Garnet-Amphibolites Mineralogy and thermobarometry in Aliabad-Damagh (south of Hamedan, Sanandaj-Sirjan Zone)

Abstract

The garnet-amphibolites in Aliabad-Damagh area, occurs as layers and are enveloped by staurolite-schist. They composed predominantly of garnet, hornblende, feldspar (± muscovite and quartz) with titanite, epidote, ilmenite and graphite as accessory minerals. The euhedral garnet porphyroblasts mainly composed of almandine and grossular components, with normal compositional zoning. The hornblende crystals as prophyroblast or in the matrix, are magnesio- and ferro-hornblende (amphibole core) to tchermakitic-hornbelende (amphibole rim) in composition. Muscovites, if present, with minor phengite and paragonite components, are foliated forming minerals. Feldspars vary from pure K-feldspar to sanidine composition in the vicinity of hornblendes and oligoclase in matrix. Epidotes as pure clinozoisite to epidote, form small crystals inside hornblende or in the matrix. Using different thermobarometry methods, T and P estimated as 600-620 (± 25) °C and 5-6 (± 1) kbar, respectively. Calculated P-T-t path, considering core and rim composition of hornblendes, is in accordance with low-pressure (at the beginning of metamorphism) to medium-pressure type (at the end). Considering P-T-t path, metamorphism could occur during Neo-Tethys subduction and collision process in the Mesozoic time

Keywords

• Garnet-Amphibolite
• Mineralogy
• thermobarometry
• Aliabad-Damagh
• Hamedan
• Sanandaj-Sirjan
• Iran