Discussion on the oil gas-uranium metallogenic mechanism in Diantou uranium deposit in southern Ordos basin
The study focused on Diantou uranium deposit in the southern Ordos basin,and clarified the characteristics of the stratigraphy,structure,oil impregnation,and uranium deposit in the study area.The mechanism of oil and gas infiltration and uranium mineralization was explored from four aspects:oil and gas seepage,oxidation,the relationship between uranium ore bodies and fractured bodies,and the interaction between uranium and oil and gas.The development of a series of NEE and near-EW trending fault fracture bodies in Diantou area,which were produced by tectonic fracture zones and high-angle jointed dense zones,were the main channels for the upward migration and accumulation of oil and gas in the deep Yanchang formation,accompanied by oil leaching,veined gypsum,pyrite,etc.The oil and gas exudation can be divided into several periods,manifested in three styles:oil-leached sandstone,fade altered sandstone,and gelatinized organic,among which the gelatinized organic matter or ground asphalt formed during the uranium metallogenic period played a key role in the uranium precipitation and enrichment.The formation of gray-green paleooxide sandstone or oil-leached sandstone after the metallogenic period only played a role in preserving uranium mineralization.In addition,radioactive elements produced catalytic pyrolysis effect on organic matter and bitumen,and the activity and reductive adsorption capacity were enhanced,and uranium elements were accumulated and enriched to form high-grade ores during the oxidation transformation process during the metallogenic period.Pitchblend or uranite in the ore occurs around gelatinized organic matter or pyrite,associated with galena,sphalerite,chalcopyrite and other medium and low temperature hydrothermal sulfides,the sandstone of Zhiluo formation in this area are usually of high hardness,high density,low porosity and permeability,which were caused by medium and high diagenesis,and also the result of water-rock reaction under the long-term action of exudated fluid.The fracture body of Diantou deposit is closely related to the industrial orebody and is an important locating factor,which provides a basis and a train of thought for the selection area and uranium exploration.The fault and associated fracture system also improve the physical properties of the host sandstone.The oil and gas from Yanchang formation migrated up to Zhiluo formation and Lower Cretaceous through the fault,providing sufficient reducing materials for uranium mineralization.The gelatinized organic matter or bitumen formed in the metallogenic period played a key role in the enrichment and precipitation of uranium,and the fade altered sandstone and oil-leached sandstone formed after the metallogenic period played a role in ore preservation,the complex water-rock reaction was the main reason for the high diagenetic degree of Zhiluo formation in this area.The organic matter was activated by the heat effect of uranium element,which resulted in the accumulation and enrichment of uranium source and formation of high-grade uranium ore.
Diantou uranium depositmetallogenic mechanismfault fractured bodyuranium mineralizationoil and gas exudationgelatinized organic matter
刘坤鹏、武正乾、毛宁、于宏伟、李亚锋、张良、王晓鹏、刘凯鹏、屈伸
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核工业二〇三研究所,陕西 西安,710086
店头铀矿床 成矿机理 断缝体 铀成矿 油气渗出 凝胶化有机质
&&&&&&&&&&中核集团青年英才项目中核集团集中研发项目Uranium Mine Survey in Xinzhuang Area,Zhenyuan County,Gansu Province&&
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