Sulfur isotope fractionation between aqueous and carbonate-associated sulfate in abiotic calcite and aragonite

Barkan, Yigal; Paris, Guillaume; Webb, Samuel M.; Adkins, Jess F.; Halevy, Itay

doi:10.1016/j.gca.2020.03.022

Cited by 36 publications

(25 citation statements)

References 101 publications

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“…We initially chose these samples as the best candidates for retaining Archean CAS because they show no sign of post-exhumation oxidation, they contain only traces of disseminated pyrite, and they display no petrographic evidence of deformation or metamorphic alteration (Paris et al, 2014), only reaching low-grade greenschist facies (Miyano and Beukes, 1984). Overall, the sulfate content of those rocks (roughly 10 to 50 ppm) is consistent with precipitation of inorganic aragonite in seawater with sulfate concentrations around 100 µmol/L or precipitation calcite at concentrations lower than 30 µmol/L (Barkan et al, 2020), a range that agrees with existing seawater sulfate concentration estimates for the Neoarchean (Crowe et al, 2014;Fakhraee et al, 2018). However, no constraints exists on dolomite, or during the aragonite-calcite diagenetic inversion (except during meteoric diagenesis, Gill et al, 2008).…”

Section: Does Post-depositional History Affect the Sulfur Isotopic Sisupporting

confidence: 75%

Deposition of sulfate aerosols with positive Δ33S in the Neoarchean

Paris

Fischer

Johnson

et al. 2020

Geochimica et Cosmochimica Acta

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Section: Does Post-depositional History Affect the Sulfur Isotopic Sisupporting

confidence: 75%

Deposition of sulfate aerosols with positive Δ33S in the Neoarchean

Paris

Fischer

Johnson

et al. 2020

Geochimica et Cosmochimica Acta

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“…To a major extent, sulphate is associated with the mineral part of the shell (as CAS; Dauphin et al, 2003; 2005; Fichtner et al, 2018; Perrin et al, 2017; Tamenori et al, 2014). During CAS incorporation in aragonite, the δ 34 S SO4 is enriched by 1‰ (Barkan et al, 2020). The fact that the δ 34 S CAS value in the A. islandica shell is not 1‰ higher but instead slightly lower than the primary seawater signal of 21.2‰ (Johnston et al, 2014) can be explained by a weak vital effect during CAS incorporation, causing slightly depleted values.…”

Section: Resultsmentioning

confidence: 99%

“… The shell experienced a preferential loss of low δ 34 S CAS values, and the δ 34 S CAS moved towards equilibrium with the δ 34 S SO4 of the incubation medium. Barkan et al (2020) reported an isotopic enrichment of 1‰ for δ 34 S CAS in aragonite compared to aqueous sulphate. However, because of the ongoing organic processes in and around the shell, it is purely speculative to what extent an equilibrium between aragonitic shell and medium could develop. In the anoxic sediment microbial sulphate reduction (MSR) occurred, which led to a 34 S‐enrichment in the aqueous sulphate.…”

Section: Resultsmentioning

confidence: 99%

“…The shell experienced a preferential loss of low δ 34 S-CAS values, and the δ 34 S CAS moved towards equilibrium with the δ 34 S SO4 of the incubation medium. Barkan et al (2020) Ultimately, any alteration of CAS requires dissolution and re-precipitation of the host carbonate. However, although dissolution features along the segment surfaces were observed via SEM (Lange et al, 2018), no indications of re-precipitation, for example altered δ 13 C CARB or δ 18 O CARB values or the presence of newly formed calcite (detectable via Raman spectroscopy) were found (Lange et al, 2018).…”

Section: Arctica Islandica Shells Incubated In S Sediminis Mediummentioning

confidence: 99%

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Microbial activity affects sulphur in biogenic aragonite

