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Gerard Muyzer - One of the best experts on this subject based on the ideXlab platform.
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Metagenomes and metatranscriptomes shed new light on the microbial-mediated Sulfur Cycle in a Siberian soda lake.
BMC biology, 2019Co-Authors: Charlotte D. Vavourakis, Maliheh Mehrshad, Cherel Balkema, Rutger L. Van Hall, Adrian-Ştefan Andrei, Rohit Ghai, Dimitry Y. Sorokin, Gerard MuyzerAbstract:The planetary Sulfur Cycle is a complex web of chemical reactions that can be microbial-mediated or can occur spontaneously in the environment, depending on the temperature and pH. Inorganic Sulfur compounds can serve as energy sources for specialized prokaryotes and are important substrates for microbial growth in general. Here, we investigate dissimilatory Sulfur cycling in the brine and sediments of a southwestern Siberian soda lake characterized by an extremely high pH and salinity, combining meta-omics analyses of its uniquely adapted highly diverse prokaryote communities with biogeochemical profiling to identify key microbial players and expand our understanding of Sulfur cycling under haloalkaline conditions. Peak microbial activity was found in the top 4 cm of the sediments, a layer with a steep drop in oxygen concentration and redox potential. The majority of Sulfur was present as sulfate or iron sulfide. Thiosulfate was readily oxidized by microbes in the presence of oxygen, but oxidation was partially inhibited by light. We obtained 1032 metagenome-assembled genomes, including novel population genomes of characterized colorless Sulfur-oxidizing bacteria (SOB), anoxygenic purple Sulfur bacteria, heterotrophic SOB, and highly active lithoautotrophic sulfate reducers. Surprisingly, we discovered the potential for nitrogen fixation in a new genus of colorless SOB, carbon fixation in a new species of phototrophic Gemmatimonadetes, and elemental Sulfur/sulfite reduction in the “Candidatus Woesearchaeota.” Polysulfide/thiosulfate and tetrathionate reductases were actively transcribed by various (facultative) anaerobes. The recovery of over 200 genomes that encoded enzymes capable of catalyzing key reactions in the inorganic Sulfur Cycle indicates complete cycling between sulfate and sulfide at moderately hypersaline and extreme alkaline conditions. Our results suggest that more taxonomic groups are involved in Sulfur dissimilation than previously assumed.
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The Microbial Sulfur Cycle at Extremely Haloalkaline Conditions of Soda Lakes
Frontiers in microbiology, 2011Co-Authors: D. Y. Sorokin, J.g. Kuenen, Gerard MuyzerAbstract:Soda lakes represent a unique ecosystem with extremely high pH (up to 11) and salinity (up to saturation) due to the presence of high concentrations of sodium carbonate in brines. Despite these double extreme conditions, most of the lakes are highly productive and contain a fully functional microbial system. The microbial Sulfur Cycle is among the most active in soda lakes. One of the explanations for that is high-energy efficiency of dissimilatory conversions of inorganic Sulfur compounds, both oxidative and reductive, sufficient to cope with costly life at double extreme conditions. The oxidative part of the Sulfur Cycle is driven by chemolithoautotrophic haloalkaliphilic Sulfur-oxidizing bacteria (SOB), which are unique for soda lakes. The haloalkaliphilic SOB are present in the surface sediment layer of various soda lakes at high numbers of up to 106 viable cells/cm3. The culturable forms are so far represented by four novel genera within the Gammaproteobacteria, including the genera Thioalkalivibrio, Thioalkalimicrobium, Thioalkalispira, and Thioalkalibacter. The latter two were only