: Sources of crystal structure data for Rietveld refinement. Mineral Source Antigorite Brucite Calcite Chrysotile Dolomite Fluorite Hydromagnesite Magnesite Magnetite Nesquehonite Palygorskite Pyroaurite Quartz Uehara(1998) Catti etal. (1995) Maslen etal. (1995) Falini et al. (2004) Ross and Reeder (1992) Batchelder and Simmons (1964) A k a o a n d l w a i (1977) Markgraf and Reeder (1985) Tsukimura et al. (1997) Giester et al. (2000) Chisholm(1992) Olowe (1995) Glinnemann et al. (1992) 87 C H A P T E R IV combined abundance of serpentine, both antigorite and chrysotile structures were used as a basis to fit serpentine in samples containing both phases. Backgrounds for samples containing chrysotile, or both chrysotile and antigorite, were modelled using third-order Chebychev polynomials with an additional l/x term to aid in the fitting of the background curve at low angles of diffraction. Second-order Chebychev polynomials were adequate to model the background for samples in which antigorite was the only serpentine phase. The zero error, Lorentzian crystallite size, strain and cell parameters were refined for all phases. Preferred orientation of phases other than serpentine was corrected for using the method of March and Dollase (March 1932; Dollase 1986). Contamination from the corundum grinding elements of the micronising m i l l accounted for less than 1% of most samples and was not treated as an additional phase in refinements. A l l Rietveld refinements were done assuming a 10 wt.% spike. In order to model the effects that weighing error for the spike may have had on results, refined abundances were recalculated using an exaggerated weighing error of ± 1 0 % relative. Refinement results were recalculated and renormalized for each sample using the method of Gualtieri (2000), assuming spike abundances of 9 and 11%. A s observed by Gualtieri (2000), the amorphous phase is underestimated with the assumption of an increased abundance of the spike phase. The absolute and relative error on the estimation of the serpentine phase decrease as the amount of that phase increases. The 10% overestimate of the spike leads to an underestimate of the disordered phase, while a 10% underestimate leads to a 88 CHAPT ER IV general overestimate. The converse holds for all other phases in the mixture, as the refined weights are compelled to increase by the normalization criterion (Fig. 4.3). To correct for microabsorption, a Brindley radius of 2.5 um was used for al l phases (Brindley 1945). Scanning electron microscopy showed that the radii of carbonate particles were seldom greater than 2.5 um, while particles of magnetite and quartz frequently exceeded this value. The radii of approximately one-half of magnetite and quartz particles are within the range 3.0 to 5.0 um. These observations suggest that the harder minerals are more resistant to particle-size reduction via mill ing. Serpentine particles, chrysotile in particular, were significantly larger than those for other phases with most particle radii falling within the range of 5.0 - 7.5 um. The serpentines were the only phases in the mixtures to be ground for less than 17 minutes, as grinding times in excess of 10 minutes were found to cause deterioration of the crystal structure. Laser- diffraction based particle-size analysis gave average particle diameters of 3.40 um (r = 1.70 um) and 4.00 urn (r = 2.00 urn) for the antigorite stock mixture ( " A l " ) and the 50 wt.% antigorite sample ( "AMIX50") , respectively. Based on observations in the scanning electron microscope, the results of the laser-diffraction based analyses, and the fact that an accurate estimate of particle size for each phase is not practical, a Brindley radius of 2.5 um was taken to be representative of a typical mixture. 89 C H A P T E R IV 100 Rietveld Results for Serpentine with Variable Spike ro Q) 1 1 •9 C D ) & i 0) c, CO =5* 30 20 30 40 50 60 70 80 Serpentine Abundance (Weight-% nominal) Rietveld Results for Hydromagnesite with Variable Spike 100 B i a 0 9 wt.% Spike O 10 wt.% Spike • 11 wt.% Spike I l l l 1:1 Relation 10 20 30 40 Hydromagnesite Abundance (Weight-% nominal) F I G U R E 4.3: Abundance of serpentine from Rietveld refinement versus nominal abundance for three different concentrations of the fluorite spike (9, 10, and 11% CaF2): (A) serpentine; (B) hydromagnesite. 90 CHAPTER PV 4.3 R E S U L T S A N D D I S C U S S I O N 4.3.1 Synthetic M i n e Tail ings Results of quantitative phase analysis for the synthetic serpentine mine tailings are displayed in Table 4.3 and Figures 4.3, 4.4, and 4.5. Measured abundance versus the nominal abundance for most phases deviates slightly from the ideal 1:1 trend (Fig. 4.5). The deviation results at least in part from the large increase in relative error for the refinements of minor phases. Raudsepp et al. (1999) and Dipple et al. (2002) report that for the conditions of data collection used in our laboratory, the relative error increases rapidly for measurements of concentrations below 6 wt.%. While the relative error is high for phases of less than approximately 6 wt.%, the absolute errors are small (Fig. 4.6). The relationship between absolute and relative errors is typical for measurements of hydromagnesite (Fig. 4.7). The relative error in the amount of hydromagnesite increases with decreasing abundance, but the corresponding absolute error is well within the range for estimates of mineral binding of CO2. A 5% relative error can be expected on estimates of hydromagnesite content for abundances greater than 10 wt.%. Relative error is expected to increase as hydromagnesite abundance approaches the 1 wt.% detection limit of our X-ray data. A relative error of 10 to 15% is expected for hydromagnesite abundances less than 10 wt.%. Thus, precise and accurate estimates of hydrated magnesium carbonate abundance can be made for samples containing 91 C H A P T E R IV T A B L E 4.3: Results of quantitative phase analysis of synthetic serpentinite mine tailings. Phase (wt.%) AMIX10 AMIX30 AMIX50 AMIX70 AMIX90 CMIX10 CMIX30 CMK50 CMIX70 CMIX90 ACMIX10 ACMIX30 Chrysotile 8.45 29.38 53.40 71.49 90.66 11.11 31.20 52.08 67.93 88.92 8.15 29.58 difference 1.55 0.62 3.40 1.49 0.66 1.11 1.20 2.08 2.07 1.08 1.85 0.42 Magnetite 37.79 27.90 18.26 12.18 3.83 34.11 26.28 18.54 10.79 3.38 37.65 26.81 difference 1.79 0.10 1.74 0.18 0.17 1.89 1.72 1.46 1.21 0.62 1.65 1.19 Quartz 17.19 14.11 10.57 5.97 2.16 16.60 13.90 9.79 5.99 2.25 16.88 13.55 difference 0.81 0.11 0.57 0.03 0.16 1.40 0.10 0.21 0.01 0.25 1.12 0.46 Calcite 7.81 7.20 3.15 1.95 0.35 9.73 7.37 4.85 4.51 1.36 8.63 6.88 difference 1.19 0.20 1.85 1.05 0.65 0.73 0.37 0.15 1.51 0.36 0.37 0.12 Dolomite 9.51 6.91 3.82 3.57 1.20 9.33 6.82 4.40 3.09 1.41 8.88 8.24 difference 0.51 0.09 1.18 0.57 0.20 0.33 0.18 0.60 0.09 0.41 0.12 1.24 Magnesite 11.28 8.69 6.18 2.35 0.75 11.22 8.26 6.08 4.81 1.90 10.98 7.91 difference 1.85 1.35 0.94 0.79 0.30 1.79 0.93 0.84 1.66 0.85 1.55 0.58 Hydromagnesite 7.97 5.82 4.61 2.48 1.05 7.90 6.17 4.26 2.88 0.77 8.83 7.04 difference 0.60 0.85 0.15 0.37 0.10 0.68 0.50 0.50 0.02 0.18 0.26 0.38 Total 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 x 2 1.76 1.89 2.15 1.89 2.20 1.20 1.17 1.14 1.19 1.26 1.37 1.31 8.08 8.22 8.33 7.10 6.80 9.45 8.27 7.67 7.37 6.95 8.19 7.03 * %2 is the reduced chi-squared statistic for the least-squares fit. f Rwp is the weighted pattern index, a function o f the least-squares residual. 92 C H A P T E R rV T A B L E 4.3 (Continued): Results o f quantitative phase analysis of synthetic serpentinite mine tailings. Phase (wt.%) ACMIX50 ACMIX70 ACMLX90 HMIX1 HMLX2 HM1X3 HMIX4 HMIX5 HMIX6 HMIX7 HM1X8 HMIX9 Chrysotile 57.00 71.57 88.68 90.80 80.47 52.83 79.87 46.02 68.03 59.38 difference 7.00 1.57 1.32 0.80 0.47 2.83 0.13 1.02 1.97 0.62 Magnetite 14.96 10.95 3.89 8.70 4.45 4.64 4.74 10.45 difference 5.04 1.06 0.11 1.30 0.55 0.36 0.26 0.45 Quartz 9.88 5.82 2.24 5.37 4.73 50.61 41.19 difference 0.12 0.18 0.24 0.37 0.27 0.94 1.19 Calcite 4.44 2.82 1.81 6.00 5.78 9.64 9.57 difference 0.56 0.18 0.81 1.00 0.78 0.29 0.43 Dolomite 6.27 3.26 1.02 10.96 10.05 difference 1.27 0.26 0.02 0.37 0.05 Magnesite 3.23 3.01 1.07 0.32 0.77 2.27 1.38 2.01 1.08 2.16 11.24 11.68 difference 2.01 0.14 0.02 0.16 0.18 0.12 0.90 0.38 0.37 0.97 0.36 0.73 Hydromagnesite 4.22 2.58 1.28 8.89 18.76 44.90 10.05 47.52 14.88 23.22 17.54 17.07 difference 0.54 0.28 0.33 0.64 0.29 2.71 0.53 0.09 0.60 0.59 1.38 1.98 Total 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 x 2 1.25 1.30 1.40 1.37 1.40 1.47 1.21 1.43 1.32 1.27 1.67 1.43 6.07 5.79 5.37 7.09 7.19 7.25 7.12 7.62 7.38 7.26 9.49 9.56 * %2 is the reduced chi-squared statistic for the least-squares fit. t Rwp is the weighted pattern index, a function o f the least-squares residual. 93 C H A P T E R IV 4,000 3,000 2-theta (Degrees) F I G U R E 4.4: Rietveld refinement plot, A C M I X 7 0 . Uppermost line - observed data overlain by calculated pattern; black line below - residual pattern; vertical lines - positions of Bragg reflections for each phase; curves under the observed and calculated patterns - calculated patterns of each phase. Axes are intensity (counts) versus 29 (degrees). 94 CHAPTER IV 100 Serpentine Calcite # 12 g> 8 c ro 73 c D O X o B / 0 g Hydromagnesite 5 60, 40 20 Magnetite Quartz B 100 0 Dolomite 12 0 40 0 12 X Values o V< O H o o o 0 0 8 8 ^ 0 9 8 8 30 60 Magnesite F 6 $K o / 12 0 Antigorite o Chrysotile • Antig/Chrys -1:1 Relation 30 60 0 50 100 Mineral Abundance (Weight-% Nominal) FIGURE 4.5: Modal abundances from Rietveld refinement versus nominal abundances in synthetic serpentinites. 95 C H A P T E R IV 10 Absolute Error on Serpentine Minerals 5 h 0 Antigorite O Chrysotile • Antig/Chrys o 10 10 20 30 40 50 60 70 Absolute Error on Mixture Phases 80 90 100 + Magnetite •ir Quartz X Calcite A Dolomite * Magnesite O ) p 5 B + t - M - •6 i 30 40 50 60 70 Absolute Error on Hydromagnesite 80 90 100 30 40 50 60 70 Mineral Abundance (Weight-% Nominal) 80 90 100 F I G U R E 4.6: Absolute (wt.%) error in estimates for all minerals versus the abundance of that mineral in a sample. 96 C H A P T E R FV o Error in Hydromagnesite for all Mixtures o • Absolute Error O Relative Error O o - ° o 8 O O O O o o X o • • 10 20 30 Hydromagnesite Abundance (Weight-% Nominal) 40 50 F I G U R E 4.7: Relative and absolute (wt.%) error in Rietveld estimates of hydromagnesite abundance for all synthetic samples. 97 C H A P T E R TV disordered mineral phases such as kaolinite-serpentine group minerals. Note that the type of serpentine used in the weighed mixtures has no significant effect on the results of the Rietveld refinement (Figs. 4 .5A and 4.6A). We do not know why the abundance of hydromagnesite is consistently underestimated at low abundances. It was initially thought that the original hydromagnesite used in the mixtures was not entirely crystalline; however, Rietveld refinements of pure hydromagnesite do not show evidence of significant deterioration of crystallinity with increased grinding time during preparation of the mixtures. Preferred orientation of hydromagnesite crystallites could also lead to severe underestimates of modal abundance, although this had largely been accounted for. The data, as reported in Table 4.3 and Figures 4.4-4.7, has already been corrected to account for the 4.8 % magnesite impurity in the hydromagnesite, a correction which failed to adequately explain the misestimates obtained for these two minerals. To determine whether the hydromagnesite was becoming nanocrystalline with increased grinding time, conventional Rietveld refinements were done on the X R P D data collected after 0, 7, and 17 minutes of grinding in the micronising mi l l (Fig. 4.8). The relative intensities of the hydromagnesite and magnesite patterns do not change with grinding, although the absolute intensities decreased as a result of the dilution effect (caused by contamination from the corundum grinding elements). These underestimates may be an artefact of the Pawley fitting procedure or the result of amorphous content in the CaF2 spike. A s such, there is no need for concern that estimates of carbonate abundance are being compromised by deterioration of crystallinity due to grinding. 98 C H A P T E R IV 7.000 6,000 5,000 4.000 3,000 2,000 1,000 0 -1.000 -2.000 0 minutes grinding Hydromagnesite95 23 % Magnesite 4.77 % 7.000 6.000 5,000 4,000 3,000 2.000 1,000 0 -1,000 -2,000 7 Iminutes gririding vj Magnesite 4.11 % Hydromagnesite86.69 "A Corundum 9.20 % — < l | , » v '"i\'y i Fn .n . . . . . . . - . . . I jjttBaeastes jeHi 30 40 50 60 4.800 3.000 Magnesite 3.38 % Hydromagnesite67.96 % Corundum 28.65 % -^—.'rY'y'^'-^'i' "'•'••'V* V** F I G U R E 4.8: Refinement results used to determine the percent magnesite contamination in the "pure" hydromagnesite sample. Relative abundances o f hydromagnesite and magnesite remain identical, with increased grinding, to within 5% relative. The curve within the observed pattern represents corundum contamination due to grinding. 