下庄竹山下铀矿床黄铁矿元素地球化学特征及其表征意义

Geochemical Characteristics and Their Geological Significance of Pyrite in Zhushanxia Deposit of Xiazhuang Uranium Orefield

竹山下铀矿床是粤北下庄铀矿田内大型铀矿床之一,铀矿化类型为"交点"型和硅化带型。在详细的野外地质调查基础上,对竹山下铀矿床4种不同类型黄铁矿进行元素含量分析及硫同位素测试,结果表明:"交点"型矿石中黄铁矿相对富集Pb、 Cu、 Co、 As、 Ni、 Se、 Bi、 U、 Sb、 Zn等微量元素;"交点"型铀矿化形成于中深部高温环境,成矿热液具有地幔流体特征,成矿过程硫来源与该区花岗岩中黄铁矿的硫来源一致或者相似,花岗岩中的黄铁矿可能为该期成矿事件的产物;竹山下矿床在垂向上表现出越往深部硫逸度越低的特征;"交点"型和硅化带型中黄铁矿具有相似的微量元素配分曲线,表明二者具有相同的成矿热液来源,且与辉绿岩中黄铁矿配分曲线相似,表明该区成矿热液具有深源性。

Zhushanxia uranium deposit is a large one in Xiazhuang uranium orefield in northern Guangdong.“Intersection type”and silicified vein type are the main types of mineralization in the region.Based on detail field geological survey,elemental content analysis and sulfur isotope test were carried out for four types pyrite in Zhushanxia deposit.The results showed that:1)The pyrite in the“intersection type”deposit is relatively enriched in trace elements such as Pb,Cu,Co,As,Ni,Se,Bi,U,Sband Zn;2)“intersection type”uranium mineralization was formed in the middle and deep part where the temperature is high and the mineralization hydrothermal fluid is of mantle source characteristics.The source of sulfur in the ore-forming process is consistent or similar to the sulfur source of pyrite in the granite.The pyrite in the granite may be the product of the mineralization event;3)Zhushanxia deposit shows a vertical zoning characteristics(has lower sulphur fusibility in deeper part);4)pyrite of“intersection type”and silicified belt type deposit are with similar element distribution curve of the diabase,which indicated that they have the same ore-forming hydrothermal fluid source from the depth.