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Structural controls on mineralization and constraints on fluid evolution at the Sacrificio Cu (Zn-Pb-Ag-Au).. Patterson, Keith Mark 2001

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STRUCTURAL CONTROLS ON MINERALIZATION AND CONSTRAINTS ON FLUID EVOLUTION AT THE SACRIFICIO Cu (Zn-Pb-Ag-Au) SKARN, DURANGO, MEXICO By KEITH MARK PATTERSON B.A.Sc., The University of British Columbia, 1994 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE In THE FACULTY OF GRADUATE STUDIES (Department of Earth and Ocean Sciences) We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA May 2001 © Keith Mark Patterson, 2001 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of tlft^w fWQ Q-ffV^ SCA^-X^ The University of British Columbia Vancouver, Canada Date Hoo\ Abstract The Sacrificio deposit, located in Durango State, Mexico, is hosted by mid-Cretaceous limestone, chert, and minor shale of the Cuesta del Cura and Indidura formations. Intrusive rocks include two temporally and compositionally distinct suites, dated at 109.1 ± 0.4 Ma (mid-Cretaceous) and 40.1 ± 0.5 Ma (Middle Eocene) by U-Pb methods. The Middle Eocene granite suite is associated with the development of skarn and related sulphide mineralization that forms the Sacrificio deposit. Three episodes of pre-intrusion regional deformation (D^ to D3) and two episodes of syn-intrusion local deformation are recognized at the Sacrificio deposit. Skarn and skarn-related mineralization is localized by these regional and local structures and their intersections. Alteration at the Sacrificio deposit is divided into pre-mineralization contact metamorphism, prograde skarn, and retrograde skarn. Styles of skarn-related sulphide mineralization include: (1) disseminated bornite and lesser chalcopyrite filling porosity in prograde garnet skarn; (2) fracture-controlled, silver-rich, bornite-chalcopyrite + sphalerite ± galena ± arsenopyrite cutting prograde garnet skarn and marble; and (3) semi-massive to massive sulphide bodies (mantos) containing sphalerite, galena, chalcopyrite, arsenopyrite, pyrrhotite, pyrite, and bornite associated with retrograde amphibole skarn. Rare quartz-arsenopyrite veins cut all alteration and mineralization. Skarn and sulphide-forming fluids at the Sacrificio deposit are interpreted to be magmatic in origin from lead isotope data. Compositions of garnet (Ad65-iooGro-35) and pyroxene (Dies^Hds-aoJo^s) from prograde skarn classify the ii Sacrificio deposit as a copper skarn. Fluid inclusion studies indicate that mineralizing fluids were dominantly H20-NaCI mixtures (0.5 - 19.7 wt. % NaCI eq.) containing divalent cations (i.e., Mg2+, Fe2+, and Ca2+). Pressures during the development of the Sacrificio deposit were approximately 0.5 to 1.0 kbar. Temperatures recorded during skarn formation and sulphide deposition show a gradual cooling of the skarn system. Prograde skarn formed at 460° to 580° C, disseminated Cu-Ag mineralization at 291° to 504° C, and mantos at 247° to 396° C. A final pulse of hotter fluids (318° to 480° C) formed the late quartz-arsenopyrite veins. Results of this study have allowed the construction of a detailed structural and fluid evolution model for the Sacrificio deposit. Application of these findings to other skarn deposits or prospects in Mexico, and elsewhere in the world, may lead to the discovery of important new orebodies. iii Table of Contents Abstract ii Table of Contents iv List of Tables viii List of Figures ix Acknowledgments xi Chapter 1 General Introduction 1 Methodology 2 Geological Field Mapping 2 Structural AnalysisU-Pb Geochronological Studies 2 Lithogeochemical Studies 3 Fluid Inclusion StudiesPb Isotope StudiesGarnet and Pyroxene Electron Microprobe Studies 4 Presentation 4 References 5 Chapter 2 The Importance of Pre- and Syn-lntrusion Deformation in Controlling the Distribution of Cu (Zn-Pb-Ag-Au) Skarn Mineralization at Cerro el Sacrificio, Durango, Mexico 6 Abstract 7 iv Table of Contents (cont.) Introduction 8 Property History 11 Methods Employed 2 Regional Geology 13 Geographical Setting 1Altiplano Stratigraphy 4 Intrusive Rocks 1Tectonic Setting 5 Property Geology 16 StratigraphyIntrusive Rocks 17 U-Pb Geochronology 9 Structure 22 Mineralization 23 Disseminated Cu-Ag mineralization 24 Fracture controlled Cu-Ag±Au mineralization 25 Manto-style Zn-Cu-Pb-Ag-Au mineralization 26 Alteration 27 Structural Evolution of the Sacrificio Skarn Deposit 29 Structural Controls on Ore Distribution at Mexican Skarn Deposits 34 San Martin 35 Charcas 36 v Table of Contents (cont.) La Colorada - Chalchihuites District 38 Conclusions 39 Acknowledgements 41 References 2 Figure Captions 51 Chapter 3 Evolution and Source of Mineralizing Fluids at the Sacrificio Cu (Zn-Pb-Ag-Au) Skarn Deposit, Durango, Mexico 76 Abstract 77 Introduction 8 Regional Geological Setting 79 Local Geological Setting 81 Skarn-Related Mineralization 2 Alteration 84 Garnet and Clinopyroxene Mineral Chemistry 87 Structural Model 89 Fluid Inclusion Microthermometry 91 Methodology 9Fluid inclusion petrography 93 Microthermometric data 4 Microthermometry results 96 Lead Isotope Study 98 vi Table of Contents (cont.) Analytical procedure 98 Results and interpretation 9 Discussion 100 Skarn classification 10Source of metals and fluids 101 Physicochemical conditions of skarn formation 101 Conclusions 104 Acknowledgements 105 References 107 Figure Captions 114 Chapter 4 General Conclusions 139 References 143 Appendices Appendix A: Location Map of Local Sacrificio Grid and Grid Coordinates 144 Appendix B: Structural Data - Sacrificio Deposit 146 Appendix C: Garnet Compositions - Sacrificio Deposit 164 Appendix D: Pyroxene Compositions - Sacrificio Deposit 171 Appendix E: Fluid Inclusion Microthermometric Data -Sacrificio Deposit 175 Appendix F: General Geology, Structure, and Alteration Map -Sacrificio Deposit 179 vii List of Tables Chapter 2 Table 1 Major Oxide Element and Rare Earth Element Abundances of Intrusive Rocks at the Sacrificio Deposit 73 Table 2 U-Pb Isotope Data 74 Table 3 Paragenesis of Alteration and Mineralization at the Sacrificio Deposit 75 Chapter 3 Table 4 Paragenesis of Alteration and Mineralization at the Sacrificio Deposit 135 Table 5 Representative Microprobe Analyses of Garnets and Pyroxenes from Prograde Skarn 136 Table 6 Microthermometric Data 137 Table 7 Pb Isotope Data 138 viii List of Figures Chapter 2 Figure 1 Location Map of the Sacrificio Deposit 56 Figure 2 Morphotectonic and Plate-Tectonic Setting of Mexico 57 Figure 3 Simplified Geologic Map of the Sacrificio Deposit 58 Figure 4 Intrusive Phases of the Sacrificio and Coloradito Intrusions 59 Figure 5 Photographs of Major Intrusive Phases 60 Figure 6 Whole-rock Chemical Compositions of Intrusive Rocks 61 Figure 7 Rare-Earth-Element abundances of Intrusive Rocks 62 Figure 8 U-Pb Concordia Plots 63 Figure 9 Structural Geology of the Sacrificio Deposit 64 Figure 10 Equal-Area Stereonet Projections of Structural Data 65 Figure 11 Map of Skarn Alteration and Mineralization 66 Figure 12 Photographs of Mineralization Styles 67 Figure 13 Interpreted Sequence of Deformation Events 68 Figure 14 Relative timing of deformation, alteration, and mineralization 69 Figure 15 Photographs of Key Structural Features 70 Figure 16 Chemical Compositions of Intrusive Rocks from San Martin 71 Figure 17 Rare-Earth-Element abundances of Intrusive Rocks from San Martin 72 Chapter 3 Figure 18 Location Map of the Sacrificio Deposit 119 Figure 19 Simplified Geologic Map of the Sacrificio Deposit 120 ix Figure 20 Photographs of the Major Mineralization Styles 121 Figure 21 Map of Skarn Alteration and Mineralization 122 Figure 22 Photographs of Skarn Minerals at the Sacrificio Deposit 123 Figure 23 Iron vs. Aluminum in Grandite Garnets 124 Figure 24 Ternary Plots of Garnet and Pyroxene Compositions 125 Figure 25 Interpreted Sequence of Deformation Events 126 Figure 26 Relative timing of deformation, alteration, and mineralization 127 Figure 27 Fluid Inclusion Microphotographs 128 Figure 28 Fluid Inclusion Microthermometric Data 129 Figure 29 Trapping Temperatures and Pressures of Manto and Disseminated Mineralization 130 Figure 30 Trapping Temperatures and Pressures of Arsenopyrite-Quartz Veins 131 Figure 31 Lead Isotope Data 132 Figure 32 Pressure-Temperature Stability of Wollastonite 133 Figure 33 Temperatures of Formation of Sacrificio Skarn and Mineralization Styles 134 x Acknowledgements This project and my education in general have been greatly enriched by the support, encouragement, and guidance provided by the entire Department of Earth and Ocean Sciences at the University of British Columbia. The list of people who have helped in countless ways would fill most of this thesis, I will try to mention those who have made particularly significant contributions. To everyone else, and those I've forgotten to include in this list: thank-you. First, I would like to thank my advisor, Dr. Stephen Rowins, for allowing me the opportunity to do this research and allowing me the latitude to pursue the aspects of this project which most interested me. Additionally, Drs. Greg Dipple, Lori Kennedy, James Mortensen, and Richard Tosdal, of the University of British Columbia have provided indispensable advice that contributed greatly to the ideas contained within this thesis. Dr. Peter Lewis of Lewis Geoscience provided critical structural advice, and is thanked for taking time out of his busy schedule to do so. Janet Gabites, Elisabetta Pani, and Mati Raudsepp are sincerely thanked for their help with lead isotope analyses, S.E.M. studies, and electron microprobe analyses, respectively. Without their generous help, none of these studies would have been possible. Alex Allen is thanked for her help in wading through all things bureaucratic, without her help it is unlikely I would have managed to stay a registered student. Field mapping forms the backbone of this thesis and many people contributed towards making my time in Mexico enjoyable and virtually hassle-xi free. David Terry and Chris Rockingham of Boliden are thanked for their support, advice, and free flow of ideas both during fieldwork and throughout this project. David Aguilar of Luismin contributed indispensable logistical support, useful geologic ideas, and spur-of-the-moment Spanish lessons. Finally, Nena Senora ensured that our house ran smoothly and kept me out of trouble in Vicente Guerrero. Funding for this project has been primarily provided by a generous industry grant from Boliden Limited. Additional funds have been received from a Thomas and Marguerite Mackay Memorial Scholarship and an SEGF student research grant. Finally, I would like to acknowledge and thank the support and encouragement of my family, particularly my late grandfather who supported me in beginning this thesis and would have been proud to see its completion. xii Chapter 1 General Introduction The Sacrificio Cu (Zn-Pb-Ag-Au) skarn is located in southeastern Durango State, Mexico, and is being actively explored by Boliden Mexico S.A. de C.V., a wholly-owned subsidiary of Boliden Limited of Canada. It is an excellent example of a structurally-controlled, intrusion-related mineral deposit. Polyphase deformation both precedes, and is synchronous with, the emplacement of Middle Eocene, multiphase granitic intrusions and associated mineralization. The development of a structural model that both explains and predicts the location of skarn-related mineralization has aided ongoing exploration efforts at Cerro Sacrificio. This structural model is also applicable to many other skarn and carbonate replacement deposits of the Mexican Altiplano. Extensive geological field mapping has been fundamental to all studies and interpretations in this thesis and has provided a solid foundation upon which to build further understanding of the Sacrificio deposit. A total of over three months were spent mapping rocks and structures in and around the Sacrificio deposit in order to ensure that interpretations derived from the laboratory-based studies are consistent with field data. Following the field program, structural data analysis, U-Pb geochronology, lithogeochemistry, fluid inclusion studies, Pb isotope studies, and electron microprobe studies were undertaken. The results of this thesis represent a significant advance in the understanding of polymetallic skarn and carbonate replacement deposits in Mexico and elsewhere in the world. Methodology Geological Field Mapping Geological mapping of the Sacrificio deposit and the surrounding 2.5 x 3 km area was undertaken by the author with the aid and cooperation of Boliden project geologist, Dr. David Terry, and the University of British Columbia thesis advisor, Dr. Stephen Rowins. In total, over 7.5 km2 were mapped at a scale of 1:2,000. Field data collected during the course of this mapping included: rock type, alteration mineralogy, style and intensity of alteration, sulphide mineralogy, style and intensity of sulphide development, structural relations, and the measurement of approximately 1,200 separate structural fabrics. Structural Analysis Subsequent to field work, structural orientation data were analyzed and interpreted by the author using a variety of data reduction methods. Stereonet projections of all data (using Stereonet 3.02 software) by area have provided the basis for the structural model presented in Chapter 2. U-Pb Geochronological Studies Four samples of intrusive rock from the Sacrificio property were dated using U-Pb techniques. The robust nature of the U-Pb isotopic system ensures that ages obtained reflect the crystallization age of the intrusion dated and are not influenced by subsequent hydrothermal or metamorphic events. All U-Pb 2 analyses were done in the Geochronology Laboratory at the University of British Columbia either by or under the direct supervision of Dr. James K. Mortensen. Lithogeochemical Studies Eighteen samples of intrusive rocks from the Sacrificio property were sampled and analyzed for major oxide element, trace element, and rare earth element concentrations. All analyses were done by Chemex Labs Ltd. of North Vancouver, British Columbia. These data allowed the author to classify intrusive suites by composition and to compare them with intrusive suites at the nearby San Martin skarn deposit. Fluid Inclusion Studies Microthermometric data were obtained from one hundred seventy eight fluid inclusions trapped in ten samples of hydrothermal quartz from three styles of mineralization at the Sacrificio deposit. Interpretation of these data provided constraints on physicochemical conditions (P-T-X) of mineralizing fluids. All analyses were done by the author at the University of British Columbia. Pb Isotope Studies A lead isotope study was undertaken by the author in order to constrain the source(s) of lead, and by inference, other metals in the Sacrificio deposit. Twenty-three samples of sulphide minerals, sedimentary host-rocks, and intrusive rocks were analyzed for lead isotope composition. These data indicate a magmatic source for metals in the Sacrificio deposit. Garnet and Pyroxene Electron Microprobe Studies Compositions of garnet and pyroxene from skarn deposits may be used to classify the deposit by metal content (Einaudi et al., 1981; Meinert, 1992). Garnet and pyroxene compositions from four samples of prograde skarn at the Sacrificio deposit were determined by the author using the electron microprobe. This data allowed the Sacrificio deposit to be classified as a copper skarn. Presentation Results of this research are presented as two separate papers that will be submitted to Economic Geology and Mineralium Deposita for publication. The first paper, entitled "The Importance of Pre- and Syn-lntrusion Deformation in Controlling the Distribution of Cu (Zn-Pb-Ag-Au) Skarn Mineralization at Cerro el Sacrificio, Durango, Mexico" presents the results of geological field mapping, structural analysis, U-Pb geochronology, and lithogeochemistry of intrusive rocks. Included in the first paper is a structural model that explains and predicts the location of skarn-related mineralization within regional and local structures. The second paper, entitled "Evolution and Source of Mineralizing Fluids at the Sacrificio Cu (Zn-Pb-Ag-Au) Skarn Deposit, Durango, Mexico" combines fluid inclusion data, Pb-isotope data, and garnet and pyroxene compositional data to identify the source, composition, and physicochemical conditions (P-T-X) of 4 skarn formation and related sulphide mineralization. Together, these two papers provide a comprehensive model for the formation of the Sacrificio Cu (Zn-Pb-Ag-Au) deposit. Due to the presentation of this thesis as two complementary research papers, a certain amount of duplication of information is unavoidable. Additionally, as the two papers will be submitted to the peer-reviewed journals, Economic Geology and Mineralium Deposits, American spelling has been used throughout chapters 2 and 3. It is hoped that any inconvenience to reviewers of this thesis is minimal and is justified by the benefits of timely publication in prestigious peer-reviewed geoscience journals. References Einaudi, M.T., Meinert, L.D., and Newberry, R.J., 1981,Skarn Deposits, in Skinner, B.J., ed., Economic Geology 75th Anniversary Volume: Economic Geology Publishing Company, El Paso, Texas, p. 317-391. Meinert, L.D., 1992, Skarns and Skarn deposits, Geoscience Canada, v. 19, p. 145-162. 5 Chapter 2 The Importance of Pre- and Syn-intrusion Deformation in Controlling the Distribution of Cu (Zn-Pb-Ag-Au) Skarn Mineralization at Cerro el Sacrificio, Durango, Mexico Keith M. Patterson (Co-Authors: Stephen M. Rowins, James K. Mortensen, and David A. Terry) 6 Abstract The structures generated during pre-intrusion regional, and syn-intrusion local, deformation events are recognized as important controls over the distribution of Cu-Zn-Pb-Ag-Au sulfide mineralization at the Sacrificio skarn deposit in southern Durango, Mexico. The Sacrificio deposit is situated in the Mexican Altiplano and is hosted by mid-Cretaceous limestone, chert, and minor shale of the Cuesta del Cura and Indidura formations. New U-Pb geochronological data indicate the presence of two temporally distinct felsic intrusive suites. The older mid-Cretaceous granodiorite-quartz monzonite suite is 109.1 + 0.4 Ma whereas the younger Middle Eocene granite suite is 40.1 ± 0.5 Ma. Importantly, it is only the Middle Eocene granite suite which is associated with the formation of skarn and related styles of sulfide mineralization. Three episodes of pre-intrusion regional deformation (Di to D3) are recognized in the carbonate rocks at the Sacrificio deposit. Di and D3 record strong east-northeast-directed shortening associated with the Mexican fold-and-thrust belt, whereas D2 records a local re-orientation of shortening directions and has resulted in the formation of rare east-trending folds. Two episodes of intrusion-related deformation post-date regional deformation and are synchronous with the formation of mineralized skarn. The older, D4, is defined by the formation of a broad dome above the Sacrificio intrusion. The younger episode, D5, represents the opening of extensional fractures and formation of veins above and peripheral to the intrusion. 7 Alteration at the Sacrificio deposit is divided into pre-mineralization contact metamorphism, prograde skarn, and retrograde skarn. Three styles of skarn-related sulfide mineralization are recognized: (1) disseminated to semi-massive bornite and lesser chalcopyrite filling secondary porosity in prograde garnet skarn; (2) fracture-controlled, silver-rich, bornite-chalcopyrite + sphalerite ± galena + arsenopyrite cutting prograde garnet skarn and marble; and (3) fine- to coarse-grained, semi-massive to massive, sulfide bodies or "mantos", which are associated with retrograde amphibole skarn and contain a sulfide assemblage of sphalerite, galena, chalcopyrite, arsenopyrite, pyrrhotite, pyrite, bornite and rare tetrahedrite, stibnite and stannite. Prograde skarn is strongly localized along D3 fold hinges and hosts disseminated Cu-Ag mineralization, especially where adjacent to D5 fractures. These fractures are interpreted as the main conduits for magmatic fluids that produced the largest and best-developed zones of disseminated Cu-Ag mineralization. The base metal-rich (Zn-Cu-Pb) mantos replace marble and mineralized garnet skarn. It is proposed that the careful application of the Sacrificio structural model to many of the skarn and carbonate-replacement deposits of the Mexican Altiplano could result in new discoveries of precious and base metal mineralization. Introduction The geochemical and mineralogical characteristics of mineralized, intrusion-related skarns have been extensively investigated and are relatively 8 well-understood (e.g., Einaudi et al., 1981; Kwak, 1987; Megaw et al., 1988; Titley, 1993; Barton et al., 1995; Bowman, 1998; Meinert, 1998, 2000). In contrast, detailed studies on the structural evolution of mineralized skarn systems are limited despite an abundance of field evidence which indicates that structural fabrics commonly exert strong local and regional controls on the development and distribution of mineralization (e.g., Megaw, 1998b, 1999). Skarns and related carbonate-replacement deposits are notoriously difficult exploration targets due to the typically narrow and discontinuous nature of the mineralized zones. Exploration strategies commonly focus on a suspected spatial zonation of mineralization in chemically reactive (i.e., calcareous) sedimentary rocks that host the skarn-forming pluton (e.g., Meinert, 1997). In many respects, the exploration strategy follows a porphyry-type model with copper and, in some cases, gold forming closest to the pluton followed by successive outward zones of silver and base metals (Zn, Pb) (e.g., Einaudi et al., 1981). Although moderately successful, this exploration model must be applied with care because it will fail if structures that focus the ore fluids are not recognized and accorded prime importance in the development of the exploration model. In this contribution, the regional structures that formed during crustal shortening associated with the Late Cretaceous to mid-Tertiary Mexican fold-and-thrust belt (temporally and kinematically similar to the Laramide of the southwest U.S.) are shown to have been the initial conduits for skarn-forming fluids. These fluids emanated from a 40.1 ± 0.5 Ma granite intrusive complex 9 centered on Cerro el Sacrificio in southern Durango, Mexico. Local structures caused by stress generated during emplacement of this intrusive complex subsequently exerted a later and more local control over the distribution of Cu-Zn-Pb-Ag-Au mineralization. This interplay between pre-intrusion regional tectonic stress and syn-intrusion magmatic stress has resulted in the present-day configuration of the mineralized zones comprising the Sacrificio deposit. Careful field studies and detailed examination of diamond drillcore has failed to demonstrate a stratigraphic control on skarn and sulfide mineralization within the thick, sequence of interbedded Cretaceous limestone and chert that hosts the deposit. Consequently, although important for the overall development of the skarn system, host-rock composition has played a subordinate role to that of pre existing structures in controlling the distribution of sulfide mineralization at the Sacrificio deposit. The exploration concepts arising from this study of the Sacrificio deposit may be directly applied to many skarn and carbonate-replacement deposits throughout the Altiplano of central Mexico. Many of these deposits are associated with comparably aged mid-Tertiary granitoids and have formed in similar metasedimentary rock sequences possessing well-developed Mexican fold-and-thrust belt deformation fabrics. Moreover, many skarn and carbonate-replacement deposits in the Altiplano have local deformation fabrics superimposed over regional ones, with the former likely due to the emplacement of mineralizing mid-Tertiary granitoids. Application of the structural model developed at the Sacrificio deposit could identify significant zones of 10 mineralization in portions of skarn and carbonate-replacement systems previously deemed unmineralized. Property History The Sacrificio deposit is located 80 km southeast of Durango, in a well-recognized northwest-trending belt of mining districts including San Martin, Fresnillo, La Colorada, Zacatecas, and Francisco I. Madero (Fig. 1). This belt occurs along the western edge of the Mexican Altiplano (Fig. 2). The Sacrificio deposit is centered on Cerro el Sacrificio which has seen a long history of small-scale mining, evidenced by the many small workings and waste-dumps scattered around the mountain. The most recent mining activity focussed on copper-rich skarn mineralization at Mina Embotelladora located on the northern flank of Cerro el Sacrificio (Fig. 3). Production data are not available, but a geological reserve of 40,000 t of ore grading 50 g/t Ag, 0.5% Cu, 0.05% Pb, and 0.05% Zn was calculated by Albinson and Sanchez (1977). In this paper, the term deposit is used to describe skarn-related sulfide mineralization at Cerro el Sacrificio because of the approximately 15 years of production activity at Mina Embotelladora. Exploration of the Sacrificio property by Luismin S.A. de C.V. began in 1977 and continued intermittently to 1997. Work during this period consisted of geological mapping, geochemical and geophysical surveys, and several reverse circulation and diamond drilling programs (32 holes totaling 7,540 m). These programs targeted skarn mineralization exposed primarily around the base of n Cerro el Sacrificio. The most significant mineralization discovered during the Luismin work was encountered in diamond drillhole (DDH) LB96-04. This hole intersected 24.3 meters of disseminated and vein/veinlet sulfide mineralization averaging 0.3 g/t Au, 120 g/t Ag, and 1.72% Cu in garnet skarn immediately north of Mina Embotelladora. In 1997, Boliden Limited entered a joint-venture agreement with Luismin to further explore the Sacrificio property. A geological re-evaluation of the property in 1998 led to a diamond drilling program which targeted the hinge zone of a large anticlinal structure (the "Central Anticline") on the northern flank of Cerro el Sacrificio (Rowins, 1998). This program identified several well-developed zones of copper, zinc, lead, and silver mineralization, including several carbonate-replacement horizons of massive to semi-massive sulfides termed "mantos". The best manto (in terms of grade and thickness) was intersected in DDH SAC98-3, located just west of the Central Anticline hinge zone on Pad 3 (Fig. 3). This hole had an intersection of 16.4 meters averaging 1.48% Zn, 1.34% Cu, 0.99% Pb and 174.6 g/t Ag (Terry et al., 1999). Further drilling by Boliden in 2000 identified additional manto-style mineralization on the south flank of Cerro Coloradito. Methods Employed Between 1998 and 2000, the authors spent approximately 145 man-days mapping the Sacrificio deposit and surrounding ~2.5 x 3 km area at a scale of 1:2,000. During this geological mapping, approximately 1,200 structural measurements were collected and plotted together with lithological units, and 12 styles and intensity of alteration and mineralization. Diamond drill programs by Boliden Limited in 1998 and 2000 were planned and directed by two of the authors (S.M.R. and D.A.T.), and 12 of the 15 holes cored on the property during these programs were logged by the authors. Eighteen representative samples of the different types of intrusive rocks at the Sacrificio deposit were analyzed for major oxide element, trace element, and rare earth element compositions by ICP-MS. Four samples of intrusive rock were dated by U-Pb geochronological methods at the University of British Columbia. To identify types and styles of alteration and mineralization, fifty-five polished thin sections were studied by transmitted and reflected light microscopy accompanied by complimentary scanning electron microscope and electron microprobe analysis. Regional Geology Geographical Setting The Sacrificio deposit lies within the Altiplano of central Mexico (Figs. 1 and 2). The Altiplano is situated north of the Trans Mexican Volcanic Belt between the Sierra Madre Occidental and the Sierra Madre Oriental tectono-stratigraphic provinces (e.g., Sedlock et al., 1993). The Sierra Madre Occidental to the west is a region of extensive, flat-lying, felsic, Tertiary volcanic rocks whereas the Sierra Madre Oriental to the east is a region of thrusted and folded Mesozoic sedimentary rocks (e.g., Campa and Coney, 1983; Sedlock et al., 1993). The Altiplano primarily consists of deformed Late Jurassic to Cretaceous marine carbonate rocks with interbedded chert and shale. This metasedimentary 13 rock sequence, which contains in excess of 3000 m of carbonate strata (e.g., Megaw et al., 1988), is intruded by mid-Tertiary plutons ranging from granite to diorite in composition. In addition to causing extensive hydrothermal alteration of the adjacent carbonate host-rocks, these plutons are largely responsible for the precious and base metal-rich mineral deposits of the Altiplano (e.g., Rubin and Kyle, 1988; Barton et al., 1995; Megaw, 1999). Altiplano stratigraphy Stratified rocks of the Altiplano are dominated by platform carbonate rocks which were deposited in the westernmost extension of the ancestral Gulf of Mexico during the Late Jurassic to Cretaceous (Longoria et al., 1999). Evaporites are locally abundant. Intercalated with the carbonate rocks and evaporites are minor shale and flysch deposits derived from a magmatic arc to the west (Sedlock et al., 1993). The composition of the pre-Jurassic basement in this region is poorly known, although inferences of Proterozoic continental crust have been made from Nd isotopic studies of xenoliths within Quaternary volcanic rocks (Ruizetal., 1988). Intrusive rocks Geochemical, mineralogical, and geochronological data for intrusive rocks of the Altiplano are sparse, excluding those intrusions associated with mineral deposits (e.g., Barton et al.,1995; Damon et al., 1981; Megaw, 1999). Available geochronological data indicate that intrusions range from 30 Ma to 46.6 Ma in 14 age (Megaw, 1999). These ages are coeval with volcanic rocks of the "lower volcanic