Geochemistry of the Newer Dolerite Suite of Intrusions within the Singhbhum Granite-A Preliminary Study

Three petrogenetic groups are recognised from petrologic and geochemical data on the Precambrian Newer Dolerite dyke swarm. They are (a) accumulates (peridotites, norites and lamprophyres), (b) products of direct magmatic crystallization (two generations of dole rites and associated micropegmatitic dolerites and micro-granites, each with distinctive trends of major-and minor-element variations), and (c) products of partial melting (leuco-granophyre and xenolithic granophyre), Geochemically, the entire suite has abnormally high K/Rb, Ni, Co and abnormally low Rb, Ba and Sr. Linear discriminant function indicates that the dolerites are typically sub-alkaline. Source magma is inferred to have been picritic and derived by partial melting of the upper mantle.