99 C H A P T E R IV Accurate determination of carbonate mineral abundances in synthetic geological samples bodes well for implementing the Rietveld method as a standard for assessing carbonate precipitation in mine tailings. Furthermore, this procedure can be applied to the measurement of acid neutralization potential of carbonate minerals in acid-generating mine tailings containing disordered mineral phases. 4.3.2 Natural Mine Tailings Two samples of mine tailings from Cassiar, B C (04CA0601 and 03CA1601), and six samples from Clinton Creek, Y T (04CC0702, 04CC0703, 04CC1001, 04CC1201, 04CC1401, and 05CC8) were analyzed using the method developed for synthetic serpentinites. Samples 03CA1601 and04CC1401 are samples of bulk tailings. Samples 04CA0601, 04CC0703, 04CC1001, and 04CC1201 are from vertical carbonate crusts. 04CA0702 is a carbonate spire and 05CC8 is a sample containing disseminated carbonate cement. In addition, two samples from a hydromagnesite playa in At l in , B C , were analyzed as an example of natural hydrated magnesium carbonate samples lacking serpentine. The results of quantitative phase analysis are given in Table 4.4. Bulk samples from Clinton Creek and Cassiar contain serpentine in excess of 80 wt.% (Table 4.4). Where present, dolomite, magnesite, quartz, and pyroaurite constitute minor components; magnetite concentrations range from 5.1 to 8.1 wt.%. Bulk geochemical data for most samples give Fe203 values in the range of 5 to 9 %, which is consistent with the results from Rietveld refinement, assuming that most of the iron was 100 C H A P T E R IV T A B L E 4.4: Results of quantitative phase analysis of natural serpentinite mine tailings renormalized to exclude 10% fluorite spike. Locality Cassiar Cassiar Clinton Clinton Clinton Clinton Clinton Clinton Clinton Clinton Atlin Atlin Creek Creek Creek Creek Creek Creek Creek Creek Predominant serpentine phase Chrysotile Chrysotile Chrysotile Chrysotile Chrysotile Chrysotile Chrysotile Chrysotile Chrysotile Chrysotile None None Mode Bulk Vertical Crust Bulk Spire Spire Cap Vertical Crust Crust Cap Vertical Crust Vertical Crust Cement Playa Playa Phase 03CA1601 04CA0601 04CC1401 04CC0702 04CC0702 04CC0703 04CC0703 04CC1001 04CC1201 05CC8 03ATC3-A 03ATC3-I Serpentine 87.62 89.42 88.35 77.95 59.49 81.33 32.34 81.13 83.33 77.30 Palygorskite 1.63 4.37 2.82 1.17 1.52 1.52 Magnetite 6.74 5.10 8.06 4.46 1.78 6.85 2.22 4.90 5.29 3.09 Quartz 3.07 0.50 1.13 0.46 0.63 0.48 0.35 0.82 Dolomite 2.56 Magnesite 0.77 1.36 1.53 2.22 7.12 9.42 1.41 Nesquehonite n/d 5.48 n/d 5.89 15.04 1.81 46.95 5.05 Hydromagnesite n/d n/d 2.18 8.43 17.48 7.72 12.25 5.39 5.84 8.72 90.58 98.59 Pyroaurite 0.14 0.51 1.38 0.30 2.94 0.48 1.38 Brucite 0.98 0.87 Total 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 x2 1.40 1.21 1.35 1.14 1.32 1.22 1.29 1.24 1.23 1.26 2.02 2.26 8.06 6.77 7.74 6.37 7.05 6.92 6.47 7.01 7.04 7.02 8.87 9.71 * x2 is the reduced chi-squared statistic for the least-squares fit. f Rwp is the weighted pattern index, a function o f the least-squares residual. % n/d means that the mineral phase was not detected above the 1 wt.% limit. 101 C H A P T E R IV partitioned into magnetite during serpentinization of the original peridotite (Wicks and Whittaker 1977). The sample of bulk tailings from Cassiar (03CA1601) contains no detectable hydrated magnesium carbonate minerals to a detection limit of 1 wt.%, whereas the sample of bulk tailings from Clinton Creek (04CC1401) contains 2.2 wt.% hydromagnesite. The disseminated cement from Clinton Creek, 05CC8, contains 8.72 wt.%) hydromagnesite. If the entire tailings pile at Clinton Creek contains hydromagnesite at the lower abundance found for 04CC1401, then a total of 82 000 tonnes of CO2 bound within minerals at this site. The crust samples (04CA0601, 04CC0703, 04CC1001, and 04CC1201) contain more than 5 wt.% hydrated magnesium carbonate minerals. These crusts, grown on vertical tailings surfaces, are readily identified in the field as hydrated carbonates based on colour, habit, and reaction to dilute HCI . The crust sampled from the tailings at Cassiar contains 5.5 wt.% nesquehonite. Sample 04CC0703 from Clinton Creek contains 7.7 wt.% hydromagnesite and 1.8 wt.% nesquehonite (Fig. 4.9). Analysis of the top 1 to 2 mm of sample 04CC0703 shows that it contains 47 wt.% nesquehonite and 12 wt.%o hydromagnesite. The same trend is observed in the carbonate spire sample, 04CC0702 (and for 04CC1001 and 04CC1201); with increasing depth, below the surface o f the carbonate crust or spire, hydromagnesite becomes more abundant than nesquehonite. Trace dypingite (below 1 wt.%) is observed in x-ray powder diffraction patterns for all the carbonate crust and spire samples. Dypingite is a metastable mineral phase, which can be created as nesquehonite decomposes to hydromagnesite (Davies and 102 C H A P T E R IV 2,500 2,000 1,500 tn c 1.000 o O — 500 -500 -900 Nesquehonite Hydromagnesite A. tL . . ^ Hi ' 4 . «̂ ŷ :̂,,jî ĵ y\jyii..ŷ ^^ I I I I I I I i i 1 1 I I i I I I i i II i II i i i n i mi {Inn II mi : V i 1 ; i i ^ ^ * :l : i i : M V mill nj II mi n II i un i im 11 li i l ill M I ill iiiniiiili i n i II ̂ i  in 1 1 1 | l i | i \'jA I fl 111 Mli1". V i'll!ili,i,l?Vil.liii'!Mfl'ti'!ililj'"",i!l,ljiV' I i U I 1 -i 1 | l ; ' ' " " ' L U 10 20 30 40 50 60 70 2-theta (Degrees) F I G U R E 4.9: Rietveld refinement plot of a chrysotile mine residue from Clinton Creek, Y T (04CC0703). Uppermost lines - observed data overlain by calculated pattern; black line below - residual pattern; vertical lines - positions of Bragg reflections for each phase; curves under the observed and calculated patterns - calculated patterns of each phase. Axes are intensity (counts) versus 20 (degrees). 103 C H A P T E R TV Bubela 1973; Canterford et al. 1984). Hydromagnesite in the tailings at Clinton Creek may be a product of the decomposition of nesquehonite forming in contact with the atmosphere. Decomposition of nesquehonite in mine tailings does not appear to be a function of humidity, but rather a function of age, with the metastable minerals forming at the interface between the tailings and the atmosphere, and the older carbonate precipitates dehydrating to increasingly stable mineral phases at depth (Fig. 4.10). The core samples taken from the hydromagnesite swamp in At l in , B C , both contained in excess of 90 wt.% hydromagnesite. A modern sample, 0 3 A T C 3 - A , was taken from the top of the core at the surface of the swamp. 03ATC3-I was taken from asection 50.5 cm beneath the surface. A clear trend toward decreasing magnesite abundance with depth has been observed at At l in , with sample 0 3 A T C 3 - A possessing the most magnesite in the core and 03ATC3-I having the least. A series of previous studies of hydromagnesite playas located on the Cariboo Plateau, interior British Columbia, indicates that magnesite commonly becomes more abundant at depth within hydromagnesite mudflats on the periphery of alkaline playas, while magnesite dominates at the surface of modern lacustrine deposits during the summer months when the playas have desiccated (e.g., Renaut and Long 1989; Renaut 1990; Renaut and Stead 1991). Possible cyanobacterially-mediated precipitation of magnesite has been observed in the laboratory by Thompson and Ferris (1990); however, direct precipitation of magnesite is thought to be kinetically inhibited in most lacustrine environments (refer to Zedef et al. 2000 for a brief review). The increased weight-percent abundance of magnesite at the 104 C H A P T E R r V F I G U R E 4.10: Detailed mineralogy for modal occurrences of hydrated magnesium carbonate crusts in serpentine-rich mine tailings: A ) carbonate spire from horizontal tailings surface, B) crust on serpentinite cobble, and C) carbonate crust from vertical tailings surface. 105 C H A P T E R TV surface of the At l i n playas may be the result of dehydration of hydromagnesite in contact with the atmosphere. Hydromagnesite playas, like those found in At l in , represent an analogue to the potential end-state of mineral carbonates in serpentinite mine tailings. These natural carbon sinks provide valuable insight into the long-term stability of hydrated magnesium carbonate minerals and the environmental impact of carbon disposal in mine tailings. Playa deposits at A t l i n conformably overly glacial sediments (Grant 1987), suggesting an early Holocene age. Furthermore, a decrease in 1 4 C content with depth in the A t l i n playa deposits is consistent with hydromagnesite precipitation over the past several thousand years (Wilson and Dipple, unpublished data). Possible evidence of decomposition of hydromagnesite to magnesite has been observed at depth within the playas of the Cariboo Plateau of interior British Columbia (Renaut and Stead 1991) and at the surface of the playas in At l in . Morphological and isotopic similarities between modern hydromagnesite playas at Salda Gol i i , western Turkey, and sedimentary magnesite deposits at Hirsizdere, Turkey, and Bela Stena, Serbia, may be demonstrative of large-scale diagenetic alteration of hydromagnesite to magnesite (Braithwaite and Zedef 1996; Zedef et al. 2000). The magnesite deposits at Hirsizdere are interbedded with Pliocene lacustrine sediments, indicating long-term stability of sedimentary magnesite on a geologic timescale. Provided that hydromagnesite playas generally dewater at depth, this process is analogous to the transformation of nesquehonite to dypingite followed by dehydration to hydromagnesite 106 C H A P T E R TV (or dehydration of lansfordite to nesquehonite, which transforms to dypingite, etc.) with increasing depth within serpentinite mine tailings (Fig. 4.11). Transformation of nesquehonite to magnesite in mine tailings would allow CO2 to be stored in a mineral phase which is potentially stable on a timescale of millions of years. Disposal of CO2 in magnesite optimizes both the thermodynamic stability and amount of bound carbon: nesquehonite, lansfordite, and magnesite have a CO2 to M g ratio of 1 per formula unit, while dypingite and hydromagnesite have a ratio of 4/5. During the decomposition of nesquehonite, one CO2 molecule per formula unit is liberated to produce the more stable hydromagnesite phase. The optimal ratio of C C V M g is regained upon decomposition to magnesite. Magnesite production is widespread within hydromagnesite playas, and w i l l likely be the end-product of mineral sequestration in serpentinite mine tailings. The amount of atmospheric CO2 that has been crystallographically bound in mineral form can be estimated from the Rietveld results for weight-percent abundance of hydrated magnesium carbonates (Table 4.5). A conservative estimate for total bound CO2 can also be estimated using the refinement results for 03 CC1601 for Cassiar and using 05CC8 and 04CC1401 to set the upper and lower limits, respectively, on bound CO2 at Clinton Creek. A s has been previously stated, a 5 to 15 % relative error is likely to apply to these estimates. This high degree of accuracy cannot be readily obtained with other methods of quantitative phase analysis. Application of this method to other geologic systems should be approached with due caution. The Rietveld method for X-ray powder diffraction can only be used 107 C H A P T E R I V 10° 101 102 103 104+ Carbonate Age (years) F I G U R E 4.11: Evolution of magnesium-carbonate mineral phases and bound carbon per mole cation ( M g 2 + ) during dehydration in a mine-tailings carbon-disposal site. 108 C H A P T E R I V T A B L E 4.5: Estimated amounts of atmospheric CO2 crystallographically bound in serpentinite mine tailings. Sample Occurrence Type CO2 Sequestered (g/kg tailings) CO2 Potentially Sequestered (in tailings pile) 04CA1601 Bulk <3.8 <64.6 kt T 04CA0601 Vertical Crust 17.4 04CC1401 Bulk 8.2 82.0 kt 1 04CC0702 Spire 50.5 04CC0703 Vertical Crust 34.8 05CC8 Cement 32.8 328 kt* * Where the upper limit on the amount of sequestration occurring in 04CA1601 has been calculated from the 1% detection limit. f For 17 M t of mine tailings at Cassiar, B C . X For 10 M t of mine tailings at Clinton Creek, Y T . 109 C H A P T E R IV indirectly as a tool for elemental analysis. A s such, estimation of bound CO2 is only feasible for phases with minor solid solution. Successful characterization of the tailings from Cassiar and Clinton Creek is due in part to the negligible solid solution to which the hydrated magnesium carbonate minerals are subject. This method does not account for additional amorphous phases and cannot be used to quantify more than one disordered phase per sample. The use of the Pawley method for complicated mineral phases may cause low-abundance mineral phases to be underestimated in refinements. Misestimates of disordered phases are likely to occur at low abundance (i.e., < 5 wt.%) due to limitations in the fundamental parameters approach and preferred orientation corrections, and the way in which complex Pawley phases usurp peaks from other phases. The effect of grinding time on the crystallinity of ordered phases should be considered prior to application of this method to any geological or synthetic samples. 