Showing papers in "Geochimica et Cosmochimica Acta in 2019"

TL;DR: In this paper, the authors show that Xe is the only noble gas that can escape as an ion in a photo-ionized hydrogen wind, possible in the absence of a geomagnetic field or along polar magnetic field lines that open into interplanetary space.

TL;DR: In this article, the authors examined pyrite geochemical and micro-textural features and relate these results to pyritic-forming processes at the active Cerro Pabellon Geothermal System (CPGS) in the Altiplano of the northern Chile.

TL;DR: In this paper, a series of experiments in which silicate liquids are evaporated in one-atmosphere (1-atm) gas-mixing furnaces under controlled f O 2 s, from the Fe-“FeO” buffer (iron-wustite, IW) to air (10 -0.68 bars), bracketing the range of most magmatic rocks.

TL;DR: In this paper, the authors combine electron probe and laser ablation micro-chemical maps of titanaugite crystals from Mt. Etna (Sicily, Italy) to explore the origin of sector zoning at the major and trace element levels, and its implications for the interpretation of magmatic histories.

TL;DR: In this paper, the authors used 7 Li-NMR spectra to identify three bonding environments, namely octahedral, outer-sphere (interlayer and adsorbed) and pseudo-hexagonal (ditrigonal cavity) Li, which can then be used to provide much needed constraints on field processes.

TL;DR: In this article, it was shown through least squares fitting that almost all features of the bulk elemental and isotopic compositions of the main carbonaceous chondrite (CC) groups, as well as the ungrouped Tagish Lake (C2) meteorite, can be reproduced using mixtures of the same four components.

TL;DR: The oxygen fugacity of nine mantle-derived komatiitic and picritic systems ranging in age from 3.55 Ga to modern day were determined using the redox-sensitive partitioning of V between liquidus olivine and KOMatiitic/picritic melt.

TL;DR: In this article, source Hg isotope signatures and process-based isotope fractionation factors are integrated into a fully coupled, global atmospheric-terrestrial-oceanic box model of MDF (δ202Hg), odd-MIF (Δ199Hg) and even-mIF ( Δ200Hg).

TL;DR: In this paper, the authors report on the extinct 26Al-26Mg and 53Mn-53Cr systems to establish fine-scale chronology of its formation and Cr and Ti isotopic anomalies to constrain the composition of the source reservoir of NWA 6704/6693.

TL;DR: In this paper, the authors measured the ages of chondrules from the unequilibrated L, L(LL) and LL ordinary chondrites (UOCs) using a CAMECA 1280 ims.

TL;DR: In this article, the microbially mediated NO3−-reducing Fe(II) oxidation process (NRFO) plays a key role in Fe/N interactions under neutral-anoxic conditions.

TL;DR: In this paper, the authors use experimentally measured solubility data for multicomponent K-free eclogite, k-free peridotite and K-bearing peridotaite rocks at upper mantle conditions from the literature to construct aqueous speciation solubilities models that enabled calibration of the thermodynamic properties of ions and metal-complex species involving the elements Na, K, Mg, Ca, Fe, Al, Si, Si and C in an extended Deep Earth Water (DEW) model.

TL;DR: In this paper, the authors measured the isotopic compositions of Ca,Al-rich inclusions (CAIs) from the Allende CV3 chondrite, as well as acid leachates and an insoluble residue from the Murchison CM2 chondlite, and combine these results with literature data for presolar grains, hibonites, chondrules, and bulk meteorites.

TL;DR: In this article, the authors report on analyses of REE plus yttrium concentrations (REY) and Ce anomalies in bulk carbonate samples from drill cores collected in the Bahamas (Clino and Unda) that allow them to track loss or retention of primary signals of initial oxic deposition through a range of subsequent alteration scenarios mostly under anoxic conditions.

TL;DR: In this paper, the authors presented experimental annealing data and models of bulk radiation damage kinetics in zircon and showed that fractional-annealing-progress depends on the extent of accumulated radiation damage.

TL;DR: In this paper, the authors examined Sb behavior during microbially-mediated reduction and transformation of Sb(V)-bearing ferrihydrite by the dissimilatory Fe(III)-reducing bacterium, Shewanella putrefaciens (strain CN32).

TL;DR: A combination of textural, micro-analytical and isotopic data for apatite from three Andean IOA deposits (Carmen, Fresia and Mariela) of Early Cretaceous age from the Coastal Cordillera of northern Chile is presented in this paper.

TL;DR: The authors studied porphyritic olivine-rich chondrules of the carbonaceous chondrite Kaba (CV3) by combined high-resolution X-ray mapping, quantitative electron microprobe analyses, and oxygen isotopic analyses via secondary ion mass spectrometry.

TL;DR: In this paper, a combination of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), Nanoscale secondary ion mass spectrometers (NanoSIMS), and NanSIMS was used to investigate the remobilization and re-concentration of gold and other trace elements during this complex replacement process and the probable mechanism.

TL;DR: In this paper, the authors demonstrate through laboratory carbonation experiments that highly negative-charged clay minerals such as illite and montmorillonite can aid the precipitation of abiotic proto-dolomite under ambient conditions, whereas nearly neutral charged kaolinite exerts negligible influence on such process.

TL;DR: In this article, the role of peat organic matter (OM) as a terminal electron acceptor for anaerobic respiration in organic soils was quantitatively demonstrated, and the reduction of OM and the resultant decrease in EACOM explained between 26 and 56% of the non-methanogenic CO2, which was between 5 and 39% of total CO2 produced.

TL;DR: In this paper, the authors present coupled Cu and Zn isotope data for a well-characterised Indian laterite weathering profile, which includes a full suite of samples from unaltered greywacke bedrock to indurated lateritic duricrust.

TL;DR: In this article, a series of unaltered to strongly altered oceanic peridotites were analyzed by analyzing their adsorption by ubiquitous secondary phases (e.g. goethite).

TL;DR: In this paper, the authors reported the first systematic use of methane Δ13CH3D and Δ12CH2D2 signatures approaching thermodynamic equilibrium in the context of continental sedimentary basins.

TL;DR: In this paper, an extensive dataset of dissolved Li isotope compositions of waters from the Lena River main channel, two main tributaries (the Aldan and Viliui Rivers) and a range of smaller sub-tributaries are presented from the post-spring flood/early-summer period at the onset of active layer development and enhanced water-rock interactions.

TL;DR: In this paper, the authors used the MultiCollector Inductively Coupled Plasma Mass Spectrometer (MC-ICP-MS) to analyze 51 geologically, geographically, and geochemically diverse oceanic basalt samples.

TL;DR: In this article, the authors provided a reconstruction of seawater carbonate ion concentration over the last 100 million years and provided simple corrections for past equilibrium constants, supported by experimental data and wellsuited for numerical models and observational studies on multi-million year time scales.

TL;DR: The negative molybdenum (Mo) isotope excursions appear coincident with previously discovered and seemingly peculiar redox-sensitive element (RSE) patterns in the same sedimentary rocks as discussed by the authors.

TL;DR: In this article, the authors reported new high-precision stable K isotope data for three martian meteorites, one lunar meteorite, one ordinary chondrite, four terrestrial igneous United States Geological Survey (USGS) reference materials, and twenty howardite-eucrite-diogenite [HED] meteorites.

TL;DR: In this article, the authors use an extensive compilation of terrigenous sediment compositions to better constrain the nature of rocks at the surface of continents at 3.25 and 250 million years ago.