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| Central Iran block | |
|---|---|
| Name | Central Iran block |
| Location | Iran |
| Type | Crustal block |
| Age | Precambrian–Mesozoic |
| Lithology | Various |
Central Iran block The Central Iran block is a major crustal domain in the Iranian Plateau bounded by the Zagros Mountains, the Alborz, the Kopet Dag, and the Lut Block, forming a tectonically complex region influenced by the convergence of the Arabian Plate and the Eurasian Plate. It hosts diverse rock packages related to the Variscan orogeny, the Cimmerian Orogeny, and the Alpine orogeny, and contains economically important mineral provinces such as the Anarak-Khur area and the Sangan deposit. The block has been the focus of studies by institutions including the Geological Survey of Iran and international teams from the USGS, the British Geological Survey, and universities such as University of Tehran.
The block occupies a central position between the Arabian Shield, the Turkestan Shield, and the Indian Plate margin and records interactions among the Eurasian Plate, the Arabian Plate, and microplates like the Afghan Block and the Neyriz-Kermanshah Block. Major bounding structures include the Zagros Thrust System, the Main Recent Fault, the North Tabriz Fault, and the Ilam Fault Zone, which link to regional features such as the Red Sea Rift and the Makran Subduction Zone. Paleotectonic reconstructions utilize data from the Paleozoic basins of Iran, the Seseh ophiolite belts, and the Sistan Suture Zone to place the block within the context of the Tethys Ocean closure and the collision history involving the Arabian–Eurasian collision. Seismicity across the block is monitored with networks established by the International Seismological Centre and the Institute of Geophysics, University of Tehran.
Stratigraphic sequences range from possible Archean remnants through Neoproterozoic successions to Mesozoic and Cenozoic cover, including carbonate platforms comparable to those in the Persian Gulf Basin and siliciclastic sequences akin to the Kerman Basin. Notable units include Precambrian crystalline basement exposures, Paleozoic marine limestones correlated with the Permian-Triassic boundary, and Jurassic-Cretaceous evaporites linked to the Hercynian basins. Fossil assemblages contain taxa correlating with the Gondwana and Laurasia faunal realms, with biostratigraphic ties to the Foraminifera zones used in the Biostratigraphic Atlas of Iran. Lithologies include granitoids analogous to those of the Urumieh-Dokhtar magmatic arc, ophiolitic mélange comparable to the Zagros ophiolites, and clastic wedges like those of the Tabas Block.
Deformation records encompass folding and thrusting associated with the Zagros orogeny, transpressional faulting linked to the North Anatolian Fault system, and strike-slip segmentation similar to deformation along the San Andreas Fault in analogue studies. Structural domains display nappes, klippen, and metamorphic core complexes reminiscent of regions studied in the Alps and the Himalaya. Basin inversion events correlate with phases known from the Cimmerian and Alpine orogenies, and structural restoration techniques adapted from work on the Appalachians elucidate shortening estimates. Active deformation produces seismic events comparable to the 1990 Manjil–Rudbar earthquake and the 2003 Bam earthquake, with paleoseismological trenching following methods used after the Gobi-Altai studies.
Magmatic suites include continental arc granites related to the Urumieh-Dokhtar magmatic arc, calc-alkaline volcanics, and A-type granites akin to those of the Saharan Metacraton. Metamorphic gradients record greenschist- to amphibolite-facies transitions comparable to metamorphism in the Variscan Belt and localized eclogite-bearing units analogized with the Hengshan Complex. Isotopic studies using U-Pb zircon and Rb-Sr systems tie magmatic pulses to events such as the Cretaceous magmatic flare-up and Eocene volcanism associated with the Alborz magmatism. Petrogenesis interpretations borrow techniques applied in studies of the Karakoram and the Tibet Plateau magmatic provinces.
The block hosts significant mineralization including porphyry copper systems like Sarcheshmeh-style deposits, iron-oxide copper-gold (IOCG) occurrences similar to Olympic Dam analogs, epithermal gold-silver veins, and SEDEX-type base-metal accumulations paralleling deposits in the Kuroko belt. Major mined deposits and prospects include Sangan phosphate, Kuh-e Zar polimetallic fields, and numerous skarn and carbonate-hosted lead-zinc occurrences related to contacts comparable to those at Kerman Copper Belt localities. Hydrocarbon potential is present in associated basins with source-rock analogs to the Asmari Formation and the Gachsaran Formation, and mineral exploration has been undertaken by entities such as the National Iranian Oil Company and multinational consortia including TotalEnergies and Glencore-affiliate teams. Environmental and resource studies reference standards from the International Mine Water Association and methodologies from the Society of Economic Geologists.
Paleogeographic reconstructions depict the block as part of Gondwanan fragments that drifted and accreted during the closure of the Neotethys and subsequent orogenic events including the Cimmerian Orogeny and final emplacement during the Alpine orogeny. Sedimentary records show transitions from shallow marine carbonate platforms to restricted evaporitic settings akin to the Messinian salinity crisis analogues and later continental sequences reflecting uplift linked to the Miocene Zagros uplift. Paleoclimatic proxies from speleothems and palynology correlate with global events like the Paleocene–Eocene Thermal Maximum and the Eocene-Oligocene transition. Ongoing work by teams from the Royal Society-funded projects, the International Union of Geological Sciences, and regional universities refines models using techniques applied in the Ocean Drilling Program and the International Continental Scientific Drilling Program.