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Magmatic evolution and genesis of the giant Reko Diq H14-H15 porphyry copper-gold deposit, District Chagai,… Razique, Abdul 2013

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MAGMATIC EVOLUTION AND GENESIS OF THE GIANT REKO DIQ H14-H15 PORPHYRY COPPER-GOLD DEPOSIT, DISTRICT CHAGAI, BALOCHISTAN-PAKISTAN  by  ABDUL RAZIQUE  M.Sc. The University of Balochistan, 1995 M.Phil. Centre of Excellence in Mineralogy, 2004  A DISSERTATION SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF  DOCTOR OF PHILOSOPHY  in  THE FACULTY OF GRADUATE STUDIES (Geological Sciences)  THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver) June, 2013  © Abdul Razique, 2013  Abstract Reko Diq porphyry Cu-Au-Mo deposit in the western Chagai belt, Pakistan, is one of the world’s largest porphyry ore deposits, containing a global resource of 5,900 million metric tons @ 0.41 % Cu and 0.22 g/t Au. The Reko Diq volcanic complex hosts a cluster of eighteen porphyry centers within a NW trending, ~10-long mineralized corridor bounded by the Drana Koh fault system to the north and Tuzgi fault to the south. The western porphyry complex at Reko Diq is linked to a distinct tectono-magmatic event of middle-late Miocene (12.9-11.9 Ma) age, which formed four economic porphyry Cu deposits and remains the focus of this study. The Reko Diq western porphyry deposits are spatially and temporally associated with a series of medium-K calc-alkaline granodiorite and quartz-diorite intrusions forming H79, H15, H14 and H13 deposits, which are spatially distributed from north to south. High Sr/Y and low Y adakitic signature and petrochemical variations in the intrusive rocks suggest normal basalt-andesite-dacite-rhyolite magmas derived from a tholeiitic to calcalkaline suite arc magma with significant upper crustal interaction. Combination of U-Pbzircon and Re-Os-molybdenite geochronology and zircon mineral chemistry suggests that a short lived (~1 Ma) fractionated magmatic-hydrothermal system with sustained mafic recharge and efficient hydrothermal fluid flow was involved in the formation of the giant H15 and H14 porphyry deposits. Much of the high-grade (up to 2.0 % Cu and 1.5 g/t Au) Cu-Au mineralization is associated with intense hydrothermal potassic alteration and early quartz “A-type” veins in the early-mineral granodiorite and intra-mineral quartz-diorite intrusions and adjacent host rocks. The main ore-stage potassic alteration is typically associated with high temperature, hypersaline magmatic-hydrothermal fluids. Fluid inclusions with co-existing vapor and brine suggest a boiling phase of two immiscible fluids responsible for the copper ore precipitation. The intensity of potassic alteration and Cu-Fe-sulfide mineralization decreases with the emplacement of late-mineral and latebarren stage quartz-diorite intrusions forming a low grade core in H15 and H14 porphyry deposits. The decline in Cu-Au grades with time is interpreted as a manifestation of the underlying magma chamber depleted in metals and volatiles.  ii  Preface The four chapters in this dissertation represent four manuscripts to be submitted for publication in refereed journals. Each chapter represent primarily my own work, except where highlighted below. My supervisor Richard Tosdal is a co-author in all manuscripts. He was involved in all stages of this research study including development of the project, field investigations and oversight on laboratory protocols and editing of the manuscripts. Chapter 3 constitutes the 1st manuscript on the geological framework, petrology and petrochemistry of Reko Diq H14 and H15 porphyry centers. As first author, I prepared geological maps and cross sections, logged over 10,000 meters of diamond drill core and RC (reverse circulation) rock-chips, collected ~180 representative drill core samples and studied 145 petrographic thin sections prepared at Vancouver Petrographics. A total of 63 drill core samples were analyzed for whole-rock geochemistry at ALS Minerals in North Vancouver. Of these 63 samples, 8 least altered samples were analyzed for radiogenic isotopes at PCIGR laboratories, University of British Columbia (UBC). I evaluated all the analytical results and generated figures, tables and text in the manuscript. The co-authors Abdul Bashir, Giuseppe Lo Grasso, Richard Tosdal and Jose Perelló provided technical advise in the field and will review the manuscript before publication. Mati Raudsepp supported petrographic analysis. Thomas Bissig and Dominique Weis provided technical insight on evaluation of the data. Reference to this article will be as follows. Razique, A., Bashir, A., Lo Grasso, G., Tosdal, R.M., and Perelló, J., Petrology and Petrochemical Evolution of the Giant Reko Diq H14-H15 porphyry Cu-Au Deposit, District Chagai, Balochistan-Pakistan. Chapter 4 represents the 2nd manuscript on the geochronology of Reko Diq western porphyry deposits. I am the lead author and Richard Tosdal and Robert Creaser are the coauthors of this manuscript. I conducted three fieldwork seasons on the geological logging of >10,000m diamond drill core and RC percussion rock-chips and systematic sampling for laboratory analysis. Out of 180 drill core samples, 145 petrographic thin sections were studied to select 10 most representative and least altered samples for zircon U-Pb and two samples for molybdenite Re-Os geochronology. James Mortensen, Hai Lin and myself prepared the zircon grains separates at PCIGR laboratory in the University of British iii  Columbia. Richard Tosdal conducted zircon-U-Pb SHRIMP-RG analysis at StanfordUSGS laboratories in California USA, whereas Robert Creaser performed molybdenite Re/Os chronometry at the University of Alberta Canada. Richard Tosdal and I evaluated all the analytical results leading to the design of figures, tables and text in the manuscript. The manuscript has been submitted for publication. Razique, A., Tosdal, R.M., and Creaser, R., Rapid Formation of the Reko Diq Western Porphyry Systems, District Chagai, Balochistan-Pakistan. Chapter 5 represents the 3rd manuscript on the cooling and fractionation history and petrogenetic evolution of Reko Diq western porphyry deposits. I am the first author and Richard Tosdal is the co-author of this manuscript. I have conducted 3 stints of fieldwork, logged over 10,000m of diamond drill core and RC percussion rock-chips and collected ~180 samples for laboratory analysis. Petrographic determination of 145 thin sections led to select 10 most representative and least altered samples for zircon trace element geochemistry. James Mortensen, Hai Lin and myself prepared the zircon separates at PCIGR laboratory (UBC). Richard Tosdal performed the U-Pb-zircon SHRIMP-RG geochemical analysis at Stanford-USGS laboratories in California USA. I evaluated the analytical database and generated all figures, tables and text in the manuscript edited by Richard Tosdal. Reference to this manuscript is as follows. Razique, A., and Tosdal, R.M., U-Pb (zircons) Geochemical Constraints on the Genesis and Evolution of the Giant Reko Diq H14-H15 Porphyry Cu-Au Deposit, District Chagai, Balochistan-Pakistan. Chapter 6 constitutes the 4th manuscript on the hydrothermal alteration and evolution of Reko Diq H15 and H14 porphyry deposits. I am the lead author of this manuscript along with Richard Tosdal and Farhad Bouzari as co-authors. As a first author, I conducted three sessions of fieldwork on detail surface mapping and geological logging of diamond drill core and RC percussion rock-chips, leading to prepare geological maps and cross sections and collection of ~180 samples from a wide range of lithology, alteration, veins and sulfides for laboratory analysis. Field mapping and petrography of 145 thin sections led to establish the lithologic and hydrothermal facies architecture, and allowed me to select 6 most representative samples for fluid inclusion analysis. I conducted a base line study of  iv  fluid inclusions petrography and microthermometry at the Mineral Deposit Research Unit (MDRU) University of British Columbia. This study was supported by Farhad Bouzari, Melissa Gregory and Murray Allan. Additionally, I have designed all figures, tables and text in the manuscript edited by Richard Tosdal and Farhad Bouzari. All co-authors advised on the technical aspects of hydrothermal alteration and will provide revisions in the manuscript before publication. This article will be referenced as follows. Razique, A., Tosdal, R.M., and Bouzari, F., Hydrothermal Alteration and Evolution of the Giant Reko Diq H14-H15 Porphyry Cu-Au Deposit: District Chagai Balochistan -Pakistan.  v  Table of Contents Abstract ................................................................................................................................ ii Preface ................................................................................................................................. iii Table of Contents................................................................................................................ vi List of Tables ...................................................................................................................... xii List of Figures ................................................................................................................... xiv Acknowledgements ....................................................................................................... xxviii Dedication ........................................................................................................................ xxix Chapter 1 - Introduction ..................................................................................................... 1 1.1 Preamble ................................................................................................................... 1 1.2 Location, access and physiography .......................................................................... 2 1.3 History of exploration and mining ........................................................................... 5 1.4 Porphyry copper deposits ......................................................................................... 7 1.5 Overview of the Reko Diq porphyry complex ....................................................... 12 1.6 Objectives of this study .......................................................................................... 14 1.7 Research approach and methodology ..................................................................... 14 1.8 Overview of the dissertation................................................................................... 15 Chapter 2 - Geological framework of Reko Diq porphyry complex............................. 19 2.1 Introduction ............................................................................................................ 19 2.2 Tectonic framework ............................................................................................... 20 2.3 Geologic framework ............................................................................................... 22 2.4 Metallogenic framework ........................................................................................ 23 2.5 Stratigraphy ............................................................................................................ 27 2.5.1 Sinjrani volcanic group ................................................................................ 27 2.5.2 Humai formation .......................................................................................... 27 vi  2.5.3 Juzzak formation .......................................................................................... 28 2.5.4 Saindak formation ........................................................................................ 28 2.5.5 Dalbandin formation .................................................................................... 31 2.5.6 Reko Diq formation ...................................................................................... 31 2.6 Miocene porphyry intrusions.................................................................................. 33 2.6.1 Diorite to quartz-diorite phase...................................................................... 34 2.6.2 Hornblende-diorite phase ............................................................................. 34 2.6.3 Granodiorite to quartz-diorite (Biotite phase) .............................................. 35 2.6.4 Diorite to microdiorite phase........................................................................ 35 2.7 Porphyry centers in the Reko Diq complex............................................................ 37 2.7.1 Tanjeel porphyry Cu deposit ........................................................................ 37 2.7.2 Northern porphyry Cu-Au centers................................................................ 39 2.7.3 Southern porphyry Cu-Au centers................................................................ 39 2.7.4 Western porphyry complex .......................................................................... 40 2.7.5 H14-H15 porphyry deposit........................................................................... 40 2.8 Discussion and conclusions .................................................................................... 43 Chapter 3 - Petrology and petrochemical evolution of Reko Diq H14-H15 ................. 45 3.1 Introduction ............................................................................................................ 45 3.2 Sequence and geometry of intrusive rocks ............................................................. 47 3.2.1 H79 porphyry complex................................................................................. 49 3.2.2 H15 porphyry complex................................................................................. 49 3.2.3 H14 porphyry complex................................................................................. 49 3.2.4 H13 porphyry complex................................................................................. 54 3.3 Petrology of intrusive rocks ................................................................................... 54 3.3.1 Granodiorite porphyry (PFB1) ..................................................................... 56  vii  3.3.2 Quartz-diorite porphyry (PFB2) ................................................................... 56 3.3.3 Quartz-diorite porphyry (PFB3) ................................................................... 57 3.3.4 Quartz-diorite porphyry (PFB4) ................................................................... 57 3.4 Geochemistry of porphyry intrusions ..................................................................... 60 3.4.1 Major elements ............................................................................................. 63 3.4.2 Alkalinity...................................................................................................... 64 3.4.3 Trace element and REE ................................................................................ 67 3.5 Pb isotope geochemistry......................................................................................... 72 3.6 Sr and Nd isotope geochemistry............................................................................. 72 3.7 Discussion .............................................................................................................. 76 3.7.1 Petrologic and petrochemical evolution ....................................................... 76 3.7.2 Isotopic compositions and petrogenetic evolution ....................................... 77 3.8 Conclusions ............................................................................................................ 78 Chapter 4 - Magmatic and hydrothermal chronology of Reko Diq H14-H15 ............. 80 4.1 Introduction ............................................................................................................ 80 4.2 Metallogenic framework ........................................................................................ 81 4.3 Overview of the western porphyry prospects ......................................................... 84 4.3.1 H79 porphyry complex................................................................................. 87 4.3.2 H15 porphyry complex................................................................................. 87 4.3.3 H14 porphyry complex................................................................................. 88 4.3.4 H13 porphyry complex................................................................................. 88 4.4 Published geochronologic data for the western porphyry cluster .......................... 93 4.5 Geochronologic data............................................................................................... 93 4.5.1 SHRIMP-RG U-Pb geochronology.............................................................. 96 4.5.1.1 H79 Complex ..................................................................................... 98  viii  4.5.1.2 H15 Complex ..................................................................................... 98 4.5.1.3 H14 Complex ................................................................................... 101 4.5.1.4 H13 Complex ................................................................................... 104 4.5.2 Molybdenite Re-Os chronology ................................................................. 107 4.6 Discussion ............................................................................................................ 108 4.6.1 Duration of magmatic and hydrothermal events ........................................ 108 4.6.2 Longevity of individual western porphyry systems ................................... 110 4.6.3 Re-Os ages versus U-Pb ............................................................................. 111 4.7 Conclusion ............................................................................................................ 112 Chapter 5 - Cooling and fractionation of Reko Diq H14-H15 .................................... 113 5.1 Introduction .......................................................................................................... 113 5.2 Reko Diq western porphyry centers ..................................................................... 115 5.3 Zircon geochemistry ............................................................................................. 119 5.3.1 Morphology of zircon grains ...................................................................... 119 5.3.2 REE patterns ............................................................................................... 122 5.3.3 Hf versus TiO2-in-zircon thermometer ...................................................... 124 5.3.4 Trace element variations ............................................................................ 130 5.3.5 Multi-valent elements ................................................................................. 132 5.4 Discussion ............................................................................................................ 135 5.4.1 Contamination and mixing of magma ........................................................ 135 5.4.2 Oxidized porphyry magmas ....................................................................... 136 5.4.3 Spatial-temporal relationships .................................................................... 137 5.5 Conclusions .......................................................................................................... 139  ix  Chapter 6 - Hydrothermal alteration and evolution of Reko Diq H14-H15 .............. 141 6.1 Introduction .......................................................................................................... 141 6.2 Porphyry intrusions and host rocks ...................................................................... 142 6.3 Hydrothermal alteration and sulfide mineralization ............................................. 145 6.3.1 Early biotite-magnetite alteration ............................................................... 150 6.3.2 Sodic-calcic alteration ................................................................................ 150 6.3.3 Ore-stage potassic alteration ...................................................................... 153 6.3.3.1 Potassic alteration (Biotite-rich) ...................................................... 153 6.3.3.2 Potassic alteration (K-feldspar-rich) ................................................ 154 6.3.3.3 Veins and Cu-Fe-sulfide mineralization .......................................... 154 6.3.4 Transitional sericite-chlorite (clay) alteration ............................................ 157 6.3.5 Sericitic (Phyllic) alteration ....................................................................... 157 6.3.6 Propylitic alteration .................................................................................... 160 6.4 Relationship of alteration and porphyry intrusions .............................................. 160 6.5 Vein generations and crosscutting relationships .................................................. 164 6.6 Fluid inclusions .................................................................................................... 167 6.6.1 Methodology .............................................................................................. 168 6.6.2 Fluid inclusion petrography ....................................................................... 170 6.6.3 Fluid inclusions microthermometry ........................................................... 172 6.7 Discussion ............................................................................................................ 176 6.7.1 Porphyry emplacement, hydrothermal alteration and Cu-Au deposition ... 176 6.7.2 Magmatic-hydrothermal fluid characteristics and evolution ..................... 179 6.8 Conclusions .......................................................................................................... 181 Chapter 7 - Conclusions .................................................................................................. 183 7.1 Future research directions .................................................................................... 187 References ........................................................................................................................ 188 x  Appendices ....................................................................................................................... 216 Appendix A: Chapter 2 background data of drill holes and geological logging ........ 216 Appendix B: Chapter 3 results of whole-rock geochemical analysis ......................... 257 Appendix C: Chapter 4 background data of U-Pb and Re-Os geochronology .......... 275 Appendix D: Chapter 6 X-ray diffraction and fluid inclusions analysis .................... 292  xi  List of Tables Table 1.1 Global mineral inventory of Chagai belt, Balochistan-Pakistan .......................... 7 Table 1.2 Characteristics of large-scale known porphyry copper deposits worldwide. ....... 9 Table 2.1 Geological characteristics of selected porphyry systems in the Chagai belt, Balochistan province, Pakistan ............................................................................................ 25 Table 2.2 Geological features of the selected porphyry systems in the Reko Diq complex, Chagai belt, Balochistan-Pakistan. ...................................................................................... 26 Table 3.1 Sequence and petrologic characteristics of Reko Diq western porphyry Cu-Au deposits, Chagai belt, Balochistan-Pakistan ........................................................................ 48 Table 3.2 Petrologic characteristics of multiple porphyry intrusions in the Reko Diq H14H15 porphyry deposits, Chagai belt, Balochistan-Pakistan ................................................ 55 Table 3.3 Representative geochemical analysis of middle to late Miocene porphyry intrusions at Reko Diq H14-H15 porphyry Cu-Au deposits ............................................... 61 Table 3.4 Pb isotopic geochemistry of the H79, H15, H14 and H13 porphyry systems at Reko Diq complex. .............................................................................................................. 74 Table 3.5 Sr and Nd isotopic geochemistry of the H79, H15, H14 and H13 porphyry systems at Reko Diq complex. ............................................................................................ 74 Table 4.1 Available geochronologic data of the intrusive, volcanic and sedimentary rocks in Chagai belt. ...................................................................................................................... 85 Table 4.2 Available geochronology of the intrusive and volcanic rocks at Reko Diq, western Chagai belt. ............................................................................................................ 86 Table 4.3 U-Pb zircon SHRIMP-RG ages of the intrusive rocks in Reko Diq western porphyry Cu-Au deposits. ................................................................................................... 94 Table 4.4 Re-Os-molybdenite ages of the Cu-sulfide mineralization in H15 and H14 porphyry deposits .............................................................................................................. 107 Table 4.5 Timing and lifespan of magmatic-hydrothermal events at the Reko Diq H15-H14 porphyry Cu deposits. ........................................................................................................ 111 Table 5.1 U-Pb (zircon) SHRIMP-RG ages of the intrusive rocks analyzed for zircon trace element geochemistry. ....................................................................................................... 115  xii  Table 5.2 Trace element concentration (ppm) for zircons. (Temp) = Minimum temperature (oC) based on TiO2-in-zircon thermometer (Watson and Harrison, 2005). Ti values are Ti49, also used to calculate temperature. .......................................................................... 125 Table 5.3 Trace element concentration (ppm) for zircons SHRIMP-RG spot analysis ... 129 Table 6.1 Geochronological constraints of the magmatic-hydrothermal events at Reko Diq H79, H15, H14 and H13 porphyry Cu deposits. ............................................................... 146 Table 6.2 Description and age relationship of hydrothermal alteration and sulfide mineralization at Reko Diq H15 and H14 porphyry Cu-Au (Mo) deposits. ..................... 151 Table 6.3 Representative fluid inclusion analysis in quartz (A-veins) from Reko Diq H14 porphyry complex (Cross section 3222200m N)............................................................... 174 Table A.1 Metadata of drill holes along E-W cross sections in H14 and H15 complex .. 216 Table A.2 Example of a geological log sheet from H14 complex (RD510) .................... 217 Table A.3 Representative summary drill log sheets for H14 and H15 deposits ............... 234 Table A.4 Description of drill core samples from the Reko Diq western porphyry ......... 242 Table B.1 Analytical techniques and ALS Minerals detection limits............................... 257 Table B.2 Whole-rock geochemical analysis in the Reko Diq western porphyry ............ 262 Table B.3 Analytical methods of the radiogenic isotope analysis .................................... 274 Table C.1 Samples for zircon U-Pb SHRIMP-RG ages and trace element analysis ........ 275 Table C.2 SHRIMP-RG technique for zircon U-Pb-Th analysis ..................................... 285 Table C.3 U-Pb zircon SHRIMP-RG spot analysis .......................................................... 287 Table C.4 Samples for molybdenite Re-Os chronometry................................................. 290 Table C.5 Analytical procedures for molybdenite Re-Os chronometry ........................... 291 Table D.1Sample descriptions for X-ray diffraction analysis .......................................... 292 Table D.2 Dataset of fluid inclusions petrography and microthermometry ..................... 303  xiii  List of Figures Figure 1.1 Location and accessibility map of the Reko Diq porphyry district, western Chagai region, Balochistan province, Pakistan. .................................................................... 3 Figure 1.2 Landscape of the Reko Diq district and surroundings, western Chagai belt, Balochistan province, Pakistan .............................................................................................. 4 Figure 1.3 Schematic illustration of the subduction related arc magmatism, evolution path and porphyry Cu deposit formation at the continental plate margins (After Sillitoe, 1972; Hildreth and Moorbath, 1988; Winter, 2001; Richards, 2003; Hollings, 2005; Tosdal et al., 2009) .................................................................................................................................... 10 Figure 1.4 (A) Reko Diq in the context of Tethyan porphyry Cu belt and global distribution of porphyry Cu deposits (Kirkham and Dunne, 2000; Goodfellow, 2006); (B) Comparison of Reko Diq amongst twenty known large-scale porphyry copper deposits worldwide (based on tonnage in Mt; Cooke et al., 2005). .................................................. 11 Figure 1.5 Satellite image of the Reko Diq igneous complex, illustrating the spatial and temporal distribution of Miocene porphyry copper deposits clustered within the inner ring structure. *Note: The Reko Diq western porphyry cluster (study area) in red.................... 13 Figure 2.1 Regional geotectonic setting of Makran-Chagai trench-arc system extended into Iran. Based on (Jacob and Quittmeyer, 1979; Dykstra and Birnie, 1979; Kukowski et al., 2001; Perelló et al., 2008).................................................................................................... 21 Figure 2.2 Location and regional geology map of the Chagai magmatic belt, Balochistan province, Pakistan. (after Hunting Survey Corporation, 1960; Perelló et al., 2008). The Reko Diq porphyry complex is highlighted to the west (box outline). ............................... 24 Figure 2.3 Generalized stratigraphic sequence of the western Chagai, Reko Diq district, Balochistan-Pakistan. (Siddiqui, 1996, 2004; Perelló et al., 2008) ..................................... 29 Figure 2.4 Field photographs of the Reko Diq complex and surrounding area. (A) Looking N: Andesitic volcanic and lava flow of the Sinjrani volcanic group; (B) Medium to coarse grained volcanic agglomerate of the Sinjrani group; (C) Looking W: Medium to thick bedded Humai limestone formation; (D) Fossil shells, fragments, oolitic and pelletic structures in Humai limestone; (E) Looking SW: Medium to thin bedded sedimentary sequence of the Saindak formation at Parra Koh; (F) Looking W: Extensive andesitic and pyroclastic rocks hosting the Reko Diq H79, H15, H14 and H13 porphyry centers.. ........ 30 xiv  Figure 2.5 Core photographs illustrating the sedimentary, intrusive and volcanic host rocks at western Reko Diq. (A) Medium grained, thin-laminated sandstone with intense potassic alteration and micro veinlets of quartz-magnetite ± sulfides cut by the late anhydrite vein; (B) Conglomerate with 5-20mm poorly sorted silica pebbles and rock fragments cemented in a quartz-sericite-clay altered matrix; (C) Fine-grained volcanogenic shale with intense biotite-magnetite alteration and quartz stockwork; (D) Porphyritic andesite with 2-15mm phenocrysts of plagioclase set in a fine-grained potassically altered and magnetic ground mass; (E) Equigranular microdiorite overprinted by intense propylitic (chlorite-epidote) alteration; and (F) Pyroclastic breccia flow containing propylitic altered volcanic clasts and fragments cemented in a siliceous matrix. .......................................................................... 32 Figure 2.6 Drill core photographs of the Miocene porphyry intrusions at Reko Diq district. (A) Early Miocene quartz-diorite (Saindak) with medium to coarse grained porphyritic texture and intense hydrothermal biotite and ser-chl alteration; (B) Early Miocene diorite porphyry (Tanjeel) with pervasive quartz-sericite (clay) alteration and sparse to fracture filled supergene chalcocite; (C) Middle Miocene hornblende-diorite with phenocrysts of plagioclase, hornblende, quartz and minor biotite set in a propylitic altered aphanitic groundmass; (D) Middle to late Miocene granodiorite crowded with plagioclase, biotite and quartz in a micro-crystalline matrix; intense biotite-K-feldspar-magnetite alteration and quartz-magnetite-K-feldspar ± sulfide veins; (E) Late Miocene diorite exhibiting coarsegrained porphyritic texture with plagioclase, biotite and amphiboles embedded in a crystalline groundmass dominated by shredy biotite; and (F) Late dacite porphyry showing well-preserved primary texture and phenocrysts of plagioclase, quartz and amphiboles set in a chlorite-epidote altered pheneric groundmass. ............................................................. 36 Figure 2.7 Satellite image and outcrop geology map of the Reko Diq porphyry complex and adjacent porphyry centers in the district. *Note: The study area to the west (box outlined) is represented by a cluster of middle to late Miocene porphyry intrusions, color coded as red. ........................................................................................................................ 38 Figure 2.8 Factual geology map of the Reko Diq western porphyry complex. H79 porphyry center in the north is associated with NE-trended hornblende-diorite and dacite porphyry intrusions, whereas H15, H14 and H13 porphyry systems to the south are  xv  centered on a cluster of NE and NW-trended granodiorite and quartz-diorite intrusions host by andesitic volcanic and pyroclastic rocks ........................................................................ 41 Figure 2.9 Surface outcrop geology map of the Reko Diq H14 and H15 porphyry centers. The middle to late Miocene granodiorite and quartz-diorite intrusions emplaced as a cluster of NE-trended stocks and dykes host by Late Oligocene andesitic volcanic rocks. ........... 42 Figure 3.1 Surface geology map of the Reko Diq western porphyry complex: The middle to late Miocene (12.9-11.9 Ma) granodiorite and quartz-diorite intrusions emplaced as a cluster of NE-trending stocks and dykes host by late-Oligocene volcanic rocks. The multiple porphyry intrusions and hydrothermal events led to the formation of H79, H15, H14 and H13 porphyry Cu-Au deposits from north to south. ............................................. 50 Figure 3.2 East-west geological section (A-A’ UTM 3223300m N) across H15 porphyry complex projecting up to 100m downhole drilling data onto the section: The multiple crosscutting porphyry intrusions emplaced upward into a sequence of volcanic and sedimentary rocks. The early granodiorite (PFB1) porphyry stock is intersected by narrow dykes of intra-mineral (PFB2) and late-mineral (PFB3) quartz-diorite intrusions. ............ 51 Figure 3.3 East-west geological section (B-B’-UTM 3222200m N) across the H14 complex projecting up to 100m downhole drilling data onto the section: The multiple crosscutting porphyry intrusions emplaced as vertical to sub-vertical stocks and dykes into volcanic and sedimentary rocks. The early granodiorite (PFB1) is cut by intra-mineral quartz-diorite (PFB2) and subsequently intersected by narrow dykes of late-mineral (PFB3) and late-barren (PFB4) quartz-diorite intrusions in the core of the system. ........... 52 Figure 3.4 Core photographs illustrating the sequence and crosscutting relationships of intrusive rocks at Reko Diq western porphyry complex. (A) Hornblende-diorite (PFH) from H79 complex; (B) Early granodiorite (PFB1) cut by intra-mineral quartz-diorite (PFB2) display chilled margins along the contact; (C) Intra-mineral quartz-diorite (PFB2) with sub-angular xenoliths of host rocks with distinct vein truncation; (D) Late-mineral quartz-diorite (PFB3) with sub-rounded xenoliths of deeper granodiorite pluton; (E) Latemineral quartz-diorite (PFB3) cut by narrow dykes of late stage barren quartz-diorite (PFB4); and (F) hornblende-rich quartz-diorite (PFB2) in H13 complex. .......................... 53 Figure 3.5 Core photographs illustrating the sequence and subtle variations in texture and composition of intrusive rocks in H14 and H15 porphyry systems. (A-A’) Early phase xvi  medium-grained, equigranular to porphyritic granodiorite (PFB1) with a holocrystalline groundmass displaying intense potassic alteration of biotite + K- feldspar + magnetite; (BB’) Intra-mineral phase, coarse-grained porphyritic quartz-diorite (PFB2) with a finer crystalline groundmass. Secondary biotite-K-feldspars-magnetite are locally overprinted by sericite-chlorite; (C-C’) Late-mineral, coarse-grained porphyritic quartz-diorite (PFB3) with 2-12mm phenocrysts of plagioclase, quartz, biotite and minor amphiboles set in an aphanitic groundmass altered to sericite-chlorite ± biotite; and (D-D’) Late-stage, coarsegrained porphyritic quartz-diorite (PFB4) with 3-15mm, euhedral phenocrysts of plagioclase, quartz, biotite and minor amphiboles set in a phaneritic groundmass. ........... 58 Figure 3.6 Photomicrographs illustrating the sequence and petrologic characteristics of intrusive rocks in H15 and H14 complexes. (A-A’) Granodiorite (PFB1) with anhedral plagioclase replaced by grey K-feldspars overprinted by sericite; biotite altered to palebrown flakes of secondary biotite; (B-B’) Quartz-diorite (PFB2) display zoned plagioclase partially altered to K-feldspars and rimmed by sericite; biotite phenocrysts alters to palebrown flaky hydrothermal biotite; (C-C’) Quartz-diorite (PFB3) with zoned plagioclase rimmed by sericitic alteration; biotite phenocrysts partially altered to chlorite and rimmed by secondary biotite; (D-D’) Quartz-diorite (PFB4) illustrating well preserved, euhedral phenocrysts of biotite, quartz and strongly zoned, intergrown plagioclase set in a phaneritic groundmass. ......................................................................................................................... 59 Figure 3.7 Major element and petrochemical discrimination diagrams of the Reko Diq H14-H15porphyry complex: (A) SiO2 vs. K2O diagram (Peccerillo and Taylor, 1976) with porphyry intrusions generally cluster within calc-alkaline composition field. Samples with high K2O and SiO2 represent the effects of hydrothermal alteration; (B) Total alkali vs. silica diagram (Le Maitre et al., 1989) generally indicates quartz-diorite composition; (C) K2O/Al2O3 vs. P2O5/Al2O3 plot (Crawford et al., 2007a) distinguishes the least altered rocks (clustered in the medium-K field) from hydrothermally altered rocks with addition and depletion of K2O (F) Loss on ignition LOI vs. K2O plot illustrating the alkalinity of the rocks and the effect of hydrothermal alteration with K2O (>2.0wt.%) and LOI (>3.0 wt.%). .................................................................................................................................. 65 Figure 3.8 Major element and petrochemical discrimination diagrams of the Reko Diq H14-H15 porphyry complex: (A) SiO2 vs. Al2O3 plot show decreasing Al2O3 content with xvii  relatively altered rocks; (B) SiO2 vs. TiO indicates depleted TiO in the early altered granodiorite PFB1 and quartz-diorite PFB2 intrusions; and (E) SiO2 vs. MgO plot reflect a normal fractionation trend. .................................................................................................. 66 Figure 3.9 (A-D) Chondrite-normalized spider diagrams for rare earth element REE in the late Oligocene volcanic and middle to late Miocene intrusive rocks at Reko Diq western porphyry complex (after Sun and McDonough, 1989). The REE patterns typically show moderate enrichment of light-REE and a flat heavy-REE profiles indicating a shallow (<50km) mantle source; (E) Eu/Eu* versus Sm/Yb plot indicates an overall garnet/amphibole fractionation trend of the intrusive rocks................................................ 68 Figure 3.10 Chondrite-normalized rare earth element REE plots of late Oligocene volcanic and middle-late Miocene intrusive rocks at Reko Diq H14 and H15 porphyry systems (after Sun and McDonough, 1989). The REE patterns typically show moderate enrichment of light-REE and a flat heavy-REE profiles indicating a shallow (~50km; lower crust) mantle source; (A-E) H15 complex show flat HREE patterns; (F-J) H14 complex indicate relatively broader spoon shaped HREE profiles, implying that H14 is slightly more fractionated than H15. ......................................................................................................... 69 Figure 3.11 Petrochemical discrimination diagrams. (A) Sr/Y vs. Y (Defant and Drummond, 1993) and (B) La/Yb vs. Yb (Castillo et al., 1999) showing Adakitic geochemical signature and normal andesite-dacite-rhyolite trend of the intrusive rocks at Reko Diq; (C) SiO2 vs. La/Yb; and (D) SiO2 vs. Sm/Yb plots display relatively higher La/Yb and Sm/Yb ratios in the younger (PFB3, PFB4) porphyry intrusions; (E) SiO 2 vs. Sr/Y plot with intrusive rocks plot within high Sr/Y (>20) adakite field; and (F) Decreasing Sr content from younger to older intrusions; an effect of K-silicate alteration. No clear distinction evident between H14 and H15........................................................................... 70 Figure 3.12 General geochemical characteristics and classification of the intrusive rocks at Reko Diq H14 and H15 porphyry centers: (A) Total alkali vs. silica plot (Le Maitre et al., 1989); (B) Nb/Y vs. Zr/TiO2 (Winchester and Floyd, 1977) and (C) SiO2 vs. Zr/TiO2 discrimination plots. Harker diagrams: (D) SiO2 vs. TiO2; (E) SiO2 vs. Zr; (F) SiO2 vs. Nb; (G) SiO2 vs. La; (H) SiO2 vs. Nd; (I) SiO2 vs. Ba; (J) SiO2 vs. Rb; (K) SiO2 vs. Sr; and (L) SiO2 vs. Y plots. Abbreviations: AND=andesite, BA=basaltic andesite, BAS=basalt, BS=basanite,  BTA=basaltic  trachyandesite,  PB=picrobasalt,  PH=phonolite, xviii  PT=phonotephrite,  TA=trachyandesite,  TB=trachybasalt,  TEP=tephrite,  TP=tephriphonolite. ............................................................................................................. 71 Figure 3.13 Pb, Sr and Nd isotope compositions of the middle to late Miocene intrusive rocks at Reko Diq. (A-B) Reko Diq and Kerman arcs (Shafiei et al., 2009) plot in the upper crust field near the crustal growth curve of Stacey and Kramers (1975); Evolution lines for mantle, lower and upper crust are from Doe and Zartman (1979); (C-D) two distinct rockgroups with increasing radiogenic Pb from H79 to H15-H14 and decrease in H13 complex; (E-F) increasing Sr and decreasing Nd from mafic to felsic composition with time. ......... 75 Figure 4.1 Geologic setting of the Reko Diq complex within the context of the Chagai belt, western Pakistan (modified after Perelló et al., 2008). The inset map shows geographical location. ............................................................................................................................... 82 Figure 4.2 Outcrop geology map of the Reko Diq complex and surrounding region, western Chagai belt, Balochistan-Pakistan.......................................................................... 83 Figure 4.3 Outcrop geology map of the Reko Diq western porphyry complex, BalochistanPakistan. The cluster of middle to late Miocene porphyry intrusions emplaced along a NWtrend forming H79, H15, H14 and H13 porphyry centers. .................................................. 89 Figure 4.4 East-west geological section (A-A’ UTM 3223300m N) across H15 porphyry complex projecting up to 100m downhole drilling data onto the section: Multiple crosscutting porphyry intrusions emplaced upward into a sequence of volcanic and sedimentary rocks. Early (PFB1) porphyry stock is intruded by thin dikes of intra-mineral (PFB2) and late mineral (PFB3) quartz diorite intrusions................................................... 90 Figure 4.5 East-west geological section (B-B’ - UTM 3222200m N) across H14 porphyry complex projecting up to 100m downhole drilling data onto the section: Multiple crosscutting porphyry intrusions emplaced as vertical to sub-vertical stocks and dykes host by volcanic and sedimentary rocks. Early porphyry (PFB1) is intruded by intra-mineral quartz-diorite (PFB2) and subsequently intersected by narrow dykes of late-mineral (PFB3) and late-barren (PFB4) quartz-diorite intrusions in the core of the system. ........... 