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51.
Low temperature volatile production at the Lost City Hydrothermal Field, evidence from a hydrogen stable isotope geothermometer 总被引:1,自引:0,他引:1
Giora Proskurowski Marvin D. Lilley Deborah S. Kelley Eric J. Olson 《Chemical Geology》2006,229(4):331-343
Although commonly utilized in continental geothermal work, the water-hydrogen and methane-hydrogen isotope geothermometers have been neglected in hydrothermal studies. Here we report δD-CH4 and δD-H2 values from high-temperature, black smoker-type hydrothermal vents and low-temperature carbonate-hosted samples from the recently discovered Lost City Hydrothermal Field. Methane deuterium content is uniform across the dataset at − 120 ± 12‰. Hydrogen δD values vary from − 420‰ to − 330‰ at high-temperature vents to − 700‰ to − 600‰ at Lost City. The application of several geothermometer equations to a suite of hydrothermal vent volatile samples reveals that predicted temperatures are similar to measured vent temperatures at high-temperature vents, and 20-60 °C higher than those measured at the Lost City vents. We conclude that the overestimation of temperature at Lost City reflects 1) that methane and hydrogen are produced by serpentinization at > 110 °C, and 2) that isotopic equilibrium at temperatures < 70 °C is mediated by microbial sulfate reduction. The successful application of hydrogen isotope geothermometers to low-temperature Lost City hydrothermal samples encourages its employment with low-temperature diffuse hydrothermal fluids. 相似文献
52.
We propose a new approach to model the geochemical evolution of continuously replenished and tapped steady-state magma chambers. We use a sinusoidal function to model cyclic magma supply. The temporal evolution of a reservoir is described using differential equations, in which the amount of refilling magma does not depend on the size of the chamber. These equations can be used to calculate incompatible trace element concentrations and magma quantities. We examine the geochemical consequences of episodic injections, noises and wall-rock assimilation. We also explore possible variations in crystallization rate. To show its potential, the theoretical treatment has been applied to the EPR 17-19°S, a site with a strong magma budget which has been the subject of several geological/geophysical studies. The practical application requires geological parameters to be constrained, as well as the extreme values of the lava concentration range. A first step specifies the incompatible trace element composition of the replenishing melt, which corresponds in the EPR case to a magnesian liquid (MgO = 9.5 wt%). It is then possible to determine other parameters such as cycle period (∼750 years), magma residence time (∼300 years), and reservoir size (from 4.1 to 8.6 km3 per 20 km segment). Lastly, variations in crystallization rate do not significantly alter the results. 相似文献
53.
Phosphorus retention in calcareous soils and the effect of organic matter on its mobility 总被引:7,自引:0,他引:7
Ray von Wandruszka 《Geochemical transactions》2006,7(1):6-8
A survey of the interactions between phosphorus (P) species and the components of calcareous soils shows that both surface
reactions and precipitation take place, especially in the presence of calcite and limestone. The principal products of these
reactions are dicalcium phosphate and octacalcium phosphate, which may interconvert after formation. The role of calcium carbonate
in P retention by calcareous soils is, however, significant only at relatively high P concentrations – non-carbonate clays
play a more important part at lower concentrations. In the presence of iron oxide particles, occlusion of P frequently occurs
in these bodies, especially with forms of the element that are pedogenic in origin. Progressive mineralization and immobilization,
often biological in nature, are generally observed when P is added as a fertilizer. 相似文献
54.
This paper presents the experimental results of the mechanical production of silica and carbonate colloidal particles below 100 nm using two types of stirred bead mills (i.e., DCP Superflow 12 and PML H/V). It is shown that the stirred bead mill with very small beads can be used as an efficient equipment for the production of the colloidal particles in nanoscale from the feed materials of several microns in sizes at high energy consumptions. The DCP Superflow mill with high power densities is superior for the effective size reduction and production rate, compared to the conventional PML H/V mill with lower power densities. The smaller particles could be produced by the DCP Superflow mill at the same level of high energy inputs as from the PML H/V mill. The “grinding limit” for the processes in the mills has been discussed. 相似文献
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Susanne Skora Lukas P. Baumgartner Nancy J. Mahlen Clark M. Johnson Sébastien Pilet Eric Hellebrand 《Contributions to Mineralogy and Petrology》2006,152(6):703-720
Garnets from the Zermatt-Saas Fee eclogites contain narrow central peaks for Lu + Yb + Tm ± Er and at least one additional small peak towards the rim. The REE Sm + Eu + Gd + Tb ± Dy are depleted in the cores but show one prominent peak close to the rim. These patterns cannot be modeled using Rayleigh fractionation accompanied by mineral breakdown reactions. Instead, the patterns are well explained using a transient matrix diffusion model where REE uptake is limited by diffusion in the matrix surrounding the porphyroblast. Observed profiles are well matched if a roughly linear radius growth rate is used. The secondary peaks in the garnet profiles are interpreted to reflect thermally activated diffusion due to temperature increase during prograde metamorphism. The model predicts anomalously low 176Lu/177Hf and 147Sm/144Nd ratios in garnets where growth rates are fast compared to diffusion of the REE, and these results have important implications for Lu–Hf and Sm–Nd geochronology using garnet. 相似文献
58.
59.
Warren J. de Bruyn Mike Harvey Jill M. Cainey Eric S. Saltzman 《Journal of Atmospheric Chemistry》2002,41(2):189-209
Atmospheric dimethyl sulfide (DMS) and sulfur dioxide (SO2) concentrations were measured at Baring Head, New Zealandduring February and March 2000. Anti-correlated DMS and SO2 diurnalcycles, consistent with the photochemical production of SO2 from DMS, were observed in clean southerly air off the ocean. The data is used to infer a yield of SO2 from DMS oxidation. The estimated yields are highly dependent on assumptions about the DMS oxidation rate. Fitting the measured data in a photochemical box model using model-generated OH levels and the Hynes et al. (1986) DMS + OH rate constant suggests that theSO2 yield is 50–100%, similar to current estimates for the tropical Pacific.However, the observed amplitude of the DMS diurnal cycle suggests that the oxidation rate is higher than that used by the model, and therefore, that theSO2 yield is lower in the range of 20–40%. 相似文献
60.
Perturbation is an operation defined on the simplex and can be used for centering compositional data in a ternary diagram, applying objective criteria. Because a straight line in the original diagram is still astraight line in the perturbed diagram, gridlines or compositional fields defined by straight lines can easily be included in the operation. Simultaneous perturbation of data, gridlines, and/or compositional fields is shown to improve both visualization and graphical interpretation of compositions in ternary diagrams. This is illustrated by some examples using simulated as well as real data. 相似文献