Coupling Sulfur and Oxygen Isotope Ratios in Sediment Melts Across the Archean-Proterozoic Transition

The Archean-Proterozoic transition marks a time of fundamental geologic, biologic, and atmospheric changes to the Earth system, including oxygenation of the atmosphere (termed the Great Oxygenation Event; GOE), and the emergence of continents above sea level. The impacts of the GOE on Earth's surface environment are imprinted on the geologic record, including the disappearance of mass-independent fractionation of sulfur isotopes (S-MIF). Temporally overlapping geologic and geo-chemical observations (e.g. a change in oxygen isotope ratio of sediments and an increase in subaerial volcanism) imply the widespread subaerial emergence of continents was coeval with atmospheric oxygenation. Here we present triple sulfur isotope ratios in pyrite and oxygen isotope ratios in garnet and zircon in a global suite of Archean and Proterozoic granitoids derived from the partial melting of sedimentary protoliths. These crustal melts record an increase in average garnet and zircon delta O-18 from 7.2 parts per thousand before 2.3 Ga to 10.0 parts per thousand post-2.3 Ga. Pre-2.3 Ga granitoids show small S-MIF signatures with Delta S-33 ranging from -0.29 parts per thousand to 0.13 parts per thousand, whereas post-2.3 Ga granitoids record S-MDF (i.e. Delta S-33 = 0 parts per thousand). The combination of sulfur and oxygen isotope signatures in the same sample with zircon U-Pb geochronology provides new insights on a potential causal link between the emergence of continents and Paleoproterozoic atmospheric oxygenation. (C) 2021 Elsevier Ltd. All rights reserved.