内蒙古东胜砂岩型铀矿床形成条件与成矿作用

The Metallogenic Condition and Epigenetic Alteration Mineralization of Dongsheng Uranium Deposit in the Inner Mongolia

鄂尔多斯盆地是中国煤、油、气、铀四大能源集一体的最大能源盆地之一,是统一在华北地台的太古宙、元古宙古老结晶岩系及古生代海、湖相台盆基础上,于中生代从华北地块分异出来并发育的中—新生代山前凹陷盆地。中—新生代盆地经历了台盆发育、断块活动及盆后活动阶段。本文分析了中—新生代盆地放射性铀成矿盆地地质及地球化学有利条件,铀的丰度(4.71×10-6～34.3×10-6)是上地壳平均丰度,甚至高出一个数量级。阐述了东胜铀矿容矿层的岩石学特征,成岩—后生—低温热液矿化蚀变特征。分析了与铀成矿作用密切相关、呈面型展布、分别产于矿体上、下盘的绿色化及漂白色蚀变形成与深盆气密切成因关系。矿床矿化蚀变作用具有:多期次多阶段成矿特点、矿化矿物组合复杂、矿化形式多样、成矿温度具低温热液特点(70～120℃)、绿色化及漂白色蚀变具面型分布,矿床属于沉积预富集—古层间氧化淋滤—后生二次还原与交代砂岩型铀矿床。

The Ordos basin is greatest one of the oil,natural gas pool,coal minee and uranium deposit collection in the same basin. This basin is component part of Archeozoic-Proterozoic crystalline basement and marine and lake sedimentary cover of Paleozoic group unite into North China Plate. On the Ordos basin was divided into Mesozoic-Cenozoic piedmont depression basin from North China in Mesozoic era. The Ordos basin of Mesozoic-Cenozoic era is undergoing three develop evolution stage from tableland basin, fault block and after basin . This paper make a concrete analysis of favourable condition of uranicum metallogenetic geological-geochemistry in Mesozoic-Cenozoic era basin. Theuranicum abundance of the host sandstone （4. 71×10^-6～ 34. 3× 10^-6） is a few multiple-outstrip one quantitative stage higher than mean vaiue of upper earth crust abundance. This paper expounds characteristics of petrology of host layer in Dongsheng uranium ore deposit and features of diagenetic-epigenetic-lowtemperature hydrothermal mineralization. The paper specifically analyses close relationship between green-bleaching mineralized alteration and uranium mineralization. The green and bleaching alteration has feature of the planer type distributed. They are hosted in upper plate and lower wall of uranium orebody respectively and have close relation of genesis to deep-basin gas. This mineralized alteration has characteristics of mineralization multi-epoch＇ and multi-stage, complex mineral association paragenesis, diversified mineralized shape and characteristics of low-temperature hydrothermal mineralization （70 ～120℃）. The sandstone-type uranicum ore deposit is the genesis of early stage of sedimentary pre-enrichment,succeed stage of leach of paleointerlayer oxidized zone and epigenetic deoxidation and epigenetic metasomatism.