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UBC Theses and Dissertations

Geology, alteration, mineralization and hydrothermal evolution of the La Bodega-La Mascota deposits,… Rodríguez Madrid, Alfonso Luis 2014

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  Geology, Alteration, Mineralization and Hydrothermal Evolution of the La Bodega-La Mascota deposits, California-Vetas Mining District, Eastern Cordillera of Colombia, Northern Andes  by Alfonso Luis Rodr?guez Madrid Geologist, Universidad Industrial de Santander, 2005  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in The Faculty of Graduate and Postdoctoral Studies (Geological Sciences) THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver) February, 2014 ? Alfonso Luis Rodr?guez Madridii  Abstract  La Bodega (LB) and La Mascota (LM) deposits (inferred resources in 2010 of 3.47 Moz Au, 19.2 Moz Ag and 84.4 Mlbs Cu at 2 g/t Au cut off) are located in the California-Vetas Mining District, 35 km NE of Bucaramanga, in the Eastern Cordillera of Colombia within the Santander Massif.  Mineralization exhibits NE-trending, NW-dipping structural control associated with the right lateral strike-slip La Baja fault. Mineralization at LB is composed of veins networks and tectonic-hydrothermal breccias while LM mineralization is largely contained in hydrothermal breccias with adjacent narrow veining zones. Mineralization is hosted in Proterozoic Bucaramanga (gneiss) Complex and Triassic-Jurassic leucogranites. Hydrothermal alteration and mineralization occur in six stages. An early porphyry-style phase comprises stages 1 and 2. Stage 1 is characterized by propylitic alteration with epidote, chlorite, calcite, specularite veins, minor pyrite and chalcopyrite, probably associated in time with Mo-Cu mineralization (Re/Os on molybdenite ~10 Ma) and porphyritic granodiorites (U/Pb in zircon ~10-8.4 Ma) cropping out in the district. Stage 2 (40Ar/39Ar on muscovite ~3.4 Ma) is characterized by phyllic alteration (muscovite/sericite ? illite, quartz, pyrite) associated with quartz+pyrite veins. Epithermal phase (stages 3-6) is related to multi-phase hydrothermal breccia development and advanced argillic (quartz-alunite) alteration which based on alunite 40Ar/39Ar geochronology took place between ~2.6 and ~1.3 Ma. Stage 3 is characterized by copper sulfide deposition. Stage 4 is characterized by wolframite deposition in veins/breccias. Stage 5 is characterized by enargite deposition. Stage 6 is characterized by minor porous quartz deposition followed by sphalerite with alunite+quartz. Pyrite is common to all these stages. Gold-silver mineralization took place in stages 2-5 associated with sulfides, sulfosalts, tellurides, as electrum and native gold. Hydrothermal events were by followed by near surface supergene alteration and fault reactivation that created intensely fractured/gouge-rich fault zones. At LM, stages 4-5 quartz primary fluid inclusions assemblages indicate boiling and they have homogenization temperatures of ~143-238?C and salinities of 0.5-5.6 wt% NaCl equiv. LM and LB pyrite exhibit light ?34S signatures: -16.9? to ?11.3? at LM and -8.3? and ?6.1? at LB. Alunite ?18O and ?D data indicate that it was precipitated largely from magmatic fluids.      iii  Preface  This research thesis is part of the Colombia Porphyry and Epithermal Gold Project, developed by the Mineral Deposit Research Unit (MDRU) with the initiative of mineral exploration companies, including Ventana Gold Corp. (taken over by AUX Colombia Ltda.) and EcoOro Minerals (former Greystar Resources) working at the California-Vetas Mining District area in Colombia. Researchers for this project in the California-Vetas Mining District area include PhD. Thomas Bissig (Research Associate and Project leader), PhD. Craig Hart (MDRU Director), PhD. Luis C. Mantilla Figueroa (Universidad Industrial de Santander, Geology Department professor) and the author of this thesis. Some analytical work provided in this thesis was conducted by other people, specifically:  ? 40Ar/39Ar geochronology was carried out by analyses by Janet Gabites in the Pacific Center for Isotopic Research (PCIGR) at The University of British Columbia. ? U/Pb geochronology on zircons was carried out by Richard Friedman in the Pacific Center for Isotopic Research (PCIGR) at The University of British Columbia. ? Stable isotope analysis on pyrite and alunite was carried out by April Vuletich and Kristen Feige at Queen?s University. Location maps in Chapter 1 Figure 1.1 are based on Google Earth 2013 information from Colombia.  The conceptual framework of this thesis, presented in Chapter 2 includes figures and tables taken, adapted and/or modified from several publications as referred in the text, including: Corbett and Leach (1998), Corbett (2002), Einaudi et al. (2003), Sillitoe and Hendenquist (2003), Simmons et al. (2005), Sillitoe (2010), Moncada et al. (2012).  Tectonic context related figures presented in Chapter 3 includes Figure 3.1, modified after Restrepo et al. (2011), Cediel et al. (2003), Ward et al. (1973); Royero and Higuera (1999); Wolff et al. (2005); and Figure 3.2, modified after Taboada et al. (2000); Prieto et al. (2012); Vargas and Mann (2013). The geological maps presented in Figures 3.3, 3.4 and 3.17 are based on previous geological maps by Ward et al. (1973), Mendoza and Jaramillo (1979), Polania (1980), Ventana Gold Corp. La Bodega project geological map by A. Bernasconi and geology team (that included the author of this thesis) provided by the company in 2010; collaborations by L. C. Mantilla Figueroa and T. Bissig and the author of this thesis for presented MDRU Colombia Porphyry and Epithermal Gold Project (this study). Maps presented in these figures were edited by Sara Jenkins (MDRU GIS expert) and the author of this thesis. Figure 3.15 summarizes field structural data collected by Parra (2007) and Pratt (2009). Figure 5.19 in Chapter 5 is modified after Einaudi et al. (2003) and adapted in the context of La Bodega and La Mascota deposits. 40Ar/39Ar geochronology results in Chapter 6 and Appendix 3 includes samples collected by T. Bissig (2011). Stable isotopic data includes samples collected by T. Bissig (2011) and one sulfur sample collected by M. Mendoza (2011) for which analytical result was provided by L. C. Mantilla Figueroa (2012). Appendix A3 includes one sample (ALR035) collected by the author for this project. U/Pb geochronoly on zircons results from this sample were presented in Bissig et al. (2012) and published on Mantilla Figueroa et al. (2013). None of the other text, figures, or data in this thesis is taken directly from previously published articles.     iv  Table of Contents   Abstract ................................................................................................................................................ ii Preface ................................................................................................................................................ iii Table of Contents ................................................................................................................................ iv List of Tables ....................................................................................................................................... xi List of Figures ..................................................................................................................................... xii List of Abbreviations ........................................................................................................................... xv Acknowledgements ........................................................................................................................... xvi Dedication ........................................................................................................................................ xviii Chapter 1. Introduction ......................................................................................................................... I 1.1 General location of the study area ............................................................................. I 1.2 Climate and physiography ........................................................................................ 2 1.3 Mining history ........................................................................................................... 3 1.4 Previous studies ....................................................................................................... 4 1.5 Colombia porphyry and epithermal gold project ........................................................ 6 1.6 Project justification and objectives ............................................................................ 6 1.6.1 Specific objectives ............................................................................................. 7 1.7 General methodology ............................................................................................... 8 1.8 Thesis organization .................................................................................................. 9 Chapter 2. Hydrothermal Systems Conceptual Framework: Porphyry Copper and Epithermal Systems ............................................................................................................................................. 11 2.1 Introduction ............................................................................................................ 11 2.2 Porphyry copper systems ....................................................................................... 11 2.2.1 Alteration and mineralization in porphyry copper systems ................................ 15 2.3 Faults and fracture networks and their role in hydrothermal.................................... 18   v  2.4 Sulfidation state ...................................................................................................... 22 2.5 Epithermal systems (high-sulfidation and low-sulfidation). ...................................... 24 2.5.1 High-sulfidation deposits .................................................................................. 29 2.5.2 Low-sulfidation deposits ................................................................................... 31 2.5.3 Summary of genetic factors related to epithermal deposits .............................. 34 Chapter 3. Tectonic, Geological and Structural Context of The California-Vetas Mining District and The La Bodega - La Mascota Gold Deposits .................................................................................... 36 3.1 Tectonic setting and location of the California-Vetas Mining district ........................ 36 3.2 Lithology of the California Vetas Mining District and its expression within La Bodega - La Mascota deposits. ................................................................................................. 42 3.2.1 Bucaramanga (Gneiss) Complex ..................................................................... 46 3.2.2 Santander Plutonic Group (Late Triassic to Early Jurassic) .............................. 50 3.2.3 Sedimentary rocks (Late Cretaceous) .............................................................. 55 3.2.4 Porphyritic bodies and related rocks (Late Miocene) ........................................ 56 3.2.5 Hydrothermal breccias (Plio-Pleistoscene) ....................................................... 58 3.3 Structural context ................................................................................................... 64 3.3.1 Main regional structures ................................................................................... 64 3.3.2 Main structures within La Bodega ? La Mascota .............................................. 66 3.4 Structural relationships, hydrothermal breccias and mineralization ......................... 70 Chapter 4. Alteration at La Bodega and La Mascota: Characteristics, Mineral Assemblages and Distribution ......................................................................................................................................... 72 4.1 Introduction ............................................................................................................ 72 4.2 Methods of identification of alteration minerals ....................................................... 72 4.3 Alteration minerals assemblage and zonation at La Bodega and La Mascota ........ 73   vi  4.3.1 Propylitic alteration: chlorite and chlorite-epidote alteration zones characteristic minerals .................................................................................................................... 77 4.3.2 Phyllic alteration: muscovite and Illite alteration zones ..................................... 81 4.3.3 Advanced argillic alteration: alunite-quartz alteration, kaolinite-alunite alteration, silicification and related textures ............................................................................... 85 4.4 Discussion of alteration assemblages ..................................................................... 93 Chapter 5. Ore Mineralogy, Mineralization Styles and Paragenetic Evolution at La Bodega and La Mascota ............................................................................................................................................. 96 5.1 Introduction ............................................................................................................ 96 5.2 Methodology ........................................................................................................... 97 5.3 Mineralization stages, veins and ore related mineral distribution at La Bodega and La Mascota .................................................................................................................. 99 5.3.1 Stage 1: pre-mineralization, specularite bearing veins ................................... 101 5.3.2 Stage 2: early mineralization, pyrite ? quartz veins ........................................ 103 5.3.3 Stage 3: mineralization stage, copper sulfide bearing structures .................... 105 5.3.4 Stage 4: mineralization stage, wolframite bearing veins and breccias ............ 113 5.3.5 Stage 5: late mineralization, enargite bearing veins ....................................... 116 5.3.6 Stage 6: Post- mineralization stage, sphalerite bearing structures ................. 120 5.3.7 Stage 7: supergene features related to mineralization, late faulting and iron oxides bearing structures. ....................................................................................... 124 5.4 Mineral zonation and gold grade distribution at La Bodega and La Mascota ........ 126 5.5 Paragenetic sequence of events at La Bodega and La Mascota .......................... 131 Chapter 6. Geochronological Constraints of Alteration and Mineralization Events at La Mascota and La Bodega ....................................................................................................................................... 136   vii  6.1 Introduction .......................................................................................................... 136 6.2 Methodology ......................................................................................................... 138 6.2.1 Sample collection ........................................................................................... 139 6.2.2 Analytical procedures ..................................................................................... 140 6.3 Results ................................................................................................................. 143 6.4 Alunite and muscovite alteration geochronology, relationship to the CVMD geological history and paragenetic sequence of mineralizing events at La Bodega and La Mascota ................................................................................................................................... 147 Chapter 7. Fluid Inclusion Microthermometry from Epithermal Quartz at La Bodega and La Mascota ......................................................................................................................................................... 150 7.1 Introduction .......................................................................................................... 150 7.2 Previous fluid inclusion studies in the California-Vetas Mining District .................. 151 7.3 Methodology ......................................................................................................... 153 7.3.1 Sample preparation, equipment configuration and data collection .................. 153 7.3.2 Salinity, pressure and depth calculation procedures ...................................... 155 7.4 Petrography of fluid Inclusions in this study .......................................................... 156 7.4.1. La Mascota sample petrography and fluid inclusion petrography summary ... 157 7.4.2 La Bodega sample petrography and fluid inclusion petrography summary ..... 162 7.5 Microthermometry results ..................................................................................... 165 7.5.1 La Mascota, sample ALR189 ......................................................................... 167 7.5.2 La Bodega, sample ALR260F ........................................................................ 168 7.6 Discussion ............................................................................................................ 170 7.6.1 Enargite related quartz fluid inclusions at La Mascota (ALR189) .................... 170   viii  7.6.2 Wolframite related quartz fluid inclusions at La Mascota (ALR189) ................ 170 7.6.3 La Bodega, enargite quartz related fluid inclusions (ALR260) ........................ 172 7.6.4 Implication of fluid inclusions microthermometry results and boiling ............... 173 7.6.5. Estimation of depth of emplacement based on primary fluid inclusion analysis ............................................................................................................................... 174 7.6.6 Comparison to other fluid inclusion studies within the California Vetas Mining District and hydrothermal environment implications ................................................ 176 Chapter 8. Origin of Mineralizing Fluids at La Bodega and La Mascota: Insights from Oxygen, Deuterium and Sulfur Stable Isotopes ............................................................................................ 180 8.1 Introduction .......................................................................................................... 180 8.2 Methodology ......................................................................................................... 184 8.2.1 Sample selection and separation ....................................................................... 184 8.2.2 Analytical methods ......................................................................................... 186 8.3 Results ................................................................................................................. 188 8.3.1 Pyrite sulfur isotopes ...................................................................................... 188 8.3.2 Alunite sulfur isotopes .................................................................................... 193 8.3.3 Geothermometry using the ?34S between alunite ? pyrite pairs ...................... 193 8.3.4 ?D and ?18O isotopes. .................................................................................... 195 8.4 Discussion ............................................................................................................ 197 8.4.1 Pyrite ?34S signatures .................................................................................... 197 8.4.2 ?34S of alunite ? pyrite pairs and geothermometry constraints at La Bodega, La Mascota  and La Plata ............................................................................................ 200 8.4.3 Origin of the hydrothermal mineralizing fluids ................................................. 200   ix  Chapter 9. Evolution of La Bodega and La Mascota Deposits: A Discussion and Comparison to Other Epithermal Deposits .............................................................................................................. 202 9.1 Late Miocene history ............................................................................................ 202 9.2 Porphyry phases at La Bodega and La Mascota: early stages 1 and 2 in the context of the CVMD............................................................................................................... 203 Stage 1 ................................................................................................................... 203 Stage 2 ................................................................................................................... 205 9.3 Epithermal phase: stages 3, 4, 5 and 6. ............................................................... 207 Stage 3 ................................................................................................................... 207 Stage 4 ................................................................................................................... 208 Stage 5 ................................................................................................................... 209 Stage 6 ................................................................................................................... 210 9.4 Oxidation state of the hydrothermal and mineralizing fluids. ................................. 213 9.5 Depth of emplacement of the mineralization and surface processes. ................... 214 9.6 Summary of mineralization characteristics at La Bodega/La Mascota and comparison to other similar epithermal and porphyry systems ................................... 218 Chapter 10. Conclusions, Exploration Implications and Recommendations for Future Work ........ 222 10.1 Conclusions ........................................................................................................ 222 10.2 Exploration implications ...................................................................................... 224 10.3 Recommendations ............................................................................................. 225 References ...................................................................................................................................... 227 Appendix A1. Drill Hole Locations. .................................................................................................. 241 Appendix A2. Sample Location within Drill Holes, Brief Descriptions, Notes and Analysis Carried out ......................................................................................................................................................... 243 Appendix A3. Gold Relationships to element concentrations at La Bodega and La Mascota. ....... 271 Appendix A4. Alteration Minerals Identification Methods at La Bodega - La Mascota Deposits. ... 278   x  Apppendix A5. Sulfides and Paragenetic Sequence Related Support Data. X-Ray Difraction Analysis on Selected Samples and Energy Dispersion X-Ray Spectrum of Seleced Samples. .... 296 Appendix A6. Geochronological Data for Samples Presented in Chapter 6. La Bodega, La Mascota, El Cuatro. ......................................................................................................................................... 302 Appendix A7. Fluid Inclusion Study Microthermometry and Data. .................................................. 318 Appendix A8. Thin Section Petrography of Selected Samples from La Bodega, La Mascota and El Cuatro .............................................................................................................................................. 326      xi  List of Tables  Chapter 2 Table 2.1. Characteristics of Principal Alteration-Mineralization Types in Porphyry Cu Systems? (from Sillitoe, 2010) ........................................................................................................................... 17 Table 2.2. Features of principal Hydrothermal Breccia Types in Porphyry Cu Systems (Sillitoe, 2010) ................................................................................................................................................. 21 Table 2.3. Examples of buffer reactions and association to sulfidation state or environment (after Einaudi et al. 2003) ........................................................................................................................... 22 Table 2.4. Summary of Hydrothermal Alteration Assemblages Forming in Epithermal Environments (Simmons et al., 2005) ...................................................................................................................... 26 Table 2.5. Principal field-oriented characteristics of epithermal types and subtypes (from Sillitoe and Hedenquist, 2003) ............................................................................................................................. 28  Chapter 4 Table 4.1. Comparison and correspondence of alteration assemblages at La Bodega and La Mascota to alteration assemblages described for epithermal environment by Simmons et al. (2005) and for porphyry environment according to Sillitoe (2010). .............................................................. 76  Chapter 5 Table 5.1. Summary of ore related minerals observed at La Bodega and La Mascota (this study except where indicated) and their relationship to alteration zones defined in Chapter 4 and mode of occurrence. ...................................................................................................................................... 100 Table 5.2 Correlation matrix for sixteen elements at La Bodega (DDH LB251 and LB327) and La Mascota (DDH LB 202 and LB205). ................................................................................................ 128  Chapter 6 Table 6.1. Summary of results of 40ArK/39Ar geochronology at La Bodega, La Mascota and El Cuatro. ............................................................................................................................................. 144  Chapter 7 Table 7.1. Fluid inclusions characterization and associated codes. ............................................... 156  Table 7.2 Summary of results from 62 fluid inclusions microthermometry analysis at La Mascota and La Bodega grouped based on common characteristics, mainly location within quartz crystal. 166  Chapter 8 Table 8.1. Natural abundance and reference standards for light stable isotopes (Adapted from Hoefs, 1997 in Campbel and Larson 1998) .................................................................................... 180 Table 8.2. Stable Isotope terminology (Campbel and Larson, 1998) .............................................. 181 Table 8.3. Stable isotope results of ?34S, ???O and ?D (?) in the California-Vetas Mining district . 189     xii  List of Figures Chapter 1 Figure 1.1. Geographic location and physiography of the project area.. ............................................ 2  Chapter 2  Figure 2.1. Worldwide locations of porphyry Cu systems cited as examples of features discussed in the text along with five additional giant examples. ............................................................................ 12 Figure 2.2. Telescoped porphyry Cu system (after Sillitoe, 2010). ................................................... 14 Figure 2.3. Common alteration mineralogy in hydrothermal systems in their relative pH and temperature stability range (after Corbett and Leach, 1998) ............................................................ 16 Figure 2.4. Dilational structures. A. Dilational veins and related structures. B. Extension mineralization styles at different crustal levels (after Corbett and Leach, 1998). ............................. 20 Figure 2.5. Log fS2 ? 1000/T diagram, contoured for Rs, illustrating fluid environments in porphyry copper, porphyry copper related base-metal veins, and epithermal Au-Ag deposits in terms of a series of possible cooling paths (from Einaudi et al., 2003). ............................................................. 23 Figure 2.6. Location of epithermal deposits in the world (modified after Simmons et al., 2005).. .... 25 Figure 2.7. Low Sulfidation and High sulfidation model and related ore textures examples. (Adapted and modified after Corbett, 2002)...................................................................................................... 27 Figure 2.8. Summary of the various silica and calcite textures observed in the epithermal environment (from Moncada et al., 2012) ......................................................................................... 33  Chapter 3  Figure 3.1 (next page). Location of California-Vetas Mining District (CVMD) within Colombia, South America; in relation to the Chibcha Terrane (Ch) (Restrepo et al., 2011) and the Maracaibo Subplate Realm triangular tectonic block (MSP) (Cediel et al., 2003). The map shows the major fault systems that divide these tectonic blocks and terranes.. .......................................................... 38 Figure 3.2 Schematic 3D model based on seismic tomography showing Bucaramanga seismic nest and relationship to interaction between the Caribbean, Nazca and South American Plates (Modified after Taboada et al., 2000; Prieto et al., 2012; Vargas and Mann, 2013) ......................................... 41 Figure 3.3 California-Vetas Mining District Geological Map. (After Polania 1980, Evans, 1976, Ward, 1973; Mantilla et al., 2012, MDRU Colombia Gold Project). ............................................................. 43 Figure 3.4. La Mascota and La Bodega area geological map showing location for geological drill holes that were sampled and studied geological sections ................................................................ 44 Figure 3.5. N-S geological cross-section B-B? at La Bodega, looking west ...................................... 45 Figure 3.6. N-S geological cross section M-M? at La Mascota, looking west. ................................... 46 Figure 3.7. Examples of the Bucaramanga Complex at La Bodega and La Mascota.. .................... 49 Figure 3.8. Jurassic intrusive rocks (leucogranites) from La Mascota and La Bodega.. .................. 52 Figure 3.9. Pegmatite rocks at La Bodega. ....................................................................................... 54 Figure 3.10. Late Cretaceous rocks (Tambor Formation). Outcrop to the west of California town. . 55 Figure 3.11 Miocene porphyritic granidiorites at the CVMD. ............................................................ 57 Figure 3.12. La Bodega typical hydrothermal breccias.. ................................................................... 60 Figure 3.13. Breccia types at La Mascota based on physical components and arrange. ................. 62 Figure 3.14. Tectonic-hydrothermal breccia (THBX) at different scales. .......................................... 63 Figure 3.15. Structural data representing main trends within La Bodega and La Mascota. ............. 68 Figure 3.16. Common examples of fractured rocks and faults and fault breccias filled with gouge at La Bodega and La Mascota. ............................................................................................................. 69 Figure 3.17. Geological map of the California Vetas Mining district showing prospective areas for the development of dilational structures along La Baja Trend (yellow ovals) where mining takes place. ................................................................................................................................................. 71    xiii  Chapter 4  Figure 4.1. B-B? North - South geological section looking west. Alteration at La Bodega. Relationship to protholith and gold (Au) mineralization. .................................................................... 74 Figure 4.2. M-M? North - South geological section looking west. Alteration at La Mascota. Relationship to protholith and gold (Au) mineralization. .................................................................... 74 Figure 4.3. Chlorite and chlorite-epidote alteration assemblages developed in amphibolite lenses at La Bodega.. ....................................................................................................................................... 79 Figure 4.4. Chlorite and chlorite-epidote alteration mineral assemblages, examples from La Mascota. ............................................................................................................................................ 80 Figure 4.5. Muscovite (sericite) and illite alteration assemblages at La Bodega. ............................. 83 Figure 4.6. Muscovite (sericite) and illite alteration assemblages at La Mascota ............................. 84 Figure 4.7. Alunite, occurrence at La Bodega related to quartz (silicification) and kaolinite. ........... 87 Figure 4.8. Alunite occurrence related to quartz and kaolinite alteration at La Mascota.. ................ 88 Figure 4.9. Macroscopic textures related to silicification-advanced argillic alteration and hydrothermal breccias at La Mascota and La Bodega. ..................................................................... 91 Figure 4.10. Microphotographs of main textures related to La Mascota Hydrothermal Breccias ..... 92  Chapter 5  Figure 5.1. Specularite veins and related minerals related to stage 1 at La Bodega and La Mascota. ......................................................................................................................................................... 102 Figure 5.2. Quartz + pyrite veins at La Bodega and La Mascota, stage 2. ..................................... 104 Figure 5.3. La Bodega. Copper sulfides bearing veins and associated alteration.. ........................ 106 Figure 5.4. La Mascota, copper sulfides and gold, stage 3. Figure 5.5. Relationship of copper sulfides, pyrite and silver sulfosalts in stage 3 ......................... 109 Figure 5.6 Gold (electrum) bearing quartz vein with minor sphalerite and chalcopyrite cross cutting quartz + cubic pyrite + hematite vein in muscovite alteration zone. ................................................ 111 Figure 5.7. Molybdenite occurrence at La Bodega and La Mascota (pre-stage 2? and early stage 3?). .................................................................................................................................................. 112 Figure 5.8. Hydrothermal breccia with quartz cement exhibiting tectonic foliation (THBX) at La Bodega. ........................................................................................................................................... 114 Figure 5.9. Wolframite (h?bnerite) occurrence at La Mascota.. ...................................................... 115 Figure 5.10. Enargite occurrence at La Bodega. ............................................................................ 117 Figure 5.11. Enargite at La Mascota. .............................................................................................. 118 Figure 5.12. Tennantite-tetrahedrite at La Mascota in relation to stages 4 and 5 and associated silver mineralization.. ....................................................................................................................... 119 Figure 5.13. Sphalerite and marcasite at La Bodega. ..................................................................... 122 Figure 5.14. Sphalerite, marcasite and sulfur at La Mascota. ......................................................... 123 Figure 5.15. Supergene alteration minerals at La Bodega and La Mascota. .................................. 125 Figure 5.16. N-S Section B-B?, looking west. Mineralization style at La Bodega based on predominant ore mineral association. ............................................................................................. 129 Figure 5.17. N-S Section M-M? looking west. Mineralization style at La Mascota based on predominant ore mineral association. ............................................................................................. 130 Figure 5.18. Paragenetic sequence for La Bodega and La Mascota. ............................................. 132 Figure 5.19. Log f S2 ? 1000/T diagram, showing sulfidation state of magmas and mineral sulfidation reactions at 1 bar (Einaudi and Hedenquist, 2003). In blue, it is represented the range of minerals within La Bodega and La Mascota deposits paragenetic sequence and the evolution path of the hydrothermal fluids is schematically shown .................................................................................... 135  Chapter 6  Figure 6.1 Recent geochronological data shown on the geological map of the California Vetas district. Map based on this study and MDRU Colombia Porphyry and Epithermal Gold Project.. .. 141 Figure 6.2 Samples selected for 40ArK/39Ar geochronology ............................................................ 142   xiv  Figure 6.3. Alunite and muscovite (sericite) 40ArK/39Ar age spectra at La Macota, La Bodega and El Cuatro.. ............................................................................................................................................ 146 Figure 6.4. 40ArK/39Ar geochronology ages on alunite and muscovite within La Bodega and La Mascota in relation to the stages of paragenetic sequence of hydrothermal events at La Mascota and La Bodega; hydrothermal events at La Perezosa and El Cuatro and magmatic events at the CVMD. ............................................................................................................................................. 149  Chapter 7  Figure 7.1. La Mascota, sample ALR189; DDH LB 202 at 203.m; approximate depth from surface: 100 m (Figure 3.6). Polymictic clast to cement supported multiple phases hydrothermal breccia. 158 Figure 7.2. La Mascota, ALR189F. FIs in enargite related quartz. ................................................. 160 Figure 7.3. La Mascota, ALR189F. FIs in wolframite related quartz. .............................................. 161 Figure 7.4. La Bodega, ALR260F. Fluid inclusions in enargite related quartz.. .............................. 164 Figure 7.5. Fluid inclusion data compiled for La Mascota and La Bodega in enargite related quartz and wolframite related quartz within this study. Total of 62 measurements. .................................. 169 Figure 7.6. Fluid inclusion trends from fluid inclusion data. Salinity vs Homogenization temperature. ......................................................................................................................................................... 171 Figure 7.7. Depth of emplacement estimate based on fluid inclusion microthermometry of hydrothermal quartz at La Mascota from sample ALR189. ............................................................. 177 Figure 7.8. Salinity (wt%NaCl equiv.) vs Homogenization temperature of FIs in quartz from different paragenetic stages with California-Vetas Mining district ................................................................. 179  Chapter 8  Figure 8.1. Selected samples for isotopic analysis from La Bodega and La Mascota.. .................. 185 Figure 8.2 ?34S values obtained at the California-Vetas Mining District compared to classic deposits types around the world including several high sulfidation deposits ................................................ 191 Figure 8.3. ?34S values obtained at the California-Vetas Mining District compared to the sample ages obtained by 40Ar/39Ar geochronology on alunite related to pyrite and the presumable age based on mineralization stages. ...................................................................................................... 192 Figure 8.4. ?34Salunite vs. ?34Spyrite plot showing data from La Mascota, La Bodega and La Plata from different paragenetic stages (colored markers). ..................................................................... 196 Figure 8.5. ?D vs ?18O plot (reported relative to VSMOW). ?18O from alunite (SO4) isotopic compositions is calculated in equilibrium with hydrothermal fluids at a temperature of 251 ?C. .... 197  Chapter 9  Figure 9.1. Schematic block diagram of the CVMD at La Baja Trend, at ~10 Ma-8 Ma over current surface. Late Miocene rocks (porphyry dikes, breccia, tuff (?) volcanic rocks) and probable volcano at Cerro Violetal are indicated. An inferred mid crustal magma chamber from which porphyries, volatiles and metals are derived is indicated. Geology adapted from (Ward et al., 1973; Mendoza and Jaramillo, 1973; Polania, 1980; Galvis, 1998; Felder et al., 2005; Bernasconi et al., 2010; MDRU Epithermal and Porphyry Gold Project, 2013).. ................................................................... 204 Figure 9.2. Schematic block diagram of the CVMD at La Baja Trend showing distribution of alteration and mineralization developed during the Pliocene (~4-3.25 Ma). ................................... 206 Figure 9.3. Schematic block diagram of the CVMD at La Baja Trend showing distribution of alteration and mineralization developed during the Pliocene-Pleistocene (~2.5-<2.2 Ma).. ........... 210 Figure 9.4. Schematic block diagram of the CVMD at La Baja Trend showing distribution of alteration and mineralization developed during the Pliocene-Pleistocene (~1.9-<1.27 Ma).. ......... 212 Figure 9.5. Cartoon showing profile along La Baja Trend from Angostura (NE) to California town (SW).. .............................................................................................................................................. 217 Figure 9.6. General hydrothermal alteration/mineralization associations in relation to relative temperature and pH indicating the evolution of the hydrothermal fluids from higher pH higher temperature to lower pH and lower temperature associations. ....................................................... 221    xv  List of AbbreviationsMineral Abbreviation alunite alu amphibole amf biotite bt bornite bn calcite ca chalcocite cc chalcopyrite cpy chlorite chl covellite cv electrum elc enargite en epidote ep feldspar fd galena gln Gold Au hornblende hb h?bnerite h?b illite ill kaolinite kao leucoxene lcx magnetite mgt montmorillonite mnt muscovite mus natroalunite nal orthoclase ocl plagioclase plg proustite prt pyrite py quartz qz rutile rt sericite ser silica  sil Silver Ag specularite spc sphalerite sph telluride tel tennantite tn tetrahedrite th titanite (sphene) ttn undefined carbonate cb Mineral Abbreviation wolframite w wurtzite wrt zircon zr  Geographic locations Abbreviation La Bodega LB La Mascota LM El Cuatro EC Angostura LA La Plata LP California Vetas Mining District CVMD Santander Massif SM  Name Abbreviation plane polarized light PPL cross polarized light XPL reflected light RL short wave infrared reflectance SWIR X-ray difraction XRD Alteration alt Silicification Sil Vein vn Veinlets vnlts Fluid inclusion FI Fluid inclusions FIs Temperature Temp Homogenization temperature Th Ice melting temperature Tm ice Pressure P Breccia BX Hydrothermal Hy Hydrothermal breccia HYBX Tectono-hydrothermal breccia THBX scanning electron microscope SEM density d   xvi  Acknowledgements  The author of this thesis wishes to thank to all the people that made this project possible through their valuable contributions, guidance, comments, help an trust. Thanks to my supervisors from the Mineral Deposit Research Unit MDRU at The University of British Columbia PhD Thomas Bissig (Research Associate) and PhD Craig Hart (Director) for giving me the opportunity to take this learning and enriching journey, the continuous guidance, attention, patience and timely  response of comments. Thanks to the members of the committee including PhD Kenneth Hickey and reviewer PhD. Roger Beckie for their interesting comments. Thanks to PhD Luis Carlos Mantilla, professor of the Universidad Industrial de Santander; for his lessons and valuable ideas regarding the magmatic evolution of the California-Vetas Mining District. Thanks to the sponsors of the Colombia Porphyry and Epithermal Gold Project who provided their continuous support in order to bring out this project including: Ventana Gold Corp and AUX Colombia Ltd., EcoOro Minerals (former Greystar Resources), Anglogold Ashanti, Anglo American, Sunward Resources, Teck Resources, Barrick Gold. Special thanks to the initial sponsors of the project, Ventana Gold Corp.; in particular to Mr. J. H. Lehmann, former VP exploration of Ventana Gold Corp. who first approached the MDRU with the interest of developing a research project at La Bodega, whom I owe his trust in starting and completing this research; to Mr. Richard Warke, founder and Chairman of Ventana Gold Corp. for supporting research; to Mrs. Stella Frias, former Ventana Gold Corp. administration and community relations manager at Ventana Gold Corp, who not only provided great support prior to and during sampling seasons in Colombia but continued to support research interest from the company side in other mining related fields as well and who has been great personal support for my carreer. Thanks to PhD Alfredo Bernasconi for all his support, lessons, comments prior initiation of the project and for being a mentor to a whole generation of exploration geologists in the study area, including me. Thanks to all the geology team from Ventana Gold Corp - CVS Explorations Ltda. in 2010 who provided support and valuable observations during sampling seasons and after AUX Colombia Ltd. take over Ventana Gold Corp.; especially to my friend and collegue the geologist Olivia Gonz?lez Morales who was the greatest support on the field and continued to act as a communication channel to AUX Colombia Ltd after field season. Thanks to Martin Rueda for the collaboration providing allowed company information for project development. Thanks to Cristian Toloza for the logistics at California town as well as Eng. Fabio Maldonado for providing environmental information about the area.   xvii  Special thanks as well to AUX Colombia Ltd., in particular to Mr. Cesar Torresini, who continued to support the thesis by providing logistics during second sampling season and necessary economic support after the taking over Ventana Gold Corp.; thanks to the geologists Ms. Margareth Guerrero and Mr. Martin Balcucho for providing necessary company information and base drill hole sections; thanks to field geologists of the company who provided important comments including Mr. Sergio Gomez, Reynaldo Arenas, Mr. Guillermo ?vila, Henry Ochoa, Wilder Coronado and Mr. Pedro Herrera. Thanks to all the people at AUX who provided support during sampling season and the people in Bucaramanga who provided logistic support including Diego J?come, Eduardo Mayorga, Juan Fuentes, Claudia Rodriguez, Grettel Tovar, among many others. Thanks to the Society of Economic Geologists SEG which provided economic support for analysis through the awards by the Alberto Terrones Fund in 2011 and by the Canada Foundation Fund in 2012. Thanks to MDRU team especially to the research associates who provided comments of great value for the development of this thesis including PhD. Murray Alan, PhD Farhad Bouzari, PhD Melissa Gregory; PhD Abraham Escalante and GIS expert Sara Jenkins. Thanks to MDRU and EOAS graduate students and friends who provided great support during this journey including: Jaime Poblete, Abdul Razique, Tatiana Alva, Esther Bordet, Brendan Scorrar, Alexandra Kushnir, Lindsay McClenaghan, Leif Bailey, Ayesha Ahmed and Shawn Hood, Jessica Norris, Trent Newkirk, Peter McDonald, Sergio Gamonal, Britt Bluemel, Brian McNulty, Mike Tucker, Ben Hames, Erin Looby, Leanne Smar, Jack Milton, Betsy Friedlander. Very special thanks to my great friend and collegue MSc. Santiago Vaca.  Thanks to all researchers at EOAS who provided support for analysis including Jenny Lai, Elizabetta Panni, Edith and professor PhD. Mati Raudsepp at the X-ray difraction and SEM laboratories; Janet Gabites for high quality geochronology, Richard Friedman for doing the impossible to get the zircons from a difficult sample. Thanks to April Vuletich and Kristen Feige at Queen?s University for their stable isotope analyses. Thanks to all people at UBC and MDRU who have provided logistics support, including Manji, Karie Smith, Fanny Yip, Curtis Marr, Teresa Woodley, Carie Thompson, Michael Herwaman, Audrey Van Slyck, Pablo Stolowics, Karim, and Sukhi. Thanks to all the friends in Vancouver and overseas who have been great support in this proccess. Thanks to all my friends and the great people in the California town, including the miners who showed me around that beautiful land. Last but not least, I am the most grateful to my family for their continuous support and patience during the completion of these studies: thanks to my girlfriend/geologist consultant/assistant/all Monika Mendoza, my son Samuel, my parents and my sister, as well as my parents in law.    xviii  Dedication      To Monika &Samuel A mis padres & hermana A mis Abuelos   I  Chapter 1. Introduction  1.1 General location of the study area La Bodega and La Mascota gold deposits are located within the California-Vetas Mining District (CVMD), ~35-55 km from the city of Bucaramanga, capital of the Santander Department, and ~450 km from Bogota, capital city of the Republic of Colombia (Figure 1.1). The district is named after the two main towns in the area where mining has been an important economic activity for centuries: California, to the west, and Vetas, to the east (Figure 1.1). In the California area, most mining activities have been developed in several locations along La Baja Trend (Figure 1.1, 3.3), a NE-SW strike-slip fault paralleliing La Baja River. These mining locations include, among others, from SW to NE: La Plata, San Celestino and Pie de Gallo, El Cuatro, La Mascota, La Bodega, La Perezosa and Los Laches, these latter two forming part of the Angostura deposit (Figure 1.1). The La Bodega and La Mascota deposits have combined NI-43-101 compliant inferred resources of 3.47 Moz Au, 19.2 Moz Ag and 84.4 Mlbs Cu at 2 g/t Au cut off (Altmann et al., 2010). The adjacent deposit, Angostura, has a NI 43-101 inferred resource estimate of 2.16 Moz of Au and 11.18 Moz of Ag at 1.5 g/t cut off (Godoy et al., 2012).   