Neoarchaean magmatism through arc and lithosphere melting: Evidence from eastern Dharwar Craton

Abstract

The Neoarchaean era is characterized by rapid crustal growth corresponding to some fundamental global changes in geodynamic processes. However, the nature of crustal growth including the mechanism and tectonic setting of the Neoarchaean are controversial issues. The eastern Dharwar Craton (EDC) exposes widespread Neoarchaean granite‐greenstone belts, which provide an opportunity to evaluate the various models proposed for Neoarchaean crustal growth. In this study, we present field, petrographic, and geochemical data and discuss the petrogenesis and significance for crustal evolution for a suite of previously undescribed banded gneisses, TTG (tonalite–trondhjemite–granodiorite), biotite granites, alkali feldspar granite and gabbro. These rocks are associated with Neoarchaean metavolcanic and metapelites rocks of the Tsundupalle greenstone belt, in the eastern fringe of the EDC. Whole‐rock major and trace element geochemical data are consistent with diverse sources, including both crust and enriched mantle in an evolving subduction zone. A convergent orogenic setting is proposed for interpreting the association of various granitoids in the Tsundupalle area. Finally, intrusion of crustally derived, highly silicic, alkali‐rich granite, and mantle‐derived gabbro emplaced in a post‐subduction regime is proposed. Lithospheric delamination and attendant mantle melting are suggested as possible mechanisms for generation of these rocks. The understanding of generation of the different granitoid types along with gabbro provides significant insights into the mechanism of Neoarchaean crustal growth.