Showing papers in "Geochimica et Cosmochimica Acta in 2013"

TL;DR: It is shown that angiosperms generally produce more n-alkanes than do gymnosperms, and furthermore that CPI values show such variation in modern plants that it is prudent to discard the use of CPI as a quantitative indicator of n-alksane degradation in sediments.

TL;DR: In this article, it was shown that hematite-magnetite intergrowths are commonly found in porphyry copper deposits, suggesting high and fluctuating oxygen fugacity (fO2).

TL;DR: In this article, the authors report the first comprehensive trace element database of pyrite from the Dexing deposit, China's largest porphyry Cu deposit, which combines high-spatial resolution and X-ray mapping capabilities of electron microprobe analysis (EMPA) with low detection limits and depth-profiling capabilities of secondary-ion mass spectrometry (SIMS) in a suite of samples from the Dextering deposit.

TL;DR: In this article, an empirical calibration of the carbonate clumped isotope thermometer based on mollusk and brachiopod shells from natural and controlled environments spanning water temperatures of −1.0 to 29.5°C is presented.

TL;DR: In this article, the authors used bulk H, C and N elemental and isotopic analyses to classify CM and CR chondrites, and proposed a different classification scheme based on the degree of hydration (wt.% H in water and OH) of a meteorite.

TL;DR: In this article, the effects of evaporative deuterium (D)-enrichment of leaf water on the δD values of leaf wax n-alkanes have not yet been directly assessed and quantified.

TL;DR: In this paper, the authors show that the extent of calcite isotope fractionation decreases with increasing calcite growth rate, which is consistent with the theoretical value calculated by Rustad et al. (2010) for Mg calcite.

TL;DR: In this paper, a detailed observational study is presented that illustrates that evaporative deuterium (D)-enrichment of leaf water also affects the δD values of leaf wax n-alkanes in plants from natural ecosystems along a 1500 km climate gradient in Northern Australia.

TL;DR: In this article, the authors derived a ratio of lower to upper mantle primordial noble gas concentrations of 6.9 − 5.6 for the inner Solar System volatiles with particular reference to the Earth.

TL;DR: In this paper, the acidity constants of surface groups on (0, 1, 0)-type edges of montmorillonite and kaolinite, which are representatives of 2:1 and 1:1-type clay minerals, respectively, were calculated with first principles molecular dynamics (FPMD) based vertical energy gap technique.

TL;DR: In this article, the authors used a finite cylinder geometry to approximate 4 He ingrowth and thermal diffusion within hexagonal prismatic apatite crystals, where the diffusion domain is approximated by the physical grain size.

TL;DR: The iron isotopic compositions of 93 well-characterized basalts from geochemically and geologically diverse mid-ocean ridge segments, oceanic islands and back arc basins were measured.

TL;DR: In this paper, the authors studied both modern soils and buried paleosols in order to understand the relationship of temperature (T°C(47)) estimated from clumped isotope compositions (Δ_(47)) of soil carbonates to actual surface and burial temperatures.

TL;DR: In this paper, the surface structure of Ferrihydrite (Fh) is elucidated in relation to that of the mineral core, showing a unique surface composition differing from the traditional mineral core.

TL;DR: In this article, the first direct measurements of anaerobic oxidation of methane (AOM) activity in freshwater and brackish coastal wetland sediments were presented, and the results showed that despite disparate sulfate concentrations, both environments supported substantial rates of AOM.

TL;DR: In this article, the effect of phosphate on the sorption of copper and lead to ferrihydrite was investigated using a combination of batch experiments, extended X-ray absorption fine structure (EXAFS) spectroscopy and surface complexation modeling with the three-plane CD-MUSIC model.

TL;DR: In this article, the authors present experimental determinations of partition coefficients for several of the first-row transition elements (FRTE) and Ga and Ge between basaltic melt and olivine, garnet, pyroxenes, and spinel at 3 GPa.

TL;DR: In this article, a model of the biochemical steps involved in bacterial sulfate reduction (BSR) was used to explore how the slope on a δ18OSO4 vs. δ34SSO4 plot relates to the net sulfate Reduction Rate (nSRR) across a diverse range of natural environments.

TL;DR: In this article, an extended triple layer model (ETLM) was used to predict the competitive interactions of As(III, V) with the coexisting ions in binary-solute systems.

TL;DR: In this paper, high pressure (P) −temperature (T) experiments were performed on mixtures of synthetic or natural silicates (tholeiitic basalt/alkali basalt, KOMAT/komatiite/fertile peridotite) and Fe-Ni−C±Co−S contained in graphite or MgO capsules, and the experiments produced immiscible Fe-rich metallic and silicate melts at oxygen fugacity (fO2) between ∼IW −1.5 and IW-1.

TL;DR: In this article, the authors compared the deuterium/hydrogen (D/H) ratios of five co-occurring tree species, A. rubrum, Platanus occidentalis, Juniperus virginiana, Pinus taeda, and Pinus strobus, and soils at forty sites along the East Coast of the US.

TL;DR: In this paper, the authors proposed that tectonic uplift may have enhanced the sink of atmospheric CO2 by silicate weathering, and thus produced the decline of pCO2.

TL;DR: In this article, the B-Zone in the northwest of the Strange Lake pluton, Canada, has been combined with numerical simulations to improve our understanding of fluid-rock interaction in peralkaline granitic systems.

TL;DR: In this paper, the authors presented ultra-high precision, multi-collector 40 Ar/ 39 Ar results for FCT and ACR sanidine, using a new generation ARGUSVI mass spectrometer.

TL;DR: In this article, a trace element based two-pyroxene thermometer is built on two parameterized lattice strain models for rare earth element (REE) partitioning between pyroxene and basaltic melt.

TL;DR: In this article, a combined U-Pb, Lu-Hf and O isotopic study has been carried out by in situ analyses of approximately 450 detrital zircon grains from the Niger, Nile, Congo, Zambezi and Orange Rivers.

TL;DR: In this article, the authors investigated the geochemistry and geobiology of groundwater springs discharging from serpentinized peridotite of The Cedars, CA, for their geochemical and geophysics.

TL;DR: The Mg/Ca ratio in calcite is one of the principal proxies used for paleoceanographic temperature reconstructions, but recent core-top sediment observations suggest that salinity may exert a significant secondary control on planktic foraminifers as mentioned in this paper.

TL;DR: In this paper, the authors measured the OH contents and D/H ratios in apatite grains in lunar basalts and showed that apatites in high-Ti basaltic samples display a relatively restricted range in OH contents (∼1500-3000 ppm) with large δD variations ( ∼600-1000 ǫ), whereas apatitic grains in low-Ti Apollo and lunar meteorites display a comparatively larger range in HO contents, each sample displaying relatively restricted variations in their HO ratios.

TL;DR: The carbon stable isotope values of the Carboniferous, Permian and Lower Triassic carbonate reservoirs of the Sichuan Basin in China have been investigated in this paper.