Showing papers in "Geochimica et Cosmochimica Acta in 2004"

TL;DR: In this paper, the authors examined the characteristics of He loss from zircon in a series of step-heating diffusion experiments, and compared the results with other thermochronometric constraints from plutonic rocks.

TL;DR: In this paper, the rare earth elements (REEs) were measured in pore waters of the upper ∼25 cm of sediment from one site off Peru and three sites on the California margin.

TL;DR: In this paper, Pb diffusion in both synthetic (CePO4) and natural monazites run under dry, 1-atm conditions is reported. And the Arrhenius relation for in-diffusion experiments on synthetic monazite is given by: D=0.94 exp (−592±39 kJ mol −1 /RT) m 2 s −1

TL;DR: In this article, the reaction between dissolved sulfide and synthetic iron (oxyhydr)oxide minerals was studied in artificial seawater and 0.1 M NaCl at pH 7.5 and 25°C.

TL;DR: In this article, rare earth element and yttrium (REE+Y) concentrations were determined in 49 Late Devonian reefal carbonates from the Lennard Shelf, Canning Basin, Western Australia, and the results suggest that most limestones should record important aspects of the REE geochemistry of the waters in which they precipitated, provided they are relatively free of terrigenous contamination and major diagenetic alteration from fluids with high, non-seawater-like REE contents.

TL;DR: In this article, a wide variation in zircon δ18O values from −10.9 to 8.5 was found in the Dabie-Sulu orogenic belt of east-central China.

TL;DR: In this article, the authors measured hydrogen isotope ratios on n-alkanes (n-C12 to n-C31) extracted from recent lake surface sediments along a N-S European transect to test if modern climate variability is recorded in these biomarkers.

TL;DR: In this paper, the authors present a theoretical framework that allows for most of the analytical limitations to high precision and accuracy to be overcome, including peak shape, correlations introduced by counting statistics, and the effect of memory on double-spike methods.

TL;DR: In this article, the authors re-examine the notion that extensive As mobilization in anoxic groundwater of Bangladesh is intimately linked to the dissolution of Fe oxyhydroxides on the basis of analyses performed on a suite of freshly collected samples of aquifer material.

TL;DR: The Li isotopic composition of the upper continental crust is estimated from the analyses of well-characterized shales, loess, granites and upper crustal composites from North America, China, Europe, Australia and New Zealand as mentioned in this paper.

TL;DR: In this paper, the structure of tecto-aluminosilicate and peraluminous glasses were studied using Raman spectroscopy, X-ray absorption at the Al K-edge and 27Al NMR spectrograms with two different high fields (400 and 750 MHz).

TL;DR: In this article, the sensitivity of calcite produced by two planktonic foraminifera species, Orbulina universa and Globige- rina bulloides, in laboratory culture experiments was investigated.

TL;DR: In this article, the main terminal processes of organic matter mineralization in anoxic Black Sea sediments underlying the sulfidic water column are sulfate reduction in the upper 2-4 m and methanogenesis below the sulfate zone.

TL;DR: Schwertmannite (ideal formula: Fe8O8(OH)6SO4) is typically found as a secondary iron mineral in pyrite oxidizing environments as discussed by the authors.

TL;DR: In this article, a semi-empirical surface complexation approach was used to describe the U(VI) experimental data more precisely as a function of aqueous chemical conditions.

TL;DR: In this article, a narrow range of variation observed in apatite-to-cholesterol spacings ( 13 Capat-bchol) suggests that cholesterol 13 C values can potentially also be used as an independent test for the isotopic integrity of apatit 13C values.

TL;DR: In this article, short sediment cores were recovered from the upper edge (UEO), within (WO) and below (BO) the oxygen minimum zone (OMZ) off Peru during cruise 147 of R/V Sonne.

TL;DR: In this article, two enrichment cultures of Fe(II)-oxidizing photoautotrophs and a culture of the genus Thiodictyon were studied with respect to their ability to fractionate Fe isotopes.

TL;DR: In this article, the authors examined the trace element uptake as a function of calcite growth rate and the mobility of atoms in the near-surface region of the calcite lattice.

TL;DR: In this paper, a suite of volcanic glasses that range from basaltic to rhyolitic in composition were measured in mixed flow reactors at pH 4 and 10.6, and temperatures from 25 to 74°C.

TL;DR: In this article, the authors presented new Hf-W data for seven carbonaceous chondrites, five eucrites, and three shergottites, and showed that mantle differentiation in the eucrite parent body (Vesta) occurred at 4563.2 ± 1.4 Ma and suggest that core formation took place 0.9 ± 0.3 Myr before mantle differentiation.

TL;DR: A series of laboratory studies were conducted to increase understanding of stable carbon (13C/12C) and hydrogen (D/H) isotope fractionation arising from methanogenesis by moderately thermophilic acetate-and hydrogen-consuming methanogens as mentioned in this paper.

TL;DR: In this paper, the authors derived a method for calculating abundances of all such species in a thermodynamically equilibrated population of isotopologues, and presented results of these calculations for O_2, CO, N_2O, NO, CO_2 and N 2O between 1000 and 193 to 77 K.

TL;DR: In this paper, the authors present the first measurements of the abundance of atmospheric CO 2 from natural and synthetic sources, discuss the factors influencing its natural distribution and demonstrate how its abundance constrains the sources of CO 2 in the Los Angeles basin.

TL;DR: Aquifer geochemical profiles of aqueous and solid phase parameters were measured in a field site in the Munshiganj district of Bangladesh where the groundwater is severely contaminated by As as discussed by the authors.

TL;DR: Isotopic analysis of nitrate and sulfate minerals from the nitrate ore fields of the Atacama Desert in northern Chile has shown anomalous 17 O enrichments in both minerals as discussed by the authors.

TL;DR: In this paper, the authors investigated the kinetics of calcite precipitation induced in response to the hydrolysis of urea by Bacillus pasteurii at different temperatures in artificial groundwater.

TL;DR: In this article, the solubility of gold was measured in aqueous sulphide solutions from 100 to 500°C at 500 bar in order to determine the stability and stoichiometry of sulphide complexes of gold(I) in hydrothermal solutions.

TL;DR: In this paper, the authors measured enthalpies of ferrihydrite and schwertmannite in 5 N HCl at 298 K. The results showed that the more stable samples become more stable with increasing crystallinity.

TL;DR: The results suggest that Fe(III) is released in a dissolved form as an inorganic aqueous complex and/or as a colloidal aggregate prior to mineral precipitation, suggesting that equilibrium processes involving free biological ligands do not account for the observed fractionation.