2    Figure 1.1. Geographic location and physiography of the project area. A. Location of the California Vetas Mining district (CVMD) in relation to Bucaramanga and Bogota cities within Colombia (South America). B. Location of the CVMD showing location of California and Vetas towns, the district (white square) and La Baja river valley (red square). C Oblique view of the La Baja trend deposits showing California town, Cerro Violetal and La Bodega ? La Mascota deposits among others. A, B and C images are modified from Google Earth (2013). D. Locations of La Baja Trend deposits, including La Mascota-La Bodega deposits (Photography looking NE taken from the S side of Vetas River, south of California town; courtesy of O. Gonz?lez Morales, 2007).  1.2 Climate and physiography The CVMD is characterized by steep terrain and peaks reaching elevations up to ~3800 m.a.s.l. (Figure 1.1). A variety of high mountain tropical environments are   3  found in the area: in general Andean forest and high Andean forest vegetation from 2400-3200 m.a.s.l. with mean temperatures between 18 and 12 ?C and paramo environment in the highest zones >3200 m.a.s.l. with annual mean temperatures between 12 and 6 ?C (P?ez et al., 2007). Two rainy seasons (March ? May and September - November) separated by dry seasons (December-February and June-August) characterize the climate in the area. Total precipitation is between 900 and 1600 mm per year (P?ez et al., 2007). 1.3 Mining history Mining activity in the California-Vetas mining district dates back to Pre-Columbian time, but was taken over in the 1600?s, by the Spanish (Ward et al., 1973, Mendoza and Jaramillo, 1979). English and French companies continued to carry out gold exploitation during the 1800?s and the early 1900?s (Reeves, 2006). Mining in the past century was mainly done by local artisanal miners and small local mining companies selectively extracting ore from gold rich veins in underground operations (Mendoza and Jaramillo, 1979). Gold recovery methods include comminution techniques that mostly imply stamp milling and ball milling grinding; gravimetric gold separation (vibrating tables, jigs and channels), amalgamation and cyanide leaching (P?ez et al., 2007). Small exploration programs were run by Anaconda Copper (late 1940?s) and Nippon Mining Co (1960?s) but the companies did not carry on with exploration, mainly due to low core recovery (Reeves, 2006). Exploration programs started again in late 1990?s with Greystar Resources Inc. (known today as Eco Oro Minerals) in the Angostura project and intensified 2000?s. Ventana Gold Corp. (and   4  its subsidiary CVS Explorations Ltda.) started exploration in 2006 on the La Bodega Concession which includes both the La Bodega and La Mascota deposits, at that time property of Sociedad Minera La Bodega. Exploration in areas adjacent to Angostura and La Bodega within the CVMD was followed by several Canadian mining exploration companies, including Galway Resources and Calvista Resources, Barracuda gold, Leyhat Colombia among others. In early 2011, AUX Colombia Limited acquired Ventana Gold Corp. and the right to its concessions within the district and continued intense exploration programs. AUX acquired the properties adjacent to the SW from La Bodega from Calvista and Galway Resources in 2012. 1.4 Previous studies Geological mapping by the Servicio Geol?gico Colombiano (formerly known as Ingeominas) in the area has been carried on since the 1970?s including the geological map of the areas H-12 and H-13 (Santander and Norte de Santander Departments) at a 1:100000 scale by Ward et al (1973). Petrography, active sediment geochemical and rock and veins geochemical studies were also carried out (Mendoza and Jaramillo, 1979). The report that accompanies the gelogical map of Santander compiles information associated with the mineralization in the including the California Vetas Mining District (Royero and Clavijo, 2001). Characterization of the uranium mineralization at San Celestino and a geological map was developed by Polania (1980, 1983). Previously published geochronology for the area includes: K-Ar geochronology on sericite (by Nippon Mining Co., 1962 in Mendoza and Jaramillo, 1973) which has been mentioned in descriptions of the   5  northern Andean epithermal and porphyry style mineralization belts Sillitoe (1983, 2008); Re-Os on pyrite concentrate from La Bodega (Mathur, 2003). These studies present a late Cretacic to Paleocene age for mineralization. U-Pb geochronology unveiled the presence of granodiorite porphyries of only 10.9-8.4 Ma which are related to porphyry style mineralization at El Cuatro (see Figure 1.1 for location) and La Plata (Mantilla et al., 2009, 2012, 2013; Leal-Mej?a, 2011; Bissig et al., 2012) as confirmed by molybdenite Re/Os ages of 10.14 ? 0.02 Ma for El Cuatro. Reports associated with the exploration and mineralization in the area includes company internal reports (for Ventana Gold Corp.-CVS Explorations: Bernasconi, 2006; Di Prisco, 2009, 2010; Pratt, 2009, 2010; Hedenquist, 2010 among others) and the NI 43-101 reports of the companies exploring in the area (Thalenhorst, 2004; Burns, 2005; Reeves, 2006, O?Prey, 2008; Altman et al., 2011; Godoy, 2013, among others). Undergraduate research thesis studies done in collaboration with the exploration companies and the Universidad Industrial de Santander, Bucaramanga, Colombia include the petrography of gold copper bearing veins from Angostura (Diaz and Guerrero, 2006); petrography of ore minerals at La Mascota (Forero, 2010), petrography of quartz textures at La Mascota (Mendoza, 2011) among others. Studies in collaboration with the Universidad de Caldas include the faults and fracture network mapping at La Bodega (Parra, 2007). All these studies provided valuable information on the complex geology and hydrothermal history of California-Vetas Mining District. Ages of mineralization, paragenetic evolution origin and nature of the mineralizing fluids remained unclear, prior to this project.   6  1.5 Colombia porphyry and epithermal gold project In 2010 Ventana Gold Corp., under the initiative of VP exploration J. H. Lehmann, approached the Mineral Research Deposit Unit of the University of British Columbia to develop a research project to address the limitations in the understanding of the geology and hydrothermal evolution La Bodega and La Mascota area. Greystar Resources (Eco Oro Minerals) followed this initiative in order to better understand the hydrothermal alteration and mineralization of the CVMD. The project also includes the collaboration with the Escuela de Geolog?a of the Universidad Industrial de Santander, specifically L.C. Mantilla F. who spent a sabbatical year at MDRU. CVS Explorations Ltd., with her legal representative Blanca Stella Frias, and Geology department team, provided continued logistic support in Colombia until April 2011. AUX Colombia Ltd., through the collaboration of C. Torresini, after their take over on Ventana Gold Corp., continued to support this research logistically and economically. After initiation of the research at CVMD the Colombia Gold and Porphyry project expanded to include the Middle Cauca Belt (Central Cordillera) with the support from Teck Resources Ltd., Barrick Gold, AngloGold Ashanti, Anglo American and Sunward in addition to AUX and Eco Oro Minerals. 1.6 Project justification and objectives This project was built based on the necessity to explain unusual and ambiguous geological characteristics found in these deposits during geological mapping and mining exploration carried out at La Bodega and La Mascota gold deposits between 2006 and 2010 as well as the previous geological studies within the area.   7  The most important observations and characteristics recognized at La Bodega and La Mascota gold deposits that justify this project include: ? Porphyry and epithermal style mineralization were observed but their relationships were not clear. Epithermal style mineralization show sulfide assemblages mostly similar to high-sulfidation systems (Forero, 2010), however, quartz textures observed in the hydrothermal breccias at La Mascota (Mendoza, 2011) resemble low-sulfidation environments. ? Neither volvanic rocks nor an evident magmatic source were clearly observed in the district, which made it and unusual geological setting for deposits located within the Andes. ? Ambiguous age contraints prior to the initiation of this research only allowed stating that mineralization was of post-Cretaceous age. ? Important resources over 10 Moz of Au within La Baja Trend at the California Vetas Mining District, including resources at La Bodega - La Mascota deposits made this an important area to study in order to unravel its geological, hydrothermal and mineralization history. 1.6.1 Specific objectives The thesis presented here aims to determine the hydrothermal evolution and to improve geological knowledge in the area by: ? Describing comprehensively the geology, alteration and mineralization of La Bodega and La Mascota.   8  ? Defining the paragenetic sequence for the mineralization events, making a comparison between the two deposits ? Determine the origin and nature of the mineralizing fluids ? Providing geochronologic data and suggesting mineralization processes and improves the exploration models. 1.7 General methodology Detailed core logging and sampling of drill core from La Bodega and La Mascota was done in two seasons: in August 2010 and from July to August 2011. Sampling was concentrated on drill holes from two representative geological sections and of La Bodega and La Mascota and an additional small set of samples from El Cuatro (Appendix A1). A total of 375 samples were collected (Appendix A2). Characteristic lithologies, alteration and mineralization of both zones were included. Only limited structural information was collected for this project since core was not oriented, core was also cut in half and quarters and in many cases broken in pieces. The collected samples were dried for analysis with Terraspec ? and X-ray diffraction. Thin section petrography was done on selected samples mainly for ore characterization with a subset analyzed with Scanning Electron Microscope (SEM) methods. Another subset of samples of alunite was selected for mineral separation for 40Ar/39Ar geochronology and stable isotope (sulfur, oxygen and deuterium) analysis. Limited fluid inclusions information was gathered from petrography and microthermometry of two samples. Location information from the drill holes and Au assays were provided by Ventana Gold Corp in 2010-2011 and AUX Colombia Ltd. in 2011. A geological map developed by Ventana Gold Corp.- CVS Explorations   9  Ltda. Geology Department under the direction of geological consultant PhD Alfredo Bernasconi was provided in 2010. Geological maps presented here are the result of the compilations by Ward et al. (1973), Mendoza and Jaramillo (1973), Polania (1983), A. Bernasconi-Ventana Gold Corp. geology team (2010) and this study (MDRU Colombia Porphyry and Epithermal Gold project, 2013). Maps and geological sections are presented in geographic coordinates (WGS 1984 datum). 1.8 Thesis organization This thesis is divided into 10 chapters: Chapter 1 is an introduction to the study area, gives its general location and physiography, and provides a summary of its long mining history including the recent mining exploration. It also summarizes previous studies, the motivation for the development of this project and its objectives. Chapter 2 provides concepts regarding ore processes associated with the development of porphyry and epithermal systems, on which the data interpretation in the following chapters is based.  Chapter 3 explains the tectonic setting and regional geology of the CVMD and specifically for La Mascota and La Bodega. Chapter 4 describes the hydrothermal alteration associations and their relative temporal relationships of La Bodega and La Mascota, and provides an interpretation of the environments under which these alteration assemblages were developed.   10  Chapter 5 describes the mineralization and the mineral paragenesis of La Bodega and La Mascota and defines 6 stages of mineralization and associated hydrothermal events. Chapter 6 gives geochronological constraints, giving absolute ages to the hydrothermal events described in Chapter 5.  Chapter 7 shows temperature constraints of the fluids associated epithermal mineralization events, determined through fluid inclusions petrography and microthermometry. Chapter 8 presents sulfur, oxygen and deuterium isotopic data on pyrite and alunite and the probable interpretations for their origins. Chapter 9 discusses and integrates the results presented in all previous chapters and compares these deposits to similar deposits in the Andes. Exploration implications associated with the mineralization style and history are also outlined. Chapter 10 provides the main conclusions of this study as well as recommendations for future research.    11  Chapter 2. Hydrothermal Systems Conceptual Framework: Porphyry Copper and Epithermal Systems 2.1 Introduction Hydrothermal systems, including magmatic-hydrothermal systems, epithermal systems are important global sources of base and precious metals. This chapter comprises important aspects of the magmatic hydrothermal systems and related deposits. It is intended to give the reader of the thesis basic concepts related to epithermal and porphyry deposits that will be used throughout the document. The conceptual framework is mainly based on some of the most complete compilations about porphyry and epithermal systems within the last 20 years including: Corbett and Leach (1998), Sillitoe and Hendenquist (2003), Simmons et al. (2005), Sillitoe (2010), among many others. 2.2 Porphyry copper systems Porphyry Copper (Cu) systems are defined as large volumes (10 to 100 km3) of hydrothermally altered rock centered on porphyry Cu stocks that may also contain skarn, carbonate-replacement, sediment-hosted, and high- and intermediate-sulfidation epithermal base and precious metal mineralization (Sillitoe, 2010).    12   Figure 2.1. Worldwide locations of porphyry Cu systems cited as examples of features discussed in the text along with five additional giant examples. The principal deposit type(s), contained metals, and age are also indicated (modified after Sillitoe, 2010). Locations include California-Vetas (this study) and Middle Cauca Belt (Colombia MDRU porphyry and epithermal gold project, 2013).   13  Porphyry Cu systems presently supply nearly three-quarters of the world?s Cu, half the Mo, perhaps one-fifth of the Au, most of the Re, and minor amounts of other metals (Ag, Pd, Te, Se, Bi, Zn, and Pb) (Sillitoe, 2010). Porphyry Cu systems and deposits occur throughout the world and are mainly related to convergent margins, occurring as belts and clusters within these zones (Figure 2.1) such as the Andean Porphyry copper deposits e.g. the giant Eocene-Oligocene Porphyry Cu deposits of Northern Chile and the Northern Andean Au (Cu) porphyry within the Middle Cauca Belt (Sillitoe et al., 2008, 2010).  Several models have been proposed for characterizing porphyry Cu deposits. Lowell and Guilbert (1970, 1974), provided the first model that determined alteration mineral associations envelopes (alteration zonation) and veining relationships which played an important role in the discovery of new porphyry copper deposits. Since then, economic geologists have been refining this model integrating other features of hydrothermal systems; e. g. Gustafson and Hunt, 1975; Giggenbach, 1997; Carten,1986; Dilles & Einaudi, 1992 and more recently Sillitoe, 2005, 2010 (Figures 2.2)    14  Figure 2.2. Telescoped porphyry Cu system (after Sillitoe, 2010) Left: spatial interrelationships of a centrally located porphyry Cu ? Au ? Mo deposit in a multiphase porphyry stock and its immediate host Right: Corresponding generalized alteration-mineralization zoning pattern for telescoped porphyry Cu deposits shown on left figure.    15  2.2.1 Alteration and mineralization in porphyry copper systems Temperature and fluid pH are the most important of many factors which influence the mineralogy of hydrothermal systems followed by host rock and absolute fluid composition. Each hydrothermal mineral has stability temperature and pH stability ranges (Corbett and Leach, 1998; Figure 2.3) that provide the basis for the alteration zonation. Sillitoe (2010) states: ?The alteration and mineralization in porphyry Cu systems, occupying many cubic kilometers of rock, are zoned outward and upward from the stocks or dike swarms; from barren, early sodic-calcic through potentially ore-grade potassic, chlorite-sericite, and sericitic, to advanced argillic, the last of these constituting the lithocaps, which may attain >1 km in thickness if unaffected by significant erosion. Low sulfidation-state chalcopyrite ? bornite assemblages are characteristic of potassic zones, whereas higher sulfidation-state sulfides are generated progressively upward in concert with temperature decline and the concomitant greater degrees of hydrolytic alteration, culminating in pyrite ? enargite ? covellite in the shallow parts of the lithocaps. The porphyry Cu mineralization occurs in a distinctive sequence of quartz-bearing veinlets as well as in disseminated form in the altered rock between them?. Relevant characteristics of alteration envelopes and veins relationships within porphyry systems are compiled in Table 2.1(Sillitoe, 2010). Overprinting of late, shallow, generally epithermal styles of precious- and base-metal mineralization over early, deep mineralization of porphyry type is a common characteristic of porphyry copper systems (Figure 2.4) widely known as telescoping (Sillitoe, 1994). Crosscutting relationships, including offset veins,   16  provide definitive evidence for the relative ages of hydrothermal events at a particular location (Seedorff et al., 2005). Duration of hydrothermal activity of 50.000 yr to 500.000 yr are common, but several large porphyry Cu deposits include multiple events span several million years (Seedorff et al., 2005).  Figure 2.3. Common alteration mineralogy in hydrothermal systems in their relative pH and temperature stability range (after Corbett and Leach, 1998)   17  Table 2.1. Characteristics of principal alteration-mineralization types in Porphyry Cu Systems? (after Sillitoe, 2010) Alteration type?  (alternative name) Position in system  (abundance) Key minerals Possible ancillary  minerals Principal sulfide  assemblages (minor) Contemporaneous  veintels? (designation) Veinlet selvages Economic  potencial Sodic-calcic Deep, including  below porphyry Cu  deposits (uncommon) Albite/oligoclase,  actinolite,  magnetite Diopside,  epidote, garnet Typically absent Magnetite + actinolite (M-type) Albite/oligoclase Normally barren,  but locally  ore bearing Potassic (K-silicate)      Core zones of  porphyry Cu deposits  (ubiquitous)    Biotite,  K-feldspar     Actinolite, epidote,  sericite andalusite,  albite, carbonate,  tourmaline, magnetite   Pyrite-chalcopyrite,  chacolpyrite + bornite, bornite + degenite + chalcocite   Biotite (EB-type), K-feldspar,  quartz-biotite-sericite- K-fedspar-andalusite- sulfides (EDM/T4-type),  quartz-sulfides + magnetite  (A-type), quartz-molybdenite  + pyrite + chalcopyrite  (central suture; B-type) EDM-type with  sericite + biotite + K-feldspar + andalusite  + disseminated  chalcopyrite + bornite;  others none, except  locally K-feldespar  around A- and B-types Main ore  contributor     Propylitic Marginal parts of  systems, below  lithocaps (ubiquitous) Chlorite,  epidote, albite,  carbonate Actinolite, hematite,  magnetite Pyrite (+ sphalerite,  galena) Pyrite, epidote  Barren, except  for subephitermal  veins Chlorite-sericite  (sericite-clay-chlorite  [SCC]) Upper parts of  porphyry Cu core  zones (common,  particularly  in Aurich  deposits) Chlorite,  sericite/illite,  hematite  (martite,  specularite) Carbonate, epidote,  smectite  Pyrite-chalcopyrite      Chlorite + sericite + sulfides      Chlorite, sericite/illite   Common ore  contributor  Sericitic (phyllic)      Upper parts of  porphyry Cu deposits  (ubiquitous, except  with alkaline  intrusions) Quartz, sericite   Pyrophyllite,  carbonate,  tourmaline,  specularite Pyrite + chalcopyrite  (pyrite-enargite + tennantite, pyrite- bornite + chalcocite,  pyrite-sphalerite) Quartz-pyrite + other  sulfides (D-type)  Quartz-sericite   Commonly  barren, but may  constitute ore Advanced argillic   Above porphyry  Cu deposits,  constitutes lithocaps  (common) Quartz (partly  residual vuggy),  alunite?,  pyrophyllite,  dickite, kaolinite  Diaspore, andalusite,  zunyite, corundum,  dumortierite, topaz,  specularite Pyrite-enargite,  pyrite-chalcocite,  pyrite-covellite    Pyrite-enargite + Cu sulfides  (includes veins)  Quartz-alunite, quartz- pyrophyllite/dickite,  quartz-kaolinite Locally  constitutes ore  in lithocaps and  their roots ? Excluding those developed in carbonate-rich rocks. ? Arranged from probable oldest (top) to youngest (bottom), except for propylitic that is lateral equivalent of potassic; advanced argillic also forms above potassic early in systems. ? Many veinlets in potassic, chlorite-sericite, and sericitic alteration contain anhydrite, which also occurs as late, largely monomineralic veinlets. ? Alunite commonly intergrown with aluminum-phosphate-sulfate (APS) minerals (see Stoffregen and Alpers, 1987)   18  2.3 Faults and fracture networks and their role in hydrothermal. Successful development of hydrothermal ore systems requires an appropriate dynamic setting to generate metal fertile fluid reservoirs; second, it requires the generation of permeable fluid pathways to drain fluids from potentially large-volume fluid reservoirs and transport them to volumetrically much smaller ore deposition sites (Cox, 2005). According to Candela and Piccoli (2005); in porphyry systems, dilational tectonic features may accommodate some high level plutons, as well as their associated cupolas and apophyses. The large scale through-going fractures that host these local zones of dilations can extent to lower crust and control magmatism (Cox, 2005). Deformation is required to re-generate permeability and facilitate the high fluid flux necessary to produce hydrothermal ore systems (Cox, 2005). Episodic fluid redistribution from breached, overpressured (i.e., suprahydrostatic) reservoirs has the potential to generate large fluid discharge and high fluid/rock ratios around the downstream parts of fault systems after large rupture events (Cox, 2005). Hydrothermal self-sealing of faults, together with drainage of the hydraulically accessible parts of reservoirs between earthquakes, progressively shuts off flow along fault ruptures (Cox, 2005).  According to Corbett and Leach (1998); different styles of dilational ore environments can be distinguished associated with different levels of the hydrothermal systems (Figure 2.4) including: tension fracture/veins, jogs (Sibson, 1989, 1992 In Corbett and Leach, 1998), flexures (Sibson, 1989 In Corbett and Leach, 1998), hanging (foot) wall splits (splays), domes and ore shoots   19  (McKinstry, 1948 In Corbett and Leach, 1998). These features may have become filled by hydrothermal minerals originating veins and veins networks (Corbett and Leach, 1998). Intense fluid activity can be indicated by abundant veins, hydrothermal alteration around veins and fracture networks, and disturbance to isotopic systems (Cox, 2005). Dilatant features mentioned here are distinguished from, and locally transitional to, breccias (Corbett and Leach, 1998). According to Corbett and Leach (1998), practically all magmatic arc gold-copper systems contain breccias, and processes of breccia formation are intimately related (e. g. El Indio Pascua, Deyell et al. 2005; Lagunas Norte, Cerpa et al., 2013). Components of a breccia include fragments or broken rock clasts, that become milled with increase deformation ? brecciation); matrix, which comprises minerals (including ore) deposited from hydrothermal fluids as well as locally-derived and introduced rock material of a finer grain size than the fragments; cement, formed by minerals precipitated from hydrothermal fluid and so occurs within the matrix; open space or cavities develop between fragments which may become filled by hydrothermal minerals including ore during or following brecciation (Corbett and Leach, 1998). Hydrothermal fluids may partially or totally replace matrix grains and this can make it hard to distinguish between these two elements (matrix and cement). Cement precipitated from aqueous fluids is a diagnostic component of most hydrothermal breccias (Davies et al., 2008). According to Sillitoe (2010), hydrothermal breccias associated with porphyry systems include magmatic-hydrothermal, phreatic at the porphyry Cu level, phreatic at the epithermal level and phreato-magmatic (Table 2.2).    20  On the other hand, tectonic breccias are formed by mechanical disruption of rocks in response to tectonic stress and tend to occur in identifiable, usually steeply dipping, fault planes (Lawless and White, 1990). Tectonic breccias on fault zones within active hydrothermal system form highly permeable channels for the passage of fluids (Lawless and White, 1990). Dike-like tectonic breccias cemented by hydrothermal fluids are referred as tectonic-hydrothermal breccias i.e. Owl Creek calcite-cemented breccias, Wyoming-Montana, US (Kats et al., 2006). Figure 2.4. Dilational structures. A. Dilational veins and related structures. B. Extension mineralization styles at different crustal levels (after Corbett and Leach, 1998).   21  Table 2.2. Features of principal Hydrothermal Breccia Types in Porphyry Cu Systems (Sillitoe, 2010)  Type Position in system (abundance) Form Relative Timing Clast Features Matrix/Cement Clast/matrix proportions Alteration Types Main Cu-bearing mineral(s) Economic Potential Magmatic Hydrothermal Within porphyry Cu deposits, locally around them (ubiquitous) Irregular, pipe-like bodies (10s-100s m in diameter) Typically intermineral Commonly monomictic Quartz-magnetite-biotite-sulfides/ quartz-muscovite-tourmaline-sulfides + rock flour + igneous rock (i. e. igneous breccia) Clast or matrix supported Potassic + chlorite-sericite + sericitec, uncommonly advanced argillic Chalcopyrite, uncommonly bornite May constitute ore, commonly high grade Phreatic (porphyry Cu level) Within and around porphyry Cu deposits (relatively common) Dikes uncommonly sills and irregular bodies Late Polymict, rounded to subrounded Muddy rock flour Matrix supported Sericitic, advanced argillic, or none Generally none Barren unless rich in pre-existing mineralization (e.g., Bisbee; Bryant, 1987) Phreatic (epithermal level) Within lithocaps, local surface manifestations as eruption breccia (relatively common) Irregular bodies (10s-100s m in diameter) Typically intermineral relative to lithocap development Chalcedony, quartz, alunite, barite, sulfides, native S Clast or matrix supported Clast or matrix supported Advanced argillic Enargite, Luzonite May constitute high sulfidation Cu/Au/Ag ore Phreato-magmatic Diatremes span porphyry Cu and epithermal environments; surface manifestations as maar volcanoes (present in ~20% of systems) Kilometer-scale, downward-narrowing conduits Commonly late, but early examples known Polymictic, centimeter-sized, rounded, and polished; juvenile (magma blob, pumice) clasts locally Rock flour with juvenile tuff or magma blob component; early examples cut by porphyry Cu mineralization Matrix dominated; accretionary lapilli in matrix-dominated layers None advanced argillig, but early examples with any alteration type depending on the exposure level Locally enargite Commonly barren, but may host porphyry Cu or high-sulfidation ore types    22  2.4 Sulfidation state  The terms "sulfur content" and "sulfidation state" denote the relative values of the chemical potential of sulfur implied by sulfide mineral assemblages in ore deposits (McKinstry, 1959, 1963 and Barton, 1970 in Einaudi, 1994). The sulfidation state is used by Einaudi et al. (2003) as defined by Barton (1970) and in a manner analogous to oxidation state, where the frame of reference is temperature and the fugacity of S2 and O2 gas, respectively. The difference between the oxygen or sulfur fugacity implied by a natural mineral assemblage compares with that of a buffer reaction (e.g., table 2.3) and forms the basis for assigning relative oxidation or sulfidation states (Einaudi et al., 2003). Table 2.3. Examples of buffer reactions and association to sulfidation state or environment (after Einaudi et al. 2003) Reactions (Buffer) Environment Limit Reactants  = Products     Fe3O4  + O2   = Fe2O3          Magnetite  + O2   = hematite        2 FeS   +  S2  = 2 FeS2     Lower limit of intermediate sulfidation states     Pyrrhotite  +  S2  = pyrite         5 CuFeS2    +  S2  = Cu5FeS4  + 4 FeS2  Boundary between intermediate and high sulfidation states     chalcopyrite   +  S2  = bornite   + pyrite     0.67Cu12As4S13   +  S2  = 2.67 Cu3AsS4      Transition between porphyry copper deposits (sensu stricto) and porphyry related base-metal veins     tennantite  +  S2  = enargite     0.47 FeAsS   + 1.41CuFeS2    +  S2  = 0.12Cu12As4S13   + 1.88 FeS2  Lower limit to sulfidation state in intermediate Sulfidation epithermal deposits Arsenopyrite   chalcopyrite   +  S2  = tennantite  + pyrite   23  Terminology based on sulfidation reactions among minerals in the system Cu-Fe-As-S common to porphyry copper deposits, porphyry-related veins, and epithermal precious-metal deposits has been introduced in order to easily compare the sulfidation state between different fluids and between fluids and mineral assemblages: "very low", "low", "intermediate", "high", and "very high" sulfidation states (Einaudi et al., 2003). Each sulfidation state has an upper thermal limit (Einaudi et al., 2003; Figure 2.5).   Figure 2.5. Log fS2 ? 1000/T diagram, contoured for Rs, illustrating fluid environments in porphyry copper, porphyry copper related base-metal veins, and epithermal Au-Ag deposits in terms of a series of possible cooling paths. Mineral symbols: asp: arsenopyrite, bn: bornite, cc: chalcocite, ch: chalcopyrite; cv: covellite, dg: digenite, en: enargite; hm: hematite, lo: loellingite, ln: luzonite, mt: magnetite, py=pyrite, po: pyrrhotite (from Einaudi et al., 2003).   24  2.5 Epithermal systems (high-sulfidation and low-sulfidation). The term ?epithermal? is derived from Lindgren?s (1933) classification of ore deposits and refers to those that formed at shallow crustal levels (Robb, 2005). Epithermal systems are an important source of precious and base metals (as gold, silver, copper and zinc); they are associated with convergent margins and commonly related to known porphyry systems (Figure 2.6): Tertiary and younger examples are found around the Pacific Rim, in the Mediterranean and Carpathian regions of Europe, older are within Tethyan arc from Europe to Asia and volcanic arcs of all ages with rare examples as old as Archean (Simmons et al., 2005). Epithermal ore deposits form over the temperature range of <150oC to approximately 300oC, and 50 m-1.5 km depth from surface (White & Hedenquist, 1995; Hedenquist et al., 2000; Simmons, 2005). They comprise epigenetic ores that are generally hosted by coeval and older volcanic rocks and/or underlying basement rocks and rarely by subvolcanic intrusions associated with predominantly calc-alkaline magmas (relatively oxidized) that form in magmatic arcs resulting from convergent plate movement and plate subduction (Sillitoe and Hedenquist, 2003; Simmons et al., 2005). These deposits and their alteration cover areas that range from <10 to >100 km2. The orebodies occur in a diversity of shapes that reflect the influence of structural and lithological controls, and they represent zones of paleopermeability within the shallow parts of once active hydrothermal systems (Simmons et al., 2005). Most commonly, orebodies occur in veins with steep dips that formed through dilation and extension; some are hosted by major faults but more commonly they are hosted by minor faults   25  (second- or third-order structures) with small displacements (<10 m) (Simmons et al., 2005). Concentric mineral alteration zonation is typical of epithermal environments (Table 2.4); however, the dominant gangue mineral is quartz, making ores hard and generally resistant to weathering, and the dominant sulfide mineral is pyrite, with sulfide contents that can range from <1 to >20 vol. percent (Simmons et al., 2005).  Figure 2.6. Location of epithermal deposits in the world (modified after Simmons et al., 2005). Abbreviations: Ba = Baguio district (Acupan); BM = Baia Mare; Bo = Boliden; CC = Cripple Creek; Ch = Chinkuashih; Che = Chelopech; CP = Cerro de Pasco and Colquijirca-San Gregorio; Cr = Cracow; CR = Cerro Rico; CV = Cerro Vanguardia; CVMD=California vetas Mining District; EI-P = El Indio-Pascua; Em = Emperor; EP = El Pe?on; Es = Esquel; Fr = Fresnillo; Fu = Furtei; Gto = Guanajuato; HB = Hope Brook; Hi = Hishikari; Ju = Julcani; Ke = Kelian; La = Ladolam; Le-Vi = Lepanto- Victoria; LC = La Coipa; Ma = Martha Hill-Favona; Mc = McLaughlin; Mi = Misima; Ov = Ovacik; Pa = Pachuca-Real del Monte; Pi = Pierina; Pj = Pajingo; Po = Porgera; PV = Pueblo Viejo; RM = Round Mountain; Ro = Rodalquilar; Ta = Tayoltita; Te = Temora; Ya = Yanacocha.     26  Table 2.4. Summary of Hydrothermal Alteration Assemblages Forming in Epithermal Environments (Simmons et al., 2005) Alteration Mineralogy Occurrence and origin Propylitic Quartz, K-feldspar (adularia), albite, illite,  chlorite, calcite, epidote, pyrite Develops at >240?C deep in the epithermal environment through alteration by near-neutral pH waters Argillic Illite, smectite, chlorite, inter-layered clays, pyrite, calcite (siderite), chalcedony Develops at <180?C on the periphery and in the shallow epithermal  environment through alteration by steam-heated CO2-rich waters Advanced. Argillic (steam-heated)   Opal, alunite (white, powdery, fine-grained, pseudocubic), kaolinite, pyrite, marcasite  Develops at <120?C near the water table and in the shallowest  epithermal environment through alteration by steam-heated acid-sulfate waters; locally associated with silica sinter but only in  geothermal systems Advanced. Argillic (magmatic  hydrothermal) Quartz, alunite (tabular), dickite, pyrophyllite,  (diaspore, zunyite) Develops at >200?C within the epithermal environment through alteration by magmatic-derived acidic waters Advanced. Argillic (supergene) Alunite, kaolinite, halloysite, jarosite, Fe oxides Develops at <40?C through weathering and oxidation of sulfide-bearing rocks  Classification schemes and models describing epithermal deposits, their genesis and possible exploration and characterization methods have been published (Hedenquist & Lowestern, 1994; White & Hedenquist, 1995; Corbett & Leach, 1998; Corbett, 2002; Sillitoe and Hedenquist, 2003; Einaudi et al., 2003; Cooke and Deyell, 2003; Simmons et al., 2005).  These models describe the ore, gangue and alteration mineralogy of the system making classification mainly based on their oxidation state and sulfidation state. Discussion about classification schemes has been done in most of these publications. All classification schemes agree that there are two contrasting end members for epithermal systems, most of them base the classification scheme on the ?sulfidation state? from which two contrasting end members can be defined: High Sulfidation and Low Sulfidation. The contrasting characteristics between low   27  sulfidation and high sulfidation deposits allow for its identification providing a powerful exploration tool. Intermediate sulfidation refers to deposits with hydbrid characteristics of both, high sulfidation and low sulfidation and exhibit characteristic ore mineralogy as well (Sillitoe and Hedenquist, 2003). The contrasting characteristics between high, low and intermediate-sulfidation deposits are summarized in Table 2.5. A general model and related textures for high sulfidation and low sulfidation deposits is illustrated in Figure 2.7.  Figure 2.7. Low Sulfidation and High sulfidation model and related ore textures examples. (Adapted and modified after Corbett, 2002). Massive bodies of vuggy quartz texture in high-sulfidation and banded, crustiform quartz in low sulfidatiojn environments.   28  Table 2.5. Principal field-oriented characteristics of epithermal types and subtypes (from Sillitoe and Hedenquist, 2003)   High sulfidation Intermediate sulfidation Low sulfidation   Oxidized magma Reduced magma   Subalkaline magma Alkaline magma Type example  El Indio, Chile (vein);  Yanacocha, Peru  (disseminated) Potos?, Bolivia  Baguio, Philippines  (Au-rich);  Fresnillo, Mexico  (Ag-rich) Midas, Nevada  Emperor, Fiji  Genetically related  volcanic rocks Mainly andesite  to rhyodacite   Rhyodacite Principally andesite  to rhyodacite,  but locally rhyolite Basalt to rhyolite Alkali basalt to  trachyte Key proximal  alteration minerals Quartz-alunite/APS;  quartz-pyrophyllite/ dickite at depth Quartz-alunite/APS;  quartz-dickite  at depht Sericite;  adularia generally  uncommon Illite/smectite- adularia Roscoelite-illite- adularia Silica gangue   Massive fine-grained silicification  and vuggy residual quartz  Vein-filling crustiform  and comb quartz  Vein-filling  crustiform and  colloform chalcedony and  quartz; carbonate- replacement texture Vein-filling  crustiform and  colloform chalcedony and  quartz; quartz deficiency  common in early stages Carbonate gangue Absent Common, typically  including manganiferous  varieties Present, but typically  minor and late Abundant, but not  manganiferous Other gangue Barite common, typically late Barite and manganiferous  silicates present locally Barite uncommon;  fluorite present locally Barite, celestite, and/or  fluorite common locally Sulfide abundance 10-90 vol % 5->20 vol. % Typically <1-2 vol %  (but up to 20 vol %  where hosted by basalt) 2-10 vol % Key sulfide species Enargite, luzonite,  famatinite, covellite Acanthite, stibnite Sphalerite, galena,  tetrahedrite-tennantite,  chalcopyrite Minor to very minor arsenopyrite ?  pyrrhotite; minor sphalerite, galena,  tetrahedrite-tennantite, chalcopyrite Main metals Au-Ag, Cu, As-Sb Ag, Sb, Sn Ag-Au, Zn, Pb, Cu Au?Ag Minor metals Zn, Pb, Bi, W, Mo,  Sn, Hg Bi, W Mo, As, Sb Zn, Pb, Cu, Mo, As, Sb, Hg Te and Se species Tellurides common; selenides present locally None known,  but few data Tellurides common locally;  selenides uncommon   Selenides common; tellurides present locally Tellurides abundant;  selenides uncommon   29  2.5.1 High-sulfidation deposits These deposits contain sulfide-rich assemblages of high sulfidation state, typically pyrite-enargite, pyrite-luzonite, pyrite- famantinite, and pyrite-covellite (Einaudi et al., 2003), hosted by leached silicic rock with a halo of advanced argillic minerals. According to Simmons et al. (2005) these deposits correspond to epithermal deposits associated with quartz + alunite ? pyrophyllite ? dickite ? kaolinite assemblages that contain Au ? Ag ? Cu ores. Native gold and electrum are the main ore-bearing minerals, with variable amounts of pyrite, Cu-bearing sulfides and sulfosalts such as enargite, luzonite, covellite, tetrahedrite, and tennantite, plus sphalerite and telluride minerals; enargite dominates the Cu sulfides and indicates a high-sulfidation state (Simmons et al., 2005). 2.5.1.1 Quartz textures in high sulfidation deposits Quartz (both massive and vuggy) and alunite are the main gangue minerals with kandite minerals (dickite and/or kaolinite) and/or pyrophyllite. Vuggy quartz is a residual product of intense acid alteration, and it is a distinctive feature that reflects the original rock texture and differential leaching of phenocrysts and/or lithic fragments (Simmons et al., 2005). Its formation predates deposition of copper and gold, which are introduced by a fluid of different composition, illustrating the importance of paleopermeability in preparation for metal deposition (e.g., White, 1991; Arribas, 1995). Vuggy quartz texture in combination with dickite and/or kaolinite and pyrophyllite indicates that initial fluids causing alteration and rock dissolution were extremely acid (pH <2 for aluminum to be soluble; Stoffregen, 1987 in Simmons et al., 2005). The presence of magmatic hydrothermal alunite   30  indicates that the fluids were relatively oxidized. The vuggy quartz zone flares upward but may narrow toward the surface where shallow rock units have low permeability, diminishing the alteration effects of acid-leaching solutions (e.g., Nansatsu; Urashima et al., 1981 in Simmons et al., 2005). 2.5.1.2 Alteration assemblages and zonation in high sulfidation deposits Concentric patterns of hydrothermal alteration envelop the zone of vuggy and massive quartz alteration, which hosts ore. Outward, these comprise zones of quartz and alunite, dickite ? kaolinite or pyrophyllite, and illite or smectite alteration, surrounded by regional propylitic alteration (Simmons et al., 2005). Zones of illite or pyrophyllite alteration occur in the roots beneath some deposits (Simmons et al., 2005). 2.5.1.3 Origin and nature of mineralizing fluids in high sulfidation deposits High Sulfidation ore deposits are commonly considered to be formed from acidic fluid because of the extreme leaching and quartz-alunite alteration during formation of the lithocap. Leaching requires a fluid with pH <2 to mobilize alumina (Stoffregen, 1987 in Sillitoe and Hedenquist, 2003), and the alunite most likely forms at a pH of 2 to 3. Ore is hosted largely by the vuggy quartz zone, in which there are no aluminosilicate minerals left to indicate the pH or to influence any subsequently introduced fluid (Sillitoe and Hedenquist, 2003). The early leaching fluid that precedes high-sulfidation mineralization is a condensate of magmatic vapor with a relatively low salinity (<1 wt% NaCl; Rye et al., 1992, Arribas, 1995; Hedenquist et al., 1998; in Sillitoe and Hedenquist, 2003).   31  Fluid inclusion data indicate that salinities in high-sulfidation deposits are typically <5 to 10 wt percent NaCl equiv but may be as high as >30 wt percent NaCl equiv. (Simmons et al., 2005). Stable isotope data indicate that the altering fluids are composed mostly of magmatic fluids with a minor to moderate component of meteoric water. Therefore, precious and base metal mineralization in hig- sulfidation deposits is intimately associated with the crystallization of igneous intrusions and exsolution of magmatic fluids (Simmons et al., 2005). 2.5.2 Low-sulfidation deposits These deposits contain the low-sulfidation pair, pyrite-arsenopyrite, the latter sulfide mineral typically present in only relatively minor quantities, within banded veins of quartz, chalcedony, and adularia plus subordinate calcite. Hedenquist (2000) introduced the term ?intermediate-sulfidation? and Corbett (2002) distinguished between low sulfidation as arc low sulfidation and rift low sulfidation depending on the environment of formation (Figure 2.7). According to Simmons et al. (2005) these deposits correspond to epithermal deposits associated with quartz ? calcite ? adularia ? illite that contain Au-Ag, Ag-Au, or Ag-Pb-Zn ores. Quartz is the principal gangue mineral accompanied by variable amounts of chalcedony, adularia, illite, pyrite, calcite, and/or rhodochrosite, the latter in more Ag- and base metal-rich deposits. Low-sulfidation deposit associated breccias in veins and subvertical pipes show evidence of multiple episodes of formation comprising jumbled angular clasts of altered host rock and earlier vein fill, supported by a matrix of mainly quartz, calcite, and/or adularia and sulfide minerals suggesting rapid pressure release and violent formation that can be ascribed to seismicity   32  (e.g., Sibson, 1987; in Simmons et al., 2005) and hydrothermal eruptions (e.g., Hedenquist and Henley, 1985 in Simmons et al., 2005). 2.5.2.2 Alteration assemblages and zonation in low sulfidation deposits Hydrothermal alteration is zoned and comprises deep regional propylitic alteration, which gives way upward to increasing amounts of clay, carbonate, and zeolite minerals; whereas quartz, adularia, illite, and pyrite form proximal alteration zones enveloping orebodies. Ore-grade mineralization commonly terminates upward, and where there has been minimal erosion, it can be concealed beneath regionally extensive blankets of clay-carbonate-pyrite or kaolinite-alunite-opal ? pyrite alteration (Simmons et al., 2005).  2.5.2.1 Textures associated with low sulfidation deposits Distinctively banded crustiform-colloform textures, and lattice textures comprising aggregates of platy calcite and their quartz pseudomorphs, are common. Crustiform banded quartz is common, typically with interbanded, discontinuous layers of sulfide minerals (mainly pyrite) and/or selenide minerals, adularia, and/or illite. At relatively shallow depths, the bands are colloform in texture and millimeter-scale, whereas at greater depths, the quartz becomes more coarsely crystalline. Lattice textures, comprised of platy calcite and its quartz pseudomorphs, occur as open-space filling in veins, and along with vein adularia indicate boiling fluids of near-neutral to alkaline pH (Simmons and Christenson, 1994; Simmons and Browne 2000b in Simmons et al., 2005). According to fluid inclusion studies on quartz and calcite in the epithermal Au-Ag deposit of Veta Madre, Guanajuato, Mexico (Moncada et al., 2012); quartz and   33  calcite textures are representative of processes under which they were deposited; including textures associated with rapid deposition, such as might occur during boiling; and textures indicative of mineral precipitating from fluids that were not boiling include (Figure 2.8)  Figure 2.8. Summary of the various silica and calcite textures observed in the epithermal environment (from Moncada et al., 2012): A. Jigsaw texture quartz; B. Feathery texture quartz; C. Flamboyant texture quartz; D. Plumose quartz; E. Colloform texture quartz; F. Lattice bladed calcite; G. Colloform-banded plumose texture quartz; H. Colloform-banded jigsaw texture quartz; I. Ghost-sphere texture quartz; J. Moss texture quartz; K. Lattice-bladed calcite replaced by quartz; L. Rhombic calcite; M. Massive quartz; N. Zonal quartz; O. Cockade quartz; P. Comb quartz;. (XP=view under crossed polars). Textures A?M are characteristic of rapid deposition, such as might occur during boiling, whereas textures N?R indicate that the fluids precipitating the mineral were not boiling.     34  2.5.2.3 Origin and nature of mineralizing fluids in low sulfidation deposits Fluid inclusion data indicate salinities in low sulfidation deposits are commonly <5 wt % NaCl equiv for Au-Ag deposits and <10 to >20 wt % NaCl equiv for Ag-Pb-Zn deposits (Simmons et al., 2005). Stable isotope data indicate that hydrothermal solutions were composed mostly of deeply circulated meteoric water, with a nil to small and variable component of magmatic water (Simmons et al., 2005). Low-sulfidation deposits fluids are reduced (Einaudi et al., 2003) comparable to geothermal fluids (Giggenbach, 1992). Geothermal systems have relatively reduced fluids from deep source with near-neutral pH which are close to or in equilibrium with the altered host rocks due to their relatively slow ascent, i.e., rock-dominated environments (Giggenbach, 1992). 2.5.3 Summary of genetic factors related to epithermal deposits According to Simmons et al. (2005); critical genetic factors for the development of epithermal deposits include: (1) At several-kilometers depth, the development of oxidized and acidic versus reduced and near-neutral pH solutions, controlled by the proportions of magmatic and meteoric components in solution, and the amount of subsequent water-rock interaction during ascent to the epithermal environment; (2) At epithermal depths, the development of boiling and/or mixing conditions which create sharp physical and chemical gradients conducive to precious and base metal precipitation; (3) At shallow level, the position of the water table, which controls the hydrostatic pressure-temperature gradients at depth where epithermal mineralization forms.    35  Gold in hydrothermal systems is transported as a chloride complex (AuCl-); which deposition is driven by changes in fugacity of oxygen, activity of sulfur, and pH, as well as temperature and salinities (Henley, 1973); or as a bisulfide complex (AuHS2-), which deposition by decreases in temperature, pressure, and salinities (Seward, 1982, Henley et al., 1984 In Corbett and Leach; 1998; White and Hedenquist, 1995).     