Showing papers in "Geochimica et Cosmochimica Acta in 1991"

TL;DR: In this paper, a revised petrographic classification of progressive stages of shock metamorphism of 26 ordinary chondrites is proposed, based on thin section microscopy, and the characteristic shock effects of each shock stage are described.

TL;DR: In this paper, the isotopic composition of carbon in soil CO2 differs from that of CO2 in soil-respired CO2, which is very close to the theoretical difference of 4.4%.

TL;DR: In this article, a negative thermal ion mass spectrometer was used to obtain intense ion beams of negatively charged oxides of Os, Re and Ir by thermal ionization, in a conventional surface ionization mass analyzer.

TL;DR: In this article, it was shown that dissolution of manganese and iron oxides may be induced by the onset of sulfate reduction, which occurs relatively late in the diagenetic sequence.

TL;DR: In this paper, the authors measured the sorption of seven divalent metals (Ba, Sr, Cd, Mn, Zn, Co, and Ni) on calcite over a large initial metal (Me) concentration range (10−8 to 10−4 mol/L) in constant ionic strength (I = 0.1), equilibrium CaCO3(s)-CaCO3 (aq) suspensions that varied in pH.

TL;DR: In this paper, the exact electron binding energies for the atoms in calcite were determined with XPS using the gold dot method, and the results are 290.1 ± 0.1 eV for C1s, 347.7 and 351.2 ± 1.15 eV respectively.

TL;DR: O'Neill et al. as mentioned in this paper used a mass balance between three components: the proto-Earth, the Impactor, and a late veneer to model the origin of the Earth-Moon system, and the model predicts that neither S, O, nor Si should be present in sufficient quantities to provide the required light element in the core.

TL;DR: In this paper, a large dataset of experimental and volcanic distribution coefficients (D's) for sodic plagioclase and calcic plagiase was used for trace element partitioning.

TL;DR: The bulk chemical composition of pyrolite is derived from experimental and petrological studies of the complementary relationships between basaltic magmas and refractory peridotites as discussed by the authors.

TL;DR: In this paper, the oxygen isotopic compositions of chondritic meteorites are used for identification of genetic association with other meteorite types and for recognition of source materials in meteoritic breccias.

TL;DR: In this paper, the relative roles of Fe(III) and dissolved oxygen (DO) in pyrite oxidation at circumneutral pH were investigated, and it was shown that Fe(II) is preferred as an adsorbate to Fe(3) due to both electrostatic and acid-base selectivity.

TL;DR: In this paper, the authors used Rutherford Backscattering to obtain diffusion profiles of zircon and apatite and fitted them with a model to determine the diffusion coefficients, which is both simple and useful in studying diffusion over a temperature range of geologic interest without inordinate annealing times.

TL;DR: In this article, the carbonate-exchange technique was used to obtain diopside, forsterite, magnetite, and calcite isotope fractionations of the form 1000 ln α = A × 106T−2, where the coefficient A is given in the following table.

TL;DR: In this paper, the reaction of Fe(II and Fe(III) solutions with polysulfide solutions prepared from freshly synthesized Na2Sx (x = 2, 4, 5) were studied at 25 and 100°C over the pH range 5.5 to 8.

TL;DR: In this article, Trace element analyses have been made of large zircon crystals from rocks of alkaline affinities by ion microprobe and the partition coefficients for the light rare earth elements (LREEs), between zircons and melt or whole rock, must therefore be significantly lower than those calculated using bulk analyses.

TL;DR: In this paper, a recalculated calcite-graphite fractionation curve based on new calculations of partition functions ratios for calcite suggests that this system is well suited for high-temperature isotopic thermometry of graphitic marbles as first proposed by Valley and O'Neill (1981).

TL;DR: In this paper, the formation of pyrite and marcasite from a FeS precursor has been examined experimentally and it was shown that pyrites and Marcasite formation proceed at a significant rate only if intermediate sulfur species (i.e., polysulfides, polythionates, or thiosulfate) are present in solution.

TL;DR: This article showed that clays are more important than zircon (or other heavy minerals) in hosting both light and heavy REE in cratonic shales and reported HREE depletions in the latter two groups may reflect incomplete dissolution of heavy minerals during sample preparation.

TL;DR: In this article, a mechanistic interpretation for the observed sorption and isotopic exchange behavior is proposed whereby cesium migrates slowly to energetically favorable interlayer sites from which it is not easily released.

TL;DR: In this paper, a theoretical model calculating the thermodynamic isotope factors of oxygen in metal oxides of geochemical interest is presented for temperatures between 0 and 1200°C on the basis of the modified increment method.

TL;DR: This article showed that the relative importance of metalliferous and terrigenous influences and the role of scavenging from seawater may be estimated from a sample's inferred depositional distance (km) from the spreading ridge, the major element chemistry, and the stratigraphie context.

TL;DR: In this article, the authors used accelerator mass spectrometers (AMS) to determine the 10Be and 26Al isotopes in a suite of sandstone boulders in several moraines in Arena Valley, a dry valley adjacent to the Taylor Glacier in the Quatermain Mountains, Southern Victoria Land, East Antarctica.

TL;DR: In this paper, the authors investigated the influence of organic electrolytes on silica mobility, quartz solubility, and dissolution kinetics of quartz in dilute aqueous organic-acid solutions.

TL;DR: In this article, the authors show that REE cycling in the Black Sea is associated with the redox cycling of Mn and not that of Fe, which is a characteristic feature of all anoxic basins so far investigated.

TL;DR: In this article, a thermodynamic analysis of F-Cl-OH partitioning between minerals and hydrothermal fluids has resulted in the retrieval of standard-state Gibbs free energies for fluormuscovite, fluorphlogopite, fluorannite and chlorannite.

TL;DR: In this paper, two new rearranged hopanoid hydrocarbons have been isolated from a Prudhoe Bay crude, Alaska, using X-ray crystallography, and the structures of these hopanes are consistent with an origin by catalytic rearrangement from hopenes during early diagenesis.

TL;DR: The activation energy for diffusion in rhyolitic glasses is well correlated with neutral species radii of He, Ne, H2O, and Ar, and supports the contention that the diffusing species for "water" is neutral molecular H 2O.

TL;DR: The dissolution rate of olivine in aqueous solutions in the pH range 2 − 12.4 at 25°C has been measured using fluidized bed and batch reactors.

TL;DR: In this paper, a study of inactive sulfide-rich tailings impoundments at the Heath Steele (New Brunswick) and Waite Amulet (Quebec) minesites has revealed two distinct types of cemented layers or hardpans.