Searching for the Great Oxidation Event in North America: A Reappraisal of the Huronian Supergroup by SIMS Sulfur Four-Isotope Analysis

Huan Cui; Kouki Kitajima; Michael J Spicuzza; John H Fournelle; Akizumi Ishida; Philip E Brown; John W Valley

doi:10.1089/ast.2017.1722

Searching for the Great Oxidation Event in North America: A Reappraisal of the Huronian Supergroup by SIMS Sulfur Four-Isotope Analysis

Astrobiology. 2018 May;18(5):519-538. doi: 10.1089/ast.2017.1722.

Authors

Huan Cui^{1

2}, Kouki Kitajima^{1

2}, Michael J Spicuzza^{1

2}, John H Fournelle², Akizumi Ishida^{1

2

3}, Philip E Brown², John W Valley^{1

2}

Affiliations

¹ 1 NASA Astrobiology Institute, University of Wisconsin-Madison , Madison, Wisconsin, USA .
² 2 Department of Geoscience, University of Wisconsin-Madison , Madison, Wisconsin, USA .
³ 3 Department of Earth Science, Tohoku University , Sendai, Japan .

PMID: 29791234
DOI: 10.1089/ast.2017.1722

Abstract

Sedimentological observations from the Paleoproterozoic Huronian Supergroup are suggested to mark the rise in atmospheric oxygen at that time, which is commonly known as the Great Oxidation Event (GOE) and typically coupled with a transition from mass-independent fractionation (MIF) to mass-dependent fractionation (MDF) of sulfur isotopes. An early in situ study of S three-isotopes across the Huronian Supergroup by Papineau et al. ( 2007 ) identified a weak MIF-MDF transition. However, the interpretation and stratigraphic placement of this transition is ambiguous. In this study, all four S isotopes were analyzed for the first time in two Huronian drill cores by secondary ion mass spectrometer (SIMS), and both Δ³³S and Δ³⁶S were calculated. Based on improved precision and detailed petrography, we reinterpret the dominance of pyrrhotite in the studied sections, which was previously proposed as "early authigenic" in origin, as resulting from regional metamorphism. Small but analytically resolvable nonzero values of Δ³³S (from -0.07‰ to +0.38‰) and Δ³⁶S (from -4.1‰ to +1.0‰) persist throughout the lower Huronian Supergroup. Neither pronounced MIF-S signals nor a MIF-MDF transition are seen in this study. Four scenarios are proposed for the genesis of small nonzero Δ³³S and Δ³⁶S values in the Huronian: homogenization by regional metamorphism, recycling from older pyrite, dilution by magmatic fluids, and the occurrence of MDF. We argue that the precise location of the MIF-MDF transition in the Huronian remains unsolved. This putative transition may have been erased by postdepositional processes in the lower Huronian Supergroup, or may be located in the upper Huronian Supergroup. Our study highlights the importance of integrated scanning electron microscopy and secondary ion mass spectrometry techniques in deep-time studies and suggests that different analytical methods (bulk vs. SIMS) and diagenetic history (primary vs. metamorphic) among different basins may have caused inconsistent interpretations of S isotope profiles of the GOE successions at a global scale. Key Words: Great Oxidation Event (GOE)-Secondary ion mass spectrometer (SIMS)-Paleoproterozoic-Sulfur isotopes-Mass independent fractionation (MIF). Astrobiology 18, 519-538.

Publication types

Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

Chemical Fractionation / methods
Geologic Sediments / analysis*
Geologic Sediments / chemistry
North America
Oxidation-Reduction
Spectrometry, Mass, Secondary Ion*
Sulfur Isotopes / analysis*

Substances

Sulfur Isotopes