Evolution of Proterozoic mafic dyke swarms of the Bundelkhand Granite Massif, Central India

The early Proterozoic Bundelkhand Granite Massif of Central India is extensively intruded by NW-SE and NE-SW trending mafic and ultramaric dykes. These dykes are mostly dolerites with subordinate pyroxenite or lamproites, and geochemical signatures are different for the NW-SE and NE-SW trending dyke suites. 40Ar/39Ar age determinations of the dolerite dykes suggest two phases of dyke activity at ca. 2150 Ma and 2000 Ma and supported by palaeomagnetic results in this region. Apart from other magmatic emplacements, there are younger deformational events recorded by minerals (1800 Ma event recorded by some mafic regions of dykes and 692-750 Ma given by plagioclase feldspars) subsequent to their magmatic emplacements. The dolerites are typically tholeiites and quartz normative types, while the ultramafics are komatiite or basaltic komatiite in composition and show an olivine-normative character. Most of the tholeiites display incompatible elements pattern indicative of an enriched mantle source, while those of the ultramafics indicate a depleted source.