found occasionally and each includes a single species, while the former two are widely distributed in various soda lakes over the world. The genus Thioalkalivibrio is the most physiologically diverse and covers the whole spectrum of salt/pH conditions present in soda lakes. Most importantly, the dominant subgroup of this genus is able to grow in saturated soda brines containing 4 M total Na+ – a so far unique property for any known aerobic chemolithoautotroph. Furthermore, some species can use thiocyanate as a sole energy source and three out of nine species can grow anaerobically with nitrogen oxides as electron acceptor. The reductive part of the Sulfur Cycle is active in the anoxic layers of the sediments of soda lakes. The in situ measurements of sulfate reduction rates and laboratory experiments with sediment slurries using sulfate, thiosulfate, or elemental Sulfur as electron acceptors demonstrated relatively high sulfate reduction rates only hampered by salt-saturated conditions. However, the highest rates of sulfidogenesis were observed not with sulfate, but with elemental Sulfur followed by thiosulfate. Formate, but not hydrogen, was the most efficient electron donor with all three Sulfur electron acceptors, while acetate was only utilized as an electron donor under Sulfur-reducing conditions. The native sulfidogenic populations of soda lakes showed a typical obligately alkaliphilic pH response, which corresponded well to the in situ pH conditions. Microbiological analysis indicated a domination of three groups of haloalkaliphilic autotrophic sulfate-reducing bacteria belonging to the order Desulfovibrionales (genera Desulfonatronovibrio, Desulfonatronum, and Desulfonatronospira) with a clear tendency to grow by thiosulfate disproportionation in the absence of external electron donor even at salt-saturating conditions. Few novel representatives of the order Desulfobacterales capable of heterotrophic growth with volatile fatty acids and alcohols at high pH and moderate salinity have also been found, while acetate oxidation was a function of a specialized group of haloalkaliphilic Sulfur-reducing bacteria, which belong to the phylum Chrysiogenetes.
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dethiobacter alkaliphilus gen nov sp nov and deSulfurivibrio alkaliphilus gen nov sp nov two novel representatives of reductive Sulfur Cycle from soda lakes
Extremophiles, 2008Co-Authors: D. Y. Sorokin, T P Tourova, M Mussmann, Gerard MuyzerAbstract:Anaerobic enrichments with H2 as electron donor and thiosulfate/polysulfide as electron acceptor at pH 10 and 0.6 M total Na+ yielded two non sulfate-reducing representatives of reductive Sulfur Cycle from soda lake sediments. Strain AHT 1 was isolated with thiosulfate as the electron acceptor from north–eastern Mongolian soda lakes and strain AHT 2—with polysulfide as the electron acceptor from Wadi al Natrun lakes in Egypt. Both isolates represented new phylogenetic lineages: AHT 1—within Clostridiales and AHT 2—within the Deltaproteobacteria. Both bacteria are obligate anaerobes with respiratory metabolism. Both grew chemolithoautotrophically with H2 as the electron donor and can use thiosulfate, elemental Sulfur and polysulfide as the electron acceptors. AHT 2 also used nitrate as acceptor, reducing it to ammonia. During thiosulfate reduction, AHT 1 excreted sulfite. dsrAB gene was not found in either strain. Both strains were moderate salt-tolerant (grow up to 2 M total Na+) true alkaliphiles (grow between pH 8.5 and 10.3). On the basis of the phenotypic and phylogenetic data, strains AHT 1 and AHT 2 are proposed as new genera and species Dethiobacter alkaliphilus and DeSulfurivibrio alkaliphilus, respectively.
Aryeh Feinberg - One of the best experts on this subject based on the ideXlab platform.