36  Chapter 3. Tectonic, Geological and Structural Context of The California-Vetas Mining District and The La Bodega - La Mascota Gold Deposits   3.1 Tectonic setting and location of the California-Vetas Mining district The California-Vetas Mining district (CVMD) is located within the Eastern Cordillera of the Colombia Andes (Northern Andes) making part of the Santander Massif, located at the intersection between the northeastern portion of the Chibcha Terrane (Restrepo and Toussaint, 1988; Restrepo et al., 2011) and the southwestern portion of the Maracaibo Subplate Realm triangular tectonic block (as defined by Cediel et al., 2003) (Figure 3.1). The Northern Andes: The Northern termination of the Andean belt is composed of the Ecuador, Colombia and Venezuela Andes (M?gard, 1987). Intracontinental deformation in the northern Andes is the result of the complex interaction between three lithospheric plates: 1) The South America plate; 2) the Nazca oceanic plate, which is converging at 6 cm/yr relative to the South America plate; and 3) the Caribbean plate, which is moving 1-2 cm/yr to E-SE relative to the South America Plate (Freymueller et al., 1993; Kellog and Vega, 1995; Taboada et al., 2000). The Colombian Andes are geomorphologically divided into three main ranges (Figure 3.1): The Western, the Central the Eastern Cordilleras, each with distinctive orogenic histories (Taboada, 2000). The Western Cordillera is composed of oceanic rocks accreted to the western margin of South America during the Mesozoic and early Cenozoic (Taboada, 2000). The Central Cordillera is   37  composed of a pre-Mesozoic, polymetamorphic basement including oceanic and continental rocks, intruded by several Mesozoic and Cenozoic plutons related to subduction; and an active volcanism belt linked to the Nazca subduction zone located along the crest of the Cordillera, south of 5?N (Taboada, 2000). The Eastern Cordillera is composed of a Precambrian and Paleozoic polymetamorphic basement, deformed during several pre-Mesozoic orogenic events (Taboada et al., 2000): basement rocks are covered by a thick sequence of Mesozoic and Cenozoic sedimentary rocks that were strongly deformed during Neogene by thrusting and folding (Taboada, 2000; Restrepo-Pace and Cediel, 2010). The Chibcha Terrane (Toussaint and Restrepo, 1988; Restrepo et al., 2011) comprises, among other features, the Eastern Cordillera of Colombia, in which the Santander Massif lies, and the Sierra Nevada de Santa Marta and it is limited to by the Guaicaramo Fault system, the Out Pericos fault system; the Oca fault and in by the northwest trending Bucaramanga-Santa Marta Fault (Figure 3.1). The Chibcha Terrane was accreted to South America during the Paleozoic. The Maracaibo Subplate Realm (Cediel et al., 2003) is a triangular shaped tectonic block that hosts numerous composite lithotectonic provinces and morphostructural features including the Santander Massif and the Sierra Nevada de Santa Marta (SNSM) as well as the Sierra de Merida (ME, also known as the ?Venezuelan Andes?), the Serrania de Perij? and the Cesar-Rancher?a and Maracaibo basins. It is limited to the north by the Oca Fault, to the south-west by the NNW striking Bucaramanga-Santa Marta fault and to the south-east by the NE striking Bocon? fault (as defined by Taboada et al., 1999, 2000) (Figure 3.1).   38  Santander Massif (Figure 3.1) is a lithotectonic province located to the east of the southern portion of the Bucaramanga-Santa Marta regional fault and it is sub divided in NW trending blocks (Royero and Clavijo, 2001). The Santander Massif comprises the oldest rocks in the region of the CVMD and is composed of two distinct geological domains: 1) The deformed and metamorphosed rocks of Pre-cambrian to Ordovicic age formed during Grenvillian including the Bucaramanga (Gneiss) Complex Orogeny, Silgar? Formation and Orthogneiss, and 2) The igneous succession developed after (1) syn-orogenic magmatism with alkaline affinity during the Paleozoic and (2) post-orogenic magmatism with calc-alkaline affinity during Triassic- Jurassic (Goldsmith et al., 1971; Ward et al., 1973; Mendoza and Jaramillo, 1979; Banks et al., 1985; Boinet et al., 1985; D?rr et al., 1995; Restrepo-Pace, 1995; Ordo?ez, 2003; Ordo?ez and Mantilla, 2005; Castellanos et al., 2008). California Vetas Mining District is located in the septentrional eastern zone of the Santander Massif in close vicinity of the Bocon? fault domain. Figure 3.1 (next page). Location of California-Vetas Mining District (CVMD) within Colombia, South America; in relation to the Chibcha Terrane (Ch) (Restrepo et al., 2011) and the Maracaibo Subplate Realm triangular tectonic block (MSP) (Cediel et al., 2003). The map shows the major fault systems that divide these tectonic blocks and terranes. Santander Massif, Sierra Nevada de Santa Marta (SNSM) and Serrania de Perij? (SP) are located in the intersection of the Chibcha Terrane and the MSP. Merida Andes are located in the MSP parallel to the NW striking Bocon? Fault. Right: Geological Map of a section of Santander department (Modified after Ward et al., 1973; Royero and Higuera, 1999; Wolff et al., 2005) showing the location of the CVMD in relation to main populations in the area and main structural trends. Cucutilla Fault and Surat? Fault are NE trending strike-slip faults sub-parallel to the Bocon? Fault located to the NE of the regional NNW trending Bucaramanga Santa - Marta Fault. Charta Fault is cross cut by Cucutilla Fault SW of the CVMD.   39     40  The tectonic evolution of the area is complex. Besides the Grenvillian episodes of accretion, recent tectonic processes are by the seismic activity in the area of the so called Bucaramanga (seismic) nest (Santander Massif, 60 to 100 km from the CVMD). Several models suggest that the Bucaramanga nest is located within the portion of the Caribbean plate that is subducting southeastward, while the Nazca plate is subducting eastward but to the south of the Bucaramanga nest (Cortes and Angelier, 2005; Pennington, 1983; Taboada et al., 2000). Another model proposed by Van der Hilst and Mann (1994) suggests that the Bucaramanga nest is located in the Nazca plate in a segment they call the redefined Bucaramanga slab. Zarifi et al. (2007) interprets that the Bucaramanga nest earthquakes suggests that the collision between the Nazca and Caribbean plates at depth is responsible for the Bucaramanga nest seismicity. Recent research interpret the Bucaramanga seismic nest as to be caused by a complex interaction between the subducting Caribbean plate under the South American Plate (Prieto et al., 2012) that implies a possible component of subduction angle change (from shallow to steep) in the area, as well as tearing and breaking processes of the Caribbean plate under the South American Plate (Prieto et al., 2012; Vargas and Mann, 2013) which are also interpreted from seismic tomography (Figure 3.2).   41   Figure 3.2 Schematic 3D model based on seismic tomography showing Bucaramanga seismic nest and relationship to interaction between the Caribbean, Nazca and South American Plates. Approximated location of the California Vetas Mining District (CVMD) is indicated. The model suggests flat subduction on the northern side. Caribbean plate suddenly changes its subduction angle and promotes a break off of the slab around the location of the Bucaramanga nest. South of the weakness zone, the Nazca plate subducts beneath the South American plate with a steeper angle and faster displacement (Modified after Taboada et al., 2000; Prieto et al., 2012; Vargas and Mann, 2013)   42  3.2 Lithology of the California Vetas Mining District and its expression within La Bodega - La Mascota deposits. The most widespread rocks within the California Vetas Mining District and within La Bodega and La Mascota areas are the metamorphic rocks from Bucaramanga Complex which are part of the so-called Santander Massif. Granitoids of the Santander Plutonic Group and related (?) pegmatites cross-cut the gneisses as exhibit as dike-like bodies in the La Bodega and La Mascota areas. Cretaceous marine sedimentary units crop out to the west of the district. Miocene porphyritic dike-like bodies cross cut previous units in certain areas of the district. Hydrothermal breccias cross-cut previously mentioned units and are cut by either late structures (faults) or structures that have been active at least during mineralization events. The main structure corresponds to La Baja fault which makes the so called La Baja trend, along which several precious metals occurrences align. Figure 3.3 illustrates the geology of the California Vetas Mining District. Figure 3.4 illustrates the local geology of the study area, La Mascota and La Bodega. The representative geological sections used for this study, which location is found in Figure 3.4, correspond to section B-B?, for La Bodega (illustrated in Figure 3.5) and section M-M?, for La Mascota (illustrated in Figure 3.6).    43     Figure 3.3 California-Vetas Mining District Geological Map. (After Polania 1980, Evans, 1976, Ward, 1973; Mantilla et al., 2012, MDRU Colombia Gold Project). White square indicates study area.   44   Figure 3.4. La Mascota and La Bodega area geological map showing location for geological drill holes that were sampled and studied geological sections: geological section M-M? at La Mascota and geological section B-B? at La Bodega. Map was redrawn and reinterpreted after Bernasconi et al., 2010 (original map provided by Ventana Gold Corp).   45   Figure 3.5. N-S geological cross-section B-B? at La Bodega, looking west. Based on diamond drill holes shown. Subtabular-irregular shaped granite intruding the Proterozoic Bucaramanga Complex with irregular amphibolite lenses. Hydrothermal and tectono-hydrothermal breccias: tabular shaped and discontinuous; distributed along NE-dipping NW-structural trend. Faulted zones are related to Paez and Perezosa faults.   46   Figure 3.6. N-S geological cross section M-M? at La Mascota, looking west. Proterozoic Bucaramanga Complex with irregular amphibolite lenses intruded by narrow tabular shaped granite dykes and late fault controlled-hydrothermal to tectono-hydrothermal breccias of La Mascota. Fault structures are related to La Baja fault.  3.2.1 Bucaramanga (Gneiss) Complex Bucaramanga Gneiss Formation was defined by Ward et al. (1973) and it was later referred as Bucaramanga Complex (Royero and Clavijo, 2001). Bucaramanga Complex consists of high grade migmatitic paragneisses of early Proterozoic age (Garc?a and R?os, 1999; Ord??ez-Cardona et al., 2006; Mantilla et al., 2012) as   47  well as migmatites, amphibolites, quartzites, marbles and granulites (Royero and Clavijo, 2001). Peak metamorphism has been dated at 1057 ? 28 Ma by U-Pb SHRIMP geochronology on zircons; this emphasizes an association with the Grenvillian Orogeny (Cordani et al., 2005 in Mantilla et al., 2012). Pressures between 5.5 and 7.2 kbar and temperatures from 660 to 750?C, have been estimated for the peak metamorphism (Urue?a and Zuluaga, 2011). 3.2.1.1 Bucaramanga Complex at La Bodega and La Mascota In the area of La Bodega and La Mascota, the Bucaramanga Complex is the most widespread rock unit. At diamond drill core scale, gneisses from Bucaramanga Complex are typically banded, therefore they are referred here as banded gneisses (Figure 3.7). Banded gneisses are composed of quartz feldspar bands (leucosomes, also referred here as quartz-feldspar gneisses) and amphibole-biotite rich bands (mesosomes, also referred here as amphibolites). Quartz feldspar bands (leucosomes) may be K-feldspar rich. The banding and segregation of K-feldspar rich leucosomes is interpreted to be the result of partial melting during high-grade metamorphism (upper amphibolite facies) resulting in migmatitization and ptygmatic folding. Mesosomes are mostly hornblende rich with minor biotite and disseminated magnetite in few cases. Locally, banded gneisses are biotite rich and may exhibit quartz and feldspar augens. Thickness of these bands may be as wide as a few meters, enough to be distinguished in geological sections (Figures 2.5 and 2.6) and deserve a separate description.    48  ? Amphibolite (mesosomes) are green colored gneisses that contain hornblende (60-80%), biotite (10-20%), plagioclase and feldspar (10-20%). They typically have a well-developed metamorphic foliation, a few leucocratic bands (plagioclase-quartz; 0.2 - 2 cm thickness) are commonly ?interstratified? in the amphibolite. Zircons are found accessory minerals (<1%). Amphibolitic rocks normally exhibit a well-developed metamorphic foliation and regularly form lenticular bodies that pinch out (Figure 3.7 C). ? Quartz-feldspar gneisses (leucosomes) are bands or lenses with quartz-plagioclase and K-feldspar composition with only scarce micas (biotite mainly). These quartz-feldspar bands range from few centimeters to tens of meters. Quartz-feldspar gneisses are coarse-grained (~0.5 ? 1 cm diameter, medium-grained (0.1-0.5 cm) or fine-grained <0.1 cm (massive texture) in some cases no obvious foliation. Coarse grain size is commonly found in the K- feldspar rich gneisses (pegmatitic-like texture) while the finer-grained texture is mostly found in plagioclase rich gneisses. Here, leucosome or quartz feldspar gneiss is informally defined as gneiss with more than 80% quartz and feldspars in total volume. Zircons are common accessory minerals (<1%) with size between <10 ?m 0.1mm and can help distinguishing the Pre-Cambrian quartz-feldspar bands in gneisses from younger granitoids (Figure 3.7 E, F).    49   Figure 3.7. Examples of the Bucaramanga Complex at La Bodega and La Mascota. A and B. Banded gneiss with quartz-feldspar bands (leucosomes) and hornblende-biotite bands (mesosomes). C. Amphibolite (mesosome). D. Banded gneiss with augen texture; biotite mesosomes (gray-black) and quartz-feldspar leucosomes (white yellowish). E. Coarse grained quartz feldspar gneiss (leucosome). F. Quartz feldspar gneisses (leucosomes) with massive texture. G. Microphotograph on cross polarized light of the amphibolite in C, showing hornblende (Hb) (altered to chlorite) abundant, altered feldspars (orthoclase-Or and plagioclase-Plg) and zircons aggregates. H. Quartz-feldspar gneiss microphotograph in cross polarized light (corresponds to E) showing sericite altered feldspars and quartz (Qz1) with undulous extinction and subgrains typical of metamorphic rocks. I. Close-up of H in plane polarized light showing zircons typical of the Bucaramanga Complex.     50  3.2.2 Santander Plutonic Group (Late Triassic to Early Jurassic) Plutons intruding the Santander Plutonic Group include the tonalites and granodiorites at P?ramo Rico (SE area of CVMD) (Goldsmith et al., 1971, Ward et al., 1973); and leucogranites and quartz monzonites (also known as alaskites) in the central part of the CVMD (Mendoza & Jaramillo, 1979; Mantilla Figueroa et al., 2013). The P?ramo Rico area intrusions U-Pb geochronology on zircons yields ages from ~210 to 205 Ma (D?rr et al., 1995). Muscovite K-Ar geochronology on the leucogranites yields to an age of 195?7 Ma (Goldsmith et al., 1971; Ward et al., 1973). According to Mantilla Figueroa et al. (2013), the igneous rocks from the Late Triassic - Early Jurassic magmatic episodes are the volumetrically most important igneous rocks in the study area and in the Colombian Eastern Cordillera. They can be divided into three groups based on their field relationships, whole rock geochemistry and U-Pb LA-MCICP-MS zircon geochronology (Mantilla Figueroa et al., 2013). These are early leucogranites (Alaskites-I; ~204 -199 Ma), Intermediate rocks (199 - 198 Ma), and late leucogranites (Alaskites-II: 198 - 196 Ma) (Mantilla Figueroa et al., 2013). This Mesozoic magmatism reflects subtle changes in the crustal stress in a setting above an oblique subduction of the Panthalassa plate beneath Pangea and was emplaced during initial uplifting of the Central Atlantic (Mantilla Figueroa et al., 2013).      51  3.2.2.1 Santander Plutonic Group at La Bodega and La Mascota Leucogranites at La Bodega and La Mascota that intrude the Bucaramanga Complex, range in composition from granite to monzogranite (Figure 3.8). Most of these rocks are equigranular and medium to fine-grained.  Quartz (~40%) is white to translucent; ranging from 0.5 to 2 mm; in thin section usually anhedral to subhedral, in suture contact to quartz and sharp contact to feldspars and other minerals. Most quartz has undulous extinction and minor evidence of intracrystalline strain. Feldspars (~55%) are white to dull color and greenish color (due to alteration) in hand sample, up to 2 mm in diameter with anhedral shape. In thin section, obliterated feldspars look are dull yellow and gray in the groundmass (due to alteration to sericite and or alunite, see chapter 3). Muscovite (up to 5%) forms randomly distributed crystals, translucent to pearl color in hand sample; with high birefringence color (green to fuchsia) in thin section. Crystals range from 0.1 to 1 mm width with tabular, flake-like crystals. Zircon (<0.1%) occurs as translucent <0.2 mm crystals with elliptical shape. Zircon is only found as a scarce accessory mineral in the granitoids.  These leucogranites are considered to be part of the Alaskite I group defined by Mantilla Figueroa et al. (2013). At La Bodega, leucogranite dikes exceed tens of meters in core intercepts (Figure 3.4) while at La Mascota, leucogranites are less common and they only form sub-tabular, steep narrow dikes (decimeters to a few meters) (Figure 3.5). Muscovite in these rocks is considered to be of magmatic   52  origin, therefore these rocks are considered to be peraluminous. U-Pb LA-MCICP-MS zircon geochronology in one leucogranite (Alaskite I) sample from La Mascota (ALR035) yields to an age of ~201 Ma (Jurassic) (See appendix A3).  Figure 3.8. Jurassic intrusive rocks (leucogranites) from La Mascota and La Bodega. A. B. C. La Mascota leucogranite (Alaskite I), DDH LB112 at 347.7 m. ALR034, adjacent to sample ALR035 (U-Pb geochronology on zircon: ~201 Ma) A. Core sample photograph. B. Microphotograph in cross polarized light of ALR034; showing quartz random distribution and feldspars altered to alunite and sericite. C. Microphotograph in plane polarized light of ALR034 pointing at the few zircons  found in this sample. C, E, F. La Bodega leucogranite (Alaskite I, according to Mantilla Fiueroa, et al. 2013), DDH LB251 at 318.3 m. ALR128. D. Core sample photograph. E. Microphotograph in cross polarized light of ALR128. Granite with phaneritic texture; random distributed of quartz crystals with undulose extinction; obliterated feldspars (altered to sericite); randomly distributed coarse grained muscovite (mus) crystals (of magmatic origin). F. Microphotograph in plane polarized light of ALR128 pointing at one zircon found in this sample.   53  3.2.2.2 Granitic pegmatites at La Bodega and La Mascota Pegmatites occur as narrow lenticular or dike-like bodies in drill core intercepts mostly at La Bodega (up to 3 m) (Figure 3.9) and few examples at La Mascota (<50cm). These pegmatites are greenish to white, coarse-grained (crystals up to 2 cm) and are granitic in composition. Granitic pegmatites cut the gneiss unit and appear to be closely related to the granites but no absolute age constraints are available. The contact between these rocks and the finer-grained equigranular granitoids mentioned above is sharp where seen but relative timing relationships are not evident. Pegmatites mentioned here are different from coarse grained (pegmatitic-like) K-feldspar rich leucosomes which are considered to be part of the Bucaramanga complex. Quartz (35-50%): White to translucent, anhedral to subhedral crystals ranging from 0.5 to 3 cm. In thin section quartz is gray and shows minor undulose extinction with straining evident as trails where undulose extinction is clearer. Feldspars (40-55%): greenish to dull white due to alteration in hand sample. Anhedral shaped crystals ranging from 0.5 to 3 cm (?). In thin section, feldspars alteration to sericite (and possibly minor illite) is evident as a groundmass of microcrystals aggregates of sericite replacing feldspars. Muscovite (1-5%): translucent tabular subhedral crystal individuals up to 0.3 mm, randomly distributed within the rock in contact to feldspars. In thin section is distinguished by the high birefringence color and its subtabular shape.  54   Figure 3.9. Pegmatite rocks at La Bodega. A. Sharp contact between granite and pegmatite. B and C. Pegmatite with altered feldspars (sericite-illite alteration). D. Microphotograph of ?A? in 2x objective with cross polarized light. E. Microphotograph of ?A? 10X on cross polarized light on pegmatite zone; note the coarse quartz crystals with minor straining.   55  3.2.3 Sedimentary rocks (Late Cretaceous) Sedimentary rocks of Cretaceous age are found in the western part of the CVMD, North and west of California town. These rocks unconformably overlie the previously described units. These rocks include the Tambor Formation (reddish limolites, sandstones and conglomerate sandstones) of Valanginian to Hauterivian age (Julivert, 1968 in Mendoza and Jaramillo, 1979) (Figure 3.9) and the Rosablanca Formation (limestone, fossiliferous limestone) of Hauterivian-Barremian age (Julivert, 1968 in Mendoza and Jaramillo 1979).  Detrital zircons from the lower Cretaceous siliciclastic Tambor Formation are of the same age populations as the metamorphic and igneous rocks present in the study area and previously mentioned, suggesting that the provenance is related to the erosion of these local rocks during the Late Jurassic or Early Cretaceous, implying a local supply of sediments to the local depositional basins (Mantilla Figueroa et al., 2013).  Figure 3.10. Late Cretaceous rocks (Tambor Formation). Outcrop to the west of California town. (Photograph courtesy of L. Osorio, 2013)   56  3.2.4 Porphyritic bodies and related rocks (Late Miocene) Porphyritic bodies that cross-cut the Santander Plutonic Group as well as the Bucaramanga Complex rocks are found within the CVMD as dikes, sills and small irregular shaped bodies (Ward et al., 1973, Mendoza and Jaramillo, 1979; Galvis, 1998; Felder et al., 2005; Mantilla et al., 2009; Mantilla et al., 2011, Mantilla Figueroa et al., 2013). At the top of Cerro Violetal (Violetal ridge), to the East of California town, a polymictic volcanic (?) breccia (which includes sedimentary rocks clasts) is found as part of a circular volcanic-like dome of approximately 9-10 km2 area, around which several porphyritic dike-like bodies of variable texture and composition are outcropping at drainages of the area (Galvis, 1998). Volcanic sands and ashes are mostly found in certain areas of the paramo within the district (Galvis, 1998; O. Gonz?lez Morales, 2007). Porphyritic-phaneritic quartz-monzodiorites and granodiorites are confined to the eastern part of the CVMD while porphyritic-aphanitic granodiorites are confined to the western part (Mantilla et al., 2011; Mantilla et al., 2013). U-Pb LA-MC-ICPMS geochronology on zircons yielded to ages of 9.0-8.4 ? 0.2 Ma for the rhyodacite porphyry bodies (Mantilla et al., 2009), 10.1 ? 0.2 for the porphyritic andesite variety and 10.9 ? 0.2 Ma for the granodiorite with prophyritic-phaneritic texture (Mantilla et al., 2011). These rocks are not observed within La Bodega and La Mascota areas. These porphyritic rocks are related porphyry Cu-Mo to mineralization in the CVMD (Bissig et al., 2012). Examples of these porphyritic rocks in the CVMD are illustrated in Figure 3.11   57   Figure 3.11 Miocene porphyritic granodiorites at the CVMD. A. Altered (rhyodacitic?) porphyry dike at El Cuatro. B. Porphyry dike at La Plata (Courtesy of T. Bissig). C. K-feldspar phenocrysts and bipyramidal quartz in porphyritic from La Machorra-Mongora area in vicinity of La Francia.   58  3.2.5 Hydrothermal breccias (Plio-Pleistoscene) Breccias at La Bodega and La Mascota represent the occurrence of magmatic-hydrothermal events and are related hydrothermal fluids that provided alteration (see Chapter 4) and mineralization (Chapter 5) of Plio-Pleistoscene age (Chapter 5). Breccias at La Bodega and La Mascota form NE-trending, NW-dipping, sub-tabular bodies along La Baja Trend (Figures 3.5, 3.6). These breccias exhibit quartz cement in which much of the mineralization is hosted. Silicification and quartz cement is related to alunite and advanced argilic alteration (See Chapter 3). At La Mascota, where these breccia bodies constitute the main ore body, they exhibit changing facies from clast-supported (gneiss clasts, breccia clasts, few granite clasts) to matrix supported or cement supported; either monomictic or polymictic (Mendoza Leon, 2010). Because of the important hydrothermal processes implied in their formation and their relationship to hydrothermal alteration and mineralization, these breccias are referred as hydrothermal breccias (e.g. Corbett and Leach, 1998; Davies et al., 2008). All of these breccias also exhibit features related to deformation associated with their origin typical of tectonic breccias (Sillitoe et al., 1985; Lawless, 1990), including tectonic foliation mainly at the walls of the breccia bodies, fine grained clasts, fine grained matrix and clasts of breccias within breccia. These breccias are produced by several breaking-healing episodes as a result fault re-activation. Because the hybrid features associated with breaking-healing processes related the hydrothermal cement (quartz) that these breccias exhibit, they are also referred as tectonic-hydrothermal breccias (e. g. Kats et al., 2006).    59  3.2.5.1 Hydrothermal Breccias at La Bodega La Bodega breccias form narrow subtabular discontinuous bodies ranging from a couple of centimeters to 10 meters in width (Geological section B-B?, Figure 3.5).  According to their physical and its mineralogical components, three kinds of breccias can be differentiated at La Bodega deposit: 1. Clast supported to matrix supported breccias with rounded resorbed edge clasts (RCBX): Rounded clasts (50-70%) with resorbed edges or corroded edges (with finer grained matrix (30-40%) and quartz and alunite cement (10-15%). Quartz alunite cement in breccias with sericite-illite altered clasts rimmed by green muscovite (Figure 3.12A). 2. Crackle jigsaw fit breccias (CJBX): monomictic clast supported (up to 90% clasts) breccia jigsaw fit distribution with quartz cement. This breccia can be found in the southern portion of La Bodega (DDH10LB327). It shows jigsaw fit clasts distribution, angular clasts of granite with very minor displacement weak silicification and renmants of sericite and alunite alteration. Pyrite + sphalerite in microcrystalline quartz cement are commonly rimming clasts. Granite clasts show euhedral quartz with sharp contacts in between crystals, minor muscovite occurrence and weak silicification (microcrystalline quartz) replacing feldspars (Figure 3.12B).  3. Polymictic to monomictic quartz cemented breccias (QCBX; THBX): Polymictic breccia may just have clasts of the different gneisses bands but clasts may include granite, gneiss and breccia clasts that can be fine grained (~1 mm) to a couple of centimeters in diameter. These breccias can   60  be cement supported, clast supported or matrix supported; nevertheless, matrix may be replaced by microcrystalline quartz. Weak tectonic foliation associated with elonged oriented clasts in matrix partly replaced by later silicification is also observed locally (Figure 3.12 C and D). These breccias form subtabular bodies and are here also referred as tectonic-hydrothermal breccias (THBX).    Figure 3.12. La Bodega typical hydrothermal breccias. A. RCBX (LB327 at 339.30 m., ALR074). Resorbed edges illite altered clasts breccias with muscovite alteration rim within alunite quartz cement. B. CJBX (LB327 at 244.60 m., ALR063) Crackled jigsaw fit breccia with granite clasts and pyrite-sphalerite-quartz cement. C. and D. QCBX (THBX) Quartz cemented breccia (LB258 at 202.50 m. ALR229 and LB022 at 216.20 m., ALR101; respectively). In D quartz + wolframite veins and cement cut by quartz+pyrite+enargite veins.   61  3.2.5.2 Hydrothermal Breccias at La Mascota Hydrothermal breccias are the most important mineralization feature at La Mascota. According to Mendoza (2011) breccias at La Mascota exhibit a great variety of proportions between clasts, matrix and cement therefore they can be described as clast, matrix or cement supported breccias (Figure 3.13). Matrix may be replaced by quartz cement which can make it hard to distinguish matrix from cement. Cement is normally fine grained quartz and alunite (Chapter 4). Most of these breccias are polymictic with clasts of gneisses, previous breccia and in some cases of granitoids. Clasts of earlier breccias are found in younger breccias; therefore these breccias are referred also as multiple-phase breccias (Figure 3.13 F). This fact indicates that La Mascota hydrothermal breccias have undergone several episodes of ?fracture-healing? or brecciation-silicification episodes.  They also locally exhibit cataclastic texture associated with fine grained matrix and foliation of probable tectonic originated prior to/during the formation of the structure to which the breccias are related (Figure 3.14). Breccias with tectonic foliation and fine grained matrix are referred here as tectonic breccias. Tectonic breccia clasts can be also found in multiple-phase hydrothermal breccias (Figure 3.13 F).   62   Figure 3.13. Breccia types at La Mascota based on physical components and arrange. A. Clasts supported breccia. B. Cement supported breccia. C. and D. Matrix (Mx) to cement supported breccia. Matrix may be replaced by quartz. Augen-shaped quartz clasts parallel to tectonic folitation. E. Contact zone between gneiss and hyodrothermal breccia where the development of tectonic foliation is evident. Gradation from left to right: from matrix/cement supported to clast supported. F. Multi-phases Breccia: BX1 corresponds to clasts of fine grained breccia with tectonic foliation (tectonic breccia clast) in BX2. BX2 is cross-cut by BX3.    63  Figure 3.14. Tectonic-hydrothermal breccia (THBX) at different scales; LB112 at 259.20 m. ALR014A. A. Quartz cement breccia with tectonic breccia clasts. B. Close up to tectonic breccia clasts with pyrite veins parallel to tectonic foliation. C. Tectonic foliation and cross cutting veins (microscopic XPL view). D and E. Close up to tectonic foliation and parallel pyrite veins cross cut by quartz, enargite, gold bearing vein. (D: XPL, E: RL).     64  3.3 Structural context The main structural trends within the district are defined by regional faulting which is evident in the topographic break caused by the NW?trending Bucaramanga?Santa Marta fault (Figure 3.1) and the NE?trending Cucutilla fault (Ward et al., 1973; Mendoza and Jaramillo, 1979; Reeves 2006; Parra, 2008). Drainage patterns near La Bodega-La Mascota are parallel to the NE-trending lineaments, faults and faulted zones and other secondary structures in the CVMD area (Parra, 2008). Faults in the area take their name from the creeks and rivers that follow their orientation. Outcrops found in these dranages exhibit fracture networks, intensely fractured rocks, gouge/clay supported breccias and slickensides. In general, there are three fault orientations: NNW, EW-NW and NE (Parra, 2008, Mantilla, 2011). Locally the main fault trends are La Baja (NE), Angosturas Creek lineament (NS), La Perezosa fault (NE), San Andr?s fault (NW) and the Paez fault zone (EW-NWW/40-60NE) (Figure 3.4).  3.3.1 Main regional structures Bucaramanga-Santa Marta Fault. It is the most important fault affecting the Santander Massif (Figure 3.2). This fault is approximately 400 km long measured from the Sierra Nevada de Santa Marta to the southernmost portion of the Santander Massif, and trends approximately N20W. It is considered a left-lateral strike-slip fault with a horizontal displacement of approximately 100-110 km (Campbell, 1965; Tschanz, et al., 1969, 1974 in Royero and Clavijo, 2002). The Bucaramanga - Santa Marta fault has an important vertical component: while in some areas it acts as a reverse fault uprising with the eastern block uprising   65  (Julivert, 1958, 1961; Ward et al., 1973; Paris and Sarria, 1988; Royero, 1994, In Clavijo and Royero, 2002) in its southernmost part it is a thrust fault (Boinet, 1985; Ulloa 1990, in Royero and Clavijo, 2002). The age of this fault is not clear. The Bucaramanga ? Santa Marta Fault crosscuts the Bucaramanga Complex but the most important activity of this fault takes place during the Late Miocene simultaneously with the Andean Orogeny (Boinet et al., 1989, in Royero and Clavijo 2002). Neotectonic activity of this fault is evident as, lineaments, triangle faces, and adapted drainage; especially in the Bucaramanga city area where Plio-Pleistocene sediments are affected by the Bucaramanga-Santa Marta Fault (Julivert, 1963; Paris and Sarria, 1988; Reyes and Barbosa, 1993; in Royero and Clavijo, 2002) Cucutilla Fault. Also known as Rio Cucutilla Fault (Ward et al., 1973), according to Royero and Clavijo (2002) the Cucutilla Fault is a right-lateral strike-slip fault trending NE-SW located to the NE of the Bucaramanga-Santa Marta fault (Figure 3.2). The Cucutilla fault considered part of the regional NE striking Bocon? Fault system (Horner, 2005 in Diaz and Guerrero, 2005). The Cucutilla fault has several fault splays to the NW (Figure 3.3). The main fault trends NE and crosses by Vetas River and P?ramo Rico where it intersects Charta fault (Ward et al., 1971). The most important splays in the area of the CVMD are the NE-trending Romeral-Cucutilla Fault (Horner, 2005 in Diaz and Guerrero, 2005) and the NE La Baja Fault (Ward et al., 1973), parallel to the Mineralized trend of the same name.     66  3.3.2 Main structures within La Bodega ? La Mascota La Baja Fault. Also known as La Baja River Fault and La Baja fault zone (Figure 3.3, 3.4). It is considered to be a splay of the Cucutilla fault and it makes a photogeologically identifiable lineament (Mendoza and Jaramillo, 1979) known here as La Baja trend which is parallel to the river with the same name. La Baja Fault is a right-lateral strike slip structure trending NE-SW. It ranges from 500 to 1500 meters wide and is considered to be the main control to mineralization in the NW portion of the CVMD (Mendoza and Jaramillo, 1979; Felder, 2005; Reeves, 2006; Parra, 2007; O?Prey, 2008; Pratt, 2010; Sim and Altmann, 2010; Mantilla Figueroa, 2009, 2011, 2012). La Bodega area is limited from La Mascota area by the intersection of La Baja fault with several other faults: the N30E striking Angosturas fault, the NE trending La Perezosa Fault zone and the EW-NWW/40-60N striking Paez fault (Figure 3.4). The NNW San Andres fault intersects La Baja and Angosturas faults in the area known as La Rosa. La Perezosa Fault is a NE structure, subparallel to La Baja Fault that is intersected by Paez Fault. La Perezosa fault constitutes the structural limit between La Bodega and the Angosturas multimillion ounces deposit to the east. Interactions in between these structures have a long and complex history (Felder, 2005; Reeves, 2006; O?Prey, 2008; Altmann et al., 2010; Sim and Altmann, 2010) and is evident in the intense faulting and fracture networks in the outcrops as well as in drill core intercepts (Parra, 2007; Pratt, 2010, this study). NNW faults are considered to be the oldest and have a history of reactivation (Julivert, 1959 in   67  Mantilla Figueroa et al., 2011). Paez fault is evident in the Paez Creek and is of reverse movement with the block to the north of Paez Creek uplifting in relation to the south block (Mantilla et al., 2013).  According to Parra, 2007, and Pratt, 2009; structural field measurements for fracture networks and faults are consistent with regional observations: the main structures are mostly trending NE and dipping 50-90? N, while secondary structures are NNW and EW-NWW (Figure 3.15). These faults are also evident in the drill core intercepts within the studied cross sections. In the geological section B-B? at La Bodega, faults are north dipping and are related to La Perezosa and Paez faults (Figure 3.4). In the geological section M-M?, the faults are steeply dipping to the north and are related to splays (?) of La Baja fault (Figure 3.5). Despite the intense fracturing, there is apparently no major displacement between rock formations in the geological sections studied here. For example, the reverse movement of the Paez fault (Mantilla et al., 2011) is not clearly identified in the studied cross section B-B?. Faults and fracture networks in the area are characterized by the development of clay supported breccias (fault breccias and gouge) with sub-rounded to sub-angular clasts (from 3 to 6 mm in diameter) adjacent to intensely fractured rocks (Figure 3.16).   68   Figure 3.15. Structural data representing main trends within La Bodega and La Mascota. A. Rose diagrams showing strike at several outcrops within La Bodega and La Mascota (after Parra, 2007) in their relative location within the geological map of La Bodega and La Mascota (legend as in Figure 3.4). B. Slickensides at La Rosa area in the vicinity of San Andres Fault (after Parra, 2007). C. Fracturation at El Casino outcrop at La Bodegathe in the vicinity of the intersection between La Baja, Angostura, Paez and San Andr?s faults, hammer indicating fault plane with gouge (after Bernasconi, 2006). C. Stereogram of fault planes measured on several outcrops within La Bodega and La Mascota (after Pratt, 2009).   69   Figure 3.16. Common examples of fractured rocks and faults and fault breccias filled with gouge at La Bodega and La Mascota. La Bodeta: A. DDH07LB013; B. DDH10LB327). La Mascota: C. DDH09LB112 and D DDH10LB202. Note the fault breccia with gouge development marked in red.   70  3.4 Structural relationships, hydrothermal breccias and mineralization Hydrothermal alteration and mineralization (Chapters 4 and 5 respectively) are related to the structural regime of La Baja Fault. The right-lateral strike ?slip structural pattern of the NE structures within the district, especially at La Baja, has provided the conditions for the development of tensional dilation structures. Tensional dilation structures are favored sites for open structures (Corbett and Leach, 1998). Dilational breccias form at varying crustal levels within open space structures, generally within competent host rocks that fracture well, developing dilatant structures or other generally linear discontinuities and are typically filled by hydrothermal minerals (Corbett and Leach, 1998). In the case of the CVMD tensional dilation structures are the favored sites for mineralization (Felder, 2005; Reeves, 2006; O?Prey, 2008; Sim and Altmann, 2010) (Figure 3.17). Hydrothermal fluids moved into these dilation structures providing alteration (Chapter 4) and formation of mineralized breccia structures (hydrothermal breccias) which are mostly trending NE (Figure 3.4) and dipping 60-80? NW (Figures 3.5 and 3.6). Multiple-phase breccias with cataclastic breccia clasts suggest that prior the multiple events of brecciation there was a major faulting-brecciation event. This event was accompanied by intrusion hydrothermal fluids and cementing (silicification) that allowed preserving the cataclastic texture. This major faulting-brecciation event provided the main conduit that was repeatedly broken. Pyrite veins parallel to tectonic foliation provides evidence that mineralization is strongly related to faulting. The hydrothermal fluids that produced alteration-silicification and   71  mineralization played a major role in the breaking and healing of the mineralized structures (veins and breccias).  Figure 3.17. Geological map of the California Vetas Mining district showing prospective areas for the development of dilational structures along La Baja Trend (yellow ovals) where mining takes place. Legend as in Figure 3.3.   72  Chapter 4. Alteration at La Bodega and La Mascota: Characteristics, Mineral Assemblages and Distribution 4.1 Introduction Magmatic-hydrothermal systems are characterized by the development of alteration mineral assemblages which are representative of the conditions under which they were formed. Unraveling the hydrothermal evolution history of the system leads to understanding the controls on mineralization within each deposit.  Typical alteration minerals at La Bodega and La Mascota deposits include epidote, chlorite, rutile, titanite, illite, muscovite (sericite), alunite, quartz and kaolinite. Assemblages of these minerals, their distribution, abundance, temporal relationships and related textures are described in detail in this chapter and the environments that they represent are discussed. 4.2 Methods of identification of alteration minerals Mineral assemblages were initially identified by hand sample observation during the core logging phase of this project. Representative samples were later analyzed by short-wave infrared reflectance (SWIR) using the ASD Terraspec TM instrument (a portable spectrometer that measures reflectance in the infrared zone), followed by petrography and X-ray diffraction (XRD) on samples of interest. Appendix A4 describes in further details methods of alteration minerals identification.   73  4.3 Alteration minerals assemblage and zonation at La Bodega and La Mascota Alteration assemblages at La Bodega and La Mascota deposits are comparable to assemblages in porphyry systems and epithermal systems and described based on the terminology used by Sillitoe (2010) and Simmons et al. (2005) (Table 4.1). Alteration assemblages were mapped on drill holes at La Bodega (section B-B?, Figure 4.1) and La Mascota (section M-M?, Figure 4.2) defining differences in abundance and distribution of these mineral assemblages with respect to host rocks and mineralized centers. Hydrothermal alteration mineral assemblages at La Bodega and La Mascota deposits are strongly controlled by faults, associated veins and structurally controlled breccias (hydrothermal and tectonic-hydrothermal breccias) as well as protholiths. There are three main types of alteration zones at La Bodega and La Mascota are Propylitic alteration zones, Phyllic alteration zones and Advanced argillic alteration zones (Table 4.1).   74   Figure 4.1. B-B? North - South geological section looking west. Alteration at La Bodega. Relationship to protholith and gold (Au) mineralization. Gold grades shown on drill hole trace. Notice the strong relationship of Advanced argillic alteration and silicification to Hydrothermal Breccias and the main mineralized centers. Propylitic alteration is mainly restricted to amphibolite lenses.   75   Figure 4.2. M-M? North - South geological section looking west. Alteration at La Mascota. Relationship to protholith and gold (Au) mineralization. Gold grades shown on drill hole trace. Notice the strong relationship of Advanced argillic alteration and silicification to Hydrothermal Breccias and the main mineralized centers.     76  Table 4.1. Comparison and correspondence of alteration assemblages at La Bodega and La Mascota to alteration assemblages described for epithermal environment by Simmons et al. (2005) and for porphyry environment according to Sillitoe (2010). Bold letters indicate the mineral association that is compared to the used terminology by Simmons et al. (2005) and Sillitoe (2010). Alteration Reference Position in system  (abundance) (according to reference) Mineralogy (according to reference) Alteration mineralogy at La Bodega and La Mascota deposits (this study) Propylitic Sillitoe, 2010 Marginal parts of porphyry systems, below  lithocaps (ubiquitous) Chlorite, epidote, albite, carbonate Chlorite, epidote, carbonate (calcite), montmorillonite (?), minor pyrite, chalcopyrite, specularite Simmons et al., 2005 Develops at >240?C deep in the epithermal environment through alteration by near-neutral pH waters Quartz, K-feldspar (adularia), albite, illite, chlorite, calcite, epidote, pyrite Phyllic (sericitic)  Sillitoe, 2010 Upper parts of  porphyry Cu deposits  (ubiquitous, except  with alkaline  intrusions)  Quartz, sericite (Sillitoe, 2010)  Muscovite (sericite), possible illite, minor quartz and pyrite  Advanced Argilic Advanced argillic   Sillitoe, 2010 Above porphyry Cu deposits, constitutes lithocaps (common).  Quartz (partly residual vuggy), alunite, pyrophyllite,  dickite, kaolinite  Quartz (porous quartz and massive silicification, quartz cement in breccias), alunite (flake-like in quartz druses, tabular, massive, replacements), natroalunite, kaolinite. Native S locally. Magmatic hydrothermal Simmons et al., 2005 Develops at >200?C within the epithermal environment through alteration by magmatic-derived acidic waters Quartz, alunite (tabular), dickite,  pyrophyllite (diaspore, zunyite) Steam-heated Simmons et al., 2005 Develops at <120?C near the water table and in the shallowest epithermal environment through alteration by steam-heated acid-sulfate waters; locally associated with silica sinter but only in geothermal systems Opal, alunite (white, powdery, fine-grained, pseudocubic), kaolinite, pyrite, marcasite, native S Supergene Simmons et al., 2005 Develops at <40?C through weathering and oxidation of sulfide-bearing rocks Alunite, kaolinite, halloysite, jarosite, Fe oxides Alunite (?)-kaolinite, iron oxides and manganese oxides     77  4.3.1 Propylitic alteration: chlorite and chlorite-epidote alteration zones characteristic minerals Characteristic minerals in propylitic alteration zones at La Bodega and La Mascota include chlorite, epidote, calcite and carbonate (calcite mostly) and titanium bearing minerals (rutile and titanite or mixtures of these). Associated veins include specularite, pyrite and calcite veins (Chapter 5). Chlorite is found as alteration of mafic minerals like hornblende, and biotite; as well as in veins that may or may not show an epidote halo (Figures 4.3, 4.4). Chlorite alteration is generally weak and is mostly recognized by the greenish appearance of the rock. Few cases of montmorillonite accompanying chlorite were documented through SWIR analysis in amphibolites mainly at La Bodega. Epidote is mainly found as veins and in narrow vein halos to epidote and chlorite veins. This epidote is replacing mafic minerals adjacent to veins in the chlorite-epidote alteration zones (Figures 4.3, 4.4). Carbonate (mostly calcite) veins are very minor but can be found accompanied by fine cubic pyrite. Carbonate veins cross-cut epidote and chlorite veins and alteration. Cubic pyrite (0.5 to 2 mm in diameter) may also be found disseminated and apparently replacing biotite (?) (Figure 4.3). Titanium bearing minerals include rutile, titanite which are products of alteration after mafic minerals such as hornblende and biotite+magnetite and can be found scattered throughout the rock and as halos of most calcite and specularite veins within the chlorite and chlorite-epidote alteration zones (Figure 4.4).   78  Specularite bearing veins and fracture coatings are common within chlorite and chlorite-epidote alteration. These veins will be described in Chapter 5. Although not common, granular magnetite (up to 2-4 mm in diameter) may also be found in biotite bands altered to chlorite at La Mascota. Chlorite-epidote beraing alteration is mainly found in the gneisses. It forms a wide envelope-like zones (>400 m) around mineralized structures at La Mascota (Figure 4.1 ) while at La Bodega it forms narrow zones mostly altering amphibolites (Figure 4.2). Although chlorite-epidote-calcite assemblage may also form as retrograde metaorphism, its spatial distribution and relation to veining suggests associations to hydrothermal events. Gold mineralization is not associated with chlorite and chlorite-epidote alteration assemblages and related veins.   79   Figure 4.3. Chlorite and chlorite-epidote alteration assemblages developed in amphibolite lenses at La Bodega. A. Amphibolite sample, drill hole LB258 at 233.20 m., sample ALR234: chlorite and epidote alteration and related veins. B, C, D, and E: Microphotographs showing the same sample as in A. B and D (XPL) show epidote alteration (epi) cut by carbonate (cb) vein with specularite (spc) on border. (B view on PPL) Chlorite alteration background also seen on C. Pyrite (py), chalcopyrite (cpy) and specularite (spc) related to carbonate (cb) vein. E (RL close up of pyrite, chalcopyrite and specularite on carbonate vein seen on C. F. Drill hole LB258 at 217.05, sample ALR233. Carbonate + pyrite vein with chlorite halo. G. Drill hole LB258 233.70 m. Epidote veinlets. H. Drill hole LB327 at 67. 4 m, sample ALR048. Amphibolite with chlorite and montmorillonite (?) alteration with carbonate veins, minor illite (overprinting?).   80    Figure 4.4. Chlorite and chlorite-epidote alteration mineral assemblages, examples from La Mascota. A. Drill hole LB205 at 412.9 m, sample ALR345. Epidote (epi) veins cut by calcite (ca) specularite veins. B and C microphotographs of A in XPL and PPL respectively. Note the chlorite (chl) alteration mainly developed on mafic minerals rather than the plagioclase (plg) and the rutile and titanite (ttn) (arrow shaped) on calcite vein walls. D. Drill hole LB112 60.50 m. sample ALR003. Chlorite vein (chlorite cemented breccia?) of 2.5 cm width with gneiss angular clasts breccia. E. Drill hole LB112 at 64.9 m. Banded gneiss with chlorite - epidote veins cut by fractures with epidote halo. F. Drill hole LB205 at 318.65 m, sample ALR337. Magnetite bearing banded gneiss with chlorite alteration. G. Drill hole LB205 at 443.65 m, sample ALR347; chlorite alteration on biotite magnetite specks band. H. Drill hole LB205 at 428.4 m., sample ALR346. Epidote vein with epidote and chlorite halo cut by minor fault filled with pyrite and clay, with illite halo. I. LB205 at 137.65 m. Epidote vein crosscutting gneiss with minor rutile and hematite.   