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Vivianite formation in ferruginous sediments from Lake Towuti, Indonesia

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Author Vuillemin Aurèle, Friese André, Wirth Richard, Schuessler Jan A., Schleicher Anja M., Kemnitz Helga, Lücke Andreas, Bauer Kohen W., Nomosatryo Sulung, von Blanckenburg Friedhelm, Simister Rachel, Ordoñez Luis G., Ariztegui Daniel, Henny Cynthia, Russell James M., Bijaksana Satria, Vogel Hendrik, Crowe Sean A., Kallmeyer Jens,
Project Climate history of the Indo-Pacific region and subsurface biosphere of Lake Towuti: The Swiss contribution to the ICDP Towuti Drilling Project (research part)
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Original article (peer-reviewed)

Journal Biogeosciences
Volume (Issue) 17(7)
Page(s) 1955 - 1973
Title of proceedings Biogeosciences
DOI 10.5194/bg-17-1955-2020

Open Access

URL http://doi.org/10.5194/bg-17-1955-2020
Type of Open Access Publisher (Gold Open Access)

Abstract

Abstract. Ferruginous lacustrine systems, such as Lake Towuti, Indonesia, are characterized by a specific type of phosphorus cycling in which hydrous ferric iron (oxyhydr)oxides trap and precipitate phosphorus to the sediment, which reduces its bioavailability in the water column and thereby restricts primary production. The oceans were also ferruginous during the Archean, thus understanding the dynamics of phosphorus in modern-day ferruginous analogues may shed light on the marine biogeochemical cycling that dominated much of Earth's history. Here we report the presence of large crystals (>5 mm) and nodules (>5 cm) of vivianite – a ferrous iron phosphate – in sediment cores from Lake Towuti and address the processes of vivianite formation, phosphorus retention by iron and the related mineral transformations during early diagenesis in ferruginous sediments. Core scan imaging, together with analyses of bulk sediment and pore water geochemistry, document a 30 m long interval consisting of sideritic and non-sideritic clayey beds and diatomaceous oozes containing vivianites. High-resolution imaging of vivianite revealed continuous growth of crystals from tabular to rosette habits that eventually form large (up to 7 cm) vivianite nodules in the sediment. Mineral inclusions like millerite and siderite reflect diagenetic mineral formation antecedent to the one of vivianite that is related to microbial reduction of iron and sulfate. Together with the pore water profiles, these data suggest that the precipitation of millerite, siderite and vivianite in soft ferruginous sediments stems from the progressive consumption of dissolved terminal electron acceptors and the typical evolution of pore water geochemistry during diagenesis. Based on solute concentrations and modeled mineral saturation indices, we inferred vivianite formation to initiate around 20 m depth in the sediment. Negative δ56Fe values of vivianite indicated incorporation of kinetically fractionated light Fe2+ into the crystals, likely derived from active reduction and dissolution of ferric oxides and transient ferrous phases during early diagenesis. The size and growth history of the nodules indicate that, after formation, continued growth of vivianite crystals constitutes a sink for P during burial, resulting in long-term P sequestration in ferruginous sediment.
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