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《Journal of Geochemical Exploration》2004,81(1-3):59-70
This study deals with the experimental determination of the rate of weathering and As release from Au-bearing sulfide ores of the Mokrsko-West deposit (Czech Republic). The elevated As contents in the ore and the possible As mobilisation must be taken into account due to the close proximity of the deposit to the Vltava River, a source of drinking water for Prague. Crushed and homogenized ore material was divided into four grain-size fractions showing uniform chemical and mineralogical composition and subjected to batch and column leaching experiments. The most important reactions controlling metal leaching include (i) oxidation of sulfides, (ii) carbonate equilibrium and (iii) precipitation of hydrated ferric oxides (HFO). Hydrated ferric oxides were found to be important sorbents of mobilized As. The highest concentration of As in the leachates was obtained from the 64–1000 μm fraction. The oxidation rate in the agitated batch experiment calculated on the basis of sulfate concentrations is an order of magnitude higher (3.8×10−9 to 4.4×10−8 mol SO42− h−1 g−1) than in the static column experiment (9.6×10−10 to 7.4×10−9 mol SO42− h−1 g−1). The higher oxidation rate of batch experiments is explained by abrasion of oxidation products (mainly HFO) and by further exposition of reaction surfaces of the sulfide grains. 相似文献
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Wet climatic episodes are known to have prevailed in the Egyptian Sahara several times during the late Quaternary, most recently during the Holocene 8000 yr ago. Earlier wet episodes have been recognized as having occurred during the past 300,000 yr and have been dated by U-series methods in speleothems and in lake travertines. We show here that the times of enhanced groundwater movement can also be determined by 230Th/234U dating of secondary U in ores of uranium, iron, and phosphate. We also present evidence that such acceleration of groundwater movements is indicated by relatively low 234U/238U activity ratios in the secondary uranium. Our new data show that pluvial periods in Egypt occurred during marine oxygen isotope stages 4, 5, 6, and 7 and therefore are consistent with the view that the wet episodes are the results of migration of the tropical monsoonal belt driven primarily by the 23,000-yr precession cycle of the Milankovich curve, modulated by the 100,000-yr eccentricity cycle. 相似文献
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ZHU Guangyou ZHANG Shuichang LIANG Yingbo DAI Jinxing & LI Jian Research Institute of Petroleum Exploration Development PetroChina Beijing China 《中国科学D辑(英文版)》2005,48(11)
Isotopic evidence of TSR origin for natural gas bearing high H2S contents 1961 As the hazardous component of natural gas, the ex-istence of H2S, due to its extremely strong toxicity and corrosivity, not only decreases the percentage of hy-drocarbon gas within natural gas and reduces its in-dustrial value, it also threatens each aspect of drilling and exploitation. It frequently causes serious safety accidents[1] and leads to the E&P cost and risk of natural gas with higher H2S contents be… 相似文献
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山东省泰安朱家庄自然硫矿床,赋存于鲁西断隆古近纪汶东陆相盆地。自然硫矿层在汶口组二段上亚段,泥质灰岩-含泥灰岩-含云灰岩-石膏岩韵律层中的白云岩-石膏岩层段发育。自然硫以胶态、晶态、土态3种形态产出,可划分为顺层型、准顺层型、斑杂型及不顺层型4大类10余种矿石类型。从矿区去膏化作用普遍、自然硫与石膏-硬石膏分别富集轻-重同位素的特征、油气显示明显及地下水主要径流方向自然硫矿化最强等各种证据,表明该矿属生物后生成因的矿床。 相似文献