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Improved tropospheric and stratospheric Sulfur Cycle in the aerosol–chemistry–climate model SOCOL-AERv2
Geoscientific Model Development, 2019Co-Authors: Aryeh Feinberg, Timofei Sukhodolov, Eugene Rozanov, Thomas Peter, Lenny H. E. Winkel, Andrea StenkeAbstract:Abstract. SOCOL-AERv1 was developed as an aerosol–chemistry–climate model to study the stratospheric Sulfur Cycle and its influence on climate and the ozone layer. It includes a sectional aerosol model that tracks the sulfate particle size distribution in 40 size bins, between 0.39 nm and 3.2 µm . Sheng et al. ( 2015 ) showed that SOCOL-AERv1 successfully matched observable quantities related to stratospheric aerosol. In the meantime, SOCOL-AER has undergone significant improvements and more observational datasets have become available. In producing SOCOL-AERv2 we have implemented several updates to the model: adding interactive deposition schemes, improving the sulfate mass and particle number conservation, and expanding the tropospheric chemistry scheme. We compare the two versions of the model with background stratospheric sulfate aerosol observations, stratospheric aerosol evolution after Pinatubo, and ground-based Sulfur deposition networks. SOCOL-AERv2 shows similar levels of agreement as SOCOL-AERv1 with satellite-measured extinctions and in situ optical particle counter (OPC) balloon flights. The volcanically quiescent total stratospheric aerosol burden simulated in SOCOL-AERv2 has increased from 109 Gg of Sulfur (S) to 160 Gg S, matching the newly available satellite estimate of 165 Gg S. However, SOCOL-AERv2 simulates too high cross-tropopause transport of tropospheric SO2 and/or sulfate aerosol, leading to an overestimation of lower stratospheric aerosol. Due to the current lack of upper tropospheric SO2 measurements and the neglect of organic aerosol in the model, the lower stratospheric bias of SOCOL-AERv2 was not further improved. Model performance under volcanically perturbed conditions has also undergone some changes, resulting in a slightly shorter volcanic aerosol lifetime after the Pinatubo eruption. With the improved deposition schemes of SOCOL-AERv2, simulated Sulfur wet deposition fluxes are within a factor of 2 of measured deposition fluxes at 78 % of the measurement stations globally, an agreement which is on par with previous model intercomparison studies. Because of these improvements, SOCOL-AERv2 will be better suited to studying changes in atmospheric Sulfur deposition due to variations in climate and emissions.
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improved tropospheric and stratospheric Sulfur Cycle in the aerosol chemistry climate model socol aerv2
Geoscientific Model Development, 2019Co-Authors: Timofei Sukhodolov, Aryeh Feinberg, Eugene Rozanov, Thomas Peter, Lenny H. E. Winkel, Andrea StenkeAbstract:Abstract. SOCOL-AERv1 was developed as an aerosol–chemistry–climate model to study the stratospheric Sulfur Cycle and its influence on climate and the ozone layer. It includes a sectional aerosol model that tracks the sulfate particle size distribution in 40 size bins, between 0.39 nm and 3.2 µm . Sheng et al. ( 2015 ) showed that SOCOL-AERv1 successfully matched observable quantities related to stratospheric aerosol. In the meantime, SOCOL-AER has undergone significant improvements and more observational datasets have become available. In producing SOCOL-AERv2 we have implemented several updates to the model: adding interactive deposition schemes, improving the sulfate mass and particle number conservation, and expanding the tropospheric chemistry scheme. We compare the two versions of the model with background stratospheric sulfate aerosol observations, stratospheric aerosol evolution after Pinatubo, and ground-based Sulfur deposition networks. SOCOL-AERv2 shows similar levels of agreement as SOCOL-AERv1 with satellite-measured extinctions and in situ optical particle counter (OPC) balloon flights. The volcanically quiescent total stratospheric aerosol burden simulated in SOCOL-AERv2 has increased from 109 Gg of Sulfur (S) to 160 Gg S, matching the newly available satellite estimate of 165 Gg S. However, SOCOL-AERv2 simulates too high cross-tropopause transport of tropospheric SO2 and/or sulfate aerosol, leading to an overestimation of lower stratospheric aerosol. Due to the current lack of upper tropospheric SO2 measurements and the neglect of organic aerosol in the model, the lower stratospheric bias of SOCOL-AERv2 was not further improved. Model performance under volcanically perturbed conditions has also undergone some changes, resulting in a slightly shorter volcanic aerosol lifetime after the Pinatubo eruption. With the improved deposition schemes of SOCOL-AERv2, simulated Sulfur wet deposition fluxes are within a factor of 2 of measured deposition fluxes at 78 % of the measurement stations globally, an agreement which is on par with previous model intercomparison studies. Because of these improvements, SOCOL-AERv2 will be better suited to studying changes in atmospheric Sulfur deposition due to variations in climate and emissions.
Andrea Stenke - One of the best experts on this subject based on the ideXlab platform.
