Showing papers in "Chemical Geology in 1993"

TL;DR: The average chemical composition of the upper continental crust (UC) as a function of age is estimated from chemical analyses, geologic maps, stratigraphic sections and isotopic ages as discussed by the authors.

TL;DR: In this article, the uplift history of eclogite in the Dabie Mountains can be subdivided into two stages: (1) fast uplift driven by thrust during continental-continental collision and deep subduction (at 221 Ma) of the continental crust; (2) later gentle uplift with rise of the Dabbie Mountains in the late Jurassic and Cretaceous (at 134 Ma).

TL;DR: Zircon exhibits an extraordinary memory as mentioned in this paper and its stability, durability, low solubility and low elemental diffusivities combine to preserve in it a record of most of the important events that have affected it, its host rocks, and the crust of which it is a part.

TL;DR: Baddeleyite is an ideal mineral for U-Pb dating because it has abundant U (up to 3000 ppm), negligible initial common Pb, rarely occurs as xenocrysts, and, in unmetamorphosed samples, experiences negligible Pb loss as discussed by the authors.

TL;DR: In this article, the authors proposed an equation for the equilibrium between monazite and Ca-poor felsic melts, which can be used as a thermometer, based on the total rare-earth elements (REE) content of natural magmatic rocks.

TL;DR: In this paper, lead diffusion has been measured in natural titanite using two different methods to introduce the diffusant: implantation of Pb ions and immersion of the crystals in a PbS powder reservoir.

TL;DR: In this article, a log-log diagram of Br − Br − vs. Cl− is presented, including the evolution of present-day marine solutions and literature values for the chloride salts between halite and tachyhydrite ((CaCl2, 2MgCl2·12H2O) deposition.

TL;DR: In this article, stable-state dissolution rates of albite were measured in aqueous solutions at 80°C and pH 8.8 as a function of solution saturation state (or the Gibbs free energy of reaction, ΔGr) using a continuously-stirred flow-through reactor.

TL;DR: In this article, the authors demonstrate that Zr can be highly mobile in hydrothermal systems, and that the availability of other trace elements probably is also governed by their mineral host.

TL;DR: Vennemann and O'Neill as discussed by the authors proposed a simple and inexpensive method of hydrogen isotope and water analyses of minerals and rocks based on zinc reagent, which is significantly simpler, faster and less expensive.

TL;DR: Inverse models which apportion watershed effluxes (geochemical mass balance) over estimated mineral surface area give weathering rates for individual silicate minerals (e.g., feldspar) 1-3 orders of magnitude slower than laboratory rates as mentioned in this paper.

TL;DR: In this article, the petrologic evolution of subducting oceanic lithosphere and the overriding continental/oceanic seafloor can be predicted by integrating thermal models with petrologics phase equilibria.

TL;DR: In this paper, the role of organic compounds on the wettability, porosity and permeability of carbonate rocks was investigated, and a wide variety of model organic compounds were tested for adsorption on calcite, dolomite and magnesite.

TL;DR: In this article, the authors measured dissolution rates in 6 small 2 m2 plots on a spodosol in eastern Maine, U.S.A. The plots were irrigated with HCl at pH's 2, 2.5 and 3; soil solutions were collected by tension lysimeters at 25 cm depth.

TL;DR: Laser micro-Raman spectroscopy has been used to study 20 of the most commonly occurring sulphides (i.e. iron sulphides, copper sulphides and some sulphosalts) as mentioned in this paper.

TL;DR: In this paper, the authors used stable isotope data from the Catalina Schist to predict mass changes along different P-T paths, and showed that both mechanisms could be effective at producing the range of observed features, even though the required equilibrium constants are only poorly estimated at the relevant P-Ts conditions.

TL;DR: In this paper, the paragenesis and U-Pb systematics of monazite in rocks from the eastern Mojave Desert, California, corroborate its potential usefulness as a prograde thermochronometer and in dating granite inheritance.

TL;DR: In this paper, a laser ablation microprobe (LAM) was coupled to a commercial inductively coupled plasma-mass spectrometer (ICP-MS) for direct dating of single pitchblende and zircon grains.

TL;DR: Early Proterozoic "A-type" granite suites in Labrador, northeastern Canada, have initial Nd isotopic compositions that lie between those of a depleted mantle reservoir and the local basement rocks.

TL;DR: In this paper, it was shown that no single fluid parameter is likely to be a sole or dominant control on carbonate mineralogy in natural environments and that thermodynamic stability differences may be as important as kinetic factors in determining mineralogy.

TL;DR: In this article, a proton microprobe was used to measure partition coefficients for Rb, Sr, Ba, Y, Zr, Nb and Ta between experimentally produced amphiboles and hydrous basaltic melts.

TL;DR: In this paper, significant modifications to the currently accepted marine phosphorus budget are proposed, which requires a reassessment of phosphorus residence time in the ocean, and a concomitant review of the role of P as a potential player in climate change over glacialinterglacial time scales.

TL;DR: In this paper, an empirical model for solution of Ti in biotite is developed and calibrated on the basis of various equilibria among Biotite and Ti-saturating assemblages.

TL;DR: In this paper, the current state of knowledge concerning the mobility of Ti during alteration and metamorphism of crustal rocks is examined. And relevant Ti-oxide solubility data from experiments and determinations of Ti concentrations in natural waters are presented.

TL;DR: In this article, it was shown that the transition from amphibolite to granulite facies is characterized by a decrease in aH2O, as well as a temperature increase.

TL;DR: In this paper, the authors investigated the properties of these Quaternary deposits and their provenance in terms of their chemical properties, and found that these properties are related to the geology of the source.

TL;DR: The question as to whether the metasomatizing-slab agent needed to form island-arc magmas is an aqueous fluid or a hydrous melt requires a knowledge of fluid-melt-rock interaction during high-pressure low-temperature metamorphism.

TL;DR: In this paper, the authors model atmospheric CO, consumption by chemical weathering of rocks, and apply it to the Garonne, Congo and Amazon basins, in the context of mining.

TL;DR: In this paper, the state of saturation of olivine, orthopyroxene and plagioclase of variable composition has been assessed in various types of natural waters in Iceland including river waters, groundwater and geothermal waters with temperatures up to 250°C.

TL;DR: In this article, the early stages of olivine weathering were studied in the laboratory and in the field, and it was shown that the pathways for dissolution are similar to those for ligand exchange around dissolved metal complexes.