Study of mineral chemistry and thermobarometry of Boland Parchin granitoids, NW Iran

Field evidences, petrographic features and geochemical studies show that the garnet-muscovite granitoids of Boland Parchin area are S-type and they have sharp contact with the host rocks (metamorphic rocks). Granitoids of Boland Parchin contain minerals such as quartz, K-feldspars, plagioclase, biotite and Al-rich minerals (such as muscovite and garnet). Chemical composition of K-feldspars, plagioclase, biotite, muscovite and garnet in the studied samples show that K-feldspars are Or-rich component, plagioclase are Ab-rich, muscovite flakes are rich in the muscovite end-member, phlogopite-annite is the dominant constituent in biotite and chemical composition of the analysed garnets show that they are Alm-rich. Temperature and pressure have been calculated 600 °C and 5-8 Kbar respectively, for the formation of the granitoid rocks. All temperatures obtained from feldspar thermometry reflect sub-solidus re-equilibrium of the feldspars. Lack of equivalent extrusive rocks, existence of restitic micaceous enclaves (restitic biotite), mineralogical features (existence of muscovite and garnet) and chemical characteristics (peraluminous) indicate that Boland Parchin granitoids are S-type. Therefore the rocks are produced from partial melting of metapelites.