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粤北书楼丘铀矿床黄铁矿原位微量元素、硫同位素组成及矿床成因指示
引用本文:刘文泉,刘斌,罗强,祁家明,吴建勇,魏文芳.粤北书楼丘铀矿床黄铁矿原位微量元素、硫同位素组成及矿床成因指示[J].地球科学,2022,47(1):178-191.
作者姓名:刘文泉  刘斌  罗强  祁家明  吴建勇  魏文芳
作者单位:1.核工业二九〇研究所, 广东韶关 512026
基金项目:科技部重点研发计划项目2017YFC06026中国核工业地质局铀矿调查与科研项目202114中国核工业地质局铀矿调查与科研项目202140-2广东省科技专项201112166271152
摘    要:书楼丘铀矿床作为长江铀矿田重要的组成部分之一,其成矿流体特征、来源及成矿环境研究相对较少. 依据黄铁矿晶型特征及其与其他矿物共生组合特征,将书楼丘铀矿床中脉石矿物黄铁矿的形成划分为成矿前期(Py Ⅰ)、成矿期(Py Ⅱ)及成矿晚期(Py Ⅲ)三个时期,成矿期又被划分为成矿早阶段(Py Ⅱa)和主成矿阶段(Py Ⅱb). 采用激光剥蚀多接收电感耦合等离子质谱仪(LA-MC-ICP-MS)对成矿前期、成矿期形成的黄铁矿进行微量元素及硫同位素分析. 结果表明,书楼丘铀矿床Py Ⅰ中Co、Ni含量大部分低于检出限,Py Ⅱa和Py Ⅱb中Co/Ni比值主要介于1~5之间,为热液成因. Py Ⅰ δ34S值为0.41‰~2.02‰,显示了地幔硫特征;Py Ⅱa δ34S值为-9.15‰~-11.3‰,与贵东复式花岗岩体黄铁矿(-10.9‰~-7.10‰)基本一致,贵东复式花岗岩体与诸广复式花岗岩体毗邻且成因相同,由此推测Py Ⅱa的硫来自诸广山复式花岗岩体;由成矿早阶段到主成矿阶段,黄铁矿δ34S值明显升高(-9.15‰~-11.3‰增加到-4.58‰~-8.48‰),表明成矿流体氧逸度降低,成矿早阶段氧化性流体淋滤赋矿围岩中的铀形成富铀流体运移,主成矿阶段富铀流体转变为还原环境,导致铀沉淀. 结合黄铁矿微量元素特征可知,书楼丘铀矿床成矿前期热液流体为高温碱交代热液,成矿期热液流体为中低温大气降水演化热液. 

关 键 词:LA-MC-ICP-MS    微量元素    硫同位素    成矿流体    书楼丘铀矿床    矿床学
收稿时间:2021-06-01

In-Situ Trace Element and Sulfur Isotope of Pyrite Constrain Ore Genesis in Shulouqiu Uranium Deposit,North Guangdong
Liu Wenquan,Liu Bin,Luo Qiang,Qi Jiaming,Wu Jianyong,Wei Wenfang.In-Situ Trace Element and Sulfur Isotope of Pyrite Constrain Ore Genesis in Shulouqiu Uranium Deposit,North Guangdong[J].Earth Science-Journal of China University of Geosciences,2022,47(1):178-191.
Authors:Liu Wenquan  Liu Bin  Luo Qiang  Qi Jiaming  Wu Jianyong  Wei Wenfang
Abstract:The Shulouqiu uranium deposit is an important part of Changjiang uranium ore field. However, there are relatively fewer studies on its ore-forming fluid properties, source and metallogenic environment. Based on the characteristics of pyrite and other mineral paragenesis, the formation of pyrite in the Shulouqiu uranium deposit is divided into three stages: pre-metallogenic period (Py Ⅰ), syn-metallogenic period (Py Ⅱ) and late-metallogenic period (Py Ⅲ). Meanwhile, the syn-metallogenic period (Py Ⅱ) is divided into early metallogenic stage (Py Ⅱa) and main metallogenic stage (Py Ⅱb). The trace elements and sulfur isotopes of pyrite formed in different periods were analyzed by inductively coupled plasma mass spectrometry (LA-MC-ICP-MS). The results show that the content of Co and Ni of Py Ⅰ is mostly lower than that of the test line, and the ratios of Co/ Ni of Py Ⅱa and Py Ⅱb are mainly 1-5, suggesting that it is the cause of hydrothermal. The δ34S value of Py Ⅰ ranges from +0.41‰ to +2.02‰, which is mantle sulfur. The δ34S value of Py Ⅱa ranges from -9.15‰ to -11.3‰, which is similar to that of the Py Ⅱa (-10.9‰ to -7.10‰) in the Guidong compound granite. Meanwhile, it has the same origin as the Zhuguang compound granite, indicating that the sulfur of Py Ⅱa comes from the Zhuguang compound granite. From the early metallogenic stage to the main metallogenic stage, the δ34S values of pyrite increase from (-9.15‰ to -11.3‰) to (-4.58‰ to -8.48‰), indicating that the oxygen fugacity of ore-forming fluid decreases. Uranium-rich fluid migration was formed in the oxidized fluid leaching of ore-bearing rocks in the early stage of mineralization, and uranium-rich fluid was changed into reducing environment in the main metallogenic period, which resulted in uranium precipitation. Combined with the characteristics of pyrite trace elements, the fluid in the early stage of uranium deposit in Shulouqiu is a high temperature magmatic hydrothermal, and the fluid in the metallogenic period is a medium-low temperature meteoric water. 
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