Capturing the Mesoarchean emergence of continental crust in the Coorg Block, southern India

Abstract

The emergence of Earth's continental crust above sea level is debated. To assess whether emergence can be observed at a regional scale, we present zircon U‐Pb‐Hf‐O isotope data from magmatic rocks of the Coorg Block, southern India. A 3.5‐Ga granodiorite records the earliest felsic crust in the region. Younger phases of magmatism at 3.37–3.27 and 3.19–3.14 Ga, comprising both reworked crust and juvenile material, record successive crustal maturation. We interpret an elevation in δ¹⁸O through time as an increase in both the amount of sediment recycling and hence, crustal thickening, as well as an increase in the emerged area of continental crust available for weathering. Geochemical signatures do not point to any apparent change in geodynamic regime. We interpret the isotopic evolution of these rocks as solely reflecting regional emergence and thickening of the continental crust, assisted by the increasing strength of the lithosphere.