Character, genesis and tectonic setting of igneous rocks in the Sistan suture zone, eastern Iran

Abstract

Igneous rocks in the Sistan suture zone have characteristics that can be correlated with important tectonic events. A Late Cretaceous ocean basin is recorded by ophiolites now exposed in numerous mélange zones. Subduction beneath the Afghan block is indicated by Late Cretaceous-Paleocene calc-alkaline volcanics. Collision of the Lut block with the subduction complex in the middle Eocene produced widespread deformation and was followed by the emplacement of late Eocene-early Oligocene calc-alkaline granitic batholiths that probably formed by widespread anatexis of marine sediments. A dominantly Oligocene magmatic event is represented by widespread alkaline volcanics and minor intrusions that appear to be related to major transcurrent faults. Miocene calc-alkaline activity was limited to sporadic volcanism in the north and minor intermediate intrusions farther south. These units are largely underformed and not related to any major faults. The youngest magmatic event is recorded by late Miocene-Pliocene mafic flows that are weakly alkaline, clearly related to right-lateral faults and probably were derived from a deep crustal or upper mantle source.