Geological evolution of the marine selenium cycle: Insights from the bulk shale δ82/76Se record and isotope mass balance modeling

Mitchell, Kristen; Mansoor, Sannan Zahid; Mason, Paul R.D.; Cappellen, Philippe Van

doi:10.1016/j.epsl.2016.02.030

Cited by 22 publications

(19 citation statements)

References 83 publications

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“…In laboratory settings, both biotic and abiotic partial reduction generate isotopic fractionations of several permil, with lighter Se isotopes being preferentially enriched in reduced compounds (33). In bulk samples from natural settings, observed fractionations tend to be smaller (range from −2 to +2‰), perhaps because the isotopic signature of reduced Se gets diluted by codeposition of biologically assimilated Se in sediments (34). Still, dissimilatory reduction can alter the Se isotopic composition of residual oxyanions dissolved in seawater, and this has been documented in the Phanerozoic (35), Neoproterozoic (24), and Archean (36).…”

Section: Resultsmentioning

confidence: 99%

“…1, SI Appendix), all consistent with a near-shore depositional environment, in contrast to the TSe-and Se" refers to the isotope ratio of a designated reservoir; "Δ" refers to the isotopic fractionation associated with a designated process. Dotted arrows for Se org burial in oxic/suboxic environments signify that this process has minor significance, but in some cases may dilute sedimentary Se isotope signatures (34). See text for further discussion.…”

Section: /78mentioning

confidence: 99%

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Selenium isotopes record extensive marine suboxia during the Great Oxidation Event

Kipp

Stüeken

Bekker

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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It has been proposed that an "oxygen overshoot" occurred during the early Paleoproterozoic Great Oxidation Event (GOE) in association with the extreme positive carbon isotopic excursion known as the Lomagundi Event. Moreover, it has also been suggested that environmental oxygen levels then crashed to very low levels during the subsequent extremely negative Shunga-Francevillian carbon isotopic anomaly. These redox fluctuations could have profoundly influenced the course of eukaryotic evolution, as eukaryotes have several metabolic processes that are obligately aerobic. Here we investigate the magnitude of these proposed oxygen perturbations using selenium (Se) geochemistry, which is sensitive to redox transitions across suboxic conditions. We find that δ 82/78Se values in offshore shales show a positive excursion from 2.32 Ga until 2.1 Ga (mean +1.03 ± 0.67‰). Selenium abundances and Se/TOC (total organic carbon) ratios similarly show a peak during this interval. Together these data suggest that during the GOE there was pervasive suboxia in near-shore environments, allowing nonquantitative Se reduction to drive the residual Se oxyanions isotopically heavy. This implies O 2 levels of >0.4 μM in these settings. Unlike in the late Neoproterozoic and Phanerozoic, when negative δ 82/78Se values are observed in offshore environments, only a single formation, evidently the shallowest, shows evidence of negative δ 82/78 Se. This suggests that there was no upwelling of Se oxyanions from an oxic deep-ocean reservoir, which is consistent with previous estimates that the deep ocean remained anoxic throughout the GOE. The abrupt decline in δ 82/78 Se and Se/TOC values during the subsequent Shunga-Francevillian anomaly indicates a widespread decrease in surface oxygenation.Paleoproterozoic | trace metals | oxygen | eukaryote evolution

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Section: Resultsmentioning

confidence: 99%

Section: /78mentioning

confidence: 99%

Selenium isotopes record extensive marine suboxia during the Great Oxidation Event

Kipp

Stüeken

Bekker

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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“…Due to significant isotopic fractionation during Se oxyanion reduction (Krouse & Thode, ; Rees & Thode, ), Se isotope measurements have received increasing interest in biogeochemistry (Clark & Johnson, ; Ellis et al, ; Herbel et al, ; Johnson et al, ; Schilling et al, ) and paleoenvironmental studies (Kipp et al, ; Layton‐Matthews et al, ; Mitchell et al, ; Pogge Von Strandmann et al, ; Rouxel et al, ; Stüeken et al, a, b; Zhu et al, ). Following important analytical advancements (Elwaer & Hintelmann, ; Layton‐Matthews et al, ; Pogge von Strandmann et al, ; Rouxel et al, ; Stüeken et al, ; Zhu et al, ), Kurzawa et al () provided a precise and accurate measuring method for δ 82/76 Se with a consumption of as low as 5 ng Se, which allows the Se isotope determination of geological samples with low ng g −1 Se levels.…”

Section: Introductionmentioning

confidence: 99%

Chemical Sample Processing for Combined Selenium Isotope and Selenium‐Tellurium Elemental Investigation of the Earth's Igneous Reservoirs

Yierpan

König

Labidi

et al. 2018

Geochem Geophys Geosyst

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The redox‐sensitive, chalcophile, and volatile Se stable isotope system offers new perspectives to investigate the origin and evolution of terrestrial volatiles and the roles of magmatic and recycling processes in the development of the redox contrast between Earth's reservoirs. Selenium isotope systematics become more robust in a well‐constrained petrogenetic context as can be inferred from Se‐Te elemental signatures of sulfides and igneous rocks. In this study, we present a high‐yield chemical sample processing method that allows the determination of Se‐Te concentrations and Se isotope composition from the same sample digest of silicate rocks by hydride generation isotope dilution (ID) quadrupole inductively coupled plasma mass spectrometry (ICP‐MS) and double spike (DS) multicollector (MC)‐ICP‐MS, respectively. Our procedure yields ∼80% Se‐Te recoveries with quantitative separation of relevant interfering elements such as Ge and HG‐buffering metals. Replicate analyses of selected international reference materials yield uncertainties better than 0.11‰ (2 s.d.) on δ82/76Se and 3% (r.s.d.) on Se concentration for DS MC‐ICP‐MS determinations for as low as ∼10 ng sample Se. The precision of Se‐Te concentration measurements by ID ICP‐MS is better than 3% and 5% (r.s.d.) for total amounts of ∼0.5–1 ng Se and ∼0.2–0.5 ng Te, respectively. The basaltic reference materials have variable Se‐Te contents, but their δ82/76Se values are rather uniform (on average 0.23 ± 0.14‰; 2 s.d.) and different from the chondritic value. This altogether provides the methodology and potential to extend the limited data set of coupled Se isotope and Se‐Te elemental systematics of samples relevant to study the terrestrial igneous inventory.

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“…It is unlikely to be in the deep ocean, if that was too anoxic to support a selenium oxyanion reservoir. (Stüeken et al 2015d;Mitchell et al 2016): The 'Great Oxidation Event' around 2.4-2.3 Gyr (Lyons et al 2014) is not obviously reflected in the selenium isotope and abundance record; Proterozoic marine shales are statistically indistinguishable from those of the Neoarchean. As before, partial reduction of selenium oxyanions produced during oxidative weathering may have retained light selenium in soils, rivers and estuaries, such that the average selenium flux into the ocean was isotopically heavy.…”

Section: Selenium Isotopes In Deep Timementioning

confidence: 99%

Selenium Isotopes as a Biogeochemical Proxy in Deep Time

Stüeken

2017

Reviews in Mineralogy and Geochemistry

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Geological evolution of the marine selenium cycle: Insights from the bulk shale δ82/76Se record and isotope mass balance modeling

Cited by 22 publications

References 83 publications

Selenium isotopes record extensive marine suboxia during the Great Oxidation Event

Selenium isotopes record extensive marine suboxia during the Great Oxidation Event

Chemical Sample Processing for Combined Selenium Isotope and Selenium‐Tellurium Elemental Investigation of the Earth's Igneous Reservoirs

Selenium Isotopes as a Biogeochemical Proxy in Deep Time

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