Showing papers in "Chemical Geology in 1996"

TL;DR: In this paper, the results of two years of systematical investigations aiming to define both the limits and potential of this method are presented, and a specific statistical method to deal with the large number of data which can be obtained on a single sample is described, and several guidelines are suggested to optimize the method.

TL;DR: In this paper, chemical (major and trace element) and isotopic (Sr, Nd) analyses of the Luochuan loess-paleosol sequence in China were performed in order to examine the following problems: (1) potential source heterogeneity; (2) element behavior during pedogenesis; (3) paleoclimatic implications; and (4) the use of loess data to determine the average composition of the upper continental crust.

TL;DR: In this article, micro-crystalline barites recovered by deep-sea drilling from Site 684 on the Peru margin and Site 799 in the Japan Sea are highly enriched in the heavy sulfur isotope relative to seawater (δ34S up to + 84%).

TL;DR: Bacteria are very small (∼ 1.5 μm3) but have the largest surface area to volume ratio of any life form as mentioned in this paper, which is mainly due to the overall anionic charge of bacterial surfaces imparted by the macromolecules which make up their fabric.

TL;DR: In this paper, the authors show that anhydrite and hydrocarbons have reacted together to produce calcite and H 2 S in the Permian Khuff Formation of Abu Dhabi.

TL;DR: The Bixiling mafic-ultramafic complex is a tectonic block within biotite gneisses in the eastern part of the Dabie ultra-high-pressure metamorphic (UHPM) terrane as discussed by the authors.

TL;DR: In this paper, a stable Eh-pH diagram for antimony and arsenic compounds at 25·gC and 1 arm total pressure has been calculated in terms of Eh pH diagrams.

TL;DR: A large number of microbes that interact with mineral substances are opportunists and have a significant impact on the mineral world by catalyzing, or controlling in other ways, key steps in mineral formation or dissolution.

TL;DR: Bacteria may potentially enhance or inhibit silicate mineral dissolution in nature by a variety of mechanisms, such as reduction in surface reactivity or reactive surface area as discussed by the authors, by creating and maintaining microenvironments where metabolite concentrations are higher than in the bulk solution.

TL;DR: In this article, a number of standards used for KAr and 40Ar39Ar dating have been intercalibrated, and the results showed that most of these standards proved to be homogeneous in 40Ar★39ArK ratio (age) K, Ca, and 36Ar contents.

TL;DR: In this article, the authors measured the viscosity of a synthetic andesite-like melt with water contents in the range 0-3.5 wt% using configurational entropy theory.

TL;DR: In this paper, the authors used the near-infrared absorption bands at 5200 cm −1 and at 4500 cm − 1 to specify concentrations of water species in glasses of alkali feldspar composition MAlSi 3 O 8 (M = Li, Na, K).

TL;DR: In this paper, a comparison between chemical oxidation and thermal treatment was conducted and the latter was shown to be inappropriate due to the polymerisation of organic matter, and acid dichromate oxidation was used to separate reactive kerogen from black carbon in a variety of lake and marine sediments.

TL;DR: In this article, the steady state of erosion was validated in each river of the Congo Basin and in the lowland rivers of the Amazon Basin, but in not verified in the rivers from the Andes (Rio Solimoes and Rio Madeira).

TL;DR: In this article, an ion microprobe was used to measure the ages of zircons from six samples collected from the southern Aravalli Mountains, and the results indicated that the southern segment of the Aravali Craton had broadly stabilized by ∼ 2.5 Ga.

TL;DR: In this paper, two geochemically distinct Low-Ti magma types (Gramado and Esmeralda) are distinguished within the flood basalt sequences of southern Parana on the basis of certain element abundances and ratios.

TL;DR: In this paper, the dissolution rate of feldspar was measured in flow-through reactors, over a pH range of 3-7, oxalic acid concentration of 0-8 mM, and a compositional range of An0An76.

TL;DR: In the case of amphibole syenite, a specialized weathering microenvironment around each mineral grain initially produces minute phyllosilicate crystallites and a rind of clay minerals forms around the dissolving parent phase, eventually culminating in abundant 5-10 μm diameter polymer-bound aggregates of face-to-face oriented clay minerals of homogeneous composition as discussed by the authors.

TL;DR: In this article, rare earth element (REE) speciation was modelled in acid (2.9 ≤ pH ≤ 3.5), hypersaline groundwaters from Australia and from the Palo Duro Basin in Texas, USA, using a combined specific ion interaction (Pitzer model) and ion pairing model.

TL;DR: In this article, the results of melting experiments have been used to establish equations relating melt composition to temperature (T ), pressure (P ), and water content of the source (Y H2O ) for tonalitic and trondhjemitic melts produced by partial melting of average Archean tholeiite (AAT).

TL;DR: In this paper, fumarole and hot spring gas chemistry of a 3-year monitoring program (1986-1988) at the seismically active Long Valley caldera (LVC) in the Sierra Nevada, eastern California.

TL;DR: In this article, the minimum age of protolith formation at ∼ 1.7 Ga, assuming their evolution from a depleted or a chondritic mantle, was calculated from geochemical analyses and isotopic age determinations.

TL;DR: The influence of native microorganisms on mineral dissolution and precipitation in a petroleum-contaminated aquifer near Bemidji, Minnesota was examined in a one-year period as discussed by the authors.

TL;DR: In this paper, the authors analyzed 25 trace elements (e.g., Sb, Tl, Sn, rare earth elements (REE), Th, U, Nb, Pb, Zr, Hf, and Y) in altered mid-ocean ridge basalts (MORB) from locations near the mouth of the Gulf of California.

TL;DR: In this paper, the authors investigated the mechanisms by which nitrilotriacetic acid (NTA) stimulated Fe(III) reduction in sediments from a petroleum-contaminated aquifer.

TL;DR: In this paper, a new method for high-purity separation of nanogram amounts of Be from environmental materials, such as silicates, oxides, or water is described.

TL;DR: A bacterial treatment system to mitigate selenium-contaminated waste streams using Pseudomonas fuorescens and Bacillus subtilis, respectively, as model Gram (−) and (+) soil bacteria is developed, demonstrating that both strains reduce selenite to elemental selenum.

TL;DR: In this paper, the authors measured track lengths and ages from Cretaceous and Tertiary sandstone samples in Vienna Basin boreholes and provided constraints for the thermal stability of the zircon FT system over a geological timescale.

TL;DR: In this paper, precise ion microprobe UPb zircon ages have been obtained from a representative set of Paleozoic igneous rocks from the Western Province of the South Island, New Zealand.

TL;DR: The results in this article show that the earliest Amphbolite-facies metamorphism of the Isua belt for which pressure and temperature conditions can be obtained (P ≈ 5 kbar; T ≈ 500-600°C) is late Archaean, and not early Archaean as had been assumed earlier by some authors.