含铀砂岩中铀与有机质、油气和煤的关系——以鄂尔多斯盆地东胜地区和吐哈盆地十红滩地区为例

Petrology of uranium-bearing sandstones and relationship of organic matters,hydrocarbons and coal with uranium:an example from Dongsheng,Ordos Basin and Shihongtan,Tuha Basin

目的探讨油、气、煤与铀的综合研究对于含油气盆地内多种能源的成因机制及盆地资源的开发利用。方法对鄂尔多斯盆地东胜地区和吐哈盆地十红滩地区砂岩型铀矿的岩石学特征、地质构造、含矿建造与古水文地质条件及铀矿的成矿特点等进行了综合分析与研究。结果源区火成岩和泥岩可能为铀的物质来源之一,铀矿化是成岩—后生阶段介质条件及环境改变的产物,受氧化-还原界面的控制;构造作用使目的层的抬升掀斜与暴露以及水动力环境是形成层间氧化带和铀矿化的重要条件;铀矿石带中黄铁矿表面及其附近存在吸附铀α径迹,有机质碎屑胞腔中沥青铀矿和黄铁矿共生,含铀砂岩中可见含沥青质的镜煤。结论铀的富集和铀矿的形成可能与黄铁矿、油气、煤等有机质有密切的成因关系。

Aim To study the petrologic characteristics of sandstone-type uranium deposits, in Dongsheng Area of the Ordos Basin and the Shihongtan Area of the Tuha Basin, which shows that igneous and mudstone rocks in the provevance might attribute to one of the uranium resources. Methods Uranium mineralization was controlled by the oxidation-reduction interface and occurred where medium condition changed from acidic oxidation into alkaline reduction during diagenesis and epidiagenesis. Results The uplifting, tilting and exposing of the uranium-bearing beds, and hydrodynamic environment are key factors for forming interlayer oxidation zones and uranium mineralization, and sand bodies in the braided channels provided favorable space for forming interlayer oxidation zones and uranium mineralization. Favorable mudstone-sandstone-mudstone succession suite provides a good preservation for the uranium deposit. Study also shows that pitchblende coexists with pyrite in the cavities of organic fragments in uranium-beating zones, and absorbed uranium α traces are found on the surface and around pyrite. The sandstonetype uranium deposits are distributed above and/or below the same or adjacent horizons where oil, natural gas and coal are preserved; temporally, the above energy resources basically occurred during or almost the same geological period. Conclusion Thus generation and accumulation of uranium has intrinsic relationship in origin with pyrite and organic matters.