Subaerial oxidative uranium mobilization at the culmination of the Great Oxidation Event

• 成果类型: Article
• 署名作者: Bauer, Ann M.; Li, Weiqiang; Rybacki, Kyle S.; Roden, Eric E.; Kump, Lee R.; Johnson, Clark M.
• 署名单位: University of Wisconsin System; University of Wisconsin Madison; National Aeronautics & Space Administration (NASA); Nanjing University; Pennsylvania Commonwealth System of Higher Education (PCSHE); Pennsylvania State University; Pennsylvania State University - University Park; Pennsylvania Commonwealth System of Higher Education (PCSHE); Pennsylvania State University; Pennsylvania State University - University Park
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-14015
• DOI: 10.1073/pnas.2510289122
• 发表日期: 2025-09-09
• 关键词: carbon-isotope excursions; trace-element; lead-isotope; continental-crust; franceville basin; st-helena; pb age; EVOLUTION; oxygen; mantle

摘要

Redox-sensitive elements figure prominently in studies of the evolution of Earth's surface redox state, including the first major rise in atmospheric O-2, the Paleoproterozoic Great Oxidation Event. Most Precambrian rocks endured multistage tectonothermal histories, however, adding ambiguity to interpretation of their chemistry. Here, we apply U-Th-Pb isotope geochronology to the highly oxidized similar to 2.06 Ga Kuetsjarvi Volcanic Formation, Pechenga Greenstone Belt, Russia, to constrain the age and extent of U oxidation. By contrasting the relative mobility of U and Th using Pb isotopes, we find that complete to near-complete oxidation and removal of U occurred shortly after eruption. We argue that this likely indicates relatively high atmospheric O-2, where oxidative weathering and alteration produced a global pulse of U to the oceans. Such a pulse could explain widespread shifts in the U-Th-Pb isotope character of mantle reservoirs at similar to 2 Ga, including a decrease in the Th-232/U-238 ratio of the mid-ocean ridge basalt source and inception of the high-U-238/Pb-204 (HIMU) source to ocean island basalts, underscoring the connections between the redox character of the Paleoproterozoic surface and deep Earth. Using Pb-207-Pb-206, U-238-Pb-206, U-235-Pb-207, and Th-232-Pb-208 geochronology, similar to 2.06 Ga oxidative loss of U may be distinguished from reintroduction of U at similar to 1.8 Ga during regional metamorphism, as well as Pb loss during a Phanerozoic tectonothermal event. Our results therefore establish the complex history of redox-sensitive element behavior in the rocks, highlighting the fact that elemental abundances, by themselves, are unlikely to capture straightforward proxy information in rocks that have seen multistage geologic histories.