DOI: 10.1016/j.epsl.2018.07.044
Scopus记录号: 2-s2.0-85051404843
论文题名: Aerobic iron and manganese cycling in a redox-stratified Mesoarchean epicontinental sea
作者: Ossa Ossa F. ; Hofmann A. ; Wille M. ; Spangenberg J.E. ; Bekker A. ; Poulton S.W. ; Eickmann B. ; Schoenberg R.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2018
卷: 500 起始页码: 28
结束页码: 40
语种: 英语
英文关键词: iron formations
; manganese deposits
; Mesoarchean
; Mozaan Group
; oxygenation
; Pongola Supergroup
Scopus关键词: Carbonates
; Deposition
; Iron compounds
; Iron deposits
; Isotopes
; Manganese deposits
; Manganese removal (water treatment)
; Molybdenum
; Organic minerals
; Oxidation
; Oxygen
; Oxygenation
; Seawater
; Surface waters
; Great Oxidation Event
; Iron and manganese cycling
; Iron formation
; Isotopic signatures
; Marine environment
; Mesoarchean
; Mozaan Group
; Pongola Supergroup
; Manganese compounds
; Archean
; continental lithosphere
; deposition
; iron
; manganese
; ore deposit
; oxygenation
; paleoclimate
; redox conditions
; seawater
; shale
; stable isotope
; South Africa
英文摘要: Redox conditions in the marine realm prior to the Great Oxidation Event (GOE; ∼2.46–2.32 Ga ago), during which the atmospheric oxygen level rose dramatically for the first time, are still debated. Here, we present C, O, Fe, and Mo stable isotope systematics of Fe-, Mn-, and carbonate-rich shales, deposited at different water depths in association with iron formations (IFs) of the Mesoarchean Mozaan Group, Pongola Supergroup, South Africa. δ13C values between −22.3 and −13.5‰ VPDB, and δ18O values between −21.1 and −8.6‰ VPDB for Fe–Mn-rich carbonate minerals indicate their precipitation out of equilibrium with seawater. Instead, early diagenetic reduction of Fe–Mn-oxyhydroxide precursor minerals, along with microbially induced oxidation of organic matter (OM), formed these carbonates. δ56FeIRMM-014 values between −1.27 and 0.14‰ and δ98MoNIST3134+0.25 values between −0.46 and 0.56‰ co-vary with Mn concentrations and inferred water depth of deposition. This suggests that, despite the diagenetic origin of the Fe–Mn carbonates, the primary light Fe and Mo isotopic signature of Fe–Mn-oxyhydroxides that originally precipitated from seawater is still preserved. While isotopically light Mo implies that Mn(II) was oxidized to Mn(IV) due to the availability of free, photosynthetically produced O2, Mn enrichment suggests that the water column was redox stratified with a Mn-redoxcline situated at a depth below the storm wave base. A trend to highly negative δ56Fe values with increasing Mn/Fe ratios and decreasing depositional depth suggests progressive oxidation of Fe(II) as deep-waters upwelled across a redoxcline towards shallow, locally oxygenated waters where Mn(IV) oxyhydroxides precipitated. Combined δ56Fe and δ98Mo data indicate pervasive oxygenation of seawater with the O2 content in the photic zone likely reaching levels higher than the maximum value of 10 μM proposed for Archean oxygen oases. Since abiotic Mn(II) oxidation is kinetically very slow in marine environments, it is likely that Mn-oxidizing microorganisms catalyzed Mn-oxidation in the oxygenated Pongola surface waters during deposition of IFs. This implies that aerobic metabolism had evolved before the GOE in shallow, aquatic habitats, where it exerted a first-order control on the deposition of shallow-marine, Mn-rich iron formations. © 2018 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/109699
Appears in Collections: 影响、适应和脆弱性 气候变化事实与影响
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作者单位: Department of Geology, University of Johannesburg, Johannesburg, 2092, South Africa; Department of Geosciences, University of Tuebingen, Tuebingen, 72074, Germany; Institute of Geological Sciences, University of Bern, Bern, 3012, Switzerland; Institute of Earth Surface Dynamics, University of Lausanne, Lausanne, 1015, Switzerland; Department of Earth Sciences, University of California, Riverside, CA 9252, United States; School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, United Kingdom
Recommended Citation:
Ossa Ossa F.,Hofmann A.,Wille M.,et al. Aerobic iron and manganese cycling in a redox-stratified Mesoarchean epicontinental sea[J]. Earth and Planetary Science Letters,2018-01-01,500