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Improved tropospheric and stratospheric Sulfur Cycle in the aerosol–chemistry–climate model SOCOL-AERv2
Geoscientific Model Development, 2019Co-Authors: Aryeh Feinberg, Timofei Sukhodolov, Eugene Rozanov, Thomas Peter, Lenny H. E. Winkel, Andrea StenkeAbstract:Abstract. SOCOL-AERv1 was developed as an aerosol–chemistry–climate model to study the stratospheric Sulfur Cycle and its influence on climate and the ozone layer. It includes a sectional aerosol model that tracks the sulfate particle size distribution in 40 size bins, between 0.39 nm and 3.2 µm . Sheng et al. ( 2015 ) showed that SOCOL-AERv1 successfully matched observable quantities related to stratospheric aerosol. In the meantime, SOCOL-AER has undergone significant improvements and more observational datasets have become available. In producing SOCOL-AERv2 we have implemented several updates to the model: adding interactive deposition schemes, improving the sulfate mass and particle number conservation, and expanding the tropospheric chemistry scheme. We compare the two versions of the model with background stratospheric sulfate aerosol observations, stratospheric aerosol evolution after Pinatubo, and ground-based Sulfur deposition networks. SOCOL-AERv2 shows similar levels of agreement as SOCOL-AERv1 with satellite-measured extinctions and in situ optical particle counter (OPC) balloon flights. The volcanically quiescent total stratospheric aerosol burden simulated in SOCOL-AERv2 has increased from 109 Gg of Sulfur (S) to 160 Gg S, matching the newly available satellite estimate of 165 Gg S. However, SOCOL-AERv2 simulates too high cross-tropopause transport of tropospheric SO2 and/or sulfate aerosol, leading to an overestimation of lower stratospheric aerosol. Due to the current lack of upper tropospheric SO2 measurements and the neglect of organic aerosol in the model, the lower stratospheric bias of SOCOL-AERv2 was not further improved. Model performance under volcanically perturbed conditions has also undergone some changes, resulting in a slightly shorter volcanic aerosol lifetime after the Pinatubo eruption. With the improved deposition schemes of SOCOL-AERv2, simulated Sulfur wet deposition fluxes are within a factor of 2 of measured deposition fluxes at 78 % of the measurement stations globally, an agreement which is on par with previous model intercomparison studies. Because of these improvements, SOCOL-AERv2 will be better suited to studying changes in atmospheric Sulfur deposition due to variations in climate and emissions.
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improved tropospheric and stratospheric Sulfur Cycle in the aerosol chemistry climate model socol aerv2
Geoscientific Model Development, 2019Co-Authors: Timofei Sukhodolov, Aryeh Feinberg, Eugene Rozanov, Thomas Peter, Lenny H. E. Winkel, Andrea StenkeAbstract:Abstract. SOCOL-AERv1 was developed as an aerosol–chemistry–climate model to study the stratospheric Sulfur Cycle and its influence on climate and the ozone layer. It includes a sectional aerosol model that tracks the sulfate particle size distribution in 40 size bins, between 0.39 nm and 3.2 µm . Sheng et al. ( 2015 ) showed that SOCOL-AERv1 successfully matched observable quantities related to stratospheric aerosol. In the meantime, SOCOL-AER has undergone significant improvements and more observational datasets have become available. In producing SOCOL-AERv2 we have implemented several updates to the model: adding interactive deposition schemes, improving the sulfate mass and particle number conservation, and expanding the tropospheric chemistry scheme. We compare the two versions of the model with background stratospheric sulfate aerosol observations, stratospheric aerosol evolution after Pinatubo, and ground-based Sulfur deposition networks. SOCOL-AERv2 shows similar levels of agreement as SOCOL-AERv1 with satellite-measured extinctions and in situ optical particle counter (OPC) balloon flights. The volcanically quiescent total stratospheric aerosol burden simulated in SOCOL-AERv2 has increased from 109 Gg of Sulfur (S) to 160 Gg S, matching the newly available satellite estimate of 165 Gg S. However, SOCOL-AERv2 simulates too high cross-tropopause transport of tropospheric SO2 and/or sulfate aerosol, leading to an overestimation of lower stratospheric aerosol. Due to the current lack of upper tropospheric SO2 measurements and the neglect of organic aerosol in the model, the lower stratospheric bias of SOCOL-AERv2 was not further improved. Model performance under volcanically perturbed conditions has also undergone some changes, resulting in a slightly shorter volcanic aerosol lifetime after the Pinatubo eruption. With the improved deposition schemes of SOCOL-AERv2, simulated Sulfur wet deposition fluxes are within a factor of 2 of measured deposition fluxes at 78 % of the measurement stations globally, an agreement which is on par with previous model intercomparison studies. Because of these improvements, SOCOL-AERv2 will be better suited to studying changes in atmospheric Sulfur deposition due to variations in climate and emissions.