91 Figure 4.6 Core photographs illustrating the sequence and subtle variations in texture and composition of intrusive rocks in H14 and H15 porphyry systems: (A-A’) Early phase medium-grained, equigranular to porphyritic rock (PFB1) with a holocrystalline groundmass displaying intense potassic alteration of biotite + K- feldspar + magnetite, (Bxix  B’) Intra-mineral phase, coarse-grained porphyritic quartz diorite (PFB2) with a finer crystalline groundmass. Secondary biotite-K-feldspars-magnetite are locally overprinted by sericite-chlorite, (C-C’) Late mineral, coarse-grained porphyritic quartz diorite (PFB3) with 2-12mm phenocrysts of plagioclase, quartz, biotite and minor amphiboles set in an aphanitic groundmass altered to sericite-chlorite ± biotite, and (D-D’) Late-stage, coarsegrained porphyritic quartz diorite (PFB4) with 3-15mm, euhedral phenocrysts of plagioclase, quartz, biotite and minor amphiboles set in a phaneritic groundmass. ........... 92 Figure 4.7 Cathodoluminescence images of the zircons from porphyry samples in H79, H15, H14, and H13 complex. Circles represent the location of spot analyses dated by SHRIMP-RG. ...................................................................................................................... 97 Figure 4.8 A-D U-Pb-zircon geochronology diagrams and  238  U/206Pb vs.  207  Pb/206Pb  concordia plots of SHRIMP-RG spot analysis from middle to late Miocene porphyry intrusions in H15 and H79 complexes. Ages are based on the 206  207  Pb-corrected and  Pb/238U weighted mean age calculation (black). Ages in grey tones have been excluded  from the age calculations based on criteria outline in the text. Weighted mean ages have 2σ uncertainties. ...................................................................................................................... 100 Figure 4.8 E-H U-Pb-zircon geochronology diagrams and  238  U/206Pb vs.  207  Pb/206Pb  concordia plots of SHRIMP-RG spot analysis from middle to late Miocene porphyry intrusions in H15 and H14 complexes. Ages are based on the 206  207  Pb-corrected and  Pb/238U weighted mean age calculation (black). Ages in grey tones have been excluded  from the age calculations based on criteria outline in the text. Weighted mean ages have 2σ uncertainties. ...................................................................................................................... 103 Figure 4.8-I-J U-Pb-zircon geochronology diagrams and  238  U/206Pb vs.  207  Pb/206Pb  concordia plots of SHRIMP-RG spot analysis from middle to late Miocene porphyry intrusions in H14 and H13 complexes. Ages are based on the 206  207  Pb-corrected and  Pb/238U weighted mean age calculation (black). Ages in grey tones have been excluded  from the age calculations based on criteria outline in the text. Weighted mean ages have 2σ uncertainties. ...................................................................................................................... 105 Figure 4.9 (A) Probability density plot and (B) composition histogram plot of all U-Pbzircon SHRIMP-RG spot ages analyzed from the porphyry intrusions in the Reko Diq H15 complex. (C) Probability density plot and (D) composition histogram plot of all U-Pbxx  zircon SHRIMP-RG spot ages analyzed from the porphyry intrusions in the Reko Diq H14 complex. ............................................................................................................................ 106 Figure 4.10 (A) Geochronological constraints of multiple porphyry intrusions and subsequent hydrothermal events in the Reko Diq western porphyry cluster; (B) Sequence of multiple porphyry intrusions and its relationship with hydrothermal alteration, veins and Cu-sulfides in the H14 and H15 porphyry systems. .......................................................... 109 Figure 5.1 Surface geology map of Reko Diq western porphyry complex, illustrating the spatial and temporal distribution of H79, H15, H14, H13 porphyry systems associated with middle to late-Miocene intermediate to felsic intrusive rocks host by late-Oligocene andesitic volcanic and pyroclastic rocks. .......................................................................... 116 Figure 5.2 Core photographs of the samples selected for SHRIMP-RG zircon trace element analysis: (A) Pre-mineral hornblende-diorite in H79 complex, (B-C) main-mineral granodiorite in H14-H15 complex, (D) syn-mineral quartz-diorite in H14 complex, (E-F) late-mineral quartz-diorite in H14-H15, (G) late-barren quartz-diorite in H14 complex, and (H) intra-mineral hornblende bearing quartz-diorite in H13 complex. ............................. 118 Figure 5.3 Representative Cathodoluminescence images of the zircon grains from hornblende-diorite (PFH) in H79 complex. Circles represent the location of SHRIMP-RG spot analysis with Hf concentrations (ppm) and TiO2-in-zircon minimum crystallization temperatures (oC) ............................................................................................................... 120 Figure 5.4 Representative Cathodoluminescence images of the zircon grains in geochronological order. (A-B) Zircons from early and late-mineral intrusive rocks at H15 complex (C) Zircons form a younger granodiorite, (D) Syn-mineral quartz-diorite, (D) and (E) Late-barren stage quartz-diorite in H14 complex. (E) Zircons from the youngest quartzdiorite in H13 complex. Circles represent the location of SHRIMP-RG spot analysis of Hfconcentrations (ppm) and TiO2-in-zircon minimum crystallization temperatures (oC). ... 121 Figure 5.5 Chondrite-normalized REE patterns in zircons from the intrusive rocks at Reko Diq western porphyry complex. All samples are characterized by elevated heavy-REE and relatively depleted light-REE, slightly negative Eu anomalies and pronounced positive Ce anomalies. .......................................................................................................................... 123 Figure 5.6 Zircon mineral-chemistry plots: (A) Hf versus minimum temperature (oC) illustrating increasing Hf concentration and decreasing crystallization temperatures of xxi  zircons through space and time; (B) Hf versus Th/U; (C) Th/U versus minimum temperature (oC); and (D) Hf versus Y/U plots showing steep and hook-like curved trends of cooling and fractionation in zircons from older H79 through younger H15, H14 and H13 porphyry centers distributed from north to south. The circled outliers inferred to inheritance of older zircons incorporated in the younger intrusive rocks. ........................ 131 Figure 5.7 Zircon mineral-chemistry plots. (A) Hf versus Y; (B) Th/U versus Y/Yb; (C) Y versus Y/Gd; and (D) Th/U versus Yb/Gd plots showing distinct fractionation trend from older H79 to younger H15, H14 and H13 porphyry zircons. The circled outliers inferred to the inheritance of zircons in the corresponding samples. Considerable scatter is evident in the H79 (PFH; RD077-608) and H14 (PFB2; RD510-1545) porphyry zircons reflecting variation in the magma composition. ................................................................................ 133 Figure 5.8 Hafnium versus multi-valent plots. (A) Hf versus Eu/Eu* plot illustrating decreasing Eu/Eu* and increasing Hf content in space and time. Eu/Eu* values (>0.4) indicate the oxidation state and/or fractionation of plagioclase feldspars (Ballard et al., 2002); (B) Hf versus Ce/Ce* ratios indicate a steeply curved trend of fractionation from older H79 through younger H15, H14 and H13 porphyry centers distributed from north to south. ................................................................................................................................. 134 Figure 5.9 Conceptual N-S cross sectional model of the Reko Diq western porphyry complex. (A) Crustal scale magmatic-hydrothermal system with deep mantle-derived mafic melts form a zone of magma mixing, assimilation, storage and homogenization (MASH) at lower crust (Hildreth and Moorbath, 1988; Schmidt and Poli, 1998, Richards, 2003). Mafic melts evolved into oxidized, sulfur and volatiles rich magma of andesitedacite composition (Hildreth, 1981; Grove et al., 2003; Chiaradia et al., 2004; Rohrlach and Loucks, 2005). The magma rises at shallow levels, assimilate upper crustal material and stall to form magma chambers of relatively felsic composition and evolve porphyry Cu deposits (Gustafson 1979; Burnham 1979; Dilles 1987; Hedenquist and Lowenstern, 1994; Candela and Piccoli, 2005; this study). (A1) Initial intrusive event of hornblende-diorite (PFH; 12.9 Ma) in H79 complex; (A2) Magma chamber evolved to form H15 complex to the south with the emplacement of early granodiorite (PFB1; 12.5 Ma) and quartz-diorite (PFB2; 12.3 Ma) intrusions during peak magmatism; (A3) Further southward shift of magmatism forming the H14 complex associated with the younger granodiorite (PFB1;12. xxii  3Ma) and quartz-diorite (PFB2; 12.0 Ma) intrusions; (A4) Emplacement of late-mineral (PFB3) and late-barren (PFB4) quartz-diorite intrusions from 12.1 to12.0 Ma, in H15-H14 and formation of the H13 complex with the youngest hornblende-bearing quartz-diorite intrusions (PFB2) at 11.9Ma. ............................................................................................ 138 Figure 6.1 (A) Field photograph showing the alteration distribution at Reko Diq western porphyry complex; (B) Surface alteration map of H79, H15, H14 and H13 porphyry deposits illustrating the central potassic alteration zones overprinted and enveloped by transitional sericite-chlorite (clay) and surrounded outward by sericitic (phyllic) and extensive propylitic alteration. .......................................................................................... 143 Figure 6.2 Core photographs illustrating the textural and compositional characteristics and comparison of multiple porphyry intrusions in H15 and H14 complexes. (A-A’) Early granodiorite (PFB1) with intense ore-stage potassic alteration, multi generation veins and disseminated to veinlet Cu-Fe-sulfides; (B-B’) Intra-mineral quartz-diorite (PFB2) with moderate potassic alteration, veins and Cu-Fe-sulfides overprinted by sericite-chlorite ± clay alteration; (C-C’) late-mineral quartz-diorite (PFB3) and (D-D’) late-barren quartzdiorite (PFB4) with relatively preserved primary mineralogy and coarse grained porphyritic textures. ........................................................................................................... 144 Figure 6.3 Surface alteration map of the Reko Diq H15-H14 complex: The central potassic alteration and associated quartz stockwork zone in H15 is largely overprinted and surrounded by transitional sericite-chlorite (clay) alteration. H14 complex to the south is characterized by a central zone of pristine potassic alteration and intense quartz-stockwork, surrounded by a mixed zone of potassic-sericitic and transitional sericite-chlorite (clay) alteration. Outer sericitic (phyllic) and peripheral propylitic alteration is developed in the peripheral volcanic host rocks to the north east and west of H15-H14 complex. ............. 147 Figure 6.4 Cross section (3223300mN) showing vertical and lateral distribution of alteration in H15 complex, interpreted from surface mapping and drill core logging. Potassic alteration (purple) is overprinted by sodic-calcic alteration at ≥950m. Overprints of sericite-chlorite (clay) alteration (blue) introduced a mixed zone of moderate potassic alteration (pink). Phyllic (yellow) and propylitic (green) alteration developed outside the main ore-zone. High sulfidation alteration-mineralization (orange) generally follows porous country rocks at the shoulders of H15 alteration system. ...................................... 148 xxiii  Figure 6.5 Cross section (3222200mN) showing vertical and lateral distribution of alteration at Reko Diq H14 complex, interpreted from surface mapping and drill core logging. Deep (~980m) potassic alteration (purple) is overprinted by sodic-calcic alteration, whereas central potassic zone is surrounded by transitional sericite-chlorite (clay) alteration (blue) introducing mixed zones of moderate potassic alteration (pink). Phyllic (yellow) and propylitic (green) alteration developed outside the main ore-zone. 149 Figure 6.6 Core photographs illustrating the textural characteristics and hydrothermal alteration in H15 and H14 porphyry centers. (A-A’) Early-dark-mica (EDM) cut by sodiccalcic alteration; (B-B’) ore-stage, biotite-rich potassic alteration; (C-C’) ore-stage Kfeldspar-rich potassic alteration; (D-D’) Transitional sericite-chlorite (clay) alteration; and (E-E’) sericitic (phyllic) alteration. ................................................................................... 152 Figure 6.7 Transmitted light photomicrographs showing characteristics of potassic alteration in H15 and H14 porphyry deposits. (A-A’) Granodiorite-PFB1 with cluster of shredy biotite (bio), fine-grained K-feldspars (Kfs) and interstitial quartz (qtz) in the groundmass; (B-B’) Granodiorite-PFB1 with intense fine-grained K-feldspars (Kfs) replacing plagioclase and in-turn overprinted by sericite (ser); quartz (qtz) occur interstitially; (C) Granodiorite-PFB1 and potassic alteration cut by quartz-diorite-PFB2 with finer grained shredy biotite (bio) cluster in the rock-matrix and rim phenocryst biotite; (C’) Quartz-diorite-PFB2 with plagioclase altered to fine-grained K-feldspars (Kfs) and rim by sericite (ser); shredy biotite (bio) occur as cluster in the matrix and disintegrate phenocryst biotite; (D’) Quartz-diorite-PFB3 illustrating weak, fine-grained secondary biotite (bio) in the matrix and rim phenocryst biotite; (D’) late quartz-diorite-PFB4 with well-preserved primary mineralogy and textures along with early-dark-mica and traces of shredy biotite. .................................................................................................................... 155 Figure 6.8 Drill core photographs and reflected light photomicrographs illustrating hypogene Cu-sulfide mineralization at Reko Diq H14 and H15 porphyry deposits. (A-A’) fine-grained, disseminated and intergrown chalcopyrite-bornite and molybdenite in biotiterich potassic alteration; (B-B’) intergrown chalcopyrite-bornite-pyrite and molybdenite in K-feldspar-rich potassic alteration; (C-C’) fine, disseminated and intergrown chalcopyrite and molybdenite associated with potassic-sericitic alteration; (D-D’) chalcopyrite  xxiv  associated with late-stage sulfide D-type veins and intense sericite-chlorite (clay) alteration. ........................................................................................................................... 156 Figure 6.9 Reflected light photomicrographs illustrating characteristics of transitional sericite-chlorite (clay) alteration in H15 and H14 porphyry deposits. (A-A’) GranodioritePFB1 with K-feldspar (Kfs) altered plagioclase as well as the groundmass overprinted by fine grained sericite + clay (illite), whereas, biotite is replaced by dark greenish-grey chlorite; (B-B’) Quartz-diorite-PFB2 showing complete replacement of plagioclase into fine-grained sericite (ser) and clay (illite) appear in dark colors. ...................................... 158 Figure 6.10 Drill core photographs and reflected light photomicrographs of highsulfidation Cu-Fe-sulfide mineralization at Reko Diq H15 complex. (A-A’) Granodiorite porphyry with intense quartz-sericite-clay and fine-grained bornite-covellite and intergrown chalcopyrite; (B-B’) Andesitic volcanic rock with intense quartz-sericite-clay alteration and fine disseminated bornite-covellite and chalcopyrite; (C-C’) Fine-grained sandstone with intense quartz-sericite-clay alteration and tinny crystals of covellite rim by bornite and pyrite; (D-D’) fine-grained volcanogenic shale with intense quartz-sericite-clay alteration and fine-grained disseminated covellite and chalcopyrite. ............................... 159 Figure 6.11 Drill core photographs and transmitted-light photomicrographs illustrating the propylitic alteration assemblage in porphyry and host rocks at Reko Diq H15 complex. (AA’) Quartz-diorite porphyry (PFB2) with phenocryst biotite and amphiboles (hbl) altered to chlorite-epidote; (B-B’) Felsic volcanic rock with phenocryst biotite and/or amphiboles partially altered to chlorite-epidote; (C-C’) Epidotization in the fine-grained volcanogenic shale. .................................................................................................................................. 161 Figure 6.12 Representative drill core log sheet showing the relationship between lithology, alteration, veins and Cu-Au grades. The highest Cu-Au grades associated with potassic alteration and intense quartz-sulfide veins in the early granodiorite (PFB1) porphyry (Data courtesy of Tethyan Copper Company Limited). .............................................................. 163 Figure 6.13 Schematic illustration of multi-generation veins, crosscutting relationships and their paragenetic sequence in relation to early (PFB1), intra-mineral (PFB2), late-mineral (PFB3) and late-barren (PFB4) porphyry intrusions in H15 and H14 porphyry Cu-Au (Mo) deposits. Nomenclature of A, B and D-type veins is from Gustafson and Hunt (1975) and M-type veins from Arancibia and Clark (1996). ............................................................... 164 xxv  Figure 6.14 Core photographs illustrating multi-generation hydrothermal veins and their crosscutting relationships: (A) Early-dark-mica cut by pegmatite dyke and barren quartz A1-veins. (B) Early-dark mica veins cut by quartz-albite and quartz-magnetite-K-feldspar (Kfs) A1-veins. (C) Quartz-albite A1-veins cut by quartz A2-veins with EDM selvages. (D) Barren quartz A1-veins cut by magnetite ± actinolite M-veins. (E, F, G, H) Quartz-Kfeldspar ± magnetite A1-veins cut by quartz-K-feldspar ± anhydrite A2-veins in the orestage potassic alteration containing up to 4-vol.% chalcopyrite + bornite ± pyrite (5:4:1) with ~1.5% Cu & 1.0/t Au. (I) Quartz-albite A1-vein cut by quart-sulfide B-vein, (J) Quartz B-vein with center-line chalcopyrite + molybdenite ± pyrite. (K-L) Late-stage pyrite ± chalcopyrite D-veins with sericite-chlorite (clay) alteration halos postdated by gypsum infill veins. ........................................................................................................... 166 Figure 6.15 (A-F) Photographs and description of drill core samples selected for fluid inclusions analysis across H14 complex. (G) Geological cross section showing the location of fluid inclusion samples collected from deep, central and shallow levels of granodiorite porphyry (PFB1) ................................................................................................................ 169 Figure 6.16 Photomicrographs of Reko Diq fluid inclusions. (A) Vapor-rich B85 fluid inclusion, (B) Vapor-liquid B60 fluid inclusion, (C) liquid-vapor B20 fluid inclusion, (D) Liquid-vapor-solid B35H fluid inclusion containing halite and single phase opaque daughter minerals, (E) Liquid rich-vapor-solid B15H fluid inclusion with halite and multiphase daughter minerals (hematite and/or chalcopyrite), (F,G,H) Scattered vapor rich B85 and B60 fluid inclusions coexist with  liquid-vapor-solid B35H and B15H fluid  inclusions indicating no obvious healed fractures, (I) Abundant liquid-vapor-solid B35H fluid inclusions coexist with and B85 fluid inclusions, (J,K) Scattered B85, B20 and B15H fluid inclusions and trails of secondary B85 fluid inclusions trapped along healed fractures of quartz veins. .................................................................................................................. 171 Figure 6.17 Fluid inclusion plots: (A) Abundance of fluid inclusion assemblage in deep, central and shallow levels of Reko Diq H14 complex; (B) Temperature of final icemelting; (C) Apparent salinity of fluid inclusions based on Bodnar et al., (1994); (D) Homogenization temperatures (vapor-liquid); (E) Scatter plot illustrating fields of homogenization temperature, apparent salinity and final ice-melting temperatures of fluid inclusion assemblage. Note the fluid inclusions in quartz veins from ore-stage potassic xxvi  alteration (red) have relatively higher homogenization temperatures and apparent fluid salinities. ............................................................................................................................ 175 Figure 6.18 North-south long section illustrating lithologic, alteration and sulfide distribution model of Reko Diq H79, H15, H14 and H13 porphyry deposits. (A) Middlelate Miocene porphyry intrusions emplaced as vertical to sub-vertical stocks and dykes into the late Oligocene to early Miocene volcanic and sedimentary rocks; (B) Vertical and lateral distribution of hydrothermal alteration; (C) Ore shells with vertical and lateral distribution of estimated Cu-sulfides and Cu-Au grades. ................................................. 178 Figure 6.19 P-X diagrams for H2O-NaCl system illustrating the salinity and estimated pressure conditions of the magmatic-hydrothermal fluids in (A) deep potassic and sodiccalcic alteration; (B) central ore-stage potassic alteration; and (C) shallow ore-related sericite-chlorite (clay) alteration. The bar graphs illustrate three distinct fluid phases and their average homogenization temperatures and apparent salinities. ................................ 180 Figure C.1 Cathodoluminescence images of zircons for SHRIMP-RG spot analysis. .... 279 Figure D.1 Representative X-ray diffraction patterns ...................................................... 293 Figure D.2 Thin section scans and photomicrographs of the fluid inclusion samples ..... 297  xxvii  Acknowledgements Thanks to Tethyan Copper Company Ltd., Antofagasta Minerals Plc. and Barrick Gold Corporation joint venture for providing funding and logistic support in this research project. I would like to appreciate all participants involved in the Reko Diq exploration programs since the inception (1993) onwards. José Perelló, Chris Arndt, Peter Leaman, Chris Ford, Saad Hussain, Sukmandaru Prehatmoko, Martin Oczlon, Adi Maryono, Eko Hartowo, Craig Riley, Abdul Fareed, Arshad Abbas, Rizwan Khurshid, Mehmood Ilyas, Akhtar Mohammed, Dost Mohammed, Bradley Parson and Sakhi Jamaldin (late) deserve special recognition for their tremendous work and contribution in the discovery of Reko Diq porphyry deposits. Special thanks are owed to John Schloderer, Tim Hargreaves, Francois Roberts, Rex Brommecker, Ricardo Muhr, Tim Fletcher, Tim Livesey, Cameron Cairns, Carl Jackman, and Nutu Groza for their significant contributions in the understanding of the geology at Reko Diq complex. I gratefully acknowledge Giuseppe Lo Grasso, Abdul Bashir, Nazir Ahmed, Naseer Ahmed, Hafeez-ur-Rehman, Asad-urRehman, Aquiles Gonzalez, Humberto Brockway, Abdul Malik, Abdul Jalil, Ejaz Ahmed, Habib-ur-Rehman, Razzaque Abdul Manan, Khurram Hassan, Esteban Acuña, Phil Wilson, Jack McMahon, Hayat Khan, Tahir Fawad, Ijaz Ahmed and Kashaf Taj for their outstanding work and contribution in the Reko Diq feasibility study and providing technical support in this research project. Thanks to all field assistants, geo-technicians, samplers and support staff in facilitating the field activities at Reko Diq. I offer my enduring gratitude to Dr. Richard Tosdal, for supervising this research project and support on all aspects of the PhD. His technical advise and guidelines left significant impacts on my professional development. The committee members Dr. James Mortensen and Dr. Farhad Bouzari are thanked for their guidance and constructive comments throughout the research study. I am grateful to Dr. Mati Raudsepp and Jenny Lai for directions in the X-ray diffraction analysis, Dominique Weis for providing the radiogenic isotope compositions, Hai Lin for contributing in the sample preparation work, and Melissa Gregory for directions in the fluid inclusions analysis. Thanks to Society for Economic Geologists (SEG) for awarding the student research grants to conduct fieldwork and geochronologic studies at the Stanford-USGS laboratories USA. Arne Toma (MDRU resource coordinator) and Karie Smith (MDRU accounts) are thanked for their office support. Special thanks to Dr. Ken Hickey, Craig Hart, John Dilles, Jeremy Richards, Brent McInnes, Brian Rusk, Antony Harris and Robert Creaser for their constructive comments. Finally thanks to my friends, colleagues (especially Kirsten Rasmussen, Tatiana Alva, Adam Simmons, Liz Stock and Jessica Norris), parents and family for their encouragement and support during this study.  xxviii  Dedication This work is dedicated to my loving family in Quetta Pakistan, in particular my father Mohammed Shafi (Haji Baba) and mother Bibi Hoora (Dada). It is also dedicated to my wonderful brothers and sisters particularly, Bari Jan and Rahima Khan as well as my wife Zubaida and friends in Pakistan and Canada. Thank you for your endless support and encouragement.  “CHI ALLAH DAR SARA MAL NA YE RAHMANA… …KA LASHKARI DAR SARA YE YAK TANHA YE” (Rahman Baba, 1728)  xxix  Chapter 1 - Introduction 1.1 Preamble The term “Porphyry” originated from Greek, which means “purple”, and is attributed to a prized igneous rock used in the construction of building projects and monuments in ancient Rome. Later on “Porphyry” was used as a textural term for a variety of igneous rocks characterized by large crystals (phenocrysts) embedded within a matrix of smaller crystals. The term “Porphyry” is also used for mineral deposits such as copper, gold, molybdenum precipitated from cooling and solidification of magma and discharge of magmatic-hydrothermal fluids. Porphyry Cu deposits are large (hundreds of megatons) low-grade (0.3-1.0% Cu) ore deposits, which account for over 50% of the world’s annual copper production and an important source of gold and molybdenum (e.g., Seedorff et al., 2005). Research over the last two decades highlight that most large-scale porphyry copper deposits including Chuquicamata (Ossandon et al., 2001), El Salvador (Gustafson et al., 2001), Rio Blanco (Deckart et al., 2005) and El Teniente (Vry et al., 2010) Chile, Grasberg Indonesia (Pollard and Taylor, 2002), Bingham Canyon, USA (Redmond and Einaudi, 2010), and Reko Diq, Pakistan (Perelló et al., 2008; this study) are characterized by multiple superimposed magmatic-hydrothermal events. Studies on such ore deposits provide vital information on the genesis, evolution and space-time relationships to understand the ore-forming processes and identify highly prospective exploration targets. The Chagai belt has over 25 years of active exploration history. Following the discovery of Saindak, Reko Diq and Koh-e-Sultan prospects, the western Chagai region has become a fertile hunting ground for the exploration and discovery of porphyry coppergold and epithermal gold deposits. This PhD research project was created to evaluate the magmatic-hydrothermal processes and develop a genetic porphyry model providing sound geological concepts for the exploration and mining activities in the region. This research project offered an excellent opportunity to define the composition, age, evolution trends and cross cutting relationships of porphyry intrusions, hydrothermal alteration and Cu-Au mineralization at western Reko Diq. Comparison studies on the petrology, petrochemistry and magmatic-hydrothermal evolution within Reko Diq complex and other porphyry 1  deposits worldwide provided valuable information on the genesis, evolution, metal deposition and characteristics of porphyry Cu deposits in general. 1.2 Location, access and physiography The Reko Diq porphyry district is situated in the western Chagai region, Balochistan-Pakistan, ~35 km south of Afghanistan and ~80 km east of Iran. The Reko Diq district covers an area of 1000 km2 within 29o, 54’ latitude and 62o, 57’ longitude and contains a number of porphyry and epithermal style copper-gold deposits (described below). Access to Reko Diq is by a 90 min flight from provincial capitals Quetta or Karachi, or by ~14 hours journey along the RCD (Regional Cooperation for Development) highway between Quetta and Taftan. Supplies are shipped via trucks from Karachi, Quetta and the nearest towns of Dalbandin, Nokkundi and Taftan using the all-weather sealed roads (Fig. 1.1). Regional exploration is mostly conducted using a network of jeepable tracks in the region however, camels are also used in difficult rugged terrain. The western Chagai-Reko Diq region has a semi-arid desert environment with frequent sand-storms (mainly in summer) and rare flash floods in winter. Landscape is characterized by subdued topography consisting of irregular low and high hills, undulating sand-dunes, extensive playas (Hamuns), and dry alluvial plains covered with scree and minor vegetation in the valleys (Fig. 1.2). Climate varies from extreme heat (up to 48oC) in summer to severe cold (down to -10oC) in winter. The prominent wind direction is NNW in summer and NNE in winter. Rainfall is low and mostly occurs during winter months, with December having the highest precipitation of up to 82mm. The wild life and vegetation is limited due to desert environment with heavy sand-storms and lack of water in the region. However, a small number of snakes, lizards, scorpions, spiders, rats and desert foxes inhabit the region. The area is also known for its migratory birds such as the Siberian Crane locally called “Churz”. Vegetation includes minor desert shrubs and small desert plants called “Gaz” in the stream beds. The western Chagai region is thinly populated mainly along the RCD highway in the towns of Nokkundi and Taftan and other scattered villages notably in Durban Chah, Mashki Chah, Humai, Siah-Reg and Amalaf. Majority of the local population is ethnically “Baloch”, working as small traders,  2  government servants, daily-wage laborers, and skilled workers in the mineral exploration, mining and other development projects in the region.  Figure 1.1 Location and accessibility map of the Reko Diq porphyry district, western Chagai region, Balochistan province, Pakistan.  3  Figure 1.2 Landscape of the Reko Diq district and surroundings, western Chagai belt, Balochistan province, Pakistan  4  1.3 History of exploration and mining Historically, there has been very limited mineral exploration and mining activities in the Balochistan province contributing small amounts of iron, chromite, lead, sulfur and travertine marble (onyx) to the mineral economy of Pakistan (Ahmad, 1969; Muslim, 1971, Nagell, 1975; Perelló et al., 2008). The earliest geological observations by McMahon and McMahon (1897) and Vrendenburg (1901) reported lead occurrences in the Chagai hills region. Hunting Survey Corporation (HSC, 1960) in the “Colombo plan project” conducted an extensive regional reconnaissance survey focused on defining coherent geo-stratigraphic units in the Chagai belt. In 1961, a regional mineral exploration program between Geological Survey of Pakistan and US Geological Survey first identified porphyry copper mineralization near Saindak in the western Chagai region (Schmidt 1968; Ahmed et al., 1972; Khan 1974). From 1971-74, a more comprehensive mineral exploration program including geological mapping, rock geochemistry, geophysical surveys and drilling was carried out at the Saindak porphyry Cu system (Taghizadeh 1974; Khan 1974; Sillitoe 1974; Farah and Nazirullah, 1974; Wolfe 1974; Menzies and Trenholme, 1974). Reconnaissance mineral exploration programs over the entire Chagai Hills region continued during 1974-75 using Landsat-1 imagery and fixed-wing aerial reconnaissance (Sillitoe, 1975b). The subsequent exploration work by United Nations Development Program (UNDP) identified a cluster of porphyry copper-gold systems at Saindak (Sillitoe, 1975b; Sillitoe and Khan, 1977). The Geological Survey of Pakistan during the regional (1:50,000) scale mapping program in 1978-79 reported porphyry style alteration and copper oxides at unspecified centers at Reko Diq formerly known as Koh-e-Dalil (Khan and Ahmed, 1981). BHP Minerals Exploration Inc. (now BHPBilliton) and Balochistan Development Authority (BDA) signed a joint venture mineral exploration agreement in 1993 to initiate an advanced exploration program for porphyry copper mineralization in the Chagai belt. Following the orientation survey at Saindak, an extensive geochemical survey was conducted over an area of ~13,000 km2 along the Chagai belt. Approximately 5000 stream sediment samples were collected from 1993-1995 and analyzed by -80 mesh, bulk leached extractable gold (BLEG) technique. Interpretation of geochemical anomalies combined 5  with geological maps prepared from satellite imageries and ground follow-up work resulted in the delineation of 10 most prospective areas including Ziarat Pir Sultan, Dashte-Kain, Basilani, Gwanshero, Kirtaka, Machi, Ting-Darguan, Koh-e-Sultan, Durban Chah, and Reko Diq. From 1996-1998, BHP geologists completed a detailed 1:2000 prospect scale geological mapping, rock-chip geochemistry, ground magnetic and induced polarization (IP) surveys; followed by ~20,000m of RC percussion and diamond core drilling at Reko Diq (Oczlon et al., 1996; Maryono et al., 1998). This program resulted in the discovery of a supergene copper enrichment blanket at Tanjeel (originally named H4 after the discovery hole (RDRC-04), and a series of hypogene porphyry systems including H8, H9, H13, H27, H35, H36, H79 and the giant H14-H15 porphyry deposits at Reko Diq. BHP Minerals from 1997-98 extended the mineral exploration outside the Reko Diq complex and discovered several other sub-economic porphyry centers in Koh-e-Dalil, Sam Koh, Bukit Pasir and Parrah Koh areas (Perelló et al., 2008). Mincor Resources of Australia entered into an alliance agreement with BHP Minerals in 1999 and formed the 100% owned Tethyan Copper Company (TCC) to continue regional exploration and drilling at Tanjeel supergene copper deposit. In the year 2000, TCC completed the initial resource drilling program and defined a potentially leachable resource of 94 M.t. @ 0.73% Cu (Perelló et al., 2008). Meanwhile, TCC geologists continued geological mapping, geochemical sampling, ground magnetic and Induced Polarization (IP) surveys in the exploration licenses northwest of Reko Diq and identified a cluster of porphyry systems in the Bukit Pasir and Sor Baroot areas. All the exploration targets were drilled from 2003-06, for a total of ~48,000 meters of RC and diamond core drilling including 24,000 meters of infill resource drilling at Tanjeel complex. In 2006, TCC declared a total indicated resource of 214 M.t. @ 0.60% leachable supergene copper mineralization at Tanjeel (Perelló et al., 2008; Table 1.1). Later in the year 2006, Antofagasta Minerals S.A. and Barrick Gold Corporation under a joint-venture agreement acquired 100% of TCC and the 75% interest in the Reko Diq and regional licenses. After the takeover, TCC accelerated the exploration and drilling campaign from 2006-2008 and completed ~150,000 meters of infill resource drilling and a comprehensive feasibility study of western Reko Diq defining a global resource of 5.9 billion tons  6  averaging 0.41 % Cu and 0.22 g/t Au including a mineable resource of 2.2 billion tons at 0.53% Cu and 0.30 g/t Au (Tethyan Copper Company, 2013; Table 1.1).  Table 1.1 Global mineral inventory of Chagai belt, Balochistan-Pakistan Prospect  Complex  Resource category  Tons (Mt)  Cu (%)  Au (g/t)  Mo (%)  1  Inferred  20  0.50  0.50  -  1  Indicated + inferred  55  0.49  0.50  ~0.00  1  Inferred  220  0.39  0.10-0.14  <0.01  2  Measured + indicated + inferred  5,900  0.41  0.22  ~0.01  3  Indicated + inferred  214  0.60  0.00  -  3  Indicated + inferred  335  0.38  0.19  <0.01  3  Inferred  212  0.37  0.40  <0.01  3  Inferred  45  0.29  0.61  <0.01  7,001  0.43  0.35  0.01  North  Saindak  South East H14-H15 Tanjeel  Reko Diq  H8 H13 H35  Total mineral resource 1  Sillitoe and Khan (1977) Tethyan Copper Company (2013) http://www.tethyan.com/TheRekoDiqProject/RekoDiqResource.aspx 3 Tethyan Copper Company presentation at 7th Annual Convention of PDAC, Toronto, March 3-5 (2008) 2  1.4 Porphyry copper deposits Porphyry deposits form in magmatic arcs at convergent plate boundaries, above zones of active subduction, in settings, which range from primitive island arcs to continental arc margins (Sillitoe, 1972, Tosdal and Richards, 2001; Richards, 2003; Fig. 1.3). Most large scale porphyry copper deposits (Ballard et al., 2001; Gustafson et al., 2001; Maksaev et al., 2004; Deckart et al., 2005; Perelló et al., 2007; Perelló et al., 2008; Redmond and Einaudi, 2010; this study) containing >1 billion tones @ 0.50 % Cu (Table 1.2) are linked to arc magmas at continental margins as in the Andes (Camus and Dilles, 2001), southwestern North America (Sillitoe, 2008) and central Neo-Tethys (Richards, 2003; Shafiei et al., 2009; Richards et al., 2012). Formation of porphyry Cu deposits involves a variety of tectono-magmatic processes and hydrothermal events (Richards, 2003; Groves et al., 2005). The size, grade 7  and metallogeny of porphyry deposits depends upon the volume, composition and evolution trends of the magma interacting with host rocks (Tosdal et al., 2009). Partial melting of lower crust (~100 km) generates hot, hydrous basaltic magma, which evolve into volatile rich, metalliferous magma of andesitic to dacitic composition (~20-30 km) intruding porphyry dykes (6-12 km) and form porphyry Cu deposits between 1-6 km (Hildreth and Moorbath, 1988; Hedenquist and Lowenstern, 1994; Gustafson, 1979; Burnham, 1979; Richards, 2003; Chiaradia et al., 2004; Rohrlach and Loucks, 2005; Candela and Piccoli, 2005; Chambefort et al., 2008). Porphyry Cu related magmas are generally oxidized and sulfur rich (~1000ppm) in the form of sulfate and chalcophile elements such as Cu and Au (Ballard et al., 2002; Field et al., 2005). Magmatic volatiles released from the underlying magma chamber result in metalliferous and sulfur-rich magmatic-hydrothermal fluids, which rise through hydrofractures and precipitate Cu-Fe-sulfides in response to fluid phase separation, cooling, fluid-rock reaction and mixing with external fluids (Gustafson and Hunt, 1975; Brimhall, 1979; Reynolds and Beane, 1985; Hemley and Hunt, 1992; Hedenquist and Lowenstern, 1994; Dilles et al., 2000; Redmond et al., 2004; Proffett, 2009; Gruen et al., 2010; Landtwing et al., 2005, 2010). Paragenetic studies suggest that most porphyry deposits are spatially and temporally associated with multiple and superimposed porphyry intrusions and hydrothermal alteration events (e.g., Gustafson et al., 2001; Vry et al., 2010; Redmond and Einaudi, 2010). Much of the copper and gold is deposited with intense potassic alteration and early quartz “A-type” veins truncated by late-stage sulfide “D-type” veins accompanied by sericite-chlorite (clay) alteration (Meyer and Hemley, 1965; Lowell and Guilbert, 1970; Gustafson and Hunt, 1975; Pollard and Taylor, 2002; Proffett, 2003; Redmond and Einaudi, 2010).  8  Table 1.2 Characteristics of large-scale known porphyry copper deposits worldwide.  Porphyry Cu-Au  Age (Ma) 411-307  Resource (Mt) 2,470  Cu (%) 0.83  Au (g/t) 0.32  Mo (%) -  Kerman, Iran  Porphyry Cu-Au (Mo)  12  1,200  1.20  0.27  0.03  Reko Diq  Chagai, Pakistan  Porphyry Cu-Au (Mo)  12-10  5,900  0.41  0.22  0.01  Pebble Copper  Alaska, USA  Porphyry Cu-Au (Mo)  90  5,942  0.42  0.35  0.01  Butte  Montana, USA  Porphyry Cu (Mo-Au)  76-61  5,230  0.67  0.04  0.03  Yerington  Nevada, USA  Porphyry Cu (Au)  169-168  1,560  0.43  0.007  -  Bingham Canyon  Utah, USA  Porphyry Cu-Au (Mo)  40-37  3,230  0.88  0.49  0.02  Highland Valley  BC, Canada  Porphyry Cu (Mo)  202-190  1,940  0.42  0.003  0.02  Batu Hijau  Sumbawa, Indonesia  Porphyry Cu-Au  5  1,640  0.44  0.348  -  Grasberg-Ertsberg  Indonesia  Porphyry Cu-Au  4-3  3,400  1.12  1.07  -  Bajo de La Alumbrera  Argentina  Porphyry Cu-Au-Mo  8-7  780  0.52  0.67  0.04  El-Teniente  Chile  Porphyry Cu (Mo)  7.1-4.6  12,480  0.63  0.035  0.02  Chuquicamata  Chile  Porphyry Cu (Mo-Au)  33-31  7520  0.55  0.04  0.024  El-Abra  Chile  Porphyry Cu (Mo)  37  1,620  0.62  -  0.01  Clark,1993; Dilles et al., 1997, Sillitoe, 1991  El-Salvador  Chile  Porphyry Cu (Au-Mo)  970  866  0.63  0.10  0.01  La Escondida  Chile  Porphyry Cu (Au-Mo)  38  2,260  1.15  0.19  0.021  Los Pelambres  Chile  Porphyry Cu (Mo)  10  4,190  0.63  0.02  0.016  Gustafson and Hunt, 1975; Cornejo et al.,1997; Clark,1993; Gustafson and Quiroga,1995; Cook et al., 2005; Lee, 2008 Alpers, 1989; Clark, 1993; Zentilli et al.,1994; Sillitoe, 1997; Skewes and Stern,1995; Garza et al., 2001; Camus, 2002 Camus et al., 1996; Camus and Dilles, 2001; Stein et al., 2002; Perelló et al., 2007  Rio Blanco Los Bronces-Andina Quellaveco  Chile  Porphyry Cu (Mo)  7.4-5.4  6,990  0.75  0.035  0.018  Clark, 1993; Serrano, et al.,1996; Vargas, et al.,1999; Warnaars, et al., 1985; Deckart, et al., 2002  Peru  Porphyry Cu (Mo)  54  974  0.65  -  0.02  Clark, 1993; Perello et al., 2003  Cadia Hill / Cadia E  Australia  Porphyry-skarn Au-Cu  440  1070  0.31  0.77  -  Holliday et al., 2002; Wilson et al., 2003, Cook et al., 2005  Deposit  Province / Country  Deposit Type  Oyu Tolgoi  Mongolia  Sar Cheshmeh  References Perelló et al., 2001; Kirwin et al., 2005; Wainwright et al., 2011 Waterman and Hamilton,1975; Carten et al.,1993; Clark,1993; Atapour and Aftabi, 2007 Perello et al., 2008; Razique et al., 2007, 2010, 2011 and Richards et al., 2012 Bouley et al., 1995; Gregory and Lang, 2011, Lang et al., 2013; Gregory et al., 2013; Goldfarb et al., 2013 Meyer et al.,1968; Dilles et al., 2003; Brimhall, 1977; Rusk et al., 2008 Dilles,1987; Dilles and Einaudi,1992; Dilles and Proffett,1995; Dilles et al., 2000 Babock et al.,1995; Keith et al., 1998; Redmond and Einaudi, 2010; Landtwing et al., 2010; Gruen, et al., 2010 Casselman et al.,1995; Lang,1995 Meldrum et al.,1994; Garwin, 2002; Arif and Baker, 2004; Mitchell et al.,1998 McDowell et al.,1996; Pollard and Taylor, 2002; Pollard et al., 2005 Carten et al.,1993; Guilbert,1995; Sillitoe, 1991; Proffett, 2003; Harris et al., 2005 Clark,1993; Camus et al., 1996; Skewes et al., 2002; Maksaev et al., 2004; Camus, 2002; Cannell et al., 2005 Clark, 1993; Sillitoe,1991; Zentilli et al.,1994; Ossandon et al., 2001; Camus, 2002  9  Figure 1.3 Schematic illustration of the subduction related arc magmatism, evolution path and porphyry Cu deposit formation at the continental plate margins (After Sillitoe, 1972; Hildreth and Moorbath, 1988; Winter, 2001; Richards, 2003; Hollings, 2005; Tosdal et al., 2009)  10  A  B  Figure 1.4 (A) Reko Diq in the context of Tethyan porphyry Cu belt and global distribution of porphyry Cu deposits (Kirkham and Dunne, 2000; Goodfellow, 2006); (B) Comparison of Reko Diq amongst twenty known large-scale porphyry copper deposits worldwide (based on tonnage in Mt; Cooke et al., 2005).  11  1.5 Overview of the Reko Diq porphyry complex Reko Diq is a large (10 x 10 km) volcano-magmatic complex represented by andesitic volcanic and volcanogenic sedimentary rocks and a cluster of diorite, granodiorite and quartz-diorite intrusions emplaced from Oligocene to Miocene. There are at least eighteen well defined economic and sub-economic porphyry Cu systems, clustered mainly along the southern and southwestern margin of Reko Diq complex. Available geochronological studies reveal that these porphyry systems are linked to at least four distinct magmatic events of Miocene age (Perelló et al., 2008; Ivascanu and Fletcher, 2008; Razique et al., 2011). Early Miocene (23.3 Ma) diorite and quartz-diorite porphyry intrusions preserve a supergene Cu enrichment blanket in the central Reko Diq Tanjeel area. The chalcocite blanket is up to 80m thick and roughly 800 x 500 meters in dimension containing an indicated and inferred resource of 214 Mt at 0.60 % Cu (Perelló et al., 2008). The 2nd phase middle Miocene event (18-16 Ma) represents weakly mineralized hornblende-rich diorite intrusions that formed the Sor Baroot porphyry cluster northwest of Reko Diq complex. The 3rd phase middle to late Miocene (12.9-11.9 Ma) magmatism is responsible for the gold-rich porphyry Cu deposits including H79, H14, H15 and H13 clustered in the western Reko Diq and are the focus of this research study (see below). Other porphyry centers such as Parrah Koh, H36, H9, H7 and H8 in the southern Reko Diq corresponds to a younger generation of late Miocene (11-10 Ma) diorite porphyry intrusions (Perelló et al., 2008, Fu et al., 2006; Fig. 1.5).  