花岗岩晶质铀矿的产出概况及其富集因素的初步研究

本文采用人工重砂法调查了同内花岗岩体中晶质铀矿的含量。初步证明,花岗岩内主要的脉型铀矿床、矿田都位于晶质铀矿含量高的(大于5g/t)花岗告体内。晶质铀矿在花岗岩岩浆中的富集,需要四方面因素的配合:重熔母岩相对富铀;重熔规模大,充分分异演化;铀含量高,钍含量低,以及REE、Nb、Ta、zr、P等含量相对较低;成岩时氧逸度较低。确定花岗岩中是否含晶质铀矿(并结合岩体出露面积大小)是判断该岩体是否具产铀潜力的最关键的依据。但由于品质铀矿有时在岩体中分布不很均匀,因而最好能有3个以上样品的测定值,以便对该岩体能否作为铀源体作出确凿的判断。

ON THE INVESTIGATION AND CONCENTRATION FACTORS OF URANINITE IN GRANITES IN CHINA

Investigation of the content of uraninite in various granitic intrusions in China by heavy fraction is an important aspect to understand the develop ment of uranium source terrain. It has been proven that the major uranium deposits of intra-granitic vein type are located in the granitic body rich in uraninite. The concentration of uraninite in granitic magma is derived from the combination of the following four factors. (1) relative concentration of uranium in anatectic parent rock; (2) large scale of anatexis and comp lete differentiation of remelting magma; (3) high content of uranium, low content of thorium and comparatively low content of rare earth elements and Nb, Ta, Zr, P etc.; (4) relatively low oxygen fugacity. The determination of uraninite in granite in combination with the size of exposed granitic body is a critical criterion to judge its uraniferous potential Owing to the inhomogeneous distribution of uraninite, more than three samples in an ade quate granitic intrusion are recommended to be obtained so as to make a judgement whether it can be considered as uranium source terrain.