D. Y. Sorokin - One of the best experts on this subject based on the ideXlab platform.
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The Microbial Sulfur Cycle at Extremely Haloalkaline Conditions of Soda Lakes
Frontiers in microbiology, 2011Co-Authors: D. Y. Sorokin, J.g. Kuenen, Gerard MuyzerAbstract:Soda lakes represent a unique ecosystem with extremely high pH (up to 11) and salinity (up to saturation) due to the presence of high concentrations of sodium carbonate in brines. Despite these double extreme conditions, most of the lakes are highly productive and contain a fully functional microbial system. The microbial Sulfur Cycle is among the most active in soda lakes. One of the explanations for that is high-energy efficiency of dissimilatory conversions of inorganic Sulfur compounds, both oxidative and reductive, sufficient to cope with costly life at double extreme conditions. The oxidative part of the Sulfur Cycle is driven by chemolithoautotrophic haloalkaliphilic Sulfur-oxidizing bacteria (SOB), which are unique for soda lakes. The haloalkaliphilic SOB are present in the surface sediment layer of various soda lakes at high numbers of up to 106 viable cells/cm3. The culturable forms are so far represented by four novel genera within the Gammaproteobacteria, including the genera Thioalkalivibrio, Thioalkalimicrobium, Thioalkalispira, and Thioalkalibacter. The latter two were only found occasionally and each includes a single species, while the former two are widely distributed in various soda lakes over the world. The genus Thioalkalivibrio is the most physiologically diverse and covers the whole spectrum of salt/pH conditions present in soda lakes. Most importantly, the dominant subgroup of this genus is able to grow in saturated soda brines containing 4 M total Na+ – a so far unique property for any known aerobic chemolithoautotroph. Furthermore, some species can use thiocyanate as a sole energy source and three out of nine species can grow anaerobically with nitrogen oxides as electron acceptor. The reductive part of the Sulfur Cycle is active in the anoxic layers of the sediments of soda lakes. The in situ measurements of sulfate reduction rates and laboratory experiments with sediment slurries using sulfate, thiosulfate, or elemental Sulfur as electron acceptors demonstrated relatively high sulfate reduction rates only hampered by salt-saturated conditions. However, the highest rates of sulfidogenesis were observed not with sulfate, but with elemental Sulfur followed by thiosulfate. Formate, but not hydrogen, was the most efficient electron donor with all three Sulfur electron acceptors, while acetate was only utilized as an electron donor under Sulfur-reducing conditions. The native sulfidogenic populations of soda lakes showed a typical obligately alkaliphilic pH response, which corresponded well to the in situ pH conditions. Microbiological analysis indicated a domination of three groups of haloalkaliphilic autotrophic sulfate-reducing bacteria belonging to the order Desulfovibrionales (genera Desulfonatronovibrio, Desulfonatronum, and Desulfonatronospira) with a clear tendency to grow by thiosulfate disproportionation in the absence of external electron donor even at salt-saturating conditions. Few novel representatives of the order Desulfobacterales capable of heterotrophic growth with volatile fatty acids and alcohols at high pH and moderate salinity have also been found, while acetate oxidation was a function of a specialized group of haloalkaliphilic Sulfur-reducing bacteria, which belong to the phylum Chrysiogenetes.
