Abstract

A new plate tectonic interpretation of the Zagros Range is presented on the basis of the available geophysical data and the distribution of the main lithofacies associations, particularly of igneous and metamorphic rocks, which are found along the ancient plate margins. Ophiolites, the remnants of the Mesozoic oceanic crust and upper mantle, are included within the imbricated zone. To the southwest they are in direct contact with the carbonate shelf sequence of almost the same age. The shelf sequence represents a northeastern margin of the African-Arabian plate. The ophiolite complex includes pelagic sediments, mostly radiolarites, with volcanic rocks and peridotite associated with gabbro and eclogite-amphibolite. The complex has partly a mélange character, and in some places it includes glaucophane schists. Low- to medium-pressure metamorphic rocks occur within the Sanandaj-Sirjan zone to the northeast. These rocks are commonly thrust slices transported from the northeast, and in many places they are intruded by Jurassic-Cretaceous and Paleogene granitic rocks. Andesites, with subordinate basalt, latite, and dacite, are included, together with the associated Paleogene sediments, within the volcanic belt; they are frequently accompanied by large masses of granodiorite, monzonite, and quartz diorite. The rocks of the andesite and granite associations define the ancient magmatic arc, probably of Andean type; to the southwest they are in contact with the ophiolites, and this contact line, now represented by the large Baft-Nain fault zone, is the relict subduction zone in front of the central-eastern Iranian microplate.

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