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Sulfur Isotopic Composition (sulfur + isotopic_composition)
Selected AbstractsMeasurement of the ,34S value in methionine by double spike multi-collector thermal ionization mass spectrometry using Carius tube digestion,RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 17 2010Jacqueline L. Mann Methionine is an essential amino acid and is the primary source of sulfur for humans. Using the double spike (33S- 36S) multi-collector thermal ionization mass spectrometry (MC-TIMS) technique, three sample bottles of a methionine material obtained from the Institute for Reference Materials and Measurements have been measured for ,34S and sulfur concentration. The mean ,34S value, relative to Vienna Canyon Diablo Troilite (VCDT), determined was 10.34,±,0.11, (n,=,9) with the uncertainty reported as expanded uncertainties (U). These ,34S measurements include a correction for blank which has been previously ignored in studies of sulfur isotopic composition. The sulfur concentrations for the three bottles range from 56 to 88,µg/g. The isotope composition and concentration results demonstrate the high accuracy and precision of the DS-MC-TIMS technique for measuring sulfur in methionine. Published in 2010 by John Wiley & Sons, Ltd. [source] Evolution of Hydrothermal System at the Dizon Porphyry Cu-Au Deposit, Zambales, PhilippinesRESOURCE GEOLOGY, Issue 2 2005Akira Imai Abstract. Evolution of hydrothermal system from initial porphyry Cu mineralization to overlapping epithermal system at the Dizon porphyry Cu-Au deposit in western central Luzon, Zambales, Philippines, is documented in terms of mineral paragen-esis, fluid inclusion petrography and microthermometry, and sulfur isotope systematics. The paragenetic stages throughout the deposit are summarized as follows; 1) stockwork amethystic quartz veinlets associated with chalcopyrite, bornite, magnetite and Au enveloped by chlorite alteration overprinting biotite alteration, 2) stockwork quartz veinlets with chalcopyrite and pyrite associated with Au and chalcopyrite and pyrite stringers in sericite alteration, 3) stringer quartz veinlets associated with molybdenite in sericite alteration, and 4) WNW-trending quartz veins associated with sphalerite and galena at deeper part, while enargite and stibnite at shallower levels associated with advanced argillic alteration. Chalcopyrite and bornite associated with magnetite in quartz veinlet stockwork (stage 1) have precipitated initially as intermediate solid solution (iss) and bornite solid solution (bnss), respectively. Fluid inclusions in the stockwork veinlet quartz consist of gas-rich inclusions and polyphase inclusions. Halite in polyphase inclusions dissolves at temperatures ranging from 360d,C to >500d,C but liquid (brine) and gas (vapor) do not homogenize at <500d,C. The maximum pressure and minimum temperature during the deposition of iss and bnss with stockwork quartz veinlets are estimated to be 460 bars and 500d,C. Fluid inclusions in veinlet stockwork quartz enveloped in sericite alteration (stage 2) consist mainly of gas-rich inclusions and polyphase inclusions. In addition to the possible presence of saturated NaCl crystals at the time of entrapment of fluid inclusions that exhibit the liquid-vapor homogenization temperatures lower than the halite dissolution temperatures in some samples, wide range of temperatures of halite dissolution and liquid-vapor homogenization of polyphase inclusions from 230d,C to >500d,C and from 270d,C to >500d,C, respectively, suggests heterogeneous entrapment of gaseous vapor and hypersaline brine. The minimum pressure and temperature are estimated to be about 25 bars and 245d,C. Fluid inclusions in veinlet quartz associated with molybdenite (stage 3) are dominated by gas-rich inclusions accompanied with minor liquid-rich inclusions that homogenize at temperatures between 350d,C and 490d,C. Fluid inclusions in vuggy veinlet quartz associated with stibnite (stage 4) consist mainly of gas-rich inclusions with subordinate polyphase inclusions that do not homogenize below 500d,C. Fluid inclusions in veinlet quartz associated with galena and sphalerite (stage 4) are composed of liquid-rich two-phase inclusions, and they homogenize into liquid phase at temperatures ranging widely from 190d,C to 300d,C (suggesting boiling) and the salinity ranges from 1.0 wt% to 3.4 wt% NaCl equivalent. A pressure of about 15 bars is