Thermobarometry and tectonic setting of the regional metamorphic rocks from South Sirjan (the Southern SSZ), Iran.

There are extensive outcrops of regional metamorphic rocks that consist of marble, calcschist, metapelite, and amphibolite in the south Sirjan (southern Sanandaj-Sirjan zone). Garnet, muscovite, biotite, calcite, quartz, and feldspar are the rock-forming minerals of calcschists. Kyanite, garnet, and staurolite constitute the index minerals of the studied metapelites. Amphibole and plagioclase are the main minerals of the massive and foliated amphibolites. The P-T conditions of the regional metamorphic event in the southern SSZ were constrained using conventional (single-reaction) and multi-equilibrium thermobarometry (THERMOCALC software). The average temperature and pressure gained by THERMOCALC software are 8 kb, 643 ˚C, and 9.6 kb, 645 ˚C for Ky-Grt schist and calcschist samples, respectively. Using revised and recalibrated conventional thermobarometry methods result in temperature from 504 to 664 °C and pressure from 6.57 to 7.88 kb for the investigated Ky-Grt schist. Mineralogical paragenesis and thermobarometry results of the investigated metamorphic rocks are in accordance with a medium P/T- type metamorphic gradient. Presumably, Neotethys subduction beneath the Sanandaj-Sirjan block and resulting crustal thickening event led to such a metamorphic gradient during Eo-cimmerian orogeny. Medium P/T metamorphic rocks of the southern Sanandaj-Sirjan zone and accompanying high P/T metamorphic rocks of the north Hajiabad could be defined as a pair of metamorphic belts that were constructed during Zagros orogeny.