Mineralogy and geochemistry of gneisses from the Gol-e-Gohar complex, south of Kerman province

Gneisses from Gol-e-Gohar metamorphic complex in the south Kerman province and in the south-east of the Sanandaj-Sirjan metamorphic zone with granitoid protolith represent the green schist to lower amphibolite facies as a result of early Cimmerian orogenic phase. The studied gneisses are composed of potassium feldspar, plagioclase, biotite, quartz and garnet as main mineralogical composition. In addition, apatite, ilmenite, titanite, chlorite and muscovite are accessory phases in gneisses. Geothermobarometric calculations estimate a temperature of 600 to 610°C, with a pressure of 8 to 10Kbar. This is in accordance with the lower amphibole facies. The partial enrichment of the LREE relative to HREE and the lack of depletion in HREE of the samples, the values of YbN greater than 10 (average 12.70), combined with the alkali nature of the primary magma, indicate an intra-plate garnet-free crustal source for the gneisses. In addition, the metamorphic processes gave them gneissic nature, however, features of the primary igneous rock are recognizable. This situation is consistent with the extensional rifting environment developed in the southern part of the Sanandaj-Sirjan zone in the lower Paleozoic era in the early stages of the Paleo-Tethys formation.