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Mimi Chen - One of the best experts on this subject based on the ideXlab platform.
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multiple Sulfur Isotope analyses support a magmatic model for the volcanogenic massive sulfide deposits of the teutonic bore volcanic complex yilgarn craton western australia
Economic Geology, 2015Co-Authors: Mimi Chen, Ian H Campbell, Yunxing Xue, Wei Tian, Trevor Ireland, Peter Holden, Raymond Alexander Fernand Cas, Patrick Calder Hayman, Ritipurna DasAbstract:We report sensitive high mass resolution ion microprobe, stable Isotopes (SHRIMP SI) multiple Sulfur Isotope analyses (32S, 33S, 34S) to constrain the sources of Sulfur in three Archean VMS deposits—Teutonic Bore, Bentley, and Jaguar—from the Teutonic Bore volcanic complex of the Yilgarn Craton, Western Australia, together with sedimentary pyrites from associated black shales and interpillow pyrites. The pyrites from VMS mineralization are dominated by mantle Sulfur but include a small amount of slightly negative mass-independent fractionation (MIF) anomalies, whereas Sulfur from the pyrites in the sedimentary rocks has pronounced positive MIF, with ∆33S values that lie between 0.19 and 6.20‰ (with one outlier at −1.62‰). The wall rocks to the mineralization include sedimentary rocks that have contributed no detectable positive MIF Sulfur to the VMS deposits, which is difficult to reconcile with the leaching model for the formation of these deposits. The Sulfur Isotope data are best explained by mixing between Sulfur derived from a magmatic-hydrothermal fluid and seawater Sulfur as represented by the interpillow pyrites. The massive sulfide lens pyrites have a weighted mean ∆33S value of −0.27 ± 0.05‰ (MSWD = 1.6) nearly identical with −0.31 ± 0.08‰ (MSWD = 2.4) for pyrites from the stringer zone, which requires mixing to have occurred below the sea floor. We employed a two-component mixing model to estimate the contribution of seawater Sulfur to the total Sulfur budget of the two Teutonic Bore volcanic complex VMS deposits. The results are 15 to 18% for both Teutonic Bore and Bentley, much higher than the 3% obtained by Jamieson et al. (2013) for the giant Kidd Creek deposit. Similar calculations, carried out for other Neoarchean VMS deposits give value between 2% and 30%, which are similar to modern hydrothermal VMS deposits. We suggest that multiple Sulfur Isotope analyses may be used to predict the size of Archean VMS deposits and to provide a vector to ore deposit but further studies are needed to test these suggestions.
Das Ritipurna - One of the best experts on this subject based on the ideXlab platform.
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Multiple Sulfur Isotope Analyses Support a Magmatic Model for the Volcanogenic Massive Sulfide Deposits of the Teutonic Bore Volcanic Complex, Yilgarn Craton, Western Australian
ECONOMIC GEOLOGY, 2015Co-Authors: Chen Mimi, Campbell, Ian H., Xue Yunxing, Tian Wei, Ireland, Trevor R., Holden Peter, Cas, Raymond A. F., Hayman, Patrick C., Das RitipurnaAbstract:We report sensitive high mass resolution ion microprobe, stable Isotopes (SHRIMP SI) multiple Sulfur Isotope analyses (S-32, S-33, S-34) to constrain the sources of Sulfur in three Archean VMS deposits Teutonic Bore, Bentley, and Jaguar from the Teutonic Bore volcanic complex of the Yilgarn Craton, Western Australia, together with sedimentary pyrites from associated black shales and interpillow pyrites. The pyrites from VMS mineralization are dominated by mantle Sulfur but include a small amount of slightly negative mass-independent fractionation (MIF) anomalies, whereas Sulfur from the pyrites in the sedimentary rocks has pronounced positive MIF, with Delta S-33 values that lie between 0.19 and 6.20 parts per thousand (with one outlier at 1.62 parts per thousand). The wall rocks to the mineralization include sedimentary rocks that have contributed no detectable positive MIF Sulfur to the VMS deposits, which is difficult to reconcile with the leaching model for the formation of these deposits. The Sulfur Isotope data