吐哈盆地克尔碱向斜构造特征与砂岩型铀矿目的层沉积相、微相及其找矿意义

Characteristics of Tectonics and Depositional Facie and Microfacies of Sandstone-type Uranium Host Rocks and Significance for Exploration in Ke'erjian Syncline,Turpan-Hami Basin

吐哈盆地的砂岩型铀矿找矿进入了攻坚期,到目前为止,除了在盆地西南缘找到了有价值的工业铀矿化以外,其他地区多年来一直没有重要突破。盆地西部布尔加地区克尔碱向斜侏罗系地层西山窑组虽然发现了若干铀矿化线索,但近年的勘查进展不大。究其原因,砂岩型铀矿的主要控制因素还没有完全弄清。本研究通过克尔碱向斜北、南、东部地区的野外露头地质调查,结合钻孔岩芯观察与镜下岩石鉴定,明确了北部的构造变形强,以逆冲断层和紧闭褶皱为特征;而南部的变形稍弱,主要是逆冲断层。铀矿目的层——中侏罗统西山窑组二段赋矿砂体主要沉积于辫状三角洲前缘河口坝微相环境,少量的为前缘席状砂微相环境。形成铀矿化的含铀含氧流体主要来自南部隆起区,渗入到西山窑组二段底部的水下分流河道砂体后,再进入河口坝砂体中形成铀矿化,仅少量的氧化流体能够到达前缘席状砂体中。综合分析表明,向斜南部目的层成矿潜力比北部的要好,下一步找矿工作应着重在南部开展。

After the uranium deposits have been found along the southwestern margin of the Turapan-Hami basin,there are no significant breakthrough for uranium exploration in the basin recent years.Although several uranium mineralization occurrences have been discovered in the Ke’erjian syncline,Buerjia area,west Turpan-Hami basin,no industrial uranium deposit has been found.It is because some basic geological controlling factors keep unclear for the exploring tenement.This study focuses on the tectonics and depositional facies and microfacies of host rocks in the north,south and east areas of the Ke’erjian syncline.Geological investigation for the outcrops shows that tectonic deformation characterized by thrusts and tight folds in the north margin is stronger than that characterized by only thrusts in the south margin of the Ke’erjian syncline.The host rock,sandbodies of the Middle-Jurassic Xishanyao FmⅡdeposited mainly in braided delta front mouth bar,minorly in sheet sand.The uranium-oxygen-bearing fluid flows(UOFF)originated from the south uplift first seepage the bottom sands of host rock deposited in subaquaceous distributary channel,then into mouth bar sands,in which uranium is reduced by reducing agents.A few UOFFs can reach the sheet sand and mineralize.It is demonstrated that the uranium potential in south part than that in north part for the Ke’erjian syncline.