Thermobarometry and tectonic setting of metamorphic rocks from the ophiolitic complex of north Torbat-E-Heidarieh

Metamorphic rocks that mostly consist of amphibolite, amphibole schist, garnet hornblendite and rarely metamorphosed chemical and terrigenous sediments are found in the ophiolitic complex of north Torbat-E- Heidarieh. Thermobarometry calculations of amphibolite samples indicate temperature higher than 800 °C and pressure less than 5 Kb. Metamorphic conditions of  amphibole schist and garnet hornblendite samples such as pressure and temperature, range between 7.5 to 13 Kb and 570 to 770 °C. These metamorphic conditions are nearly compatible with the pressure and temperature calculated for the adjoining garnet schist. According to the amphibole chemical composition, textural and mineralogical evidences, thermobarometry calculations and the variations of metamorphic gradient, amphibolite samples have been considered as the product of hydrothermal system of mid ocean ridge. While the other samples are created owing to sole metamorphism during subduction initiation. The co-existence of metapelite with sole metabasites in the ophiolitic complex of north Torbat-E-Heidarieh confirming that the subduction process initiation and ophiolite emplacement took place has been in the vicinity of a continental margin.