右江褶皱带东南缘西大明山矿集区铅同位素地球化学特征及其地质意义  

Lead isotope geochemical characteristics of Xidamingshan ore concentration area on the southeastern margin of Youjiang fold belt, and their significance

作　　者：肖昌浩 刘欢[3] 申玉科[1] 韦昌山[1] 乐兴文 欧德功 张亮 XIAO ChangHao;LIU Huan;SHEN YuKe;WEI ChangShan;LE XingWen;OU DeGong;ZHANG Liang(Laboratory of Dynamic Digenesis and Metallogenesis,Institute of Geomechanics,Chinese Academy of Geological Sciences,Beijing 100081,China;School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China;MNR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037,China;No.4 Geological Party of Guangxi Zhuang Autonomic Region,Nanning 530031,Guangxi,China)

机构地区：[1]中国地质科学院地质力学研究所动力成岩成矿实验室,北京100081 [2]中国地质大学地球科学与资源学院,北京100083 [3]中国地质科学院矿产资源研究所自然资源部成矿作用与资源评价重点实验室,北京100037 [4]广西壮族自治区第四地质队,广西南宁530031

出　　处：《矿床地质》2018年第5期1037-1051,共15页Mineral Deposits

基　　金：国家自然科学基金项目(编号:41702095);中国地质调查项目(编号:DD20160053;DD20160124);广西找矿突破战略行动方案项目(桂国土资函﹝2015﹞480号)联合资助

摘　　要：广西西大明山多金属矿集区是右江褶皱带东南缘近年找矿突破的重要地区,发育凤凰山特大型银矿床、罗维中型钨锌多金属矿床、弄屯大型铅锌矿床及一些中、小型矿床等。其中罗维和弄屯矿床是近年新发现的矿床,矿体分别呈层状赋存于寒武系碎屑岩和呈脉状赋存于寒武系与泥盆系接触界面附近或断裂破碎带中。笔者对矿集区内层状和脉状矿床矿石硫化物铅同位素进行研究,并与赋矿围岩、隐伏二长花岗岩进行对比。铅同位素数据显示:罗维层状矿床矿石硫化物铅同位素组成为:^(206)Pb/^(204)Pb=18.1320~18.5980,^(207)Pb/^(204)Pb=15.5920~15.7988,^(208)Pb/^(204)Pb=38.4041~39.0461;弄屯脉状矿床矿石硫化物铅同位素组成为:^(206)Pb/^(204)Pb=18.3240~18.5060,^(207)Pb/^(204)Pb=15.7321~15.9140,^(208)Pb/^(204)Pb=38.6511~39.2311;二者具有相似的同位素组成,但弄屯矿床矿石硫化物^(207)Pb/^(204)Pb比值略高于罗维矿床矿石硫化物。罗维矿床矿石硫化物铅同位素组成与深部隐伏二长花岗岩铅同位素组成一致;而弄屯矿床矿石硫化物^(208)Pb/^(204)Pb值介于二长花岗岩和地层铅同位同位素组成之间,且矿石^(207)Pb/^(204)Pb比值指示矿石铅可能来源于上泥盆统莲花山组碎屑岩与中寒武统黄洞口组碎屑岩。渌井和大新铅锌矿床显示出异常高的^(207)Pb/^(204)Pb,暗示可能还有其他富铀的地质体为成矿提供放射成因铅,铅同位素特征值(μ值、ω值)揭示矿石硫化物和岩体都具有壳源铅的特征;从垂向上,各矿床距罗维隐伏岩体顶界距离增加,岩浆铅减少,地层铅增加。综合研究认为,西大明山多金属矿集区应属于典型的与深部燕山期岩体侵入有关的岩浆热液充填交代型矿床,成矿物质主要来源于燕山期岩浆和围岩地层。The Xidamingshan ore concentration area is one of the prospecting breakthrough areas on the southeastern margin of Youjiang fold belt, South China. It consists of the Fenghuangshan large silver deposit, the Luowei mid- dle zinc-tungsten polymetallic deposit, the Nongtun large lead-zinc deposit, and some small ore deposits or ore spots. The Luowei and Nongtun deposits were found in recent years. The stratiform orebodies are hosted in the Cambrian clastic rocks; vein-type orebodies are hosted in the fracture zones and the boundary between the Cam- brian and Devonian. In this paper, the Pb isotope compositions of the two types of ores, the Yanshannian monzo- nitic granite, and strata were studied to investigate the genetic relationship between the two types of ores. It is shown that the sulfides of the Luowei and the Nongtun deposit have the uniform lead isotope compositions, with the data ^206pb/^204Pb=18.1320-18.5980, ^207Pb/^204Pb=15.5920-15.7988,^208Pb/^204Pb=38.4041-39.0461, ^206pb/^204pb= 18.3240-18.5060, ^207Pb/^204Pb=15.7321-15.9140, and ^208Pb/^204Pb=38.6511-39.2311, respectively. The lead isotopic compositions of the Luowei deposit are close to those of the concealed monzonitic granite, but the ：^207Pb/^204Pb ratios of the Nongtun deposit are higher than those of the Luowei deposit, the lead isotopic compositions of the Nongtun deposit are between that of the monzonitic granite and that of country rocks, and the ：^207Pb/^204Pb ratios of ores in the Nongtun deposit suggest that the lead was probably mainly derived from the Lower Devonian Lian- huashan Formation and the Middle Cambrian Huangdongkou Formation clastic rocks. ^207Pb/^204Pb ratios of ores in the Lujing and the Daxin lead-zinc deposit are obviously high, which reveal that there may be another U-bearing geological body which provided radiogenic lead for ores. The values of μ and ω reveal that the lead in ores and the monzonitic granite were crust-derived. In vertical direction, magma-derived lead decreases and the strata-de- rived lead incre

关 键 词：地球化学 铅同位素 燕山期 西大明山矿集区 右江褶皱带东南缘 

分 类 号：P618.42[天文地球—矿床学] P618.43[天文地球—地质学]