Iron Isotopes Reveal a Benthic Iron Shuttle in the Palaeoproterozoic Zaonega Formation: Basinal Restriction, Euxinia, and the Effect on Global Palaeoredox Proxies

Type Article
Date 2021-04
Language English
Author(s) Mänd KaarelORCID1, 2, Lalonde Stefan3, Paiste Kärt1, 4, Thoby Marie3, Lumiste Kaarel1, Robbins Leslie J.ORCID5, Kreitsmann Timmu6, Romashkin Alexander E.7, Kirsimäe Kalle1, Lepland Aivo1, 8, 9, 10, Konhauser Kurt O.2
Affiliation(s) 1 : Department of Geology, University of Tartu, 50411 Tartu, Estonia
2 : Department of Earth & Atmospheric Sciences, University of Alberta, Edmonton, AB T6G 2E3, Canada
3 : CNRS-UMR 6538 Laboratoire Géosciences Océan, European Institute for Marine Studies, Technopôle Brest-Iroise, 29280 Plouzané, France
4 : Department of Earth and Planetary Sciences, Washington University in St. Louis, St. Louis, MO 63130, USA
5 : Department of Geology, University of Regina, Regina, SK S4S 0A2, Canada
6 : Department of Physics and Earth Sciences, Jacobs University Bremen, 28759 Bremen, Germany
7 : Institute of Geology, Karelian Research Centre, Russian Academy of Sciences, 185610 Petrozavodsk, Russia
8 : CAGE—Centre for Arctic Gas Hydrate, Environment and Climate, Department of Geosciences, UiT The Arctic University of Norway, 9037 Tromsø, Norway
9 : Geological Survey of Norway, 7491 Trondheim, Norway
10 : Tallinn University of Technology, Institute of Geology, 19086 Tallinn, Estonia
Source Minerals (2075-163X) (MDPI AG), 2021-04 , Vol. 11 , N. 4 , P. 368 (25p.)
DOI 10.3390/min11040368
Note This article belongs to the Special Issue Copper and Other Metallic Isotope Systems
Keyword(s) isotope geochemistry, redox stratification, benthic Fe shuttle, dissimilatory iron reduction
Abstract

The Zaonega Formation in northwest Russia (~2.0 billion years old) is amongst the most complete successions that record the middle of the Palaeoproterozoic era. As such, geochemical data from the formation have played a central role in framing the debate over redox dynamics in the aftermath of the Great Oxidation Event (GOE). However, uncertainty over local redox conditions and the degree of hydrographic restriction in the formation has led to contradictory interpretations regarding global oxygen (O2) fugacity. Here, we provide new iron (Fe) isotope data together with major and trace element concentrations to constrain the local physiochemical conditions. The Zaonega Formation sediments show authigenic Fe accumulation (Fe/Al ≫ 1 wt.%/wt.%) and δ56Fe ranging from −0.58‰ to +0.60‰. Many of the data fall on a negative Fe/Al versus δ56Fe trend, diagnostic of a benthic Fe shuttle, which implies that Zaonega Formation rocks formed in a redox-stratified and semi-restricted basin. However, basin restriction did not coincide with diminished trace metal enrichment, likely due to episodes of deep-water exchange with metal-rich oxygenated seawater, as evidenced by simultaneous authigenic Fe(III) precipitation. If so, the Onega Basin maintained a connection that allowed its sediments to record signals of global ocean chemistry despite significant basinal effects

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Mänd Kaarel, Lalonde Stefan, Paiste Kärt, Thoby Marie, Lumiste Kaarel, Robbins Leslie J., Kreitsmann Timmu, Romashkin Alexander E., Kirsimäe Kalle, Lepland Aivo, Konhauser Kurt O. (2021). Iron Isotopes Reveal a Benthic Iron Shuttle in the Palaeoproterozoic Zaonega Formation: Basinal Restriction, Euxinia, and the Effect on Global Palaeoredox Proxies. Minerals, 11(4), 368 (25p.). Publisher's official version : https://doi.org/10.3390/min11040368 , Open Access version : https://archimer.ifremer.fr/doc/00688/79959/