Showing papers in "Geochimica et Cosmochimica Acta in 2018"

TL;DR: In this paper, the authors used paired measurements of calcium (44Ca/40Ca or δ44Ca) and magnesium (26Mg/24Mg) isotope ratios in sedimentary carbonates and associated porefluids as a tool to understand the mineralogical and diagenetic history of Neogene shallow-water carbonate sediments from the Bahamas and southwest Australia.

TL;DR: In this paper, a numerical model of marine carbonate diagenesis was developed that tracks the elemental and isotopic composition of calcium, magnesium, carbon, oxygen, and strontium, during dissolution of primary carbonates and re-precipitation of secondary carbonate minerals.

TL;DR: In this paper, the authors presented new compositional data for carbonaceous chondrites with an emphasis on the origin of the volatile element depletion pattern, and showed that parent body alteration and terrestrial weathering only have minor effects on the bulk chondrite compositions.

TL;DR: In this article, the structural variation of Fe(II) entities during the oxidation of Fe-II-bearing clay minerals by O2 was identified and the mechanisms of electron transfer within the mineral structure and from mineral to O2 for hydroxyl radicals (OH) production were unraveled.

TL;DR: In this article, the role of sulfate-reducing microorganisms (SRM) in the nucleation and growth of sedimentary iron sulfide minerals was investigated in laboratory experiments.

TL;DR: In this article, the primordial internal differentiation of the Moon into mantle and crust was investigated using graphite capsules in piston cylinder (1.35-0.80 GPa) and internally-heated pressure vessels.

TL;DR: In this article, a new surface complexation model was developed for montmorillonite, that specifically accounts for the spillover effect using the edge surface speciation model by Tournassat et al.

TL;DR: In this article, the authors analyzed ancient atmospheric gases trapped in fluid inclusions contained in minerals of Archean (3.3 Ga) to Paleozoic (404 Ma) rocks in an attempt to document the evolution of the elemental composition and isotopic signature of the atmosphere with time.

TL;DR: In this paper, the authors applied the 182Hf-182W chronometer to metal, silicate, and chondrule separates from four Renazzo-type carbonaceous (CR) chondrites.

TL;DR: In this paper, the relative abundances of several methane isotopologues (including 13CH3D, a clumped isotopologue containing two rare isotope substitutions) in hot-spring source fluids sampled from four geochemically-distinct hydrothermal vent fields (Rainbow, Von Damm, Lost City, and Lucky Strike) were determined.

TL;DR: In this paper, the variability in uranium isotopes, trace metal and rare earth element (REY) concentrations in carbonate successions that have undergone several common types of diagenetic alteration was explored.

TL;DR: The authors examined the effects of diagenetic alteration on the U isotope composition in carbonate sediments, which are crucial to understand the accurate reconstruction of marine δ238U, are currently poorly constrained.

TL;DR: Wang et al. as discussed by the authors investigated the interactive effects of weathering, hydraulic sorting and sedimentary recycling on river sediment chemistry, and further validated the application of various weathering indices by measuring mineralogical and geochemical compositions of bank sediments and suspended particulate matters (SPMs) from five rivers in East China bearing various sizes, geologic settings and climatic regimes.

TL;DR: In this paper, the authors developed a unified model for the kinetics of heavy metal adsorption and desorption in soil based on the equilibrium models WHAM 7 and CD-MUSIC, which specifically consider metal kinetic reactions with multiple binding sites of SOM and soil minerals simultaneously.

TL;DR: In this paper, the speciation of tin and the solubility of cassiterite in H2O+HCl were determined at temperatures to 600°C using in situ Raman spectroscopy.

TL;DR: In this paper, the authors investigated the origin and distribution of authigenic minerals and their diagenetic characteristics, processes, and pathways at the scale of lacustrine laminae within the Es4s-Es3x shale sequence of the Bohai Bay Basin (BBB).

TL;DR: In this article, the authors demonstrate that Fe(II) was the main electron donor to O2 to produce hydroxyl radical (OH) in the environment, which is a highly reactive oxidant of dissolved organic carbon (DOC).

TL;DR: In this article, high precision Fe and Zn stable isotope analyses of Baffin Island picrites have been performed, with δ56Fe ranging from −0.03 to 0.28.

TL;DR: In this article, the authors measured the Mg isotope compositions of a set of samples of altered oceanic crust (AOC) recovered from the Ocean Drilling Program Hole 801C, the reference site for old crust (∼170 Ma) subducting in the Pacific.

TL;DR: In this article, a gold-bearing laminated quartz breccia ore zone and its sulfide-bearing alteration halo in the (+6 Moz Au) structurally-controlled Archean Waroonga deposit located in the Eastern Goldfields Superterrane of the Yilgarn Craton, Western Australia were investigated.

TL;DR: In this paper, the impact of surface roughness on reaction rates in 2D rough fractures is investigated. But the results show that the reaction rate is not linearly proportional to the surface area, rather, local concentration gradients resulting from flow and transport processes limit the increase in the rate.

TL;DR: In this paper, the authors measured molybdenum (Mo) and uranium (U) abundances in the water column, sinking particles, sediments and pore waters of the marine euxinic Lake Rogoznica (Adriatic Sea, Croatia) over a two year period, with the aim of shedding light on the specific processes that control Mo-U accumulation and isotope fractionations in anoxic sediment.

TL;DR: The Izu-Bonin-Mariana (IBM) island arc formed following initiation of subduction of the Pacific plate beneath the Philippine Sea plate at about 52 Ma as discussed by the authors.

TL;DR: In this article, the trajectory of Fe mineral transformation under redox fluctuations is unclear and has been reported to result in both increases and decreases in Fe phase crystallinity in redox-active soils and sediments.

TL;DR: In this paper, the authors show that contaminated sediments can be significant sources of Hg in aquatic ecosystems and, through re-emission processes, to the atmosphere and that transformation and release of contaminated Hg may be enhanced by...

TL;DR: In this paper, a detailed geochemical comparison on bulk samples of different units was undertaken using stable Cr isotopes coupled with trace and major elements, and it was shown that the heavy δ53/52Cr values of Fe-lutites from outcrop Ijzermijn IF samples reported here and in a previous study are the product of modern oxidative weathering rather than an indicator for Mesoarchaean oxidative weatherings at ca. 2.95 Ga.

TL;DR: In this article, the authors conducted various biogeochemical and molecular genetic analyses to characterize substrate availability, rates of methanogenesis, and methanogen community composition, and further evaluated the contribution of different substrates and pathways for methane production in deltaic surface and subsurface sediments.

TL;DR: Titanium isotopic compositions (mass-dependent fractionation and isotopic anomalies) were measured in 46 calcium-, aluminum-rich inclusions (CAIs) from the Allende CV chondrite.

TL;DR: This paper measured the U isotope composition of modern and ancient corals, a limestone and a dolostone, as well as 43 shallow-water carbonate sediments from the ODP Leg 166 Site 1009 drill core, on the slope of the Bahamas platform.

TL;DR: The results of reaction path modelling at the CarbFix site in SW-Iceland indicate that this “sweet spot” for mineralisation of CO2 is at pH from ∼5.2 to 6.4 as discussed by the authors.