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Economic Geology, 95, 429-446. 118 C H A P T E R V CHAPTER V: Conclusions Atmospheric carbon dioxide is being crystallographically bound in hydrated magnesium carbonate minerals in the mine tailings piles at Clinton Creek, Yukon and Cassiar, B . C . Although the rate of natural mineral carbonation in mine tailings is trivial to the global carbon cycle, study of this process provides valuable insight into the pathways by which mineral carbonation occurs. Metastable Mg-carbonate minerals grow as efflorescences on vertical and horizontal tailings surfaces, as coatings on cobbles of serpentinite, and as disseminated cements within the tailings. Magnesium cations are derived from weathering of chrysotile fibres and carbon dioxide and bicarbonate are brought into contact with M g - rich solutions through dissolution in meteoric water. Precipitation of lansfordite and nesquehonite occurs subaerially by evaporation and/or freeze-out, at the surface of the mine tailings, giving rise to atmospheric values for 5 I 3 C and an evaporative 8 1 8 0 signature. A t depth within the tailings piles, within crusts and spires, and on the sheltered surfaces of serpentinite cobbles, dypingite and hydromagnesite are forming. These minerals precipitate under less extreme evaporative conditions and within an increasingly C-rich microbial atmosphere. The covariation in 8 C and 8 O values displayed for carbonate samples from Clinton Creek and Cassiar is representative of a transition between the subaerial, environment in which lansfordite and nesquehonite develop and the C-depleated, microbially-mediated environments in which dypingite 119 C H A P T E R V and hydromagnesite form. Isotopic fingerprinting has confirmed that the ultimate source of carbon dioxide for all hydrated magnesium carbonates is the atmosphere. It may be feasible to modify historical and active tailings environments to increase the rate and scale of carbonation to achieve appreciable uptake of atmospheric CO2. One possibility is to mi l l the tailings more finely to increase surface area and thereby accelerate the rate of silicate dissolution. More thorough mechanical separation of individual fibres and fine mil l ing of massive serpentine could increase the rate of silicate dissolution and CO2 uptake from the atmosphere. It may also be possible to mediate precipitation of. magnesium carbonates with salinity, M g / C a ratios, and microbes; tailings environments may be re-engineered accordingly, driving carbonation reactions toward more stable phases such as hydromagnesite and magnesite. Skimming of carbonate crusts from the surface of tailings and subsequent indoor storage may become necessary in environments with high annual precipitation as a measure to prevent dissolution. Also , by uncovering fresh tailings surfaces it is likely to renew more vigorous reaction with the atmosphere. The Rietveld method for X-ray powder diffraction data provides a precise and accurate means by which the amount of carbon dioxide bound in carbonate minerals can be quantified (Chapter 4). The characteristic planar disorder associated with the serpentine-kaolinite group minerals has been overcome using structureless pattern fitting and a mineral spike to model the disordered minerals as amorphous phases. The accuracy and precision of this refinement method has been tested using synthetic serpentine-rich mine tailings of known composition. Estimates of the abundance of 120 C H A P T E R V hydrated magnesium carbonates in these tailings have a precision of 5 to 15% relative for mineral species present in amounts greater than 10 wt.%. The application of this method to natural tailings samples from Clinton Creek and Cassiar has allowed for precise estimates of carbonate mineral content and crystallographically-bound atmospheric CO2. Rietveld results for mine tailings have been compared to mineralogically similar samples from a carbonate playa at At l in , British Columbia. Possible dehydration of metastable hydrated magnesium carbonate phases to geologically stable minerals in mine tailings and carbonate playa lakes is representative of long-term stability of the products of mineral sequestration in mine tailings. Furthermore, evidence for microbially-mediated precipitation of dypingite and hydromagnesite in mine tailings suggests that mineral carbonation reactions can be driven to produce more stable hydrated magnesium carbonate phases in regions of high photosynthetic activity. The Rietveld method for quantitative phase analysis and isotopic fingerprinting are an effective verification protocol for carbon storage in mine tailings. Stable and radiogenic isotopes confirm an atmospheric source for CO2 and the Rietveld method quantifies crystallographic trapping. The goal of this research has been to provide an initial characterization of natural mineral carbonation processes in the mine tailings environment and to introduce a procedure by which sequestration of atmospheric and anthropogenic carbon dioxide can be both confirmed and quantified. The next step in developing a framework for economically feasible, large-scale carbon sequestration in mine tailings w i l l be to apply the results of this work to demonstration projects in active mining environments. 121 A P P E N D I X A APPENDIX A: Whole-rock geochemistry for Clinton Creek and Cassiar Bulk geochemical analysis was done on 22 samples from Cassiar and 21 samples from Clinton Creek for major element oxides, N i , V , Z n and volatiles (Tables A l and A2) . The most striking distinction between the tailings samples from the two localities is the difference in CO2 content. Carbon dioxide abundance at Cassiar ranges from 0.29 ± 0.01 % to 1.06 ± 0.01 %, while reaching values high as 5.38 ± 0.01 % at Clinton Creek and averaging 2.78 ± 0.01 %. The high bedrock carbonate content of the tailings at Clinton Creek is expressed in the results for bulk geochemical analysis and carbon dioxide content can be quantified from these data. There is however, no means by which to determine the source; bedrock carbon, anthropogenic carbon, and atmospheric carbon are indistinguishable. The source of carbon must be identified by the fractionation of light stable isotopes, as has been done with carbon and oxygen (Chapter 3). The amount of atmospherically-derived carbon crystallographically-bound within carbonate mineral phases cannot be determined from these data, necessitating the use of the Rietveld method (Chapter 4). 122 A P P E N D I X A T A B L E A l : Bulk geochemical analyses for Cassiar. Results for the abundance of major element oxides are expressed as weight- percent values. Trace element abundances and detection limits are expressed in parts per mil l ion (ppm). The total iron present in each sample has been recalculated as Fe203. 3c detection limits have been employed. Sample Si0 2 T i 0 2 A I 2 O 3 Fe 2 0 3 MnO MgO CaO Na 20 K 2 0 p2o5 Cr 2 Oj Ni V Zn LOI Total C 0 2 (%) H 2 0- H 20+ MMI03-1-1 39.33 0.021 1.37 7.83 0.082 38.09 0.19 0.12 0.12 0.011 4010 2028 44 13 12.97 100.74 0.32 2.62 11.09 MMI03-1-2 38.56 0.018 1.00 8.00 0.094 39.31 0.04 0.07 0.02 0.008 3592 2174 41 12 13.16 100.86 0.47 2.92 14.09 MMI03-1-3 38.47 0.024 1.14 9.14 0.100 38.35 0.04 0.07 0.04 0.009 4141 2214 38 21 12.79 100.81 0.35 2.62 10.66 MMI03-1-4 38.40 0.018 0.98 8.57 0.092 39.13 0.02 0.05 0.01 0.008 3618 2216 38 7 13.03 100.90 0.42 2.50 10.97 MMI03-1-5 38.01 0.016 0.99 9.09 0.087 38.75 0.03 0.03 0.01 0.008 3650 2279 42 9 13.14 100.76 0.35 2.79 10.98 MMI03-1-6 38.03 0.021 1.09 8.63 0.104 38.73 0.07 0.09 0.02 0.009 4582 2236 42 29 13.26 100.74 0.41 2.95 11.81 MMI03-1-7 38.23 0.019 1.05 8.73 0.103 38.83 0.10 0.05 0.01 0.008 4212 2246 42 20 13.07 100.85 0.35 3.06 11.88 MMI03-1-8 38.09 0.018 0.98 9.16 0.095 38.70 0.04 0.10 0.01 0.009 3503 2281 39 11 13.11 100.90 0.40 2.98 10.82 MMI03-1-9 38.28 0.025 1.10 9.99 0.101 37.77 0.12 0.08 0.05 0.009 3980 2295 45 20 12.79 100.95 0.40 1.18 9.93 MMI03-1-10 38.04 0.017 0.96 8.48 0.094 38.95 0.07 0.06 0.01 0.008 2959 2248 37 <d/l 13.43 100.64 0.48 0.91 9.51 MMI03-1-11 38.43 0.017 1.10 7.91 0.087 39.10 0.05 0.07 0.01 0.008 3609 2265 42 4 13.35 100.72 0.38 0.84 9.77 MMI03-1-12 38.58 0.028 1.18 8.86 0.093 38.30 0.22 0.07 0.02 0.009 3459 2261 42 8 12.96 100.90 0.33 2.05 10.07 03CA03-02 38.51 0.021 1.03 8.10 0.091 39.08 0.04 0.06 0.02 0.008 4062 2261 42 20 13.03 100.63 0.33 0.71 11.18 03CA06-01 39.55 0.022 1.11 7.36 0.094 38.55 0.10 0.05 0.04 0.011 3308 2166 43 7 13.29 100.73 0.66 0.37 11.65 03CA06-02 39.04 0.025 1.12 7.96 0.086 38.85 0.05 0.06 0.02 0.009 3422 2214 46 6 12.95 100.74 0.32 1.69 11.11 03CA06-03 39.22 0.031 1.22 7.69 0.094 38.76 0.16 0.05 0.02 0.009 3784 2260 44 12 12.76 100.62 0.34 2.24 10.35 03CA07-01 38.52 0.018 1.03 8.45 0.095 38.60 0.03 0.10 0.03 0.009 3338 2181 39 6 13.18 100.62 0.53 1.76 11.19 03CA07-02 38.73 0.019 1.08 8.23 0.100 38.77 0.02 0.09 0.03 0.010 4185 2231 41 30 13.03 100.76 0.46 0.09 11.60 03CA08-01 38.77 0.025 1.15 8.40 0.104 38.28 0.11 0.09 0.04 0.011 3597 2205 40 16 13.20 100.77 1.06 4.16 9.55 03CA08-02 38.36 0.021 1.07 9.13 0.101 38.15 0.06 0.08 0.03 0.010 3978 2341 40 21 12.93 100.58 0.42 0.33 17.28 03CA09-01 38.79 0.018 0.98 7.47 0.096 38.98 0.04 0.08 0.03 0.011 2787 2261 39 35 13.86 100.87 0.67 2.33 8.80 03CA09-02 38.12 0.015 0.94 9.04 0.092 38.84 0.03 0.04 0.01 0.008 3790 2130 38 13 13.13 100.86 0.29 0.35 9.90 Detection Limits 60 35 120 30 30 95 15 75 25 35 15 3 10 2 100 0.01% 123 A P P E N D I X A T A B L E A 2 : Bulk geochemical analyses for Clinton Creek. Abundances of major element oxides are expressed as weight-percent values. Trace element abundances and detection limits are expressed in parts per mill ion (ppm). The total iron present in each sample has been recalculated as Fe203. 3a detection limits have been employed. Sample Si0 2 T i 0 2 A1 20 3 Fe 2 0 3 MnO MgO CaO Na 20 K 2 0 P 2 O s C r 2 0 3 Ni V Zn LOI Total C 0 2 (%) H 2 0- H 20+ 03CC01-A 36.62 0.030 0.93 7.90 0.093 38.82 0.50 0.04 0.01 0.009 4238 2288 33 12 15.16 100.77 2.71 0.48 10.38 03CC01-B 52.47 0.019 0.68 5.31 0.074 26.81 0.55 0.06 0.04 0.010 4867 1741 29 2 13.22 99.91 4.23 2.14 7.77 03CC01-C 37.81 0.044 1.31 7.19 0.100 37.45 0.52 0.07 0.04 0.012 4072 2090 34 21 15.20 100.37 3.08 0.67 9.53 03CC01-D 36.91 0.042 1.14 9.11 0.100 37.51 0.76 0.08 0.02 0.010 3976 2256 41 14 14.18 100.49 2.00 1.63 10.49 03CC0201A 33.76 0.026 0.71 9.09 0.098 37.72 0.82 0.09 0.02 0.009 4980 2539 23 9 17.48 100.58 5.21 1.83 10.92 03CC0201B 36.57 0.026 0.90 8.91 0.100 38.70 0.17 0.07 0.01 0.008 4191 2392 33 20 14.50 100.63 1.89 0.23 10.52 03CC0301A 36.77 0.054 1.32 8.24 0.078 36.80 1.25 0.07 0.09 0.019 2660 2260 36 <d/l 15.39 100.58 3.30 0.72 9.80 03CC0301B 35.86 0.029 1.13 6.90 0.066 39.45 0.18 0.06 0.01 0.009 25350 2315 45 41 14.26 100.73 1.47 0.34 8.92 03CC0401A 37.51 0.052 1.27 8.61 0.083 37.60 0.71 0.09 0.05 0.016 2423 2192 36 <d/l 14.47 100.92 1.97 3.22 9.86 03CC0401B 38.81 0.031 0.91 6.62 0.108 39.50 0.20 0.05 0.02 0.010 4185 2359 36 20 13.73 100.65 0.64 2.03 9.93 03CC0501A 36.71 0.037 1.02 8.38 0.074 38.26 0.53 0.06 0.04 0.013 2424 2136 34 <d/l 14.94 100.52 2.04 0.81 10.74 03CC0601A 37.04 0.046 1.12 8.02 0.090 38.36 0.61 0.04 0.03 0.013 3732 2614 34 <d/l 14.75 100.76 2.61 1.38 10.36 03CC0601B 36.72 0.036 1.05 8.50 0.099 38.58 0.36 0.06 0.01 0.010 3856 2373 39 9 14.70 100.75 1.51 0.77 9.23 03CC0701A 37.04 0.066 1.59 8.41 0.079 36.16 0.75 0.10 0.07 0.026 2140 2127 42 <d/l 15.86 100.58 5.38 0.62 9.60 03CC0701B 36.73 0.063 1.52 8.91 0.081 36.40 1.11 0.11 0.05 0.019 2192 2181 38 <d/l 14.85 100.28 2.95 3.51 9.99 03CC0801A 36.66 0.053 1.34 9.17 0.085 37.14 0.92 0.09 0.04 0.015 2579 2185 37 <d/l 14.73 100.72 2.94 3.05 9.76 03CC0801B 35.76 0.045 1.00 9.40 0.095 37.92 0.70 0.10 0.02 0.011 3841 2291 31 2 15.26 100.93 3.40 1.15 9.28 03CC0901A •36.85 0.058 1.42 9.21 0.083 36.98 0.87 0.08 0.05 0.018 2198 2129 40 <d/l 14.76 100.81 3.01 2.62 10.09 03CC0901B 39.13 0.039 0.69 5.27 0.058 39.63 0.51 0.07 0.01 0.011 4956 2596 21 <d/l 13.97 100.14 1.43 1.25 9.19 (BCC 1001A 35.04 0.038 1.09 9.19 0.088 37.22 1.15 0.07 0.03 0.014 2651 2329 37 <d/l 15.97 100.40 4.11 1.55 9.70 03CC1001B 36.10 0.036 1.01 8.89 0.087 38.12 0.75 0.08 0.02 0.010 2982 2325 33 <d/l 15.16 100.80 2.47 3.42 10.43 Detection Limits 60 35 120 30 30 95 15 75 25 35 15 3 10 2 100 0.01% 124 A P P E N D I X B A P P E N D I X B : X-ray powder diffraction data for qualitative analysis S U M M A R Y O F M I N E T A I L I N G S M I N E R A L O G Y The samples under study were collected during the 2003 and 2004 summer field seasons. In 2003, 23 samples were taken from Clinton Creek at the surface of the tailings pile by Bob Anderson. Bob Anderson, Gregory M . Dipple, and Mi tch Mihalynuk collected forty samples from Cassiar at depths varying from 0 to 1.7 m below the surface of the tailings pile. These samples can be characterized as crust-like material, loose tailings, or bulk auger samples. Because samples were not specifically selected for carbonate mineral content, modal abundance of carbonate phases is low in the 03 C C , 0 3 C A , and M M I 0 3 series of samples. Having set some early constraints on the appearance and the occurrence of hydrated magnesium carbonate minerals in mine residues, the goal of the 2004 field season was to find and sample carbonate-rich crusts. During this season, 19 samples of surface tailings and 11 samples from the waste rock pile were collected from Clinton Creek. Fourteen samples were collected from the surface of the tailings pile and one sample was collected from the waste rock pile at Cassiar. Mineralogical data, collected with X R P D and analysed using the I C D D PDF-4 Database in Bruker A X S Eva 10.0 software, are summarized in Tables B l , B 2 , B 3 , and 125 A P P E N D I X B B4. X-ray powder diffractograms for all smear-mounted samples and two back-mounted Rietveld samples are ordered by sample name in Figures B l through B120. 