complex" of the Sierra Madre Occidental magmatic arc (Coney, 1978). The intrusions are commonly multiphase and cut by late felsic dykes. The compositions of both intrusions and dykes vary widely and include granite, granodiorite, quartz monzonite, and diorite (e.g., this study; Barton et al.,1995). Tectonic setting Rocks of the Altiplano have undergone a long history of progressive deformation including both contractional and extensional strain (Campa and Coney, 1983; Sedlock et al., 1993). The dominant northwest-trending structural fabric of the area is attributed to strong north-northeast-directed contraction associated with the Late Cretaceous to Middle Eocene (~70 to 45 Ma) Mexican fold-and-thrust belt. This deformation event is both temporally and kinematically equivalent to the "Laramide" orogeny of the southwestern United States (e.g., Sedlock et al., 1993). The Sacrificio deposit lies in the westernmost or hinterland portion of the Mexican fold-and-thrust belt, where regional folding is intense f (Campa and Coney, 1983). Deformation associated with the Mexican fold-and-thrust belt is generally thin-skinned with only minor local involvement of Precambrian crystalline basement (e.g., Sutter, 1987; Sedlock et al., 1993). In the Altiplano and Sierra Madre Oriental, folding and thrusting verges generally northeast to east-northeast, consistent with deformation throughout the North American Cordillera (e.g., Drewes, 1991). Cumulative east-northeast displacement across the belt is 15 on the order of 40 to 200 kms, with up to 30% shortening (Sedlock et al., 1993). The deformation front of the Mexican fold-and-thrust belt was spatially time-transgressive, with deformation younging to the east (de Cserna, 1989). Importantly, magmatism occurred simultaneously with deformation, but somewhat west of the thrust front and therefore after peak deformation (Sedlock et al., 1993). This simple relationship explains the post- to syn-deformational timing of pluton emplacement at Cerro el Sacrificio and at many other intrusion-related mineral deposits in central Mexico (e.g., Megaw, 1999). Contraction in the fold-and-thrust belt ended by approximately 31 Ma and was followed by east-northeast-directed extension (Henry et al., 1991; James and Henry, 1991). This extension is marked by block tilting, normal faulting, and magmatism throughout the basin-and-range province of the southwestern United States and north-central Mexico. In the Altiplano, normal faulting and associated basaltic magmatism were initiated by approximately 24 Ma and continues to the present. This has resulted in the broad basin-and-range topography developed throughout the region today (Sedlock et al., 1993). Property Geology Stratigraphy Sedimentary rocks exposed on and around Cerro el Sacrificio belong to the mid-Cretaceous (Albian to Cenomanian; Longoria et al., 1999) Cuesta del Cura Formation and are composed mainly of 10 to 40 cm thick beds of grey limestone interbedded with 1 to 10 cm thick beds of chert. These rocks are 16 conformably overlain by limestone and shale of the mid-Cretaceous (Cenomanian to Santonian) Indidura Formation. The contact between formations is gradational in nature and is defined by the presence of shale beds in the Indidura Formation. Together, the Cuesta del Cura and Indidura formations comprise a thick, monotonous, succession of marine sedimentary rocks with no discernable marker horizon(s). These rocks are moderately to strongly recrystallized, with limestone transformed to marble and chert to an assemblage of quartz, albite, and scapolite. Intrusive rocks Intrusive rocks on the property are divided into two suites based on age and chemical composition. The oldest suite, dated at 109.1 ± 0.4 Ma (see U-Pb geochronology section below), consists of a large northwest-trending dike (Dique Viejo) exposed on Cerro el Sacrificio and several narrower dikes cropping out immediately southeast of Cerro Coloradito (Fig. 4). Dique Viejo is a 10 to 30 m wide, feldspar-phyric dike of monzonitic composition (see below). It is cut by the Sacrificio intrusion (Fig. 4), and is essentially unaltered with the exception of minor chlorite and epidote (Figs. 5A and B). The narrow dikes exposed on Cerro Coloradito are petrographically and geochemically very similar to Dique Viejo (see below) and, consequently, are interpreted to be of the same age. The 39.8 ±0.1 Ma Sacrificio intrusion is exposed on the western flank of Cerro el Sacrificio and forms the core of the mountain as indicated by exploration drilling and geophysical surveys (Fig. 3). A relatively homogeneous body of 17 medium-grained granite that is weakly quartz- and feldspar-phyric is the dominant rock type (Figs. 5C and D). Portions of the intrusion are surrounded by a thin margin of highly felsic, possibly rhyolitic, quartz-phyric porphyry. This felsic margin is analogous in it's geometry and composition to the quartz-phyric rhyolite that envelopes the Cerro del Gloria stock at the San Martin Cu-Zn-Pb-Ag skarn deposit (Rubin and Kyle, 1988). Geophysical data suggest that the subsurface extent of the Sacrificio intrusion is approximately 1500 x 2000 metres in plan view (Fig. 3). The 40.3 ± 0.2 Ma Coloradito intrusion is exposed one kilometer northwest of the Sacrificio intrusion on the western flank of Cerro Coloradito. It appears smaller in subsurface extent than the Sacrificio intrusion based on geophysical data (Terry et al., 1999). The Coloradito intrusion is multiphase and consists of a granite core characterized by medium- to coarse-grained phenocrysts of quartz, orthoclase, and plagioclase in a fine-grained groundmass of quartz and minor feldspar (Figs. 5E and F). This core is surrounded by a thin (5 to 15 m wide) margin of fine- to medium-grained, biotite-rich granite (Figs. 5G and H). Immediately adjacent to these intrusive phases is a 15 to 100 m wide zone of intense silicification. Relict quartz phenocrysts indicate that this silicified rock was originally granitic in origin. The granite dykes cropping out on Cerro Coloradito are typically porphyritic with a variable phenocryst assemblage of quartz, orthoclase, and rare plagioclase. Representative samples of all intrusive phases were analyzed for major oxide elements, trace elements and rare earth elements (REE). These data, 18 plotted in figures 6 and 7 and listed in Table 1, illustrate that there are distinct compositional differences between the older and younger intrusive suites. The Middle Eocene suite is granite in composition whereas the older Cretaceous suite ranges in composition from quartz monzonite to granodiorite. Rare earth element abundances, normalized to the primitive mantle values of Sun and McDonough (1989), are consistent with major element compositional differences between the two suites (c.f., Fig. 6). The Cretaceous dykes are enriched in light REE, with primitive mantle-normalized REE diagrams displaying steep slopes and small negative europium anomalies, whereas the Eocene intrusions possess much flatter REE patterns and have large negative europium anomalies. It is beyond the scope of this study to address the petrogenetic and tectonic significance of these features in detail, especially given the lack of consensus on the tectonic setting of this part of Mexico in the Middle Eocene (e.g. Henry et al., 1991; Sedlock et al., 1993). As a generalization, however, the REE patterns of the Cretaceous suite are characteristic of magmas derived from deep crustal or mantle sources, whereas the REE patterns of the Eocene suite are typical of shallow crustal melts that have undergone significant fractionation of plagioclase (Rollinson, 1993). U-Pb geochronology Four samples of intrusive rock from the Sacrificio deposit were dated by U-Pb methods at the University of British Columbia. Zircon concentrates were prepared from 15-20 kg samples using conventional crushing, grinding, Wilfley 19 table, heavy liquids and magnetic separation techniques. The methodology for zircon grain selection, abrasion, dissolution, geochemical preparation and mass spectrometry is described by Mortensen et al. (1995). Most zircon fractions were air abraded (Krogh, 1982) prior to dissolution to minimize the effects of post-crystallization Pb-loss. Procedural blanks were 5 to 2 pg for Pb and 1 pg for U. Uranium-lead data are given in Table 2, and are shown on conventional U-Pb concordia plots in Figure 8. Errors attached to individual analyses were calculated using the numerical error propagation method of Roddick (1987). Decay constants used are those recommended by Steiger and Jager (1977). Compositions for initial common Pb were taken from the model of Stacey and Kramer (1975). All errors are given at the 2a level. Sample KP-11 is porphyritic granite from the Coloradito intrusion (Fig. 4). The sample yielded abundant high quality zircons, mostly comprising clear, pale to medium brown, square, stubby prismatic forms. The grains displayed faint igneous growth zoning; they typically contained rare to abundant clear, bubble-shaped inclusions but no inherited cores were observed. The best quality, least magnetic, most inclusion-free grains were strongly abraded and then split into five subequal fractions for analysis. Measured U-contents are very high (8713-14149 ppm; Table 2). Four of the analyses yield concordant analyses (Fig. 8A). The interpreted crystallization age for the sample is assigned on the basis of the total range 206Pb/238U ages of fractions B and C (40.3 ± 0.2 Ma). Two of the fractions (D and E) are also concordant but give slightly younger 206Pb/238U ages, and are interpreted to have suffered minor post-crystallization Pb-loss. Fraction A 20 is discordant with an older Pb/ Pb age (57.8 Ma) and is interpreted to have contained a minor inherited component, presumably as "cryptic cores" that could not be detected visually. Sample KP-14 is porphyritic granite from a large dike at Cerro Coloradito. Zircons from this sample are similar to those from the previous sample, except that these grains are typically less clear due to the presence of fractures and inclusions. Four fractions of the best quality zircon available were analyzed following strong abrasion. As with the previous sample, measured U-contents are very high (8013-12904 ppm; Table 2). Three of the four analyses are concordant (Fig. 8B) and the interpreted age for the sample of 40.2 ± 0.2 Ma is based on the total range 206Pb/238U ages of fractions C and D. Fraction B has suffered post-crystallization Pb-loss, and fraction A contained a minor inherited zircon component. Sample KP-7 is medium-grained granite collected from the Sacrificio intrusion (Fig. 4). The sample yielded abundant clear, colorless, stubby to elongate, square prismatic zircons, with rare to abundant clear inclusions but no visible inherited cores. Five strongly abraded fractions were analysed (Table 2). Two fractions (B and D) yield concordant analyses, and the 206Pb/238U age of fraction B (39.8 ± 0.1 Ma) is interpreted to provide a minimum crystallization age for the sample (Fig. 8C). Fraction D is interpreted to have experienced Pb-loss, and the other three fractions (A, C and E) contain an inherited zircon component. Sample KP-9 is porphyritic monzodiorite from Dique Viejo. Zircons from this sample are quite different in appearance from those in the previous three 21 samples. The grains are pale yellow, stubby to elongate, square prisms with simple to multifaceted terminations. Several grains in the coarser, non-magnetic fractions contain cloudy inherited cores. Initially five fractions of the best quality, core-free, least magnetic zircon were analyzed; these all gave Early Mesozoic to mid-Paleozoic 207Pb/206Pb ages and clearly contained a significant inherited zircon components. Subsequent fractions were selected on the basis of grain morphology to try to avoid inherited cores, including two fractions (H and I) that consisted of tips broken from grains with visible cloudy cores. Despite these efforts, all of the coarser fractions still appear to have contained inherited components. Finally two fractions of fine-grained, very elongate needles were selected (fractions J and K, Fig. 8D), and were analyzed without abrasion. The finest grained fraction (K) yields a concordant analysis with a 206Pb/238U age of 109.1 ± 0.4 Ma. As this fraction was not abraded prior to dissolution, it is likely that it has suffered at least minor post-crystallization Pb-loss; however the analysis is concordant, and it is therefore unlikely that the crystallization age of this body is significantly older than the 206Pb/238U age. Structure The most striking structural feature at the Sacrificio deposit are the many north-northwest trending folds (Fig. 9). These are divided into two types (Di and D3) based on fold morphology, overprinting relationships, and vergence. D1 folds are tight to isoclinal, asymmetric, inclined to rarely recumbent, and typically display west vergence. This vergence contrasts with the general east-vergence 22 of the Mexican fold-and-thrust belt. Folds associated with the D3 event are large amplitude (hundreds of metres), gentle to open, upright folds which refold Di folds with similarly oriented fold axes (i.e. type 3 refolding; McClay, 1987). Between the D-i and D3 folding events there was a minor re-orientation of shortening directions resulting in rare east-trending folds that refold folds (i.e. type 2 refolding; McClay, 1987). D2 had limited effect on the present form of stratified rocks at the Sacrificio deposit, but it is mapped unambiguously at several locations. Similar in style to D-i folds, the D2 folds generally possess close to tight interlimb angles. D4 is defined by the plunges of Di and D3 fold axes. In rocks above the northern half of the intrusion, Di and D3 fold axes plunge to the north-northwest whereas above the southern half of the intrusion, these fold axes plunge to the south-southeast (Fig. 10). The resulting structure is a broad dome centered on Cerro el Sacrificio, directly above the Sacrificio intrusion. D5 is defined by fractures and veins that cut all other mapped structures, generally have steep dips, and strike east-northeast. Detailed interpretation of the origin of all these structural fabrics is given below in the section on structural evolution of the deposit. Mineralization Mineralization and related calc-silicate skarn at the Sacrificio deposit is largely confined to metasedimentary host-rocks adjacent to the Middle Eocene intrusions (exoskarn). The intrusive rocks are devoid of skarn and sulfide 23 minerals other than very near the intrusive margin where weak endoskarn is rarely developed. Three different styles of sulfide mineralization are recognized at the Sacrificio deposit. These are: (1) disseminated to semi-massive bornite and lesser chalcopyrite filling secondary porosity in garnet skarn; (2) fracture-controlled bornite-chalcopyrite + sphalerite + galena ± arsenopyrite with high silver contents, typically on the order of several hundred grams per tonne; and (3) fine- to coarse-grained semi-massive to massive sulfide bodies (mantos) which have replaced marble or garnet skarn and comprise a variable assemblage of sphalerite, galena, chalcopyrite, arsenopyrite, pyrrhotite, pyrite, and bornite (Fig. 11). Fracture-controlled and disseminated styles of mineralization are related both spatially and genetically but distinct differences in mineralogy and areal distribution require that they be classified as separate styles of mineralization. Note that where fractures are filled by minerals, they are referred to as veins in accordance with the terminology of the American Geological Institute (AGI) (Bates and Jackson, 1983). Disseminated Cu-Ag mineralization Disseminated Cu-Ag mineralization is synchronous with, but also slightly post-dates, the D5 fracture-controlled mineralization. It is the most widespread style of mineralization at the Sacrificio deposit and consists of small (0.1 to 3 mm in diameter) disseminations of bornite and lesser chalcopyrite in secondary porosity within garnet and wollastonite skarn (Fig. 12A). Relatively large areas 24 (hundreds to thousands of square metres, e.g., Fig. 11) host uniformly disseminated sulfide minerals on surface. Significant drill intersections of this style of mineralization include 1.72% Cu and 121 g/t Ag over 24.3 metres (Terry etal., 1999). Fracture controlled Cu-Ag+Au mineralization The oldest mine workings at the Sacrificio deposit are located along narrow zones of intense fracture-controlled mineralization (Fig. 12B). Although these zones are generally of limited tonnage, they commonly contain very high grades of copper and silver (drill core intersections include 6.51% Cu and 554 g/t Ag over 1.5 m). Fractures generally strike between 060° and 100° and dip steeply to either the north or south. Where fractures are filled by sulfide and gangue minerals to form banded veins, mineral growth fibers are consistent with the veins having formed by extensional processes (e.g., Fig. 12C). Sulfides in the fracture-controlled style of mineralization may occur as coatings on fractures, as fillings in veins, and as disseminations proximal (i.e., within about 30 cm) to the fractures. This disseminated mineralization proximal to the fractures grades into the more widespread disseminated mineralization described above, but is differentiated from it based on the presence of sulfides other than bornite and chalcopyrite, and it's greater concentrations nearest to the fractures. Veins associated with the fractures typically are filled with quartz, calcite, and up to about 5% sulfide minerals. The sulfide mineral assemblage is dominated by chalcopyrite and/or bornite with minor sphalerite, galena, and 25 arsenopyrite. Veins are composed rarely of massive to semi-massive sulfide. Fractures and veins commonly occur together in zones several tens of metres wide with centimetre- to metre-scale spacing between individual fractures. Vein widths range from millimetres to tens of centimetres, with typical thicknesses on the order of 1 to 10 cm. Secondary copper minerals such as malachite, azurite, and chrysocolla commonly are developed in fracture zones through oxidative weathering of primary sulphide minerals. Manto-style Zn-Cu-Pb-Ag-Au mineralization The recent discovery of massive to semi-massive polymetallic mantos at the Sacrificio deposit greatly improves it's economic potential and bodes well for the likelihood of delineating further mantos. The sulfide mineralogy of the mantos consists of sphalerite, galena, chalcopyrite, arsenopyrite, pyrrhotite, pyrite, bornite and rare tetrahedrite, stibnite and stannite (Fig. 12D). High abundances of silver and, locally, gold are present in several of the mantos. The most economically important drill intersection of this style of mineralization occurs in diamond drill hole SAC98-03 drilled off Pad 3 (e.g., Fig. 3). This hole intersected 16.43 m of 1.48% Zn, 1.34% Cu, 0.99% Pb, and 174.6 g/t Ag. Other significant zones of manto-style mineralization identified on surface include Rosas de Diciembre, Santo Nino, Pad 4, Verde Pit, Windmill shaft and Hueco Grande (Fig. 3). Contact relationships between the mantos, prograde garnet-wollastonite skarn, and marble reveal that the mantos post-date the development of prograde 26 skarn and marble. The common gangue minerals in the mantos are characteristic of retrograde skarn assemblages and include amphibole, chlorite, and calcite. Together, these data indicate that the manto mineralization post-dates the disseminated Cu-Ag and fracture-controlled Cu-Ag ± Au mineralization. Alteration Alteration is divided into three types at the Sacrificio deposit. These are (1) pre-mineralization contact metamorphism, (2) prograde skarn, and (3) retrograde skarn. As noted above, disseminated and fracture-controlled Cu-Ag ± Au mineralization is associated with prograde skarn whereas the polymetallic mantos are associated with retrograde skarn. The contact metamorphism forms a large halo around the intrusions unlike the distribution of prograde and retrograde skarn, which is strongly controlled by proximity to well-developed structures. The general paragenetic sequence of alteration and corresponding mineralization events is given in Table 3. The earliest and largest-scale alteration event identified at the Sacrificio deposit is the pervasive development of hornfels in limestone and chert during emplacement of the Sacrificio and Coloradito intrusions (Fig. 11). Alteration minerals formed during this contact metamorphic event include quartz, albite, scapolite, and minor chlorite-sericite. This assemblage preferentially replaces chert beds (but locally also replaces limestone) in a concentric halo up to 500 m around the intrusions. The distribution of hornfels is controlled only by proximity to the intrusions - it is unaffected by the structures that localized prograde and 27 retrograde skarn. This hornfels is a product of heat generated by the intrusions and likely involves meteoric waters circulating locally within the rocks (e.g., Einaudi et al., 1981). Structurally controlled prograde skarn is the most strongly developed and widespread type of hydrothermal alteration developed on surface at the Sacrificio deposit (Fig. 11). It hosts disseminated bornite-chalcopyrite mineralization. The prograde skarn is dominantly massive to poddy andradite garnet with lesser wollastonite, clinopyroxene, and vesuvianite. The euhedral, coarse-grained (up to 2 cm in diameter) garnet crystals invariably display both optical and compositional zonation. From thin section petrography it is estimated that garnet skarn contains 10 to 15% intergranular porosity. This porosity and corresponding permeability have played a key role in localizing subsequent disseminated bornite-chalcopyrite mineralization. At the scale of outcrop, garnet, wollastonite, clinopyroxene, and vesuvianite generally occur together as prograde skarn, although at the scale of hand sample and thin section, a zonation is recognized from proximal, garnet to garnet+clinopyroxene to more distal wollastonite+vesuvianite as distance from a fracture increases. Retrograde skarn is not particularly widespread but does occur at several locations on the Sacrificio property. It is commonly associated with manto-style mineralization and is defined by dark green, pervasive, poddy to irregular veinlets of amphibole and chlorite. Retrograde skarn exposed on surface occurs in zones tens to hundreds of square meters in size distributed peripherally to the Sacrificio and Coloradito intrusions (Fig. 11). Significant retrograde skarn is cut by several 28 old mine workings created to access the polymetallic mantos. These include the Santo Nino shaft and the Rosas de Diciembre adit (e.g., Fig. 3). The most geologically interesting and economically important intersection of retrograde skarn occurs in drillhole SAC98-03 where amphibole skarn clearly post-dates prograde garnet-wollastonite skarn and is associated with a high-grade polymetallic manto. In addition to the major types of alteration described above, there are several other less abundant styles of alteration present at the Sacrificio deposit. These include (1) pervasive silicification of early phases of the Coloradito intrusion, (2) zones of quartz vein stockworks peripheral to the Sacrificio intrusion, and (3) small zones of quartz-cemented limestone breccia above the Sacrificio intrusion (Fig. 11). Intense silicification peripheral to the Coloradito intrusion is probably deuteric in origin and almost completely replaces earlier intrusive phases (whole-rock analyses of this silicified zone identify rock compositions containing up to 93.9% SiC>2; Table 1). The quartz vein stockworks exposed at the margins of the Sacrificio and Coloradito intrusions are generally weakly developed although there are local zones of intense development. These stockworks likely are related to the same late-stage, volatile-rich, magmatic fluid exsolution event that produced a small zone of post-skarn breccia above the Sacrificio intrusion (Fig. 11). 29 Structural Evolution of the Sacrificio Skarn Deposit Five separate deformation events are recognized in rocks exposed on and around Cerro el Sacrificio. With the exception of the latest events (D4 and D5), which are due to pluton emplacement, all likely formed during progressive deformation associated with the Mexican fold-and-thrust belt. A sequential rendition of deformation and associated mineralization from D-i to D5 is schematically illustrated in Figure 13. The relevant paragenetic relationships are shown in Figure 14. is a relatively ductile, passive, folding event that records an estimated 100 to 150% shortening in the area of Cerro el Sacrificio. Di folds are tight to isoclinal, rarely recumbent, and generally have amplitudes between 10 cm and 3 m. Di folds are strongly asymmetric and typically verge to the west (Fig. 15A). This contrasts with the general east-vergence of the Mexican fold-and-thrust belt and likely places the Sacrificio deposit in a back-thrust portion of the fold-and-thrust belt hinterland (Sutter, 1987). Di fold axes trend towards 330° with a maximum shortening direction of east-northeast. D2 is a minor event likely caused by a local realignment of regional stresses as a result of strain partitioning or extreme competency contrast. It has limited effect on the present form of the stratified rocks in the mapped area, but it is unambiguously recognized at several outcrops (e.g., Fig. 15B). The style of folding is similar to D-\ and hence D2 is interpreted to predate the less passive and intense D3 event. D2 consists of type 2 refolding of Di folds (fold axial surfaces approximately perpendicular). D2 fold axial surfaces presently strike 30 approximately 100° and dip 40° to the south, although because this orientation has been rotated by an undefined amount of younger deformation, it bears little relation to the D2 stress orientations. It is not possible to separate the effects of D2 from the bulk of the bedding orientation data (Fig. 10), but it is likely that D2 is responsible for the moderate scatter of poles to bedding from the great circle girdle which defines Di and D3 folding. D3 folding is the most important deformation event defined at Sacrificio with respect to control over mineralization. D3 folds are large amplitude (hundreds of metres), gentle to open, upright folds (Fig. 15C) which refold Di folds with similarly oriented fold axes (type 3). As discussed below, D3 fold axial surfaces, particularly in anticlines, have focussed ascending metalliferous and skarn-forming magmatic fluids leading to the present distribution of garnet skarn and disseminated Cu-Ag mineralization. The largest and most strongly mineralized D3 fold mapped at the Sacrificio deposit is termed the Central Anticline (Fig. 3). D3 is separated from Di based on distinct differences in fold style and by the consistent west-vergence of Di folds irrespective of their location within D3 fold geometries. D3 fold axes trend toward 330° and plunge gently to the north or south depending on their location within the dome produced by D4 (Figs. 9 and 10). D4 is attributed to the forceful emplacement of the Sacrificio intrusion, which has resulted in the gentle doming of rocks above and around the intrusion. As noted above, D4 is defined by the opposing plunges of Di and D3 fold axes in rocks above the northern and southern halves of the intrusion, respectively (Figs. 31 9 and 10). Fluids released from the crystallizing Sacrificio intrusion were channeled upward along D3 fold axial surfaces as evidenced by the localization of prograde skarn. The exact mechanism(s) by which these fluids were channeled into fold hinges is unknown, but probably involves the combined effects of contrasting permeabilities between metasedimentary beds and the presence of axial-planar fractures and/or cleavages in the hinge areas of both anticlines and synclines. Upward channelization of fluid along bedding planes into antiform hinges is a well documented process (i.e., the oil-trap analogy), as is fluid migration up axial-planar cleavages (North, 1985). Where magmatic fluids reacted with limestone, garnet skarn with significant porosity was produced and accompanying permeability was localized along D3 fold hinges. At the Sacrificio deposit, secondary porosity is observed in both thin sections and hand samples of mineralized and unmineralized garnet skarn. Continued exsolution of magmatic fluids from the crystallizing Sacrificio intrusion (or a subsequent intrusive phase) is proposed to have raised local pore fluid-pressure sufficiently to cause mode I (extension) hydrofractures (D5) to form above the intrusion. D5 fractures are dominantly steeply dipping and generally strike east-northeast (Fig. 9), an orientation possibly indicating weak east-northeast oriented regional compressional stress was still operative at this time. These newly formed fractures preferentially channeled metalliferous fluids exsolved from the intrusion. Fluids then migrated from the fractures into porous garnet skarn. This fluid channelization has resulted in significant concentrations of disseminated bornite and lesser chalcopyrite in garnet skarn proximal to the D5 32 fractures (Fig. 15D). The sequence of events presented here is consistent with field evidence that shows intersections between garnet skarn and D5 fractures characteristically host strong disseminated bornite-chalcopyrite mineralization. The precise mechanism(s) controlling the localization of manto-style mineralization is less well understood than that of the disseminated and fracture-controlled styles, but the late development of the mantos is consistent with fluid evolution models in many mineralized skarn systems (e.g., Einaudi and Burt, 1982; Meinert, 1997). Moreover, such a temporal relationship is documented in many Mexican skarns and carbonate-replacement deposits similar to Sacrificio (e.g., Megaw, 1999). However, the mantos at Sacrificio do differ from those found in typical polymetallic skarns in one respect: they do not occur outboard of the "copper" zone (e.g., Meinert, 1997). Rather, they occur within the copper zone near the intrusive contact where they have replaced both mineralized and unmineralized prograde garnet skarn. This intrusion-proximal position of the Sacrificio mantos may indicate that a deeper intrusive phase(s) is responsible for their formation. Alternatively, the proximal position of the mantos may be a function of the cooling intrusive complex. Analogous to a porphyry copper system, earlier formed structures may channel late, retrograde, fluids back into the central portions of the ore system where replacement and base metal deposition occurs (e.g., Einaudi and Burt, 1982; Johnson and Norton, 1985). 