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Magmatic evolution and genesis of the giant Reko Diq H14-H15 porphyry copper-gold deposit, District Chagai, Balochistan-Pakistan Razique, Abdul
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 calc-alkaline suite arc magma with significant upper crustal interaction. Combination of U-Pb-zircon 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 late-barren 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.
Item Metadata
Title |
Magmatic evolution and genesis of the giant Reko Diq H14-H15 porphyry copper-gold deposit, District Chagai, Balochistan-Pakistan
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
2013
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Description |
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 calc-alkaline suite arc magma with significant upper crustal interaction. Combination of U-Pb-zircon 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 late-barren 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.
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Genre | |
Type | |
Language |
eng
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Date Available |
2013-07-03
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Provider |
Vancouver : University of British Columbia Library
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Rights |
Attribution-NonCommercial-ShareAlike 3.0 Unported
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DOI |
10.14288/1.0073930
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
2013-11
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Campus | |
Scholarly Level |
Graduate
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Rights URI | |
Aggregated Source Repository |
DSpace
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Rights
Attribution-NonCommercial-ShareAlike 3.0 Unported