DOI: 10.1111/gbi.12265
Scopus记录号: 2-s2.0-85040323966
论文题名: Environmental insights from high-resolution (SIMS) sulfur isotope analyses of sulfides in Proterozoic microbialites with diverse mat textures
作者: Gomes M.L. ; Fike D.A. ; Bergmann K.D. ; Jones C. ; Knoll A.H.
刊名: Geobiology
ISSN: 1472-4677
EISSN: 1472-4669
出版年: 2018
卷: 16, 期: 1 起始页码: 17
结束页码: 34
语种: 英语
Scopus关键词: desiccation
; geological record
; grain size
; hydrogen sulfide
; isotopic analysis
; isotopic fractionation
; microbial mat
; overprinting
; porewater
; Proterozoic
; pyrite
; sphalerite
; sulfate-reducing bacterium
; sulfur cycle
; sulfur isotope
Scopus学科分类: Earth and Planetary Sciences: General Earth and Planetary Sciences
; Environmental Science: General Environmental Science
; Agricultural and Biological Sciences: Ecology, Evolution, Behavior and Systematic
英文摘要: In modern microbial mats, hydrogen sulfide shows pronounced sulfur isotope (δ34S) variability over small spatial scales (~50‰ over <4 mm), providing information about microbial sulfur cycling within different ecological niches in the mat. In the geological record, the location of pyrite formation, overprinting from mat accretion, and post-depositional alteration also affect both fine-scale δ34S patterns and bulk δ34Spyrite values. We report μm-scale δ34S patterns in Proterozoic samples with well-preserved microbial mat textures. We show a well-defined relationship between δ34S values and sulfide mineral grain size and type. Small pyrite grains (<25 μm) span a large range, tending toward high δ34S values (−54.5‰ to 11.7‰, mean: −14.4‰). Larger pyrite grains (>25 μm) have low but equally variable δ34S values (−61.0‰ to −10.5‰, mean: −44.4‰). In one sample, larger sphalerite grains (>35 μm) have intermediate and essentially invariant δ34S values (−22.6‰ to −15.6‰, mean: −19.4‰). We suggest that different sulfide mineral populations reflect separate stages of formation. In the first stage, small pyrite grains form near the mat surface along a redox boundary where high rates of sulfate reduction, partial closed-system sulfate consumption in microenvironments, and/or sulfide oxidation lead to high δ34S values. In another stage, large sphalerite grains with low δ34S values grow along the edges of pore spaces formed from desiccation of the mat. Large pyrite grains form deeper in the mat at slower sulfate reduction rates, leading to low δ34Ssulfide values. We do not see evidence for significant 34S-enrichment in bulk pore water sulfide at depth in the mat due to closed-system Rayleigh fractionation effects. On a local scale, Rayleigh fractionation influences the range of δ34S values measured for individual pyrite grains. Fine-scale analyses of δ34Spyrite patterns can thus be used to extract environmental information from ancient microbial mats and aid in the interpretation of bulk δ34Spyrite records. © 2017 John Wiley & Sons Ltd Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/85023
Appears in Collections: 影响、适应和脆弱性
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作者单位: Washington University, Saint Louis, MO, United States; Harvard University, Cambridge, MA, United States; Massachusettes Institute of Technology, Cambridge, MA, United States
Recommended Citation:
Gomes M.L.,Fike D.A.,Bergmann K.D.,et al. Environmental insights from high-resolution (SIMS) sulfur isotope analyses of sulfides in Proterozoic microbialites with diverse mat textures[J]. Geobiology,2018-01-01,16(1)