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摘要
The Turpan-Hami basin, covering an area of approximately 50,000 km(2) in NW China, contains concealed sandstone-type U deposits in a Jurassic sequence of sandstone, mudstone and coal beds. Sampling of soil profiles over the Shihongtan concealed U deposit in this basin shows that fine-grained soil collected from the clay-rich horizon contains U concentrations three times higher than similar soils at background areas. Selective leaching studies of these soils show that U is mainly associated with clay minerals, which comprise from 17.9% to 40% (average 30.4%) of the total mineral content. This may indicate that U is converted to uranyl ions [UO(2)](2+) under oxidizing conditions and is sorbed on clay minerals to accumulate in anomalous concentrations. Fine-grained soil (<120 mesh, <0.125 mm) from the clay-rich horizon, generally occurring at a depth of 0-40 cm, is shown to be an effective sampling medium for deep-penetrating geochemical surveys. A wide-spaced geochemical survey at a density of approximately 1 site per 100 km(2) was carried out throughout the whole basin using this sampling medium. Samples were analyzed for 30 elements by ICP-MS following a 4-acid extraction. Three large-scale geochemical anomalies of U and Mo were delineated over the whole basin. One of the anomalies is consistent with the known U deposit at Shihongtan in the western part of the basin. A new potential target in the eastern part of the basin was selected for a follow-up survey at a density of 1 sample per 4 km(2). A drilling exploration programme at the center of the geochemical anomaly delineated by this follow-up survey discovered a new U deposit.
- 出版日期2011-12
- 单位中国地质科学院地球物理地球化学勘查研究所
