Geodynamic oxidation of Archean terrestrial surfaces

Abstract

One of the paradoxes of the Archean rock record is how evidence for oxidative continental weathering is plausible when the atmosphere lacked oxygen prior to the Great Oxidation Event ca. 2.5 billion years ago. We detected reactive oxygen species (ROS) production at various silicate-water interfaces in a simulated Archean atmosphere and calculated homolysis rates of silicon–oxygen bonds in these minerals. We find that ROS can be produced while silicates were eroded and transported by streams to depositional basins. The magnitude of ROS production increases from mafic- to felsic-silicates. During early continent formation, e.g., the Kaapvaal and Pilbara basins in the Paleoarchean, the emplacement of granitoids and their subsequent exposure to physical weathering might have annually provided at least 1.73 × 108 mol O2 before the biological O2 production. Importantly, this process could have oxidatively mobilized redox-sensitive elements to seawater, increasing the availability of bioessential nutrient elements for the Archean biosphere.