DOI: 10.1016/j.epsl.2020.116201
论文题名: Evaluating a primary carbonate pathway for manganese enrichments in reducing environments
作者: Wittkop C. ; Swanner E.D. ; Grengs A. ; Lambrecht N. ; Fakhraee M. ; Myrbo A. ; Bray A.W. ; Poulton S.W. ; Katsev S.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2020
卷: 538 语种: 英语
中文关键词: carbon isotopes
; carbonates
; ferruginous lake
; manganese
; redox-stratified
英文关键词: Calcite
; Calcium carbonate
; Carbonates
; Carbonation
; Crystallization
; Dissolution
; Dissolved oxygen
; Lakes
; Manganese
; Sedimentary rocks
; Sedimentology
; Sulfur compounds
; Carbon isotopes
; Dissolved inorganic carbon
; Dissolved oxygen concentrations
; Mn concentrations
; Oxidizing conditions
; redox-stratified
; Reducing environment
; Sulfate reduction
; Manganese removal (water treatment)
; calcite
; carbon isotope
; carbonate rock
; concentration (composition)
; dissolved oxygen
; manganese
; sediment chemistry
; sediment trap
; sedimentary rock
; water column
; Minnesota
; United States
; Scomberomorus semifasciatus
英文摘要: Most manganese (Mn) enrichments in the sedimentary rock record are hosted in carbonate minerals, which are assumed to have formed by diagenetic reduction of precursor Mn-oxides, and are considered diagnostic of strongly oxidizing conditions. Here we explore an alternative model where Mn-carbonates form in redox-stratified water columns linked to calcium carbonate dissolution. In ferruginous Brownie Lake in Minnesota, USA, we document Mn-carbonates as an HCl-extractable phase present in sediment traps and in reducing portions of the water column. Mn-carbonate becomes supersaturated in the Brownie Lake chemocline where dissolved oxygen concentrations fall below 5 μM, and Mn-oxide reduction increases the dissolved Mn concentration. Supersaturation is enhanced when calcite originating from surface waters dissolves in more acidic waters at the chemocline. In the same zone, sulfate reduction and microaerobic methane oxidation add dissolved inorganic carbon (DIC) with negative δ13C. These observations demonstrate that sedimentary Mn enrichments may 1) develop from primary carbonate phases, and 2) can occur in environments with dissolved oxygen concentrations <5 μM. Primary Mn-carbonates are likely to originate in environments with high concentrations of dissolved Mn (>200 μM), and where Mn and Fe are partitioned by S cycling, photoferrotrophy, or microaerophilic Fe-oxidation. A shallow lysocline enhances Mn-carbonate production by providing additional DIC and nucleation sites for crystal growth. This carbonate model for Mn-enrichments is expected to be viable in both euxinic and ferruginous environments, and provides a more nuanced view of the relationships between Mn and carbon cycling, with applications throughout the rock record. © 2020 Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/165348
Appears in Collections: 气候变化与战略
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作者单位: Department of Chemistry and Geology, Minnesota State University, 241 Ford Hall, Mankato, MN 56001, United States; Department of Geological and Atmospheric Sciences, Iowa State University, 2337 Osborn Drive, Ames, IA 50011, United States; Large Lakes Observatory, University of Minnesota Duluth, 2205 East 5th Street, Duluth, MN 55812, United States; St. Croix Watershed Research Station, Science Museum of Minnesota, 16910 152nd St North, Marine on St. Croix, MN 55047, United States; School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, United Kingdom; Department of Physics, University of Minnesota Duluth, 1049 University Drive, Duluth, MN 55812, United States
Recommended Citation:
Wittkop C.,Swanner E.D.,Grengs A.,et al. Evaluating a primary carbonate pathway for manganese enrichments in reducing environments[J]. Earth and Planetary Science Letters,2020-01-01,538