Showing papers in "Chemical Geology in 2004"

TL;DR: In this paper, a laser ablation-inductively coupled plasma-mass spectrometer (LA-ICP-MS) was used for in situ U-Pb zircon geochronology.

TL;DR: In this article, the authors investigated correlations between the age offsets and P, Sm and Nd abundances in the zircons, and concluded that the presence of Nd is not the primary cause of the apparent matrix effect.

TL;DR: In this paper, the authors developed a multiproxy technique for assessing redox facies in black shale samples: euxinic conditions were considered to have existed if at least two of four trace-indicator trace elements (Mo, U, V, Zn, and Pb), and nonsulfidic anoxic conditions were inferred otherwise.

TL;DR: In this paper, the authors examined the levels of precision and accuracy obtainable by laser ablation Hf-isotope analysis of zircons in real-world situations using a 193-nm ArF excimer laser coupled to a Nu Plasma MC-ICPMS.

TL;DR: The degree of anoxia that existed during accumulation of Devonian-mississippian black shales in central Kentucky has been extensively studied in this article, where the authors used geochemical data to elucidate paleodepositional environments for these units.

TL;DR: In this article, a double-focusing MC-ICP-MS was used to obtain a Pb isotope analytical method using a 207Pb-204Pb double spike (DS).

TL;DR: In this article, a review of biogeochemical processes at ancient methane-seeps is presented, focusing on carbonate fabrics and phases, including inverted stromatactoid cavities, globular fabrics, botryoidal aragonite, micritic nodules, fractures, clotted micrites, and constructive seams representing fossilised biofilms.

TL;DR: In this article, the authors determined the geochemical characteristics of sediments and measured rates of the anaerobic oxidation of methane (AOM) and sulfate reduction (SR) in samples collected near thermogenic (structure II) gas hydrate mounds and in areas lacking hydrates along the continental slope in the Gulf of Mexico.

TL;DR: One hundred fifty-six biogenic calcites and 96 whole rock carbonate samples of Paleozoic and Mesozoic age have been analysed for their sulfur isotopic composition as mentioned in this paper, which substantially enhances our knowledge about secular variations of the global sulfur cycle during the Phanerozoic.

TL;DR: In this paper, the authors measured the chemical and isotopic compositions of two major river systems (Wujiang River and Yuanjiang River) in karst-dominated regions, and during winter were measured.

TL;DR: In this paper, the authors studied the geology, petrology, geochemistry and geochronology of two mafic-ultramafic intrusions in the Huangshanxi and Huangshandong intrusions.

TL;DR: In this paper, the role played by sulfur-rich organic matter (OM) in ancient marine deposits is emphasized, and it is shown that OM is systematically more enriched relative to other redox-sensitive/sulfide-forming elements studied (U, V, Ni, Cu, Zn, Cr), and Mo enrichment is positively correlated with the amount of sulfurized OM but not with pyrite abundance.

TL;DR: In this paper, the PGE systematics for peridotite xenoliths from N. Lesotho (on-craton), S. Namibia (circum-cratonic), the Vitim volcanic field (Baikhal Rift), plus massif peridotsites from Beni Bousera, N. Morocco are presented.

TL;DR: In this paper, the authors investigated the microbial reduction kinetics of Fe(III) iron oxyhydroxides and found that the solubility appears to be a rate-controlling parameter in both the abiotic and enzymatic reduction.

TL;DR: In this paper, a metal-chelating organic ligand 3,4 dihydroxybenzoic acid (3,4 DHBA) was used as a source of chelated ferric iron, and a carbon source, to investigate mineral weathering rate and microbial metabolism.

TL;DR: In this article, the lithium concentration and isotopic composition of two saprolites developed on a granite and diabase dike from South Carolina have been measured in order to document the behavior of lithium isotopes during continental weathering.

TL;DR: In this article, the Hf and Lu isotopic ratios of the zircon standard 91500 have been redefined by multiple collector inductively coupled plasma mass spectrometry (MC-ICP-MS).

TL;DR: In this article, the authors used the Meade Peak Phosphatic Shale Member of the Phosphoria Formation, a phosphate deposit of Permian age in the northwest United States, to model accumulation rates of Cd, Cr, Cu, Mo, Ni, V, and Zn on the seafloor.

TL;DR: In this paper, a review of the geology of Hydrate Ridge and its biogeochemistry is presented, which summarizes recently published data on geomicrobiology and biogeochemical, and derives a local methane budget.

TL;DR: Granulite xenoliths sampled from the Hannuoba basalts, North China craton, allow recognition of three types of ancient lower crustal components as discussed by the authors, including felsic granulite-facies metamorphism.

TL;DR: In this paper, a comparison of apatite fission-track ages measured by using conventional thermal neutron irradiation and Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) to determine sample uranium content was made.

TL;DR: In this paper, the authors used submersibles and piston cores to sample two chemosynthetic communities in the Gulf of Mexico continental slope at ~ 540 m water depth. And they found that the C2−C5 hydrocarbons of vent gas initially most depleted in 13C (ethane, isobutane, and isopentane) are least affected by microbial oxidation, whereas hydrocarbon carbonates initially enriched in 13c (propane, normal butane and normal pentane), not only methane, are most affected.

TL;DR: In this paper, the authors show that the pyrite and chalcopyrite ranges of these two minerals do not overlap, suggesting that the Fe is probably a mixture between sedimentary and igneous sources.

TL;DR: In this paper, a technique which uses laser ablation sampling and multiple collector inductively coupled plasma mass spectrometry (MC-ICPMS) was proposed to obtain relatively accurate in situ Sr isotope ratios in a range of common geologic materials.

TL;DR: In this paper, the results of a study of the geologically important copper isotope (65Cu/63Cu) fractionation between aqueous Cu(II) and copper sulphide were reported.

TL;DR: In this paper, the pre-edge X-ray absorption near edge structure (XANES) and Mossbauer spectra were collected on synthetic glasses of basaltic composition and of glasses on the sodium oxide-silica binary to establish a relation between the preedge of the XANES at the K-edge and the Fe oxidation state of depolymerised glasses.

TL;DR: In situ Re-Os analysis of sulfide phases in peridotite xenoliths from kimberlites in the Kaapvaal Craton has been used to analyse relationships between crustal events and the modification of the subcontinental lithospheric mantle (SCLM).

TL;DR: In this article, the authors determined the major, trace, and rare-earth element (REE) compositions of evaporite and detrital minerals in loess and desert sand from the central Loess Plateau (CLP), where 80% of the loess deposits in China are found.

TL;DR: In this paper, the authors reported the abundance of Ru, Rh, Pd, Re, Os, Ir and Pt in 11 high and low-abundance reference materials (RMs) that are currently in use for platinum group element (PGE) analysis.