Mafic dykes are a kind of minor intrusions, usually occur within granitic pluton in Chittoor district, Andhra Pradesh, India. The origin of these dykes and its implications to the formation of granitic plutons in Chittoor were studied. The analytical results suggest that these mafic dykes are alkali dolerite and derived from continental arc. The mafic dyke samples contain 5.61wt % MgO; exhibit negative Ba, Nb, Sr, Zr and Ti anomalies and they are enriched in Cs, Rb, U, K, Nd and Sm. It suggests that the mafic dykes are subduction related and contaminated during their intrusion. It is concluded that mantle wedge melting during the subduction process and basaltic underplating had provided the necessary heat to cause partial melting of continental crust, and generation of voluminous felsic magma.
Mafic dykes, Geochemistry, Petrogenesis, Subalkaline and alkaline