The Bainiuchang deposit,located at the central tin-polymetallic ore belt of southeast Yunnan,is associated with large scale Ag,Pb,Zn reserves.However,the genesis of the deposit is controversial.With early Pb isotopic data of ore minerals from the Bainiuchang deposit,former researchers concluded that lead was mainly derived from the leaching of basement rocks,and the deposit was formed through two mineralization stages,i.e.,hydrothermal sedimentation stage and magmatic hydrothermal metallogenetics stage.Lead isotopic composition of the Bainiuchang deposit was systematically studied with the latest lead isotopic data in this study.The Pb isotope ratios of ore minerals from the B ainiuchang deposit are 206Pb/204Pb =17.264-18.537,207Pb/204Pb =14.843-15.862,208Pb/204Pb =38.481-39.424.As for the Pb isotopic composition of feldspar of monzogranite from the Bozhushan granite rocks,the ratio s are 206pb/204pb =18.301-18.387,207pb/204pb =15.611-15.67,208pb/204pb =38.677-38.904,while those of ore minerals from contact zone type deposits (ore spots) of the Bozhushan granite rocks are 206pb/204pb =18.302-18.417,207pb/204pb =15.603-15.692,208pb/204pb =38.596-38.868.The Pb isotope ratios of the samples from regional strata and drilling of mining strata are 206pb/204pb =18.307-19.206,207pb/204pb =15.622-15.809,208pb/204pb =38.436-39.932.The orebodies have lead isotopic compositions similar to those of feldspar in granites,but are different from those of strata samples.Therefore,lead in the Bainiuchang deposit was mainly derived from magmatism,but may be contaminated slightly by strata in the process of magma intrusion.Based on geological characteristics and recently geochemistry and chronology data,sedimentary mineralization is not the main process in the Bainiuchang deposit,and magmatism is the key factor for mineralization.%白牛厂矿床位于滇东南锡多金属成矿带中部,是一个Ag、Pb、Zn、Sn等共生的多金属矿床,但成因争议较大.前人引用早期矿床矿石矿物铅同位素数据得出矿石铅主要来源于基底岩石淋滤,矿床经历了热水沉积+岩浆热液叠加两个成矿阶段的结论.本文采用最新铅同位素数据系统研究了白牛厂矿床的铅同位素组成,其中,白牛厂矿床矿石矿物的铅同位素组成206Pb/204Pb、207Pb/204Pb和208Pb/204Pb分别为17.264～18.537、14.843～15.862和38.481～39.424;薄竹山花岗岩长石铅同位素组成206Pb/204Pb、207Pb/204Pb和208Pb/204Pb分别为18.301～18.387、15.611～15.670和38.677～38.904;薄竹山岩体接触带型矿床(点)矿石矿物铅同位素组成206Pb/204Pb、207Pb/204Pb和208Pb/204Pb分别为18.302～18.417、15.603～15.692和38.596～38.868;区域地层及矿区地层钻孔样品铅同位素组成206Pb/204Pb、207Pb/204Pb和208Pb/204Pb分别为18.307～19.206、15.622～15.809和38.436～39.932.对比四者铅同位素组成特征,白牛厂矿床矿石矿物、薄竹山花岗岩长石、薄竹山岩体接触带型矿床(点)矿石矿物具有一致的铅同位素组成,与地层铅同位素组成相差甚远,表明白牛厂矿床铅主要来自岩浆作用,在侵入的过程中可能受到了地层的轻度混染.矿床地质特征及近期地球化学和年代学研究成果表明,白牛厂矿床的形成主要受岩浆作用影响,沉积成矿作用在白牛厂矿床很可能是不存在的.
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