12  Figure 1.5 Satellite image of the Reko Diq igneous complex, illustrating the spatial and temporal distribution of Miocene porphyry copper deposits clustered within the inner ring structure. *Note: The Reko Diq western porphyry cluster (study area) in red.  13  1.6 Objectives of this study Reko Diq western porphyry complex is a classic example of multiple and superimposed magmatic-hydrothermal systems leading to large-scale economic porphyry Cu deposits (e.g., Gustafson et al., 2001; Pollard and Taylor, 2002; Redmond and Einaudi, 2010; this study). The H14 and H15 porphyry systems host some of the world’s largest concentrations of copper and gold, and contain a global resource of 5.9 billion tons with an average grade of 0.41% Cu and 0.22 g/t Au, plus additional 212 million tons @ 0.40% Cu and 0.40g/t Au in the adjacent H13 complex (Perelló et al., 2008; Tethyan Copper Company, 2013). The H14 and H15 porphyry deposits are centered on multiple crosscutting porphyry dykes emplaced into andesitic volcanic, pyroclastic and the underlying volcanogenic sedimentary rocks. These deposits are characterized by typical concentric patterns of hydrothermal alteration with a central potassic zone surrounded outwards by transitional sericite-chlorite (clay), sericitic (phyllic) and propylitic alteration zones (e.g., Myer and Hemley, 1965; Lowell and Guilbert 1970). Interaction of porphyry intrusions and hydrothermal alteration played a vital role in the formation of the giant H14 and H15 porphyry Cu deposits. Both are genetically similar in lithology and hydrothermal facies architecture however, there are fundamental variations in the timing of porphyry emplacement, intensity and distribution of hydrothermal alteration, veins and Cu-Fe-sulfides. These variations provide an excellent opportunity to examine important aspects of porphyry Cu deposit formation and understand the anomalies that characterize the large-scale H14 and H15 ore deposits. The main objectives of this research study were to (1) establish the geological framework of Reko Diq complex; (2) constrain the relative and absolute timing of porphyry intrusions, hydrothermal alteration and sulfide deposition; (3) define the evolution and space-time relationship of magmatichydrothermal events; (4) characterize the ore-bearing hydrothermal fluids; and (5) develop an overall 4-D genetic model of Reko Diq H14-H15 porphyry deposit. 1.7 Research approach and methodology A stepwise approach employing field investigations and analytical techniques was adopted to achieve the research goals and objectives. As a first step, detailed 1:2000 scale lithology and alteration maps were prepared with two east-west geological sections across 14  H14 and H15 porphyry deposits. Over 10,000m of RC percussion rock-chip and diamond drill core logging was carried out in 18 most representative drill holes along east-west sections in H14 and H15 complexes (Table A.1). Geological logging was focused on recording the lithological units, mineral constituents, textures, veins and other key features like chilled margins, vein truncation and xenoliths of pre-existing rocks (Tables A.2, A3). These characteristics are used to establish the paragenetic sequence of porphyry intrusions, hydrothermal alteration, veins and Cu-Fe-sulfides, and allowed systematic collection of samples for laboratory analysis (Table A.4). Interpretation of geological maps, cross sections, drill logs as well as compilation and review of previous work established the lithologic and hydrothermal facies architecture and allowed collecting ~180 samples for further laboratory analysis (given below). A total of 145 petrographic thin sections were studied leading to the selection of 63 most representative and least altered samples for litho-geochemistry, 8 samples for radiogenic isotopes, 10 samples for zircon U-Pb SHRIMP-RG geochronology and trace element geochemistry, 2 samples for molybdenite Re-Os chronometry, 12 samples for X-ray diffraction, and 6 samples for fluid inclusion analysis presented in corresponding chapters in this dissertation. 1.8 Overview of the dissertation This dissertation is presented as five chapters (Chapter 2-6), four of which are manuscripts to be published in refereed journals. Field work and systematic sampling is a key component of this research study conducted in three separate field seasons including (i) 2 months from July-August in 2008; (ii) 3 months from May-July in 2009; and (iii) 3 months from February-April in 2010. Field investigations included detailed (1:2000) geological mapping on UTM-grid in temperatures ranging from -10oC to +40oC, on-site (outdoors), geological logging of several thousand meters of RC percussion rock-chips and diamond drill core with simultaneous sample collection for laboratory analysis presented in this dissertation.  15  Chapter 2 describes the overall geological framework of Reko Diq district. Literature review and compilation of previous work combined with field observations established the regional geo-tectonic setting, metallogeny and stratigraphy of the district. Extensive geological mapping, drill core examination and petrographic thin section studies presented in this chapter described the local stratigraphic units and four distinct episodes of Miocene porphyry intrusions at the Reko Diq complex. Additional selective field mapping (1:5000) based on satellite images is integrated with project’s historic data leading to define the spatial and temporal framework of all known porphyry deposits in the district. Chapter 3 is focused on the petrology and petrochemical evolution of middle to late Miocene porphyry Cu-Au (Mo) deposits at western Reko Diq. Surface geology maps and cross sections (1:2000-scale) supported by zircon U-Pb (SHRIMP-RG) ages are presented to establish the sequence and geometry of intrusive rocks, and space-time distribution of Reko Diq western porphyry systems. Additional drill core examination and petrographic thin sections in this chapter describes the textural and compositional characteristics of multiple porphyry intrusions in H14 and H15 complexes. The whole-rock geochemistry from ALS Minerals, North Vancouver, combined with radiogenic isotope compositions from PCIGR (UBC) is used to link the petrochemical data with absolute geochronologic ages for Reko Diq region. Interpretation of major and trace element (REE) concentration and ratios, together with radiogenic Pb, Sr and Nd isotopic compositions constrain the composition and petrogenetic evolution of Reko Diq H14 and H15 porphyry deposits. Chapter 4 reveals the magmatic-hydrothermal geochronology of Reko Diq western porphyry systems. Evaluation of available geochronologic data (Fu et al., 2006; Perelló et al., 2008; Ivascanu and Fletcher, 2008) provided initial temporal constraints of Miocene magmatic events in the western Chagai Reko Diq region. An outcrop geology map (1:2000-UTM-grid) is presented to illustrate the distribution and field relationship of Miocene porphyry intrusions and late Oligocene volcanic rocks in western Reko Diq. A comprehensive study of zircon U-Pb (SHRIMP-RG) analysis at Stanford-USGS micro analyzer center (SUMAC) in California and molybdenite Re-Os (NTIMS) chronometry from University of Alberta is presented in this chapter. This dataset provides the absolute timing and duration of porphyry intrusions and ore-forming hydrothermal events occurred 16  in the western porphyry complex. Moreover, precise age constraints of distinct porphyry intrusions and sulfide mineralization established the space-time evolution and lifespan of H79, H15, H14 and H13 porphyry Cu deposits at Reko Diq. Chapter 5 presents the 1st study on the cooling and fractionation history, and physio-chemical environment of the magma chamber that formed the giant H15 and H14 ore systems. A surface geology map (1:2000-UTM-grid) illustrate the sequence and spacetime distribution of porphyry intrusions in western Reko Diq. Representative drill core examination is presented to describe the compositional and textural characteristics of intrusive rocks in H15 and H14 complexes. Zircon SHRIMP-RG trace element geochemistry (REE, Y, and Hf and Ti-in-zircon thermometry) combined with U-Pb ages obtained at Stanford-USGS laboratories are the main research components presented in this chapter. Evaluation and interpretation of these datasets provided an excellent framework of magma crystallization, mixing, cooling and fractionation trends associated with H79, H15, H14 and H13 porphyry deposits. Furthermore, variation in multi-valent trace element (EuN/EuN* and CeN/CeN*) values in zircons offered insights into the oxidation state and metallogenic fertility of the magma that formed the giant H15 and H14 porphyry deposits. Chapter 6 is focused on the hydrothermal alteration, paragenesis and evolution of Reko Diq H15-H14 porphyry deposit. The porphyry intrusions and host rocks are briefly described using core photographs, whereas the spatial distribution of hydrothermal alteration assemblages is illustrated using the surface alteration maps. Extensive geological logging of diamond core and RC drill holes led to the constructions of east-west alteration sections, defining the vertical and lateral distribution of hydrothermal facies in H15 and H14 porphyry centers. The drill core examinations and petrographic thin sections presented herein describes the mineralogical characteristics in the deep potassic, sodic-calcic, orestage potassic, transitional sericitic and outer phyllic and propylitic alteration zones in H15 and H14 porphyry systems. Additional drill core observations are presented to illustrate the relationship between porphyry intrusions, hydrothermal alteration and multi-generation veins. The north-south long section is presented to illustrate the overall lithologic, alteration and sulfide distribution model of the entire western porphyry complex. A reconnaissance study of fluid inclusions petrography and microthermometry is presented to 17  define the characteristics and evolution of magmatic-hydrothermal fluids in the deep, central and shallow levels of the H14 complex. All research contributions in this dissertation revolve around Reko Diq western porphyry complex with a particular focus on the geology and evolution of H15 and H14 porphyry Cu-Au (Mo) deposits. Chapter 3, 4, 5 and 6 have been prepared as a stand-alone publication based on integrated studies which result in some overlapping and repetition between chapters.  18  Chapter 2 - Geological framework of Reko Diq porphyry complex 2.1 Introduction The discovery of Reko Diq porphyry complex along with other porphyry Cu prospects identifies Chagai magmatic arc terrane as an important emerging metallogenic province within the Tethyan orogenic belt. Reko Diq is one of the world’s largest porphyry copper-gold districts, containing 18 porphyry Cu and Cu-Au deposits and prospects clustered within Miocene volcanic complex encompassing an area of 10 x 10 km2. Reko Diq porphyry complex is located at 290, 05 latitude and 620, 00 longitude in the Chagai magmatic belt, western Pakistan bordered with Afghanistan in the north and Iran to the west (Figs. 2.1 and 2.2). The Reko Diq western porphyry complex includes H79, H15, H14 and H13 porphyry centers, in which the H14 and H15 porphyry systems constitutes the main copper-gold resource of 5.9 billion metric tons @ 0.41% Cu and 0.22g/t Au (Tethyan Copper Company, 2013) and is the focus of this research study. Placing porphyry Cu deposits from Chagai belt within a geo-tectonic, stratigraphic, magmatic and metallogenic context is important, as most economic mineral deposits are found within specific rock units of volcanic arcs at convergent plate boundaries such as the central Andes (Camus and Dilles, 2001), southwestern North America (Sillitoe, 2008), Papua New Guinea and Philippines (Gow and Walshe, 2005) Kerman Iran (Shafiei et al., 2009) and Chagai belt Pakistan (Siddiqui et al., 2004; Perelló et al., 2008). The magmatic sequences from the Chagai belt evolved in response to changes in the tectonic events such as rifting and collision with aseismic ridges and continental margins (Clift, 1995; Tosdal et al., 2001; Richards, 2003; Hollings et al., 2005). Geodynamic changes in the plate tectonics including arc reversals (Solomon, 1990), subduction of young lithosphere, the geometry and rate of subduction (Mungall, 2002), flat subduction (Kay and Mpodozis, 2001) or even the cessation of subduction (Sillitoe, 1997) can also lead to the environments conductive for porphyry copper deposit formation. Multiple magmatic and hydrothermal events as in most porphyry systems (e.g., Gustafson and Hunt, 1975; Garwin, 2002; Redmond and Einaudi, 2010) appear to have 19  played an important role in the formation of economic porphyry copper-gold deposits at western Reko Diq. A first step towards a geologic model for Reko Diq is an understanding of the geological framework of the Chagai belt and Reko Diq region. This chapter describes the regional geology, tectonic setting and stratigraphy as well as periodic magmatic events leading to form porphyry Cu deposits in Chagai belt. Field observations combined with available U-Pb-zircon and K-Ar-biotite ages are presented to define the regional geologic and metallogenic framework emphasizing the spatial and temporal framework of Reko Diq porphyry cluster. Detailed lithological and hydrothermal facies architecture, textural, mineralogical and geochemical characteristics of Reko Diq H14 and H15 porphyry deposits are discussed in Chapter 3. 2.2 Tectonic framework Reko Diq porphyry complex lies in the western Chagai magmatic arc terrane of Balochistan province, Pakistan. The Chagai magmatic belt (Sillitoe and Khan, 1977), also known as Chagai Island arc (Siddiqui, 2004) and Makran magmatic arc (Doebrich et al., 2007), is an east-west oriented, 400 km long and 140 km wide magmatic belt of calcalkaline suite volcanic, plutonic rocks and associated sedimentary rocks. In a regional geotectonic framework, Chagai belt is a segment of the several thousand km-long MakranZagros belt (Farhoudi and Karig, 1977) which extends from southwestern Iran through western Pakistan and adjacent southern Afghanistan (Fig. 2.1). In the regional geotectonic context, the Chagai magmatic arc is part of the ~5000 km long continental-scale Tethyan belt which spans eastern Europe and Asia. Makran-Zagros belt is interpreted to have been constructed as a result of northward subduction of the Arabian oceanic plate beneath the southern edge of the Eurasian plate, contemporaneous with the amalgamation of central Iran and Afghanistan micro-continental blocks (Sillitoe, 1975a, 1978; Sillitoe and Khan, 1977; Lawrence et al., 1981). This subduction system formed a 500 km wide trench-arc system in southwest Pakistan which extends from Makran subduction complex in the south to Chagai magmatic arc in the north (Jacob and Quittmeyer, 1979; Dykstra and Birnie, 1979). Five major morphostructural units, including (1) Makran trench-arc; (2) Hamun-e-Mashkel fore-arc basin; (3) Ras KohMirjawa uplift block; (4) Dalbandin Trough; and (5) Chagai magmatic arc (Hunting 20  Survey Corporation, 1960; Arthurton et al., 1982), form the trench-arc system from south to north. Major arc parallel faults such as the Great Chapper fault on the south and NNE trending Chaman transform fault separate some of the morphostructural blocks (Perelló et al., 2008; Fig. 2.1). The Reko Diq igneous complex in the western Chagai belt is bounded by Drana Koh fault in the north and Tuzgi in the south. These east-west oriented sub parallel fault systems are intersected by NE-SW trending faults that correspond to the regional structural trend favorable for porphyry Cu formation. The Miocene porphyry intrusions generally follow these trends as indicated by the NW alignment of porphyry intrusions in the southern Reko Diq complex (Fig. 2.2).  Figure 2.1 Regional geotectonic setting of Makran-Chagai trench-arc system extended into Iran. Based on (Jacob and Quittmeyer, 1979; Dykstra and Birnie, 1979; Kukowski et al., 2001; Perelló et al., 2008).  21  2.3 Geologic framework Chagai magmatic arc is a large east-west oriented antiform involving rocks as young as Late Cretaceous Sinjrani volcanic and younger sedimentary sequences. Most of the igneous complexes in the Chagai belt are aligned parallel to the southerly convex shaped Great Chapper and Laki Koh faults with continuous exposures (>100 km) along east, northwest and northeast strikes (Fig. 2.2). Deformation in the region is interpreted to have occurred prior to the deposition of the Late Oligocene Reko Diq volcano-sedimentary sequence and emplacement of Miocene porphyry intrusions (Perelló et al., 2008). The Chagai magmatic belt is composed of alkaline to calc-alkaline volcanic, plutonic and associated sedimentary rocks. The Late Cretaceous Sinjrani volcanic group (Hunting Survey Corporation, 1960; Ahmed et al., 1972; Sillitoe and Khan, 1977; Arthurton et al., 1979, 1982; Siddiqui, 1986, 1996, 2004) was intruded by km-scale batholiths of Chagai intrusions (Hunting Survey Corporation, 1960; Nagell, 1975; Breitzman, 1979; Breitzman et al., 1983) emplaced during multiple magmatic episodes of Eocene (55-44 Ma) age (Perelló et al., 2008). Chagai intrusions represent older diorite to granodiorite intrusions and younger granodiorite and quartz-monzonite with lesser monzogranite and granite intrusions, extensively exposed in the eastern Chagai belt (Dykstra, 1978). In contrast, the western Chagai Reko Diq region is dominated by isolated stocks, domes, lopoliths, dikes and sills of mainly dacitic composition collectively known as the Sor Koh intrusions (Fig. 2.2; Hunting Survey Corporation, 1960; Arthurton et al., 1982). The Sinjrani volcanic group is overlain by a ~2,000-m-thick sequence of calcareous rocks of the Latest Cretaceous Humai formation and clastic sedimentary rocks of the Paleocene Juzzak, Eocene Saindak and Oligocene Dalbandin formations, widely exposed in the western Chagai Reko Diq region (Perelló et al., 2008). The Late Oligocene andesitic volcanic and volcaniclastic rocks of Reko Diq and Amalaf formations, and the underlying red bed clastic sedimentary rocks of Dalbandin formation are intruded by a series of porphyry Cu related Miocene diorite, quartz-diorite and granodiorite intrusions, notably in the Reko Diq porphyry district (Tables 2.1 and 2.2). Younger volcanism from Pliocene to Pleistocene (2.0±0.8Ma; Perelló et al., 2008) led to the formation of a 2,500-m-high and 22  35-km-long Koh-e-Sultan stratovolcanic complex along a NW trend in the region (Perelló et al., 2008). Other younger volcanic centers such as Dam Koh, Grim Koh, Koh-e-Dalil, Speghar Koh and the isolated lava domes of Alam-Reg and Humai-Sam are scattered between Koh-e-Sultan and Reko Diq volcanic complexes. Younger terrace surfaces composed of silt, sand, fan gravel and interbedded air-fall and tuffs of early Pliocene Kamanrod formation (Arthurton et al., 1982) conform to the regional pedimented surface of Balochistan Plateau (Fig. 2.2; Perelló et al., 2008). 2.4 Metallogenic framework Porphyry Cu mineralization in the Chagai belt is associated with at least five distinct episodes of magmatic-hydrothermal events. The earliest Middle to Late Eocene (43-37 Ma) event formed the Ziarati and Gwanshero (Missi Koh) porphyry systems associated with sericitic alteration, silicification and quartz vein stock-work within quartzmonzodiorite porphyry intrusions (Breitzman, 1979; Perelló et al., 2008). The second event of early Miocene age (24-22 Ma) led to the formation of Ting Dariguan and Ziarat Pir Sultan prospects in eastern Chagai, as well as Saindak (Ahmed et al., 1972) and Reko Diq (Tanjeel) porphyry Cu deposits in the western Chagai belt (Perelló et al., 2008; Fig. 2.2). The Saindak porphyry Cu deposit contains ~300Mt with an average grade of 0.46% Cu, and 0.35g/t Au, associated with potassically altered quartz-diorite and tonalite porphyry intrusions (Sillitoe and Khan, 1977). The early Miocene magmatichydrothermal event at Reko Diq formed significant supergene copper enrichment at Tanjeel prospect. The chalcocite blanket at Tanjeel contains an indicated resource of 214Mt @ 0.6% Cu within sericitic and argillic altered diorite and quartz-diorite intrusions and andesitic volcanic host rocks (Perelló et al., 2008). The third magmatic-hydrothermal event occurred during the middle Miocene (1814 Ma), forming a number of sub-economic porphyry Cu systems including Sor Baroot, Reko Diq H11, Koh-e-Dalil (NE), Sam Koh and Kirtaka, all located in the western Chagai region. This event is characterized by distinct amphibole-rich diorite porphyry intrusions with a moderate grade of ~0.30% Cu and 0.15 g/t Au restricted to potassic alteration (Table 2.1). 23  The fourth middle to Late Miocene (12.9 -11.9 Ma; this study) event is responsible for the large-scale gold-rich porphyry Cu mineralization at western Reko Diq. This magmatic-hydrothermal event is the focus of this research study described in the following chapters. The fifth late Miocene (11-10 Ma) magmatic event result in the formation of all other porphyry Cu deposits at Reko Diq and the adjacent porphyry systems at Koh-e-Dalil, Parrah Koh and Bukit Pasir (Schloderer and McInnes, 2006; Razique et al., 2007; Perello et al., 2008). These porphyry deposits are linked to a series of hydrothermally altered stocks and dykes of diorite, quartz-diorite and granodiorite intrusions clustered within Reko Diq complex (Table 2.2). Younger Late Miocene to early Pliocene (~6-4 Ma) mineralization is minor and includes the high-sulfidation epithermal system at Washaab prospect in Koh-e-Sultan volcanic complex (Fig. 2.2; Perelló et al., 2008).  Figure 2.2 Location and regional geology map of the Chagai magmatic belt, Balochistan province, Pakistan. (after Hunting Survey Corporation, 1960; Perelló et al., 2008). The Reko Diq porphyry complex is highlighted to the west (box outline).  24  Table 2.1 Geological characteristics of selected porphyry systems in the Chagai belt, Balochistan province, Pakistan Porphyry intrusions Prospect  Hydrothermal alteration  Ore mineralogy  Lithology  Age (Ma)  Method  Dimension (m2)  Saindak3  Quartz-diorite, Tonalite  22.18 ± 0.4  U-Pb-Zr  1000x800  Pot, ser, prop, anhydrite  Concentric  2000  Cpy, bor ± cov  Sor Baroot3  Hornblende-diorite  16.9 ± 0.91  200x150  Pot, ser-chl, ser-arg, prop  Concentric  1000  Quartz-diorite Granodiorite, diorite  11.0 ± 1.1  WR-hblbio WR-bio  400x200  Pot, ser-arg, prop  Concentric  2000  12.5 ± 0.2  U-Pb-Zr  1000x800  Pot, ser-chl, arg, ser, prop  Concentric  4000  Bukit Pasir  2  1  Reko Diq -H15  Quartz-  Zones  Geometry  (m2)  Hypogene  Supergene (Weak-minor)  Avg. Grade Cu%  Aug/t  Cc, Cu-oxi  0.40  0.25  Cpy, bor  Cu-oxi  0.35  0.20  Cpy ± bor Cpy, bor, cov, mol  Cc, Cu-oxi  0.35  <0.20  Cc, Cu-oxi  0.50  0.30  0.60  <0.01  Diorite, late dacite  12.45 ± 0.17  U-Pb-Zr  300 x 200  Pot, ser-chl, ser, prop  Concentric  1000  Cpy, bor  Cc-blanket,, Cov, Cu-oxi Cu-oxi  0.40  0.20  Koh-e-Dalil4  Diorite, late dacite  10.1 ± 0.1  K-Ar- bio  400x200  Pot, ser-chl, ser, prop  Concentric  1800  Cpy ± bor  Mal, azu  0.45  0.25  Sam Koh  Diorite, late dacite  ND  ND  300x300  Pot, ser-chl, ser, prop  Concentric  1500  Cpy ± bor  Mal.  0.40  0.20  Durban Chah  Diorite  ND  ND  100x150  Pot, ser, prop, calc-silicate  Linear  1000  Cpy  Mal, azu  0.30  0.10  Koh-e-Sultan2  Diorite, dacite  5.9 ± 2.8  Ar-Ar-alu  200x100  Pot, ser-chl, advance arg  Vertical  2000  Cpy, bor  Cu-oxides  0.35  0.20  Kirtaka2  Quartz-diorite  18.35 ± 0.16  Ar-Ar-bio  300x200  Pot, ser ± arg, prop  Concentric  1500  Cpy  Mal.  0.35  <0.20  Ting Darguan2  Diorite, Quartz-diorite  23.84 ± 0.17  Ar-Ar-bio  400x300  Pot, ser ± arg, prop  Concentric  1800  Cpy ± bor  Mal, azu  0.35  <0.20  Machi2  Diorite, Quartz-diorite Granodiorite, Monzonite Quartz-diorite, Granodiorite Granodiorite, Monzodiorite Quartz-diorite  24.3 ± 1.0  WR-ser  200x100  Pot, ser ± arg, prop  Concentric  800  Cpy ± bor  Chry  0.45  <0.20  37.2 ± 0.2  Ar-Ar-bio  800x500  Ser ± arg, prop  Linear  1500  ND  Mal.  ND  ND  ND  ND  600x300  Ser ± arg, prop  Linear  1200  ND  Mal.  ND  ND  21.0 ± 0.17  WR-bio  400x250  Pot, ser-chl ± arg, prop  Concentric  1000  Cpy ± bor  Mal, azu  0.34  <0.2  ND  ND  30 x100  Pot, ser-chl ± arg, prop  Concentric  1000  Cpy ± bor  Mal, azu  0.40  <0.20  3  Tanjeel  Parrah Koh  3  2  Ziarate  Gwanshero Ziarat Pir Sultan2 Dasht-e-Kain  Diorite, Quartz-diorite  23.3 ± 0.2  U-Pb-Zr  1000x1500  Ser-arg, prop  Linear  2000  Cpy, bor  Abbreviations: ND = no data available (undefined), volc = volcanic rocks, WR = whole-rock, Zr = zircon, bio = biotite, Pot = potassic, ser = sericite, chl = chlorite, arg = argillic, prop = propylitic, Cpy. = chalcopyrite, bor. = bornite, oxi = oxides, cc = chalcocite, cov = covellite, cup = cuprite, mol = molybdenite, Mal = malachite, azu = azurite, Chry = chrysocolla 1 Age determinations in this study by Stanford-USGS Micro-Analysis Center in California, USA 2  Age determinations by Geological Survey of Chile (SERNAGEOMIN), Santiago Chile (Perelló et al., 2008)  3  Age determinations by GEMOC Macquarie University, Australia (Fu et al.,2006)  4  Age determination by Amdel Limited Mineral Services, Australia  25  Table 2.2 Geological features of the selected porphyry systems in the Reko Diq complex, Chagai belt, Balochistan-Pakistan. Lithology Prospect  Au (g/t)  Cpy, bor  0.40  0.20  U-Pb-Zr  Granodiorite, Quartz-diorite  12.5 ± 0.2  U-Pb-Zr  1000 x 800  pot ± ser-chl + late-veins  1500  Cpy, bor  Cc, Cov, Cu-oxi  0.50  0.30  H141  Granodiorite, Quartz-diorite  12.1 ± 0.2  U-Pb-Zr  1200 x 800  pot ± ser-chl + late-veins  1800  Cpy, bor  Cc, Cu-oxi  0.50  0.30  Quartz-diorite, late-dacite  11.9 ± 0.2  U-Pb-Zr  500 x 400  pot ± ser-chl + late-veins  1500  Cpy, bor,  Cu-oxi (mal)  0.40  0.35  H14E  Diorite  14.2 ± 0.1  U-Pb-Zr  300 x 200  pot + ser-chl  400  Cpy ± bor  Cu-oxi (mal)  0.40  0.25  H15W  Diorite, Quartz-diorite  ND  ND  400 x 300  pot + ser-chl  500  Cpy  Cu-oxi  ND  ND  2  H35  3  pot + ser-chl  Foot prints (m2) 1000  Cu (%)  12.9 ± 0.3  H13  Ore related  Supergene (minor-weak) Cu-oxi (mal)  Hornblende-diorite  1  Method  Avg. grade  1  H15  Age-Ma  Cu-ore mineralogy  Dimension (m2) 500 x 300  H791  Porphyry intrusions  Hydrothermal alteration  Hypogene  Quartz-diorite, late-dacite  13.8 ± 0.1  K-Ar-bio  400 x 300  pot ± ser-chl + late-veins  1000  Cpy, bor  Cu-oxi (mal-azu)  0.40  0.35  H12  Diorite, Quartz-diorite  ND  ND  400 x 300  pot ± ser-chl + late-veins  700  Cpy ± bor  Cu-oxi  0.35  0.20  H11  Diorite  ND  ND  200 x 150  pot + late-veins  800  Cpy  Cu-oxi (mal)  0.35  0.20  Tanjeel3  Diorite, Quartz-diorite  23.3 ± 0.2  U-Pb-Zr  1700 x 500  ser ± chl-clay  2000  Cpy >250m  Cc, Cov, Cu-oxi  0.60  0.10  Tanjeel-N  Diorite, late-dacite  ND  ND  300 x 200  pot + ser-chl + late-veins  500  Cpy, bor  Cu-oxi  ND  ND  H10  Quartz-diorite  ND  ND  300 x 200  ser ± chl-clay  800  Minor cpy  Cc, Chry  0.30  0.10  H2  Diorite, late-dacite  ND  ND  400 x 250  pot + ser-chl + late-veins  600  Cpy, bor  Cu-oxi (mal)  0.40  0.25  H364  Diorite, Quartz-diorite  11.3 ± 0.2  K-Ar-bio  800 x 500  pot + ser-chl + late-veins  1500  Cpy, bor  Cu-oxi (mal-azu)  0.40  0.30  Diorite, late-dacite  10.6 ± 0.2  U-Pb-Zr  400 x 300  pot + ser-chl + late-veins  1000  Cpy, bor  Cu-oxi (mal-chry)  0.45  0.30  Diorite, Quartz-diorite, dacite  ND  ND  600 x 400  pot + ser-chl + late-veins  800  Cpy ± bor  Cu-oxi (mal)  0.40  0.25  Diorite, late-dacite  10.8 ± 0.2  K-Ar-bio  200 x 150  pot + ser-chl + late-veins  500  Cpy  Cu-oxi (mal-chry)  0.40  0.20  Diorite, Quartz-diorite, late-dacite  10.8 ± 0.2  K-Ar-bio  800 x 400  pot + ser-chl + late-veins  1000  Cpy, bor  Cu-oxi (chry)  0.45  0.25  H9  2  H27 H74 H8  4  4  Abbreviations: ND = no data available (undefined), and = andesitic, pyro = pyroclastic, sed = sedimentary, pot = potassic, ser = sericite, chl = chlorite, cpy = chalcopyrite, bor = bornite, oxi = oxides, cc = chalcocite, cov = covellite, mal = malachite, azu = azurite, chry = chrysocolla 1  Age determinations in this study by Stanford-USGS Micro-Analysis Center in California, USA Age determinations by PCIGR, University of British Columbia UBC, Canada 3 Age determinations by GEMOC Macquarie University, Australia 4 Age determination by Amdel Limited Mineral Services, Australia 2  26  2.5 Stratigraphy 2.5.1 Sinjrani volcanic group The Late Cretaceous Sinjrani volcanic group (Hunting Survey Corporation, 1960; Ahmed et al., 1972; Sillitoe and Khan, 1977; Arthurton et al., 1979, 1982; Siddiqui, 1986, 1996, 2004) crops out widely to the north and northwest of Reko Diq complex (Fig. 2.2). Sinjrani volcanic group is composed of massive andesitic and basaltic lava flows, agglomerates, lapilli tuff, and fragmental volcanic rocks (Figs. 2.3 and 2.4 A, B). The lava flow is mainly aphanitic and locally porphyritic in texture containing phenocrysts of plagioclase embedded in a dark grey, fine-grained groundmass altered to chlorite and epidote of metamorphic origin (Khan and Ahmed, 1978). The Sinjrani volcanic group is cut by extensive batholith-scale granodiorite, granite and monzonite plutonic rocks of Eocene Chagai intrusions (54-44Ma; Breitzman, 1979; Perelló et al., 2008). 2.5.2 Humai formation The Humai formation consists of a sequence of ~2,000 m thick calcareous and clastic sedimentary rocks including the ~300-m-thick massive limestone exposures in Humai (type locality) located ~20 km east of Reko Diq complex (Fig. 2.3). The limestone is pinkish grey and creamy in color, containing Latest Cretaceous (Maastrichtian) marine fauna (Arthurton et al., 1979). The lower part of Humai formation is composed of medium to thin bedded mudstone, siltstone and sub-ordinate shale and has a discontinuous contact with the underlying Sinjrani volcanic group. The upper limestone sequence is characterized by abundant corals, foraminifers, oolitic and pellitic structures indicating a shallow marine depositional environment with minor intra-basonal reworking (Razique and Siddiqui, 2002; Fig. 2.4 C, D). The Humai formation is overlain by a thick (>4000m) sequence of shallow-marine to fluviatile shale, sandstone, conglomerate, shaly limestone and sub-ordinate volcanic lava flows of Paleocene Juzzak, Eocene Saindak and Oligocene Reko Diq formations described below (Hunting Survey Corporation, 1960; Ahmed et al., 1972; Arthurton et al., 1979, 1982; Siddiqui, 1996, 2004).  27  2.5.3 Juzzak formation The Paleocene Juzzak formation is widely exposed around Reko Diq complex. It is composed of medium to thinly bedded marine shale, fluviatile or deltaic maroon sandstone, siltstone and discontinuous interbeds of conglomerates. The lower Juzzak formation exposed to the far north, northeast and east of the Reko Diq complex is characterized by medium to fine grained, locally porphyritic andesitic lava flows, minor volcanic agglomerate, tuff and thin interbeds of marine limestone (Sillitoe, 1977; Razique and Siddiqui, 2002; Fig. 2.3). The Juzzak formation in the Reko Diq district is characterized by moderate to weak chlorite-epidote ± carbonate alteration related to the magmatic and hydrothermal activities in the Sor Baroot, Bukit Pasir, Reko Diq, Koh Dalil and Sam Koh igneous complexes. 2.5.4 Saindak formation The Eocene Saindak formation appears as discontinuous outcrops in the immediate surroundings of the Reko Diq complex, notably in Bukit Pasir to the north and Parrah Koh, H2 and H36 complexes in the south (Fig. 2.4 E). The Saindak formation is inferred to be the deeper host for porphyry Cu mineralization at Reko Diq western porphyry complex. Geological logging of deep resource holes in H14 and H15 porphyry centers indicate interbedded sandstone, siltstone, shale and sub-ordinate conglomerate, intermediate volcanic rocks and lava flow of Saindak formation. Sandstone is medium to fine grained, thinly bedded, laminated and composed of more than 65% quartz grains and minor lithic fragments cemented within a fine grained matrix dominated by hydrothermal biotite (Fig. 2.5 A). Intermediate volcanic rocks are coarse grained and tuffaceous displaying intense chlorite-sericite alteration, marking the contacts between conglomerate units and andesitic lava flows. Two distinct marker horizons of conglomerates at depths of 450m and 700m from surface are recognized in the drill core logging. These units range from 50cm to 10m in thickness with sharp upper and lower contacts with sedimentary rocks. The conglomerate facies are characterized by rounded, poorly sorted, clast supported, polymictic silica altered pebbles (0.5-5cm) cemented in a fragmented siliceous matrix (Fig. 2.5 B).  28  Figure 2.3 Generalized stratigraphic sequence of the western Chagai, Reko Diq district, Balochistan-Pakistan. (Siddiqui, 1996, 2004; Perelló et al., 2008)  29  Figure 2.4 Field photographs of the Reko Diq complex and surrounding area. (A) Looking N: Andesitic volcanic and lava flow of the Sinjrani volcanic group; (B) Medium to coarse grained volcanic agglomerate of the Sinjrani group; (C) Looking W: Medium to thick bedded Humai limestone formation; (D) Fossil shells, fragments, oolitic and pelletic structures in Humai limestone; (E) Looking SW: Medium to thin bedded sedimentary sequence of the Saindak formation at Parra Koh; (F) Looking W: Extensive andesitic and pyroclastic rocks hosting the Reko Diq H79, H15, H14 and H13 porphyry centers..  30  2.5.5 Dalbandin formation The Oligocene Dalbandin formation consists of ~300m thick sequence of interbedded redbed sedimentary rocks widely exposed to the south of the Reko Diq complex. At Parrah Koh prospect, these redbeds contain the erosional products of the Saindak formation as evident by the presence of detrital zircons with U-Pb ages of 41 and 35 Ma (middle Eocene to early Oligocene; Fu et al., 2006). Drill core logging in H14 and H15 complexes indicate that the Dalbandin formation has a gradational upper contact with the Reko Diq formation at ~280m from surface. Dalbandin formation comprises thinly bedded and laminated intercalations of mainly reddish colored sandstone, shale-siltstone units, intensely altered to fine grained hydrothermal biotite and magnetite (Fig. 2.5 C). The hornfels facies of shale-siltstone overprinted by epidote alteration is evident in the deeper flanks of the porphyry intrusions at western Reko Diq. 2.5.6 Reko Diq formation The Reko Diq formation of Late Oligocene (23-25 Ma; Perelló et al., 2008) age comprises interbedded andesitic lava flows, volcanic breccia and pyroclastic rocks, widely exposed in the surroundings of the Reko Diq complex (Fig. 2.4 F). These volcanic rocks are at least 400m thick and interpreted to be coeval with massive porphyritic andesite flows, volcanic breccias and tuffaceous volcanic rocks of the Amalaf formation (Siddiqui, 2004) present outside the Reko Diq complex. The basal part of Reko Diq formation is dominated by andesite with minor basaltic andesite, felsic volcanic rocks and equigranular microdiorite intrusions. Andesite is characterized by greenish grey, fine to medium grained massive lava flows, locally fragmented and porphyritic in texture. The porphyritic andesite also forms sub-volcanic intrusions that have a maximum thickness of ~200m. These rocks are characterized by 2-4 mm phenocrysts of plagioclase feldspars, amphiboles and minor pyroxenes equally distributed along a fine-grained aphanitic groundmass (Fig. 2.5 D). They are commonly magnetic, intensely altered and well mineralized in close proximity to the porphyry intrusions. The mafic volcanic facies at Reko Diq includes subsurface dykes and lava flows of basaltic andesite composition with euhedral elongated phenocrysts of plagioclase feldspars exhibiting flow textures. The lava flows range from 1-10m in thickness and appear as massive, black to dark-green rocks with intense disseminated 31  Figure 2.5 Core photographs illustrating the sedimentary, intrusive and volcanic host rocks at western Reko Diq. (A) Medium grained, thin-laminated sandstone with intense potassic alteration and micro veinlets of quartz-magnetite ± sulfides cut by the late anhydrite vein; (B) Conglomerate with 5-20mm poorly sorted silica pebbles and rock fragments cemented in a quartz-sericite-clay altered matrix; (C) Fine-grained volcanogenic shale with intense biotite-magnetite alteration and quartz stockwork; (D) Porphyritic andesite with 2-15mm phenocrysts of plagioclase set in a fine-grained potassically altered and magnetic ground mass; (E) Equigranular microdiorite overprinted by intense propylitic (chlorite-epidote) alteration; and (F) Pyroclastic breccia flow containing propylitic altered volcanic clasts and fragments cemented in a siliceous matrix.  32  hydrothermal biotite and magnetite. These mafic volcanic units locally host some highgrade (~0.80% Cu, 0.5g/t Au) Cu-Au mineralization at Reko Diq H14-H15 complex. The intermediate intrusive rocks consist of equigranular microdiorite overprinted by intense propylitic alteration (Fig. 2.5 E). The felsic volcanic rocks to the west of the Reko Diq complex consist of pale-grey dacite with shattered quartz phenocrysts set within a finegrained siliceous groundmass. The pyroclastic, tuffaceous volcanic and volcaniclastic rocks are dominant in the upper Reko Diq formation, and have a maximum thickness of ~150m. The pyroclastic breccia flows crop out in the northwest and southeast of Reko Diq complex and are composed of sub-angular to sub-rounded (1-10cm size), polymictic volcanic clasts embedded within a siliceous matrix (Fig. 2.5 F). These rocks have undergone intense propylitic alteration of chlorite-epidote assemblage along the margins of the Reko Diq porphyry cluster. The volcaniclastic breccia dominates the uppermost part of Reko Diq formation and is characterized by sub-rounded (1-50cm), poorly sorted, polymictic volcanic clasts cemented in a relatively unconsolidated volcanic matrix. 2.6 Miocene porphyry intrusions The porphyry Cu deposits at Reko Diq and adjacent prospects are spatially and temporally associated with Miocene diorite, hornblende-diorite, granodiorite and quartzdiorite intrusions (Sillitoe and Khan, 1977; Breitzman, 1979, Siddiqui, 2004; Perelló et al., 2008). The intrusions are characterized by medium to coarse grained porphyritic textures with phenocrysts of plagioclase feldspars (30-35 vol. %), biotite, amphibole (~10 vol. % combined), and quartz (3-10 vol. %) embedded in a micro-crystalline groundmass of similar mineralogy (Fig. 2.6; Table A.4). A minimum of four distinct intrusive phases are recognized, having more or less similar petrologic and metallogenic characteristics. The early Miocene (23.3 Ma) quartz-diorite and diorite porphyry intrusions host significant hypogene Cu-sulfide mineralization at Saindak and supergene Cu enrichment at the Reko Diq (Tanjeel) prospects. The middle Miocene (18-14Ma; Perelló et al., 2008) hornblendediorite intrusions resulted in the formation of a number of small porphyry centers located within and outside Reko Diq complex. The middle to Late Miocene (12.9-11.9 Ma) granodiorite and quartz-diorite intrusions are characterized by abundant phenocryst biotite 33  and host the gold-rich porphyry Cu deposits in the Reko Diq western porphyry complex (Chapter 3). Other porphyry Cu systems clustered in the north and south of the Reko Diq complex correspond to a younger generation of Late Miocene (11-10 Ma) amphibole bearing diorite intrusions. 2.6.1 Diorite to quartz-diorite phase The early Miocene (23.3 ± 0.24 Ma; Fu et al., 2006) Tanjeel porphyry Cu deposit with a supergene chalcocite blanket of 0.6% Cu is centered on NW-trending diorite and quartz-diorite porphyry intrusions. The main diorite porphyry (PFQ) stock with a dimension of ~1000 x 500m is cut by several isolated, 50 x 100m wide stocks and dykes of intra-mineral quartz-diorite (QFP) intrusions. The diorite porphyry is characterized by 26mm anhedral phenocrysts of plagioclase (35-45 vol.%) quartz, (<5 vol.%) and amphiboles (5-8 vol.%) set in a fine-grained groundmass dominated by sericitic and argillic alteration (Fig. 2.6 B). Quartz-diorite is relatively coarser grained in texture and contains 2-10mm phenocrysts of plagioclase (30-35 vol.%) amphiboles (~5 vol.%) and abundant magmatic quartz (~10-15 vol.%) embedded in a fine-grained groundmass dominated by a mosaic of hydrothermal quartz. 2.6.2 Hornblende-diorite phase The middle Miocene (18-14 Ma; Ivascanu and Fletcher, 2008) magmatic phase represent distinct hornblende-diorite suite porphyry intrusions emplaced as 150 x 200m wide stocks in the Sor Baroot, H14E, H12, H35, H11, Koh-e-Dalil (NE) and Sam Koh prospects. This intrusive phase displays well preserved medium to coarse grained porphyritic textures with euhedral phenocrysts of plagioclase (~30 vol.%), hornblende (510 vol.%), quartz (3-5 vol.%) and minor biotite set within an aphanitic groundmass. Hydrothermal alteration in these intrusive rocks consists of fine-grained secondary biotite and magnetite, intensely overprinted by chlorite-epidote alteration (Fig. 2.6 C). This intrusive phase is accompanied by moderate hypogene Cu-sulfide mineralization with an average grade of ~0.35% Cu and 0.2g/t Au (Table 2.1).  34  2.6.3 Granodiorite to quartz-diorite (Biotite phase) The middle to Late Miocene (12.9-11.9 Ma) magmatic event is represented by a distinct suite of biotite-rich porphyry intrusions accompanied by significant gold-rich hypogene Cu-sulfide mineralization at the Reko Diq western porphyry complex (Table 2.1). Multiphase granodiorite and quartz-diorite intrusions emplaced as a cluster of NEtrended stocks and dykes forming H79, H15, H14 and H13 porphyry centers from north to south (See below). The early granodiorite and intra-mineral quartz-diorite intrusions are volumetrically dominant, and are intersected by ~10 x 30m wide stocks and dykes of latestage quartz-diorite intrusions with relatively coarse-grained and preserved porphyritic textures. The granodiorite intrusions are medium to coarse grained, locally equigranular and porphyritic in texture, crowded with 2-10mm size, anhedral phenocrysts of plagioclase (40-45 vol.%), magmatic quartz (5-10 vol.%), biotite (~10-15 vol.%) and rare amphiboles set in a micro-crystalline groundmass dominated by hydrothermal biotite (Fig. 2.6 D). The intra-mineral quartz-diorite has relatively well preserved and coarser grained porphyritic textures with euhedral to subhedral phenocrysts of plagioclase, quartz, biotite and minor amphiboles embedded in an aphanitic groundmass. Both early granodiorite and quartzdiorite intrusions have been affected by intense potassic and chlorite-sericite (clay) alteration. Conversely, the late-mineral and late-barren porphyry intrusions are relatively fresh and exhibit well preserved primary mineralogy and textures (Chapter 3). 2.6.4 Diorite to microdiorite phase The Late Miocene (10.68±0.21 Ma; Ivascanu and Fletcher, 2008) diorite intrusions correspond to the youngest magmatic event at Reko Diq complex. This event resulted in small scale porphyry Cu-Au systems including H36, H9, H8 and H7 complexes (Table 2.2). Diorite is medium to coarse grained, porphyritic and locally equigranular in texture with up to 10mm subhedral phenocrysts of plagioclase (35-40 vol.%), amphiboles (5-10 vol.%) and magmatic quartz (<5 vol.%) set within a fine-grained potassically altered groundmass (Fig. 2.6 E). The diorite intrusions are generally less than 400 x 300m in diameter and centrally intruded by ~150m2 wide barren hornblende-dacite porphyry intrusions (Fig. 2.6 F). A distinct intra-mineral quartz-diorite is also recognized in the H36 and H2 porphyry centers. The porphyry Cu mineralization with an average grade of 0.40% 35  Cu and 0.20 g/t Au is associated with hydrothermal potassic and sericite-chlorite (clay) alteration and veins in the diorite porphyry and adjacent andesitic volcanic rocks.  Figure 2.6 Drill core photographs of the Miocene porphyry intrusions at Reko Diq district. (A) Early Miocene quartz-diorite (Saindak) with medium to coarse grained porphyritic texture and intense hydrothermal biotite and ser-chl alteration; (B) Early Miocene diorite porphyry (Tanjeel) with pervasive quartz-sericite (clay) alteration and sparse to fracture filled supergene chalcocite; (C) Middle Miocene hornblende-diorite with phenocrysts of plagioclase, hornblende, quartz and minor biotite set in a propylitic altered aphanitic groundmass; (D) Middle to late Miocene granodiorite crowded with plagioclase, biotite and quartz in a micro-crystalline matrix; intense biotite-K-feldspar-magnetite alteration and quartzmagnetite-K-feldspar ± sulfide veins; (E) Late Miocene diorite exhibiting coarse-grained porphyritic texture with plagioclase, biotite and amphiboles embedded in a crystalline groundmass dominated by shredy biotite; and (F) Late dacite porphyry showing well-preserved primary texture and phenocrysts of plagioclase, quartz and amphiboles set in a chlorite-epidote altered pheneric groundmass.  