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dethiobacter alkaliphilus gen nov sp nov and deSulfurivibrio alkaliphilus gen nov sp nov two novel representatives of reductive Sulfur Cycle from soda lakes
Extremophiles, 2008Co-Authors: D. Y. Sorokin, T P Tourova, M Mussmann, Gerard MuyzerAbstract:Anaerobic enrichments with H2 as electron donor and thiosulfate/polysulfide as electron acceptor at pH 10 and 0.6 M total Na+ yielded two non sulfate-reducing representatives of reductive Sulfur Cycle from soda lake sediments. Strain AHT 1 was isolated with thiosulfate as the electron acceptor from north–eastern Mongolian soda lakes and strain AHT 2—with polysulfide as the electron acceptor from Wadi al Natrun lakes in Egypt. Both isolates represented new phylogenetic lineages: AHT 1—within Clostridiales and AHT 2—within the Deltaproteobacteria. Both bacteria are obligate anaerobes with respiratory metabolism. Both grew chemolithoautotrophically with H2 as the electron donor and can use thiosulfate, elemental Sulfur and polysulfide as the electron acceptors. AHT 2 also used nitrate as acceptor, reducing it to ammonia. During thiosulfate reduction, AHT 1 excreted sulfite. dsrAB gene was not found in either strain. Both strains were moderate salt-tolerant (grow up to 2 M total Na+) true alkaliphiles (grow between pH 8.5 and 10.3). On the basis of the phenotypic and phylogenetic data, strains AHT 1 and AHT 2 are proposed as new genera and species Dethiobacter alkaliphilus and DeSulfurivibrio alkaliphilus, respectively.
Donald E. Canfield - One of the best experts on this subject based on the ideXlab platform.
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Sulfur isotopes in coal constrain the evolution of the Phanerozoic Sulfur Cycle
Proceedings of the National Academy of Sciences of the United States of America, 2013Co-Authors: Donald E. CanfieldAbstract:Sulfate is the second most abundant anion (behind chloride) in modern seawater, and its cycling is intimately coupled to the cycling of organic matter and oxygen at the Earth’s surface. For example, the reduction of sulfide by microbes oxidizes vast amounts of organic carbon and the subsequent reaction of sulfide with iron produces pyrite whose burial in sediments is an important oxygen source to the atmosphere. The concentrations of seawater sulfate and the operation of Sulfur Cycle have experienced dynamic changes through Earth’s history, and our understanding of this history is based mainly on interpretations of the isotope record of seawater sulfates and sedimentary pyrites. The isotope record, however, does not give a complete picture of the ancient Sulfur Cycle. This is because, in standard isotope mass balance models, there are more variables than constraints. Typically, in interpretations of the isotope record and in the absence of better information, one assumes that the isotopic composition of the input sulfate to the oceans has remained constant through time. It is argued here that this assumption has a constraint over the last 390 Ma from the isotopic composition of Sulfur in coal. Indeed, these compositions do not deviate substantially from the modern surface-water input to the oceans. When applied to mass balance models, these results support previous interpretations of Sulfur Cycle operation and counter recent suggestions that sulfate has been a minor player in Sulfur cycling through the Phanerozoic Eon.
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a cryptic Sulfur Cycle in oxygen minimum zone waters off the chilean coast
Science, 2010Co-Authors: Donald E. Canfield, Frank J Stewart, Bo Thamdrup, Loreto De Brabandere, Tage Dalsgaard, Edward F Delong, Niels Peter Revsbech, Osvaldo UlloaAbstract:Nitrogen cycling is normally thought to dominate the biogeochemistry and microbial ecology of oxygen-minimum zones in marine environments. Through a combination of molecular techniques and process rate measurements, we showed that both sulfate reduction and sulfide oxidation contribute to energy flux and elemental cycling in oxygen-free waters off the coast of northern Chile. These processes may have been overlooked because in nature, the sulfide produced by sulfate reduction immediately oxidizes back to sulfate. This cryptic Sulfur Cycle is linked to anammox and other nitrogen cycling processes, suggesting that it may influence biogeochemical cycling in the global ocean.