126 A P P E N D I X B T A B L E B l : Mineralogy of Cassiar samples collected during the 2003 field season. V ar ie ty  Sa m pl e A m ph ib ol e?  (A ct in ol ite ) Hydrated Magnesium Carbonates Se rp en tin e M ag ne tit e Q ua rt z C hl or ite  B ru ci te  M ic a C al ci te  D ol om ite  M ag ne si te  S id er ite  A ra go ni te  Sa m pl e V ar ie ty  Sa m pl e A m ph ib ol e?  (A ct in ol ite ) C on fir m ed  P re se nt ? A rt in ite  B ar ri ng to ni te  D yp in gi te  G io rg io si te  H yd ro m ag ne si te  La ns fo rd ite  N es qu eh on ite  Se rp en tin e M ag ne tit e Q ua rt z C hl or ite  B ru ci te  M ic a C al ci te  D ol om ite  M ag ne si te  S id er ite  A ra go ni te  Sa m pl e Bulk Auger Samples MMI03-1-1 none +* + + + + MMI03-1-1 MMI03-1-2 none +* + + MMI03-1-2 MMI03-1-3 none +* + + + MMI03-1-3 MMI03-1-4 none +* + MMI03-1-4 MMI03-1-5 none +* + + MMI03-1-5 MMI03-1-6 none +* + + + + MMI03-1-6 MMI03-1-7 none +* + MMI03-1-7 MMI03-1-8 none +* + + + MMI03-1-8 MMI03-1-9 none +* + + + MMI03-1-9 MMI03-1-10 none +* + + MMI03-1-10 MMI03-1-11 none +* + MMI03-1-11 MMI03-1-12 none +* + + + + MMI03-1-12 Confirmed present by XRD ? Near detection limit Non-fibrous actinolite Major phase in sample 127 A P P E N D I X B T A B L E B l (continued): Mineralogy of Cassiar samples collected during the 2003 field season. Hydrated Magnesium Carbonates ila ni te  V ar ie ty  Sa m pl e A m ph ib ol e?  (A cti no lU e)  C on fi rm ed  P re se nt ? Ar tin ite  Ba rr in gt on ite  D yp in gi te  G io rg io sit e H yd ro m ag ne sit e La ns fo rd ite  Ne sq ue ho ni te  Se rp en ti ne  M ag ne ti te  Q ua rt z C hl or it e B ru ci te  Sm ec ti te /M on tm or i C al ci te  D ol om it e M ag ne si te  Si de ri te  A ra go ni te  Sa m pl e 03CA01-02 none + + 03CA01-02 03CA02-02 ? +* + 03CA02-02 03CA04-02 none ? +* + + + + + 03CA04-02 03CA05-01 none +* + 03CA05-01 Crust 03CA05-02 none +* + + 03CA05-02 Samples 03CA06-01 none +* + + + 03CA06-01 03CA08-O1 none +* + + + 03CA08-01 03CA09-01 none +* + + + 03CA09-01 03CA11-01 none + + 03CA11-01 03CA12-01 none 03CA12-01 03CA15-O1 none +* + + 03CA15-01 Confirmed present by XRD '.' Near detection limit Non-fibrous actinolite Major phase in sample 128 A P P E N D I X B T A B L E B l (continued): Mineralogy of Cassiar samples collected during the 2003 field season. Hydrated Magnesium Carbonates V ar ie ty  Sa m pl e A m ph ib ol e?  (A cti no lit e) C on fi rm ed  P re se nt ? Ar tin ite  Ba rr in gt on ite  D yp in gi te  G io rg io sit e H yd ro m ag ne sit e La ns fo rd ite  Ne sq ue ho ni te  Se rp en ti ne  M ag ne ti te  Q ua rt z C hl or it e B ru ci te  D ia sp or e C al ci te  D ol om it e M ag ne si te  Si de ri te  A ra go ni te  O PX  Sa m pl e 03CA02-01 none +* + + + + + 03CA02-01 03CA03-01 none +* + + 03CA03-01 03CA03-02 none +* + + 03CA03-02 03CA03-03 +* +* + + 03CA03-03 03CA03-04 none +* + + 03CA03-04 03CA03-05 +* +* + + + 03CA03-05 03CA04-01 none +* + + 03CA04-01 Bulk (Loose 03CA06-02 none +* + + + 03CA06-02 Tailings) Samples 03CA06-03 none + + + 03CA06-03 03CA07-01 none +* + 03CA07-01 03CA07-02 none +* + 03CA07-02 03CA08-02 none +* + + 03CA08-02 03CA09-02 none +* + + 03CA09-02 03CA14-01 none + 03CA14-01 03CA15-02 none 03CA15-02 03CA16-01 none +* + 03CA16-01 Confirmed present by XRD Near detection limit Non-fibrous actinolite Major phase in sample 129 A P P E N D I X B T A B L E B 2 : Mineralogy of Cassiar samples collected during the 2004 field season. 04CA0601 is the only sample from Cassiar which has been found to contain hydrated magnesium carbonate minerals. V ar ie ty  Sa m pl e A m ph ib ol e?  (A cti no lit e) Hydrated Magnesium Carbonates Se rp en ti ne  M ag ne ti te  Q ua rt z C hl or it e M ic a T al c F el ds pa r C al ci te  D ol om it e M ag ne si te  A ra go ni te  M on oh yd ro ca lc it e Sm ec ti te /M on tm or ill an it w  O P X  Sa m pl e V ar ie ty  Sa m pl e A m ph ib ol e?  (A cti no lit e) C on fi rm ed  P re se nt ? Ar tin ite  Ba rr in gt on ite  D yp in gi te  G io rg io sit e H yd ro m ag ne sit e La ns fo rd ite  Ne sq ue ho ni te  Se rp en ti ne  M ag ne ti te  Q ua rt z C hl or it e M ic a T al c F el ds pa r C al ci te  D ol om it e M ag ne si te  A ra go ni te  M on oh yd ro ca lc it e Sm ec ti te /M on tm or ill an it w  O P X  Sa m pl e Cobble Samples 04CA02-02A +* + + + 04CA02-02A 04CA02-02B none +* + + 04CA02-02B 04CA02-02C none +* + + 04CA02-02C 04CA02-02D none +* + + + 04CA02-02D 04CA03-01A none +* + + + 04CA03-01A 04CA03-02 + + + + + 04CA03-02 04CA04-01 +* 04CA04-01 Confirmed present by XRD ? Near detection limit Non-fibrous actinolite Major phase in sample 130 A P P E N D I X B T A B L E B2 (continued): Mineralogy of Cassiar samples collected during the 2004 field season. 04CA0601 is the only sample from Cassiar which has been found to contain hydrated magnesium carbonate minerals. V ar ie ty  Sa m pl e A m ph ib ol e?  (A ct in ol ite ) Hydrated Magnesium Carbonates Se rp en ti ne  M ag ne ti te  Q ua rt z C hl or it e B ru ci te  T al c Fe ld sp ar  C al ci te  D ol om it e M ag ne si te  A ra go ni te  M on oh yd ro ca lc it e Sm ec ti te /M on tm or ill an it e O PX  Sa m pl e V ar ie ty  Sa m pl e A m ph ib ol e?  (A ct in ol ite ) C on fi rm ed  P re se nt ? Ar tin ite  Ba rr in gt on ite  D yp in gi te  G io rg io sit e H yd ro m ag ne sit e La ns fo rd ite  Ne sq ue ho ni te  Se rp en ti ne  M ag ne ti te  Q ua rt z C hl or it e B ru ci te  T al c Fe ld sp ar  C al ci te  D ol om it e M ag ne si te  A ra go ni te  M on oh yd ro ca lc it e Sm ec ti te /M on tm or ill an it e O PX  Sa m pl e Crust Samples 04CA01-01 none +* + + + 04CA01-01 04CA02-01 none +* + 04CA02-01 04CA02-04 none +* + + 04CA02-04 04CA05-01 none +* + 04CA05-01 04CA06-01 none + + +* + + 04CA06-01 04CA08-01 none 04CA08-01 04CA09-01 none +* + 04CA09-01 04CA10-01 none + + + 04CA10-01 Soil Samples 04CA02-03 none +* + + + 04CA02-03 Mud Samples 04CA07-01 none +* + 04CA07-01 04CA07-02 none +* + 04CA07-02 Confirmed present by XRD ? Near detection limit Non-fibrous actinolite Major phase in sample 131 A P P E N D I X B T A B L E B3: Mineralogy of Clinton Creek samples collected during the 2003 field season. V ar ie ty  Sa m pl e A m ph ib ol e?  (A cti no lit e) Hydrated Magnesium Carbonates Se rp en ti ne  M ag ne ti te  Q ua rt z C hl or it e B ru ci te  M ic a T al c C al ci te  D ol om it e M ag ne si te  A ra go ni te  P yr oa ur it e Sm ec ti te /M on tm or ill an it e G ro up  Sa m pl e V ar ie ty  Sa m pl e A m ph ib ol e?  (A cti no lit e) C on fi rm ed  P re se nt ? Ar tin ite  Ba rr in gt on ite  D yp in gi te  G io rg io sit e H yd ro m ag ne sit e La ns fo rd ite  Ne sq ue ho ni te  Se rp en ti ne  M ag ne ti te  Q ua rt z C hl or it e B ru ci te  M ic a T al c C al ci te  D ol om it e M ag ne si te  A ra go ni te  P yr oa ur it e Sm ec ti te /M on tm or ill an it e G ro up  Sa m pl e Crust Samples 03CC01B none + + + +* + + + + 03CC01B 03CC0201A none + +* + + + + 03CC0201A 03CC0501A none +* + + + + + 03CC0501A 03CC0601A none +* + + + + + + 03CC0601A 03CC0701A none + + +* + + + + + + 03CC0701A 03CC0801A none +* + + + + + + + 03CC0801A 03CC0901A none +* + + + + 03CC0901A 03CC1001A none + + + +* + + + + + + + 03CC1001A + Confirmed present by XRD Either or both phases denoted by this symbol are present ? Near detection limit Non-fibrous actinolite Major phase in sample 132 APPENDIX B TABLE B3 (continued): Mineralogy of Clinton Creek samples collected during the 2003 field season. Hydrated Magnesium Carbonates G ro up  V ar ie ty  Sa m pl e A m ph ib ol e?  (A ct in ol ite ) C on fi rm ed  P re se nt ? A rt in ite  B ar ri ng to ni te  D yp in gi te  G io rg io si te  H yd ro m ag ne si te  La ns fo rd ite  N es qu eh on ite  Se rp en ti ne  M ag ne ti te  Q ua rt z C hl or it e B ru ci te  M ic a T al c C al ci te  D ol om it e M ag ne si te  A ra go ni te  P yr oa ur it e Sm ec ti te /M on tm or ill an it e Sa m pl e 03CC01A none t + + +* + + + + + 03CC01A 03CC01C none + + +* + + + + 03CC01C 03CC01D none + + + +* + + + 03CC01D 03CC0201B none + + +* + + + + 03CC0201B 03CC0301A none +* + + + + + 03CC0301A Bulk (Loose 03CC0301B none + + + +* + + + + 03CC0301B Tailings) Samples 03CC0401A none +* + -t + + + + + 03CC0401A 03CC0601B none + + + +* + + + + 03CC0601B 03CC0701B none +* + + + -t- + 03CC0701B 03CC0801B none + + + +* + + + + + + + 03CC0801B 03CC0901B none + + + + + 03CC0901B 03CC1001B none + + + + + + + + + + (BCC 100 IB Mixture 03CC0401B none + +* + + + + + 03CC0401B Confirmed present by XRD Either or both phases denoted by this symbol are present ? Near detection limit Non-fibrous actinolite Major phase in sample 133 APPENDIX B T A B L E B4: Mineralogy of Clinton Creek samples collected during the 2004 field season and one sample from the 2005 season. V ar ie ty  Sa m pl e 5- Hydrated Magnesium Carbonates Se rp en ti ne  M ag ne ti te  Q ua rt z C hl or it e B ru ci te  C al ci te  D ol om it e M ag ne si te  A ra go ni te  P yr oa ur it e H ex ah yd ri te  E ps om it e G yp su m  Sm ec ti te /M on tm or ill an it e G ro up  Sa m pl e V ar ie ty  Sa m pl e A m ph ib ol e?  ( A ct in ot it C on fi rm ed  P re se nt ? Ar tin ite  Ba rr in gt on ite  D yp in gi te  G io rg io sit e H yd ro m ag ne sit e La ns fo rd ite  Ne sq ue ho ni te  Se rp en ti ne  M ag ne ti te  Q ua rt z C hl or it e B ru ci te  C al ci te  D ol om it e M ag ne si te  A ra go ni te  P yr oa ur it e H ex ah yd ri te  E ps om it e G yp su m  Sm ec ti te /M on tm or ill an it e G ro up  Sa m pl e Cobble Samples 04CC0104 none + +* + 04CC0104 04CC0105 none + + + +* + 04CC0105 04CC0107 none +* + + + 04CC0107 04CC0108 none +* + + + 04CC0108 04CC0109 none + + +* + + 04CC0109 04CC0301 none + +* 04CC0301 04CC0401 none + + + + + 04CC0401 04CC1301 none + 04CC1301 Bulk Samples 04CC1401 none + + + + + 04CC1401 05CC8 none + + +* + + 05CC8 Confirmed present by XRD Near detection limit Non-fibrous actinolite Major phase in sample 134 APPENDIX B T A B L E B4 (continued): Mineralogy of Clinton Creek samples collected during the 2004 field season. Hydrated Magnesium Carbonates G ro up  V ar ie ty  Sa m pl e A m ph ib ol e?  (A ct in ol tt C on fir m ed  P re se nt ? Ar tin ite  Ba rr in gt on ite  D yp in gi te  G io rg io sit e H yd ro m ag ne sit e La ns fo rd ite  N es qu eh on ite  Se rp en tin e M ag ne tit e Q ua rt z C hl or ite  B ru ci te  C al ci te  D ol om ite  M ag ne si te  A ra go ni te  P yr oa ur ite  H ex ah yd rit e Ep so m ite  G yp su m  S m ec tit e/ M on tm or ill an ite  Sa m pl e 04CC0106 none + + +* + + + + 04CC0106 04CC0111 none + +* + 04CC0111 04CC0201A none + + + +* + + + 04CC021A 04CC0201B none + + +* + + 04CC021B Crust Samples 04CC0202A none + + + +* + 04CC022A 04CC0202B none + + + +* + 04CC022B 04CC0601A none + + +* + + 04CC0601A 04CC0601B- CA none + + + +* + + 04CC0601B- CA 04CC0601B- CB none + + 04CC0601B- CB Confirmed present by XRD Near detection limit Non-fibrous actinolite Major phase in sample 135 A P P E N D I X B T A B L E B4 (continued): Mineralogy of Clinton Creek samples collected during the 2004 field season. V ar ie ty  Sa m pl e Hydrated Magnesium Carbonates Se rp en ti ne  M ag ne ti te  Q ua rt z C hl or it e B ru ci te  C al ci te  D ol om it e M ag ne si te  A ra go ni te  P yr oa ur it e H ex ah yd ri te  E ps om it e G yp su m  Sm ec ti te /M on tm or ill an it e G ro up  Sa m pl e V ar ie ty  Sa m pl e A m ph ib ol e?  ( A ct in ol  C on fi rm ed  P re se nt ? Ar tin ite  Ba rr in gt on ite  D yp in gi te  G io rg io sit e H yd ro m ag ne sit e La ns fo rd ite  Ne sq ue ho ni te  Se rp en ti ne  M ag ne ti te  Q ua rt z C hl or it e B ru ci te  C al ci te  D ol om it e M ag ne si te  A ra go ni te  P yr oa ur it e H ex ah yd ri te  E ps om it e G yp su m  Sm ec ti te /M on tm or ill an it e G ro up  Sa m pl e Crust Samples 04CC0701 none + 04CC0701 04CC0703 none + 04CC0703 04CC0901 none + + + 04CC0901 04CC1001 none + + + 04CC1001 04CC1101 none + + +? + 04CC1101 04CC1201 none + + +* + + + 04CC1201 Chrysotile Mat Samples 04CC0101 none + + + + + + 04CC0101 04CC0102 none +* + + 04CC0102 Chrysotile 04CC0110 none +* 04CC0110 Spire & Q-tip Samples 04CC0702 none + + + + +* + + 04CC0702 04CC0801 none + + + +* + + 04CC0801 04CC0902 none + + + + + K + + 04CC0902 Confirmed present by XRD ? Near detection limit Non-fibrous actinolite Major phase in sample 1 3 6 A P P E N D I X B 3500 3000 MMI03-1-1 hAjMMI03-1-1 |MjOO-010-0380 (D) - Chrysotile ' ±100-019-0629 (*) - Magnetite, syn 00-046-1045 (*) - Quartz, syn • 00-005-0586 (*) - Calcite, syn 1100-041-1475 (*) - Aragonite s 25001 C q ii. 2000 1 c J2 15001 c 1000 500 JJL U 10 30 40 50 60 70 2-theta (degrees) F I G U R E B l : X-ray diffractogram for MMI03-1-1 . MM 103-1-2 4000 fcAjMMI03-1-2 ? 