Showing papers in "Geochimica et Cosmochimica Acta in 2001"

TL;DR: Menzies et al. as mentioned in this paper used spinel-bearing mantle peridotites from a common fertile source (PUM) between 1 and 2 Ga ago to estimate the chemical composition of domains within the mantle.

TL;DR: Isotope fractionation during sulfate reduction was explored for natural populations of sulfate-reducing bacteria in this paper, where high fractionations of 30" to 40" were produced when the natural population metabolized with indigenous organic substrate at environmental temperatures of 15°C to 25°C.

TL;DR: In this paper, steady state basaltic glass dissolution rates were measured as a function of aqueous aluminum, silica, and oxalic acid concentration at 25° C and pH 3 and 11.

TL;DR: In this paper, a general kinetic description of major rock forming multioxide silicate dissolution is developed by assuming the relative rates at which various metal-oxygen bonds are broken within a multioxide structure are consistent with the relative dissolution rates of the single (hydr)oxides.

TL;DR: Trace element concentrations and combined Sr- and Nd-isotope compositions were determined on stromatolitic carbonates (microbialites) from the 2.52 Ga Campbellrand carbonate platform (South Africa) as discussed by the authors.

TL;DR: In this article, ICP-MS and TIMS measurements were performed on both solid samples (fresh granite, soil, and suspended load of the stream) and waters (soil solutions, springwater, and streamwater) to determine their respective REE concentrations and Sr and Nd isotopic compositions.

TL;DR: In this article, the adsorption experiments of rare-earth elements (REE) onto δ-MnO2 and Fe oxyhydroxide precipitates suspended in aqueous NaCl solutions have been conducted.

TL;DR: In this article, an experimental study of the reaction of dissolved CO2 in the presence of olivine under hydrothermal conditions (300°C, 350 bar) was conducted, and the results indicated that the potential for abiotic formation of hydrocarbons during serpentinization may be much more limited than previously believed.

TL;DR: In this article, the authors determined concentrations and isotopic compositions of inorganic nitrogen (IN), organic nitrogen (ON), total nitrogen (TN), and total organic carbon (TOC) on one short core recovered from sediments of the eastern subtropical Atlantic, between the Canary Islands and the Moroccan coast.

TL;DR: In this article, the authors examined the different rates of plagioclase and K-feldspar weathering commonly observed in bedrock and soil environments in terms of chemical kinetic and solubility controls and hydrologic permeability.

TL;DR: In this article, a set of synthetic isotope mixtures were prepared gravimetrically from high purity Ag2S materials enriched in 32S, 33S, and 34S. All materials were converted into SF6 gas and subsequently, their sulfur isotope ratios were measured on the SF5+ species using a special gas source mass spectrometer equipped with a molecular flow inlet system (IRMM's Avogadro II amount comparator).

TL;DR: In this article, the authors compared the affinity and reactivity of three different minerals for natural organic matter (NOM) in forest floor leachate (FFL) from hardwood and pine forests.

TL;DR: The decay constants used in geo- and cosmochronology usually are assigned uncertainties of ca. 1% but there are very much larger unaccounted discrepancies between decay constants reported by different "counting groups" as well as differences between results derived from counting experiments and from the comparison of ages obtained on the same samples by utilizing different radioactive clocks.

TL;DR: In this article, hydrogen isotope ratios (D/H) of lipid biomarkers extracted from aquatic sediments were measured to determine whether they can be used as a proxy for D/H of environmental water.

TL;DR: A large data set of single and multi-grain zircon and titanite analyses from a sample of the Oligocene Fish Canyon Tuff (FCT), a voluminous ash flow from the San Juan Mountains of Colorado and widely used 40Ar/39Ar geochronological standard, has been used to evaluate the influence of various sources of analytical and geological uncertainty on the calculated age of this tuff by the isotope dilution U-PbZircon method as discussed by the authors.

TL;DR: The results indicate that a wide range of bacterial species exhibit nearly identical Cd adsorption behavior as a function of pH, and it is proposed that metal-bacteria Adsorption is not dependent on the bacterial species involved.

TL;DR: In this article, the acid/base properties of goethite at pH. 4 in a 0.7 M NaCl solution can be reproduced successfully using either the Constant Capacitance (CCM), the Basic Stern (BSM), or the Triple Layer models (TLM) when two surface acidity constants are considered.

TL;DR: A metaconglomerate from the Yilgarn Craton (Western Australia) contains detrital zircons with ages > 4.40 Ga as discussed by the authors.

TL;DR: In this article, the authors carried out a series of experiments using a karst-analogue set-up in a chamber of constant temperature and 100% humidity, where NaHCO3 and CaCl2 solutions at PCO2 around 10−3 were mixed just before passage through a tube and allowed to drip onto a surface, analogous to a stalagmite.

TL;DR: In this article, the role of water column methanotrophy (microbial methane oxidation) as a control on methane release was quantified by measuring water column methane profiles (concentration and δ13C) and oxidation rates at eight stations in an area of active methane venting in the Eel River Basin, off the coast of northern California.

TL;DR: In this article, Δ 14 C values were reported for 31 different lipid biomarker molecules obtained from Santa Monica Basin and Santa Barbara Basin surface sediments, including long-chain n-alkanes, fatty acids (as methyl esters; FAMEs), n -alcohols, C 30 midchain ketols and diols, sterols, hopanols, and C 40 isoprenoid side chains from the ether-linked glycerols of Archaea.

TL;DR: In this article, a peat core from a Swiss bog represents 12,370 14C years of peat accumulation and provides the first complete record of atmospheric Pb deposition for the entire Holocene.

TL;DR: In this paper, a new box model for the global carbon-calcium-strontium cycle is developed to simulate the evolution of Cretaceous and Cenozoic seawater and atmosphere.

TL;DR: In this paper, the authors determined the oxygen isotope composition of nitrate generated by microbial nitrification in acid forest floors and found that up to two of the three oxygen atoms in newly formed nitrate are derived from water.

TL;DR: The biomarker contents of three fossil conifer species (Athrotaxis couttsiae, Taxodium balticum, Pinus palaeostrobus) and the clay sediment from the Eocene Zeitz formation, Germany, have been analyzed by gas chromatography-mass spectrometry as mentioned in this paper.

TL;DR: Investigating the distributions and δ13C values of biomarkers for Archaea associated with anaerobic methane oxidation in disparate settings throughout two Eastern Mediterranean mud dome fields suggests that archaeal communities differ amongst the sites examined.

TL;DR: In this paper, a volumetric model was proposed to evaluate the effect of exposure of anoxic subsurface sediment containing partly degraded organic material to oxygen via irrigated worm burrows or by reworking.

TL;DR: In this article, the authors investigated the variation in Fe-oxide reactivity by studying the kinetics of bulk reductive dissolution of a suite of synthetic Fe-oxides in 10 mM ascorbic acid at pH 3.

TL;DR: In this article, the solubilization of coprecipitated Co(III) and Ni(II) from goethite (α-FeOOH) during dissimilatory bacterial iron reduction was investigated to provide insights on biogeochemical factors controlling trace-element fluxes in anoxic environments.

TL;DR: A single quartz powder was dissolved at 200°C and 250°C under far from equilibrium conditions in atmosphere-equilibrated deionized water during a sequential series of experiments performed over one year in a titanium open system mixed flow reactor.