Mineral chemistry and petrogenesis of the Amphibolites of Geysour metamorphic complex, east of Gonabad

The Geysour area is located east of Gonabad and is a part of the northern Lut block. The rocks in this area include granitoid and metamorphic rocks. Based on field and mineralogical evidence, the protolith of amphibolite rocks are calc-silicate. The metamorphic rocks of this region are divided into metapelites and amphibolites. Textures, such as post-tectonic garnet and random amphiboles, are indicative of contact metamorphism in amphibolites. Garnets behave from ideal to non-ideal. The end members of the garnet are varied in these rocks and include Al-schorlomite, uvarovite, spessartine, pyrope, almandine, grossular, andradite, morimotoite, and majorite, but their profile patterns are flat. The amphibole is of the ferrohornblende type to the ferrochermakite and chermakite, and has zoning. Biotite has converted to chlorite. The presence of titanite, hematite and epidote are an indication of the effect of oxygen fugacity. Temperature and pressure were calculated in the range of 534-609 oC and 2-<4 Kbar, respectively.  Geysour amphibolites have progressed to the mid-amphibolite facies in the metamorphic aureole. Also, these rocks were undergone a retrograde metamorphism where the temperature and pressure were 489oC and 2.8 kbar, respectively, and the chloritizied biotites exhibit temperatures below 150 oC.