A review of paleo- To neoarchean crustal evolution in the dharwar craton, southern India and the transition towards a plate tectonic regime

Abstract

An emerging view is that Earth's geodynamic regime witnessed a fundamental transition towards plate tectonics around 3.0 Ga (billion years). However, the manifestations of this change may have been diachronous and craton-specific. Here, we review geological, geophysical and geochronological data (mainly zircon U-Pb age-Hf isotope compositions) from the Dharwar craton representing over a billion year-long geologic history between ~3.5 and 2.5 Ga. The Archean crust comprises an oblique section of ~12 km from middle to deep crust across low- to mediumgrade granitegreenstone terranes, the Western and Eastern Dharwar Cratons (WDC and EDC), and the highgrade Southern Granulite Terrain (SGT). A segment of the WDC preserving Paleo- to Mesoarchean gneisses and greenstones is characterised by 'dome and keel' structural pattern related to vertical (sagduction) tectonics. The geology of the regions with dominantly Neoarchean ages bears evidence for convergent (plate) tectonics. The zircon U-Pb age- Hf isotope data constrain two major episodes of juvenile crust accretion involving depleted mantle sources at 3.45 to 3.17 Ga and 2.7 to 2.5 Ga with crustal recycling dominating the intervening period. The Dharwar craton records clear evidence for the operation of modern style plate tectonics since ~2.7 Ga.