Mineral chemistry of clinopyroxene, guidance on thermobarometry and tectonic setting of Gaz Boland basalts, northwest of Shahr-e-Babak

The Gaz Boland area is located in Kerman Province, northwest of Shahr-e-Babak. This area is a part of the volcanic-plutonic belt of Urumieh-Dokhtar. Most of the exposed rocks in this region belong to Eocene age, however, the basalts with Pleio-Pleistocene age have also a relatively limited distribution in the region. The main texture of the basalts is microlithicporphyric and olivine, clinopyroxene and plagioclase form the main minerals. Due to the weathering and alteration processes, secondary minerals such as calcite, chlorite, and iron oxides have formed in these rocks. Based on the analysis of X-ray microprobe, the composition of pyroxenes is diopside-augite. The chemical composition of clinopyroxenes confirms the calc-alkaline nature for their parent magma of, which originates from the subduction-related tectonic setting. Based on clinopyroxene thermobarometric studies, the parent magma of the rocks, when crystallization of the clinopyroxene mineral with approximately 10% water under a pressure of 2 to 8 kbar occured, formed during uplift and before the eruption. The magma temperature variations during the crystallization of clinopyroxenes ranges between 1130 and 1249 °C.