Petrography and application of mineral chemistry in thermodynamic studies of metamorphic rocks, Zarineh region, S- Qorveh, Kurdistan

Metamorphic area, which is a subject of this study, is located in S-Qorveh (Zarineh region), northwest of the Sanadaj-Sirjan zone. According to the recent dating, the S-Qorveh plutonic body consists of a complex of granitoids, granodiorites, quartz monzonites, and gabbros, have intruded into the host metamorphic rocks, about 149-152 Ma and have generated contact metamorphism. Intrusions of various masses and protolites, such as politic and basic layers, have made metamorphic rocks of this area to be different. Regional metamorphic rocks include slates, schists, and amphibolites which are metamorphosed in the range of middle green schists to the early amphibolites facies. Contact metamorphic rocks include spotted slates, mica hornfels, and cordierite hornfels which have been subject to metamorphism from albite-epidote hornfels to hornblende- hornfels facies. In cordierite hornfelses facis, by getting far from the intrusion, cordierite crystals become smaller in size and larger in number. According to the petrographic evidence, metamorphic rocks of this area have been subject to 3 phases of metamorphisms including probably high pressure regional metamorphism, regional metamorphism, and medium contact metamorphism. To estimate the metamorphism pressure-temperature state of this zone, TERMOCALC computer software and also linear calibrations have been used. Pressure-temperature calculations for regional metamorphic M1, have shown 3.9 Kbar pressure and 539°C temperature. For contact metamorphism M2, by using the software, average pressure of 4.3 Kbar and average temperature of 607°C have been calculated. Also, for the contact metamorphism M2, using the experimental calibration of biotite-muscovite equilibrium, the temperature estimated to be 581.3°C and using chlorite-muscovite equilibrium for this phase (stage) of metamorphism, pressure and temperature have been yielded 3.65Kbar and 620°C, respectively. In generally, results of temperatures for all metamorphic rocks are acceptable and satisfactory, but in contact metamorphic rocks, data of pressure may be higher due to emplacement of the granitoid intrusive body.