00-010-0380 (D) - Chrysotile | M 00-019-0629 (") - Magnetite, syn I 00-046-1045 (") - Quartz, syn • 01-079-1270 (C) - Clinochlore w % 3000 in § 2000 F I G U R E B2 : X-ray diffractogram for MMI03-1-2 . 137 A P P E N D I X B c 3 c 3000 2000 1000 MMI03-1-3 Wl)MMI03-1-3 » 00-010-0380 (D) - Chrysotile • 00-019-0629 (*) - Magnetite, syn T 00-046-1045 (*) - Quartz, syn ? 01-079-1270 (C) - Clinochlore Lai ..JL..tjA 10 20 30 40 2-theta (degrees) 50 60 70 F I G U P v E B 3 : X - r a y d i f f ractogram for M M I 0 3 - 1 - 3 . MMI03-1-4 WUMMI03-1-4 i 00-010-0380 (D) - Chrysotile |i]0O-O19-O629 O - Magnetite, syn 4000 ^ 3000 in <jj 2000 JL 10 20 30 40 2-theta (degrees) 50 60 70 F I G U R E B 4 : X - r a y d i f f ractogram for M M I 0 3 - 1 - 4 . 138 A P P E N D I X B m c O 2000 in §5 1500 500 MMI03-1-5 U\JMMI03-1-5 H00-010-0380 (D) - Chrysotile M 00-019-0629 (•) - Magnetite, syn \ 01-079-1270 (C) - Clinochlore " * , - ' f c « ^ * » l J i i 1 l I l l f > M j M t 30 40 2-theta (degrees) F I G U R E B5 : X-ray diffractogram for MMI03-1-5 . c 3 _< 2000 c s 1000 MM 103-1-6 W\jMMI03-1-6 = 00-010-0380 (D) - Chrysotile I»]00-019-0629 (*) - Magnetite, syn - 00-046-1045 (*) - Quartz, syn I 00-005-0586 (•) - Calcite, syn 01-079-1270 (C) - Clinochlore L J J 10 20 30 40 2-theta (degrees) 50 •' >.i 70 F I G U R E B6 : X-ray diffractogram for MMI03-1-6. 139 A P P E N D I X B 3500 3000 c 2000 to § 1500 C 1000 500 3 10 20 MM 103-1-7 30 40 2-theta (degrees) (AJMMI03-1-7 • 00-010-0380 (D) - Chrysotile • 00-019-0629 (*) - Magnetite, syn 60 F I G U R E B7: X-ray diffractogram for MMI03-1-7. MMI03-1-8 WUMMI03-1-8 7 00-010-0380 (D) - Chrysotile = 00-019-0629 (*) - Magnetite, syn » 00-046-1045 (•) - Quartz, syn 7 01-079-1270 (C) - Clinochlore 10 20 30 40 50 60 70 2-theta (degrees) F I G U R E B8 : X-ray diffractogram for MMI03-1-8 . 140 A P P E N D I X B 3500 MM 103-1-9 WUMMI03-1-9 « 00-010-0380 (D) - Chrysotile = 100-019-0629 (*) - Magnetite, syn I 00-046-1045 (*) - Quartz, syn TJ 01-079-1270 (C) - Clinochlore ^ 2500 c 10 c 0) 1500 1000 500 2-theta (degrees) F I G U R E B 9 : X-ray diffractogram for MMI03-1-9 . MMI03-1-10 4000 h/l|MMI03-1-10 A 00-010-0380 (D) - Chrysotile T_00-019-0629 O - Magnetite, syn » 01-079-1270 (C) - Clinochlore Si 3000 | c C 2000 <D 1000 L ••- i • - . .J^^Va.. . jJ- 10 30 40 2-theta (degrees) 50 F I G U R E BIO: X-ray diffractogram for MMI03-1-10. 141 A P P E N D I X B 4000 3000 c I i o o co 2000 c £ 1000 MMI03-1-11 WUMMI03-1-11 • 00-010-0380 (D) - Chrysotile I»i00-019-0629 (•) - Magnetite, syn 10 20 30 40 50 60 70 2-theta (degrees) F I G U R E B11: X-ray diffractogram for M M I 0 3 -1-11. to c D O u >> 2000 C O c CD J MMI03-1-12 WyMMI03-1-12 *100-010-0380 (D) - Chrysotile :"JOO-019-0629 0) - Magnetite, syn i 00-046-1045 (•) - Quartz, syn MJ01-074-1687 (C) - Dolomite M|O1-O79-1270 (C) - Clinochlore 10 20 2-theta (degrees) F I G U R E B12: X-ray diffractogram for MMI03-1-12. 142 A P P E N D I X B 10 03CA|0102 Coating 20 WJ03CA0102 !, • !00-005-0586 C) - Calcite, syn • 00-046-1045 (*) - Quartz, syn * 01-074-1687 (C) - Dolomite 30 40 2-theta (degrees) 50 60 70 F I G U R E B13: X-ray diffractogram for calcite coating on 03 CAO 102. 2300 2000 If) C 1500 O O in c 0) 1000 500 II. Al 03CA0201 10 ffl03CA0201 x 00-010-0380 (D) - Chrysotile • 00-019-0629 (*) - Magnetite, syn M 00-046-1045 (') - Quartz, syn • 00-005-0586 (*) - Calcite, syn iM|01-079-1270(C) -Clinochlore 01-072-1268 (C) - Diaspore i J I L J L I U J A L 30 40 2-theta (degrees) 50 60 70 F I G U R E B14: X-ray diffractogram for 03CA0201. 143 A P P E N D I X B 3000 2500 <fl c D 8 2000 m 1500 c 1000 500 10 03CA0202 UU03CA0202 * 00-010-0380 (D) - Chrysotile It 00-019-0629 C) - Magnetite, syn • 00-046-1045 (*) - Quartz, syn Si. 20 30 40 2-theta (degrees) F I G U R E B15: X-ray diffractogram for 03CA0202. 5 0 60 70 3400 3000 2500 2000 1500 1000 500 10 03CA0301 20 30 40 2-theta (degrees) bAl03CA0301 » 00-010-0380 (D) - Chrysotile I* 00-019-0629 (*) - Magnetite T 00-046-1045 (*) - Quartz, syn • 01-079-1270 (C) - Clinochlore 70 F I G U R E B16: X-ray diffractogram for 03CA0301. 144 A P P E N D I X B 4000 TO 3000 C O O CO C 2000 Q) c 1000 03CA0302 10 20 kAJ03CA0302 ^00-010-0380 (D) - Chrysotile HoO-019-0629 (*) - Magnetite, syn I 00-046-1045 (') - Quartz, syn X 01-086-2347 (C) - Magnesite I 01-079-1270 (C) - Clinochlore 30 40 2-theta (degrees) 50 60 70 F I G U R E B 1 7 : X-ray diffractogram for 03CA0302. 4000 3000 c 2000 CO c 1000 03CA0303 A 1 20 30 40 2-theta (degrees) WU03CA0303 T 00-010-0380 (D) - Chrysotile • 00-019-0629 (*) - Magnetite, syn » 00-046-1045 (*) - Quartz, syn [X 01-089-5378 (C) - ActinolNe id 1—-^ bXiti 50 70 F I G U R E B 1 8 : X-ray diffractogram for 03CA0303. 1 4 5 A P P E N D I X B 4000 ' 3000 c O o 2000 0) c 1000 10 03CA0304 hAi03CA0304 • 00-025-0645 (Q) - Chrysotile 500-019-0629 (•) - Magnetite, syn * 01-079-1270 (C) - Clinochlore .1--* 20 30 40 50 60 70 2-theta (degrees) F I G U R E B19: X-ray diffractogram for 03CA0304. F I G U R E B20: X-ray diffractogram for 03CA0305. 146 A P P E N D I X B 3400 3000 2500 CO -*—• c 2000 C 1500 1000 500 03CA0401 WU03CA0401 * 00-010-0380 (D) - Chrysotile I* 00-019-0629 (•) - Magnetite, syn ' 00-046-1045 (*) - Quartz, syn ii . A.. .... ,L 20 30 40 50 70 2-theta (degrees) F I G U R E B21: X-ray diffractogram for 03CA0401. 4000 3000 03CA0402 \J03CA0402 • 00-010-0380 (D) H00-019-0629 0 - 1 1 00-046-1045 (•) - M 01-074-1687 (C) H 01-079-1270 (C) 00-021-0958 C) • • Chrysotile Magnetite, syn • Quartz, syn - Dolomite - Clinochlore Palygorskite c 3 o o >. 2000 CO c s 1000 30 40 2-theta (degrees) 70 F I G U R E B22: X-ray diffractogram for 03CA0402. 147 A P P E N D I X B 03CA0501 2-theta (degrees) F I G U R E B23: X-ray diffractogram for 03CA0501. WU03CA0501 • 00-010-0380 (D) - Chrysotile f* 100-019-0629 (*) - Magnetite, syn 70 2500 2000 (fl -4—' c g 1500 O tn c B 1000 c 500 10 20 03CA0502 ul,A.J.]La,....j/ I 30 40 2-theta (degrees) r\AJ03CA0502 » 00-010-0380 (D) - Chrysotile •100-019-0629 (•) - Magnetite, syn » 00-046-1045 (*) - Quartz, syn • 01-079-1270 (C) - Clinochlore 50 60 70 F I G U R E B24: X-ray diffractogram for 03CA0502. 148 A P P E N D I X B 03CA0601 H03CA0601 » 00-010-0380 (D) - Chrysotile IT100-019-0629 (•) - Magnetite, syn » 00-046-1045 (") - Quartz, syn * 01-079-1270 (C) - Clinochlore C 3 O >. 2000 co c CD 1000 0 2-theta (degrees) F I G U R E B25: X-ray diffractogram for 03CA0601. 03CA0602 (AI03CA0602 » 00-010-0380 (D) - Chrysotile * 00-019-0629 (•) - Magnetite, syn * 00-046-1045 (*) - Quartz, syn * 01-079-1270 (C) - Clinochlore 20 30 40 2-theta (degrees) 50 60 70 F I G U R E B26: X-ray diffractogram for 03CA0602. 149 A P P E N D I X B 4000 30oq c o >• 2000| in c CD 1000 03CA0603 WJ03CA0603 LJ00-010-0380 (D) - Chrysotile • 00-019-0629 (*) - Magnetite, syn 1 00-046-1045 (") - Quartz, syn * 101-074-2220 (C) - Brucite 10 20 30 40 2-theta (degrees) 60 70 F I G U R E B27: X-ray diffractogram for 03CA0603. 03CA0701 tAJ03CA0701 A 00-010-0380 (D) - Chrysotiie HoO-019-0629 C) - Magnetite, syn z 00-046-1045 (*) - Quartz, syn C o o en c tu 2000 1000 0 2-theta (degrees) F I G U R E B28: X-ray diffractogram for 03CA0701. 150 A P P E N D I X B 4000 3000 c 3 8 ~ 2000 to c CD 1000 03CA0702 tAIO3CA0702 x 100-010-0380 (D) - Chrysotile S00-019-0629 O - Magnetite, syn ' 00-046-1045 (*) - Quartz, syn = 01-079-1270 (C) - Clinochlore 10 20 30 40 2-theta (degrees) F I G U R E B29: X-ray diffractogram for 03CA0702. 3000 c 3 2000 c CD c 1000 J 03CA0801 Wy03CAO801 = 00-010-0380 (D) - Chrysotile H 00-019-0629 (*) - Magnetite, syn z 00046-1045 (*) - Quartz, syn • 01-079-1270 (C) - Clinochlore 10 30 40 2-theta (degrees) 70 F I G U R E B30: X-ray diffractogram for 03CA0801. 151 A P P E N D I X B 3500 3000 2500 2000 1500 1000 500 L 10 20 03CA0802 30 40 2-theta (degrees) WJO3CA0802 A 00-010-0380 (D) - Chrysotile I 00-019-0629 (*) - Magnetite, syn » 00-046-1045 (*) - Quartz, syn 50 60 70 F I G U R E B31: X-ray diffractogram for 03CA0802. 03CA0901 hAJ03CA0901 X 00-010-0380 (D) - Chrysotile • 00-019-0629 (*) - Magnetite, syn I 00-046-1045 (•) - Quartz, syn • 01-086-2347 (C) - Magnesite X 01-079-1270 (C) - Clinochlore 30 40 2-theta (degrees) 50 60 70 F I G U R E B32: X-ray diffractogram for 03CA0901. 152 A P P E N D I X B 03CA0902 Wy03CA0902 • 00-010-0380 (D) - Chrysotile • iOO-019-0629 (*) - Magnetite, syn * 00-046-1045 (") - Quartz, syn 30 40 2-theta (degrees) F I G U R E B33: X-ray diffractogram for 03CA0902. 10 20 03CA1101 hA)03CA1101 I i00-010-0380 (D) - Chrysotile •iOO-019-0629 (*) - Magnetite, syn • 00-046-1045 (") - Quartz, syn :01-079-1270 (C) - Clinochlore 30 40 2-theta (degrees) 60 F I G U R E B34: X-ray diffractogram for 03CA1101. 153 A P P E N D I X B 20 03CA1201 30 40 2-Theta - Scale H03CA1201 • 00-010-0380 (D) - Chrysotile • 100-019-0629 (*) - Magnetite, syn F I G U R E B35: X-ray diffractogram for 03CA1201. 03CA1401 3500 tfy03CA1401 • 00-010-0380 (D) - Chrysotile • 00-019-0629 C) - Magnetite, syn 3000 "ST 2500 c 2-theta (degrees) F I G U R E B36: X-ray diffractogram for 03CA1401. 154 A P P E N D I X B 4000 3000 C O ~ 2000 CO c a) c 1000 03CA1501 Wli03CA1501 • 00-025-0645 (Q) - Chrysotile ! • 00-019-0629 (*) - Magnetite, syn ' 00-046-1045 (") - Quartz, syn y 20 30 40 2-theta (degrees) 50 60 70 F I G U R E B37: X-ray diffractogram for 03CA1501. HI 3000 c D o o CO C 2000 0) 1000 03CA1502 03CA1502 = 00-010-0380 (D) - Chrysotile • 00-019-0629 (") - Magnetite, syn I 00-046-1045 (*) - Quartz, syn 1101-086-2347 (C) - Magnesite x 01-079-1270 (C) - Clinochlore 01-088-1919 (C) - Ferrosilite 10 20 30 40 2-theta (degrees) F I G U R E B38: X-ray diffractogram for 03CA1502. 155 A P P E N D I X B 03CA1601 2-theta (degrees) bA|03CA1601 * 00-010-0380 (D) - Chrysotile • 00-019-0629 C) - Magnetite, syn i 00-046-1045 (') - Quartz, syn •101-088-1919 (C) - Ferrosilite 60 70 F I G U R E B39: X-ray diffractogram for 03CA1601. 04CA0101 USJ04CA0101 00-010-0380 (D) - Chrysotile • 100-046-1045 O - Quartz, syn • 00-019-0629 (*) - Magnetite, syn i 01-088-1919 (C) - Ferrosilite 30 40 2-theta (degrees) F I G U R E B40: X-ray diffractogram for 04CA0101. 156 A P P E N D I X B ILL 04CA0201 Wy04CA0201 •100-010-0380 (D) - Chrysotile • 00-019-0629 (*) - Magnetite, syn ' 00-046-1045 (*) - Quartz, syn m™H H...L 10 20 30 40 50 60 2-theta (degrees) F I G U R E B41: X-ray diffractogram for 04CA0201. 04CA0202 Cobble A 10 Wy04CA0202CA II 00-010-0380 <D) M 00-019-0629 (*) - !! 00-046-1045 0 - T 00-005-0586 O - 01-079-1270(C) l l 01-089-5378 <C) [j 01-088-1919 (C) • Chrysotile Magnetite, syn Quartz, syn Calcite, syn - Clinochlore • Actinolite - Ferrosilite 40 50 60 70 2-theta (degrees) F I G U R E B42: X-ray diffractogram for cobble coating from 04CA0202 cobble A . 157 A P P E N D I X B 3500 3000 in 2500 c 3 2000 in c CD •£ 1500 1000 500 04CA0202 Cobble B 10 20 r\AJ04CA0202CB * 00-010-0380 (D) - Chrysotile ! • 00-019-0629 (*) - Magnetite, syn » 00-005-0586 (*) - Calcite, syn i 00-041-1475 (*) - Aragonite 30 40 2-theta (degrees) F I G U R E B43: X-ray diffractogram for cobble coating from 04CA0202 cobble B . 3000 2500 04CA0202 Cobble C 2000 1500 1000 500 kAJ04CA0202CC • 100-025-0645 (Q) - Chrysotile fxl00-019-0629 O " Magnetite, syn • 00-046-1045 (*) - Quartz, syn *i00-005-0586 (*) - Calcite, syn [ = ]01 -074-1687 (C) - Dolomite 01-079-1270 (C) - Clinochlore M 01-072-1503 (C) - Muscovite Jr Li font. .riirU.-,lt 30 40 2-theta (degrees) 50 60 70 F I G U R E B44: X-ray diffractogram for cobble coating from 04CA0202 cobble C. 158 A P P E N D I X B 04CA0202 Cobble D A \*J 20 30 40 2-theta (degrees) 50 hAi04CA0202CD X 00-010-0380 (D) - Chrysotile • 00-019-0629 (*) - Magnetite, syn • 00-046-1045 <*) - Quartz, syn * 00-005-0586 (*) - Calcite, syn • 00-041-1475 (*) - Aragonite 60 70 F I G U R E B45: X-ray diffractogram for cobble coating from 04CA0202 cobble D . 4000 3000 c o o CO 2000 c CD 1000 04CA0203 fflu4CA0203 • 00-010-0380 (D) - Chrysotile 1^00-019-0629 O - Magnetite, syn • 00-046-1045 C) - Quartz, syn i 00-005-0586 (*) - Calcite, syn 30 40 2-theta (degrees) F I G U R E B46: X-ray diffractogram for 04CA0203. 159 A P P E N D I X B 5000 4000 c D o O 3000 c C 2000 1000 10 20 04CA0204 30 40 2-theta (degrees) WW4CA0204 • iOO-010-0380 (D) - Chrysotile •100-019-0629 (*) - Magnetite, syn • 01-088-1919 (C) - Ferrosilite F I G U R E B47: X-ray diffractogram for 04CA0204. 04CA0301 Cobble A iAJ04CA0301CA II 00-010-0380 (D) - Chrysotile A 00-019-0629 (*) - Magnetite, syn -• 00-046-1045 (*) - Quartz, syn 00- 041 -1475 C) - Aragonite II 01-083-1923 (C) - Monohydrocalcite 01- 086-1386 (C) - Muscovite 2M1 H01-076-0803 (C) - Anorthoclase 10 20 30 40 2-theta (degrees) 60 70 F I G U R E B48: X-ray diffractogram for cobble coating from 04CA0301 cobble A . 