81  4.3.2 Phyllic alteration: muscovite and Illite alteration zones Phyllic alteration zones where muscovite and illite are the main alteration minerals have been identified at La Bodega as well as at La Mascota. The procedures for identification of muscovite versus illite are described in Appendix A4. Muscovite is more widespread than illite but both minerals are intimately related and can be found in the same samples. 4.3.2.1 Muscovite>>>illite alteration Muscovite alteration is developed in gneisses, granites and pegmatites. It is locally overprinting or crosscutting chlorite and epidote alteration and related veins. Rocks with muscovite alteration generally have a ?bleached? appearance, that is generally white colors but pale green colors are also common on feldspars with muscovite alteration. While magmatic muscovite in the granites is coarse grained (up to 2 mm), microcrystaline muscovite commonly makes non-oriented aggregates (with high birefringence colors in thin section) and individual crystals ranging from <10 ?m to 0.05 mm when replacing feldspars. The term sericite is used here as a textural term referring to fine grained muscovite as a product of alteration. Muscovite can also be found as veins with individual crystals up to 0.05 mm and as replacements of biotite(?) mesosomes (Figure 4.5 and 4.6). Few cases of titanium bearing minerals (leucoxene, titanite and rutile) were found related to muscovite>>>illite alteration assemblages, mainly as a product of alteration of biotite and amphiboles. Sericite alteration can be pervasive and texturally destructive. It is the principal background alteration at La Bodega, while at La Mascota it constitutes relatively   82  narrow envelopes (10-20 m) around the core of mineralized structures, and is more abundant than illite. Veins related to muscovite and illite alteration zones are: specularite veins, coarse pyrite + quartz veins, quartz+molybdenite vein, and quartz+pyrite+copper sulphides veins (these veins will be described in more detail in the mineralization section in Chapter 5). 4.3.2.2 Illite>muscovite alteration Alteration to illite has been identified on micaceous and mafic minerals in weakly altered rocks as well as alteration of feldspars (mainly plagioclase) in more pervasively altered rocks. It is more common in amphibolite lenses than in other gneisses but it can also be found in a few halos of specularite, pyrite, quartz or alunite veins. Rocks with illite alteration exhibit light greenish and yellowish colors in hand specimens (Figure 4.5 and 4.6). In some cases where illite is overprinting chlorite-montmorillonite (?) alteration in amphibolite lenses, amphibolites exhibit a light gray-greenish color (Figure 4.3 F). Illite at La Bodega and La Mascota is replacing micas and feldspars (mainly plagioclase). In thin section, illite has been identified making non-oriented aggregates with yellowish-gray tabular individual crystals ranging from <10?m to 0.05 mm, when replacing feldspars (Figure 4.5 G, 4.6 I) and is commonly accompanied by sericite.    83   Figure 4.5. Muscovite (sericite) and illite alteration assemblages at La Bodega. A. Drill hole LB327 at 58.2 m, sample ALR047. Amphibolite with greenish gray illite alteration, ?swollen? apparence. B. Drill hole LB013 at 278.65 m, sample ALR283. Amphibolite with yellowish illite alteration and greenish illite alteration possibly overprinting chlorite alteration. C. Drill hole LB037 at 74 m, sample ALR249. Weak illite alteration after feldspars on banded gneiss. D. Drill hole LB022 at 35.20 m, sample ALR076. Illite altered gneiss, yellowish color. E. LB022 at 107.00 m, sample ALR082. Weak muscovite alteration after or overprinting chlorite (?) on banded gneiss. F. LB022 at 136.60 m., ALR088. Sericite alteration and muscovite microvein in granitoid cut by quartz pyrite vein. G. Microphotograph of F on XPL showing muscovite vein, sericite and illite (?) alteration on feldspars. H. Drill hole LB037 at 168.90 m, sample ALR262. Pervasive muscovite alteration on amphibolite. J. Drill hole LB037 at 178.80 m, sample ALR263. Coarse muscovite coarse on banded gneiss after biotite bands (cream color). E. and H. Drill hole LB327 at 115.60 m, sample ALR050. Sericite alteration on qz-fd gneiss, H., same as G, muscovite as seen in microphotograph.   84  Figure 4.6. Muscovite (sericite) and illite alteration assemblages at La Mascota A. Drill hole LB114 at 221.7 m, sample ALR141. Muscovite alteration on gneiss with pyrite vein. B. Drill hole LB205 at 215.40 m, sample ALR317. Muscovite alteration on banded gneiss, in micas (cream color) and feldspars (white to light green). C. Drill hole LB112 at 248.40 m, sample ALR358. Muscovite (sericite) alteration and crosscutting vein relationships: Quartz+pyrite (stage 2) vein cut by hematite+pyrite vein (stage 2) cut by pyrite+chalcocite+quartz vein (stage 3). D Microphotograph in cross polarized light of C showing the muscovite (sericite) alteration on the gneiss rock cut by later quartz veins. E. Drill hole LB114 at 235.60 m, sample ALR143. Altered gneiss; chlorite overprinted by muscovite (green muscovite) and muscovite alteration related to quartz+pyrite+molybdenite vein. F Drill hole LB112 at 347.70 m, sample ALR034. Hand sample. Sericite-illite alteration with minor scattered pyrite on a granite cut by alunite+pyrite vein; G. to microphotograph on XPL of F (sample ALR034). Primary magmatic muscovite grains, sericite (microcristaline muscovite) with higher birefringence colors and illite (fine grainded yellowish birefringence colors. H and I. Drill hole LB112 at 336.70 m, sample ALR033. Illite alteration cut by specularite vein and alunite veinlets. G. LB114 at 563.70 m. ALR185. Specularite vein with hematite halo and illite halo overprinting chlorite in amphibolite.     85  4.3.3 Advanced argillic alteration: alunite-quartz alteration, kaolinite-alunite alteration, silicification and related textures 4.3.3.1 Alunite, kaolinite and quartz alteration Alunite is found as a product of alteration in veins, breccia cement and cavity fillings at La Bodega (Figures 4.7) and at La Mascota (Figure 4.8). Alunite is intimately associated with quartz (silicification) and with kaolinite. Silicification (quartz alteration, replacement, microcrystalline quartz), alunite-quartz alteration and kaolinite-alunite alteration cross-cut and overprints muscovite and illite alteration. Alunite bearing alteration zones are found spatially related to the mineralized structures mostly in the ?core? of the mineralized centers at La Bodega (Figure 4.1) and at La Mascota (Figure, 4.2). Alunite at La Mascota and La Bodega occurs as: 1. A product of alteration of feldspars and micaceous minerals including muscovite and illite. Alunite alteration commonly crosscuts muscovite and illite alteration and can be accompanied by kaolinite. Titanite is commonly found adjacent to alunite veins with alunite halo probably as a relict from previously developed alteration, probably propylitic mostly on amphibolite lenses (Figure 4.7 B, 4.8E). 2. Alunite alteration halo of quartz veins with related sulfides and copper sulfides and copper arsenic sulfides (Figures 4.7, 4.8).  3. Alunite can be part of hydrothermal and tectono-hydrothermal breccias as cement associated with quartz and sulfides or as alunite replacement of clasts in the breccias, fractures and drusy quartz cavity fills of veins and   86  breccias (Figure 4.7), mainly at La Mascota. Alunite alteration and alunite cement in breccias is commonly obscured by the intense silicification.  4. Small alunite-kaolinite zones make isolated blebs (<5 m) overprinting illite and sericite alteration. Kaolinite associated with alunite is also found in veins and drusy quartz cavity fillings. Kaolinite is also found as fine grained matrix of fault breccias. Kaolinite may also be accompanied by manganese oxides and different amounts of iron oxides which are of supergene (weathering) origin.  5. Sodium bearing alunite (or natroalunite-alunite solid solution, see appendix A4) has been identified as veins and replacing feldspars in weakly silicified breccias, but its relationship to alunite (potassium bearing) and kaolinite is not clear.  Figure 4.7 (page 87). Alunite, occurrence at La Bodega related to quartz (silicification) and kaolinite. A. Drill hole LB327 at 41.00 m, sample ALR043. Alunite overprinting muscovite and illite alteration on pervasively altered gneiss (amphibolite?). B. Microphotograph of A under cross polarized light and reflected light showing alunite and kaolinite alteration, kaolinite veinlet with pyrite and adjacent pyrite clast, muscovite relics (pinkish-fuchsia), illite (yellow) and microcristaline aggregate of illite-muscovite (?) (yellowish-gray), titanite (metallic gray) aggregate adjacent to kaolinite vein, kaolinite+alunite fine grained aggregate (gray-white, shaded pattern). C. Drill hole LB327 at 34.60 m, sample ALR041B.  Alunite (white creamy color) and quartz (porous-like silica?, gray) alteration overprinting muscovite (?) alteration in granite. D. Drill hole LB251 at 243.30 m. ALR122. Alunite-quartz-pyrite vein. E. Drill hole LB327 at 249.80 m, sample ALR065. Alunite+pyrite vein with minor quartz and silicification halo. F. Drill hole LB013 at 231.80 m, sample ALR281. Hydrothermal breccia with alunite + cubic pyrite cement with minor quartz, silicified clasts (gray). G. Drill hole LB327 at 238.50 m, sample ALR060. Alunite with quartz and pyrite in breccia cement. H. Drill hole LB037 197.15 m. ALR264. Alunite+quartz+pyrite+enargite vein (stage 4) cross cutting gneiss with muscovite alteration overprinted by silicification (gray). Figure 4.8 (page 88). Alunite occurrence related to quartz and kaolinite alteration at La Mascota. A.Drill hole LB112 at 253.10 m., sample ALR012. Alunite altered clasts in contact with gneiss cut by covellite vein. B. Microphotograph of A showing that pyrite is intergrown with alunite. C. Drill hole LB112 at 328.80 m, sample ALR027. Alunite + pyrite (cubic) vein cutting silicified-alunitizied gneiss. D. Microphotograph of C in cross polarized light showing quartz alunite alteration (shaded pinkish aggregate) and comb quartz veins. E. Drill hole LB112 at 295.95 m, sample ALR367; alunite alteration halo of quartz + pyrite + enargite vein cutting gneiss. Pinkish color associated with alunite   87  altetration superimposed on rutile (?) after mafic minerals. F Microphtograph of E showing quartz alunite alteration and quartz vein. G. Drill hole LB112 at 347.70 m. ALR034; alunite + pyrite (cubic) vein cutting granite with illite-muscovite alteration. H. Microphotograph of G, halo of alunite + pyrite (cubic) vein in cross polarized light showing flaky-like (tabular) alunite halo quartz grains and minor magmatic muscovite. I Drill hole LB112 at 312.50 m., sample ALR024; sodium bearing alunite (natroalunite) in contact zone between gneiss and breccia. J. Drill hole LB205 at 280 m, sample ALR329. Alunite cement breccia cutting breccia with quartz cement. Pyrite and sphalerite adjacent to alunite. K. Drill hole LB112 at 312.9 m., sample ALR025 Kaolinite, minor alunite filling drussy quartz cavity in breccia.   Figure 4.7. Alunite, occurrence at La Bodega related to quartz (silicification) and kaolinite. Description on page 86   88   Figure 4.8. Alunite occurrence related to quartz and kaolinite alteration at La Mascota. Description on page 86-87.   89  4.3.3.2 Silicification and related quartz textures There are three main groups of quartz textures associated with silicification and advanced argillic alteration assemblages. Some of these textures are evident in hand sample (Figure 4.9) while others are clearer in thin section (Figure 4.10). 1. Quartz textures associated with breccia cement are readily evident at La Mascota zone. This group of textures was reported by Mendoza (2011) and has also been confirmed and studied in this research. Quartz textures associated with La Mascota hydrothermal breccias include examples of textures that, according to Moncada et al. (2012), are developed under of rapid deposition conditions (i.e. boiling conditions) such as: banded quartz, regularly colloform and crustiform (alternating bands of quartz, sulfides and/or alunite), bladed or lattice bladed (quartz replacing barite?), flamboyant and plumose (Figure 4.9, 4.10). These textures commonly alternate with textures considered to be indicative of non-boiling conditions (Moncada et al., 2012) such as comb, massive and cockade textures. Fluid inclusions are an important component of these textures making part of growth planes within zoned quartz crystals (Figure 4.10). Alternation between these textures may be evidence for episodic boiling. The above mentioned textures are commonly found in low sulfidation epithermal systems (Corbett, 2002; Simmons et al., 2005). 2. Porous quartz is associated with wall-rock alteration. This texture corresponds with massive silicification (replacement by fine grained quartz) with non-interconnected pores (porosity ~15%) of drusy texture at   90  microscopic scale. This texture is developed in discrete spots mostly in the wall rock of hydrothermal breccias at La Mascota and La Bodega (Figure 4.9), and in some cases associated with breccias containing sphalerite. Porous quartz has also been found southwest of the study area, at El Cuatro zone, related to sphalerite bearing tectonic-hydrothermal breccias where pores in quartz may be filled with alunite and kaolinite. This texture resembles vuggy quartz developed under highly acidic conditions in which the rock is leached only leaving fine grained quartz which is very common in high-sulfidation deposits (Simmons et al., 2005). Nevertheless, porous quartz at La Bodega and La Mascota seems to be developed by the introduction of silica rather than intense leaching. 3. Quartz associated with tectonic foliation: quartz is replacing the matrix but is also part of the cement of tectonic-hydrothermal breccias (Chapter 3, section 3.1.5; Figure 4.9). Quartz cement in tectonic-hydrothermal breccias is fine grained (<<50?m). In thin section, quartz related to the development of deformation processes regularly shows undulose extinction and fractures with secondary fluid inclusion trails (see Chapter 6).   91    Figure 4.9. Macroscopic textures related to silicification-advanced argillic alteration and hydrothermal breccias at La Mascota and La Bodega. A. Cockade texture (colloidal quartz cement around rounded clast of fine grained breccia) and drusy quartz cavities (La Mascota), B. Bladed and Lattice-bladed texture quartz (probably after replacement of barite?) adjacent to hydrothermal breccia with wolframite in quartz cement (La Mascota). C. Cockade-crustiform texture (quartz and sulfide bands) around gneiss clasts and colloform-coloidal quartz texture (La Mascota). D. Crustiform (quartz and sulfides bands) texture rimming clasts and drusy quartz-comb texture vein (La Mascota). E. Silicification at breccia wall rock; transition from silicification to sericite-illite alteration; porous quartz (La Mascota). F. Silicification on granite adjacent to THBX. Porous quartz quartz (resembling vuggy quartz). Alunite filling pores (La Bodega). G. Silicification related to tectonic foliation texture on THBX (La Bodega).   92    Figure 4.10. Microphotographs of main textures related to La Mascota Hydrothermal Breccias A. ALR015. XPL. Crustiform texture with bands that alternate mainly between comb-plumose and massive textures. Close up on B and D. B (XPL) Plumose-flamboyant texture on XPL. C. same as B seen on PPL+RL. Notice the dark zig-zag fluid inclusions zone in the quartz growth planes, adjacent to the left of tetrahedrite-tennantite. D. Close up to Massive microcrystalline quartz seen on A. E and F.  ALR018; XPL and PPL+RL respectively: colloform texture, comb quartz rimming enargite (?) bands grade and alternate with pyrite bands with renniform shape. G. ALR018, XPL: crustiform concentric bands rimming enargite and cut by en veinlet; with massive quartz band, comb to comb-drusy quartz bands. H. ALR012, XPL: Quartz vein with comb texture with fine grained quartz and alunitewith sacaroidal texture. I. ALR150, XPL: cavity rimmed by crustiform quartz with massive and comb quartz. J. Crustiform quartz vein with pyrite band (opaque mineral); massive quartz band and possible clast of breccia with jigsaw-fit quartz (PPL). K. ALR023 XPL: Cock-ade texture with breccia clasts rimmed by comb-flamboyant quartz. L. ALR027, XPL: comb quartz vein with quartz and minor alunite halo with massive to sacaroidal texture.    93  4.4 Discussion of alteration assemblages Alteration mineral assemblages at La Bodega and La Mascota are found in porphyry and epithermal systems (Table 4.1). In general, the same alteration assemblages and paragenetic evolution is observed at La Bodega and at La Mascota. Nevertheless, there are important differences in terms of intensity and distribution of alteration zones between the two zones. These differences can be attributed to (1) variations in host rocks and (2) structural controls: 1. Alteration types, such as chlorite+- epidote and illite>muscovite and illite alteration, seem to be have some lithological control. Chlorite and epidote alteration at La Bodega are mostly evident as blebs or relicts mostly restricted mesosomes/amphibolitic lenses of the gneisses to the north, while at La Mascota chlorite - epidote alteration (propylitic) is distal from mineralized structures and restricted to the gneisses, constituting the wider envelope alteration distal from mineralization centers.  2. At La Bodega muscovite>>>illite alteration (phyllic alteration) forms the ?background? alteration and is related mainly to quartz + pyrite veins, while at La Mascota it forms narrow envelopes mostly around the main mineralized structures. Quartz - alunite alteration and silicification (advanced argillic alteration) is structurally controlled and mostly related to hydrothermal breccias and the mentioned mineralized veins and breccias. At La Mascota, the breccias and veins are broader (~5-20 m locally up to 30 m wide) and much more continuous than at La Bodega (~1-5 m, locally up to 15 m wide).   94  Temporal relationships can be inferred from the cross-cutting relationships between the different alteration assemblages defining at least three main hydrothermal environments and events:  1. Chlorite and chlorite-epidote alteration (propylitic alteration) are the earliest assemblages formed in the system within La Bodega and La Mascota. Propylitic alteration develops in marginal parts of porphyry systems, below lithocaps (Sillitoe, 2010)  deep in the epithermal environment through alteration by near-neutral pH  waters at temperatures >240?C (Simmons et al., 2005)  2. Muscovite and illite alteration assemblages (phyllic alteration) is found mostly as part of halos of veins that cross cut propylitic or potassic alteration zones. Phyllic alteration is representative of the shallow parts of porphyry copper deposit environments (Sillitoe, 2010).  3. Quartz-alunite alteration and silicification (advanced argillic alteration) are cross-cutting and overprinting muscovite and illite alteration. Kaolinite-alunite and natroalunite (advanced argillic alteration as well) are associated with the latest stages of alteration. Kaolinite may also be found associated with supergene alteration and faulting (in fault planes). Advanced argillic alteration is representative of environments above porphyry copper deposits (Sillitoe, 2010) or epithermal environments (Simmons, 2005) and forms under acidic conditions (Sillitoe and Hedenquist, 2003; Simmons, 2005). However, the limited amount of vuggy quartz suggests that acidic fluids were restricted at La Bodega and La Mascota. Porous quartz as seen at La   95  Bodega and La Mascota is not extensive and may have formed by addition of SiO2 and indicates moderately acidic fluids rich in silica. Other quartz textures associated with hydrothermal breccias at La Bodega and especially at La Mascota reveal that deformation was important during hydrothermal activity. Quartz textures related to La Mascota hydrothermal breccias are interpreted to be produced by episodic boiling. The presence of alunite, silica rich fluids and textures indicating tectonic deformation during mineralization suggests near neutral to acidic conditions (pH ~3-5?) and episodic boiling driven by fracture-healing processes within the main structural conduit where the breccias were emplaced. Lateral alteration zonation at La Bodega and La Mascota, described above, reveals that early alteration assemblages representative of deeper hydrothermal environment (shallow porphyry environments) are found at the same depth level of late alteration assemblages representative of shallower environments (epithermal environment). Late epithermal events overprinting early porphyry events at the same depth may be explained at least in part by change in the surface level caused by erosion.   96  Chapter 5. Ore Mineralogy, Mineralization Styles and Paragenetic Evolution at La Bodega and La Mascota  5.1 Introduction The La Bodega and La Mascota gold mineralization is hosted in quartz veins and hydrothermal breccias. Previous studies have determined a complex mineral association to gold mineralization at La Bodega and La Mascota. Forero (2010) describes gold bearing mineral associations in three main paragenetic assemblages: 1) pyrite ? chalcopyrite ? tennantite ? sphalerite ? chalcocite ? gold; 2) pyrite ? wolframite ? tennantite ? chalcocite ? chalcopyrite ? gold; 3) pyrite ? tennantite ? chalcopyrite. Metallurgy studies by Di Prisco (2009), determined that main gold and silver ores at La Bodega and La Mascota include native gold, electrum, and gold-silver tellurides; silver antimony/arsenic sulfides, and a variety of copper sulfides associated with variable amounts of silver. Gold/Silver particles are predominately very fine-grained intergrown with pyrite and copper sulfides and, for the most part; occur at mineral grain boundaries (Di Prisco, 2009). Expected gold, silver and copper recoveries with a combination of methods, at La Mascota are ~90.2%, 93.6% and 90.9% respectively (Sim and Altmann, 2010).  The paragenetic sequence of La Bodega and La Mascota is determined by describing ore-related minerals associated with seven identified stages of hydrothermal evolution, their relationships to alteration zones and gold grades as   97  well as it outlines similarities and differences in mineralization styles between La Bodega and La Mascota.  5.2 Methodology Definition of main ore related mineral assemblages, mineralization zones and preliminary paragenetic sequence was based on drill core logging within B-B?and M-M? North-south sections (Figure 3.4). Ventana Gold Corp and AUX Colombia Ltd allowed access to core assays of the logged drill holes. Access to assays was important since it allowed identification of the gold mineralized zones, and key elements in minerals related to gold mineralization. From a collection of samples for ore microscopy and petrography a subset of samples was selected for further studies under scanning electron microscope (SEM). Qualitative compositional characterization on ore minerals was done at the Electron Microbeam / X-Ray Diffraction Facilities of the Department of Earth, Ocean and Atmospheric Sciences at The University of British Columbia. Samples were carbon coated with an Edwards Auto 306 carbon coater. A thin (~1 mm thick, ~4mm wide) copper tape was placed on the back of every carbon coated polished thin section for better fixation of X-ray beam on specimens during analysis on the scanning electron microscope (SEM). Samples were analyzed with a Philips XL30 electron microscope with Bruker Quanta 200 energy-dispersion X-ray microanalysis system with Xflash 4010 SDD detector and image analysis systems. This equipment allows quick examination and digital imaging of minerals and materials at both low and high magnifications using secondary electrons, backscattered electrons, characteristic X-rays, and cathodoluminescence signals.   98  When placed into the instrument, the camera records back scattered electron (BSE) (black - gray scale) images in which brightness and contrast were adjusted to find the previously chosen zones of interest and to define crystals to focus study on. In general, the brighter the crystals/grains the higher atomic number of the element related to the mineral crystal/grains. Spot analysis and element maps were collected through these methods using the ESPRIT software imaging interface. Spot analysis allowed identification of elements in discrete points within chosen crystals by comparison of X-ray spot signatures and databases. Element maps analysis (or Energy dispersion X-ray spectrometry; EDS maps) allowed defining distribution of elements of interest within a zone in the sample. Signatures were checked for noise during analysis in order to avoid misinterpretation. Complementary XRD analysis was done on ?black sulfide? mineral separates, such as enargite and chalcocite, to confirm results from petrography and SEM analysis and to better differentiate sulfides of the epithermal mineralizing environment. XRD data were processed by matching sample signatures to minerals in the EVA software which makes use of the International Centre for Diffraction Data PDF-4+ database (Appendix 5).     99  5.3 Mineralization stages, veins and ore related mineral distribution at La Bodega and La Mascota Seven mineralization stages have been defined for La Bodega and La Mascota based on cross-cutting relationships between veins, breccias and alteration assemblages. These stages are described for La Bodega and La Mascota outlining mineral characteristic of each stage and differences between La Bodega and La Mascota.  Pyrite is the most common sulfide mineral and occurs in the different alteration assemblages (Chapter 3) as disseminations, within veins and in hydrothermal breccias. Other ore minerals accompanying precious metal mineralization include copper sulfides (e.g. chalcopyrite, chalcocite, bornite and covellite), tennantite-tetrahedrite, enargite, wolframite (h?bnerite type) and sphalerite. Specular hematite (specularite) occurs mainly adjacent to mineralized veins and breccias and in minor veins within chlorite and epidote alteration or in transition zones to muscovite and/or illite alteration zones. Table 5.1 summarizes the identified minerals from these stages and their mode of occurrence.  Based on characteristic ore minerals, ore zonation is defined determining veins and breccias zones related to low and high gold grade at La Bodega and La Mascota. These main zones include: 1. Specularite veins zones, 2. Pyrite veining zones 3. Copper sulfides zone, 4. Wolframite zones, 5. Enargite zones, 6 Sphalerite zones,  7. Iron oxide zones.     100  Table 5.1. Summary of ore related minerals observed at La Bodega and La Mascota (this study except where indicated) and their relationship to alteration zones defined in Chapter 4 and mode of occurrence. Mineral Group  Mineral Chemical Formula Alteration zone (Bodega-Mascota) Mode of occurrence Sulfide   Pyrite  FeS2 Propylitic/Phyllic/ Advanced Argillic Five habits: cubic fine grained, cubic  coarse grained, dodecahedric, anhedral, colloform. Vein and breccias. Cu bearing sulfide Chalcopyrite CuFeS2 Veins and breccias Bornite Cu5FeS4 Advanced Argillic Associated and zoned with pyrite in breccias and veins Chalcocite Cu2S Covellite CuS   Marcasite  FeS2 Not common, in drusy quartz with fine colloform pyrite? and sphalerite? (Pratt, 2009; Mendoza, 2011) Sphalerite/wurtzite (Zn,Fe)S Mainly in breccias. Anhedral, fine grained. Molybdenite MoS2 Phyllic/Advanced Argillic Fine grained platy crystals in veins selvages and in breccia cement (scarce) Tungstate Wolframite (H?bnerite) MnWO4 Advanced Argillic Tabular prismatic crystals. In breccias quartz cement and quartz veins. Sulfosalt/sulfide Enargite Cu3AsS4 Anhedral habit. In breccias and quartz-alunite veins Sulfosalt   Tennantite-Tetrahedrite (Cu,Fe)12As4S13-(Cu,Fe)12Sb4S13 In breccias and veins  Gold/Silver bearing minerals Proustite Ag3AsS3 In breccias and veins associated with copper sufides and sulfosalts. Telluride Sylvanite AgAuTe4 Advanced Argillic/phyllic Anhedral, fine grained. In D veins as pyrite inclusions, in breccia cement  Calaverite AuTe2 Hessite Ag2Te Advanced Argillic In breccia cement mostly in the periphery of sulfosalts. Alloy Electrum Au;Ag (Ag>20%) Advanced Argillic/phyllic Associated with sulfides, sulfosalts, as pyrite inclusions, in quartz veins and breccias. Native Native Gold Au Mainly free in quartz veins and breccia cement associated with copper sulfides and sulfosalts.   Sulfur S Advanced Argillic In drusy quartz cavities (Forero, 2010; Mendoza, 2011) Oxide Hematite Fe2O3 Supergene alteration In veins, breccias, fracture fills.  Goethite FeO(OH) Sulfate Jarosite KFe3(SO4)2(OH)6 Supergene alteration, Advanced Argillic. Mainly seen on outcrop, porous quartz Chalcantite CuSO4 - 5H2O After copper bearing sulfides and sulfosalts     101  5.3.1 Stage 1: pre-mineralization, specularite bearing veins Stage 1 veins are not related to gold mineralization and are the paragenetically oldest recognized in this study. Characteristic oxide and sulfide minerals that were deposited in this early stage include pyrite 1, chalcopyrite 1 and specularite.  Pyrite: stage 1 pyrite is fine grained, up to 2 mm in diameter, regularly with euhedral cubic habit. Pyrite is found in chlorite, specularite and calcite veins in some cases associated with chalcopyrite Fine grained pyrite can also be found scattered in the rock (traces), in some cases replacing biotites (?) (Figure 5.1) Chalcopyrite: from stage 1 is anhedral and fine grained fine grained (~10 ?m ? 1 mm), regularly as isolated grains within pyrite 1 and specularite bearing veins.  Specularite occurs as anhedral to tabular and platy subhedral, 1-3 mm crystals in veins with minor pyrite and is also found in carbonate (calcite) veins related to chalcopyrite and pyrite (Figure 5.1). Specularite bearing veins may have a chlorite and epidote alteration halo. Chlorite veins and epidote veins are cross cut by pyrite + chalcopyrite bearing veins which are also cut by carbonate bearing veins. Carbonate veins may carry specularite but are also cross-cut by specularite veins which can carry traces of pyrite 1 and chalcopyrite 1 (Figure 5.1). Specularite bearing veins are and in zones of transition to muscovite and illite alteration zones (Figure 5.1).     102   Figure 5.1. Specularite veins and related minerals related to stage 1 at La Bodega and La Mascota. A. La Bodega. DDH LB258 at 233.2 m, sample ALR234, amphibolite. Chlorite and epidote veins cut by carbonate+pyrite+chalcopyrite+specularite vein which is cut by specularite+pyrite+chalcopyrite vein. B. Microphotograph of A under transmitted and reflected light. C. Close up of B: pyrite and chalcopyrite in specularite vein under reflected light. D. La Mascota. DDH LB221 at 489.70 m, sample ALR308, gneiss; chlorite epidote alteration. Pyrite+chalcopyrite vein cutting epidote vein. E. La Mascota, gneiss. DDH LB221 at 489.80 m, sample ALR308. Pyrite1+chalcopyrite1 vein cut by calcite vein. F. La Mascota, amphibolite. DDH LB205 at 412.90 m, sample ALR345. Epidote vein cut by calcite+specularite vein. G. La Mascota, amphibolite in chlorite alteration zone. Specularite+hematite+calcite vein with hematite and illite halo. H. La Bodega, gneiss. DDH LB258 at 85.64 m, sample ALR216. Gneiss, sericite alteration zone. Specularite vein. I. La Mascota, DDH LB112 at 336.70 m. ALR033. Gneiss with muscovite alteration; specularite vein.    103  5.3.2 Stage 2: early mineralization, pyrite ? quartz veins Pyrite is the dominant ore mineral of stage 2 at La Bodega and La Mascota. It is found as disseminations and pyrite ? quartz veins within phyllic alteration zones (Figure 5.2). Pyrite ? quartz veins cross-cut chlorite and epidote vein assemblages from propylitic alteration and related veins. Two types of pyrite deposited within this stage: 1) Scattered to disseminated fine grained pyrite (0.1% to 1%)  of~1-2 mm, with cubic subhedral to anhedral habit, in the rock within muscovite/illite alteration zones adjacent to veins quartz + pyrite  bearing veins (figure 5.2). 2) Coarse pyrite of ~2-10 mm in diameter with cubic euhedral to subhedral habit is associated with quartz gangue (Figure 5.2) making veins of ~3 mm up to ~20 cm width). Quartz + pyrite veins are typically sub-parallel to each other and sheeted veins (Bernasconi, 2006) and are striking mostly NE dipping 53NW (Pratt, 2009). Based on the limited structural information from core logging at La Bodega, it can be inferred that these quartz + pyrite veins are sub vertical or dipping 50-70? to the North forming wide veining zones. At La Mascota, in contrast, quartz + pyrite veins typically occur in narrow zones within the narrow muscovite alteration envelope around the principal mineralized structures (see below). These sheeted quartz-pyrite veins with sericitic halo are herein interpreted as analogous to D-veins (Gustafson and Hunt, 1975, Sillitoe, 2010). Quartz + molybdenite ? pyrite veins in phyllic zones (Figure 5.7) are scarce at La Bodega and La Mascota. In these veins, molybdenite is usually part of vein   104  selvages not exceeding a width of 1 mm but it is not clear if these veins correspond to stage 2 or previous stages. At El Cuatro, SW of La Mascota molybdenite bearing veins are cross cut by pyrite bearing veins (Ventana Gold Corp. internal drill logs, 2009) suggesting that these veins predate Stage 2.  Figure 5.2. Quartz + pyrite veins at La Bodega and La Mascota, stage 2. A. La Bodega, DDH LB327 at 115.60 m. ALR050. Moderately brecciated? quartz + pyrite vein cutting granite with muscovite alteration. B. Microphotograph of A under reflected light showing moderately fractured cubic pyrite and disseminated fine grained pyrite. C. La Bodega, DDH LB327 at 117.15 m. Quartz + coarse cubic pyrite vein cutting pyrite microveins in granite with muscovite alteration. D. La Bodega, DDH LB251 at 293.40 m. Granite with muscovite alteration cut by quartz+coarse cubic pyrite vein. E. La Mascota, DDH LB114 at 221.70 m, sample ALR141. Parallel quartz + cubic pyrite veins cutting gneiss and granite with muscovite (greenish-yellowish) alteration. F. La Mascota, DDH LB114 at 233.60 m, sample ALR142.  Quartz + coarse grained cubic pyrite cutting gneiss with muscovite alteration. Minor hematite (red) at vein walls or coating pyrite.   105  5.3.3 Stage 3: mineralization stage, copper sulfide bearing structures Mineralization stage 3 is characterized by the occurrence of copper and copper-iron sulfides such as chalcopyrite, bornite and chalcocite at La Bodega as well as La Mascota and covellite mainly at La Mascota. This stage is also related to deposition of gold, silver and tellurides at La Bodega as well as La Mascota. Silver sulfosalts accompany the deposition of the mentioned copper sulfides at La Mascota. Stage 3 copper sulfides at La Bodega are making pyrite + copper sulfides ? quartz (? alunite) veins that cross cut two alteration zones: 1) Phyllic alteration zones. Sulfides in veins cross cutting these zones include: dodecahedric (pyritohedric) habit pyrite (~1-3 mm typically) with oval microinclusions (~5-10 ?m) of chalcopyrite and gold-silver minerals (tellurides: calaverite/hessite? or electrum?); chalcocite in pyrite walls (up to 1 mm width) in some cases accompanied by bornite that may at the periphery of the chalcocite (Figure 5.3). This particular occurrence of chalcocite and bornite are more abundant in veins with moderately fractured pyrite. These veins that cross cut quartz + pyrite (cubic habit) veins of stage 2.  Chalcocite and bornite are late as compared to dodecahedric pyrite with mentioned inclusions (Figure 5.3).  2) Advanced argillic alteration/silicified zones and associated tectonic hydrothermal breccias. Sulfides in veins cross cutting these zones include: Subhedral to anhedral fine grained pyrite (~1-2 mm), anhedral chalcocite   106  (~1 mm) intergrown with pyrite or adjacent to pyrite walls in veins commonly accompanied by alunite and quartz veins (Figure 5.3).   Figure 5.3. La Bodega. Copper sulfides bearing veins and associated alteration. A. B. C. D. Granite. DDH LB251 at 331.9 m, sample ALR126. Muscovite alteration. Quartz+pyrite veins cut by quartz+pyrite+CuS (chalcopyrite, chalcocite and bornite) vein. A. Drill core sample. B. Microphotograph of A under reflected light. and D. Close up to copper sulfides adjacent to pyrite. C. Scanning electron microscope close up showing occurrence of precious metals, Fe related to pyrite and Cu related to bornite and chalcocite. D. RL microphotograph equivalent to C showing occurrence of pyrite, bornite, chalcocite in borders, chalcopyrite microinclusion in pyrite and Au Ag Te bearing mineral (electrum, tellurides: calaverite/sylvanite?) microinclusion in pyrite. E. DDH LB037 at 107.55 m. weakly silicified breccia (THBX) with gneiss clast. F. LB037 at 239.00 m, ALR268 (see appendix A5). Gneiss wth phyllic alteration crosscut by chalcocite+pyrite (fine grained) + quartz ? alunite vein.     107  Stage 3 copper and copper-iron sulfides (bornite, covellite, chalcocite, chalcopyrite) at La Mascota are forming quartz + pyrite (cubic and dodecahedric habit) + copper sulfides veins. These veins are found within muscovite alteration zones, in veining zones adjacent to hydrothermal breccias, but more commonly related to or cross cutting tectonic-hydrothermal breccias (structurally-controlled breccias with quartz and alunite cement and tectonic foliation texture) or as clasts within hydrothermal breccias.  Copper sulfides in the veins and breccias at La Mascota occur as anhedral aggregates of 10?m ? 2mm width around pyrite (cubic habit), pyrite clasts or fractured pyrite (Figures 5.4, and 5.5). In general, copper and copper iron sulfides show concentric zoned texture from center to periphery as follows:  1) Minor chalcopyrite and pyrite (cubic and dodecahedric) crystals or clasts. 2) Anhedral chalcocite rim around pyrite/chalcopyrite. 3) Bornite - covellite aggregates intergrown with chalcopyrite in a few cases. 4) Anhedral tetrahedrite-tennantite aggregates found at the borders of copper sulfides. Stage 3 gold and silver mineralization at La Mascota is late in general as compared to copper sulfides. Gold (2-200?m width) is generally found as electrum in the peripheries of copper sulfides and in microveins within and sub-parallel to quartz-copper sulfides bearing veins (Figure 5.4). Silver is found as argentotennantite and silver sulfosalts (proustite) mainly in the periphery of copper sulfides (Figure 5.5).    108   Figure 5.4. La Mascota, copper sulfides and gold, stage 3. DDH LB112 at 259.2 m, sample ALR14A-1. Microphotograph under reflected light and cross polarized light showing pyrite vein cutting tectonic quartz cemented breccia (THBX) and cross cut by copper sulfides-gold vein. B. Microphotograph of A at higher magnification showing copper-iron sulfide zonation: bornite at centre, chalcopyrite and tetrahedrite-tennantite at border, gold in microfractures. C. Microphotograph under reflected light showing copper sulfides zonation with chalcocite and chalcopyrite at center, bornite and pyrite outward and, at the border, chalcopyrite and tetrahedrite-tennantite with minor gold. D. Close up of A (upper square) under reflected light showing bornite, covellite, chalcopyrite, tetrahedrite-tennantite zonation and gold as electrum (Au>>Ag). E. BSE SEM image, same zone as in D showing elements in analyzed points. F. Close up of E under SEM; BSE Au element map showing electrum grain.   109   Figure 5.5. Relationship of copper sulfides, pyrite and silver sulfosalts in stage 3. La Mascota, DDH LB112 at 253.1 m, sample ALR012. A. Microphotograph under reflected light showing pyrite clasts and fractured pyrite  with bornite and covellite in the periphery of pyrite. B. SEM microphotograph showing elements on analyzed spots. C. Element map distribution of silver from A and B. D. Element map of copper as in C. E. Covellite, bornite pyrite and proustite distribution. F. Silver SEM element map showing elements within analyzed spots.     110  One case of a gold (electrum) bearing quartz vein with traces of sphalerite and chalcopyrite (detected by SEM) was found in the phyllic alteration zone at La Mascota in the hanging wall of the breccia. This gold bearing vein cross cuts a stage 2 quartz + cubic pyrite + hematite (as pyrite coating) vein (Figure 5.6). Sphalerite and chalcopyrite occur at the borders of the veins cutting pyrite in contact to gold. The cross cutting relationship between  quartz + pyrite + hematite vein and the quartz + gold (electrum) + sphalerite + chalcopyrite vein, defines that the latter vein is more probable part of the mineralization stage 3. Molybdenite at La Mascota breccias occurs as fibrous/platy habit aggregates which do not exceed 3 mm width but its occurrence is scarce. It is found in drusy cavities of quartz cemented breccias at La Mascota where molybdenite is surrounded by copper sulfides (bornite mainly) and it is associated with early phases of stage (Figure 5.7).   111   Figure 5.6 Gold (electrum) bearing quartz vein with minor sphalerite and chalcopyrite cross cutting quartz + cubic pyrite + hematite vein in muscovite alteration zone. La Mascota, DDH LB112 at 214.9 m; sample ALR005. A. Core sample. B. Microphotograph of A under reflected light. C. Microphotograph of B with SEM showing elements based on spot analysis.     112   Figure 5.7. Molybdenite occurrence at La Bodega and La Mascota (pre-stage 2? and early stage 3?). A. La Bodega, DDH LB327 at 228.5 m, sample ALR058. Granite with muscovite alteration cut by quartz+pyrite  vein with molybdenite as vein selvages (pre-stage 2?). B. La Bodega, DDH LB327 at 243.15 m. Clast supported jigsaw fit breccia (CJBX). Clasts include granite clasts exhibiting muscovite alteration and quartz + pyrite + molybdenite vein clasts (post-stage 2?). Cement is quartz and pyrite. C. La Mascota, DDH LB221 at 320.7 m, sample ALR292. Quartz+ + molybdenite + pyrite (fine grained) parallel veins cutting gneiss with weak muscovite alteration (stage 2?).  D. La Mascota, DDH LB114 at 235.6 m, sample ALR143. Gneiss with muscovite alteration cut by quartz + pyrite  + molybdenite (at vein walls) vein (pre-stage 2? or early stage 2?). E, F, G, H. La Mascota, DDH LB112 at 251.65 m; sample ALR010. Tectonic-hydrothermal breccia with quartz cement. Molybdenite in quartz cement adjacent to fractured cubic pyrite or clasts of cubic pyrite (early stage 3?). E. Core sample. F. Close up of E around indicated zone showing molybdenite. G. Microphotograph of F under reflected light showing molybdenite, bornite and fractured pyrite (early stage 3?). H. SEM element map of G showing occurrence of Molybdenite and copper and Microphotograph with EDS element map highlighting Molybdenum (lime green) and Copper (blue). A more opaque green on pyrite (FeS2) is associated with close range superimposition of molybdenite peaks and sulfur peak. Notice the fibrous habit of molybdenite.    113  5.3.4 Stage 4: mineralization stage, wolframite bearing veins and breccias Mineralization stage 4 is characterized by the occurrence of manganese-bearing wolframite (h?bnerite) at both, La Bodega and La Mascota.  Wolframite occurs within quartz-alunite alteration zones, specifically related to quartz cement in tectonic-hydrothermal breccias and in drusy quartz veins in these zones. At La Bodega, wolframite is very scarce. It is found as subhedral, tabular to arrow-shaped crystals and clasts (50 ?m to 1 mm) within quartz cement of the tectono-hydrothermal breccias. Wolframite bearing breccias and quartz veins are crosscutting zones with copper sulfides of Stage 3 (Figure 5.8).  At La Mascota, wolframite is a common mineral associated with white drusy quartz and quartz cement in hydrothermal breccias (Figure 5.9). Wolframite forms reddish-brown tabular crystals typically 0.5-3 mm long regularly. It is found in quartz veins cross cutting breccias, in quartz cement of tectonic-hydrothermal breccias. Common textures found in quartz cement and veins associated with wolframite include drusy, comb, plumose, zonal, bladed (barite-like) and cockade textures. Clasts of previous brecciation events are found in wolframite bearing quartz cement in hydrothermal breccias. Minor cubic pyrite may be related to wolframite. Tabular (flaky) alunite has been found in wolframite bearing quartz veins druses. Gold is associated with late phases of this stage. It is found as native gold (associated with tennantite-tetrahedrite?) microveins in wolframite + quartz veins/bands in breccias and microveins.    114   Figure 5.8. Hydrothermal breccia with quartz cement exhibiting tectonic foliation (THBX) at La Bodega. LB037 at 142.9 m, sample ALR090. A. Core sample. B. Thin section (cross polarized light) showing quartz vein/breccia cutting fine grained silicified matrix with tectonic foliation. C. 2X close up in cross polarized light showing mosaic quartz and foliated texture. D same as in C in reflected light. E. Close up of enargite + pyrite vein cutting quartz cement with wolframite. F. same as in E under plane polarized light. G. Scanning electron microscope image of E and F. H to O. Single element maps of Ag, Au, Cu, As, W, S, Fe, Mn, respectively. Brighter spots in the Ag map are related to enargite. Au is related to enargite and there is apparent relationship to wolframite walls (or superimposing signal on EDS map?).   115   Figure 5.9. Wolframite (h?bnerite) occurrence at La Mascota. A. DDH LB202 at 230.60 m, sample ALR199. Cross cutting drusy quartz + wolframite veins in moderatetly silicified-brecciated gneiss.  B. DDH LB 202 at 231.80 m, sample ALR200. Crustiform quartz vein bands with alternating fine grained and medium grained tabular shaped wolframite cross cutting quartz cement breccia, to the right of the vein: rounded clast with cockade texture with colloform quartz and wolframite rimming clasts. C. Quartz-wolframite cementing breccia with cockade-coloform texture adjacent to bladed quartz vein with minor wolframite. D. DDH LB169 at 207.05 m. Native Au associated with wolframite band. E. DDH LB202 at 203.15 m, sample ALR189. Wolframite + quartz cement breccia. F.. Microphotograph from D in transmitted light. G. DDH LB112 at 256.5 m, sample ALR013. Microphotograph SEM image showing tabular, arrow shaped wolframite and elements detected by EDS.    116  5.3.5 Stage 5: late mineralization, enargite bearing veins  Mineralization stage 5 is characterized mainly by the occurrence of copper arsenic sulfides and sulfosalts, including enargite, stibioenargite (?) and minor tetrahedrite-tennantite. Alunite-quartz alteration and veins as well as strong silicification are related to this stage. Enargite is the most easily identifiable mineral of this stage. It is forming anhedral aggregates in some cases is found associated with fine grained colloform pyrite and very scarce amount of previously mentioned copper sulfides. At La Bodega, enargite is found in quartz + alunite + enargite veins forming zones of 1-2% veins per volume of rock, in tectonic-hydrothermal breccia cement in some cases filling cavities and in other as part of the cement that may be cutting previous veins. In a few cases inclusions of wolframite can be found in enargite anhedral-zoned crystals. Zonation of enargite and colloform fine grained pyrite is common (Figure 5.10).  At La Mascota, enargite is found as microveins cross cutting hydrothermal wolframite bearing quartz veins and breccia cement, as drusy quartz cavity fillings and in quartz veins cross cutting veins and breccias with mineralogy typical of previous stages (Figure 5.11). Native gold, electrum and silver (sulfosalts, proustite, argentotennantite?) are found mainly at enargite borders and where enargite is in contact to late copper sulfides such as bornite, covellite and chalcopyrite which are uncommon in this stage.   117   Figure 5.10. Enargite occurrence at La Bodega. A. DDH LB037 at 187.15 m, sample ALR264. Alunite vein with enargite and pyrite. B. Microphotograph of A under reflected light showing coarse pyrite cut by enargite + fine grained colloform pyrite. C. DDH LB037 at 151.35 m, sample ALR260; Pyrite (cubic and dodecahedric habit) vein cut by alunite-quartz + enargite irregular vein. D. Microphotograph of C under reflected light showing coarse pyrite and clasts of pyrite cross cut by enargite + fine grained colloform pyrite. E. Microphotograph of C by SEM (back scattered electron image) showing zonation related to enargite replacement and As, Cu, Fe as main elements in analyzed grain. F.  Close up of E showing grain of wolframite (approximately 40 ?m width). G, H and I. Element maps of F. G. Iron H. Copper. I. Arsenic. J. Microphotograph of C under reflected light showing enargite vein cross-cutting coarse pyrite vein and enargite + fine pyrite concentric zonation. K. Microphotograph of C showing fractured pyrite 4. L. Close up on K showing fractured pyrite with enargite in fractures and minor gold.    118   Figure 5.11. Enargite at La Mascota. DDH LB112 at 264.15 m, sample ALR014B. A. Core sample showing silicified tectonic breccia (THBX) clasts cut by quartz wolframite veins with pyrite (py4 and py5) with colloform texture which is also cross cut by drusy quartz with enargite at center. Banded quartz (chalcedony is crosscut by enargite bearing vein. B. Reflected light microphotograph showing enargite quartz vein cross cutting clasts and veins with pyrite. C. D. Close up on C; SEM backscatter image showing main elements in analyzed spots. E. Same as D under reflected light showing Close up to B showing copper and copper-iron sulfides (covellite, bornite, chalcopyrite and tetrahedrite tennantite; clast relict?) and gold-silver electrum) at enargite border.     