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Sulfur Isotopes (sulfur + isotope)

Distribution by Scientific Domains

Earth and Environmental Science	100%

Selected Abstracts

Mineral Paragenesis, Fluid Inclusions and Sulfur Isotope Systematics of the Lepanto Far Southeast Porphyry Cu-Au Deposit, Mankayan, Philippines

RESOURCE GEOLOGY, Issue 3 2000
Akira IMAI
Abstract: The Lepanto Far Southeast porphyry Cu-Au deposit is located beneath and to the southeast of the Lepanto enargite-luzonite Cu,Au deposit in Mankayan, Benguet Province, Philippines. The principal orebody consists of potassic alteration subjected to partial retrograde chlorite alteration that rims stock-work of quartz-anhydrite veinlets. Fluid inclusions found in stockwork quartz and anhydrite in the biotitized orebody center are dominated by polyphase inclusions that homogenize at temperatures of >500C. Sulfur isotopic thermometry applied to the sulfides-anhydrite pairs suggests around 500C. The principal ore minerals associated with quartz-anhydrite stockworks are chalcopyrite and pyrite with minor bornite and Bi,Te,bearing tennantite, with trace of native gold. Rounded pyrite grains appear fractured and corroded and are interpreted as remnants of primary intermediate solid solution + pyrite assemblage. A breccia pipe truncates the deposit. Mineralization in the breccia pipe is brought by quartz-anhydrite veinlets and infilling in the interstices between clasts. Chalcopyrite-Au mineralization associated with molybdenite is recognized in the deeper zone in the breccia pipe. Fluid inclusion microthermometry on polyphase inclusions in veinlet quartz as well as sulfur isotope thermometry applied for the pair of anhydrite and sulfides suggests >450C. Fluid inclusions in veinlet quartz and anhydrite in the fringe advanced argillic alteration are chiefly composed of coexisting liquid-rich inclusions and gas-rich inclusions, in addition to coexisting polyphase inclusions and gas-rich inclusions. These inclusions exhibit a wide range of homogenization temperatures, suggesting heterogeneous entrapping in the two-fluid unmixing region. Sulfur isotopes of aqueous sulfide and sulfate exhibit a general trend from the smallest fractionation pairs (about 11%) in the biotitized orebody center to the largest fractionation (about 25%) pairs in the fringe advanced argillic alteration, suggesting a simple evolution of hydrothermal system. The slopes of arbitrary regression lines in ,34S versus 34S[SO4 = ,H2S] diagram suggest that the abundance ratio of aqueous sulfate to sulfide in the hydrothermal fluid has been broadly constant at about 1:3 through temperature decrease. The intersection of these two regression lines at the ,34S axis indicates that the bulk ,34S is about +6%. Thus, the Lepanto FSE deposit is a further example which confirms enrichment in 34S in the hydrous intermediate to silicic magmas and associated magmatic hydrothermal deposits in the western Luzon arc. [source]

Mass-independent fractionation of sulfur isotopes in sulfides from the pre-3770 Ma Isua Supracrustal Belt, West Greenland

GEOBIOLOGY, Issue 4 2006
D. PAPINEAU
ABSTRACT Redox chemistry of the coupled atmosphere,hydrosphere system has coevolved with the biosphere, from global anoxia in the Archean to an oxygenated Proterozoic surface environment. However, to trace these changes to the very beginning of the rock record presents special challenges. All known Eoarchean (c. 3850,3600 Ma) volcanosedimentary successions (i.e. supracrustal rocks) are restricted to high-grade gneissic terranes that seldom preserve original sedimentary structures and lack primary organic biomarkers. Although complicated by metamorphic overprinting, sulfur isotopes from Archean supracrustal rocks have the potential to preserve signatures of both atmospheric chemistry and metabolic fractionation from the original sediments. We present a synthesis of multiple sulfur isotope measurements (32S, 33S and 34S) performed on sulfides from amphibolite facies banded iron-formations (BIFs) and ferruginous garnet-biotite (metapelitic) schists from the pre-3770 Ma Isua Supracrustal Belt (ISB) in West Greenland. Because these data come from some of the oldest rocks of interpretable marine sedimentary origin, they provide the opportunity to (i) explore for possible biosignatures of sulfur metabolisms in early life; (ii) assess changes in atmospheric redox chemistry from ,3.8 Ga; and (iii) lay the groundwork to elucidate sulfur biogeochemical cycles on the early Earth. We find that sulfur isotope results from Isua do not unambiguously indicate microbially induced sulfur isotopic fractionation at that time. A significantly expanded data set of ,33S analyses for Isua dictates that the atmosphere was devoid of free oxygen at time of deposition and also shows that the effects of post-depositional metamorphic remobilization and/or dilution can be traced in mass-independently fractionated sulfur isotopes. [source]

Isotope applications in environmental investigations part II: Groundwater age dating and recharge processes, and provenance of sulfur and methane

REMEDIATION, Issue 2 2003
Julie 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]