كاربرد عناصر فلزي، عناصر با شدت ميدان بالا و عناصر ليتوفيل يون بزرگ در تشخيص جايگاه تكتونيكي پشت كمان منطقه جنوب كهريزك (جنوب تهران)

Application of metallic, high field strength, and large ion lithophile elements to discriminate back arc tectonic settings in South Kahrizak, South Tehran.

Incompatible elements ratios (Th/Ta, Th/Hf, Ta/Hf, Th/Yb and Ta/Yb) in volcanic rocks reflect the tectonomagmatic evolution of magmatic suites in different regions. On the basis of the behavior of these elements, the tectonic environment of Eocene volcanogenic rocks of South Kahrizak (South Tehran), were examined. Petrologic facies in this area are mainly composed of pyroclastics and acid to basic lava flows. In geochemical diagrams, rhyolite-trachyandesite and basalt lavas always plot within the active continental margin field with tendency toward within-plate volcanic zone, especially for basic rock units. Enrichment of light rare earth elements (LREE) compared to chondrites without Eu anomalies in basaltic rocks (unlike rhyolite and trachyandesite rocks) and similarity in rare elements ratio between Kahrizak rocks and some back arc environments, are geochemical evidences for the tendency of South Kahrizak rocks to a extensional region especially for basic and intermediate lavas. Volcanic rocks of this erea are enriched in incompatible elements relative to compositions such as depleted MORB mantle (DMM) or primitive mantle (PM). The distribution of metallic elements in these rocks, reveals that, they are more aboundant in basalts compared to rhyolites and intermediate rocks. Basaltic rocks also show enrichment in Co, Sc, Cu, Au, V and deplation in Pb, Ni, Zn, to some degree respect to continental lithosphere.