Fichtner

Lange

Krause

et al. 2021

The Depositional Record

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Carbonates that exhibit obvious diagenetic alteration are usually excluded as archives in palaeoenvironmental studies. However, the potential impact of microbial alteration during early diagenesis is still poorly explored. To investigate the sensitivity of sulphur concentration, distribution, oxidation state and isotopic composition in marine aragonite to microbial alteration, Arctica islandica bivalves and Porites sp. corals were experimentally exposed to anaerobic microbial activity. The anoxic incubation media included a benthic bacterial strain Shewanella sediminis and a natural anoxic sediment slurry with a natural microbial community of unknown species. Combined fluorescence microscopy and synchrotron‐based analysis of the sulphur distribution and oxidation state enabled a comparison of organic matter and sulphur content in the two materials. Results revealed a higher proportion of reduced sulphur species and locally stronger fluorescence within the pristine bivalve shell compared to the pristine coral skeleton. Within the pristine bivalve specimen, reduced sulphur was enriched in layers along the inner shell margin. After incubation in the anoxic sediment slurry, this region revealed rust‐brown staining and a patchy S2‐ distribution pattern rather than S2‐‐layers. Another effect on sulphur distribution was rust‐brown coloured fibres along one growth line, revealing a locally higher proportion of sulphur. The δ34S value of carbonate‐associated sulphate remained largely unaffected by both incubation media, but a lower δ34S value of water‐soluble sulphate reflected the degradation of insoluble organic matter by microbes in both experiments. No significant alteration was detected in the coral samples exposed to microbial alteration. The data clearly identified a distinct sensitivity of organically bound sulphur in biogenic aragonite to microbial alteration even when ‘traditional’ geochemical proxies such as δ18OCARB or δ13CCARB in the carbonate did not show any effect. Differences in the intensity of microbial alteration documented are probably due to inherent variations in the concentration and nature of original organic compositions in the samples.

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“…A minor amount of sulfate is incorporated into biogenic and abiogenic carbonate phases. Biogenic carbonates often contain part‐per‐thousand sulfate by mass, while inorganic cements typically contain hundreds of parts‐per‐million (Barkan et al, 2020; Busenberg & Plummer, 1985; Giri & Swart, 2019; Paris, Fehrenbacher, et al, 2014; Staudt & Schoonen, 1995). Recent sediments from various peritidal carbonate platform environments include CAS with δ 34 S values similar to modern seawater, which suggests that marine carbonate rocks may preserve sulfate and its δ 34 S from ancient seawater (Lyons et al, 2004).…”

Section: Discussionmentioning

confidence: 99%

Variability in Sulfur Isotope Records of Phanerozoic Seawater Sulfate

Present

Adkins

Fischer

2020

Geophysical Research Letters

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The δ 34 S of seawater sulfate reflects processes operating at the nexus of sulfur, carbon, and oxygen cycles. However, knowledge of past seawater sulfate δ 34 S values must be derived from proxy materials that are impacted differently by depositional and postdepositional processes. We produced new time series estimates for the δ 34 S value of seawater sulfate by combining 6,710 published data from three sedimentary archives-marine barite, evaporites, and carbonate-associated sulfate-with updated age constraints on the deposits. Robust features in multiple records capture temporal trends in the δ 34 S value of seawater and its interplay with other Phanerozoic geochemical and stratigraphic trends. However, high-frequency discordances indicate that each record is differentially prone to depositional biases and diagenetic overprints. The amount of noise, quantified from the variograms of each record, increases with age for all δ 34 S proxies, indicating that postdepositional processes obscure detailed knowledge of seawater sulfate's δ 34 S value deeper in time. Plain Language Summary Sedimentary rocks deposited in ancient marine basins preserve a record of seawater composition. We compare the sulfur isotopic composition of three sedimentary materials that contain sulfate-a major ion in seawater important for carbon and oxygen cycling. Evaporite salts, the mineral barite, and trace sulfate in limestone each reveal the same first-order trends over the last 541 × 10 6 years and also display substantial shorter-order discrepancies that reflect how the materials capture and store paleooceanographic information. These discrepancies partially obscure understanding of the relationship between life, ocean chemistry, and climate.

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Sulfur isotope fractionation between aqueous and carbonate-associated sulfate in abiotic calcite and aragonite

Cited by 36 publications

References 101 publications

Deposition of sulfate aerosols with positive Δ33S in the Neoarchean

Deposition of sulfate aerosols with positive Δ33S in the Neoarchean

Microbial activity affects sulphur in biogenic aragonite

Variability in Sulfur Isotope Records of Phanerozoic Seawater Sulfate

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