Investigation of mineral chemistry, temperature–pressure measurement and mineral equilibrium in Sabalan Quaternary volcanic rocks

Sabalan is a young member of the Sanuzui volcanic assemblages, belonging to the Alborz Magmatic Arc (AMA(. In Sabalan mountain range, a series of volcanic rocks with a combination of andesite, basaltic andesite, rhyodacite and trachyandesite are present. The  texture of these rocks is often porphyritic with microlithic paste, porous porphyritic and sometimes glomeroporphyria, sieve and trachyte. Major minerals include clinopyroxene, plagioclase, and one or more mafic minerals such as hornblende and pyroxene. Secondary minerals include opaque minerals, iddensite, biotite, chlorite and calcite. Investigation of mineral chemistry of basaltic rocks in the region shows that the composition of calcium plagioclase crystals is moderate (An72-93(. Based on temperature–barometric diagrams of plagioclase and amphibole, a temperature of 540 to 750 oC and pressure of 5.30 to 7k have been calculated, which corresponds to the depth of the middle to lower crust. Mineralogical studies and whole rock geochemical analysis show that these rocks formed in a tensile and intercontinental zone.