沙子江铀矿外围地化特征、元素迁移及铀成矿机理

Geochemistry, Element Migration and Mechanism of Uranium Mineralization in the Periphery of the Shazijiang Uranium Ore Deposit

沙子江矿床外围某钻孔不同矿化蚀变位置具有U含量与SiO_2、CaO、Fe_2O_3、LOI、HREE含量正相关、Na均消失殆尽、稀土和微量元素配分型式相似、LREE呈较富集的右倾特征。与新鲜围岩相比,蚀变围岩Sb、U明显增高,Ni、W略有增加;与新鲜围岩和蚀变围岩二者相比,碎裂花岗岩(矿石)中Cd、Sb明显增高,W、Ni、Pb略有增加,Be、Bi明显减少;相对于新鲜围岩,碎裂花岗岩(矿石)和蚀变围岩分别表现出Sb、U和Sb、Cd、U明显增高,共同表现出W、Ni略有增加的特征。矿化蚀变带元素迁移研究表明,矿化蚀变带样品Sb、LOI、CaO、Ni、Cu、In、Sr均迁入,Na2O、FeO、Be、Cs、Th、Nb均迁出,迁入率最大的组分均为Sb,迁出率最大的组分均为Na_2O。地球化学特征及元素迁移规律指示花岗质围岩是重要的U源及组分来源,成矿流体呈碱性,氧逸度较高。

The uranium content has positive correlations with the abundance of SiO2,CaO,Fe2O3,LOI and HREEs and Na is almost depleted at the mineralization and alteration positions of a drill core in the Shazijiang uranium ore-deposit.In trace element spider diagram and REEs distribution pattern diagram,the shapes of different mineralized and altered belt samples are very similar.The REEs distribution pattern shows that LREEs are enriched and the distribution lines are lean to right.Compared with the fresh surrounding rocks,the altered surrounding rocks have elevated Sb and U concentrations and a few more Ni and W concentrations.Compared with the fresh surrounding rocks and altered surrounding rocks,the cataclastic granites(ore)have significantly increased Cd and Sb concentrations,while W,Ni and Pb concentrations increase slightly,and Be and Bi concentrations reduce sharply.Compared with the fresh surrounding rocks,cataclastic granites(ore)and the altered surrounding rocks are characterized by significantly increased Sb and U concentrations and Sb,Cd and U concentrations,respectively.In addition,both W and Ni increase slightly.Research of element migration in mineralization and alteration belts shows that Sb,LOI,CaO,Ni,Cu,In and Sr moved in,of which Sb has the largest positive mobility value.In contrast,Na2O,FeO,Be,Cs,Th and Nb all moved out,of which Na2O has the largest negative mobility value.Based on the results and discussion of geochemistry and element migration,we deduce that the granitic surrounding rocks are one of the most important sources of uranium and other components,and the ore-forming fluid is alkaline with high oxygen fugacity.