are best explained by mixing between Sulfur derived from a magmatic-hydrothermal fluid and seawater Sulfur as represented by the interpillow pyrites. The massive sulfide lens pyrites have a weighted mean Delta S-33 value of -0.27 +/- 0.05 parts per thousand (MSWD = 1.6) nearly identical with -0.31 +/- 0.08 parts per thousand (MSWD = 2.4) for pyrites from the stringer zone, which requires mixing to have occurred below the sea floor. We employed a two component mixing model to estimate the contribution of seawater Sulfur to the total Sulfur budget of the two Teutonic Bore volcanic complex VMS deposits. The results are 15 to 18% for both Teutonic Bore and Bentley, much higher than the 3% obtained by Jamieson et al. (2013) for the giant Kidd Creek deposit. Similar calculations, carried out for other Neoarchean VMS deposits give value between 2% and 30%, which are similar to modern hydrothermal VMS deposits. We suggest that multiple Sulfur Isotope analyses may be used to predict the size of Archean VMS deposits and to provide a vector to ore deposit but further studies are needed to test these suggestions.ARC Linkage Project [LP110200747]; NSFC [41121062]SCI(E)EIARTICLEIan.Campbell@anu.edu.au61411-142311
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Multiple Sulfur Isotope Analyses Support a Magmatic Model for the Volcanogenic Massive Sulfide Deposits of the Teutonic Bore Volcanic Complex, Yilgarn Craton, Western Australia
'GeoScienceWorld', 2015Co-Authors: Chen Mimi, Campbell, Ian H., Xue Yunxing, Tian Wei, Ireland, Trevor R., Holden Peter, Hayman, Patrick C., Cas, Raymond A.f., Das RitipurnaAbstract:We report sensitive high mass resolution ion microprobe, stable Isotopes (SHRIMP SI) multiple Sulfur Isotope analyses (32S, 33S, 34S) to constrain the sources of Sulfur in three Archean VMS deposits—Teutonic Bore, Bentley, and Jaguar—from the Teutonic Bore volcanic complex of the Yilgarn Craton, Western Australia, together with sedimentary pyrites from associated black shales and interpillow pyrites. The pyrites from VMS mineralization are dominated by mantle Sulfur but include a small amount of slightly negative mass-independent fractionation (MIF) anomalies, whereas Sulfur from the pyrites in the sedimentary rocks has pronounced positive MIF, with ∆33S values that lie between 0.19 and 6.20‰ (with one outlier at –1.62‰). The wall rocks to the mineralization include sedimentary rocks that have contributed no detectable positive MIF Sulfur to the VMS deposits, which is difficult to reconcile with the leaching model for the formation of these deposits. The Sulfur Isotope data are best explained by mixing between Sulfur derived from a magmatic-hydrothermal fluid and seawater Sulfur as represented by the interpillow pyrites. The massive sulfide lens pyrites have a weighted mean ∆33S value of –0.27 ± 0.05‰ (MSWD = 1.6) nearly identical with –0.31 ± 0.08‰ (MSWD = 2.4) for pyrites from the stringer zone, which requires mixing to have occurred below the sea floor. We employed a twocomponent mixing model to estimate the contribution of seawater Sulfur to the total Sulfur budget of the two Teutonic Bore volcanic complex VMS deposits. The results are 15 to 18% for both Teutonic Bore and Bentley, much higher than the 3% obtained by Jamieson et al. (2013) for the giant Kidd Creek deposit. Similar calculations, carried out for other Neoarchean VMS deposits give value between 2% and 30%, which are similar to modern hydrothermal VMS deposits. We suggest that multiple Sulfur Isotope analyses may be used to predict the size of Archean VMS deposits and to provide a vector to ore deposit but further studies are needed to test these suggestions.We acknowledge the support from the ARC Linkage Project LP110200747 and its sponsors, especially the Independence Group NL for access to the VMS deposits of Teutonic Bore volcanic complex, and to their data and for their hospitality at the mine. Mimi Chen and Wei Tian’s study in the ANU was also supported by NSFC grant 41121062 and a PKU shortterm oversea visiting scholar
Shuhei Ono - One of the best experts on this subject based on the ideXlab platform.