36  2.7 Porphyry centers in the Reko Diq complex 2.7.1 Tanjeel porphyry Cu deposit Tanjeel porphyry Cu deposit is centered on a large, 1000 x 500m wide early Miocene (23.3 Ma) diorite porphyry stock and a cluster of quartz-diorite porphyry intrusions host by late Oligocene andesitic volcanic rocks (Fig. 2.7). The Tanjeel porphyry Cu deposit, containing an indicated resource of 214 Mt @ 0.60% Cu is the most significant supergene Cu enrichment in the Reko Diq district (Perelló et al., 2008). The supergene Cu enrichment is typically associated with supergene clays, residual silica and hypogene sericitic alteration as seen in Sarcheshmeh Iran (Atapour and Aftabi, 2007), Escondida (Garza et al., 2001; Camus, 2002) and Chuquicamata Chile (Sillitoe, 1991; Ossandon et al., 2001; Camus, 2002). The supergene copper enrichment at Tanjeel forms an irregular 50-100m thick chalcocite blanket beneath a 40-50m thick leached cap dominated by hematite. The leached cap is characterized by a mosaic of hydrothermal quartz, quartz-limonite veins, supergene clays (kaolinite ± alunite), Fe-oxides (jarosite + hematite ± goethite) and Cu-oxides (chalconthite + chrysocolla) minerals. Discontinuous, 1-2 m thick perched sulfide zones of pyrite ± chalcocite are common in the quartz-diorite intrusions generally near the contact with the underlying chalcocite blanket. Relicts of sulfides (chalcocite precursor) and multiple zones of intense hematization in the leach cap indicate cyclic leaching and enrichment of chalcocite blanket. The leached cap is generally barren in copper with the exception of locally preserved perched sulfide zones containing up to 0.4% Cu trapped in the highly siliceous portions of quartz-diorite intrusion. The underlying chalcocite blanket contains around 5-10% disseminated and vein pyrite coated by chalcocite with an average grade of 0.6 % Cu. It has a sharp upper contact with the leached cap and an irregular gradational lower contact with hypogene Cu-sulfides containing up to 0.30% Cu (Maryono et al., 2008).  37  Figure 2.7 Satellite image and outcrop geology map of the Reko Diq porphyry complex and adjacent porphyry centers in the district. *Note: The study area to the west (box outlined) is represented by a cluster of middle to late Miocene porphyry intrusions, color coded as red.  38  2.7.2 Northern porphyry Cu-Au centers The porphyry centers including H14E, H12, H35, H11 and H4N are generally restricted to ~200m2 wide hornblende-bearing diorite porphyry stocks hosted by andesitic volcanic rocks and microdiorite intrusions (Fig. 2.7). These porphyry centers are typically associated with intense potassic alteration of biotite ± K-feldspar and magnetite in the center, surrounded by discontinuous and poorly developed sericitic alteration and extensive propylitic alteration assemblages. The disseminated and veinlet hypogene Cu-sulfides (chalcopyrite ± bornite) are associated with intense potassic alteration and quartz-magnetite veins, that is overprinted by chlorite and epidote. All the northern porphyry centers generally represent an average grade of ~0.35% Cu and 0.20g/t Au with the exception of H35 complex that is intersected by late-stage NE and NW trending quartz veins contributing to higher gold content. The H35 porphyry deposit contains an inferred resource 45 Mt at 0.40% Cu and 0.61g/t Au (Perelló et al., 2008). 2.7.3 Southern porphyry Cu-Au centers The porphyry centers including Parrah Koh, H36, H3, H9, H27, H7 and H8 are clustered along a NW trend in the southern part of the Reko Diq complex (Fig. 2.7). Available geochronologic results suggest that these porphyry centers are related to the late Miocene (11-10 Ma) diorite porphyry intrusions emplaced into the andesitic volcanic rocks and the underlying sedimentary sequence (Table 2.2). Individual porphyry centers are generally ~500m2 in dimension including lateral sericitic alteration halos. The mineralized diorite and quartz-diorite porphyry stocks are commonly truncated by ~100m2 wide latestage hornblende-dacite porphyry forming a barren core in the Parrah Koh, H3, H9, H27 and H8 porphyry centers. A 300m2 wide, weakly mineralized hydrothermal tourmaline breccia cuts the H8 porphyry system (Fig. 2.7). The southern porphyry centers host disseminated and veinlet chalcopyrite-pyrite ± bornite typically associated with intense potassic alteration, quartz and quartz ± magnetite veins. An average grade of ~0.4% Cu and 0.20g/t Au characterized these systems. Locally, however, the gold content is augmented by 1-20cm thick, late-stage quartz veins as seen in H36 and H9 porphyry centers (Maryono et al., 1998). Amongst the southern porphyry cluster, H8 complex contain an inferred resource of 335Mt @ 0.38% Cu and 0.19g/t Au (Perelló et al., 2008). 39  2.7.4 Western porphyry complex The Reko Diq western porphyry Cu deposits are linked to a distinct phase of biotiterich porphyry intrusions emplaced during middle to late Miocene (12.9-11.9 Ma). The porphyry centers including H79, H15, H14 and H13 are aligned for 4 km, along a NEtrended corridor of faults correlated with magnetic lineaments, veins and local structural fabric. These faults are recognized as pre and syn-mineral to the porphyry emplacement and have a very limited impact on the western porphyry deposits. The porphyry Cu mineralization is associated with a cluster of granodiorite and quartz-diorite porphyry stocks and dykes emplaced into andesitic volcanic, pyroclastic, volcaniclastic and sedimentary rocks (Fig. 2.7 and 2.8). The cross cutting relationships in surface outcrops and in drill core indicates at least four textural phases of intrusive rocks with intense hydrothermal alteration and Cu-Fe-sulfides (Chapter 3). The older granodiorite porphyry intrusions in H14-H15 complex contain the highest grade (up to 2.0% Cu and 1.5 g/t Au) hypogene Cu-sulfide mineralization (see below). Exploration and resource drilling until 2008 has delineated a global resource of 5,900 Mt @ 0.41% Cu and 0.22g/t Au in H14-H15 complex (Tethyan Copper Company, 2013). The H13 porphyry center on the south has a relatively higher average gold content and contains an indicated resource of 212Mt @ 0.40% Cu and 0.40g/t Au (Perelló et al., 2008). The H79 porphyry center in the north is smaller (300 x 400m) in size and invaded by NE trending, 25-50m-wide, late-stage barren hornblende-dacite porphyry in the central part of the system (Fig. 2.8). 2.7.5 H14-H15 porphyry deposit The Reko Diq H14-H15 porphyry Cu-Au (Mo) deposit, the focus of this dissertation, is typically associated with multiple and superimposed magmatic-hydrothermal events that lasted over a short period of time (Chapter 4). The H14-H15 porphyry deposit, including the central potassic and flanking sericitic alteration, extends for 2 x 3 km along NE-trended porphyry intrusions (Fig. 2.9). The propylitic alteration forms a large halo around the entire western porphyry complex. The four distinct porphyry phases of quartz-diorite to granodiorite intrusions were emplaced at different times with variable Cu-Au grades and tenor in H14 and H15 complexes. The bulk of the high-grade (0.8% Cu, 0.4g/t Au) coppergold mineralization is associated with intense potassic 40  Figure 2.8 Factual geology map of the Reko Diq western porphyry complex. H79 porphyry center in the north is associated with NE-trended hornblende-diorite and dacite porphyry intrusions, whereas H15, H14 and H13 porphyry systems to the south are centered on a cluster of NE and NW-trended granodiorite and quartz-diorite intrusions host by andesitic volcanic and pyroclastic rocks  41  Figure 2.9 Surface outcrop geology map of the Reko Diq H14 and H15 porphyry centers. The middle to late Miocene granodiorite and quartz-diorite intrusions emplaced as a cluster of NE-trended stocks and dykes host by Late Oligocene andesitic volcanic rocks.  42  alteration of biotite + K-feldspar + magnetite in the early granodiorite (PFB1) and intramineral quartz-diorite (PFB2) porphyry phases. The early mineralized porphyry intrusions are truncated by narrow (~10 x 30m) stocks and dykes of weakly-altered (PFB3) and freshbarren (PFB4) quartz-diorite intrusions, leading to a low grade core in H14 and H15 complexes (e.g., Clark, 1990; Van Norte et al., 1991; Seedorff et al., 2005). The detailed petrologic and petrochemical characteristics of H14 and H15 porphyry deposits are discussed in Chapter 3, whereas the geochronology of magmatic and hydrothermal events of the entire western porphyry complex is presented in Chapter 4. 2.8 Discussion and conclusions The Chagai porphyry Cu belt is related to the multimillion-year history of subduction of Arabian oceanic crust beneath the southern Eurasia continental plate (Perelló et al., 2008). Subduction is accompanied by short-lived contraction events and periods of volcanic calm, magmatism, arc construction and evolution similar to those in contractional belts at convergent margins containing large-scale porphyry Cu deposits (Richards, 2003; Gow and Walshe, 2005; Goldfarb et al., 2013). The construction of Chagai magmatic arcs and corresponding porphyry Cu formation occurred episodically during the last 55 Ma (Perelló et al., 2008). Chagai arc contains at least 50 economic and sub-economic porphyry Cu systems. The field investigations and geochronological records suggest that these porphyry systems are linked to at least five discrete magmatic events occurred during middle to late Eocene (43-36 Ma), early Miocene (24-22 Ma), middle Miocene (18-14 Ma), middle-late Miocene (12.9-11.9 Ma), late Miocene (11-10 Ma) (Perelló et al., 2008; this study). The extensive exposures of volcanic and plutonic rocks in eastern Chagai magmatic belt suggests a higher uplift and erosion rate preserving the Eocene (37-36 Ma) porphyry systems in the Ziarati and Gwanshero (Missi Koh) prospects. These porphyry systems are linked to felsic intrusions of granodiorite and monzonite compositions accompanied by K-feldspar-rich potassic, outer sericitic and flanking propylitic alteration. The western Chagai-Reko Diq region is dominated by widespread Miocene porphyry Cu-Au (Mo) systems associated with calc-alkaline biotite-amphibole bearing porphyry 43  intrusions of quartz-diorite to granodiorite compositions (Siddiqui, 2004; Perelló et al., 2008; this study). The hydrothermal alteration includes potassic, propylitic, transitional sericitechlorite (clay), sericitic and advanced argillic, the later in transition to epithermal environments. The hypogene Cu-Fe-sulfides in the porphyry systems are mainly associated with hydrothermal potassic alteration, quartz, and quartz-magnetite veins. Supergene Cu enrichment in the Chagai porphyry systems is irregular, typically restricted to thin and patchy zones of supergene chalcocite, mostly of the sooty variety coated on to the hypogene sulfides. The chalcocite blanket at central Reko Diq (Tanjeel prospect) is by far the most important supergene Cu deposit in Chagai belt. Intense leaching, relicts of sulfides and multiple hematite zones across the leach cap indicate multiple cycles of supergene oxidation and enrichment; a characteristic of the Chilean porphyry copper province (Sillitoe and McKee, 1996; Garza et al., 2001). The giant Reko Diq H14-H15 porphyry deposit is interpreted to have been developed at a time of faster regional uplift and exhumation (~1.5km) in western Chagai arc during middle-late Miocene age (Fu et al., 2006). The western porphyry cluster including H79, H15, H14 and H13 systems appear to be linked with a dynamic magmatic-hydrothermal system that spans for about 1 m.y. only (Chapter 4). These type of magmatic systems include differentiated magmatic events that result in the formation of multiple porphyry systems of approximately the same age as evident in Yerington Nevada (1 m.y., Dilles and Wright, 1988; Dilles and Proffett, 1995) and El Abra-Fortuna Chile (1-2 m.y., Dilles et al., 1997; Campbell et al., 2006).  44  Chapter 3 - Petrology and petrochemical evolution of Reko Diq H14-H15 3.1 Introduction Porphyry deposits formed in continental margin and island arcs are major sources of the world’s annual copper production and an important source of gold and molybdenum (e.g., Seedorff et al., 2005; Sillitoe, 2010). The origin, composition, and evolution of the porphyry Cu related magmas are important research avenues leading to understand the tectono-magmatic processes at convergent plate margins and exploration of magmatichydrothermal ore deposits. Magmatic arcs at continental margins develop in response to the subduction of oceanic lithosphere beneath the oceanic or continental plate (Sillitoe, 1972; Richard, 2003; Gow and Walshe, 2005). Subduction of oceanic lithosphere to greater depth (>100 km) results in partial melting of the asthenospheric mantle wedge generating hot, hydrous and relatively oxidized basaltic magma above the subducting oceanic slab (e.g., Ringwood, 1977; Gill, 1981; Pearce and Peate, 1995; Poli and Schmidt, 2002, Richards, 2011, Richards et al., 2012). Chambefort et al. (2008) suggest that these magmas may lie at depths of 20-30 km, with subsequent intrusions to depths of 6-12 km typical for the batholitic rocks to magmatic ores. The hydrous basalts accumulate at the base of the crust forming a zone of magma mixing, assimilation, storage and homogenization (Hildreth and Moorbath, 1988; Schmidt and Poli, 1998, Richards, 2003). Crystallization of these magmas generates heat, leading to partial melting and assimilation of lower crustal material to form a more evolved, volatile rich, metalliferous magma of andesitic to dacitic composition (Hildreth, 1981; Grove et al., 2003; Chiaradia et al., 2004; Rohrlach and Loucks, 2005). The magma rises to shallow crustal levels, where they stall to form magma chambers. In these chambers, the magma assimilates crustal material and generally fractionates into more felsic composition. Magma chambers with sufficient volumes of evolved magma may evolve significant porphyry copper deposits (Gustafson 1979; Burnham 1979; Dilles 1987; Hedenquist and Lowenstern, 1994; Candela and Piccoli, 2005; Lang et al., 2013). 1  A version of this chapter will be submitted for publication: Razique, A., Bashir, A., Lo Grasso, G., Tosdal, R. M., and Perelló, J., Petrology and Petrochemical Evolution of the Giant Reko Diq H14-H15 Porphyry Cu-Au Deposit, District Chagai, Balochistan-Pakistan.  45  Porphyry Cu related magmas are generally oxidized, sulfur rich (~1000ppm) in the form of sulfate, and chalcophile elements such as Cu and Au, which are incompatible and retained in the melt (Hedenquist and Richards, 1998; Field et al., 2005; Chambefort et al., 2008). Typical porphyry Cu deposits (e.g., Gustafson and Hunt, 1975; Dilles et al., 2000; Pollard and Taylor, 2002; Proffett 2003; Vry et al., 2010; Redmond and Einaudi 2010) are associated with a series of porphyritic intrusions emplaced as stocks and dykes in and above the cupola zone of a calc-alkaline batholith in the upper (1-3 km) crust (Dilles et al., 1987). Conditions favorable to generate these magmas are subjected to considerable debate. Several authors proposed that slab melting in the petrogenetic evolution of primary magmas (referred to as adakitic magmas) is an important source of metals for giant porphyry-related ore deposits (Thieblemont et al., 1997; Sajona and Maury, 1998; Oyarzun et al., 2001; Mungall, 2002). Adakite-type rocks have a unique geochemical signature of SiO2 (≥ 56%) higher MgO (< 3%), higher Sr/Y and La/Yb ratios (≥ 20) and low Y (≤ 18 ppm) and Yb (≤ 1.9 ppm) concentrations (Kay, 1978). Defant and Drummond (1990, 1993) distinguished adakite magmas from normal island-arc basalt-andesite-dacite-rhyolite suite magmas using a range of Sr/Y ratios versus Y content. Richards and Kerrich (2007) argue that the adakitic geochemical signature can be generated by normal asthenosphere-derived tholeiitic to calcalkaline arc magmas as a result of crustal assimilation, amphibole-garnet fractionation and addition of H2O (Richards, 2011; Richards et al., 2012). Kay et al., (2001) suggested that ore deposits in the central Andes are linked to the calc-alkaline arc magmatism and crustal thickening. The lower crustal intermediate magmas trapped in a crustal compression environment may also evolve significant porphyry Cu deposits as in southern Philippines (Rohrlach and Loucks, 2005). Repeated input of mafic magma into intermediate and or felsic magmatic complexes is also known in some porphyry Cu deposits (Cornejo et al., 1997; Hattori and Keith, 2001; Maughan et al., 2002; Pollard and Taylor, 2002; Wainwright et al., 2011). The large-scale porphyry Cu-Au deposits such as Batu Hijau (Arif and Baker, 2004) Grasberg (Pollard and Taylor, 2002), El-Teniente (Vry et al., 2010), Bingham Canyon (Redmond and Einaudi, 2010) and Reko Diq (Perelló et al., 2008; this study) containing >1 billion tons of copper ore (>0.50% Cu) are considered as the prime exploration targets. These 46  porphyry deposits involve several magmatic and hydrothermal processes. The size, grade and metallogeny of the deposit depend upon the source, evolutionary trends, composition and volume of the magma interacting with the host rocks (Sillitoe, 2000; Seedorff et al., 2005; Tosdal et al., 2009). The main goal of this chapter is to define the petrologic and petrochemical characteristics of middle to late Miocene porphyry Cu-Au (Mo) deposits at Reko Diq and monitor the igneous evolution in response to the hydrothermal alteration and sulfide mineralization at the H79, H15, H14 and H13 porphyry deposits. Field relationships, petrographic observations, lithogeochemistry and radiogenic isotope analysis are presented and compared with other porphyry deposits in the context of overall porphyry deposit model. The magmatic-hydrothermal geochronology is given in Chapter 4, whereas the detailed petrogenetic evolution, cooling and fractionation of the magma in the Reko Diq western porphyry deposits is discussed in Chapter 5. 3.2 Sequence and geometry of intrusive rocks The Reko Diq western porphyry Cu-Au (Mo) deposits are spatially and temporally associated with a cluster of middle to late Miocene porphyry stocks and dykes forming H79, H15, H14 and H13 porphyry systems from north to south (Table 3.1). The crosscutting relationships in the field as well as petrographic observations and U-Pb-zircon ages of porphyry intrusions in this study suggest five texturally distinct intrusive rocks in the western porphyry centers described below.  47  Table 3.1 Sequence and petrologic characteristics of Reko Diq western porphyry Cu-Au deposits, Chagai belt, Balochistan-Pakistan Avg. Grades Cu. % Au. g/t 0.40 0.20  Complex  UTM-E (m)  UTM-N (m)  Lithology  Age (U-Pb-Zir)  Alteration and sulfide mineralogy  H79  409400  3224200  Hornblende-diorite  12.9 ± 0.3 Ma  Potassic (biotite-K-feldspar-magnetite) largely overprinted by sericite-chlorite (clay) alteration; disseminated-veinlet pyrite-chalcopyrite-bornite ratio (3:6:1) and traces of molybdenite  H15  408700  3223300  Granodiorite and quartz-diorite  12.5 ± 0.2 Ma  Intense potassic (biotite-K-feldspar-magnetite) alteration overprinted by sericite-chlorite (clay) + specular hematite assemblage. Disseminated and veinlet pyrite-chalcopyrite-bornite ratio (3:5:2) and molybdenite; weak high-sulfidation covellite and supergene chalcocite.  0.50  0.30  H14  408300  3220200  Granodiorite and quartz-diorite  12.1 ± 0.2 Ma  Intense potassic (biotite-K-feldspar-magnetite) alteration overprinted by sericite-chlorite (clay) and specular hematite. Disseminated-veinlet pyrite-chalcopyrite-bornite (2:5:3) ± molybdenite and trace of digenite.  0.60  0.40  H13  408250  3220750  Quartz-diorite  11.9 ± 0.2 Ma  Potassic (biotite-K-feldspar-magnetite) overprinted by sericite-chlorite-clay and hematite. Disseminated-veinlet pyrite-chalcopyrite-bornite (3:5:2) ± molybdenite  0.40  0.35  *The average grades are based on the sulfide and Cu estimation (this study) integrated with the assays from Tethyan Copper Company Limited.  48  3.2.1 H79 porphyry complex The H79 porphyry complex is centered on the earliest (12.9 Ma) hornblende-diorite (PFH) porphyry intrusions emplaced in the north of Reko Diq western porphyry complex. These intrusions are volumetrically restricted to narrow (50 x 100m), NE trending (050o) dykes cut by late-stage barren dacite porphyry in the central part of the system (Fig. 3.1). Hornblende-diorite is potassically altered in the center and overprinted by intense sericiticchlorite (clay) and propylitic alteration at the flanks of the porphyry system. Hydrothermal quartz stockwork and cm-scale, angular to sub-angular xenoliths of host volcanic and sedimentary rocks are also common in this intrusive phase. 3.2.2 H15 porphyry complex The H15 porphyry complex to the south is developed over a large (800m2 wide) early-stage granodiorite porphyry stock cut by of NE and NW oriented, 25-50m wide and 100-200m long dykes of intra-mineral quartz-diorite intrusions (Figs. 3.1 and 3.2). A discontinuous, 5-15m wide contact breccia zone is developed at the contact between the early granodiorite porphyry (PFB1) and adjacent host rocks. The intra-mineral quartz-diorite (PFB2) intrusions locally preserved cm-scale chilled margins along the contacts with granodiorite porphyry (Fig. 3.4 B). These intrusive rocks contain cm-scale sub-angular xenoliths of andesitic volcanic and sedimentary rocks, and indicate intense potassic-sericitic alteration and multistage hydrothermal veins. The porphyry intrusions and associated hydrothermal alteration, veins and Cu-sulfides in H15 complex are subsequently cut by volumetrically smaller (30 x 20m), late-mineral quartz-diorite (PFB3) intrusions (Fig. 3.2). 3.2.3 H14 porphyry complex The H14 porphyry complex further to the south is centered on younger, ~100 x 250m wide granodiorite (PFB1) porphyry stocks cut by a series of NE-trending, 25-50m wide and 100-200m long stocks and dykes of quartz-diorite (PFB2) intrusions (Figs. 3.1 and 3.3). These intrusive rocks are characterized by intense potassic-sericitic alteration, network of multi-generation hydrothermal veins and sub-angular (1-10cm) xenoliths of pre-existing volcanic, sedimentary and intrusive rocks (Fig. 3.4 C). The granodiorite (PFB1) and quartzdiorite (PFB2) intrusions and associated hydrothermal alteration, veins and sulfides in H14 is 49  Figure 3.1 Surface geology map of the Reko Diq western porphyry complex: The middle to late Miocene (12.911.9 Ma) granodiorite and quartz-diorite intrusions emplaced as a cluster of NE-trending stocks and dykes host by late-Oligocene volcanic rocks. The multiple porphyry intrusions and hydrothermal events led to the formation of H79, H15, H14 and H13 porphyry Cu-Au deposits from north to south.  50  Figure 3.2 East-west geological section (A-A’ UTM 3223300m N) across H15 porphyry complex projecting up to 100m downhole drilling data onto the section: The multiple crosscutting porphyry intrusions emplaced upward into a sequence of volcanic and sedimentary rocks. The early granodiorite (PFB1) porphyry stock is intersected by narrow dykes of intra-mineral (PFB2) and late-mineral (PFB3) quartz-diorite intrusions.  51  Figure 3.3 East-west geological section (B-B’-UTM 3222200m N) across the H14 complex projecting up to 100m downhole drilling data onto the section: The multiple crosscutting porphyry intrusions emplaced as vertical to sub-vertical stocks and dykes into volcanic and sedimentary rocks. The early granodiorite (PFB1) is cut by intra-mineral quartz-diorite (PFB2) and subsequently intersected by narrow dykes of late-mineral (PFB3) and late-barren (PFB4) quartz-diorite intrusions in the core of the system.  52  Figure 3.4 Core photographs illustrating the sequence and crosscutting relationships of intrusive rocks at Reko Diq western porphyry complex. (A) Hornblendediorite (PFH) from H79 complex; (B) Early granodiorite (PFB1) cut by intra-mineral quartz-diorite (PFB2) display chilled margins along the contact; (C) Intramineral quartz-diorite (PFB2) with sub-angular xenoliths of host rocks with distinct vein truncation; (D) Late-mineral quartz-diorite (PFB3) with sub-rounded xenoliths of deeper granodiorite pluton; (E) Late-mineral quartz-diorite (PFB3) cut by narrow dykes of late stage barren quartz-diorite (PFB4); and (F) hornblende-rich quartz-diorite (PFB2) in H13 complex.  53  subsequently cut by narrow dykes (10 x 30m) of late-mineral (PFB3) quartz-diorite (Fig. 3.3). This intrusive phase contains xenoliths of pre-existing intrusive rocks (Fig. 3.4 D) and is postdated by 2mm to 2cm thick pyrite-chalcopyrite ± quartz “D-type” veins (Gustafson and Hunt, 1975; Chapter 6). The late-stage barren quartz-diorite (PFB4) dykes (20 x 15m) were intersected only in the deep resource drill holes at depths >800m from surface. These intrusions cut across all the earlier intrusive and hydrothermal phases, and are characterized by relatively fresh coarse-grained porphyritic textures (Fig. 3.4 E). 3.2.4 H13 porphyry complex The southernmost H13 porphyry complex is associated with the youngest (11.9 Ma), NW-trending, hornblende-rich quartz-diorite dykes cut by narrow 10 x 20m wide, isolated dacite porphyry stocks and a distinct hydrothermal breccia crop out in the central part of the system (Fig. 3.1). Similar to H15 and H14, the quartz-diorite (intra-mineral-PFB2) in the H13 complex is characterized by intense hydrothermal potassic, sericitic-chlorite (clay) alteration, multi-generation veins and xenoliths of host volcanic and sedimentary rocks (Fig. 3.4 F). 3.3 Petrology of intrusive rocks The Reko Diq western porphyry complex consists of five compositionally discrete intrusive rocks emplaced during middle to late Miocene (12.9-11.9 Ma; Fig. 3.4). The intrusive rocks in H14 and H15 porphyry deposits are similar in texture, mineralogy and chemical compositions. However, based on slight variations in texture, mineralogy and cross cutting relationships, the intrusive sequence is divided into medium-grained porphyritic (PFB1), coarse-grained porphyritic (PFB2) coarse-grained porphyritic with aphanitic groundmass (PFB3), and coarse-grained porphyritic with phaneritic groundmass (PFB4) varieties (Table 3.2). In general, all the intrusive rocks display coarse grained porphyritic textures with abundant phenocrysts of plagioclase and variable amounts of biotite, magmatic quartz and amphiboles embedded in a micro-crystalline to aphanitic groundmass (Fig. 3.5). The early granodiorite (PFB1) and quartz-diorite (PFB2) are intensely altered to hydrothermal biotite- K-feldspar-magnetite and locally overprinted by sericite-chlorite (clay) alteration destroying the primary textures and mineral constituents. The late-mineral quartzdiorite (PFB3) suite displays both intense chlorite-sericite (clay) alteration at shallow levels, 54  Table 3.2 Petrologic characteristics of multiple porphyry intrusions in the Reko Diq H14-H15 porphyry deposits, Chagai belt, Balochistan-Pakistan Essential mineral constituents Phase  Lithology  Texture Minerals  PFB1  PFB2  PFB3  PFB4  Granodiorite  Quartz-diorite  Quartz-diorite  Quartz-diorite  Medium-gained porphyritic, locally equigranular with holocrystalline groundmass and xenoliths of host rock. Coarse grained porphyritic with finer crystalline groundmass, altered and veined xenoliths of PFB1 and host rocks, locally preserved chilled margins. Coarse-grained porphyritic with aphanitic ground mass and xenoliths of altered and veined PFB1, PFB2 and the granodiorite pluton.  Coarse-grained porphyritic with phaneritic ground mass contain xenoliths of PFB3 and granodiorite pluton.  Size (mm)  Vol. (%)  Plagioclase  2-6  40-45  Quartz  4-6  5-8  Biotite  2-10  12-15  Plagioclase  2-10  35-40  Quartz  4-10  ~12  Biotite  3-8  ~10  Amphiboles  2-8  <5  Plagioclase  2-12  30-35  Quartz  5-10  10-15  Biotite  3-10  8-10  Amphiboles  2-8  ~5  Plagioclase  2-15  45-50  Quartz  4-12  15-20  Biotite  2-10  ~12  Amphiboles  2-10  ~5  Phen : Gmass  8:2  7:3  Accessories  Alteration Mineralogy  Zircon, apatite, opaque (magnetite, pyrite, chalcopyrite, bornite and molybdenite)  Intense early dark mica, shredy biotite, K-feldspar, magnetite, anhydrite locally overprinted by sericite, chlorite ± clay alteration  Zircon, apatite and opaque (magnetite, hematite, pyrite, chalcopyrite, bornite and molybdenite)  Moderate potassic alteration of flaky biotite, K-feldspar, magnetite, hematite, anhydrite, overprinted sericite, chlorite ± clay alteration  Zircon, apatite, opaque (magnetite, hematite and minor Cu-sulfides)  Weak hydrothermal biotite ± Kfeldspar ± magnetite ± specular hematite. Intense sericite, chlorite ± clays ± epidote overprints  Zircon, apatite, magnetite and traces of Cu-sulfides  Traces of hydrothermal biotite mainly in the groundmass overprinted by weak chlorite, epidote alteration  6:4  9:1  55  and weaker chlorite-sericite-biotite in the deeper core of the system. In contrast, the latebarren stage quartz-diorite (PFB4) is characterized by well-preserved primary minerals and coarse-grained porphyritic textures (Fig. 3.5). 3.3.1 Granodiorite porphyry (PFB1) The early granodiorite (PFB1) porphyry is grey to pink grey in color, characterized by medium to coarse grained, locally equigranular porphyritic textures crowded with subhedral to anhedral phenocrysts of 2-6mm plagioclase (40-50 vol. %), 2-10mm biotite (1215 vol. %), 4-6mm quartz (5-8 vol. %) and minor accessory zircon, apatite, magnetite and sulfides embedded in a finer grained holocrystalline groundmass (Fig. 3.5A-A’ and Table 3.2). In cross nicols, the zoned plagioclase phenocrysts largely altered to K-feldspars with light-grey colors. The phenocryst biotite and hornblende are completely replaced by irregular flakes of secondary (hydrothermal) biotite, which occurs as concentrations along phenocrysts and cluster in the groundmass exhibiting strong pale-brown interference colors (Fig. 3.6 AA’). The secondary biotite after hornblende is locally altered to pale-green chlorite. The groundmass displays equigranular hydrothermal quartz, shreddy biotite and opaques consisting of disseminated granular magnetite, chalcopyrite, bornite and molybdenite (Chapter 6). 3.3.2 Quartz-diorite porphyry (PFB2) The intra-mineral quartz-diorite (PFB2) is grey in color and characterized by subhedral phenocrysts of 2-10mm plagioclase (30-40 vol. %), 3-8mm biotite (~10 vol. %), sub-rounded 5-10mm quartz (~12 vol. %) and minor amphiboles set in a microcrystalline to aphanitic groundmass, containing accessory zircon, apatite, magnetite and sulfides (Fig. 3.5 B-B’ & Table 3.1). In cross nicols, the zoned plagioclase partially alters to K-feldspars and overprinted by muscovite (sericite), whereas primary phenocryst biotite is partially altered and generally rimmed by secondary (hydrothermal) biotite and chlorite (Fig. 3.6 B-B’). The groundmass is clustered with pale-brown shreddy biotite and opaque minerals including disseminated granular magnetite, pyrite, chalcopyrite, minor bornite and molybdenite (Chapter 6).  56  3.3.3 Quartz-diorite porphyry (PFB3) The late-mineral quartz-diorite (PFB3) is characterized by 2-12mm, euhedral, zoned and intergrown plagioclase (30-35 vol. %), 3-10mm biotite phenocrysts (~10 vol. %), subrounded 5-15mm quartz eyes (10-15 vol. %) and minor 4-10mm hornblende laths (<5 vol. %) set in a fine grained aphanitic groundmass containing accessory zircon, apatite, magnetite and minor sulfides (Fig. 3.5 C-C’ & Table 3.1). In cross nicols, the plagioclase appears fresh and display parallel twinning, and is locally replaced by weak K-feldspar and overprinted by muscovite (sericite). The phenocryst phase biotite and minor amphiboles are weakly altered to secondary biotite, which locally rim biotite phenocrysts but are generally disseminated in the groundmass (Fig. 3.6 C, C’). 3.3.4 Quartz-diorite porphyry (PFB4) The late-barren quartz-diorite (PFB4) postdates all other porphyry and hydrothermal events and retains its primary mineralogy and textures. This intrusive phase is characterized by light grey color, coarser grained porphyritic texture with interlocking euhedral phenocrysts of 2-15mm plagioclase (45-50 vol. %), 2-10mm biotite (~12 vol. %), subrounded translucent 4-10mm quartz (15-20 vol. %) and minor 2-10mm hornblende (<5 vol. %) set in a phaneritic groundmass containing accessory zircon, apatite and magnetite (Fig. 3.5 D-D’ and Table 3.2). In cross nicols, the plagioclase phenocrysts display strong zonation, twinning and intergrown crystal structures. The biotite has strong pale-brown interference colors as well as typical bird’s eye textures. Quartz forms sub-rounded, translucent phenocrysts scattered within a crystalline groundmass containing opaque minerals dominated by granular magnetite and traces of sulfides (Fig. 3.6 D-D’).  57  Figure 3.5 Core photographs illustrating the sequence and subtle variations in texture and composition of intrusive rocks in H14 and H15 porphyry systems. (A-A’) Early phase medium-grained, equigranular to porphyritic granodiorite (PFB1) with a holocrystalline groundmass displaying intense potassic alteration of biotite + K- feldspar + magnetite; (B-B’) Intra-mineral phase, coarse-grained porphyritic quartz-diorite (PFB2) with a finer crystalline groundmass. Secondary biotite-K-feldspars-magnetite are locally overprinted by sericitechlorite; (C-C’) Late-mineral, coarse-grained porphyritic quartz-diorite (PFB3) with 2-12mm phenocrysts of plagioclase, quartz, biotite and minor amphiboles set in an aphanitic groundmass altered to sericite-chlorite ± biotite; and (D-D’) Late-stage, coarse-grained porphyritic quartz-diorite (PFB4) with 3-15mm, euhedral phenocrysts of plagioclase, quartz, biotite and minor amphiboles set in a phaneritic groundmass.  58  Figure 3.6 Photomicrographs illustrating the sequence and petrologic characteristics of intrusive rocks in H15 and H14 complexes. (A-A’) Granodiorite (PFB1) with anhedral plagioclase replaced by grey K-feldspars overprinted by sericite; biotite altered to pale-brown flakes of secondary biotite; (B-B’) Quartz-diorite (PFB2) display zoned plagioclase partially altered to K-feldspars and rimmed by sericite; biotite phenocrysts alters to pale-brown flaky hydrothermal biotite; (C-C’) Quartz-diorite (PFB3) with zoned plagioclase rimmed by sericitic alteration; biotite phenocrysts partially altered to chlorite and rimmed by secondary biotite; (D-D’) Quartz-diorite (PFB4) illustrating well preserved, euhedral phenocrysts of biotite, quartz and strongly zoned, intergrown plagioclase set in a phaneritic groundmass.  59  3.4 Geochemistry of porphyry intrusions A total of 63 drill core samples covering the petrologic range of middle to late Miocene intrusive rocks at the Reko Diq H14-H15 porphyry complex were analyzed for whole-rock major and trace element geochemistry. The geochemical analyses were carried out at ALS Minerals laboratories, North Vancouver Canada. Samples were initially treated with lithium meta-borate fusion employing inductively coupled plasma atomic emission spectrometry (ICP-AES) for major elements. The trace and rare earth elements REE were determined using inductively coupled plasma mass spectrometry (ICP-MS). The base metals such as Cu, Pb, Zn and Ni were analyzed using the 4-acid digest ICP-AES method, whereas volatiles (As, Bi, Hg etc.) were determined with the Aqua Regia ICP-MS technique. The analytical techniques and ALS detection limits are given in Table B.1. All the samples are representative of the Reko Diq H14 and H15 porphyry deposits; therefore, partial alteration of biotite and weak sericite chlorite alteration was inevitable. However, a great deal of care was taken to select the most representative and least altered samples through field screening and thin section evaluation. Visible alteration and quartz veins were cut off where necessary using a diamond saw during sample preparation. Representative analysis of intrusive rocks from H15 and H14 complexes are presented in Table 3.3 and all the analytical results are given in the Table B.2.  60  Table 3.3 Representative geochemical analysis of middle to late Miocene porphyry intrusions at Reko Diq H14-H15 porphyry Cu-Au deposits Complex Sample Intrusive phase Major elements (wt.%)  Trace elements (ppm)  H14 Complex  SiO2 Al2O3 Fe2O3 CaO MgO Na2O K2O Cr2O3 TiO2 MnO P2O5 SrO BaO S LOI Total Nb Zr Y Sr U Rb Th Ga Pb Zn Ag Cu Mo  H15 Complex  RD130-805  RD008-788  RD107-576  RD510-1530  RD068-518  RD567-499  RD341-440  RD567-1196  PFB1 58.38 11.34 3.38 4.50 0.92 1.96 4.09 <0.01 0.26 0.02 0.10 0.04 0.04 4.02 5.88 98.1 5.60 58 10.4 335 0.4 95.40 5.32 10 9.00 23 5.50 5510 51.00  PFB2 61.04 16.11 4.28 4.90 1.84 3.78 1.69 <0.01 0.34 0.03 0.06 0.06 0.05 0.60 2.95 100 6.40 108 8.5 520 1.09 46.60 6.95 15.3 5.00 28 <0.50 850 17.00  PFB3 61.91 16.34 5.51 4.32 1.99 3.86 1.84 <0.01 0.35 0.03 0.15 0.06 0.05 0.45 2.38 100.5 7.10 78 8.5 487 1.71 53.40 8.52 16.3 8.00 32 0.70 1240 3.00  PFB4 73.17 11.31 4.36 3.08 1.13 3.12 0.97 <0.01 0.22 0.03 0.07 0.04 0.05 0.17 1.06 99.8 5.20 50 4.8 346 0.68 34.00 6.45 13.5 <5.00 22 <0.50 166 <1.00  PFB1 63.02 12.10 8.43 3.05 1.27 3.58 1.72 <0.01 0.27 0.02 0.14 0.04 0.04 1.48 3.1 99.9 5.30 74 6.3 353 0.58 44.00 5.42 14.6 6.00 42 0.7 3450 2.00  PFB2 62.08 16.13 5.09 4.91 1.80 3.94 1.75 <0.01 0.35 0.02 0.18 0.06 0.05 0.92 1.93 100 6.50 74 9 523 0.97 48.80 6.56 14.9 6.00 30 1.2 3150 <2.00  PFB3 59.85 13.24 5.00 3.13 2.12 4.25 1.31 <0.01 0.33 0.04 0.07 0.05 0.03 0.98 3.75 98.3 5.30 72 8.3 401 0.64 57.00 5.98 17.7 12.00 49 1.2 4040 2.00  PFB4 61.60 15.59 4.73 5.09 1.97 3.56 1.32 <0.01 0.36 0.03 0.13 0.06 0.05 0.87 2.84 100 6.70 82 9.4 509 1.32 49.20 6.68 14.2 6.00 30 <0.50 479 12.00  61  Table 3.3 Continue… Complex Sample ID Intrusive phase Trace elements (ppm)  H14 Complex  Ni Cr V Ba La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Yb Lu C Co Cs Hf Sn Ta Tm W As Bi Hg Sb Se Te  H15 Complex  RD130-805  RD008-788  RD107-576  RD510-1530  RD068-518  RD567-499  RD341-440  RD567-1196  PFB1 19.00 10.00 79 383.00 14.9 28.20 3.42 13.00 2.45 0.56 2.17 0.34 1.76 0.38 1.09 1 0.14 <0.01 3.50 3.06 1.7 4.00 0.3 0.13 33 5.6 7.64 0.008 0.140 10.0 0.23  PFB2 10.00 10.00 70 435.00 16.4 29.70 3.33 11.80 2.07 0.61 1.83 0.28 1.42 0.3 0.86 0.99 0.15 0.02 6.90 2.28 3 1.00 0.4 0.12 2 1.5 0.28 <0.005 0.090 1.0 0.03  PFB3 7.00 10.00 74 443.00 19 34.00 3.70 13.00 2.07 0.59 1.86 0.27 1.46 0.31 0.94 0.96 0.16 0.02 8.30 3.69 2.2 1.00 0.5 0.13 2 1.3 0.32 0.005 0.060 1.6 0.06  PFB4 <5.00 10.00 58 398.00 9.9 16.80 1.94 6.70 1.17 0.42 1.13 0.15 0.86 0.18 0.55 0.56 0.09 0.07 5.70 2.15 1.6 <1.00 0.4 0.07 1 0.8 0.03 0.005 0.060 0.3 <0.01  PFB1 12.00 10.00 96 313.00 12.2 21.70 2.43 8.50 1.46 0.48 1.43 0.2 1.13 0.24 0.7 0.79 0.12 0.01 7.20 0.99 2 1.00 0.3 0.11 3 1.3 0.4 <0.005 0.070 3.5 0.12  PFB2 6.00 10.00 67 443.00 18 32.20 3.53 12.50 2.22 0.73 2.15 0.31 1.69 0.34 1.01 1.09 0.17 0.01 8.00 1.25 2.1 1.00 0.4 0.14 2 0.9 0.91 <0.005 0.050 2.6 0.07  PFB3 14.00 20.00 91 308.00 14.8 27.00 2.92 10.70 1.98 0.56 1.82 0.26 1.49 0.31 0.92 0.97 0.15 0.15 8.30 3.63 1.9 1.00 0.3 0.16 1 0.9 1.54 <0.005 0.070 4.3 0.13  PFB4 11.00 10.00 77 441.00 20.6 35.90 3.90 13.30 2.32 0.72 2.11 0.31 1.71 0.35 1.08 1.1 0.17 0.01 10.00 2.37 2.3 1.00 0.4 0.16 5 0.6 0.16 <0.005 <0.050 0.9 0.02  62  3.4.1 Major elements The intrusive rocks at Reko Diq H15-H14 porphyry deposit plot as primarily medium-K calc-alkaline series on the major element and petrochemical plots. The SiO2 vs. K2O plot (Peccerillo and Taylor, 1976) indicate that most of the intrusive rocks fall within the calc-alkaline field, along with a scatter in the early (PFB1, PFB2) porphyry intrusions due to hydrothermal alteration (Fig. 3.7 A). The TAS (Total Alkalies vs. SiO2) classification diagram (Le Maitre et al., 1989), reflect an overall quartz-diorite composition of the intrusive rocks as evident by the cluster of least altered samples. Scatter in the early-phase (PFB1, PFB2) intrusive rocks is interpreted as the effects of hydrothermal alteration (Fig. 3.7 B). The K2O/Al2O3 vs. P2O5/Al2O3 petrochemical discrimination diagram (Crawford et al., 2007a), show that majority of the intrusive rocks plot within the medium-K composition field. However, the outliers (PFB1 and PFB2) in this plot clearly indicate the effects of hydrothermal alteration as evident by the addition and/or depletion of K2O content in the intrusive rocks (Fig. 3.7 C). The addition of K2O is also evident by the presence of abundant K-feldspars in potassic alteration and slightly higher (>3.0 wt.%) loss on ignition (Fig 3.7 D). Overall, the intrusive rocks range from 55.7 to 73.1 wt.% (average 61.6 wt.%) SiO2, from 0.24 to 4.69 wt.% (average 3.6 wt.%) Na2O3, and from 0.96 to 5.13 wt.% (average 1.9 wt.%) K2O (Table 3.3). The intrusive rocks with higher K2O (>2.0 wt.%) and SiO2 (>65 wt.%) are considered to be affected by the K-silicate alteration as evident in the drill core and petrographic thin section studies. The Al2O3 contents range from 9.9 to 16.7 wt.% (average 14.5 wt.%) showing distinct depletion in the hydrothermally altered granodiorite (PFB1) and quartz-diorite (PFB2) porphyry intrusions (Fig. 3.8 A). Decreasing TiO2 contents in the altered intrusive rocks at a given 60 wt. % SiO2 is also evident (Fig. 3.8 B). MgO ranges from 0.83 to 3.8 wt.% (average 1.8 wt.%) indicating a normal fractionation trend of increasing SiO 2 and decreasing MgO content (Fig. 3.8 C). In general, the major element compositions of the latestage least altered intrusive rocks (PFB3 & PFB4) reflect primary melt compositions, whereas the addition of K2O and depletion of Al2O3 and TiO2 in the early PFB1 and intramineral PFB2 rock types indicate the effects of hydrothermal potassic alteration in both H14 and H15 porphyry deposits. 63  3.4.2 Alkalinity The intrusive rocks at Reko Diq H15 and H14 porphyry deposits generally represent a medium-K calc-alkaline composition as illustrated in the petrochemical discrimination diagrams (Fig. 3.7). Most of the least altered samples are represented by less than 2.0 wt.% K2O, indicating a uniform alkalinity of the intrusive rocks. The K2O content in the rocks may increase due to hydrothermal alteration. This effect is common in the early granodiorite (PFB1) and intra-mineral quartz-diorite (PFB2) porphyry intrusions with potassic alteration of K-feldspars leading to higher (>2.0 wt.%) K2O content (Table 3.3). Nonetheless, the consistency of K2O content (<2.0 wt.%) in all least altered rocks suggests that this effect is minor. Furthermore, the correlation between loss on ignition (LOI), a proxy for hydrous hydrothermal alteration and K2O content also support the interpretation distinguishing the uniform alkalinity of intrusive rocks and the alteration effects illustrated in K2O vs. LOI diagram (Fig. 3.7 D).  64  Figure 3.7 Major element and petrochemical discrimination diagrams of the Reko Diq H14-H15porphyry complex: (A) SiO2 vs. K2O diagram (Peccerillo and Taylor, 1976) with porphyry intrusions generally cluster within calc-alkaline composition field. Samples with high K2O and SiO2 represent the effects of hydrothermal alteration; (B) Total alkali vs. silica diagram (Le Maitre et al., 1989) generally indicates quartz-diorite composition; (C) K2O/Al2O3 vs. P2O5/Al2O3 plot (Crawford et al., 2007a) distinguishes the least altered rocks (clustered in the medium-K field) from hydrothermally altered rocks with addition and depletion of K 2O (F) Loss on ignition LOI vs. K2O plot illustrating the alkalinity of the rocks and the effect of hydrothermal alteration with K2O (>2.0wt.%) and LOI (>3.0 wt.%).  65  Figure 3.8 Major element and petrochemical discrimination diagrams of the Reko Diq H14-H15 porphyry complex: (A) SiO2 vs. Al2O3 plot show decreasing Al2O3 content with relatively altered rocks; (B) SiO2 vs. TiO indicates depleted TiO in the early altered granodiorite PFB1 and quartz-diorite PFB2 intrusions; and (E) SiO2 vs. MgO plot reflect a normal fractionation trend.  66  3.4.3 Trace element and REE The middle to late Miocene intrusive rocks at Reko Diq are characterized by moderate enrichment of light rare earth elements (LREE) and flat heavy rare earth element (HREE) profiles in the chondrite normalized REE plots (Fig. 3.9; Sun and McDonough, 1989). The depleted high field-strength elements (HFSE) such as Nb range from 4.9 to 21.5 ppm (average 6.8 ppm) and TiO2 ranging from 0.21 to 0.49 wt.