Showing papers in "Geochimica et Cosmochimica Acta in 2008"

TL;DR: In this paper, the authors investigated changes in molecular form and surface charge of black carbon (BC) due to long-term natural oxidation and examined how climatic and soil factors affect BC oxidation.

TL;DR: In this article, the authors report variations of the 238U/235U isotope ratio in natural samples (basalts, granites, seawater, corals, black shales, suboxic sediments, ferromanganese crusts/nodules and BIFs) of ∼1.3.

TL;DR: The TEX86 (TetraEther indeX of tetraethers consisting of 86 carbon atoms) paleothermometer is based on the relative distribution of archaeal lipids and is increasingly used to reconstruct past sea water temperatures as discussed by the authors.

TL;DR: In this article, the biochemical stability of black carbon (BC) was assessed in a chronosequence of high-BC-containing Anthrosols from the central Amazon, Brazil, using a range of spectroscopic and biological methods.

TL;DR: In this paper, an analysis of coexisting silicate melt and fluid inclusions, entrapped in quartz crystals in volatile saturated magmatic systems, allowed direct quantitative determination of fluid/melt partition coefficients.

TL;DR: The East Qinling-Dabie molybdenum belt is part of a larger East-West trending metallogenic belt in eastern China as mentioned in this paper, where most of the molybordenum deposits occur as porphyries or porphyry-skarn type, but there are also some vein type deposits.

TL;DR: In this article, an updated phase diagram of the Na2SO4-H2O system based on a careful review of the available thermodynamic data of aqueous sodium sulfate and the crystalline phases is presented.

TL;DR: The voluminous 2.5-Ga banded iron formations (BIFs) from the Hamersley Basin (Australia) and Transvaal Craton (South Africa) record an extensive period of Fe redox cycling.

TL;DR: This article used a transect of 32 lake surface sediments across large gradients of precipitation, relative humidity, and vegetation composition in the southwestern United States to study the natural factors affecting sedimentary δ D wax.

TL;DR: In this paper, the chemical and isotopic compositions of the dissolved load of the rivers of the Changjiang Basin, one of the largest riverine systems in the world, were analyzed.

TL;DR: In this article, the authors examined the applicability of clumped isotope thermometry to reconstructing the growth temperatures of speleothems, by examining the glacial/interglacial variations of the Δ47 values of the speleothem carbonates from Soreq cave, Israel.

TL;DR: In this article, the trace element and Nd isotope geochemistry of very shallow-water banded iron formations (IFs) from the Pongola Supergroup, South Africa, was discussed to gain a better understanding of solute sources to Mesoarchean shallow coastal seawater.

TL;DR: Fractionation of Cu and Zn isotopes during adsorption of the metal onto amorphous ferric oxyhydroxide was examined in experimental mixtures of metal-rich acid rock drainage and relatively pure river water and during batch adaption experiments using synthetic ferrihydrite.

TL;DR: As3+-pyrite as discussed by the authors is a new form of arsenian pyrite, in which As substitutes for Fe [(Fe,As)S2], in contrast to the more common form of As1-substitutes for S [Fe(As,S)2].

TL;DR: In this paper, the authors conduct flow-through experiments on unhydrated volcanic ash samples from a variety of locations and sources, measuring the concentrations and fluxes of elements into de-ionized water and two contrasting ocean surface waters.

TL;DR: In this article, a tri-octahedral Li-Mg smectites (hectorites) were synthesized at temperatures ranging from 25 to 250°C, in the presence of solutions highly enriched in lithium.

TL;DR: Tang et al. as mentioned in this paper showed that both precipitation rate and temperature dominantly control Ca isotope fractionation, and that an increase in temperature results in less 44Ca fractionation and the impact of precipitation rate on 44CA fractionation is reduced.

TL;DR: In this article, the authors collected 500 stream waters and associated bed-load sediments over an 400 km 2 region of Eastern Canada and analyzed these samples for Fe, Mn, and the rare earth elements (REE + Y).

TL;DR: In this article, the authors investigated the Mn-Cr systematics in a number of primitive meteorites, differentiated planetesimals and terrestrial planets in order to address the chronology of the early stages of protoplanetary disk evolution and planetary formation.

TL;DR: In the Mediterranean area, lamproites are derived from melts with three components involved in their origin, characterized by contrasting geochemical features which appear in 206Pb/204Pb, 87Sr/86Sr, and 143Nd/144Nd space as discussed by the authors.

TL;DR: In this article, the results of 57 noble gas determinations in CO2 rich fields (>82%) from three natural reservoirs to the east of the Colorado Plateau uplift province, USA (Bravo Dome, NM, Sheep Mountain, CO. and McCallum Dome, CO.), and from two reservoirs from within the uplift area (St. John’s Dome, AZ, and McElmo dome, CO.).

TL;DR: In this article, in situ resonant surface X-ray scattering measurements of arsenate adsorption at pH 5 in 0.01 M NaCl on corundum and hematite (012) surfaces demonstrate that arsenate surface complexation is unexpectedly bimodal, adsorbing simultaneously as inner and outer-sphere species.

TL;DR: In this article, a series of synthesis experiments were carried out at 70 C and pH 1, 2, 3 and 4.5 from solutions with Fe/As molar ratios of 1 over the pH range of 1--4.5.

TL;DR: In this paper, the authors provided new constraints on the petrogenesis and protolith of peralkaline, metaluminous and peraluminous intrusions and rhyolitic tuffs in Emeishan large igneous province, with significant bearing on crustal melting associated with mantle plumes.

TL;DR: In this article, the authors show that low-degree CO2-rich potassic silicate melts from the convective upper mantle were preferentially channelled into an older, pre-existing MARID-type vein network at the base of the North Atlantic craton lithosphere, where they froze to form new phlogopite-carbonate dominated veins.

TL;DR: In this paper, the authors explore Fe/Mn and Nb/Ta ratios of basalts as potential tracers for differentiating melts of recycled mafic crustal lithologies from peridotitic melts.

TL;DR: In this article, the edge and basal surface sites of kaolinite were determined by batch titration experiments at 25°C in the presence of NaNO3 and in the pH range 3-9.

TL;DR: In this paper, high-precision quadruple sulfur isotope analyses (32S/33S/34S/36S) of barite, pyrite in barite and sulfides in related hydrothermal and igneous rocks occurring in the Dresser Formation, Western Australia, were performed.

TL;DR: In this article, Sideroxydans lithotrophicus (ES-1, a novel FeOB) was found to tolerate low-O2 environments where they can more successfully compete with abiotic Fe(II) oxidation.