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Sulfur Isotope evidence for low and fluctuating sulfate levels in the late devonian ocean and the potential link with the mass extinction event
Earth and Planetary Science Letters, 2015Co-Authors: Min Sub Sim, Shuhei Ono, Matthew T HurtgenAbstract:High amplitude positive carbon Isotope excursions in the Late Devonian, the punctata and Kellwasser events, reflect major perturbations in the global carbon cycle that have been attributed to increased continental weathering and subsequent ocean eutrophication. Despite the comparable carbon Isotope anomalies, however, a major extinction has been reported only for the Kellwasser Events, while the punctata Event is marked by low extinction intensity. This study presents multiple Sulfur Isotope records of carbonate-associated sulfate (CAS) and pyrite from Late Devonian sections in the Great Basin, USA, in order to document changes in the coupled (or decoupled) geochemical cycles of carbon and Sulfur during the punctata and Upper Kellwasser events. A positive Sulfur Isotope shift in both CAS and pyrite accompanies the onset of the punctata Event, but to a larger extent in the latter. As a result, the Sulfur Isotope offset between CAS and pyrite (Δ^(34)S_(CAS-py)) dropped to less than 10‰. In the middle of the punctata Event, a sharp negative δ^(34)S_(CAS) excursion and negative Δ^(34)S_(CAS-py) values coincide with the Alamo impact. Unlike the rapid δ^(34)S_(py) and δ^(34)S_(CAS) oscillations associated with the punctata Event, the Upper Kellwasser was a period of relative stability, except for a brief δ^(34)S_(CAS) drop before the event. Paired Sulfur Isotope data, aided by a simple box model, suggest that the geochemical cycle of Sulfur may have been partly responsible for the contrasting biological responses that define these events. High stratigraphic δ^(34)S_(py) and δ^(34)S_(CAS) variability, coupled with strong reservoir effect, demonstrates a relatively small oceanic sulfate pool existed during the punctata Event. Further, the Alamo impact likely triggered the rapid oxidation of microbially-produced sulfide within this event. The expansion of sulfidic bottom water thus may have been impeded during the punctata Event. In contrast, the lack of a positive shift in δ^(34)S_(CAS) and sizable Δ^(34)S_(CAS-py) values (>15‰) throughout the Upper Kellwasser Event imply higher relative sulfate levels. A larger seawater sulfate reservoir may have promoted the development of sulfidic bottom waters in the eutrophic epicontinental seas, increasing biological stress and potentially contributing to the mass extinction.
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multiple Sulfur Isotope effects during photolysis of carbonyl sulfide
Atmospheric Chemistry and Physics, 2011Co-Authors: Ying Lin, Min Sub Sim, Shuhei OnoAbstract:Laboratory experiments were carried out to de- termine Sulfur Isotope effects during ultraviolet photolysis of carbonyl sulfide (OCS) to carbon monoxide (CO) and elemental Sulfur (S 0 ). The OCS gas at 3.7 to 501 mbar was irradiated with or without a N2 bath gas using a 150 W Xe arc lamp. Sulfur Isotope ratios for the product S 0 and residual OCS were analyzed by an Isotope ratio mass-spectrometer with SF6 as the analyte gas. The iso- tope fractionation after correction for the reservoir effects is 6.8 ‰ for the ratio 34 S/ 32 S, where product S 0 is de- pleted in heavy Isotopes. The magnitude of the overall iso- tope effect is not sensitive to the addition of N 2 but in- creases to 9.5 ‰ when radiation of > 285 nm is used. The measured Isotope effect reflects that of photolysis as well as the subsequent Sulfur abstraction (from OCS) reac- tion. The magnitude of Isotope effects for the abstraction reaction is estimated by transition state theory to be between 18.9 and 3.1 ‰ for 34 S which gives the photolysis iso- tope effect as 10.5 to +5.3 ‰. The observed triple Isotope coefficients are ln( 33 S + 1)/ln( 34 S + 1) = 0.534± 0.005 and ln( 36 S + 1)/ln( 34 S + 1) = 1.980± 0.021. These values dif- fer from canonical values for mass-dependent fractionation of 0.515 and 1.90, respectively. The result demonstrates that the OCS photolysis does not produce large Isotope effects of more than about 10 ‰ for 34 S/ 32 S, and can be the ma- jor source of background stratospheric sulfate aerosol (SSA) during volcanic quiescence.
