Trondhjemites from the Western Dharwar Craton, Southern India: Implications for Mesoarchean crustal growth

Abstract

Trondhjemite, together with tonalite and granodiorite (TTG) are important building blocks of the Archean continental crust and their studies provide insights into the formation of the early continents. The Western Dharwar Craton (WDC) in southern India contains voluminous TTG rocks that record prolonged Archean crustal evolution history with evidence for multiple episodes of magmatic accretion and metamorphic events from the Paleoarchean (∼3600 Ma) to Archean-Proterozoic transition (∼2500 Ma ago). In this study, we investigate trondhjemites from different typical locations in the WDC. Petrological, geochemical and zircon UPb, REE and LuHf data are presented and evaluated to understand the timing of magma emplacement and petrogenetic history. The trondhjemites in our study were generated from partial melting of juvenile hydrous basalt with arc features. The melting depth is variable, mainly shallow, while some melts originated at greater depths with variable plagioclase, amphibole with or without garnet, ilmenite or rutile in source residue. The age data presented here suggest that the crust accretion of the Mesoarchean Western Dharwar Craton occurred dominantly at 3.13–3.27 Ma followed by reworking of lower crustal basement 3.0–2.9 Ga.