33 Structural Controls on Ore Distribution in Mexican Skarn Deposits Studies of skarn deposits in Mexico and elsewhere typically have focussed on the mineralogical and geochemical aspects of the skarn and associated intrusive rocks (e.g., Gilmer et al., 1988; Graf, 1997; Meinert, 1998; Rubin and Kyle, 1988). The effect of structure in controlling the distribution and development of skarn and associated mineralization is rarely addressed in detail. A review of the literature reveals that several major skarn-related deposits in Mexico appear to exhibit a significant degree of structural control over their development. These include San Martin/Sabinas (Ruben and Kyle, 1988), La Colorada (Moore, 1999), Charcas (Castaheda, 1991), Velardeha (Gilmer et al., 1988; Hernandez, 1991), Providencia (Sawkins, 1964), Ojuela (McLeroy et al., 1986) and Naica (Palacios et al., 1991). In this section, the geological characteristics of the best studied of these skarn deposits are reviewed and the structural controls over mineralization are investigated. Although data are insufficient for our analysis to be comprehensive, we believe it is possible to assess the general compatibility of the structural model developed for the Sacrficio deposit with the structures and patterns of mineralization present in the aforementioned deposits. San Martin The San Martin (and neighboring Sabinas) deposit is the largest skarn deposit in Mexico (Megaw, 1998a). Total reserves and past production are approximately 70 Mt at average grades of 3.8% Zn, 1% Cu, 0.5% Pb, and 125 g/t 34 Ag (Megaw, 1999). The mine site is located approximately 20 kilometers south of Cerro el Sacrificio (Fig. 1). Mineralization at San Martin is localized along the west side of the Cerro de la Gloria stock, a polyphase granitic intrusion dated at 46.2 ±0.1 Ma by K-Ar methods (Damon et al., 1983). Compositions of the intrusive phases of the Cerro de la Gloria stock vary from granite to granodiorite, similar to those of the Middle Eocene intrusions associated with the Sacrificio deposit (Fig. 16). A single sample of intrusive rock from San Martin plots within the mid-Cretaceous field for Sacrificio but owing to the similarity of REE abundances (Fig. 17), this sample probably represents a less differentiated phase of the Eocene Cerro de la Gloria stock rather than a mid-Cretaceous granodiorite as at Sacrificio. Rare earth element abundances of the Middle Eocene mineralizing intrusions at the Sacrificio deposit are remarkably similar to those of intrusions at San Martin. This demonstrates that both intrusive centers have likely formed during the same tectonomagmatic event. The pre-mineralization structures at San Martin are very similar to those at the Sacrificio deposit: tight, northwest-trending folds are ubiquitous within Cuesta del Cura Formation limestone and are attributed to shortening during formation of the Mexican fold-and-thrust belt. Large-scale doming is evident around the Cerro de la Gloria stock (Rubin and Kyle, 1988), however, skarn and stratified rocks above the intrusion have been eroded away unlike the Sacrificio deposit where this mineralized cap remains. 35 Skarn mineralization at San Martin is centered around three main east-northeast-striking veins: (1) the Ibarra, (2) the Ramal Ibarra, and (3) the San Marcial (Rubin, 1986). These veins likely represent the conduits for mineralizing fluids that produced the extensive manto mineralization peripheral to the veins (e.g., Aranda Gomez, 1978; Rubin and Kyle, 1988). Rubin and Kyle (1988) propose that the main veins at San Martin formed late in the evolution of the magmatic-hydrothermal system because they cut structures that predate the granitic intrusion and extend slightly into the intrusive rocks. Although Graf (1997) interprets the veins and fractures peripheral to the Cerro de la Gloria stock at San Martin as radial and concentric features associated with the emplacement of the stock, both the study of Rubin and Kyle (1988), and the maps of major veins and fractures in Graf (1997 - see Figure 2) show them to be preferentially oriented between 060° and 120°. Consequently, the D5 fractures at Cerro Sacrificio are analogous to these veins at San Martin in terms of their orientation, temporal relationship to the intrusions, and role as mineralizing fluid conduits. Charcas The Charcas district is located in San Luis Potosi state, approximately 110 km north of San Luis Potosi city along the eastern margins of the Mexican Altiplano (Fig. 1). Base metal mineralization in the Charcas district is hosted within several veins and associated manto deposits. Past production of 35 Mt and reserves of over 12 Mt at average grades of 4.5% Zn, 0.32% Pb, 0.26% Cu, 36 and 67 g/t Ag (Megaw, 1999) make this district a significant past and present producer. The 46.6 ± 1.6 Ma (dated by K-Ar methods) El Temeroso quartz latite porphyry is the main intrusive body in the Charcas district (Castaheda, 1991). It has controlled the localization of mineralization in the area by producing steeply-dipping, east-striking fractures that have been subsequently mineralized (Castaheda, 1991). The porphyry is strongly elongated in plan-view, which suggests that a differential stress field was active during emplacement (Tosdal and Richards, 2001). Mineralization is hosted within Cretaceous argillaceous limestone of the Taraises and Cupido formations, which was strongly folded prior to mineralization during Mexican fold-and-thrust belt deformation. The dominant structural feature of the region is a large, overturned, north-trending, anticline. It is on the eastern flank of this structure where the ore bodies are located (Castaheda, 1991). Mantos are the most important style of mineralization at Charcas in a commercial sense. Mineralogically, they are very similar to mineralized veins, to which they are "connected" at some localities (e.g., Castaheda, 1991). The mantos are interpreted to have formed where the ascending metalliferous fluids, channeled along fractures, encountered chemically receptive host rocks (Castaheda, 1991). This channelization of metalliferous fluids by intrusion-related fractures which post-date northwest trending regional structures is similar to the proposed mineralization model at Cerro el Sacrificio. D5 fractures, like the 37 intrusion-related fractures at Charcas, functioned as conduits for mineralizing fluids. La Colorada - Chalchihuites District The La Colorada deposit is located approximately 50 km south of Cerro el Sacrificio (Fig. 1) and may represent the exposed upper level of a mineralized skarn system like that at Sacrificio and San Martin. Historically, veins striking east to northeast have comprised the main style of mineralization exploited (Albinson, 1988). However, recent exploration activity has delineated base metal-rich chimneys and mantos below the mined veins, and several deeper exploration drillholes have intersected calc-silicate skarn and associated sulfide mineralization (Moore, 1999). The deeper skarn and chimney-manto mineralization is hosted by folded Cuesta del Cura and Indidura Formation limestone. Mineralization is interpreted to be 30 to 35 Ma old from cross cutting relationships with the overlying volcanic strata (Albinson, 1988). Structural similarities between the La Colorada and Sacrificio deposits include the orientations of mineralized veins and pre-intrusion regional folds at La Colorada (Moore, 1999). These features are analogous to the D5 fractures and the pre-intrusion D3 folds at Sacrificio. 38 Conclusions The Sacrificio deposit is a copper exoskarn hosted by mid-Cretaceous limestone, chert, and minor shale of the Cuesta del Cura and Indidura formations. Skarn formation and sulfide mineralization are related to a Middle Eocene (40.1± 0.5 Ma) granite intrusive complex that underlies most of Cerro el Sacrificio. An older, mid-Cretaceous (109.1 ± 0.4 Ma) granodiorite-quartz monzonite intrusive suite is also present, but field relations indicate that it is unrelated to skarn or mineralization. Sulfide mineralization at the Sacrificio deposit is classified, from youngest to oldest, as (1) disseminated Cu-Ag, (2) fracture-controlled Cu-Ag ± Au and, (3) manto-style Zn-Cu-Pb-Ag-Au. The disseminated mineralization is intimately associated with prograde garnet skarn, whereas the polymetallic mantos are associated with the development of late, retrograde, amphibole skarn. Detailed field studies demonstrate the importance of structural fabrics in localizing skarn and related Cu (Zn-Pb-Ag-Au) sulfide mineralization at the Sacrificio deposit. This differs from many other skarn deposits where lithological controls are as at least as important in controlling the distribution of mineralization (e.g., Santa Eulalia, Hewitt, 1968; Cantung, Dick and Hodgson, 1982; Bingham and Ely, Einaudi, 1982). Three episodes of pre-intrusion regional deformation are recognized at the Sacrificio deposit. D-i and D3 record strong east-northeast shortening associated with the Mexican fold-and-thrust belt whereas D2 shows a minor re-orientation of shortening directions to produce rare east-trending folds. Two episodes of intrusion-related deformation post-date 39 regional deformation and are synchronous with the mineralization event. D4 is the formation of a broad dome above the Sacrificio intrusion and D5 is the opening of extensional fractures and veins above and peripheral to this intrusion. Distribution of garnet skarn along D3 fold axial traces indicates that skarn-forming fluids were preferentially channeled along axial surfaces of large amplitude D3 folds. Later mineralizing fluids were focussed dominantly by D5 fractures (but some migration along D3 is possible as well) with bornite ± chalcopyrite precipitating where fluids infiltrated porous garnet skarn. Thus, intersections between late-stage, intrusion-related, fractures and permeable lithologies (i.e., garnet skarn along D3) are the most favorable sites for localization of Cu-Ag ± Au mineralization on Cerro el Sacrificio. The exact mechanism(s) controlling the location of mantos in the Sacrificio skarn system is poorly understood at this time. Their association with retrograde skarn that replaces both mineralized and unmineralized prograde skarn is consistent, however, with the channeling of late retrograde fluids back into the central portions of the ore system using earlier formed D3 and D5 structures. A review of mid-Tertiary skarn and carbonate-replacement deposits occurring in the Mexican Altiplano reveals that skarn and skarn-related mineralization generally does not exhibit simple concentric zonation patterns. Rather, deposits such as San Martin, La Colorada, and Charcas all exhibit major, syn-intrusive, approximately east-striking veins and/or fractures which, by analogy with the Sacrifcio skarn system, are interpreted to have channeled the mineralizing fluids and localized the ore bodies. Thus, there appears to be ample 40 evidence that the structural model developed for the Sacrificio deposit could be successfully applied to other skarn deposits or, more importantly, to deposits and prospects which are only partly explored or exposed. Acknowledgements This contribution forms part of the senior author's M.Sc. research at the University of British Columbia. Funding has been generously provided by Boliden Limited, NSERC grant 22R80466 to Rowins, a Thomas and Marguerite MacKay memorial scholarship to Patterson, and an SEGF student research grant to Patterson. Logistical and geological support has been provided by Boliden Limited and Luismin S.A. de C.V. In particular, we would like to thank Chris Rockingham of Boliden and David Aguilar, Ricardo Flores, and Florentino Munoz of Luismin for their aid in the development of the ideas presented here. Informal reviews, editing, and discussions with Greg Dipple, Lori Kennedy, Peter Lewis, Stephen Piercey, and Richard Tosdal have greatly improved interpretation of the data and clarity of the presentation. 41 References Albinson, T.F., 1988, Geologic reconstruction of the paleosurface in the Somberete, Colorada, and Fresnillo districts, Zacatecas State, Mexico: ECONOMIC GEOLOGY, V. 83, p. 1647-1667. Albinson, T.F. and Sanchez, E., 1977, Geologic evaluation of the Sacrificio Prospect, Puanas Municipality, Durango: Minas San Luis, S.A. geologic report, 51 p. Aranda Gomez, J.J., 1978, Metamorphism, mineral zoning, and paragenesis in the San Martin mine, Zacatecas, Mexico: Unpublished M.Sc. thesis, Colorado School of Mines, 90 p. Barton, M.D., Staude, J-M.G.,Zurcher, L., and Megaw, P.K.M., 1995, Porphyry copper and other intrusion-related mineralization in Mexico, in Pierce, F.W. and Bolm, J.G., eds., Porphyry copper deposits of the American Cordillera: Arizona Geological Society Digest, v. 20, p. 487-524. Bates, R.L., and Jackson, J.A., 1983, Dictionary of Geological Terms, 3rd Edition: American Geological Institute, Doubleday Anchor, New York, 571 p. Bowman, J.R., 1998, Basic aspects and applications of phase equilibria in the analysis of metasomatic Ca-Mg-AI-Fe-Si skarns, in Lentz, D.R. ed., Mineralized intrusion-realted skarn systems: Mineralogical Association of Canada Short course series, v. 26, p. 1-50. Campa, M.F., and Coney, P.J., 1983, Tectono-stratigraphic terranes and mineral resource distributions in Mexico: Canadian Journal of Earth Sciences, v. 20, p. 1040-1051. 42 Castaheda, A.F., 1991, Economic geology of the Charcas mining district, San Luis Potosi, in Salas, G.P., ed., Economic Geology, Mexico: Geological Society of America, Boulder, Colorado, DNAG P-3, p. 279-286. Coney, P.J., 1978, Mesozoic-Cenozoic Cordilleran plate tectonics: Geological Society of America Memoir 152, p. 33-50. Damon, P.E., Shafiqullah, M., and Clark, K.F., 1981, Age trends of igneous activity in relation to metallogenesis in the southern cordillera: Geological Society of Arizona Digest, v. 14, p. 137-154. Damon, P.E., Shafiqullah, M., and Clark, K.F., 1983, Geochronology of the porphyry copper deposits and related mineralization of Mexico: Canadian Journal of Earth Sciences, v. 20, p. 1052-1071. de Cserna, Z., 1989, An outline of the Geology of Mexico, in Bally, A. W., and Palmer, A. R., eds., The Geology of North America - An overview: Boulder, Colorado, Geological Society of America, The Geology of North America, v. A. Dick, L.A., and Hodgson, C.J., 1982, The Mactung W-Cu (-Zn) conatct metasomatic and related deposits of the northeastern Canadian Cordillera: Economic Geology, v. 77, p. 845-867. Drewes, H., 1991, Description and Development of the Cordilleran Orogenic Belt in the Southwestern United States and Northern Mexico: U.S. Geological Survey Professional Paper 1512, 87 p. 43 Einuadi, M.T., 1982, Skarns associated with porphyry copper plutons.1. Description of deposits, southwestern U.S., In S.R. Titley, ed., Advances in the geology of the porphyry copper deposits, southwestern United States: Tucson, University of Arizona Press, p. 185-210. Einaudi, M.T., Meinert, L.D., and Newberry, R.J., 1981,Skarn Deposits, in Skinner, B.J., ed., Economic Geology 75th Anniversary Volume: Economic Geology Publishing Company, El Paso, Texas, p. 317-391. Einaudi, M.T., and Burt, D.M., 1982, Terminology, classification, and composition of skarn deposits: ECONOMIC GEOLOGY, V. 77, p.745-754. Gilmer, A. L, Clark, K. F., Conde, J., Hernandez, I., Figueroa, S., and Porter, E.W., 1988, Sierra de Santa Maria, Velardena Mining District, Durango, Mexico: ECONOMIC GEOLOGY, V. 83, p. 1802-1855. Graf, A, 1997, Geology and pophyry-style mineralization of the Cerro de la Gloria stock associated with high-T, carbonate-hosted Zn-Cu-Ag(-Pb) skarn mineralization, San Martin District, Zacatecas, Mexico: Unpublished M.Sc. Thesis, University of Arizona, 154 p. Henry, CD., Price, J.G., and James, E.W., 1991, Mid-Cenozoic Stress Evolution and Magmatism in the Southern Cordillera, Texas and Mexico: Transition from Continental Arc to Intraplate Extension: Journal of Geophysical Research, v. 96, no. B8, p. 13,545-13,560. 44 Hernandez, C, 1991, Economic geology of the Velardena mining district, Durango, in Salas, G.P., ed., Economic Geology, Mexico: Geological Society of America, Boulder, Colorado, DNAG P-3, p. 279-286. Hewitt, W.P., 1968, Geology and mineralization of the Main mineral zone of the Santa Eulalia district, Chihuahua, Mexico: American Institute of Mining and Engineering Transactions, v. 240, p. 229-260. James, E.W. and Henry, CD., 1991, Compositional Changes in Trans-Pecos Texas Magmatism Coincident with Cenozoic Stress Realignment: Journal of Geophysical Research, v. 96, no. B8, p. 13,561-13,575. Johnson, J.W., and Norton, D., 1985, Theoretical prediction of hydrothermal conditions and chemical equilibria during skarn formation in porphyry copper systems: Econ. Geol., v. 80, p.1797-1823. Krogh, T.E., 1982, Improved accuracy of U-Pb zircon ages by the creation of more concordant systems using an air abrasion technique: Geochimica et Cosmochimica Acta, v. 46, p. 637-649. Kwak, T.A.P., 1987, W-Sn skarn deposits and related metamorphic skarns and granitoids: Amsterdam, Elsevier Press, 439 p. LeMaitre, R.W., 1989, A classification of igneous rocks and glossary of terms: Blackwell, Oxford, 193 p. Lentz, D.R., 2000, Mass-balance considerations in mineralized skarn systems: implications for permeability evolution and carbonate mobility: Geocanada 2000, conference proceedings with abstracts, cd-ROM. Longoria, J.F., Clowes, D.M., and Monreal, R., 1999, Type Mesozoic succession of northern Mexico: Canon La Casita, in Bartolini, C, Wilson, J.L., and Lawton, T.F., eds., Mesozoic sedimentary and Tectonic History of North-Central Mexico: Boulder Colorado, Geological Society of America Special Paper 340, p. 287-318. McClay, K.R., 1987, The Mapping of Geological Structures, John Wiley and Sons, West Sussex, England, 161 p. McLeroy, D.F., Francisco Franquesa, R., and Saul Romero, M., 1986, Origin of the breccia pipes and mantos of the Ojuela lead-silver district, Mapimi, Durango, In Clark, K.F., Megaw, P.K.M., and Ruiz, J. eds., Lead-Zinc-Silver Carbonate-Hosted Deposits of Northern Mexico, Society of Economic Geologists, Guidebook for Field and Mine Excursions, 325 p. Megaw, P. K. M., 1998a, Polyphase skarn mineralization associated with a polyphase differentiated composite intrusion, San Martin - Sabinas District, Zacatecas, Mexico, in Geological Association of Canada: Mineralogical Association of Canada 1998 Abstract Volume, p. A-122. Megaw, P. K. M., 1998b, Carbonate-hosted Pb-Zn-Ag-Cu-Au replacement deposits: An exploration perspective, in Lentz, D.R., ed., Mineralized intrusion-related skarn systems: Mineralogical Association of Canada, short course volume 26, p. 337-356. 46 Megaw, P.K.M., 1999, The high-temperature, Ag-Pb-Zn-(Cu) carbonate-replacement deposits of central Mexico in Jambor, J.L., ed., VMS and carbonate-hosted polymetallic deposits of central Mexico; Cordilleran Roundup, 1999, p. 81-84. Megaw, P.K.M., Ruiz, J., and Titley, S.R., 1988, High-temperature, carbonate-hosted Ag-Pb-Zn(Cu) deposits of northern Mexico: ECONOMIC GEOLOGY, v.83, p. 1856-1885. Meinert, L.D., 1997, Application of skarn zonation models to mineral exploration: Exploration and Mining Geology, v. 6, no. 2, p. 185-208. Meinert, L.D., 1998, A review of skarns that contain gold, in Lentz, D.R. ed., Mineralized intrusion-realted skarn systems: Mineralogical Association of Canada Short course series, v. 26, p. 359-414. Meinert, L.D., 2000, Gold in skarns related to epizonal intrusions: Reviews in Economic Geology, v. 13, p. 347-371. Moore, R., 1999, The geology and development of the La Colorada Ag-Pb-Zn deposit, Zacatecas State, mexico. in Jambor, J.L., ed., VMS and carbonate-hosted polymetallic deposits of central Mexico; Cordilleran Roundup, 1999, p. 81-84. Mortensen, J.K., Ghosh, D., and Ferri, F., 1995, U-Pb age constraints of intrusive rocks associated with copper-gold porphyry deposits in the Canadian Cordillera, in Schroeter, T.G., ed., Porphyry deposits of the northwestern Cordillera of North America: Canadian Institute of Mining and Metallurgy, Special Volume 46. 47 North, F.K., 1985, Petroleum Geology: Allen and Unwin Inc. Winchester, Mass. 607 p. Palacios, H.A.M., Querol, F.S., and Lowther, G.K., 1991, Geology and genesis of the Naica mineral deposits, Chihuahua, in Salas, G.P., ed., Economic Geology, Mexico: Geological Society of America, Boulder, Colorado, DNAG P-3, p. 279-286. Roddick, J.C., 1987, Generalized numerical error analysis with application to geochronology and thermodynamics: Geochimica et Cosmochimica Acta, v. 51, p. 2129-2135. Rollinson, H.R., 1993, Using Geochemical Data: evaluation, presentation, Interpretation: Longman Scientific and Technical, John Wiley and Sons, 352 p. Rowins, S.M., 1998, A review of Cu-Zn skarn and epithermal Au-Ag mineralization at Cerro Sacrificio and a proposed drilling program: Boliden Limited, Unpublished report, 10 p. Rubin, J.N., 1986, Mineralogy and Ore Genesis at the San Martin Mine, Zacatecas, Mexico: Unpublished M.Sc. Thesis, The University of Texas at Austin, 97 p. Rubin, J. N. and Kyle, J. R., 1988, Mineralogy and geochemistry of the San Martin skarn deposit, Zacatecas, Mexico: ECONOMIC GEOLOGY, V. 83, p. 1782-1801. 48 Ruiz, J., Patchett, P.J., and Ortega-Gutierrez, F., 1988, Proterozoic and Phanerozoic basement terranes of Mexico from neodymium isotopic studies: Geological Society of America Bulletin, v. 100, p. 274-281. Sawkins, F.J., 1964, Lead-zinc ore deposition in the light of fluid inclusion studies, Providencia mine, Zacatecas, Mexico: ECONOMIC GEOLOGY, V. 59, p. 883-919. Sedlock, R. L, Ortega-Gutierrez, F., and Speed, R. C, 1993, Tectonostratigraphic terranes and tectonic evolution of Mexico: Geological Society of America Special Paper 278, 151 p. Shoji, T., 1975, Role of temperature and C02 pressure in the formation of skarn and its bearing on mineralization: ECONOMIC GEOLOGY, V. 70, p. 739-749. Stacey, J.S. and Kramer, J.D., 1975, Approximation of terrestrial lead isotope evolution by a two-stage model: Earth and Planetary Science Letters, v. 26, p. 207-221. Steiger, R.H. and Jager, E., 1977, Subcommission on geochronology: convention on the use of decay constants in geo- and cosmochronology: Earth and Planetary Science Letters, v. 36, p. 359-362. Sutter, M., 1987, Structural traverse across the Sierra Madre Oriental fold-thrust belt in east-central Mexico: Geological Society of America Bulletin, v. 98, p. 249-264. 49 Sun, S.S. and McDonough, W.F., 1989, Chemical and isotopic systematics of ocean basalts; implications for mantle composition and processes In Magmatism in the Ocean Basins, Saunders, A.D. and Norry, M.J. eds., Geological Society Special Publication 42, p. 313-345. Terry, D.A., Patterson, K.P., Warman, T., and Gibson, K., 1999, Report on diamond drilling, geological mapping, and geophysical surveys carried out on the Cerro Sacrificio project, Durango state, Mexico (November 1998 to July 1999): Boliden Limited, Unpublished report, 49 p. Titley, S.R., 1993, Charactaristics of high temperature carbonate-hosted massive sulfide ores in the United States, Mexico, and Peru, in Kirkham, R.V., Sinclair, W.D., Thorpe, R.I., and Duke, J.M., eds., Mineral deposit modeling: Geological Association of Canada Special Paper 40, p. 585-614. Tosdal, R.M. and Richards, J.P., 2001, Magmatic and structural controls on the development of porphyry Cu±Mo+Au deposits, in Richards, J.P. and Tosdal, R.M. eds., Structural controls on ore genesis: Reviews in Economic Geology, v. 14, p. 157-181. 50 Figure Captions Figure 1. Location map of the Sacrificio deposit, Durango, Mexico. Solid squares and circles represent major cities and significant mineral deposits in the district, respectively. Figure 2. Major morphotectonic features and plate-tectonic setting of Mexico (modified after Sedlock et a/.,1993). Heavy lines denote plate boundaries, whereas lighter lines mark morphotectonic boundaries. The Trans Mexican Volcanic Belt is abbreviated as TMVB. Figure 3. Simplified geological map of the Sacrificio property. Heavy dashed line is the approximate subsurface extent of the Sacrificio intrusion inferred from geophysical data (Terry et al., 1999). Figure 4. Intrusive phases of the mid-Tertiary Coloradito and Sacrificio intrusions (40.1 ± 0.5 Ma) and the mid-Cretaceous Dique Viejo (109.1+ 0.4 Ma). Solid circles and squares represent the locations of samples collected for whole-rock geochemistry and geochronology, respectively. Figure 5. Photographs and microphotographs of major intrusive phases from the Sacrificio deposit. A. Slabbed sample of monzonite from Dique Viejo. White phenocrysts are plagioclase and orthoclase. B. Photomicrograph of monzonite from Dique Viejo with phenocrysts of plagioclase (PI) and orthoclase (Or). C. Slabbed sample of medium-grained biotite granite from the Sacrificio intrusion. Irregular black patches are primary biotite. D. Photomicrograph of medium-grained biotite granite from the Sacrificio intrusion (Qtz = quartz, Or = orthoclase). E. Slabbed sample of granite from the Coloradito intrusion. Grey, 51 subrounded phenocrysts are quartz. F. Photomicrograph of granite from the Coloradito intrusion with phenocrysts of quartz (Qtz) and plagioclase (PI). G. Slabbed sample of biotite-rich granite from the Coloradito intrusion. H. Photomicrograph of biotite-rich granite from the Coloradito intrusion with phenocrysts of quartz (Qtz), plagioclase (PI) and biotite (Bt). Figure 6. Whole-rock compositions of intrusive rocks from Cerro el Sacrificio cast in terms of quartz, alkali feldspar, and plagioclase (method of classification after LeMaitre, 1989). The Middle Eocene intrusive suite clusters in the granite field, whereas the mid-Cretaceous dykes lie in the granodiorite and quartz-monzonite fields. Note that the prefix "kp" has been omitted from data labels. Sample locations are shown in Figure 4. Figure 7. Primitive mantle-normalized rare earth element abundances of intrusive rocks from the.Sacrificio deposit. Mantle normalization factors are those of Sun and McDonough (1989). A. Mid-Cretaceous intrusive rocks including Dique Viejo and several smaller dykes exposed on Cerro Coloradito. B. Middle Eocene intrusive rocks from the Sacrificio and Coloradito intrusions. Note the change in vertical scale between A and B. Complete chemical analyses of samples shown here are given in Table 1. Sample locations are shown in Figure 4. Figure 8. Uranium-lead concordia plots of dated intrusive rocks. A. Porphyritic granite from the core of the Coloradito intrusion. B. Porphyritic granite from a large dike exposed on Cerro Coloradito. C. Medium-grained 52 biotite-granite from the Sacrificio intrusion. D. Porphyritic monzodiorite from Dique Viejo. All sample locations shown in Figure 4. Figure 9. Structural geology map of Cerro el Sacrificio including selected bedding, fold axis (Di and D3), and fracture measurements. Plunges of fold axes define D4 doming of sedimentary strata over the Sacrificio intrusion. Areas A, B, and C correspond to areas represented by stereonet projections of all data in Figure 10. Figure 10. Equal-area stereonet projections of all structural data collected at Cerro el Sacrificio. Poles to bedding are contoured with mean girdles added. Open circles represent measured Di and D3 fold axes; open squares represent poles to D5 fractures. The northerly plunge of fold axes in area B, and the southerly plunge of fold axes in area C, define the doming of sedimentary strata over the Sacrificio intrusion. The relative consistency of fracture orientations in the northern (Area B) and southern (Area C) areas compared with the pronounced doming of bedding and fold axes demonstrates that the fracturing event (D5) post-dated the doming event. Figure 11. Surface distribution of skarn alteration and sulfide mineralization on Cerro el Sacrificio. Garnet skarn and disseminated bornite-chalcopyrite mineralization are strongly controlled by D3 fold axial surfaces and their intersections with major and minor D5 fracture sets. Only the major fracture sets and fold axial traces are shown here. Note the localization of most skarn alteration and mineralization above the intrusion rather than around the margins as is typical of many skarn deposits. 53 Figure 12. A. Photomicrograph of garnet skarn with bornite (Bn) and chalcopyrite (Ccp) filling intermiperal porosity created by the formation of garnet (Grt). This texture is typical of disseminated bornite-chalcopyrite mineralization. B. Typical east-northeast-striking mineralized vein (filled D5 fracture) which has been extensively mined at Sunlight Shaft. Dashed line delineates the boundary between the vein and disseminated sulfide mineralization in garnet skarn. C. D5 vein with crustified bands of coarse-grained quartz and calcite. Fibrous growth of quartz and calcite perpendicular to vein walls is indicative of pure extension (mode 1). Pen is 15 cm in length. D. Margin of typical polymetallic manto replacing marble in drillcore. Manto is composed mainly of fine-grained pyrite, arsenopyrite, sphalerite, galena, pyrrhotite and chalcopyrite (see text for further description of the mineralogy). Figure 13. Interpreted sequence of deformation events affecting Cerro el Sacrificio. D1 - Tight to isoclinal, west-verging, inclined folds. D2 - Type 2 refolding of Di folds. D3 - Large amplitude, gentle to open, upright folds trending 330° that refold D<\ and D2 folds. D4 - Doming of previously deformed strata over the intrusion during it's emplacement, with exsolved magmatic fluids focussed along D3 axial surfaces. D5 - Increase in pore fluid pressure above the intrusion and opening of mode 1 fractures oriented east-northeast, parallel to maximum compressive stress. Mineralizing fluids are channeled by these fractures, with bornite and chalcopyrite filling secondary porosity in garnet skarn proximal to the D5 fractures. Retrograde skarn and manto formation, which postdate D5, are not included in this schematic diagram. 