Geology and geochemical evaluation of Taftan Volcano,Sistan and Baluchestan Province,southeast of Iran

At a glance of its stratighraphy,the Taftan Volcano can be classified as three groups: pre-,syn-and post-volcanic deposits. The pre-volcanic deposits consist mostly of flysch facies and colored mélange complex. The syn-volcanic deposits are mainly the product of the Taftan Volcano which is mostly composed of pyroclastic and lava flows from the main body of this volcano. The post-volcanic deposits are mostly epiclastic and reworked materials from the Taftan Volcano due to its erosion and weathering. Major and trace elements,and Sr/Rb isotopic composi-tions determined on whole-rock samples from the Taftan Volcano showed that the volcano was formed at the conti-nental margin. The whole-rock isotopic composition of the Taftan Volcano showed a feature of strong enrichment with 87Sr/86Sr=0.705326-0.705921. Geochronological samples of the Taftan Volcano determined by the 40K/40Ar method gave an age range of 6.95±0.72 to 0.71±0.03 Ma. The rare-earth element patterns are characterized by high LREE and nearly strongly linear patterns for MREE to HREE,suggesting that distinctive minerals such as olivine and pyroxene crystallized in the early magmatic stage and then were involved in reaction between the lower crust and residual magma. The integrated isotope and trace element systematics and tectonic structure beneath the Taftan Volcano suggested the lower-crust assimilation by the primary magma. The primary magma had generated from a heterogeneous mantle source and a secondary petrogenetical process. This magma could have been affected by the subduction of the Oman Sea underneath the continental Eurasia plate.