湖南铜山岭层状钨多金属矽卡岩形成时代、成因机制及其找矿启示  

Timing and genesis of the Tongshanling stratiform W-Mo skarn deposit in Hunan Province:Implications for exploration

作　　者：谭富诚 孔华[1,2] 刘飚[1,2] 吴堑虹[1,2] 刘玉国 杨齐智[3] TAN Fucheng;KONG Hua;LIU Biao;WU Qianhong;LIU Yuguo;YANG Qizhi(Schoolof Geoscience and Info-Physics,Ministry of Education,Central South University,Changsha 410083,China;Key Laboratory of Metallogenic Prediction of Nonferrous Metalsand Geological Environ-ment Monitoring,Ministry of Education,Central South University,Changsha 410083,China;Mineral Resources Investigation Institute of Hunan Province,Chenzhou Hunan 423002,China)

机构地区：[1]中南大学地球科学与信息物理学院,长沙410083 [2]中南大学有色金属成矿预测与地质环境监测教育部重点实验室,长沙410083 [3]湖南省矿产资源调查所,湖南郴州423002

出　　处：《地质科技通报》2024年第2期123-142,共20页Bulletin of Geological Science and Technology

基　　金：国家重点研发计划(2018YFC0603901);中南大学研究生自主创新项目(2022ZZTS0458)。

摘　　要：湖南铜山岭矿床位于南岭成矿带西段,是与I型花岗闪长岩有关的矽卡岩型铜多金属矿床。近年在远离花岗闪长岩体的棋梓桥组灰岩地层中发现了厚层状矽卡岩型钨钼矿体,其地质特征、矿物组合与金属类型均与岩体接触带型矿体不同。通过系统的野外观察、显微鉴定、石榴石原位U-Pb定年、白钨矿LA-ICP-MS微量元素分析对该矿床矽卡岩形成时代、成因机制进行了研究。结果表明:(1)矽卡岩成矿作用可划分为石榴石矽卡岩、绿帘石绿泥石矽卡岩、石英硫化物、石英方解石4个阶段;(2)石榴石U-Pb谐和年龄为(160.4±4.2)Ma(MSWD=0.79),明显晚于花岗闪长岩体(约167 Ma),与花岗斑岩(约161 Ma)的年龄一致;(3)核部石榴石稀土元素配分型式为轻稀土元素富集、重稀土元素平坦型,与花岗斑岩全岩稀土元素配分型式相似,边缘石榴石的稀土元素配分型式为轻稀土元素亏损、重稀土元素平坦型,与接触带矽卡岩中石榴石不同;(4)与绿帘石共生的白钨矿主要可分为3个世代,3个世代的白钨矿稀土元素配分型式均为轻稀土元素富集、重稀土元素亏损型,但稀土元素总质量分数从第一阶段(Sch1-a,332×10^(-6)~353×10^(-6))到第二阶段(Sch1-b,144×10^(-6)~301×10^(-6))到第三阶段(Sch1-c,4.05×10^(-6)~31.8×10^(-6))呈显著渐进式下降趋势,与绿泥石共生的白钨矿(Sch2)稀土元素配分型式显示轻稀土元素富集,重稀土元素亏损,稀土元素总质量分数为51.2×10^(-6)~139×10^(-6);(5)钨钼矿化主要集中在退变质阶段,其中Sch1-b及Sch2阶段具有较高的氧逸度,为钨沉淀的主要阶段,Sch1-a与Sch1-c阶段氧逸度较低,为钼沉淀的主要阶段。综合分析认为,层状矽卡岩与铜山岭及魏家接触带矽卡岩均不为同一成矿系统,可能与分异程度更高的花岗斑岩有关,未来铜山岭矿床深边部找矿应该更加关注晚期花岗斑岩体。[Objective] The Tongshanling deposit in the western Nanling metallogenic belt of Hunan Province is a skarn Cu polymetallic deposit related to I-type granodiorite.Recently,a thick stratiform W-Mo skarn ore body has been found in the limestone of the Qiziqiao Formation far from the granodiorite intrusion.Its geological characteristics,mineral assemblages and genetic types are different from those of the ore bodies in the contact zone of the intrusion.[Methods] In this study,timing and genesis of the Tongshanling stratiform are analysed,through field investigation,microscopic identification,in situ U-Pb dating of garnet,and LA-ICP-MS trace element analysis of scheelite.[Results] The following four stages of mineralization are identified:garnet skarn,epidote and chlorite skarn,quartz sulfide and quartz calcite.The U-Pb concordant age of garnet is(160.4±4.2) Ma(MSWD=0.79),is significantly later than that of the granodiorite(~167 Ma) and similar to that of the granite porphyry(~161 Ma).The total rare earth element(ΣREE) distribution pattern of the garnet core is light rare earth element(LREE) enrichment and heavy rare earth element(HREE) flat and is similar to the whole-rock ΣREE model of granite porphyry.The ΣREE distribution pattern of garnet rims is LREE-depleted and is different from that of garnet in contact zone skarns.Scheelite associated with epidote can be divided into three stages.ΣREE modes of the three stages are all LREE enrichment and HREE depletion,but the ΣREE content decreases significantly from the first stage(Sch1-a,332×10^(-6)-353×10^(-6)) to the second stage(Sch1-b,144×10^(-6)-301×10^(-6)) and the third stage(Sch1-c,4.05×10^(-6)-31.8×10^(-6)).Scheelite associated with chlorite(Sch2) shows LREE enrichment and HREE depletion,and their ΣREE content is 51.2×10^(-6)-139×10^(-6).W-Mo mineralization is mainly concentrated in the retrograde stage.The Sch1-b and Sch2 stages have higher oxygen fugacities are the main stage of W mineralization,while the other stages(Sch1-a and Sch1-c) with lowe

关 键 词：层状矽卡岩 石榴石 白钨矿 LA-ICP-MS 湖南铜山岭 

分 类 号：P618.6[天文地球—矿床学]