Geochemistry of the Biotite from Pegmatites of Kudi Valley, Paddar area, District Kishtwar, Jammu and Kashmir

Abstract

The pegmatites of Kudi valley, Paddar area are mineralogically characterised by the presence of Na-plagioclase, quartz, perthite, tourmaline, biotite with minor amount of muscovite, sillimanite, and garnet. The biotite mineral from the pegmatites show higher Al2O3, FeO, K2O, moderate SiO2, MgO, Cr2O3, TiO2, F; and low Na2O, CaO, MnO, Cl concentration. They are classified as siderophyllite type. The geochemical signature of biotite indicates the peraluminous nature of the pegmatitic melt generated from the melting of continental crust in the syn-tectonic collision setting. They are mostly magmatic; however, some of them also show reequilibrated nature. The biotite crystallised at high temperature (600°C–700°C) at low oxygen fugacity. 3Mg↔2Al and coupled substitution between LiIV+SiIV=(Fe2+)IV played an important role during the crystallisation of the studied biotite.