119   Figure 5.12. Tennantite-tetrahedrite at La Mascota in relation to stages 4 and 5 and associated silver mineralization. DDH LB112 at 265.15 m, sample ALR015. A. Multiple phases breccia quartz-wolframite bands, tetrahedrite-tennantite in drusy quartz cavities, cross cut by enargite microveins. Rounded clasts cemented and matrix and replaced by quartz of colloform texture (cockade texture breccia at left). Colloform fine pyrite vein with quartz and tetrahedrite-tennantite. B. Microphotograph of A under reflected light showing tetrahedrite-tennantite with fine pyrite and relationship to fine grained quartz and wolframite band with enargite in pore. C. Tetrahedrite-tennantite band with pyrite (cubic habit) and enargite in second band. D. Close up of tetrahedrite-tennantite showing typical brownish gray and blueish gray tints. E. SEM microphotograph showing main elements in analyzed spots. F, G, H, I, and J. Element maps of E showing copper, arsenic, antimony, silver (proustite?) and tellurium (hessite?) respectively.    120  Tennantite-tetrahedrite (anhedral, <3 mm) is found in alternating quartz-wolframite bands cavities in late phases of stage 4 and early phases of stage 5 where enargite is the dominant sulfide-sulfosalt and in enargite microveins crosscut tenantite-tetrahedrite microstructures. Proustite and hessite (?) may occur at tennantite-tetrahedrite borders (Figure 5.12) 5.3.6 Stage 6: Post- mineralization stage, sphalerite bearing structures Stage 6 is characterized by the occurrence of sphalerite in quartz cement and alunite-quartz cement in breccias. Sphalerite occurrence is minor and mostly restricted to borders of breccias and silicified zones. At La Bodega sphalerite occurs as fine grained pyrite (and/or marcasite?) + sphalerite + quartz cement of clasts (granite) supported jig-saw fit breccias (CJBX) in close vicinity to granites and and/or related to porous quartz (vuggy-like silica) replacements (Figure 5.13). At La Mascota sphalerite occurs as pyrite + sphalerite + alunite>quartz open space fillings in breccias and alunite cemented breccias and veins cutting earlier breccias (Figure 5.14). In alunite filling cavities, sphalerite may be accompanied by its wurtzite. Sphalerite bearing veins and breccias do not seem to correlate with Au-Ag mineralization at La Bodega and La Mascota. Other mineral occurrences likely to be related to stage 6 (either post-stage 5 early stage 6 or late phases of stage 6) have been reported by other authors. Forero (2010) reports native sulfur in drusy quartz cavity. Mendoza (2011) reports fine grained marcasite associated with fine grained colloform/botroydal pyrite (?) from   121  drusy quartz veins with cavities filled with native sulfur in discrete areas of La Mascota which is indicative of native sulfur being late respect to sulfides from stage 5 (Figure 5.14). Pratt (2009, unpublished reports for Ventana Gold Corp.) show botroydal marcasite vein crosscutting breccia at La Bodega which is likely associated with sphalerite. Sphalerite has also been reported at El Cuatro, SW of La Mascota, associated with hydrothermal breccias, fine grained pyrite/marcasite (?) silicified zones with porous quartz textures and alunite infilling pores (Rodriguez, 2009; Ventana Gold Corp. internal report) and black hydrothermal breccias with uranium bearing minerals (torbernite) in fracture fills. At the San Celestino area, SW of El Cuatro, Polania (1980, 1983) reports sphalerite/wurtzite late as compared to enargite and earlier as compared to uranium bearing minerals in veins/breccias. Reported uranium bearing minerals in the San Celestino veins/breccias include pitchblende, autunite and torbernite (Pagnacco, 1962; Mendoza and Jaramillo, 1973; Ward et al., 1973; Polania, 1980, 1983; Bissig et al., 2012).   122   Figure 5.13. Sphalerite and marcasite at La Bodega. LB327 at 246.60 m., sample ALR064. Monolithic clast supported jigsaw fit breccia with granite clasts (CJBX). Quartz cement with pyrite/marcasite? + sphalerite (sph). A. Macroscopic sample. B. 10X in cross polarized light; early quartz in clast (qz1), denotes quartz vein (qz2). C. reflected light of B picture showing sphalerite occurrence in cement associated with fine pyrite/marcasite (?). D and E. close up on C showing titanite associated with granite clasts in contact to crosscutting fine pyrite/marcasite? + sphalerite + quartz microvein (?). F and G. LB037 at 134.8 m. ALR257. F. Microphotograph on cross-polarized light of sphalerite bearing vein cutting alunite-quartz vein cutting silicified leucogranite with porous quartz with alunite. G. Close up of sphalerite vein from F on plane polarized light    123   Figure 5.14.  Sphalerite, marcasite and native sulfur at La Mascota. A. DDH LB114 at 305.7 m, sample ALR150. Hydrothermal breccia. Drusy quartz-alunite cavity filled with alunite-sphalerite-pyrite. Kaolinite drusy quartz filling. B. Microphotograph of A under plane polarized light, showing sphalerite in alunite filling and wolframite in drusy quartz. C. DDH LB205 at 280.0 m, sample ALR329. Multiple phases hydrothermal breccia, cut by pyrite-enargite vein cut by alunite-sphalerite vein. D. Microphotograph of C under reflected light showing pyrite-enargite vein cut by pyrite-sphalerite vein. Pyrite is broken and is partially replaced by enargite. E. Close up to C under transmitted light showing sphalerite. F. Close up to E seen by BSE, showing analysed spots with zinc (from sphalerite) and tungsten (from wolframite clast). G. and H. Marcasite and native sulfur in drusy quartz cavity of multiple-phase hydrothermal breccia at La Mascota with porous quartz clasts (after Mendoza, 2011). H Close up of G.   124  5.3.7 Stage 7: supergene features related to mineralization, late faulting and iron oxides bearing structures.  A weathering profile of ~20 m to as deep as 100 m is developed in some areas of La Bodega and La Mascota. The main products of supergene alteration include goethite, hematite (mainly as fracture coatings) and undetermined mixtures of these oxides with jarosite, here referred as limonite (Figure 5.16). Boxwork textures after pyrite oxidation are common in veins and breccias. Other products of supergene alteration are jarosite (related to the surface occurrence of pyrite bearing vein networks), chalcanthite (mainly related to copper sulfide weathering at La Mascota) and manganese oxides. Jarosite and chalcanthite can be found on some core samples that have been exposed to water and air for a couple of months. Fault reactivation after mineralization events generated intensely fractured and gouge-rich fault zones. These faulted zones may play an important role in the weathering profile since they provide paths for surface waters to circulate deeper and allow rocks and veins to oxidize. Complete oxidation of sulfides in veins and iron bearing minerals in rock is common up to 10 m below surface. Passing this zone, oxidation is incomplete and oxides are observed together with sulfides (Figure 5.18). Deeper weathering profile zones are associated with permeable structures. Zones with specularite veining may also exhibit fractures with specular hematite fracture coatings and goethite.   125   Figure  5.15. Supergene alteration minerals at La Bodega and La Mascota. A. La Bodega, DDH LB013 at 5.25 m. Oxidized hydrothermal breccia. Goethite vein with boxwork texture. FeO fracture coating and after biotite, in clasts. Kaolinite within veins. B. La Bodega, DDH LB022 at 5.50 m. Gneiss with muscovite alteration cut by oxidized vein: goethite and glassy limonite (?) with boxwork texture. C. La Bodega, LB037 at 52.00 m. Clay (kaolinite) supported breccia; silicified and limonite in matrix. Goethite and glassy limonite with boxwork texture. D. La Mascota, DDH LB114 at 77.10 m., sample ALR134. Specularite vein weakly altered to hematite cutting chlorite veinlet; specularite-hematite fracture coating; limonite after bitote (?). E. La Mascota, DDH LB205 at 291.20 m., sample ALR334. Silicified rock with porous quartz. Core sample after exposure to weathering showing surficial growth of chalcantite and jarosite. F. La Bodega, DDHLB072 at 100.00 m. Gneiss cut by enargite-fine pyrite vein in quartz ? alunite alteration. Core sample exposed to weather showing surficial growth of chalcantite, gypsum.   126  5.4 Mineral zonation and gold grade distribution at La Bodega and La Mascota Ore minerals found in the different stages for La Bodega and La Mascota show zonation and different mineralization styles can be outlined based on sulfides, sulfosalts and oxides that predominate in each evolution stage. Thus, mineralization zones were mapped and defined for La Bodega (Figure 5.16) and La Mascota (Figure 5.17) and gold grades distribution was characterized visually in general terms a as follows: ? Specularite bearing vein zones are found adjacent or in close distance to the mineralized zones as low frequency veinlet networks (<0.5% veins per rock volume) at La Bodega as well as La Mascota exhibiting gold regularly grades below 0.1 ppm. ? Pyrite veining zones (with D-type veins), associated with phyllic alteration, exhibit grades between ~0.1 ppm.and ~2.00 ppm at La Bodega and La Mascota. The most frequent grade at La Bodega in this zone is ~0.5-1 ppm.  ? Copper sulfides bearing veins and breccias exhibit gold grades in average around 1.00 ppm at La Bodega with grades ranging from from ~0.5 ppm (associated with copper sulfide bearing vein networks with low vein density) to ~10.00 ppm at La Bodega.  At La Mascota Copper sulfide zones are mostly associated with hydrothermal breccias and may exhibit gold grades higher than 13 ppm.   127  ? Wolframite is scarce at La Bodega therefore it does not make wide zones. At La Mascota wolframite zones are associated with hydrothermal breccias and may exhibit gold grades >13.5 ppm. ? Enargite associated zones, in general show the highest gold grades probably associated with superimposing events mainly in hydrothermal breccias. Gold grades in enargite zones at La Bodega range from 0.5 ppm (associated with enargite bearing vein network zones with low density) to 10.00 ppm and higher (see probability plot in Appendix A3). At La Mascota enargite gold grades in enargite zones range from 1.00 and 13.5 ppm and higher (see probability plot in Appendix A3). The highest grades at La Bodega and La Mascota are associated with the hydrothermal and tectonic-hydrothermal breccias. These observations are broadly consistent with element correlation and association to gold (Table 5.2). Gold has a 0.51 correlation coefficient (cce) to silver at La Mascota which is explained by the fact that most of the gold is found as electrum and as native gold while silver is also associated with copper with a cce of 0.72. On the other hand, at La Bodega, gold shows a higher correlation to arsenic (cce= 0.66), antimony (cce=0.87) and tellurium (cce=0.67) which may be explained by the fact that gold occurrence at La Bodega is associated with sulfosalts and tellurides in veins networks as well as the tectonic-hydrothermal breccias exhibiting a wide range of values. Tellurium shows correlation (cce > 0.5) to gold, silver and copper.    128   Table 5.2 Correlation matrix for sixteen elements at La Bodega (DDH LB251 and LB327) and La Mascota (DDH LB 202 and LB205).  Correlation Au_ppm Ag_ppm Cu_pct As_ppm Bi_ppm Fe_pct Mn_ppm Mo_ppm P_ppm Pb_ppm S_pct Sb_ppm Te_ppm U_ppm W_ppm Zn_ppmAu_ppm 1 0.33 0.29 0.66 0.37 0.4 -0.036 0.099 0.21 0.51 0.32 0.87 0.67 0.053 0.11 0.43Ag_ppm 1 0.77 0.32 0.6 0.38 -0.052 0.31 -0.012 0.3 0.41 0.32 0.65 0.062 0.41 0.1Cu_ppm 1 0.33 0.66 0.42 -0.048 0.32 -0.089 0.078 0.43 0.3 0.59 0.097 0.31 0.013As_ppm 1 0.2 0.47 -0.075 0.16 0.21 0.48 0.45 0.77 0.4 0.14 0.21 0.56Bi_ppm 1 0.39 -0.074 0.32 -0.055 0.069 0.41 0.22 0.76 0.16 0.11 0.055Fe_pct 1 0.15 0.39 0.2 0.28 0.83 0.41 0.44 0.32 0.22 0.32Mn_ppm 1 -0.11 0.13 -0.024 -0.17 -0.049 -0.055 -0.046 -0.03 0.023Mo_ppm 1 -0.042 0.095 0.44 0.19 0.19 0.089 0.18 0.22P_ppm 1 0.35 0.05 0.24 0.037 0.031 0.022 0.29Pb_ppm 1 0.27 0.57 0.24 0.054 0.27 0.43S_pct 1 0.35 0.42 0.36 0.24 0.31Sb_ppm 1 0.48 0.027 0.18 0.51Te_ppm 1 0.1 0.13 0.21U_ppm 1 0.086 0.1W_ppm 1 0.025Zn_ppm 1Au_ppm 1 0.51 0.42 0.02 0.01 0.029 -0.0085 0.16 0.034 0.098 0.068 0.031 0.0067 0.008 0.0085 0.098Ag_ppm 1 0.73 0.051 0.013 -0.0024 0.0022 0.043 0.048 0.02 0.052 0.027 0.024 -0.011 0.011 0.031Cu_pct 1 0.065 0.02 -0.0057 0.015 0.03 0.068 0.0053 0.065 0.033 0.041 -0.009 0.013 0.018As_ppm 1 0.65 0.52 -0.14 0.49 -0.2 0.27 0.7 0.55 0.38 0.25 0.66 0.14Bi_ppm 1 0.54 -0.067 0.33 -0.15 0.057 0.55 0.36 0.49 0.18 0.57 0.053Fe_pct 1 0.29 0.37 0.089 0.046 0.63 0.38 0.45 0.25 0.39 0.18Mn_ppm 1 -0.16 0.27 -0.16 -0.16 -0.093 -0.032 -0.12 -0.077 0.088Mo_ppm 1 -0.19 0.42 0.57 0.36 0.45 0.41 0.42 0.24P_ppm 1 -0.19 -0.33 -0.15 -0.13 -0.18 -0.16 -0.034Pb_ppm 1 0.35 0.2 0.049 0.27 0.33 0.3S_pct 1 0.47 0.46 0.49 0.53 0.22Sb_ppm 1 0.3 0.17 0.51 0.18Te_ppm 1 0.2 0.25 0.056U_ppm 1 0.17 0.27W_ppm 1 0.11Zn_ppm 1La Bodega (LB251, LB327)La Mascota (LB202, LB205)  129   Figure 5.16. N-S Section B-B?, looking west. Mineralization style at La Bodega based on predominant ore mineral association. Notice that higher gold grades are controlled by breccias and higher superimposition of mineralization styles that coincides mostly with enargite zones.  130    Figure 5.17. N-S Section M-M? looking west. Mineralization style at La Mascota based on predominant ore mineral association. Notice that higher gold grades are controlled by breccias and higher superimposition of mineralization styles that coincides mostly with enargite zones.  131  5.5 Paragenetic sequence of events at La Bodega and La Mascota Seven stages have been defined at La Bodega and La Mascota determining the the paragenetic and therefore the hydrothermal evolution of these deposits (Figure 5.18). Early stages exhibit analog characteristics that share with porphyry copper deposits. Stage 1 is characterized by chlorite and epidote alteration associations and veins analog to propylitic alteration zones typical of the outer envelops of porphyry copper and epithermal deposits and are accompanied by specularite bearing veins. Specularite  bearing veins are formed at this stage by oxidized fluids or fluids depleted in sulfur that interact with the iron bearing minerals host rocks providing alteration and slightly later veining systems. Stage 2 is characterized by phyllic alteration assemblages, as described in Chapter 3, that is, alteration minerals such as muscovite, variable amounts of illite, quartz and pyrite. Both muscovite and illite alteration in this stage 2 is accompanied by quartz + pyrite (+ hematite) veins that are analogous to D-type veins in porphyry copper models. According to mineral zonation and assay results, is associated with this stage to this stage but is not easily detectable through petrography or by means of SEM analysis, therefore it is expected to be very fine grained and related to pyrite.  Stages 3 through 6 are associated with advanced argillic alteration (quartz-alunite and silicification) characteristic of epithermal environment and associated with hydrothermal and tectonic-hydrothermal breccias formation at La Bodega and La Mascota.    132   Figure 5.18. Paragenetic sequence for La Bodega and La Mascota. Black lines: occurrence at La Bodega and La Mascota. Purple Lines: occurrence mainly at La Mascota. Orange lines: occurrence at La Bodega.  Line continuity and width indicates relative abundance compared to other minerals. Late SupergenePre-mineralizationSupergeneStage 1Chlorite-EpidoteSpeculariteStage 2Muscovite-Illite PyriteStage 3Quartz-Alunite Copper sulphidescpy, cc, cv, bnStage 4Quartz-Wolframite (h?bnerite)Stage 5 Quartz-AluniteEnargiteStage 6Quartz-Alunite SphaleriteStage 7KaoliniteGoethiteEpidoteChloriteCarbonate (Calcite)Montmorillonite                    ?                  ?                    ?        ?RutileTitaniteMuscoviteIlliteAlunite       Bladed (platty) alunite (in quartz druses)       Natroalunite+alunite               ?               ?JarositeQuartz       Dull massive quartz veins       Comb quartz (veins, breccias)       Banded silica       Bladed texture quartz (breccias)       Flamboyant/plumose zoned texture quartz       Chalcedonic quartz       Drusy quartz (veins and breccias)       Porous quartz (vuggy-like quartz)KaoliniteSpecularite (in veins)Pyrite     Fine, cubic/anhedral, disseminated, in veins     Fine grained, disseminated (scattered)     Coarse cubic habit     Dodecahedric habit mostly coarse     Fine grained (colloform/botroydal)HematiteMolybdeniteChalcopyriteChalcociteBorniteCovelliteTetrahedrite-TennantiteSilver sulphosalts (proustite)TelluridesGold-silver tellurides (hessite, calaverite)Gold-silver (electrum) ?Native goldWolframite (h?bnerite)EnargiteMarcasiteSphalerite/wurtziteNative Sulfur                            ?  ?                   ?          ?Glassy limoniteGoethiteChlorite+epidoteEpidoteSpecularite+chalcopyrite+pyrite+calciteQuartz+molybdenite+pyriteD-type: quartz+pyrite (cubic)(+hematite)Quartz+pyrite+copper sulfidesAlunite+pyriteQuartz+wolframite+pyrite?sulfosaltsQuartz+alunite+enargiteQuartz+goethite (D veins oxidation)Tectonic foliation,  multiple phases ( THBX)Gray quartz cement, multiple phases (QCBX)Clast supported (granite) jigsawfit (CJBX)                ?                        Resorbed clasts edges  breccia (RCBX)                          ?           ?                        ? ?Fault, clay matrix (FBX)HYBXVeinsBrecciasOre MineralogyMiddleMineralsMineralization stagesEarlyPorphyry style Epithermal styleAlteration minerals  & gangue  133  Stage 3 is the beginning of main brecciation events and the precipitation of gold/silver associated with copper and copper iron sulfides. At La Bodega copper sulfides are found mainly within quartz + pyrite + chalcocite-bornite veins cutting quartz + pyrite veins in muscovite>illite alteration zones but also in some hydrothermal breccias (mainly tectono-hydrothermal breccias). At La Mascota, copper sulfides are mostly found within hydrothermal breccias with quartz-alunite cement and quartz ?alunite alteration envelopes; but also forming narrow vein zones around breccias and quartz?alunite altered zones. During subsequent brecciation events additional quartz-alunite and associated ore minerals were emplaced. Gold is found associated with silver and tellurium in pyrite inclusions, as native gold in quartz veins, in copper sulfide borders associated with sulfosalts. Silver is also found as silver sulfosalts associated with copper sulfides. Stage 4 is characterized by the occurrence of manganese bearing wolframite in quartz with textures related to boiling (Chapter 4) and bladed textured quartz interpreted as quartz replacing barite (?). Gold is late in stage 4 and it is found as native gold grains and gold associated with minor tetrahedrite-tennantite. Mn-Wolframite deposition is controlled by the solubility of tungsten and manganese, which depends on pH and temperature (Hornet, 1979). Mn-Wolframite is precipitated under near neutral pH conditions (5 to 6) and temperatures above 200?C (Hornet, 1979). The presence of wolframite and quartz textures indicative of boiling suggest near neutral pH conditions and temperatures ~200?C. These conditions may suggest temporary fluid mixing with a second fluid source (probably   134  meteoric waters) or changes in pH driven by boiling that allowed for higher pH to deposit tungsten and manganese as wolframite during stage 4.  Stage 5 is characterized by the deposition of enargite in veins with quartz and alunite and in breccias and drusy quartz cavities. Tetrahedrite-tennatite is deposited in late phases of stage 3, in some phases of stage 4 and mostly in early phases of stage 5. Gold and silver are found mainly as electrum in the borders of anhedral enargite in some cases associated with minor amounts of copper sulfides. Stage 6 is related to the deposition of sphalerite under low temperature and possible strongly acidic conditions (pH~2-3) that allowed for the deposition of alunite and the formation of porous quartz textures (vuggy-like silica) in some zones of La Bodega. There is no evidence for significant gold deposition in this stage. Stage 7 corresponds to the more current ongoing weathering and supergene alteration due to the exposure of the deposit to surface conditions, forming kaolinite, iron oxides and sulfates (iron, copper, calcium). Stages 3 through 5 provided the highest grades for gold and silver mineralization related to epithermal mineralization. Gold grain size typically ranges from 10 to 100 ?m. Silver is found as silver tellurides, electrum (related to gold), silver sulfosalts (proustite) and hessite. Silver seems to be is more abundant at La Mascota than at La Bodega.   135  Sulfide minerals related to stages 3 through 5 for La Bodega and La Mascota are representative of mostly high-sulfidation conditions (Figure 5.17). In addition, sulfides zonation and replacements at microscopic scale are common in stages 2 through 6 reflecting the changes in sulfidation state, pH and temperature conditions in every stage and through the evolution of the system. Concentric zonation of sulfides resembles colloform and crustiform textures associated with quartz textures (Chapter 4) presumably derived from boiling. The late occurrence of sphalerite in Stage 6 is consistent with the general temperature decline (Figure 5.20) in the whole system at La Bodega as well as La Mascota.  Figure 5.19. Log f S2 ? 1000/T diagram, showing sulfidation state of magmas and mineral sulfidation reactions at 1 bar (Einaudi and Hedenquist, 2003). In blue, it is represented the range of minerals within La Bodega and La Mascota deposits paragenetic sequence and the evolution path of the hydrothermal fluids is schematically shown: Fluids are striving between intermediate and high- sulfidation conditions but high-sulfidation condition dominate last stages.   136  Chapter 6. Geochronological Constraints of Alteration and Mineralization Events at La Mascota and La Bodega  6.1 Introduction Geochronological constraints for the timing of mineralization and alteration events within the California-Vetas Mining District are important in order to properly define the relationships between the rocks outcropping in the area and the hydrothermal events within the district. Previous studies have obtained wide range of ages for the California-Vetas Mining District alteration, mineralization and related host rocks. ? Isotopic K?Ar dating of alteration minerals from the granodiorite porphyry that intrudes the Cretaceous sedimentary rocks from the district yielded Upper Cretaceous to Early Tertiary ages for the porphyry that range from 60 to 66 Ma (Nippon Mining Co. Ltd, 1967; in Mathur et al., 2003). ? Mendoza and Jaramillo (1979) describe a dacititic porphyry that intrudes the Cretaceous sediment sequence in the area, indicating post-Cretaceous magmatic activity. ? Sillitoe (1982) refers to geochronology done on sericite found at the margin of a dacite porphyry (Mendoza and Jaramillo, 1979) which yielded to a K-Ar age of 144 ? 3 m.y. and suggests this is the preferred age for the porphyry style mineralization in the CVMD area.   137  ? Mathur et al. (2003), defined a Re-Os isochron age of 57 + 10 Ma (MSWD = 0.8), using gold-rich pyrite concentrates from several artisanal mines in the California area, which is similar to an alteration age obtained by the Nippon Mining Co. Ltda, 1967 (In: Mathur et al, 2003). ? Sillitoe (2008), using Mathur?s age, assigns a Late Cretaceous - Early Tertiary age to mineralization at the CVMD. ? Recent published data by Mantilla Figueroa et al. (2013), unravels the magmatic history of the District defining the main tectono-magmatic events through U-Pb geochronology on zircons: (1) the Grenville Orogeny and high grade metamorphism and migmatitization between ~1240 and 957 Ma; (2) early Ordovician calc-alkalic magmatism, which was synchronous with the Caparonensise-Famatinian Orogeny (~477 Ma); (3) Middle to Late Ordovician post-collisional calc-alkalic magmatism (~466-436 Ma); (4) Late Triassic to Early Jurassic magmatism between ~204 and 196 Ma, characterized by both S- and I-type calc-alkalic intrusions which at La Mascota is represented by a leucogranite dike sample (ALR035, collected by the author of this thesis) of ~201 Ma (Jurassic) and; (5) late Miocene shallowly emplaced intermediate calc-alkaline intrusions of porphyritic texture with a range of ages between 10.9 ? 0.2  to  8.4 ? 0.2 Ma based on U-Pb geochronology on zircons (Mantilla et al., 2009, Mantilla et al., 2011; Leal-Mej?a et al., 2011; Bissig et al., 2012).   138  The recent studies reveal that the district has undergone a complex magmatic history that includes magmatic events much more recent than previously expected. Therefore, hydrothermal history in the district needed to be better constrained. New geochronological 40Ar/39Ar data that constrain the alteration and mineralization within the paragenetic evolution of La Bodega and La Mascota (as seen in Chapter 5) are presented in this chapter. The geochronological data were obtained by collaborators within the MDRU Colombia Porphyry and Epithermal Gold project. Figure 6.1 shows the compiled geochronological information. The data shown here are gathered mainly within the framework of MDRU Colombia Porphyry and Epithermal Gold project but it also refers to recent studies by other authors but still within the CVMD.   6.2 Methodology The 40Ar/39Ar geochronology (developed by Merrihue and Turner, 1966) is a modification of the conventional K-Ar dating technique, in which a proportion of the 39K in the sample is converted to 39Ar by neutron activation. The 40K/40Ar* (radiogenic Ar) ratio is measured directly in terms of 40ArK/39Ar using a mass spectrometer (Richards and Noble, 1998) through step-heating experiments that allow to differentiate between different sources of Ar and make the appropriate calculation for the age of the dated mineral.   139  6.2.1 Sample collection Samples were collected from drill core at La Bodega La Mascota and El Cuatro. Mineral paragenetic sequence was taken into account (Chapter 5). Samples representative of hydrothermal events that contained hypogene alunite (See Chapter 8) with different mineral associations (Stages 3 through 6, Chapter 5) were the main focus. Sampling by T. Bissig (2011) included two muscovite (sericite) samples (Stage 2) at La Bodega from DDH LB251. Alunite samples included, 2 samples from La Bodega from DDH LB037 and DDH LB013, 6 alunite samples at La Mascota from DDH LB112 and DDH LB156 and 1 alunite sample approximately 0.5 Km to the south-west of the study area at El Cuatro zone from DDH LB278. Samples are illustrated in figure 6.2. A list of the analyzed samples and their description is provided in Table 6.1.  Prior to separation, samples were analyzed by Terraspec? to confirm alunite presence (procedure described in Chapter 4 and appendix A4). Samples were carefully separated from rock and cleaned off intermixed sulfides when present. Final sample grain size was approximately 50-500 ?m in most cases. Samples were stored in sealed vials. Duplicate samples were taken to carry out X-ray diffraction analysis that would determine the alunite occurrence and the sulfide association related to the alunite sample (see appendix A6). Similar procedure was carried out on the muscovite (sericite) samples (T. Bissig, comm. pers., 2012).      140  6.2.2 Analytical procedures 40Ar/39Ar geochronology analysis was carried out at the Pacific Centre for Isotopic and Geochemical Research, Department of Earth, Ocean and Atmospheric Sciences at The University of British Columbia. The samples were wrapped in aluminum foil and irradiated at the McMaster Nuclear Reactor in Hamilton, Ont. Isotope flux monitors (Fish Canyon Tuff Sanidine 28.02 Ma) were interspersed in the samples during irradiation to determine the J-value. The samples were analyzed at the Noble Gas Laboratory, Pacific Centre for Isotopic and Geochemical Research, University of British Columbia, Vancouver, BC, Canada. The separates were step-heated at increasing laser powers in the defocused beam of a 10-W CO2 laser. The gas evolved from each step was analyzed using a VG5400 mass spectrometer equipped with an ion-counting electron multiplier. All measurements were corrected for total system blank, mass spectrometer sensitivity, mass discrimination, radioactive decay during and subsequent to irradiation, as well as interfering Ar from atmospheric contamination and the irradiation of Ca, Cl and K (isotope production ratios: (40Ar/39Ar)K = 0.0302, (37Ar/39Ar)Ca = 1416.4306, (36Ar/39Ar)Ca = 0.3952, Ca/K = 1.83 (37Ar Ca/39ArK). The plateau and correlation ages were calculated using Isoplot ver.3.09 (Ludwig, 2003). Errors are quoted at the 2-sigma (95% confidence) level and are propagated from all sources except mass spectrometer sensitivity and age of the flux monitor.     141   Figure 6.1 Recent geochronological data shown on the geological map of the California Vetas district. Map based on this study and Colombia Porphyry and Epithermal Gold MDRU Project. Map is based on Ward et al. (1973), Evans (1976), Polania (1980), MDRU Colombia Porphyry and Epithermal Gold project and this study. Locations and age data mentioned in this report are shown.   142   Figure 6.2 Samples selected for 40ArK/39Ar geochronology (see Table 6.1 for detailed description). A, B, C, D, E, F; alunite at La Mascota. A. ALR012, alunite Stage 3. Age: 2.63 ? 0.09 Ma. B. ALR024, natroalunite (stage 6?). Age: 1.87 ? 0.30 Ma. C. ALR026, alunite (Late stage 4 to early stage 5). Age: 2.47 ? 0.27 Ma. D. ALR027, alunite (Stage 3? to late 4?). Age: 2.31 ? 0.26 Ma. E. ALR034, alunite. Age: 2.26 ? 0.31 Ma. F.  ALR038, alunite (Stage 6). Age: 1.60 ? 0.69 Ma. G, I; alunite at La Bodega. G. ALR264, alunite (stage 5). Age:  2.22 ? 0.05 Ma. I. ALR281, natroalunite (stage 6?). Age: 1.63 ? 0.29 Ma. J. Alunite at El Cuatro, ALR040, alunite associated with pyrite cut by chalcocite vein (Late stage 2 to early stage 3?). Age: 3.26 ? 0.30 Ma. K, L., Muscovite (sericite at La Bodega. K. TB-CV-019, muscovite (sericite; Stage 2). Age: 3.54 ? 0.13 Ma. L. TB-CV-023, muscovite (sericite, stage 2). Age: <10 Ma.   143  6.3 Results Alunite and muscovite samples from La Bodega, La Mascota and El Cuatro all yielded Pliocene to Pleistocene ages and are summarized in Table 6.1. Analyzed samples for 40ArK/39Ar geochronology are illustrated in Figure 6.3. Given the young age, the precision of the 40Ar/39Ar method is affected by the relatively small amount of radiogenic 40Ar and the comparatively large amount of atmospheric 40Ar. Consequently, the analytical errors can be considerable. Nevertheless, most samples yielded reliable plateau ages (the preferred age with this technique) containing 99-100% 39Ar. The mean standard weighted deviation (MSWD) on the plateau age is generally below 1.5 to as low as 0.103 adding confidence in the plateau ages. Based on the analyzed samples, 40ArK/39Ar ages from alteration associations related to mineralization may be summarized as follows: At La Mascota, age of hypogene alunite associated with mineralization ranges from 2.63 ? 0.09 Ma (alunite from stage 3) to 1.56 ? 0.70 Ma. (natroalunite, stage 6). At La Bodega, age of alteration minerals associated with mineralization ranges from <10 Ma to 3.343 ? 0.072 Ma for muscovite (sericite) samples (stage 2); 2.22 ? 0.05 Ma (alunite, stage 5) and 1.63 ? 0.29 Ma (natroalunite, stage 6?). At El Cuatro, an alunite replacing feldspar phenocrysts (stage 2-3?) gave an age of 3.21 ? 0.49 Ma. Duplicate analysis yielded an age of 3.47?0.50 Ma.    144  Table 6.1 Summary of results of 40ArK/39Ar geochronology at La Bodega, La Mascota and El Cuatro. Zone Sample DDH ID Depth (m) Mineral 40Ar K/39Ar  age (Ma) Sample Description (analyzed separates in bold) Analytical Result Discussion La Mascota ALR012 LB112 253.10 Alunite Stage 3 2.63 ? 0.09 Clast supported breccia. Alunitized gneiss clasts and quartz + alunite cement with cubic and dodecahedric pyrite; covellite and bornite overgrown on pyrite. Drusy quartz+ pyrite + covellite + bornite+ chalcocite cutting breccia. A plateau age of 2.63 ? 0.09 Ma containing 100% of the 39Ar released in 6 heating steps was obtained (MSWD = 1.2). However, more than 96% of the 39Ar was released in two heating steps. Coinciding normal and inverse isochron ages of 2.66 ? 0.1 Ma (MSWD = 1.04 and 0.91) provide confidence in the plateau age which is considered reliable. Atmospheric argon in the two most reliable heating steps is less than 50%. La Mascota ALR024 LB112 312.60 Natroalunite Stage 6? 1.87 ? 0.30 Cement to matrix supported breccia. Alunite (natroalunite) + quartz cement with scattered pyrite  and fine grained pyrite  A plateau age of 1.87 ? 0.30 Ma was yielded containing 5 heating steps and 99.9% of 39Ar  (MSWD = 1.01). Four of these steps have atmospheric argon contents of 82 to 91.16% whereas the remaining steps contain essentially no radiogenic argon. The normal and inverse isochron ages of 1.92 ? 0.73 (MSWD = 3.0) and 1.89 ? 0.75 Ma (MSWD = 3.1), respectively, match the plateau age. The plateau age is considered reliable. La Mascota ALR026 LB159 337.70 Alunite. Late stage 4 to early stage 5  2.47 ? 0.27 Hydrothermal breccia. Clasts supported mainly. Flaky (tabular) alunite (magmatic steam-like origin, cf Rye, 1993) in cavity of drusy quartz + fine grained pyrite and wolframite cavity. A plateau age of 2.47 ? 0.27 Ma was obtained containing 100% of the 39Ar released in 13 steps (MSWD = 0.41). Most of the 39Ar was released in three consecutive steps containing about 80% of the 39Ar fraction. However only one step containing 38% of the 39Ar has atmospheric argon below 50%. The age of that step is 2.44 ? 0.32 Ma which is very close to the overall plateau age. Normal and inverse isochron ages = 2.49 ? 0.26 and 2.50 ? 0.27 Ma (MSWD = 0.48 and MSWD = 0.36, respectively) are very similar to the plateau age. The latter is considered reliable La Mascota ALR027 LB112 328.80 Alunite. Stage  3-4 2.31 ? 0.26 Alunite + cubic pyrite vein cutting alunite and quartz altered gneiss and banded quartz + fine pyrite vein (?) A plateau age of 2.31 ? 0.26 Ma was obtained containing 7 steps and 100% of the 39Ar released (MSWD = 0.42). About 85% of the 39Ar was released in two heating steps that contain around 50% atmospheric argon. The normal and inverse isochron ages are, at 2.36 ? 0.28 Ma (MSWD = 0.35) and 2.36 ? 0.26 Ma (MSWD = 0.31), respectively, very similar to the plateau age. The latter is considered reliable. La Mascota ALR034 LB112 347.70 Alunite 2.26 ? 0.31 Alunite + Pyrite veinlet cutting Leucogranite (illite + alunite alteration); equivalent to ALR035. U/Pb geochronology on zircons: 210?3.5 Ma (Mantilla et al., 2013) A plateau age of 2.26 ? 0.31 Ma was obtained  containing  100% of the 39Ar released in 7 heating steps (MSWD = 0.13). Only 4 steps have atmospheric argon contents below 87% (66.4 to 87%) and jointly contain more than 98% of the 39Ar. The isochron ages 2.35 ? 0.57 (normal, MSWD = 0.26) and 2.32 ? 0.57 Ma (inverse, MSWD = 0.15) coincide well with the plateau but are slightly less precise. The plateau age is considered reliable.  La Mascota ALR038 LB112 357.80 Alunite. Stage 6 1.39 ? 0.73 Clast supported breccia cut by alunite + kaolinite + fine pyrite and cubic pyrite + sphalerite vein with brecciated texture. Only one heating step yielded less than 90% of atmospheric argon. The age of this step is 1.39 ? 0.73 Ma which is similar to the plateau age of 1.27 ? 0.65 which considers 99.7% of the 39Ar (MSWD = 1.5). The isochron ages are 1.60 ? 0.69 (normal, MSWD = 1.2) and 1.56 ? 0.70 Ma (inverse, MSWD = 1.3). The best step age in this case is probably somewhat more reliable than the Plateau and isochron ages although they are all within error of each other.   145  Zone Sample DDH ID Depth (m) Mineral 40Ar K/39Ar  age (Ma) Sample Description (analyzed separates in bold) Analytical Result Discussion El Cuatro ALR040 LB282 131.30 Alunite. Late stage 2 to early stage 3? 3.26 ? 0.30 Dacitic porphyry with alunite alteration overprinting illite alteration (?). Alunite replacing feldspars. Rock is cut by pyrite + chalcocite veinlet. A  plateau age of 3.26 ? 0.30 Ma was obtained  including all of 10 heating steps and 100% of the 39Ar. Atmospheric argon contamination is only between 24 and 36% for those heating steps where most of the 39Ar was released. Isochron ages of 3.14 ? 0.45 (normal) and 3.21 ? 0.49 Ma (inverse) coincide well with the plateau age. A duplicate run of this sample did not yield a plateau age but three ages of individual heating steps lie between 3.3 and 3 Ma and the isochron ages are 3.29 ? 0.48 Ma and 3.27 ? 0.50 Ma (normal and inverse, respectively).  La Bodega ALR264 LB037 197.15 Alunite. Stage 5  2.22 ? 0.05 Gneiss with illite alteration cut by Alunite + fine pyrite + cubic pyrite + enargite vein A plateau age of 2.221 ? 0.053 Ma was obtained including 99.93% of the 39Ar in 11 of 13 heating steps,(MSWD = 0.97) which is matched by the isochron ages 2.25 ? 0.19 Ma (normal, MSWD = 2.2) and 2.12 ? 0.13 Ma (inverse, MSWD = 0.83). The Plateau age is considered reliable La Bodega ALR281 LB013 231.80 Natroalunite Stage 6? 1.63 ? 0.29 Silicified tectonic breccia (THBX). Alunite cement with cubic pyrite and fine grained pyrite and pyrite clasts. A plateau age of 1.63 ? 0.29 Ma was obtained (99.16% of the 39Ar, 6 of 9 heating steps, (MSWD = 0.72). Isochron ages are slightly older at 1.99 ? 0.33 Ma (normal, MSWD = 0.33) and 2.00 ? 0.34 Ma (inverse, MSWD = 0.34) but error ranges overlap between the plateau and isochron ages. The relatively large errors are attributed to the high relative atmospheric argon content (77 to 89%) which is to be expected in young samples. The plateau age is considered reliable. La Bodega TB-CV-019 LB251 175.26 Muscovite (Sericite). Stage 2. 3.54 ? 0.13 Granitic Pegmatite: Coarse pegmatoid feldspar phyric rock intensely quartz-muscovite (sericite) altered. Sericite is greenish, replacing feldspars, white quartz in matrix. This sample has been analyzed twice and the results were reproducible. Run 1 yielded a plateau age of 3.34 ? 0.07 Ma (Mean Standard Weighted Deviation: MSWD = 0.53) which Includes 93.7% of the 39Ar and 13 of 16 heating steps. The Isochron ages agree well with the plateau age and are 3.54 ? 0.13 Ma (normal, MSWD = 3.3) and 3.37 ? 0.11 Ma (inverse, MSWD = 1.3). The repeat analysis yielded an essentially identical result (Plateau age 3.39 ? 0.06 Ma, MSWD = 0.91, 96.7% of the 39Ar and 12 of 14 heating steps, normal isochron = 3.49 ? 0.13 Ma, MSWD = 2.1; inverse isochron = 3.45 ? 0.08, MSWD = 1.3).Both analytical runs show evidence for minor argon loss in the first heating steps but the plateau ages are considered reliable. La Bodega TB-CV-023 LB251 326.50 Muscovite (Sericite). Stage 2. <10 Ma Granitic Pegmatite: Coarse pegmatoid rock altered to white quartz matrix and rusty-greenish muscovite (sericite) altering feldspar phenocrysts. There were two analytical runs on this sample as well but the results were neither reproducible nor reliable. The first run yielded an apparent plateau age of 8.3 ? 0.21 Ma including 75.1% of the 39Ar (MSWD = 2.1) and 3 of 10 heating steps. The heating steps not included in the plateau yield both younger and higher ages at either end of the spectrum. The second analytical run did not yield a plateau age and individual heating steps yield ages between 3.8 and 7.2 Ma. Neither of the analytical runs yielded meaningful isochron ages. Overall one may interpret this age as a mixing age of alteration and an inherited component from the host rock. The alteration age is likely younger than ~10 Ma.   146   Figure 6.3. Alunite and muscovite (sericite) 40ArK/39Ar age spectra at La Macota, La Bodega and El Cuatro. For each sample, Top: Plateau age through heating steps; plateau steps are gray, rejected steps are white. Bottom: Inverse isochron age. Duplicate analysis for ALR040 at El Cuatro did not yield a plateau. Other duplicate analysis for ALR281 and TB-CV-023 did not yield to accurate reliable results (See appendix A6 for details).    147  6.4 Alunite and muscovite alteration geochronology, relationship to the CVMD geological history and paragenetic sequence of mineralizing events at La Bodega and La Mascota Reliable 40ArK/39Ar geochronology on muscovite and alunite shows an age spectrum between ~3.5 Ma and 1.6 Ma,  for La Bodega, La Mascota, and El Cuatro; which is much younger than previously published (Nippon Mining Company,1967; Mathur et al., 2003) in the California Vetas Mining District. Moreover, 40ArK/39Ar geochronology at La Perezosa area (adjacent-NE of La Bodega) gives ages of ~3.97-3.91 Ma, for muscovite, 2.48 ? 0.13 Ma from pink yellow alunite vein cutting phyllic alteration and pyrite-enargite mineralization (Bissig et al., 2012) and another age for alunite of 1.81 ? 0.90 Ma (T. Bissig, pers. comm., 2013; MDRU Colombia Porphyry and Epithermal Gold project). Furthermore, alunite from the southwestern zone of La Baja trend at La Plata (alunite on leucogranite) and San Celestino (alunite-quartz-pyrite) give ages of 3.43 ? 0.07 Ma and 3.23 ? 0.06 Ma respectively (Bissig et al., 2012). The range of ages reported here falls into the Late Miocene and mostly within the Pliocene and Pleistocene. On the other hand, alunite vein (sample ALR034, 2.26 ? 0.31 Ma in age) cross cutting leucogranite (sample ALR035, ~210 Ma, Late Triassic age; see appendix A6) at La Mascota, reveal that there is no genetic relationship whatsoever between the Triassic-Jurassic intrusive bodies and the recent hydrothermal history of the study area. The most recent magmatic events known in the CVMD correspond to the emplacement of porphyritic bodies (and associated volcanic rocks) during the Late Miocene of ages between 10.9 ? 0.2 and 8.4 ? 0.2   148  Ma (Mantilla Figueroa et al., 2009, Mantilla et al., 2011; Leal-Mej?a, 2011). Porphyry style alteration and mineralization at El Cuatro and La Plata is intimately associated with 10.1-10.2 Ma granodiorite porphyry dikes as indicated by two 10.14 ? 0.04 Ma molybdenite Re-Os ages in quartz + molybdenite veins from El Cuatro (Bissig et al., 2012). Petrographic study (Chapters 4 and 5) indicates that muscovite of stage 2 (porphyry) is older than alunite which is representative of stages 3 through 6 (epithermal). Furthermore, alunite with mineral associations from earlier stages (with copper sulfides) show older ages than alunite with mineral associations from late stages (enargite or sphalerite) and the paragenetic evolution fits the new geochronologic information in the study area (Figure 6.4). The hydrothermal evolution took place on several pulses during approximately 8-9 Ma in the area with a first- magmatic-hydrothermal pulse associated with the Mo mineralization at 10.14 Ma, then a second pulse associated with the phyllic alteration and quartz + pyrite veins associated with minor gold mineralization at ~4-3.5 Ma. Then, early high-sulfidation epithermal alteration-mineralization took place after a ~0.3 and ~0.9 Ma time gap, at El Cuatro and La Mascota, respectively. High-sulfidation epithermal alteration and mineralization was periodically active for ~1.7 m. y. Much of the gold mineralization at La Mascota and La Bodega took place in stages 3 through 5, that is, from ~2.60 Ma to ~1.9 Ma. No igneous rocks of ages similar to the gold/silver mineralization have been recognized at CVMD. Ages of hydrothermal alteration related mineralization events at La Bodega and La Mascota in the CVMD are the youngest determined in this area as compared to previous studies. These ages overlap with the ages of Paipa-Iza (~200 km south of the CVMD) magmatism in the Eastern Cordillera of Colombia (Pardo et al., 2005)   149  but no igneous rocks or mineralization of the same age has been reported there.  Figure 6.4. 40ArK/39Ar geochronology ages on alunite and muscovite within La Bodega and La Mascota in relation to the stages of paragenetic sequence of hydrothermal events at La Mascota and La Bodega; hydrothermal events at La Perezosa and El Cuatro and magmatic events at the CVMD. Early stages fit with older ages and late stages matches younger ages. Main gold mineralization is associated with stages 3 through 5. (Key: alu: alunite; nal: natroalunite; py: pyrite; cc: chalcocite, CuS: copper sulfides including bornite, covellite, chalcopyrite, chalcocite; qz: quartz; w: wolframite; en:enargite, sph: sphalerite; mo: molybdenite).   150  Chapter 7. Fluid Inclusion Microthermometry from Epithermal Quartz at La Bodega and La Mascota  7.1 Introduction Fluid Inclusion (FI) analysis has the potential to provide some of the best data on the chemical and physical processes that result in mineral growth, deformation and recrystallization (Brown, 1998). Origin and theories related to fluid inclusion research, methodologies and assumptions have been proposed and largely discussed in several review papers (Roedder, 1962, 1984; Shepperd et al., 1985; Brown, 1998; Bakker, 2003; Bodnar, 2003; Diamond, 2003; among others). Fluid inclusions from La Bodega and La Mascota deposits have been studied in relation to the previously defined paragenesis and hydrothermal stages in this zone (Chapter 04). The main objective of this study is to constrain the nature and conditions of the mineralizing fluids associated with the epithermal stage of mineralization by petrographic observation and limited thermometry. These results are discussed together with previous fluid inclusion studies in the California-Vetas Mining District.     151  7.2 Previous fluid inclusion studies in the California-Vetas Mining District Previous microthermometric fluid inclusion studies done on samples within La Baja Trend (see Figure 3.3, Chapter 3 for location) La Mascota, Angostura (NE of La Mascota and La Bodega) and La Plata (SW of La Mascota) are summarized here. La Plata Raley (2011) studied fluid inclusions in quartz on two vein types at La Plata: ? D-type vein (quartz + pyrite + chalcopyrite with sericite halo) fluid inclusions in general showed a range of salinities between 17-26 wt. % NaCl equiv., with one outlier at 10wt. % NaCl equiv. and homogenization temperatures ranging from 341?C to 412?C.  ? A-type vein (quartz + chalcopyrite ? pyrite sinuous veins) fluid inclusions showed opaque solids. These fluid inclusions yielded salinities between 12-25 wt. % NaCl equiv. and homogenization temperatures ranging from 305?C to 432?C.  Angostura Fluid inclusions studies at Angostura have been reported by Albinson (2000) and Mantilla et al. (2012): ? Albinson (2000) studied primary fluid inclusions in of stage I quartz (associated with specularite flakes) and stage II quartz (associated with chalcopyrite and bornite). He determined homogenization temperatures between 318 and 373 ?C and average salinities of about 10 wt. % NaCl equiv.   152  ? Mantilla et al. (2012) studied fluid inclusions at La Angostura from of quartz-pyrite ? chalcopyrite veins associated with quartz-sericite alteration.  Mantilla et al. (2012) determined that primary fluid inclusions have salinities around 5 wt% NaCl equiv. and homogenization temperatures of ~335 to 350? C which is broadly consistent with the findings of Albinson (2000) and fluids observed elsewhere in phyllic alteration zones related to porphyry style mineralization (Seedorff et al., 2005). Homogenization temperatures from secondary fluid inclusions are slightly lower at 296-313?C and the salinity varies between 0.5 and 9 wt% NaCl equiv. La Mascota Two microthermometry studies at La Mascota have previously analyzed fluid inclusions on quartz from veins and breccia cement: ? Forero (2010) determined that the homogenization temperatures for fluid Inclusions in quartz veins (paragenetically associated with wolframite?) were between 201 and 306 ?C with ice melting temperatures between -4.5 and -1.6 ?C, which indicates salinity ranging between 2.7 and 7.2 wt% NaCl equiv.  ? Mendoza (2011) studied primary fluid inclusions on La Mascota hydrothermal breccia cement. These fluid inclusions yielded homogenization temperatures between 190 and 255 ?C (Mendoza, 2011) and although not reported, salinities ranged from 0.4 to 6.2 wt% NaCl equiv. (M. Mendoza, 2011 pers. com.).   153  Despite the valuable information these studies provided, relationships of quartz hosting the fluid inclusions to the mineral paragenetic sequence is not clear. 7.3 Methodology Suitable samples that provided the necessary information to properly characterize the epithermal fluid were carefully chosen, prepared and studied. The main objective was to characterize the homogenization temperature ranges, as well as the salinity and composition for the fluids most closely related to the enargite stage of the paragenetic sequence (stage 5, see Chapter 5) and at La Bodega and La Mascota. Based on previous petrographic observations on several polished thin sections, two samples were selected for this study, one at La Bodega and one at La Mascota. Doubly polished thick sections (200 ?m thickness) were prepared for fluid inclusion studies for the chosen samples. Samples with a clear paragenetic relationship between fluid inclusion assemblages (FIAs) and host minerals were chosen.  