GEOCHEMICAL AND PETROGRAPHICAL STUDIES OF PRECAMBRIAN GRANITOIDS FROM HYDERABAD BATHOLITH, TELANGANA, INDIA

The granitoids from the Hyderabad area of the Telangana State are confined to Precambrian gneissic complex of the northern-eastern part of Eastern Dharwar Craton. They cover 7760Sq.km of the study area and fall between latitudes 16° 52'- 17°42'N and between East longitudes 77° 21'- 77°51'E. The granitoids are mainly classified into grey and pink granites, granodiorites and aplites. They occasionally contain older mafic enclaves in the form of lensoid bodies and thin bands and cut by younger dolerite dykes, pegmatite and quartz veins. Granitoids form batholitic domes, pointed hillocks, small mounds and sheeted outcrops in the study area. Under the microscope they show varied textural features such as intergrowth perthitic texture between alkali feldspar and plagioclase feldspar and symplectic myrmekitic texture between plagioclase, quartz at the margin of K- feldspar. Norm data sets when plotted in QAP diagram, the samples restricted to the field of syeno granite to monzogranite to granodiorite. They are mainly composed of feldspar (microcline and plagioclase) and quartz as essential minerals. Biotite, hornblende,epidote, chlorite, apatite and iron oxide occur as accessory minerals. The negative correlation between SiO2 vs CaO, TiO2 and MgO indicate plagioclase fractionation.These granitoids lie in the fields of granite and granodiorite on the SiO2 vs Na2O+K2O diagram. Majority of granitoid samples fall in granite, few in quartz monzonite and granitic field of Na2O+K2O vs SiO2binary diagram. The granitoid samples are classified into granites and trondhjemite and at the margins of granodiorite (GGT) in the normative An-AbOr ternary diagram.The granitic rocks of the study area are plotted within cal-alkaline field and show typical calc alkaline trend on the AFM diagram.The granitoids are described as both metaluminous and peraluminous types further the granitoids of Hyderabad area in MALI digram, spread over calcic to alkali fields. This shows that the studied suites are not derived from the differentiation of a single parental magma. These granitoids are described as subsolvus in character that are formed at below solvus temperature (<4000C)under wet conditions. Based on the field, petrography and major element analyse of the granitoids of the Hyderabad area reveal that they are formed from the melts that are generated by partial melting of lower crust due to magma-upwelling.