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| Zagros ophiolite | |
|---|---|
| Name | Zagros ophiolite |
| Location | Zagros Mountains, Iran, Iraq |
| Geology | Ophiolite sequence, peridotite, gabbro, basalt, sheeted dikes |
| Age | Late Cretaceous–Paleogene (variable) |
| Type | Ophiolite complex |
Zagros ophiolite. The Zagros ophiolite is an exposed mafic–ultramafic assemblage in the Zagros Mountains of Iran and Iraq that records obducted oceanic lithosphere related to Neotethyan closure. The complex is a regional marker for plate interactions involving the Arabian Plate, Eurasian Plate, and former microcontinents such as Cimmeria and Gondwana fragments, and is central to models of Paleotethys and Neotethys geodynamics. Studies integrate field mapping, geochemistry, geochronology, and structural analysis used also in investigations of the Makran Trench, Alborz Mountains, and Bitlis-Zagros suture.
The Zagros ophiolite occurs along sutures and thrust belts adjacent to major orogens including the Zagros Mountains and the Taurus Mountains, and is compared with other famous ophiolite complexes such as the Semail Ophiolite, Troodos Ophiolite, and Bay of Islands Ophiolite. It has been studied in the context of events like the closure of the Neotethys Ocean and collision of the Arabian Plate with Eurasia and the emplacement history of regional nappes like the Sanandaj-Sirjan Zone and the Urmia-Dokhtar Magmatic Arc.
The ophiolite sits within the collisional framework defined by the convergence history of the Arabian Plate and Eurasian Plate following breakup of Pangaea and dispersal of Gondwana. Its emplacement is linked to suture zones mapped near the Bitlis Suture and correlates with magmatic and metamorphic belts such as the Sanandaj-Sirjan Zone and the Urmia-Dokhtar Magmatic Arc. Regional tectonic events cited include the closure episodes of the Neotethys Ocean and interactions with microplates like the Anatolian Plate and the Caucasus domain, comparable to processes recorded in the Himalayan orogen and the Alpine orogeny.
Lithological components include residual peridotites (harzburgite and lherzolite), layered gabbros, sheeted dike complexes, and basaltic pillow lavas, with associated cherts and pelagic sediments similar to those in the Semail Ophiolite and Troodos Ophiolite. Petrological studies document spinel-peridotite fabrics, mantle melting residues, and melt-rock reaction textures analogous to processes inferred for the Mid-Atlantic Ridge and the Izu-Bonin-Mariana system. Geochemical signatures show both mid-ocean ridge basalt (MORB) affinities and supra-subduction zone (SSZ) characteristics, invoking comparisons to arcs like the Lesser Antilles and back-arc basins such as the Mariana Trough.
The ophiolite exhibits strong deformation: high-strain peridotite mylonites, stacked gabbroic nappes, and thrust-bounded allochthons emplaced onto continental units including the Zagros Fold and Thrust Belt. Structures record obduction mechanisms similar to those proposed for the Semail Ophiolite emplacement onto Oman and match kinematic indicators known from studies of the Himalaya and the Caledonides. Fault systems and shear zones in the complex relate to major regional faults like the Main Recent Fault and the Kazerun Fault, and deformational histories are tied to far-field stresses from events comparable to the Eocene Orogeny and Late Cretaceous shortening episodes.
Radiometric ages from zircon, spinel, and basaltic phases indicate a range centered on Late Cretaceous to Paleogene intervals, overlapping timing for closure of the Neotethys Ocean and collision between the Arabian Plate and Iranian Plate. Competing models invoke formation at a mid-ocean ridge, supra-subduction zone spreading, or back-arc basin evolution similar to interpretations for the Sulu Ophiolite and the Izu-Bonin-Mariana arc. Tectonic evolution integrates episodes correlated with the Cretaceous–Paleogene boundary, regional magmatism in the Urumieh-Dokhtar Magmatic Arc, and later deformation synchronous with the rise of the Zagros Mountains and activity along the Anatolian Fault System.
The ophiolite hosts ultramafic-associated mineralization, including chromite, nickel, cobalt, and platinum-group element (PGE) concentrations analogous to deposits in the Semail Ophiolite and the Troodos Massif. Serpentinized peridotites produce asbestos and chrysotile occurrences documented in regional mining reports, and later hydrothermal alteration has generated base-metal sulfide mineralization akin to ophiolite-hosted volcanogenic massive sulfide (VMS) systems studied in the Bathurst Mining Camp and Kuroko deposits. Exploration ties to regional petroleum systems in the Zagros Fold Belt and mineral policy discussions involving the National Iranian Oil Company and regional ministries highlight economic intersections.
Research began with mapping and petrological description by regional geologists and comparative studies involving institutions such as local universities and international teams from centers like the British Geological Survey, U.S. Geological Survey, and continental research groups that previously worked on the Semail Ophiolite and Troodos Ophiolite. Methods include field structural mapping, thin-section petrography, major- and trace-element geochemistry, isotopic systems (U-Pb zircon, Ar-Ar, Sm-Nd, Rb-Sr), and geophysical surveys using seismic reflection and magnetotelluric profiles similar to investigations across the Makran and Persian Gulf regions. Recent work integrates thermomechanical modeling and plate reconstructions using databases maintained by organizations like the International Commission on Stratigraphy and regional geological surveys.
Category:Ophiolites Category:Geology of Iran Category:Zagros Mountains