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Lithofacies control on multiple-Sulfur Isotope records and Neoarchean Sulfur cycles
Precambrian Research, 2008Co-Authors: Shuhei Ono, James Farquhar, Alan J. Kaufman, Dawn Y. Sumner, Nicolas J BeukesAbstract:Abstract Triple-Sulfur Isotope ratios ( 32 S/ 33 S/ 34 S) were measured for 141 bulk rock samples from two Agouron scientific drill cores (GKP01 and GKF01) that recovered Neoarchean successions of the Transvaal Supergroup, South Africa. These two deep-time cores are correlated to each other with 14 tie lines using volcanic and impact spherule layers in a sequence stratigraphic framework, allowing us to evaluate both lithofacies and temporal controls over multiple-Sulfur Isotope systematics. The ca. 2.5 Ga (giga-annum before present) basinal Klein Naute Formation and the ca. 2.6 Ga peritidal Boomplaas and Vryburg Formations yield an array of data characterized by δ 33 S ≈ 1.4 × δ 34 S. These linear trends are found in both shallow water and deepwater facies but are characteristic to rocks with high-iron content suggesting these may reflect isotopic compositions of aqueous sulfide-elemental Sulfur reservoirs in the Neoarchean oceans. Data that deviate from this linear array are interpreted as resulting from additional inputs of sulfide from microbial sulfate reduction with or without contribution from Sulfur disproportionation. Sulfate-derived Sulfur evolved to be either enriched or depleted in 34 S depending on the local depositional environment. For example, the Reivilo Formation in core GKF01 is characterized by abundant microbialite textures and shows an isotopic signature of closed system sulfate reduction. Rapid cementation of these carbonate fabrics may have attenuated the supply of sulfate to pore waters resulting in the progressive 34 S enrichments during bacterial sulfate reduction below the sediment–water interface. In contrast, signatures of open-system sulfate reduction are associated with slope facies, dominated by granular dolostones, preserved in the upper Nauga Formations in GKF01 and GKP01. The two different Sulfur Isotope patterns, interpreted to reflect closed versus open-system sulfate reduction are both found in the lower Reivilo Formation in both cores. This lateral variation of Isotope signals documents that observed 34 S shifts can be controlled locally, and may not have temporal significance. This study demonstrates critical importance of recovering Sulfur Isotope data from stratigraphically correlated drill cores to evaluate both geographical and temporal shifts of Sulfur cycles, and their links to the great oxidation event at the end of the Archean Eon.
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quadruple Sulfur Isotope analysis of ca 3 5 ga dresser formation new evidence for microbial sulfate reduction in the early archean
Geochimica et Cosmochimica Acta, 2008Co-Authors: Yuichiro Ueno, Shuhei Ono, Douglas Rumble, Shigenori MaruyamaAbstract:Abstract Multiple Sulfur Isotope system is a powerful new tracer for atmospheric, volcanic, and biological influences on Sulfur cycles in the anoxic early Earth. Here, we report high-precision quadruple Sulfur Isotope analyses (32S/33S/34S/36S) of barite, pyrite in barite, and sulfides in related hydrothermal and igneous rocks occurring in the ca. 3.5 Ga Dresser Formation, Western Australia. Our results indicate that observed isotopic variations are mainly controlled by mixing of mass-dependently (MD) and non-mass-dependently fractionated (non-MD) Sulfur reservoirs. Based on the quadruple Sulfur Isotope systematics (δ34S–Δ33S–Δ36S) for these minerals, four end-member Sulfur reservoirs have been recognized: (1) non-MD sulfate (δ34S = −5 ± 2‰; Δ33S = −3 ± 1‰); (2) MD sulfate (δ34S = +10 ± 3‰); (3) non-MD Sulfur (δ34S > +6‰; Δ33S > +4‰); and (4) igneous MD Sulfur (δ34S = Δ33S = 0‰). The first and third components show a clear non-MD signatures, thus probably represent sulfate and Sulfur aerosol inputs. The MD sulfate component (2) is enriched in 34S (+10 ± 3‰) and may have originated from microbial and/or abiotic disproportionation of volcanic S or SO2. Our results reconfirm that the Dresser barites contain small amounts of pyrite depleted in 34S by 15–22‰ relative to the host barite. These barite–pyrite pairs exhibit a mass-dependent relationship of δ33S/δ34S with slope less than 0.512, which is consistent with that expected for microbial sulfate reduction and is significantly different from that of equilibrium fractionation (0.515). The barite–pyrite pairs also show up to 1‰ difference in Δ36S values and steep Δ36S/Δ33S slopes, which deviate from the main Archean array (Δ36S/Δ33S = −0.9) and are comparable to Isotope effects exhibited by sulfate reducing microbes (Δ36S/Δ33S = −5 to −11). These new lines of evidence support the existence of sulfate reducers at ca. 3.5 Ga, whereas microbial Sulfur disproportionation may have been more limited than recently suggested.
