Showing papers in "Geochimica et Cosmochimica Acta in 1992"

TL;DR: An isolation method relying totally on chemical steps was developed to separate large quantities (10-200 g) of clean mono-minerallic quartz samples from a variety of terrestrial rocks and soils for the purpose of measuring Be-10 (t 1/2 = 1.5 Myr) and Al-26 (t1 2 = 0.705 Myr) produced by cosmic rays in situ in the quartz phase.

TL;DR: In this article, an open-system chemostat technique was employed to study temperature and precipitation rate effects on carbon isotopic fractionation during the inorganic precipitation of aragonite and calcite from solutions held at constant chemical and isotopic composition.

TL;DR: In this paper, the pyritization of reactive trace elements in different anoxic marine sediments was investigated to determine the importance of factors such as reactive-Fe, pyrite content and salinity in controlling this process.

TL;DR: Model V describes the binding of ions by humic substances in terms of complexation at discrete sites, modified by electrostatic attraction and/or repulsion, and also takes account of nonspecific binding due to counterion accumulation.

TL;DR: The various pathways for the oxygenation of ferrous iron and for the dissolution of Fe(III) (hydr) oxides, especially by reducing ligands with oxygen donor atoms in thermal and photochemical processes, are assessed on the basis of laboratory experiments for application to natural systems.

TL;DR: In this paper, negative thermal ionization mass spectrometry was used to analyze the boron isotopic compositions of modern marine carbonates with a 2σ reproducibility of standards and samples better than 0.7%.

TL;DR: In this article, the effects of post-depositional alteration of 87Sr86Sr and δ13C on organic carbon burial in Late Proterozoic oceans were evaluated.

TL;DR: In this article, an equation of state (EOS) for the CH4-CO2-H2O system covering a wide T-P range has been developed and applied to the pure endmembers.

TL;DR: Strontium concentrations and isotope ratios have been measured in river and ground waters from the Ganges, Orinoco, and Amazon river basins as mentioned in this paper, and the data set has allowed a detailed examination of the controls over the strontium isotope systematics of riverine input to the oceans in the following environments: 1. Typical drainage basins containing limestones, evaporites, shales, and alumino-silicate metamorphic and igneous rocks; shield terrains containing no chemical or biogenic sediments; and 3.

TL;DR: In this paper, a chemical model for simulating the sources of the lunar mare basalts was developed by considering a modified mafic cumulate source formed during the combined equilibrium and fractional crystallization of a lunar magma ocean (LMO).

TL;DR: In this paper, it was concluded that in order to prohibit unreasonably high levels of atmospheric CO2, weathering during the Precambrian and early Paleozoic must have taken place under essentially closed-system abiotic conditions (linear feedback) or via strong regulation by primitive biota such as lichens and cyanobacteria.

TL;DR: In this paper, the RbCs ratio in the Silicate Earth is estimated to be about 28, based upon studies of the continental crust, MORB source, and OIB (plume) source.

TL;DR: In this article, the immiscible Fe-S-O liquid saturation surface for basaltic liquids in T-X-ƒ o 2 -ƒ s 2 space is made through consideration of the heterogeneous equilibrium 1 2 S 2 (gas) + FeO (silicate melt) = FeS (sulfide melt) + 1 2 O 2(gas), using standard state thermodynamic data.

TL;DR: In this article, the authors present results of a wide-ranging isotopic investigation of the Antarctic angrite LEW-86010 (LEW), and reassess the type angrites Angra dos Reis (ADOR) in order to obtain precise radiometric ages and initial Sr isotopic compositions, and search for the erstwhile presence of the short-lived nuclei Sm-146 and Al-26 via their daughter products.

TL;DR: A review of recent developments in the geological analysis of lunar mare volcanism can be found in this paper, where the authors show that mare volcanic activity began prior to the end of heavy bombardment (the period of cryptomare formation), in pre-Nectarian times, and continued until the Copernical Period, the total duration approaching 3.5-4 Ga.

TL;DR: In this article, the authors report the results of a geochronological and geochemical study of these zircons which, together with data on grain morphology and inclusion mineralogy, are used in an attempt to place constraints on their source rocks.

TL;DR: This paper showed that the water column in the western North Pacific is stratified with respect to the isotopic composition of Nd as well as Nd/La, Sm/Nd, and Er/La.

TL;DR: In this paper, it was shown that the Neoproterozoic silica cycle was dominated by inorganic reactions among dissolved silica, clay and zeolite minerals, and organic matter.

TL;DR: The texture and modal composition of fourteen carbonaceous chondrites of the CM group were studied in detail to unravel the origin of their various components and the evolution of their parent body as mentioned in this paper.

TL;DR: In this article, a model for the solubility of methane in brines (0 − 6 m) for temperatures from 0 to 250°C and for pressures from 0 − 1600 bar (or slightly above) is presented.

TL;DR: In this article, the authors used the Pitzer interaction model to estimate the stability constants for the formation of rare earth complexes over a wide range of ionic strengths, including carbonate, NO3, SO42, OH−, HCO3−, HPO42−, and CO32−.

TL;DR: In this paper, a critical review of thermodynamic data for aqueous and solid V species is presented to evaluate dissolution, transport, and precipitation of V under natural conditions, especially those for which the experimental conditions are near those found in nature.

TL;DR: In this paper, the dissolution of kaolinite is interpreted in terms of the surface complexation model, and the dissolution reaction can be interpreted as a coupled release of Al and Si with the detachment of the Al center from the surface lattice structure as the rate-limiting step.

TL;DR: In the Catalina Schist subduction-zone metamorphic complex (California), metasedimentary rocks show a decrease in N concentration and an increase in δ15Nair with increasing metamorphics grade.

TL;DR: In this paper, the classification, sources, and overall petrogenesis of mare basalts are reviewed, and all mare basalt analyses are used to define a sixfold classification scheme using TiO2 contents as the primary division.

TL;DR: An extensive suite of thirty lignin-derived phenolic dimers and fourteen additional monomers has been identified among the CuO reaction products of twenty-four different vascular plant tissues.

TL;DR: In this article, surface water and soil samples were collected from a series of small catchments on granitic gneiss in the Canton of Ticino in southern Switzerland.

TL;DR: It is shown that under a constant phytoplankton demand for CO2 an inverse, nonlinear SPOM delta 13C response to ambient [CO2(aq)] is expected, unlike the negative linear relationships indicated by data from the NABE Site and or from Southern Hemisphere waters.

TL;DR: In this paper, two kinetic models incorporating Freundlich isotherms and an irreversible process are used to describe sorption data spanning a range of cesium concentrations, and they predict that effectively instantaneous and reversible kinetic processes control ceium sorption over time scales of a few days and less.