% (average 0.34 wt.%) is indicative of volcanic arcs (e.g. Wilson, 1989; Foley and Wheller, 1990; Brenan et al., 1994). The enriched low field-strength elements (LFSE) and relatively depleted high field-strength elements (HFSE) as in Reko Diq western porphyry centers typically indicates a suprasubduction zone environment (Richards, 2003; Candela and Piccoli, 2005; Hollings et al., 2005; Richards and Kerrich, 2007; Richards, 2011). The intrusive rocks in both H14 and H15 porphyry systems are depleted in heavy rare earth elements (HREE) and generally lack a negative Europium anomaly (Fig. 3.10). A distinction between H15 and H14 porphyry systems is evident using the REE patterns of the volcanic rocks as a bench mark. The chondrite normalized spider diagrams (Fig. 3.10 A, B, C, D, E) indicates spoon shaped listrict profiles of REE with relatively flat heavy-REE patterns in H15 as compared to the H14 complex (Fig. 3.10 F, G, H, I, J). Furthermore, H15 complex is characterized by relatively narrow range of REE (less enriched) as compared to the wider range of REE (enriched) in H14 complex. These variations implies that the intrusive rocks in H14 complex are slightly fractionated through time (e.g. Gromet and Silver, 1987; Klein et al., 1997; Prowatke and Klemme, 2006). High Sr/Y ratio (25 to 97, average 52), low Y (7.8 -11ppm, average 8.8 ppm) and low Yb (0.38-1.29 ppm, average 0.97 ppm) content suggest an adakitic geochemical signature to the intrusive rocks (Fig. 3.11 A; Defant and Drummond, 1993). A higher and narrow range of the Sr/Y ratios (48-72) in least altered (PFB3, PFB4) intrusions is evident compared to a lower and wider range of Sr/Y ratios (25-97) in the K-altered (PFB1, PFB2) porphyry intrusions (Fig. 3.11 A). Samples with higher La/Yb ratio (≥20) generally cluster at the boundary between adakite and normal andesite-dacite-rhyolite composition fields illustrated in the La/Yb versus Yb discrimination plot (Fig. 3.11 B; Castillo et al., 1999). The La/Y, Sm/Yb and Sr/Y ratios when plotted at a given 60% SiO2 content (Fig. 3.10 C, D, E), suggest 67  Figure 3.9 (A-D) Chondrite-normalized spider diagrams for rare earth element REE in the late Oligocene volcanic and middle to late Miocene intrusive rocks at Reko Diq western porphyry complex (after Sun and McDonough, 1989). The REE patterns typically show moderate enrichment of light-REE and a flat heavyREE profiles indicating a shallow (<50km) mantle source; (E) Eu/Eu* versus Sm/Yb plot indicates an overall garnet/amphibole fractionation trend of the intrusive rocks.  68  Figure 3.10 Chondrite-normalized rare earth element REE plots of late Oligocene volcanic and middle-late Miocene intrusive rocks at Reko Diq H14 and H15 porphyry systems (after Sun and McDonough, 1989). The REE patterns typically show moderate enrichment of light-REE and a flat heavy-REE profiles indicating a shallow (~50km; lower crust) mantle source; (A-E) H15 complex show flat HREE patterns; (F-J) H14 complex indicate relatively broader spoon shaped HREE profiles, implying that H14 is slightly more fractionated than H15.  69  Figure 3.11 Petrochemical discrimination diagrams. (A) Sr/Y vs. Y (Defant and Drummond, 1993) and (B) La/Yb vs. Yb (Castillo et al., 1999) showing Adakitic geochemical signature and normal andesite-daciterhyolite trend of the intrusive rocks at Reko Diq; (C) SiO2 vs. La/Yb; and (D) SiO2 vs. Sm/Yb plots display relatively higher La/Yb and Sm/Yb ratios in the younger (PFB3, PFB4) porphyry intrusions; (E) SiO 2 vs. Sr/Y plot with intrusive rocks plot within high Sr/Y (>20) adakite field; and (F) Decreasing Sr content from younger to older intrusions; an effect of K-silicate alteration. No clear distinction evident between H14 and H15.  70  Figure 3.12 General geochemical characteristics and classification of the intrusive rocks at Reko Diq H14 and H15 porphyry centers: (A) Total alkali vs. silica plot (Le Maitre et al., 1989); (B) Nb/Y vs. Zr/TiO 2 (Winchester and Floyd, 1977) and (C) SiO2 vs. Zr/TiO2 discrimination plots. Harker diagrams: (D) SiO2 vs. TiO2; (E) SiO2 vs. Zr; (F) SiO2 vs. Nb; (G) SiO2 vs. La; (H) SiO2 vs. Nd; (I) SiO2 vs. Ba; (J) SiO2 vs. Rb; (K) SiO2 vs. Sr; and (L) SiO2 vs. Y plots. Abbreviations: AND=andesite, BA=basaltic andesite, BAS=basalt, BS=basanite, BTA=basaltic trachyandesite, PB=picrobasalt, PH=phonolite, PT=phonotephrite, TA=trachyandesite, TB=trachybasalt, TEP=tephrite, TP=tephriphonolite.  71  that early mineralized intrusive rocks (PFB1, PFB2) correlate with the fertile arc reference from Lut block, Iran (Richards et al., 2012). A progressive decrease of Sr content at 60 wt.% SiO2 is evident from late-barren PFB4 (Sr avg. 535 ppm) through late-mineral PFB3 (Sr avg. 471 ppm) intra-mineral PFB2 (Sr avg. 463 ppm) and early PFB1 (Sr avg. 384 ppm) clearly indicate the depletion of Sr in plagioclase with K-silicate and sericitic alteration (Table 3.3; Fig. 3.12 K). This alteration effect is well recognized in the Sr versus loss on ignition (LOI) plot, illustrating the addition of K2O and depletion of Sr with K-silicate alteration mainly in the early-mineral granodiorite (PFB1) and intra-mineral quartz-diorite (PFB1) porphyry intrusions (Fig. 3.11 F). 3.5 Pb isotope geochemistry Eight representative whole-rock samples of the intrusive rocks from Reko Diq western porphyry systems were analyzed for Pb isotopic composition at the Pacific Centre for Isotopic and Geochemical Research (PCIGR), University of British Columbia. The sample selection was based on similar composition range of hornblende-diorite (PFH), orehosting granodiorite (PFB1), quartz- diorite (PFB2, PFB3) and late-barren quartz-diorite (PFB4) with minimal effects of hydrothermal alteration and weathering based on petrographic observations and loss on ignition (L.O.I. wt. % = H2O+CO2; McLemore et al., 1993). The analytical procedure is given in Table B.3. Lead isotope values of the Reko Diq samples generally plot within the upper-crust field and along the crustal evolution curve of Stacey and Kramers (1975) (Fig. 3.13 A, B). At Reko Diq, the Pb isotope compositions have a narrow range of 207  Pb/204Pb (15.63-15.64) and  206  Pb/204Pb (18.62-18.77),  208  Pb/204Pb (38.79-38.99) ratios (Table 3.4). A distinct  fractionation trend is evident from the older (12.9 Ma) hornblende-diorite in H79 to biotitedominant granodiorite and quartz-diorite in H15-H14 and back into younger (11.9 Ma) hornblende-rich quartz-diorite in H13 porphyry centers (Fig. 3.13 C, D). 3.6 Sr and Nd isotope geochemistry Strontium and Nd isotopic compositions were analyzed in the above eight least altered whole-rock samples. Measured 143  87  Sr/86Sr ratio range from 0.705133 to 0.705369 and  Nd/144Nd ratio range from 0.512685 to 0.512725 (Table 3.5). There is a general trend of 72  increasing  87  Sr/86Sr ratio and decreasing  143  Nd/144Nd with time. The  206  Pb/204Pb versus  87  Sr/86Sr plot indicate a distinct fractionation trend from early hornblende-rich quartz-diorite  in H79 to biotite-rich granodiorite and quartz-diorite in H15-H14 and back into hornblende bearing quartz-diorite in H13 complex (Fig. 3.13 E). A similar trend is evident with increasing 87Sr/86Sr and decreasing 143Nd/144Nd ratios from H79 through H15, H14 and H13 porphyry systems (Fig. 3.13 F).  73  Table 3.4 Pb isotopic geochemistry of the H79, H15, H14 and H13 porphyry systems at Reko Diq complex. Sample No  Complex  Rock-type  Lith-code  Alteration  208  2δ  207  2δ  206  2δ  RD077-608 RD077-608-d RD545-578 RD567-554 RD545-1480 RD130-805 RD130-884 RD008-820 RD147-558 G-2 BHVO-2  H79  Hornblende-diorite Hornblende-diorite Granodiorite Quartz-diorite Quartz-diorite Granodiorite Quartz-diorite Quartz-diorite Quartz-diorite  PFH PFH PFB1 PFB2 PFB3 PFB1 PFB3 PFB4 PFB2  Weak potassic-sericitic Weak potassic-sericitic Intense potassic Moderate potassic Weak potassic Intense potassic Weak potassic Fresh to weak potassic Moderate potassic  38.80630309 38.7964495 38.95722205 38.99254481 38.93142003 38.90455702 38.96514561 38.96777599 38.79834196 38.90741743 38.20129302  0.001784 0.001820 0.001610 0.001786 0.002300 0.002200 0.002100 0.002360 0.001642 0.002140 0.001386  15.64023053 15.6367973 15.64709527 15.64522564 15.63849697 15.63672112 15.64377992 15.64605953 15.63840084 15.63752099 15.48888646  0.000712 0.000632 0.000624 0.00066 0.000794 0.000732 0.00075 0.000898 0.000706 0.000866 0.000546  18.62972768 18.62648763 18.75937306 18.77224165 18.73585564 18.71186039 18.76005612 18.76559563 18.63322737 18.40418768 18.6441057  0.00081 0.000838 0.000708 0.000846 0.00074 0.000868 0.000864 0.000846 0.000764 0.000984 0.000538  H79 H15 H15 H15 H14 H14 H14 H13  USGS reference material PCIGR reference material  Pb/204Pb  Pb/204Pb  Pb/204Pb  Abbreviations: RD077-608-d = duplicate, G-2 = granite USGS reference (Pretorius et al., 2007), BHVO-2 = Hawaiian basalts PCIGR reference (Weis et al., 2005)  Table 3.5 Sr and Nd isotopic geochemistry of the H79, H15, H14 and H13 porphyry systems at Reko Diq complex. Sample No  Complex  RD077-608 RD077-608-d RD545-578 RD567-554 RD545-1480 RD130-805 RD130-884 RD008-820 RD147-558 G-2  H79 H79 H15 H15 H15 H14 H14 H14 H13  Lithcode Hornblende-diorite PFH Hornblende-diorite PFH Granodiorite PFB1 Quartz-diorite PFB2 Quartz-diorite PFB3 Granodiorite PFB1 Quartz-diorite PFB3 Quartz-diorite PFB4 Quartz-diorite PFB2 USGS reference material Rock-type  Alteration  87  Sr/86Sr  2δ  143  Nd/144Nd  2δ  Weak potassic-sericitic Weak potassic-sericitic Intense potassic Moderate potassic Weak potassic Intense potassic Weak potassic Fresh to weak potassic Moderate potassic  0.705129 0.705121 0.705204 0.705149 0.705154 0.705365 0.705167 0.705166 0.705198 0.709776  0.000008 0.000007 0.000008 0.000009 0.000008 0.000008 0.000007 0.000007 0.000007 0.000007  0.512725 0.512729 0.512711 0.512718 0.512730 0.512689 0.512703 0.512706 0.512704 0.512225  0.000007 0.000007 0.000006 0.000007 0.000007 0.000006 0.000007 0.000007 0.000007 0.000008  Abbreviations: RD077-608-d = Duplicate, G-2 = Granite USGS reference (Pretorius et al., 2007)  74  Figure 3.13 Pb, Sr and Nd isotope compositions of the middle to late Miocene intrusive rocks at Reko Diq. (A-B) Reko Diq and Kerman arcs (Shafiei et al., 2009) plot in the upper crust field near the crustal growth curve of Stacey and Kramers (1975); Evolution lines for mantle, lower and upper crust are from Doe and Zartman (1979); (C-D) two distinct rock-groups with increasing radiogenic Pb from H79 to H15-H14 and decrease in H13 complex; (E-F) increasing Sr and decreasing Nd from mafic to felsic composition with time.  75  3.7 Discussion 3.7.1 Petrologic and petrochemical evolution Porphyry Cu deposits (Seedorff et al., 2005; Sillitoe, 2010) are associated with arc magmas at convergent plate boundaries (Sillitoe, 1972; Richard, 2003; Chiaradia et al., 2004; Gow and Walshe, 2005). Typical porphyry Cu (Au ± Mo) deposits are characterized by multiple intrusions of intermediate to felsic magmas (e.g., Gustafson et al., 2001; Vry et al., 2010; Redmond and Einaudi, 2010) and subsequent hydrothermal alteration. Evolution from mafic to felsic composition and increasing porphyritic textures is recognized in many porphyry copper districts (e.g., Lang and Titley, 1998; Lickfold et al., 2003, Lee et al., 2008). Additionally, most large scale economic porphyry Cu deposits are characterized by repeated influx of volatiles leading to extensive hydrothermal alteration and sulfide mineralization (Richards, 2003). The field relationships, petrographic and geochemical studies revealed that Reko Diq H15 and H14 porphyry centers are associated with four intrusive phases characterized by similar primary mineralogy and porphyritic textures. The early granodiorite and quartzdiorite (PFB1, PFB2) show relatively intense ore-stage hydrothermal alteration, veins and Cu-Fe-sulfides as compared to late-mineral (PFB3) and late-barren (PFB4) quartz-diorite intrusions, which explain the slight variation in petrochemical signatures. Abundant hydrous mineral phases (biotite, magnetite ± hornblende) in the early (PFB1, PFB2) intrusions suggests an oxidized melt composition with higher H2O content favorable for porphyry copper deposition (Burnham, 1979; Dilles, 1987, Chambefort et al., 2008, Richards, 2011, Richards et al., 2012). Phenocryst biotite, hornblende as well as apatite suggests volatile rich magma (Mueller and Forrestal 1998; Rohrlach and Loucks, 2005) formed the Reko Diq western porphyry deposits. The intrusive rocks at Reko Diq with enriched light-REE and depleted heavy-REE signatures suggest a shallow mantle source (~50 km) typical of calc-alkaline porphyry deposits. Major and trace element geochemistry show that early altered granodiorite and quartz-diorite intrusive rocks (PFB1, PFB2) have higher K2O and lower TiO2 and Al2O3 contents in conjunction with depleted Sr/Y ratios as compared to the late-stage, least altered 76  intrusive rocks (PFB3, PFB4), which fall into medium K2O with increasing TiO2, Al2O3 and SiO2 contents and relatively higher concentration of REE. The effect of hydrothermal alteration is apparent in all major element discrimination diagrams. The K2O/Al2O3 vs. P2O5/Al2O3 plot (Fig 3.7 C; Crawford et al., 2007a) in particular, demonstrates the effects of hydrothermal K-silicate alteration (K2O enriched) in the early (PFB1, PFB2) intrusions as evident in the drill core and petrographic thin section studies. The hydrothermal fluids in potassic alteration result in the destruction of plagioclase, leading to the removal of Sr as indicated by the depletion of Sr content with increasing loss on ignition (LOI) apparent in the early mineralized (PFB1, PFB2) porphyry intrusions (Fig 3.11 F). High Sr/Y and La/Yb ratios (≥20), high MgO (>3 wt.%) and low Y (1.9 ppm) and Yb (18 ppm) concentration in the intrusive rocks are consistent with an adakitic geochemical signature (Kay et al., 1978; Defant and Drummond 1990). Adakitic rocks were originally attributed to basalts from melting of subducting oceanic slab, however in case of Reko Diq and other porphyry deposits in the Andes (Castillo et al., 2006; this study), the petrochemical variations through time suggest that these rocks are linked to magma derived from the asthenospheric mantle wedge as a result of amphibole-garnet fractionation and/or crustal assimilation (Richards and Kerrich, 2007; Richards, 2011). Similar geochemical signatures and fractionation trends are reported in the intrusive rocks from the Shadan and Maher Abad porphyry deposits in the Lut block Iran (Richards et al., 2012). The overall petrochemical signatures at Reko Diq suggest an intermediate composition oxidized magma; fractionated and evolved into more felsic composition due to assimilation of upper crustal material (Hildreth and Moorbath 1988; Tosdal et al., 2009, Richards et al., 2012). 3.7.2 Isotopic compositions and petrogenetic evolution The Pb, Sr and Nd isotopic compositions at Reko Diq are generally uniform and suggest that middle to late Miocene (12.9-11.9 Ma) porphyry intrusions were emplaced in the upper crust along the crustal growth line of Stacey and Kramers (1975). Slightly radiogenic Pb corresponds to the orogenic Pb isotopic signatures (Doe and Zartman, 1979). The ore-hosting porphyry intrusions at Reko Diq have similar radiogenic Pb isotopic signatures as compared to the porphyry intrusions from the adjacent Kerman arc in Iran (Shafiei et al, 2009), reflecting crustal interaction in both magmatic arcs. The middle to late 77  Miocene event at Reko Diq represents an interesting trend of increasing radiogenic Pb with time and decreasing with the waning magmatism. A similar evolution pattern is evident with increasing Sr and decreasing Nd with time. These variations suggests periods of compression and relaxation in the tectonic environment (Tosdal and Richards, 2001). The early mafic to intermediate intrusive rocks (hornblende-diorite) in H79 appear to have been evolved and fractionated to relatively silicic compositions (quartz diorite) in H15H14 with input of mafic melts in H13 complex as evident by the hornblende-rich quartz diorite (PFB2; H13) with identical radiogenic isotope signature as in H79 complex (Fig 3.13). Periodic input of mafic melts is also evident in the zircon trace element geochemistry, introducing a discordant trend of cooler (high-Hf) zircon core and hotter (low-Hf) zircon rim analysis (Chapter 5). The mafic or intermediate to silicic trend is a common characteristic of many multi-intrusions porphyry Cu systems (Titley and Bean, 1981) in which the Cu-sulfide mineralization tend to occur with the later silicic porphyry intrusions (Cornejo et al., 1995; Casselman et al., 1995; Dilles et al., 2000; Maughan et al., 2002). 3.8 Conclusions Magmatic arcs containing large, high-grade hypogene porphyry Cu (Au-Mo) deposits (e.g., Sillitoe and Gappe, 1984, Camus and Dilles, 2001; Sillitoe, 2008; Perelló et al., 2008) represent a variety of petrologic and petrochemical characteristics. The middle to late Miocene (12.9-11.9 Ma) intrusive rocks at Reko Diq H15 and H14 porphyry Cu deposits are characterized by (1) crystallization of phenocryst biotite, hornblende, apatite and magnetite; (2) slightly negative Eu-anomalies; (3) fractionation from intermediate to felsic compositions and mafic recharge; and (4) equigranular to porphyritic textures through time as evident in many other porphyry Cu districts (Dilles, 1987; Cornejo et al., 1995; Redmond and Einaudi, 2010). The presence of phenocryst biotite, hornblende and magnetite suggest an oxidized and volatile-rich magma formed the Reko Diq western porphyry deposits. The sustain mafic recharge is evident in the zircon mineral chemistry with a discordant trend of lowtemperature high-Hf in the zircon core surrounded by high-temperature, low-Hf and relatively higher Th/U ratios in the corresponding rim analysis (Chapter 5).  78  The high Sr/Y and low Y and Yb adakitic signature (Kay, 1978) in the intrusive rocks is interpreted to have been associated with normal island-arc basalt-andesite-dacite-rhyolite magmas (Defant and Drummond 1990, 1993, 2001) linked to a tholeiitic to calc-alkaline suit arc magmatism with significant upper crustal interaction (Richards and Kerrich, 2007, Richards et al., 2012). The Pb isotope geochemical signatures in the intrusive rocks also suggest assimilation of crustal components and evolution of rising magma to form the giant Reko Diq porphyry Cu deposits.  79  Chapter 4 - Magmatic and hydrothermal chronology of Reko Diq H14-H15 4.1 Introduction The petrogenetic, geochemical and tectonic processes led to the formation of economic porphyry copper deposits, some of which account for much of the global copper, gold and molybdenum production (Whiting et al., 1993; Cooke et al., 2005; Sillitoe, 2010). Extensive exploration and research investigations over the last century have provided an excellent understanding of the geology, timing and ore-forming processes involved in the formation of large-scale porphyry copper deposits (Gustafson and Hunt, 1975; Ossandon et al., 2001; Pollard and Taylor, 2002; Seedorff et al., 2005; Sillitoe, 2010; Redmond and Einaudi, 2010; Barra et al., 2012; Lang et al., 2013). Just how long these systems operate is a subject of disagreement, as time frames as short as a hundred thousand years or episodically over as much as 3 to 4 million years have been proposed (Dilles and Wright, 1988; Campbell et al., 2006; Gustafson et al., 2001; Lund et al., 2002; Dilles et al., 2003; Deckart et al., 2005; Sillitoe and Mortensen, 2010). Some of the uncertainty stems from the inherent difficulty of precisely dating events in a complex magmatic and hydrothermal setting particularly those deposits of early Tertiary or older age where a complex post-mineral history or protracted cooling history of the more deeply emplaced porphyry systems may disturb the isotopic systems or give ages that span a considerable range of time (Richards and Noble, 1998; McInnes et al., 2005a; Harris et al., 2008). Furthermore, a superposition of age distinct magmatic and (or) hydrothermal events that each contributed Cu and other metals suggest that a long period of active or more likely episodic hydrothermal circulation is required to form a giant porphyry Cu deposit (Gustafson et al., 2001; Lund et al., 2002; Dilles et al., 2003; Harris et al., 2008; Sillitoe and Mortensen, 2010; Deckart et al., 2005; in press). Conversely, there is a growing body of evidence that suggest individual porphyry Cu deposits regardless of size may have formed over a short period of time, commonly measured in hundreds of thousand years or even less (e.g., Garwin, 2002; von Quadt et al., 2011; Îmer et al., in press). 2  A version of this chapter is submitted for publication: Razique, A., Tosdal, R.M., and Creaser, R., Rapid formation of the Reko Diq western porphyry systems, District Chagai, Balochistan-Pakistan.  80  The clusters of porphyry Cu-Au prospects, known as the western porphyry systems, at Reko Diq in the Chagai belt of western Balochistan (Pakistan) (Fig. 4.1) provide an excellent site to evaluate the question of porphyry Cu longevity. The four spatially and temporally distinct porphyry systems known as H79, H15, H14 and H13 complexes from north to south, are associated with Miocene porphyry stocks and dikes, intruded into early Miocene and older volcanic and sedimentary rocks (Fig. 4.2; Perelló et al., 2008; Razique et al., 2011). Mapping and extensive drill core data suggests that based on cross cutting relationships, the deposits young from north to south that is from H79 to H15 to H14 to H13 complex. With a global resource of 5.9 billion tons of ore with an average copper grade of 0.41% and gold grade of 0.22 g/t including a mineable resource of 2.2 billion tons with an average 0.53% Cu and 0.30 g/t Au largely in the combined H15-H14 prospects (Tethyan Copper Company 2013) clearly represent a significant example of giant Au-rich porphyry Cu deposits. This chapter builds upon published geochronologic data for the Reko Diq complex (Tables 4.1 and 4.2) to define the temporal constraints on the (1) crystallization of porphyry Cu-related magma; (2) sequence of emplacement of porphyry centers; (3) timing and duration of overlapping hydrothermal alteration and ore forming events; which lead to the formation of the western porphyries, including the enormous H15-H14 porphyry Cu-Au deposit at Reko Diq (Fig. 4.2). 4.2 Metallogenic framework In the Chagai belt of southwest Pakistan (Fig. 4.1), Perelló et al., (2008) recognized four magmatic episodes in the middle Eocene to late Miocene containing porphyry Cu-type alteration. The oldest magmatic event of middle to late Eocene led to the formation of Ziarate (43.1±1.1 Ma) and Gwanshero (36.1± 1.1Ma; Breitzman, 1979) prospects in the eastern part of Chagai belt. Late Oligocene and early Miocene magmatism (~24 to ~22 Ma) was accompanied by the formation of the Saindak and Tanjeel systems in the Reko Diq district (Fig. 4.2) and several other porphyry deposits elsewhere in the Chagai belt (Maryono et al., 1998; Perelló et al., 2008; Fu et al., 2006; Razique et al., 2011). A slightly younger, early Miocene magmatic event is characterized by amphibole-rich porphyry intrusions in Sor Baroot (16.9 ± 0.9 Ma), northeast Koh-e-Dalil (18.66 ± 0.2 Ma) (Fig. 4.2) and Ting Darguan  81  Figure 4.1 Geologic setting of the Reko Diq complex within the context of the Chagai belt, western Pakistan (modified after Perelló et al., 2008). The inset map shows geographical location.  82  Figure 4.2 Outcrop geology map of the Reko Diq complex and surrounding region, western Chagai belt, Balochistan-Pakistan  83  prospects (Perelló et al., 2008). A middle and late Miocene (14-10 Ma) magmatic event and associated porphyry Cu prospects dominate the Reko Diq complex (Table 4.2) but is also known elsewhere along the Chagai belt (Perelló et al., 2008). The youngest magmatic and associated metallogenic event is late Miocene and Pliocene in age, and represented by quartz-alunite epithermal and porphyry Cu-type alteration centers.  Published U-Pb, K-Ar and Re-Os isotope geochronology indicate that all the western porphyry centers including the giant H15 and H14 porphyry deposits formed within the middle to late Miocene (Table 4.2). Although the published age data provided initial temporal constraints on the emplacement of western porphyry systems, the ages did not provide sufficient constraints to address the question of longevity of multiple porphyry magmatic activity and duration of overlapping hydrothermal alteration. 4.3 Overview of the western porphyry prospects The Reko Diq western porphyry Cu-Au ± Mo deposits are spatially and temporally associated with a cluster of middle to late Miocene porphyry stocks and dikes (Figs. 4.2-4.5). The stocks are part of a complex magmatic sequence that intruded the late Oligocene and early Miocene (28-22 Ma) volcanic and sedimentary rocks forming the host Reko Diq volcanic complex (Table 4.1; Perelló et al., 2008; Richards et al., 2012) and underlying Oligocene red beds of the Dalbandin formation. Paleocene sedimentary rocks of the Juzzak formation and Eocene rocks of the Saindak formation are also present in the region and presumably are present at depth (Siddiqui, 1996, 2004; Perelló et al., 2008).  Five compositionally and texturally discrete calc-alkaline suite porphyry intrusions are recognized (Fig. 4.6; Table 4.3). The least altered porphyry intrusions are calc-alkaline, medium-K diorite to granodiorite in composition (SiO2 = ~58 – 63 weight %) (Richards et al., 2012; Razique A., unpublished data) with the older units having the greatest compositional scatter due to the overprinting hydrothermal K-silicate and sericitic alteration. The rock are normal arc-type magmatic rocks with adakitic characteristics, somewhat enriched in incompatible elements and depleted in compatible elements, and characterized by La/Yb ratios between 10 and 25 (Richards et al., 2012; Razique A., unpublished data). 84  Table 4.1 Available geochronologic data of the intrusive, volcanic and sedimentary rocks in Chagai belt. Complex  Rock type  Dated Material  Method  Age (Ma)  References  3  Quartz-diorite  Zircon  U-Pb  22.18±0.2  Fu et al., 2006  Saindak3  Quartz-diorite  Zircon  (U-Th)/He  20.83±0.3  Fu et al., 2006  4  Saindak Saindak  Quartz-diorite  Hydrothermal biotite  K-Ar  22.40±0.4  BHP unpub. report, 1997  Sor Baroot2  Gabbro (amphibole-bio)  Magmatic biotite  K-Ar  54.80±1.9  Perelló et al., 2008  Sor Baroot3  Andesitic volcanic rock  Whole-rock sericite  K-Ar  16.90±0.9  Perelló et al., 2008  Bukit Pasir2  Tonalite porphyry  Zircon  (U-Th)/He  10.36±0.2  Fu et al., 2006  Bukit Pasir3  Tonalite porphyry  Whole-rock biotite  K-Ar  11.00±1.1  Perelló et al., 2008  Reko Diq W  Fresh diorite porphyry  Zircon  U-Pb  13.36±0.2  Ivascanu and Fletcher, 2008  Reko Diq dykes1  Basaltic andesite  Zircon  U-Pb  26.04±0.3  Ivascanu and Fletcher, 2008  Reko Diq SW1  Andesitic volcanic rock  Zircon  U-Pb  27.42±0.5  Ivascanu and Fletcher, 2008  Felsic Dome1  Felsic ring-dyke  Zircon  U-Pb  14.29±0.3  Ivascanu and Fletcher, 2008  Reko Diq S1  Basaltic andesite  Zircon  U-Pb  22.42±0.5  Ivascanu and Fletcher, 2008  Reko Diq2  Quartz-diorite  Hydrothermal biotite  K-Ar  12.0±0.20  BHP unpub. report, 1997  1  Parrah Koh  3  Sandstone  Zircon  U-Pb  44.00±0.2  Fu et al., 2006  Parrah Koh3  Massive sandstone  Zircon  U-Pb  35.00±0.2  Fu et al., 2006  Parrah Koh3  Hornblende-diorite  Zircon  U-Pb  12.45±0.1  Fu et al., 2006  Parrah Koh3  Hornblende-diorite  Zircon  (U-Th)/He  9.75±0.18  Fu et al., 2006  Speghar Koh1  Dacite volcanic dome  Zircon  U/Pb  9.95±0.18  Ivascanu and Fletcher, 2008  Koh-e-Dalil N  Hornblende-andesite  Zircon  U/Pb  18.66±0.2  Ivascanu and Fletcher, 2008  Koh-e-Dalil NE2  Hornblende-diorite  Whole rock biotite  K-Ar  18.4±2.50  Perelló et al., 2008  Koh-e-Dalil S4  Diorite porphyry  Hydrothermal biotite  K-Ar  10.1±0.20  BHP unpub. report, 1997  Koh-e-Dalil S3  Diorite porphyry  Zircon  (U-Th)/He  9.14±0.24  Fu et al., 2006  Koh-e-Dalil Plug2  Hornblende-andesite  Amphibole  K-Ar  2.0±0.80  Perelló et al., 2008  Alam Reg  Basaltic flow  Amphibole  K-Ar  2.0±0.80  Perelló et al., 2008  Koh-e-Sultan2  Quartz-alunite vein  Hypogene alunite  40  5.9±2.8  Perelló et al., 2008  Kirtaka2  Granodiorite stock  Magmatic biotite  40  18.35±0.1  Perelló et al., 2008  Ting Darguan2  Porphyritic andesite  Hydrothermal biotite  40  23.84±0.1  Perelló et al., 2008  Ting Darguan4  Andesite porphyry dyke  Amphibole  K-Ar  18.8±1.5  Perelló et al., 2008  Ting Darguan4  Granodiorite batholith  Magmatic biotite  K-Ar  48.9±1.2  Perelló et al., 2008  1  2  Ting Darguan  4  Ar-39Ar Ar-39Ar Ar-39Ar  Granite batholith  Magmatic biotite  K-Ar  48.9±0.8  Perelló et al., 2008  Machi2  Andesitic volcanics  Sericite  K-Ar  24.3±1.0  Perelló et al., 2008  Ziarate2  Felsic porphyry  Hydrothermal biotite  40  37.2±0.2  Perelló et al., 2008  Ziarate2  Felsic porphyry  Muscovite (sericite)  K-Ar  43.1±1.1  Perelló et al., 2008  Basilani2  Granodiorite batholith  Magmatic biotite  K-Ar  44.2±0.8  Perelló et al., 2008  Granite pluton  Magmatic biotite  K-Ar  44.8±0.8  Perelló et al., 2008  Talaran  2  Ar-39Ar  1  Age determinations by Pacific Center for Isotopic and Geochemical Research (PCIGR), University of British Columbia, Canada  2  Age determinations by Geological Survey of Chile (SERNAGEOMIN), Santiago Chile  3  Age determinations by GEMOC Macquarie University, Australia  4  Age determination by BHP Minerals in Amdel Limited Mineral Services, Australia  85  Table 4.2 Available geochronology of the intrusive and volcanic rocks at Reko Diq, western Chagai belt. Complex  Downhole (m)  Lithology  Code  Mineral  Method  Age (Ma)  References  3  RDDT203-127  Andesitic volcanic  VIN  Zircon  U-Pb  23.75 ± 0.1  Fu et al., 2006  3  RDDT203-127  Diorite porphyry  PFQ  Zircon  U-Pb  23.29 ± 0.2  Fu et al., 2006  4  Tanjeel  Surface  Diorite porphyry  PFQ  Hyd. sericite  K-Ar  22.4 ± 0.20  BHP unpub. report, 1997  Tanjeel5  NR  Diorite porphyry  PFQ  Molybdenite  Re-Os  22.41 ± 0.07  Perelló et al., 2008  Tanjeel Tanjeel  4  Tanjeel  Surface  Diorite porphyry  PFQ  Sup. alunite  K-Ar  3.8 ± 1.6  BHP unpub. report, 1997  H35  4  Surface  Andesitic volcanic  VIN  Hyd. biotite  K-Ar  13.8 ± 0.1  BHP unpub. report, 1997  H35  3  RDDT150-316  Diorite porphyry  PFQ  Zircon  (U-Th)/He  11.45 ± 0.1  Fu et al., 2006  H794  Surface  Andesitic volcanic  VIN  Hyd. biotite  K-Ar  13 ± 0.20  BHP unpub. report, 1997  H79  1  Surface  Quartz-diorite  PFB2  Zircon  U-Pb  12.72 ± 0.3  Ivascanu and Fletcher, 2008  H15  3  RDDT52-320  Quartz-diorite  PFB2  Zircon  (U-Th)/He  9.79 ± 0.1  Fu et al., 2006  H15  5  NR  NR  NR  Molybdenite  Re-Os  11.73 ± 0.04  Perelló et al., 2008  H143  Surface  Quartz-diorite  PFB2  Zircon  U-Pb  12.22 ± 0.1  Fu et al., 2006  H14  4  Surface  Andesitic volcanic  VIN  Hyd. biotite  K-Ar  12 ± 0.20  BHP unpub. report, 1997  H14  5  NR  NR  NR  Molybdenite  Re-Os  11.82 ± 0.04  Perelló et al., 2008  H14  3  Surface  Quartz-diorite  PFB2  Zircon  U-Th  10.29 ± 0.2  Fu et al., 2006  H143  RDDT014-270  Quartz-diorite  PFB1  Zircon  (U-Th)/He  11.4 ± 0.1  Fu et al., 2006  H14  3  RDDT014-570  Quartz-diorite  PFB2  Zircon  (U-Th)/He  9.78 ± 0.1  Fu et al., 2006  H13  4  Surface  Andesitic volcanic  VIN  Hyd. biotite  K-Ar  12 ± 0.2  BHP unpub. report, 1997  PFH  Zircon  U-Pb  14.26 ± 0.1  Ivascanu and Fletcher, 2008  Surface  Hornblendediorite  H8  4  Surface  Dacite-porphyry  PFH  Hyd. biotite  K-Ar  10.8 ± 0.2  BHP unpub. report, 1997  H8  4  Surface  Andesitic volcanic  VIN  Hyd. biotite  K-Ar  11.4 ± 0.2  BHP unpub. report, 1997  H7  4  Surface  Andesitic volcanic  VIN  Hyd. biotite  K-Ar  10.8 ± 0.2  BHP unpub. report, 1997  H9  2  Surface  Andesitic volcanic  VIN  Hyd. biotite  K-Ar  10.5 ± 0.2  BHP unpub. report, 1997  Surface  Diorite porphyry  PFQ  Hyd. biotite  K-Ar  11.3 ± 0.2  BHP unpub. report, 1997  1  H14E  H364  Abbreviations: H=discovery hole (complex name), RDDT=Reko Diq diamond tail, NR=not recorded, VIN=andesitic volcanic rocks, PFB1=granodiorite, PFB2=quartz-diorite, PFQ=diorite-porphyry, PQF=quartz-diorite, PFH=hornblende-diorite, Hyd=hydrothermal, Sup=supergene, Mol=molybdenite. 1 Age determinations by Pacific Center for Isotopic and Geochemical Research (PCIGR), University of British Columbia, Vancouver Canada 2 Age determinations by Geological Survey of Chile (SERNAGEOMIN), Santiago Chile 3 Age determinations by GEMOC Macquarie University, Australia (Fu et al., 2006) 4 Age determination by BHP Minerals through Amdel Limited Mineral Services, Australia 5 Age determination by AIRE Program, Colorado State University, Colorado, USA  86  With the exception of the hornblende-diorite in H79 (PFH on Table 4.3), the intrusive rocks in the H13, H14, and H15 porphyry deposits share similar texture, mineralogy chemical compositions, and temporal relations (Table 4.3). Based on these characteristics, the quartz diorite to granodiorite sequence in the latter three prospects (Table 4.3) are from oldest to youngest, medium-grained porphyritic (PFB1), coarse-grained porphyritic (PFB2) coarse-grained porphyritic with aphanitic groundmass (PFB3), and coarse-grained porphyritic with phaneritic groundmass (PFB4) varieties. In general, all the intrusive rocks display porphyritic textures with abundant phenocrysts of plagioclase and variable amount of biotite, magmatic quartz, and amphibole embedded in a fine-grained microcrystalline to aphanitic groundmass (Fig. 4.6). The early granodiorite porphyry (PFB1) and quartz-diorite (PFB2) are intensely altered to hydrothermal biotite + K-feldspar + magnetite and locally overprinted by sericite + chlorite; each alteration assemblage destroyed the primary igneous textures and mineral constituents. Late mineral quartz-diorite (PFB3) displays both pervasive chlorite + sericite + clay alteration at shallow levels and weaker chlorite + sericite + biotite in the deeper core of the system. In contrast, late barren quartz-diorite (PFB4) is characterized by well-preserved primary mineralogy and coarse-grained porphyritic textures (Fig. 4.6). 4.3.1 H79 porphyry complex H79 porphyry complex is centered on hornblende-diorite (PFH) porphyry intrusions emplaced in the north of Reko Diq western porphyry complex (Fig. 4.3). The intrusions are volumetrically restricted to narrow (50 x 100m), NE trending (050o) dike swarm cut by latestage barren dacite porphyry in the central part of the system. Hornblende-diorite is characterized by intense potassic, overprinted by sericitic-chlorite and fringed by propylitic alteration assemblages. A network of hydrothermal veins is associated with the hydrothermal alteration assemblages. Angular to sub-angular, cm-scale xenoliths of host volcanic and sedimentary rocks are common in the porphyry intrusions. 4.3.2 H15 porphyry complex H15 porphyry complex is developed over a large (800m2 wide) porphyry stock intruded by NE and NW oriented, 25-50m wide and 100-200m long dikes of syn-mineral quartz-diorite porphyry (Fig. 4.3, 4.4). Xenolith-rich contact zones characterize the early 87  porphyry (PFB1) whereas younger quartz-diorite (PFB2) intrusions locally have preserved cm-scale chilled margins adjacent to the early porphyry. The intrusive rocks contain cmscale sub-angular xenoliths of andesitic volcanic and sedimentary rocks and are overprinted by pervasive potassic and sericitic alteration assemblages, and cut by multistage hydrothermal veins (Fig. 4.6). Volumetrically small (30 x 20m), late mineral quartz-diorite porphyry (PFB3) in H15 complex (Fig. 4.4 and 4.6) intruded older porphyry and associated hydrothermal alteration, veins and Cu-sulfide mineralized rock is cut by the late-stage barren quartz-diorite porphyry intrusions (Fig. 4.4). 4.3.3 H14 porphyry complex H14 porphyry complex is centered on a ~100 x 250m wide early porphyry stocks (PFB1) intruded by a series of NE oriented, 25-50m wide and 100-200m long stocks and dikes of quartz-diorite porphyry (PFB2) (Fig. 4.3 and 4.5). Pervasive potassic alteration, overprinted sericitic alteration assemblages, networks of multi-generation veins characterizes the older rocks in the complex (Fig. 4.6). Abundant sub-angular (1-10cm) xenoliths of volcanic, sedimentary and intrusive rocks are also present. The early (PFB1), quartz-diorite (PFB2) porphyry intrusions and associated hydrothermal mineralogy, veins and sulfide minerals are cut by narrow (10-50m2) late mineral porphyry (PFB3) intrusions (Fig. 4.5). This intrusive phase contains xenoliths of older intrusive rocks and is cut by 2 mm to 2 cm thick pyrite, chalcopyrite ± quartz-sericite veins. Late-barren quartz-diorite (PFB4) dikes intruded at depth (>800m) and cut all older intrusive and hydrothermal phases, as evident in one of the deep resource holes (RD510) at Reko Diq. This youngest porphyry is characterized by relatively fresh coarse-grained porphyritic textures (Fig. 4.6). 4.3.4 H13 porphyry complex The southernmost H13 porphyry complex is associated with NW-trending, hornblenderich quartz-diorite dikes intruded by narrow 10 x 20m wide, isolated dacite porphyry stocks (Fig. 4.3). A hydrothermal breccia crops out in the central part of the system. Similar to H15 and H14 porphyry centers, the quartz-diorite in H13 complex is characterized by hydrothermal potassic and sericitic-chlorite alteration assemblages, multi-generation veins, and xenoliths of host volcanic and sedimentary rocks. 88  Figure 4.3 Outcrop geology map of the Reko Diq western porphyry complex, Balochistan-Pakistan. The cluster of middle to late Miocene porphyry intrusions emplaced along a NW-trend forming H79, H15, H14 and H13 porphyry centers.  89  Figure 4.4 East-west geological section (A-A’ UTM 3223300m N) across H15 porphyry complex projecting up to 100m downhole drilling data onto the section: Multiple crosscutting porphyry intrusions emplaced upward into a sequence of volcanic and sedimentary rocks. Early (PFB1) porphyry stock is intruded by thin dikes of intra-mineral (PFB2) and late mineral (PFB3) quartz diorite intrusions.  90  Figure 4.5 East-west geological section (B-B’ - UTM 3222200m N) across H14 porphyry complex projecting up to 100m downhole drilling data onto the section: Multiple crosscutting porphyry intrusions emplaced as vertical to sub-vertical stocks and dykes host by volcanic and sedimentary rocks. Early porphyry (PFB1) is intruded by intra-mineral quartz-diorite (PFB2) and subsequently intersected by narrow dykes of late-mineral 91 (PFB3) and late-barren (PFB4) quartz-diorite intrusions in the core of the system.  Figure 4.6 Core photographs illustrating the sequence and subtle variations in texture and composition of intrusive rocks in H14 and H15 porphyry systems: (A-A’) Early phase medium-grained, equigranular to porphyritic rock (PFB1) with a holocrystalline groundmass displaying intense potassic alteration of biotite + K- feldspar + magnetite, (B-B’) Intra-mineral phase, coarse-grained porphyritic quartz diorite (PFB2) with a finer crystalline groundmass. Secondary biotite-K-feldspars-magnetite are locally overprinted by sericite-chlorite, (C-C’) Late mineral, coarse-grained porphyritic quartz diorite (PFB3) with 2-12mm phenocrysts of plagioclase, quartz, biotite and minor amphiboles set in an aphanitic groundmass altered to sericitechlorite ± biotite, and (D-D’) Late-stage, coarse-grained porphyritic quartz diorite (PFB4) with 3-15mm, euhedral phenocrysts of plagioclase, quartz, biotite and minor amphiboles set in a phaneritic groundmass.  92  4.4 Published geochronologic data for the western porphyry cluster Previously published geochronology for western porphyry complex is limited to U-Pb zircon crystallization age of 12.72 ± 0.3 Ma for H79 (Ivascanu and Fletcher, 2008) and 12.22 ± 0.15 Ma for the H14 complex (Fu et al., 2006). Maryono et al. (1998) reported a late Miocene age for the H14-H15 porphyry Cu-Au deposit based on a single K-Ar age (12.0 ± 0.1 Ma) for potassic alteration in the andesitic volcanic rocks at H14 complex. An identical K-Ar age of 12.0 ± 0.2 Ma for potassic alteration in H13 complex has also been reported (Maryono et al., 1998). These ages agree within the limits of their analytical uncertainty with the Re-Os ages on molybdenite associated with Cu-sulfide minerals in H14 (11.82 ± 0.04 Ma) and H15 (11.73 ± 0.04 Ma) porphyry deposits (Perelló et al., 2008). Clearly the available chronologic data indicate a middle Miocene age for porphyry Cu formation. 4.5 Geochronologic data New U-Pb geochronologic data (Table 4.3) reported herein includes ten U-Pb-zircon ages determined using the Sensitive High-mass Resolution Ion Microprobe - Reverse Geometry (SHRIMP-RG) combined with two Re-Os-molybdenite ages (Table 4.4) using Negative Thermal Ionization Mass Spectrometry (NTIMS). One new age for the H79 complex, four new ages for the H15, four new ages for the H14 complex, and one for the H13 complex are reported. The U-Pb zircon geochronology confirms the field relation documenting a sequence from oldest to youngest porphyry intrusions spatially distributed from north to south in H79, H15, H14 and H13 porphyry centers respectively. The two new Re-Os ages on molybdenite reported herein are identical to the U-Pb ages for the H15 and H14 complex, but are also older than previously published ages from the same complexes. The U-Pb zircon and Re-Os molybdenite ages are presented to constrain the magmatic and hydrothermal evolution of the western porphyry prospects. Sample descriptions for zircon grains separates are given in (Table C.1). The cathodoluminescence images of zircons and the location of zircon spot analysis are presented in (Fig. C.1). The SHRIMP-RG analytical technique for zircon UP-Pb-Th analysis is given in (Table C.2) and the complete dataset of U-Pb-zircon spot analysis is given in (Table C.3). Samples for Re-Os molybdenite geochronology are described in (Table C.4) and the analytical procedure is given in (Table C.5). 93  Table 4.3 U-Pb zircon SHRIMP-RG ages of the intrusive rocks in Reko Diq western porphyry Cu-Au deposits. Sample ID  Area Lithology  Code  Mineral  Method  Age (Ma) ± 2σ  MSWD  RD077-608  H79  Hornblendediorite  PFH  Zircon  U-Pb  12.9 ± 0..2  0.4  Hornblende rich quartz-diorite with phenocrysts of plagioclase, quartz, and biotite embedded in a finer crystalline groundmass.  RD341-197  H15  Granodiorite  PFB1  Zircon  U-Pb  12.5 ± 0.1  1.4  Main ore-stage, potassic altered, granodiorite crowded with plagioclase + biotite + quartz set in a crystalline groundmass.  RD068-518  H15  Granodiorite  PFB1  Zircon  U-Pb  12.2 ± 0.2  1.21  Main ore-stage, potassic altered granodiorite with plagioclase + biotite + quartz set in a crystalline groundmass.  RD341-500  H15  Quartz diorite  PFB2  Zircon  U-Pb  12.1 ± 0.2  2.8  Intra-mineral quartz diorite containing subhedral feldspars, biotite, and quartz set in a fine K-altered aphanitic groundmass.  RD341-440  H15  Quartz diorite  PFB3  Zircon  U-Pb  12.1 ± 0.4  0.69  Late-mineral quartz-diorite with plagioclase + biotite + hornblende + quartz set in a fine aphanitic, chloritesericite altered groundmass.  RD008-668  H14  Granodiorite  PFB1  Zircon  U-Pb  12.0 ± 0.15 0.31  Main ore-stage, potassically altered granodiorite porphyry crowded with plagioclase + biotite + quartz set in a crystalline ground-mass.  RD510-1545  H14  Quartz diorite  PFB2  Zircon  U-Pb  12.05 ± 0.16 0..42  Deep intra-mineral quartz-diorite with preserved primary texture and mineral constituents. Weak hydrothermal biotite + magnetite.  RD116-506  H14  Quartz diorite  PFB3  Zircon  U-Pb  12.01 ± 0.16 0.51  RD008-820  H14  Quartz diorite  PFB4  Zircon  U-Pb  12.0 ± 0.1  Late-mineral quartz-diorite with euhedral plagioclase + biotite ± hornblende + smokey quartz embedded in an aphanitic, chloritic groundmass. Late-barren quartz-diorite with euhedral plagioclase, biotite + quartz eyes set in a sub-crystalline matrix weakly altered to biotite.  RD147-561  H13  Quartz diorite  PFB2  Zircon  U-Pb  11.93 ± 0.2 2.04  0.56  Description  Potassic-sericitic altered quartzdiorite with euhedral feldspars + quartz + biotite ± amphiboles set in a finer crystalline ground-mass.  * U-Pb-zircon (SHRIMP-RG) ages in this study determined at Stanford-USGS Micro Analysis Center, California, USA,  94  For young zircons, U-Pb SHRIMP-RG ages are calculated from the weighted mean 207  Pb-corrected 206Pb/238U ages of spot analyses on individual crystals, due to the poor ability  of the SHRIMP-RG to precisely measure small amounts of  204  Pb, the isotope used to ensure  proper correction for any common Pb (Ireland and Williams, 2003). Individual analyses characterized by measurable common Pb may be included in the age calculation even though their inclusion may degrade the statistical validity of the age. Zircon spot analyses containing distinct chemical characteristics, such as elevated Th/U or high U concentrations from the normal population may also be excluded. Tera-Wasserburg (1972) inverse concordia diagrams were utilized to confirm the exclusion of data points as this diagram easily evaluates the possibility for (i) Pb loss from zircons; (ii) the presence of older zircons; and (iii) the influence of common Pb on the interpreted ages. These plots are shown adjacent to the weighted mean histogram plots for each sample. A concordia intercept age calculated where possible for each sample is generally within the analytical uncertainty of weighted mean 207Pb-corrected 206Pb/238U age.  Zircon is a refractory mineral that can have a complicated magmatic growth history, forming xenocrysts, inherited cores within newly crystallized zircons, as well as antecrysts. Xenocrysts are zircon crystals incorporated into magma from the country rocks that lack any new magmatic zircon overgrowths. In contrast, inherited zircons form cores to new zircons crystallized from the magma. Antecrysts are zircon crystals formed early within the magma chamber that may be slightly older than the age of final crystallization (Miller et al., 2007; von Quadt et al., 2011). Studies of recent volcanic rocks suggest antecrystic zircons can be as much as 300,000 years older than the age of the eruption (Bacon and Lowenstern, 2004; Bachman et al., 2007). Antecrystic zircons are in essence part of the crystallizing magma that may have been plucked off the walls of a convecting and deeper crustal level magma chamber, and incorporated in the rising porphyry stock (Miller et al., 2007). Because of their slightly older ages, their presence can, particularly for spot instruments such as the SHRIMPRG, cause analytical scatter in zircons of Tertiary age, thereby increasing the uncertainty in the calculated ages. There is suggestive evidence that antecrysts might be present in the Reko Diq porphyry intrusions.  95  4.5.1 SHRIMP-RG U-Pb geochronology The ten samples of intrusive rocks at Reko Diq western porphyry complex were selected based on field relationships and petrography with the goal of defining the temporal distribution of intrusive rocks in porphyry centers. Emphasis was placed on H15-H14 as these represent the main Cu-Au resource and the complexes where the geological knowledge is best developed. The H79 and H13 systems were included to complete the temporal evolution of the closely spaced western porphyry complex. Initial sample preparation and zircon grain separation was done at the PCIGR Laboratories, University of British Columbia. Zircon crystals from the intrusive rocks at Reko Diq western porphyry complex show a variety of sizes, morphologies and colors ranging from clear to pale white and/or yellow. Zircons from hornblende-diorite in H79 complex are smaller in size and less abundant compared to the tabular and prismatic zircons of quartz-diorite in H14, H15 and H13 complexes (Fig. 4.7).  96  Figure 4.7 Cathodoluminescence images of the zircons from porphyry samples in H79, H15, H14, and H13 complex. Circles represent the location of spot analyses dated by SHRIMP-RG.  97  4.5.1.1 H79 Complex Hornblende-rich quartz-diorite (PFH) in the H79 complex is the oldest intrusive unit in the Reko Diq western porphyry complex. Sample (RD077-608) contains clear to pale, euhedral to subhedral, granular (<300µm) zircons, which display concentric zonation pattern and less common sector zonation and inherited cores visible under cathodoluminescence (Fig. 4.7 A). Measured U-Pb ages for individual crystals range over 1.2 million years with a calculated mean age of 12.64 ± 0.29 (MSWD = 1.2) for ten of the twelve crystals (Fig. 4.8 A). Two older zircons with late Oligocene ages of 24.2 ± 0.3 and 25.5 ± 0.4 Ma are not included in the age calculation. These zircons are clearly xenocrysts and reflect incorporation of wall rock, either from the host Reko Diq volcanic sequence (evident as xenoliths) or from the intrusions associated with that magmatic episode (Table 4.1).  Of the ten crystals, three are characterized by slightly younger ages, and form a distinct cluster well above the concordia curve suggesting the presence of common Pb and perhaps minor Pb loss. Excluding those three crystals, the remaining seven coherent crystals defined a weighted mean U-Pb age of 12.87 ± 0.27 Ma (MSWD = 0.4), which is interpreted to be the age of crystallization in H79 complex (Fig. 4.8 B). A U-Pb zircon age of 12.72 ± 0.37 Ma reported for the hornblende-diorite (PFH) in H79 complex (Ivascanu and Fletcher, 2008) agrees within analytical uncertainty. The ~150 ka difference between the two hornblendediorite (PFH) porphyry intrusions is consistent with the age range that characterizes the H15 and H14 complex (see below). 4.5.1.2 H15 Complex An early mineral porphyry stock intruded by intra-mineral and late-mineral stocks and dikes forms the H15 complex. Zircons from the early porphyry (PFB1) and intra-mineral quartz-diorite (PFB2, PFB3) samples in H15 complex are elongated, tabular, 200-400µm in size, pale-white in color and display systematic zircon growth patterns (Fig. 4.7 B,C,D). Overall, the U-Pb systematics of the zircons from the H15 complex are somewhat complex, with a greater degree of scatter in ages than is encountered in the adjacent and younger H14 complex (see below).  98  Ten zircons (sample RD341-197) from the oldest recognized suite (PFB1) yielded an age of 12.40 ± 0.20 Ma (Fig. 4.8 B), but with a slightly high MSWD = 2.9. Two zircons are displaced to younger ages than the bulk of the zircons on the concordia diagram (Fig. 4.8 B). These zircons are considered to have undergone minor Pb loss. A weighted mean age of 12.49 ± 0.11 Ma (MSWD = 1.11) for the remaining eight zircons is interpreted to be the crystallization age of the rocks. A regression through the same zircons on the concordia diagram suggests an essentially identical age of 12.33 ± 0.16 Ma (MSWD=1.4). Zircons from a second early porphyry (PFB1; RD068-518) yielded a younger U-Pb age of 12.18 ± 0.19 Ma (MSWD = 1.2) considering all twelve analyzed crystals (Fig. 4.8 C). This age, although younger than the other PFB1 porphyry (see above), agrees within their analytical uncertainties. Three of the grains have calculated ages that are slightly older than the remainder, although they agree with the others within their analytical uncertainty. These three ages range from 12.5 ± 0.2 to 12.6 ± 0.3 Ma, whereas the majority of zircons range from 11.9 ± 0.3 to 12.3 ± 0.3 Ma. These two groups of U-Pb ages in zircons might represent distinct ages of zircon growth, either the widespread presence of Pb loss in the younger zircons or conversely the presence of antecrystic and slightly older zircons. Whether this is the case for this sample is unknown as the groups are not sufficiently distinct in age. However, the older age group is similar in age to that for the other PFB1 porphyry, whereas the younger group is more similar to the ages of the H14 complex (see below). Ten zircons from an intra-mineral porphyry (PFB2; RD341-500) scatter in U-Pb ages over 1.2 million years. Collectively, the ten crystals suggest an age of 12.58 ± 0.29 Ma (Fig. 4.8 D), with a high degree of scatter (MSWD = 2.8). On the concordia diagram, it appears possible that there might be the potential for two populations, one with an age of 12.90 ± 0.24 Ma, and the other with a poorly defined age of 12.19 ± 0.27 Ma. The older age is consistent with these zircons being xenocrysts incorporated from rocks associated with the H79 complex. The younger age is consistent with field relations whereby the PFB2 suite of samples intruded the PFB1 porphyry suite. However, there is no compelling reason to believe that there are two ages of zircons in the rock particularly since a still younger porphyry (see below) has an older age around 12.5 Ma. 99  Figure 4.8 A-D U-Pb-zircon geochronology diagrams and 238U/206Pb vs. 207Pb/206Pb concordia plots of SHRIMP-RG spot analysis from middle to late Miocene porphyry intrusions in H15 and H79 complexes. Ages are based on the 207Pb-corrected and 206Pb/238U weighted mean age calculation (black). Ages in grey tones have been excluded from the age calculations based on criteria outline in the text. Weighted mean ages have 2σ uncertainties. 100  Twelve zircons from a late-mineral porphyry (PFB3; RD341-440) define a U-Pb age of 12.45 ± 0.20 Ma (MSWD = 1.5). As with the other porphyry intrusions in the H15 complex, slightly older zircons with ages of 12.9 Ma appear to be present. One zircon with a spot age of 13.2 ± 0.4 Ma is likely a xenocryst inherited from older magmatic rocks (Fig. 4.8 E). Another crystal with an age of 12.9 ± 0.3 Ma may also be a xenocryst, but the age clearly overlaps with the bulk of the analytical data within the limits of the analytical uncertainty. In addition, a third zircon has an age slightly younger and displaced slightly from the bulk of the zircons on the concordia diagram. Excluding the oldest and youngest zircons results in an essentially identical age of 12.49 ± 0.16 Ma (MSWD = 0.69), in good agreement with the ages of the other porphyry intrusions within the H15 complex. In view of the growing evidence that individual porphyry centers, although part of larger magmatic systems, probably formed over short time intervals (von Quadt et al., 2011), probability plots permit the examination of the range of zircons found in the porphyry intrusions. Overall, zircons in the three related porphyry intrusions dated in H15 have U-Pb ages that dominantly are between 12 and 13 Ma. The older and younger zircons are clearly in a minority. The peak of the probability plot is 12.39 Ma, which is consistent with interpreted ages from the individual porphyry intrusions (Fig. 4.9 A). On an age histogram plot, the distribution of ages is more evident. A coherent group with an age based on 39 zircons is 12.42 + 0.15/ – 0.11 Ma can be defined for the entire complex. This age is the best estimate for the age of H15 magmatic complex (Fig. 4.9 B), suggesting the magmatic history of the complex took place in ~260 ka. 4.5.1.3 H14 Complex The mineralized H14 complex contains an early porphyry stock (PFB1) intruded into volcanic, volcaniclastic, and sedimentary rocks (Fig. 4.3 and 4.5). Intra-mineral and late mineral stocks and dikes (PFB2, PFB3) intrude the early porphyry and supracrustal country rocks. The porphyry samples from H14 complex contain abundant, large (<500µm), pale to clear zircons displaying well-developed concentric zonation (Fig. 4.7 E, F). The early porphyry (PFB1; RD008-668) intruded northwest of H14 complex yielded an age of 12.26 ± 0.24 Ma (MSWD = 2.9) based on twelve zircon grains (Fig. 4.8 F). Two 101  zircon grains with ages of 13.0 ± 0.2 and 12.7 ± 0.2 Ma are older beyond the analytical uncertainties and plot outside the main cluster of ages on the concordia diagram. Excluding these zircons from the sample set results in a weighted mean age of 12.05 ± 0.15 Ma (MSWD = 0.31) on ten crystals. Twelve zircons from an intra-mineral porphyry (PFB2; RD510-1545), range over 1.4 million years (Fig. 4.8 G). Three zircons having ages younger than 11.6 Ma are considered to have lost Pb as they are displaced from the main cluster of the data on the concordia diagram. Excluding the young zircons resulted in an age of 12.29 ± 0.17 Ma, but with a slightly large MSWD of 2.11. A fourth zircon with an age of 12.5 ± 0.1 Ma is slightly older than the remainder and lies at the extreme limit of the analytical uncertainty of the weighted mean age. Exclusion of this crystal, which has high uranium contents, from the age calculation changes that age slightly to 12.06 ± 0.16 Ma (MSWD = 0.42). This latter age is the preferred crystallization age for the rock. Zircons from late mineral porphyry (PFB3; RD116-506) are a mixed population (Fig. 4.8 H). Two zircons have early Miocene ages of 22.9±0.4 and 22.4±0.4 Ma, suggesting incorporation of zircons from the host wall rocks. The remaining ten zircons give a weighted mean age 12.10 ± 0.22 Ma (MSWD = 1.7). However, two of these zircons have ages that are only slightly older, being 13.4±0.6 and 12.6 ± 0.2 Ma, and are displaced from the main cluster of eight remaining zircons. Using just the eight clustered zircons results in a weighted mean age of 12.00 ± 0.16 Ma (MSWD = 0.51) (Fig. 4.8 H). Either age is compatible with the other rocks from the complex. However, the younger age is preferred as the slightly older but concordant zircons are clearly not consistent with the main group. Twelve zircons in the late-stage quartz-diorite (PFB4; RD008-820) yielded ages ranging over 1.1 million years, with a weighted mean age of 12.12 ± 0.22 Ma and slightly high MSWD = 2.5 (Fig. 4.8). One grain with an age of 12.7 ± 0.2 Ma appears too old and is displaced from the bulk of the zircons. Similarly, a second crystal with an age of 11.2 ± 0.2 Ma appears younger and is also displaced from the main group. Excluding these two crystals result in an identical age of 12.14 ± 0.14 Ma (MSWD = 0.56), which is interpreted to be the age of the youngest intrusion in the complex. 102  Figure 4.8 E-H U-Pb-zircon geochronology diagrams and 238U/206Pb vs. 207Pb/206Pb concordia plots of SHRIMP-RG spot analysis from middle to late Miocene porphyry intrusions in H15 and H14 complexes. Ages are based on the 207Pb-corrected and 206Pb/238U weighted mean age calculation (black). Ages in grey tones have been excluded from the age calculations based on criteria outline in the text. Weighted mean ages have 2σ uncertainties.  103  Overall, zircons in the four related porphyry intrusions dated in H14 complex have U-Pb ages that dominantly are between 12 and 13 Ma. Older and younger zircons are in a minority. The peak of the probability plot is 12.11 Ma, which is consistent with interpreted ages from the individual porphyry intrusions (Fig. 4.9 C). On an age histogram plot, the distribution of ages is more evident. A coherent group with an age based on 40 zircons is 12.09 + 0.8/ – 0.4 Ma (Fig. 4.9 D). These ages are inferred to best estimate the formation age for the H14, suggesting magmatism in the complex took place in less than ~120 ka. 4.5.1.4 H13 Complex Hornblende-bearing mineralized porphyry (PFB2; RD147-561) is the youngest mineralized intrusion in H13 complex, the southernmost of the western porphyry complex. Abundant, large (200-500µm), clear to pale white, elongated zircons exhibiting well-developed concentric zircon growth bands are present (Fig. 4.7 G). Eleven of twelve zircon grains gave a weighted mean U-Pb age of 11.93 ± 0.14 Ma (MSWD = 1.2) (Fig. 4.8 J). The excluded zircon is slightly younger, presumably due to Pb loss as evident from the Tera-Wasserburg concordia plot; this zircon was not included in the age calculation. The age distribution of the eleven zircons suggests the potential for two populations of zircons. Seven zircons with ages <12 Ma suggest an age of 11.77 ± 0.16 Ma; these zircons dominate the zircon population of the rock. There is however, a group of four zircons that form a cluster, although overlapping within the limits of the analytical uncertainty, suggest the potential for a slightly older zircons with a mean age of 12.11 ± 0.16 Ma, essentially identical to the interpreted age for the adjacent H14 complex (Fig. 4.3). As there is no valid reason for excluding any of the eleven zircons from the age calculation, the age of 11.93 Ma ± 0.14 Ma is interpreted to be the age of the intra-mineral porphyry in H13 complex.  104  Figure 4.8-I-J U-Pb-zircon geochronology diagrams and 238U/206Pb vs. 207Pb/206Pb concordia plots of SHRIMP-RG spot analysis from middle to late Miocene porphyry intrusions in H14 and H13 complexes. Ages are based on the 207Pb-corrected and 206Pb/238U weighted mean age calculation (black). Ages in grey tones have been excluded from the age calculations based on criteria outline in the text. Weighted mean ages have 2σ uncertainties.  105  Figure 4.9 (A) Probability density plot and (B) composition histogram plot of all U-Pb-zircon SHRIMPRG spot ages analyzed from the porphyry intrusions in the Reko Diq H15 complex. (C) Probability density plot and (D) composition histogram plot of all U-Pb-zircon SHRIMP-RG spot ages analyzed from the porphyry intrusions in the Reko Diq H14 complex.  106  4.5.2 Molybdenite Re-Os chronology The Cu-sulfide minerals at Reko Diq H15 and H14 porphyry deposits are accompanied by molybdenite in micro veinlets within quartz veins. Molybdenite commonly overgrows pyrite, chalcopyrite, or bornite in potassic alteration zones, and is thus generally younger and late in the paragenesis. Molybdenite from two drill core samples was dated, one each from H15 and H14 using the Re-Os methods in order to help constrain the timing of sulfide precipitation events (Table 4.5). The older Re-Os age of 12.50 ± 0.06 Ma (RD567-1398) was obtained from a coarsegrained molybdenite vein in the potassic-altered volcaniclastic rock overprinted by sericite in H15 complex. This age is consistent with the U-Pb crystallization age for the porphyry complex of 12.42 + 0.15/ – 0.11 Ma. In the H14 complex, sample RD130-813 yielded a molybdenite ReOs age of 12.14 ± 0.05 Ma in potassic-altered early porphyry (PFB1). This age agrees with the zircon U-Pb crystallization age of 12.09 + 0.8/ – 0.4 Ma for the H14 porphyry intrusions. The Re-Os ages for molybdenite reported herein are older than two molybdenite Re-Os ages of 11.82 ± 0.04 Ma (H14 complex) and 11.73 ± 0.04 Ma (H15 complex) (Table 4.4) reported by Perelló et al., (2008). The published ages are also associated with potassic and transitional sericite-chlorite alteration. Table 4.4 Re-Os-molybdenite ages of the Cu-sulfide mineralization in H15 and H14 porphyry deposits Complex H15  1  Sample ID  Description  Mineral  Re (ppm)  Os (ppb)  Age (Ma)± 2σ  RD567-1398  Coarse grained, flaky molybdenite vein intersecting disseminated and vein pyrite-chalcopyrite within pervasive quartz-sericite-chlorite alteration.  Mol  348.2  45.9  12.59 ± 0.06  H152  MDID-588  Mol  254.1  31.22  11.73 ± 0.04  H141  RD130-813  Quartz-molybdenite-chalcopyrite veinlet with K-feldspar halos within potassic (K-feldspar-biotite-magnetite) alteration. Disseminated and micro-veinlet chalcopyrite-bornite + overgrown molybdenite within intense K-feldspar + biotite + magnetite alteration.  Mol  384.2  48.86  12.14 ± 0.05  H142  MDID-589  Quartz + pyrite-chalcopyrite + molybdenite veinlet with sericitechlorite-clay alteration selvages  Mol  117.98  14.60  11.82 ± 0.04  1 2  Re-Os-molybdenite age determinations in this study performed at radiogenic isotope facility, University of Alberta, Canada. Re-Os-molybdenite ages determinations by AIRIE Program, Colorado State University, Colorado, USA (Perelló et al., 2008)  107  4.6 Discussion 4.6.1 Duration of magmatic and hydrothermal events The U-Pb zircon and Re-Os molybdenite ages obtained in this study indicate a short time span, from 12.87 ± 0.27 Ma to 11.93 Ma ± 0.14 Ma, for magmatic activity in the western porphyry prospects at Reko Diq (Fig. 4.10). The time frame for the formation of four spatially distinct magmatic centers is ~1 Ma or as much as 1.3 Ma if full analytical uncertainties are incorporated. As hydrothermal activity in porphyry Cu systems is intimately tied to the emplacement of porphyry intrusions (Seedorff et al., 2005; Sillitoe, 2010), the associated metalliferous event is assumed to have similar duration. The K-Ar-biotite ages of ~12 Ma in H15 and H13 (Table 4.1) are consistent with a rapid cooling of the system, and likely emplacement at shallow depths in the crust. In detail, the evolution in the four complexes begins with emplacement of an amphibole-rich magma associated with the 12.9-Ma H79 complex, followed by more biotite-rich magmatic composition in the ~12.5 Ma H15 and ~12.1 Ma H14 complexes, followed by more hornblende-rich compositions in the ~11.9 Ma H13 complex. The compositional trends in porphyry intrusions from more mafic to more felsic and finally to more mafic is commonly recognized in many porphyry Cu deposits and districts (Cornejo et al., 1997; Lee et al., 2007; Lickfold et al., 2007). The trend overall must reflect the effects of fractionation and crystallization in the magma chamber that underlay and fed the porphyry Cu related magma at higher crustal levels (Seedorff et al., 2005). The giant H14-H15 porphyry Cu-Au deposit was generated by multiple superimposed ore-forming hydrothermal events related to the intrusions of felsic magma (Fig. 4.10). Episodic and spatially overlapping magmatic and hydrothermal activity appears to be common in many, but certainly not all giant porphyry Cu deposits (Maksaev et al., 2002, 2004; Serrano et al., 1996; Deckart et al., 2005, in press; Reynolds et al., 1988; Ballard et al., 2001; Ossandon et al., 2001; Padilla et al., 2003; Stein et al., 2002; Bertens et al., 2003; Lee et al., 2007). Superposition of multiple overlapping but also temporally distinct magmatic and hydrothermal events focused within a single ore body appear to be the fundamental controls on generating giant and supergiant ore deposits. In some of those deposits, the events spanned considerable geologic time, locally as much as 3 to 4 million years (e.g., Deckart et al., 2005, in press; Sillitoe and Mortensen 2010; Simmons et al. in press), whereas in others such as Reko Diq the 108  superposed magmatic and associated hydrothermal events encompass a much shorter time frame (Garwin, 2002; von Quadt et al., 2001), and at least in Reko Diq are spatially distinct such that the contribution of different magmatic complexes can be distinguished.  Figure 4.10 (A) Geochronological constraints of multiple porphyry intrusions and subsequent hydrothermal events in the Reko Diq western porphyry cluster; (B) Sequence of multiple porphyry intrusions and its relationship with hydrothermal alteration, veins and Cu-sulfides in the H14 and H15 porphyry systems.  109  The SHRIMP-RG U-Pb ages reported herein for the porphyry intrusions associated with the four western porphyry show limited evidence for incorporation of significantly older xenocrystic zircons, with only two rocks containing zircons from the immediate late Oligocene and early Miocene country rocks. However, it is also apparent that zircons only slightly older than the accepted age for that rock sample are present. Examples include sample RD068-518 and RD341-500 in the H15 complex and sample RD147-561 in the H13 complex. The zircons that form small clusters at slightly older ages may represent antecrysts plucked from the crystallizing wall rocks of the larger magma chamber that would have underlain the porphyry Cu complexes. However as their analytical data overlaps with the vast bulk of the data within the limits of their analytical precision, it is impossible to confirm this possibility. Overall, the U-Pb systematics of the porphyry intrusions is simplest for the younger two complexes that are H14 and H13, whereas the U-Pb systematics in H15 and H79 show a greater degree of scatter, also evident in the published zircon U-Pb ages (Table 4.2). No obvious explanation present itself as the U-Pb systematics generally form reasonably interpreted ages that are consistent with known geologic constraints. The only difference between H15 and H14 for example lies in their hydrothermal history wherein the H15 complex is varyingly overprinted by late low-temperature intermediate argillic (illite-chlorite stable) alteration, an alteration assemblage that is weak in H14. 4.6.2 Longevity of individual western porphyry systems The closely spaced ages from two different isotopic systems at least in the H15 and H14 deposit suggest that the magmatic history, and by inference the hydrothermal history, may have taken place in a very short period of geologic time, perhaps on the order of a few hundred thousand years or less (Table 4.5). Evidence that short time frames within the much longer magmatic, hydrothermal and thermal event are associated with the emplacement and formation of the upper crustal porphyry Cu system is becoming common (e.g., Garwin, 2002; Valencia et al., 2005; von Quadt et al., 2011; Îmer et al., in press) and presumably represent a more accurate view of the lifetime of a porphyry Cu magmatic and hydrothermal system. In this context, the longevity of the porphyry Cu deposit is thus not dissimilar to some epithermal deposits (Henry et al., 1997; Simmons and Browne, 2006). Nonetheless, depending upon the depth of formation and the duration and episodicity of magmatism and thus thermal 110  perturbation of the porphyry Cu environment (McInnes et al., 2005a; Harris et al., 2008), full cooling of the system could persist for some time after metal deposition, thus obscuring the longevity of individual metalliferous events. Table 4.5 Timing and lifespan of magmatic-hydrothermal events at the Reko Diq H15-H14 porphyry Cu deposits. Complex  H15  H14  Event  Age (2σ)  Granodiorite-PFB1  12.5±0.3  Mineralization-Mol  12.5±0.05  Granodiorite-PFB1  12.2±0.2  Quartz-diorite-PFB2  12.1±0.2  Quartz-diorite-PFB3  12.1±0.4  Mineralization-Mol  11.7±0.04  Granodiorite - PFB1  12.2±0.2  Mineralization-Mol  12.1±0.05  Quartz-diorite-PFB2  12.0±0.1  Quartz-diorite-PFB3  12.0±0.2  Quartz-diorite-PFB4  12.0±0.1  Lifespan (Years) Crystallization  400,000  200,000  Mineralization  800,000  400,000  Description Ore-forming event commenced immediately after the crystallization of granodiorite- PFB1 and continued with the crystallization and cooling of synmineral-PFB2 and late-mineral PFB3 intrusions in H15 complex overprinted by H14 complex.  Magmatic-hydrothermal system shifted southward and sustained with subsequent crystallization and cooling of granodiorite- PFB1, intra-mineralPFB2 and late-mineral-PFB3 intrusions in H14 complex. Late-barren PFB4 porphyry crystalized later.  Mineralization-Mol 11.82±0.04 Abbreviations: PFB1, PFB2, PFB3 and PFB4 are field terms used for early, syn-mineral, late-mineral and late-barren stage porphyry intrusions respectively. Ages of intrusions are from zircon U-Pb SHRIMP-RG analysis and mineralization from molybdenite Re-Os geochronometry.  4.6.3 Re-Os ages versus U-Pb The Re-Os ages for molybdenite reported herein are essentially concordant with the U-Pb ages determined in this study. In contrast, previously published ages for the same two deposits but from different samples are younger, with H15 having a published Re-Os age of 11.7 ± 0.04 Ma and H14 an age of 11.82 ± 0.04 Ma (Perelló et al., 2008). These ages are within analytical uncertainty of the 11.93 ± 0.14 Ma age for the intra-mineral porphyry in the H13, the youngest porphyry Cu hydrothermal system in the western porphyry Cu prospects. In view of age similarity, it is possible that the young Re-Os ages for the late molybdenite veins cutting potassic alteration in the H14 and H15 systems reflect the superposition of a younger and temporally distinct hydrothermal event that is associated in time with H13 complex.  111  4.7 Conclusion The combination of isotopic dating methods identified a succession of felsic intrusions and hydrothermal events in the Reko Diq western porphyry copper-gold deposits. SHRIMP-RG U-Pb-zircon geochronologic data demonstrate that Miocene porphyry Cu magmatism spanned ~1 million years between ~12.9 and 11.9 Ma. It was initiated with the hornblende-rich quartzdiorite in H79, followed southward by successively younger H15, H14, and H13 porphyry systems. Lifespans between ~0.26 and ~0.12 Ma for at least the H15 and H14 magmatic complexes, respectively, are suggested. The H15 and H14 systems are linked to at least two temporally and spatially distinct, but overlapped hydrothermal events. The early ore-forming hydrothermal event in the system initiated at 12.5 ± 0.05 Ma with the younger event taking place at 12.1 ± 0.05 Ma. The mineralized, hornblende-rich intra-mineral porphyry (PFB2) in H13 emplaced at 11.93 ± 0.14 Ma in the H13 complex record a further southward shift to the magmatic-hydrothermal system. Overall the geochronologic dataset suggests a short-lived magmatic system with repeated magma injection and multiple episodes of efficient and fertile hydrothermal fluid flow result in the formation of Reko Diq western porphyry Cu-Au (Mo) deposits.  112  Chapter 5 - Cooling and fractionation of Reko Diq H14-H15 5.1 Introduction Porphyry deposits, formed in the continental margin and island arcs, as well as in ancient orogenic belts are the principle source of annual copper production and an important source of gold and molybdenum (Seedorff et al., 2005; Sillitoe, 2010). Reko Diq in Chagai belt, Pakistan is one of the world’s largest porphyry districts, hosts a cluster of eighteen porphyry systems with a resource of 5.9 billion metric tons @ 0.41% Cu and 0.25g/t Au at the H14-H15 porphyry complex (Tethyan Copper Company 2013). Porphyry Cu deposits have been intensively studied over the last two decades with a particular focus on tectono-magmatic processes involved in generating “fertile” (Cu and S rich) magmas (e.g., Ringwood, 1977; Hildreth and Moorbath, 1988; Pearce and Peate, 1995; Poli and Schmidt, 2002, Richards, 2003, 2011; Richards et al., 2012). Porphyry deposits are commonly associated with intermediate composition arc magmas derived from the asthenospheric mantle wedge as a result of amphiboles and/or garnet fractionation and/or by assimilation and mixing of crustal material (Tosdal et al., 2001; Richards and Kerrich, 2007; Richards 2003, Richards et al., 2012). Porphyry deposits form with a series of porphyritic stocks and dykes originated from the roof zones of an underlying batholith and emplaced at shallow (1-3 km) depths (Gustafson and Hunt, 1975; Dilles, 1987, Seedorff et al., 2005; Sillitoe, 2010). A typical porphyry deposit (e.g., Maksaev et al., 2002, 2004; Proffett, 2003; Padilla et al., 2001; Stein et al., 2002; Bertens et al., 2003; Lee et al., 2007) is associated with multiple superimposed magmatic and hydrothermal systems linked to magmas of calc-alkaline (Gustafson, 1979; Dilles, 1987) and alkaline composition (Sillitoe, 1997; Muller et al., 2002, Lickfold et al., 2009). These magmas contain high magmatic waters (≤ 4wt. % H2O) leading to distinctively high Sr/Y and La/Yb geochemical signatures (Baldwin and Pearce, 1982; Richards, 2011), originally attributed to the adakitic rocks (Kay, 1978; Chapter 3). Overall, the porphyry related magmas are hydrous, generally oxidized, sulfur and volatile-rich, and composed of plagioclase, quartz, biotite and/or amphiboles and minor accessary zircons, apatite and magnetite. 3  A version of this chapter will be submitted for publication: Razique, A., and Tosdal, R.M., U-Pb (zircon) Geochemical Constraints on the Genesis and Evolution of the Giant Reko Diq H14-H15 Porphyry Cu-Au Deposit, District Chagai, Balochistan-Pakistan.  113  Zircon is a robust accessary mineral found in many rock-types in diverse geological environments (e.g., Heaman et al., 1990; Hoskin and Schaltegger, 2003). The compositional and isotopic information in zircon remain preserve in response to high grade metamorphism, deformation and/or hydrothermal alteration (Cherniak and Watson, 2003; Scherer et al., 2007). Therefore, zircon trace element geochemistry have been effectively used in provenance (e.g., Hoskin and Ireland, 2000; Belousova et al., 2002, Grimes et al., 2007) and petrogenetic studies of magmas forming ore-deposits (Ballard et al., 2002; Belousova et al., 2006; Liang et al., 2006; Harris et al., 2007). Furthermore, zircon mineral chemistry and compositional variation through time (and within single zircon grains) makes it possible to track specific geochemical signatures of the magma chambers and processes involved in porphyry Cu deposit formation (e.g., Blevin and Chappell, 1992; Candela, 1992, Hedenquist and Lowenstern, 1994; Mungall 2002, Sun et al., 2004; Claiborne et al., 2006). This association involves redox control on the speciation/solubility of magmatic sulfur and its influence on the fractionation of chalcophile elements. Sulfur is relatively soluble in basaltic melts and a small addition of mafic material into felsic porphyry root pluton could supply the required sulfur to the hydrothermal system (Dilles and Proffett, 1995). Additionally, primitive mafic-melts injected into the intermediate magma chamber may also contribute in the genesis of giant porphyry deposits (e.g., Waite et al., 1998; Hattori and Keith, 2001; Maughan et al., 2002; Pollard and Taylor, 2002; Wainwright et al., 2011; Cornejo et al., 1997). Zircon mineral chemistry in porphyry Cu deposits may provide a better understanding of the physio-chemical environment of the parent magma chambers critical to explain the ore deposit genesis, location in space and time and geological concepts in the exploration programs targeting metallic ore deposits associated with magmas. In this chapter, zircon (SHRIMP-RG) trace element geochemistry is used to investigate the evolution of Reko Diq western porphyry systems and establish possible linkages between large scale porphyry Cu deposits and middle to late Miocene magmatism in the region. Zircon mineral chemistry is presented in chronological order to define the paragenetic sequence, spatial and temporal evolution of multiple porphyry centers at western Reko Diq. Additionally, the data is used to investigate the physio-chemical conditions of the root magma chamber prior to, during and after the formation of porphyry systems. Trace element geochemistry of zircons is interpreted to identify unique characteristics of “fertile” versus “non-fertile” magma chambers leading to multiple, overlapping magmatic114  hydrothermal events as seen many other porphyry deposits (e.g., Maksaev et al., 2004; Padilla et al., 2003; Stein et al., 2002; Pollard and Taylor, 2002; Redmond and Einaudi, 2010; Lee, 2008). 5.2 Reko Diq western porphyry centers Reko Diq western porphyry complex host a cluster of four individual porphyry centers including H79, H15, H14 and H13 aligned along a north north-east trend (Fig. 5.1). These porphyry systems are linked to a distinct episode of middle-late Miocene (12.9-11.9 Ma) magmatism at Reko Diq complex (Table 5.1). Field relationships, petrochemistry and U-Pbzircon ages indicate that the western porphyry deposits are spatially and temporally associated with a series of calc-alkaline porphyry intrusions host by andesitic volcanic, pyroclastic and the underlying sedimentary rocks (Chapters 3 and 4). The porphyry intrusions display typical medium to coarse grained porphyritic textures with abundant phenocryst of plagioclase and variable proportion of biotite, quartz and minor amphiboles embedded in a finer crystalline to aphanitic groundmass (Fig. 5.2). Table 5.1 U-Pb (zircon) SHRIMP-RG ages of the intrusive rocks analyzed for zircon trace element geochemistry. Sample ID  Complex  Rock type  Lithcode  U-Pb Age (2σ)  Method  Reference  RD077-608  H79  Hornblende-diorite  PFH  12.9 ± 0.3  SHRIMP-RG  Chapter 4  RD341-197  H15  Granodiorite  PFB1  12.5 ± 0.1  SHRIMP-RG  Chapter 4  RD068-518  H15  Granodiorite  PFB1  12.2 ± 0.2  SHRIMP-RG  Chapter 4  RD341-500  H15  Quartz-diorite  PFB2  12.1 ± 0.2  SHRIMP-RG  Chapter 4  RD341-440  H15  Quartz-diorite  PFB3  12.1 ± 0.4  SHRIMP-RG  Chapter 4  RD008-668  H14  Quartz-diorite  PFB1  12.2 ± 0.2  SHRIMP-RG  Chapter 4  RD510-1545  H14  Quartz-diorite  PFB2  12.0 ± 0.1  SHRIMP-RG  Chapter 4  RD116-506  H14  Quartz-diorite  PFB3  12.0 ± 0.2  SHRIMP-RG  Chapter 4  RD008-820  H14  Quartz-diorite  PFB4  12.0 ± 0.1  SHRIMP-RG  Chapter 4  RD147-561  H13  Quartz-diorite  PFB2  11.9 ± 0.2  SHRIMP-RG  Chapter 4  Abbreviations: H = discovery hole name of deposits, PFH = feldspar hornblende porphyry, PFB1 = early granodiorite, PFB2 = syn-mineral, PFB3 = late-mineral and PFB4 = late-barren quartz-diorite porphyry intrusions.  115  Figure 5.1 Surface geology map of Reko Diq western porphyry complex, illustrating the spatial and temporal distribution of H79, H15, H14, H13 porphyry systems associated with middle to late-Miocene intermediate to felsic intrusive rocks host by late-Oligocene andesitic volcanic and pyroclastic rocks.  116  H79 complex in the north is associated with the earliest (12.9 Ma) hornblende-diorite porphyry, crop out as narrow (50x100m), NE trending dykes cut by late-barren dacite porphyry in the central part of the system (Fig. 5.1). The hornblende-diorite (PFH; RD077-608) display medium to coarse grained porphyritic textures with moderate potassic alteration, veins and intense overprinting of sericitic-chlorite ± clay and chlorite-epidote alteration (Fig. 5.2 A). Moderate Cu-sulfide mineralization (0.35% Cu and 0.20g/t Au) is restricted to the early potassic alteration in the porphyry intrusion and immediate host rocks. H15 complex to the south is centered on a large (800m2) early-stage equigranular granodiorite stock (PFB1; RD068-518) and NE-trending, 25-50m-wide and 100-200m-long porphyritic quartz-diorite (PFB2) dykes emplaced between 12.5-12.2Ma (Fig. 5.1; Table 5.1). These porphyry intrusions display intense potassic alteration, multi-generation hydrothermal veins and are overprinted by sericite-chlorite ± clay alteration obliterating the primary mineralogy and textures (Fig. 5.2 B). The granodiorite porphyry (PFB1) contains some of the highest copper-gold grades (up to 1.5 % Cu and 1.0 g/t Au) in the H15 complex. Late-mineral quartz-diorite (PFB3; RD341-440) however, has weak potassic and intense chlorite-sericite ± clay alteration, the latter commonly linked to the D-type sulfide veins (Fig. 5.2 C; Gustafson and Hunt, 1975). H14 complex further to the south is associated with younger granodiorite and quartzdiorite intrusions emplaced between 12.1-12.0Ma (Table 5.1). As in H15, the early granodiorite (PFB1; RD008-668) and intra-mineral quartz-diorite (PFB2; RD510-1545) intrusions in H14 complex have also been affected by intense potassic-sericitic alteration and network of multigeneration hydrothermal veins (Fig. 5.2 D, E). The granodiorite porphyry (PFB1) contains the highest grades (up to 2.0 % Cu and 1.5 g/t Au) Cu-sulfide mineralization at Reko Diq. The latemineral quartz-diorite (PFB3; RD116-506) in H14 complex show weak potassic and sericitechlorite (clay) alteration dominantly in the aphanitic groundmass (Fig. 5.2F); In-contrast, the late-barren quartz-diorite (PFB4; RD008-820) has well preserved primary minerals and coarsegrained phaneritic textures (Fig. 5.2 G). H13 complex corresponds to the youngest (11.9 Ma) hornblende-rich quartz-diorite intrusion cut by narrow (10 x 20m) isolated stocks of barren dacite porphyry in the central parts of the system (Fig. 5.1). The hornblende-quartz-diorite (PFB2; RD147-561) has intense potassic 117  alteration overprinted by sericite-chlorite (clay) alteration, quartz ± sulfide veins and contain an average grade of 0.4% Cu and 0.30 g/t Au (Fig. 5.2 H).  Figure 5.2 Core photographs of the samples selected for SHRIMP-RG zircon trace element analysis: (A) Premineral hornblende-diorite in H79 complex, (B-C) main-mineral granodiorite in H14-H15 complex, (D) synmineral quartz-diorite in H14 complex, (E-F) late-mineral quartz-diorite in H14-H15, (G) late-barren quartzdiorite in H14 complex, and (H) intra-mineral hornblende bearing quartz-diorite in H13 complex.  118  5.3 Zircon geochemistry Zircon trace element data was acquired using two analytical techniques on the Sensitive High-mass Resolution Ion Microprobe-Reverse Geometry (SHRIMP-RG) at the StanfordUSGS micro analyzer center (SUMAC) in California USA. The first technique involves simultaneous acquisition of trace element and U-Pb geochronology data in the core of zircon grains, whereas trace element routine technique is used to acquire zircon core-to-rim analysis as well as Ti-in-zircon thermometry (Table C.2). A total of ten representative samples of granodiorite to quartz-diorite porphyry intrusions selected for zircon trace element geochemistry. Out of ten a subset of seven samples including one from H79 complex, two from H15, three from H14, and one from H13 complex were selected for zircon trace element routine analysis (Table 5.2). All of the intrusive rocks contain abundant zircons used for SHRIMP-RG trace element geochemistry, acquiring a large set of trace elements including 49Ti, all the REE, Hf, Pb, Th and U (Mazdab, 2009). Representative cathodoluminescence images of zircons are presented in (Figs. 5.3 and 5.4) and the trace element data is given in (Table 5.2 and 5.3). 5.3.1 Morphology of zircon grains Morphology of a single zircon grain or population is used to identify the changes in zircon mineral-chemistry reflecting the mixing of magma and changes in the composition of the magma through mingling processes and progressive crystallization (Heaman et al., 1990; Belousova et al., 2002, 2006; Scherer et al., 2007). The intrusive rocks at Reko Diq western porphyry complex contain abundant zircons characterized by a variety of sizes, shapes and morphologies (Table C.1 and Fig. C.1). Hornblende-diorite (PFH; RD077-068) in H79 complex contain less-abundant clear to pale, euhedral to subhedral and granular (up to 300µm) zircons exhibiting concentric growth patterns under cathodoluminescence (Fig. 5.3). Zircons from the intrusive rocks in H15 and H14 porphyry deposits are relatively coarser grained (up to 400µm), tabular to prismatic, transparent, pale-white in colors and display concentric zonation patterns (Fig. 5.4 A, B, C, D, E). The youngest hornblende bearing quartz-diorite (PFB2; RD147-561) in H13 complex contain abundant coarser grained (up to 500µm), transparent, pale-white, prismatic  zircons  exhibiting  well-developed  systematic  growth  patterns  under  cathodoluminescence (Fig. 5.4 F). The overall abundance, size and morphologies of zircons  119  distinguish the early hornblende-rich intrusive rocks in H79 complex from relatively felsic intrusions in H15, H14 and H13 porphyry centers.  Figure 5.3 Representative Cathodoluminescence images of the zircon grains from hornblende-diorite (PFH) in H79 complex. Circles represent the location of SHRIMP-RG spot analysis with Hf concentrations (ppm) and TiO2-in-zircon minimum crystallization temperatures (oC)  120  Figure 5.4 Representative Cathodoluminescence images of the zircon grains in geochronological order. (A-B) Zircons from early and late-mineral intrusive rocks at H15 complex (C) Zircons form a younger granodiorite, (D) Syn-mineral quartz-diorite, (D) and (E) Late-barren stage quartz-diorite in H14 complex. (E) Zircons from the youngest quartz-diorite in H13 complex. Circles represent the location of SHRIMP-RG spot analysis of Hfconcentrations (ppm) and TiO2-in-zircon minimum crystallization temperatures (oC).  121  5.3.2 REE patterns The chondrite-normalized rare-earth element patterns in zircons from all intrusive rocksuite of Reko Diq western porphyry centers are characterized by patterns typical for zircon, including heavy-REE enrichment relative to light-REE, slightly negative Eu and pronounced positive Ce-anomalies with respect to chondrite (Fig. 5.5). In H15 complex, two samples including early granodiorite (PFB1; RD341-197) and late-mineral quartz-diorite (PFB3; RD341-440) represent outliers and a scatter in the zircon analysis (Fig. 5.5 B, D). Similar scatter is evident in the intra-mineral quartz-diorite (PFB2; RD510-1545) and late-barren quartz-diorite (PFB4; RD008-820) samples from H14 complex (Fig. 5.5 F, G). In general, the REE patterns in zircons from western porphyry deposits reflect homogeneity of the source magma however, subtle variation in the slopes measured from heavy to middle REE based on the Yb/Gd ratio reflect a fractionation trend from older to younger porphyry zircons (See below).  122  Figure 5.5 Chondrite-normalized REE patterns in zircons from the intrusive rocks at Reko Diq western porphyry complex. All samples are characterized by elevated heavy-REE and relatively depleted lightREE, slightly negative Eu anomalies and pronounced positive Ce anomalies.  