7.3.1 Sample preparation, equipment configuration and data collection After petrography, samples were left immersed in acetone overnight to dissolve the glue between rock and glass. Rock was separated from glass and chips of up to ~3mm diameter carefully separated to isolate quartz grains for study. Petrographic and microthermometric studies were done at the FI laboratory facilities of the Mineral Deposit Research Unit at the Earth and Ocean Sciences Department within the University of British Columbia in Vancouver, BC. The equipment consists of an Olympus BX60 petrographic microscope with a Retiga 2000R for photographing; a Linkam freezing and heating stage with the control   154  panel hooked to the related computer interface that allowed modifying heating and cooling rate using liquid nitrogen (N2). Magnification with the petrographic microscope was possible up to 40X objective and could be duplicated (80X) using additional 2X secondary lens. Microthermometric observations were made on fluid inclusions larger than 2.5 ?m. Based on measurements made on synthetic fluid inclusions, ice melting temperatures for pure H2O shows a precision of  +0.5 ?C and a precision of +15 ?C for homogenization temperatures around 370 ?C. In order to measure eutectic temperatures and to avoid metastability phenomena, the fluid inclusions were frozen at temperatures between -180 and -120 ?C. Then, changes within the FIs were recorded during gradual heating to room temperature. Eutectic temperature (i.e., temperature of first melting observed), and final ice melting temperature were recorded. Most freezing experiments were done for one fluid inclusion at a time. Eutectic temperatures were hard to measure and are reported as range of temperatures through which internal changes (i.e. glassy solid formation, ice crystal formation) were observed after cooling experiments.  After freezing experiments, heating experiments were conducted to determine homogenization temperature, taking in account that fluid inclusions with lower homogenization temperatures should be measured first in order to avoid overpressuring and leaking of these fluid inclusions.     155  7.3.2 Salinity, pressure and depth calculation procedures Salinity was calculated assuming a H2O-NaCl fluid for all fluid inclusions, based on the ice melting temperature using equation 1 for salinities up to 23.2 wt% NaCl equiv (Equation 1). Equation 7.1: Salinity (wt. %) = 1.78Tm ice- 0.0442Tm ice2 + 0.000557Tm ice3 where Tm ice is the freezing point depression (FPD) regularly known as ice melting temperature (Bodnar, 1993 in Brown, 1998). Density (d) and pressure (P) at homogenization of fluid inclusions was estimated using the program BULK (Bakker, 2003), in which calculations use the ice melting temperature (Tm ice) and homogenization temperature (Th) found for each fluid inclusion assuming a H2O-NaCl chemical system.  Estimation of depth of formation of the fluid inclusions was done assuming hydrostatic pressure conditions using equation 2. Equation 7.2:  P = dgh, where P is pressure at homogenization; d is the fluid inclusion density at homogenization; g is the gravity acceleration (g=9.8 ms-2); and h is the depth at which the FI is believed to have formed. Therefore, Equation 7.3: h [m] = P / (d*g) [cbar/{(g/cc)*(m*s-2)}]    156  7.4 Petrography of fluid Inclusions in this study Table 7.1 shows features and codes used in this study to characterize, differentiate and classify fluids inclusions assemblages and families in this study. Detail information regarding the studied fluid inclusions including fluid inclusion size and shape as well as microthermometry measurements is found on appendix A 7 Table 7.1. Fluid inclusions characterization and associated codes. Fluid inclusion code is composed of: 1. Zone, 2. Quartz paragenetic association, 3. Location in quartz crystal (assemblage), 4. Fluid inclusion type based on components, 5. Fluid inclusion post-entrapment modification (when observed). Feature Code Description Remarks Zone B La Bodega   M La Mascota   Quartz paragenetic association E Enargite Stage 5 W Wolframite Stage 4 Location within quartz crystal (Family, fluid inclusion assemblage) C Quartz core   G Quartz growth plane For zoned quartz A Fluid inclusions aligned within trail associated with a post- quartz crystalization fracture Associated with secondary fluid inclusions. This code is accompanied by a number which also denotes secondary fluid inclusions within this trail Genetic-temporal class (based on Goldstein, 2003)  P Primary Entrapped during crystalization PS Pseudo secondary  Aligned, but entraped during crystalization. Data treated as primary S Secondary Entraped after quartz crystalization. Accompanied by a number which relates it to a trail (fracture). Formed by crack-healing (Samson et al., 2003) U Undetermine Unclear Components L Liquid   V Vapor   S Solid Anhydrite (?) in most cases except one where solid correspond to oxide (MnO/FeO?) or wolframite Fluid Inclusion type based on Components (liquid, vapor, solid) I Liquid>vapor, solid. Mainly liquid rich (40-75%), vapor (15-30%) and solid (15-30%) II Liquid>vapor.   Liquid rich (60-80%) with vapor (20-40%) III Vapour>liquid. Vapor rich (80-95%) with minor liquid (5-15%). Mostly <2.5 ?m. Difficult to analyze. Fluid inclusion post-entrapment modification  k Leaking Loss of components via diffusion (Bodnar, 2003) n Necking Splitting into smaller FIs (Bodnar, 2003) t Stretching Irreversable volume expansion (Bodnar, 2003). Irregular shape. Shape   oval, oval-elonged, rounded (circular), tabular (rectangular), tabular-elonged and irregular Irregular fluid inclusions or with leaking and necking evidence were avoided in most samples for the microthermometry analysis      157  7.4.1. La Mascota sample petrography and fluid inclusion petrography summary 7.4.1.1. La Mascota sample description.  ALR189. LB202 at 203.m; approximate depth from surface: 100 m. Polymictic, clasts to cement supported breccia (hydrothermal breccia, HYBX) (Figure 7.1).  Clasts (~50%): are subangular, 5mm to 3 cm wide.  Clasts include gneiss and breccia clasts. Breccia clasts are composed of fine grained matrix replaced by quartz and quartz cement, with pyrite and pyrite ? copper sulfides (covellite, bornite, chalcopyrite; mainly in pyrite borders and microfractures) crystals.   Cement (~50%): composed of zoned quartz (~65% of cement) with wolframite crystals (~30% of cement; tabular-elongated habit) and minor fine pyrite (~3%). Fine grained pyrite clasts are embedded in quartz-wolframite cement (~2%). The breccia is cross-cut by quartz + enargite veins and fractures filled with enargite. Fine pyrite (py5) is overgrown at the border of enargite veins. Quartz in these veins has plumose-zonal texture Quartz crystals in veins in which center enargite precipitated as well as quartz associated with wolframite were analyzed for fluid inclusion petrography and microthermometry.   158   Figure 7.1. La Mascota, sample ALR189; DDH LB 202 at 203.m; approximate depth from surface: 100 m (Figure 3.6). Polymictic clast to cement supported multiple phases hydrothermal breccia: Breccia clasts with pyrite and pyrite+CuS (bornite, covelilite+chalcopyrite in border and microfractures) clasts cemented and crosscut by quartz + wolframite (h?bnerite, reddish mineral) and minor pyrite veins. The breccia is cut by quartz veins and fractures filled with enargite. A. Core sample. B. Photograph of the analyzed thick section. C. Sample analyzed under reflected light and transmitted light. Wolframite (reddish brown tabular-elonged mineral) and quartz (coloform jigsaw?) surrounding breccia clast (dull brownish zones, BX) and cross cut by quartz with zone-flamboyant texture with enargite (greyish brown). Red circles indicate zones where quartz crystals were taken from to study its fluid inclusions.   159  7.4.1.2. La Mascota fluid inclusion petrography summary Enargite related quartz fluid inclusionsThese fluid inclusions are mostly primary and very few pseudo-secondary (Figure 7.2; appendix A7). Enargite related quartz fluid inclusions are grouped in two fluid inclusion assemblages: the fluid inclusion assemblage found co-existing within the quartz core, including type I (size: 5.25 ?m to 7.5 ?m; all are P FIs), II (size: 2.2 to 10 ?m; P and PS FIs) and III (size: <2.5 ?m ; P and PS FIs) fluid inclusions, and the fluid inclusion assemblage found close to or within the quartz growth plane which were mostly type II (size: 2.75 to 6.5 ?m; P FIs) and III (size: <2.5 ?m; P and PS FIs).  Wolframite related quartz fluid inclusions Fluid inclusions were studied in two separate quartz crystals: In the first quartz crystal, fluid inclusion assemblage in growth plane and fluid inclusions aligned in trail A1 were studied; including type I (size: 3.75 to 6.5 ?m) and  type II (size: 3.75-7.5 ?m) fluid inclusions. Solids corresponding to type I fluid inclusion are possibly anhydrite except for one case of brownish solid presence (wolframite?, FeO?) which is not considered part of the fluid inclusion assemblage. Aligned fluid inclusions from trail A1 were mainly primary type II (size: 2.5-3.75 ?m) except for one type I (6 ?m). In the second quartz crystal, primary fluid inclusions in the core were studied including type I (size: 5-5.25 ?m) and type II (size: 2.5-12.5 ?m) while secondary fluid inclusions from trail A2 included type II (3.75-6.25 ?m).  Paragenetic relationships primary and pseudo-secondary studied fluid inclusions within La Mascota hydrothermal breccia quartz is summarized in Figure 7.4.   160    Figure 7.2. La Mascota, ALR189F. FIs in enargite related quartz. A. Quartz core fluid inclusions type I, II and III co-existing, mainly primary FIs, except for some aligned pseudo secondary type III FIs. B. FIs in close proximity to quartz growth plane including type II and type III. C. FIs in quartz growth plane, including type II and type III.   161   Figure 7.3. La Mascota, ALR189F. FIs in wolframite related quartz. A. FIs in quartz growth plane (G) refer to FIs found in quartz growth lines. P, refers to Primary FIs while PS to pseudo secondary FIs. Types of fluid inclusions found here include type I (LVS), II (LV), III (VL) FIs. From top to bottom: A. Quartz growth line with type I, II and III FIs. B. Same as A, focusing up on the same sample to show one type I FI with FeO or wolframite (w) as solid within FI. Other solids in Type I FIs correspond to anhydrite. C. Aligned A1 secondary (S) type II and III FIs within trail or fracture 1. D. Quartz core related FIs and A2 related to trail or fracture 2 secondary (S) FIs.     162  7.4.2 La Bodega sample petrography and fluid inclusion petrography summary 7.4.2.1 La Bodega sample description ALR260: LB037 at 151.35 m; approximated depth from surface: 125 m. Matrix to cement supported alunite bearing narrow breccia (tectonic-hydrothermal breccia, THBX) of 3 cm width with quartz-alunite halo (Figure 7.2). Clasts (~30%): 1-3 mm clasts of veins, including pyrite, quartz (irregular borders and undulose extinction), alunite and very minor wolframite (<<<1%).  Matrix (~40%): fine grained milled particles (~100?m to 1mm width) from pyrite, quartz, alunite. Cement (30%): alunite (~60% of cement), fine grained dull color; enargite zoned and intergrown with fined grained rimmy pyrite (py5) (~25% of cement); quartz (~15% of cement), fine grained 1-2 mm in diameter with euhedral hexagonal with zoned texture moderately fractured and undulouse extinction. This breccia shows multiple events reflected in these features. 1) Alunite + pyrite altered gneiss is cut by 2) alunite + pyrite veins. These veins are cut by 3) euhedral cubic and pyritohedric pyrite. All of these are cut and cemented by 4) enargite + fine grained pyrite with alunite and very minor euhedral zoned quartz. Pyrite clasts from previous events are cut by enargite. Few grains of enargite with wolframite in its core were found (Figure 5.10). Deformation post-dating mineralization made it impossible to find undeformed quartz related to the enargite stage. Only one quartz   163  grain was suitable for the petrographic study of fluid inclusions but only a small number of fluid inclusions were large enough for microthermometry. 7.4.2.2 La Bodega fluid inclusion petrography summary  In the studied sample, fluid inclusions are too small in general (<3?m), not abundant and commonly stretched. These fluid inclusions corresponded to type II and type III fluid inclusions. Type III fluid inclusions due to their small size were not studied. No unequivocal primary fluid inclusions were found. The few measured undetermined (U) fluid inclusions were found as discrete individual fluid inclusions rather than groups of fluid inclusions. Still, these fluids were not related to a particular trail and were clearly larger than the ones in trails; therefore they may be considered primary (?). Nevertheless, some of these undetermined fluid inclusions had some evidence of stretching and possibly leaking and one was clearly necked down. At least three fluid inclusions trails were recognized and two of them had fluid inclusions large enough to be analyzed. These fluid inclusions within trails (A1, A2 and A3) were considered to be secondary. Based on the cross cutting relationship between fluid inclusion trails, A1 was considered the oldest and A3 the latest. All trails had type II and III fluid inclusions but only type II fluid inclusions were analyzed. Trail A3 fluid inclusions were too small to be measured (Figure 7.3).   164   Figure 7.4. La Bodega, ALR260F. Fluid inclusions in enargite related quartz. A. Narrow tectonic-hydrothermal breccia (3 cm width) where alunite + pyrite altered gneiss is cut by alunite + pyrite, later by euhedral cubic and dodecahedrid pyrite, later by enargite with very minor euhedral zoned quartz. Clast of pyrite from previous stages is overgrown by enargite. B. Thick section of sample ALR260F. C. Reflected light microphotograph showing relationship between enargite, pyrite and studied quartz grain. D. Same as C transmitted light, euhedral to subhedral quartz grain (~1mm diameter), weakly fractured. E. FIs found in quartz studied quartz grain. U (possibly primary) type II fluid inclusions in quartz core with leaking, necking and one at higher level of focus  (black square)with probable stretching. Great abundance of aligned secondary fluid inclusions: three recognized fracture or trails with cross cutting relationships where S1 is cut by S2 and S2 is crosscut by S3.    165  7.5 Microthermometry results A total of 62 fluid inclusion microthermometry measurements were recorded (see Appendix A7). Homogenization temperatures and ice melting temperatures from fluid inclusions measurements could be recorded with a high degree of confidence in type I and II fluid inclusions. Type III fluid inclusions were not analyzed because of their small size (<2.5 ?m).  Eutectic temperatures were difficult to measure and are herein reported as a range in which the true eutectic temperature would likely to be which indicates that the chemical system of the fluid in the fluid inclusions contain to H2O, NaCl and likely other salt components (KCl?). Calculations of salinities are done assuming a pure H2O-NaCl system since NaCl provide good average values for unknown mixtures of these salts (Brown, 1998). FIAs are grouped based on quartz paragenetic relationships to ore minerals and the fluid inclusions relationships within the quartz crystals. Results from all 62 measurements are graphically displayed in in Figure 7.5 within the Homogenization temperature (ThL-V?L) vs. Ice melting temperature (Tmice) and Salinity plot and the Homogenization temperature frequency plot. Table 7.2 summarizes results for fluid inclusion analysis in these samples in which assemblages are grouped and outliers and fluid inclusions with post-entrapment phenomena are reported individually.  Entrapment pressure and depth below paleowater level are done based on density of fluid rich type I and II fluid inclusions  primary fluid inclusions with no recognized post-entrapment  phenomena (Table 7.2).      166  Table 7.2 Summary of results from 62 fluid inclusions microthermometry analysis at La Mascota and La Bodega grouped based on common characteristics, mainly location within quartz crystal. Fluid inclusion density and pressure at homogenization calculation based on Bulk program (Bakker, 2002). Associated calculation of depth based on this information.  Zone Vein Type Location within quartz crystal Assemblage Genetic Class Types Te  [?C] Tm ice [?C] Average Tm ice [?C] wt% NaCl equiv. [Bodnar, 1993] Average wt% NaCl equiv. [Bodnar, 1993] Th L-V?L [?C] Average Th L-V?L [?C] Density [g/cc] Ph[bar] Depth=Ph/(g*d) [m]; g=9.8 m/s2 Number of measurements Remarks LM En-Qz Quartz core MEC P I, II  -47.0 -  -13.0  -2.8 - -1.6 -1.9 2.7 - 4.6 3.2 180 - 217 200 0.89 12.77 146 17   LM En-Qz Quartz growth plane MEG P I, II  -45.0 -  -14.4  -4.2 - -2.2 -2.7 3.5 - 6.7 4.5 143 - 202 186 0.92 9.95 111 7   LM W-Qz1 Quartz growth plane MWG P I, II  -38.0 -  -14.6  -1.4 -   -1.2 -1.3 2.1 - 2.4 2.2 188 - 222 200 0.88 12.88 149 7   LM W-Qz1 Quartz growth plane MWGw P I  -35.5 - -15.7 -1.4 -1.4 2.4 2.4 237 237       1 Solid: FeO? Wolframite Crystal? LM W-Qz1 Quartz growth plane MWGs P I  -23.4 -    -17.2 -1.3 -1.3 2.2 2.2 238 238       1 Stretched? LM W-Qz2 Quartz core MWC P I, II   -39.1 -  -14.9  -0.5 - -0.3 -0.4 0.5 - 0.9 0.6 195 - 200 197 0.87 11.80 138 5   LM W-Qz1 Trail A1 MWA1 S II  -45.0 -  -11.0  -3.4 - -2.1 -2.7 3.5 - 5.6 4.4 196 - 264 247       7   LM W-Qz2 Trail A2 MWA2 S II  -39.0 -  -14.0  -3.7 - -2.7 -3.3 4.5 - 6.0 5.4 285 - 310 304       5   LB En-Qz Core BECt U t II  -19.0 -  -15.0 -3.5 -3.5 5.7 5.7 217 217 0.89 18.56 212 1 Weakly stretched (posible primary) LB En-Qz Core BECk U k II  -32.0 -  -16.0 -5.8 -5.8 8.9 8.9 210 210       1 Leakage? LB En-Qz Core BECn U n II ? -6.1 -6.1 9.3 9.3 307 307       1 Necking LB En-Qz Trail A1 BEA1 S II  -38.0 -  -16.0  -3.1 -    -2.6 -3.0 4.3 - 5.1 4.9 238 - 312 275       4   LB En-Qz Trail A2 BEA2 S II  -35.0 -  -15.0  -5.8 - -2.9 -4.6 4.8 - 8.9 7.3 203 - 328 261       5 Trail A2 cross cuts trail A1      167  7.5.1 La Mascota, sample ALR189 Enargite related quartz fluid inclusions: Enargite related quartz fluid inclusions that were identified included primary type I, II and II fluid inclusions and two aligned pseudosecondary type II fluid inclusions (see result summary Table 7.2, appendix A7 for details). Pseudosecondary fluid inclusions in quartz core are treated as part of the assemblage of the primary fluid inclusions in quartz core. Microthermometry analysis was done only on type I and II fluid inclusions. Results are summarized in Table 7.2 (detailed measurements in Appendix A7) as two different fluid inclusion assemblages including: primary fluid inclusions located in the quartz core, with average Th=200?C, average Tmice=-1.9?C and average salinity=3.2 wt% NaCl equiv.; and primary fluid inclusions located in the quartz growth plane with average Th=186?C, average Tmice=-2.7?C and average salinity=4.5 wt% NaCl equiv. Wolframite related quartz fluid inclusions: Fluid inclusion assemblage in quartz core and quartz growth planes included type I II and type III fluid inclusions; but only type I and II were analyzed. Quartz core fluid inclusion assemblage has average Th=197?C, average Tmice=-0.4?C and average Salinity=0.6 wt% NaCl equiv. Quartz growth plane primary fluid inclusion assemblage has average Th=200?C, average Tmice=-1.3?C and average salinity=2.2 wt% NaCl equiv. Secondary fluid inclusions corresponded to type II and III fluid inclusions but microthermometry was only done on type II fluid inclusion homogenization temperatures were measured (see result summary Table 7.2, appendix A7 for details). Two different trails were measured which in general showed higher showed higher temperature and higher salinities than primary fluid inclusions of   168  quartz core and quartz growth plane. Secondary fluid inclusion from trail A1 had average Th=247?C, average Tmice=-2.7?C and average Salinity=4.4 wt% NaCl equiv. Secondary fluid inclusion from trail A2 had average Th=304?C, average Tmice=-3.3?C and average Salinity=5.4 wt% NaCl equiv. 7.5.2 La Bodega, sample ALR260F Appropriate quartz crystals related to enargite stages were difficult to find in the chosen sample since most crystals exhibited evidence of deformation (i.e. subhedral habit, fractures and undulous extinction). Type II and type III fluid inclusions were recognized, but only type II were analyzed. Microthermometry measurements are grouped in secondary fluid inclusions according to trails A1 and A2 fluid inclusions (Table 7.2). Undetermined fluid inclusions showed to have post-entrapment phenomena: weak stretching (?) undetermined fluid inclusion had Th=217?C, Tmice= -3.5 ?C and salinity=5.7 wt% NaCl equiv.; leaking (?) fluid inclusion had Th=210?C, Tmice=-5.8?C and Salinity=8.3 wt% NaCl equiv.; necked down fluid inclusion showed Th=307?C, Tmice=-6.1 and Salinity=9.3 wt% NaCl equiv.    169   Figure 7.5. Fluid inclusion data compiled for La Mascota and La Bodega in enargite related quartz and wolframite related quartz within this study. Total of 62 measurements. Fluid inclusion codes as described in Table 7.1. A. Homogenization temperature vs. Ice meting temperature and salinity. Secondary fluid inclusions (non-filled markers in A) are dispersed as compared to primary fluid inclusions (filled markers). B. Homogenization temperature frequency. Primary fluid inclusions mostly group around 200-220 ?C.  Secondary fluid inclusions show higher temperature than primary fluid inclusions, but also more dispersed values. C. Paragenetic relationships of primary and pseudosecondary fluid inclusions to quartz enargite and wolframite and hydrothermal stages (Chapter 5).    170  7.6 Discussion 7.6.1 Enargite related quartz fluid inclusions at La Mascota (ALR189) Fluid inclusions petrography in enargite related quartz at La Mascota shows that primary and pseudosecondary were entrapped at the time of quartz crystallization and had no evidence of post-entrapment modifications; i.e stretching, leakage (Figure 7.2). Therefore they are considered to be good representative of the conditions of the fluid at the time of entrapment of the fluid. Ranges of homogenization temperatures and salinity values for these primary fluid inclusions are typical of epithermal systems (Wilkinson, 2001). The co-existence of type I, II and III primary fluid inclusions with clear differences in liquid-vapor proportions is typical of fluids composed of a vapor and a liquid phase as in the case of a boiling fluid (Wilkinson, 2001). Primary fluid inclusions within quartz core have, in average, slightly higher homogenization temperatures and lower salinities than primary fluid inclusions entrapped in the quartz growth plane (Figure 7.5; 7.6) which is typical of fluids following boiling and cooling path (Shepherd et al., 1985; Hedenquist and Henley, 1985; Wilkinson, 2001) (Figure 7.6).  7.6.2 Wolframite related quartz fluid inclusions at La Mascota (ALR189) Primary fluid inclusions in wolframite related quartz found in quartz core and growth planes include type I, II and III. The occurrence of the three types of fluid inclusions may be indicative of a boiling assemblage (as interpreted for enargite related quartz). Figure 7.6 C shows the homogenization temperature vs. salinity plot for wolframite related quartz fluid inclusions. Primary fluid inclusions from quartz core show in average lower salinities than primary fluid inclusions found in   171  quartz growth lines. It is interpreted that, in general, primary fluid inclusions within wolframite related quartz are either following an isothermal mixing trend or a boiling path with slight cooling (as shown these paths are described by Shepherd et al.,1985; Wilkinson, 2001).   Figure 7.6. Fluid inclusion trends from fluid inclusion data. Salinity vs Homogenization temperature. A. Schematic diagram showing typical trends in Homogenization temperature and salinity due to various processes including boiling, cooling, isothermal mixing, heating and depressurization (After Wilkinson 2001). B. Primary fluid inclusions from quartz related to enargite and possible associated processes (boiling and cooling). C. Primary and secondary fluid inclusions from quartz related to wolframite and possible associated processes (boiling, isothermal mixing? for primary and depressurization, heterogeneous entrapment for secondary?).   172  Analyzed type II secondary fluid inclusions associated with trails (fractures) have higher homogenization temperatures and higher salinities than the primary fluid inclusions. The reasons for these values are unclear. Higher temperature fluids may be a possibility but it would also be expected to cause post-entrapment modifications i.e. stretching, leaking or breaking or necking, of most primary fluid inclusions. Dispersion in salinity and homogenization temperature values may be explained by heterogeneous entrapment phenomena (Brown, 1998). Heterogeneous entapment of two immiscible fluids in a boiling system causes homogenization temperatures readings to be higher than trapping temperatures (Brown, 1998). Depressurization may also be a reason for higher homogenization temperatures (Wilkinson, 2001) in this case associated with trails/fractures in quartz.  7.6.3 La Bodega, enargite quartz related fluid inclusions (ALR260) Primary fluid inclusions at La Bodega were not clearly identified; and undetermined fluid inclusions, presumably corresponding to primary fluid inclusions, have evidence of post-entrapment modifications, therefore only limited assumptions about the conditions of fluid inclusion entrapment within quartz at La Bodega can be made. Weakly stretched undetermined fluid inclusion provides a homogenization temperature of 217 ?C and salinity of 5.7 wt%NaCl equiv. which falls in the range of primary fluid inclusions from La Mascota, nevertheless stretching causes the homogenization temperature to rise (Velazco, 2004), therefore this temperature may be higher than actual homogenization temperature at entrapment. Undetermined fluid inclusion with leakage had salinities higher than   173  average (8.9 wt% NaCL equiv.). Necked undetermined fluid inclusions show higher homogenization temperature (in this case, Th= 307?C) not representative of the conditions fluid from which quartz precipitated (Shepperd et al., 1985). Type II secondary fluid inclusions within trails A1 and A2 microthermometry data in a homogenization temperature vs. salinity plot looks dispersed (Figure 7.5), however, these data are partially consistent with the secondary fluid inclusions from wolframite related quartz at La Mascota, which as explained before has higher homogenization temperature and salinities than primary fluid inclusions. The occurrence of different generations of secondary fluid inclusions and fluid inclusions with port-entrapment modification suggests important deformation processes and fracture-healing processes at La Bodega after precipitation of mineralizing fluids.  7.6.4 Implication of fluid inclusions microthermometry results and boiling  Fluid inclusion results at La Mascota suggests that quartz in the hydrothermal breccias was precipitated during boiling. Inclusions trapped from an ore fluid undergoing boiling will homogenize in the laboratory at the temperature of trapping assuming that individual inclusions trapped either only liquid or only vapor (Brown, 1998). Boiling has been recognized as an important process for ore deposition in epithermal systems (Buchanan, 1981 In Panteleyev, 1988; Arribas, 1995; Moncada, 2012) but  has not been reported yet in other areas within California Vetas Mining district different from La Mascota. Boiling has significant effects in hydrothermal fluids including great changes in temperature of the fluid as well as changes on the chemistry of a hydrothermal solution associated with the exsolution   174  of CO2 and H2S from an originally homogeneous fluid phase (Drummond and Ohmoto, 1985). CO2 exsolution causes dramatic changes in pH while H2S exsolution destabilizes sulfides and perturbs the oxidation state (Drummond and Ohmoto, 1985). These changes in epithermal systems may also lead to decrease in gold solubility and consequently its precipitation (Henley et al., 1984). Boiling of hydrothermal fluids occurs above a depth known as the boiling horizon which is represented by a change in the fluid inclusion types that are observed, but also represents a change in ore metal distribution with depth (Moncada, 2012).  In geothermal systems boiling occurs in the central upflowing column of fluid down to 1 to 2 km depth below the water table, controlled by near-hydrostatic pressure-temperature conditions (Simmons et al., 2005). The spatial relationship between boiling, fluid inclusion characteristics and precious metal mineralization provides a potentially valuable tool in exploration for epithermal precious metals deposits (Moncada, 2012). Boiling evidence at La Mascota is found within the high grade zones associated with copper sulfides, sulfosalts, gold and silver mineralization. 7.6.5. Estimation of depth of emplacement based on primary fluid inclusion analysis Minimum pressure at homogenization and fluid inclusion density was estimated using the BULK program (Bakker, 2002) based on  the averages of ice melting temperatures and homogenization temperatures of primary fluid inclusions assemblages which were considered representative of the entrapment conditions since they represented boiling assemblages (Table 7.2). Estimations of average depth below paleo-water table at homogenization were done using Equation 3   175  based on estimated averages of pressure (hydrostatic pressure) and density for the different assemblages of primary fluid inclusions (Type I and II; liquid rich fluid inclusions). The actual density of the hydrothermal fluid was not estimated since type III fluid inclusions were not measured. Thus, estimate for the minimum depth of entrapment at La Mascota based on all enargite quartz related fluid inclusions is ~140 m depth (below paleo-water table) which falls in the shallow end of depth ranges in which epithermal deposits are formed. This estimate is also consistent with the range of depths predicted from the boiling point with depth curve for H2O-NaCl solutions (Figure 7.7A). The current water table level is located at approximately 80-100 m depth below surface and varies depending on rain or dry season (F. Maldonado pers. comm., 2013). Sample ALR189 was taken at ~100 m depth from surface (~2600 m.a.s.l.). If assuming a similar paleo-water table level depth from paleo-surface as the depth from surface of the curent water-table, approximate minimum depth of entrapment of these fluid inclusions below surface was ~220-240 m. suggesting that minimum erosion at La Mascota, since the emplacement of the hydrothermal breccias is approximately ~120-140 m (Figure 7.7 B). The bottom part of the boiling zone boiling level is predicted to have been below minimum ~600 m depth, based on quartz textures associated with boiling  and mineralization observed in drill hole LB221 (Figure 7.7B). According to Simmons et al. (2005); in geothermal systems, the boiling level may locate up to 1-2 km depth.   176  7.6.6 Comparison to other fluid inclusion studies within the California Vetas Mining District and hydrothermal environment implications Primary fluid inclusions within La Mascota show clearly lower homogenization temperatures and lower salinities when compared to fluid inclusions at La Plata (SW of La Mascota) and Angostura (NE of La Bodega) (Figure 8.9). Veins in which microthermometry studies were carried out at La Plata (D-type and A-type veins; Raley, 2011) and Angostura (D-type veins; Mantilla et al., 2012) suggest that these veins are representative of shallow porphyry environments. Early stages of evolution at La Mascota and La Bodega (stages 1 and 2 see Chapter 5) are representative of shallow porphyry environments as well. The comparison between the paragenetic evolution at La Mascota and La Bodega to La Plata and La Angostura shows that veins studied from the latter two areas match partially the early paragenetic stages at La Mascota. Also at La Mascota and La Bodega it is evident the most shallow portions (epithermal environments) of the whole hydrothermal system within La Baja Trend. Therefore, the evolution of the mineralizing fluids of the system within California-Vetas Mining district and specifically La Baja Trend, shows strong evidence for cooling hydrothermal system overtime, culminating in a boiling epithermal system at at La Mascota.   177   Figure 7.7. Depth of emplacement estimate based on fluid inclusion microthermometry of hydrothermal quartz at La Mascota from sample ALR189. A. Boiling point with depth curve for 0 m and 2 m H2O-NaCl solutions containing 0-5% mol CO2 and 2 m NaCl (after Wilkinson, 2001) showing estimated ranges of depth below paleo-water table level at La Mascota (gray box) based on primary fluid inclusions with 0.5-1.7 m NaCl estimated using Bulk program developed by Bakker (2003). B. Schematic geological alteration section M-M? at La Mascota showing minimum depth of entrapment below paleowater table level of primary fluid inclusions and possible paleosurface and water-table at ~2.2 Ma as well as hypothetic boiling bottom below 600 m depth (approximately 1-2 km? depth if compared to geothermal systems).    178  Minimum depth of entrapment estimated for fluid inclusions in quartz + pyrite+ chalcopyrite veins within La Perezosa zone (at approximate 2800 m. a. s. l. today) at La Angostura (limit between La Bodega and Angotura, see Figure 3.3) is >700m (Mantilla et al., 2012) which is at least 550 m below the minimum depth of entrapment estimated for fluid inclusions in quartz within breccias from the later stages of mineralization (wolframite and enargite related) estimated for La Mascota (~140 m). La Perezosa quartz + pyrite+ chalcopyrite veins may be considered representative of earlier stages and deeper zones of the hydrothermal system within La Baja Trend (as described in Chapter 3) compared to the paragenetic evolution determined for La Bodega-La Mascota (stage 2-3). The Angostura veins are found today at higher elevation than the breccias and veins from La Mascota (~2600 m), representative of epithermal environment (stage 5). This suggests that erosion has played an important role in the exhumation of the porphyry system environment which may have been accompanied by uplifting of the Angostura and La Bodega areas in relation to La Mascota through reverse faulting associated with Paez fault (as proposed by Mantilla et al., 2011; see Figures 3.3, 3.4).    179   Figure 7.8. Salinity (wt%NaCl equiv.) vs Homogenization temperature of FIs in quartz from different paragenetic stages with California-Vetas Mining district, including La Plata (SW of La Mascota) (Raley, 2012), La Angostura (Albinson, 2000; Mantilla et al., 2012); La Mascota (Forero, 2010; Mendoza, 2011; this study). Epithermal and porphyry deposits field after Wilkinson (2001).  180  Chapter 8. Origin of Mineralizing Fluids at La Bodega and La Mascota: Insights from Oxygen, Deuterium and Sulfur Stable Isotopes 8.1 Introduction Stable isotopes can provide information in four critical areas: 1) temperature of mineral deposition, 2) sources of the hydrothermal fluids, 3) sources of sulfur and carbons (and by extrapolation, metals), and 4) water-wall rock interaction (Campbell & Larson, 1998). Light stable isotopes commonly used in hydrothermal mineralization research include oxygen, hydrogen, sulfur, and carbon (Table 8.1; Campbell & Larson, 1998). Stable isotopes are usually expressed in the delta (?) notation which described their variation in per mil. Stable isotopes terminology, notation and associated concepts are summarized in Table 2 (Campbell & Larson, 1998). Table 8.1. Natural abundance and reference standards for light stable isotopes (Adapted from Hoefs, 1997 in Campbel and Larson 1998) ELEMENT ISOTOPE ATOMIC ABUNDANCE RATIO INTERNATIONAL STANDARDS Oxygen 16O 99.763%  18O /16O Vienna Standard Mean Ocean Water (VSMOW) Vienna Pee Dee Belemnite (VPDB) (for carbonates) 17O 0.0375%  18O 0.1995% Hydrogen 1H 99.9844% D/H VSMOW 2H (D) 0.0156% Sulfur 32S 95.02% 34S /32S Canon Diablo Troilite (CDT) 33S 0.75% 34S 4.21% 36S 0.02% Carbon 12C 98.89% 13C /12C VPDB 13C 1.11%      181  Table 8.2. Stable Isotope terminology (Campbel and Larson, 1998) NAME SYMBOL DEFINITION Absolute abundance ratio R R= (Moles of heavy isotope/moles of Light isotope) Relative Isotopic enrichment (delta) ? ? (%o, or per mil) = ((Rsamp/RStd)-1))*103 Isotopic Fractionation Factor (alpha) ? ?xy= Rx/Ry ?xy=(?x+103)/ (?y+103) 103ln ?xy= ?xy Relative Isotopic fractionation (big delta) ?xy ?xy= ?x- ?y   Sulfate minerals in nearly all environments tend to reflect sulfur isotopic fractionation between reduced and oxidized sulfur species and, in some cases, to reflect oxygen isotopic fractionation between SO42- and water (Rye, 2005). Advanced techniques to determine nature of fluids in epithermal systems include the use of stable isotope analysis (?D, ?18O, ?34S, ?C) in gangue minerals (e.g., alunite, illite, calcite and kaolinite) and co-existing sulfide bearing phases (Rye et al., 1992; Arribas, 1995; Hedenquist et al., 1998; Deyell et al., 2004; Bethke et al., 2005; Fifarek and Rye, 2005, Simmons et al., 2005). Nature and genesis of mineralizing fluids in epithermal deposits varies between high-sulfidation deposits and low-sulfidation deposits. High to intermediate-sulfidation state deposits are associated with quartz + alunite ? pyrophyllite ? dickite ? kaolinite gangue, precious and base metal mineralization (Simmons et al., 2005). These deposits are intimately associated with the crystallization of igneous intrusions and exsolution of magmatic fluids (Simmons et al., 2005). Stable isotope data indicate that the altering fluids are composed mostly of magmatic fluids with a minor to moderate component of meteoric water (Simmons et al., 2005).   182  Pyrite ?34S values may provide some constraints on the oxidation state of the system (Rye, 1993; Rye 2005) and possible processes that could have generated these signatures (Gemmell et al., 2004). Pyrite ?34S values at La Bodega and La Mascota and other areas in the CVMD are presented compared to ?34S values characteristic of other systems and processes systems including high-sulfidation systems and porphyry systems (Figure 8.2).  Alunite (KAl3(SO4)2(OH)6) can be analyzed for four stable-isotopes: two from the SO4 site ?34SSO4 and ?18OSO4 and two from the OH site; ?DOH, ?18OOH (Wasserman et al., 1992). Therefore, alunite can provide information on the isotopic composition of water and sulfur species in pre-ore parental fluids (Rye, 2005). Based on experimental data on the fractionation of sulfur isotopes between aqueous sulfates and sulfides (Ohmoto and Rye, 1979; Ohmoto and Lasaga,1982); the ? 34S values and ? 34Salunite-pyrite precipitation temperatures can be determined for disseminated alunite and pyrite occurring in equilibrium allowing for an alternate method for fluid temperature estimation (Rye, 1992). The sulfur-isotope data of alunite-pyrite pairs produce one of the best isotope geothermometers for epithermal systems in the temperature range of 200-400 ?C (Rye, 2005). Then, temperature can be calculated through Equation 8.1 (Ohmoto and Rye, 1979 In: Rye et al., 1992): Equation 8.1:                                  ?34S of alunite ? pyrite pairs are used here to calculate the temperature of the fluids that precipitated these minerals. These temperatures are compared to the results   183  from the fluid inclusions microthermometry on quartz from stages 4 and 5 of the paragenetic evolution of La Mascota and La Bodega hydrothermal system (Chapter 7). ?D, ?18O isotope analysis on alunite (and alunite-natroalunite solid solution) are used to fingerprint the fluids from which these minerals precipitated and determine their most probable origin within their corresponding paragenetic state. Alunite-water fractionation factor (?Dalunite-water ranges from -19 at 450?C to -6 at 250?C and does not appear to be strongly dependent on temperature (Stoffregen et al.,1994). Since the ?18O fractionation factor between alunite and water is temperature dependent and a temperature corrections needs to be applied to make inferences about the origin of the fluid (Stoffregen et al.,1994). Equation 8.2 accounts for this correction over a temperature range of 250-450?C (Stoffregen et al.,1994).  Equation 8.2:                  -          (      )          Values of ?D, ?18O and ?34S from stable isotope analysis on ore related sulfates and sulfides; including alunite, natroalunite and pyrite in breccia cement, veins and host rock alteration are presented in this chapter and are used to characterize the fluids and processes involved in the alteration and mineralization of the hydrothermal systems La Bodega and La Mascota as well as in other areas of the La Baja Trend.    184  8.2 Methodology 8.2.1 Sample selection and separation Samples were separated mainly from drill holes from La Mascota, La Bodega and El Cuatro. Surface sample separates, collected by T. Bissig (2011) from other deposits within La Baja Trend; including San Celestino, La Plata and Angostura (La Perezosa and Los Laches), and La Francia (to the East of La Baja Trend but within the CVMD) are also presented here (Table 8.3). Separates were extracted from hydrothermal breccia cement, druse infillings, veins and altered minerals (Figure 8.1; Table 8.3) SWIR and XRD analyses were carried out on the samples selected for stable isotope analysis (Chapter 3), to confirm alunite occurrence and abundance in the separate samples. Samples were separated from rock using scratcher, needles and tweezers through the Wasserman et al. (1992) methods. In most samples for alunite-pyrite pairs, these minerals were finely intergrown with pyrite at grain sizes down to <10 ?m. Pyrite microcrystals (<5?m) may have not completely been separated from alunite. Pure separates were possible for pyrite with coarser grain sizes to 0.5 mm - ~1 mm in diameter. Alunite separates had a smaller grain size distribution to minimize content of fine grained pyrite. Final alunite separates grain size ranged from <0.1 mm to 1 mm in diameter.   185   Figure 8.1. Selected samples for isotopic analysis from La Bodega and La Mascota. A, ALR012 hand sample. B microphotograph of A under  XPL. C. ALR038  close up showing alunite (nal-alu), sphalerite and pyrite. D. microphotograph of C under RL+XPL showing alunite, pyrite and quartz. E. ALR264, alunite veins with enargite and pyrite. F. microphotograph of E. G, H. ALR024 hand sample hydrothermal breccia with alunite+natroalunite and quartz. G. Microphotograph of H under RL+XPL. I. ALR034. Alunite+pyrite vein cutting granite. J..Microphotograph of I under RL+XPL showing pyrite remaining from pyrite-alunite vein and alunite alteration adjacent to vein. M. ALR026 of flaky (bladed) alunite in dryssy quartz. N Close up of M. O. ALR027 alunite+pyrite vein. O. close up of O. Q. ALR323 alunite vein cutting breccia with enargite. R. Close up of Q.     186  8.2.2 Analytical methods Samples were analyzed at the Queen?s Facility for Isotopic Research. Provided laboratory protocols are described below. Oxygen Isotopes: Alunite was dissolved in 7N NaOH (bubbled with Ar gas to avoid atmospheric CO2 absorption) for 24 hours at 80?C. BaSO4 was precipitated by addition of saturated BaCl2 to the hot dissolved alunite solution.  BaSO4 precipitate was recovered by centrifugation and was washed with 20 % HCl to remove any carbonate phases that formed, and rinsed in RO water before a final centrifuge step. BaSO4 was degassed for 1 hour at 100 ?C to remove any adsorbed water. BaSO4 was analyzed by TC/EA-IRMS, weighed into silver capsules and dropped into a 1450 ?C graphite crucible, with 1% H2 auxiliary gas to aid in combustion which converts the sample to CO gas which was separated by a PORAPLOT-Q gas chromatograph column and measured with a ThermoFinnigan DeltaXP Plus IRMS. Oxygen isotope values are reported in ?18O notation, relative to Vienna Standard Mean Ocean Water (VSMOW). The reproducibility of ?18O measurements based on repeat measurements of reference materials and samples is ?0.2?.  Deuterium Isotopes: ? D values from aluniteOH were measured on a Thermo Finnigan thermo-combustion elemental analyzer (TC/EA) using procedures from Uvarova et al. (2011) based on modified procedures from Sharp et al. (2001). Samples were weighted in silver capsules, degassed for 1 h at 100 ?C, then compacted and loaded into a zero-blank auto sampler and later dropped into a graphite crucible at 1450 ?C, converting the released H2O into H2, which was   187  separated by a PORAPLOT-Q gas chromatograph column and measured with a Thermo Finnigan DELTAplusXP IRMS. ?D results are reported with respect to VSMOW. The reproducibility of ?D measurements based on repeat measurements of reference materials and samples is ?3?. Sulfur Isotopes: Stable sulfur isotopic measurements on pyrite were done following procedures described by Polito et al. (2007). Samples are weighed into tin buckets. Pyrite samples were analyzed using a Carlo Erba CNOS elemental analyser coupled to a Finnigan MAT 252 mass spectrometer with a Finnigan MAT Conflo 11 interface and are reported in the ? notation in units of per mil (?) relative to the standard Vienna-Canyon Diablo troilite (V-CDT). For alunite V2O5 was added to help catalyze the reaction and the same procedures as for pyrite analysis were conducted. Replicate ?34S analyses are reproducible to ?0.3?.     188  8.3 Results Stable isotope results of ?34S, ?18O and ?D (?) are summarized in Table 8.3. Results presented here include samples from La Mascota, La Bodega, El Cuatro and others within the California Vetas Mining district (see map in Figure 3.2 for location of district prospects) in the context of the paragenetic sequence presented in Chapter 5. The paragenetic stages proposed for other areas different from La Bodega and La Mascota corresponds to probable equivalent stages within the proposed paragenetic sequence (Chapter 5). This is based on described mineral relationships as well as the geochronological constrains for the paragenetic stages. 8.3.1 Pyrite sulfur isotopes ?34S values for pyrite are very light, ranging from -16.9? to ?11.3? at La Mascota and -9.4? and ?6.1? at La Bodega (Table 8.3). A single pyrite sample from La Plata yielded a less negative ?34S value of -1? at La Plata. Native sulfur from La Mascota (Mendoza, 2011) also has a very light value of -20.1? (L. C. Mantilla Figueroa, 2012, unpublished data). Figure 8.2 shows the distribution of ?34S compared to the distribution in other environment. Figure 8.3 show variation of isotopic signature through time and compared to the established hydrothermal stages (Chapters 5 and 6 respectively).    189  Table 8.3. Stable isotope results of ?34S, ???O and ?D (?) in the California-Vetas Mining district. Samples at La Mascota and La Bodega include alunite, natroalunite, pyrite (this study) and native sulfur (L.C. Mantilla, 2012, Unpubl.). Samples from other areas include San Celestino, Angosturas (Los Laches and La Perezosa), La Plata and La Francia (sampling by T. Bissig in 2011, Unpubl). Zone Sample Code HOLE ID Depth (m) Stage Age [Ma] Analyzed Minerals Isotopes Oxygen Amount % Alunite ???O (?) Alunite ?D (?) Alunite  ???S (?) Pyrite ???S (?) ? 34Salunite-pyrite Temperature [?C] (alunite-pyrite pairs fractionation: Rye et al 1992) Alunite ???O (?) (Oxygen Isotopic fractionation at 250?C; Stoffregen et al.,1994) Sample description La Bodega (LB) ALR264 LB037 197.15 5 2.22?0.05  Alunite Pyrite 27 17.5 -52 10 -8.3 18.3 355 9.2 Alu+py+en vein La Bodega (LB) ALR281 LB013 231.8 6 1.63?0.29  Natro-alunite Pyrite 28 18 -68 8.8 -6.1 14.9 466 9.7 Alu+py (cubic)+qz cement. Secondary LB THBX structure La Bodega (LB) TBCV 019 LB251 175.86 2? 3.54 ? 0.13 Pyrite         -9.4       Coarse pegmatoid feldspar phyric rock intensely quartz-illite altered. Illite is greenish, replacing feldspars, white quartz in matrix. El Cuatro (EC) ALR040 LB282 131.3  2-3 3.26?0.30 Alunite 21 10.9 -49 13.2       2.6 Alu replacing feldspar phenocrysts La Mascota (LM) ALR012 LB112 253.1  3-4 2.63?0.096 Alunite Pyrite 26 15.3 -43 8.1 -11.3 19.4 329 7.0 Alu in breccia replacing gneiss clasts with covelite veins and py La Mascota (LM) ALR024 LB112 312.6 6 1.87?0.30  Natroalunite 29 9.5 -58 6.7       1.2 Natroalunite in THBX  La Mascota (LM) ALR026 LB159 337.7  4-5 2.47?0.27  Alunite Pyrite     -78   -15.4       Alu (bladed) + py? in w+qz+py (fine colloform) drusy cavity   190  Zone Sample Code HOLE ID Depth (m) Stage Age [Ma] Analyzed Minerals Isotopes Oxygen Amount % Alunite ???O (?) Alunite ?D (?) Alunite  ???S (?) Pyrite ???S (?) ? 34Salunite-pyrite Temperature [?C] (alunite-pyrite pairs fractionation: Rye et al 1992) Alunite ???O (?) (Oxygen Isotopic fractionation at 250?C; Stoffregen et al.,1994) Sample description La Mascota (LM) ALR027 LB112 328.8  4-5? 2.31?0.26  Alunite 37 21.6 -67 6       13.3 Alu cross cutting gneiss La Mascota (LM) ALR034 LB112 347.7  3-5? 2.26?0.31  Alunite Pyrite 31 19 -54 7.7 -16 23.7 251 10.7 Alu cross cutting granite La Mascota (LM) ALR038 LB112 357.8 6 1.60?0.69 Alunite Pyrite 15 10.8 -70 0.8 -16.9 17.7 371 2.5 Sph+py+alu vein cutting THBX La Mascota (LM) ALR152 LB114 317.05 4   Alunite     -52 9.3         Alu+w cavity filling La Mascota (LM) ALR323 LB205 243.5 6   Alunite Pyrite 21 15.1 -53 5.8 -13.7 19.5 327 6.8 Alu+py (fine colloform)+en cutting THBX La Mascota (LM) MBM-04  LB278 575.35 6   Native S         -20.1       Native sulfur in Drusy quartz+ fine pyrite (fine colloform) cavity. (Sampled by M. Mendoza, 2011; analysis result by L. C. Mantilla F., 2012; Unpubl.) San Celestino (SC) TBCV 001      2-3? 