Showing papers in "Geochimica et Cosmochimica Acta in 1975"

TL;DR: In this paper, the use of zloPb and 13'Cs radioactivity measurements to determine the rates of sedimentation in the Great Lakes was described. But the results were limited to eight locations in Lake Michigan.

TL;DR: The seeded precipitation of aragonite and calcite from sea water, magnesium-depleted sea water and magnesium-free sea water has been studied by means of the steady-state disequilibrium initial rate method.

TL;DR: In this article, plagioclase feldspar/magmatic liquid partition coefficients were determined experimentally at 1 atm total pressure in the temperature range 1150-1400°C.

TL;DR: In this article, it is suggested that polycyclic aromatic hydrocarbons are formed in natural fires, are dispersed and mixed by air transport and eventually deposited into surface sediments.

TL;DR: In this paper, the origin of the Early Precambrian greenstone-granite complex of northeastern Minnesota consists of four major groups: metavolcanic tholeiitic basalt and basaltic andesite, trondhjemite, tonalite, extrusive and hypabyssal dacite and rhyodacite.

TL;DR: In this article, a tentative, revised, graphical calibration is offered, based on microprobe-analyzed high-grade metamorphic pairs and pairs from basaltic pumice.

TL;DR: A model for the mixing of H2O and silicate melts has been derived from the experimentally determined effects of H 2O on the viscosity (fluidity), volumes, electrical conductivities, and especially the thermodynamic properties of hydrous aluminosilicate melts as mentioned in this paper.

TL;DR: In this paper, a mechanism of origin for chromite-rich layers in stratiform ultramafic-gabbroic intrusions is proposed whereby the layers are precipitated on occasions when the basic parental magma of the intrusion is suddenly extensively contaminated with granitic liquid melted from salic roof rocks.

TL;DR: In this paper, it was found that the fractionation is not a smooth function of rare earth ionic radius, but varies in an extremely irregular pattern, and that rare earth elements are predicted to be extremely depleted in the early condensate.

TL;DR: In this paper, two types of white, coarse-grained, Ca-Al-rich inclusions were found in Allende and Grosnaja, New Mexico: Type A inclusions contain 80-85 per cent melilite, 15-20 per cent spinel, 1-2 per cent perovskite and rare plagioclase.

TL;DR: The phase relations for this join provide part of the essential framework of the model peridotite system CaO-MgO-SiO_8-CO_2-H_2O, which has particular application to the origin of carbonatitic and kimberlitic magmas.

TL;DR: Empirical oxygen barometers based on Eu(2+)/Eu(3+) ratios in plagioclase feldspar and magmatic liquid were developed using Philpott's (1970) approach and the experimental data of Drake (1972) as discussed by the authors.

TL;DR: In this article, the authors derived activity composition relations for ideal substitutional solid solutions through the Helmholtz free energy expressed in terms of the partition function, and derived ideal activity expressions for solid solutions of albite and anorthite.

TL;DR: In this paper, the enthalpies of enstatite, synthetic cordierite, forsterite and spinel were measured in a melt of composition 2PbO · B2O3 at 970 ± 2K.

TL;DR: In this article, the relative and absolute REE content of a wide variety of clay mineral groups have been analyzed using radiochemical neutron activation and have been found to be quite variable in absolute and relative REE contents.

TL;DR: In this paper, it was shown that antigorite-bearing serpentinite bodies containing zoned grains of accessory chromite occur beneath Paleozoic sediments southwest of the Manitoba Nickel Belt.

TL;DR: In this paper, the ages of lead-lead mineral isochrons were determined for eight intrusive bodies in the Kalgoorlie-Norseman area of Western Australia, ranging from 2630 to 2760 m.y.

TL;DR: In this article, two samples of the Murchinson C2 chondrite were analyzed for organic nitrogen compounds, using mass spectrometry in combination with paper and thin-layer chromatography.

TL;DR: The ophiolite association is assumed to be created along accreting plate boundaries in the oceanic lithosphere as discussed by the authors, and it is suggested that podiform chromite deposits form as magmatic cumulates in elongate magma pockets along the accrebing plate boundaries.

TL;DR: In the Deep Sea Drilling Project (DSDP) samples of interstitial solutions of deeply buried marine sediments throughout the World Ocean have been obtained and analyzed as discussed by the authors, and these changes can be grouped into a few consistent patterns that facilitate identification of the diagenetic reactions occurring in the sediments.

TL;DR: The relationship between 87Sr 86 Sr and major and trace element geochemistry is variable and complex as mentioned in this paper, and Lavas from the same volcano sometimes show significant differences in 87 Sr 86 Sr despite close geochemical relationships.

TL;DR: In this article, an ion exchange-X-ray fluorescence procedure was used to determine the abundances of are-earth (REE) and yttrium (Yttrium) for whole-rock (14) and mineral (87) samples from Oka carbonatite complex.

TL;DR: In this article, neutron activation data on 14 elements in eight enstatite-chondrite falls are reported, and literature data on an additional 28 elements show that intragroup elemental fractionations generally fall into one of three basic patterns: 1) siderophilic and chalcophilic-element abundances are about 1.5 times greater in E4-5 than in E6 chondrites; 2) non-volatile lithophile-element abundance is generally 1.0-1.2 times those in E 6 chondites; 3

TL;DR: In this paper, the equilibrium distribution of oxygen isotopes between calcium carbonate and water was determined at 500°C at pressures from 1 to 20 kbar and at 700°c at pressures of 0.5 and 1 kbar.

TL;DR: The isotopic fractionation between inorganic and organic carbon in Precambrian sediments is about the same as in geologically younger rocks ( Δδ ≅ 25%) as mentioned in this paper.

TL;DR: In this paper, the authors studied the adsorption of cobalt on synthetic hydrous manganese dioxide and showed that cobalt adsorbed increased sharply at pH 6, a significantly lower pH than that required for significant hydrolysis of Co(II) or precipitation of Co (OH) 2 (S) in bulk solution.

TL;DR: In this paper, the authors analysed the sediment of the shelf off Walvis Bay (S.W. Africa) for lipid material and found that the lipid contents consist of a mixture of hydrocarbons, alcohols, ketones, fatty acids, sterols, carotenoid pigments and chlorophylls.

TL;DR: In this article, the authors made a detailed examination of the mineralogy, textures, and assemblages of six calcium-aluminum-rich inclusions (CAI) in the Allende meteorite.

TL;DR: In this article, the Earth-atmosphere evolution models are mathematically simulated and the resulting present isotopic ratio (40Ar/36Ar) in the mantle is given for each.