开鲁盆地砂岩型铀矿中黄铁矿与铀矿化成因关系探讨  

Discussion of the Genetic Relationship between Pyrite and Uranium Mineralization in Sandstone-type Uranium Deposits in Kailu Basin

作　　者：陈梦雅 聂逢君[1] Mostafa FAYEK CHEN Meng-ya;NIE Feng-jun;Mostafa FAYEK(State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang,Jiangxi 330013;Department of Geological Sciences,University of Manitoba,Winnipeg,Canada MB R3T 2N2)

机构地区：[1]东华理工大学核资源与环境国家重点实验室,江西南昌330013 [2]曼尼托巴大学地质科学系,加拿大温尼伯MB R3T 2N2

出　　处：《地球学报》2021年第6期868-880,共13页Acta Geoscientica Sinica

基　　金：国家自然科学基金项目(编号:U2067202;41772068;41562006);国家重点基础研究发展规划973计划“中国北方砂岩型铀矿流体成矿过程研究”(编号:2015CB453002)联合资助。

摘　　要：开鲁盆地位于松辽盆地西南部,是中国北方砂岩型铀矿勘查的重点地区,自钱家店铀矿床发现以来,盆地内上白垩统姚家组目的层中相继发现了一些具有工业价值的铀矿床。为查明该层位中黄铁矿成因及其形成机制,探讨其与铀矿化之间的关系,本研究对含矿层砂岩中黄铁矿与铀矿物矿物学特征、黄铁矿S同位素开展细致研究。研究表明:(1)开鲁盆地姚家组砂岩中铀主要以独立铀矿物及吸附铀形式存在,独立铀矿物以沥青铀矿为主,含少量的钛铀矿及部分铀石,多数沿黄铁矿周边生长。吸附态的铀与黏土矿物密切相关。(2)姚家组砂岩中黄铁矿主要以草莓状、胶状及粒状产出,多与沥青铀矿共生,其中黄铁矿S同位素(d^(34)S=–55.6‰~23.2‰),平均值–20.87‰,变化范围很大,说明硫的分馏程度较高,硫的来源范围较广。(3)分析表明黄铁矿具有细菌硫酸盐还原作用及热化学硫酸盐还原作用两种成因,并探讨了这2种成因黄铁矿的形成机制。综合前人研究,结合研究区成矿地质背景,认为黄铁矿为铀成矿作用提供了发生还原反应所需要的还原剂,且黄铁矿及铀矿物的形成与区内热流体存在紧密联系。Kailu Basin is located in the southwest of Songliao Basin, which is the key area of sandstone type uranium exploration in northern China. Since the discovery of Qianjiadian uranium deposit, some uranium deposits with industrial value have been found in the target strata of Upper Cretaceous Yaojia formation in the basin.In order to find out the genesis and formation mechanism of pyrite in this layer, and to explore the relationship between pyrite and uranium mineralization, the mineralogical characteristics of pyrite, uranium minerals in sandstone of ore bearing layer, and S isotope of pyrite are studied in detail.The results show that:(1) Uranium in the sandstones of Yaojia formation in Kailu Basin mainly exists in the form of independent uranium minerals and adsorbed uranium. The independent uranium minerals are mainly pitchblende, containing a small amount of brannerite and some coffinite, most of which grow along the periphery of pyrite. The adsorbed uranium is closely related to clay minerals.(2) Pyrite in sandstones of Yaojia formation mainly occurs in framboid, colloidal and granular forms, and most of them are associated with pitchblende. The S isotope of pyrite(d^(34)S=–55.6‰~ 23.2‰), with an average value of –20.87‰, varies widely, indicating a high degree of sulfur fractionation and a wide range of sulfur sources.(3) The analysis shows that pyrite has two genesis: bacterial sulfate reduction and thermochemical sulfate reduction, and the formation mechanism of pyrite in these two genesis is discussed.Based on previous studies and combined with the metallogenic geological background of the study area, it is considered that pyrite provides the reducing agent for uranium mineralization, and the formation of pyrite and uranium minerals is closely related to the thermal fluid in the area.

关 键 词：姚家组 黄铁矿 硫同位素 砂岩型铀矿 开鲁盆地 

分 类 号：P597.2[天文地球—地球化学]