DOI: 10.1038/s41561-017-0036-x
论文题名: Isotopic evidence for oxygenated Mesoarchaean shallow oceans
作者: Eickmann B. ; Hofmann A. ; Wille M. ; Bui T.H. ; Wing B.A. ; Schoenberg R.
刊名: Nature Geoscience
ISSN: 17520894
出版年: 2018
卷: 11, 期: 2 起始页码: 133
结束页码: 138
语种: 英语
Scopus关键词: anoxic conditions
; Archean
; diagenesis
; dolomite
; iron
; isotopic fractionation
; marine environment
; microbial activity
; oxidation
; oxygen isotope
; oxygenation
; photochemistry
; sediment analysis
; sulfate-reducing bacterium
; sulfur isotope
; tidal flat
; KwaZulu-Natal
; Pongola
; South Africa
英文摘要: Mass-independent fractionation of sulfur isotopes (MIF-S) in Archaean sediments results from photochemical processing of atmospheric sulfur species in an oxygen-depleted atmosphere. Geological preservation of MIF-S provides evidence for microbial sulfate reduction (MSR) in low-sulfate Paleoarchaean (3.8-3.2 billion years ago (Ga)) and Neoarchaean (2.8-2.5 Ga) oceans, but the significance of MSR in Mesoarchaean (3.2-2.8 Ga) oceans is less clear. Here we present multiple sulfur and iron isotope data of early diagenetic pyrites from 2.97-Gyr-old stromatolitic dolomites deposited in a tidal flat environment of the Nsuze Group, Pongola Supergroup, South Africa. We identified consistently negative Δ33S values in pyrite, which indicates photochemical reactions under anoxic atmospheric conditions, but large mass-dependent sulfur isotope fractionations of ~30‰ in δ34S, identifying active MSR. Negative pyrite δ56Fe values (-1.31 to -0.88‰) record Fe oxidation in oxygen-bearing shallow oceans coupled with biogenic Fe reduction during diagenesis, consistent with the onset of local Fe cycling in oxygen oases ~3.0 Ga. We therefore suggest the presence of oxygenated near-shore shallow-marine environments with ≥5 μM sulfate at this time, in spite of the clear presence of an overall reduced Mesoarchaean atmosphere. © 2018 The Author(s) [2017], under exclusive licence to Macmillan Publishers Limited, part of Springer Nature. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/105616
Appears in Collections: 气候减缓与适应 科学计划与规划
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作者单位: Department of Geology, University of Johannesburg, Johannesburg, South Africa; Department of Geosciences, University of Tübingen, Tübingen, Germany; Department of Earth and Planetary Sciences, McGill University, Montreal, QC, Canada; Department of Geological Sciences, University of Colorado, Boulder, CO, United States; Institute of Geological Sciences, University of Bern, Bern, Switzerland
Recommended Citation:
Eickmann B.,Hofmann A.,Wille M.,et al. Isotopic evidence for oxygenated Mesoarchaean shallow oceans[J]. Nature Geoscience,2018-01-01,11(2)