3.23 ? 0.06 Alunite 19 13.6 -48 9.7       5.3 Alu altering porphyry La Francia (LF) TBCV 056     2-3? <10 Alunite, with sericite 20 13.9 -45 9.2       5.6 Alu altering porphyry La Plata (LP) TBCV 073     2-3? 3.43 ? 0.07 Alunite Pyrite 21 17.3 -39 10.7 -1 11.7 650 9.0 Alu altering granitoid Angostura; Los Laches (AL) TBCV 10      2-3? 2.77 ? 0.11 Alunite 25 20.7 -43 9.7       12.4 Alu with chalcedonic qz altering gneiss Angostura; La Perezosa (AP) TBCV 69     6? 2.12 ? 0.07 Alunite Pyrite 24 14.9 -66 10       6.6 Pinkish alu (nal-alu) vn cutting qz -py vn and ill alteration   191    Figure 8.2 ?34S values obtained at the California-Vetas Mining District compared to classic deposits types around the world including several high sulfidation deposits (Arribas, 1995), low sulfidation deposits (Field and Fifarek, 1985), Alkalic-type epithermal deposits (Richards, 1995), alkali volcanism related Conical Seamount and Ladolam (Gemmell et al., 2004),  Butte Montana porphyry deposit (Field et al., 2007); porphyry and high sulfidation deposits at Baguio District, Philippines (Cooke et al, 2011) and the Sur-Sur tourmaline breccia, R?o Blanco-Los Bronces porphyry Cu-Mo deposit in Chile Andes (Frikken et al., 2005); Pascua-Lama high sufidation deposit in the Andes, limit between Chile and Argentina. La Mascota native sulfur analysis was provided by L.C.Mantilla, 2012). Angostura, San Celestino, La Francia and La Plata samples, collected by T. Bissig (2011).    192   Figure 8.3. ?34S values obtained at the California-Vetas Mining District compared to the sample ages obtained by 40Ar/39Ar geochronology on alunite related to pyrite and the presumable age based on mineralization stages. ?34S values  at La Plata are the heaviest in the district (-1?). ?34S values at La Bodega are -9.4? and ?6.1? (<10?), while ?34S values at La Mascota are -16.9? to ?11.3? for pyrite and for native sulfur -20.1?. Despite the limited amount of samples, it is evident that later stages ?34S values for pyrite and native sulfur are lighter than earlier stages.    193  8.3.2 Alunite sulfur isotopes ?34S values for alunite at La Bodega are 8.8 and 10 ?, at La Mascota ?34S values range from 0.8 to 8.1?; in other areas from the CDMV within La Baja trend ?34Sso4 values are: San Celestino 9.7?, La Plata 10.7?, and in the Angosturas deposit; Los Laches 9.7? and La Perezosa 10?; and at La Francia (east of La Baja Trend) 9.2?. 8.3.3 Geothermometry using the ?34S between alunite ? pyrite pairs  Paleo-temperature calculation based on the ?34S between alunite ? pyrite (pairs in textural equilibrium) geothermometer was done using Equation 8.1 (Ohmoto and Rye, 1979 In: Rye et al., 1992). According to these calculations, at La Bodega and La Mascota samples from stages 2-6 have a range of values between 251 and 466?C. Most results are above 300?C except for sample, ALR034 which yielded to a temperature of 251 ?C (Figure 8.1). This sample corresponds to a vein of alunite and pyrite (cubic-coarse) in textural equilibrium cross-cutting the leucogranite unit. ALR034 alunite-pyrite pair likely corresponds to Stage 4-5 based on 39Ar/40Ar geochronology done on alunite. Fluid inclusion microthermometry for La Mascota (Chapter 7) indicates that temperatures above 220 ?C are not expected for stages 4 and 5. In the case of La Plata area (SW of La Mascota, Figure 3.3), the temperature of 653?C is significantly above the temperature range for the alunite-pyrite geothermometer, above alunite stability and above the  maximum homogenization temperature of 453?C determined for early porphyry style fluids which clearly pre-date alunite-pyrite mineralization at La Plata (Raley, 2012).   194  The stability field for alunite is 15?C-~400 ?C and the stability field of the alunite-pyrite pair geothermometer is 200-400 ?C (Rye et al., 2005); therefore most of the calculated temperatures for La Mascota, La Bodega and La Plata are neither realistic nor consistent with the fluid inclusion microthermometry data and its paragenetic associations. The discrepancy is interpreted as either the effect of very fine grained pyrite (<5?m) that could not completely be removed from alunite or, alternatively, may indicate that sulfide-alunite pairs were not in isotopic equilibrium. Reasons for lack of isotope equilibrium between minerals include the following: (1) insufficient time for the aqueous species to reach equilibrium at the temperature and pH of the parent fluids after an event such as boiling, mixing, or wallrock alteration; (2) non-contemporaneous deposition of sulfide and sulfate minerals from a fluid or magma of changing composition; and (3) retrograde isotope exchange between one or both minerals and later fluids with different temperatures and compositions than those of the parent fluids. Following events such as boiling, fluid mixing and mineral precipitation or dissolution, there may not be enough time for reaching isotopic equilibrium between minerals (Rye, 2005). At La Mascota, samples of alunite-pyrite pairs with two or more populations of pyrite grain sizes may correspond to pairs in which isotopic equilibrium might have not entirely been reached due to changes in the rate of the deposition of these minerals resulting in lower ?34Salunite-pyrite values therefore leading to unrealistically higher temperatures. This hypothetical isotopic disequilibrium may also be explained by the boiling processes for which evidence have been previously provided and discussed.   195  The degree of approach to equilibrium can be used to constrain the nature and rates of processes (Rye, 2005). The most reliable temperature obtained at La Mascota is 251?C. This is based on its value close to homogenization temperature from microthermometry, and the fact that pyrite in this sample was coarse grained and a complete separation from alunite was possible. A plot ?34Salunite vs. ?34Spyrite (Figure 8.4) illustrates graphically the alunite-pyrite pairs values in respect to locus with slopes of +1 representing  each a different temperature (isotherms lines). ALR034 with a calculated temperature of 251?C, is found in the middle between the 200 and 300?C isotherms but all other data fall between 300 and 400 ?C. This graph also shows that La Bodega and La Mascota alunite data do not define an array with a negative or near to 0 slopes, which is consistent with their different timing, as compared to the coeval alunite data from Pierina high sulfidation deposit (Fifarek and Rye, 2004).  8.3.4 ?D and ?18O isotopes.  ?D values from the CVMD (including La Bodega and La Mascota) range from -70 to -39?. ?18O raw values range from 9.5 to 21.6?. ?18O isotopic fractionation was calculated using on the Equation 8.2 in order to account for values in equilibrium with hydrothermal fluids at a temperature of 251 ?C based on the most reliable result of the ?34S geothermometry and the acceptable temperature range for the use of Equation 8.2 (250 and 400 ?C). ?18O fluid in equilibrium with alunite at T=251?C ranges from 1.2 to 14?. These results were used for construct ?D vs ?18O and the ?34S and ?18OSO4 plots (Figure 8.5). Reference fields for metamorphic waters (Taylor, 1974), volcanic vapor (Giggenbach, 1992), magmatic waters   196  (Taylor, 1974), the meteoric waters line (Craig, 1961) and the isotopic compositions of meteoric recent waters in Eastern Cordillera in the Colombian Andes (Mora, 2001) are also shown.   Figure 8.4. ?34Salunite vs. ?34Spyrite plot showing data from La Mascota, La Bodega and La Plata from different paragenetic stages (colored markers). The graph shows the best fit lines for La Mascota and La Bodega-La Mascota together with positive slope consitent with their non- coeval origin. These data are compared to the Pierina high-sulfidation deposit, which data, in black and white markers, are making an array with a negative slope close to zero best-fit line (Fifarek and Rye, 2004).    197   Figure 8.5. ?D vs ?18O plot (reported relative to VSMOW). ?18O from alunite (SO4) isotopic compositions is calculated in equilibrium with hydrothermal fluids at a temperature of 251 ?C. Reference fields are from Taylor (1974) for the magmatic waters, Taylor (1974) for metamorphic waters, Giggenbach (1992) for Volcanic Vapour, Craig (1961) for meteoric water line and Mora et al. (2001) meteoric water in the Colombian Andes. LB: La Bodega; LM: La Mascota; EC: El Cuatro; SC: San Celestino; LF: La Francia; LP: La Plata; AL: Los Laches at Angostura; AP: La Perezosa at Angostura (for these locations see map in Figure 3.3).  8.4 Discussion  8.4.1 Pyrite ?34S signatures ?34S isotopes from pyrite show a broad range of values within the CVMD (Figure 8.2). ?34S pyrite values for La Plata are within the reported  for porphyry deposits (i.e., Butte Montana, Field et al., 2005; Baguio District, Philippines, Cooke et al., 2011). La Bodega ?34S pyrite values are lighter than alunite-enargite-pyrite   198  associations ?34S sulfide values from high-sulfidation Pascua-Lama deposit in the Chile-Argentina Andes (Deyell et al., 2005); however, La Bodega ?34S pyrite values are within the normal values reported for high-sulfidation deposits (Arribas, 1995), e.g. Baguio District, Phillipines (Cooke et al., 2011). La Mascota deposit is considered to be a high-sulfidation deposit, based on its ore mineralogy (Chapter 5), however ?34S pyrite values at La Mascota are the lightest known in the CVMD and they show a range of values that are lighter than sulfides from most high-sulfidation epithermal deposits sulfides (Arribas, 1995), therefore the origin of these signatures is not entirely clear. La Mascota light ?34S pyrite values are numerically within the range reported for sulfides from alkalic epithermal deposits (Richards, 1995 In Gemmel et al., 2004), and sulfides from alkalic volcanic hydrothermal environment reported at Ladolam gold deposit (Gemmell, 2004); nonetheless, porphyritic rocks from recent magmatic events associated with mineralization at the CVMD are of calc-alkalic affinity not alkalic (Mantilla et al., 2013). ?34S pyrite values at La Mascota are within the wide field of the ?34S values from sulfides within modern marine deposits (Faquhar, 2010). In marine environments, biogenic sulfate reduction is the main process to produce sulfur fractionation and therefore pronounced negative ?34S isotope signatures at temperatures below 100?C (Clark and Fritz, 1997; Ohmoto and Goldhaber, 1997; Krouse and Mayer, 2000 In: Stam, 2006).  In the area of La Mascota, the host rocks for the mineralized hydrothermal breccias are mainly Precambrian gneisses from the Bucaramanga Complex (Chapter 3)   199  derived from metasedimentary rocks, including metapelitic rocks, that underwent regional amphibolite-facies metamorphism during the Proterozoic (Ward et al., 1973, Mendoza and Jaramillo, 1973). Sulfides within the Bucaramanga Complex are scarce and their ?34S is currently unknown, therefore conclusive arguments for the negative ?34S signatures at La Mascota being inherited from the metapelitic rocks from the Bucaramanga Complex cannot be made.  On the other hand, at Conical Seamount, a submarine alkali basalt volcano 10 Km south of Lihir in Papua New Guinea (Gemmell et al., 2004), ?34S sulfides isotopic signatures (?17.5 to +6.1?) were originally interpreted as the result of bacteriogenic sulfate reduction (Petersen et al., 2002), but later these signatures were interpreted as to be the product of intense boiling (Gemmell et al., 2004). As exposed in Chapter 7, boiling processes, accompanied by separation of volatiles, can cause radical changes on the chemistry of a hydrothermal solution associated with the exolution of CO2 and H2S which leads to dramatic changes in pH and oxidation state (Drummond and Ohmoto, 1985). Moreover, boiling produces variation in the isotopic composition of the sulfides and an increase in the oxidation state of the residual liquid, leading to significant fractionation of sulfur isotopes (McKibben and Eldridge, 1990).  This fractionation can cause rapid shifts from positive to negative ?34S values of sulfides that may be highly variable at the sulfide grain scale, with isotopic heterogeneity in individual samples (McKibben and Eldridge, 1990). Evidence for episodic boiling at La Mascota, during epithermal stages (3-6) have been provided in Chapters 4, 5 and 7. In a broad sense, at La Mascota late stages pyrite and native sulfur have lighter ?34S signatures than early   200  pyrite (Figure 8.3); thereby, boiling at the epithermal level is a possible explanation for La Mascota?s pyrite light ?34S signatures and the gradual isotopic shift towards light signatures from early stages to late stages. 8.4.2 ?34S of alunite ? pyrite pairs and geothermometry constraints at La Bodega, La Mascota  and La Plata  Geothermometry from alunite-pyrite pairs, in general show anomalous temperatures that do not fit within the constraints derived from homogenization temperatures recorded from primary fluid inclusions in epithermal stages at La Mascota (Chapter 7). Figure 8.4 shows that in the plot ?34Salunite vs. ?34Spyrite, La Plata is above the alunite geothermometer temperature limit and La Bodega and La Mascota alunite data does not make an array with a negative nor near to 0 slopes as compared to the coeval alunite data from Pierina high-sulfidation deposit (Fifarek and Rye, 2004), which is expected since most samples are not coeval.   8.4.3 Origin of the hydrothermal mineralizing fluids The ?D vs ?18O plot (Figure 8.5) shows that CVMD data collected for this study mainly plot within or in close vicinity of the magmatic waters field. Therefore most fluids from which alunite precipitated are associated with a magmatic source. Samples ALR027 and ALR034 from La Mascota and sample TBC-010 from Angosturas deposit, Los Laches prospect, are plotting to the right of the magmatic waters field into the metamorphic waters field; which is interpreted as a possible interaction between the magmatic fluids and the metamorphic host rocks. In general, samples from late stage (6) have lower ?D than samples from earlier stages and two samples from stage 6, ALR024 and ALR038 show the lowest ?18O   201  values. This isotopic shift in the ?18O and ?D values in late stages is interpreted as evidence for minor but increasing interaction of the hydrothermal fluids with meteoric waters in later stages. The relatively light ?18O value of 2.4? at El Cuatro may result from a minor interaction with meteoric water may be explained by similar processes.  In summary, the main origin of the alunite associated with the fluids that provided hydrothermal alteration and mineralization within the CVMD (in La Baja Trend area) is a magmatic fluid dominated source; as in most high-sulfidation deposits (Simmons et al., 2005). Minor interaction of these fluids with the metamorphic host rock took place and minor interaction with meteoric waters might have occurred in late stages of the hydrothermal evolution of the system (stage 6). Furthermore, at La Mascota and more evidently at La Bodega, in drill core as well as in outcrop, porphyry style phyllic alteration and associated D-type veins were developed prior to the emplacement of epithermal style mineralization veins and breccias associated with alunite alteration (Chapter 4).  This fact indicates that in general the uppermost part of the hydrothermal system is preserved and no major erosion has taken place since the emplacement of the epithermal veins and breccias and associated alteration. No source rock representing the magma from which the hydrothermal fluids were derived is exposed but is suspected at depth.    202  Chapter 9. Evolution of La Bodega and La Mascota Deposits: A Discussion and Comparison to Other Epithermal Deposits  9.1 Late Miocene history Epithermal and porphyry style mineralization in the La Bodega and La Mascota is of late Pliocene to Pleistocene age and is hosted by Proterozoic gneisses and Mesozoic granitoids. The most recent magmatic episode is represented by the intrusion of granodioritic porphyry dikes in a few magmatic pulses between ~10.9-8.4 Ma (Mantilla et al., 2009, 2011; Leal-Mej?a et al., 2011, Mantilla et al., 2013). According to Mantilla et al. (2013), Miocene magmatism in the CVMD, coincides in age with the collision of the Baud?-Panama terrane and was emplaced in a generally compressive stress regime probably associated with the subduction of the Caribbean plate beneath this part of the northern Andes (Dengo and Covey, 1993; Kellogg and Vega, 1995; Taboada et al., 2000; Prieto et al., 2012 and Vargas and Mann, 2013). Evidence for Miocene extrusive magmatism is exceedingly scarce in the district and is restricted to a few suspected tuff occurrences and breccias at Cerro Violetal (Galvis, 1998; Figure 3.3) where diatreme (?) breccias have been reported (Galvis, 1998; Bissig et al., 2012). Early porphyry style mineralization in the CVMD is represented by the quartz-molybdenite veins, dated at 10.14 +/- 0.04 Ma (Bissig et al., 2012), which are mainly hosted in the Late Triassic to early Jurassic leucogranites and Bucaramanga (Gneiss) Complex at El Cuatro, approximately 500 m south-west of La Mascota and La Bodega (Figure 9.2). D-type veins (quartz + pyrite +   203  chalcopyrite) and A-type vein (quartz + chalcopyrite ? pyrite sinuous veins) at La Plata are hosted by porphyries (Raley, 2012) and according to fluid inclusions studies are associated with moderate-high temperature (305-432?C) and highly saline fluid (12-26 wt.% NaCl equiv.). A-type and D-type veins at La Plata seem to be closely associated in time to this early porphyry style mineralization event but no direct geochronological evidence is available. Following this late Miocene hydrothermal alteration and mineralization event, hydrothermal activity occurred in two main gold mineralizing episodes in the La Baja Trend 1) quartz-pyrite veins associated with quartz-sericite alteration, representative of a shallow porphyry environment, followed by 2) vein and breccia hosted high-sulfidation mineralization associated with quartz-alunite alteration representative of the epithermal environment. Hydrothermal stages are defined based on paragenetic stages determined in Chapter 5. In the following section, the observations from La Bodega and La Mascota are put into context at a district scale within the CVMD.  9.2 Porphyry phases at La Bodega and La Mascota: early stages 1 and 2 in the context of the CVMD Stage 1 Stage 1 pre-dates gold and silver mineralization at La Bodega and La Mascota. It is dominated by the development of widespread propylitic alteration including chlorite and epidote alteration and veins; carbonate veins and specularite vein networks in the late phases of this stage. Propylitic alteration and associated veins   204  are characteristic of outer envelopes of porphyry copper deposits (Sillitoe, 2010) suggesting temperatures >>240?C and near neutral pH (6-8?) for this stage.  Figure 9.1. Schematic block diagram of the CVMD at La Baja Trend, at ~10 Ma-8 Ma over current surface. Late Miocene rocks (porphyry dikes, breccia, tuff (?) volcanic rocks) and probable volcano at Cerro Violetal are indicated. An inferred mid crustal magma chamber from which porphyries, volatiles and metals are derived is indicated. Geology adapted from (Ward et al., 1973; Mendoza and Jaramillo, 1973; Polania, 1980; Galvis, 1998; Felder et al., 2005; Bernasconi et al., 2010; MDRU Epithermal and Porphyry Gold Project, 2013). Molybdenite vein mineralization at El Cuatro dated at 10.14 ? 0.04 Ma (Bissig et al., 2012) is shown. A-type and D-type veins at La Plata and probable associated alteration are indicated as well: underlying potassic alteration (?), phyllic alteration and propylitic alteration from Stage 1 evident at La Bodega/La Mascota.   205  The relationship of this early alteration event observed at La Mascota and La Bodega with the early ~10 Ma Mo vein mineralization at El Cuatro and San Celestino (Bissig et al., 2012) is not entirely clear. However, stage 2 type veins (quartz + pyrite veins) cross cut these molybdenite bearing veins at El Cuatro (Ventana Gold Corp. internal drill log reports, 2009, 2010) suggesting that stage 1 alteration at La Bodega/La Mascota may have formed in the distal halo of this early porphyry Mo mineralization which is closely related to the ~10 Ma porphyry intrusions at El Cuatro (Figure 9.1).  Stage 2 Stage 2 is dominated by phyllic alteration and veins quartz + pyrite veins (D-type) with muscovite (sericite) halos and in some cases minor illite. D-type veins at La Bodega-La Mascota are mainly associated with zones of low grade gold/silver/copper copper mineralization. Veins of similar characteristics have been reported throughout the CVMD, and are prominent at Angostura. Mantilla et al. (2012) determined that primary fluid inclusions from D-type veins (quartz + pyrite + chalcopyrite) at La Perezosa (Angostura deposit) have salinities around 5 wt% NaCl equiv. and homogenization temperatures of ~335 to 350? C which is consistent with previous studies reported by Albinson (2000). Phyllic alteration is widespread along La Baja Trend (Figure 9.2) and is currently best exposed at La Bodega and La Angostura in the Northeastern zones of the Trend as well as in the road-cut along the road from, California to Vetas. Phyllic alteration in the southwestern reaches of the La Baja trend (e.g. La Plata) does not seem to be as widespread. D-type veins associated with phyllic alteration zones are considered to   206  be typical of shallow porphyry environments (Sillitoe, 2010) and suggests acidic conditions with pH ~3-4(?) for this stage. Based on the 40Ar/39Ar geochronology on muscovite, phyllic alteration is determined to be 4 to 3.4 Ma (Bissig et al., 2012; Chapter 6).  Figure 9.2. Schematic block diagram of the CVMD at La Baja Trend showing distribution of alteration and mineralization developed during the Pliocene (~4-3.25 Ma). Phyllic alteration and associated D-veins were emplaced at a depth between 700 and 1400 m. D-veins had temperatures between ~335 and 350 ?C (Mantilla et. al., 2012). 40Ar/39Ar on alunite at La Plata ~3.5 Ma and at Angostura ~4 Ma (Bissig et al., 2012)    207  9.3 Epithermal phase: stages 3, 4, 5 and 6. These stages are associated with the development of advanced argillic alteration characterized by quartz precipitated mainly as breccia cement, massive silicification and alunite-quartz alteration and replacements precipitated from acidic hydrothermal fluids of magmatic origin. The sulfide mineral assemblage at La Bodega/La Mascota is consistent with high-sulfidation epithermal systems. The epithermal mineralization stages were emplaced during fracture-healing episodes driven by the several hydrothermal pulses, which are evident in the characteristic multi-phase hydrothermal/tectonic-hydrothermal breccias in the area. These breccias were developed under right lateral strike-slip dynamics that allowed for the emplacement of hydrothermal breccias along La Baja Trend in zones where the strike orientation of the main fault deviates slightly from the general NE trend.  Stage 3 Stage 3 is the early epithermal stage. It is characterized by the deposition of copper sulfides such as chalcocite, bornite and chalcopyrite as well as pyrite (cubic and dodecahedric habit mainly, minor fine grained colloform) at La Bodega and La Mascota and covellite only at La Mascota. Tellurides (mostly at La Bodega) were deposited together with pyrite during early phases of this stage. Late phases of this mineralization stage deposited sulfosalts such as tetrahedrite-tennantite together with silver sulfosalts, electrum and native gold at the rims of copper sulfides and in late fractures. These ore mineralogy suggest intermediate to high-sulfidations conditions during this stage. Oxygen and deuterium isotopes analyses on alunite indicate that the fluids from which these minerals precipitated were mainly of   208  magmatic origin (Chapter 8). The presence of fine grained and massive alunite and quartz replacing host rock and clasts indicates acidic conditions with pH between 2 and 3. Alunite 40Ar/39Ar data constrain this stage to approximately ~2.6 Ma. Stage 4 Stage 4 is characterized by the deposition of manganese bearing wolframite as well as minor amounts of tennantite-tetrahedrite and gold in fractures within chalcedonic quartz and banded quartz veins with textures typical observed in low and intermediate-sulfidation deposits (flamboyant, plumose, zonal, cockade, banded; Simmons et al., 2005). Minor fine grained colloform pyrite and bladed alunite was deposited in the final phase of this stage rimming or within drusy quartz-wolframite cavities. The age of this stage is estimated ~2.5-2.3 Ma based on alunite 40Ar/39Ar geochronology. Magmatic fluids are the main source from which alunite at the end of this stage precipitated, based on oxygen and deuterium stable isotopes (Chapter 8). Fluid inclusions indicate that stage 4 wolframite associated quartz precipitated at temperatures between (188 and 238?C) from low salinity fluids (0.6 -2.2 wt % NaCl equiv.). In contrast, deposition of manganese bearing wolframite occurs at temperatures above 200 ?C and near neutral pH (Henley, 1986). Thus, wolframite precipitation is attributed to a brief episode of near neutral pH (pH~5-6) followed by more acidic hydrothermal fluids responsible for alunite depositon. This could be explained by: 1. Mixing of magmatic fluids and meteoric waters allowing for the precipitation of chalcedonic quartz as well (?) as quartz-wolframite-pyrite associations. This has been described for the San Cristobal vein, Peru (Beuchat et al.,   209  2004) where mineral deposition is explained by dilution by the meteoric fluids. 2. Boiling followed by cooling and exsolution of H2S and CO2 vapor. Quartz textures such as colloform, crustiform, banded, cockade; in most cases observed are produced by boiling (Moncada et al., 2012). These textures observed at La Mascota together with the fluid inclusion studies provide evidence for the importance of boiling as a mechanism for pH increase and precipitation of wolframite. Alunite precipitated during the final phases of this stage from largely magma derived fluids and provides evidence of an acidification of the system after wolframite emplacement.  Stage 5 Stage 5 is characterized by quartz-alunite veins, quartz veins and breccia cement development associated with deposition of enargite with minor tennantite-tetrahedrite and copper sulfides together with significant amounts gold and silver mostly as electrum sulfosalts and tellurides. This stage represents the last stage of important gold and silver deposition. Alunite 40Ar/39Ar data constrain this stage to approximately ~2.3-2.2 Ma. Based on fluid inclusions studies, temperatures of deposition associated with this stage are estimated to be 140-217 ?C and boiling and cooling are interpreted to be responsible for deposition of ore minerals. Alunite-quartz alteration suggests conditions of pH ~2-3. Oxygen and deuterium stable isotope analysis on alunite indicates that fluids associated with this stage are mostly magmatic. Mineralization and alteration distribution associated with stages 3-5 is schematically shown in Figure 9.3.   210    Figure 9.3. Schematic block diagram of the CVMD at La Baja Trend showing distribution of alteration and mineralization developed during the Pliocene-Pleistocene (~2.5-<2.2 Ma). Epithermal style alteration and mineralization showing advanced argillic alteration superimposed on phyllic alteration. Hydrothermal breccias associated with mineralization, based on fluid inclusion studies had temperatures ~140 ? ~300?C (Forero, 2010; Mendoza, 2011; this study). Stage 6 Stage 6 is characterized by the deposition of sphalerite at La Bodega and La Mascota. Alunite from this stage have precipitated from magmatic waters which probably have been mixed  with meteoric waters, as evidenced by the general shift towards lighter oxygen and deuterium isotopic values in alunite compared to those from  earlier stages. 40Ar/39Ar geochronology of alunite related to stage 6 yielded   211  ages of 1.87 ? 0.30 Ma to 1.27?0.65 Ma, the large errors attributed to incorporation for atmospheric argon into the alunite, which is consistent with a surface near emplacement depth. Minor porous quartz (vuggy-like silica as described in Chapter 4) was found adjacent to very few fractures in which sphalerite and alunite deposition occurred. Sphalerite has also been found in tectono-hydrothermal breccias associated with adjacent well-developed porous quartz textures in drill core from El Cuatro, in a few cases associated with fracture filling uranium bearing minerals such as torbernite (Ventana Gold Corp., 2010) (Figure 9.4). According to Polania (1980, 1983) sphalerite is found in the San Celestino area in uranium bearing breccias and has been considered to be later than enargite and earlier than uranium bearing minerals such as pitchblende. Temperatures related to this stage have not been determined but the presence of sphalerite is consistent with a gradual temperature drop in the hydrothermal system at La Bodega and La Mascota. Vuggy texture with residual silica is a result of intense leaching under pH conditions below 2 (Arribas et al., 1995; White and Hedenquist, 1995; Corbett and Leach, 1998; Simmons et al., 2005). However, porous quartz (Chapter 4) seems to have been developed also by intense introduction of SiO2 replacing the protolith possibly after minor leaching. Thus, pH for this stage is estimated to have started at slightly below 2 (?) during initial leaching and increased to ~2-3 (?) during quartz, sphalerite, alunite deposition in this stage.   212   Figure 9.4. Schematic block diagram of the CVMD at La Baja Trend showing distribution of alteration and mineralization developed during the Pliocene-Pleistocene (~1.9-<1.27 Ma). Epithermal style alteration and mineralization showing advanced argillic alteration superimposed on phyllic alteration. Occurrence of sphalerite bearing breccias and uranium bearing breccias is indicated.      213  9.4 Oxidation state of the hydrothermal and mineralizing fluids. The ?34S signatures of sulfides at La Bodega are lighter than typical of high-sulfidation systems (Arribas, 1995; Rye at al., 2005). At La Mascota, the pyrite ? 34S signatures are even lighter than at La Bodega and a isotopic shift towards negative values  from early stages to late stages may be reflecting more oxidizing conditions than at La Bodega. This isotopic shift towards lighter values over time is herein attributed to boiling within La Mascota hydrothermal breccia main conduit but other explanations are possible (Chapter 8). Oxidizing conditions of the hydrothermal fluids from which ore mineral precipitated from are consistent with the high-sulfidation style mineralization (Simmons et al., 2005). Oxidizing conditions derived from hydrothermal fluids are also inferred in the SW zone of La Baja Trend at San Celestino in the latest stages of the hydrothermal system within La Baja trend associated with uranium mineralization (Polania, 1980, 1983) which also manifests at El Cuatro (Ventana Gold Corp., internal log reports, 2009, 2010). According to Polania (1983), uranium bearing minerals are found within  veins and breccias at San Celestino are hosted in the Triassic-Jurassic leucogranites but are associated with hydrothermal mineralization paragenetically later than copper sulfides, enargite and sphalerite; minerals which at La Bodega - La Mascota correspond to stages 3-6. These uranium minerals include a pitchblende + pyrite deposition stage and a later supergene stage associated with pyrite oxidation with coffinite deposition (Polania, 1983) and probably torbernite deposition in microfractures as observed at El Cuatro. Oxidizing and acidic conditions are necessary for uranium dissolution and remobilization (Polania, 1983). It is   214  interpreted that oxidized-acidic hydrothermal fluids interacted with the granitic host rocks creating a suitable environment for uranium remobilization and a brief period of neutralization of these fluids allowed for the deposition of the pyrite-pitchblende associations at San Celestino. The presence of uranium mineralization (pitchblende+pyrite) is consistent with the inferred oxidized nature of the hydrothermal fluids in southern portions of La Baja trend just as at La Mascota and La Bodega in the latest stages of the hydrothermal system. The presence of coffinite, torbernite and autunite is consistent with the later near surface supergene alteration along La Baja Trend. 9.5 Depth of emplacement of the mineralization and surface processes. The high rate of erosion observed today at La Baja river valley, typical of a tropical environment, and structural and tectonic activity in the area have played an important role in the exhumation of the deposits in the CVMD located at La Baja Trend. Throughout the district, D-type veins with phyllic alteration associated with shallow porphyry environment are clearly crosscut by epithermal veins and breccias and are located at the same topographic levels today. Late Miocene porphyry style mineralization evident at El Cuatro with quartz+moybdenite veins (Bissig et al., 2012) and at La Plata with D-type and A-type veins (Raley et al., 2012) are representative of porphyry environments. The highest elevations today in the study area are probably closely representing the Late Miocene paleosurface which NW of La Mascota lies at ~3600 m.a.s.l. and NE of Angostura at ~3750 m.a.s.l. which allows inferring the initial porphryry system profile (Figure 9.7). According to Mantilla Figueroa et al. (2012) depth of emplacement of D-type veins   215  of porphyry style mineralization associated with phyllic alteration at La Perezosa at ~3.5 Ma, is between ~500 m (below the paleo surface if lithostatic pressure is assumed) and ~1400 m (below the paleo-water table level if hydrostatic pressure is assumed). These D-veins at La Perezosa are located today at ~2850 m. a. s. l., approximately 700 m below Los Laches where ~4 Ma alunite alteration has been observed (Mantilla Figueroa et al., 2012). La Perezosa at Angostura, just as La Bodega, is considered to represent a shallowly-emplaced porphyry system cut and overprinted by high-sulfidation alteration and sulfide assemblages (quartz-alunite-woodhouseite, pyrite, enargite; Mantilla Figueroa et al., 2012). Early alunite alteration of ~ 3.26 Ma has also been observed at El Cuatro therefore this information allows to infer the profile of the hydrothermal system at 4~4-3.25 Ma (Figure 9.7). In general, high-sulfidation alteration and sulfide assemblages are present at Angostura over a vertical extent of 650 m (Mantilla Figueroa et al., 2012). Epithermal style high-sulfidation gold/silver mineralization that took place between ~2.6-2.2 Ma at La Mascota was emplaced above boiling level. Hydrothermal breccias observed in the deepest drill holes analyzed for this study at La Mascota (LB114 and LB221) exhibit epithermal features and quartz textures associated with boiling. These textures extend between the present day surface at ~2750 m. a. s. l. and 2350 m. a. s.l. at ~400 m depth. Minimum erosion at La Mascota since the emplacement of epithermal style mineralization with stage 4 and stage 5 associations is predicted to be higher than 140 m (Chapter 7, Figure 7.7). Thus, minimum boiling level depth at the time of the emplacement of these breccias (in stage 4-5) is estimated >600 m (?). Therefore, a profile of the hydrothermal system may be inferred for the time ~2.5-2 Ma (Figure 9.6).    216  The preserved paleosurface at Angostura (Los Laches, ~3750 m) indicate that erosion rates to the NE of La Bodega have been lower than along the La Baja river valley and its southern portions. Therefore, at San Celestino >1000 m of erosion is predicted since the emplacement of Mo-Cu mineralization and porphyritic bodies (Figure 9.5). Better exposure of porphyry style mineralization at La Bodega as compared to La Mascota is evident. This may be explained by the fact that La Bodega was at a higher level than La Mascota during epithermal and porphyry style mineralization, but also that higher erosion rates may have occurred at La Bodega. La Bodega is limited by structures represented on the drainage pattern: the limit between La Bodega and La Mascota is the intersection between La Baja (river) fault (NE/NW), Paez (creek) fault (NWW/NE) and the Angostura (creek) lineation (NNE); while the limit between Angostura and La Bodega is Perezosa (creek) fault (Figure 3.3). The intersection in between these structures at La Bodega may play an important role in its erosion rates. The Paez fault forms a NWW trending /~50? NE dipping fracture zone of 50-70 m width and reverse movement is proposed herein. Thus, minor uplift of La Bodega in relation to La Mascota along to this fault may have caused erosion at La Bodega to expose deeper portions of the epithermal systems compared to La Mascota (?).     217   Figure 9.5. Cartoon showing profile along La Baja Trend from Angostura (NE) to California town (SW). Surface evolution at the CVMD from Late Miocene until Pleistoscene showing superimposing alteration through time. (Modified after Bissig et al., 2012).    218  9.6 Summary of mineralization characteristics at La Bodega/La Mascota and comparison to other similar epithermal and porphyry systems Ages of formation of the hydrothermal system at La Bodega and La Mascota and other deposits within La Baja Trend (Late Miocene-Pleistocene) in this study are partially consistent with spectrum of ages for porphyry systems and associated epithermal systems in the Andes, which mostly range from Eocene to Pliocene (Sillitoe, 2010). Ore minerals deposited at La Bodega and La Mascota are representative of high-sulfidation to intermediate sulfidation conditions. Typical host rocks in high to intermediate sulfidation deposits in the Andes are mostly genetically associated andesites/rhyodacites (Sillitoe and Hedenquist, 2003; i.e. Pierina, Fifarek and Rye, 2004); while at La Bodega/La Mascota host rocks correspond to Pre-Cambrian gneisses and Triassic-Jurassic granitoids and only few Late Miocene porphyry granodiorites (Mantilla et al., 2008, 2010, 2012) have been reported. Mineralization style at La Mascota and La Bodega is dominated by porphyry style D-type veins and overprinting epithermal style hydrothermal (tectonic-hydrothermal) breccias. Vein style and breccia style mineralization is common in low and intermediate-sulfidation deposits such as Mexican epithermal deposits (i.e. Veta Madre, Guanajuato; Moncada et al., 2012); Baguio District in the Philippines (Waters et al., 2012), Kelian gold mine in Kalimantan, Indonesia (Davies et al., 2008). However, hydrothermal breccias at La Bodega/La Mascota exhibit quartz-alunite cement associated with high-sulfidation alteration/mineralization which are comparable to quartz-alunite cemented breccia bodies, as observed at Lagunas   219  Norte, high-sulfidation epithermal deposit in Peru (Cerpa et al., 2013) or Pascua-Lama (Chouinard et al. 2005). Intermediate to high sulfidation conditions are evident in stages 3-5 associated with gold mineralization. However, stage 4 is characterized by higher pH conditions that allowed for the deposition of wolframite which may be either associated with fluid mixing, neutralization or boiling. High-sulfidation conditions are evident in stage 5 where alunite-enargite-quartz the main characterizing minerals.  In most high-sulfidation deposits vuggy residual quartz alteration representing intense acid leaching, takes place prior to ore deposition associated with alunite-enargite-pyrite stage (e.g., Hedenquist and Taran, 2013). However, at La Bodega/La Mascota evidence for residual quartz alteration prior to stage 5 gold mineralization is absent. Scarce evidence of highly acidic conditions are found in transition to the early phases of stage 6 associated with sphalerite deposition in discrete areas of La Bodega/La Mascota but more are evident at El Cuatro (Hedenquist, 2010; unpub internal report for Ventana Gold Corp). This is not associated with important gold deposition.  Ore mineral deposition sequence at La Bodega/La Mascota type is comparable to the general sequence ore deposition established for porphyry systems (Corbett and Leach, 1998) in which gold mineralization occurs at shallow levels associated with the deposition of sulfides and sulfosalts in a determined sequence that includes in order: chalcopyrite, molybdenite, bornite, chalcocite and covellite, enargite and tetrahedrite-tennantite and finally sphalerite. However, the presence of h?bnerite (Mn bearing wolframite) in high sulfidation epithermal deposits has   220  also been reported at at El Indio, Chile (Jannas et al., 1990) deposited in a stage of transition from copper mineralization to gold mineralization. Main gold and silver deposition under epithermal conditions at La Bodega and La Mascota took place in stages 3 through 5. Fluid inclusions evidence suggests that gold deposition at La Mascota (and probably at La Bodega) was driven by episodic boiling followed by cooling of the hydrothermal fluids. Each hydrothermal stage seems to have been associated with structural activation and fracture-healing episodes that allowed hydrothermal breccias/mineralization emplacement and related alteration.  In summary, pH and temperature conditions change is evident from early stages to late stages. Alteration mineralogy ore mineralogy and the different fluid inclusions studies allows to determine that higher temperature and pH conditions are dominating porphyry phase in early stages (1-2) while later stages (3-6) of the epithermal phase are associated with lower temperatures  and lower pH conditions (Figure 9.6).     221   Figure 9.6. General hydrothermal alteration/mineralization associations in relation to relative temperature and pH indicating the evolution of the hydrothermal fluids from higher pH higher temperature to lower pH and lower temperature associations.    222  Chapter 10. Conclusions, Exploration Implications and Recommendations for Future Work  10.1 Conclusions 1. La Bodega and La Mascota mineralization occurs mostly within structurally controlled advanced argillic alteration and related hydrothermal breccias crosscutting and superimposed on phyllic alteration and quartz pyrite veins. The latter is more wide-spread at La Bodega than at La Mascota. Mineralization is hosted in Precambrian gneisses of the Bucaramanga Complex and Triassic-Jurassic leucogranites and occurs largely within tabular tectonic-hydrothermal breccia bodies. These ore hosts are emplaced in dilatant structural settings along the La Baja trend right lateral strike-slip fault zone.  2. At La Bodega and La Mascota six stages of hydrothermal alteration and mineralization were identified. Early stages include propylitic alteration (stage 1) and phyllic alteration (stage 2) associated with porphyry events. Stages 3 through 6 correspond to epithermal style high-sulfidation alteration and introduced the bulk of the mineralization.  3. Early porphyry Mo-Cu mineralization is represented by 10 Ma molybdenite bearing veins mostly evident at El Cuatro whereas other vein types (A and D-type veins) of this event are evident at La Plata. Propylitic alteration, observed at la Mascota is likely associated with this early event.   223  4. Phyllic alteration at ~4-3.5 Ma, associated with D-veins, corresponds to a second clearly distinct porphyry event and is typical for the shallow portions of a porphyry system. 5. Advanced argilic alteration and associated mineralization occurs between ~2.6 and 2.2 Ma at La Bodega and La Mascota.  Gold and silver deposition starts in stage 2 but is much more important in stages 3 through 5. Gold and silver occur as electrum, tellurides and as microinclusions in pyrite and occurs together with pyrite, copper sulfides, sulfosalts (enargite, tetrahedrite-tennantite).  6. Advanced argillic alteration (alunite-quartz) from stage 6 took place between ~1.9-1.27 Ma and is characterized by sphalerite occurrence and minor porous silica, but no important gold deposition took place at this stage.  7. In general, hydrothermal alteration and mineralization at the CVMD and La Bodega/La Mascota took place in four discrete episodes at ~10, ~4-3.4 and ~2.6 to 2.2, and 1.9 to 1.3 Ma, overall spanning a time period of ~9 Ma. 8. A general temperature and pH drop is evident from alteration mineralogy and fluid inclusion studies. While early stages are dominated by higher temperature and pH (stage 1 temperature>240?C, pH ~6-8; stage 2 temperature ~335-413 ?C, pH ~3-5?), later epithermal stages (3-6) are characterized by lower pH (2-4) and lower temperatures (140-300?C). 9. The main origin from the hydrothermal fluids seems to have been magmatic, however, minor mixing with meteoric water in late stages is evident. The main processes for ore deposition seem to have been boiling. Pyrite that precipitated   224  from these fluids has very light ?34S values (-6.1 - -16.9 ?) as compared to other Andean high-sulfidation epithermal systems which may indicate oxidizing conditions possibly associated with boiling.  10.2 Exploration implications Mineral zonation at La Mascota/La Bodega can be used as an important vector to mineralization. E. g. Propylitic alteration and associated specularite veins developed distal from a probable potassic alteration core indicating deep porphyry mineralization potential.  Advanced argillic alteration associated with mineralized centers is preceded by phyllic alteration and associated D-type veins that cross cut propylitic alteration and veins. Shallow porphyry environment crosscut by epithermal style mineralization environment indicates exhumation of the porphyry environment through erosion mostly.  At La Mascota, erosion since the emplacement of epithermal mineralization is estimated to be >~140 m.  At La Mascota, boiling level associated with epithermal environment was not intersected by the logged drill holes and this level may be located at depths deeper than 600 m. A deeper porphyry environment potentially hosting Cu mineralization is likely present at depth but there is no direct evidence from drilling to confirm that. Mineralization is not restricted to Triassic-Jurassic granitoids and these granitoids are not genetically associated with mineralization, therefore exploration should be focused in structures related to advanced argilic alteration. Most precious metal   225  occurrences are associated with the development of hydrothermal breccias and other dilatant structures in a strike-slip environment along NE faults parallel or subparallel to Cucutilla fault, where exploration should be focused on. The hydrothermal history of the district indicates that at least two distinct porphyry events occurred prior to epithermal gold mineralization which is the current focus of exploration. Porphyry style mineralization includes Mo-Cu and Cu-Au metal associations at 10 Ma and 4-3.4 Ma, respectively but its possible importance within the district has not been established by exploration thus far. 10.3 Recommendations To further understand the history of La Bodega and La Mascota deposits as well as the CVMD these recommendations for further work are provided: 1. Lithogeochemistry of the intrusives at La Bodega and La Mascota which was not covered in this study. 2. Lithogeochemistry and U-Pb geochronology of the granitic pegmatite dikes found at both, La Bodega and La Mascota, as well as additional U-Pb geochronology on La Bodega leucogranites.  3. Fluid inclusion studies are recommended to be done in the different veins and breccia cement from several locations within La Baja Trend and other areas of the CVMD, at different depths and at different stages of mineralization. Fluid inclusion analysis may also be carried out in sphalerite in order to define the temperature associated with late stages of the hydrothermal system.    226  4. A more complete characterization of the isotopic signatures of sulfides and sulfosalts from La Bodega/La Mascota is necessary. The initial results show apparent lower values at La Mascota as compared to La Bodega therefore, testing consistency with a higher density of analysis is recommended. This characterization should include sulfides from each stage and different levels of the system and from different prospects within the CVMD, as well as background samples from the Bucaramanga gneiss and unaltered granitoids. 5. Structural studies at the district scale are necessary in order to define dilational structures associated with prospective areas where mineralization may have been emplaced. 6. Regional alteration studies by means of X-ray diffraction and short-wave infrared means may provide methods to define vectors to higher temperature alteration environments that could be associated with mineralization.     227  References Albinson, T. 2000. Fluid inclusion Study of Samlpes B-026115, B-026476, and B-027534 Angostura Deposit, Colombia. MAGSA. Microtermometr?a y Asesor?a Geol?gica-Minera, S. A. de C. V. Mexico. Altmann, K., Sim, R., Davis, B., Prenn, N., Elfen, S., Fisher, B. 2010. Canadian National Instrument 43-101 Technical Report Preliminary Assesment La Bodega Project Department of Santander, Colombia. Prepared by Samuel Engeneering, Inc. for Ventana Gold Corp. Arribas, Jr., A. 1995. Characteristics of high-sulfidation epithermal deposits, and their relation to magmatic fluid: Mineralogical Association of Canada Short Course Series, v. 23, p. 419?454. Bakker, R. J., 2003. Package FLUIDS 1. Computer programs for analysis of fluid inclusion data and for modeling bulk fluid properties. Chemical Geology, vol. 194, 3 ? 