海南抱板金矿铅同位素化探评价

通过对海南抱板金矿几个切穿矿脉剖面的矿石和围岩的铅同位素组成分析。发现铅同位素组成与矿的产出具有相关关系。铅同位素的异常可能反映了成矿物质来源深度的差异，据此可进行铅同位素化探评价，提出了“正异常以深部找矿为主。负异常注意扩大横向找矿”的原则，土外山地区是地表的浅层金矿化，而二甲，北牛为深源金矿化，在土外山地区深部应可能找到对应于二甲，北牛的深源金矿化层。

Application of lead isotopes to geochemical exploration in the Baoban gold deposits, Hainan Province, China

The study of lead isotopes is widely used in geochemical exploration and evaluation of deposit as well as in ascertaining age and source of mineralization. Practice shows that the method of lead isotope targeting is somewhat efficient for macro evaluation of forecasting areas but not satisfactory for forecasting the concealed deposit. As the U content and the variation of U/Pb ratio distinctly decrease with the depth in the lithosphere, U Th Pb isotopic differentiation must have occurred during the crust mantle evolution. The lead isotopic ratios show large variation range, vary in the front of mineralization and shallow derived ores, but very stable in the major ore body and usually close to the average isotopic compositions of the crust and mantle of the continent block from which the deposit derived. Therefore, the lead isotopic composition canact as a scale for indicating the positions of mineralization. The lead isotopegeochemistry was applied to the exploration and evaluation in the Baoban gold deposits of Hainan Province, China. The analysis results of the mineral veins andadjacent rocks show the correlation between the lead isotope data and the position of ore body. Based on the experience in Baoban gold deposits and other deposits in Yunnan Province, an exploration principle was established, that is positive anomalies of the lead isotope eigenvectors for prospecting deep seated ore body and negative anomalies of eigenvectors for enlarging lateral exploration surrounding known deposit. The ore beds from the Erjia and Beiniu mineralization districts should be the deep part of the ore body and that from the Tuwaishan district should be the shallow part, so the ore beds corresponding with the Erjia andBeiniu districts may be found in the Tuwaishan district.