THERMOBAROMETRY OF MALAYER S-TYPE GRANITES, WESTERN IRAN

Malayer granitoids, are emplaced into the Sanandaj-Sirjan Metamorphic Belt tectonic zone. This zone consists predominantly of multiply deformed, low to medium-grade metasediments and gneisses. On regional scale, the margins of the main plutonic body are parallel to the country rock foliation. These granitoids are high potassium calk-calkaline intrusive rocks which composed of granite, granodiorite, tonalite, diorite and some small body of gabbros. The best way is to estimate final equilibration or consolidation of the magma, directly from magmatic mineral assemblages in the granitic rock. For estimating of temperature and pressure, four samples were selected as representative of pluton's several phases. Al-in-hornblende barometry suggest a 2.6 to 3.5 kb for emplacement depth of igneous rocks (the experimental calibration of Schmidt (1992) was used for barometric component). The hornblende-plagioclase thermometry indicate that the late stages of crystallization of magma are near solidus condition (550-700ºC). The Ti-in- hornblende thermometry method results have ranges between 610 to 640ºC. Garnet-biotite thermometry indicates temperature ranges of 670-700ºC. Schmidt, M.W.1992. Amphibole composition in tonalite as a function of pressure: an experimental calibration of Al-inhornblende barometer. Contrib. Mineral. Petrol., 110: 304-310.