Showing papers in "Chemical Geology in 1979"

TL;DR: Birnessite and hematite have been identified as the Mn-and Fe-oxide phases in desert varnish by IR spectroscopic and chemical techniques as discussed by the authors, and these oxides are in intimate physical association with the mixed-layer illite-montmorillonite clay minerals.

TL;DR: In this article, triterpane fingerprinting was used to identify pentacyclic triterpanes in crude-oil samples from three oilfields in the east and west of the Tertiary Niger delta, Nigeria.

TL;DR: The reaction products and the accompanying sulfur isotope fractionations during the reaction of H 2 S with goethite in aqueous media at 22-24°C for periods from 0.5 hr to 65 days were studied as mentioned in this paper.

TL;DR: A simulation experiment carried out by heating the immature shale at 300°C in vacuo (0.4 Torr) for ten days resulted in a triterpane composition similar to that of the delta oils as discussed by the authors.

TL;DR: In this article, chemical data for 56 elements in soils from three regions of Brazil (Bahia, Amazon, Goias) indicate that intense chemical weathering leads to a product soil essentially in the system, SiO2Al2O3Fe2O 3H2O. The major minerals of the leached soils are quartz, kaolinite, gibbsite, goethite and hematite.

TL;DR: In this article, K/1bAr and Rb 1bSr ages are reported for high-grade metamorphic rocks from pre-Hercynian elements in the Hercynian orogen of NW Spain and for an early hercynian suite of granites (half-life 37 Rb = 5.0 · 10 10 10 a; errors 2σ).

TL;DR: The reduction potential of a soil-derived fulvic acid (SFA) sample is 0.57 V (vs. NHE) as discussed by the authors, and the reduction potential increases with decreasing pH which means that H+ is consumed when SFA acts as an oxidizing agent.

TL;DR: In this article, the authors used the ion microprobe mass analyzer (IMMA) to determine the ages of radiogenic Pb isotopes in terrestrial, lunar and meteoritic phases.

TL;DR: Analyses of rare-earth elements (REE) in Gulf Coast sediments indicate that the absolute REE content of the bulk sample is nearly constant between 174 and 165 ppm at depths of 1.81 and 3.67 km, respectively; but it increases perceptibly to 212 ppm at a depth of 4.77 km.

TL;DR: In this article, a sequential extraction scheme was used to determine the geochemical fractionation of Fe, Mn, Cr, Cu and Zn in different grain size classes for sediment samples collected from within and around Little Traverse Bay, Lake Michigan.

TL;DR: In this paper, the amount of hydroxonium or hydroxyl ion sorbed by the sodium form of clays (kaolin, illite or montmorillonite) has been found to increase in proportion with the amount added (i.e., data fits a Boedeker type equation).

TL;DR: A re-evaluation of the isotopic geochemistry of oxygen involved in the exogenic sulfur cycle leads to a model in which δ 18OSO4 of seawater is determined by a dynamic balance of four fluxes: inputs by erosion of evaporite sulfate and by oxidative erosion of sulfide, and outputs of sulfate into evaporites and of carbon dioxide into seawater by bacterial reduction of sulfates to sulfide.

TL;DR: In this article, chemical criteria have been developed to distinguish plutonic rock suites from compressional and extensional plate margins by comparing type examples of Mesozoic and Cenozoic Plutonic suites generated at these plate boundaries.

TL;DR: In contrast to the cases of interpolation and extrapolation trace elements and trace-element ratios can be used as evidence in solving petrogenetic problems as discussed by the authors, however, on the whole trace elements should only serve as contributory evidence, together with geological, structural and textural data.

TL;DR: The hypothesis that sulfate-reducing bacteria cannot initiate degradation of oil but rather grow on the residues resulting from the aerobic degradation ofOil is supported.

TL;DR: The chemistry and hydrology of river, swamp and ground waters suggest that Fe is supplied by lateral and vertical migration of corrosive, acidic ground waters up through Fe-rich sediments toward aerated surfaces.

TL;DR: In this article, the authors compared the results from the MLE approach and the standard errors of the D. York method on three well-known sets of lunar data and the results of a previous method of D.York and from the maximum likelihood estimation approach are quite comparable.

TL;DR: Following the Hargraves model of crustal evolution, it is proposed that as one goes back in time volcanogenic sources eventually predominate as discussed by the authors, which is reflected in Sr-isotope and rare-earth patterns in sediments and by the nature and size of Archaen ore deposits.

TL;DR: In this paper, a peat bog of Mirochov (Bohemia) was used to study the sorption of (UO2)2+ by humic acids at 20.00 ± 0.03°C.

TL;DR: Titanomagnetites separated from 15 different rock samples (including ocean-floor basalts from DSDP Legs 37, 45 and 46) were analyzed together with whole-rock samples by instrumental neutron activation analysis for Sc, Cr, Co, Zn, Hf, Ta, Th and the REE La, Ce, Nd, Sm, Eu, Gd, Tb, Dy, Tm, Yb and Lu.

TL;DR: In this article, the authors analyzed 250 canned rock samples from three exploration wells for content and composition of light hydrocarbons (C 2 /1bC 7 ) from depth plots of these data and showed that the process of hydrocarbon generation in source beds can be monitored as a function of the temperature and facies of organic matter.

TL;DR: The sediment mineral and trace-element contents of silicified wood and associated sediments from the Petrified Forest National Park, Arizona, indicate that silica mineralization occurs within the compositional range of most stream and groundwaters as mentioned in this paper.

TL;DR: In this article, the concentration of mononuclear dissolved Al is determined in samples of natural waters and of solutions separated from experimental suspensions of clay minerals, by solvent extraction and spectrophotometry of aluminum 8-hydroxyquinoline.

TL;DR: The heat effect from a basalt dyke was found to alter the composition of saturated and aromatic hydrocarbons in the surrounding immature shales up to a distance of about half the thickness of the dyke.

TL;DR: In this article, the rare earth element (REE) and stable isotope distribution patterns in calcites from the mining areas of St. Andreasberg, Clausthal and Bad Grund, western Harz, Germany, have been determined.

TL;DR: In this article, the important uses of X-ray photoelectron spectroscopy (XPS or ESCA) in mineralogy and geochemistry are described, and future improvements in intensity and resolution will greatly enhance the crystal chemical applications of ESCA.

TL;DR: In this article, Karelian shungite is shown to have a high level of organic metamorphism that is approximately equivalent to the meta-anthracitic stage of the coalification series.

TL;DR: Siderite and calcite are two forms of carbonate commonly associated with Permian Australian coals as mentioned in this paper, and are characterized by isotopic enrichments to δ13C values of +25 PDB.

TL;DR: In this paper, the authors determined the 87.87 Sr 86 Sr ratios for one oil and fourteen brines collected from three petroleum reservoirs in southeastern Ohio: the North Logan and Triadelphia fields, both of which are contained within the Clinton sandstone; and the Macksburg field which is contained in the Berea sandstone.