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
Abstract. Oxidation and reduction processes can influence extent of leaching of elements from solid waste. Three samples of municipal solid waste combustion fly ash were subjected to oxidizing and reducing conditions in order to evaluate leaching of elements in the Milli-Q water and fly ash (liquid to solid ratio, 100) mixtures. Although the oxidizing and reducing conditions were applied for 6 hours only, elements like Cs, Li, Mg, Sb, Tl and V leached more under oxidizing condition than under reducing condition in the case of all three ash samples. Cadmium, Pb and Zn leached more from all samples under reducing condition than under oxidizing condition. Leaching of other elements like Al, Ba, Cr, Cu, Ni and Rb was inconsistent with oxidizing or reducing conditions and varied from sample to sample, suggesting that factors other than redox may be more important in controlling leaching of these elements. Strong acid neutralization capacity of the fly ash samples let the pH vary within a narrow range, and thus severely limited the extent of leaching during the course of the experiment. Lead and Zn were the most sensitive while K and Na were the least sensitive to changes in redox conditions. 相似文献
Argillaceous rocks cover about one thirds of the earth's surface. The major engineering problems encountered with weak- to medium-strength argillaceous rocks could be slaking, erosion, slope stability, settlement, and reduction in strength. One of the key properties for classifying and determining the behavior of such rocks is the slake durability. The concept of slake durability index (SDI) has been the subject of numerous researches in which a number of factors affecting the numerical value of SDI were investigated. In this regard, this paper approaches the matter by evaluating the effects of overall shape and surface roughness of the testing material on the outcome of slake durability indices.
For the purpose, different types of rocks (marl, clayey limestone, tuff, sandstone, weathered granite) were broken into chunks and were intentionally shaped as angular, subangular, and rounded and tested for slake durability. Before testing the aggregate pieces of each rock type, their surface roughness was determined by using the fractal dimension. Despite the variation of final values of SDI test results (values of Id), the rounded aggregate groups plot relatively in a narrow range, but a greater scatter was obtained for the angular and subangular aggregate groups. The best results can be obtained when using the well rounded samples having the lowest fractal values. An attempt was made to analytically link the surface roughness with the Id parameter and an empirical relationship was proposed. A chart for various fractal values of surface roughness to use as a guide for slake durability tests is also proposed. The method proposed herein becomes efficient when well rounded aggregates are not available. In such condition, the approximate fractal value for the surface roughness profile of the testing aggregates could be obtained from the proposed chart and be plugged into the empirical relation to obtain the corrected Id value. The results presented herein represent the particular rock types used in this study and care should be taken when applying these methods to different type of rocks. 相似文献