54 Figure 14. Relative timing of deformation, alteration, and mineralization events at the Sacrificio deposit. Absolute ages are derived from U-Pb dating of intrusive rocks; all other timing is relative (i.e., the time axis is not to scale). Figure 15. Photographs of key structural features mapped at Cerro el Sacrificio. Fold axial surfaces are highlighted by dashed white lines. A. Mesoscopic Di folds. Hammer is 30 cm in length. B. D2 folds refolding Di folds. C. Broad, open D3 fold. D. Typical, steeply-dipping D5 fractures with associated Cu-Ag±Au mineralization. Figure 16. Whole-rock compositions (classification scheme after LeMaitre, 1989) of intrusive phases from the Cerro de la Gloria Stock, San Martin mine (data from Graf, 1997). San Martin data are represented by black squares. Shaded field represents the compositional range of intrusive rocks from the Sacrificio deposit (data from Fig. 6). Figure 17. Primitive mantle-normalized rare earth element abundances of intrusive rocks from the Cerro de la Gloria Stock, San Martin (data from Graf, 1997). Range of rare earth element abundances for intrusive rocks from the Sacrificio deposit are represented by the shaded area (data from Fig. 7). 55 Patterson et al.: Figure 1 56 Patterson et al.: Figure 2 57 Patterson et al.: Figure 3 58 A |kp-14 kp-6 Coloradito Intrusion kp-4 600 m 40.1 +/- 0.5 Ma Granite ] Quartz-Feldspar-Phyric Granite Egg} Quartz-Feldspar-Biotite-Phyric Granite Ilil&ISSlI Quartz-Phyric Granite 1 Zones of Intense Silicification Sacrificio Intrusion 4P Cuesta del Cura Formation (limestone and chert) B—n Indidura Formation (limestone and shale) 109.1 +/- 0.4 Ma Monzodiorite I Feldspar-Phyric Monzodiorite Patterson et al.: Figure 4 59 Patterson et al.: Figure 5 60 Quartz Alkali Plagioclase Feldspar Patterson et al.: Figure 6 61 100 10 • kp-2 °kp-4 *kp-8 Dkp-9 Akpl0 La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu 100 La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Patterson et al.: Figure 7 62 Patterson et al., Figure 8 63 x f" •J. tY* £ \ff» AREA B y V 1 s« 0 200 400 600 m *' I I SCALE • • • Cuesta del Cura Formation (limestone and chert) Indidura Formation (limestone and shale) 40.1 +/- 0.5 Ma Granite 109.1 +/- 0.4 Ma Monzodiorite s7. Bedding Orientation Measured Fold Axis Fracture Orientation Fold Axial Trace, Antiform -r •4— Fold Axial Trace, Synform Patterson et al.: Figure 9 64 Patterson et al.: Figure 10 65 Lithologic Units • • • Cuesta del Cura Formation (limestone and chert) Indldura Formation (limestone and shale) 40.1 •/- 0.S Ma Granite 109 Ma Monzodiorlte Approximate boundary of mineralized fracture set 4 0 V~""' 200 400 600 m i h SCALE Alteration and Related Mineralization Hornfels j Quartz-Scapolite-Albite+/-Sericite Prograde Skarn Garnet Skarn M Disseminated Bomite-Chalcopyrite and Fracture-Controlled Mineralization j Intense Silicification Quartz Vein Stockwork FljSl Quartz-Cemented Limestone Breccia Retrograde Skarn r."\l Pervasive Amphibole-Chlorite Liii'iij +/- Base and Precious Metal Mantos ,' Mapped contact between the Cuesta del ' Cura and Indldura Formations Patterson et al.: Figure 11 66 Patterson et al.: Figure 12 67 240* 60* 240* 60* Opening of extensional fractures, fluids channeled up fractures D5 Patterson et al.: Figure 13 68 TIME-Emplacement of Dique _| Viejo and related dykes \ and Coloradito granites D4 doming -Quartz-Albite-Scapolite Hornfels -Prograde garnet skarn -D5 mode 1 fractures -Disseminated bornite+/- _ chalcopyrite mineralization Fracture-controlled mineralization -Retrograde amphibole skarn -Manto mineralization -D, folding -D2 folding -D3 folding -? Emplacement of Sacrificio Crystalization Exsolving magmatic fluids 109 Ma 40 Ma Patterson et al.: Figure 14 69 Patterson et al.: Figure 15 70 Quartz Quartz-rich Granitiods Patterson et al.: Figure 16 71 1 OOF ~I 1 r n i i r 10 • • •U-21 -11-136 "MP-U-44 ASM94-MP TSMQP-S J 1 L_ J I I L La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Patterson et al.: Figure 17 72 Q. 00 I Q. in 00 ro <D cn r~~ ro CM m o CO CD o O ro cn o iri d CM d d d d CO d d a V a O 'o. a Q. a. o. JC up Q. a CO I a a. 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Paragenesis of Alteration and Mineralization at the Sacrificio Deposit Style Contact Metamorphism Prograde Skarn Alteration Mineralogy Style quartz-albite-scapolite None ± sericite ± chlorite garnet-wollastonite-clinopyroxene-vesuvianite Minor Silicification quartz Disseminated Cu-Ag Fracture-controlled Cu-Ag±Au Mineralization Mineralogy None bornite ± chalcopyrite chalcopyrite ± bornite ± sphalerite ± galena ± arsenopyrite Retrograde Skarn amphibole-chlorite ± Massive Manto sphalerite-galena-epidote ± calcite Zn-Cu-Pb-Ag±Au chalcopyrite-arsenopyrite-pyrite-pyrrhotite-bornite Notes: only the major minerals are listed; secondary copper-oxide minerals are variably developed near surface in all styles of mineralization. 75 Chapter 3 Evolution and source of mineralizing fluids in the Sacrificio Cu (Zn-Pb-Ag-Au) skarn deposit, Durango, Mexico Keith M. Patterson (Co-Author: Stephen M. Rowins) 76 Abstract The Sacrificio deposit, which is located in southeastern Durango State, Mexico, is hosted by mid-Cretaceous limestone, chert, and minor shale of the Cuesta del Cura and Indidura formations. Intrusive rocks include two temporally and compositionally distinct suites, dated at 109.1 ± 0.4 Ma (mid-Cretaceous) and 40.1 ± 0.5 Ma (Middle Eocene). The Middle Eocene granite suite is associated with the development of skarn and related sulfide mineralization that forms the Sacrificio deposit. Three episodes of pre-intrusion regional deformation (Di to D3) and two episodes of syn-intrusion local deformation are recognized at the Sacrificio deposit. Skarn and skarn-related mineralization is localized within these regional and local structures and their intersections. Alteration at the Sacrificio deposit is divided into pre-mineralization contact metamorphism, prograde skarn, and retrograde skarn. Three styles of skarn-related sulfide mineralization are present: (1) disseminated to semi-massive bornite and lesser chalcopyrite filling secondary porosity in prograde garnet skarn; (2) fracture-controlled bornite-chalcopyrite ± sphalerite + galena ± arsenopyrite with high Ag contents; and (3) fine- to coarse-grained semi-massive to massive sulfide bodies or "mantos", which are associated with retrograde amphibole skarn and contain a sulfide assemblage of arsenopyrite, pyrite, pyrrhotite, bornite, chalcopyrite, sphalerite and galena. Rare quartz-arsenopyrite veins post-date all alteration and mineralization. Skarn and sulfide-forming fluids at the Sacrificio deposit are interpreted to be magmatic in origin from lead isotope data. Compositions of garnet (Ad65-77 iooGro-35) and pyroxene (Di68-94Hd5.3oJoi.3) from prograde skarn that hosts disseminated bornite-chalcopyrite mineralization classify the Sacrificio skarn as a copper skarn. Fluid inclusion studies indicate that mineralizing fluids were dominantly H20-NaCI mixtures, although depressed eutectic temperatures indicate the presence of additional divalent cations (i.e., Mg2+, Fe2+, and Ca2+). Disseminated and manto-style mineralization formed from fluids containing 0.5 -13.8 wt. % NaCI equivalent, whereas post-skarn quartz-arsenopyrite veins were formed from fluids containing 6.1 - 19.7 wt. % NaCI equivalent. Pressures during the development of the Sacrificio deposit are estimated at approximately 0.5 to 1.0 kbar from stratigraphic reconstructions and geologic evidence. Temperatures of skarn formation and sulphide deposition show a gradual cooling of the skarn system. Prograde skarn formed at 460° to 580° C, disseminated Cu-Ag mineralization at 291° to 504° C, and mantos at 247° to 396° C. This was then overprinted by a final pulse of hotter fluids (318° to 480° C) which formed the late quartz-arsenopyrite veins. Introduction The Mexican Altiplano is host to numerous skarn and carbonate replacement deposits, which are significant past and present producers of Ag, Zn, Pb, and Cu (e.g., San Martin, Fresnillo, Chalchihuites, Concepcion del Oro, Velardeha; Megaw, 1999). The Sacrificio Cu (Zn-Pb-Ag-Au) skarn deposit occurs within this district (Fig. 18) and exhibits many of the features that characterize this class of mineral deposit. Pre- and syn-intrusion deformation is critically 78 important in controlling the distribution of mineralization at the Sacrificio deposit. The structural model developed at Sacrificio to explain the location of mineralization within regional and local structures (Patterson et al., in review) can be applied to many of the skarn and carbonate replacement deposits in the Altiplano. In this contribution, fluid inclusion, lead isotope, and mineralogical studies are used to investigate the source of the mineralizing fluids and the physicochemical conditions (P-T-X) of skarn formation and related mineralization at the Sacrificio deposit. Understanding fluid evolution and the localization of skarn-related mineralization at the Sacrificio deposit is important not only for local exploration activity, but also for predicting the location of undiscovered zones of mineralization in skarn and carbonate replacement deposits throughout the Mexican Altiplano. Regional Geological Setting The Sacrificio deposit is situated 80 km southeast of Durango, in a well-recognized northwest-trending belt of skarn and carbonate replacement deposits which include San Martin, Fresnillo, and Chalchihuites (Fig. 18). In this paper, the term deposit is used to describe the skarn-related sulfide mineralization at Cerro el Sacrificio owing to the -15 years of production activity in the 1970's and 1980's at Mina Embotelladora, a small underground copper mine located on the northern flank of Cerro el Sacrificio. Additionally, numerous small historic adits and pits are present in the area (Fig. 19) and are evidence of previous mining activity. 79 The Sacrificio deposit lies within the Altiplano ("high plateau") of central Mexico which is underlain by thick Jurassic to Lower Cretaceous metasedimentary rocks which consist primarily of marine carbonate rocks with interbedded chert and shale (Sedlock et al., 1993). Mid-Tertiary plutons ranging from granite to diorite in composition intrude the Jura-Cretaceous strata. In addition to causing extensive hydrothermal alteration of adjacent host-rocks, these intrusions are thought to be responsible for the precious and base metal-rich mineral deposits of the Altiplano (e.g., Rubin and Kyle, 1988; Barton et al., 1995; Megaw, 1999). The dominant structural fabric of the Altiplano is attributed to strong north-northeast-directed contraction associated with the Late Cretaceous to Middle Eocene Mexican fold-and-thrust belt (Sutter, 1987; Sedlock et al., 1993). The Sacrificio deposit lies in the westernmost or hinterland portion of the Mexican fold-and-thrust belt where regional folding is intense. In the Altiplano, folding and thrusting generally verges northeast to east-northeast, consistent with deformation throughout the North American Cordillera (e.g., Drewes, 1991). Deformation in the Mexican fold-and-thrust belt occurred during latest Cretaceous to Middle Eocene time (~ 70 to 45 Ma) and is temporally and kinematically similar to "Laramide" deformation in the southwestern U.S. (e.g, Sedlock et al., 1993). The Mexican fold-and-thrust belt deformation front was spatially time transgressive, with deformation younging to the east (de Cserna, 1989). Magmatism associated with the orogeny was simultaneous with deformation but 80 localized some distance west of the thrust front and therefore after peak deformation (Sedlock et al., 1993). This simple relationship explains the post- to syn-deformation timing of pluton emplacement at Cerro el Sacrificio and at many other intrusion-related mineral deposits in central Mexico (e.g., Megaw, 1999). Local Geological Setting Supracrustal rocks which host the Sacrificio deposit consist of limestone, chert, and minor shale of the Cuesta del Cura (Upper Albian-Cenomanian) and overlying Indidura (Cenomanian to Santonian) formations (Longoria et al., 1999) (Fig. 19). Thick beds (10 to 40 cm) of grey limestone are interbedded with thin beds (1 to 10 cm) of white to grey chert in the Cuesta del Cura Formation. The Indidura Formation is similar, but also contains rare beds of black argillaceous shale. At the San Martin mine 30 km to the southeast, these formations are in excess of 1000 m in thickness (Rubin, 1986) and form a compositionally monotonous succession of chemically receptive host-rocks. Intrusive rocks at the Sacrificio deposit comprise two temporally and compositionally distinct magmatic suites. The older suite is mid-Cretaceous in age (109.1 ± 0.4 Ma; U-Pb zircon age) and consists of feldspar-phyric quartz monzodiorite dikes of which Dique Viejo is the largest (e.g., Fig. 19). The younger suite is Middle Eocene in age (40.1 ± 0.5 Ma; U-Pb zircon age) and consists of the Sacrificio and Coloradito intrusions, both of which are multiphase, equigranular granites (Patterson et al., in review). A variety of geological evidence led Patterson et al. (in review) to conclude that skarn formation, sulfide 81 mineralization, and some of the local structures were caused by the emplacement of the Middle Eocene intrusive suite (Fig. 19). Skarn-related Mineralization Three styles of skarn-related sulfide mineralization are recognized at the Sacrificio deposit. These are (1) disseminated Cu-Ag mineralization in prograde skarn, (2) fracture-controlled Cu-Ag ± Au mineralization in prograde skarn, and (3) massive to semi-massive sulfide or manto-style Zn-Cu-Pb-Ag-Au mineralization associated with retrograde skarn development. The fracture-controlled and disseminated styles of mineralization are spatially and genetically related, but macroscopic differences discussed below require that they be classified separately. Note that fractures are referred to as veins where filled by minerals in accordance with the terminology of the American Geological Instutute (AGI) (Bates and Jackson, 1983). Rare, 1 to 3 cm wide, quartz-arsenopyrite veins cross-cut all mineralization styles and intrusive rocks. Disseminated Cu-Ag mineralization is the most widespread style of mineralization at the Sacrificio deposit. It is charactarized by small disseminations (up to 3 mm in diameter) and large, irregularly shaped clots (up to 2 cm in longest dimension) of bornite and lesser chalcopyrite filling secondary porosity in prograde garnet and wollastonite skarn (Fig. 20A). Relatively large areas (hundreds to thousands of square meters - Fig. 21) host disseminated bornite-chalcopyrite mineralization in prograde skarn on surface. Significant drill 82 core intersections of this style of mineralization include 1.72% Cu and 121 grams per tonne (g/t) Ag over 24.3 m (Terry etal., 1999). Zones of fracture-controlled Cu-Ag ± Au mineralization commonly contain very high grades of copper and silver (channel samples include up to 6.51% Cu and 554 g/t Ag over 1.5 m), but are generally of limited extent and tonnage. Sulfide minerals in this style of mineralization occur as coatings on fractures, as fillings in veins, and as disseminations concentrated within about 30 cm of the fractures (Fig 20B). This disseminated mineralization proximal to the fractures grades into the more widespread disseminated mineralization described above, but is differentiated from it based on the presence of sulfides other than bornite and chalcopyrite, and the concentration of this mineralization style near the fractures. Veins typically are filled with quartz, calcite, and up to about 5% chalcopyrite and/or bornite plus minor sphalerite, galena, and arsenopyrite. Some rare veins, however, are composed almost entirely of sulfide minerals. Fractures and veins commonly occur together in zones several tens of meters in width with centimeter- to meter-scale spacing between individual fractures. Vein widths range from millimeters to tens of centimeters, with typical thicknesses on the order of 1 to 10 cm. Secondary copper minerals such as malachite, azurite, and chrysocolla commonly are developed in fracture zones due to the secondary oxidization of primary sulfide minerals. Polymetallic mantos are becoming recognized as an increasingly important style of mineralization in the Sacrificio deposit (Terry et al., 1999). The 83 recent discovery of several new mantos by exploration diamond drilling has greatly increased the economic attractiveness of the deposit by increasing its metal potential from one of copper and minor silver to one of copper, zinc, silver and gold. Sulfide minerals identified in the mantos by reflected light microscopy and scanning electron microscopy (SEM) include sphalerite, galena, chalcopyrite, arsenopyrite, pyrite, pyrrhotite and bornite with rare tetrahedrite, stibnite, and stannite (Fig. 20C). Several mantos contain high concentrations of silver and locally gold. The best manto intersection includes 16.43 m of 1.48% Zn, 1.34% Cu, 0.99% Pb, and 174.6 g/t Ag (Terry et al., 1999). Contact relationships between the mantos, prograde skarn, and marble indicate that the mantos post-date the prograde skarn and marble development. Common gangue minerals occurring with the mantos are characteristic of retrograde skarns (e.g., Einaudi et al., 1981) and include amphibole, chlorite, epidote, and calcite. In combination, these data indicate that polymetallic manto mineralization post-dates the disseminated and fracture-controlled Cu-Ag ± Au mineralization. Alteration Alteration is divided into three types at the Sacrificio deposit. These are (1) pre-mineralization contact metamorphism, (2) prograde skarn, and (3) retrograde skarn. The contact metamorphism forms a large halo around the Sacrificio and Coloradito intrusions whereas the distribution of both prograde and retrograde skarn is strongly controlled by proximity to well-developed structures (Fig. 21). 84 The timing and association of mineralization and alteration styles is given in Table 4. The earliest and most widespread style of alteration identified at the Sacrificio deposit is the pervasive development of hornfels in limestone and chert surrounding the Sacrificio and Coloradito intrusions (Fig. 21). Alteration minerals formed during this event include quartz, albite, scapolite, and minor sericite. This assemblage preferentially replaces chert beds (but locally also replaces limestone) in a halo up to 500 m wide surrounding the intrusions. The distribution of this alteration is controlled by proximity to the intrusions - it is unaffected by the structures that localized prograde and retrograde skarn. This hornfels is interpreted as a product of heat generated by the intrusions. Structurally controlled prograde skarn, which hosts the disseminated bornite-chalcopyrite mineralization, is the most strongly developed hydrothermal alteration exposed on surface at the Sacrificio deposit (Fig. 21). Prograde skarn dominantly consists of massive to poddy garnet but also includes wollastonite, clinopyroxene, and vesuvianite. The garnets, as determined by electron microprobe analysis (see below), are members of the grossular-andradrite solid solution series using the method of classification of Rickwood (1968). They occur as euhedral, coarse-grained, apple green crystals up to 2 cm in diameter. In thin section, garnets invariably display compositional zoning and weak anisotropism (Fig. 22A). Wollastonite occurs as white, bladed, commonly radiating crystals up to 3 cm in length. Clinopyroxene is typically dark green and occurs as masses of anhedral to subhedral crystals that in thin section generally show evidence of 85 alteration and/or replacement (Fig. 22B). Vesuvianite is present as brown, subhedral to euhedral laths ranging up to 1 cm in length that characteristically display weak compositional zonation in thin section. At the scale of outcrop, garnet, wollastonite, clinopyroxene, and vesuvianite generally occur together as prograde skarn. At the scale of hand sample or thin section, a zonation is developed from proximal garnet, to garnet+clinopyroxene, to more distal wollastonite + vesuvianite with increasing distance from a fracture or vein. Retrograde skarn occurs at several locations on the Sacrificio property and is commonly associated with manto-style mineralization. Dark green, pervasive, poddy and veinlet-controlled amphibole typify this alteration style. Associated minerals include chlorite, quartz, calcite, and epidote. On surface, retrograde skarn forms zones tens to hundreds of square meters in area peripheral to both the Sacrificio and Coloradito intrusions (Fig. 21). In thin section, amphibole generally occurs as fine-grained, subhedral to anhedral crystals, although rare occurrences of course-grained, euhedral, laths are noted (Fig. 22C). Most amphibole examined is actinolite to ferro-actinolite with rare hornblende in some zones. In drillcore, retrograde skarn clearly post-dates prograde garnet-wollastonite skarn (Fig. 22D). Quartz-arsenopyrite veins cut all styles of mineralization, alteration, and types of lithologies at the Sacrificio deposit. These veins are generally 1 to 3 cm in width and are surrounded by a weak alteration halo (up to 10 cm in width) consisting mainly of quartz and sericite. Quartz-arsenopyrite veins are best 86 recognized in drill core where they commonly cut the Coloradito and Sacrificio intrusions. Garnet and Clinopyroxene Mineral Chemistry Einaudi et al. (1981) demonstrated that skarn deposits are best classified by their dominant economic metals into six types, namely: iron, tungsten, copper, zinc-lead, molybdenum, and tin. Meinert (1989) subsequently classified gold skarns as a separate type. Classification of the polymetallic Sacrificio skarn deposit is somewhat problematic because it contains elements of both copper and zinc skarns (e.g., Einuadi et al., 1981). For example, the extensive zones of fracture-controlled and disseminated bornite-chalcopyrite mineralization at Mina Embotelladora are characteristic of copper skarns, whereas the sphalerite-rich mantos mined at Rosas de Diciembre (Fig. 19), and intersected in diamond drill core, are typical of zinc skarns. Fortunately, the compositions of garnet and clinopyroxene associated with the formation of prograde skarn can be used, in addition to metal abundances, to discriminate between copper and zinc skarns (e.g., Einaudi et al., 1981; Meinert, 1992). To this end, the compositions of garnet and clinopyroxene in a suite of prograde skarn samples were determined by electron microprobe analysis in order classify the Sacrificio skarn deposit. Classification of the Sacrificio deposit allows for comparison with other similar deposits and application of genetic models developed elsewhere to the Sacrificio skarn. Samples containing both garnet and pyroxene in close association with 87 disseminated bornite-chalcopyrite mineralization were collected from large exposures of prograde skarn directly above the Sacrificio intrusion. Garnet microprobe analyses were recast into mol. % end-members grossular (Gr), Andradite (Ad), Spessartine (Sp), and Almadine (Ad) following the procedure of Rickwood (1968). These data indicate that garnets are members of the Ad - Gr solid-solution series (i.e., grandite garnet) and range in composition from nearly pure Ad to 35 mol. % Gr; Representative analyses are given in Table 5. This chemical variation is explained by a nearly perfect 1:1 substitution of Al3+ for Fe3+ (Fig. 23). This chemical substitution is reflected optically in garnets by the lighter colored bands having more grossular-rich (Al-rich) compositions than the darker colored bands which are more andradite-rich (Fe-rich). Clinopyroxene analyses were recalculated into mol.% end-members hedenbergite (Hd), diopside (Di) and johannsenite (Jo) following the method of Deer et al. (1992). The microprobe analyses reveal that clinopyroxenes lie along the Di-Hd solid-solution series and have only a minor Jo component. Compositions range from 68 to 94 mol. % Di, 5 to 30 mol. % Hd, and 1 to 3 mol. % Jo. Representative analyses are given in Table 5. Clinopyroxene compositions are evenly distributed along these ranges with an average composition of Di84Hdi4Jo2. Zoning was not observed in the clinopyroxene. These garnet and clinopyroxene compositions fall within the range of compositions for copper skarns as defined by Meinert (1992) (Fig. 24). This finding, in addition to the relative abundance of copper mineralization compared to zinc mineralization, classifies the Sacrificio deposit as a copper skarn. 88 Structural Model The localization of skarn mineralization and alteration within structures at the Sacrificio deposit is explained within a framework of five distinct episodes of deformation (Patterson et al., in review). Briefly, the three earliest deformation events (Di to D3) recognized at the Sacrificio deposit are attributable to long-lived, progressive, deformation within the Mexican fold-and-thrust belt. The final two events (D4 and D5) are attributed to the emplacement of the Sacrificio intrusion. A sequential rendition of deformation and associated mineralization from D: to D5 is schematically illustrated in Figure 25. The paragenetic relationships between the structures and the various styles of alteration and mineralization are detailed in Figure 26. Di is a relatively ductile folding event, which records an estimated 100 to 150% shortening in the area of Cerro el Sacrificio. Di folds are tight to isoclinal, inclined to recumbent, and generally have amplitudes of ten centimeters to three meters. Di folds are strongly asymmetric and typically verge to the west. Di fold axes trend towards 330° with a maximum shortening direction of east-northeast. D2 is a minor event likely due to a local realignment of regional stresses as a result of strain partitioning or extreme competency contrast. It has limited effect on the present form of stratified rocks in the mapped area, but is unambiguously recognized at several outcrops. D2 consists of type 2 refolding of D-i folds (fold axial surfaces approximately perpendicular; McClay, 1987). With respect to localization of skarn, D3 folding is the most important deformation event defined at Sacrificio. D3 folds are large amplitude (hundreds of 89 meters), gentle to open, upright folds which refold Di folds with similarly oriented fold axes (type 3: McClay, 1987). D3 fold axial surfaces, particularly in anticlines, have focussed ascending metalliferous and skarn-forming magmatic fluids leading to the present distribution of garnet skarn and disseminated mineralization. The largest and most strongly mineralized D3 fold mapped at the Sacrificio deposit is the Central Anticline (Fig. 19). D3 fold axes trend toward 330° and plunge gently to the north or south depending on their location within the dome produced by D4. D4 is attributed to the forceful emplacement of the Sacrificio intrusion, which resulted in the gentle doming of rocks above and around the intrusion as defined by the plunges of D, and D3 fold axes. In rocks above the northern half of the intrusion, Di and D3 fold axes plunge to the north-northwest, whereas in rocks above the southern half of the intrusion, these fold axes plunge to the south-southeast. Fluids released from the crystallizing intrusion at this time were channeled upward along D3 fold axial surfaces as evidenced by the localization of prograde skarn. Elevated pore fluid pressures due to continued exsolution of magmatic fluids and/or their interaction with carbonate host rocks causing an increase in the partial pressure of H2C03, (e.g., Shoji, 1975; Johnson and Norton, 1985), are proposed to have caused mode I (extension) fractures to form above the intrusion (D5). D5 fractures are dominantly steeply dipping and generally strike east-northeast (Fig. 21), possibly indicating that a weak east-northeast oriented regional compressional stress field still existed at this time. Metalliferous fluids 90 exsolved from the intrusion were preferentially channeled into these newly formed fractures and subsequently into porous garnet skarn. This channeling of fluids resulted in significant concentrations of disseminated bornite and lesser chalcopyrite in garnet skarn proximal to the D5 fractures. The sequence of events presented here is consistent with field evidence that show intersections between garnet skarn and D5 fractures invariably host strong disseminated bornite-chalcopyrite mineralization. Fluid Inclusion Microthermometry A study of fluid inclusions trapped in hydrothermal quartz from several styles of mineralization and post-mineralization quartz-arsenopyrite veins was undertaken in order to determine the temperatures of mineralization and the composition of the metalliferous fluids. In addition, these data are used to document fluid evolution in the skarn system and provide insight into the processes responsible for mineral deposition (i.e., fluid mixing, fluid boiling or phase separation, etc.). Integration of these fluid inclusion data with lead isotope studies (see below) and detailed structural, petrological, and geochronological data (Patterson et al., in review), permit the construction of a comprehensive mineralization model for the Sacrificio deposit. Methodology Microthermometric data were collected from one hundred and seventy eight fluid inclusions in ten rock-samples considered representative of (1) 91 disseminated Cu-Ag mineralization associated with prograde skarn, (2) polymetallic manto mineralization associated with retrograde skarn, and (3) unmineralized quartz-arsenopyrite veins that post-date skarn formation. Note that because the fractured-controlled Cu-Ag ± Au mineralization is genetically related to the disseminated Cu-Ag mineralization, its fluid inclusion characteristics can be approximated by the microthermometric data collected for the disseminated Cu-Ag style. Microthermometric measurements of fluid inclusions were conducted using a FLUID INC.