Preliminary Geochemistry and Emplacement Mechanism of Mafic Dykes of Anantapur Area, Andhra Pradesh

The granite - gneiss terrain of Dharwar Craton in Anantapur area of Andhra Pradesh is intruded by mafic dolerite dykes. These dykes are quartz or olivine-normative sub-alkalic tholeiites. Their Mg numbers range between 0.34 and 0.70 with low Ni (50-150 ppm), Cr(50-337 ppm) and Co( 41-70 ppm), indicating some degree of fractionation. The REE abundances show LREE - enriched patterns (La/Yb_N - 2.7 to 5.5). These dykes appear to be genetically related and were derived from a single magma.