160 A P P E N D I X B 04CA0302 Cobble A ffiO4CA03O2CA • 00-010-0380 (D) - Chrysotile fx 00-019-0629 (*) - Magnetite, syn * 00-046-1045 (*) - Quartz, syn X 01-074-1687 (C) - Dolomite * 00-041-1475 (*) - Aragonite 01-079-1270 (C) - Clinochlore L 40 50 60 70 2-theta (degrees) F I G U R E B49: X-ray diffractogram for cobble coating from 04CA0302 cobble A . 04CA0302 Cobble A Sample 2 EJ04CA0302-CA • 00-010-0380 <D) - Chrysotile • 00-019-0629 (*) - Magnetite, syn BoO-046-1045 (*) - Quartz, syn * 00-041-1475 (*) - Aragonite = 01-079-1270 (C) - Clinochlore •^01-083-1768 (C) - Talc N 01-089-5378 (C) - Actinolite 10 20 30 40 50 60 70 2-theta (degrees) F I G U R E B50: Duplicate X-ray diffractogram for cobble coating 04CA0302 cobble A . 161 A P P E N D I X B 64CA0401 J j l i » 30 40 2-theta (degrees) 50 kAJ04CA0401 • 00-025-0645 (Q) - Chrysotile ••101-086-1351 (C) - Magnetite » 00-041-1475 (*) - Aragonite • 100-041 -1366 (I) - Actinolite F I G U R E B51: X-ray diffractogram for 04CA0401. 9000 8000 7000 _ 6000 co c O 5000 o (0 4000 c 0) c — 3000 2000 04CA0501 i j i i l- 30 40 2-theta (degrees) ^04CA0501 •:00-010-0380 (D) - Chrysotile * 00-019-0629 (*) - Magnetite, syn 50 70 F I G U R E B52: X-ray diffractogram for 04CA0501. 162 A P P E N D I X B 04CA0601 c 3000 CO c £ 2000! c 1000 10 20 30 40 2-theta (degrees) 04CA0601 « 00-010-0380 (D) - Chrysotile • 00-019-0629 (•) - Magnetite, syn i 00-020-0669 (•) - Nesquehonite, syn • 00-029-0857 (N) - Dypingite * 01-070-2150 (C) - Pyroaurite 00-025-0781 (•) - Rectorite F I G U R E B53: X-ray diffractogram for 04CA0601. 8000 04CA0701 fcAl04CA0701 • 00-010-0380 (D) - Chrysotile • 00-019-0629 (*) - Magnetite, syn 6000 5000 4000 — 3000 2000 1000 10 20 30 40 2-theta (degrees) 50 60 70 F I G U R E B54: X-ray diffractogram for 04CA0701. 163 A P P E N D I X B 04CA0702 Wy04CA0702 • 00-010-0380 (D) - Chrysotile ! • 00-019-0629 C) - Magnetite, syn V, ~d "V~J 20 30 40 2-theta (degrees) 50 70 F I G U R E B55: X-ray diffractogram for 04CA0702. 04CA0801 tA)04CA0801 •100-010-0380 (D) - Chrysotile •\00-019-0629 (") - Magnetite, syn 4000 W 30001 c 8 <5 20001 B c 1000 10 20 30 40 2-theta (degrees) 50 60 70 F I G U R E B56: X-ray diffractogram for 04CA0801. 164 A P P E N D I X B 4000 w 30oq c 3 <2 2000| -»—' c iooq 10 20 04CA0901 30 40 2-theta (degrees) UU04CA0901 • 00-010-0380 (D) - Chrysotile • 00-019-0629 (•) - Magnetite, syn F I G U R E B57: X-ray diffractogram for 04CA0901. i2 c g 1000 co c C 500 04CA1001 0 \\u*^M 3 10 20 KM04CA1001 • 00-010-0380 (D) - Chrysotile 1*100-019-0629 (*) - Magnetite, syn • 00-005-0586 (*) - Calcite, syn T 00-041 -1475 (*) - Aragonite 70 2-theta (degrees) F I G U R E B58: X-ray diffractogram for 04CA1001. 165 A P P E N D I X B 3000 2500 CO 2000 1500 1000 500 03CC01A o6J03CC01A ^00-010-0380 (D) - Chrysotile A00-019-0629 (*) - Magnetite * 00-046-1045 (*) - Quartz ^01-074-1687 (C) - Dolomite •_01-086-2347 (C) - Magnesite 01-070-2150 (C) - Pyroaurite ^t»i-uJi J.-Î -̂̂ JJLJIJLII _ \l.:&A**bP^,i, lint!., i, J.if.hM-1,1 . i J v ^ w L ^ c l i i u l f » 10 20 30 40 50 2-theta (degrees) 60 70 F I G U R E B59: X-ray diffractogram for 03CC01 A . 03CC01B 4000 W y o 3 c c o i B = 00-010-0380 (D) Hi00-019-0629(*)- » 00-046-1045 0- '•j01 -074 1687(C) = 01-086-2347 (C) 00-029-0857 (Q) = 01-070-2150 (C) - Chrysotile Magnetite Quartz - Dolomite - Magnesite - Dypingite - Pyroaurite 3000 O >. CO c <D 2000 -4—* c 1000 tV- • Li.iJA* Ji ai^J=l\ AS- Haiti ijir'ctdi^. 10 20 30 50 60 2-theta (degrees) F I G U R E B60: X-ray diffractogram for 03CC01B. 166 A P P E N D I X B 1500 1000 tn c in c CD 500 4 10 03CC01B 20 30 40 50 2-theta (degrees) 03CC01B ~ 00-010-0380 (D) "100-019-0629 (•)- • 00-046-1045 (•) • " 01-074-1687 (C) = 101-086-2347 (C) 00- 029-0857 (Q) 01- 070-2150(0) - Chrysotile Magnetite Quartz - Dolomite - Magnesite • Dypingite - Pyroaurite F I G U R E B61: Close-up of X-ray diffractogram for 03CC01B. 03CC01B Crust 303CC01B Crust I 00-010-0380 (D) - Chrysotile [• 01-070-1433 (C) - Nesquehonite i 00-029-0857 (Q) - Dypingite M 01-070-2150 (C) - Pyroaurite 10 30 40 50 2- theta ( d e g r e e s ) F I G U R E B62: X-ray diffractogram for vertical crust from 03CC01B. 167 A P P E N D I X B 3000 2500 2000 03CC01C 03CC01C • 00-010-0380 (D) - Chrysotile LxjoO-019-0629 (") - Magnetite MJ00-046-1045 (") - Quartz l=J01-074-1687 (C) - Dolomite I»i01-086-2347 (C) - Magnesite C O O 1500 tn c CD -t—' C 1000 500 2-theta (degrees) F I G U R E B63: X-ray diffractogram for 03CC01C. 3000 2500 tn •g 2000 8 & 1500 tn c CD 1000 500 03CC01D Wl)03CC01D = 00-010-0380 (D) N00-O19-O629 (")• 00-046-1045 C) • 00- 005-0586 (") • • 01-074-1687 (C) 01- 086-2347 (C) • 01-070-2150 (C) - Chrysotile Magnetite Quartz Calcite - Dolomite - Magnesite - Pyroaurite I .LI 10 20 30 40 50 60 70 2-theta (degrees) F I G U R E B64: X-ray diffractogram for 03CC01D. 168 A P P E N D I X B 2900 2000 c IS 1500 CO c 0) 1000 500 10 20 03CC0201A ha|03CC0201A 'I 00-010-0380 (D) - Chrysotile LJoO-019-0629 (*) - Magnetite 00- 046-1045 0 - Quartz •J01-074-1687 (C) - Dolomite [•101-086-2347 (C) - Magnesite 01- 070-0361 (C) - Hydromagnesite H 01-070-2150 (C) - Pyroaurite 30 40 50 2-theta (degrees) 60 70 F I G U R E B65: X-ray diffractogram for 03CC0201A. c O o (O c o 500 10 03CC0201A r . ttr kt J T M» J t 1 hi: WJ03CC0201A • 00-010-0380 (D) - Chrysotile [•]01 -070-0361 (C) - Hydromagnesite • 01-070-2150 (C) - Pyroaurite 20 30 2-theta (degrees) 40 50 F I G U R E B66: Close-up o f X-ray diffractogram for 03CC0201A using higher count rate. 169 A P P E N D I X B c O o c CD 2500 2000 1500 1000 03CC0201B WJ03CC0201B • 00-010-0380 (D) - Chrysotile ?|00-019-0629 C) - Magnetite I 01-074-1687 (C) - Dolomite l|01-086-2347 (C) - Magnesite x|01-070-2150 (C) - Pyroaurite I i L L.AJLI 20 30 40 2-theta (degrees) 60 F I G U R E B67: X-ray diffractogram for 03CC0201B. c O o c 2500 2000 1500 03CC0301A 30 40 2-theta (degrees) r\&l03CC0301A • 00-010-0380 (D) LJOO-019-0629(*)- 00-046-1045 0 - 00- 005-0586 (*) - 01- 074-1687 (C) 01-086-2347 (C) 01-070-2150 (C) 01-079-1270 (C) 00-021-0958 0 - 60 Chrysotile Magnetite Quartz Calcite Dolomite • Magnesite • Pyroaurite • Clinochlore Palygorskite F I G U R E B68: X-ray diffractogram for 03CC0301A. 170 A P P E N D I X B 03CC0301B tA)03CC0301 B x 00-010-0380 (D) - Chrysotile ! ^ 00-019-0629 (*) - Magnetite M 01-070-2150 (C) - Pyroaurite = 00-021-0958 (") - Palygorskite l l 01-074-2220 (C) - Brucite <2 3000 c 3 o o to c £ 1000 2-theta (degrees) 60 70 F I G U R E B69: X-ray diffractogram for 03CC0301B. 3000 2500 c -t—' 3 8 -•—• C 1500 <D 2000 1000 500 03CC0401A 10 40 50 2-theta (degrees) k\J03CC0401A l l 00-010-0380 (D) 11100-019-0629 (*)• is 00-046-1045 (*) • = !01-074-1687(C) = 101-086-2347 (C) 01-070-2150 (C) = 01-079-1270 (C) I I 00-021-0958 (*)• - Chrysotile Magnetite Quartz - Dolomite - Magnesite - Pyroaurite - Clinochlore Palygorskite - H - T i l l - f T f * Ii 60 70 F I G U R E B70: X-ray diffractogram for 03CC0401A. 171 A P P E N D I X B 3900 3000 03CC0401B 03CC0401 B MIOO-010-0380 (D) - Chrysotile =]00-019-0629 (*) - Magnetite M 01-086-2347 (C) - Magnesite MJOO-029-0857 (Q) - Dypingite = i01-070-2150 (C) - Pyroaurite 01-079-1270 (C) - Clinochlore C 3 -T- 2000 c 1000 2-theta (degrees) F I G U R E B71: X-ray diffractogram for 03CC0401B. •g 3000 o o <jj 2000 03CC0401B Crust Wil03CC0401B • 00-010-0380 (D) - Chrysotile • 00-029-0857 (Q) - Dypingite • 01-070-2150 (C) - Pyroaurite * 00-025-0781 (*) - Redorite f It .ft I i i . f I m l i t L\ \\ i ,ii I l r l . U I 40 2-theta (degrees) F I G U R E B72: X-ray diffractogram for 03CC0401B using higher count rate. 172 A P P E N D I X B 4000 3000 c D O o c CD 1000 03CC0501A 10 20 30 [5AJ03CC0501A = 00-010-0380 (D) • |=.00-019-0629 (•)- I 00-046-1045 0 - - 01-074-1687 (C) = 01-086-2347 (C) 01-070-2150 (C) '' 01-079-1270 (C) Chrysotile Magnetite Quartz - Dolomite - Magnesite - Pyroaurite - Clinochlore '^*^»»'lsw{nJm lt« lilaMiii 50 60 2-theta (degrees) F I G U R E B73: X-ray diffractogram for 03CC0501A. 3000 § 2000 <2 1500 CD 1000 500 03CC0601A Wy03CC0601A =̂ 00-010-0380 (D) fl 1100-019-0629 O - = 00-046-1045 (*) • L=)01-074-1687 (C) II i01-086-2347 (C) 01-070-2150 (C) N 01-079-1270(C) = 01-074-2220(0 - Chrysotile Magnetite Quartz - Dolomite - Magnesite - Pyroaurite - Clinochlore - Brucite 20 30 40 2-theta (degrees) F I G U R E B74: X-ray diffractogram for 03CC0601A. 173 A P P E N D I X B c 8 CO c CD 3000 2500 2000 1500 1000 500 03CC0601B I03CC0601B [x 100-010-0380 (D) - Chrysotile [MJ00-019-0629 (*) - Magnetite 01-086-2347 (C) - Magnesite ixl01-070-2150 (C) - Pyroaurite | M 01-079-1270 (C) - Clinochlore 00-021-0958 (*) - Palygorskite 2-theta (degrees) F I G U R E B75: X-ray diffractogram for 03CC0601B. 03CC0701A 2000 1500 CO c s c 1000 500 E303CC0701A i 00-010-0380 (D) =i00-019-0629 (*)- ~ 00-046-1045 (•) - = 101-074-1687 (C) = 01-086-2347 (C) 01-070-2150 (C) | 01-079-1270 (C) - 00-021-0958 O - • Chrysotile Magnetite Quartz • Dolomite • Magnesite • Pyroaurite • Clinochlore Palygorskite 30 40 2-theta (degrees) 50 60 70 F I G U R E B76: X-ray diffractogram for 03CC0701 A . 174 A P P E N D I X B 03CC0701B \J03CC0701B • 00-010-0380 (D) • 100-019-0629 O - N 00-046-1045 (*) - » 01-074-1687 (C) H 01-086-2347 (C) 01-079-1270 (C) — 1500 c D O o (0 c CD 500 • Chrysotile Magnetite, syn Quartz, syn • Dolomite • Magnesite • Clinochlore 20 30 40 2-theta (degrees) 70 F I G U R E B77: X-ray diffractogram for 03CC0701B. 2400 2000 to "£ 1500 o o CO c CD 500 03CC0801A 03CC0801A 00- 010-0380 (D)- 11 00-019-0629 (*)- 11 0O-046-1045O- - 00-005-0586 C) - = 01-074-1687 (C) 01- 086-2347 (C) ll 01-070-2150 (C) 01-079-1270 (C) • Chrysotile Magnetite Quartz Calcite • Dolomite • Magnesite • Pyroaurite • Clinochlore 10 20 30 40 2-theta (degrees) 50 F I G U R E B78: X-ray diffractogram for 03CC0801 A . 175 A P P E N D I X B 03CC0801B bAJ03CC0801 B • 00-010-0380 (D) HioO-019-0629 (*)- M 00-046-1045 (*)- M 00-005-0586 (') - *:01 -074-1687(C) 01-086-2347 (C) H 01-070-2150 (C) = 01-079-1270 (C) - Chrysotile Magnetite Quartz Calcite - Dolomite - Magnesite - Pyroaurite - Clinochlore 30 2-theta (degrees) F I G U R E B79: X-ray diffractogram for 03CC0801B. 03CC0901A \|03CC0901A [•100-010-0380 (D) - Chrysotile [=100-019-0629 (*) - Magnetite II 00-046-1045 (•)- Quartz 01-074-1687 (C) - Dolomite 01-086-2347 (C) - Magnesite 01-079-1270 (C) - Clinochlore 10 20 30 40 2-theta (degrees) F I G U R E B80: X-ray diffractogram for 03CC0901A. 176 A P P E N D I X B 3000 2500 (/> C O 2000 >, C 1500 CD 500 03CC0901B WU03CC0901B • 00-010-0380 (D) = 00-019-0629 (')- l l 00-046-1045 0 - 00- 005-0586 O - 01- 074-1687(0) 01-086-2347 (C) • 01-070-2150 (C) - Chrysotile Magnetite • Quartz Calcite - Dolomite - Magnesite - Pyroaurite V..«—... AAAMAJJ I. ^Vr,ttltfV <̂̂ - itMl i l L j j J - i f c j ^ } jfrjl.ji 10 20 30 40 50 60 70 2-theta (degrees) F I G U R E B81: X-ray diffractogram for 03CC0901B. 3400 2500 C O 2000 >, CO C 1500 CD 1000 500 03CC1001A WJ03CC1001A Hi 00-010-0380 (D) Fl00-019-0629 (*)• 00- 046-1045 0 • • 00-005-0586 (*) • • 01-074-1687 (C) 01- 086-2347 (C) • 01-070-2150 (C) • 01-079-1270 (C) - Chrysotile Magnetite Quartz Calcite - Dolomite - Magnesite - Pyroaurite - Clinochlore 20 30 40 50 2-theta (degrees) 60 70 F I G U R E B82: X-ray diffractogram for 03CC1001A. 177 A P P E N D I X B c • o o 3500 3000 2500 2000 <o c £ 1500 c 1000 500 03CC1001B h&J03CC1001B l l 00-010-0380 (D) 00-019-0629 f ) ' 00-046-1045 O • • 00-005-0586 C) • • 01-074-1687 (C) 01- 086-2347 (C) • 01-070-2150(0) • 01-079-1270(0) - Chrysotile Magnetite • Quartz • Calcite - Dolomite - Magnesite - Pyroaurite - Clinochlore 20 30 40 2-theta (degrees) 50 F I G U R E B83: X-ray diffractogram for 03CC1001B. 1400 04CC0101 1000 c D o o CO c £ 500 04CC0101 I 00-010-0380 (D) M!OO-019-0629 (*) - * 01-070-2516 (C) 00- 005-0586 (•) - II 01-086-2347 (C) 01- 079-1270 (C) 00-021-0958(*)- • Chrysotile Magnetite • Quartz Calcite • Magnesite • Clinochlore Palygorskite 20 30 40 2-theta (degrees) F I G U R E B84: X-ray diffractogram for 04CC0T0T. 178 A P P E N D I X B 400 C 300 O o CO § 200 100 04CC0102 •AJ04CA0102 x 100-010-0380 (D) - Chrysotile M]00-019-0629 (*) - Magnetite 11 00-005-0586 (*) - Calcite 01-074-1687 (C) - Dolomite i 101-079-1270 (C) - Clinochlore 10 20 30 40 2-theta (degrees) F I G U R E B85: X-ray diffractogram for 04CC0102. 20 04CC0104 30 40 2-theta (degrees) 04CC0104 A 00-010-0380 (D) - Chrysotile • 01-086-2347 (C) - Magnesite I 01-070-2150 (C) - Pyroaurite • t i l ̂  I tl: 60 70 F I G U R E B86: X-ray diffractogram for 04CC0104. 179 A P P E N D I X B 3000 2500 i2 2000 c '1500 C O c CD C 1000 500 0 ™ 04CC0105 rA)04CC0105 ^00-010-0380 (D) - Chrysotile N ;00-019-0629 (*) - Magnetite = 00-023-1218 (Q) - Dypingite HJ01-070-0361 (C)- Hydromagnesite i01-070-2150 (C) - Pyroaurite 30 40 2-theta (degrees) 70 F I G U R E B87: X-ray diffractogram for 04CC0105. 04CC0106 U04CC0106 XJOO-010-0380 (D) - Chrysotile X|00-O19-0629 C) - Magnetite i" 00-046-1045O -Quartz : 01-070-1433 (C) - Nesquehonite II 00-023-1218 (Q) - Dypingite 00-021-0958 O - Palygorskite 30 40 2-theta (degrees) 70 F I G U R E B88: X-ray diffractogram for 04CC0106. 