Grengs, A., Ledesma, G., Xiong, Y. et al. (4 more authors) (2024) Direct precipitation of siderite in ferruginous environments. Geochemical Perspectives Letters, 30. pp. 1-6. ISSN 2410-339X
Abstract
Siderite (FeCO₃) is often assumed to precipitate from dissimilatory reduction of Fe-(oxyhydr)oxides, but geochemical and mineralogical analyses from ferruginous (anoxic, Fe-rich) Canyon Lake, USA, suggest Fe-carbonate represents a direct early precipitate unrelated to substantial oxide burial. X-ray absorption near edge structure (XANES) spectroscopy of sediment trap materials and an anoxic sediment core indicated a mixture of Fe(II) and Fe(III) in water column particulates and ferruginous surface sediments, while all Mn phases were reduced. About 60 cm below the sediment–water interface, Fe-Mn carbonates were detected by X-ray diffraction and XANES, while Fe extended X-ray absorption fine structure (EXAFS) spectra were best fit with combinations of a biogenic Fe-oxyhydroxide (“Bio Fe”), greigite, and siderite. Sediment Fe speciation indicates a large pool of reduced Fe with a minor component of oxides. Although we found no evidence of significant carbonate phases above or below the 60 cm horizon, equilibrium modelling indicates siderite supersaturation throughout surface sediment porewater, with pH as the primary control on supersaturation. We conclude that delivery of wildfire ash to sediments increased pH, initiating siderite precipitation from ferruginous porewater.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | Copyright © 2024 The Authors Published by the European Association of Geochemistry under Creative Commons License CC BY-NC-ND 4.0. |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) > Earth Surface Science Institute (ESSI) (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 25 Mar 2024 14:59 |
Last Modified: | 17 May 2024 13:56 |
Published Version: | https://www.geochemicalperspectivesletters.org/art... |
Status: | Published |
Publisher: | European Association of Geochemistry |
Identification Number: | 10.7185/geochemlet.2414 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:210804 |
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