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    中国北方6种新的砂岩型铀矿对铀资源潜力的提示

    The implication of six kinds of new sandstone-type uranium deposits to uranium resources potential in North China

    • 摘要: 提要:经过近10多年的努力,在中国北方中新生代沉积盆地发现和探明了6种新的大型、特大型砂岩型铀矿,暂时定名为伊犁式、吐哈式、东胜式、乌兰察布式、马尼特式、通辽式砂岩型铀矿。各种式样的铀矿产于不同构造背景的沉积盆地,矿床地质、矿体地质和控矿因素也有明显的差异性特征。成矿演化基本特点是:伊犁式、吐哈式都是典型的层间氧化-还原作用成矿,但前者在单斜整体抬升和差异升降构造活动背景下的不断叠加富集为重要特征,后者则在斜坡带隆升加断层及小型背斜构造活动的背景下在断裂南北两侧分带成矿;东胜式主要受古层间氧化带控制并接受后期还原改造再富集;乌兰察布式最新研究认为是重要的沉积成岩型铀矿,与湖泛事件演变密切相关;马尼特式是潜水氧化-还原作用与层间氧化-还原作用交替转化形成的古河谷型铀矿床;通辽式是“构造剥蚀天窗+断裂活动+深部还原物质”控矿,也可能还与基性岩脉(热源)有关。上述6种式样铀矿的另一规律是从西部向东部,西部(前三种)均产于中下侏罗统含煤碎屑岩系,东部(后三种)均产于上白垩统泥质砂岩和细砂岩。笔者指出,6种新的砂岩型铀矿的意义不仅仅在于发现和探明的本身增强了中国铀资源保障能力,更重要的意义还在于对中国铀资源潜力及今后找矿方针、勘查部署等多方面的重要提示。

       

      Abstract: Abstract:Through ten years’ effort, six kinds of new large and superlarge sandstone-type uranium deposits have been found and explored in Mesozoic-Cenozoic sedimentary basins within North China, which are named temporarily as Yili pattern, Turpan-Harmi pattern, Dongsheng pattern, Ulanchap pattern, Manite pattern and Tongliao pattern. They occur in sedimentary basins of different tectonic settings and are different in deposit geology, ore body geology and controlling factors., but they have some common basic characteristics in metallogenic evolution. In Yili pattern and Turpan-Harmi pattern, mineralization is of typical interlayer redox feature; nevertheless, the former pattern is characterized by uranium superimposition and enrichment under the condition of whole uplift of monocline or different uplifting and falling conditions of ore-bearring strata, whereas the latter pattern is characterized by mineralized zonation on the southern and northern sides of the fault superimposed on the structural slope and small anticline structure under tectonic uplifting. In Dongsheng pattern, mineralizaton is mostly dominated by paleo-interlayer oxidation zone modified by later reduction; in Ulanchap pattern, mineralization is closely related to the evolution of lake flooding events; In Manite pattern, mineralization is of paleovalley type formed by alternation between phreatic redox and interlayer redox; in Tongliao pattern, mineralization is controlled by “tectonic window, fault and reducing matters in the deep part”, and is also probably related to dikes of basic rock (heat source). In the above six patterns , a rule may occur in their rock assemblage from west to east. The west three pattern are controlled by Upper and Middle Jurassic coal-bearing clastic rocks, while the east three patterns are controlled by Lower Cretaceous argillaceous sandstone and fine sandstone. It is indicated that the discovery and exploration of the six new kinds of sandstone-type uranium deposits not only strengthen insurable capability of uranium resources in China but also indicate the orientation and deploy for uranium resources potential evaluation and prospecting in the future.

       

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