黔西北福来厂铅锌矿床Pb同位素研究及地质意义  

Pb Isotope Composition of the Fulaichang Lead-Zinc Ore Deposit in Northwest Guizhou and its Geological Implications

作　　者：汤世凯[1] 马筱[1] 李学刚[1] 戴传固 张慧 周琦 况顺达 杨坤光[1,3] 

机构地区：[1]中国地质大学(武汉)构造与油气资源教育部重点实验室,湖北武汉430074 [2]贵州省地质调查研究院,贵州贵阳550005 [3]中国地质大学(武汉)地球科学学院,湖北武汉430074

出　　处：《大地构造与成矿学》2012年第4期549-558,共10页Geotectonica et Metallogenia

基　　金：贵州省国土资源厅"贵州区域构造特征;构造演化与矿产空间分布关系研究";国家自然科学基金项目(批准号:40972137)联合资助

摘　　要：单阶段演化正常铅用H-H法可获得高准确性的模式年龄,在黔西北福来厂铅锌矿床中采集16件矿脉和围岩样品,测定它们的Pb同位素组成,206Pb/204Pb为18.5346～18.7294(均值18.5935),207Pb/204Pb为15.7408～15.7603(均值15.7519),208Pb/204Pb为38.9718～39.1766(均值39.0731)。分析结果表明该矿区铅是正常铅,利用Pb-Pb同位素测年方法,获得了矿脉铅的主模式年龄为240～229Ma,围岩铅的主模式年龄为254～230Ma。研究表明该矿脉Pb模式年龄能代表成矿年龄,反映铅主成矿期在印支期,印支期区域隆升导致NW向区域正断层活动,这些断裂控制本区铅锌矿床的分布。矿脉与围岩的Pb同位素组成相似,年龄相近,结合Pb同位素构造模式和Δβ-Δγ图解,我们认为上地壳围岩是福来厂铅锌矿床成矿物质的主要来源,基底能提供部分物质。峨眉山玄武岩后期热液对成矿物质有一定的影响。Precise model age of single-stage evolution ordinary lead can be calculated by Holmes-Houtormans method.Sixteen samples of ore veins and wall rocks from the Fulaichang lead-zinc ore deposit were analyzed for their Pb isotopic compositions.Both the ore veins and wall rocks present similar geochemical characteristics：206 Pb/204 Pb =18.5346～18.7294（average 18.5935）,207 Pb/204 Pb= 15.7408-15.7603（average 15.7519）,208 Pb/204 Pb =38.9718~ 39.1766（average 39.0731）.Accordingly,the lead in the lead-zinc ore deposit belongs to ordinary lead.Using Pb-Pb dating method,we get Pb model age of the ore veins（240~229 Ma） and the wall rock（254~230 Ma）.Pb model ages of the ore veins are consistent with the ages of the wall rocks.Thus,the Pb model ages of the veins represent the major Pb mineralization period and indicate that the lead-zinc ore deposit was formed during Indosinian.The regional NW normal faults are products of regional uplift in Indosinian.These faults controlled the distribution of lead-zinc ore deposits in this area.According to Pb isotope tectonic model diagram and Δβ-Δγ diagram,we conclude that the metallogenic materials were derived from the upper crust.The upper crustal capping rocks（wall rocks） provided the major source of ore metals.Additionally,the metamorphic basement may also provide part of Pb.The Emeishan basalts are unlikely the source of the metals.

关 键 词：PB同位素 成矿年龄 物质来源 铅锌矿 黔西北 

分 类 号：P597[天文地球—地球化学] P611[天文地球—地质学]