Mineralogy, metamorphism and geothermobarometry of the Ghandab metamorphic Complex, SE Fariman, NE Iran

The study area is located about 110 kilometers southeast of Mashhad and approximately 40 kilometers southeast of Fariman. The area is considered to be a part of the central Iran zone. It includes metamorphic rocks with different protoliths consisting of pelitic, carbonate and quartz - feldspathic rocks. The metamorphism in the study area is considered to be a contact regional metamorphism with a low pressure - high temperature grade. According to petrographic studies, the metamorphism in the region reached the upper limit of amphibolite facies.  On the basis of different mineral assemblages, three zones were recognized, including Andalusite-Cordierite, Sillimanite - Andalusite, and Sillimanite – K-Feldspar zones. Using Thermocalc software, the average temperature and pressure for the peak of metamorphism in the metapelitic rocks are 664 ºC and 2.5 Kbar respectively. Based on calculated maximum pressure (2.5 Kbar), the depth of ~7.8 Km for the metamorphism is estimated.