Stable chromium isotope compositions of hydrogenetic ferromanganese crusts potentially linked to primary productivity

Wang, Xiangli; Zhu, Jiang; Wu, Ganguo; Liu, Wenjing; Chen, Lin; Yang, Wei; Zhou, Xiqiang; Hein, James R.

doi:10.1016/j.chemgeo.2023.121613

Cited by 2 publications

(2 citation statements)

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“…Recent research has revealed negative δ 53 Cr values in marine ferromanganese crusts ( 0.42‰ on average; Wei et al, 2018) and hydrothermal sediments ( 0.36‰ on average; Bauer et al, 2019). The negative δ 53 Cr values in Fe-Mn crusts were attributed to the adsorption of Cr(VI) or Cr (III) onto Mn-oxides (Wang et al, 2023;Wei et al, 2018). Bauer et al (2019) suggested that the partial reduction of Cr(VI) by Fe(II) imparts a light δ 53 Cr signature in hydrothermal sediments.…”

Section: Seafloor Weatheringmentioning

confidence: 99%

“…The overall Cr isotope fractionation during Cr removal from seawater has been proposed to be approximately −0.8‰, with light Cr isotopes removed from seawater, likely linked to the reduction of Cr(VI) to Cr(III) (e.g., Goring‐Harford et al., 2018; Huang et al., 2021; Janssen et al., 2020, 2021; Moos et al., 2020; Nasemann et al., 2020; Rickli et al., 2019; Scheiderich et al., 2015; Wang, 2021). The adsorption of Cr(VI) onto ferromanganese crusts, and its incorporation into hydrothermal sediments have also been proposed to remove light Cr isotopes from seawater (Bauer et al., 2019; Wang et al., 2023; Wei et al., 2018). However, the elemental and isotope fractionation of Cr during seafloor alteration has been much less examined (Farkaš et al., 2013; Wang et al., 2016).…”

Section: Introductionmentioning

confidence: 99%

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Stable Chromium Isotope Fractionation During the Alteration of Abyssal Peridotite: Implications for Marine Chromium Isotope Mass Balance

Liu,

Xu,

et al. 2024

JGR Solid Earth

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The stable chromium isotope system has been widely used as a redox proxy to reconstruct the oxygenation history of ocean atmosphere systems. However, the Cr isotope mass balance in modern oceans (i.e., inputs and outputs) remains poorly constrained. To investigate the influence of seawater‐peridotite reaction on the global marine Cr isotope mass balance, we report high‐precision Cr isotope data (δ53Cr) on a series of fresh and altered abyssal peridotites from the Gakkel Ridge and the Southwest Indian Ridge (SWIR). The least altered peridotites give a δ53Cr value of −0.08 ± 0.06‰ (2SD, n = 4) for the oceanic mantle which is consistent with the established δ53Cr of the Bulk Silicate Earth. Compared to fresh peridotites, a subset of altered peridotites exhibit a loss of isotopically light Cr with relatively positive δ53Cr values (up to 0.04‰). These altered peridotites are characterized by significant Cr loss and likely have been subject to serpentinization. By contrast, seafloor weathering has limited influence on the Cr concentrations and isotopic compositions of the altered peridotites. Monte Carlo (MC) simulations of marine alteration suggest a net Cr flux into seawater from altered abyssal peridotites of ∼3.5 × 108 mol/yr, which is on the same order of magnitude as the riverine input flux of 108–109 mol/yr. Furthermore, the MC results suggest that the peridotite‐sourced net Cr flux has a negative δ53Cr signature (−0.33 ± 0.21‰, 2SD). Thus, seawater‐peridotite interactions must be considered when evaluating the modern oceanic Cr isotope mass balance.

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