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mass dependent fractionation of quadruple stable Sulfur Isotope system as a new tracer of Sulfur biogeochemical cycles
Geochimica et Cosmochimica Acta, 2006Co-Authors: Shuhei Ono, Boswell A. Wing, James Farquhar, D Johnston, Douglas RumbleAbstract:Abstract Sulfur Isotope studies of post-Archean terrestrial materials have focused on the ratio 34S/32S because additional Isotopes, 33S and 36S, were thought to carry little information beyond the well-known mass-dependent relationship among multiple-Isotope ratios. We report high-precision analyses of Δ33S and Δ36S values, defined as deviations of 33S and 36S from ideal mass-dependent relationships, for international reference materials and sedimentary sulfides of Phanerozoic age by using a fluorination technique with a dual-inlet Isotope ratio mass spectrometer. Measured variations in Δ33S and Δ36S are explained as resulting from processes involve branching reactions (two or more reservoirs formed) or mixing. Irreversible processes in closed systems (Rayleigh distillation) amplify the Isotope effect. We outline how this new Isotope proxy can be used to gain new insights into fundamental aspects of the Sulfur biogeochemical cycle, including additional constraints on seawater sulfate budget and processes in sedimentary sulfide formation. The Isotope systematics discussed here cannot explain the much larger variation of Δ33S and Δ36S observed in Archean rock records. Furthermore, Phanerozoic samples we have studied show a characteristic Δ33S and Δ36S relationship that differs from those measured in Archean rocks and laboratory photolysis experiments. Thus, high precision analysis of Δ33S and Δ36S can be used to distinguish small non-zero Δ33S and Δ36S produced by mass-dependent processes from those produced by mass-independent processes in Archean rocks and extraterrestrial materials.
Ritipurna Das - One of the best experts on this subject based on the ideXlab platform.
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multiple Sulfur Isotope analyses support a magmatic model for the volcanogenic massive sulfide deposits of the teutonic bore volcanic complex yilgarn craton western australia
Economic Geology, 2015Co-Authors: Mimi Chen, Ian H Campbell, Yunxing Xue, Wei Tian, Trevor Ireland, Peter Holden, Raymond Alexander Fernand Cas, Patrick Calder Hayman, Ritipurna DasAbstract:We report sensitive high mass resolution ion microprobe, stable Isotopes (SHRIMP SI) multiple Sulfur Isotope analyses (32S, 33S, 34S) to constrain the sources of Sulfur in three Archean VMS deposits—Teutonic Bore, Bentley, and Jaguar—from the Teutonic Bore volcanic complex of the Yilgarn Craton, Western Australia, together with sedimentary pyrites from associated black shales and interpillow pyrites. The pyrites from VMS mineralization are dominated by mantle Sulfur but include a small amount of slightly negative mass-independent fractionation (MIF) anomalies, whereas Sulfur from the pyrites in the sedimentary rocks has pronounced positive MIF, with ∆33S values that lie between 0.19 and 6.20‰ (with one outlier at −1.62‰). The wall rocks to the mineralization include sedimentary rocks that have contributed no detectable positive MIF Sulfur to the VMS deposits, which is difficult to reconcile with the leaching model for the formation of these deposits. The Sulfur Isotope data are best explained by mixing between Sulfur derived from a magmatic-hydrothermal fluid and seawater Sulfur as represented by the interpillow pyrites. The massive sulfide lens pyrites have a weighted mean ∆33S value of −0.27 ± 0.05‰ (MSWD = 1.6) nearly identical with −0.31 ± 0.08‰ (MSWD = 2.4) for pyrites from the stringer zone, which requires mixing to have occurred below the sea floor. We employed a two-component mixing model to estimate the contribution of seawater Sulfur to the total Sulfur budget of the two Teutonic Bore volcanic complex VMS deposits. The results are 15 to 18% for both Teutonic Bore and Bentley, much higher than the 3% obtained by Jamieson et al. (2013) for the giant Kidd Creek deposit. Similar calculations, carried out for other Neoarchean VMS deposits give value between 2% and 30%, which are similar to modern hydrothermal VMS deposits. We suggest that multiple Sulfur Isotope analyses may be used to predict the size of Archean VMS deposits and to provide a vector to ore deposit but further studies are needed to test these suggestions.
