Geochemistry and petrogenesis of Alamdar rhyolites from East of Tasouj town (Northwest of Iran)

The Alamdar rhyolite has been cropped out at the highest top of Mishow Mountain Ranges (i.e. Alamdar top), east of Tasouj. Considering that the rhyolite has been intruded the Kahar Formation, its Precambrian age is more probable. The constituent minerals are quartz, K-feldspar and rare plagioclase characterizing by crystalline to hyalo-crystalline, microlitic porphyric, perthitic, hyalo porphyric and flow textures. Magmatic series of the rocks are high K calc-alkaline and shoshonite. In the view of Al-index, they are peraluminous. The investigated rocks have been classified as A-type (A2 subgroup) granitoids. REE diagrams show high enrichment of LREE relative to HREE and MREE. Spider diagrams have positive anamolies of K, Nd, Rb and negative anomalies of Ta, Nb, and Ti indicating their likely crustal source generation. On the basis of discrimination diagrams they are formed related to Post-COLG tectonic setting. Extensional regimes following to continental collision between Northern lands with Gondwanian terrains during Ediacaran has been caused decompression melting of continental crust and the Alamdar rhyolite has been originated at the Mishow collisional zone.