180 A P P E N D I X B 1 04CC0106 1^ 10 20 2-theta (degrees) WJ04CC0106 » 00-010-0380 (D) - Chrysotile S 01 -070-1433 (C) - Nesquehonite M 00-023-1218 (Q) - Dypingite = 00-021-0958 (*) - Palygorskite 30 40 F I G U R E B89: Close-up o f X-ray diffractogram for 04CC0106 using higher count rate. 2000 „ 1500 to H—' c • o o % 1000 c CD c 500 0 ilMU^dtiin^iia 04CC0107 Cobble A .^..A..^j\huJ tyil04CC0107CA •00-010-0380 (D) - Chrysotile I 00-019-0629 (•) - Magnetite • W-041-1475 C) - Aragonite = 00-021-0958 (") - Palygorskite lAU.q.i, 20 30 40 50 70 2-theta (degrees) F I G U R E B90: X-ray diffractogram for cobble coating from 04CC0107 cobble A . 181 A P P E N D I X B 04CC0108 Cobble A 2000 hflJ04CC0108CA XiOO-010-0380 (D) - Chrysotile I =l00-019-0629 (•) - Magnetite II 00-046-1045 0-Quartz 00-041-1475 O - Aragonite Lrj01-070-2150 (C) - Pyroaurite 00-021-0958 O - Palygorskite tf> 1500 c -*—' c 1000 <D c 500 i jj jft JIL̂ JLJ JUL Ji^L/ uL,..̂ 10 20 30 40 2-theta (degrees) so 60 70 F I G U R E B91: X-ray diffractogram for cobble coating from 04CC0108 cobble A . 3500 3000 04CC0109 rAI04CC0109 • 00-010-0380 (D) - Chrysotile S00-019-0629 O - Magnetite M 00-023-1218 (Q) - Dypingite = 01-070-2150 (C) - Pyroaurite •I 00-025-0781 O - Rectorite 2500 c O 2000 CO C 1500 CD 1000 500 30 40 2-theta (degrees) 70 F I G U R E B92: X-ray diffractogram for 04CC0109. 182 A P P E N D I X B 04CC0109 J. . i. I I •! In Wjo4CC0109 • 00-010-0380 (D) - Chrysotile _*j00-023-1218 (Q) - Dypingite • 01-070-2150 (C) - Pyroaurite * 00-025-0781 (') - Rectorite 10 20 30 2-theta (degrees) 40 F I G U R E B93: Close-up o f X-ray diffractogram for 04CC0109 using higher count rate. 04CC0110 30 40 2-theta (degrees) tAj04CC0110 • 00-010-0380 (D) - Chrysotile *k 4 1 V - f •• . .1... .1 *—-L- 50 60 70 F I G U R E B94: X-ray diffractogram for 04CC0110. Pure chrysotile used in synthetic tailings (Chapter 4). 183 A P P E N D I X B c O o CO c £ 5000 4000 3000 2000 1000 04CC0111 30 40 2-theta (degrees) bft(04CC0111 "00-010-0380 (D) - Chrysotile HoO-046-1045 (•) - Quartz 01-079-1270 (C) - Clinochlore 00-021 -0958 (') - Palygorskite • 01-072-1068 (C) - Hexahydrite I 00-033-0311 (*) - Gypsum 60 70 F I G U R E B95: X-ray diffractogram for 04CC0111. 4000 CO 3000 4—< c D O o >, " 2000 CD c 1000 04CC0201A 20 30 40 2-theta (degrees) 04CC0201A 00- 010-0380 (D) - Chrysotile l»j00-019-0629 (*) - Magnetite » 00-035-0680 (I) - Lansfordite x 01-070-1433 (C) - Nesquehonite = 00-023-1218 (Q) - Dypingite 01- 070-2150 (C) - Pyroaurite F I G U R E B96: X-ray diffractogram for 04CC0201 A . 184 A P P E N D I X B 2000 1500 c 8 >, 1000 CO c cu 500 04fcC0201A Uy04CC0201A • 00-010-0380 (D) - Chrysotile • 00-019-0629 (*) - Magnetite » 00-035-0680 (I) - Lansfordite H 01-070-1433 (C> - Nesquehonite = 00-023-1218 (Q) - Dypingite 01-070-2150 (C) - Pyroaurite 10 20 2-theta (degrees) F I G U R E B97: Close-up o f X-ray diffractogram for 04CC0201 A . 5000 4000 04CC0201B ffi04CC0201B Li 00-010-0380 (D) - Chrysotile [•00-019-0629 (*) - Magnetite T 00-035-0680 (I) - Lansfordite x 01-070-1433 (C) - Nesquehonite 00-023-1218 (Q) - Dypingite 3 2000 1000 2-theta (degrees) F I G U R E B98: X-ray diffractogram for 04CC0201B. 185 A P P E N D I X B 2000 1500 c D O o 1000 CO c 0J 500 04 :C0201B WU04CC0201B • 00-010-0380 (D) - Chrysotile ! • 00-019-0629 (*) - Magnetite " 00-035-0680 (I) - Lansfordite X 01-070-1433 (C) - Nesquehonite - 00-023-1218 (Q) - Dypingite 10 20 30 2-theta (degrees) F I G U R E B99: Close-up o f X-ray diffractogram for 04CC0201B. 04CC0202A •iOO-010-0380 (D) - Chrysotile ® 00-023-1218 (Q) - Dypingite M 01-072-1068 (C) - Hexahydrite = 00-036-0419 (*) - Epsomite 10 20 30 40 2-theta (degrees) F I G U R E B100: X-ray diffractogram for 04CC0202A. 186 A P P E N D I X B 5000 4000 3000 tn c •2 2000 1000 04CC0202B 30 40 2-theta (degrees) ffi)04CC0202B » 00-010-0380 (D) - Chrysotile X i 00-023-1218 (Q) - Dypingite * 01-072-1068 (C) - Hexahydrite = 00-036-0419 (') - Epsomrte 60 70 F I G U R E B101: X-ray diffractogram for 04CC0202B. 15000 tn -*—' c 3 10000 o o tn c CD 04bC0301 E304CC0301 \ •100-010-0380 (D) - Chrysotile !*l01-074-1687 (C) - Dolomite ' 01-086-2347 (C) - Magnesite 70 2-theta (degrees) F I G U R E B102: X-ray diffractogram for 04CC0301. 187 A P P E N D I X B 04CC0401 Cobble A EJ04CC0401CA ix 00-010-0380 (D) - Chrysotile [= 00-019-0629 (*) - Magnetite • 01-086-2347 (C) - Magnesfte • 00-023-1218 (Q) - Dypingite ill 01-070-2150 (C) - Pyroaurite 00-025-0781 (") - Rectorite 30 40 2-theta (degrees) 50 60 F I G U R E B103: X-ray diffractogram for cobble coating from 04CC0401 cobble A . 3000 2500 | ? 2000 D o •~ 1500 CO c Q) 1000 500 04CC0601A bAI04CC0601A Ul00-010-0380 (D) - Chrysotile HoO-019-0629 C) - Magnetite ' | 00-046-1045 0-Quartz ^101-086-2347 (C) - Magnesite 11 00-023-1218 (Q) - Dypingite 01-070-2150 (C) - Pyroaurite 20 30 40 2-theta (degrees) 60 70 F I G U R E B104: X-ray diffractogram for 04CC0601 A . 188 A P P E N D I X B 04CC0601B Cobble A KM04CC0601B-CA ii 00-010-0380 (D) - Chrysotile "00-019-0629 (') - Magnetite II 00-046-1045 (*) - Quartz n 00-023-1218 (Q) - Dypingite E01-070-0361 (C) - Hydromagnesite 01-070-2150 (C) - Pyroaurite 10 20 30 40 2-theta (degrees) 50 70 F I G U R E B105: X-ray diffractogram for cobble coating from 04CC0601B cobble A . 10 04CC0601B Cobble B 1 04CC0601 B-CB 00-010-0380 (D) - Chrysotile IAJ00-023-1218 (Q) - Dypingite • 00-025-0781 (") - Rectorite 20 30 40 50 2-theta (degrees) 60 70 F I G U R E B106: X-ray diffractogram for cobble coating from 04CC0601B cobble B . 189 A P P E N D I X B 04CC0701 4000 CO -i—' c 3 g 3000 CO c CD -p. 2000 1000 04CC0701 l l 00-010-0380 (D) - Chrysotile i 01-070-1433 (C) - Nesquehonite • 00-023-1218 (Q) - Dypingite 01 -070-0361 (C) - Hydromagnesite • 01-070-2150 (C) - Pyroaurite 00-021-0958 O - Palygorskite 10 20 30 40 2-theta (degrees) 50 F I G U R E B107: X-ray diffractogram for 04CC0701. 2400 f 2000 2 1500 8 CO C 1000 CD 500 let* W 10 04CC0701 T rJi \4\ i i J Uyo4cco7oi • 00-010-0380kD) • 01-070-1433|(C) • 00-023-121 * 01-070-0361 [Ti01 -070-21 Chrysotile Nesquehonite Dypingite |(C) - Hydromagnesr|e Pyroaurite ska) 50(C) i I 20 30 2-theta (degrees) F I G U R E B108: Close-up of X-ray diffractogram for 04CC0701. 190 A P P E N D I X B 2500 2000 i2 c O o 1500 c CD -«—» c — 1000 500 04CC0702 tAJ04CC0702 • 00-025-0645 (Q) W00-019-0629 (•)- 01-070-1433(0) • 00-023-1218 (Q) • 01-070-0361 (C) • 01-070-2150 (C) • •00-021-0958 0 - - Chrysotile Magnetite - Nesquehonite - Dypingite - Hydromagnesite - Pyroaurite Palygorskite 10 20 J ! i,. ..i -^̂ ^̂ ^̂ ^ 50 60 70 2-theta (degrees) F I G U R E B109: X-ray diffractogram for 04CC0702. 8000 7000 "5J~ 6000 c 8 5000 * 4000 s 3000 2000 1000 04CC0703 U04CC0703 I 00-010-0380 (D) - Chrysotile • 01-070-1433 (C) - Nesquehonite • 00-023-1218 (N) - Dypingite T]01-070-0361 (C) - Hydromagnesite Tiffri-kfUntiarirfi 30 40 2-theta (degrees) 60 70 F I G U R E B l 10: X-ray diffractogram for 04CC0703. 191 A P P E N D I X B tA)04CC0801 •100-010-0380 (D) - Chrysotile r*l00-019-0629 O - Magnetite K 00-046-1045 0 -Quar tz M 01-070-1433 (C) - Nesquehonite = 00-023-1218 (Q) - Dypingite 01-070-2150 (C) - Pyroaurite 3 10 20 30 40 50 60 70 2-theta (degrees) 2000 04CC0801 F I G U R E B i l l : X-ray diffractogram for 04CC0801. 3500 04CC0801 £ 2500 c 8 ^ 2000 | *—1 tn c CD •g 1500 | 1000 500 AJ tAi04CC0801 •^00-010-0380 (D) - Chrysotile > 01-070-1433 (C) - Nesquehonite • 00-023-1218 (Q) - Dypingite * 01-070-2150 (C) - Pyroaurite I. It!, t fc f I .I • Ul lit J 10 20 30 2-theta (degrees) F I G U R E B l 12: X-ray diffractogram for 04CC0801 using higher count rate. 192 A P P E N D I X B 4000 3000 c 3 <5. 2000 CD 04CC0901 Wl!04CC0901 •100-010-0380 (D) - Chrysotile •100-019-0629 (*) - Magnetite I 00-023-1218 (Q) - Dypingite • 101-070-2150 (C) - Pyroaurite •i01-072-1068 (C) - Hexahydrite 30 40 2-theta (degrees) 70 F I G U R E B l 13: X-ray diffractogram for 04CC0901. 04CC0902 ij04CC0902 II 00-010-0380 (D) 00-O19-0629O- 00- 046-1045 0 - II 01-074-1687 (C) 01- 086-2347 (C) 01-070-1433 (C) • 00-023-1218 (Q) • 01-070-0361 (C) 00-021-0958O- - Chrysotile Magnetite Quartz - Dolomite - Magnesite - Nesquehonite - Dypingite - Hydromagnesrte • Palygorskite A, 30 40 2-theta (degrees) F I G U R E B l 14: X-ray diffractogram for 04CC0902. 193 A P P E N D I X B 4000 3000 c O o m c CO 1000 04CC1001 tA,.iJ\iJ 10 20 30 40 2-theta (degrees) tA]04CC1001 [xloO-010-0380 (D) - Chrysotile BoO-019-0629 (*) - Magnetite 01-086-2347 (C) - Magnesite • 01-070-1433 (C) - Nesquehonite X 00-023-1218 (Q) - Dypingite H 0 1 -070-0361 (C) - Hydromagnesite ill r¥--* 50 60 70 F I G U R E B l 15: X-ray diffractogram for 04CC100T. 04CC1101 1J04CC1101 » 00-010-0380 (D) - Chrysotile • 01-070-1433 (C) - Nesquehonite J 00-023-1218 (Q) - Dypingite • 01-070-1177 (C) - Hydromagnesite 10 20 30 40 2-theta (degrees) 50 F I G U R E B l 16: X-ray diffractogram for 04CC1101. 194 A P P E N D I X B 2400 2000 co C 1500 o o 1000 500 04CC1201 WU04CC1201 II 00-010-0380 (D) !• 00-019-0829 O - • 01-086-2347 (C) II 00-020-0669 0- • 00-023-1218 (Q) 01-070-0361 (C) » 00-021-0958 0' I 01-072-1068 (C) - Chrysotile Magnetite - Magnesite Nesquehonite - Dypingite - Hydromagnesite • Palygorskite - Hexahydrite - M. U' , FC 1 ) it j fl j ,, 10 20 30 40 2-theta (degrees) 50 60 70 F I G U R E B l 17: X-ray diffractogram for 04CC1201. 13000 12000 11000 10000 9000 CO un l 8000 o o 7000 (0 6000 c CD In t 5000 4000 3000 2000 1000 0 A. 04CC1301 10 20 30 40 2-theta (degrees) fcAJ04CC1301 >100-010-0380 (D) - Chrysotile H01-074-1687 (C) - Dolomite " 01-086-2347 (C) - Magnesite 60 70 F I G U R E B l 18: X-ray diffractogram for 04CC1301. 195 APPENDIX B 2500 2000 c 8 1500 tn c CD 1000 500 04CC1401 i with CaF2 Spike Al04CC1401 with CaFj spike • 100-010-0380 (D) - Chrysotile ii00-019-0629 (') - Magnetite, syn » 00-046-1045 (*) - Quartz, syn II101-086-2347 (C) - Magnesite XJ01-070-0361 (C> 00-023-1218 (Q) • 01-070-2150 (C) "00-035-0816 (•)• Hydromagnesite Dypingite Pyroaurite Fluorite, syn 10 20 30 40 50 60 2-theta (degrees) 70 80 FIGURE Bl 19: X-ray diffractogram for 04CC1401 with 10 wt.% spike for Rietveld refinement. 3500 3000 c —- 2000 tn c CD •g 1500 1000 500 05CC8 with CaF2 spike il05CC8with CaF 2 ' 00-010-0380 (D) - I 00-019-0629 (*)• : 01-086-2347(0) I 01-070-0361 (C) i 00-023-1218 (Q) 01-070-2150(0) ' 00-021-0958 (*)• \ 00-044-1482 (*) 00-035-0816 C) spike Chrysotile Magnetite, syn Magnesite • Hydromagnesite - Dypingite • Pyroaurite Palygorskite Brucite, syn Fluorite, syn 10 20 40 50 2-theta (degrees) 90 FIGURE B120: X-ray diffractogram for 05CC8 with 10 wt.% spike for Rietveld refinement. 196 A P P E N D I X C APPENDIX C: Sieving data Grain size analysis was performed by dry-sieving 60 bulk tailings samples collected during the 2003 field season (Tables C I , C2 , and C3). Standard sieve sizes ranging from 16 mm to 0.053 mm were used. Chrysotile-rich samples do not give particularly accurate grain size data due to the fibrous nature of the mineral. Long fibres do not pass easily through sieves and as such are generally included in larger size fractions which do not reflect the higher surface area associated with fibres. A separate method of wet sieving, developed by James Thorn at the department of Earth and Ocean Sciences at U B C , was used to determine the "fibre fraction" of one bulk sample from each sample locality (Table C4). Accounting for the fibre fraction allows for improved quantification of surface area within chrysotile-rich samples. For each locality, the bulk sample was dry-sieved and bundles of fibres were hand-picked from the larger size fractions. The remaining, predominantly non-fibrous material was washed in deionised water in an ultrasonic bath and mechanically stirred to disaggregate small fibres. The fibre-rich water was decanted from the bath and passed through filter-cloth to collect the fine fibre fraction. Surface-area analysis was done on A65-grade chrysotile from Cassiar with the B E T N-gas absorption isotherm technique. The data presented in Tables C I , C2 , and C3 was collected by Elizabeth Castle. Wet-sieving of sample 03CA1601 (Table C4) was done by James Thorn. Sample 04CC1601 was wet-sieved by the author with the assistance of Joanne Woodhouse. 197 A P P E N D I X C T A B L E C I : Results of grain size analyses for the 03CC series of samples from Clinton Creek. Size 0 3 C C 0 1 A 0 3 C C 0 1 B 0 3 C C 0 1 C 0 3 C C 0 1 D (mm) wt.% % passing wt.% % passing wt.% % passing wt.% >16.0 21.54 78.46 38.64 61.36 25.29 74.71 13.47 86.53 >9.51 13.54 64.92 9.12 52.24 9.30 65.42 9.85 76.68 >4.76 25.87 39.04 18.03 34.21 22.93 42.49 14.14 62.54 >2.00 19.21 19.84 15.28 18.93 17.29 25.19 20.04 42.50 >0.850 8.50 11.34 8.98 9.94 9.03 16.16 19.30 23.20 >0.425 5.64 5.70 5.12 4.83 7.60 8.56 12.99 10.21 >0.212 3.54 2.15 3.06 1.77 5.19 3.37 7.30 2.91 >0.180 0.14 2.01 0.14 1.63 0.61 2.76 0.56 2.34 >0.150 0.51 1.50 0.42 1.20 0.70 2.05 0.57 1.77 >0.106 0.91 0.59 0.85 0.35 1.46 0.60 1.42 0.35 >0.075 0.45 0.14 0.27 0.08 0.49 0.10 0.26 0.09 >0.053 0.08 0.05 0.04 0.03 0.07 0.04 0.07 0.02 <0.053 0.05 0.00 0.03 0.00 0.04 0.00 0.02 0.00 T O T A L 100.00 100.00 100.00 100.00 Size 0 3 C C 0 2 0 1 A 0 3 C C 0 2 0 1 B 0 3 C C 0 3 0 1 A 0 3 C C 0 3 0 1 B wt.