Chapter 6 - Petrogenetic Evolution of Chromite Deposits in the Archean Greenstone Belts of India

Abstract

This chapter reviews the Archean greenstone belt-hosted chromite deposits of India. These deposits are significant in tracing the crustal and mantle evolution of the Earth. This is because chromites are important petrogenetic tools that retain the composition of the parental melt from which they crystallize in a particular tectonic setting. However, chromites may not all be robust and can be altered during serpentinization and metamorphism (prograde and retrograde), which is common in Archean greenstone belts. It is therefore necessary to identify unaltered chromites through meticulous petrographic study. Archean greenstone belt-hosted chromite deposits from the Nuasahi-Sukinda Massifs in the Singhbhum craton (eastern India), and the Nuggihalli greenstone belt in the Western Dharwar craton (WDC; southern India) are discussed in this review. The major- and trace-element compositions of chromites from these deposits indicate derivation from a komatiitic basalt or boninitic parental melt, generated in a suprasubduction zone setting in the Archean. The Sm-Nd and Re-Os isotopic characters of the ultramafic-mafic rocks from these deposits indicate derivation from a depleted mantle source, with no signatures indicating contamination of the parental melt. The composition of the Indian Archean chromites is comparable with those from other globally occurring early Archean greenstone belts. The occurrences of Archean greenstone belt-hosted chromite deposits coincide with peaks in komatiitic magmatism observed in the Earth’s geological record, which is linked with supercontinent cycles. The Indian Archean chromite deposits may have been linked with the amalgamation stage of a supercontinent that culminated around 2.7Ga.