Tectonic History of the Area East of Khammam, Andhra Pradesh

East of Khammam town in Andhra Pradesh, the Precambrian rocks are classified into three distinct lithological groups as (a) Peninsular Granites (b) Pakhals and (c) Gncissic Complex. Detailed structural studies on foliation, lineation, joints, folds, trends of dykes, basic enclaves, pegmatite and quartz veins of these groups show that the Peninsular Granite area with its NNW trend is structurally quite distinct from the remaining area which shows NW as well as NE trends. Mineralogical variation diagrams drawn for acid granulites, as a part of the quantitative petrological studies, show that the emplacement of these granulites has been structurally controlled by NE trend. Petrological studies in the Gneissic Complex show increasing grade of metamorphism roughly from northwest to southeast. It is concluded that the area in general is affected by two phases of disturbance, one, Dharwarian and another, late' Eastern Ghat' orogeny. It is also suggested that the demarcation line between 'charnockitic region' and 'non-charnockitic region' of Fermor should pass through the contact between Peninsular Granites and Pakhals.