-adapted USGS gas-flow heating-freezing stage at the University of British Columbia. Accuracy of the measurements was ensured by calibration against the triple point of pure C02 (-56.6° C), the freezing point of water (0.0° C), and the critical point of water (374.1° C), using synthetic fluid inclusions supplied by FLUID INC. Accuracy of the temperatures obtained in this study was ±0.2° C for freezing runs, and ±3.0° C for heating runs between 40° to 600° C. Measurements were made using a heating rate of approximately 1° C per minute. Freezing runs were conducted prior to heating runs in order to minimize the possibility of stretching and post-entrapment leakage of fluid inclusions (e.g., Roedder, 1984). Wafers of doubly polished thin sections containing fluid inclusions were cooled rapidly to approximately -120° C and then warmed slowly in order to measure both the first ice melting or eutectic temperature (Te) and the final ice melting temperature (Tm). Continued heating permitted the determination of total homogenization temperatures (Th) for these same inclusions. In some wafers it was possible to collect additional Th data where suitable inclusions occurred in the same field of 92 view as the inclusions undergoing complete microthermometric analyses (i.e., both freezing and heating runs). Reduction of microthermometric data was done with the MacFlincor software program (Brown and Hagemann, 1995). Fluid inclusion petrography Doubly polished thin sections of each sample were examined in detail to record the nature of fluid inclusion distribution, size, and types, and to determine their spatial, temporal, and textural relationships. All inclusions studied were hosted in crystals of quartz with petrographic evidence for co-precipitation with sulfide mineralization. Genetic classification of inclusions as primary, pseudosecondary, or secondary follows the criteria given by Roedder (1984). In this study only primary, or rarely pseudosecondary, inclusions with regular edges and rounded shapes were used in order to minimize the possibility of analyzing secondary inclusions unrelated to mineralization (or arsenopyrite crystallization in the case of the quartz-arsenopyrite veins). Finally, microthermometric analysis was conducted only on inclusions with diameters greater than 8 [irr\ to permit the determination of phase changes with a high degree of accuracy. Primary and pseudosecondary fluid inclusions encountered during the course of this study are remarkably similar in appearance at room temperature. They normally range from 5 to 30 urn in diameter (averaging about 12 ^m) and contain separate aqueous liquid and vapor phases (Fig. 27). A separate carbonic phase is not present. All inclusions studied are liquid-rich (i.e., >50 volume % liquid), with 84% containing greater than 70 volume % liquid. Interestingly, those primary 93 and/or pseudosecondary inclusions localized in trails and clusters invariably display consistent proportions of liquid and vapor. Daughter minerals are rare, although approximately 16% of the inclusions studied contain a small rounded solid (1 to 3 \xm in diameter) with high birefringence under crossed-polars in transmitted light. This daughter mineral is almost certainly a carbonate species (e.g., Shepherd et al., 1985). Halite is notably absent in all inclusions studied, but a small irregularly shaped opaque solid in small percentage of inclusions may be a sulfide mineral. Microthermometric data The microthermometric data of fluid inclusions from the two styles of mineralization and the late-stage quartz-arsenopyrite veins are summarized in Table 6 and discussed below. Eutectic temperatures were measured for sixty-three fluid inclusions associated with disseminated and manto mineralization and the post-mineralization quartz-arsenopyrite veins in order to determine the cation composition of the fluids. The range of eutectic temperatures (-19.7° to -47.0° C) is similar for both styles of mineralization and the quartz-arsenopyrite veins (Figs. 28A-C). The depression of Te below -21.2° C is suggestive of the presence of divalent cations such as Mg2+, Fe2+, and Ca2+ in the fluids in addition to Na+ (e.g., Borisenko, 1977; Crawford, 1981; Davis et al., 1990). This finding is consistent with the presence of carbonate daughter minerals and expected fluid compositions in the calcic skarn environment (e.g., Bowman, 1998). The overlapping range of eutectic temperatures for the disseminated and manto \ 94 mineralization associated with prograde and retrograde skarn, and the post-skarn quartz-arsenopyrite veins, suggests that overall fluid compositions did not change systematically during evolution of the Sacrificio skarn system. The final ice melting temperatures from sixty-eight fluid inclusions were used to estimate the salinity of the mineralizing fluids (e.g., Bodnar, 1993). Although fluids were not pure H20-NaCI mixtures, the presence of additional cations does not introduce appreciable error into the calculation of salinities (Clynne and Potter, 1977), which are expressed as weight percent NaCl equivalents (wt.% NaCl eq.). Clathration did not occur during any heating or freezing runs supporting the lack of optical evidence (i.e., a separate carbonic phase) for significant CO2-CH4 in the fluid. Final melting temperatures of inclusions from the disseminated Cu-Ag mineralization vary from -0.8° to -9.9° C indicating a salinity of 1.3 to 13.8 wt.% NaCl eq. (Fig. 28D). The Tm of inclusions from the mantos vary from -0.3° to -5.4° C, equivalent to a salinity of 0.5 to 8.4 wt.% NaCl eq. (Fig. 28E). These data are virtually identical to those of inclusions from the disseminated Cu-Ag mineralization (Figs. 28D & E). Inclusions in the quartz-arsenopyrite veins, however, have Tm between -5.0° and -16.4° C which correspond to salinities between 6.1 to 19.7 wt % NaCl eq., a range significantly higher than that of both the disseminated and manto styles of mineralization (Fig. 28F). Homogenization temperatures were measured for one hundred and fifty eight fluid inclusions in order to place constraints on the temperatures of mineralization. Homogenization temperatures of the disseminated Cu-Ag 95 mineralization vary between 251° and 389° C and display two broad maxima: a lower temperature maximum at about 300° C and a higher temperature maximum at around 370° C (Fig. 28G). The Th measured for manto mineralization are lower and range from 205° to 306° C with a broad maximum at around 275° C (Fig. 28H). Homogenization temperatures of inclusions in the quartz-arsenopyrite veins are similar to those in the disseminated mineralization and range from 278° to 383° C and lack any pronounced maximum (Fig. 28I). Microthermometry results The absence of vapor-rich inclusions and groups of inclusions with substantially variable liquid/vapor ratios indicates that fluid boiling or phase separation (e.g., Pichavant et al., 1982; Bodnar et al., 1985; Brown 1998) did not occur during formation of the Sacrificio deposit. The fact that all inclusions homogenized to the liquid phase also supports this conclusion. Consequently, the homogenization temperatures measured in this study provide only minimum estimates of the temperatures of mineralization (Roedder, 1984). In order to estimate the true trapping temperatures, a "pressure-correction" must be added to the measured temperatures of homogenization (e.g., Potter, 1977). To calculate this pressure correction for H20-NaCI fluids, it is necessary to estimate the trapping pressure under which the mineralization formed. At the Sacrificio deposit, trapping pressure can be estimated from an approximation of the thickness of overlying strata at the time of mineralization. Graf (1987) estimates that at the time of ore formation at the nearby San Martin mine, the thickness of 96 strata above the mineralizing intrusion was 1.5 to 3.0 km. The Sacrificio deposit occurs at the same stratigraphic level as the San Martin mine (i.e., just below the Indidura/Cuesta del Cura Formation contact) and likely formed under a similar depth of cover. From these stratigraphic considerations and assuming an average crustal density of 2.7 g/cm3 (i.e., lithostatic conditions), it is estimated that the Sacrificio deposit has formed at pressures between 0.5 and 1.0 kbar. Details on the method of calculation are given in Shepherd et al. (1985). These pressure estimates are robust and do not change more than 0.1 or 0.2 kbar if the values for depth of cover and crustal density are varied to reflect geological uncertainty. The assumption that mineralization formed under near-lithostatic pressure conditions appears justified for the Sacrificio deposit as the calculated range of pressures using a lithostatic load is similar to that expected for copper skarn deposits (e.g., Einaudi et al., 1981; Bowman, 1998). Using these pressure estimates and assuming a fluid salinity of 5 wt.% NaCl eq., the figures of Potter (1977) indicate that pressure corrections of 40° to 115°C and 40° to 90°C are required the for disseminated Cu-Ag and polymetallic manto styles of mineralization, respectively. These pressure corrections give trapping temperatures of 291° to 504°C for disseminated Cu-Ag mineralization and 247° to 396°C for polymetallic manto mineralization. Similar calculations for the quartz-arsenopyrite veins assuming a fluid salinity of 10 wt.% NaCl eq. result in pressure corrections of 40° to 97° C. This yields trapping temperatures of 318° to 480° C. These pressure correction data are represented graphically in figures 97 29 and 30, which are pressure-temperature plots of isochores for the system H20-NaCI (Bodnar and Vityk, 1994). Lead Isotope Study A lead isotope study was undertaken in order to constrain the source(s) of lead and, by inference, other metals in the Sacrificio deposit. Under the appropriate geological conditions, lead isotope studies are a very effective means of identifying the source(s) of metals in a wide variety of ore deposits (e.g., Richards et al., 1991; Rowins et al., 1997; Tosdal et al., 1999). Samples of potential source rocks including intrusions and meta-sedimentary host rocks were analyzed, as were samples of the different styles of mineralization (Table 7). Lead isotope compositions were obtained for sixteen samples of sulfide minerals using galena where possible and trace lead in other sulfides where galena was unavailable. Whole rock lead isotope compositions were obtained from three samples of unaltered limestone and shale. Lead isotope compositions from four samples of intrusive rock were determined using feldspar. Analytical procedure Lead isotope analyses were done in the geochronology laboratory at the University of British Columbia. Small clean cubes of galena were handpicked, washed, and dissolved in dilute HCI. Trace lead analyses of sulfide and feldspar samples were prepared from pure, hand-picked grains. Sulfide samples for trace Pb analysis were leached in HCI to remove surface contamination before 98 dissolution in nitric acid. Feldspar samples were ground and sieved and the 100-200 mesh fraction was first leached in a mixture of HF and HCL, and subsequently dissolved in concentrated HF. Trace lead whole rock samples were prepared from approximately 50mg of crushed rock, that was leached in dilute hydrochloric acid then dilute hydrofluoric and hydrobromic acids to remove surface contamination before dissolution in hydrofluoric acid and nitric acid. Separation and purification of Pb for trace Pb analyses employed ion exchange column techniques. The samples were converted to bromide, and the solution was passed through ion exchange columns in HBr, and the lead eluted in 6N HCI. The total procedural blank on the trace lead chemistry was 100-110 pg. Approximately 10-25 ng of lead in chloride form was loaded on a rhenium filament and isotopic compositions were determined on a Faraday collector using a modified VG54R thermal ionization mass spectrometer. The measured ratios were corrected for instrumental mass fractionation of 0.12% per mass unit based on repeated measurements of the N.B.S. SRM 981 Standard Isotopic Reference Material. Errors reported in Table 7 were obtained by propagating all mass fractionation and analytical errors through the calculation. Results and Interpretation Thorogenic (208Pb/204Pb vs. 206Pb/204Pb), uranogenic (207Pb/204Pb vs. 206Pb/204Pb), and 208Pb/206Pb vs. 207Pb/206Pb lead plots (Fig. 31) show lead compositions of all styles of mineralization to cluster tightly with those of the intrusive rocks. Lead compositions of sedimentary host rocks including limestone 99 and shale from the Cuesta del Cura and Indidura Formations are considerably more radiogenic. From these data it is interpreted that lead and, by inference, other metals (e.g., Henley et al., 1984; James and Henry, 1993; Megaw et al., 1996; Tosdal et al., 1999) in mineralization at the Sacrificio deposit were derived almost exclusively from magmatic-hydrothermal fluids originating from the intrusions. Implicit in this interpretation is the assumption that if sedimentary host rocks contributed significant lead to the mineralization, lead isotope signatures in the mineralization would trend towards the values of the host rocks. The fact that both the older (109.1 ± 0.4 Ma) and younger (40.1 ± 0.5 Ma) intrusive suites have similar lead isotopic signatures makes it impossible to assign one or the other as the source of mineralization based solely on lead isotope data. However, the spatial distribution of alteration and mineralization styles, together with the weak alteration of the older Dique Viejo, conclusively identifies the younger intrusive suite (i.e., the Coloradito and Sacrificio intrusions) as the source of mineralization and alteration on the property. Discussion Skarn Classification Garnet and pyroxene compositional data in addition to relative metal abundances allow the classification of the Sacrificio deposit as a copper skarn. The deposit shares many of the features found in copper skarns as detailed by Einaudi et al. (1981). These include a zonation from proximal garnet to garnet-100 pyroxene to distal wollastonite-vesuvianite prograde skarn as distance from a fluid pathway increases, and high overall garnet to pyroxene ratios. Source of Metals and Fluids The source of mineralizing fluids at the Sacrificio deposit has been very effectively constrained through the use of lead isotope data. These data (Fig. 31 and Table 7) show that sulfides in all styles of mineralization have similar lead isotopic signatures to the intrusive rocks on the property. Given that the sedimentary host rocks, the only other likely source of lead in the district, have significantly more radiogenic lead isotope signatures, it is concluded that the lead and, by inference, other metals in the sulfide minerals are derived from the intrusions. Consequently, it may be tentatively concluded that skarn and sulfide mineralization at the Sacrificio deposit formed from fluids of magmatic origin. This lead isotope evidence of a magmatic origin for the skarn- and sulfide-forming fluids is consistent with the timing of mineralization with respect to the development of late structures at the Sacrificio deposit. D4 (dome formation) is attributed to emplacement of the Sacrificio intrusion and D5 (east-northeast-striking fractures) to elevated pore fluid pressures associated with exsolving magmatic fluids. Physicochemical Conditions of Skarn Formation and Related Mineralization The pressures and temperatures attending evolution of the Sacrificio skarn system have been constrained with fluid inclusion data and stratigraphic 101 reconstructions. Pressure is assumed to have remained relatively constant throughout the development of the skarn system at 0.5 to 1.0 kbar, whereas temperature varied considerably. Maximum temperatures in wallrock surrounding the Sacrificio intrusion can be estimated using heat flow-balance considerations (Bowman, 1998). Heat flow-balance gives a maximum temperature in wallrock of approximately 60% of the difference between initial magma and initial wallrock temperature plus the initial wallrock temperature (Turcotte and Schubert, 1982). Assuming intrusion crystallization temperatures of approximately 900° C (Philpotts, 1990), a geothermal gradient of 35° C per kilometer (Blackwell et al., 1990), and 1.5 to 3.0 km depth of burial, maximum wallrock temperature is calculated to be approximately 560° to 580° C. These temperatures represent maximum temperatures for prograde skarn formation. Minimum temperatures of prograde skarn formation are constrained by the presence of wollastonite. Pressure-temperature conditions of the reaction forming wollastonite from quartz and calcite at a mol. fraction [X(C02)] of 0.1 are shown in Figure 32. Low X(C02) in skarn-forming fluids (likely <0.04) is indicated by the lack of immiscible carbonic phases in fluid inclusions studied (e.g., Bowers and Helgeson, 1983). Given these considerations, a X(C02) of 0.1 is an appropriate maximum approximation for fluids forming prograde skarn. Estimated pressures of 0.5 to 1.0 kbar give minimum temperatures of prograde skarn formation of 460° to 510° C (Fig. 32). Together with the maximum temperatures given by heat flow-balance calculations, it is concluded that the temperatures of 102 prograde skarn formation are 460° to 560° C at 0.5 kbar and 510° to 580° C at 1.0 kbar. Disseminated Cu-Ag mineralization (and by inference the genetically related fracture-controlled Cu-Ag ± Au mineralization) postdates the prograde skarn and formed at significantly lower temperatures. The temperatures of disseminated Cu-Ag mineralization given by fluid inclusion data range from 291° to 444° C at 0.5 kbar and 333° to 504° C at 1.0 kbar. Manto mineralization and associated retrograde skarn formation postdates both prograde skarn and disseminated Cu-Ag mineralization. It records an overall cooling of the skarn system as the intrusive heat source wanes. Fluid inclusion data give temperatures of formation of manto mineralization from 247° to 346° C at 0.5 kbar and 286° to 396° C at 1.0 kbar. Temperatures of formation of prograde skarn, disseminated mineralization, and manto mineralization record a consistent cooling of the skarn system (Fig. 33). Quartz-arsenopyrite veins, which postdate skarn formation and cut both the Sacrificio and Coloradito intrusions, represent a reversal in this cooling trend with higher temperatures of 318° to 423° C at 0.5 kbar and 368° to 480° C at 1.0 kbar. This temperature increase late in the evolution of the system, and the significantly higher salinity of the fluids forming these veins (6.1 - 19.7 wt.% NaCl eq. versus 0.5 - 13.8 wt. % NaCl eq. for the disseminated and manto mineralization; Table 6), suggest that the quartz-arsenopyrite veins may have formed from fluids related to a late, more deeply buried, intrusive phase that has yet to be identified. 103 The evolutionary trends in trapping temperatures identified in this study will remain valid regardless of the exact pressures of skarn formation and related sulfide mineralization due to the relative constancy of pressure during formation of the deposit. Consequently, changes to the trapping pressure will simply shift the trapping temperatures for all styles of mineralization and the unmineralized quartz-arsenopyrite veins to uniformly higher or lower temperatures depending on the nature of the pressure change. Conclusions The source, composition, and pressure-temperature conditions of fluids forming calc-silicate skarn, and the various styles of sulfide mineralization, at the Sacrificio Cu (Zn-Pb-Ag-Au) deposit have been determined using lead isotope, fluid inclusion, and geological data. The Sacrificio deposit has been classified as a copper skarn through the use of garnet and pyroxene compositional data in addition to metal abundances. Fluids responsible for skarn and sulfide mineralization at the Sacrificio deposit are identified as magmatic in origin through lead isotope studies of intrusive rocks, metasedimentary host rocks, and different styles of mineralization. Fluid inclusion studies indicate that mineralizing fluids were dominantly H20-NaCI mixtures, although depressed eutectic temperatures indicate the presence of additional divalent cations (i.e., Mg2+, Fe2+, and Ca2+). Disseminated Cu-Ag and manto-style mineralization formed from fluids containing 0.5 to 13.8 wt. % NaCI eq., whereas post-skarn quartz-arsenopyrite 104 veins formed from fluids containing 6.1 to 19.7 wt. % NaCl eq. Pressures of mineralization at the Sacrificio deposit are estimated to range from 0.5 to 1.0 kbar based on stratigraphic reconstructions and assuming near-lithostatic conditions. Temperatures of skarn formation and sulfide deposition indicate a gradual cooling of the skarn system. Prograde skarn formed at 460° to 580° C, disseminated Cu-Ag mineralization at 291° to 504° C, and mantos at 247° to 396° C. The final hydrothermal event recorded at the Sacrificio deposit is the formation of unmineralized quartz-arsenopyrite veins from fluids with higher temperatures (318° to 480° C) than those which formed the mantos and retrograde skarn. Consideration of the geochemical and isotopic data from this study, together with the structural and geochronological data from Patterson et al. (in review), has enabled the construction of a detailed fluid evolution model for skarn formation at Cerro el Sacrificio. Application of the findings from this study to other large, polymetallic, skarn deposits or prospects in Mexico could lead to the discovery of new orebodies. Acknowledgments This paper is a portion of the senior author's M.Sc. research undertaken at the University of British Columbia. The research was supported both financially and logistically by Boliden Limited. Additional financial assistance was provided by NSERC grant 22R80466 to Rowins, a Thomas and Marguerite MacKay memorial scholarship to Patterson, and an SEGF student research grant to Patterson. In 105 particular, we would like to thank David Terry and Chris Rockingham for the many ideas they have contributed throughout the course of this study. Additionally, James Mortensen is thanked for a critical review of this manuscript. Fieldwork could not have been undertaken without the logistical aid of David Aguilar Ortiz, Ricardo Flores, and Florentino Munoz of Luismin, S.A. de C.V. Mati Raudsepp and Elisabetta Pani contributed much knowledge and expertise to the microbeam analyses. Finally, Janet Gabites, from the Geochronology Laboratory at the University of British Columbia, is thanked for the lead isotope analyses. 106 References Albinson, T., 1988, Geologic reconstructions of paleosurfaces in the Sombrerete, Colorada, and Fresnillo Districts, Zacatecas State, Mexico: Econ. Geol., v. 83, p. 1647-1667. Barton, M.D., Staude, J-M.G.,Zurcher, L, and Megaw, P.K.M., 1995, Porphyry copper and other intrusion-related mineralization in Mexico, in Pierce, F.W. and Bolm, J.G., eds., Porphyry copper deposits of the American Cordillera: Arizona Geological Society Digest, v. 20, p. 487-524. Bates, R.L., and Jackson, J.A., 1983, Dictionary of Geological Terms, 3rd Edition: American Geological Institute, Doubleday Anchor, New York, 571 p. Blackwell, D.D., Steele, J.L., Frigme, C.F., Murphey, C.F., Priest, G.R., and Black, G.L., 1990, Heat flow in the Oregon Cascade Range and its correlation with regional gravity, Curie point depths, and geology: Journal of Geophysical Research, V.95-B12, p. 19475-19493. Bodnar, R.J., 1993, Revised equation and table for determining the freezing point depression of H20-NaCI solutions: Geochimica Cosmochimica Acta, v. 57, p. 683-684. Bodnar, R.J., Reynolds, T.J., and Kuehn, C.A., 1985, Fluid inclusion systematics in epithermal systems, In B.R. Berger & P.M. Bethke, eds., Geology and Geochemistry of Epithermal Systems: Society of Economic Geology Reviews in Economic Geology, v. 2, p. 73-96. Bodnar, R.J. and Vityk, M.O., 1994, Interpretation of microthermometric data for 107 H20-NaCI fluid inclusions, in De Vivo, B. and Frazzotti, M.L. eds., Fluid inclusions in minerals: methods and applications, Short course of the working group (IMA) "Inclusions in Minerals" Pontignano, Italy, p. 117-130. Borisenko, A.S., 1977, Study of salt composition and solutions of gas-liquid inclusions in minerals by the cryometric method: Geologiya i Geofizka, v. 8, p. 16-27. Bowers, T.S. and Helgeson, H.C., 1983, Calculation of the thermodynamic and geochemical consequences of nonideal mixing in the system H20-C02-NaCI on phase relations in geologic systems: metamorphic equilibria at high pressures and temperatures: American Mineralogist, v. 68, p 1059-1075. Bowman, J.R., 1998, Basic aspects and applications of phase equilibria in the analysis of metasomatic Ca-Mg-AI-Fe-Si skarns, in Lentz, D.R. ed., Mineralized intrusion-realted skarn systems: Mineralogical Association of Canada Short course series, v. 26, p. 1-50. Brown, P.E., 1998, Fluid inclusion modeling for hydrothermal systems, In Richards, J.P. & Larson, P.B., eds., Techniques in Hydrothermal Ore Deposits Geology: Society of Economic Geology Reviews in Economic Geology, v. 10, p. 151-169. Brown, P.E. and Hagemann, S.G., 1995, MacFlinCor: A computer program for fluid inclusion data reduction and manipulation, in De Vivo, B. and Frazzotti, M.L. eds., Fluid inclusions in minerals: methods and applications, Short course of the working group (IMA) "Inclusions in Minerals" Pontignano, Italy, p. 231-250. Crawford, M.L., 1981, Phase equilibria in aqueous fluid inclusions: Mineralogical Association of Canada Short Course Handbook, v. 6, p. 75-100. Davis, D.W., Lowenstern, T.K., and Spencer, R.J., 1990, The melting behavior of fluid inclusions in laboratory-grown halite crystals in the systems NaCI-H20, NaCI-KCI-H20, NaCI-MgCI2-H20, and NaCI-CaCI2-H20: Geochimica et Cosmochimica Acta, v. 54, p. 591-601. Deer, W.A., Howie, R.A., and Zussman, J., 1992, An introduction to the rock-forming minerals: 2nd edition, Longman Group UK Limited, Essex, U.K., 696 p. de Cserna, Z., 1989, An outline of the Geology of Mexico, in Bally, A. W., and Palmer, A. R., eds., The Geology of North America - An overview: Boulder, Colorado, Geological Society of America, The Geology of North America, v. A. Drewes, H., 1991, Description and Development of the Cordilleran Orogenic Belt in the Southwestern United States and Northern Mexico: U.S. Geological Survey Professional Paper 1512, 87 p. Einaudi, M.T., Meinert, L.D., and Newberry, R.J., 1981, Skarn Deposits, in Skinner, B.J., ed., Economic Geology 75th Anniversary Volume: Economic Geology Publishing Company, El Paso, Texas, p. 317-391. Graf, A, 1997, Geology and pophyry-style mineralization of the Cerro de la Gloria 109 stock associated with high-T, carbonate-hosted Zn-Cu-Ag(-Pb) skarn mineralization, San Martin District, Zacatecas, Mexico: Unpublished M.Sc. Thesis, University of Arizona, 154 p. Henley, R.W., Truesdell, A.H., Barton, P.B., and Whitney, J.A., 1984, Fluid-mineral equilibria in hydrothermal systems: Society of Economic Geologists, Reviews in Economic Geology, v. 1, 267 p. James, E.W. and Henry, CD., 1993, Pb isotopes of ore deposits in Trans-Pecos Texas and northeastern Chihuahua, Mexico: Basement, igneous, and sedimentary sources of metals: Econ. Geol., v. 88, p. 934-947. Johnson, J.W. and Norton, D.L., 1985, Theoretical prediction of hydrothermal conditions and chemical equilibria during skarn formation in porphyry copper systems: Economic Geology, v. 80, p. 1797-1823. Kretz, R.,1983, Symbols for rock-forming minerals: American Mineralogist, v. 68, p. 277-279. Longoria, J.F., Clowes, D.M., and Monreal, R., 1999, Type Mesozoic succession of northern Mexico: Canon La Casita, in Bartolini, C, Wilson, J.L., and Lawton, T.F., eds., Mesozoic sedimentary and Tectonic History of North-Central Mexico: Boulder Colorado, Geological Society of America Special Paper 340, p. 287-318. McClay, K.R., 1987, The Mapping of Geological Structures, John Wiley and Sons, West Sussex, England, 161 p. Megaw, P.K.M., 1999, The high-temperature, Ag-Pb-Zn-(Cu) carbonate-replacement deposits of central Mexico in Jambor, J.L., ed., VMS and no carbonate-hosted polymetallic deposits of central Mexico; Cordilleran Roundup, 1999, p. 81-84. Megaw, P.K.M., Barton, M.D., and Falce, J.I., 1996, Carbonate-hosted lead-zinc (Ag, Cu, Au) deposits of northern Chihuahua, Mexico, In D.F. Sangster, ed., Carbonate-hosted Lead-Zinc Deposits: Society of Economic Geologists Special Publication Number 4, p. 277-289. Meinert, L.D., 1989, Gold skarn deposits - Geology and Exploration Criteria, In R.R. Keays, W.R.H. Ramsay, & D.I. Groves , eds., The Geology of Gold Deposits: Economic geology monograph 6, Society of Economic Geologists, p. 537-552. Meinert, L.D., 1992, Skarns and Skarn deposits, Geoscience Canada, v. 19, p. 145-162. Meinert, L.D., 1997, Application of skarn zonation models to mineral exploration: Exploration and Mining Geology, v. 6, no. 2, p. 185-208. Patterson, K.M., Rowins, S.M., Mortensen, J.K., and Terry, D.A., in review, Controls on the distribution of polymetallic skarn mineralization by pre-and syn-intrusion deformation at Cerro el Sacrificio, Durango, Mexico: Economic Geology. Philpotts, A.R., 1990, Principals of igneous and metamorphic petrology, Prentice Hall, New Jersey, 498 p. Pichavant, M., Ramboz, C, and Weisbrod, A., 1982, Fluid immiscibility in natural processes: Use and misuse part 1: Phase equilibria analysis - A theoretical and geometrical approach: Chemical Geology, v. 37, p. 1-27. in Potter, R.W., 1977, Pressure corrections for fluid-inclusion homogenization temperatures based on the volumetric properties of the system NaCI-H20: Journal of Research of the United States Geological Survey, v. 5, no. 5, p. 603-607. Richards, J.P., McCulloch, M.T., Chappell, B.W., and Kerrich, R., 1991, Sources of metals in the Porgera gold deposit, Papua New Guinea: Evidence from alteration, isotope and noble gas geochemistry: Geochimica et Cosmochimica Acta, v. 55, p. 565-580. Rickwood, P.C., 1968, On recasting analyses of garnet into end-member molecules: Contributions to Mineralogy and Petrology, v. 18, p. 175-198. Roedder, E., 1984, Fluid Inclusions. Reviews in Mineralogy: Mineralogical Society of America, v. 12, 646 p. Rowins, S.M., Groves, D.I., McNaughton, N.J., Palmer, M., and Eldridge, C.S., 1997, A reinterpretation of the role of granitoids in the genesis of Neoproterozoic gold mineralization in the Telfer Dome, Western Australia: Economic Geology, v. 92, p. 133-160 Rubin, J.N., 1986, Mineralogy and Ore Genesis at the San Martin Mine, Zacatecas, Mexico: Unpublished M.Sc. Thesis, The University of Texas at Austin, 97 p. Rubin, J. N. and Kyle, J. R., 1988, Mineralogy and geochemistry of the San Martin skarn deposit, Zacatecas, Mexico: Economic Geology, v. 83, p. 1782-1801. Sedlock, R. L, Ortega-Gutierrez, F., and Speed, R. C, 1993, 112 Tectonostratigraphic terranes and tectonic evolution of Mexico: Boulder, Colorado, Geological Society of America Special Paper 278. Shepherd, T.J., Rankin, A.H., and Alderton, D.H.M., 1985, A Practical Guide to Fluid Inclusion Studies: Blackie, London, U.K., 239 p. Shoji, T., 1975, Role of temperature and C02 pressure in the formation of skarn and its bearing on mineralization: Economic Geology, v. 70, p. 739-749. Sutter, M., 1987, Structural traverse across the Sierra Madre Oriental fold-thrust belt in east-central Mexico: Geological Society of America Bulletin, v. 98, p. 249-264. Terry, D.A., Patterson, K.P., Warman, T., and Gibson, K., 1999, Report on diamond drilling, geological mapping, and geophysical surveys carried out on the Cerro Sacrificio project, Durango state, Mexico (November 1998 to July 1999): Boliden Limited, Unpublished report, 49 p. Tosdal, R. M., Wooden, J. L, and Bouse, R. M., 1999, Pb Isotopes, Ore Deposits, and Metallogenic Terranes In Lambert, D.D. and Ruiz, J. eds., Application of Radiometric Isotopes to Ore Deposit Research and Exploration, Society of Economic Geologists, Reviews in Economic Geology, v. 12, p. 1-28. Turcotte, D.L. and Schubert, G., 1982, Geodynamics, John Wiley and Sons, New York, 450 p. Zartman, R.E. and Doe, B.R., 1981, Plumbotectonics - the model: Tectonophysics, v. 75, p. 135-162. Figure Captions Figure 18. Location map for the Sacrificio deposit, Durango State, Mexico. Solid squares and circles represent major cities and significant mineral deposits in the region, respectively. Figure 19. Simplified geological map of the Sacrificio property. Heavy dashed line is the approximate subsurface extent of the Sacrificio intrusion inferred from geophysical and drillhole data (Terry et al., 1999). Solid squares are sites of previous mining activity (after Patterson et al., in review). Figure 20. Examples of the main styles of mineralization in the Sacrificio deposit. A. Disseminated Cu-Ag mineralization. Photomicrograph of prograde garnet skarn with bornite (Bn) and chalcopyrite (Ccp) filling intermineral porosity between euhedral crystals of garnet (Grt). B. Fracture-controlled Cu-Ag ± Au mineralization. Historic adit exploiting an east-northeast-striking vein (filled D5 fracture). Dashed line marks the boundary between the vein and the disseminated sulfide mineralization in prograde garnet skarn- C. Drillhole intersection of massive polymetallic manto showing contact with marble. Figure 21. Surface distribution of skarn alteration and related sulfide mineralization at the Sacrificio deposit (after Patterson et al., in review). Garnet skarn and disseminated bornite-chalcopyrite mineralization are strongly controlled by D3 fold axial planes and their intersections with major and minor D5 fracture sets. Only the major fracture sets and folds are shown. Note the localization of most skarn alteration and mineralization above the intrusion rather than around the margins as is typical of many skarn deposits (Meinert, 1997). 