Boswell A. Wing - One of the best experts on this subject based on the ideXlab platform.
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Sulfur Isotope Fractionation by Sulfate-Reducing Microbes Can Reflect Past Physiology
2018Co-Authors: André Pellerin, Itay Halevy, Christine B. Wenk, Boswell A. WingAbstract:Sulfur (S) Isotope fractionation by sulfate-reducing microorganisms is a direct manifestation of their respiratory metabolism. This fractionation is apparent in the substrate (sulfate) and waste (sulfide) produced. The sulfate-reducing metabolism responds to variability in the local environment, with the response determined by the underlying genotype, resulting in the expression of an “Isotope phenotype”. Sulfur Isotope phenotypes have been used as a diagnostic tool for the metabolic activity of sulfate-reducing microorganisms in the environment. Our experiments with Desulfovibrio vulgaris Hildenborough (DvH) grown in batch culture suggest that the S Isotope phenotype of sulfate respiring microbes may lag environmental changes on time scales that are longer than generational. When inocula from different phases of growth are assayed under the same environmental conditions, we observed that DvH exhibited different net apparent fractionations of up to −9‰. The magnitude of fractionation was weakly correlated with physiological parameters but was strongly correlated to the age of the initial inoculum. The S Isotope fractionation observed between sulfate and sulfide showed a positive correlation with respiration rate, contradicting the well-described negative dependence of fractionation on respiration rate. Quantitative modeling of S Isotope fractionation shows that either a large increase (≈50×) in the abundance of sulfate adenylyl transferase (Sat) or a smaller increase in sulfate transport proteins (≈2×) is sufficient to account for the change in fractionation associated with past physiology. Temporal transcriptomic studies with DvH imply that expression of sulfate permeases doubles over the transition from early exponential to early stationary phase, lending support to the transport hypothesis proposed here. As it is apparently maintained for multiple generations (≈1–6) of subsequent growth in the assay environment, we suggest that this fractionation effect acts as a sort of isotopic “memory” of a previous physiological and environmental state. Whatever its root cause, this physiological hysteresis effect can explain variations in fractionations observed in many environments. It may also enable new insights into life at energetic limits, especially if its historical footprint extends deeper than generational
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Sulfur Isotope homogeneity of lunar mare basalts
Geochimica et Cosmochimica Acta, 2015Co-Authors: Boswell A. Wing, James FarquharAbstract:Abstract We present a new set of high precision measurements of relative 33S/32S, 34S/32S, and 36S/32S values in lunar mare basalts. The measurements are referenced to the Vienna-Canyon Diablo Troilite (V-CDT) scale, on which the international reference material, IAEA-S-1, is characterized by δ33S = −0.061‰, δ34S ≡ −0.3‰ and δ36S = −1.27‰. The present dataset confirms that lunar mare basalts are characterized by a remarkable degree of Sulfur isotopic homogeneity, with most new and published SF6-based Sulfur Isotope measurements consistent with a single mass-dependent mean isotopic composition of δ34S = 0.58 ± 0.05‰, Δ33S = 0.008 ± 0.006‰, and Δ36S = 0.2 ± 0.2‰, relative to V-CDT, where the uncertainties are quoted as 99% confidence intervals on the mean. This homogeneity allows identification of a single sample (12022, 281) with an apparent 33S enrichment, possibly reflecting cosmic-ray-induced spallation reactions. It also reveals that some mare basalts have slightly lower δ34S values than the population mean, which is consistent with Sulfur loss from a reduced basaltic melt prior to eruption at the lunar surface. Both the Sulfur Isotope homogeneity of the lunar mare basalts and the predicted sensitivity of Sulfur Isotopes to vaporization-driven fractionation suggest that less than ≈1–10% of lunar Sulfur was lost after a potential moon-forming impact event.
