滇西龙川江盆地团田地区砂岩型铀矿元素地球化学特征

Element Geochemical Characteristics of Sandstone-Type Uranium Deposit in the Tuantian Area, Longchuanjiang Basin, Western Yunnan

本文通过系统的取样分析,详细研究龙川江盆地团田地区新获砂岩型铀矿床的元素地球化学特征,以期为初步揭示区域铀成矿模式提供有效信息。分析表明:矿段岩石成熟度较差,岩性为长石砂岩;矿段定位于氧化-还原过渡带且存在含氧地下水二次氧化破坏可能;U元素与Mo的双峰富集式样可以作为该区砂岩型铀矿化元素模型;本次见矿层位(芒棒组下段下亚段)古铀量较低,存在沉积期后铀元素预富集作用,且本身也可作为盖层铀源供给铀元素;该区铀成矿过程为表生来源,不具备深部热液作用特征,该区芒棒组各含矿层具有较统一的物质来源、沉积环境和构造背景;稀土元素与铀元素离子在该区地下水水溶液中主要呈REE(CO3)^0、UO2(CO3)^0、[REE(CO3)2^-2]、[UO2(CO3)2^-2]四种形式的络离子共迁移,并在适当的Eh和pH条件下与有机碳、Fe2+等还原剂发生反应而沉淀富集于矿物颗粒裂隙中。

A sandstone-type uranium deposit is found out in the Tuantian area, Longchuanjiang basin, west Yunnan. The arkose as host rock is characterized by low maturity. The uranium mineralization occurs in the redox transitional zone and may underwent secondary oxidation which is reflected by the double peak phenomenon(double peak representing U and Mo) in the spider diagram. The Lower Member of the Mangbang Formation as host horizon is an uranium source bed. The uranium deposit is a supergene deposit. Uranium and REE migrated as REE(CO3)^0, UO2(CO3)^0, [REE(CO3)2^-2] as [UO2(CO3)2^-2] in groundwater and deposited out under the suitable pH, Eh and redox conditions.