114 Figure 22. Photomicrographs of common skarn minerals from the Sacrificio deposit. A. Optically and compositionally zoned crystal of grandite garnet in prograde skarn. B. Subhedral clinopyroxene (Cpx) and euhedral garnet (Grt) crystals in prograde skarn. C. Mass of medium-grained, euhedral hornblende crystals in retrograde skarn. D. Retrograde amphibole (Amp) skarn replacing garnet (Grt) - wollastonite (Wo) prograde skarn and marble (Mb). Figure 23. Mol. % iron versus mol. % aluminum in grandite garnets from prograde skarn. Analyses show an almost perfect 1:1 substitution (correlation coefficient, 1^=0.995) between iron and aluminum in the octahedral site. High iron values correspond to high mol. % andradite, whereas high aluminum values correspond to high mol. % grossular. Figure 24. Ternary diagrams of garnet (Gr-Ad-Sp+AI) and pyroxene (Di-Hd-Jo) compositions from the Sacrificio deposit. Circles are individual analyses. Shaded fields indicate typical garnet and pyroxene compositions from Zn (Pb), Fe, and Cu skarns (after Meinert, 1992). Abbreviations for garnet end-members are as follows: Gr = grossular, Ad = andradite, Sp = spessartine, Al = almandine, Di = diopside, Hd = hedenbergite, Jo = johannsenite. See text for further discussion. Figure 25. Interpreted sequence of deformation events affecting Cerro el Sacrificio (after Patterson et al., in review). D1 - Tight to isoclinal, west-verging, recumbent folds. D2 - Type 2 refolding of Di folds. D3 - Large amplitude, gentle to open, upright folds trending 330° that refold Di and D2 folds. D4 - Doming of previously deformed strata over the intrusion during its emplacement, with 115 exsolved magmatic fluids focused along D3 axial surfaces. D5 - Increase in pore fluid pressure above the intrusion and opening of mode 1 fractures oriented east-northeast, parallel to maximum compressive stress. Mineralizing fluids are channeled by these fractures with bornite and chalcopyrite filling secondary porosity in garnet skarn proximal to the D5 fractures. The formation of retrograde skarn and mantos postdate D5 and are not included in this schematic diagram. Figure 26. Relative timing of deformation, alteration, and mineralization events at the Sacrificio deposit. Absolute ages are derived from U-Pb dating of intrusive rocks; all other timing is relative, i.e. the time axis is not to scale (after Patterson et al., in review). Figure 27. Fluid inclusion microphotographs. A. Fluid inclusions in quartz associated with disseminated Cu-Ag mineralization. Note rare carbonate daughter mineral. B. Fluid inclusions in quartz associated with polymetallic manto mineralization. C. Fluid inclusions in quartz in quartz-arsenopyrite veins. Figure 28. Microthermometric fluid inclusion data for the Sacrificio deposit. A. Eutectic temperatures from disseminated mineralization. B. Eutectic temperatures from manto mineralization. C. Eutectic temperatures from quartz-arsenopyrite veins. D. Fluid salinities (in wt.% NaCl eq.) calculated from final ice melting temperatures in disseminated mineralization. E. Fluid salinities (in wt.% NaCl eq.) calculated from final ice melting temperatures in manto mineralization. F. Fluid salinities (in wt.% NaCl eq.) calculated from final ice melting temperatures in quartz-arsenopyrite veins. G. Temperatures of homogenization (to liquid) for fluid inclusions in disseminated mineralization. H. Temperatures of 116 homogenization (to liquid) for fluid inclusions in manto mineralization. I. Temperatures of homogenization (to liquid) for fluid inclusions in quartz-arsenopyrite veins. Figure 29. Trapping temperatures of manto (247° to 396°C; light shaded field, overlapping with dark shaded field) and disseminated (291° to 504°C; dark shaded field) mineralization at pressures of 0.5 to 1.0 kbar and fluid salinities of 5 wt % NaCl eq. The trapping temperatures are obtained from projection along isochores corresponding to the homogenization temperatures of the disseminated (251° to 389°C) and manto (205° to 306°C) styles of mineralization, respectively (Table 6). Figure modified from Bodnar and Vityk (1994). Figure 30. Trapping temperatures of arsenopyrite-quartz veins (318° to 480°C; shaded field) at pressures of 0.5 to 1.0 kbar and a salinity of 10 wt.% NaCl eq. The trapping temperatures are obtained from projection along isochores corresponding to the homogenization temperatures (278° to 383°C) of the veins (Table 6). Figure modified from Bodnar and Vityk (1994). Figure 31. Lead isotope data for sulfide mineralization and host-rocks from the Sacrificio deposit. A. 208Pb/206Pb vs. 207Pb/206Pb. B. 207Pb/204Pb vs. 206pb/204pb c 208pb/204pb vs 206pb/204pb Symbo|s used in tne diagrams are as follows: Diamonds = fracture-controlled mineralization; triangles = quartz-arsenopyrite veins; squares = manto mineralization; open circles = disseminated mineralization; vertical crosses = intrusive rocks; and inclined crosses = sedimentary host-rocks. Filled circles and associated trend-lines are the upper crust and orogene growth curves of Zartman and Doe (1981). 117 Figure 32. Pressure-temperature stability of wollastonite in H20-rich fluid with X(C02) of 0.1 (modified after Bowman, 1998). The presence of wollastonite in prograde skarn formed at pressures of 0.5 to 1.0 kbar gives minimum temperatures of prograde skarn formation between 460° to 510° C. Figure 33. Temporal evolution of temperature in the Sacrificio skarn system. Dashed and solid lines are fluid trapping temperatures calculated at 0.5 and 1.0 kbar, respectively (minimum and maximum pressures estimated for skarn formation and related mineralization at Sacrificio). Note the cooling trend from prograde skarn to manto mineralization, whereupon a reversal occurs with the formation of post-skarn quartz-arsenopyrite veins. See text for further discussion. 118 Patterson and Rowins: Figure 18 119 Patterson and Rowins: Figure 19 120 Patterson and Rowins: Figure 20 121 Lithologic Units • • • Cuesta del Cura Formation (limestone and chert) Indldura Formation (limestone and shale) (.0.1 •/- 0.S Ma Granite 109 Ma Monzodiorite — Approximate boundary of mineralized fracture set Mapped contact between the Cuesta del ' Cura and Indidura Formations 200 400 600 m i I SCALE Alteration and Related Mineralization Hornfels I Quartz-Scapolite-Albite+/-Sericite Prograde Skarn Garnet Skarn M Disseminated Born ite-Cha I copy rite and Fracture-Controlled Mineralization j Intense Silicification Quartz Vein Stockwork Eil^ Quartz-Cemented Limestone Breccia Retrograde Skarn F."/l Pervasive Amphibole-Chlorite L-^ J +/- Base and Precious Metal Mantos Patterson and Rowins: Figure 21 122 Patterson and Rowins: Figure 22 123 1.0 J , , , , I 0 0.2 0.4 0.6 0.8 1.0 mol. % Al3+ Patterson and Rowins: Figure 23 124 Patterson and Rowins: Figure 24 125 240* 60* 240* 60* Opening of extensional fractures, fluids channeled up fractures D5 Patterson and Rowins: Figure 25 126 •TIME-Emplacement of Dique J Viejo and related dykes | and Coloradito granites D„ doming -Quartz-Albite-Scapolite Hornfels -Prograde garnet skarn -D5 mode 1 fractures -Disseminated bornite+/-chalcopyrite mineralization Fracture-controlled mineralization -Retrograde amphibole skarn -Manto mineralization -D, folding -D2 folding -D3 folding -? Emplacement of Sacrificio Crystalization Exsolving magmatic fluids 109 Ma 40 Ma Patterson and Rowins: Figure 26 127 Patterson and Rowins: Figure 27 128 <« CO N *- C UlVfOCNT-O Aouenbajj Aouanbajj Aouanbajj uoj}ezj|ej3Uj|Aj uo!)ezj|ej3Uj|Aj SUJSA Ad\/-z}D pajeujuiassia 0)ue|/\| 129 Temperature (C) Patterson and Rowins: Figure 29 130 Temperature (°C) Patterson and Rowins: Figure 30 131 207pb/206pb 0.82 A —i 1 X X Upper Crusty— • Orogene 2.020 Q. a. 2.040 § 15.80 CL .Q a. B X X A + Upper Crust M x ++ • Orogene 18.50 18.70 18.90 19.10 19.30 19.50 19.70 19.90 206PB/204PB .Q Q. 38.9 n o. c X X / X \ / / W /Upper J / Crust Orogene^ n J / / . . 18.50 18.70 18.90 19.10 19.30 19.50 19.70 19.90 206Pb/2°4Pb Patterson and Rowins: Figure 31 132 Patterson and Rowins: Figure 32 133 1.0 kbar 0.5 kbar Prograde Garnet Skarn Disseminated Cu-Ag Mineralization Polymetallic Manto Mineralization Qtz-Apy Veins -] Temperature (°C) Patterson and Rowins: Figure 33 134 Table 4. Paragenesis of Alteration and Mineralization at the Sacrificio Deposit LU Style Contact Metamorphism Prograde Skarn Alteration Mineralogy quartz-albite-scapolite ± sericite ± chlorite garnet-wollastonite-clinopyroxene-vesuvianite Minor Silicification quartz Retrograde Skarn amphibole-chlorite ± epidote ± calcite Mineralization Style None Disseminated Cu-Ag Fracture-controlled Cu-Ag+Au Massive Manto Zn-Cu-Pb-Ag±Au Mineralogy None bornite ± chalcopyrite chalcopyrite ± bornite ± sphalerite ± galena ± arsenopyrite sphalerite-galena-chalcopyrite-arsenopyrite-pyrite-pyrrhotite-bornite Note: only major minerals are listed; secondary copper-oxide minerals are variably developed near surface in all styles of mineralization. 135 Table 5. Representative Microprobe Analyses of Garnets and Pyroxenes from Prograde Skarn Garnet Pyroxene Analysis no. kp-40a kp-40b kp-41a kp-41b kp-47a kp-47b kp-48a kp-48b kp-47c kp-47d kp-48c kp-48d Si02 35.14 35.93 34.86 35.74 35.63 36.02 35.76 36.34 53.28 53.94 52.62 54.43 Ti02 0.00 0.06 0.00 0.06 0.01 0.27 0.05 0.10 0.04 0.00 0.01 0.00 Al203 1.65 6.37 1.44 5.34 4.05 7.53 3.47 6.43 0.03 0.09 0.03 0.05 Cr203 0.00 0.01 0.02 0.00 0.00 0.00 0.01 0.00 0.02 0.00 0.00 0.02 FeO 5.95 3.21 8.97 2.15 Fe203(1) 28.55 22.50 28.94 23.58 25.37 20.59 25.38 21.86 MnO 0.09 0.09 0.16 0.10 0.12 0.16 0.08 0.15 0.77 0.58 0.69 0.59 MgO 0.08 0.08 0.06 0.08 0.10 0.13 0.11 0.22 14.34 16.26 12.52 17.06 CaO 34.04 35.04 33.53 34.73 33.65 34.25 33.63 33.78 25.08 25.67 25.15 25.65 Na20 0.01 0.00 0.00 0.00 0.02 0.01 0.00 0.01 0.04 0.00 0.04 0.01 total 99.54 100.07 99.02 99.63 98.94 98.95 98.47 98.89 99.54 99.74 100.03 99.96 Number of cations on the basis of 8 oxygens Number of cations on the basis of 4 oxygens Si 2.95 2.93 2.95 2.94 2.97 2.95 3.00 2.99 1.99 1.98 1.98 1.98 Ti 0.00 0.00 0.00 0.00 0.00 0.02 0.00 0.01 0.00 0.00 0.00 0.00 Al 0.16 0.61 0.14 0.52 0.40 0.73 0.34 0.62 0.00 0.00 0.00 0.00 Cr 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Fe3*|2) 1.81 1.38 1.84 1.46 1.59 1.27 1.60 1.36 0.03 0.04 0.05 0.03 Fe2* 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.16 0.06 0.24 0.04 Mn 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.02 0.02 0.02 0.02 Mg 0.01 0.01 0.01 0.01 0.01 0.02 0.01 0.03 0.80 0.89 0.70 0.93 Ca 3.06 3.06 3.04 3.06 3.01 3.01 3.03 2.98 1.00 1.01 1.01 1.00 Na 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 total 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 4.00 4.00 4.00 4.00 Endmembers (mol %) Andradite131 91.71 70.69 93.70 74.46 80.39 64.53 82.36 68.44 80.18 89.90 71.24 92.979 Diopside1"1 Grossularite 7.75 28.75 5.57 24.95 18.90 34.55 16.97 30.31 17.40 8.28 26.52 5.216 Hedenbergite Spessartine 0.21 0.22 0.39 0.24 0.28 0.37 0.19 0.34 2.41 1.82 2.24 1.805 Johannsenite Almandine 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Pyrope 0.33 0.32 0.27 0.34 0.43 0.55 0.45 0.90 Uvarovite 0.00 0.02 0.06 0.01 0.00 0.00 0.03 0.01 Microprobe analyses on CAMECA SX-50 microprobe, University of British Columbia. Operating conditions: excitation voltage, 15 kV; beam current, 20 nA; peak-count time, 20 s; background count time, 10 s; beam diameter, 5 (im. Standards used in pyroxene analysis: diopside, MgKa, SiKa, TAP; diopside, CaKa, PET; rutile, TiKa, PET; synthetic Fe2SiO,, FeKa, LIF, synthetic MgCr204, CrKa, LIF; synthetic MnSi03, MnKa, LIF; albite, NaKa, TAP; kaersutite, AlKa, TAP. Standards used in garnet analysis: almandine, MgKa, SiKa, TAP; almandine, Fe Ka, LIF; grossular, CaKa, PET; grossular, AlKa, TAP; rutile, TiKa, PET; synthetic MgCr20„, CrKa, LIF; synthetic MnSi03, MnKa, LIF; elemental V, VKa, PET (corrected for overlap of TiK/3) Notes: 1. Total iron as Fe203 2. Fe2*/Fe3* ratios calculated by charge balance 3. Garnet end-member calculations after Rickwood (1968) 4. Pyroxene end-member calculations after Deer et al. (1992) Patterson and Rowins: Table 5 136 Table 6. Microthermometric Data sample mineralization type Te CO mean ± 1u wt % NaCl eq' mean ± 1<r T„ (°C) mean ± 1<r SAC98-3-260.6 Qtz-Apy vein -38.0 to -39.1 (6) -38.4 ± 0.4 6.1 to 10.5 (7) 8.1 ±1.3 278 to 305 (6) 300 ± 11 COL-99-4-316A Qtz-Apy vein -26.9 to 32.6 (5) -30.0 ± 2.6 14.2 to 19.7 (5) 16.7 ±2.4 336 to 383 (9) 357 ± 13 SAC-98-4-62.2 disseminated -20.0 to -41.5 (4) -30.6 ± 9.9 5.5 to 13.8 (4) 7.9 ±4.0 282 to 386 (18) 360 ± 28 Kp-53 disseminated -25.6 to -33.4(18) -29.1 ±2.5 3.6 to 4.7 (18) 4.2 ±0.4 251 to 375 (24) 315 ±38 Kp-40 disseminated -28.3 (1) 6.1 (D n/a SAC-98-3-185.8 disseminated -24.9 to -38.0 (6) -29.5 ± 5.1 1.3 to 8.0 (6) 5.1 ±2.6 285 to 389 (22) 338 ± 32 SAC-98-3-100A manto -28.1 to -36.0(4) -32.6 ±3.3 4.3 to 7.3 (5) 6.2 ± 1.2 205 to 306 (24) 269 ± 26 SAC-98-3-209A manto -24.0 to-37.1 (10) -30.0 ±4.3 5.6 to 8.4 (9) 6.4 ± 0.9 224 to 292 (26) 269 ± 22 ROS-99-102A manto -38.0 to -47.0 (4) -43.8 ± 4.0 5.0 to 7.1 (4) 5.9 ±0.9 205 to 292 (10) 258 ± 43 SAC-98-3-103A manto -19.7 to -33.2(6) -28.2 ±4.9 0.5 to 6.8 (9) 2.9 ±2.1 216 to 287(14) 263 ± 18 Abbreviations: Apy = arsenopyrite; Qtz = quartz; mean ± 1 cr = mean value ± one standard deviation, Te = eutectic temperature; Th = homogenization temperature to liquid; wt % NaCl eq. = weight percent NaCl equivalent 1 Determined from freezing point depressions using the equations of state of Bodnar and Vityk (1994) Patterson and Rowins: Table 6 137 Table 7. Lead Isotope Analyses Sample Sample type Mineral 206pb/204pb % 1CT 207Pb/204Pb % ^a 208Pb/2MPb % 1CT 207Pb/206Pb % 1(T 208pb/206pb % 1a Kp-34 fracture Sx 18.945 0.05 15.695 0.05 38.937 0.05 0.828 0.003 2.055 0.005 Kp-50b fracture Sx 18.946 0.05 15.688 0.05 38.859 0.05 0.828 0.007 2.051 0.008 Kp-50b fracture Sx 18.901 0.14 15.701 0.14 38.896 0.14 0.831 0.020 2.058 0.010 KP-50 fracture Bn 18.865 0.08 15.696 0.08 38.838 0.09 0.832 0.029 2.059 0.023 COL9901-316.6 Qtz-Apy vein Apy 18.981 0.01 15.730 0.00 39.012 0.01 0.829 0.011 2.055 0.005 LB9604-425 diss Bn 18.919 0.05 15.668 0.04 38.961 0.07 0.828 0.021 2.059 0.047 SAC-PAD-4 diss Bn 18.899 0.01 15.665 0.00 38.842 0.01 0.829 0.007 2.055 0.004 SAC9803-147 diss Bn 18.893 0.03 15.664 0.02 38.830 0.03 0.829 0.013 2.055 0.017 Kp-38 diss Sp 18.903 0.08 15.706 0.05 38.997 0.18 0.831 0.055 2.063 0.160 Kp-39 diss Sp 18.906 0.02 15.661 0.02 38.824 0.02 0.828 0.003 2.054 0.000 Kp-42 manto Mo 18.914 0.02 15.684 0.02 38.902 0.02 0.829 0.011 2.057 0.007 Kp-44 manto Gn 18.893 0.01 15.678 0.01 38.871 0.02 0.830 0.011 2.057 0.007 Kp-49 manto Gn 18.903 0.03 15.687 0.02 38.955 0.04 0.830 0.024 2.061 0.021 SAC98-03-76.3 manto Sx 18.903 0.02 15.668 0.02 38.833 0.02 0.829 0.004 2.054 0.003 SAC9803-249.7 manto Bn 18.915 0.02 15.707 0.01 38.977 0.03 0.830 0.016 2.061 0.020 SAC9803-100.7 manto Apy 18.927 0.04 15.697 0.04 38.875 0.04 0.829 0.010 2.054 0.011 SAC9804-205 manto Sp 18.874 0.04 15.662 0.03 38.809 0.06 0.830 0.029 2.056 0.047 COL9901-291.2 manto Po 18.874 0.05 15.643 0.05 38.655 0.05 0.829 0.011 2.048 0.014 Kp-15 Ls Wr 19.557 0.16 15.775 0.15 39.048 0.17 0.807 0.064 1.997 0.052 Kp-17 Ls Wr 19.662 0.51 15.783 0.51 39.144 0.51 0.803 0.043 1.991 0.054 Kp-52 shale Wr 19.122 0.12 15.660 0.09 39.087 0.14 0.819 0.088 2.044 0.066 Kp-01 Intr Fs 18.913 0.02 15.679 0.01 38.903 0.02 0.829 0.018 2.057 0.010 Kp-07 Intr Fs 18.847 0.01 15.656 0.01 38.786 0.01 0.831 0.009 2.058 0.004 Kp-09 Intr Fs 18.934 0.03 15.719 0.03 38.993 0.04 0.830 0.009 2.059 0.021 Kp-12 Intr Fs 18.877 0.03 15.655 0.02 38.785 0.03 0.829 0.018 2.055 0.006 Notes: analyses by Janet E. Gabites, Geochronology Laboratory, Department of Earth and Ocean Sciences, UBC. Mineral abbreviations: Gn = galena; Sx = mixed sulphide; Sp = sphalerite; Po = pyrrhotite; Apy = arsenopyrite; Bn = bornite; Mo = molybdenum; Fs = feldspar; Wr = whole rock. Sample Types: Fracture = fracture-controlled mineralization; Diss = disseminated Cu-Ag mineralization; Manto = polymetallic manto mineralization; Ls = limestone; Intr = intrusive rocks. Patterson and Rowins: Table 7 138 Chapter 4 General Conclusions The development of a detailed structural and fluid evolution model to explain the location of skarn-related Cu (Zn-Pb-Ag-Au) mineralization within regionally and locally developed structures has greatly enhanced understanding of the formation of the Sacrificio deposit. The results of this research show that both pre- and syn-mineralization deformation has strongly controlled the present-day distribution of the known mineralization. Extensive field mapping combined with detailed structural analysis, lithogeochemistry, and U-Pb geochronology have been used to understand the mineralizing process at the Sacrificio deposit. Additionally, the source and physicochemical conditions (P-T-X) of fluids forming calc-silicate skarn and sulphide mineralization have been determined using lead isotope, fluid inclusion, and mineralogical data. The Sacrificio deposit is classified as a copper skarn based on garnet and pyroxene compositions in addition to known metal abundances and dominant styles of mineralization. This study provides one of the most complete descriptions of a large, polymetallic skarn deposit in Mexico. Three phases of pre-intrusion regional deformation are recognized in rocks at the Sacrificio deposit. Di and D3 record strong east-northeast shortening associated with the Mexican fold-and-thrust belt, whereas D2 indicates a minor re-orientation of shortening directions to produce rare east-trending folds. Two episodes of intrusion-related deformation post-date regional deformation. D4 is 139 the formation of a broad dome above the Sacrificio intrusion and D5 is the opening of extensional fractures and veins above and peripheral to the intrusion. Skarn-forming fluids were preferentially channeled along axial surfaces of large amplitude, D3 folds. This has resulted in the localization of garnet skarn along D3 fold axial traces. Late mineralizing fluids were focussed mainly by D5 fractures and precipitated bornite ± chalcopyrite where they infiltrated porous garnet skarn. Thus, where late-stage, intrusion-related, east-striking fractures (D5) intersect D3 fold axial surfaces, disseminated Cu-Ag mineralization is formed. This structural intersection is a critical feature in the localization of skarn mineralization at the Sacrificio deposit. Uranium-lead isotopic dating of four samples of intrusive rocks from the Sacrificio deposit revealed two temporally distinct intrusive suites. Lithogeochemical analysis of these suites revealed a correlative compositional distinction. The older suite, including Dique Viejo and several smaller dykes at Cerro Coloradito is interpreted to be 109.1 ± 0.4 Ma. The younger suite, which includes the Sacrificio and Coloradito intrusions is interpreted to be 40.1 ± 0.5 Ma. This younger Middle Eocene suite is interpreted to have caused the calc-silicate skarn and related mineralization at the Sacrificio deposit based on a variety of geological evidence. Fluid inclusion studies of mineralization associated with prograde and retrograde skarn (disseminated Cu-Ag and manto mineralization, respectively) and of post-skarn quartz-arsenopyrite veins demonstrate that mineralizing fluids are predominantly NaCI-H20 mixtures with additional divalent cations including 140 Mg , Fe , and Ca . The disseminated Cu-Ag and polymetallic manto mineralization was formed from fluids ranging in salinity from 0.5 to 13.8 wt. % NaCI equivalent, whereas late arsenopyrite veins were formed from fluids with salinities 6.1 to 19.7 wt. % NaCI equivalent. Temperatures of homogenization range from 251° to 389° C in disseminated mineralization, and 205° to 306° C in manto mineralization. Post-skarn quartz-arsenopyrite veins give homogenization temperatures of 278° to 383° C. Pressures during the development of the Sacrificio deposit are estimated at approximately 0.5 to 1.0 kbars based on evidence from stratigraphic reconstructions. Trapping temperatures are obtained by applying pressure corrections (dependant on both pressure and salinity of the fluid) to the measured temperatures of homogenization. Trapping temperatures obtained from fluid inclusion data and temperatures of prograde skarn formation obtained from mineral stability data demonstrate a gradual cooling of the skarn system. Prograde skarn formed at 460° to 580° C, disseminated mineralization at 291° to 504° C, and polymetallic manto mineralization was formed at cooler temperatures of 220° - 390° C. This was then overprinted by a final pulse of hotter fluids (330° - 495° C) which formed the post-skarn quartz-arsenopyrite veins. Studies of Pb-isotope compositions of mineralization and potential lead 'reservoirs' commonly are used to trace the source of metals in mineral deposits (e.g., Richards et al., 1991; Tosdal et al., 1999). At the Sacrificio deposit, Pb-isotope compositions of sulphide minerals associated with mineralization, intrusive rocks, and sedimentary host-rocks strongly indicate a magmatic source 141 has contributed the lead, and by inference, other metals that now comprise the mineralization at the Sacrificio deposit. In summary, the results of this study provide constraints on the structures, fluid sources, and physicochemical conditions of skarn formation and related mineralization at the Sacrificio deposit. It has been demonstrated that both pre-and syn-intrusion structures are key elements in the development of the Sacrificio skarn system. The structural model developed at the Sacrificio deposit may be applied to other skarn and carbonate replacement deposits of the Mexican Altiplano and elsewhere in the world. 142 References Richards, J.P., McCulloch, M.T., Chappell, B.W., and Kerrich, R., 1991, Sources of metals in the Porgera gold deposit, Papua New Guinea: Evidence from alteration, isotope and noble gas geochemistry: Geochimica et Cosmochimica Acta, v. 55, p. 565-580. Tosdal, R. M., Wooden, J. L, and Bouse, R. M., 1999, Pb Isotopes, Ore Deposits, and Metallogenic Terranes: In Lambert, D.D. and Ruiz, J., eds., Application of Radiometric Isotopes to Ore Deposit Research and Exploration, Society of Economic Geologists, Reviews in Economic Geology, v. 12, p. 1-28. 143 Appendix A Location Map of Local Sacrificio Grid and Grid Coordinates 144 145 Appendix B Structural Data - Sacrificio Deposit 146 Sacrificio Structural Data Note: all data reported using right-hand-rule Locations given in grid coordinates as shown in appendix A Location bedding fractures fold axes axial planar fracture easting northing strike dip strike dip trend plunge strike dip 1020 700 145 65 1736 713 90 90 1010 780 144 70 1628 817 165 75 2010 820 111 65 1794 867 185 74 2030 875 5 45 1656 923 155 72 1014 927 144 70 1752 943 160 71 1728 944 154 70 2010 950 145 62 2030 950 60 83 1522 982 135 70 1830 1010 325 68 1912 1014 115 85 1595 1015 142 75 1610 1015 147 75 1920 1020 286 64 1370 1025 152 88 1420 1025 154 83 1460 1025 155 84 1502 1026 174 73 1520 1030 182 69 1021 1030 160 87 1850 1080 166 58 1960 1080 143 90 1975 1080 249 68 . 1990 1090 19 40 2100 1110 40 43 1030 1115 165 70 1200 1120 120 81 1650 1120 90 90 1990 1120 184 75 2190 1120 15 18 2250 1120 30 72 1600 1130 160 74 1915 1130 355 70 1950 1130 140 57 1970 1130 2 77 1658 1132 120 43 1248 1133 183 72 2151 1135 176 67 1468 1139 145 78 1613 1147 135 77 1627 1157 138 22 1568 1216 45 60 1520 1220 135 60 -1780 1220 1885 1220 140 44 1960 1220 135 37 2215 1220 25 90 1612 1223 180 90 1300 1225 155 76 1490 1225 150 83 2150 1225 270 82 2200 1225 285 75 1944 1227 155 47 1974 1229 144 59 1469 1229 115 74 1180 1230 155 90 1340 1230 275 65 147 Location bedding fractures fold axes axial planar fracture easting northing strike dip strike dip trend plunge strike dip 2070 1230 130 53 2100 1230 175 80 2255 1230 15 88 1415 1231 155 76 1242 1232 225 90 1601 1232 160 45 2234 1234 275 70 1435 1234 148 77 1861 1237 130 43 1027 1237 236 69 1964 1239 290 58 1386 1239 178 71 1368 1240 173 74 1990 1240 175 81 1001 1244 140 76 1768 1245 143 52 1240 1250 257 75 2179 1258 130 77 1983 1260 165 86 2060 1280 170 40 2160 1280 95 56 1985 1285 165 72 1985 1315 160 72 1480 1320 255 74 1590 1320 120 90 1810 1320 250 70 1875 1320 252 60 1950 1320 150 67 2040 1320 25 77 1280 1324 148 60 1497 1324 170 90 1293 1325 158 69 1915 1325 258 90 2320 1325 165 54 1061 1326 176 57 1196 1328 130 84 1230 1330 157 75 1250 1330 75 75 1365 1330 130 84 1990 1330 155 9 2010 1330 100 77 2115 1330 277 77 1021 1330 142 80 1165 1333 130 80 1932 1334 165 80 1205 1335 120 58 2205 1335 162 66 2076 1339 155 67 1640 1340 140 50 2060 1340 285 75 2098 1340 170 77 2180 1340 260 72 2160 1341 160 53 1871 1344 165 90 1263 1348 160 70 2009 1365 125 36 2082 1371 170 18 2129 1374 174 28 1160 1375 170 57 2055 1375 140 35 2188 1376 190 30 2258 1376 140 25 2031 1388 190 28 2233 1389 220 85 1165 1390 265 76 2000 1400 265 90 148 Location bedding fractures fold axes axial planar fracture easting northing strike dip strike dip trend plunge strike dip 2050 1400 75 30 2100 1400 190 45 2300 1400 178 65 1165 1410 30 66 1890 1415 237 90 1915 1415 170 66 2252 1418 55 26 1049 1420 152 69 1185 1420 155 70 1530 1420 160 90 1620 1420 16 80 1672 1420 5 90 1805 1420 165 70 1640 1422 165 90 1036 1423 233 90 2159 1425 65 30 1200 1425 145 82 1220 1425 140 76 1395 1425 155 90 1485 1425 254 90 1505 1425 154 82 1600 1425 135 90 1705 1425 25 59 1734 1425 20 82 1775 1425 170 72 1820 1425 265 76 1835 1425 175 10 1793 1428 170 15 1757 1429 180 88 1305 1430 30 76 1960 1430 158 72 1935 1435 255 75 1010 1438 144 78 1530 1466 286 74 1030 1467 2119 1469 150 35 1971 1472 196 35 1996 1472 136 40 2083 1475 165 28 1093 1477 265 50 1070 1477 140 65 1816 1479 105 30 2026 1480 132 10 2169 1481 142 23 1301 1481 105 70 1254 1482 168 35 2143 1484 104 20 1857 1484 100 50 2054 1485 205 10 1350 1485 125 60 2277 1485 168 35 1230 1490 150 70 2207 1491 152 15 2306 1491 90 90 1124 1497 65 90 2000 1500 106 40 1094 1508 36 85 1782 1508 118 60 1724 1514 28 53 2078 1517 55 80 1836 1519 1767 1523 170 30 2232 1523 90 30 1265 1525 16 20 1931 1533 135 40 1024 1550 150 80 149 Location bedding fractures fold axes axial planar fracture easting northing strike dip strike dip trend plunge strike dip 2293 1565 154 22 1222 1570 130 62 2005 1570 154 40 2058 1573 155 48 2197 1573 165 14 2324 1574 154 32 2137 1575 170 20 2231 1576 144 28 2077 1578 172 20 2252 1579 148 30 2270 1579 75 22 2373 1580 145 20 1739 1581 80 40 2167 1581 105 20 2540 1592 158 55 1992 1595 258 78 1972 1595 120 30 2200 1600 100 20 2584 1610 330 90 1903 1612 45 40 2613 1615 350 80 1854 1616 80 35 1726 1618 18 35 2182 1620 272 50 1768 1621 130 50 2239 1622 85 20 1958 1625 28 30 1995 1628 150 22 2552 1629 355 5 1305 1641 1989 1649 178 8 2025 1650 210 25 2025 1650 28 50 2025 1650 75 90 1936 1657 95 90 2156 1659 135 20 1970 1659 198 90 2051 1662 200 68 2178 1663 115 20 2139 1665 260 85 2016 1672 85 80 1922 1679 75 20 2510 1679 140 25 2496 1679 155 10 1962 1681 140 28 2571 1682 134 42 2223 1684 145 20 2193 1689 135 50 2248 1691 90 20 1575 1706 295 52 2524 1709 330 75 2401 1709 10 40 2461 1710 326 60 2012 1713 158 15 1854 1715 70 80 2079 1716 160 35 2221 1717 260 75 1277 1719 220 80 2122 1719 136 40 1925 1719 255 75 1793 1720 75 30 2050 1720 258 80 1889 1721 8 35 2103 1721 148 20 2341 1722 108 28 2026 1724 180 15 150 Location easting 183 139 136 217 124 199 115! 108 199 1302 203! 2121 2082 2145 northing 3 172 2 172 2 172 1 173 3 173 3 173 3 174 174, 176' ! 176! 