23. Banks, P., Vargas, R., Rodr?guez, G.I., Shagam, R. 1985. Zircon U-Pb ages from orthogneiss, Pamplona, Colombia. VI Cong. Latinoam. Geol. Bogot?. Res?menes. Barton, P. B., Jr., 1970. Sulfide petrology: Mineralogical Society of America, Special Paper No. 3, p. 187-198 (In: Einaudi et al., 2003). Bauer, A.; Velde, B.; Gaupp, R. 2000. Experimental constraints on illite crystal morphology. Clay Minerals, 35, 3, 587-597, 2000. Beuchat, S., Moritz, R., Pettke, T. 2004. Fluid evolution in the W?Cu?Zn?Pb San Cristobal vein, Peru: fluid inclusion and stable isotope evidence. Chemical Geology 210 (2004) 201? 224. Bernasconi, A. 2006. La Bodega Gold Project ? CVS Explorations Ltda.- Colombia. Progress Report on the Geology and Mineralization of the Mine Property and Adjacent Areas. Unpublished report from Gondwanaland Exploration for CVS Explorations Ltda. Bethke, P.M., Rye, R.O., Stoffregen, R.E., and Vikre, P. 2005. Evolution of the Summitville magmatic-hydrothermal acid-sulfate system. Chemical Geology. Bissig, T.; Clark, C. H., Lee, J. K. W., Hodgson, C. J. 2002. Miocene Landscape Evolution and Geomorphologic Controls on Epithermal Processes in the El Indio-Pascua Au-Ag-Cu Belt, Chile and Argentina Bissig, T., Mantilla Figueroa, L. C., Rodriguez M. A. L., Raley, C., Hart, C., J. 2012. The California-Vetas District, Eastern Cordillera, Santander, Colombia: Late Miocene Porphyry and Late Pliocene-Pleistocene Epithermal Mineralization Hosted in Proterozoic gneisses and Late Triassic intrusive rocks. Abstract. Society of Economic Geologists. SEG Peru Conference. 2012   228  Bissig, T., Rodriguez, A., Mantilla, L. C., Hart, C. J. R. 2012. Hydrothermal Evolution of the California-Vetas District, Santander Colombia: New Age Constraints on Hydrothermal Minerals. MDRU Colombia Project - Technical Meeting 1 ? Sep. 2012 Bodnar, R. J. 1992. The system H2O-NaCl. PACROFI IV, Program and Abstracts, 108-111. Bodnar, R. J. 1993. Revised equation and Table for Determining the Freezing point Depression of H2O-NaCl solutions. Geochemica et Cosmochemica Acta, v. 57. P. 683-684. In Brown, P. E. 1998. Fluid Inclusion Modeling for Hydrothermal Systems. Techniques in Hdrothermal Ore Deposits Geology. Chapter 7. Reviews in Economic Geology. Volume 10. Society of Economic Geology, Inc. Bodnar, R. J. 2003a. Interpretation of data from aqueous-electrolyte fluid inclusions. In I. Bodnar, R. J., Vityk, M.O., 1994. Interpretation of microthermometric data for H2O-NaCl fluid inclusions. In De Vivo B. and Frezzotti M. L. (eds) Fluid Inclusions in Minerals: Methods and Applications. Blacksburg, VA: Virginia Tech, pp. 117-130. Boinet, T., Bourgois, J., Bellon, H., and Toussaint, J. (1985). Age et repartition du magmatism premesozoique des Andes de Colombie. Comptes rendus hebdomadaires des s?aces de L?Acad?mie des Sciences. Serie D: Sciences Naturalles, Vol. 300(II), 445-450. Brown, P. E. 1998. Chapter 7. Fluid inclusion modeling for hydrothermal systems.  Techniques in Hydrothermal Ore deposits Geology. Reviews in Geology Volume 10. Editors: Richards, J. P. & Larson, P. B. Society of Economic Geologists. Buchanan, L. J. 1981. Precious metal deposits associated with volcanic environments in the southwest In: Panteleyev, A. 1986. A Canadian Cordilleran Model for Epithermal Gold-Silver Deposits. Ore Deposits. Geoscience Canada. Buhl, JC-. and Willgallis, A. 1986. The low-temperature crystallization of (Fe, Mn) WO4 (Wolframite), (Zn, Fe)WO4 (Sanmartinite) and (Zn, Mn)WO4 solid solutions under hydrothermal conditions. Chemical Geology, 56 (1986) 271-279. Elsevier Science Publishers B. V., Amsterdam. Candela, P.A., and Piccoli, P.M. 2005. Magmatic processes in the development of porphyry-type ore systems: Economic Geology 100th Anniversary Volume, p. 25?37. Campbell, C.J. 1965. The Santa Marta wrench fault of Colombia and its regional setting. Fourth Caribbean Geological Conference. Memoir : 247-261. Trinidad. (In: Royero and Clavijo, 2002) Campbell, A. R., & Larson, P. B. 1998. Introduction to stable isotope applications in hydrothermal systems. Chapter 8. Richards, J. P. & Larson, P. B., eds., Techniques in hydrothermal ore deposits geology. Reviews in Economic Geology, v. 10, p. 173-193.    229  Carten, R.B., 1986, Sodium-calcium metasomatism: Chemical, temporal, and spatial relationships at the Yerington, Nevada, porphyry copper deposit: Economic Geology, v. 81, p. 1495?1519. Castellanos, O M., Rios, C. A., Takasu, A. 2008. A New Approach on the Tectonometamorphic Mechanisms Associated with P?T Paths of the Barrovian-Type Silgar? Formation at the Central Santander Massif, Colombian Andes. Earth Sciences Research Journal. Vol. 12, No. 2 (December 2008): 125-155. Cediel, F., Shaw, R.P., C?ceres, C. 2003. Tectonic Assembly of the Northern Andean Block. In: ?The Circum-Gulf of Mexico and Caribbean: Hydrocarbon habitats, basin formation, and plate tectonics?, C. Barto lini, R. T. Buffler y J. Blickwede, eds. AAPG Memoir, 79, 815 - 848. Cerpa, L. M., Bissig, T., Kyser, K., McEvan, C., Macassi, A., Rios, H. W. 2013 Lithologic controls on mineralization at the Lagunas Norte high-sulfidation epithermal gold deposit, northern Peru. Miner Deposita (2013) 48:653?673 Chouinard, A., Williams-Jones, A., Leonardson, R. W., Hodgson, J., Silva, P., T?llez, C., Vega, J., Rojas, F. 2005. Geology and Genesis of the Multistage High-Sulfidation Epithermal Pascua Au-Ag-Cu Deposit, Chile and Argentina. Economic Geology, v. 100, pp. 463?490 Clark, I. and Fritz, P. 1997. Environmental isotopes in hydrogeology. CRC press, 145 In Stam, 2006. Craig, H. 1963. The isotopic geochemistry of water and carbon in geothermal areas: Nuclear geology of geothermal areas: Spoleto, Pisa, Consiglio Nazionale della Richerche, Laboratorio de Geologia Nucleare, p. 17?53. Corbett, G., Leach, T. 1998. Southwest Pacific Rim Gold-Copper Systems: Structure, Alteration, and Mineralization. Society of Economic Geologists. Special Publication No 6, 1998, pp. ii-x Corbett, G. 2002. Epithermal Gold for Explorationists. AIG Journal ? Applied geoscientific practice and research in Australia. Paper 2002-01, February 2002. Cooke, D. R., & Deyell, C. L. 2003. Descriptive names for epithermal deposits: their implications for genetic classifications and inferring ore fluid chemistry: in Eliopoulos, D. et al., eds., Mineral exploration and sustainable development: Rotterdam, Millpress. Proceedings of the Seventh Biennial SGA Meeting on Mineral Exploration and Sustainable Development, Athens, Greece, August 24-28, v. 1, p. 457-460. Cooke, D., R.; Deyell, C. L., waters, P., J., Gonzales, R. I., Zaw, K. 2011. Evidence for Magmatic-Hydrothermal Fluids and Ore-Forming Processes in Epithermal and Porphyry Deposits of the Baguio District, Philippines. Economic Geology, v. 106, pp. 1399?1424  Cordani, U., Cardona, A., Jimenez, D., Liu, D., Nutman, A., 2005. Geochronology of Proterozoic basement inliers in Colombian Andes: tectonic history of remnants   230  of a fragmented Grenville belt. In: Vaughan, A., Leat, P., Pankhurst, R. (Eds.), Terrane Processes at Margins of Gondwana. Geological Society, London, Special Publications, vol. 246, pp. 329e346. Cortes, M., Angelier, J., 2005. Current states of stress in the northern Andes as indicated by focal mechanisms of earthquakes. Tectonophysics 403, 29?58. Cox, S. 2005. Coupling between Deformation, Fluid Pressures, and Fluid Flow in Ore-Producing Hydrothermal Systems at Depth in the Crust. Economic Geology; Bulletin of the Society of Economic Geologists, vol. 100, pp. 39-75. Davies, A. G. S., Cooke, D. R., Gemmell, J. B., van Leeuwen, T., Cesare, P. Hartshorn, G. 2008. Hydrothermal Breccias and Veins at the Kelian Gold Mine, Kalimantan, Indonesia: Genesis of a Large Epithermal Gold Deposit.  Economic Geology, v. 103, pp. 717?757. Deyell, C.L., Bissig, T., Rye, R.O., 2004, Isotopic evidence for magmatic dominated epithermal processes in the El Indio-Pascua Au-Cu-Ag belt and relationship to geomorphologic setting: Society of Economic Geologists Special Publication 11, p. 55?73. Deyell, C. L., Rye, R. O., Landis, G. P., Bissig, T. 2005. Alunite and the role of magmatic fluids in the Tambo high-sulfidation deposit, El Indio?Pascua belt, Chile: Economic Geology v. 100, pp. 131?148. Society of Economic Geologists, Inc. Di Prisco, G. 2009. Characterization of gold ore from La Mascota Deposit, California District, Colombia. Mineralogical Report. Terra Mineralogical Services. Prepared for Jon Lehmann. Ventana Gold Corporation. Di Prisco, G. 2009. SEM ?EDS analyses and Semi-quantitative analyses of La Bodega Gold mineralization and associated minerals. Terra Mineralogical Services. Memorandum prepared for Jon Lehmann. Ventana Gold Corporation. Diamond, L. W. Systematics of H2O Fluid inclusions. In: Samson, A. Anderson, & D. Marshall, eds. Fluid Inclusions: Analysis and Interpretation. Mineral. Assoc. Can., Short Course Ser. 32, 81-100. Diaz L. A., Guerrero M. 2006. Asociaciones Mineral?gicas de las Menas Auroargent?feras y su Distribuci?n en el Yacimiento Angostura (California, Santander). Proyecto de Grado para optar al t?tulo de Ge?logo. Facultad de Ingenier?as Fisicoqu?micas. Escuela de Geolog?a. Bucaramanga, Colombia. Dilles, J.H., and Einaudi, M.T., 1992, Wall-rock alteration and hydrothermal flow paths about the Ann-Mason porphyry copper deposit, Nevada a 6?km vertical reconstruction: Economic Geology, v. 87, p. 1963?2001. D?rr, W., Gr?sser, J., Rodriguez, G., Kramm, U., 1995. Zircon U-Pb age of the Paramo Rico tonalite-granodiorite, Santander Massif (Cordillera Oriental, Colombia) and its geotectonic significance. Journal of South American Earth Sciences 8(2), 187-194.   231  Drummond, S. E., Ohmoto, H. 1985. Chemical Evolution and Mineral Deposition in Boiling Hydrothermal Systems. Economic Geology Vol. 80, 1985, pp. 126-147. Dunoyer de Segonzac G., Ferrero, J. and K?bler, B. 1968. Sedimentology, 10, 137-143. Einaudi, M.T., Hedenquist, J.W., Inan, E., 2003, Sulfidation state of fluids in active and extinct hydrothermal systems: Transitions from porphyry to epithermal environments: Society of Economic Geologists Special Publication 10, p. 285?314. Evans, J., 1977. Geological and Geochemical Reconnaissance in the Central Santander Massif. Departments of Santander and Norte de Santander, Colombia, p. 43. U. S. Geological Survey. Farquhar, J., Wu, N., Canfield D., Oduro, H. 2010. Connections between Sulfur Cycle Evolution, Sulfur Isotopes, Sediments, and Base Metal Sulfide Deposits. Economic Geology, v. 105, pp. 509?533 Felder, G., Ortiz, G., Campos, C., Monsalve, I., Silva, A. 2005. Angostgura project, a High Sulfidation Gold-Silver Deposit located in the Santander Complex of North Eastern Colombia. Greystar Resources Ltd. Thech. Report. (http://www.greystarresources.com/i/pdf/Angostura_Greystar_ ProExplo_2005Final.pdf) Field, C.W., and Fifarek, R.H., 1985, Light stable isotope systematics in epithermal systems: Reviews in Economic Geology, v. 2, p. 99?128. Field, C. W., Zhang, L., Dilles, J. H., Rye, R. O., Reed, M. H. 2005. Sulfur and oxygen isotopic record in sulfate and sulfide minerals of early, deep, pre-Main Stage porphyry Cu?Mo and late Main Stage base-metal mineral deposits, Butte district, Montana. Chemical Geology 215 (2005) 61? 93 Fifarek, R.H., Rye, R.O. 2005. Stable-isotope geochemistry of the Pierina high-sulfidation Au-Ag deposit, Peru: Influence of hydrodynamics on SO42?-H2S sulfur isotopic exchange in magmatic-steam and steam-heated environments: Chemical Geology, v. 215, p. 253?279. Frikken, P. H., Cooke, D. R., Walshe, J. L., Archibald, D., Skarmeta, J., Serrano, L., Vargas, R. 2005 Mineralogical and Isotopic Zonation in the Sur-Sur Tourmaline Breccia, R?o Blanco-Los Bronces Cu-Mo Deposit, Chile: Implications for Ore Genesis. Economic Geology, v. 100, pp. 935?961. Forero, A. R., 2010. Parag?nesis minerales de las brechas mineralizadas del sector La Mascota (California, Santander). Trabajo de Grado para optar al T?tulo de Ge?logo. Universidad Industrial de Santander. Facultad de Ingenier?as Fisicoqu?micas. Escuela de Geolog?a. Bucaramanga, Colombia. Galvis, V.J., 1998. Una caldera volc?nica en el Macizo de Santander, Colombia. Revista Academia Colombiana de Ciencias 22 (84), 355e362. Garc?a, C., R?os, C., 1999. Metamorfismo y metalog?nia asociada del Macizo de Santander, Cordillera Oriental, Colombia. Informe final Proyecto de Investigaci?n   232  1102-05-083-95 Colciencias-Universidad Industrial de Santander (Bucaramanga), pp. 1e191. Garc?a, C. A.; R?os, C. A. & Castellanos, O. M. 2005. Medium- pressure, metamorphism in the Central Santander Massif, Eastern Cordillera, Colombian Andes. Bolet?n de Geolog?a. Volumen 27, No 2 (2005). Gemmel, J, Harpe R., Jonasson, I. R., Herzig, P. 2004. Sulfur Isotope Evidence for Magmatic Contributions to Submarine and Subaerial Gold Mineralization: Conical Seamount and the Ladolam Gold Deposit, Papua New Guinea. Economic Geology December 2004 v. 99 no. 8 p. 1711-1725 Giggenbach, W.F. 1992. Isotopic shifts in waters from geothermal and volcanic systems along convergent plate boundaries and their origin: Earth and Planetary Science Letters, Vol. 113, pp. 495?510. Godoy, M., Farr, G., McKittrick, R., Engeles, J. 2012. Updated Preliminary Economic Assessment on the Angostura Gold-Silver Underground Project, Santander Department, Colombia. Prepared for Golder Associates Per? S. A. Eco Oro Minerals Corp.  Goldsmith, R., Marvin, R., and Mehnert, H. 1971. Radiometric ages in the Santander Massif, eastern Cordillera, Colombian Andes. U.S. Geological Survey Professional Paper, Vol. 750-D, D41-D49 Graton, L.C., and Bowditch, S.I., 1936. Alkaline and acid solutions in hypogene zoning at Cerro de Pasco, Peru: Economic Geology, v. 31, p. 651-698 Guilbert, J.M., Lowell, J.D.  1974. Variations in zoning patterns in porphyry ore deposits. Can. Inst. Min. Metall. Bull., 61 (742) Gustafson, L.B., and Hunt, J.P., 1975. The porphyry copper deposit at EI Salvador, Chile: Economic Geology, v. 70, p. 857-912. Hedenquist, J. W., Henley, R. W. 1985. The Importance of CO2 on Freezing Point Measurements of Fluid Inclusions: Evidence from Active Geothermal Systems and Implications for Epithermal Ore Deposition. Economic Geology. Vol. 80, 1985, pp. 1379-1406 Hedenquist, J. W., Lowenstern, J.B. 1994. The role of magmas in the formation of hydrothermal ore deposits: Nature, v. 370, p. 519?527. Hedenquist, J.W., Arribas, A., & Gonzalez-Urien, E. 2000. Exploration for epithermal gold deposits: Reviews in Economic Geology, v. 13, p. 221?244.  Hedenquist, J. W. 2010. Comments on the La Bodega Project, California District, Colombia. Report for Ventana Gold Corp. Hedenquist Consulting, Inc. July, 2010.  Henley, J. J., Hostetler, P. B., Gude, J. A. Mountjoy, W. T. 1969. Some Stability Relations of Alunite. Economic Geology, v. 64, pp. 599-612.    233  Henley, R. W. 1973. Solubility of gold in hydrothermal chloride solutions. Chemical Geology. Volume 11, Issue 2, April 1973, Pages 73?87 (In: Corbett and Leach, 1998)  Henley, R.W., Ellis, A.J. 1983. Geothermal systems, ancient and modem: A geochemical review. Earth Sci. Reviews 19, 1-50 Henley, R. W., Truesdall, A. H., Barton, P.B. Jr, eds. 1984. Fluid mineral equilibria in hydrothermal systems: Reviews in Economic Geology, v. 1, 267 p. (In: Corbett and Leach, 1998)  Hildreth, W., 1981, Gradients in silicic magma chambers: Implications for lithospheric magmatism: Journal of Geophysical Research, v. 86, p. 10,153?10,192 (In Simmons et al., 2005) Hoefs, J. 1997. Stable Isotope Geochemistry. Berlin. Springer-Verlag   Horner, C.1979. Solubility and hydrolysis of FeWO, and MnWO4 in the 25?C -300?C range, and the zonation of wolframite. Chemical Geology, 27 : 85-97.  Horner J. 2005. Final report ?Structural geology and tectonics of the Angostura Proyect area? . Ic consulenten. pp 32. In: Diaz L. A., Guerrero M. 2006. Asociaciones Mineral?gicas de las Menas Auroargent?feras y su Distribuci?n en el Yacimiento Angostura (California, Santander). Proyecto de Grado para optar al t?tulo de Ge?logo. Facultad de Ingenier?as Fisicoqu?micas. Escuela de Geolog?a. Bucaramanga, Colombia.  Jannas, R. R., Beane, R. E., Ahler, B. A., Brosnahan, D. R. 1990. Gold and copper mineralization at the El Indio deposit, Chile. Journal of Geochemical Exploration, 36 (1990) 233 ? 266. Elsevier science publishers B. V., Amsterdam ? Printed in Netherlands.  Julivert, M., 1958. La morfoestructura de la zona de Mesas al SW de Bucaramanga. Universidad Industrial de Santander. Bolet?n de Geolog?a, (1): 7-44. Bucaramanga. (In: Clavijo and Royero, 2002)  Julivert, M. 1961. Las estructuras del Valle Medio del Magdalena y su significaci?n. Universidad Industrialde Santander. Bolet?n de Geolog?a, (6) : 33-52. Bucaramanga. (In: Clavijo and Royero, 2002) Julivert, M.1968. Lexique Stratigraphique International Amerique Latine: Centre National de La Reserche Scientifique, u. V., fascicule 4 a Colombie Kats, D. A., Eberli, G. P., Swart, P. K., Smith, L. B. Jr. 2006. Tectonic-hydrothermal brecciation associated with calcite precipitation and permeability destruction in Mississippian carbonate reservoirs, Montana and Wyoming. AAPG Bulletin, v. 90, no. 11 (November 2006), pp. 1803?1841.   234  Krouse, H. R. and Mayer, B., 2000. Sulphur and oxygen isotopes in sulphate. In: In Stam, 2006. Lawless, J. V.; White, P. J. 1990. Ore-related breccias: a revised genetic classification, with particular reference to epithermal deposits. 12th New Zealand Geothermal Workshop.  Leal-Mej?a, H. 2011. Phanerozoic Gold Metallogeny in the Colombian Andes: A tectono-magmatic approach. PhD. Thesis. Universidad de Barcelona.  Lindgren ,W., 1933. Mineral deposits, 4th ed.: New York, McGraw-Hill, 930 p. Lowell, J.D., Guilbert, J.M. 1970, Lateral and vertical alteration-mineralization zoning in porphyry copper deposits: Economic Geology, v. 65, p. 363-408. Mantilla F., L. C.; Valencia, V. A.; Barra, F. Pinto, J. & Colegial, J. 2009. Geocronolog?a U-Pb de los cuerpos Porfir?ticos del Distrito Aur?fero de Vetas- California (Santander, Colombia). Bolet?n de Geolog?a/Universidad Industrial de Santander. V. 31 (1): 31-43. Mantilla Figueroa, L. C., Bissig, T., Cottle, J., Hart, C. J.  2012. Remains of early Ordovician mantle-derived magmatism in the Santander Massif (Colombian Eastern Cordillera). Journal of South American Earth Sciences 38 (2012) 1-12. Mantilla Figueroa, L. C., Bissig, T., Hart, C. J. R. 2012. Wall-rock Alteration and Mineralization of the Angostura Au-Ag-Cu Prospect, Vetas-California Mining District (VCMD). Colombia Gold and Porphyry Project. Year 1 Technical Report edited by Bissig, T; Hart, C. Mineral Deposit Research Unit (MDRU). The University of British Columbia. Mantilla Figueroa, L. C., Bissig, T., Valencia, V., Hart, C. J. 2013. The magmatic history of the Vetas-California mining district, Santander Massif, Eastern Cordillera, Colombia. Journal of South American Earth Sciences 45 (2013). Mathur, R., Ruiz, J., Herb, P., Hahn, L. Burgath, K. P. 2002. Re?Os isotopes applied to the epithermal gold deposits near Bucaramanga, northeastern Colombia. Journal of South American Earth Sciences 15 (2003) 815?821 McKibben, M.A., and Eldridge, C.S., 1990, Radical sulfur isotope zonation of pyrite accompanying boiling and epithermal gold deposition: A SHRIMP study of the Valles caldera, New Mexico: ECONOMIC GEOLOGY, v. 85, p. 1917?1925. McKinstry, H. E. 1948 Mining Geology. New York, Prentice-Hall, 680 p. In Corbett and Leach (1998) M?gard, F. 1987. Cordilleran Andes and marginal Andes: A review of Andean geology north of the Arica elbow (18?s), in Circum-Pacific Orogenic Belts and Evolution of the Pacific Ocean Basin, Geodyn. Ser., vol. 18, edited by J. W. H. Monger and J. Francheteau, pp. 71?95, AGU, Washington, D. C., doi:10.1029/GD018p0071   235  Mendoza, H.; Jaramillo, L. 1979. Geolog?a y geoqu?mica del ?rea de California, Santander. Bolet?n Geol?gico Ingeominas, 22: 3-52. Mendoza, M. 2011. Estudio textural de las brechas del sector La Mascota (plataforma 9600: pozos de perforaci?n LB278 y LB140), proyecto La Bodega (municipio de California, departamento de Santander). Trabajo de Grado para optar al T?tulo de Ge?logo. Universidad Industrial de Santander. Facultad de Ingenier?as Fisicoqu?micas. Escuela de Geolog?a. Bucaramanga, Colombia. Meyer, C., and Hemley, J. J., 1967, Wall-rock alteration, in Barnes, H. L., ed., Geochemistry of hydrothermal ore deposits: New York, Holt, Rinehart, and Winston, p. 166-235. (In: Einaudi et al. 2003). Meunier, A. and Velde, B., 2004, Illite, origins, evolution and metamorphism: Springer, New York, p.286. Moncada, D., Mutchler, S., Nieto, A., Reynolds, T. J., Rimstidt, J. D., Bodnar, R. J. Mineral textures and fluid inclusion petrography of the epithermal Ag?Au deposits at Guanajuato, Mexico: Application to exploration. Journal of Geochemical Exploration 114 (2012) 20?35. Mora, G., Pratt, P. 2001. Isotopic Evidence for cooler and drier conditions in the tropical Andes during the last glacial stage. Geology June, 2001 v. 29, no. 6, p. 519-522 Nippon Mining Co. Ltd.1967. The Report of the Prospection of the California Mine. Unpublished company report. (In: Mendoza, H.; Jaramillo, L. 1979; Mathur et al., 2002)  Norris, J.R. 2012. Evolution of Alteration and Mineralization at the Red Chris Cu-Au Porphyry Deposit East Zone, Northwestern British Columbia, Canada. A Thesis submitted in Partial Fulfillment of the Requirements for the degree of Master of Science. The Faculty of Graduate Studies. The University of Bristish Columbia, Vancouver, Canada. O?Prey, M. 2008. NI 43-101. Technical report. On the California-Vetas  Property California-Vetas Mining District Department of Santander, Colombia Approximate Geographic Coordinates  7? 19? 50?N 72? 54? 16? W. Prepared for Ventana Gold Corp. Ohmoto, H., & Lasaga, A.C. 1982. Kinetics of reactions between aqueous sulfates and sulfides in hydrothermal systems: Geochimica et Cosmochimica Acta, v. 46, p. 1727?1746. Ohmoto, H . & Rye, R. O. 1979. Isotopes of sulfur and carbon, in Barnes, H. L., ed., Geochemistry of hydrothermal ore deposits: New York, John Wiley, p. 509-567. In: Rye et al., 1992. Ohmoto, H. and Goldhaber, M. B. 1997. Sulfur and carbon isotopes. In Stam, 2006.   236  Ordo?ez, J. 2003. Petrology and geochemistry of the granitoids at the Santander Massif, Eastern Cordillera, Colombian Andes. Unpublished Master Tesis, Shimane University, Matsue (Japan), 150 pp. Ord??ez, J., and Mantilla, L. 2004. Significance of an early Cretaceous Rb-Sr age in the Pescadero Plut?n, Santander Massif. Bolet?n de Geolog?a UIS, Vol. 26 (43), pp. 115-126. P?ez, E. H., Su?rez., C. A., Villalba, R., Duarte, M. A., Rueda, S., L., Abimelec, N., Bar?n, A., Oliveros, S. E. 2007. Plan de ordenamiento y Manejo Ambiental Subcuenca R?o Surat?. Grupo Asesor de Ordenamiento Ambiental Territorial. Corporaci?n para la Defensa de la Meseta de Bucaramanga CDMB. 2007. Available on line at: http://www.cdmb.gov.co/web/files/gestion_ambiental/gestion%20del%20territorio/POMCA%20SUBCUENCA%20SURATA.pdf Paggnacco, P. F. 1962. Estudio Minerogen?tico del Fil?n Uran?fero de San Celestino (California, Santander). Geolog?a Colombiana N? 1 45- 54. 1962. Par?s, G. & Sarria, A. 1988. Proyecto Geof?sico del Nordeste Colombiano. Ingeominas. Informe interno (in?dito), 48 p. Cali. (In: Clavijo and Royero, 2002) Parra P.  A. 2007. An?lisis Estructural Detallado con fines Exploratorios en el Sector de La Bodega, Municipio de California Deartamento de Santander. Proyecto de grado modalidad pasant?a para optar al t?tulo de ge?logo. Universidad de Caldas. Facultad de Ciencias Exactas y Naturales. Programa de Geolog?a. Manizales. 2007. Pennington, W.D., 1983. The role of shallow phase changes in the subduction of oceanic crust. Science 220, 1045?1047. Peppin, Bill J. 2001. SpecWin Application Version 1.9 Pontual, S., Merry, N., and Gamson, P., 1997, Spectral interpretation field manual: Kew, Victoria 3101, Australia, Ausspec International Pty. Ltd., G-Mex, v.1, p.169. Polania, J.H., 1980. Die Uranvorkommen von California bei Bucaramanga (Kolumbien), p. 152. Stuttgart. Polania, J.H., 1983. Mineralizaciones de Uranio y otros metales en California (Santander del Sur). Geolog?a Norandina, 57e65. Polito, P., Kyser, K., Lawie, D., Cook, S., Oates, C. 2007. Application of sulphur isotopes to discriminate Cu?Zn VHMS mineralization from barren Fe sulphide mineralization in the greenschist to granulite facies Flin Flon?Snow Lake?Hargrave River region, Manitoba, Canada. Geochemistry: Exploration, Environment, Analysis, Vol. 7 2007, pp. 129?138 Pratt, W. 2009. La Mascota and La Bodega Gold Project, Santander, Colombia. Internal report prepared for: Ventana Gold Corp. Specialized Geological Mapping Ltd. August, 2009.   237  Prieto, G. A., Beroza, G. C., Barrett, S. A., L?pez, G. A., Florez, M. 2012. Earthquake nests as natural laboratories for the study of intermediate-depth earthquake mechanics. Review Article. Tectonophysics 570?571 (2012) 42?56. Raley, C. 2012. Mineralogical Characterization of Sulfide Mineralization, Alteration and Microthermometry of Related Fluid Inclusions of the La Plata Prospect, Colombia. A Thesis Submitted in Partial Fulfillment of the requirements for the degree of Bachelor of Science (Honours). The Faculty of Science (Geological Sciences). The University Of British Columbia. Richards, J.P., 1995, Alkalic-type epithermal gold deposits?a review: Mineralogical Association of Canada Short Course Series, v. 23, p. 367?400. In: Gemmel et al., 2004. Reeves, J. R. 2006. La Bodega Property California ? Vetas Mining District Santander Province, Colombia. Technical Report. Prepared for Augusta Capital Corp. and Comcorp Ventures Inc. April 10, 2006 Restrepo, J.J. and Toussaint J.F. 1988. Terranes and continental Accretion in the Colombian Andes. Episodes, 11, 189 - 193. Restrepo, J.J., Ord??ez-Carmona, O., Armstrong, R., Pimentel, M., 2011. Triassic metamorphism in the northern part of the Taham? Terrane of the central cordillera of Colombia. Journal of South American Earth Sciences, 1e11. Restrepo-Pace, P. 1995. Late Precambrian to Early Mesozoic tectonic evolution of the Colombian Andes, based on new geochronological, geochemical and isotopic data. Unpublished Ph.D Thesis, University of Arizona, 195 p. Restrepo-Pace, P; Cediel, F. 2010. Northern South America basement tectonics and implications for paleocontinental reconstructions of the Americas. Journal of South American Earth Sciences Volume 29, Issue 4, October 2010, p. 764?771 Reyes, G. y Barbosa, G. 1993. Contribuci?n al conocimiento de la geolog?a de los santanderes. Cuarto Simposio de Geolog?a Regional. Ingeominas. Gu?a de Excursiones Geol?gicas,: 56-73. Bucaramanga. (In: Royero and Clavijo, 2002) Roedder, E., 1984. Fluid Inclusions. Mineralogical Society of America, Reviews in Mineralogy, Vol. 12. 646 p. Robb, L. 2005. Introduction to Ore-Forming Processes. Blackwell Science Ltd. 373 pag. Royero, J.M., 1994. Geolog?a de la Plancha 65, Tamalameque (Departamentos del Cesar y Bol?var). Ingeominas. Memoria Explicativa., 76 p. Bucaramanga Royero, G.J.M., Clavijo, J., 2001. Mapa Geol?gico generalizado Departamento de Santander. Escala 1: 400.000. Informe Ingeominas, p. 92. Royero Guti?rrez, J.M.  Vargas Higuera, R. 1999. Geolog?a del Departamento del SANTANDER 1:300 000 (compilaci?n). INGEOMINAS. Bogot?.   238  Rye, R.O., Bethke, P.M., & Wasserman, M.D. 1992. The stable isotope geochemistry of acid-sulfate alteration: Economic Geology, v. 87, p. 225?262 Rye, R.O. 1993. The evolution of magmatic fluids in the epithermal environment: The stable isotope perspective: Economic Geology, v. 88, p. 733?753. Rye, R. O. 2005. A review of the stable-isotope geochemistry of sulfate minerals in selected igneous environments and related hydrothermal systems: Geochemistry of sulfate minerals in high and low temperature environments: Chemical Geology, v. 215, p. 5-36. Seward, T. M. 1982. The transport of gold in hydrothermal systems in Gold ?82 Rotterdam, A. A. Bolkema, p. 165-181. (In: Corbett and Leach, 1998) Sharp, Z. D., Atudorei, V., Durakiewicz, T. 2001. A rapid method for determination of hydrogen and oxygen isotope ratios from water and hydrous minerals. Chemical Geology 178 ?2001. 197?210. Shepherd, T.J., Ranbin, A.H., Alderton, D.H.M., 1985. A Practical Guide to Fluid Inclusion Studies. Blackie, Glasgow, 239 pp. Sibson, R. H. 1989. Earthquake faulting as a structural process: Journal of Structural Geology, v. 11, p1-14; In Corbett and Leach, 1998. Sibson, R. H. 1992. Earthquake fauting, induced fluid flow and fault-hosted gold mineralization. In Corbett and Leach (1998). Sillitoe, R. 1982. Setting, Characteristics, and Age of the Andean Porphyry Copper Belt in Colombia. Economic Geology. v. 77, 1982, p. 1837-1850.  Sillitoe, R. H. 1985. Ore-related breccias in volcano plutonic arcs. Economic Geology, October 1985, v. 80, p. 1467-1514,  Sillitoe, R. 1994. Erosion and collapse of volcanoes: Causes of telescoping in intrusion-centered ore deposits Geology, October, 1994, v. 22, p. 945-948  Sillitoe, R.H., and Hedenquist, J.W., 2003, Linkages between volcanotectonic settings, ore-fluid compositions, and epithermal precious metal deposits: Society of Economic Geologists Special Publication no. 10, 315-343.  Sillitoe, R. H. 2005, Supergene oxidized and enriched porphyry copper and related deposits: Economic Geology 100th Anniversary Volume, p. 723?768.  Sillitoe, R. H. 2008, Major gold deposits and belts of the North and South American Cordillera: Distribution, tectonomagmatic settings, and metallogenic considerations: Economic Geology, v. 103, p. 663-687. Sillitoe, R. H. 2010. Porphyry Copper Systems. Economic Geology , vol. 105, no. 1, pp. 3-41.   239  Simmons, S.F., White, N.C., & John, D.A. 2005. Geologic characteristics of epithermal precious and base metal deposits: Economic Geology 100th Anniversary Volume, p. 485?522.  Sim, R., Altmann, K. A. 2010. Canadian National Instrument 43-101 Technical Report for La Bodega Project California-Vetas Mining District Department of Santander, Colombia. Project Number 9163-05. Prepared for Ventana Gold Corp Prepared by Samuel Engineering, Inc.  Stam, M. 2006. Sulfur isotopes as a tracer for biogenic sulfate reduction in natural environments: A link between modern and ancient ecosystems. Utrecht University, Faculty of Geosciences.  Taboada, A., Rivera, L. A., Fuenzalida, A., Cisternas, A., Philip, H., Castro J. E. and Rivera, C. 1999. Geodynamics of the Northern Andes: Intra-continental subduction and The Bucaramanga Seismicity Nest (Colombia). Fourth ISAG, Goettingen (Germany), pp. 719-723.  Taboada A., Rivera, L. A., Fuenzalida, A., Cisternas, A., Philip, H., Bijwaard, H., Olaya, J. and Rivera, C. 2000. Geodynamics of the Northern Andes: Subductions and Intracontinental Deformation (Colombia). Tectonics, 19: 787-813.  Tschanz, C.et al., 1969. Geology of the Sierra Nevada de Santa Marta area Colombia. Ingeominas. Informe 1829. Preliminary report, 288 p. Bogot?. (In: Royero and Clavijo, 2002)  Tschanz, C., et al. 1974. Geologic evolution of the Sierra Nevada de Santa Marta, North Eastern Colombia. Bulletin Geological Society of America, (85) : 273-284. Colorado. (In: Royero and Clavijo, 2002)  Taylor, H.P. 1979. Oxygen and hydrogen isotope relationships in hydrothermal mineral deposits, in Barnes, H.L. ed., Geochemistry of hydrothermal ore deposits, 2nd ed.: New York, John Wiley, p. 236?277.  Toussaint, J. 1993. Evoluci?n Geol?gica de Colombia: Pre Cambriano ? Paleozoico. Universidad Nacional de Colombia. Facultad de Minas. Medell?n.  Toussaint J.F. 1995. Evolucion Geologica de Colombia. Medellin, Colombia, Tomo 1, 1 - 229 and Tomo 2,1 - 94.  Urue?a, S.C.L., Zuluaga, C.A., 2011. Petrograf?a del Gneis de Bucaramanga en cercan?as a Cepit?, Berl?n y Vetas e Santander. Geolog?a Colombiana 36 (1), 37e55.  Uvarova, Y. A., Kurtis Kyser, T., Soxolova, E., Kazansky, V, I., Lobanov, K. V. 2011. Significance of stable-isotope variations in crustal rocks from the Kola   240  Superdeep Borehole and their surface analogues. Precambrian Research 189 (2011) 104? 113.  van der Hilst, R., Mann, P., 1994. Tectonic implications of tomographic images of subducted lithosphere beneath northwestern South America. Geology 22, 451?454  Vargas, C. A., Mann, P. 2013. Tearing and Breaking Off of Subducted Slabs as the Result of Collision of the Panama Arc-Indenter with Northwestern South America. Bulletin of the Seismological Society of America, Vol. 103, No. 3, pp. 2025?2046, June 2013.  Ventana Gold Corp. 2010. LB214 Brief Report. Internal Report.  Ward, E.D., Goldsmith, R., Cruz, B., Jaramillo, C., Restrepo, H. 1973. Geolog?a de los Cuadr?ngulos H-12, Bucaramanga y H-13 Pamplona. Departamento de Santander. U. S. Geological Survey e Ingeominas. Boletin Geol?gico de Ingeominas 21 (1?3), 1?132.  Wilkinson, J. J. 2001. Fluid inclusions in hydrothermal ore deposits. Lithos 55 2001. 229?272.  White, N.C., Hedenquist, J.W. (1995). Epithermal gold deposits: Styles, characteristics and exploration: Society of Economic Geologists Newsletter 23, p. 1?13.  Wolff Carre?o, E., Pinz?n Angel, J. M., Contreras Moreno, R., Bernardy, C. 2005. Geological setting of the mercury vapor contamination in the gold-silver district of Vetas-California (Santander-Colombia). Episodes, Vol. 28, no. 4. 252-256.  Zarifi, Z., Havskov, J., Hanyga, A., 2007. An insight into the Bucaramanga nest. Tectonophysics 443, 93?105.   241  Appendix A1. Drill Hole Locations.  Collar locations of sampled and logged drill holes for this project are shown in geographic coordinates  as shown on maps within the document. UTM coordinates (Colombia National Grids) referenced to Bogot? Observatory. Coordinates were provided by AUX Colombia Ltd.   242  HOLE ID ZONE UTM (BOGOTA - OBSEVATORY) GEOGRAPHIC (BOGOTA - OBSERVATORY) Length [m] Azimuth [?] DIP [?] LOGGED SAMPLED LOCATION_X LOCATION_Y LOCATION_Z Longitud (W) [?] Latitud (N) [?] Elevation [m.a.s.l.] LB001 LA BODEGA 1130417.21 1308273.03 2918.21 -72.899753 7.38507 2918.21 290 195 -55 NO 1 SAMPLE LB013 LA BODEGA 1130385.35 1308243.67 2882.97 -72.900042 7.384805 2882.97 320 180 -55 Yes YES LB022 LA BODEGA 1130369.04 1308353.78 2847.18 -72.900187 7.385801 2847.18 308.5 180 -55 Yes YES LB037 LA BODEGA 1130373.64 1308302.7 2875.17 -72.900147 7.385339 2875.17 310.15 180 -55 Yes YES LB072 LA BODEGA 1130243.19 1308144.23 2738.66 -72.901332 7.383909 2738.66 172 155 -50 Yes 1 SAMPLE LB112 LA MASCOTA 1129352.11 1307820.48 2833.94 -72.909409 7.381004 2833.94 398.5 180 -75 Yes YES LB114 LA MASCOTA 1129351.94 1307820.64 2833.93 -72.90941 7.381005 2833.93 566.2 170 -85 Yes YES LB159 LA MASCOTA 1129252.1 1307841.16 2838.72 -72.910314 7.381193 2838.72 381 180 -63 NO 1 SAMPLE LB202 LA MASCOTA 1129353.98 1307822.39 2834.59 -72.909392 7.381021 2834.59 364.23 180 -58 Yes YES LB205 LA MASCOTA 1129353.96 1307822.69 2834.58 -72.909392 7.381024 2834.58 481.58 180 -68 YES YES LB221 LA MASCOTA 1129351.33 1307945.27 2899.07 -72.909413 7.382132 2899.07 537.36 180 -74 Yes YES LB251 LA BODEGA 1130369.11 1308351.25 2847.11 -72.900186 7.385778 2847.11 370.33 180 -75 Yes YES LB258 LA BODEGA 1130369.16 1308351.41 2847.13 -72.900186 7.385779 2847.13 375.2 180 -82 Yes YES LB267 EL CUATRO 1128706.45 1307234.31 2706.31 -72.915269 7.37572 2706.31 367.89 180 -75 NO 1 SAMPLE LB282 EL CUATRO 1128399.62 1307182.56 2678.14 -72.918049 7.37526 2678.14 326.74 180 -67 NO YES LB327 LA BODEGA 1130362.51 1308128.96 2823.81 -72.900252 7.383769 2823.81 370.63 180 -57 Yes YES      243  Appendix A2. Sample Location within Drill Holes, Brief Descriptions, Notes and Analysis Carried out  Sample photograph Zone HOLE ID Depth [m] Sample Code Company Sample ID Rock Type Code Brief Description and Notes Analysis   La Mascota LB112 295.6 ALR001 73258 BG Gneiss. Feldspar quartz ?) Granoblastic texture. Leucograniteensesely altered to Alunite>quartz. Silica+pyrite veinlets cutting alunitizied gneiss. Py speckss in gneiss. SWIR Petrography Ar/Ar geochronology  Stable Isotopy   La Mascota LB112 49.3 ALR002 73002 THBX Tectonic hydrothermal breccia in contact with gneiss with illite alteration. Alunite and quartz in breccia with cataclastic texture. SWIR Petrography   La Mascota LB112 60.5 ALR003 73013 BG Gneiss crosscut by  2 cm chlorite vein/chlorite cemented breccia with gneiss angular clasts (~1 cm each). Tectonic foliation at vein walls. SWIR   La Mascota LB112 136.8 ALR004 73090 BG Gneiss . Banded gneiss. Quartz feldspar (leucosomes), Amphibolite-biotite (mesosomes). Chlorite alteration. ttn, Epidote, Magnetite occurrence. SWIR   La Mascota LB112 214.9 ALR005 73173 BG Gneiss. Sericite-illite alteration. Cross cut by qz+ crs py vein also cut by ("difuse silica") light gray dull quartz+fine py + Au + sph and cpy vein. SWIR Petrography    SEM   La Mascota LB112 223.65 ALR006 73783 THBX Tectonic hydrothermal breccia. Tectonic foliation. Alunite and quartz bands parallel to tectonic foliation. Pyrite crustals and clasts in cement Two pieces.  SWIR   La Mascota LB278 238-238.85 ALR007 I575747 INT Leucogranite. Mostly equigranular texture with few Qz and Fd. Phenocrysts. Few Illite veinlets. Weakly silicified veins. Pyrite scatered in weakly silicified veins. SWIR   La Mascota LB112 238.4 ALR008 73195 BG Gneiss. Banded, granolepidoblastic texture. Alunitizied Leucograniteermediate gneiss. Pyrite-silica veinlets. SWIR   La Mascota LB112 249.25 ALR009 73206 BG-THBX Gneiss. Phyllic alteration with superimposed silicification.  Contact to THBX. Crosscutting veins. Qz+w+py+-cpy?cc vein cutting Sil(bx text)+cc+cpy+py vein cutting py+quartz vein. SWIR   La Mascota LB112 251.65 ALR010 73209 HYBX Hydrothermal breccia (~15 cm). Drusy quartz vein with clasts replaced by quartz and in breccia and breccia walls. Py within replacement texture. Black-gray sulphide. Very bright (possibly enargite)(gives dirty fingers) Kaolinite-Alunite in Drusy Qz Cavity. Illitizied and Silicified SWIR Petrography    SEM   244  Sample photograph Zone HOLE ID Depth [m] Sample Code Company Sample ID Rock Type Code Brief Description and Notes Analysis clasts. Clasts: 50%; Cement: 30% Qz-Silica; Matrix: 20% (finer grained clasts). Clasts Supported breccia.    La Mascota LB112 243.3 ALR011 73200 BG Gneiss. Quartz feldspar gneiss with minor micas. Granoblastic to granolepidoblasitic textures. Muscovite/illite alteration. Pyrite scattered. SWIR   La Mascota LB112 253.1 ALR012 73211 BG / HYBX Gneiss, Leucograniteensely altered. Alunite>quartz replacement.  Vein cutting alunitizied gneiss. qz+Alu(?)+Py+cv+bn+cc vein with possibly clasts of gneiss. Drussy Qz cavities. SWIR Petrography Ar/Ar geochronology  Stable Isotopy SEM   La Mascota LB112 256.5 ALR013 73214 THBX Tectonic hydrothermal breccia. Multiple phases of brecciation. Clasts with tectonic foliation. Three recognized breccias. BX1: Tectonic hydrothermal breccia. Tectonic foliation (@<20?) Jigsaw breccia texture. tectonic breccia clasts (cataclastite or milonite?).  BX2: (@<20?).  BX3: Clasts supported: clasts of breccia and cataclastite. Veins cutting breccias: DrusyQz+Py+W+cv(?) vein(<35? 3mm). Drusy Qz+Alunite (?)+Py vein (<40? 18mm) SWIR Petrography    SEM   La Mascota LB112 259.2 ALR014A 73218 THBX Tectonic hydrothermal breccia. Multiple phases breccia. Silicified. Py in Bx as clasts in silica. Gneiss clasts with Illite alt (?). Clasts of breccia (3.2) and milonite or cataclastite. Silica+alunite+CuS (cc, cv mainly), Py vein; Drusy qz with cc, cv, alu and w  blades (~1 mm) (vein @ 50?). 6. Irregular chalcedonic qz+alunite vein with drusy quartz cavities andcc-cv. . Possible Alu+qz+py clast (?)  SWIR Petrography    SEM   La Mascota LB112 264.15 ALR014B 73223 THBX Multiple phases breccia. BX. 1. TBX tectonic breccia (milonite?) (cataclastite?). Matrix supported.  Matrix: Fine Grained 70%. Clasts (rounded): 20%. Cement (silica): 10%. 2. Drusy Qz vein. Bladed texture. Py rimming "blades" (vein @<50?) 20mm. 3. Drusy Qz+W+En+dg (?) (in drusy qz cavities) vein (@<65?), 35 mm, cuts 2. 4. Drusy Qz+en (high content)+py+w vein (@<40?) (3 mm). En is possibly Luzonite. 5. Coloidal banded silica with Py-en (?) 6. Coloidal sil.  SWIR Petrography    SEM   La Mascota LB112 265.2 ALR015 73225 HYBX Multiple phase BX. 1. Clasts of milonite or tectonic breccia. 2. Multiple phases breccia. Clasts:60%, subangular to rounded, polimictic, py with clasts; Matrix: 20%. Fine grained clasts; Cement: 20% silica, coloidal silica(?).3. Tn-th cut by en veinlet (?).  Py+qz+minor cc+cv vein @<25? 11mm. Drusy qz silica irregular vein or cement; Tn-th in drusy qz cavity. W within drusy Qz. Fine grained py+en vein SWIR Petrography   245  Sample photograph Zone HOLE ID Depth [m] Sample Code Company Sample ID Rock Type Code Brief Description and Notes Analysis   La Bodega LB072 100 ALR016A 805576 BG Gneiss. Feldspar-quartz-biotite gneiss, granolepidoblastic texture (?). Leucograniteense alteration. Alunite-quartz alteration adjacent to finepyrite+quartz vein. Possible Illite-Sericite alteration adjacent to alunite alteration.. SWIR   La Bodega LB072 118.2 ALR016B 805596 BG Gneiss. Feldspar-quartz-biotite gneiss, granolepidoblastic texture (?).Possible Illite-Ser alt. Crosscut by pyrite-enargite(?) veinlets. SWIR   La Bodega LB072 128.4 ALR017 805607 BG Gneiss. Banded. Sericite. Possible Smectite alt. SWIR   La Mascota LB112 281.55 ALR018 73241 HYBX Hydrothermal breccia. Banded, mainly Silica supported. Gneiss silicified clasts. Clasts: 20%; Matrix: 10%; Cement: 70%, 1. Silica-banded colidal silica (chalcedonic qz?) with py (coloform texture). 2. Drusy Qz cc+cv+bn+cpy veinlet. 3. Py coloform text. 4. W-DrusyQz vein; 5. Gneiss clasts. 6. Py CuS (cc, bn) veinlet cutting coloidal banded silica (1). SWIR Petrography    SEM   La Mascota LB112 294.45 ALR019 73257 BG / HYBX Hydrothermal breccia (Narrow, 4 cm). Silica+en+cc+-w vein with Visible gold.  (vein @<60?-58mm) cutting drusy qz+py+cc+cv veinlet@<40?. SWIR Petrography    SEM   La Mascota LB112 294.8 ALR020 73257 BG / HYBX Contact gneiss to hydrothermal breccia. Hydrothermal breccia: Polimictic, multiple phases. Angular clasts. Silicified (silica cement). Finer grained and clastic matrix with Py. Py also in cement. Cavities in cement. Clasts: 30%. Cement: 40%. Matrix: 25%. Cavities: (5%) SWIR   La Mascota LB112 296.7 ALR021 73259 HYBX Hydrothermal breccia. Polimictic silicified, multiple phases. 1. Gneiss clasts, illite/sericite alt. Py veinlets. 2. Polimictic BX. White, gray and coloidal silica cement. Qz+py+alunite(?) band adjacent to drusy qz cavity (@<55?)1 cm. 3. Polimictic clasts supported breccia silica-W cement rimming clasts. En speckss. Qz+-w+py veins. SWIR Petrography  La Mascota LB112 296.9 ALR022 73259 HYBX Jigsaw breccia (?). Polimictic. Clasts rimmed by silica+W+Py. Clasts of silica rimmed by silica+W-Py. Drusy Qz coloid sil cement. Drusy Qz cavities. Clasts: 40%-50%. Cement: 35-45%. Matrix: 5-10%. Cavities 5-10%. Possible en occ. SWIR Petrography   La Mascota LB112 312.5 ALR023 73275 BG / HYBX Contact Gneiss/ BX (@<45?). Alunite altered gneiss cut by crackled breccia, gneiss clasts in silica cement. Clasts: 55%, Cement:40%, Cavities: 5%. 3. Clasts supported breccia, polimictic (gneiss and breccia clasts) SWIR Petrography   246  Sample photograph Zone HOLE ID Depth [m] Sample Code Company Sample ID Rock Type Code Brief Description and Notes Analysis   La Mascota LB112 312.6 ALR024 737275 HYBX Hydrothermal breccia. Alunite rich+ quartz cement/matrix supported breccia (fine grained matrix) 80%. Alunitizied clasts (10%). Cement (silica) (10%). Limited by py veins.; contact to Clasts supported alunitizied BX. Alunitizied clasts gneiss clasts (40%). Matrix: 30%. Cement: 30%. SWIR Petrography Ar/Ar geochronology  Stable Isotopy   La Mascota LB112 312.9 ALR025 737275 HYBX Mainly clasts supported multiple phases hydrothermal breccia. Alunitizied gneiss clasts (titanite in clasts). 2. Py veinlet in clast. Drussy qz cement with cavities; crackled monomictic (?) (gneiss clasts) breccia. Tabular black w crystals in quartz. Kaolinite filling drusy quartz cavities. SWIR Petrography   La Mascota LB159 337.7 ALR026 992356 HYBX Hydrothermal breccia. Clasts supported. Gneiss clasts. Quartz cement with coloform textures, minor wolframite. Fine grained coloform pyrite rimming quartz. Drusy quartz cavity filled with tabular (flake-like, platty) alunte. SWIR  Ar/Ar geochronology  Stable Isotopy   La Mascota LB112 328.8 ALR027 73292 BG Gneiss. Alunite-quartz alteration superimposed to muscovite alteration (?). Micas are altertred to titanite (?)Veins: 1. Qz+py veinlet cut by 2. Qz+fine py vein (drusy qz). likely cut by 3. alunite+-py (cubic) vein. SWIR Petrography Ar/Ar geochronology  Stable Isotopy   La Mascota LB112 326.3 ALR028 73289 BG Gneiss. Feldspar-quartz (?). Granoblastic texture. Alunite-quartz alteration (Leucograniteense). Porous quartz with pores filled by alunite. SWIR   La Mascota LB112 329.55 ALR029 73293 BG Gneiss. Alunitizied gneiss, cut by stockwork-like veins. 2. Silica+py veinlet (@<65? 3mm), cut by 4. 3. Silica supported breccia with py and sphalerite within cement. 4. Drusy Qz+Py+W vein(@<25? 3 mm). 5. Drusy qz+py+w+en vein (@<35? 3 mm). Sphalerite bearing breccia. SWIR Petrography   La Mascota LB112 329.7 ALR030 73293 HYBX SWK. 1. Silica supported breccia. Py silica cc cement. 2. Drusy Qz-Py-Sph-cc cutting 1 (@<50? 5cm). Possibly alunite-Py adjacent to Qzvein SWIR Petrography   La Mascota LB112 332.9 ALR031 73297 HYBX Hydrothermal breccia. Clasts to cement supported breccia. Black-dark gray silica cement with clasts (gneiss?). Cut by hematite veinlet @<90? 2 mm. Tectonic foliation @<70? 4. Alunite SWK@<30? 2mm. SWIR   La Mascota LB112 334.3 ALR032 73298 THBX Tectonic to tectonic hydrothermal breccia. Tectonic foliation, silica+py, silica (reddish with hyp hem?, titanite?) veinlets@<40?. Subparallel silica-Al-Py sphalerite vein @<50? aprox 1cm. ttn and Py specksks in halos. SWIR Petrography   La Mascota LB112 336.7 ALR033 73300 BG Gneiss, illite ttn alt. Alunite veinlets cutting illite/sericite and ttn alt.. Silica-specks vein @<20? 2mm cutting gneiss. SWIR Petrography   247  Sample photograph Zone HOLE ID Depth [m] Sample Code Company Sample ID Rock Type Code Brief Description and Notes Analysis   La Mascota LB112 347.7 ALR034 73312 INT Leucogranite. Sericite-Illite alt. Alunite+ coarse py vein with alunite halo.  SWIR Petrography Ar/Ar geochronology  Stable Isotopy   La Mascota LB112 347.40 & 347.80-348.40 ALR035 73312-73313 INT Same as ALR034. Leucogranite. Mainly sericite-Illite alteration. For U/Pb geochronology and total rock geochemistry. SWIR  U/Pb geochronology   La Mascota LB112 348.5 ALR036 73313 INT Broken contact Leucogranite/Gneiss. Py+Silica+Sphalerite. Alunite filling at contact @<25?(?). SWIR   La Mascota LB112 358.7 ALR037 73324 BG Silica W veinlets. 1. Illite Altered gneiss. 2. Py veinlets subparallel. To foliation cut by 3 (?). 3. Silica+-Py+W vein (difuse silica)@<20? 8 mm. Alunite (dickite (?) veinlet cutting 3. SWIR   La Mascota LB112 357.8 ALR038 73323 HYBX Multiple phase hydrothermal breccia. Partially brecciated gneiss with ill/ser alt. Sil-Illite alt minorpy. Tectonic foliation. 3. Drusy qz+py vein (@<50?) 3cm. 4. Py vein <30-5? deflection 6 mm. 5. Alunite infilling with possible clasts of py, sphalerite. Fine grained py and mrc? SWIR Petrography Ar/Ar geochronology  Stable Isotopy   El Cuatro LB267 280.9 ALR039 I573234 INT Leucogranite. Illite/ser alt.. Illite alt plg phenocrysts. Qz+mo veins? SWIR   El Cuatro LB282 131.3 ALR040 I565248 POR Porphyry (dacitic?) Fine grained gorund mass illite-alunite altered feldspars. Plg (?) phenocrysts altered to alunite, minor pyrite. Cross cut cc (?) vein. SWIR Petrography Ar/Ar geochronology  Stable Isotopy   La Bodega LB001 94.8 ALR041A 467101 INT Leucogranite. Fine grained equigranular. Sericite alt SWIR   La Bodega LB327 34.6 ALR041B J633646 BG Gneiss. Qz+py veinlets. Alunite-quartz alteration superimposed to illite/sericite, minor lcx (?) SWIR   La Bodega LB327 39.75 ALR042 J633651 A Amphibolite (?). Tectonic foliation (?). Greenish micas. Kao filling microveins SWIR   La Bodega LB327 41 ALR043 J633652 A Amphibolite. Cc vnlets & cc coating Py. Weak sil-alunite alt superimposing to ill-ser alt SWIR Petrography   La Bodega LB327 41.6 ALR044 J633652 A Amphibolite. Cc vnlets & cc coating Py. Weak sil-alunite alt superimposing to ill-ser alt SWIR   La Bodega LB327 42.3 ALR045 J633653 A Amphibolite. Cc vnlets & cc coating Py. Weak sil-alunite alt superimposing to ill-ser alt SWIR   248  Sample photograph Zone HOLE ID Depth [m] Sample Code Company Sample ID Rock Type Code Brief Description and Notes Analysis   La Bodega LB327 52.4 ALR046 J633662 A Amphibolite?. Ill-ser alt, weak sil. cc-py vnlts. lcx truc at veins SWIR   La Bodega LB327 58.2 ALR047 J633669 A  Amphibolite. Musc/Illite superimposed to chl alt?. Cc+py vnlet SWIR   La Bodega LB327 67.4 ALR048 J633678 A Amphibolite. Illite-chl alt. Lcx as vnlets halos. Py vnlets SWIR   La Bodega LB327 108.6 ALR049 J633720 QVN Hydrothermal qz vein (Gray qz), white and gray silica. Py (cubic) and cc. green CuO SWIR   La Bodega LB327 115.6 ALR050 J633727 INT Leucogranite. Ser alt. qz-py vein. SWIR Petrography   La Bodega LB327 117.15 ALR051 J633729 INT Leucogranite. Sericite alteration. Qz-Py vein (D veins). Porphyry style mineralization.  SWIR   La Bodega LB327 120-121 ALR052 J633732 INT Leucogranite. Ill ser alt. For U/Pb geochronology and Total rock geochemistry. SWIR   La Bodega LB327 131.15 ALR053 J633743 BG Gneiss. Contact to pegmatite. Chl/illite alt (?). Lcx after bt  SWIR   La Bodega LB327 139.8 ALR054 J633751 INT Leucogranite. Equigranular texture. Qz-py-green CuO veins SWIR   La Bodega LB327 149.7 ALR055 J633762 INT Leucogranite. Equigranular texture. Qz+py veins SWIR   La Bodega LB327 198.4 ALR056 J633810 A