铀矿地质

本文通过用铀矿石的U Ra平衡系数修正样品的铀含量 ,再进行U Pb等时线拟合 ,获得了北方主要产铀盆地的实际成矿年龄 :伊犁盆地为 1 2Ma、 5～ 6Ma、 1～ 2Ma ;吐哈盆地为 48Ma和2 8Ma ;巴彦塔拉凹陷为 7Ma;鄂尔多斯盆地东胜地区为 1 0 7Ma。对含矿砂体中的碎屑锆石与相应蚀源区中酸性火成岩类的锆石U Pb同位素年龄进行对比 ,发现含矿砂体的物质成分直接来自中酸性火成岩类的剥蚀产物。该物源是形成富铀砂体的物质基础。通过对蚀源区岩石和盆地含矿地层不同部位砂体岩石样品的U Pb同位素体系演化特征的研究 ,论证了可地浸砂岩型铀矿的铀源主要来自两方面 ,一是蚀源区活性铀含量高的中酸性火成岩类 ,另一是已经发生铀预富集的沉积砂体。

The research achievements of isotope geologic characteristics of sandstone hosted uranium deposits are introduced in this paper.Authors have developed a method for correcting uranium content in uranium ore samples by considering the U?Ra equilibrium coefficient,then a U Pb isochron is drawn up.By performing the above correction,ore formation ages of sandstone hosted uranium mineralization which may be more realistic have been obtained.They are:12 Ma,5～6 Ma,1～2 Ma in Yili basin;48 Ma and 28 Ma in Turfan Hami basin;7 Ma in Bayantala sag,Erlian basin;107 Ma in Dongsheng area,Ordos basin. The comparative research on U?Pb isotopic ages of detritic zircon in ore hosting sandstone and zircon in intermediate acid igneous rocks in corresponding provenance area indicates that the ore hosting sandstone is originated from the erosion of intermediate?acid igneous rocks and the latters are the material basis for the formation of the uranium rich sandstone beds. On the basis of the study on U?Pb isotopic system evolution of the provenance rocks and sandstones from ore hosting series, it is verified that the uranium sources of sandstone hosted uranium deposits are:the intermediate acid igneous rocks with high content of mobile uranium,and the sandstone bodies pre concentrated with uranium.