The Late Archean-Early Proterozoic Mahakoshal greenstone belt (MGB) in central India is a 500 km long, ENE-trending mid-continent rift filled with a thick metavolcano-sedimentary sequence. The igneous activity, east of Katni town, in the western part of the MGB records four phases of magmatism represented by komatiite, basalt, diorite-granodiorite and rhyolite. This study focuses on the chemical and Nd and Sr isotopic characteristics of these magmatic rocks to evaluate their source characteristics and magmatic processes. Convex-up REE patterns, codepletion of Nb with LREE, and variably negative Zr anomalies of the Al-depleted Katni komatiites reflect melt segregations that included an extremely incompatible element depleted component, with majorite garnet in the residue, at great depths. The geochemical and Nd and Sr isotopic variations in the Katni basalts are best explained by a model involving limited amount of lithospheric mantle involvement in addition to the depleted and relatively shallow dominant asthenospheric mantle components. Partial melting modelling suggests that these basalts were derived by about 6% melting of peridotite containing no garnet. Chemical variations in the diorite-granodiorites indicate a significant crustal derived component. The Rb-Sr whole-rock isochron age (1504 Ma) of rhyolites suggests Mesoproterozoic reactivation of MGB. Trace element and Sr isotopic compositions of these rhyolites suggest generation of magma due to crustal melting induced by rifting and rise of geotherm.
|Number of pages
|Published - 2012
|International Geological Congress (34th : 2012) - Brisbane, Australia
Duration: 5 Aug 2012 → 10 Aug 2012
|International Geological Congress (34th : 2012)
|5/08/12 → 10/08/12