176E 1766 1767 1772 bedding strike 5 3 12 3 15 3 12 3 14 3 14 2 15! t > 12C 17; 14C dip 3 4 5 7 3 6 3 4 2 6( 5 5( ) 3C 2J 2C fractures strike 5 3 3 ) 10C dip ) 2t fold axes trend 17 13 ) 156 plunge 0 3 5 12 axial plana strike 5 2 r fracture dip 240C 1774 336 4C 2648 1774 17C 7C 2434 1775 148 80 2511 1775 120 25 1932 1776 160 20 2540 1777 145 4 1326 1779 2172 1781 98 30 1208 1781 148 55 2705 1782 340 80 2331 1782 60 20 2622 1783 345 2 2370 1786 138 12 2260 1787 162 25 1164 1787 154 50 2236 1788 190 25 1972 1790 260 83 1248 1790 130 50 1920 1792 245 90 -2297 1794 126 20 2480 1797 70 18 2640 1800 95 85 2024 1805 228 76 1837 1807 250 85 2427 1813 133 15 1361 1814 1321 1815 2356 1823 335 30 2223 1824 145 17 2077 1825 180 16 1970 1829 152 30 1474 1829 125 60 1073 1830 135 65 2201 1835 160 30 1406 1839 152 55 1347 1849 153 40 2617 1852 80 90 2158 1870 162 20 1253 1872 170 45 2653 1874 342 41 1898 1876 130 6 2224 1877 110 12 2173 1878 110 15 1962 1879 90 20 2007 1879 156 48 2112 1880 168 8 2544 1880 352 40 2505 1882 320 20 2047 1882 138 45 2345 1884 143 10 2619 1884 162 65 2313 1886 150 10 151 Location bedding fractures fold axes axial planar fracture easting northing strike dip strike dip trend plunge strike dip 2260 1895 146 7 2701 1896 140 7 2140 1900 166 5 2284 1909 60 85 2367 1909 238 14 2168 1911 30 90 1944 1912 246 85 2574 1913 85 90 2141 1914 262 70 2452 1916 156 7 2052 1918 245 85 2515 1919 85 90 2394 1919 85 18 1866 1920 115 12 1990 1920 270 75 1438 1923 152 48 1966 1924 128 25 2319 1925 200 15 1066 1925 145 80 1296 1925 145 65 1920 1926 150 12 1106 1926 140 45 1214 1926 178 45 2105 1932 156 15 2476 1942 185 18 1835 1960 200 80 1857 1964 100 35 2663 1964 175 50 2012 1967 136 28 2482 1970 348 5 2029 1977 100 33 1826 1977 242 80 2609 1980 170 35 2246 1981 160 14 2542 1981 145 50 2227 1981 130 15 2089 1985 135 25 2343 1986 146 5 2052 1986 105 90 1340 1987 158 54 2191 1987 125 5 2217 1987 200 85 2292 1990 166 8 1816 1995 260 85 1223 1996 170 9 1150 2000 152 10 2125 2000 170 10 2625 2000 168 24 2358 2002 105 90 1843 2005 148 20 1734 2008 50 20 1474 2012 154 50 2714 2012 316 55 1759 2014 0 40 1253 2014 1862 2016 338 20 1697 2018 140 10 2474 2019 345 15 1178 2019 348 75 2581 2020 350 5 2423 2021 110 15 2154 2021 190 20 1294 2022 155 50 2644 2022 94 90 2695 2022 166 28 1906 2023 124 25 152 Location bedding fractures fold axes axial planar fracture easting northing strike dip strike dip trend plunge strike dip 2044 2024 140 2 1949 2024 145 23 2183 2026 135 20 2295 2026 106 90 2341 2027 154 25 2665 2027 315 18 2124 2028 340 30 2615 2032 314 20 1258 2035 2509 2071 148 20 2008 2071 280 80 2569 2071 155 40 2059 2073 152 12 1751 2074 236 90 2082 2076 150 30 2189 2076 158 60 2805 2078 155 50 1789 2080 152 90 2550 2080 190 15 1936 2081 275 90 2122 2083 160 55 2159 2084 145 30 1093 2085 144 65 2046 2088 60 90 2340 2089 100 90 2180 2089 235 74 2222 2091 146 4 1173 2091 158 20 2276 2093 140 27 1823 2093 105 32 1945 2094 270 90 2372 2095 142 35 1850 2100 30 20 2300 2100 350 5 2350 2100 145 5 2400 2100 197 20 2435 2100 320 11 2600 2100 175 15 2730 2100 330 65 2760 2100 348 78 2850 2100 150 58 2020 2106 102 10 2004 2109 320 45 2803 2116 334 10 2027 2118 104 10 1193 2119 22 40 1735 2119 248 12 1987 2120 246 90 2491 2122 80 80 1926 2122 125 15 2343 2124 352 2 1814 2124 175 35 2711 2127 200 27 1243 2127 152 50 1148 2127 147 55 2661 2128 160 30 1285 2128 124 53 2685 2128 320 10 2181 2130 106 90 2217 2130 323 2 2199 2132 130 35 2280 2132 345 5 2163 2132 335 2 1894 2137 240 82 2001 2138 235 75 2162 2159 325 2 153 Location bedding fractures fold axes axial planar fracture easting northing strike dip strike dip trend plunge strike dip 2112 2167 175 10 2590 2167 185 25 2194 2168 165 15 2378 2168 160 30 2081 2169 92 25 2429 2169 142 25 2326 2169 155 10 2137 2171 160 3 1239 2172 160 55 1933 2172 338 12 2510 2173 160 75 1201 2173 153 58 2687 2173 350 60 1704 2175 320 2 1649 2176 138 40 2011 2177 160 8 2049 2178 164 25 2178 2179 68 85 1665 2179 120 80 2850 2180 130 35 1162 2180 150 20 2476 2181 165 30 2996 2182 160 65 2909 2183 162 44 1106 2185 150 60 2159 2185 185 20 2221 2185 80 80 1635 2187 222 75 1900 2189 163 26 2076 2192 80 85 1476 2195 145 40 1400 2200 140 42 2561 2204 340 80 2534 2205 145 15 2790 2207 328 45 1929 2210 244 85 1968 2211 270 18 2470 2214 100 90 1738 2216 1712 2218 308 15 2691 2218 346 10 2388 2219 120 15 2493 2221 137 35 2616 2222 326 10 2356 2222 298 85 2368 2223 345 10 1794 2224 134 25 2287 2224 100 90 2092 2225 104 90 1846 2226 313 24 2211 2227 5 70 2065 2228 145 18 2419 2228 336 5 2247 2231 100 90 1553 2233 175 60 2028 2236 148 25 2138 2241 130 22 2401 2259 152 23 2566 2266 153 75 1975 2269 157 12 2452 2269 185 15 2036 2270 175 75 2356 2271 150 25 1601 2271 160 10 2897 2271 240 85 2315 2272 180 20 154 Location bedding fractures fold axes axial planar fracture easting northing strike dip strike dip trend plunge strike dip 2835 2273 345 65 2527 2274 170 5 2128 2275 146 30 1256 2275 155 70 1497 2278 155 60 2179 2280 82 80 1717 2280 95 20 2951 2281 340 80 2620 2281 170 55 1619 2282 162 22 1859 2283 77 70 2503 2284 98 5 2649 2290 55 90 1991 2291 260 75 2240 2300 60 90 2270 2300 184 20 2231 2303 95 90 2712 2309 170 60 2251 2309 347 20 2873 2310 225 80 1864 2311 144 20 2153 2313 325 5 2301 2314 85 90 2281 2314 352 6 1357 2315 108 10 1752 2315 345 30 1880 2317 170 20 2379 2317 316 12 1782 2318 95 80 2625 2318 344 10 1903 2319 140 15 2185 2320 168 22 1947 2323 156 20 1714 2324 328 8 2482 2324 95 90 1199 2325 148 58 2084 2327 167 50 2009 2328 85 90 1832 2328 152 26 1995 2328 162 15 2106 2329 95 85 2308 2332 140 12 2056 2333 100 12 2011 2339 70 72 2800 2340 86 90 2540 2341 145 12 2042 2346 320 10 2129 2360 305 12 2184 2362 135 45 1813 2366 340 30 2030 2374 322 45 1657 2376 275 65 1843 2376 340 6 2861 2377 178 50 2255 2379 85 90 2447 2379 328 74 1305 2380 160 65 1466 2380 165 60 1950 2381 148 32 1737 2382 160 20 2405 2382 100 85 2353 2382 182 35 1904 2383 145 35 2003 2384 160 15 1559 2384 155 50 1406 2385 165 30 155 ) Location bedding fractures fold axes axial planar fracture easting northing strike dip strike dip trend plunge strike dip 2694 2386 354 20 1985 2387 110 60 2013 2388 30 85 1246 2390 155 60 1860 2390 74 73 2675 2391 178 90 2000 2400 285 75 2000 2400 107 65 1879 2403 240 75 2094 2405 328 20 2352 2411 85 90 1531 2411 135 40 1761 2411 330 2 2306 2412 338 15 1979 2414 66 65 1955 2415 340 15 2864 2417 306 58 1791 2418 152 25 2031 2419 200 24 2262 2419 180 25 2404 2421 325 70 2327 2421 163 35 2150 2423 144 35 2472 2423 155 45 1881 2424 228 25 2055 2424 326 15 2080 2424 334 50 2210 2428 340 5 2382 2429 154 40 1654 2430 154 50 2099 2433 100 78 2072 2450 85 80 2078 2463 305 20 2276 2465 312 8 2497 2469 312 25 2559 2469 285 17 2334 2469 160 75 1347 2471 154 75 2411 2472 168 35 2598 2474 335 90 1493 2474 150 48 1866 2475 154 30 2351 2475 100 90 2170 2475 214 12 2693 2476 180 15 1310 2479 168 70 1193 2479 160 75 1269 2480 165 68 1427 2481 167 45 2479 2483 172 25 2451 2485 178 15 2569 2490 290 20 2063 2490 10 12 1620 2500 118 80 2030 2500 66 86 2939 2505 330 30 2107 2508 340 5 2339 2510 330 45 2285 2511 315 22 2756 2511 324 70 2375 2512 85 90 2090 2512 347 20 2156 2514 180 20 2201 2517 148 75 1597 2518 150 30 2001 2518 320 70 156 Location bedding fractures fold axes axial planar fracture easting northing strike dip strike dip trend plunge strike dip 1763 2519 315 12 1810 2519 275 20 1913 2519 150 45 2314 2519 142 40 2056 2521 300 44 2474 2521 338 20 2025 2523 0 10 2578 2524 45 90 2711 2525 290 28 2521 2526 332 6 1880 2527 8 10 1453 2528 346 10 2501 2535 230 10 2792 2540 340 10 1980 2550 325 60 2212 2561 315 25 1826 2562 305 12 2295 2563 350 2 1859 2568 165 25 880 2571 348 90 2073 2573 288 20 1952 2574 350 25 2268 2574 146 30 1742 2576 165 40 748 2576 335 80 830 2578 275 60 2220 2579 104 90 1103 2579 155 72 2976 2582 174 60 1705 2584 150 64 2646 2585 178 12 2137 2586 102 90 975 2600 175 85 1950 2600 165 20 2350 2600 5 90 2350 2600 200 85 2350 2600 276 85 2450 2600 185 12 2531 2605 227 20 2934 2605 185 30 2403 2607 286 20 2755 2609 325 55 2261 2611 90 90 2018 2612 66 80 1992 2613 315 55 1771 2613 90 90 3004 2613 60 90 1967 2615 285 30 1789 2615 325 30 1880 2616 158 30 2983 2617 336 10 2201 2618 142 24 2216 2619 334 15 2157 2624 285 30 2340 2625 334 8 1857 2626 157 40 1825 2626 184 30 2295 2631 315 25 2332 2632 318 12 2370 2633 208 10 2501 2634 184 25 1681 2635 168 45 2250 2638 324 90 2008 2646 158 85 2375 2650 83 85 1985 2653 183 2 157 Location bedding fractures fold axes axial planar fracture easting northing strike dip strike dip trend plunge strike dip 1646 2653 85 90 2036 2654 90 85 1779 2656 160 57 600 2658 164 65 1703 2659 242 85 2404 2659 210 90 2343 2660 275 85 1905 2661 312 24 2648 2665 335 30 2224 2666 335 5 2016 2666 235 25 2382 2666 335 90 2036 2667 4 40 1983 2670 324 30 2484 2672 158 20 1772 2673 280 75 2729 2675 208 26 2010 2675 135 30 2690 2676 175 60 902 2677 175 75 1127 2680 157 60 2075 2681 345 25 2161 2681 100 90 2518 2683 30 90 2885 2683 320 40 2417 2688 85 90 1941 2700 10 5 2717 2706 222 80 1738 2709 173 35 2649 2713 345 8 2848 2714 320 70 2476 2715 130 30 2697 2715 350 15 2190 2716 205 25 2351 2716 166 43 2223 2717 320 30 2732 2717 310 25 1684 2720 186 10 1666 2721 170 65 2310 2723 158 70 2135 2723 184 25 1443 2723 162 70 2155 2725 332 25 2388 2725 332 55 1082 2727 168 45 2539 2729 358 65 844 2729 185 70 1498 2730 140 75 2076 2748 350 28 2061 2762 335 66 2140 2762 250 15 2556 2762 320 25 2035 2764 94 90 2754 2767 170 60 2432 2769 316 35 1195 2770 170 70 2003 2773 136 20 1571 2773 170 52 2270 2773 170 70 2576 2774 308 44 1619 2775 90 80 2495 2776 140 20 934 2776 250 90 1789 2776 162 30 2786 2778 134 65 2531 2779 315 2 158 Location bedding fractures fold axes axial planar fracture easting northing strike dip strike dip trend plunge strike dip 756 2780 185 75 1647 2781 160 43 994 2782 190 80 2776 2783 185 75 2310 2783 265 82 1967 2784 288 85 2034 2788 62 60 2959 2789 235 30 872 2790 165 70 2873 2793 90 90 2804 2795 82 80 2000 2800 356 85 2280 2800 345 30 2540 2801 246 85 1973 2803 60 90 2261 2804 280 25 2070 2806 32 90 2612 2807 302 47 1287 2809 178 60 2499 2809 310 10 2361 2811 332 58 2547 2811 284 85 1947 2812 255 28 708 2813 2 70 1668 2813 95 90 2733 2815 164 50 2230 2815 298 45 2704 2816 345 70 2772 2816 322 50 2512 2816 338 90 2049 2816 322 65 2668 2817 160 28 1156 2819 332 55 2098 2819 342 48 1732 2820 172 45 2148 2821 340 8 2334 2822 174 40 1697 2822 170 40 2192 2823 280 35 2855 2825 165 70 2478 2825 320 85 1091 2827 2309 2829 210 30 2032 2830 320 20 2984 2830 215 4 2283 2831 315 5 1995 2835 328 45 2013 2842 135 38 2498 2847 220 85 2464 2852 210 20 1951 2853 282 85 2348 2860 324 22 2254 2869 320 35 2006 2871 158 90 2661 2871 320 21 2513 2876 290 20 2113 2879 280 15 2898 2879 320 70 2604 2880 335 68 2500 2880 140 65 2500 2880 235 85 2500 2880 240 90 2029 2882 94 68 2479 2883 210 15 962 2883 164 74 2732 2885 148 26 159 Location bedding fractures fold axes axial planar fracture easting northing strike dip strike dip trend plunge strike dip 2583 2885 175 60 743 2887 200 90 2086 2888 350 64 2436 2888 215 30 2284 2889 155 52 2515 2896 95 85 800 2900 202 60 1700 2900 167 45 2315 2900 185 50 2517 2906 350 10 2539 2908 326 65 2633 2908 337 45 1935 2909 320 24 2218 2911 325 40 2856 2911 330 65 2764 2911 200 30 950 2913 8 56 2506 2914 344 90 2240 2914 350 8 913 2916 185 90 2449 2918 325 10 2564 2919 325 60 2735 2919 330 25 2008 2920 316 42 2681 2920 290 35 722 2920 30 80 2175 2921 315 30 2290 2921 340 15 2653 2921 315 65 2138 2921 184 25 2414 2921 195 30 1132 2925 185 85 790 2925 185 71 860 2925 1050 2925 360 80 2042 2926 356 45 2120 2928 320 70 1168 2929 172 70 1214 2929 180 82 1253 2929 165 65 895 2930 198 17 2096 2934 50 10 2020 2940 2074 2943 300 20 2000 2950 295 25 1053 2960 170 90 2010 2960 340 12 845 2960 222 70 872 2973 290 78 2160 2980 316 33 2170 2980 350 22 2195 2980 162 35 2220 2980 160 59 2245 2980 160 48 889 2982 130 65 824 2984 90 20 2743 2985 204 45 2842 2985 170 25 837 2986 295 74 2661 2990 235 25 1727 3000 170 30 2700 3000 326 65 2000 3005 320 26 2886 3009 274 30 1698 3019 350 10 2050 3020 395 36 160 Location bedding fractures fold axes axial planar fracture easting northing strike dip strike dip trend plunge strike dip 2090 3020 340 40 2100 3020 325 20 2150 3020 298 72 2320 3020 163 83 2450 3020 329 56 2490 3020 158 62 1680 3025 172 50 590 3025 167 90 680 3025 355 74 760 3025 167 67 940 3025 120 90 1055 3025 324 66 1110 3025 175 68 1985 3025 295 20 2280 3025 155 80 2768 3028 282 25 1089 3028 140 90 1145 3030 165 73 1165 3030 165 73 1190 3030 170 72 1210 3030 170 72 1225 3030 200 54 1245 3030 163 64 1260 3030 185 66 1320 3030 182 77 1360 3030 185 76 1385 3030 294 84 2813 3031 148 50 2258 3032 345 25 1404 3038 176 75 1956 3061 310 54 1547 3063 1615 3068 165 65 2345 3073 160 70 1110 3075 172 85 1130 3075 175 50 1230 3075 175 50 2787 3076 178 50 2173 3077 44 90 2148 3078 218 16 2723 3081 172 30 2000 3100 325 63 2270 3100 330 72 2654 3110 325 22 2666 3111 328 30 2121 3112 330 20 2086 3113 320 50 2429 3115 200 30 2767 3115 315 28 2736 3116 325 45 1948 3117 280 25 633 3121 0 85 660 3123 105 65 700 3130 152 75 960 3130 275 75 1010 3130 90 90 1040 3130 5 81 1090 3130 175 90 1110 3130 261 78 1140 3130 267 79 1185 3130 158 69 1210 3130 164 60 1275 3130 152 79 1300 3130 134 59 1320 3130 157 68 1355 3130 164 68 161 Location bedding fractures fold axes axial planar fracture easting northing strike dip strike dip trend plunge strike dip 1370 3130 162 75 1395 3130 165 66 1430 3130 160 67 1450 3130 165 70 1460 3130 147 70 1485 3130 157 74 675 3140 65 80 1405 3142 165 67 1157 3168 2761 3169 195 20 653 3174 158 30 2260 3175 195 15 2156 3175 168 45 2931 3177 165 70 2513 3179 330 36 1121 3179 160 90 1394 3180 152 70 2590 3181 305 45 1305 3183 160 74 2681 3184 188 10 2805 3186 95 80 1484 3195 148 75 650 3200 153 30 2072 3207 336 40 2426 3209 340 55 2961 3211 330 60 2701 3218 180 45 1558 3219 158 45 667 3220 0 40 622 3221 0 55 1178 3222 160 80 2120 3225 320 65 2786 3227 178 30 1268 3227 156 80 1221 3228 145 70 607 3228 135 50 2090 3244 330 60 2538 3270 324 30 2798 3271 307 20 2882 3273 145 50 2620 3275 335 60 2256 3276 2 20 1431 3280 147 65 1555 3288 160 75 1317 3288 158 70 1220 3290 155 60 1397 3291 150 45 1165 3292 155 45 2210 3300 330 60 2561 3305 230 40 2790 3311 55 90 2756 3314 352 85 2792 3321 265 80 2542 3324 70 65 2310 3325 300 35 2512 3327 150 82 2525 3329 356 22 2771 3337 350 8 2819 3356 318 70 2120 3360 200 25 2500 3380 200 65 635 3381 165 90 1310 3381 150 85 1549 3381 155 70 1450 3400 140 65 1824 3403 170 23 162 Location bedding fractures fold axes axial planar fracture easting northing strike dip strike dip trend plunge strike dip 1992 3412 198 60 2902 3417 184 75 2720 3418 190 45 2556 3422 330 60 2340 3425 320 60 2410 3425 140 50 1219 3427 155 90 2154 3431 325 62 2660 3432 330 60 2510 3450 340 20 2793 3459 155 60 2815 3470 160 65 1564 3473 170 22 692 3479 194 35 2270 3489 280 40 1989 3491 178 40 2369 3492 164 35 2009 3492 2287 3495 2540 3506 45 85 2976 3507 260 40 2735 3507 230 45 2520 3509 160 30 1627 3509 164 55 2851 3510 20 35 2927 3512 310 90 2798 3513 310 60 961 3514 352 50 2239 3515 292 73 2892 3515 340 60 1233 3518 153 75 1006 3520 350 70 1342 3521 144 70 2599 3522 165 55 2024 3523 290 25 2526 3524 304 80 2387 3533 275 35 2580 3538 130 80 2555 3549 75 70 2539 3554 175 65 2403 3561 250 20 2516 3562 40 45 2452 3573 200 30 2022 3578 177 45 163 Appendix C Garnet Compositions - Sacrificio Deposit 164 Weight Percent Oxides in Garnets as determined by Electron Microprobe Analysis (Operating conditions and standards used given in Table 2, Paper 2) Sample Si02 Ti02 AI203 Cr203 Fe203 MnO MgO CaO Na20 Total 40-1 34.7736 0.0070 1.5605 0.0325 28.3538 0.1241 0.1814 33.4106 0.0227 98.4662 40-2 35.3119 0.0002 3.4962 0.0002 25.6616 0.1596 0.1710 33.7407 0.0098 98.5512 40-3 35.2213 0.0002 2.8431 0.0002 26.4915 0.1395 0.0972 33.8671 0.0165 98.6766 40-4 35.8311 0.0951 4.8533 0.0062 24.1092 0.1416 0.0798 34.3312 0.0003 99.4478 40-5 36.0337 0.1025 5.8836 0.0002 22.7514 0.1585 0.0855 34.4521 0.0135 99.4810 40-6 35.3507 0.0002 1.6229 0.0041 28.6781 0.1208 0.0677 33.7117 0.0180 99.5742 40-7 35.7547 0.0002 6.4077 0.0165 22.0731 0.1370 0.0823 34.9413 0.0192 99.4320 40-8 36.0094 0.0005 6.7883 0.0641 21.4541 0.0318 0.0994 34.4349 0.0051 98.8876 40-9 34.8242 0.0002 1.5647 0.0002 28.0072 0.1076 0.1606 33.7521 0.0003 98.4171 40-10 35.3387 0.0043 3.1256 0.0002 26.2422 0.1442 0.1160 33.3756 0.0003 98.3471 40-11 35.5625 0.0851 4.8002 0.0002 24.2110 0.1983 0.0942 34.3776 0.0003 99.3294 40-12 35.8234 0.1036 5.5907 0.0002 22.8374 0.2187 0.0776 34.4899 0.0341 99.1756 40-13 35.1393 0.0002 1.6475 0.0002 28.5461 0.0877 0.0770 34.0407 0.0047 99.5434 40-14 35.7994 0.0582 6.3823 0.0002 21.6648 0.1572 0.1634 34.3898 0.0306 98.6459 40-15 35.9611 0.0411 6.5048 0.0434 21.7990 0.0585 0.0898 34.6848 0.0280 99.2105 40-16 34.9802 0.0100 1.6232 0.0002 27.8950 0.1573 0.2023 33.5650 0.0120 98.4452 40-17 35.1817 0.0002 3.4748 0.0225 25.9209 0.1013 0.1942 34.0347 0.0124 98.9427 40-18 35.7931 0.1660 5.3065 0.0144 23.4932 0.2435 0.0869 34.1370 0.0003 99.2409 40-19 35.1220 0.0006 1.5800 0.0081 28.5442 0.0745 0.0546 34.0402 0.0087 99.4329 40-20 35.8714 0.0002 5.0838 0.0002 24.0547 0.0850 0.0841 34.3762 0.0045 99.5601 40-21 36.1215 0.0412 6.5285 0.0062 22.0315 0.0150 0.0906 34.3286 0.0045 99.1676 40-22 35.1834 0.0002 1.9389 0.0002 27.7060 0.1375 0.1692 33.6548 0.0007 98.7909 40-23 35.2933 0.0039 3.4584 0.0002 25.6142 0.1944 0.1551 34.1460 0.0517 98.9172 40-24 35.7476 0.1970 4.7393 0.0390 24.2665 0.1766 0.1030 34.2450 0.0003 99.5143 40-25 35.9262 0.0631 6.3703 0.0062 22.5011 0.0918 0.0780 35.0370 0.0003 100.0740 40-26 35.9403 0.0473 5.4189 0.0002 23.4996 0.2017 0.0982 34.4877 0.0103 99.7042 40-27 34.8685 0.0054 1.5190 0.0041 28.5293 0.1258 0.2189 33.6596 0.0003 98.9309 40-28 34.9542 0.0020 1.2263 0.0002 28.6885 0.0744 0.1633 33.3682 0.0247 98.5018 40-29 34.7189 0.0074 1.8736 0.0002 27.8998 0.1591 0.1792 33.8346 0.0007 98.6735 40-30 35.5534 0.0002 3.6754 0.0002 25.4084 0.1746 0.1361 33.9143 0.0026 98.8652 40-31 35.7492 0.1138 5.6582 0.0144 23.2008 0.2336 0.0708 34.7138 0.0148 99.7694 40-32 35.8164 0.0156 5.6603 0.0227 22.8419 0.0951 0.1077 34.3257 0.0003 98.8857 40-33 36.0128 0.0056 6.8559 0.0002 21.5055 0.0937 0.0962 35.3054 0.0159 99.8912 40-34 34.8104 0.0061 0.8514 0.0041 29.1569 0.1389 0.3086 33.3493 0.0040 98.6297 40-35 34.5440 0.0002 0.6803 0.0304 29.8100 0.2198 0.3113 33.7246 0.0020 99.3226 40-36 35.0959 0.0002 1.2408 0.0264 28.7309 0.1126 0.1431 33.8901 0.0100 99.2500 40-37 35.2275 0.0178 3.0518 0.0002 26.5546 0.1228 0.1207 34.0120 0.0003 99.1077 40-38 35.7878 0.1569 4.8560 0.0002 24.0107 0.1450 0.1113 34.1417 0.0003 99.2099 40-39 35.9316 0.0439 6.6625 0.0083 21.8489 0.0518 0.0782 35.0899 0.0204 99.7355 41-1 35.7780 0.0287 3.9697 0.0184 25.5596 0.1229 0.0784 33.7728 0.0003 99.3288 41-2 35.0886 0.0002 2.1996 0.0002 27.7823 0.0613 0.0869 33.5076 0.0199 98.7466 41-3 35.1014 0.0347 2.0366 0.0002 27.5004 0.0265 0.1092 33.5912 0.0192 98.4194 41-4 35.6139 0.0449 4.1084 0.0287 24.8647 0.0799 0.0989 34.3335 0.0039 99.1768 41-5 35.9863 0.0256 5.8105 0.0002 23.1474 0.1385 0.0783 34.2362 0.0090 99.4320 41-6 35.0948 0.0068 1.4702 0.0325 28.5275 0.1043 0.1381 33.8822 0.0033 99.2597 41-7 35.6989 0.0333 4.1821 0.0002 24.7996 0.1197 0.0819 34.1342 0.0003 99.0502 41-8 34.7472 0.0125 2.3552 0.0041 27.2086 0.0613 0.1457 33.8981 0.0003 98.4330 41-9 35.4629 0.0002 4.4145 0.0002 24.5899 0.1315 0.0925 34.2881 0.0003 98.9801 41-10 35.5667 0.0082 5.8084 0.0002 22.7431 0.1751 0.0760 34.1503 0.0154 98.5434 41-11 35.0100 0.0044 2.3770 0.0002 27.1903 0.0978 0.1059 33.4901 0.0337 98.3094 41-12 35.1866 0.0367 4.7441 0.0002 24.4509 0.0983 0.0950 34.4078 0.0003 99.0199 41-13 35.0342 0.0462 4.4402 0.0002 25.1997 0.0865 0.0714 34.2705 0.0111 99.1600 41-14 35.9072 0.0002 6.8425 0.0166 21.3095 0.1054 0.0744 34.7351 0.0003 98.9912 41-15 35.3232 0.0033 3.0849 0.0002 26.5694 0.0764 0.0904 33.7860 0.0003 98.9341 41-16 35.8283 0.0764 6.1227 0.0002 22.3213 0.1554 0.0621 34.7632 0.0003 99.3299 41-17 34.9605 0.0115 2.1649 0.0041 27.7815 0.0977 0.1178 33.4987 0.0146 98.6513 41-18 35.2391 0.0002 3.8827 0.0002 25.5096 0.1197 0.0808 34.2896 0.0052 99.1271 41-19 34.2537 0.0002 0.0142 0.0283 29.5339 0.1834 0.1407 33.4177 0.0067 97.5788 41-20 35.9103 0.1449 6.9527 0.0002 21.1755 0.2208 0.0719 34.6678 0.0003 99.1444 41-21 35.0722 0.0002 3.4671 0.0002 26.1594 0.0432 0.0876 34.0502 0.0013 98.8814 41-22 35.6183 0.0002 4.7686 0.0002 23.8783 0.0400 0.0988 34.2017 0.0045 98.6106 165 Weight Percent Oxides in Garnets as determined by Electron Microprobe Analysis (cont.) (Operating conditions and standards used given in Table 2, Paper 2) Sample Si02 Ti02 AI203 Cr203 Fe203 MnO MgO CaO Na20 Total 41-23 36.1473 0.0003 6.8110 0.0002 21.3777 0.1221 0.0546 34.5150 0.0025 99,0307 41-24 35.4546 0.0002 3.6599 0.0205 25,6238 0.1064 0.0897 34,3512 0.0003 99.3066 41-25 35.7442 0.0331 4.6448 0.0002 24.3145 0.1149 0.0561 34.0972 0.0389 99.0439 41-26 35.4872 0.0149 4.3091 0.0002 25.1602 0.0848 0,0772 34.3282 0.0007 99.4625 41-27 34.9349 0.0002 1.7012 0.0305 28.4883 0.0944 0.0737 33.7658 0.0067 99.0957 41-28 35.7597 0.0168 4.9212 0.0002 24.3110 0.1133 0.0619 34.4281 0.0013 99.6135 41-29 34.7471 0.0195 0.7809 0.0385 29.1985 0.0943 0.1469 33.2232 0.0003 98.2492 41-30 35.4701 0.0761 4.3231 0.0471 24.7602 0,1630 0.1002 34.2193 0.0003 99.1594 41-31 34.8219 0.0002 0.1275 0.0081 30.3582 0.1173 0.1163 33.4546 0.0169 99.0210 41-32 35.2567 0.0357 3.7130 0.0002 25.3132 0.1381 0.0778 34.3096 0.0003 98,8446 41-33 35.7666 0.0139 5.0246 0.0103 23,5069 0.2118 0.1243 33,9631 0.0129 98.6344 41-34 34.7882 0.0002 1.4068 0.0002 28.3026 0.1391 0,0790 33.9026 0.0003 98.6190 41-35 35.4262 0,0202 3.8461 0.0002 25.2364 0.0732 0.1459 34.2533 0.0003 99.0018 41-36 35.6906 0.0310 5.3061 0.0002 23.6520 0.1668 0.0840 34.7466 0.0003 99.6776 41-37 35.0043 0.0071 1.1477 0.0325 29.0853 0.0414 0.1402 33.9014 0.0003 99.3602 41-38 35.6505 0.0002 5.5959 0.0002 23.3291 0.2002 0.0930 34.4417 0.0103 99.3211 41-39 34.9669 0.0002 0.4484 0.0002 30.3523 0.0908 0.1187 33.8936 0.0003 99.8714 41-40 35.7406 0.0602 5.3390 0.0021 23.5787 0.1017 0.0814 34.7258 0.0003 99.6298 41-41 35.4877 0.0327 3.3774 0.0002 25.5919 0.0981 0.0868 33.9007 0.0003 98.5758 41-42 34.8633 0.0002 1.4440 0.0183 28.9427 0.1622 0.0630 33.5282 0.0003 99.0222 47-1 36.0176 0.2651 7.5295 0.0002 20.5921 0.1567 0.1319 34.2479 0.0132 98.9542 47-2 35.6986 0.0248 4.7929 0.0265 24.3238 0.1276 0.1018 32.8522 0.0006 97.9488 47-3 35.9263 0.2925 7,1844 0.0002 21.0992 0.1700 0.1384 33.6079 0.0038 98.4227 47-4 36.2708 0.2312 8.8007 0.0002 18.7605 0.1120 0.1080 33.9582 0.0255 98.2671 47-5 35.6246 0.0055 4.0513 0.0002 25.3722 0.1176 0.1038 33.6497 0,0150 98.9399 47-6 35.7449 0.0284 4.1190 0.0002 24.7516 0.2834 0.0502 33.0798 0,0260 98.0835 47-7 36.1674 0.2775 7.1210 0.0186 20.8848 0.1183 0.1389 34.1050 0.0233 98.8548 47-8 36.0327 0.1145 6.8477 0.0144 21.3273 0.1149 0.1025 33.7448 0.0003 98.2991 47-9 36.0216 0.0943 6.0450 0.0002 22.3642 0.0915 0.1197 33.7077 0.0178 98.4620 47-10 36.0458 0.1066 6.2009 0.0226 22.2286 0.1198 0.0940 33.4775 0.0197 98.3155 47-11 36.1996 0.2104 6.8903 0.0002 21.3181 0.1716 0.0900 33.7299 0.0165 98.6266 47-12 36.1726 0.2749 7.4966 0.0392 20.9233 0.0817 0.1127 33.7848 0.0003 98.8861 48-1 35.8353 0.0624 5.3496 0.0348 22.8281 0.1612 0.3190 32.6331 0.0122 97,2357 48-2 35.2822 0.0209 3.4383 0.0002 25.3343 0.1457 0,2668 32.9485 0.0163 97,4532 48-3 36.3397 0.0977 6.4335 0.0021 21.8626 0.1465 0.2171 33.7749 0,0140 98.8881 48-4 35.1391 0.0138 1.4988 0.0002 28.3058 0.0891 0.0838 32.7219 0.0146 97.8671 48-5 34.6729 0.0002 0.8039 0.0002 28.3505 0.1088 0.1628 32.6273 0.0093 96.7359 48-6 35.7562 0.0522 3.4646 0.0082 25.3811 0.0795 0.1050 33.6264 0.0003 98.4735 48-7 35.4360 0.0576 3.0272 0.0061 26.4104 0.1009 0.1211 32.6414 0.0003 97.8010 48-8 35.8686 0.0508 4.5231 0.0002 24.0124 0.1842 0.2842 33.0548 0.0003 97.9786 48-9 35.8795 0.1790 6.1512 0.0288 21.7818 0.1614 0.1777 33.2026 0.0003 97.5623 48-10 34.8965 0.0002 1.5776 0.0243 27.4677 0.0924 0.1549 32.8879 0.0318 97.1333 48-11 35.4925 0.1392 5.7302 0.0205 21.7920 0.1763 0.2523 33.2755 0.0003 96.8788 48-12 35.6279 0.0783 3.9496 0.0102 24.6690 0.1575 0.2157 33.2718 0.0045 97.9845 48-13 35.9195 0.0619 5.9074 0.0002 21.8399 0.1548 0.2446 33.1373 0.0223 97.2879 48-14 35.9113 0.0155 4.8457 0.0470 24.0855 0.1559 0.1415 33.2671 0.0155 98.4850 48-15 35.8167 0.0246 5.5752 0.0021 22.8854 0.1562 0.1611 33.6526 0.0352 98.3091 166 Mole Percent Cations in Garnet Unit Formula (calculation based on 8 oxygen atoms) 40-1 40-2 40-3 40-4 Sample Si (T) Al (T) Sum_T Al (VI) total Al Fe3 (A) Ti (A) Cr (A) Sum_A Mg (B) Mn (B) Ca (B) Na (B) Sum_B 2.953 0.047 3.000 0.109 0.156 1.812 0.000 0.002 1.924 0.023 0.009 3.040 0.004 3.076 2.964 0.036 3.000 0.310 0.346 1.621 0.000 0.000 1.931 0.021 0.011 3.035 0.002 3.069 2.963 0.037 3.000 0.245 0.282 1.677 0.000 0.000 1.922 0.012 0.010 3.053 0.003 3.078 2.962 0.038 3.000 0.434 0.472 1.500 0.006 0.000 1.940 0.010 0.010 3.040 0.000 3.060 40-5 2.961 0.039 3.000 0.530 0.569 1.407 0.006 0.000 1.943 0.010 0.011 3.033 0.002 3.057 40-6 2.971 0.029 3.000 0.131 0.160 1.813 0.000 0.000 1.945 0.008 0.009 3.035 0.003 3.055 40-7 2.930 0.070 3.000 0.548 0.618 1.361 0.000 0.001 1.910 0.010 0.010 3.067 0.003 3.090 40-8 2.961 0.039 3.000 0.619 0.658 1.328 0.000 0,004 1.951 0.012 0.002 3.034 0.001 3.049 40-9 2.956 0.044 3.000 0.113 0.157 1.789 0.000 0.000 1.902 0.020 0.008 3.070 0.000 3.098 40-10 2.981 0.019 3.000 0.292 0.311 1.666 0.000 0.000 1.958 0.015 0.010 3.017 0.000 3 042 40-11 2.944 0.056 3.000 0.412 0.468 1.508 0.005 0.000 1 925 0.012 0.014 3.049 0.000 3.075 40-12 2.955 0.045 3.000 0.498 0.543 1.417 0.006 0.000 1.922 0.010 0.015 3.048 0.005 3.078 40-13 2.952 0.048 3.000 0.115 0.163 1.805 0.000 0.000 1.919 0.010 0.006 3.064 0.001 3,081 40-14 2.954 0.046 3.000 0.574 0.620 1.345 0.004 0.000 1.923 0.020 0.011 3.041 0.005 3.077 40-15 2.951 0.049 3.000 0.580 0.629 1.346 0.003 0.003 1.931 0.011 0.004 3.049 0.004 3.069 40-16 2.967 0.033 3.000 0.129 0.162 1.781 0.001 0.000 1.911 0.026 0.011 3.051 0.002 3.089 40-17 2.942 0.058 3.000 0.284 0.342 1.631 0.000 0.001 1.917 0.024 0.007 3.050 0.002 3.083 40-18 2.959 0.041 3.000 0.476 0.517 1.462 0.010 0.001 1.948 0.011 0.017 3.024 0.000 3.052 40-19 2.954 0.046 3.000 0.111 0.157 1.807 0.000 0.001 1.918 0.007 0.005 3.068 0.001 3.082 40-20 2.959 0.041 3.000 0.452 0.493 1.493 0.000 0.000 1.945 0.010 0.006 3.038 0.001 3.055 40-21 2.968 0.032 3.000 0.600 0.632 1.362 0.003 0.000 1.965 0.011 0.001 3.022 0.001 3 035 40-22 2.971 0.029 3.000 0.164 0.193 1.760 0.000 0.000 1.924 0.021 0.010 3.045 0.000 3,076 40-23 2.950 0.050 3.000 0.290 0.340 1.611 0.000 0.000 1.901 0,019 0,014 3.057 0.008 3.099 40-24 2.955 0.045 3.000 0.417 0.462 1.510 0.012 0.003 1.941 0.013 0.012 3.033 0.000 3.059 40-25 2.928 0.072 3.000 0.540 0.612 1.380 0.004 0.000 1.924 0.009 0.006 3.060 0.000 3,076 40-26 2.954 0.046 3.000 0.479 0.525 1.454 0.003 0.000 1.935 0.012 0.014 3.037 0.002 3,065 40-27 2.948 0.052 3.000 0.099 0.151 1.815 0.000 0.000 1.915 0.028 0.009 3.049 0.000 3.085 40-28 2.972 0.028 3,000 0.095 0.123 1.835 0.000 0.000 1.930 0,021 0.005 3.040 0.004 3.070 40-29 ' 2.937 0.063 3.000 0.123 0.186 1.776 0.000 0.000 1.900 0.023 0.011 3.066 0.000 3.100 40-30 2.972 0.028 3.000 0.334 0.362 1.598 0.000 0.000 1.933 0.017 0.012 3.038 0.000 3.067 40-31 2.933 0.067 3.000 0.480 0.547 1.433 0.007 0.001 1.921 0.009 0.016 3.052 0.002 3.079 40-32 2.962 0.038 3.000 0.514 0.552 1.422 0.001 0.001 1.938 0.013 0.007 3.042 0.000 3.062 40-33 2.929 0.071 3.000 0.586 0.657 1.316 0.000 0,000 1,903 0,012 0.006 3.077 0.003 3.097 40-34 2.960 0.040 3.000 0.045 0.085 1.866 0.000 0.000 1.912 0.039 0.010 3.038 0.001 3.088 40-35 2.922 0.068 2.989 0.000 0.068 1.897 0.000 0.002 1.899 0.039 0.016 3.056 0.000 3.111 40-36 2.961 0.039 3.000 0.084 0.123 1.824 0.000 0.002 1.909 0.018 0.008 3.063 0 002 3.091 40-37 2.950 0.050 3.000 0.251 0.301 1.673 0.001 0.000 1.925 0.015 0.009 3.051 0.000 3.075 40-38 2.965 0.035 3.000 0.439 0.474 1.497 0.010 0.000 1.945 0.014 0.010 3.031 0.000 3.055 40- 39 2.932 0.068 3.000 0.572 0.640 1.341 0.003 0.001 1,916 0.010 0.004 3.067 0.003 3.084 41- 1 2.977 0.023 3.000 0.367 0.390 1.601 0.002 0.001 1.970 0.010 0.009 3.011 0.000 3.030 41-2 2.964 0.036 3.000 0.183 0.219 1.766 0.000 0.000 1.949 0.011 0.004 3.033 0.003 3.051 41-3 2.974 0.026 3.000 0.177 0.203 1.753 0.002 0.000 1.932 0.014 0.002 3.049 0.003 3.068 41-4 2.961 0.039 3.000 0.363 0.402 1.556 0.003 0.002 1,923 0.012 0.006 3.058 0.001 3.077 41-5 2.962 0.038 3.000 0.525 0.563 1.434 0.002 0.000 1.960 0.010 0.010 3.019 0.001 3.040 41-6 2.958 0.042 3.000 0.104 0.146 1.809 0.000 0.002 1.915 0.017 0.007 3.059 0.001 3.085 41-7 2.972 0.028 3.000 0,382 0,410 1.553 0.002 0.000 1.937 0.010 0.008 3.044 0.000 3.063 41-8 2.939 0.061 3.000 0.173 0.234 1.732 0.001 0.000 1.906 0.018 0.004 3.071 0.000 3.094 41-9 2.951 0.049 3.000 0.383 0.432 1.540 0.000 0.000 1.923 0.011 0.009 3.057 0.000 3.077 41-10 2.951 0.049 3.000 0.519 0.568 1.420 0.001 0.000 1.940 0.009 0.012 3.036 0.002 3.060 41-11 2.965 0.035 3.000 0.202 0.237 1.733 0.000 0.000 1.935 0.013 0.007 3.039 0.006 3.065 41-12 2.923 0.077 3.000 0.388 0.465 1.529 0.002 0.000 1.918 0.012 0.007 3.063 0.000 3.082 41-13 2.914 0.086 3.000 0.349 0.435 1.577 0.003 0.000 1.929 0.009 0.006 3.054 0.002 3.071 41-14 2.948 0.052 3.000 0,610 0.662 1.317 0.000 0.001 1.928 0.009 0.007 3.056 0.000 3.072 41-15 2.964 0.036 3.000 0.268 0.304 1.677 0.000 0.000 1.946 0.011 0.005 3.037 0.000 3.054 41-16 2,944 0.056 3.000 0,536 0.592 1.380 0.005 0.000 1.921 0.008 0.011 3.060 0.000 3.079 41-17 2.956 0.044 3.000 0.172 0.216 1.768 0.001 0.000 1.941 0.015 0.007 3.035 0.002 3.059 41-18 2.937 0.063 3.000 0.318 0.381 1.600 0.000 0.000 1.918 0.010 0.008 3.062 0.001 3.082 41-19 2.956 0.001 2.958 0,000 0.001 1.918 0.000 0.002 1.920 0.018 0.013 3.090 0.001 3.123 41-20 2.944 0.056 3.000 0.615 0.671 1.306 0.009 0.000 1.931 0.009 0.015 3.045 0.000 3.069 41-21 2.938 0.062 3.000 0.280 0.342 1.649 0.000 0.000 1.929 0.011 0.003 3.056 0.000 3.071 41-22 2.967 0.033 3.000 0.435 0.468 1.497 0.000 0.000 1.932 0.012 0.003 3.053 0.001 3.068 167 Mole Percent Cations in Garnet Unit Formula (cont.) (calculation based on 8 oxygen atoms) Sample Si (T) Al (T) Sum_T Al (VI) total Al Fe3 (A) Ti (A) Cr (A) Sum_A Mg (B) Mn (B) Ca (B) Na (B) Sum_B 41-23 2.968 0.032 3.000 0.627 0.659 1.321 0,000 0.000 1.948 0.007 0.008 3.037 0.000 3.052 41-24 2.952 0.048 3.000 0.311 0.359 1.605 0.000 0.001 1.917 0.011 0.008 3.064 0.000 3.083 41-25 2.969 0.031 3.000 0.423 0.454 1.520 0,002 0.000 1,945 0.007 0.008 3 034 0.006 3.055 41-26 2.943 0,057 3.000 0.364 0.421 1.570 