123  5.3.3 Hf versus TiO2-in-zircon thermometer The Hf concentration in zircon-melts tends to increase with cooling and fractional crystallization of the magma relative to zirconium, which has a much higher zircon-melt partition coefficient compared to Hf. Therefore, Hf is used as a proxy for cooling zircons related to the fractionation and evolution of the magmatic systems (Claiborne et al., 2006). The minimum crystallization temperatures of zircons are determined by the TiO2-in-zircon thermometry (Watson and Harrison, 2005) using a calibration of aTiO2 = 0.7 (Claiborne et al., 2006). This calibration was established under rutile-saturated conditions (aTiO2 = 1) because rutile saturation is rare in magmas, whereas aTiO2 in most felsic magmas is saturated at approximately fixed values of >0.5 compared to other titanium bearing phases. Hence, aTiO2 = 0.7 is used as the most preferred calibration for the titanite and titanomagnetite saturation phase (Watson and Harrison, 2006; Claiborne et al., 2006). The minimum crystallization temperatures from zircon trace element routine analyses presented herein (Table 5.2) are calculated using 49  Ti isotope instead of more abundant 48Ti which may have interference from 96Zr (Claiborne et  al., 2006). The TiO2-in-zircon thermometry indicated that zircon cores are generally hotter with lower-Hf concentrations compared to their corresponding rim analysis. However, in some cases low-temperature, high-Hf cores are surrounded by high-temperature, low-Hf growth zones (Fig. 5.4 C, F). Hafnium concentration in the hornblende-diorite sample (PFH; RD077-068) from H79 complex range from 8749 ppm to 10691 ppm and the TiO2-in-zircon minimum crystallization temperature range from 671oC to 780oC (average 731oC) (Table 5.2). An outlier of the highest minimum crystallization temperature (801oC) in this sample indicates a hot intermediate magma in H79 porphyry complex (Table 5.2). Hafnium versus temperature plot generally indicates increasing Hf with cooling of H79, H15 and H14 porphyry centers in space and time (Fig. 5.6 A). Hafnium concentration in zircons from the early granodiorite (PFB1; RD068-518) in H15 complex range from 9786 ppm to 11507 ppm with TiO2-in-zircon minimum crystallization temperature analyzed between 665oC to 720oC (average 689oC) (Table 5.2). Hf concentrations in the late-mineral quartz-diorite (PFB3; RD341-440) range from 9545 ppm to 12135 ppm with minimum temperatures range from 660oC to 721oC (average 686oC). The Hf versus temperature 124  Table 5.2 Trace element concentration (ppm) for zircons. (Temp) = Minimum temperature (oC) based on TiO2-in-zircon thermometer (Watson and Harrison, 2005). Ti values are Ti49, also used to calculate temperature. Spot  Ti  Y  La  Ce  Nd  Sm  Eu  Gd  Ho  Tb  Dy  Er  Tm  Yb  Lu  Hf  Th  U  Temp  0.54 0.27 0.36 0.23 0.43 0.18 0.30 0.32 1.79 1.27 1.49 0.25 0.13  1.50 0.74 0.48 0.53 1.01 0.64 0.64 0.78 2.79 2.12 2.71 0.67 0.18  0.87 0.38 0.35 0.28 0.51 0.36 0.53 0.40 1.76 1.24 1.34 0.36 0.17  15 6 6 5 10 6 8 7 24 17 19 7 3  35 13 11 12 23 13 21 15 35 26 32 13 6  6.01 2.45 2.02 1.78 4.31 2.33 3.26 2.68 7.76 5.64 6.49 2.58 0.95  75 29 26 24 53 29 42 34 85 64 76 29 13  183 75 61 67 120 71 107 77 168 120 159 70 30  44 18 16 18 29 18 27 18 38 28 36 17 7  411 191 162 187 267 181 273 184 343 259 331 165 77  86 41 35 43 55 41 61 40 69 55 70 38 18  8749 10149 10100 14471 9888 10529 10545 10459 8681 10691 9312 9318 10576  67 35 52 150 41 48 74 224 113 138 93 30 23  136 74 97 368 77 87 173 356 152 198 113 56 51  801 740 736 671 780 743 728 693 764 694 755 747 719  0.20 0.20 0.21 0.19 0.24 0.23 0.47 0.25 0.26 0.23 0.35 0.23  0.53 0.48 0.53 0.48 0.64 0.57 1.14 0.61 0.80 0.50 0.86 0.58  0.29 0.28 0.31 0.30 0.43 0.35 0.56 0.32 0.41 0.29 0.48 0.27  6 5 5 5 6 7 9 6 9 4 6 5  12 12 11 13 15 14 14 12 20 9 11 11  2.10 2.08 1.94 2.12 2.59 2.55 2.83 2.12 3.68 1.58 2.33 2.06  29 29 25 27 32 33 35 27 48 21 26 26  67 71 55 68 76 75 72 66 112 51 57 59  18 18 14 18 20 19 18 16 29 13 14 14  174 179 134 194 198 182 168 162 279 140 140 145  40 41 30 45 45 40 37 36 64 33 32 34  10121 10615 10877 11304 10090 10679 9786 11142 11075 10731 11027 11507  69 74 49 70 71 139 51 126 171 56 52 123  153 160 98 165 156 235 82 235 279 127 102 226  681 682 683 665 720 682 717 686 695 683 681 688  RD077-608 (Hornblende diorite - PFH in H79 complex) 608-10.1 608-10.2 608-12.1 608-12.2 608-3.1 608-3.2 608-4.1 608-4.2 608-5.1 608-5.2 608-7.1 608-7.2 608-7.3  17.50 9.36 9.01 4.23 14.18 9.72 8.23 5.53 12.05 5.56 11.00 10.07 7.42  920 368 319 335 613 359 571 416 922 699 819 358 154  0.009 0.002 0.022 0.228 0.002 0.006 0.007 0.007 0.118 0.009 0.020 0.011 0.008  16 8 8 18 12 9 12 15 14 14 11 7 5  RD068-518 (Granodiorite - PFB1 in H15 complex) 518-1.1 518-1.2 518-3.1 518-3.2 518-5.1 518-5.2 518-6.1 518-6.2 518-7.1 518-7.2 518-9.1 518-9.2  4.79 4.86 4.92 3.91 7.52 4.82 7.29 5.08 5.66 4.93 4.77 5.18  321 334 293 361 472 387 382 343 508 263 322 310  0.003 0.009 0.007 0.004 0.003 0.003 0.042 0.011 0.021 0.005 0.009 0.000  8 12 8 11 8 15 8 15 17 8 7 14  125  Table 5.2 Continue… Spot  Ti  Y  La  Ce  Nd  Sm  Eu  Gd  Ho  Tb  Dy  Er  Tm  Yb  Lu  Hf  Th  U  Temp  0.26 0.20 0.29 0.24 0.38 0.06 0.15 0.37 0.11 0.28 0.14 1.40 0.21  0.51 0.48 0.75 0.74 0.91 0.20 0.67 0.77 0.26 0.86 0.37 2.81 0.64  0.29 0.27 0.54 0.34 0.56 0.12 0.38 0.48 0.17 0.51 0.21 1.46 0.34  5 5 8 7 8 2 6 8 3 8 4 20 6  12 10 16 14 15 6 16 14 6 19 9 29 15  1.94 1.75 2.94 2.47 2.55 0.96 2.34 2.68 1.13 3.27 1.49 6.28 2.57  27 23 37 30 33 12 34 33 14 41 20 73 34  59 55 85 72 82 30 86 74 34 103 48 144 83  15 14 22 19 20 7 23 19 9 25 12 33 21  149 151 221 177 199 79 233 189 93 266 123 311 214  35 35 49 40 44 18 54 43 22 61 28 67 49  10957 10446 9881 12135 8059 10665 10364 9545 11423 9821 11162 10117 10415  122 43 54 197 34 44 89 59 85 129 102 156 103  220 111 124 374 73 113 209 103 223 235 221 226 206  688 681 689 666 770 674 686 721 660 680 684 699 706  0.16 0.19 0.40 0.07 0.08 0.24 1.36 0.16 0.29 0.27 0.18 0.14 0.10  0.42 0.38 1.11 0.24 0.26 0.60 2.39 0.48 0.80 0.83 0.39 0.38 0.29  0.25 0.27 0.73 0.11 0.13 0.32 1.38 0.20 0.52 0.35 0.25 0.26 0.17  4 4 14 2 2 6 17 4 8 8 5 4 3  8 9 29 5 6 16 26 10 19 20 10 10 7  1.59 1.62 4.78 1.01 0.93 2.63 5.59 1.58 3.33 3.10 1.77 1.72 1.28  19 21 64 13 14 34 64 22 42 42 22 23 16  44 49 148 32 35 87 129 58 104 111 53 57 39  11 12 37 9 9 22 29 14 27 29 13 15 10  111 117 363 88 95 228 283 156 271 286 129 161 101  27 27 81 20 21 51 61 35 62 66 31 38 24  9684 10463 12210 11536 11366 10346 10237 12641 10463 10782 10072 11196 11050  33 104 223 47 28 81 137 110 160 138 51 54 67  70 210 349 121 80 184 204 316 275 306 116 137 162  690 677 696 665 659 692 711 630 688 684 694 673 678  RD341-440 (Quartz diorite - PFB3 in H15 complex) 440-11.1 440-11.2 440-12.1 440-12.2 440-2.1 440-2.2 440-2.3 440-3.1 440-3.2 440-6.1 440-6.2 440-9.1 440-9.2  5.21 4.80 5.27 4.00 12.91 4.41 5.07 7.60 3.67 4.70 4.99 5.92 6.43  326 308 465 379 418 158 454 429 187 492 248 745 434  0.003 0.000 0.007 0.009 0.010 0.005 0.003 0.003 0.007 0.012 0.009 0.017 0.010  13 7 9 19 9 7 14 10 12 11 12 15 14  RD008-668 (Granodiorite - PFB1 in H14 complex) 668-1.1 668-1.2 668-2.1 668-2.2 668-3.1 668-3.2 668-5.1 668-5.2 668-8.1 668-8.2 668-8.3 668-9.1 668-9.2  5.33 4.54 5.69 3.93 3.62 5.47 6.83 2.49 5.21 4.96 5.59 4.35 4.60  230 270 604 164 175 442 745 283 542 562 277 265 207  0.009 0.009 0.010 0.007 0.005 0.012 0.018 0.005 0.005 0.007 0.005 0.005 0.007  6 11 24 8 6 12 15 14 16 20 9 7 10  126  Table 5.2 Continue… Spot  Ti  Y  La  Ce  Nd  Sm  Eu  Gd  Ho  Tb  Dy  Er  Tm  Yb  Lu  Hf  Th  U  Temp  1.12 0.10 0.11 0.14 0.10 2.35 0.49 0.24 0.23 0.18 0.84 0.34 0.25  1.90 0.46 0.54 0.28 0.33 4.08 0.97 0.50 0.89 0.46 1.96 0.75 0.57  0.92 0.21 0.23 0.19 0.20 1.63 0.49 0.28 0.37 0.22 0.88 0.34 0.29  13 4 4 3 4 30 9 5 8 4 15 6 5  20 10 9 7 8 45 19 13 17 10 25 15 13  4.34 1.57 1.73 1.17 1.44 9.54 3.46 2.20 2.78 1.56 5.17 2.72 2.21  51 21 22 15 18 110 45 28 37 21 60 33 29  103 54 51 37 44 210 98 69 91 55 119 81 73  24 13 13 10 11 49 23 17 24 15 28 20 19  230 139 136 100 120 447 229 172 253 161 266 198 208  50 31 31 23 27 99 51 40 63 39 57 45 48  10166 11325 11131 11575 11083 9917 10726 10669 10165 11949 11163 10382 10657  124 60 101 38 57 339 289 80 238 53 146 79 79  187 152 253 95 152 427 441 193 352 164 232 175 197  689 675 672 687 666 711 700 694 680 653 663 688 676  0.29 0.88 0.25 0.16 0.26 0.18 0.34 0.55 0.35 0.32 0.17 1.32  0.76 2.17 0.56 0.48 0.67 0.59 1.11 0.87 0.60 0.93 0.44 2.77  0.42 1.25 0.29 0.22 0.44 0.30 0.43 0.48 0.26 0.58 0.29 1.40  8 27 6 4 5 6 9 10 4 11 5 23  18 60 13 9 13 14 24 23 9 27 10 36  3.21 10.65 2.30 1.53 2.21 2.34 3.97 3.74 1.70 4.53 1.67 7.82  41 136 29 21 30 31 51 49 21 57 23 91  96 300 68 51 74 72 118 121 50 143 55 182  25 71 18 13 19 19 30 30 13 35 13 43  244 677 175 132 190 184 280 294 131 390 135 408  55 147 40 31 45 41 65 67 32 87 32 90  10423 10762 10376 11334 8794 12401 10290 10635 10459 10744 11020 10888  116 713 65 90 49 217 231 184 116 196 126 342  213 891 146 240 114 443 377 344 142 405 268 467  694 748 684 675 714 655 810 704 738 703 679 684  RD510-1545 (Quartz-diorite - PFB2 in H14 complex) 1545-1.1 1545-1.2 1545-1.3 1545-10.1 1545-10.2 1545-2.1 1545-2.2 1545-3.1 1545-3.2 1545-5.1 1545-5.2 1545-9.1 1545-9.2  5.27 4.46 4.28 5.16 3.96 6.79 5.97 5.61 4.74 3.38 3.84 5.22 4.50  553 284 263 191 230 1251 528 346 523 280 667 473 369  0.022 0.004 0.002 0.015 0.004 0.045 0.022 0.004 0.002 0.004 0.002 0.023 0.004  12 10 11 7 9 33 22 12 13 8 18 11 11  RD008-820 (Quartz-diorite - PFB4 in H14 complex) 820-1.1 820-1.2 820-2.1 820-2.2 820-4.1 820-4.2 820-5.2 820-5.1 820-6.1 820-6.2 820-8.2 820-8.1  5.61 10.24 4.96 4.47 7.05 3.47 19.05 6.26 9.19 6.18 4.67 4.98  523 1698 331 254 391 406 643 602 271 765 298 967  0.006 0.020 0.028 0.006 0.016 0.011 0.064 0.619 0.345 0.009 0.005 0.023  15 59 9 11 8 22 23 20 10 21 14 27  127  Table 5.2 Continue… Spot  Ti  Y  La  Ce  Nd  Sm  Eu  Gd  Ho  Tb  Dy  Er  Tm  Yb  Lu  Hf  Th  U  Temp  0.38 0.51 0.29 0.40 0.32 0.34 0.71 0.39 0.21 0.21 0.46 0.73 0.26  6 9 5 7 5 6 13 6 4 4 9 15 5  11 21 12 14 14 12 23 14 10 11 23 32 12  2.08 3.60 2.03 2.86 2.19 2.07 4.81 2.46 1.74 1.66 3.71 5.85 1.94  26 47 28 33 30 29 59 31 21 25 49 71 26  60 122 67 72 79 66 120 75 52 64 118 169 68  15 31 18 18 21 16 28 19 13 17 30 41 18  162 302 198 177 225 154 267 192 122 174 295 401 190  38 70 46 39 54 34 58 45 28 44 66 91 47  11069 9743 10769 10420 12057 10801 9675 11615 10913 11513 10371 11184 10271  72 139 74 346 81 154 446 226 109 58 153 307 80  160 314 203 513 250 300 396 443 233 166 302 486 185  658 722 653 705 646 693 804 675 689 659 703 709 667  RD147-561(Hornblende-Quartz-diorite - PFB2 in H13 complex) 561-1.1 561-1.2 561-2.1 561-2.2 561-3.1 561-3.2 561-6.1 561-6.2 561-7.2 561-7.1 561-9.3 561-9.2 561-9.3  3.61 7.72 3.37 6.37 3.09 5.53 18.02 4.44 5.29 3.66 6.21 6.69 4.03  339 616 345 390 401 353 539 395 271 227 640 891 333  0.003 0.007 0.003 0.003 0.008 0.014 1.743 0.003 0.010 0.011 0.009 0.015 0.013  9 16 9 21 12 14 23 18 12 8 18 32 8  0.22 0.37 0.18 0.42 0.19 0.21 1.34 0.29 0.15 0.11 0.28 0.50 0.18  0.78 0.87 0.48 0.81 0.56 0.49 1.44 0.76 0.38 0.40 0.85 1.48 0.46  128  Table 5.3 Trace element concentration (ppm) for zircons SHRIMP-RG spot analysis Spot  La  Ce  Nd  Sm  Eu  Gd  Dy  Y  Er  Yb  RD341-197 Granodiorite - PFB1 in H15 complex) 197-1 0.499 30 197-2 0.015 20 197-3 0.015 17 197-4 0.053 29 197-5 0.019 9 197-6 0.047 39 197-7 0.022 21 197-8 0.129 222 197-9 0.016 24 197-10 0.024 27  1.14 0.51 0.45 0.47 0.23 1.03 0.46 4.34 0.75 0.64  8.65 4.52 3.58 4.22 1.92 8.99 4.33 34.25 7.00 5.00  16.91 6.31 5.55 6.13 3.16 16.87 6.37 40.16 10.14 7.67  71 32 25 33 13 85 30 227 51 36  242 131 103 140 59 329 118 752 191 137  467 275 211 302 114 607 228 1367 380 261  813 505 390 557 215 1092 428 2414 704 462  1758 1287 1000 1440 566 2292 1004 4919 1655 1048  RD341-500 (Quartz-diorite – PFB2 in H15 complex) 500-1 0.212 22 500-2 0.086 21 500-3 0.009 8 500-4 0.021 23 500-5 0.012 9 500-6 0.028 16 500-7 0.015 14 500-8 0.012 25 500-9 0.018 20 500-10 0.086 15  0.62 0.51 0.28 0.74 0.22 0.34 0.30 0.60 0.52 0.33  4.71 4.05 2.44 5.60 1.90 2.70 2.62 4.86 4.31 3.17  7.14 6.61 3.72 8.72 3.30 4.89 3.78 6.80 7.12 4.51  36 35 17 41 15 21 19 34 35 23  148 139 69 174 60 88 80 129 138 92  288 287 136 364 119 175 166 252 293 189  554 536 249 684 215 328 313 464 517 349  1276 1345 659 1661 532 817 847 1092 1228 859  RD116-506 (Quartz-diorite – PFB3 in H14 complex) 506-4 0.006 19 506-10 0.222 29 506-11 0.024 12 506-6 0.021 18 506-8 0.024 21 506-12 0.021 23 506-7 0.027 8 506-5 0.018 20 506-1 0.023 21 506-2 0.015 16 506-3 0.094 26 506-9 0.166 24  0.44 0.77 0.28 0.40 0.44 0.57 0.19 0.46 0.39 0.32 3.54 4.14  4.32 6.14 2.39 3.91 4.10 4.48 1.84 3.72 3.59 2.98 19.69 24.75  5.47 7.44 3.26 5.30 5.65 6.48 2.82 5.48 4.77 4.01 16.81 22.77  34 44 17 32 31 32 12 26 28 21 102 149  129 158 76 126 131 134 48 98 115 83 270 410  236 302 154 260 269 288 90 186 244 163 420 648  425 543 287 479 484 527 167 338 442 296 691 1098  933 1209 755 1215 1197 1344 408 782 1085 707 1123 1775  129  plot for these samples indicates a correlation between increasing Hf and decreasing temperatures, with cooling of the H15 porphyry system (Fig. 5.6 A). Hafnium concentration from a younger granodiorite (PFB1; RD008-668) in H14 complex range from 9684 ppm to 12641 ppm and minimum temperatures from 630oC to 711oC (average 680oC) whereas Hf in the quartz-diorite sample (PFB2; RD510-1545) range from 9917 ppm to 11949 ppm and minimum temperatures from 653oC to 711oC (Table 5.2). These results indicate an overall increase in Hf concentration with cooling in H14 complex (Fig. 5.6 A). However, a discordant trend in zircons with cooler core (659oC), high-Hf (11368 ppm) surrounded by a hotter rim (692oC) and low-Hf (10346 ppm) concentrations is also evident (Fig. 5.4 C). Moreover, zircons from the late-barren quartz-diorite (PFB4; RD008-820) have Hf range from 8794 ppm to 11334 ppm and temperatures from 655oC to 748oC (average 698oC) with an outlier of high-temperature (810oC) and relatively low-Hf (10290 ppm) concentrations. These results indicate slightly lower-Hf and higher temperature ranges compared to the granodiorite (PFB1) and quartz-diorite (PFB2) samples in H14 complex (Table 5.2). Hafnium concentration in zircons from the youngest hornblende bearing quartz-diorite (PFB2; RD147-561) in H13 complex range from 10271 ppm to 12057 ppm and minimum crystallization temperature range from 646oC to 709oC (average 678oC). This sample yielded two outliers with higher temperatures (722oC and 804oC) and corresponding low-Hf (9743 ppm and 9675 ppm) in the H13 complex (Table 5.2). The discordant results in zircons with cooler (646oC) high-Hf (9675 ppm) core and relatively hotter (689 oC), low-Hf (10913 ppm) growth zone (Fig. 5.4 F) may be attributed to the input of mafic magmas as evident in the drill core as well as slightly higher Th/U values in this sample (Fig 5.6 B). 5.3.4 Trace element variations Zircon trace element abundances and ratios can be used to evaluate the genesis and fractionation of the magma chamber and establish the space-time relationship between H79, H15, H14 and H13 porphyry centers. Th/U values in trace element analyses range from 0.41 to 0.83 in H79, from 0.38 to 0.69 in H15, from 0.32 to 0.82 in H14 and from 0.32 to 0.68 in the H13 porphyry zircons. Th/U versus Hf plot shows a hook-shape trend of decreasing Th/U and increasing Hf concentration with time (Fig. 5.6 B). The H79 porphyry zircons with highest130  temperature have the highest Th/U overall. The Th/U versus TiO2-in-zircon temperature plot illustrates a scatter at higher temperature (˃720oC) and two shallow trends of decreasing Th/U ratio with cooling at (˂720oC; Fig. 5.6 C). Y/U values in the U-Pb routine analysis range from 1.5 to 7.8 for H79, from 1.2 to 7.3 for H15, from 1.2 to 3.2 for H14 and 1.1 to 2.7 for H13 porphyry zircons. The Y/U versus Hf plot indicates decreasing Y/U trend and increasing Hf concentration with time reflecting crustal assimilation and evolution of the magma from H79 to H15 to H14 and H13 porphyry centers (Fig. 5.6 D).  Figure 5.6 Zircon mineral-chemistry plots: (A) Hf versus minimum temperature (oC) illustrating increasing Hf concentration and decreasing crystallization temperatures of zircons through space and time; (B) Hf versus Th/U; (C) Th/U versus minimum temperature (oC); and (D) Hf versus Y/U plots showing steep and hook-like curved trends of cooling and fractionation in zircons from older H79 through younger H15, H14 and H13 porphyry centers distributed from north to south. The circled outliers inferred to inheritance of older zircons incorporated in the younger intrusive rocks.  131  The Y concentrations range from 154 ppm to 922 ppm in H79, from 187 ppm to 745 ppm in H15, from 164 ppm to 967 ppm in H14 and from 227 ppm to 897 ppm in H13 porphyry zircons (Table 5.2). On the Y versus Hf diagram, all the intrusive rocks show an overall steep hook-shape trend of decreasing Y and increasing Hf concentration from older H79, through younger H15, H14 and H13 porphyry centers. An outlier with high-Hf analyzed in the outermost zircon growth-rim implies the cooling of H79 porphyry system. High-Y outliers in this plot relates to the scatter in younger intrusive rocks (Fig. 5.7A). The Y/Yb and Th/U plot indicate a shallow trend of decreasing Y/Yb and Th/U ratios from older to younger porphyry zircons. There is a scatter at high Th/U ratios, where older H79 porphyry zircons overlap with the younger H14 and H13 porphyry zircons (Fig. 5.7 B). Yb/Gd ratios range from 14.4 to 38.6 in the early porphyry zircons from H79, from 15.8 to 39.3 in H15, from 14.8 to 43.9 in H14 and from 26.1 to 42.7 in the youngest porphyry zircons in H13 complex. Yb/Gd ratios are used to measure the steepness of heavy to light REE patterns. The Yb/Gd ratios generally increase with decreasing Y concentrations and Th/U ratios from older to younger porphyry zircons. Scatter is evident at high-Y, high-Th/U and lowYb/Gd ratios, which implies that hotter zircons from older H79 and younger H14 and H3 porphyry complexes have higher Yb/Gd and thus slightly different REE patterns. An outlier with highest Yb/Gd and lowest Th/U ratio (Fig. 5.7 C, D) is inferred to inherited felsic melt composition reflecting magma mixing as evident by the scatter in Th/U ratios in the youngest H13 porphyry system (Fig. 5.7 B). 5.3.5 Multi-valent elements EuN/EuN* ratio quantifies the magnitude of negative Eu anomalies in the REE patterns and is used as a proxy for the oxidation state of the magma (Ballard et al., 2002). The EuN/EuN* values range from 0.49 to 0.72, in H79, from 0.46 to 0.69 in H15, from 0.41 to 0.71 in H14 and from 0.47 to 0.60 in H13 porphyry zircons. The EuN/EuN* versus Hf plot indicate multiple flat trends of decreasing EuN/EuN* ratios and increasing Hf concentrations with time. High EuN/EuN* and low-Hf values in the hornblende-diorite sample (PFH; RD077-608) distinguish H79 complex from H15, H14 and H13 complexes with progressively lower EuN/EuN* and higher-Hf values (Fig. 5.8 A). Considerable scatter in EuN/EuN* values (0.4 to 0.6) and a wide  132  range of increasing-Hf in the quartz-diorite (PFB2; RD510-1545) is attributed to later mafic melt injections in H14 complex (Fig. 5.8 A). Ce/Ce* values range from 23 to 499 in the oldest H79 porphyry zircons, from 42 to 547 in H15, from 15 to 708 in H14 and from 7 to 638 in the youngest porphyry zircons from H13 complex. The Ce/Ce* versus Hf concentration plot shows a steep trend of increasing Ce/Ce* with increasing Hf content. The Ce/Ce* values at a given (9000 ppm) Hf distinguish H79 from H15, H14 and H13 porphyry centers with an overall Ce/Ce* values at a given (10,000 ppm) Hf content (Fig. 5.8 B). The Ce/Ce* values (>300) in zircons are inferred to the higher oxidation state of the magma (Ballard et al., 2002).  Figure 5.7 Zircon mineral-chemistry plots. (A) Hf versus Y; (B) Th/U versus Y/Yb; (C) Y versus Y/Gd; and (D) Th/U versus Yb/Gd plots showing distinct fractionation trend from older H79 to younger H15, H14 and H13 porphyry zircons. The circled outliers inferred to the inheritance of zircons in the corresponding samples. Considerable scatter is evident in the H79 (PFH; RD077-608) and H14 (PFB2; RD510-1545) porphyry zircons reflecting variation in the magma composition.  133  Figure 5.8 Hafnium versus multi-valent plots. (A) Hf versus Eu/Eu* plot illustrating decreasing Eu/Eu* and increasing Hf content in space and time. Eu/Eu* values (>0.4) indicate the oxidation state and/or fractionation of plagioclase feldspars (Ballard et al., 2002); (B) Hf versus Ce/Ce* ratios indicate a steeply curved trend of fractionation from older H79 through younger H15, H14 and H13 porphyry centers distributed from north to south.  134  5.4 Discussion Trace element geochemistry of distinct zircon grains and populations in igneous rocks is a robust technique employed in the understanding of source rocks, contamination, magma mixing, mingling processes and metallogenic fertility of the magma chambers (Belousova et al., 2002, 2006; Griffin et al., 2002a, 200 7). The implications of zircon mineral-chemistry in porphyry copper environment include crystallization, mixing, cooling and fractionation histories of differentiated magmas leading to form giant porphyry copper deposits. Integration of zircon crystal morphology, trace element signatures and U-Pb ages in this study provided detailed records of the evolution, oxidation state and metallogenic fertility of the magma (Griffin et al., 2007) responsible for the giant H15 and H14 porphyry deposits (Fig. 5.9). 5.4.1 Contamination and mixing of magma Zircon chemistry data presented herein indicate several discordant trends within rock suites, rock-type and individual zircon grains from corresponding porphyry centers at western Reko Diq. Individual zircons, particularly from H79 and H14 porphyry centers, have different Yb/Gd ratios and Y concentrations, which provide evidence for magma heterogeneity, and contamination of material from multiple sources or mixing of discrete melts with distinct fractionation histories. Variations in Th/U, Y/Yb and Yb/Gd ratios in most of the intrusive rocks suggest distinct fractionation and/or mixing of magma from H79 through H15, H14 and H13 porphyry centers (Fig. 5.7 B, C, and D). In general, zircon cores as well as the interior concentric zones are represented by higher-temperature and low-Hf concentration as compared to the corresponding exterior-rim analysis. However, some discordant trends of cooler, high-Hf lower Th/U zircon core surrounded by hotter, low-Hf and higher Th/U rims are also evident in H14 (RD008-668) and H13 (RD147-561) porphyry centers (Fig. 5.4). This correlation may be explained by the mafic melt injections observed in several other magmatic systems leading to form porphyry Cu (Au ± Mo) deposits (e.g., Hattori and Keith, 2001; Pollard and Taylor, 2002; Maughan et al., 2002; Wainwright, et al. 2011). Although, majority of the zircons from the intrusive rocks in Reko Diq western porphyry centers are homogeneous, however inherited zircon-grains, zircon-core as well as zircons with discordant trends within a single rock unit suggests variety of magma mixing scenarios. For example, magma mixing and contamination may be a product of chamber 135  dynamics where material from older solid-intrusions and/or chilled margins may break-off, mix and re-melt with subsequent magma batches (Chappell, 1996). In this case, the older refractory minerals such as zircons are re-cycled into the new magma. The recent field investigations and geochronologic studies in other porphyry deposits revealed complex sequences of intrusions, partial mixing, disruptions and re-mobilization of slightly older pulses in the plutonic rocks such as documented in Sierra Nevada Batholith, California (Miller et al., 2001). Similarly, zircon recycling into new pulses of magma in the Spirit Mountain Batholith indicated remobilization of pre-existing crystal mush (Walker et al., 2007). At Reko Diq, the presence of older xenocrystic zircons in H79 porphyry complex suggests contamination and mixing of material from pre-existing intrusive and or volcanic rocks (Chapter 4). Furthermore, xenocrystic zircons with discordant core-to-rim temperatures, Hf-content and Th/U ratios in the intrusive rocks reflects active mixing of discrete aliquots responsible in generating fertile magma that formed the Reko Diq H15, H14 and H13 porphyry deposits. 5.4.2 Oxidized porphyry magmas Porphyry intrusions associated with the Reko Diq western porphyry complex have elevated high EuN/EuN* and CeN/CeN* values, typical for porphyry Cu deposits. Research investigations by Ballard et al., (2002) identified that porphyry related intrusive complexes in northern Chile are associated with oxidized magmas of high Ce4+/Ce3+ values (>300) and high EuN/EuN* values (>0.4). The EuN/EuN* and CeN/CeN* values in zircon-grains and populations in different rock-suits can be used to track the oxidation state of the magma with zircon growth. Besides the oxidation state, EuN/EuN* and CeN/CeN* values may also be affected by temperature (Liang et al., 2006) and plagioclase fractionation (Belousova et al., 2002) during the magma evolution. The CeN/CeN* values in this study are calculated to quantify the magnitude of Ce anomalies, however, these values can be correlated with Ce4+/Ce3+ values of Ballard et al., (2002) because the oxidized Ce4+ tend to behave as zirconium or hafnium in zircons during evolution (Belousova et al., 2006). EuN/EuN* values from Chuquicamata-El Abra igneous complexes northern Chile range from 0.1 to 0.77, where porphyry copper related magmas have EuN/EuN* values ≥0.4 (Ballard et al., 2002). Similarly, the EuN/EuN* values at El Salvador Chile (0.4; Lee, 2008) and Oyo Tolgoi Mongolia (0.3; Wainwright et al., 2011) indicate that most fertile magmas contain 136  higher EuN/EuN* values than the igneous rocks not associated with porphyry systems. Zircons from the western porphyry deposits at Reko Diq have EuN/EuN* values from 0.41 to 0.72 with increasing Hf content from older to younger porphyry zircons, suggesting an overall effect of increasing oxidation state in the magma. The EuN/EuN* values slightly decrease with cooling and increasing Hf, most likely due to the fractionation of plagioclase feldspars during the evolution (Fig. 5.8 A). On the other end, a wide range of CeN/CeN* values from 15 to 708 at any given Hf content reflect significant variation in the oxidation state. However, most of the CeN/CeN* values (≥300) in zircons from early-mineral (PFB1) and syn-mineral (PFB2) rocksuits suggest that these intrusions are genetically linked to a more oxidized magma (Carmichael and Ghiorso, 1986; Blevin et al., 1992; Cherniak et a., 1997; Ballard et al., 2002) responsible for the giant H15 and H14 porphyry Cu-Au deposits (Fig. 5.8 B). 5.4.3 Spatial-temporal relationships Geochronological studies at Indio Muerto porphyry district El-Salvador, Chile (Gustafson et al., 2001), Quellaveco Peru (Sillitoe and Mortensen, 2010), Butte Montana (Lund et al., 2002; Dilles et al., 2003) suggest that most magmatic systems with multiple porphyry intrusions and subsequent hydrothermal alteration and Cu-Au mineralization commonly span from 1 to 4 million years. Magmatic systems with a short life-span may also result in a cluster of porphyry deposits as documented in Yerington, Nevada (1 m.y., Dilles and Wright, 1988), El Abra-Fortuna Chile (1-2 m.y., Campbell et al., 2006), Batu Hijau (1 m.y., Garwin, 2002), and Reko Diq Pakistan (1 m.y., this study). Integrated zircon mineral-chemistry and U/Pb geochronology data (Chapter 4) provides insights into cooling, fractionation and longevity of the magma chamber and individual porphyry centers at western Reko Diq. The middle to late-Miocene (12.9-11.9 Ma; Chapter 4) magmatic activity was initiated with the emplacement of hornblende-diorite (PFH) forming H79 porphyry complex in the north at 12.9 Ma. (Fig. 5.9 A1). The magma advanced southward and evolved into a succession of felsic intrusions of granodiorite (PFB1) and quartz-diorite (PFB2) compositions forming the H15 (12.5 to 12.1 Ma) and H14 (12.3 to 12.0 Ma) porphyry deposits during the peak magmatism, followed by the subsequent emplacement of late-stage (PFB3, PFB4) porphyry intrusions (Fig. 5.9 A2, A3). A further southward shift of the magmatic activity is recorded with the emplacement of the youngest hornblende-rich quartz-diorite 137  Figure 5.9 Conceptual N-S cross sectional model of the Reko Diq western porphyry complex. (A) Crustal scale magmatic-hydrothermal system with deep mantle-derived mafic melts form a zone of magma mixing, assimilation, storage and homogenization (MASH) at lower crust (Hildreth and Moorbath, 1988; Schmidt and Poli, 1998, Richards, 2003). Mafic melts evolved into oxidized, sulfur and volatiles rich magma of andesite-dacite composition (Hildreth, 1981; Grove et al., 2003; Chiaradia et al., 2004; Rohrlach and Loucks, 2005). The magma rises at shallow levels, assimilate upper crustal material and stall to form magma chambers of relatively felsic composition and evolve porphyry Cu deposits (Gustafson 1979; Burnham 1979; Dilles 1987; Hedenquist and Lowenstern, 1994; Candela and Piccoli, 2005; this study). (A1) Initial intrusive event of hornblende-diorite (PFH; 12.9 Ma) in H79 complex; (A2) Magma chamber evolved to form H15 complex to the south with the emplacement of early granodiorite (PFB1; 12.5 Ma) and quartz-diorite (PFB2; 12.3 Ma) intrusions during peak magmatism; (A3) Further southward shift of magmatism forming the H14 complex associated with the younger granodiorite (PFB1;12. 3Ma) and quartz-diorite (PFB2; 12.0 Ma) intrusions; (A4) Emplacement of late-mineral (PFB3) and late-barren (PFB4) quartz-diorite intrusions from 12.1 to12.0 Ma, in H15-H14 and formation of the H13 complex with the youngest hornblende-bearing quartz-diorite intrusions (PFB2) at 11.9Ma. 138  (PFB2) porphyry forming the H13 porphyry deposit at 11.9 Ma (Fig. 5.9 A4). Overall, the porphyry copper magmatism spanned for ~1 m.y. forming the Reko Diq western porphyry cluster from north to south (Fig. 5.9). Similar space-time relationship is established by TiO2in-zircon thermometry, suggesting higher crystallization temperatures (average 736oC) for the northern H79 complex as compared to the southern H15, H14 and H13 porphyry centers with average crystallization temperatures of 689oC, 680oC and 678oC respectively. Furthermore, the older H79 complex have distinctively higher Th/U ratios and lower Hf concentrations compared to the younger H15, H14 and H13 porphyry centers, suggesting crustal contribution in the younger porphyry centers. The trace element data indicate intermittent magma mixing at Reko Diq. However, the overall trend of decreasing Th/U, Y/U and Yb/Gd ratios, decreasing temperatures, and increasing Hf content with time suggests progressive crustal assimilation and fractionation of mafic to felsic compositions (Richards and Kerrich, 2007; Richards, 2011; Richards et al., 2012). 5.5 Conclusions The trace element geochemistry of zircons suggests that the Reko Diq western porphyry deposits are genetically linked to an oxidized and differentiated magma chamber. The initial mafic melts (Hildreth and Moorbath 1988, Richards, 2003) appear to have undergone significant crustal assimilation and feldspar and amphibole fractionation leading to the formation of intermediate composition magmas at western Reko Diq. The TiO2-inzircon thermometry suggests that H79 porphyry complex was genetically linked to a typical andesitic magma with minimum crystallization temperature of ~736oC. With time, the magma cooled and fractionated into felsic compositions forming the H15 (689oC), H14 (680oC) and H13 (678oC) porphyry deposits. Although fractionation and cooling histories are complicated by sustained mafic recharge into the magma chamber; however, increasing Th/U and Yb/Gd ratios, higher EuN/EuN* and CeN/CeN* values as well as increasing Hf and decreasing Y content, suggest a general trend of cooling and fractionation from older H79, through the younger H15, H14 and H13 porphyry systems spatially distributed from north to south. The younger H14 and H13 porphyry centers generally follow the cooling and fractionation trend with spikes of high-temperature, low-Hf and higher Th/U ratios indicates intermittent mafic recharge during 139  the waning stage magmatism as seen in Bingham Canyon (Waite et al., 1998; Hattori and Keith, 2001; Maughan et al., 2002) Grasberg (Pollard and Taylor, 2002), Oyo Tolgoi (Wainwright et al., 2011) and El Salvador (Cornejo et al., 1997). Overall, the study of zircons geochemistry reveal that source heterogeneity, oxidation state, contamination and magma mixing are the main processes involved in the genesis of Reko Diq western porphyry deposits. Minor population of xenocrystic zircons with discordant trends and changes in temperature and Hf content reflect a high energy magma chamber capable of mixing and melting heterogeneous source material. The zircon inheritance in H15, H14 and H13 porphyry is limited, which reflect fairly homogeneous source magma with no significant re-melting and contamination from host rocks. However, mixing of oxidized mafic melts is suggested to have played a key role in the fertility of the magma chamber that formed the giant Reko Diq H14 and H15 porphyry Cu-Au deposits.  140  Chapter 6 - Hydrothermal alteration and evolution of Reko Diq H14-H15 6.1 Introduction The interplay between porphyry intrusions and hydrothermal events played an important role in the formation of giant Reko Diq H15 and H14 porphyry deposits. Research suggests that most large scale porphyry Cu-Au (Mo) deposits (e.g., Reynolds et al., 1998; Deckart et al., 2005; Gustafson et al., 2001; Maksaev et al., 2004; Pollard and Taylor, 2002) formed as a result of multiple and overlapping magmatic-hydrothermal systems linked to a sulfur and volatile-rich magma chamber. Magmatic-hydrothermal processes in porphyry environments are well established based on the geological mapping and petrologic studies (Gustafson and Hunt, 1975; Dilles and Einaudi, 1992), fluid inclusion characteristics (Roedder, 1971; Bodnar, 1995; Hedenquist et al., 1998; Ulrich et al., 2001; Redmond, et al., 2004; Landtwing et al., 2005; Davidson et al., 2006; Klemm et al., 2007; Audetat et al., 2008; Rusk et al., 2008), stable isotope analysis (Sheppard et al., 1969; Sheppard, 1971; Hedenquist et al., 1998; Harris et al., 2005; Field et al., 2005) and relationship with active volcanic and geothermal systems (Hedenquist and Lowenstern, 1994). Porphyry deposits worldwide have a typical suite of alteration style and zonation from sodic-calcic to potassic, transitional sericite-chlorite, sericitic and advanced argillic assemblages (Meyer and Hemley, 1967; Lowell and Guilbert, 1970; Seedorff et al., 2005; Sillitoe 2010). Detailed research on the evolution of porphyry Cu deposits establish that the ore-stage potassic alteration and quartz veins are associated with hot (>400oC), hypersaline magmatic fluids, whereas the transitional stage sericite-chlorite and sericitic (phyllic) alteration derive from cooler, less-saline hydrothermal fluids incorporating meteoric water (Roedder, 1971; Reynolds and Bean, 1985; Hedenquist et al., 1998; Lickfold and Cook, 2003; Harris et al., 2005; Rusk et al., 2008). Advanced argillic alteration is interpreted to have been formed late in the life of porphyry intrusions (Sillitoe 1993). However, some authors debated this relationship and treated advanced argillic as a shallow alteration type formed at the same time as potassic alteration (Hedenquist and Arribas, 1997). 4  A version of this chapter will be submitted for publication: Razique, A., Tosdal, R. M., and Bouzari, F., Hydrothermal Alteration and Evolution of the Giant Reko Diq H14-H15 Porphyry Cu-Au Deposit: Chagai District, Balochistan-Pakistan.  141  The western Reko Diq complex consists of several porphyry intrusions and pulses of hydrothermal alteration, veins and Cu-Fe-sulfides leading to the formation of the H79, H15, H14 and H13 porphyry Cu deposits (Perelló et al., 2008; Fig. 6.1). This chapter deals with magmatic-hydrothermal events in the H15 and H14 porphyry centers. Field mapping and drill core logging show that these porphyry centers are characterized by typical potassic, sodic-calcic, transitional sericite-chlorite (clay), sericitic (phyllic) and propylitic alteration generally consistent with the typical alteration model (Meyer and Hemley, 1965; Lowell and Guilbert, 1970; Seedorff et al., 2005; Sillitoe, 2010). Understanding of hydrothermal alteration, its intensity, distribution and space-time relationship with the intrusive and host rocks remains a key for the exploration and discovery of new ore-deposits. This chapter will define the paragenetic sequence of multiple, superimposed hydrothermal alteration assemblages, veins and Cu-sulfides, and constrains the space-time relationship with the porphyry and host rocks in H15 and H14 complexes. A reconnaissance study of fluid inclusions across the H14 complex has been conducted to characterize the hydrothermal fluids in the deep-barren potassic, central ore-bearing potassic and shallow sericite-chlorite alteration zones, and track the evolution of the magmatichydrothermal system in H14 and H15 complexes. 6.2 Porphyry intrusions and host rocks The H15 and H14 porphyry deposits are spatially and temporally associated with closely spaced cluster of middle to late Miocene (12.5-12.0 Ma) porphyry intrusions host by late Oligocene andesitic volcanic and clastic sedimentary rocks (Perelló et al., 2008; this study). These intrusions display typical coarse-grained porphyritic textures with abundant phenocrysts of plagioclase and variable amounts of biotite, magmatic quartz and minor amphiboles embedded in a finer crystalline to aphanitic groundmass (Fig. 6.2; Chapter 3). The H15 porphyry deposit is centred on a large (800m2 wide) granodiorite porphyry stock (PFB1; 12.5 Ma) cut by a series of intra-mineral quartz-diorite (PFB2; 12.1 Ma) porphyry intrusions. These intrusions are characterized by intense hydrothermal potassic and sericitic alteration, multi-generation veins and disseminated to vein-hosted Cu-Fe-sulfides (Fig. 6.2 A, B). The granodiorite porphyry (PFB1) commonly forms a 5-15m wide 142  Figure 6.1 (A) Field photograph showing the alteration distribution at Reko Diq western porphyry complex; (B) Surface alteration map of H79, H15, H14 and H13 porphyry deposits illustrating the central potassic alteration zones overprinted and enveloped by transitional sericite-chlorite (clay) and surrounded outward by sericitic (phyllic) and extensive propylitic alteration.  143  Figure 6.2 Core photographs illustrating the textural and compositional characteristics and comparison of multiple porphyry intrusions in H15 and H14 complexes. (A-A’) Early granodiorite (PFB1) with intense orestage potassic alteration, multi generation veins and disseminated to veinlet Cu-Fe-sulfides; (B-B’) Intra-mineral quartz-diorite (PFB2) with moderate potassic alteration, veins and Cu-Fe-sulfides overprinted by sericitechlorite ± clay alteration; (C-C’) late-mineral quartz-diorite (PFB3) and (D-D’) late-barren quartz-diorite (PFB4) with relatively preserved primary mineralogy and coarse grained porphyritic textures.  144  discontinuous contact breccia zone along the contacts with andesitic volcanic and volcanogenic sedimentary host rocks. The early (PFB1; 12.5 Ma) and intra-mineral (PFB2; 12.1 Ma) porphyry intrusions and associated hydrothermal alteration and veins in H15 complex are truncated by narrow dykes of weakly altered quartz-diorite (PFB3; 12.1±0.4 Ma) and fresh barren quartz-diorite (PFB4; 12.0 Ma) intrusions (Fig. 6.2 C, D; Table 6.1).  The H14 porphyry deposit to the south is associated with younger granodiorite (PFB1; 12.2 Ma) and quartz-diorite (PFB2; 12.0 Ma) intrusions having similar hydrothermal alteration patterns, veins and Cu-Fe-sulfides to the H15 complex (Fig. 6.2 A’, B’). These porphyry intrusions and associated hydrothermal alteration and veins are subsequently cut by narrow dykes of younger quartz-diorite (PFB3) at 12.0±0.2 Ma, and (PFB4) at 12.0±0.1Ma (Table 6.1). The late-stage intrusions are deep seated in H14 complex, and display coarsegrained porphyritic textures with well-preserved primary minerals as well as traces of hydrothermal biotite and rare K-feldspar alteration (Fig. 6.2 C’, D’). 6.3 Hydrothermal alteration and sulfide mineralization The early fine-grained biotite-magnetite alteration in H15 complex occurred in the deeper andesitic volcanic and clastic sedimentary rocks outside the main ore zone. The coarser grained early-dark-mica (EDM; Meyer, 1995) and magnetite is commonly associated with deep-barren potassic alteration in the early (PFB1, PFB2) porphyry intrusions. The drill core from deep resource hole (RD567, >950m) show that potassic alteration is overprinted by poorly developed sodic-calcic alteration (described below). The main ore-stage potassic alteration occurs as a broad, 1000 x 800m wide zone in the central part of H15 complex. The bulk of Cu-sulfide mineralization in H15 is associated with intense potassic alteration and early quartz ± magnetite ± K-feldspar veins in the porphyry intrusions and adjacent host rocks. Potassic alteration is largely overprinted and rimmed by transitional sericite-chlorite (clay) alteration; surrounded outward by extensive sericitic (phyllic) alteration containing <0.15% Cu and 0.1g/t Au. Propylitic alteration is extensively developed in peripheral volcanic and underlying sedimentary rocks to the north, east and west of H15 complex (Figs. 6.3 and 6.4).  145  Table 6.1 Geochronological constraints of the magmatic-hydrothermal events at Reko Diq H79, H15, H14 and H13 porphyry Cu deposits. Sample No.  Area  Events  Rock type  Code  Mineral  Method  Age (Ma±2σ)  1  H79  Crystallization  Hornblende-diorite  PFH  Zircon  U-Pb  12.9 ± 0.3  2  H79  Crystallization  Hornblende-diorite  PFH  Zircon  U-Pb  12.7 ± 0.3  4  H79  K-silicate alteration  Andesitic volcanic rock  VIN  Biotite  K-Ar  13.0 ± 0.2  1  H15  Crystallization  Granodiorite  PFB1  Zircon  U-Pb  12.5 ± 0.1  1  H15  Cu sulfide mineralization  Granodiorite  PFB2  Mol  Re-Os  12.5 ± 0.06  1  H15  Crystallization  Granodiorite  PFB1  Zircon  U-Pb  12.2 ± 0.2  1  H15  Crystallization  Quartz-diorite  PFB2  Zircon  U-Pb  12.1 ± 0.2  1  H15  Crystallization  Quartz-diorite  PFB3  Zircon  U-Pb  12.1 ± 0.4  5  H15  Cu sulfide mineralization  NR  NR  Mol  Re-Os  11.7 ± 0.04  1  H14  Crystallization  Granodiorite  PFB1  Zircon  U-Pb  12.2 ± 0.2  1  H14  Crystallization  Quartz-diorite  PFB2  Zircon  U-Pb  12.0 ± 0.1  1  H14  Crystallization  Quartz-diorite  PFB3  Zircon  U-Pb  12.0 ± 0.2  1  H14  Crystallization  Quartz-diorite  PFB4  Zircon  U-Pb  12.0 ± 0.1  3  H14  Crystallization  Quartz-diorite  PFB2  Zircon  U-Pb  12.2 ± 0.1  4  H14  K-silicate alteration  Andesitic volcanic rock  VIN  Biotite  K-Ar  12.0 ± 0.2  1  H14  Cu sulfide mineralization  Granodiorite  PFB1  Mol  Re-Os  12.1 ± 0.05  5  H14  Cu sulfide mineralization  NR  NR  Mol  Re-Os  11.8 ± 0.04  1  H13  Crystallization  Quartz-diorite  PFB2  Zircon  U-Pb  11.9 ± 0.2  4  H13  K-silicate alteration  Andesitic volcanic rock  VIN  Biotite  K-Ar  12.0 ± 0.2  RD077-608 RK-015 H79-K-Ar RD341-197 RD567-1398 RD068-518 RD341-500 RD341-440 MDID-588 RD008-668 RD510-1545 RD116-506 RD008-820 RD004-2 H14-K-Ar RD130-813 MDID-589 RD147-561 H13-K-Ar  Abbreviations: H79, H15, H14, H13 = discovery holes and complexes, Hbl = hornblende, NR = not recorded, 1 Age determination on zircon U-Pb SHRIMP-RG at Stanford-USGS Micro Analysis Center California, USA (This study) 2 Age determinations by Pacific Center for Isotopic and Geochemical Research UBC, Canada (Ivascanu and Fletcher, 2008) 3 Age determinations by GEMOC Macquarie University, Australia (Fu et al., 2006) 4 Age determination by BHP Minerals through Amdel Limited Mineral Services, Australia (BHP unpub. report, 1997) 5 Age determination by AIRE Program, Colorado State University, Colorado, USA (Perelló et al., 2008)  146  Figure 6.3 Surface alteration map of the Reko Diq H15-H14 complex: The central potassic alteration and associated quartz stockwork zone in H15 is largely overprinted and surrounded by transitional sericitechlorite (clay) alteration. H14 complex to the south is characterized by a central zone of pristine potassic alteration and intense quartz-stockwork, surrounded by a mixed zone of potassic-sericitic and transitional sericite-chlorite (clay) alteration. Outer sericitic (phyllic) and peripheral propylitic alteration is developed in the peripheral volcanic host rocks to the north east and west of H15-H14 complex.  