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.
The Tethyan Tectonic History and Cu-Au Metallogeny of Iran
Published:January 01, 2016
Jeremy P. Richards, Ali Sholeh, 2016. "The Tethyan Tectonic History and Cu-Au Metallogeny of Iran", Tectonics and Metallogeny of the Tethyan Orogenic Belt, Jeremy P. Richards
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Iran is a resource-rich country, with large deposits of iron, copper, zinc, and gold, as well as industrial minerals and oil and gas. Most of these resources were formed in response to complex and protracted contractional deformation events related to the subduction and eventual closure of the Neotethys ocean in the late Mesozoic and Cenozoic. Here we focus on porphyry Cu ± Mo ± Au and related epithermal Au deposits, which were once thought to be synonymous with subduction, but are now recognized to also form during collisional and other postsubduction tectonic processes. Recent advances in tectonic and paleogeographic reconstructions, and new geochronological and geochemical data reveal that in fact most of Iran’s major porphyry and epithermal deposits fall into this postsubduction category (e.g., Sungun, Sari Gunay, Meiduk, Sar Cheshmeh). The same applies to several major deposits in neighboring Turkey (e.g., Kişladağ, Çöpler), whereas continued subduction beneath the Makran in western Pakistan accounts for some of the only “normal” subduction-related porphyry deposits in the region (e.g., Saindak, Reko Diq).
Few igneous rocks or mineral deposits associated with the Paleotethys ocean occur in Iran, although several Paleozoic ophiolite belts are preserved, and Early Cambrian Kiruna-type iron oxide-apatite deposits are found in the Bafq district of eastern Central Iran. Arc magmatism associated with Mesozoic subduction of the Neotethys ocean is widespread in the Sanandaj-Sirjan zone, but no porphyry or epithermal deposits of this age have been discovered to date, likely due to erosion down to batholithic levels. Arc magmatism shifted to the Urumieh-Dokhtar magmatic arc and the Lut block in the late Paleogene-early Neogene, and the first significant porphyry deposits formed in the Eocene and Oligocene. However, the main period of porphyry formation occurred later in the early to mid-Miocene, synchronous with terminal collision between the Afro-Arabian and Eurasian plates. Several large porphyry Cu (Sungun, Meiduk, and Sar Cheshmeh), as well as the porphyry-related Sari Gunay epithermal Au deposit, were formed at this time (~20–11 Ma) along the length of the orogen. Active subduction continues only beneath the Makran of southeastern Iran and western Pakistan, where the large Saindak (~22 Ma) and Reko Diq (13–10 Ma) porphyry deposits occur.
Mineral exploration in Iran to date has been largely restricted to areas of outcrop, but the potential for extensions of known deposits, or “blind” discoveries below widespread Quaternary cover is considered to be high.
- copper ores
- epithermal processes
- Kerman Iran
- Lut Desert
- metal ores
- Middle East
- mineral deposits, genesis
- molybdenum ores
- ophiolite complexes
- plate collision
- plate tectonics
- porphyry copper
- Sanandaj-Sirjan Zone
- silver ores
- Saindak Deposit
- Sari Gunay Deposit
- Reko Diq Deposit