气候变化领域集成服务门户(CCPortal): Molybdenum isotope fractionation in glacial diamictites tracks the onset of oxidative weathering of the continental crust

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DOI	10.1016/j.epsl.2020.116083
	Molybdenum isotope fractionation in glacial diamictites tracks the onset of oxidative weathering of the continental crust
	Greaney A.T.; Rudnick R.L.; Romaniello S.J.; Johnson A.C.; Gaschnig R.M.; Anbar A.D.
发表日期	2020
ISSN	0012821X
卷号	534
英文摘要	Molybdenum isotopes in twenty-four composites of glacial diamictites spanning depositional ages of 2900 to 300 Ma show a systematic shift to lighter compositions and a decrease in Mo concentration over time. The diamictites fall into three age groups relative to the Great Oxidation Event (GOE): pre-GOE (2.43 – 2.90 Ga), syn-GOE (2.20 – 2.39 Ga), and post-GOE (0.33 – 0.75 Ga). Pre-GOE composites have an average δ98MoNIST3134 of +0.03‰ (± 0.18‰), syn-GOE composites average −0.29‰ (± 0.60‰), and post-GOE composites average −0.45‰ (± 0.51‰). These groups are statistically different at p=0.05. We use the pre-GOE data to estimate the average Archean upper continental crust (UCC) δ98Mo signature as +0.03 ± 0.18‰ (2σ), which falls within the range of previous estimates of modern igneous rocks. As the diamictites represent a mixture of igneous and weathered crust, the shift to lighter Mo values over time likely reflects Mo isotope fractionation during oxidative weathering and increased retention of light Mo isotopes in weathered regolith and soils. We hypothesize that this fractionation is due to the mobilization of oxidized Mo following the GOE, and subsequent adsorption of light Mo onto Fe-Mn oxides and/or organic matter in weathered regolith. We conclude that Mo isotopes in continental weathering products record the rise of atmospheric oxygen and onset of oxidative weathering. As the regolith formed under oxidative conditions is isotopically lighter than average continental igneous rocks, mass balance dictates that Mo isotope fractionation during oxidative weathering should result in isotopically heavy groundwater and river water, which is observed in modern systems. © 2020 Elsevier B.V.
关键词	continental crust great oxidation event isotope fractionation molybdenum weathering
英文关键词	Binary alloys; Glacial geology; Groundwater; Igneous rocks; Iron alloys; Iron oxides; Isotopes; Manganese alloys; Molybdenum; Oxidation; Atmospheric oxygen; Continental crusts; Great Oxidation Event; Isotope fractionation; Molybdenum isotopes; Oxidative conditions; Oxidative weathering; Upper continental crust; Weathering; Archean; continental crust; diamictite; glacial deposit; isotopic fractionation; molybdenum; oxidation; sediment chemistry; weathering
语种	英语
来源期刊	Earth and Planetary Science Letters
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/202617
作者单位	Department of Earth Science and Earth Research Institute, University of California - Santa Barbara, Santa Barbara, CA 93106, United States; Department of Geology, University of Maryland - College Park, College Park, MD 20742, United States; School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85281, United States; Department of Earth and Planetary Sciences, University of Tennessee - Knoxville, Knoxville, TN 37996, United States; Department of Environmental, Earth and Atmospheric Sciences, University of Massachusetts - Lowell, Lowell, MA 01854, United States; School of Molecular Sciences, Arizona State University, Tempe, AZ 85281, United States
推荐引用方式 GB/T 7714	Greaney A.T.,Rudnick R.L.,Romaniello S.J.,et al. Molybdenum isotope fractionation in glacial diamictites tracks the onset of oxidative weathering of the continental crust[J],2020,534.
APA	Greaney A.T.,Rudnick R.L.,Romaniello S.J.,Johnson A.C.,Gaschnig R.M.,&Anbar A.D..(2020).Molybdenum isotope fractionation in glacial diamictites tracks the onset of oxidative weathering of the continental crust.Earth and Planetary Science Letters,534.
MLA	Greaney A.T.,et al."Molybdenum isotope fractionation in glacial diamictites tracks the onset of oxidative weathering of the continental crust".Earth and Planetary Science Letters 534(2020).