globalchange  > 气候变化与战略
DOI: 10.1016/j.epsl.2020.116534
论文题名:
The role of authigenic carbonate in Neoproterozoic carbon isotope excursions
作者: Laakso T.A.; Schrag D.P.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2020
卷: 549
语种: 英语
中文关键词: authigenic carbonate ; carbon isotopes ; Neoproterozoic
英文关键词: Budget control ; Carbonates ; Carbonation ; Isotopes ; Seawater effects ; Sulfur compounds ; Authigenic carbonates ; Carbon isotope excursions ; Diffusion-reaction model ; Dissolved inorganic carbon ; Geochemical conditions ; Isotopic fractionations ; Large-scale precipitation ; Sulfate concentrations ; Organic carbon ; authigenic mineral ; carbon isotope ; carbonate rock ; concentration (composition) ; dissolved inorganic carbon ; isotopic composition ; isotopic fractionation ; Proterozoic ; sedimentary rock
英文摘要: Sedimentary carbonates from the Neoproterozoic Era host some of the largest carbon isotope excursions in the geological record, in some cases as large as 12‰ to 15‰. The origin of these signals remains a matter of debate – including whether they reflect local diagenetic effects, or record changes in the dissolved inorganic carbon (DIC) of global seawater that are indicative of shifts in the larger carbon cycle. Producing such changes through oxidation of organic carbon or methane requires unreasonably large fluxes that imply massive perturbations to carbon and oxygen budgets that are not observed. We present a plausible way to drive large changes in the δ13C of the global ocean via large-scale precipitation of isotopically fractionated authigenic carbonates distributed globally at modest concentrations in terrigenous sediments, particularly if the isotopic fractionation of authigenic carbonate shifts rapidly relative to average marine carbonate. We suggest that changes in the fractionation associated with authigenic carbonate precipitation could therefore be responsible for at least some of the variability in isotopic records drawn from primary marine carbonate. Using a diffusion-reaction model, we find that oscillations in sulfate concentrations are one mechanism for altering the isotopic composition of authigenic carbonates, thus forcing abrupt changes in seawater δ13C. This mechanism is particularly effective under the geochemical conditions that likely prevailed during the Neoproterozoic. A sulfate-driven, authigenic origin for Neoproterozoic carbon isotope excursions makes testable predictions for the expression of the anomaly over depth transects, and for the evolution of δ34S through such events. © 2020 Elsevier B.V.
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资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/165089
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作者单位: Department of Earth and Planetary Sciences, Harvard University, 20 Oxford St., Cambridge, MA 02139, United States

Recommended Citation:
Laakso T.A.,Schrag D.P.. The role of authigenic carbonate in Neoproterozoic carbon isotope excursions[J]. Earth and Planetary Science Letters,2020-01-01,549
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