% % passing wt.% % passing wt.% % passing wt.% >16.0 4.09 95.91 3.14 96.86 0.00 100.00 31.17 68.83 >9.51 4.16 91.75 15.33 81.54 0.00 100.00 20.89 47.94 >4.76 5.04 86.71 12.31 69.23 0.49 99.51 20.23 27.71 >2.00 17.26 69.46 17.88 51.34 2.87 96.64 10.72 16.99 >0.850 24.91 44.55 20.61 30.74 14.77 81.86 5.49 11.51 >0.425 24.02 20.52 15.38 15.36 15.47 66.40 5.10 6.40 >0.212 14.66 5.86 10.15 5.21 16.58 49.82 2.03 4.37 >0.180 1.22 4.64 0.69 4.52 5.40 44.42 0.39 3.98 >0.150 1.50 3.14 1.50 3.03 6.93 37.49 0.66 3.32 >0.106 2.35 0.78 2.26 0.76 12.19 25.30 1.09 2.23 >0.075 0.64 0.15 0.63 0.14 14.08 11.22 1.06 1.18 >0.053 0.12 0.03 0.10 0.03 7.86 3.36 0.73 0.45 <0.053 0.03 0.00 0.03 0.00 3.36 0.00 0.45 0.00 T O T A L 100.00 100.00 100.00 100.00 Size 0 3 C C 0 4 0 1 A 0 3 C C 0 4 0 1 B 0 3 C C 0 6 0 1 A 0 3 C C 0 6 0 1 B wt.% % passing wt.% % passing wt.% % passing wt.% >16.0 7.49 92.51 0.00 100.00 4.28 95.72 24.69 75.31 >9.51 0.00 92.51 63.80 36.20 9.34 86.39 14.52 60.79 >4.76 1.82 90.69 12.91 23.29 13.92 72.46 15.59 45.20 >2.00 2.94 87.75 5.51 17.78 8.47 63.99 14.22 30.98 >0.850 20.52 67.24 2.93 14.85 10.28 53.71 10.69 20.29 >0.425 9.06 58.18 2.36 12.49 17.81 35.90 9.09 11.20 >0.212 10.67 47.51 2.55 9.94 8.21 27.69 5.60 5.60 >0.180 2.17 45.34 0.58 9.36 1.41 26.28 0.88 4.72 >0.150 3.30 42.03 0.93 8.43 2.29 23.99 0.96 3.76 >0.106 8.59 33.44 1.98 6.45 5.79 18.20 1.58 2.18 >0.075 15.66 17.77 2.60 3.85 8.69 9.51 1.26 0.92 >0.053 11.26 6.51 2.64 1.21 8.97 0.54 0.66 0.26 <0.053 6.51 0.00 1.21 0.00 0.54 0.00 0.26 0.00 T O T A L 100.00 100.00 100.00 100.00 198 A P P E N D I X C T A B L E C I (continued): Results of grain size analyses for the 03CC series of samples from Clinton Creek. Size 0 3 C C 0 7 0 1 A 0 3 C C 0 7 0 1 B 0 3 C C 0 8 0 1 A 0 3 C C 0 8 0 1 B wt.% % passing wt.% % passing wt.% % passing % passing wt.% >16.0 25.82 74.18 0.00 100.00 0.00 100.00 9.91 90.09 >9.51 22.42 51.76 5.32 94.68 2.56 97.44 14.69 75.40 >4.76 11.28 40.48 27.46 • 67.21 6.09 91.35 17.81 57.59 >2.00 10.44 30.04 32.18 35.03 8.94 82.41 18.13 39.46 >0.850 5.41 24.62 12.37 22.66 8.96 73.45 11.20 28.26 >0.425 6.47 18.15 8.22 14.44 17.23 56.21 9.45 18.81 >0.212 4.29 13.86 4.49 9.95 2.90 53.31 7.83 10.98 >0.180 0.47 13.39 0.42 9.52 1.98 51.33 1.40 9.58 >0.150 0.79 12.60 0.89 8.63 10.75 40.59 1.64 7.94 >0.106 2.39 10.20 2.20 6.43 9.73 30.85 2.66 5.29 >0.075 3.37 6.83 2.61 3.82 12.41 18.44 2.63 2.66 >0.053 3.74 3.09 2.79 1.03 12.92 5.52 1.82 0.84 <0.053 3.09 0.00 1.03 0.00 5.52 0.00 0.84 0.00 T O T A L 100.00 100.00 100.00 100.00 Size 0 3 C C 0 9 0 1 A 0 3 C C 0 9 0 1 B 0 3 C C 1 0 0 1 A 0 3 C C 1 0 0 1 B wt.% % passing wt.% % passing wt.% % passing % passing wt.% >16.0 1.18 98.82 49.33 50.67 0.00 100.00 2.29 97.71 >9.51 4.55 94.27 4.39 46.28 4.71 95.29 4.65 93.05 >4.76 6.51 87.76 10.50 35.78 13.62 81.67 9.71 83.34 >2.00 6.71 81.04 9.21 26.56 11.23 70.45 16.45 66.89 >0.850 12.62 68.42 6.52 20.04 12.91 57.53 9.43 57.46 >0.425 21.28 47.14 7.26 12.78 18.83 38.70 15.84 41.62 >0.212 10.78 36.36 5.68 7.10 16.45 22.25 14.10 27.53 >0.180 2.44 33.91 0.87 6.22 3.07 19.18 2.82 24.71 >0.150 3.43 30.49 1.01 5.21 3.44 15.75 5.92 18.79 >0.106 8.69 21.79 1.63 3.58 5.84 9.91 5.59 13.20 >0.075 13.06 8.73 1.55 2.03 5.97 3.94 5.92 7.27 >0.053 7.97 0.76 1.15 0.88 3.70 0.24 5.29 1.99 <0.053 0.76 0.00 0.88 0.00 0.24 0.00 1.99 0.00 T O T A L 100.00 100.00 100.00 100.00 199 A P P E N D I X C T A B L E C2: Results of grain size analyses for the M M I 0 3 series from Cassiar. Size MMI031-1 MM 1031-2 MMI031-3 MMI031-4 (mm) wt.% % passing wt.% % passing wt.% % passing wt.% % passing >16.0 0.00 100.00 4.79 95.21 7.71 92.29 7.10 92.90 >9.51 7.56 92.44 5.90 89.31 1.14 91.16 29.43 63.47 >4.76 20.55 71.89 19.35 69.96 12.00 79.16 19.88 43.59 >2.00 19.69 52.20 28.11 41.84 26.06 53.09 13.29 30.31 >0.850 21.41 30.79 17.14 24.70 25.81 27.28 11.40 18.90 >0.425 14.00 16.79 11.83 12.87 18.48 8.80 7.70 11.20 >0.212 9.17 7.62 7.14 5.73 1.89 6.91 5.28 5.92 >0.180 1.02 6.60 0.72 5.00 1.05 5.85 0.77 5.15 >0.150 1.45 5.15 1.21 3.79 1.47 4.38 1.38 3.77' >0.106 2.41 2.74 1.83 1.97 2.23 2.15 1.85 1.92 >0.075 1.34 1.39 1.07 0.90 1.22 0.93 0.98 0.94 >0.053 1.02 0.38 0.52 0.38 0.55 0.38 0.57 0.37 <0.053 0.38 0.00 0.38 0.00 0.38 0.00 0.37 0.00 TOTAL 100.00 100.00 100.00 100.00 Size MMI031-5 MMI031-6 MMI031-7 MMI031-8 wt.% % passing wt.% % passing wt.% % passing wt.% % passing >16.0 10.49 89.51 0.00 100.00 3.51 96.49 7.57 92.43 >9.51 2.14 87.36 16.67 83.33 9.78 86.71 5.66 86.76 >4.76 11.84 75.52 13.73 69.61 15.39 71.32 9.70 77.06 >2.00 17.39 58.13 7.32 62.28 19.08 52.23 22.49 54.57 >0.850 19.17 38.96 17.36 44.93 16.21 36.03 21.26 33.31 >0.425 17.19 21.77 19.78 25.14 14.43 21.59 16.32 16.99 >0.212 11.71 10.06 13.61 11.53 10.82 10.78 9.93 7.07 >0.180 1.48 8.58 1.33 10.21 1.59 9.19 0.84 6.23 >0.150 1.85 6.73 1.90 8.30 2.25 6.94 1.63 4.60 >0.106 2.74 3.99 3.75 4.56 3.06 3.88 2.30 2.30 >0.075 1.62 2.38 1.44 3.11 1.44 2.44 1.18 1.12 >0.053 1.29 1.09 2.83 0.29 1.29 1.14 0.62 0.50 <0.053 1.09 0.00 0.29 0.00 1.14 0.00 0.50 0.00 TOTAL 100.00 100.00 100.00 100.00 Size MMI031-9 MMI031-10 MMI031-11 MMI031-12 wt.% % passing wt.% % passing wt.% % passing wt.% % passing >16.0 0.00 100.00 0.00 100.00 0.00 100.00 0.00 100.00 >9.51 5.80 94.20 0.00 100.00 0.00 100.00 1.32 98.68 >4.76 3.88 90.32 12.45 87.55 17.90 82.10 20.14 78.53 >2.00 15.82 74.50 16.80 70.74 16.45 65.65 26.70 51.83 >0.850 26.09 48.41 11.58 59.16 17.35 48.30 19.89 31.94 >0.425 24.75 23.66 20.94 38.23 26.78 21.52 15.37 16.57 >0.212 13.73 9.93 23.44 14.79 16.18 5.35 9.84 6.73 >0.180 1.63 8.31 3.43 11.36 1.22 4.12 0.98 5.75 >0.150 2.21 6.09 4.30 7.07 1.50 2.63 1.49 4.26 >0.106 3.13 2.96 2.66 4.40 1.68 0.95 2.09 2.17 >0.075 1.38 1.59 1.69 2.72 0.23 0.72 0.89 1.28 >0.053 0.88 0.71 1.58 1.14 0.32 0.41 0.72 0.55 O.053 0.71 0.00 1.14 0.00 0.41 0.00 0.55 0.00 TOTAL 100.00 100.00 100.00 100.00 200 A P P E N D I X C T A B L E C3: Results of grain size analyses for the 0 3 C A series of samples from Cassiar. Size (mm) 03CA0101 03CA0201 03CA0202 03CA0203 wt.% % passing wt.% % passing wt.% % passing wt.% % passing >16.0 18.92 81.08 49.22 50.78 8.77 91.23 14.92 85.08 >9.51 10.74 70.34 10.12 40.67 12.82 78.41 19.66 65.42 >4.76 16.75 53.58 10.10 30.57 15.44 62.97 15.78 49.64 >2.00 19.07 34.51 10.46 20.10 19.30 43.67 15.11 34.53 >0.850 11.72 22.80 7.36 12.74 17.13 26.54 12.95 21.58 >0.425 9.55 13.24 5.43 7.31 12.25 14.29 9.69 11.89 >0.212 6.59 6.65 3.67 3.64 7.79 6.50 6.81 5.08 >0.180 0.90 5.76 0.54 3.10 1.01 5.48 0.67 4.41 >0.150 1.15 4.61 0.64 2.46 1.22 4.27 1.20 3.21 >0.106 1.63 2.98 0.91 1.55 1.86 2.41 2.11 1.10 >0.075 1.81 1.17 0.88 0.68 1.31 1.10 0.43 0.67 >0.053 0.93 0.24 0.50 0.18 0.63 0.46 0.38 0.29 <0.053 0.24 0.00 0.18 0.00 0.46 0.00 0.29 0.00 TOTAL 100.00 100.00 100.00 100.00 Size 03CA0301 03CA0302 03CA0303 03CA0304 wt.% % passing wt.% % passing wt.% % passing wt.% % passing >16.0 9.13 90.87 0.00 100.00 3.29 96.71 5.30 94.70 >9.51 10.20 80.67 12.35 87.65 12.60 84.12 4.94 89.77 >4.76 12.15 68.52 10.72 76.93 10.24 73.87 8.06 81.71 >2.00 16.67 51.86 17.96 58.96 18.49 55.38 16.69 65.02 >0.850 18.33 33.53 18.12 40.84 16.25 39.13 19.14 45.88 >0.425 16.17 17.36 18.05 22.79 17.05 22.08 19.23 26.65 >0.212 9.80 7.56 12.40 10.39 11.39 10.68 13.17 13.48 >0.180 1.28 6.28 1.89 8.49 1.71 8.97 2.00 11.48 >0.150 1.48 4.80 2.00 6.49 2.03 6.94 2.35 9.13 >0.106 1.99 ' 2.81 3.05 3.44 2.82 4.12 3.64 5.49 >0.075 1.43 1.38 2.13 1.30 2.91 1.21 2.45 3.04 >0.053 0.92 0.46 0.92 0.38 0.89 0.32 1.80 1.24 O.053 0.46 0.00 0.38 0.00 0.32 0.00 1.24 0.00 TOTAL 100.00 100.00 100.00 100.00 Size 03CA0305 03CA0401 03CA0402 03CA0501 wt.% % passing wt.% % passing wt.% % passing wt.% % passing >16.0 0.40 99.60 9.28 90.72 1.54 98.46 79.75 20.25 >9.51 0.56 99.05 7.11 83.61 3.12 95.34 0.80 19.45 >4.76 13.48 85.57 16.84 66.77 11.96 83.38 1.92 17.53 >2.00 26.74 58.83 20.00 46.77 18.87 64.51 4.86 12.67 >0.850 24.14 34.68 16.87 29.90 24.68 39.84 3.66 9.01 >0.425 16.27 18.41 12.80 17.11 18.19 21.65 3.60 5.41 >0.212 9.97 8.44 8.84 8.26 11.03 10.61 2.74 2.68 >0.180 1.27 7.17 1.15 7.11 1.32 9.29 0.29 2.39 >0.150 1.55 5.62 1.47 5.65 1.85 7.44 0.51 1.88 >0.106 2.17 3.45 2.22 3.42 2.78 4.66 0.82 1.06 >0.075 1.43 2.02 1.39 2.03 1.71 2.95 0.53 0.53 >0.053 1.07 0.95 1.14 0.89 1.52 1.43 0.35 0.18 O.053 0.95 0.00 0.89 0.00 1.43 0.00 0.18 0.00 TOTAL 100.00 100.00 100.00 100.00 201 APPENDIX C TABLE C3 (continued): Results of grain size analyses for the 03CA series of samples from Cassiar. Size (mm) 03CA0502 03CA0601 03CA0602 03CA0603 wt.% % passing wt.% % passing wt.% % passing wt.% % passing >16.0 6.96 93.04 0.00 100.00 0.00 100.00 0.00 100.00 >9.51 3.20 89.83 0.00 100.00 0.69 99.31 0.00 100.00 >4.76 11.92 77.91 4.25 95.75 10.62 88.69 21.23 78.77 >2.00 17.73 60.19 15.63 80.12 19.70 69.00 37.05 41.72 >0.850 15.83 44.36 23.35 56.77 32.41 36.58 24.20 17.52 >0.425 15.34 29.01 20.73 36.04 19.46 17.12 9.72 7.80 >0.212 13.15 15.87 17.46 18.57 10.85 6.27 5.00 2.80 >0.180 1.94 13.93 2.42 16.15 1.42 4.85 0.47 2.33 >0.150 2.68 11.25 3.34 12.82 1.39 3.46 0.63 1.70 >0.106 3.80 7.45 6.74 6.08 2.04 1.42 0.92 0.77 >0.075 3.28 4.17 2.55 3.53 0.66 0.76 0.31 0.46 >0.053 2.61 1.56 1.90 1.64 0.45 0.31 0.24 0.22 <0.053 1.56 0.00 1.64 0.00 0.31 0.00 0.22 0.00 TOTAL 100.00 100.00 100.00 100.00 Size 03CA0701 03CA0702 03CA0801 03CA0802 wt.% % passing wt.% % passing wt.% % passing wt.% % passing >16.0 1.21 98.79 0.00 100.00 0.00 100.00 6.72 93.28 >9.51 0.87 97.91 3.43 96.57 6.31 93.69 8.64 84.63 >4.76 16.45 81.46 18.82 77.75 10.29 83.40 15.63 69.01 >2.00 20.13 61.33 20.77 56.98 19.21 64.19 22.59 46.41 >0.850 15.09 46.25 14.94 42.04 21.29 42.90 20.23 26.18 >0.425 16.54 29.71 16.36 25.68 18.75 24.16 13.20 12.98 >0.212 15.70 14.01 14.33 11.35 11.72 12.44 7.35 5.63 >0.180 2.78 11.23 2.36 8.99 1.92 10.52 0.73 4.89 >0.150 4.10 7.13 2.07 6.92 1.92 8.60 1.02 3.87 >0.106 2.83 4.30 3.22 3.70 3.54 5.06 1.54 2.33 >0.075 1.62 2.68 1.43 2.27 1.73 3.33 1.03 1.30 >0.053 1.56 1.12 1.24 1.03 1.78 1.55 0.72 0.58 <0.053 1.12 0.00 1.03 0.00 1.55 0.00 0.58 0.00 TOTAL 100.00 100.00 100.00 100.00 Size 03CA0901 03CA0902 03CA1001 03CA1002 wt.% % passing wt.% % passing wt.% % passing wt.% % passing >16.0 70.61 29.39 9.26 90.74 0.00 100.00 5.08 94.92 >9.51 3.69 25.70 17.30 73.43 0.53 99.47 11.34 83.58 >4.76 3.99 21.71 20.86 52.57 5.67 93.80 18.65 64.93 >2.00 3.54 18.17 11.27 41.30 11.92 81.87 21.76 43.17 >0.850 3.94 14.23 14.12 27.17 12.64 69.23 18.10 25.08 >0.425 4.54 9.69 12.24 14.94 21.53 47.71 9.99 15.08 >0.212 3.59 6.10 8.09 6.85 22.29 25.41 8.09 6.99 >0.180 0.42 5.68 1.37 5.47 3.55 21.87 1.00 5.99 >0.150 0.67 5.01 1.33 4.15 3.93 17.93 2.04 3.95 >0.106 1.66 3.35 2.15 2.00 6.82 11.11 0.76 3.19 >0.075 0.92 2.43 0.64 1.36 3.51 7.61 0.71 2.48 >0.053 1.16 1.26 0.76 0.60 3.97 3.63 0.42 2.06 <0.053 1.26 0.00 0.60 0.00 3.63 0.00 2.06 0.00 TOTAL 100.00 100.00 100.00 100.00 202 A P P E N D I X C T A B L E C3 (continued): Results of grain size analyses for the 0 3 C A series of samples from Cassiar. Size (mm) 0 3 C A 1 1 0 1 0 3 C A 1 1 0 2 0 3 C A 1 2 0 1 0 3 C A 1 2 0 2 wt.% % passing wt.% % passing wt.% % passing wt.% % passing >16.0 0.00 100.00 9.63 90.37 5.86 94.14 15.46 84.54 >9.51 1.03 98.97 9.86 80.51 5.18 88.96 13.05 71.49 >4.76 7.20 91.76 12.92 67.59 9.58 79.38 23.28 48.21 >2.00 19.70 72.06 21.17 46.42 12.78 66.60 19.39 28.82 >0.850 15.04 57.02 18.57 27.85 11.01 55.59 10.82 18.00 >0.425 17.31 39.71 13.40 14.45 17.82 37.78 7.89 10.11 >0.212 16.86 22.85 8.16 6.28 17.41 20.36 5.31 4.80 >0.180 2.70 20.15 1.12 5.17 2.55 17.82 0.73 4.07 >0.150 2.94 17.21 1.19 3.98 3.17 14.64 0.78 3.29 >0.106 6.15 11.06 1.82 2.16 6.09 8.55 1.52 1.77 >0.075 3.35 7.71 0.96 1.20 2.72 5.83 0.75 1.02 >0.053 3.88 3.84 0.73 0.48 3.00 2.83 0.59 0.43 <0.053 3.84 0.00 0.48 0.00 2.83 0.00 0.43 0.00 T O T A L 100.00 100.00 100.00 100.00 203 A P P E N D I X C T A B L E C4: Wet-sieving data for bulk samples from Clinton Creek (04CC1401) and Cassiar (03CC1601) Sieve Size 04CC1401 (mm) Sample Non-fibrous Fibrous wt.% %passing wt.% %passing wt.% %passing >9.51 13.38 86.62 14.29 85.71 0.18 99.16 >1.68 44.37 42.25 45.09 40.61 2.17 64.75 >1.41 6.02 36.23 6.00 34.62 2.96 58.37 >0.850 11.21 25.02 11.64 22.97 1.30 53.15 >0.595 7.38 17.64 7.38 15.59 2.79 45.78 >0.350 8.61 9.03 8.70 6.89 2.37 38.48 >0.212 4.96 4.07 4.51 2.38 6.27 27.34 >0.180 0.74 3.33 0.59 1.79 10.95 24.42 >0.106 1.93 1.40 1.26 0.53 16.03 13.36 >0.053 1.06 0.34 0.42 0.11 25.84 3.53 O.053 0.34 0.00 0.11 0.00 29.15 0.00 TOTAL 100.00 100.00 100.00 Sieve Size 04CC1601 (mm) Sample Non-fibrous Fibrous wt.% %passing wt.% %passing wt.% %passing > 16.0 4.30 95.70 4.83 95.17 0.00 100.00 >9.50 8.13 87.56 9.13 86.04 0.00 100.00 >4.76 18.44 69.13 20.68 65.36 0.17 99.83 >2.00 22.50 46.63 23.07 42.28 17.83 82.00 >0.850 20.60 26.02 18.35 23.93 38.93 43.07 >0.425 10.43 15.59 8.31 15.62 27.73 15.34 >0.212 7.21 8.38 6.21 9.41 15.34 0.00 >0.150 2.10 6.28 2.36 7.06 0.00 0.00 >0.106 2.02 4.26 2.27 4.79 0.00 0.00 >0.075 1.62 2.65 1.82 2.97 0.00 0.00 >0.053 1.16 1.48 1.30 1.67 0.00 0.00 <0.053 1.48 1.67 0.00 TOTAL 100.00 100.00 100.00 204

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