Marine ferromanganese oxide: A potentially important sink of light chromium isotopes?

Wei, Wei; Chen, Tianyu; Klaebe, Robert; Liu, Huan; Li, Da; Wei, Guang‐Yi

doi:10.1016/j.chemgeo.2018.08.006

Cited by 36 publications

(25 citation statements)

References 83 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…250 and 500 µm), the variability in foraminiferal Cr isotopes reported by Wang et al (2017) can be explained by potential differences in the sizes of the foraminifera analysed (Figure 8). The negative modelled δ 53 Cr values for foraminifera smaller than approximately 250 µm are similar to the δ 53 Cr composition of ferromanganese crusts, which ranges from -0.85 to -0.15‰ (Wei et al, 2018), while modelled foraminiferal δ 53 Cr compositions for larger specimens are more similar to seawater δ 53 Cr (Figure 8; Bonnand et al, 2013;Scheiderich et al, 2015;Paulukat et al, 2016;Goring-Harford et al, 2018). Foraminifera larger than 500 µm are therefore more likely to record a primary Cr signature, with a maximum isotopic offset of 0.1 -0.2‰ (Figure 8).…”

Section: Chromium Isotopic Composition Of Core-top Planktic Foraminiferasupporting

confidence: 58%

Post-depositional overprinting of chromium in foraminifera

Remmelzwaal

Sadekov

Parkinson

et al. 2019

Earth and Planetary Science Letters

View full text Add to dashboard Cite

Present-day ocean deoxygenation has major implications for marine ecosystems and biogeochemical cycling in the oceans. Chromium isotopes are used as a proxy to infer changes in past oceanic redox state. Chromium isotopes in carbonates, including the prime proxy carrier foraminifera, were initially thought to record the seawater composition during crystallisation. However, the uptake of Cr into foraminiferal tests and carbonates is still poorly understood and recent studies question this assumption. We assess whether Cr in foraminiferal calcite is taken up during biomineralisation, has a postdepositional origin or is a combination of the two. Laser Ablation-MC-ICP-MS analyses and NanoSIMS imaging of individual tests were used to characterise the distribution of Cr in both planktic and benthic foraminifera. Foraminifera in sediment core-top samples have up to two orders of magnitude more Cr than sediment trap, plankton net, and culture samples. In cultured specimens, Cr is incorporated in foraminiferal tests at low concentrations (0.04-0.13 ppm) with a distribution coefficient of ~250 ± 43 (2SE) which is an upper estimate due to substantial loss of dissolved Cr during the experiment. Part of the Cr signal in sedimentary foraminifera may be primary, but this primary signal is likely often overprinted by the uptake of Cr from bottom and pore waters. In sediment samples, there is no significant isotopic offset between individual species and bulk foraminiferal calcite from the same size fraction. The >500 µm fraction has a heavier isotopic composition than the smaller 250-500 µm fraction with an offset of-0.3 to-0.5‰ due to an increase in surface area to volume. We propose that Cr in foraminifera is predominantly post-depositional and records bottom/pore water signals. This is contrary to current interpretations of the foraminiferal Cr isotope proxy as a surface seawater redox proxy.

show abstract

Section: Chromium Isotopic Composition Of Core-top Planktic Foraminiferasupporting

confidence: 58%

Post-depositional overprinting of chromium in foraminifera

Remmelzwaal

Sadekov

Parkinson

et al. 2019

Earth and Planetary Science Letters

View full text Add to dashboard Cite

show abstract

“…The light δ 53 Cr values of the hydrothermal sediments at site are unique compared to most oxygenated marine sediments studied to date (Bonnand et al, 2013;Gueguen et al, 2016;Reinhard et al, 2014;Wei et al, 2018). Based on our results from DSDP site 598, we argue that partial reduction of seawater Cr(VI) and oxidative diagenesis combine to leave hydrothermal sediments isotopically light (depleted relative to the ISE).…”

Section: Isotopically Light Cr In Hydrothermal Sedimentsmentioning

confidence: 70%

“…al. (2017);Berger and Frei (2014),Wei et al (2018)), and here through Cr redox cycling in hydrothermal plume fallout sediments. Examination of existing δ 53 Cr records reveals occurrences of isotopically light δ 53 Cr values in Neoproterozoic hydrothermal sediments(Sial et al, 2015), implying deposition from oxygenated deep ocean waters at this time.…”

mentioning

confidence: 89%

See 1 more Smart Citation

Chromium isotopes in marine hydrothermal sediments

et al. 2019

View full text Add to dashboard Cite

show abstract

“…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%

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

et al. 2020

Self Cite

View full text Add to dashboard Cite

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.

show abstract

Marine ferromanganese oxide: A potentially important sink of light chromium isotopes?

Cited by 36 publications

References 83 publications

Post-depositional overprinting of chromium in foraminifera

Post-depositional overprinting of chromium in foraminifera

Chromium isotopes in marine hydrothermal sediments

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

Contact Info

Product

Resources

About