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dc.contributor.authorGomes, Manuela
dc.contributor.authorFike, D
dc.contributor.authorBergmann, K
dc.contributor.authorJones, C
dc.contributor.authorKnoll, Andrew
dc.date.accessioned2019-09-06T11:18:12Z
dc.date.issued2017-10-19
dc.identifier.citationGomes ML, DA Fike, KD Bergmann, C Jones, and AH Knoll. 2018. Environmental Insights From High-Resolution (SIMS) Sulfur Isotope Analyses of Sulfides in Proterozoic Microbialites With Diverse Mat Textures. Geobiology 16, no. 1 (January): 17-34.en_US
dc.identifier.issn1472-4677en_US
dc.identifier.urihttp://nrs.harvard.edu/urn-3:HUL.InstRepos:41292726*
dc.description.abstractIn modern microbial mats, hydrogen sulfide shows pronounced sulfur isotope (δ34 S) 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 δ34 S patterns and bulk δ34 Spyrite values. We report μm-scale δ34 S patterns in Proterozoic samples with well-preserved microbial mat textures. We show a well-defined relationship between δ34 S values and sulfide mineral grain size and type. Small pyrite grains (<25 μm) span a large range, tending toward high δ34 S values (-54.5‰ to 11.7‰, mean: -14.4‰). Larger pyrite grains (>25 μm) have low but equally variable δ34 S values (-61.0‰ to -10.5‰, mean: -44.4‰). In one sample, larger sphalerite grains (>35 μm) have intermediate and essentially invariant δ34 S 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 δ34 S values. In another stage, large sphalerite grains with low δ34 S 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 δ34 Ssulfide values. We do not see evidence for significant 34 S-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 δ34 S values measured for individual pyrite grains. Fine-scale analyses of δ34 Spyrite patterns can thus be used to extract environmental information from ancient microbial mats and aid in the interpretation of bulk δ34 Spyrite records.en_US
dc.description.sponsorshipEarth and Planetary Sciencesen_US
dc.language.isoen_USen_US
dc.publisherWileyen_US
dash.licenseMETA_ONLY
dc.titleEnvironmental Insights From High-Resolution (SIMS) Sulfur Isotope Analyses of Sulfides in Proterozoic Microbialites With Diverse Mat Texturesen_US
dc.typeJournal Articleen_US
dc.description.versionVersion of Recorden_US
dc.relation.journalGeobiologyen_US
dash.depositing.authorKnoll, Andrew
dc.date.available2019-09-06T11:18:12Z
dash.workflow.commentsFAR2017en_US
dash.funder.nameNASA Astrobiology Instituteen_US
dash.funder.nameNSF Major Research Instrumentationen_US
dash.funder.nameDOE/BER Bioimaging Technologyen_US
dash.funder.award1229370en_US
dash.funder.awardDE-SC0014613en_US
dc.identifier.doi10.1111/gbi.12265
dc.source.journalGeobiology
dash.source.volume16;1
dash.source.page17-34
dash.contributor.affiliatedGomes, Manuela
dash.contributor.affiliatedKnoll, Andrew


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