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Connections between Sulfur Cycle Evolution, Sulfur Isotopes, Sediments, and Base Metal Sulfide Deposits
Economic Geology, 2010Co-Authors: James Farquhar, Donald E. Canfield, Harry OduroAbstract:Significant links exist between the Sulfur Cycle, Sulfur geochemistry of sedimentary systems, and ore deposits over the course of Earth history. A picture emerges of an Archean and Paleoproterozoic stage of the Sulfur Cycle that has much lower levels of sulfate (
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connections between Sulfur Cycle evolution Sulfur isotopes sediments and base metal sulfide deposits
Economic Geology, 2010Co-Authors: James Farquhar, Donald E. Canfield, Nanping Wu, Harry OduroAbstract:Significant links exist between the Sulfur Cycle, Sulfur geochemistry of sedimentary systems, and ore deposits over the course of Earth history. A picture emerges of an Archean and Paleoproterozoic stage of the Sulfur Cycle that has much lower levels of sulfate (<200 μM ), carries a signal of mass-independent Sulfur, and preserves evidence for temporal and spatial heterogeneity that reflects lower amounts of Sulfur cycling than today. A second stage of ocean chemistry in the Paleoproterozoic, with higher atmospheric oxygen and oceanic sulfate at low millimolar levels, follows this stage. The isotopic record in sedimentary rocks and in sulfide-bearing ore deposits suggests abundant pyrite burial and implies a missing 34S-depleted pool that may have been lost via deep ocean deposition and possibly subduction. Proterozoic ocean chemistry appears to be quite complex. The surface waters of the Proterozoic oceans are believed to have been oxygenated, but geologic evidence from ore deposits and sedimentary rocks supports coexistence of significant sulfidic and nonsulfidic, anoxic, intermediate water and deep-water pools in the Mesoproterozoic. This stage in ocean chemistry ends with the second major global oxidation event in the latest Neoproterozoic (~600 Ma). This event started the transition to more oxygenated intermediate and deep waters, and higher but variable oceanic sulfate concentrations. The event set the scene for the formation in the Phanerozoic of the first significant MVT deposits and possibly is reflected in changes in other sedimentary rock-hosted base metal sulfide deposits.
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Evolution of the oceanic Sulfur Cycle at the end of the Paleoproterozoic
Geochimica et Cosmochimica Acta, 2006Co-Authors: David T. Johnston, Donald E. Canfield, Simon W. Poulton, Philip Fralick, Boswell A. Wing, James FarquharAbstract:Here, we present new measurements of 32 S, 33 S, 34 S, and 36 S in sedimentary sulfides and couple these measurements with modeling treatments to study the Sulfur Cycle of a late Paleoproterozoic marine basin. We target the transition in ocean chemistry from the deposition of Paleoproterozoic iron formations (Gunflint Formation, Biwabik Formation, Trommald Formation, and Mahnomen iron formations) to the inferred sulfidic ocean conditions recorded by overlying shale (Rove Formation). The data suggest that certain features of the global Sulfur Cycle, such as a control by sulfate reducing prokaryotes, and low (mM) concentrations of oceanic sulfate, were maintained across this transition. This suggests that the transition was associated with changes in the structure of the basin-scale Sulfur Cycle during deposition of these sediments. Sulfide data from the iron formations are interpreted to reflect sedimentary sulfides formed from microbial reduction of pore-water sulfate that was supplied through steady-state exchange with an overlying oceanic sulfate reservoir. The sulfide data for the euxinic Rove Formation shales reflect the operation of a Sulfur Cycle that included the loss of sulfide by a Rayleigh-like process. We suggest that the prevalence of large and variable heavy isotope enrichments observed in Rove Formation sulfide minerals reflect a sustained and significant net loss of sulfide from the euxinic water column, either as a result of a shallow chemocline and degassing to the atmosphere or as a result of a water column pyrite sink. The inclusion of 36 S measurements (in addition to 32 S, 33 S, and 34 S) illustrates the mass-dependent character of these sedimentary environments, ruling out contributions from the weathering of Archean sulfides and pointing to at least modest levels of sustained atmospheric oxygen (>10 � 5 present atmospheric levels of O2).
