Petrography, Tectonic Setting and Genesis of Oligocene - Miocene Igneous Rocks in Northern Part of Razan Area

The area is located about 230 km of southwest of Tehran. Based of geological observations، the plutonic rocks in the area consist of Neogene (Miocene) alkaline gabbro، gabbrodiorite، locogabbro and diabase. The Oligo - Miocene calc-alkaline extrusive rocks are dacite - ryodacite، andesite trachyandesite، hornblendandesite، basaltic andesite and trachybasalt. Studing on isotopic analyses of Nd and Sr indicate that surveyed area were contaminated with crustal rocks of Sialic composition. In isotopy geochemical studies، The Andesite samples are plotted in the limit of BSE; however، it seems that mantling rocks besides being settled in crust (esp. the upper continental crust) have been contaminated with in. The combination of BSE towards enrichment، from the proportion of 87Sr/86Sr has shifted; a sample of rocks shows this position. Spider diagrams related to trace elements of plutonic samples which are used for identifying the tectonic setting show intrusives are in the extensive regime; while the lavas don’t have a steady trend and are similar to subduction zones. This shows that the intrusives of the the investigated area are different genesis from the southern volcanic rocks.