Tectonics and Metallogeny of the Tethyan Orogenic Belt
The Tethyan orogenic belt stretches from the Alps, through the Carpathians and Balkans, Taurides and Caucasus, Zagros, Makran, and Himalayas, to Indochina and into the southwest Pacific Ocean. It represents a complete Wilson Cycle, from opening and closure of the Paleotethys Ocean in the mid-Paleozoic to the Late Triassic, opening of the Neotethys Ocean in the Permian-Early Triassic, and its progressive closure throughout the late Mesozoic and Cenozoic eras. The current state of the orogen includes all stages of convergence from active subduction beneath the Makran and eastern Mediterranean, through advanced continental collision in the Caucasus/Taurides and Zagros, to syn- to postcollisional readjustment in the Carpathians, Balkans, Himalayas, and Indochina (Richards, 2015).
The region has been the focus of significant recent attention from geologists interested both in its tectonic evolution and metallogeny, made possible by increased accessibility to many of the geographic sections of the orogen. Key breakthroughs in understanding its tectonic history have come through improved geochronological techniques and expansion of the database of samples and events dated, combined with more accurate paleogeographic and tectonic models. In parallel, an improved understanding of the subtle relationships between tectonomagmatic and metallogenic processes have refined interpretations that were once based on simplistic assumptions (e.g., that porphyry deposits only form above active subduction zones). Indeed, economic geologists have been among the key drivers of these advances by demanding more accurate and predictive tectonomagmatic models for ore formation that can reliably inform mineral exploration.
Consequently, the Tethyan orogen is now understood to be the best preserved global example of a collisional orogen, where all stages of convergence can be observed in real or recent geological time, and the detailed relationships to ore formation, commonly reflecting tectonic changes measured on submillion-year timescales, can be accurately documented and modeled.
In this volume, we present a selection of papers that showcase this advancement in knowledge, with examples from Eastern Europe to South Asia.Beginning in the Balkans, Knaak et al. (2016) describe the variety of mineral deposits that occur in the emergent worldclass Timok region of eastern Serbia. The origin of the Late Cretaceous Timok Magmatic Complex remains debated, but the authors propose that arc magmatism was focused by dextral transtensional structures, followed by complex structural rearrangement in the Cenozoic. Porphyry Cu-Au deposits, polymetallic replacement deposits, and sedimentary rockhosted Au deposits occur in close spatial, and possibly genetic, relationship to the Late Cretaceous arc rocks. A key contribution of this study is the detailed reconstruction of later Cenozoic fault movements that led to structural dislocation and oroclinal bending, complicating geologic and metallogenic correlations in the region.
Anatomical Similarities and Differences Between Spatially Associated Porphyry Copper-Gold Deposits at the Reko Diq H14 and H15 Complex, Balochistan, Pakistan
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Published:January 01, 2016
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CiteCitation
Abdul Razique, Richard Tosdal, Farhad Bouzari, 2016. "Anatomical Similarities and Differences Between Spatially Associated Porphyry Copper-Gold Deposits at the Reko Diq H14 and H15 Complex, Balochistan, Pakistan", Tectonics and Metallogeny of the Tethyan Orogenic Belt, Jeremy P. Richards
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Abstract
The Reko Diq porphyry cluster in the western Chagai magmatic belt, Pakistan, contains a geologic resource of 5.9 billion tons (5.35 Bt) @ O.41% Cu and O.22 g/t Au, largely in the H14 and H15 porphyry deposits. These two deposits, located approximately 1 km apart, are related to a series of petrologically similar, middle Miocene (12.6–12.O Ma), calc-alkaline porphyry intrusions hosted by Oligocene andesitic volcanic and clastic sedimentary rocks. The porphyry intrusions are characterized by phenocrysts of plagioclase, biotite, quartz, and amphibole in a microcrystalline mafic silicate-bearing quartzofeldspathic groundmass. Potassic, sericite-chlorite, sericitic, and propylitic alteration assemblages are zoned about the porphyry intrusions. The early and intermineral porphyry intrusions are overprinted by a pervasive potassic alteration assemblage composed of hydrothermal biotite-K-feldspar-magnetite ± anhydrite with associated chalcopyrite and bornite. Chalcopyrite, bornite, and lesser pyrite are disseminated or are associated with a stockwork of quartz ± magnetite ± K-feldspar A- and B-type and less common sulfide-only veins. Bornite characterizes a distinct high-grade core to the H14 deposit, but it is less common and always subsidiary in volume to chalcopyrite in the slightly older H15 deposit. Local sulfide mineral assemblages of pyrite-covellite-bornite-chalcopyrite associated with pervasive quartz-sericite alteration assemblages in the H15 deposit form narrow, steeply dipping vein-like zones or strata-bound horizons restricted to felsic tuff or sandstone. The late porphyry intrusions are weakly altered and mineralized, lack volumetrically significant veins, and generally have low Cu and Au concentrations.
Sulfide-deficient potassic alteration assemblages at greater than 1,OOO m depth are overprinted by a texturally destructive alteration assemblage of albite-epidote ± actinolite ± chlorite, inferred to represent a sodic-calcic alteration assemblage. Total sulfide contents at these depths are less than 1%. At shallow depths, a sericite-chlorite alteration assemblage overprints potassic alteration mainly along late-stage centimeter-scale chalcopy-rite-pyrite D-type veins. The sericite-chlorite assemblage is much more extensive in the H15 deposit than in the H14 deposit. An outer sericitic alteration assemblage composed of quartz-muscovite-pyrite ± chalcopyrite flanks the sericite-chlorite assemblage. An intermediate argillic alteration assemblage composed of clay minerals (illite, smectite, montmorillonite) and carbonate is common in remnants of plagioclase within the sericite-chlorite and sericitic alteration assemblages. A propylitic alteration assemblage of chlorite-epidote-albite ± pyrite-carbonate is developed in the peripheral volcanic and sedimentary host rocks surrounding the H14-H15 porphyry complex.
- actinolite
- albite
- alkali feldspar
- amphibole group
- andesites
- Asia
- Baluchistan Pakistan
- calc-alkalic composition
- Cenozoic
- chain silicates
- chlorite
- chlorite group
- clinoamphibole
- copper ores
- Cretaceous
- epidote
- epidote group
- feldspar group
- framework silicates
- gold ores
- hydrothermal alteration
- igneous rocks
- Indian Peninsula
- K-feldspar
- magmas
- Mesozoic
- metal ores
- metallogeny
- metasomatism
- mineral assemblages
- mineral deposits, genesis
- molybdenum ores
- Oligocene
- orthosilicates
- Pakistan
- Paleogene
- plagioclase
- porphyry copper
- sheet silicates
- silicates
- sorosilicates
- sulfides
- Tertiary
- Upper Cretaceous
- volcanic rocks
- Chagai Belt
- Sinjrani Group
- Reko Diq Complex
- Reko Diq Deposit
- Siarat Pir Sultan Prospect
- Ting Dariguan Prospect