estimated for the dilute aqueous solution of 190d,C from which veinlet quartz associated with galena and sphalerite precipitated. In addition to a change in temperature-pressure regime from lithostatic pressure during the deposition of iss and bnss with stockwork quartz veinlets to hydrostatic pressure during fracture-controlled quartz veinlet associated with galena and sphalerite, a decrease in pressure is supposed to have occurred due to unroofing or removal of the overlying piles during the temperature decrease in the evolution of hydrothermal system. The majority of the sulfur isotopic composition of sulfides ranges from ±0 % to +5 %. Sulfur originated from an iso-topically uniform and homogeneous source, and the mineralization occurred in a single hydrothermal system. [source] Bacterial formation of phosphatic laminites off PeruGEOBIOLOGY, Issue 3 2009E. T. ARNING Authigenic phosphatic laminites enclosed in phosphorite crusts from the shelf off Peru (10°01, S and 10°24, S) consist of carbonate fluorapatite layers, which contain abundant sulfide minerals including pyrite (FeS2) and sphalerite (ZnS). Low ,34Spyrite values (average ,28.8,) agree with bacterial sulfate reduction and subsequent pyrite formation. Stable sulfur isotopic compositions of sulfate bound in carbonate fluorapatite are lower than that of sulfate from ambient sea water, suggesting bacterial reoxidation of sulfide by sulfide-oxidizing bacteria. The release of phosphorus and subsequent formation of the autochthonous phosphatic laminites are apparently caused by the activity of sulfate-reducing bacteria and associated sulfide-oxidizing bacteria. Following an extraction,phosphorite dissolution,extraction procedure, molecular fossils of sulfate-reducing bacteria (mono- O -alkyl glycerol ethers, di- O -alkyl glycerol ethers, as well as the short-chain branched fatty acids i/ai -C15:0, i/ai -C17:0 and 10MeC16:0) are found to be among the most abundant compounds. The fact that these molecular fossils of sulfate-reducing bacteria are distinctly more abundant after dissolution of the phosphatic laminite reveals that the lipids are tightly bound to the mineral lattice of carbonate fluorapatite. Moreover, compared with the autochthonous laminite, molecular fossils of sulfate-reducing bacteria are: (1) significantly less abundant and (2) not as tightly bound to the mineral lattice in the other, allochthonous facies of the Peruvian crusts consisting of phosphatic coated grains. These observations confirm the importance of sulfate-reducing bacteria in the formation of the phosphatic laminite. Model calculations highlight that organic matter degradation by sulfate-reducing bacteria has the potential to liberate sufficient phosphorus for phosphogenesis. [source] Isotope applications in environmental investigations part II: Groundwater age dating and recharge processes, and provenance of sulfur and methaneREMEDIATION, Issue 2 2003Julie K. Sueker Measurement of the isotopic composition of solids, solutes, gases, and water complement standard hydrogeological investigation techniques by providing information that may not otherwise be obtainable. Groundwater age estimates determined from the decay of radio-isotopes or from groundwater concentrations of anthropogenic gases such as chlorofluorocarbons (CFCs) and sulfur hexafluoride (SF6) are used to verify flow regimes and constrain or calibrate hydrologic flow models. Groundwater recharge rates are estimated by measuring the concentrations or activities of a variety of isotopes including 2H, 3H, 18O, and 36Cl. Excess sulfur causes salinization of water supplies and acidification of precipitation, surface water, and groundwater. The wide range of sulfur isotopic compositions exhibited by different sulfur species and sources allows the application of sulfur isotopes to trace sources and fate of sulfur in the environment. Methane is a ubiquitous gas that has economic value when located in extractable reservoirs. Methane is also a greenhouse gas and is a potential explosion and health hazard when it accumulates in buildings and water distribution systems. The carbon and hydrogen isotopic composition of methane can be used to determine the provenance of methane, distinguishing between thermogenic and biogenic sources. The addition of isotopic analyses to environmental investigations can be a cost-effective means of resolving intractable issues. © 2003 Wiley Periodicals, Inc. [source] | ||||||||||