Multiple isotope (O, S, Sr) constraints on the early Paleoproterozoic Great Oxidation Event from barite-bearing deposits of the Minas Supergroup, Minas Basin, Brazil

• Grant number: 19/16066-7
• Support type: Scholarships abroad - Research Internship - Post-doctor
• Effective date (Start): January 01, 2020
• Effective date (End): December 31, 2020
• Field of knowledge: Physical Sciences and Mathematics - Geosciences - Geology
• Principal Investigator: Pascal Andre Marie Philippot
• Grantee: Camille Yann Rossignol
• Supervisor abroad: Pierre Cartigny
• Home Institution: Instituto de Astronomia, Geofísica e Ciências Atmosféricas (IAG). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Local de pesquisa : Institut de physique du globe de Paris, France
• Associated to the scholarship: 18/02645-2 - Chronostratigraphy and isotopic tracing of the Paleoproterozoic Minas Supergroup, BP.PD

Abstract

The early Paleoproterozoic (2.5 - 2.1 Ga) was a period of major environmental and climatic changes, marked by the rise of atmospheric oxygen and the onset of multiple glaciations, the oldest one at ca. 2.45 Ga of possible global extension (Snowball Earth event). This is at odd with the sedimentary successions of similar age in the Minas Basin, São Francisco Craton, for which no evidence of glacial horizons have been reported so far. The aim of this BEPE project is to analyze S, O and Sr isotope compositions of early diagenetic barite preserved in carbonates of the Gandarela Formation. This unit was deposited at ca. 2.42 Ga and therefore should record the global oxygenation and glaciogenic changes reported in other cratons worldwide.Barite, a sulfate mineral (BaSO4) relatively resistant to post-depositional alteration, forms by the mixing of Ba-bearing fluid with another containing sulfate (SO42-). Sulfate derives from sulfide oxidation during weathering of the continental surface, where oxygen derives primarily from ambient H2O. As a non-labile oxyanion, sulfate thus retains initial H2O signatures, constituting a direct recorder of past H2O. These properties permit ancient sulfate to record extreme 18O depletions indicative of glacial conditions. Sulfur from sulfate bears complementary information, as S isotopes carry a signal of the oxygenation of the atmosphere, through the transition from Mass Independent (MIF) to Mass Dependent Isotope Fractionation (MDF). Thus, sulfate-bearing barite offers a direct way to track atmospheric oxygenation and associated glacial conditions through paired S and O isotopic records. Moreover, barite Sr isotope compositions are excellent tracers of Ba-bearing fluid sources. In combination with S isotopes, Sr isotopes can provide constraints on the depositional environment of barite (e.g., sedimentary vs. hydrothermal). This 12 months BEPE project intends to obtain S, O and Sr isotope compositions of barite collected in the Gandarela Formation to document the major environmental changes (oxygenation of the atmosphere and related glacial events) that occurred during the early Paleoproterozoic.

Scientific publications

(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)

ROSSIGNOL, CAMILLE; REGO, ERIC SICILIANO; NARDUZZI, FRANCESCO; TEIXEIRA, LIVIA; AVILA, JANAINA N.; SILVA, MARCO A. L.; LANA, CRISTIANO; PHILIPPOT, PASCAL. Stratigraphy and geochronological constraints of the Serra Sul Formation (Carajas Basin, Amazonian Craton, Brazil). Precambrian Research, v. 351, DEC 2020. Web of Science Citations: 0.