147  Figure 6.4 Cross section (3223300mN) showing vertical and lateral distribution of alteration in H15 complex, interpreted from surface mapping and drill core logging. Potassic alteration (purple) is overprinted by sodic-calcic alteration at ≥950m. Overprints of sericite-chlorite (clay) alteration (blue) introduced a mixed zone of moderate potassic alteration (pink). Phyllic (yellow) and propylitic (green) alteration developed outside the main ore-zone. High sulfidation alteration-mineralization (orange) generally follows porous country rocks at the shoulders of H15 alteration system. 148  Figure 6.5 Cross section (3222200mN) showing vertical and lateral distribution of alteration at Reko Diq H14 complex, interpreted from surface mapping and drill core logging. Deep (~980m) potassic alteration (purple) is overprinted by sodic-calcic alteration, whereas central potassic zone is surrounded by transitional sericite-chlorite (clay) alteration (blue) introducing mixed zones of moderate potassic alteration (pink). Phyllic (yellow) and propylitic (green) alteration developed outside the main ore-zone.  149  The H14 complex to the south has similar alteration patterns to the H15 complex. The early fine-grained biotite-magnetite alteration occurs in the deep andesitic volcanic and clastic sedimentary rocks outside the H14 ore zone, whereas early-dark-mica (EDM) and fine-grained magnetite is most common in the deeper porphyry intrusions and adjacent host rocks. Drill core logging and petrographic studies show distinct sodic-calcic alteration overprinting early-dark-mica at a depth of ~980m below surface. The central H14 complex represents a well-preserved, 800 x 800m wide ore-stage potassic alteration and intense hydrothermal quartz ± K-feldspar ± magnetite veins carrying much of the high-grade Cu-Fesulfide mineralization. The central potassic zone is concentrically surrounded by a mixed zone of potassic-sericitic alteration, transitional sericitic-chlorite (clay) and outer sericitic (phyllic) alteration, which contain <0.15% Cu and 0.1g/t Au. Propylitic alteration of chloriteepidote ± pyrite assemblage is well developed in the peripheral volcanic and underlying sedimentary rocks to the east and west of the H14 complex (Figs. 6.3 and 6.5). 6.3.1 Early biotite-magnetite alteration Early fine-grained biotite-magnetite alteration is identified in the geotechnical holes drilled outside the H15 and H14 complexes. The deep (>950m) andesitic lava flow and interbeds of shale, siltstone, and sandstone units in these holes represent very fine-grained biotite and associated magnetite alteration; locally characterized by pervasive dark green chloritization due to hornfelsing from contact metamorphism. Early biotite-magnetite alteration in the central granodiorite (PFB1) and quartz-diorite (PFB2) porphyry intrusions occur as disseminated small (µm-size) flakes and mm-scale irregular patches and discontinuous veins of early-dark-mica invading the matrix and weak cleavage planes of plagioclase feldspars (Fig. 6.6 A-A’). 6.3.2 Sodic-calcic alteration Sodic-calcic alteration is characterized by Na and Ca-rich minerals replacing K and Fe-rich minerals (Carten, 1981; Dilles and Einaudi, 1992). Sodic-calcic alteration of albite + epidote ± actinolite ± chlorite assemblage is identified in four deep (>1000m) resource drill holes at H15-H14 porphyry complex (Figs. 6.4, 6.5, Table 6.2). Albite replaces primary Kfeldspars and occurs as cream-white Na-rich plagioclase and in mm-scale suture zones and selvages along quartz veins (Fig. 6.6 A-A’ and Fig. D.1). 150  Table 6.2 Description and age relationship of hydrothermal alteration and sulfide mineralization at Reko Diq H15 and H14 porphyry Cu-Au (Mo) deposits. Sequence  Alteration style  Description  Veins  Cu-Fe-sulfide mineralization  Space - time distribution  Stage-1  Biotite-magnetite  Fine-grained pervasive biotite-magnetite; hornfelsing features in the andesitic volcanic and sedimentary host rocks.  Absent  Uncommon  Associated with deeper host rocks outside H15 and H14 ore-zones.  Early-dark-mica  Medium-coarse grained flaky, dark mica in the rock matrix and along weak cleavage plans of plagioclase.  Irregular trails of early biotite veins  Uncommon  Alters PFB1, PFB2 intrusions and adjacent wall-rocks in H15-H14.  Stage-2  Sodic - calcic  Albite-epidote ± actinolite-chlorite + magnetite assemblage; albite occur as Na plagioclase replacing K-feldspars; also present in sutures and selvages along quartz “AB veins” and actinolite-magnetite “M-veins”; epidote replace plagioclase and/or hornblende; actinolite ± chlorite replace mafic sites.  Quartz ± Kfeldspar ± magnetite AB and magnetite ± actinolite M-veins  Traces of chalcopyrite ± bornite ratio (8:2), weak < 0.1% Cu and 0.05g/t Au.  Alters PFB1, PFB2 intrusions and wall-rocks (>1000m) peripheral to the core of H15-H14 complex; albitization of plagioclase replacing K-feldspars.  Stage-3  Potassic (Biotite-rich)  Intense biotite-magnetite ± K-feldspar overprinted by chlorite-sericite; shredded biotite overgrow and rim phenocryst biotite and amphiboles; K-feldspar replace plagioclase and locally occur as vein-selvages; magnetite is granular, veined and martitized.  Quartz, K-feldspar, magnetite, sulfide AB-veins ± anhydrite  Chalcopyrite + bornite + pyrite ratio (5:2:3) ± molybdenite; main ore-stage @ average 0.5%Cu and 0.3g/t Au  Occur in PFB1, PFB2, PFB3 and host rocks in H15-H14; overprint early sodic-calcic ± K-feldspar alteration.  Potassic (K-feldspar rich)  Intense K-feldspars-biotite-magnetite alteration; K-feldspar replace plagioclase, occur as veinlets, selvages along quartz "AB-veins" and locally replace groundmass with mosaic of quartz; shredded biotite replace phenocryst biotite and amphiboles; magnetite is granular, veined and disseminated.  Quartz, K-feldspar, magnetite, sulfide AB-veins ± anhydrite  Chalcopyrite + bornite ± pyrite ratio (6:3:1) ± molybdenite; main ore-stage @ average 0.6% Cu and 0.4g/t Au.  Pervasive K-feldspars common in early granodiorite porphyry (PFB1) in both H15 and H14 complexes.  Stage-4  Sericite-chlorite (Transitional)  Sericite-chlorite ± clay (illite) overprint potassic assemblage mainly as selvages along "D-type" sulfide veins; fine soapy sericite replace plagioclase and coarser sericite (muscovite) + chlorite replace mafics; magnetite is oxidize to hematite.  Quartz ± sulfide AB-veins cut by pyrite-chalcopyrite D-veins  Pyrite + Chalcopyrite ± bornite ratio (6:4:1) ± molybdenite; moderate Cu-Au @ 0.4% Cu and 0.2g/t Au.  Closely linked with PFB3; overprint K-silicate in PFB1, PFB2 intrusions and host rocks in H15-H14 complex.  Stage-5  Phyllic  Pervasive quartz-sericite-pyrite ± illite-chlorite alteration mainly in peripheral host rocks cut by discontinuous pyrite "D-veins".  Trails of Quartzanhydrite-illite ± pyrite-chalcopyrite  Pyrite ± Chalcopyrite ratio (9:1) @< 0.2%Cu, 0.1 g/t Au  Extensive phyllic surrounds inward sericite-chlorite and potassic zones in H15-H14; cut by late pyrite "D-veins".  Stage-6  Propylitic  Pervasive chlorite ± epidote-hematite ± carbonate alteration in peripheral host rocks; propylitic alteration is locally cut by late chlorite-illite and pyrite veins.  Micro-veinlets of Chlorite-illite and pyrite  Cu-Fe-sulfides uncommon, minor disseminated pyrite @<0.10% Cu and 0.05g/t Au  Outermost propylitic zone surrounds deeper sodic-calcic and potassic core, and upper sericitic zone in H15-H14  Alteration mineralogy and paragenesis determined using petrographic observations combined with portable short wave-length infrared (SWIR) field spectrometer analysis. Alteration terminology from (Meyer and Hemley, 1965; Lowell and Guilbert, 1970) and vein terminology including A, B, D veins from Gustafson and Hunt (1975) and M-veins from Sillitoe, (2000)  151  Figure 6.6 Core photographs illustrating the textural characteristics and hydrothermal alteration in H15 and H14 porphyry centers. (A-A’) Early-dark-mica (EDM) cut by sodic-calcic alteration; (B-B’) ore-stage, biotiterich potassic alteration; (C-C’) ore-stage K-feldspar-rich potassic alteration; (D-D’) Transitional sericitechlorite (clay) alteration; and (E-E’) sericitic (phyllic) alteration.  152  Epidote is fine grained, disseminated and usually replaces amphiboles and/or plagioclase. The ferromagnesian minerals including early-dark-mica locally alter to greyish green actinolite and dark green chlorite (Fig. 6.6 A-A’). The early-dark-mica, sodic-calcic alteration and quartz veins in H15 and H14 porphyry centres are typically poor in sulfides (<1.0% total sulfide content) comprising coarse-grained chalcopyrite, bornite and rare pyrite mineralization. 6.3.3 Ore-stage potassic alteration The ore-stage potassic alteration in H15 and H14 porphyry Cu-Au (Mo) deposits is characterized by variable intensities and proportions of biotite + K-feldspar + magnetite + quartz assemblage and associated quartz ± magnetite ± K-feldspar veins. Much of the highgrade Cu-Fe-sulfide mineralization is associated with intense potassic alteration and quartz stockwork in the porphyry intrusions and adjacent country rocks (Perelló et al., 2008; this study). Potassic alteration is grouped into biotite-rich and K-feldspar-rich assemblages based on the intensity and paragenesis of K-silicates and Cu-Fe-sulfides and its relationship with porphyry intrusions (see below). 6.3.3.1 Potassic alteration (Biotite-rich) The biotite-rich potassic alteration comprises intense shredy biotite + magnetite ± Kfeldspar assemblage. Shredy biotite replaces phenocryst biotite ± amphiboles and occurs as concentrations of complexly intergrown clusters obliterating the shape of former phenocrysts, and when intense, develop as randomly oriented clusters in the matrix. Magnetite is granular and occurs as small (<1mm) disseminated crystals in the matrix and strings of micro-veinlets with quartz ± K-feldspars ± sulfides (Fig. 6.6 B-B’ and Fig. 6.7 AA’). The biotite-rich assemblage is the dominant type of potassic alteration in the earlyPFB1, syn-mineral PFB2 and in a large volume of andesite and volcanogenic sedimentary host rocks surrounding H15 and H14 porphyry centers. The biotite-rich potassic alteration is accompanied by quartz ± magnetite ± K-feldspar “A-type” veins (Gustafson and Hunt, 1975), disseminated and vein-hosted chalcopyrite + bornite ± pyrite containing up to ~1.5 % Cu and 1.0 g/t Au in H15 and H14 complexes (Table 6.2).  153  6.3.3.2 Potassic alteration (K-feldspar-rich) The K-feldspar-rich potassic alteration assemblage (K-feldspar + quartz + biotite + magnetite ± anhydrite) mainly occurs in the granodiorite porphyry (PFB1) indicating a strong host rock effect on potassic alteration assemblage in H15 and H14 complexes (Table 6.2). The K-feldspar-rich potassic alteration is locally observed in the quartz-diorite (PFB2) and adjacent andesitic volcanic rocks when in contact with granodiorite porphyry (PFB1). Kfeldspar replaces plagioclase and occurs in selvages and suture zones of A and B-type (Gustafson and Hunt, 1975) quartz veins (described below). The groundmass is commonly replaced by pervasive fine-grained K-feldspar and mosaic of hydrothermal quartz with locally preserved pseudomorphs of hydrothermal biotite replacing mafic sites. Magnetite is mainly disseminated, granular and occurs as hair-line micro-veinlets (Fig. 6.6 C-C’ and Fig. 6.7 B-B’). The K-feldspar-rich potassic alteration and multi-generation quartz ± K-feldspar A-type (Gustafson and Hunt, 1975) veins host intense (up to 4.0%) disseminated and micro veinlets of chalcopyrite + bornite ± pyrite ± molybdenite containing the highest grade Cu-Au mineralization (up to 2.0 % Cu and 1.5 g/t Au) in H15 and H14 porphyry deposits. 6.3.3.3 Veins and Cu-Fe-sulfide mineralization Copper-sulfide mineralization in the H15 and H14 complex is typically associated with intense potassic alteration and hydrothermal quartz, quartz-magnetite and quartz-Kfeldspar “A-type” veins as documented in many other porphyry Cu deposits (e.g., Gustafson and Hunt, 1975; Dilles and Einaudi, 1992; Proffett, 1998, 2003; Padilla-Garza et al., 2004; Vry, et al., 2010; Redmond and Einaudi, 2010). The ore-stage Cu-Fe-sulfides consist of disseminated and micro-veinlets of fine-grained, intergrown chalcopyrite + bornite ± pyrite (6:3:1) and molybdenite mainly in potassic alteration and quartz A-veins (Fig. 6.8 A-A’, BB’, C-C’). Coarser grain molybdenite + chalcopyrite generally occur as center line in quartzsulfide B-type veins. The main ore-stage potassic alteration, A and B type veins are truncated by 1-20 mm thick chalcopyrite-pyrite ± quartz D-veins introducing up to 5 cm wide sericitechlorite (clay) alteration halos overprinting potassic alteration (Fig. 6.8 D-D’). The intensity of Cu-Fe-sulfides increases (~4.0 vol. %) with intensity of early quartz A-veins and potassic alteration in the porphyry intrusions as well as in the adjacent host rocks and contain up to 2.0% Cu and 1.5g/t Au mineralization in H15 and H14 complexes (Perelló et al., 2008). 154  Figure 6.7 Transmitted light photomicrographs showing characteristics of potassic alteration in H15 and H14 porphyry deposits. (A-A’) Granodiorite-PFB1 with cluster of shredy biotite (bio), fine-grained K-feldspars (Kfs) and interstitial quartz (qtz) in the groundmass; (B-B’) Granodiorite-PFB1 with intense fine-grained Kfeldspars (Kfs) replacing plagioclase and in-turn overprinted by sericite (ser); quartz (qtz) occur interstitially; (C) Granodiorite-PFB1 and potassic alteration cut by quartz-diorite-PFB2 with finer grained shredy biotite (bio) cluster in the rock-matrix and rim phenocryst biotite; (C’) Quartz-diorite-PFB2 with plagioclase altered to fine-grained K-feldspars (Kfs) and rim by sericite (ser); shredy biotite (bio) occur as cluster in the matrix and disintegrate phenocryst biotite; (D’) Quartz-diorite-PFB3 illustrating weak, fine-grained secondary biotite (bio) in the matrix and rim phenocryst biotite; (D’) late quartz-diorite-PFB4 with well-preserved primary mineralogy and textures along with early-dark-mica and traces of shredy biotite. 155  Figure 6.8 Drill core photographs and reflected light photomicrographs illustrating hypogene Cu-sulfide mineralization at Reko Diq H14 and H15 porphyry deposits. (A-A’) fine-grained, disseminated and intergrown chalcopyrite-bornite and molybdenite in biotite-rich potassic alteration; (B-B’) intergrown chalcopyrite-bornite-pyrite and molybdenite in K-feldspar-rich potassic alteration; (C-C’) fine, disseminated and intergrown chalcopyrite and molybdenite associated with potassic-sericitic alteration; (D-D’) chalcopyrite associated with late-stage sulfide D-type veins and intense sericite-chlorite (clay) alteration.  156  6.3.4 Transitional sericite-chlorite (clay) alteration Sericite-chlorite (clay) is a distinct alteration assemblage, which occur in the transition between central potassic and outer sericitic (phyllic) alteration of Meyer and Hemley (1965) and Lowell and Guilbert (1970). Sericite-chlorite (clay) alteration is an important component of Reko Diq H14 and H15 porphyry Cu-Au (Mo) deposits. In hand specimen, it appears as a pale-green alteration assemblage of greenish soapy sericite (finegrained muscovite), random flakes of green chlorite and subordinate grey-green clay (illite) along with variable proportions of albite, calcite and rutile (Perelló et al., 2008; Fig. 6.6 DD’, Table D.1 and Fig. D.1). Fine-grained flakes of sericite (muscovite) replace plagioclase, overgrow secondary K-feldspars, and randomly cluster in the rock matrix. Sericite is generally abundant in selvages along millimetric to centimetric scale sulfide D-type veins (Gustafson and Hunt, 1975). Chlorite mainly occurs in concentrations and irregular patches replacing magmatic hornblende and/or biotite and/or hydrothermal biotite. Clay minerals mainly consist of greyish green, fine-grained micaceous illite replacing plagioclase feldspars as evident in the drill core, petrographic thin sections (Fig. 6.9) and X-ray diffraction analysis (Table D.1 and Fig. D.1). Magnetite is commonly martitized and locally transformed into specular hematite. Sulfides in the sericite-chlorite (clay) alteration consist mainly of cmscale chalcopyrite-pyrite D-type veins as well as disseminated grains along vein halos contributing around 0.40 % Cu and 0.20 g/t Au in H15 and H14 deposits (Perelló et al., 2008; Table 6.2). 6.3.5 Sericitic (Phyllic) alteration Sericitic (phyllic) alteration occurs as broad halos occupying sizeable volume of volcanic and sedimentary rocks around H14 and H15 porphyry centers. The alteration assemblage typically consists of pale-white, texturally destructive aggregates of quartz, fine grained sericite (muscovite), clay minerals (kaolinite ± montmorillonite), minor tourmaline, anhydrite, abundant (up to 5 vol. %) pyrite and traces of chalcopyrite (Perelló et al., 2008; Fig. 6.6 E-E’). The sericitic alteration is pervasive in close proximity to the porphyry system and is characterized by discontinuous veins and trails of quartz-anhydrite and late-stage 1-20 mm thick pyrite ± chalcopyrite D-veins containing less than 0.2% Cu and 0.1g/t Au (Table 6.2). 157  Figure 6.9 Reflected light photomicrographs illustrating characteristics of transitional sericite-chlorite (clay) alteration in H15 and H14 porphyry deposits. (A-A’) Granodiorite-PFB1 with K-feldspar (Kfs) altered plagioclase as well as the groundmass overprinted by fine grained sericite + clay (illite), whereas, biotite is replaced by dark greenish-grey chlorite; (B-B’) Quartz-diorite-PFB2 showing complete replacement of plagioclase into fine-grained sericite (ser) and clay (illite) appear in dark colors.  Petrographic observations in the H15 complex indicate a distinct sulfide assemblage of covellite ± bornite + chalcopyrite + pyrite in association with quartz + sericite ± clay alteration. This alteration and sulfide assemblage is commonly developed in sub-vertical narrow structural zones and laterally in 1 to 20 meter thick stratigraphic units of sandstone, siltstone, conglomerates and volcanic host rocks at the flanks of H15 porphyry deposit. These zones are generally characterized by abundant (up to 8 vol. %) tiny (300 to 400 µm), disseminated and micro-veinlet pyrite ± chalcopyrite (7:3) crystals intergrown with bornite and/or covellite leading to some higher Cu-grades (~1.0% Cu) in H15 complex (Fig. 6.10). 158  Figure 6.10 Drill core photographs and reflected light photomicrographs of high-sulfidation Cu-Fe-sulfide mineralization at Reko Diq H15 complex. (A-A’) Granodiorite porphyry with intense quartz-sericite-clay and fine-grained bornite-covellite and intergrown chalcopyrite; (B-B’) Andesitic volcanic rock with intense quartzsericite-clay alteration and fine disseminated bornite-covellite and chalcopyrite; (C-C’) Fine-grained sandstone with intense quartz-sericite-clay alteration and tinny crystals of covellite rim by bornite and pyrite; (D-D’) finegrained volcanogenic shale with intense quartz-sericite-clay alteration and fine-grained disseminated covellite and chalcopyrite.  159  6.3.6 Propylitic alteration Propylitic alteration of chlorite + epidote with accessory pyrite and carbonate is extensively developed in the peripheral volcanic and the underlying sedimentary host rocks around the H15-H14 complex. Propylitic alteration extends to depth and occurs as a large ring that surrounds and partly overlaps potassic alteration in the deeper core of the H14 and H15 complexes. The deep potassic alteration in PFB1 and PFB2 porphyry intrusions are commonly overprinted by fine-grained disseminated (~2 vol.%) chlorite + epidote replacing biotite and/or amphiboles (Fig. 6.11 A-A’). Drill core from intermediate to felsic volcanic rocks display intense (~5 vol.%) mmscale irregular specks of epidote and chlorite (Fig. 6.11 B). In cross-polar transmitted light, epidote reflect strong interference colors and appear as randomly distributed cluster replacing amphiboles and plagioclase. Chlorite appears as dark flakes overprinting sites of pale-brown biotite and/or amphiboles (Fig. 6.11 B’). Fine-grained volcanogenic sedimentary host rocks locally undergone intense epidotization and chlorite alteration of ferromagnesian minerals (Fig. 6.11 C-C’). Propylitic alteration generally lack quartz-veins and sulfides (except latepyrite veins) and contain no significant Cu sulfide mineralization (Table 6.2). 6.4 Relationship of alteration and porphyry intrusions Fine-grained biotite-magnetite is interpreted to be the earliest potassic alteration occurring in the deep peripheral volcanic and sedimentary host rocks outside H15 and H14 ore zones. This alteration contains no sulfides and appears to have occurred prior to the 1st ore-forming hydrothermal event as evident in other porphyry Cu deposits (e.g., Dilles and Einaudi, 1992; Meyer, 1995; Gustafson and Quiroga, 1995; Dilles et al., 2000; Bouzari and Clark 2006; Redmond and Einaudi, 2010). The deeper potassic alteration in early (PFB1, PFB2) intrusions and adjacent country rocks in H15-H14 complex with abundant early-darkmica and magnetite is locally overprinted by sodic-calcic alteration, where plagioclase transforms to albite and ferromagnesian minerals alter to actinolite and/or chlorite. As in Yerington Nevada (Dilles and Einaudi, 1992) and El Salvador Chile (Gustafson and Quiroga, 1995) the deep potassic and sodic-calcic alteration at Reko Diq are generally barren and have no significant sulfide mineralization.  160  Figure 6.11 Drill core photographs and transmitted-light photomicrographs illustrating the propylitic alteration assemblage in porphyry and host rocks at Reko Diq H15 complex. (A-A’) Quartz-diorite porphyry (PFB2) with phenocryst biotite and amphiboles (hbl) altered to chlorite-epidote; (B-B’) Felsic volcanic rock with phenocryst biotite and/or amphiboles partially altered to chlorite-epidote; (C-C’) Epidotization in the fine-grained volcanogenic shale.  161  Paragenetic studies indicate that the deep barren potassic and sodic-calcic alteration in the early porphyry (PFB1) is followed upward by intense ore-stage potassic alteration and quartz ± magnetite ± K-feldspar A-veins (Gustafson and Hunt, 1975) containing up to 2.0% Cu and 1.5g/t Au. The intra-mineral quartz-diorite (PFB2) intrusion is accompanied by a similar sequence of alteration and vein formation; however, it has relatively less intense potassic alteration and Cu-Fe-sulfides containing up to 0.6% Cu and 0.4g/t Au. These relationships indicate that potassic alteration, quartz ± magnetite ± K-feldspar A-veins and much of the Cu-Au mineralization was formed with the emplacement of early (PFB1, PFB2) porphyry intrusions (Fig. 6.12). The quartz ± magnetite ± K-feldspar A-veins in these intrusions are cut by quartz B-type veins comprising a distinct center-line chalcopyrite + molybdenite ± pyrite mineralization. The B-veins are subsequently cut by late-stage pyrite ± chalcopyrite D-veins (Gustafson and Hunt, 1975), which result in the widespread sericitechlorite (clay) wall-rock alteration in H15 and H14 porphyry centers. The early (PFB1), intra-mineral (PFB2) and hydrothermal alteration, veins and sulfides in H15 and H14 are truncated by the late-mineral quartz-diorite (PFB3) porphyry intrusions. These intrusions are characterized by weak potassic alteration of less than 2 vol.% secondary biotite + magnetite and less-abundant pyrite ± chalcopyrite D-veins, indicating a late-stage emplacement in the magmatic-hydrothermal system. All porphyry intrusions and hydrothermal events are in turn cut by the final-stage barren quartz-diorite (PFB4) dykes emplaced in the deeper (>1000) core of H15 and H14 porphyry centers. Propylitic alteration in H15 and H14 porphyry deposits has a greater lateral and vertical extension. It surrounds and overlaps potassic alteration in the deeper core of H15H14 complex. The early (PFB1, PFB2) porphyry intrusions with overprints of around 2.0 vol. % chlorite + epidote assemblage reflect that propylitic alteration predates and partly overlap the post-mineral PFB3 and PFB4 porphyry intrusions. The propylitic alteration is interpreted as a footprint of dilution of the outward moving magmatic brine with meteoric or connate fluids circulating through wall rocks (Bowman et al., 1987).  162  Figure 6.12 Representative drill core log sheet showing the relationship between lithology, alteration, veins and Cu-Au grades. The highest Cu-Au grades associated with potassic alteration and intense quartz-sulfide veins in the early granodiorite (PFB1) porphyry (Data courtesy of Tethyan Copper Company Limited).  163  6.5 Vein generations and crosscutting relationships Geological logging of drill core and petrographic thin sections have been used to describe and classify the hydrothermal veins, and their paragenetic sequence in relation to early-mineral (PFB1), intra-mineral (PFB2), late-mineral (PFB3) and late-barren (PFB4) porphyry intrusions. Hydrothermal veins are described as early-dark-mica (EDM) (Meyer, 1995) and magnetite ± actinolite “M-veins” (Arancibia and Clark, 1996; Sillitoe, 2000) followed by quartz ± magnetite ± K-feldspar “A-veins, quartz-sulfide “B-veins” and sulfide only “D-veins” using the nomenclature of Gustafson and Hunt, (1975) (Fig. 6.13).  T Figure 6.13 Schematic illustration of multi-generation veins, crosscutting relationships and their paragenetic sequence in relation to early (PFB1), intra-mineral (PFB2), late-mineral (PFB3) and late-barren (PFB4) porphyry intrusions in H15 and H14 porphyry Cu-Au (Mo) deposits. Nomenclature of A, B and D-type veins is from Gustafson and Hunt (1975) and M-type veins from Arancibia and Clark (1996).  164  he early-dark-mica in the granodiorite porphyry (PFB1) consist of fine-grained disseminated flakes, irregular patches and mm-scale discontinuous veins of hydrothermal biotite that cut across the rock matrix and phenocrysts of plagioclase. The granodiorite (PFB1) and associated EDM veins are cut by the earliest hair-line seams and strings of magnetite ± quartz ± sulfides with or without K-feldspar halos. These veinlets are truncated by pegmatite dykes and subsequently cut by the 1st generation of quartz A1-veins (Fig. 6.14 A, B). The quartz A1-veins below 1500m are generally steep, up to 50-cm thick and are characterized by anhedral to polygonal quartz with albite ± K-feldspar halos. These veins are cut by the 2nd generation of relatively narrow (0.5 to 5cm) quartz A2-veins locally with thin halos of earlydark-mica (Fig. 6.14 C). The 1st and 2nd generation quartz veins are than cut by mm-scale magnetite ± actinolite “M-veins” exhibiting albite halos, which suggest that sodic-calcic alteration overprints the potassic alteration (Fig. 6.14 D). The main ore-stage potassic alteration in the central core (1200-600m) of the H15 and H14 porphyry deposits represent intense network of millimetric to centimetric scale quartzsulfide A1 and A2 veins with fine-grained K-feldspar in suture zones and along vein selvages. These veins are accompanied by intense (~4.0 %) disseminated, veined and vein hosted bornite + chalcopyrite ± pyrite (6:4:1) mineralization (Fig. 6.14 E, F, G, H). The orestage potassic alteration and early A1 and A2 generation veins are cut by quartz-sulfide Bveins characterized by imperfect coarser grained quartz with banded center-line of medium to coarse grained chalcopyrite + pyrite ± molybdenite mineralization in H15 and H14 porphyry deposits (Fig. 6.14 I-J). The quartz-sulfide B-type veins are relatively straighter, planer and more continuous than quartz A-veins, and may occur as parallel sets with preferred orientation. Late stage sulfide D-veins truncate all A and B veins, ore-stage potassic alteration and associated sulfides in PFB1, PFB2 intrusions and adjacent host rocks. The D-veins are characterized by millimetric to centimetric scale coarse-grained pyrite ± chalcopyrite with 1mm to 50cm wide sericite-chlorite (clay) alteration halos, which in turn are cut by infill gypsum veins (Fig. 6.14 K-L). The D-veins are spatially distributed around porphyry stocks leading to the development of transitional sericite-chlorite (clay) alteration zones in both H15 and H14 porphyry deposits.  165  Figure 6.14 Core photographs illustrating multi-generation hydrothermal veins and their crosscutting relationships: (A) Early-dark-mica cut by pegmatite dyke and barren quartz A1-veins. (B) Early-dark mica veins cut by quartz-albite and quartz-magnetite-K-feldspar (Kfs) A1-veins. (C) Quartz-albite A1-veins cut by quartz A2-veins with EDM selvages. (D) Barren quartz A1-veins cut by magnetite ± actinolite M-veins. (E, F, G, H) Quartz-K-feldspar ± magnetite A1-veins cut by quartz-K-feldspar ± anhydrite A2-veins in the ore-stage potassic alteration containing up to 4-vol.% chalcopyrite + bornite ± pyrite (5:4:1) with ~1.5% Cu & 1.0/t Au. (I) Quartz-albite A1-vein cut by quart-sulfide B-vein, (J) Quartz B-vein with center-line chalcopyrite + molybdenite ± pyrite. (K-L) Late-stage pyrite ± chalcopyrite D-veins with sericite-chlorite (clay) alteration halos postdated by gypsum infill veins.  166  6.6 Fluid inclusions Porphyry Cu deposits form as a result of volatile-rich magmatic fluids released from the underlying magma chamber and precipitate sulfides due to cooling, fluid-rock interaction, boiling and/or mixing with meteoric waters (Gustafson and Hunt, 1975; Brimhall, 1979; Reynolds and Beane, 1985; Hemley and Hunt, 1992; Hedenquist and Lowenstern, 1994; Proffett, 2009; Gruen et al., 2010; Landtwing et al., 2005, 2010). Magmatic fluids are interpreted to be the principle source of early potassic alteration and CuAu mineralization in porphyry deposits (Meyer and Hemley, 1967; Lowell and Guilbert, 1970; Beane and Titley, 1981). Therefore, it is critical to characterize the magmatichydrothermal fluids and establish their relationship with Cu-sulfide mineralization in the deep, central and shallow levels of Reko Diq H14-H15 porphyry Cu deposit. Fluid inclusions trapped in quartz veins from porphyry deposits have a wide range of fluid compositions, pressure and temperature conditions. Hydrothermal fluids within a single ore-deposit may originate from magmatic, sedimentary or meteoric water sources (Bowman et al., 1987; Dilles, 1987). Fluids salinity may range from 0-70 wt.% NaCl equiv., temperature from ~300oC to 800oC, pressure from hydrostatic to lithostatic (<10 to ~150 MPa) representing depths of 1 to 5 km, and densities from <0.1 to >1.3 g/cm3 (Rusk et al., 2008; references therein). Research on fluids suggests both high and low-salinity fluids capable of transporting metals and sulfur in a porphyry environment (Audétat et al., 2008). For example potassic alteration in porphyry deposits generally have high-salinity, hightemperature magmatic fluids, whereas low-salinity vapor-rich fluids in El-Teniente Chile (Klemm et al., 2007), Rosia Poieni Rumania (Damman et al., 1996), and other experimental studies (Heinrich et al., 1992, 1999; Audetat et al., 1998; Ulrich et al., 1999) suggested a vapor transport of metals (e.g., Williams et al., 1995; Archibald et al., 2002; Williams-Jones, et al., 2002; William-Jones and Heinrich, 2005; Pokrovski et al., 2005, 2008). Conversely, Lerchbaumer and Audétat, (2011) in a recent experimental study argued that vapor transport of metals and suggested that metal concentration in vapor-rich fluids is a secondary feature in fluid dynamics.  167  6.6.1 Methodology Over 10,000 meters of drill core was logged at a scale of 1:100, focusing the spatial and temporal distribution of porphyry intrusions, hydrothermal alteration, veins and Cu-Fesulfides in the twin H15 and H14 porphyry deposits (Tables A.2, A.3). A total of 180 samples covering a wide range of lithology, alteration types and veins across H15 and H14 complexes were selected for laboratory analysis (Table A.4). Based on detail drill core logging and petrographic thin section studies, six most representative samples of quartz A1veins were selected for a base-line study of fluid inclusions in the deep, central and shallow levels of H14 complex, leaving a gap between samples RD596-1094 and RD246-288 due to lack of drill holes in this zone (Fig. 6.15). Over 120 quartz-hosted fluid inclusion assemblages from six ~100-µm-thick doubly-polished sections were analyzed for inclusion types, abundance, spatial distribution, size and its relationship with barren and ore-bearing quartz veins (Fig. D.2). Microthermometric measurements were obtained on Linkam THMSG-600 heating freezing stage, calibrated to ± 0.2oC for the melting point of CO2 (56.6oC) and melting point of H2O (0.0oC), and to ± 0.3oC for the critical point of pure H2O (374.1oC). Fluid inclusion homogenization temperatures (Th  V-L)  and ice-melting  temperatures (Tm-ice) were obtained following the definition of Goldstein and Reynolds, (1994). Apparent fluid salinity in wt. % NaCl equiv. was determined from final temperature of ice-melting (Tm-ice) using the equation of Bodnar et al., (1994).  168  Figure 6.15 (A-F) Photographs and description of drill core samples selected for fluid inclusions analysis across H14 complex. (G) Geological cross section showing the location of fluid inclusion samples collected from deep, central and shallow levels of granodiorite porphyry (PFB1) 169  6.6.2 Fluid inclusion petrography Petrographic determination of fluid inclusions indicated abundant primary, secondary and pseudosecondary inclusions based on the definition of Roedder, (1984) and Goldstein, (2003). Five distinct types of primary fluid inclusions determined at room temperature, and classified as vapor-rich (B85), vapor-liquid (B60), liquid-vapor (B20), liquid-vapor-solid (B35H) and liquid-rich-vapor-solid (B15H) inclusions using the nomenclature of Rusk et al., (2008). In this classification scheme, the letter “B” refers to bubble, the number represent the vol.% occupied in corresponding inclusion type and the letter “H” indicate the presence of halite daughter mineral (Fig. 6.16 A-E). Fluid inclusions commonly range from 5-50µm in diameter, however the majority of the inclusions range between 5-20µm in diameter (Fig. 6.16). The fluid inclusion assemblages in all samples consist of B85, B60, B20, B35H and B15H type inclusions with different proportions (Table D.2). The fluid inclusion assemblages in quartz A1-veins from deep (1668m) barren potassic and sodic-calcic alteration is dominated by up to ~50 % vapor-rich B85 inclusions containing ~85 vol. % vapor, ~15 vol. % liquid and rare single opaque daughter minerals. Vapor-rich B85 inclusions are accompanied by less-abundant vapor-liquid (B60) and liquidvapor (B20) inclusions (Fig. 6.16 F, G; Table D.2). The vapor-rich (B85, B60) types are high-temperature, low-density fluid inclusions and coexist along the same growth lines with less abundant high-temperature, high-density liquid-vapor-solid (B35H) inclusions indicating a boiling phase of two unmixed fluid phases at hydrostatic conditions. The high-salinity, low temperature liquid-rich-vapor-solid (B15H) fluid inclusions at depth (1668m) are minor (<20%), but increase upward with cooling of magmatic-hydrothermal fluids (Table 6.3). Fluid inclusion assemblages in ore-bearing quartz A1-veins from central (1094m) potassic alteration consist of vapor-rich (B85, 30%), vapor-liquid (B60, 10%), liquid-vapor (B20, 10%), liquid-vapor-solid (B35H, 20%) and liquid-rich-vapor-solid (B15H, 30%). The vapor-rich (B85, B60) type are high-temperature, low salinity fluids, whereas B35H type with ~35 vol. % vapor, ~65 vol. % liquid, halite and single-phase opaque daughter minerals (hematite + chalcopyrite) represent a distinct high-temperature, 170  Figure 6.16 Photomicrographs of Reko Diq fluid inclusions. (A) Vapor-rich B85 fluid inclusion, (B) Vapor-liquid B60 fluid inclusion, (C) liquid-vapor B20 fluid inclusion, (D) Liquid-vapor-solid B35H fluid inclusion containing halite and single phase opaque daughter minerals, (E) Liquid rich-vapor-solid B15H fluid inclusion with halite and multiphase daughter minerals (hematite and/or chalcopyrite), (F,G,H) Scattered vapor rich B85 and B60 fluid inclusions coexist with liquid-vapor-solid B35H and B15H fluid inclusions indicating no obvious healed fractures, (I) Abundant liquid-vapor-solid B35H fluid inclusions coexist with and B85 fluid inclusions, (J,K) Scattered B85, B20 and B15H fluid inclusions and trails of secondary B85 fluid inclusions trapped along healed fractures of quartz veins.  171  high-density ore-bearing brine-vapor phase in the hydrothermal system. The vapor-rich (B85) inclusions coexist along the same growth zone with liquid-vapor-solid B35H inclusions reflecting a boiling phase in the system (Fig. 6.16 H, I; Table D.2). The liquidrich-vapor-solid (B15H) type are typical brine inclusions containing ~15% vapor, single and multi-phase halite, and daughter hematite and/or chalcopyrite. These are high-density, relatively low-temperature inclusions and progressively increase with cooling of magmatichydrothermal fluids from potassic to shallow sericite-chlorite (clay) alteration (Table 6.3). The fluid inclusion assemblages in quartz A1-veins from shallow (288m and 102m) sericite-chlorite (clay) alteration zones consist of abundant high-density and relatively lowtemperature liquid-rich-vapor-solid (B15H, ~50%), vapor-rich (B85, ~30%) and minor vapor-liquid (B60 ~10%), liquid-vapor (B20 ~10%) and liquid-vapor-solid (B35H ~10%) type inclusions (Fig. 6.16 J-K; Table D.2). The B15H inclusions contain ~15% vapor, single and multi-phase halite, sylvite and coarser grained daughter hematite and/or chalcopyrite; indicating a distinct low-temperature ore-bearing brine-vapor phase at shallow levels (Table 6.3). Trails and strings of abundant secondary vapor-rich (B85) inclusions along healed fractures of quartz indicate escape of low-salinity hydrothermal fluids at shallow levels. 6.6.3 Fluid inclusions microthermometry Microthermometry of fluid inclusion assemblages indicate variable homogenizations temperatures and salinities measured in the deep (1668m), central (1094m) and shallow (102m) levels across H14 complex. The deep low-density vapor-rich (B85) and vapor-liquid (B60) fluid inclusions in barren quartz A1-veins are characterized by high homogenization temperatures (Th V-L) of 400oC to 578oC and low melting temperatures of ice (Tm-ice) from 20oC to -32oC with apparent salinities between 22 to 30 wt. % NaCl equiv. The high-density liquid-rich-vapor-solid (B15H) fluid inclusions in this zone have lower homogenization temperatures of halite (T-salt) that range from 260oC to 343oC with higher apparent salinities from 35 to 42 wt. % NaCl equiv. reflecting a separate fluid phase formed with cooling of magmatic-hydrothermal fluids (Table 6.3; Fig. 6.17).  172  Microthermometry of low-density vapor-rich B85 and B60 fluid inclusions from orebearing quartz A1-veins in the central (1094m) potassic zone indicated higher homogenization temperatures (Th  V-L)  ranging from 546oC to >600oC, typically by vapor  disappearance in B60 inclusions. Apparent salinities from final melting temperature of ice (T-ice) in B60 inclusions remain between 24 to 27 wt. % NaCl equiv. Coexisting highdensity liquid-vapor-solid B35H inclusions in ore-bearing quartz A1-veins have similar higher homogenization temperatures (Th  V-L)  range from 435oC to >600oC reflecting a  boiling phase of magmatic-hydrothermal fluids. The few liquid-vapor-solid B35H inclusions in this zone with homogenization temperature of halite (T-salt) from 370oC to >428oC and corresponding apparent salinities of 44 to 51 wt.% NaCl equiv. are interpreted as a separate fluid phase, which may have formed with cooling and/or slight pressure of boiling assemblage (Bouzari and Clark, 2006; references therein). The liquid-rich-vapor-solid (B15H) brine inclusions in the ore-bearing quartz A1-veins are characterized by homogenization temperatures (Th  V-L)  of 300oC to 309oC and highest homogenization  temperature of halite (T-salt) from 527oC to 593oC with highest apparent salinities between 63 to 73 wt.% NaCl equiv. (Table 6.3; Fig. 6.17). Microthermometric data of low-density vapor-rich B85, B60 fluid inclusions from shallow (102m) quartz A-1 veins also indicate high homogenization temperatures (Th  V-L)  from  400oC to 578oC. The melting temperature of ice (Tm-ice) from -20oC to -35oC in these inclusions calculated apparent salinities of 22 to 38 wt.% NaCl. Conversely, the liquid-richvapor-solid brine inclusions (B15H) in this zone have distinctively lower homogenization temperatures (Th  V-L)  range from 263oC to 457oC with apparent salinities between 35 to 47  wt. % NaCl equiv. (Table 6.3; Fig. 6.17).  173  Table 6.3 Representative fluid inclusion analysis in quartz (A-veins) from Reko Diq H14 porphyry complex (Cross section 3222200m N) Sample  Area  Lith.  Alteration  Sulfides  Mineral  Fluid inclusions  V  L (%) 10  Solids  Type  Te (-)  Tm-ice (-)  Tsalt  Salinity  Th (L-V) 502  Th (Final)  RD044-102  H14  PFB1  Transitional sericitic  py-cpy  Quartz  Vapor-rich  (%) 90  0  B85  48  19  NV  (wt.% NaCl) 22  RD044-102  H14  PFB1  Transitional sericitic  py-cpy  Quartz  Vapor-rich  90  10  0  B85  69  20  NV  22  400  400  RD044-102  H14  PFB1  Transitional sericitic  py-cpy  Quartz  Vapor-liquid  60  40  op  B60  28  23  NV  24  498  498  RD044-102  H14  PFB1  Transitional sericitic  py-cpy  Quartz  Vapor-liquid  60  40  H, op  B60  78  20  NV  22  502  502  RD044-102  H14  PFB1  Transitional sericitic  py-cpy  Quartz  Liquid-rich-vapor-solids  15  85  H, hm  B15H  40  35  304  38  263  304  RD044-102  H14  PFB1  Transitional sericitic  py-cpy  Quartz  Liquid-rich-vapor-solids  15  85  H, op  B15H  40  34  302  38  265  302  RD044-102  H14  PFB1  Transitional sericitic  py-cpy  Quartz  Liquid-rich-vapor-solids  15  85  H  B15H  38  32  377  45  282  377  RD044-102  H14  PFB1  Transitional sericitic  py-cpy  Quartz  Liquid-rich-vapor-solids  15  85  H, S  B15H  42  21  334  41  290  334  RD044-102  H14  PFB1  Transitional sericitic  py-cpy  Quartz  Liquid-rich-vapor-solids  15  85  H, hm  B15H  58  25  277  36  335  335  RD044-102  H14  PFB1  Transitional sericitic  py-cpy  Quartz  Liquid-rich-vapor-solids  15  85  H, S, cpy  B15H  60  29  262  35  457  457  RD044-102  H14  PFB1  Transitional sericitic  py-cpy  Quartz  Liquid-rich-vapor-solids  15  85  H, S, op  B15H  69  28  395  47  345  395  RD044-102  H14  PFB1  Transitional sericitic  py-cpy  Quartz  Liquid-rich-vapor-solids  15  85  H, S, hm  B15H  NM  NM  282  37  260  282  RD596-1094  H14  PFB1  Ore-stage potassic  cpy-bor-py  Quartz  Vapor-rich  90  10  0  B85  55  22  NV  24  546  546  RD596-1094  H14  PFB1  Ore-stage potassic  cpy-bor-py  Quartz  Vapor-liquid  60  40  op  B60  48  24  NV  25  >600  >600  RD596-1094  H14  PFB1  Ore-stage potassic  cpy-bor-py  Quartz  Vapor-liquid  60  40  op  B60  52  28  NV  27  574  574  RD596-1094  H14  PFB1  Ore-stage potassic  cpy-bor-py  Quartz  Liquid-vapor-solids  35  65  H, op  B35H  88  42  370  44  >600  >600  RD596-1094  H14  PFB1  Ore-stage potassic  cpy-bor-py  Quartz  Liquid-vapor-solids  35  65  H, op  B35H  50  23  395  47  >600  >600  RD596-1094  H14  PFB1  Ore-stage potassic  cpy-bor-py  Quartz  Liquid-vapor-solids  35  65  H, op  B35H  70  26  428  51  590  590  RD596-1094  H14  PFB1  Ore-stage potassic  cpy-bor-py  Quartz  Liquid-vapor-solids  35  65  H, op  B35H  50  22  370  44  435  435  RD596-1094  H14  PFB1  Ore-stage potassic  cpy-bor-py  Quartz  Liquid-rich-vapor-solids  15  85  H, op  B15H  50  29  527  63  300  527  RD596-1094  H14  PFB1  Ore-stage potassic  cpy-bor-py  Quartz  Liquid-rich-vapor-solids  15  85  H, S, cpy  B15H  NM  NM  593  73  302  593  RD596-1094  H14  PFB1  Ore-stage potassic  cpy-bor-py  Quartz  Liquid-rich-vapor-solids  15  85  H, S, op  B15H  60  24  580  71  309  580  RD596-1668  H14  PFB1  Potassic, sodic-calcic  trace cpy-bor  Quartz  Vapor-rich  90  10  0  B85  NM  32  NV  30  457  457  RD596-1668  H14  PFB1  Potassic, sodic-calcic  trace cpy-bor  Quartz  Vapor-liquid  60  40  0  B60  30  22  NV  24  537  537  RD596-1668  H14  PFB1  Potassic, sodic-calcic  trace cpy-bor  Quartz  Vapor-liquid  60  40  0  B60  40  20  NV  22  400  400  RD596-1668  H14  PFB1  Potassic, sodic-calcic  trace cpy-bor  Quartz  Liquid-vapor-solids  35  65  H, op  B35H  38  19  332  41  314  332  RD596-1668  H14  PFB1  Potassic, sodic-calcic  trace cpy-bor  Quartz  Liquid-rich-vapor-solids  15  85  H, hm  B15H  40  20  343  42  393  393  RD596-1668  H14  PFB1  Potassic, sodic-calcic  trace cpy-bor  Quartz  Liquid-rich-vapor-solids  15  85  H, hm  B15H  46  32  279  37  294  294  RD596-1668  H14  PFB1  Potassic, sodic-calcic  trace cpy-bor  Quartz  Liquid-rich-vapor-solids  15  85  H, op  B15H  28  24  260  35  436  436  RD596-1668  H14  PFB1  Potassic, sodic-calcic  trace cpy-bor  Quartz  Liquid-rich-vapor-solids  15  85  H, hm  B15H  41  21  272  36  321  321  502  Abbreviations: Lith=litholog