نتایج جستجو برای: sulfur isotopes

تعداد نتایج: 56644  

Journal: :Science 2010
Itay Halevy David T Johnston Daniel P Schrag

Sulfur isotopes in ancient sediments provide a record of past environmental conditions. The long-time-scale variability and apparent asymmetry in the magnitude of minor sulfur isotope fractionation in Archean sediments remain unexplained. Using an integrated biogeochemical model of the Archean sulfur cycle, we find that the preservation of mass-independent sulfur is influenced by a variety of e...

Journal: :Bulletin of the Chemical Society of Japan 1958

Journal: :Bulletin of the Chemical Society of Japan 1958

Journal: :iranian journal of science and technology (sciences) 2007
b. alizadeh

for this study, asmari (oligo-miocene) and bangestan (cretaceous) reservoir oils from themarun oilfield were studied geochemically. gas chromatograms and stable isotopes of carbon and sulfur indifferent oil fractions were studied. normal alkanes nc15+ are as high as 93% with a saturate percentage up to53.9% which reveal a high maturity of asmari and bangestan reservoir paraffinic oils. carbon p...

Karst springs in the western and eastern regions of Ilam province have different physical and chemical properties. The springs of  the western regions, are sulfuric and thermal with high salinity; while, springs in the eastern regions, are fresh and cold. Geological, hydrogeological, hydrogeochemical and isotope studies were performed to compare and determine the factors affecting the physical ...

Journal: :Science 2000
Farquhar Bao Thiemens

Mass-independent isotopic signatures for delta(33)S, delta(34)S, and delta(36)S from sulfide and sulfate in Precambrian rocks indicate that a change occurred in the sulfur cycle between 2090 and 2450 million years ago (Ma). Before 2450 Ma, the cycle was influenced by gas-phase atmospheric reactions. These atmospheric reactions also played a role in determining the oxidation state of sulfur, imp...

2018
Mojtaba Fakhraee Sean A Crowe Sergei Katsev

Abrupt disappearance of mass-independent fractionation of sulfur isotopes (MIF-S) from the geologic record and an apparent ingrowth in seawater sulfate around 2.45 billion years ago (Ga) signal the first large-scale oxygenation of the atmosphere [the Great Oxygenation Event (GOE)]. Pre-GOE O2 production is evident from multiple other terrestrial and marine proxies, but oceanic O2 concentrations...

2008
Amy Kelly

Introduction According to Anbar & Knoll (2002), the Proterozoic ocean was in a transition stage from euxinic with oxygenated shallow water to the fully oxygenated water column of the present day. Though there is no direct proxy for the concentration of oxygen in the past, carbon and sulfur isotopes help constrain these concentrations. The carbon and sulfur cycles underwent vast transitions in t...

2011
Bing Shen Shuhai Xiao Huiming Bao Alan J. Kaufman Chuanming Zhou Xunlai Yuan

In order to understand spatial variations of stable isotope geochemistry in the Quruqtagh basin (northwestern China) in the aftermath of an Ediacaran glaciation, we analyzed carbonate carbon isotopes (dCcarb), carbonate oxygen isotopes (dOcarb), carbonate associated sulfate sulfur (d SCAS) and oxygen isotopes (d OCAS), and pyrite sulfur isotopes (d Spy) of a cap dolostone atop the Ediacaran Han...

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