Geothermobarometry of Sarmeshk granitoids in the Northwest of Sarduiyeh

Abstract

The Sarmeshk granitoid pluton is located in southeast of the Urumieh-Dokhtar magmatic zone in the Kerman province. Based on petrographic studies, the granitoid consist of three rock type of diorite, granodiorite and monzogranite. They are mainly composed of plagioclase, alkali-feldspar, quartz, amphibole and biotite. Mineral chemistry of diorite, granodiorite and monzogranite indicate that the feldspars are orthoclase and oligoclase-andesin in composition. The calcic amphiboles have magnesiohornblende composition that is feature of I-type granite. The biotites with Fe/ (Fe+Mg)>0.33 are magnesio-biotites. The amounts of Al2O3, TiO2 and Mg# in amphiboles indicate crust and mantle mixing in the formation of Sarmeshk granitoid magma. Thermobarometer studies indicate that the pressure of hornblende crystallization in the Sarmeshk intrusion is about 1 to 2 Kbar and have been formed in the depth of 5.8 km. The thermometer of the hornblende- plagioclase reveal temperatures of 650-750 °C for the intrusion. The composition of hornblendes suggests their formation in high oxygen fugacity condition, which is in accordance with their mineralogical characteristics and active continental margin tectonic setting of Sarmeshk granitoid pluton.

Keywords

• urumieh-dokhtar magmatic zone
• sarmeshk
• granitoid
• amphibole
• plagioclase
• biotite
• geothermobarometry