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Sulfur Isotope and trace element data from ore sulfides in the noranda district abitibi canada implications for volcanogenic massive sulfide deposit genesis
Mineralium Deposita, 2015Co-Authors: Elizabeth R Sharman, Bruce E Taylor, William G Minarik, B Dube, Boswell A. WingAbstract:We examine models for volcanogenic massive sulfide (VMS) mineralization in the ~2.7-Ga Noranda camp, Abitibi subprovince, Superior Province, Canada, using a combination of multiple Sulfur Isotope and trace element data from ore sulfide minerals. The Noranda camp is a well-preserved, VMS deposit-rich area that is thought to represent a collapsed volcanic caldera. Due to its economic value, the camp has been studied extensively, providing a robust geological framework within which to assess the new data presented in this study. We explore previously proposed controls on mineralization within the Noranda camp and, in particular, the exceptional Au-rich Horne and Quemont deposits. We present multiple Sulfur Isotope and trace element compositional data for sulfide separates representing 25 different VMS deposits and “showings” within the Noranda camp. Multiple Sulfur Isotope data for this study have δ34SV-CDT values of between −1.9 and +2.5 ‰, and Δ33SV-CDT values of between −0.59 and −0.03 ‰. We interpret the negative Δ33S values to be due to a contribution of Sulfur that originated as seawater sulfate to form the ore sulfides of the Noranda camp VMS deposits. The contribution of seawater sulfate increased with the collapse and subsequent evolution of the Noranda caldera, an inference supported by select trace and major element analyses. In particular, higher concentrations of Se occur in samples with Δ33S values closer to 0 ‰, as well as lower Fe/Zn ratios in sphalerite, suggesting lower pressures and temperatures of formation. We also report a relationship between average Au grade and Δ33S values within Au-rich VMS deposits of the Noranda camp, whereby higher gold grades are associated with near-zero Δ33S values. From this, we infer a dominance of igneous Sulfur in the gold-rich deposits, either leached from the volcanic pile and/or directly degassed from an associated intrusion.
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Sulfur Isotope fractionation during the evolutionary adaptation of a sulfate-reducing bacterium.
Applied and Environmental Microbiology, 2015Co-Authors: André Pellerin, Luke Anderson-trocme, Grant M. Zane, Judy D. Wall, Lyle G. Whyte, Boswell A. WingAbstract:ABSTRACT Dissimilatory sulfate reduction is a microbial catabolic pathway that preferentially processes less massive Sulfur Isotopes relative to their heavier counterparts. This Sulfur Isotope fractionation is recorded in ancient sedimentary rocks and generally is considered to reflect a phenotypic response to environmental variations rather than to evolutionary adaptation. Modern sulfate-reducing microorganisms isolated from similar environments can exhibit a wide range of Sulfur Isotope fractionations, suggesting that adaptive processes influence the Sulfur Isotope phenotype. To date, the relationship between evolutionary adaptation and isotopic phenotypes has not been explored. We addressed this by studying the covariation of fitness, Sulfur Isotope fractionation, and growth characteristics in Desulfovibrio vulgaris Hildenborough in a microbial evolution experiment. After 560 generations, the mean fitness of the evolved lineages relative to the starting isogenic population had increased by ∼17%. After 927 generations, the mean fitness relative to the initial ancestral population had increased by ∼20%. Growth rate in exponential phase increased during the course of the experiment, suggesting that this was a primary influence behind the fitness increases. Consistent changes were observed within different selection intervals between fractionation and fitness. Fitness changes were associated with changes in exponential growth rate but changes in fractionation were not. Instead, they appeared to be a response to changes in the parameters that govern growth rate: yield and cell-specific sulfate respiration rate. We hypothesize that cell-specific sulfate respiration rate, in particular, provides a bridge that allows physiological controls on fractionation to cross over to the adaptive realm.
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intracellular metabolite levels shape Sulfur Isotope fractionation during microbial sulfate respiration
Proceedings of the National Academy of Sciences of the United States of America, 2014Co-Authors: Boswell A. Wing, Itay HalevyAbstract:We present a quantitative model for Sulfur Isotope fractionation accompanying bacterial and archaeal dissimilatory sulfate respiration. By incorporating independently available biochemical data, the model can reproduce a large number of recent experimental fractionation measurements with only three free parameters: (i) the Sulfur Isotope selectivity of sulfate uptake into the cytoplasm, (ii) the ratio of reduced to oxidized electron carriers supporting the respiration pathway, and (iii) the ratio of in vitro to in vivo levels of respiratory enzyme activity. Fractionation is influenced by all steps in the dissimilatory pathway, which means that environmental sulfate and sulfide levels control Sulfur Isotope fractionation through the proximate influence of intracellular metabolites. Although Sulfur Isotope fractionation is a phenotypic trait that appears to be strain specific, we show that it converges on near-thermodynamic behavior, even at micromolar sulfate levels, as long as intracellular sulfate reduction rates are low enough (<<1 fmol H2S·cell �1 ·d �1 ).
