Petrography, mineral chemistry and geothermobarometry of amphibolits in Gol-e-Gohar area (Sirjan), Kerman Province

The Gol-e- Gohar iron ore mine, in southwest of Sirjan city, is structurally located in the Sanandaj-Sirjan zone and is mostly composed of Paleozoic metamorphic rocks. The highest degree of metamorphism of the rocks of the region is related to the amphibolite facies. The studied of amphibolite indicates that the hornblende and plagioclase are the main and biotite, sphene, quartz, tourmaline and opaque minerals are the accessory minerals. Secondary minerals include chlorite, epidote, calcite, iron oxides, and sericite that have been developed during the alteration phases, as well as chloritization and epidotization of biotites and amphiboles as evidence of retrograde metamorphism. Based on amphibole mineral chemistry studies, amphiboles are formed as a combinations of magnesio hornblende, paragasite and winchite types. According to Geothermobarometry studies, amphiboles are formed under conditions of high oxygen fugacity and at a temperature of 600 to 750° and an approximate pressure of 3 to 7 kbar.