0,001 0.000 1.934 0.010 0.006 3.050 0.000 3.066 41-27 2.949 0.051 3.000 0.118 0.169 1.809 0.000 0.002 1.929 0.009 0.007 3.054 0.001 3.071 41-28 2.951 0.049 3.000 0.429 0.478 1.510 0.001 0.000 1.940 0.008 0.008 3.044 0.000 3.060 41-29 2.970 0,030 3.000 0.049 0.079 1.878 0.001 0.003 1.931 0.019 0.007 3.043 0.000 3,069 41-30 2.948 0.052 3.000 0.372 0.424 1.549 0.005 0.003 1.928 0 012 0.011 3.048 0.000 3,072 41-31 2.964 0.013 2.977 0.000 0.013 1.945 0.000 0.001 1.945 0.015 0.008 3.051 0.003 3.077 41-32 2.947 0.053 3.000 0.313 0.366 1.592 0.002 0.000 1.907 0.010 0.010 3.073 0.000 3.093 41-33 2.975 0.025 3.000 0.468 0.493 1.471 0,001 0.001 1.941 0.015 0.015 3.027 0.002 3.059 41-34 2.951 0.049 3.000 0.092 0.141 1.807 0,000 0,000 1.899 0.010 0.010 3.081 • 0.000 3,101 41-35 2.954 0,046 3.000 0,332 0 378 1.584 0,001 0.000 1.916 0.018 0,005 3.060 0.000 3,084 41-36 2.936 0,064 3,000 0.450 0.514 1.464 0.002 0.000 1.916 0.010 0.012 3.062 0.000 3.084 41-37 2.953 0.047 3.000 0.067 0.114 1.846 0.000 0.002 1.915 0.018 0.003 3.064 0.000 3.085 41-38 2.939 0.061 3.000 0.483 0.544 1.447 0.000 0.000 1.930 0.011 0.014 3.043 0.002 3.070 41-39 2.948 0.045 2.992 0.000 0.045 1.925 0 000 0.000 1.925 0.015 0.006 3.061 0.000 3.083 41-40 2.941 0,059 3.000 0,458 0517 1.460 0,004 0.000 1.922 0.010 0.007 3.061 0,000 3,078 41-41 2,980 0,020 3.000 0.314 0.334 1,617 0,002 0.000 1,933 0,011 0.007 3.050 0.000 3.067 41-42 2.951 0.049 3.000 0.095 0.144 1.844 0,000 0.001 1.940 0.008 0.012 3.041 0.000 3.060 47-1 2.951 0.049 3.000 0.678 0.727 1.270 0.016 0.000 1.964 0.016 0.011 3.007 0.002 3.036 47-2 3.002 0.000 3.002 0.475 0.475 1.516 0.002 0.002 1.994 0.013 0.009 2.960 0.000 3.004 47-3 2.968 0.032 3.000 0.666 0.698 1.311 0,018 0.000 1.996 0.017 0.012 2.974 0.001 3.004 47-4 2.973 0.027 3.000 0.822 0.849 1.157 0,014 0.000 1.993 0.013 0.008 2.982 0.004 3.007 47-5 2.974 0.026 3.000 0.372 0.398 1.594 0,000 0.000 1.967 0.013 0.008 3.010 0.002 3.033 47-6 3.008 0.000 3.008 0.408 0.408 1.568 0.002 0.000 1.978 0.006 0.020 2.983 0.004 3.014 47-7 2.971 0,029 3.000 0.660 0.689 1.291 0.017 0.001 1.969 0.017 0.008 3.002 0.004 3.031 2.988 0.012 3.000 0.578 0.590 1.396 0.006 0.000 1.980 0.015 0.006 2.996 0.003 3.020 2.994 0.006 3.000 0.600 0.606 1.389 0.007 0.001 1.998 0.012 0.008 2.979 0.003 3.002 47-8 2.983 0.017 3.000 0.650 0.667 1.328 0.007 0.001 1,987 0,013 0.008 2.993 0.000 3.013 47-9 47-10 47-11 2.987 0.013 3.000 0.656 0.669 1.324 0.013 0.000 1.993 0.011 0.012 2.982 0.003 3,007 47- 12 2 970 0,030 3.000 0.695 0.725 1,293 0.017 0.003 2.008 0.014 0.006 2.973 0.000 2 992 48- 1 3,018 0,000 3.018 0 531 0.531 1,423 0.004 0.002 1.960 0.040 0.011 2.945 0.002 3.022 48-2 2.994 0.006 3.000 0.338 0.344 1.618 0.001 0.000 1.957 0.034 0.010 2.996 0.003 3,043 48-3 2.994 0.006 3.000 0.618 0.624 1.355 0.006 0.000 1.980 0.027 0.010 2.981 0,002 3.020 48-4 3,006 0,000 3.006 0.151 0.151 1.822 0.001 0.000 1.974 0.011 0.006 3,000 0,002 3.019 48-5 3.006 0,000 3.006 0.082 0.082 1.850 0.000 0.000 1.932 0.021 0.008 3.031 0.002 3.062 48-6 3.004 0.000 3.004 0.343 0.343 1.604 0.003 0.001 1.951 0.013 0.006 3.026 0.000 3.045 48-7 3.011 0.000 3.011 0.303 0.303 1.667 0.004 0.000 1.974 0.015 0.007 2.971 0,000 3,015 48-8 48-9 48-10 3.000 0.000 3.000 0.160 0.160 1.777 0.000 0.002 1.938 0.020 0.007 3.029 0.005 3.061 48-11 2.991 0,009 3.000 0.559 0.568 1.382 0.009 0.001 1.951 0.032 0.013 3.004 0.000 3.049 48-12 3.000 0.000 3.000 0.391 0.391 1.563 0.005 0.001 1.960 0.027 0.011 3.001 0.001 3.040 48-13 3.012 0.000 3.012 0.583 0.583 1.378 0.004 0.000 1.965 0.031 0.011 2,977 0.004 3,022 48-14 2.999 0.001 3.000 0.475 0.476 1.513 0.001 0.003 1.993 0.018 0011 2.976 0.003 3.007 48-15 2.981 0.019 3.000 0.527 0.546 1.433 0.002 0.000 1.962 0.020 0.011 3.001 0.006 3.038 3.011 0.000 3.011 0.447 0.447 1.517 0.003 0.000 1.967 0.036 0.013 2.973 0.000 3.022 3.001 0.000 3.001 0.606 0.606 1.366 0.011 0.002 1.985 0.022 0.011 2.975 0.000 3.014 168 Garnet Compositions Expressed as Percentage of End-Members (Method of calculation after Rickwood et al., 1968) Sample Almadine Andradite Grossular Pyrope Spessartine Uvarovite 40-1 0.00 92.03 6.78 0.78 0.30 0.11 40-2 0.00 82.41 16.48 0.73 0.39 0.00 40-3 0.00 85.61 13.64 0.42 0.34 0.00 40-4 0.00 76.01 23.30 0.33 0.34 0.02 40-5 0.00 71.27 28.01 0.35 0.37 0.00 40-6 0.00 91.84 7.57 0.29 0.29 0.01 40-7 0.00 69.68 29.60 0.34 0.33 0.06 40-8 0.00 67.25 32.06 0.41 0.08 0.21 40-9 0.00 91.95 7.09 0.70 0.27 0.00 40-10 0.00 84.27 14.89 0.49 0.35 0.00 40-11 0.00 76.84 22.29 0.40 0.47 0.00 40-12 0.00 72.28 26.88 0.32 0.52 0.00 40-13 0.00 91.71 7,75 0.33 0.21 0.00 40-14 0.00 68.42 30.52 0.68 0.37 0.00 40-15 0.00 68.42 30.93 0.37 0.14 0.14 40-16 0.00 91.65 7.09 0.88 0.39 0.00 40-17 0.00 83.16 15.70 0.82 0.24 0.08 40-18 0.00 74.09 24.93 0.36 0.58 0.05 40-19 0.00 92.00 7.57 0.23 0.18 0.03 40-20 0.00 75.69 23.76 0.35 0.20 0.00 40-21 0.00 68.84 30.73 0.37 0.04 0.02 40-22 0.00 90.12 8.82 0.73 0.34 0.00 40-23 0.00 82.54 16.33 0.66 0.47 0.00 40-24 0.00 76.62 22.40 0.43 0.42 0.13 40-25 0.00 70.69 28.75 0.32 0.22 0.02 40-26 0.00 73.80 25.32 0.41 0.48 0.00 40-27 0.00 92.35 6.39 0.94 0.31 0.01 40-28 0.00 93.72 5.39 0.71 0.18 0.00 40-29 0.00 90.70 8.14 0.77 0.39 0.00 40-30 0.00 81.53 17.48 0.58 0.42 0.00 40-31 0.00 73.25 25.85 0.30 0.55 0.05 40-32 0.00 71.98 27.27 0.45 0.23 0.08 40-33 0.00 67.40 31.98 0.40 0.22 0.00 40-34 0.00 95.61 2.70 1.34 0.34 0.01 40-35 0.00 97.40 0.61 1.34 0.54 0.10 40-36 0.00 93.58 5.44 0.62 0.28 0.09 40-37 boo 85.08 14.11 0.51 0.30 0.00 40-38 0.00 75.94 23.25 0.47 0.34 0.00 40-39 0.00 68.63 30.89 0.32 0.12 0.03 41-1 0.00 80.64 18.69 0.33 0.29 0.06 41-2 0.00 89.37 10.11 0.37 0.15 0.00 41-3 0.00 89.60 9.86 0.47 0.07 0.00 41-4 0.00 79.36 19.93 0.42 0.19 0.10 41-5 0.00 72.60 26.75 0.32 0.33 0.00 41-6 0.00 92.43 6.62 0.59 0.25 0.11 41-7 0.00 79.10 20.27 0.35 0.29 0.00 41-8 0.00 88.38 10.83 0.63 0.15 0.01 41-9 0.00 78.27 21.03 0.39 0.31 0.00 41-10 0.00 72.18 27.09 0.32 0.42 0.00 41-11 0.00 87.95 11.36 0.45 0.24 0.00 41-12 0.00 78.43 20.93 0.40 0.24 0.00 41-13 0.00 81.19 18.30 0.30 0.21 0.00 41-14 0.00 66.99 32.40 0.31 * 0.25 0.06 41-15 0.00 84.90 14.54 0.38 0.18 0.00 41-16 0.00 70.32 29.05 0.26 0.37 0.00 41-17 0.00 89.69 9.55 0.50 0.24 0.01 41-18 0.00 81.71 17.66 0.34 0.29 0.00 41-19 0.00 99.82 0.00 0.08 0.00 0.10 41-20 0.00 66.56 32.62 0.30 0.52 0.00 41-21 0.00 84.19 15.34 0.37 0.10 0.00 41-22 0.00 76.17 23.32 0.42 0.10 0.00 169 Garnet Compositions Expressed as Percentage of End-Members (cont.) (Method of calculation after Rickwood et al., 1968) Sample Almadine Andradite Grossular Pyrope Spessartine Uvarovite 41-23 0.00 66.75 32.74 0.23 0.29 0.00 41-24 0.00 81.66 17.64 0.38 0.25 0.07 41-25 0.00 76.97 22.53 0.24 0.27 0.00 41-26 0.00 80.03 19.45 0.32 0.20 0.00 41-27 0.00 92.04 7.31 0.31 0.23 0.10 41-28 0.00 76,74 22.74 0.26 0.27 0.00 41-29 0.00 95.85 3.15 0.64 0.23 0.13 41-30 0.00 78.79 20.24 0.42 0.39 0.16 41-31 0.00 99.32 0.00 0.50 0.15 0.03 41-32 0.00 81.31 18.02 0.33 0.33 0.00 41-33 0.00 74.89 24.05 0.52 0.51 0.03 41-34 0.00 92.78 6.54 0.34 0.34 0.00 41-35 0.00 80.73 18.48 0.62 0.18 0.00 41-36 0.00 74.80 24.45 0.35 0.40 0,00 41-37 0.00 94.07 5.12 0.60 0.10 0,11 41-38 0.00 73.86 25.27 0.39 0.48 0.00 41-39 0.00 97.98 1.30 0.51 0.22 0.00 41-40 0.00 74.46 24.95 0.34 0.24 0.01 41-41 0.00 82.87 16.52 0.37 0.24 0.00 41-42 0.00 93.70 5.57 0.27 0.39 0.06 47-1 0.00 64.53 34,55 0.55 0.37 0.00 47-2 0.26 76.07 22.85 0.43 0.30 0.09 47-3 0.00 66.29 32.74 0.57 0,40 0.00 47-4 0.00 58.38 40.91 0.44 0.26 000 47-5 0.00 80.39 18.90 0.43 0,28 0.00 47-6 0.00 79.32 19.79 0.21 0.68 0,00 47-7 0.00 65.18 33.91 0.57 0.28 0.06 47-8 0,00 66.81 32.45 0.42 0.27 0.05 47-9 0.00 70.25 29.04 0.50 0.22 0.00 47-10 0.00 69.61 29.65 0.39 0.28 0.07 47-11 0.00 66.47 32.76 0.37 0.40 0.00 47-12 0.00 65.29 33.93 0.46 0.19 0.13 48-1 0.00 72.74 25.39 1.37 0.39 0.12 48-2 0.00 82.47 16.03 1.15 0.36 0.00 48-3 0.00 68.44 30.31 0.90 0.34 0.01 48-4 0.00 92.34 7.08 0.36 0.22 0.00 48-5 0.00 95.75 3.25 0.73 0.28 0.00 48-6 0.00 82.36 16.97 0.45 0.19 0.03 48-7 0.00 84.60 14.62 0.52 0,25 0.02 48-8 0.00 77.21 21.13 1.21 0.44 0.00 48-9 0.00 69.19 29.59 0.75 0.39 0.10 48-10 0.00 91.67 7.33 0.68 0.23 0.09 48-11 0.00 70.78 27.64 1.08 0.43 0.07 48-12 0.00 79.92 18.74 0.92 0.38 0.04 48-13 0.00 70.24 28.35 1.04 0.37 0,00 48-14 0.00 75.92 22.97 0.59 0.37 0.16 48-15 0.00 72,37 26.58 0.67 0.37 0,01 170 Appendix D Pyroxene Compositions - Sacrificio Deposit 171 Weight Percent Oxides in Pyroxenes as determined by Electron Microprobe Analysis (operating conditions and standards used are given in Table 5, Chapter 3) Sample Si02 Ti02 AI203 FeO Cr203 MnO MqO CaO Na20 Total 47-1 53.3016 0.0002 0.0330 5.8241 0.0002 0.6694 14.5958 25.0947 0.0307 99.5497 47-2 53.9416 0.0183 0.0448 4.2246 0.0086 0.6285 15.4422 25.3486 0.0206 99.6778 47-3 53.2785 0.0348 0.0299 5.9481 0.0193 0.7668 14.3404 25.0795 0.0418 99.5391 47-4 53.8792 0.0002 0.0894 4.8629 0.0387 0.3936 15.4633 25.5405 0.0022 100.2700 47-5 53.0738 0.0002 0.0290 5.6330 0.0064 0.6340 14.5848 25.2934 0.0159 99.2705 47-6 53.2419 0.0002 0.0749 5.6808 0.0150 0.4274 14.8838 25.2453 0.0290 99.5983 47-7 53.1100 0.0140 0.1148 5.6811 0.0300 0.3094 14.7748 25.2861 0.0230 99.3432 47-8 53.1918 0.0284 0.1435 6.0449 0.0002 0.3091 14.6491 25.2819 0.0214 99.6703 47-9 53.2378 0.0002 0.0837 5.6403 0.0002 0.4308 14.8220 25.2607 0.0088 99.4845 47-10 53.2762 0.0342 0.0971 5.1759 0.0002 0.3798 15.0117 25.1807 0.0234 99.1792 47-11 52.9620 0.0002 0.0868 5.5415 0.0150 0.3779 14.8502 25.1643 0.0170 99.0149 47-12 53.3055 0.0002 0.0846 5.8434 0.0321 0.4170 14.6527 25.1053 0.0192 99.4600 47-13 52.5911 0.0134 0.1455 7.0029 0.0107 0.3377 13.8889 25.2319 0.0216 99.2437 47-14 53.1103 0.0002 0.1096 6.2578 0.0278 0.3569 14.2530 25.0379 0.0003 99.1538 47-15 53.0219 0.0002 0.0889 5.5859 0.0002 0.4069 14.8477 25.4208 0.0038 99.3763 47-16 53.9362 0.0005 0.0867 3.2063 0.0002 0.5785 16.2640 25.6687 0.0003 99.7414 47-17 53.0591 0.0002 0.0553 5.4111 0.0086 0.6667 14.7512 25.0426 0.0120 99.0068 47-18 52.5692 0.0207 0.0880 9.3443 0.0002 0.6435 12.0537 24.5368 0.0374 99.2938 47-19 54.0330 0.0002 0.1171 2.8147 0.0259 0.2681 16.5580 25.6336 0.0160 99.4666 47-20 53.4598 0.0002 0.0956 5.7251 0.0300 0.3863 14.7820 25.1827 0.0003 99.6620 48-1 54.4284 0.0002 0.0540 2.1520 0.0238 0.5864 17.0562 25.6469 0.0074 99.9553 48-2 54.0797 0.0108 0.0329 2.3680 0.0002 0.5275 16.7565 25.7927 0.0016 99.5699 48-3 54.5098 0.0002 0.0339 2.1714 0.0065 0.5108 17.0480 25.7138 0.0127 100.0071 48-4 54.4142 0.0108 0.0803 3.4484 0.0108 0.6362 16.3681 25.7154 0.0011 100.6853 48-5 54.4812 0.0002 0.1013 2.4916 0.0130 0.5260 16.7994 25.7930 0.0085 100.2142 48-6 54.1275 0.0002 0.1116 3.1201 0.0002 0.6094 16.3066 25.8524 0.0145 100.1425 48-7 54.3025 0.0131 0.2347 2.4949 0.0002 0.5875 16.7186 25.6028 0.0096 99.9639 48-8 54.3966 0.0002 0.0442 2.4008 0.0108 0.5824 16.9619 25.9024 0.0003 100.2996 48-9 53.6743 0.0052 0.5036 3.1608 0.0280 0.5747 16.1029 25.8820 0.0016 99.9331 48-10 54.3735 0.0218 0.0399 2.1383 0.0002 0.3336 17.0311 25.9217 0.0042 99.8643 48-11 52.7880 0.0002 0.0815 8.5351 0.0002 0.5949 12.7015 24.6450 0.0860 99,4324 48-12 54.4167 0.0071 0.0915 2.1820 0.0195 0.6238 16.9810 25.9630 0.0228 100.3074 48-13 54.6066 0.0046 0.0433 2.9122 0.0002 0.6011 16.4945 25.8280 0.0003 100,4908 48-14 54.3180 0.0002 0.0988 2.4622 0.0692 0.5960 16.9170 25.9737 0.0112 100.4463 48-15 55.0449 0.0091 0.0356 1.8406 0.0002 0.4421 17.0903 25.7104 0.0159 100.1891 48-16 54.3153 0.0002 0.0418 2.5848 0.0238 0.6014 16.7873 25.7604 0.0293 100.1443 48-17 54.2512 0.0002 0.0857 2.7148 0.0002 0.7832 16.5644 25.6679 0.0203 100.0879 48-18 54,3215 0.0120 0.0584 2.9963 0.0497 0.5255 16.8177 25.7457 0.0003 100.5271 48-19 54,0442 0.0206 0.1808 3.6344 0.0237 0.7733 16.1137 25.3451 0.0178 100.1536 48-20 54,1896 0.0318 0.0308 2.2522 0.0455 0.6326 16.7701 25.6776 0.0064 99.6366 48-21 54,5451 0.0139 0.0747 2.3852 0.0151 0.6116 16.9172 25.9293 0.0106 100.5027 48-22 54,4254 0.0002 0.0476 2.3261 0.0433 0.5261 16.9299 25.8305 0.0207 100.1498 48-23 54,3381 0.0176 0.1316 2.4471 0.0195 0.6239 16.4059 25.5046 0.0607 99.5490 48-24 52.8571 0.0147 0.0394 7.2949 0.0002 0.7599 13.3633 24.5143 0.0980 98.9418 48-25 54.7162 0.0002 0.0238 2.2566 0.0650 0.5004 16.9945 25.7472 0.0106 100.3145 48-26 52.6171 0.0125 0.0278 8.9695 0.0002 0.6932 12.5154 25.1526 0.0362 100,0245 48-27 52.7581 0.0002 0.0421 7.8549 0.0002 0.7030 13.0359 24.4270 0.0302 98.8516 48-28 52.8864 0.0002 0.0003 8.4046 0.0340 0.6446 12.8282 24.8000 0.0259 99,6242 48-29 52.9502 0.0086 0.0128 7.3998 0.0490 0.6831 13.4660 25.0379 0.0658 99.6732 48-30 53.1058 0.0021' 0.0150 7.8601 0.0002 0.7643 13.3655 25.2623 0.0257 100,4010 48-31 53.3489 0.0002 0.0317 6.8287 0.0149 0.7776 13.7453 25.1997 0.0305 99.9775 48-32 52.7684 0.0002 0.0559 8.7819 0.0002 0.6968 12.5076 24.9701 0.0468 99,8279 48-33 53.5984 0.0103 0.0317 6.5246 0.0235 0.6433 13.9856 25.3953 0.0498 100.2625 48-34 53.3330 0.0002 0.0125 6.6144 0.0171 0.6603 14.1097 25.2617 0.0332 100,0421 48-35 53.2492 0.0023 0.0104 7.1058 0.0213 0.6784 13.6068 25.1655 0.0178 99.8575 48-36 52.7177 0.0002 0.0165 7.6250 0.0002 0.7867 13.3818 25.1236 0.0592 99,7109 48-37 53.0710 0.0002 0.0113 8.0275 0.0002 0.7828 13.0769 25.0964 0.0454 100.1117 172 Mole Percent Cations in Pyroxene Unit Formula (calculation based on 6 oxygen atoms and 4 cations) Sample Si (T) Al (T) Fe3 (T) Al (M1) Ti (M1) Fe3 (M1)Fe2 (M1)Fe_t (M1)Cr (M1) Mg (M1) Mn (M2) Ca (M2)Na (M2) 47-1 1.984 0.001 0.015 0.000 0.000 0.019 0.148 0.167 0.000 0.810 0.021 1.001 0.002 47-2 1.992 0.002 0.006 0.000 0.001 0.008 0.117 0.125 0.000 0.850 0.020 1.003 0,001 47-3 1.986 0.001 0.013 0.000 0.001 0.015 0.158 0.173 0.001 0.797 0.024 1.002 0.003 47-4 1.980 0.004 0.016 0.000 0.000 0.019 0.115 0.134 0.001 0.847 0.012 1.006 0.000 47-5 1.980 0.001 0.019 0.000 0.000 0.021 0.136 0.157 0.000 0.811 0.020 1.011 0.001 47-6 1.977 0.003 0.020 0.000 0.000 0.025 0.131 0.156 0.000 0.824 0.013 1.004 0.002 47-7 1.977 0.005 0.018 0.000 0.000 0.023 0.136 0.159 0.001 0.820 0.010 1.009 0.002 47-8 1.976 0.006 0.018 0.000 0.001 0.024 0.146 0.170 0.000 0.811 0.010 1.006 0.002 47-9 1.979 0.004 0.017 0.000 0.000 0.021 0.137 0.158 0.000 0.821 0.014 1.006 0.001 47-10 1.983 0.004 0.013 0.000 0.001 0.017 0.131 0.148 0.000 0.833 0.012 1.004 0.002 47-11 1.977 0.004 0.019 0.000 0.000 0.024 0.130 0.154 0.000 0.826 0.012 1.006 0.001 47-12 1.984 0.004 0.012 0.000 0.000 0.016 0.154 0.170 0.001 0.813 0.013 1.001 0.001 47-13 1.971 0.006 0.022 0.000 0.000 0.029 0.168 0.197 0.000 0.776 0.011 1.013 0.002 47-14 1.988 0.005 0.007 0.000 0.000 0.011 0.177 0.188 0.001 0.795 0.011 1.004 0.000 47-15 1.973 0.004 0.024 0.000 0.000 0.028 0.122 0.150 0.000 0.823 0.013 1.013 0.000 47-16 1.980 0.004 0.016 0.000 0.000 0.020 0.062 0.082 0.000 0.890 0.018 1.010 0.000 47-17 1.982 0.002 0.015 0.000 0.000 0.018 0.135 0.153 0.000 0.822 0.021 1.002 0.001 47-18 1.995 0.004 0.001 0.000 0.001 0.006 0.290 ' 0.296 0.000 0.682 0.021 0.998 0.003 47-19 1.984 0.005 0.011 0.000 0.000 0.017 0.059 0.076 0.001 0.906 0.008 1.008 0.001 47-20 1.985 0.004 0.011 0.000 0.000 0.014 0.153 0.167 0.001 0.818 0.012 1.002 0.000 48-1 1.984 0.002 0.014 0.000 0.000 0.016 0.036 0.052 0.001 0.927 0.018 1.002 0.001 48-2 1.981 0.001 0.017 0,000 0.000 0.018 0.037 0.055 0.000 0.915 0.016 1.013 0,000 48-3 1.986 0.001 0.013 0.000 0.000 0.015 0.039 0.054 0.000 0.926 0.016 1.004 0.001 48-4 1.980 0.003 0.016 0.000 0.000 0.019 0.070 0.089 0.000 0.888 0.020 1.003 0,000 48-5 1.984 0.004 0.012 0.000 0.000 0.016 0.048 0.064 0.000 0.912 0.016 1.006 0,001 48-6 1.979 0.005 0.017 0.000 0.000 0.022 0.057 0.079 0.000 0.889 0.019 1.013 0.001 48-7 1.983 0.010 0.007 0.000 0.000 0.017 0.052 0.069 0.000 0.910 0.018 1.002 0.001 48-8 1.978 0.002 0.020 0.000 0.000 0.022 0.031 0.053 0.000 0.920 0.018 1.009 0.000 48-9 1.967 0.022 0.012 0.000 0.000 0.032 0.053 0.085 0.001 0.880 0.018 1.016 0.000 48-10 1.983 0.002 0.015 0.000 0.001 0.016 0.034 0.050 0.000 0.926 0.010 1.013 0.000 48-11 1.991 0.004 0.005 0.000 0.000 0.015 0.249 0.264 0.000 0.714 0.019 0.996 0.006 48-12 1.977 0.004 0.019 0.000 0.000 0.023 0.024 0.047 0.001 0.920 0.019 1.011 0.002 48-13 1.988 0.002 0.010 0.000 0.000 0.012 0.067 0.079 0.000 0.895 0.019 1.007 0.000 48-14 1.973 0.004 0.023 0.000 0.000 0.026 0.026 0.052 0.002 0.916 0.018 1.011 0.001 48-15 2.000 0.000 0.000 0.002 0.000 0.000 0.056 0.056 0,000 0.926 0.014 1.001 0.001 48-16 1.980 0.002 0.018 0.000 0.000 0.022 0.039 0.061 0.001 0.912 0.019 1.006 0.002 48-17 1.981 0.004 0.015 0.000 0.000 0.020 0.048 0.068 0,000 0.902 0.024 1.004 0.001 48-18 1.975 0.002 0.023 0.000 0.000 0.023 0.045 0.068 0.001 0.911 0.016 1.003 0.000 48-19 1.980 0.008 0.013 0.000 0.001 0.020 0.079 0.099 0,001 0.880 0.024 0.995 0.001 48-20 1.984 0.001 0.014 0.000 0.001 0.013 0.042 0.055 0.001 0.916 0.020 1.007 0.000 48-21 1.980 0.003 0.017 0.000 0.000 0.020 0.036 0.056 0.000 0.915 0.019 1.008 0.001 48-22 1.982 0.002 0.016 0.000 0.000 0.019 0.036 0.055 0.001 0.919 0.016 1,008 0.001 48-23 1.994 0.006 0.000 0.000 0.000 0.009 0.066 0.075 0.001 0.898 0.019 1.003 0004 48-24 1.994 0.002 0.004 0.000 0.000 0.012 0.213 0.225 0.000 0.752 0.024 0,991 0.007 48-25 1,989 0.001 0.010 0.000 o.ooo 0.010 0.048 0.058 0.002 0.921 0.015 1.003 0.001 48-26 1 978 0.001 0.021 0.000 o.ooo 0.024 0.237 0.261 0.000 0.701 0.022 1.013 0.003 48-27 1,998 0.002 0.000 0.000 0.000 0.004 0.244 0.248 0.000 0.736 0.023 0.991 0.002 48-28 1,991 0.000 0.009 0.000 0.000 0.010 0.246 0.256 0.001 0.720 0.021 1.000 0.002 48-29 1.983 0.001 0.016 0.000 0.000 0.020 0.196 0.216 0.001 0.752 0.022 1.005 0.005 48-30 1.978 0.001 0.021 0.000 0.000 0.024 0.200 0.224 0.000 0.742 0.024 1.008 0.002 48-31 1,988 0.001 0.010 0.000 0.000 0.013 0.189 0.202 0.000 0.764 0.025 1.006 0.002 48-32 1.986 0.002 0.011 0.000 0.000 0.017 0.248 0.265 0.000 0.702 0.022 1.007 0.003 48-33 1.988 0.001 0.010 0.000 0.000 0.014 0.178 0.192 0.001 0.773 0.020 1.009 0.004 48-34 1.982 0.001 0.017 0.000 0.000 0.020 0.169 0.189 0.001 0.782 0.021 1.006 0.002 48-35 1.989 0.000 0.010 0.000 0.000 0.011 0.200 0.211 0.001 0.758 0.021 1.007 0.001 48-36 1.975 0.001 0.024 0.000 0.000 0.029 0.186 0.215 0.000 0.747 0.025 1.009 0.004 48-37 1.985 0.000 0.014 0.000 0.000 0.018 0.219 0.237 0.000 0.729 0.025 1,006 0.003 173 Pyroxene Compositions Expressed as Percentage of End-Members (method of calculation after Deer et al., 1992; Q, J, WO, EN, and FS as defined by Morimoto, 1989) Sample diopside hedenbergite johannsenite Q J WO EN FS 47-1 81.162 16.733 2.104 1.958 0.004 49.714 40.232 10.054 47-2 85.427 12.563 2.010 1.970 0.003 50.067 42.438 7.494 47-3 80.181 17.404 2.414 1.957 0.006 49.878 39.683 10.439 47-4 85.297 13.494 1.208 1.968 0.000 49.920 42.053 8.027 47-5 82.085 15.891 2.024 1.957 0.002 50.101 40.197 9.702 47-6 82.981 15.710 1.309 1.959 0.004 49.767 40.825 9.407 47-7 82.912 16.077 1.011 1.964 0.003 50.049 40.690 9.261 47-8 81.837 17.154 1.009 1.964 0.003 49.937 40.260 9.802 47-9 82.679 15.911 1.410 1.964 0.001 49.896 40.736 9.369 47-10 83.887 14.904 1.208 1.969 0.003 49.954 41.436 8.610 47-11 83.266 15.524 1.210 1.962 0.002 49.879 40.956 9.166 47-12 81.627 17.068 1.305 1.968 0.003 49.828 40.465 9.707 47-13 78.862 20.020 1.118 1.958 0.003 50.173 38.427 11.400 47-14 79.980 18.913 1.107 1.976 0.000 50.040 39.634 10.326 47-15 83.469 15.213 1.318 1.959 0.001 50.079 • 40.698 9.223 47-16 89.899 8.283 1.818 1.962 0.000 50.077 44.148 5.775 47-17 82.530 15.361 2.108 1.959 0.002 49.769 40.790 9.441 47-18 68.268 29.630 2.102 1.970 0.006 49.962 34.150 15.887 47-19 91.515 7.677 0.808 1.973 0.002 50.182 45.102 4.716 47-20 82.046 16.750 1.204 1.973 0.000 49.843 40.708 9.449 48-1 92.979 5.216 1.805 1.965 0.001 49.778 46.062 4.160 48-2 92.799 5.578 1.623 1.965 0.000 50.207 45.384 4.410 48-3 92.972 5.422 1.606 1.968 0.002 49.898 46.030 4.073 48-4 89.067 8.927 2.006 1.961 0.000 49.755 44.064 6.181 48-5 91.935 6.452 1.613 1.967 0.001 50.056 45.363 4.581 48-6 90.071 8.004 1.925 1.958 0.002 50.239 44.092 5.669 48-7 91.274 6.921 1.805 1.964 0.001 49.931 45.366 4.704 48-8 92.836 5.348 1.816 1.960 0,000 49.969 45.528 4.503 48-9 89.522 8.647 1.831 1.949 0.000 50.542 43.753 5.705 48-10 93.915 5.071 1.014 1.973 0.001 50.283 45.968 3.749 48-11 71.615 26.479 1.906 1.960 0.013 49.838 35.739 14.423 48-12 93.306 4.767 1.927 1.955 0.003 50.135 45.624 4.241 48-13 90.131 7.956 1.913 1.970 0.000 50.126 44.541 5.334 48-14 92.901 5.274 1.826 1.953 0.002 50.041 45.349 4.610 48-15 92.972 5.622 1.406 1.983 0.002 50.141 46.375 3.483 48-16 91.935 6.149 1.915 1.957 0.004 49.913 45.257 4.830 48-17 90.744 6.841 2.414 1.954 0.003 49.885 44.793 5.322 48-18 91.558 6.834 1.608 1.959 0.000 49.606 45.087 5.307 48-19 87.737 9.870 2.393 1.954 0.003 49.489 43.778 6.733 48-20 92.432 5.550 2.018 1.965 0.001 50.084 45.512 4.404 48-21 92.424 5.657 1.919 1.960 0.001 50.044 45.430 4,526 48-22 92.828 5.556 1.616 1.962 0.003 50.042 45.635 4.323 48-23 90.524 7.560 1.915 1.967 0.009 50.270 44.993 4,737 48-24 75.125 22.478 2.398 1.956 0.014 49.621 37.637 12 742 48-25 92.656 5.835 1.509 1.972 0.001 49.946 45.870 4,184 48-26 71.240 26.524 2.236 1.951 0.005 50.189 34.747 15.063 48-27 73.088 24.628 2.284 1.971 0.004 49.596 36.827 13.577 48-28 72.217 25.677 2.106 1.967 0.004 49.881 35.900 14.220 48-29 75.960 21.818 2.222 1.952 0.010 49.986 37.405 12.609 48-30 74.949 22.626 2.424 1.950 0.004 49.927 36.753 13.319 48-31 77.094 20.383 2.523 1.960 0.004 50.129 38.045 11 826 48-32 70.981 26.795 2.224 1.957 0.007 50.162 34,961 14.877 48-33 78.477 19.492 2.030 1.961 0.007 50.332 38.567 11.101 48-34 78.831 19.052 2.117 1.957 0.005 49.945 38,815 11.240 48-35 76.566 21.313 2.121 1.965 0.003 50.150 37.728 12.122 48-36 75.684 21.783 2.533 1.942 0.009 49.931 37.004 13.064 48-37 73.562 23.915 2.523 1.954 0.007 50.017 36.262 13.721 Note: Q = Ca + Mg + Fe2+ J = 2Na WO = Ca2Si2Oe EN = Mg2Si206 FS = Fe2Si206 174 Appendix E Fluid Inclusion Microthermometric Data - Sacrificio Deposit 175 SACRIFICIO FLUID INCLUSION DATA Notes: 1. L:V:S ratios by visual estimation at room temperature (25° C) 2. Freezing data accurate to within plus or minus 0.2° C 3. Heating data accurate to within plus or minus 3.0° C 4. Salinities calculated using the MacFlincor program and the equations of state of Bodnar and Vityk (1995) 5. sx = sulphide minerals; cb = carbonate solid Mineralization Te Tm salinity Th Sample Style ratio (L:V:S) solid (deg C) (deg C) (wt % NaCI eq.) (deg C) SAC98-3-260.6(A) asp-qz vein 80:20 -5.0 7.82 SAC98-3-260.6(A) asp-qz vein 70:30 -38.0 -7.0 10.48 SAC98-3-260.6(A) asp-qz vein 80:20 -38.3 -5.2 8.10 303.4 SAC98-3-260.6(A) asp-qz vein 80:20 -38.3 -5.2 8.10 304.8 SAC98-3-260.6(A) asp-qz vein 80:20 -38.3 -5.2 8.10 302.9 SAC98-3-260.6(A) asp-qz vein 80:20 -38.3 -5.2 8.10 302.7 SAC98-3-260.6(A) asp-qz vein 75:25 -39.1 -3.8 6.08 307.2 SAC98-3-260.6(A) asp-qz vein 278.1 COL-99-4-316A (D) asp-qz vein 70:30 -27.6 -10.3 14.26 360.2 COL-99-4-316A (D) asp-qz vein 80:20:<1 sx? -32.1 -10.2 14.16 354.2 COL-99-4-316A (D) asp-qz vein 60:40 -30.6 -14.4 18.12 352.8 COL-99-4-316A (D) asp-qz vein 75:25:<1 sx? -26.9 -13.2 17.07 367.1 COL-99-4-316A(D) asp-qz vein 70:30:<1 sx? -32.6 -16.4 19.74 335.9 COL-99-4-316A (D) asp-qz vein 347.2 COL-99-4-316A (D) asp-qz vein 351.9 COL-99-4-316A (D) asp-qz vein 363.8 COL-99-4-316A (D) asp-qz vein 383.4 SAC-98-4-62.2 (A) disseminated 60:40 -20.0 382.2 SAC-98-4-62.2 (A) disseminated 377.7 SAC-98-4-62.2 (A) disseminated -9.9 13.84 367.8 SAC-98-4-62.2 (A) disseminated 376.5 SAC-98-4-62.2 (A) disseminated 367.7 SAC-98-4-62.2 (A) disseminated 363.6 SAC-98-4-62.2 (A) disseminated 365.4 SAC-98-4-62.2 (A) disseminated 373.3 SAC-98-4-62.2 (A) disseminated 369.3 SAC-98-4-62.2 (A) disseminated 362.5 SAC-98-4-62.2 (A) disseminated 375.5 SAC-98-4-62.2 (C) disseminated 62:35:3 unidentified -36.0 -3.5 5.62 313.0 SAC-98-4-62.2 (C) disseminated 70:30 -41.5 -4.1 6.52 313.9 SAC-98-4-62.2 (C) disseminated 65:35 -24.8 -3.4 5.47 369.9 SAC-98-4-62.2 (C) disseminated 281.7 SAC-98-4-62.2 (C) disseminated 363.3 SAC-98-4-62.2 (C) disseminated 370.5 SAC-98-4-62.2 (C) disseminated 386.3 KP-SAC-99-53 (E) disseminated 69:30:1 cb -27.7 -2.9 4.70 258.8 KP-SAC-99-53 (E) disseminated 70:30 -26.3 -2.8 4.70 258.2 KP-SAC-99-53 (E) disseminated 70:30 -33.0 -2.6 3.92 313.7 KP-SAC-99-53 (E) disseminated 70:30 -33.0 -2.4 4.23 312.1 KP-SAC-99-53 (E) disseminated 65:30:5 unidentified -27.0 -2.3 3.76 308.7 KP-SAC-99-53 (E) disseminated 80:20 -25.6 -2.7 4.39 250.8 KP-SAC-99-53 (E) disseminated 282.1 KP-SAC-99-53 (E) disseminated 282.8 KP-SAC-99-53 (E) disseminated 313.0 KP-SAC-99-53 (E) disseminated 312.7 KP-SAC-99-53 (E) disseminated 271.2 KP-SAC-99-53 (E) disseminated 302.6 KP-SAC-99-53 (E) disseminated 291.9 KP-SAC-99-53 (E) disseminated 295.2 KP-SAC-99-53 (E) disseminated 310.8 KP-SAC-99-53 (F) disseminated 79:20:1 cb -27.5 -2.4 3.92 361.6 KP-SAC-99-53 (F) disseminated 75:25 -25.9 -2.3 3.76 343.3 KP-SAC-99-53 (F) disseminated 74:25:1 cb? -26.5 -2.2 3.60 362.6 KP-SAC-99-53 (F) disseminated 74:25:1 cb? -27.6 -2.3 3.76 342.7 KP-SAC-99-53 (F) disseminated 82:15:3 cb -33.4 -2.5 4.07 KP-SAC-99-53 (F) disseminated 68:30:2 cb -30.0 -2.3 3.76 365.1 KP-SAC-99-53 (F) disseminated 363.6 KP-SAC-99-53 (F) disseminated 374.9 KP-SAC-99-53 (F) disseminated 352.5 KP-SAC-99-53 (F) disseminated 361.9 KP-SAC-99-53 (A) disseminated 85:15 -30.4 -2.8 4.55 KP-SAC-99-53 (A) disseminated 85:15 -29.6 -2.9 4.70 176 SACRIFICIO FLUID INCLUSION DATA (cont.) Mineralization Te Tm salinity Th Sample Style ratio (L:V:S) solid (deg C) (deg C) (wt % NaCl eq.) (deg C) KP-SAC-99-53 (A) disseminated 85:15 -29.0 -2.7 4.39 KP-SAC-99-53 (A) disseminated 75:25 -30.1 -2.7 4.39 KP-SAC-99-53 (A) disseminated 85:15 -31.9 -2.8 4.55 293.8 KP-SAC-99-53 (A) disseminated 90:10 -30.1 -2.7 4.39 KP-SAC-99-53 (A) disseminated KP-SAC-99-40 (A) disseminated 85:15 -28.3 -3.8 6.08 KP-SAC-99-40 (A) disseminated KP-SAC-99-40 (A) disseminated SAC-98-3-185.8 (A) disseminated 50:50 -24.9 -3.5 5.62 355.6 SAC-98-3-185.8 (A) disseminated 65:35 -30.1 -2.4 3.92 306.6 SAC-98-3-185.8 (A) disseminated 90:10 -27.9 -0.8 1.32 SAC-98-3-185.8 (A) disseminated 70:30 -26.8 -2.4 3.92 319.9 SAC-98-3-185.8 (A) disseminated 330.6 SAC-98-3-185.8 (A) disseminated 353.1 SAC-98-3-185.8 (A) disseminated 317.3 SAC-98-3-185.8 (A) disseminated 299.1 SAC-98-3-185.8 (A) disseminated 306.5 SAC-98-3-185.8 (A) disseminated 349.9 SAC-98-3-185.8 (A) disseminated 306.1 SAC-98-3-185.8 (A) disseminated 317.0 SAC-98-3-185.8 (A) disseminated 361.8 SAC-98-3-185.8 (A) disseminated 286.5 SAC-98-3-185.8 (A) disseminated 284.7 SAC98-3-185.9(B) disseminated 90:10 -38.0 -5.1 7.96 SAC98-3-185.9(B) disseminated 70:30 -31.6 -5.1 7.96 359.2 SAC98-3-185.9(B) disseminated 70:30 362.1 SAC98-3-185.9(B) disseminated 357.0 SAC98-3-185.9(B) disseminated 356.8 SAC98-3-185.9(B) disseminated 357.2 SAC98-3-185.9(B) disseminated 388.5 SAC98-3-185.9(B) disseminated 387.8 SAC98-3-185.9(B) disseminated 372.6 SAC-98-3-100A (A) manto 90:10 -33.4 -4.6 7.25 279.5 SAC-98-3-100A(A) manto 90:10 291.4 SAC-98-3-100A (A) manto 262.8 SAC-98-3-100A (A) manto 257.7 SAC-98-3-100A (A) manto 267.4 SAC-98-3-100A(A) manto 274.1 SAC-98-3-100A (A) manto 279.2 SAC-98-3-100A (A) manto 305.6 SAC-98-3-209A (B) manto 60:40 -32.0 -3.8 6.08 277.2 SAC-98-3-209A (B) manto 85:15 -34.4 -3.9 6.23 SAC-98-3-209A (B) manto 85:15 -34.4 -3.7 5.93 SAC-98-3-209A (B) manto 75:25 -37.1 -5.4 8.38 283.4 SAC-98-3-209A (B) manto 280.9 SAC-98-3-209A (B) manto 282.3 SAC-98-3-209A (B) manto 288.2 SAC-98-3-209A (B) manto 276.9 SAC-98-3-209A (B) manto 283.8 SAC-98-3-209A (B) manto 288.9 SAC-98-3-209A (B) manto 291.8 SAC-98-3-100A (B) manto 90:10 -36.0 -4.0 6.37 273.7 SAC-98-3-100A (B) manto 80:20 -28.1 -4.6 7.25 290.8 SAC-98-3-100A (B) manto 85:15 266.7 SAC-98-3-100A (B) manto 90:10 -33.0 -3.7 5.93 247.0 SAC-98-3-100A (B) manto 88:10:2 unidentified 212.0 SAC-98-3-100A (B) manto 85:15 -2.6 4.23 204.6 SAC-98-3-100A (B) manto 70:30 253.2 SAC-98-3-100A (B) manto 293.9 SAC-98-3-100A (B) manto 277.8 SAC-98-3-100A (B) manto 228.5 SAC-98-3-100A (B) manto 286.2 SAC-98-3-100A (B) manto 256.6 SAC-98-3-100A (B) manto 287.6 SAC-98-3-100A (B) manto 296.3 SAC-98-3-100A (B) manto 295.1 177 SACRIFICIO FLUID INCLUSION DATA (cont.) Mineralization Te Tm salinity Th Sample Style ratio (L:V:S) solid (deg C) (deg C) (wt % NaCl eq.) (deg C) SAC-98-3-209A (C) manto 80:20 -26.6 -3.6 5.78 272.1 SAC-98-3-209A (C) manto 70:30 -28.5 -3.5 5.62 266.1 SAC-98-3-209A (C) manto 65:35 -28.0 -3.8 6.08 270.5 SAC-98-3-209A (C) manto 60:40 -29.0 -4.8 7.54 275.4 SAC-98-3-209A (C) manto 90:10 -26.0 SAC-98-3-209A (C) manto 80:20 -24.0 -4.0 6.37 . 271.8 SAC-98-3-209A (C) manto 245.2 SAC-98-3-209A (C) manto 278.0 SAC-98-3-209A (C) manto 240.5 SAC-98-3-209A (C) manto 224.2 SAC-98-3-209A (C) manto 240.9 SAC-98-3-209A (C) manto 241.4 SAC-98-3-209A (C) manto 285.3 SAC-98-3-209A (C) manto 205.8 SAC-98-3-209A (C) manto 281.6 SAC-98-3-209A (C) manto 281.3 SAC-98-3-209A (C) manto 279.0 SAC-98-3-209A (C) manto 276.1 ROS-99-102A (A) manto 80:20 -38.0 -3.8 6.08 290.8 ROS-99-102A (A) manto 75:25 -47.0 -3.1 5.47 292.4 ROS-99-102A (A) manto 90:10 -46.0 -3.4 5.01 209.6 ROS-99-102A (A) manto 80:20 -44.0 -4.5 7.11 292.2 ROS-99-102A (A) manto 205.0 ROS-99-102A (A) manto 209.4 ROS-99-102A (A) manto 289.8 ROS-99-102A (A) manto 288.6 ROS-99-102A (A) manto 292.2 ROS-99-102A (A) manto 208.4 SAC-98-3-103A (B) manto 90:10 -26.8 -3.7 5.93 256.0 SAC-98-3-103A (B) manto 90:10 -33.2 -4.3 6.82 275.2 SAC-98-3-103A (B) manto 95:5 -0.7 1.16 SAC-98-3-103A (B) manto 90:10 -32.8 -0.3 0.50 SAC-98-3-103A(B) manto 267.1 SAC-98-3-103A (B) manto 276.1 SAC-98-3-103A (B) manto 215.8 SAC-98-3-103A(B) manto 254.7 SAC-98-3-103A (B) manto 263.7 SAC-98-3-103A(B) manto 271.0 SAC-98-3-103A (B) manto 273.2 SAC-98-3-103A (B) manto 234.5 SAC-98-3-103A (A) manto 95:5 -19.7 -1.4 2.31 SAC-98-3-103A (A) manto 95:5 -0.9 1.49 SAC-98-3-103A (A) manto 95:5 -1.6 2.63 SAC-98-3-103A (A) manto 95:5 -28.4 -1.6 2.63 SAC-98-3-103A (A) manto 95:5 -28.4 -1.4 2.31 SAC-98-3-103A (A) manto 262.0 SAC-98-3-103A (A) manto 286.5 SAC-98-3-103A (A) manto 272.4 SAC-98-3-103A (A) manto 271.8 Total numbers asp-qz vein 11.0 12.0 12.0 15.0 disseminated 29.0 29.00 29.00 64.0 manto 24.0 27.00 27.00 74.0 Total Inclusions 64.0 68.00 68.00 153.00 Minimum asp-qz vein -39.1 -16.4 6.1 278.1 disseminated -41.5 -9.9 1.3 250.8 manto -47.0 -5.4 0.5 204.6 Total Inclusions -47.0 -16.4 0.5 204.6 Maximum asp-qz vein -26.9 -5.0 19.7 383.4 disseminated -20.0 -0.8 13.8 388.5 manto -19.7 -0.3 8.4 305.6 Total Inclusions -19.7 -0.3 19.7 388.5 Note: Te = eutectic temperature Tm = final ice melting temperature Th = total homogenization temperature 178 Appendix F General Geology, Structure, and Alteration Map - Sacrificio Deposit 179 

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