Petrology and Geochemistry of the Ultramafic Rocks of Yerrabali Schist Belt, Eastern Dharwar Craton, Telangana, India

The Yerrabali schist Belt (YSB) is a NW-SE trending 10 km long and 4 km wide belt located at the north eastern corner of Eastern Dharwar Craton (EDC) consisting of Banded Magnetite Quartzite (BMQ), ultramafic rocks, quartz-cordierite- gedrite +/- garnet bearing schist, sillimanite-garnet-cordierite schist, metadolomite, amphibolite, ferruginous quartzite, tremolite schist and dolerite dyke. The ultramafic rocks consist of olivine, orthopyroxene, clinopyroxene and spinel. The Fe content of olivine varies from 88-91 and consists of high amount of NiO (0.3-0.511%). Orthopyroxone are enstatitic and clinopyroxene are Mg-augite in nature. The spinel grains are rich in Al2O3 (48.32-59.09%) and show very low Cr# values (0.08-0.29). Thermo-barometric analyses show equilibrium condition of 700 degrees-1100 degrees C temperature and 19-21 kb pressure. Oxygen fugacity of the ultramafic rocks range from -0.035 to -1.356 log units below FMQ buffer. Low Cr# values of spinel along with low oxygen fugacity suggest their formation by low degrees of partial melting from a less refractory Mid Oceanic Ridge (MOR) type mantle.