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

Mallikharjuna Rao, J.; Poornachandra Rao, G.V.S.; Widdowson, M. and Kelley, S.P. (2005). Evolution of Proterozoic mafic dyke swarms of the Bundelkhand Granite Massif, Central India. Current Science, 88(3) pp. 502–506.

URL: http://www.ias.ac.in/currsci/feb102005/502.pdf

Abstract

The early Proterozoic Bundelkhand Granite Massif of
Central India is extensively intruded by NW–SE and
NE–SW trending mafic and ultramafic 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 olivinenormative character. Most of the tholeiites display incompatible elements pattern indicative of an enriched mantle source, while those of the ultramafics indicate a depleted source.