松辽盆地南部辉绿岩侵入热力作用与砂岩铀矿中铀的超常富集  

The relationship between thermal intrusion of diabase and super-enrichment of uranium elements in sandstone uranium deposits of the southern Songliao basin

作　　者：王苗 吴柏林[1] 刘池洋[1] 张涛[3] 张才利[2] 张雷[2] 胡琮 杨松林[4] 刘明义 李琪 林周洋[1] 张效瑞 WANG Miao;WU Bailin;LIU Chiyang;ZHANG Tao;ZHANG Caili;ZHANG Lei;HU Cong;YANG Songlin;LIU Mingyi;LI Qi;LIN Zhouyang;ZHANG Xiaorui(State Key Laboratory of Continental Dynamic,Department of Geology,Northwest University,Xi'an,Shaanxi 710069,China;Research Institute of Exploration and Development,PetroChina Changqing Oilfield Company,Xi'an,Shaanxi 710018,China;Department of Exploration,PetroChina Changqing Oilfield Company,Xi'an,Shaanxi 710018,China;Research Institute of Exploration and Development,PetroChina Liaohe Oilfield Company,Panjin,Liaoning 124010,China)

机构地区：[1]西北大学地质学系,大陆动力学国家重点实验室,陕西西安710069 [2]中国石油长庆油田分公司勘探开发研究院,陕西西安710018 [3]中国石油长庆油田分公司勘探事业部,陕西西安710018 [4]中国石油辽河油田分公司勘探开发研究院,辽宁盘锦124010

出　　处：《地质学报》2024年第12期3788-3813,共26页Acta Geologica Sinica

基　　金：国家重点研发计划项目(编号2023YFC2906702);陕西省自然科学基础研究计划(重点)项目(编号2022JZ-18);中核铀业“揭榜挂帅”科技攻关项目(编号202302);中石油煤层气有限责任公司科学研究与技术开发项目(编号2023-KJ-22)联合资助的成果。

摘　　要：松辽盆地南部钱家店铀矿作为特大型砂岩型铀矿,矿区内出露的辉绿岩对铀成矿影响特殊,但针对辉绿岩侵入与铀超常富集关系有待进一步研究。本文在野外地质调研基础上,选择钱家店凹陷的辉绿岩和赋矿砂岩样品为研究对象,开展岩相学、扫描电镜、电子探针、全岩主微量元素、铀矿物原位微区U-Pb测年、锆石U-Pb年龄、矿物C-O同位素和流体包裹体测试等研究。电子探针测试表明赋矿岩石存在较高温度成因的网格状含钛铀矿物;赋矿砂岩中碳酸盐胶结物及辉绿岩中方解石脉的包裹体温度测试均发现存在与中低温流体作用相对应的包裹体特征;矿物原位微区C-O同位素组成显示赋矿岩石受较高温度岩浆热流体作用的影响;含泥砾砂岩的岩相学特征指示存在岩浆热流体及火山灰(屑)作用的痕迹,高倍扫描电镜分析观察到非砂金成因的纯金细颗粒、含钛铀矿和沥青铀矿中具有不同含量的高温元素(Pt、Os、Re)。上述结果表明,松辽盆地南部钱家店铀矿的热力作用及部分深部矿质来源与辉绿岩侵入作用有关。辉绿岩地球化学特征和LA-ICP-MS锆石U-Pb定年数据表明拉斑系列的辉绿岩形成于41.6±0.78 Ma,即始新世晚期源自过渡型地幔的基性岩浆向地壳浅部侵入结晶形成辉绿岩,同时也提供了热、深部铀源及伴生的金属元素,这大大增强了铀富集的速度和规模。不同系列的辉绿岩侵入热力作用与多期次多阶段成矿的铀矿床具有较好的时空耦合关系,辉绿岩侵入对铀成矿发挥主要作用的阶段在始新世时期(53~40 Ma)。综合认为盆地南部铀矿床为多成因、多来源、多阶段成矿的“多因复成”矿床。The Qianjiadian uranium deposit,located in the southern Songliao basin,is a super-large sandstone-type uranium deposit.The exposed diabase in the mining area exerts a significant impact on uranium mineralization.However,the precise relationship between diabase intrusion and abnormal uranium enrichment requires further investigation.This study,based on field geological investigations,focuses on diabase and uranium ore samples collected from the Qianjiadian depression.A comprehensive suite of analytical techniques was employed,including petrography,electron probe microanalysis(EPMA),scanning electron microscopy(SEM),major and trace element analysis,in-situ U-Pb dating of uranium minerals,zircon U-Pb dating,in-situ carbon-oxygen(C-O)isotope analysis of minerals,and fluid inclusion studies.EPMA revealed the presence of grid-like,titanium-bearing uranium minerals within the ore,indicative of high-temperature genesis.Fluid inclusion analysis of carbonate cement and calcite veins in ore-bearing sandstone and diabase indicated fluid interactions characteristic of medium to low temperatures.In-situ C-O isotope compositions of minerals suggest the influence of high-temperature magmatic hydrothermal fluids on the ore-bearing rocks.Lithological characteristics of mudstone and sandstone further support the presence of magmatic hydrothermal fluids and volcanic ash(debris).Highresolution SEM analysis identified distinct contents of high-temperature elements(Pt,Os,Re)in nativegold particles,brannerite deposits,and pitchblende deposits,suggesting diverse origins.These findings strongly suggest that the thermal effects and deep-sourced mineral contributions associated with the Qianjiadian uranium deposit are related to diabase intrusion.Geochemical characteristics and LA-ICPMS zircon U-Pb dating of the diabase reveal a tholeiitic composition with a formation age of 41.6±0.78 Ma.This Late Eocene magmatism,originating from the transitional mantle,intruded and crystallized in the shallow crust,forming diabase.The intrusion provided

关 键 词：钱家店铀矿 辉绿岩侵入 热力作用 深部铀源 超常富集 松辽盆地 

分 类 号：P619.14[天文地球—矿床学]