中国北方中新生代盆地深部砂岩铀矿成矿条件与找矿方向

摘要

受开采技术、成本和成矿理论制约,现有的砂岩型铀矿勘查主要选择在盆地边缘700m以浅的地区,对盆地深部的铀矿找矿潜力研究较少.总结中国北方重要中新生代盆地的含铀岩系、构造特征,结合近年开展的北方砂岩型铀矿深部找矿,分析了盆地深部成矿有利的沉积建造、构造与流体改造、还原条件等,指明了盆地的深部找矿潜力.同时指出,作为战略储备,当前盆地深部寻找砂岩型铀矿要优先重视2个方向:①在盆地边缘斜坡区,重点以发育红-黑岩系结构的含铀地层为目标,寻找与浅部成矿条件相似的深部矿床;②在盆地中心区,以含铀的红色岩系为重点,优先寻找延伸至盆地深部的正向构造区和砂体发育区.这些认识在松辽盆地的铀矿调查中得到验证.%The exploration of sandstone-hosted uranium deposits has only been focused on the basin margins with the depth less than 700m because of restrictions of mining technology, cost and metallogenic theory. The prospecting potentiality of deep uranium deposits in basins has always been ignored. In this study, favorable sedimentary structure, tectonic movement, geological fluid and re-duction condition of deep sandstone-hosted uranium deposits were discussed based on the summary of tectonic settings and urani-um-bearing strata of known shallow sandstone-hosted uranium deposits in Mesozoic-Cenozoic basins in North China and new find-ings from the exploration of deep sandstone-hosted uranium deposits in recent years. Meanwhile, prospecting potentiality of deep sandstone-hosted uranium deposits was assessed and two directions were preferentially pointed out:( 1) at the margin slope of the ba-sin, the"red and black"strata series should be preferentially targeted in search for the potential deep deposits whose formation condi-tions are similar to the conditions of the shallow deposits;(2) at the center of the basin, emphasis should be put on the red layer withpositive structure and sand body developed areas in the deep buried basin. These suggestions have been proved to be effective in the uranium investigation in Songliao basin.