Geology of Corundum Occurrances in Parts of Khammam Schist Belt, Andhra Pradesh, India

KhammamSchistBeltinAndhraPradeshisconsidered as a northern extension of the Nellore Schist Belt (NSB). Both KSB and NSB are referred to a single unit of 600 km long west- vergent Nellore-Khammam Schist Belt (NKSB) occurring as a paleo - proterozoic/late archaean greenstone belt on the basis of similar geological and structural setup in the Precambrian terrain of South India. The Nellore Khammam Schist Belt (NKSB) is considered to be the equivalent of Sargur Schist Belt (3.3 Ga, Peucat, et al; 1995). The Khammam Schist Belt (KSB) forms a curvilinearbelt in parts of Khammam and Krishna districts of Andhra Pradesh. The KSB is inferred to be a tectonised belt sandwiched between the Dharwar Craton in the West and the Eastern Ghat Mobile Belt (EGMB) in the East. (Leelanandam, C and Narasimha Reddy, M, 1988). The KSB mainly consists of metamorphosed felsic and mafic volcanic, now preserved as quartzo-felspathic gneisses, hornblende schists and schistose amphibolites, with or without garnet. The pelitic meta-sediments such as sillimanite-kyanite schists, sillimanite- cordierite- orthopyroxene-corundum bearing rocks, pegmatites and banded iron formations (quart-magnetites). Garnet bearing quartzites are rare and insignificant in volume in the KSB. The present study area is bounded by 17o10’: 17o20’: 80o15’: 80o25’.Mafic and Felsic rocks are exposed in the area. The dominant lithology comprises amphibolites, which may be described as banded, foliated, garnetiferous or massive based on its field appearance. The lithological formations of KSB form a basement for the proterozoic pakhals and phanerozoic gondwana sediments. The KSB is endowed with economically viable corundum (ruby variety) and podiform chromite occurrences; however, they are significantly controlled by both lithology and structure.