Mineral chemistry and thermo-barometry of Ziyaran intrusion (West Taleghan)

In the north of Ziaran village, a Sill olivine gabbro to monzodiorite composition is injected into the Karaj tuffs. The dominate minerals composition of plutonic rock are Plagioclase, Alkali feldspar, Pyroxene, Olivine and Biotite. Plagioclase composition is varies, and it’s changed from Labradorite to Bytownite. Alkali feldspar is in the Orthoclase range and Pyroxene is part of Diopside. Olivine composition change from Chrysolite to Hortonolite and most of the indicators are in the Hyalosiderite range. Biotite is one of the most prominent ferromagnesian mineral in the studied bodies. Compositionally, it is plotted between the field of annite and siderophylite. Most of these biotites are primary magmatic and some are plotted in the reequilibrated area. Based on the FeO*, MgO and Al2O3 binary and ternary diagrams, the studied biotites plot in the calc-alkaline orogenic field or crystallization temperature the have been calculated between 690º to 780 ºC. The chemical composition of the pyroxenes shows that these rocks have been crystallized in a subduction geological setting. The average crystallization temperature of clinopyroxenes is about 1215 °C. Furthermore, the calculated pressure for clinopyroxenes is less than 9 Kbars.