Chromium isotopes in marine hydrothermal sediments

Bauer, Kohen W.; Cole, Devon B.; Asael, Dan; François, Roger; Calvert, S. E.; Poulton, Simon W.; Planavsky, Noah J.; Crowe, Sean A.

doi:10.1016/j.chemgeo.2019.119286

Cited by 23 publications

(24 citation statements)

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“…Thus, the Cr isotope data from microbialites of the Jaíba Member are early diagenetic and record pore water δ 53 Cr signals engendered by aerobic and anaerobic, direct and indirect microbial reduction. Light δ 53 Cr compositions have been observed as the result of oxidative remobilization of Cr(III) in paleosols and modern soils, in oxidizing ferromanganese nodules (e.g., Berger & Frei, 2014; Crowe et al., 2013; Wei et al., 2018), in deep ocean hydrothermal plume fallout sediments (Bauer et al., 2019) and here in lower Cambrian microbialites. Our study suggests caution to the use of ancient microbialites to infer past seawater Cr records until further research unravels metal diffusion models and Cr reduction and reoxidation in microbial mats, and the reliability of ancient microbialites as records of seawater Cr isotopes.…”

Section: Discussionmentioning

confidence: 99%

“…Also, the lack of significant positive Eu anomalies and absence of correlation between Eu/Eu* and δ 53 Cr do not support high‐T hydrothermal input as a cause for low δ 53 Cr values (Frei et al., 2009, 2011). Deep ocean carbonates associated with metalliferous Fe‐rich hydrothermal precipitates have isotopically light δ 53 Cr showing a clear genetic link between Cr and Fe (Bauer et al., 2019). Although the δ 53 Cr values of such reservoir are similar to our samples, the Jaíba microbialites were deposited in the shallow water of coastal environments and far from any hydrothermal plume purportedly active.…”

Section: Discussionmentioning

confidence: 99%

“…This significant positive covariation suggests a small post‐depositional addition of isotopically heavy Cr with increasing Mn, Fe, and 87 Sr content. We argue that manganese oxides formed in oxic surface waters and settled to the O 2 ‐rich zone of microbial mats may have contributed to the reoxidation of some Cr(III), thus making available soluble oxyanions of 53 Cr‐rich chromate and Mn 2+ to pore water and increasing water pH (Shaw et al., 1990; Bauer et al., 2019; Equation 1).

Cr(III) + 3 MnOOH \to {HCrO}_{4}^{‐} + 3 Mn(II) + 2 {OH}^{‐}

…”

Section: Discussionmentioning

confidence: 99%

“…Furthermore, lighter δ 13 C values are also moderately correlated to higher Mn/Sr ratios ( R 2 = 0.31; not shown), which also suggests minor isotopic re‐equilibrium. Cr concentrations are independent of δ 53 Cr, Mn/Sr, Fe/Sr, or 87 Sr/ 86 Sr variations; in other words, there is no Cr uptake or loss during these pore reactions (e.g Bauer et al., 2019; Remmelzwaal et al., 2019). Finally, it lacks evidence to suggest that the negatively fractionated values of Jaíba microbialites are an artifact of fluid‐rock interaction during diagenetic stages.…”

Section: Discussionmentioning

confidence: 99%

“…53 Cr-and ferromanganese-rich diagenetic calcites can thus precipitate if physio-chemical parameters are attended (e.g. Dromgoole & Walter, 1990;Tang et al, 2007 Bauer et al, 2019;Remmelzwaal et al, 2019). Finally, it lacks evidence to suggest that the negatively fractionated values of Jaíba microbialites are an artifact of fluid-rock interaction during diagenetic stages.…”

Section: Diagenetic Fluid-rock Interaction and Alteration Of δ 53 Crmentioning

confidence: 99%

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Microbially induced chromium isotope fractionation and trace elements behavior in lower Cambrian microbialites from the Jaíba Member, Bambuí Basin, Brazil

