Investigation of Ultra-18O Depleted "Slushball" Earth Rocks from Karelia, Russia and the Timing of Paleoproterozoic Glaciations and the Great Oxidation Event

University Of Oregon Eugene, Eugene OR

Investigators

Abstract

Investigation of Ultra-18-O Depleted "Slushball" Earth Rocks from Karelia, Russia and the Timing of Paleoproterozoic Glaciations and the Great Oxidation Event This proposal seeks support to investigate and interpret the Paleoproterozoic rocks from Karelia, Russia, which are extraordinarily depleted with respect to oxygen 18 (these rocks have the world's lowest known values). Rocks with such depleted 18O require derivation from interaction with glacial meltwaters during panglobal glaciation. These depletions now characterize 11 localities along a 450 km long belt and are spatially associated with the 2.45-2.2 Ga mafic intrusions formed in subglacial rifting environment zones. Since Karelia was located near equatorial latitudes throughout the Paleoproterizoic, these rocks provide isotopic evidence of ice at low latitudes, and a robust hydrologic cycle, in which low latitude oceans remained unfrozen (a "Slushball" climate state). As there were three panglobal glaciations between 2.45 and 2.2 Ga, precise determination of age of the mafic intrusions with the subglacial ultra-depleted meteoric hydrothermal features in Karelia will provide the most direct constraints on the timing of these global glaciations. Furthermore, this research may constrain which of the glaciations preceded the rise of atmospheric oxygen and disappearance of mass-independent fractionation of sulfur isotopes. The scope of this project will include mapping and sample collection in the field at the anomalously depleted areas, subsequent isotope analysis to identify the characteristic bulls-eyes meteoric hydrothermal features, dating the timing of such depletion by in situ and solution geochronology, geochemical modeling of these unique hydrothermal alteration trends, and investigation of the unmetamorphosed coeval early Paleoproterozoic Sariolian, and Sumian volcanic and sedimentary sequences of the Vetreny Belt in the context of the global oxidation event. The proposal will promote international collaboration, involve and support students including those traditionally underrepresented in geosciences, continue to involve large number of undergraduate and community college students into geochemical, geochronologic, and stable isotope research and expose them to science and international collaboration. The proposal will support the analytical infrastructure of the recently established stable isotope lab through work done by the PI and members of the research group and collaborators. PI will continue his outreach activities, public lectures and articles to popular journals.