Geochemistry and Origin of Northern Closepet Granite from Gudur-Guledagudda Area, Bagalkot District, Karnataka

摘要

The late Archaean Closepet Granite of the Gudur-Guledagudda area consists of equigranular pink and grey biotite granites, and porphyritic pink biotite granodiorite to quartz-monzodiorite. The granitoids exhibit intrusive relation with the Hungund-Kushtagi schist belt at places. The equigranular granites show limited range of major oxide compositions and compared to the porphyritic granodiorite and quartz-monzodiorite, are enriched in SiO_2, K_2O and Rb but depleted in Al_2O_3, FeO, Fe_2O, MgO, P_2O_5, Sr, Ba, Y, Nb and REE. The granitoids fall near the boundary HREE patterns and a negative Eu anomaly characterize all the samples. Field evidences indicate mainly post-kinematic nature of the granitoids. The equigranular granites appear to be minimum melt derived from anatexis of Peninsular Gneiss without fractional crystallization. The porphyritic granodiorite and quartz-monzodiorite represent non-minimum melt derived from a different source enriched in REE. Geochemical signatures indicate that the Closepet Granite of Gudur-Guledagudda area is the product of melting at shallower level compared to the southern Closepet Granite.