Euxinia in the Neoarchean: The starting point for early oxygenation in a Brazilian Craton

Author(s)

Bosco-Santos, Alice ^{[1, 2]} ; Gilhooly, III, William Patrick ; Fouskas, Fotios ^[3] ; Fabricio-Silva, Wendell ^{[4, 5]} ; Oliveira, Elson Paiva ^[2]

Affiliation

^[1] Indiana Univ Purdue Univ, Dept Earth Sci, Indianapolis, IN 46202 - USA

^[2] Univ Estadual Campinas, Dept Geol & Nat Resources, BR-13083855 Campinas, SP - Brazil

^[3] Gilhooly, William Patrick, III, Indiana Univ Purdue Univ, Dept Earth Sci, Indianapolis, IN 46202 - USA

^[4] Univ Brasilia, Geosci Inst, BR-70910900 Brasilia, DF - Brazil

^[5] Univ Wurzburg, Bavarian Georesources Ctr, Inst Geog & Geol, D-97074 Wurzburg - Germany

• Document type: Journal article
• Source: Precambrian Research; v. 341, JUN 2020.
• Web of Science Citations: 0

Abstract

Geochemical evidence for local redox transitions is observed 300 Ma years prior to the Great Oxygenation Event (GOE ca. 2400 Ma) and suggests evolving environmental conditions through a continuous sequence where euxinia (anoxic and sulfidic) preceded the expansion of more oxidizing conditions. Based on multiproxy data such as iron speciation (Fe-Py/Fe-HR > 0.7) and Mo enrichments (varying from 3 to 64), we present one of the oldest records of euxinia from the Archean Pitangui greenstone belt (similar to 2700 Ma), Minas Gerais, Brazil. The sulfur isotopic composition of sedimentary sulfides indicates early inputs of sulfate from oxidative weathering and an attenuation of sulfur mass independent fractionation that combined with other geochemical signatures (Fe-HR/Fe-T, Ce anomalies and rare earth element fractionation) is consistent with the expansion of oxygen availability, and suggests localized oxic conditions before the GOE. (AU)

• FAPESP's process: 16/02933-2 - Isotope geochemistry and biomarkers in Archaean terranes and in their modern analogues systems: environmental constraints and ecology of early Earth life
• Grantee: Alice Bosco Santos
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 12/15824-6 - Evolution of archaean terranes of the São Francisco Craton and the Borborema Province, Brazil: global environmental and geodynamic implications
• Grantee: Elson Paiva de Oliveira
• Support Opportunities: Research Projects - Thematic Grants