et al. 2020

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In east‐central Brazil, the Ediacaran‐Cambrian Bambuí Basin has the potential to provide a record of unique geochemical responses of Earth's ocean and atmosphere evolution during this key time interval. From this perspective, we studied an interval of the upper Bambuí Basin using sedimentologic, stratigraphic, and chemostratigraphic tools. The lower Cambrian Jaíba Member of the uppermost Serra da Saudade Formation is an interval of up to 60 m‐thick of carbonate rocks disposed into two shallowing upward trends. Inner to outer ramp and high‐energy shoal deposits are described, in which laminated microbialites are the prevailing sedimentary facies. REE + Y data suggest contamination by iron (oxy)hydroxides that are dissociated from the riverine detritic flux. Sedimentary iron enrichment may be related to the settling of iron nanoparticles in coastal environments, diagenetic iron mobilization, or both. MREE enrichment is caused by microbial degradation of organic matter in the iron reduction zone during the anoxic early‐diagenetic stage. Chromium isotopes yielded negatively fractionated values (δ53Cr = −0.69 to −0.27‰), probably resulting from biotic and abiotic reduction of dissolved Cr(VI) to light and less toxic Cr(III) within pores of microbial mats. The δ53Cr data of the Jaíba microbialite are thus a product of metabolic reactions in microbial mats and do not reflect seawater signal. The isotopic offset from seawater is feasible from molecular diffusion of Cr into pore water and reduction reactions occurring deep inside the mat, although the exact mechanism and consequences are not yet fully understood due to the poor preservation of metabolic reactions in the geological record. Our study suggests that Cr isotopes can be used to reconstruct Cr and other metals cycling within ancient microbial mats, and that caution should be taken when using past microbialites to infer seawater Cr records and redox state of the atmosphere and ocean.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Cr(III) + 3 MnOOH \to {HCrO}_{4}^{‐} + 3 Mn(II) + 2 {OH}^{‐}

…”

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Diagenetic Fluid-rock Interaction and Alteration Of δ 53 Crmentioning

confidence: 99%

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Microbially induced chromium isotope fractionation and trace elements behavior in lower Cambrian microbialites from the Jaíba Member, Bambuí Basin, Brazil

et al. 2020

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Release from biogenic particles, benthic fluxes, and deep water circulation control Cr and δ 53 Cr distributions in the ocean interior

Janssen

Rickli

Abbott

et al. 2021

Preprint

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Chromium (Cr) has shown promise as a paleoceanographic proxy due to the redox-driven control of dissolved Cr concentrations ([Cr]) and stable isotope composition (δ 53 Cr). To improve the mechanistic understanding of Cr cycling in the modern ocean and strengthen its potential proxy applications, we present new data from regeneration incubations, bottom and sediment pore waters, and a compilation of intermediate and deep water data. While Cr removal and biological export from the surface ocean is associated with organic carbon export, the deep water release of dissolved Cr from sinking particles is not directly dependent on organic carbon respiration, as indicated by differing trends between Cr, oxygen utilization and the regeneration of organic-associated macronutrients (e.g. N, P). Pore water and bottom water data demonstrate that benthic Cr fluxes are locally important and may be significant globally. The pore water dissolved Cr flux at our CaCO 3 -rich site is likely driven by the re-release of Cr scavenged from the water column by sinking particles, with minor contributions from lithogenic phases. We argue this is consistent with the highest open ocean [Cr] to date being found in the water column below oxygen minimum zones, likely reflecting the release of scavenged Cr in deep waters or surface sediments. Chromium released from suspended particles and surface sediments follows the global δ 53 Cr-[Cr] array, supporting the proposed role of biological export and regeneration in shaping global Cr and δ 53 Cr distributions. Global intermediate and deep water [Cr], δ 53 Cr and Cr:macronutrient relationships are thus shaped by a synergy of circulation patterns, water mass mixing, a deep Cr regeneration cycle, and benthic Cr sources. A biogenic control on global Cr distributions indicates that sedimentary Cr records may reflect biogenic as well as O 2 -dependent processes, while more research is needed to assess sediment Cr record fidelity based on an active diagenetic cycle.

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Metal stable isotopes in the marine realm

Little,

de Souza,

Xie

2025

Treatise on Geochemistry

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Chromium isotopes in marine hydrothermal sediments

Abstract: This is a repository copy of Chromium isotopes in marine hydrothermal sediments.

Cited by 23 publications

References 70 publications

Microbially induced chromium isotope fractionation and trace elements behavior in lower Cambrian microbialites from the Jaíba Member, Bambuí Basin, Brazil

Microbially induced chromium isotope fractionation and trace elements behavior in lower Cambrian microbialites from the Jaíba Member, Bambuí Basin, Brazil

Release from biogenic particles, benthic fluxes, and deep water circulation control Cr and δ 53 Cr distributions in the ocean interior

Metal stable isotopes in the marine realm

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