Mineral chemistry of pyroxenes and geothermobarometry of the basic rocks, NE-Qorveh (Kurdistan)

The Plio- Quaternary volcanoes are located in the NE-Qorveh (Kurdistan) in the Qorveh-Takab volcanic belt, in the Hamedan-Tabriz Zone (HTZ). The volcanic rocks consist of basalt to olivine-basalt. The electron microprobe (EMP) analyses of pyroxenes show occurrence of one type of clinopyroxene, as diopside (Fs 2.65-6.42 En 40.44-50.47 Wo45.97-53.14) with Mg # = 84-98. The compositions of the pyroxenes suggest that rocks belong to alkaline-subalkaline magmatic series.  Considering different methods of geothermometry of clinopyroxene, the temperature of  crystallization stage for pyroxene was 800-1300°C. Distribution of Al in octahedral and tetrahedral sites of pyroxenes displays that this mineral is crystallized from a magma with ˂ 10% water contents, in low-medium pressure which is in accordance with their formation the depth of 18-30 km. Fe+3 content of clinopyroxenes  implies crystallization in high oxygen fugacity condition.