右江盆地大际山U-(Mo)矿床围岩蚀变特征及微量元素迁移规律——对区域内U、Au成生关系的指示  

The characteristics of wall-rock alteration and the trace element migration in Dajishan U-(Mo)deposit,Youjiang basin:Implications for genetic relationship between the uranium and gold mineralization

作　　者：田建吉[1] 刘畅 吴玉[1] 李秋实 TIAN Jianji;LIU Chang;WU Yu;LI Qiushi(CNNC Key Laboratory of Uranium Resources Exploration and Evaluation Technology,Beijing Research Institute of Uranium Geology,Beijing 100029,China)

机构地区：[1]核工业北京地质研究院,中核集团铀资源勘查与评价技术重点实验室,北京100029

出　　处：《世界核地质科学》2024年第3期434-449,共16页World Nuclear Geoscience

基　　金：中国核工业地质局地勘费项目“川藏地区雅安-林芝段铀多金属资源评价研究”(编号:地GT2201);“全国共伴生铀资源远景评价”(编号:地D2003);“幕阜山地区花岗-伟晶岩型铀多金属成矿作用与远景评价”(编号:22045408);核工业北京地质研究院院长青年科技创新基金项目“白杨河矿床中铍、铀成因关系研究:来自流体包裹体及H-O-Sr-Nd同位素的约束”(编号:地QJ2103)联合资助。

摘　　要：位于扬子地块西南缘的右江盆地,是全球第二大的卡林型Au矿(共伴生有Sb、Hg、Tl异常/矿化)矿集区,有着滇黔桂“金三角”的美誉。值得注意的是,该区除发育Au(-Sb-Hg-Tl)矿床外,还产有大量赋矿岩性和控矿构造相似的U矿床(点),成矿特色鲜明。前人对该区Au矿开展了大量研究,而U矿研究较少,对U、Au的成生关系尚不清楚。基于此,文章选取右江盆地内典型的U矿床——大际山U-(Mo)矿床为研究对象,通过开展岩矿相学研究和地球化学分析,厘定了矿化的围岩蚀变为硫化、沥青质化、磷铝锶石化、硅化和伊利石化,揭示了矿化过程中Re、Tl、Mo、U、Cd、Ni、Co、As、Sb、MREE的相对富集。蚀变矿物组合及元素迁移规律约束大际山U-(Mo)矿床中成矿物质可能来源于牛蹄塘组,成矿流体应为还原性有机流体与地表-近地表酸性、氧化性流体的混合,矿质沉淀发生在低温、酸性、还原环境中。综合分析认为,右江盆地内U、Au分布特征及矿床成因具有明显差异,二者应是不同成矿事件的产物。Located in the southwest margin of the Yangtze Block,Youjiang basin is the second largest cluster area of Carlin-type gold deposits(associated with Sb,Hg,Tl anomaly and mineralization)in the world,is also known as“Golden Triangle”of Dian-Qian-Gui.Beside the gold deposit,a large number of U deposits(occurrences)with similar ore-hosting lithology and ore-controlling structure are also developed in this area.However,previous research were mostly focused on the gold,a few was on uranium.The genetic relationship between U and Au is still unclear.In this paper,Dajishan U-(Mo)deposit in the Youjiang basin was studied as a case of a large number of U and Au deposits(or ore occurrences)discovered in the region.In space,uranium and gold mineralization are closely related which provided an ideal research object for understanding the regional mineralization process and the relationship between Au and U mineralization.In this paper,petrography,mineragraphy and geochemistry was used to study the alteration mineral in the Dajishan U-(Mo)deposit,sulfides,bitumen,goyazite,quartz and illite were examined,and the relative enrichment of Re,Tl,Mo,U,Cd,Ni,Co,As,Sb and MREE was discovered during the mineralization process.The alterated mineral assemblage and trace element migration constrain that the ore-forming materials of Dajishan U-(Mo)deposit probably came from Niutitang Formation,and the ore-forming fluid should be a mixture of reductive organic fluid and surface to near surface acidic and oxydic fluid,and the mineralization occurred in low temperature,acidic and reductive environment.Comprehensive analysis suggests that there is significant differences in the distribution characteristic and genesis of U and Au deposits in the Youjiang basin,and U and Au deposits should be products of different mineralization events.

关 键 词：围岩蚀变特征 元素迁移规律 大际山U-(Mo)矿床 U、Au成生关系 右江盆地 

分 类 号：P595[天文地球—地球化学]