Showing papers in "Geochimica et Cosmochimica Acta in 2010"

TL;DR: In this article, a statistical optimization approach was proposed for estimating the 40Ar/39Ar decay constants from 40K activity data, K-Ar isotopic data, and pairs of 238U-206Pb and 40Ar-39Ar data for rigorously selected rocks to estimate the partial decay constants (λe and λβ).

TL;DR: In this article, the authors determined the distribution of crenarchaeotal isoprenoid glycerol dibiphytanyl glyceroline tetraethers (GDGTs) in 116 core-top sediments mostly from (sub)polar oceans and combined these data with previously published core top data.

TL;DR: In this paper, the Mg isotope composition of the Earth and chondrites has been investigated using high-precision (±0.13 ± 0.06) analyses of Mg-IoS for 47 mid-ocean ridge basalts.

TL;DR: In this article, the authors reported seawater boron concentration and chlorinity values measured in seawater samples collected at various depths in the North Pacific and North Atlantic oceans and the East/Japan Sea (located in the western temperate North Pacific).

TL;DR: XANES analyses at the sulfur K-edge were used to determine the oxidation state of S species in natural and synthetic basaltic glasses and to constrain the fO2 conditions for the transition from sulfide (S 2� ) to sulfate (S 6+ ) in silicate melts as mentioned in this paper.

TL;DR: In this paper, the authors present new chemical analyses of Fe formation samples from 18 units, ranging in age from ca. 3.0 to 1.8 billion years old (Ga), which allow a reevaluation of the depositional mechanisms and significance of Precambrian Fe formations.

TL;DR: Fluids from the ultramafic-hosted Lost City hydrothermal field were analyzed for total dissolved organic carbon and dissolved organic acids as discussed by the authors, showing that formate (36−158μmol/kg) and acetate (1−35μm/kg).

TL;DR: In this article, a mass balance approach and the thermodynamic computer programs T hermocalc and PerpleX were used to constrain the P-T range of pyrite breakdown to pyrrhotite (which liberates sulfur) in common metamorphic lithologies.

TL;DR: In this paper, the clumped isotope signature of carbonatites was measured to assess the integrity of the carbonatite paleothermometer over long timescales and the susceptibility of the proxy to closed system re-equilibration of isotopes during burial diagenesis.

TL;DR: In this article, the authors investigated the distribution of branched glycerol dialkyl glyceroline tetraethers (GDGTs) in recently deposited sediments from 46 lakes in tropical East Africa.

TL;DR: In this article, the authors compared the early Cretaceous adakites from the Lower Yangtze River Belt (LYRB) and the South Tan-Lu Fault (STLF), and found that the latter is associated with oceanic slab melting, not with recycling of the ancient lower continental crust.

TL;DR: This article measured δD values of precipitation (δD_p), groundwater, xylem water, and leaf water to understand their impact on the D/H ratio of plant leaf wax nalkanes in an arid ecosystem.

TL;DR: In this paper, the authors report Zn, Mn and Fe systematics in mafic and ultramafic systems (whole-rocks and minerals) and explore their use for detecting lithological heterogeneities that deviate from peridotitic mantle dominated by olivine and orthopyroxene.

TL;DR: Benthic iron fluxes from sites along the Oregon-California continental shelf determined using in situ benthic chambers, range from less than 10μmolm−m−2 ǫd−1 to values in excess of ∼300μmol m−2 d−1 as discussed by the authors.

TL;DR: In this article, the Global Meteoric Water Line (GMWL) ford 17 O and d 18 O is presented, which indicates an excess of 17 O in meteoric waters with respect to the ocean.

TL;DR: In this paper, high-precision Mg isotopic data are reported for 100 well-characterized samples (granites, loess, shales and upper crustal composites) that were previously used to estimate the upper continental crust composition.

TL;DR: A conceptual model for authigenic particle formation at pelagic redoxclines, which is based on the tight coupling of Mn, Fe, and P cycles, is presented in this article.

TL;DR: In this article, the authors proposed a correction procedure that attempts to calculate the δ13C values that would have been obtained under pre-industrial conditions using nonlinear regression, but the magnitude of the adjustment made is restricted by two logical constraints based on the physiological response of trees.

TL;DR: In this paper, the authors report Li isotope compositions for river waters and suspended sediments, of about 40 rivers sampled within the Mackenzie River Basin in northwestern Canada, and characterize the behaviour of Li and its isotopes during weathering at the scale of a large mixed lithology basin.

TL;DR: In this paper, the effects of dissolution of primary phases and the formation of secondary minerals during the weathering of basalt glass and olivine were assessed using X-ray diffraction.

TL;DR: In this paper, the authors report the results of a comprehensive, high precision survey of the Cr isotopic compositions of primitive chondrites, along with some differentiated meteorites, and show that carbonaceous and ordinary chondites share a common 54Cr-enriched carrier, which is characterized by a large excess in 54Cr/52Cr (up to 200e) associated with a very small deficit in 53Cr/ 52Cr (<2e).

TL;DR: In this paper, the authors measured magnesium isotopes in pore-fluids and sediment samples from Ocean Drilling Program sites (1082, 1086, 1012, 984, 1219, and 925) that span a range of oceanographic settings.

TL;DR: In this article, the authors used soil cores augered at the highest point of the watershed and along a subsurface water flowline on a planar hillslope to investigate mineral transformations and physical/chemical weathering fluxes.

TL;DR: In this paper, a long-term study was conducted to investigate the viability of two ecologically important reef-building coral species, massive Ponies sp. and Stylophora pistillata, exposed to high pCO(2) (or low pH) conditions and to observe possible changes in physiologically related parameters as well as skeletal isotopic composition.

TL;DR: In this article, the elemental and isotopic compositions of insoluble organic material (IOM) isolated from several previously unanalyzed meteorites, as well as the reanalyses of H isotopic composition of some previously measured samples were reported.

TL;DR: In this article, the local coordination and structure of Fe(III)-precipitates formed in aerated Fe(II)- and As(III)containing water (buffered to pH 7 by 8mM bicarbonate) using synchrotron-based X-ray absorption spectroscopy (XAS) at the K -edges of Fe, P, Ca, and As.

TL;DR: In this paper, aureole thicknesses, defined as the zone of elevated metamorphism relative to the background level, vary within 30-250% of the sill thickness, depending on the temperature of the host-rock and intrusion, besides the sherpa thickness.

TL;DR: In this paper, the abundances of the highly siderophile elements (HSE) Re, Os, Ir, Ru, Pt, Rh, Pd and Au, and 187Os/188Os isotope ratios have been determined for a set of carbonaceous, ordinary, enstatite and Rumuruti chondrites, using an analytical technique that permits the precise and accurate measurement of all HSE from the same digestion aliquot.

TL;DR: In this paper, the transformation and dissolution of As-bearing ferrihydrite and subsequent As repartitioning amongst secondary phases during biotic sulfate reduction were examined, showing that sulfidogenesis occurring in proximity with Fe (hydr)oxides induce Fe solid phase transformation and changes in As partitioning; formation of As sulfide minerals, in particular, is inhibited by reactive Fe(III) or Fe(II) either through sulfide oxidation or complexation.

TL;DR: In this paper, the authors measured stable isotope ratios (δ 65 Cu, δ 66 Zn) in three soils at distances of 1.1, 3.8, and 5.3 kilometers from a Slovak Cu smelter and in smeltter wastes (slag, sludge, ash) to trace sources and transport of Cu and Zn in soils.