Showing papers in "Geochimica et Cosmochimica Acta in 2002"

TL;DR: The mass-dependent fractionation laws that describe the partitioning of isotopes are different for kinetic and equilibrium reactions as discussed by the authors, characterized by the exponent relating the fractionation factors for two isotope ratios such that α2/1 = α3/1β.

TL;DR: In a series of oxic and anoxic incubation experiments, the authors examined the fate of organic matter and the alteration of its carbon and nitrogen isotopic composition during microbial degradation.

TL;DR: In this article, the authors proposed that gradual changes in the composition of volatiles that have been added to the atmosphere-ocean system are responsible for the Great Oxidation Event (G.O.) ca. 2.3 Ga.

TL;DR: The chemical evolution of seawater during the Phanerozoic is still a matter of debate as mentioned in this paper, and the available data for the composition of fluid inclusions in marine halite and for the mineralogy of marine evaporites.

TL;DR: In this article, the authors measured the kinetics of isotope exchange between aqueous ferrous and ferric species measured over a range of chloride concentrations (0, 11, 110 mM Cl−) and at two temperatures (0 and 22°C) indicate that Fe isotope fractionation is a function of temperature but independent of chloride contents over the range studied.

TL;DR: In this paper, the authors provide compelling evidence of U incorporation within the hematite structure and show that U incorporation in the structure provides evidence of the presence of U in hexavalent oxidizing environments.

TL;DR: In this article, partial melting of an eclogitic component of different modal compo- sitions may explain both subchondritic and super chondritic Zr/Hf ratios.

TL;DR: In this paper, the Humic Ion-Binding Model VI was used to examine the pH dependence of Al and Fe binding by dissolved organic matter (DOM) in freshwaters, by simulating the titration with Ca(OH)2 of an initially acid solution.

TL;DR: In this article, the relationship between δ17O and δ18O for entity a measured with respect to reference b is accurately represented by the linear function: 1000 ln 1+ δ 17 O 1000 =λ1000 ln [1+k a,b ](α 18/16 ) λ where ka,b is a measure of the offset (if any) of a from the mass-dependent fractionation line, of slope on which b lies.

TL;DR: In this article, the molar solubilities of zircon and hafnon in water-saturated granitic melts have been determined as a function of melt composition at 800° and 1035°C at 200 MPa.

TL;DR: In this article, the Cibicidoides Mg/Ca-temperature calibration has been revised with a significantly different preexponential constant, resulting in different predicted absolute temperatures.

TL;DR: In this paper, the sorption of Cs+ was investigated over a large concentration range (10−9−10−2 mol/L) on subsurface sediments from a United States nuclear materials site (Hanford) where high-level nuclear wastes (HLW) have been accidentally released to the vadose zone.

TL;DR: In this paper, a thermodynamically possible anaerobic microbial FeS 2 and FeS oxidation with NO 3 − or amorphous Fe(III) oxide as electron acceptor was studied.

TL;DR: The oxygen fugacity of the Dar al Gani 476 martian basalt is determined to be quartz-fayalite-magnetite (QFM) −2.3 ± 0.4 through analysis of olivine, low-Ca pyroxene, and Cr-spinel as discussed by the authors.

TL;DR: In this article, a detailed geochemical study of the Yamuna River System (YRS) was carried out to determine the relative significance of silicate, carbonate and evaporite weathering in contributing to its major ion composition; CO2 consumption via silicate weathering; and the factors regulating chemical weathering of silicates in the basin.

TL;DR: The Global/Regional Interhemispheric Mercury Model (GRIMM) as mentioned in this paper is a box model of mercury cycling between the atmosphere and ocean, which is used to estimate Hg fluxes on a global scale.

TL;DR: In this article, the 2-site protolysis no electrostatics surface complexation and cation exchange (2SPNE/CE) model used in previous work to model the sorption of Ni and Zn on Na- and Ca-montmorillonites was applied to sorption edges and isotherms measured for Eu on these two montmorillonite forms.

TL;DR: In this article, the authors evaluate changes in phosphorus content and density along the axial lengths of three developing ungulate teeth to illustrate the protracted nature of mineral accumulation in a volume of developing enamel.

TL;DR: In this article, X-ray absorption fine structure (XAFS) measurements were used at the U L3-edge to directly determine the pH dependence of the cell wall functional groups responsible for the absorption of aqueous UO22+ to Bacillus subtilis from pH 1.67 to 4.80.

TL;DR: In this paper, the authors analyzed Al, Ti, Fe, Mn, Cu, Ba, Cd, Mo, Re, U, and V in water column, settling particulate, and sediment (0 to 22 cm) samples from the intense oxygen minimum zone (OMZ) of the eastern tropical North Pacific near Mazatlan, Mexico.

TL;DR: In this paper, the tetrad effect is observed as a split of rare earth element (REE) patterns into four rounded segments, and the significance of observed tetrad effects is evaluated by taking analytical errors into account.

TL;DR: In this paper, the authors examined the attenuation of particulate organic carbon (POC) through the oxygen deficient waters in the eastern tropical North Pacific and found that degradation proceeded at similar rates under oxic and suboxic conditions, but a greater fraction of bulk POC was resistant to degradation in the suboxic experiments.

TL;DR: A suite of 47 carbonaceous, enstatite, and ordinary chondrites are examined for Re-Os isotopic systematics in this paper, and the results indicate that the Re/Os ratios of meteorites within each group are, in general, quite uniform.

TL;DR: In this article, the formation of Fe(III) oxyhydroxide colloids by oxidation of Fe (II) and their subsequent aggregation to larger particles were studied in laboratory experiments with natural water from a freshwater lake and a brackish coastal sea.

TL;DR: In this article, a tritagonal FeS1−x mackinawite was synthesized by reacting metallic iron with a sodium sulfide solution and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), transmission Mossbauer spectroscopy (MMS), and X-Ray photoelectron spectroscopic analysis (XPS) based on XRD and TEM analyses.

TL;DR: In this paper, the local structures of divalent Zn, Cu, and Pb sorbed on the phyllomanganate birnessite (Bi) have been studied by powder and polarized extended X-ray absorption fine structure (EXAFS) spectroscopy.

TL;DR: In this paper, the isotope compositions of transition element isotopes were measured by multiple-collector inductively coupled plasma mass spectrometry and it was found that for pure Cu solutions, the elution curves are consistent with a 63Cu/65Cu mass fractionation coefficient of 0.46‰ in 7 mol/L HCl and 0.67

TL;DR: Chromites separated from the upper mantle or lower crustal portions of 18 ophiolites ranging in age from 900 Ma to 50 Ma were examined for Re-Os isotopic systematics as mentioned in this paper.

TL;DR: In this paper, a suite of 20 young midocean ridge basalts from the East Pacific Rise axis between 9°28′ and 9°52′N were collected within the axial summit trough using the submersible Alvin.

TL;DR: In this paper, a number of cores of the massive hermatypic scleractinian coral Porites, from the central Great Barrier Reef, have been analyzed for Sr/Ca at weekly to monthly resolution.