Showing papers in "Chemical Geology in 1994"

TL;DR: The amount and type of organic matter in the sediments of lakes and oceans contribute to their paleoenvironmental and paleoclimatological records as discussed by the authors, but only a small fraction of the initial aquatic organic matter survives destruction and alteration during sinking and sedimentation.

TL;DR: In this article, eight geochemical indices used for the interpretation of bottom water palaeo-oxygen concentrations for argillaceous sedimentary rocks have been calculated for a suite of Upper Jurassic mudstones drawn from the Draupne and Heather Formations of the Norwegian North Sea, and the Kimmeridge Clay Formation from onshore England.

TL;DR: A comprehensive review on igneous petrological characteristics of mantle-derived spinel peridotites was made on the basis of their olivine-spinel compositional relationships as discussed by the authors.

TL;DR: Enhanced preservation is observed in low-O2 and euxinic environments, and aspects of the biochemistries of the aerobic and anaerobic process are reviewed, and a new model for organic carbon decomposition, the "pseudo-G" model, is developed.

TL;DR: A variety of field and laboratory observations demonstrate that particle reworking and irrigation activities of benthic fauna promote the remineralization of organic matter in bioturbated Corg-rich sediments.

TL;DR: In this paper, the relationship between mineral specific surface area and organic carbon (OC) concentration was examined for sediments and soil A-horizons from throughout the world, and the nature of mineral surfaces was examined using N2 adsorption-desorption isotherms, and most surface area was found to be present as pores with

TL;DR: Partition coefficients for Th, U, Pb, rare earth elements (REE), high field strength elements (HFSE), alkaline-earth elements, Sc, Cr, V and K were measured by ion microprobe techniques in two experiments on a natural high-alumina basalt composition from Medicine Lake, California as discussed by the authors.

TL;DR: In this paper, the crystal/melt partition coefficients were estimated as the concentration ratios between leucosome samples appearing to be pure melts and mesosome minerals, which were analyzed for trace elements with a laser probe coupled to an ICP mass spectrometer.

TL;DR: In the 16 years since the Sedona Conference on the behavior of trace elements in silicate systems, numerous studies providing new data have filled many of the gaps in knowledge of trace-element partitioning evident at that conference.

TL;DR: In situ proton microprobe analyses are used to calculate partition coefficients (D ) for Mn, Fe, Cu, Zr, Ga, Rb, Sr, Y, Zn, Ba and Pb, and more restricted data for Ni, Ge, Nb and As, in pyroxenes, olivines, biotites, hornblendes, feldspars and Fe-Ti-oxides, from 32 volcanic rocks as mentioned in this paper.

TL;DR: Sediment studies indicate that most sedimentary pyrite is formed rapidly from iron oxides, with smaller amounts formed more slowly from iron silicates (if sufficient geologic time is available), so it is recommended that the degree of pyritisation be defined with respect to the dithionite-extractable pool and/or the boiling HCl-extracted pool for the recognition of iron-limited pyritification.

TL;DR: In this paper, the authors measured trace-element abundances in situ by ion microprobe in five samples of hornblende and melt ranging from basaltic andesite to high-silica rhyolite.

TL;DR: In this article, it was shown that the partitioning of trivalent cations into olivine is maintained by a coupled REE, Mg−1-Al,Si−1 substitution rather than by creating vacancies or interstitials.

TL;DR: In this paper, the effects of trapped melt fraction (TMF) are accounted for by including in the calculation a phase (the trapped melt) with a mineral/melt partition coefficient of 1, and adjusting the rock's mode to reflect removal of the TMF.

TL;DR: The existence of excess Ar in phengites from coesite-bearing ultrahigh-pressure eclogites of the Dabie Mountains and SuLu terrain, China, has been confirmed by dating of minerals using SmNd, RbSr and 40Ar39Ar methods as mentioned in this paper.

TL;DR: In this article, the authors analyzed stream sediments from mixed low and high-silica sources in the Wet Mountains of Colorado for their mineralogic and selected elemental composition, and found that the high-silica source rocks tend to contain higher concentrations of REE, Th, Hf and Ba, lower concentrations of Fe, Sc and Cr, and more negative Eu anomalies than the low-siliac source rocks.

TL;DR: In this article, it was shown that an important marine flux of many minor elements through the ocean is in the form of biogenic matter, with a composition approaching that of plankton.

TL;DR: In this article, the sulfide melt-silicate melt partition coefficients for Ir and Pd have been determined from experiments run in a piston-cylinder apparatus at 1450°C, 8 kbar and under ƒ O 2 ǫ S 2 conditions appropriate for mafic magmas.

TL;DR: In this paper, the authors evaluated the extent and source of variation of clinopyroxene-silicate melt partition coefficients (D) on natural basalts (picrite, alkaline basalt, nephelinite, high-alumina basalt; 1235-1300°C; 1.8 GPa).

TL;DR: An electron microprobe was used to measure partition coefficients (D-values) for Ti, Sr, La, Sm, Ho and Lu in amphiboles, clinopyroxenes and Sr- and REE-enriched basanitic melts as mentioned in this paper.

TL;DR: Partition coefficients for the elements Ta, Nb, Hf, Zr, Sc, V, Ga, Zn and Co have been determined by laser ablation ICP-MS and/or electron microprobe between spinel and melt using an alkali olivine basalt at 1 atm as mentioned in this paper.

TL;DR: The ability of the Gram-positive bacterium B. subtilis to bind and nucleate precipitates from silicate anions has been studied over 24 weeks in the presence of Fe and A1 at concentrations close to those levels in soils, and at slightly acid (5.5) and basic (8.0) pH.

TL;DR: In this article, a passive extension model was proposed for the geodynamic evolution of this region, which involves continental extension followed by magma generation via lithosphere-asthenosphere interaction, should be applicable to other areas of Cenozoic rift magmatism around the South China Sea and in the eastern Eurasian continental margin.

TL;DR: In this paper, the effects of composition and temperature on the partitioning behavior of Sc, Ni, V, U and Th, and the high field strength elements (HFSE) Zr, Nb, Ta and Hf between magnetite and natural silicate melts were evaluated from doped experiments on natural mafic-to intermediate-composition lavas at 1-atm pressure.

TL;DR: In this paper, the authors report enhanced compatibility for Ru compared to previous work for spinels in an Fe-free system, but to a lesser degree, and suggest that Ru should be concentrated in spinels crystallizing in Earth's atmosphere, either within micrometeroids, or from atmospheric crystallization of impact ejecta.

TL;DR: In this paper, the authors studied Cenozoic basalts from eastern China with SiO2 contents ranging from 38.63 to 55.24 wt%, and Na2O + K2O from 3.1 to 9.4 wt%.

TL;DR: In this paper, the authors present comprehensive geochemical analyses on samples from the active volcanoes of the Society and Austral hotspot chains, including data for major, trace and rare-earth elements, and Sr, Nd, Pb and Th isotopes.

TL;DR: In this article, the majorion chemistry, Sr and U isotope systematics of the Indus system, particularly its headwaters, were reported, and the results showed that on an average about a third of the cations in the waters can be from silicate weathering; however, most of the (Ca + Mg) is likely to be from weathering of carbonates and evaporites.

TL;DR: In this paper, aqueous magmatic-derived fluids trapped in fluid inclusions were determined by ICP-MS after crush-leach extraction of the fluids in 4 samples.