个旧锡多金属硫化物矿床铅同位素组成特征及其成因意义

主要研究了个旧锡多金属硫化物矿床的矽卡岩型和层间硫化物型两类矿床。矽卡岩型矿床铅同位素组成与矿区花岗岩铅一致。层问硫化物型矿床铅同位素在同位素比值图上的投点比较分散,2／3投点较集中且与矿区花岗岩铅一致,另有部分硫化物型与矿区印支期火山岩一致,位于铅演化线的上地幔区域,其他少部分投点位于铅演化线的上地壳区域,因受到地层铅的加入而明显高于花岗岩铅。铅同位素组成特征表明,矽卡岩型矿床的形成与燕山期花岗岩直接相关,其矿质主要来源于花岗岩,较少部分源于地层;层间硫化物型矿床的矿质部分来源印支期的热水沉积作用,少部分来源于地层,并受到燕山期花岗岩的岩浆热液叠加改造。个旧超大型锡矿床的形成是多种成矿作用叠加的结果。

Pb ISOTOPIC COMPOSITIONS AND ITS SIGNIFICANCE IN ORE GENESIS IN GEJIU TIN-POLYMETALLIC DEPOSITS

In the present paper, the stress is laid on two types of ore deposits in the Gejiu tin-polymetallic ore field. One type is skarn-type, and the other is interbeddedsulfide type. The Pb isotopic composition of the skarn-type is similar tothat of granite. The data of the interbeddedsulfide type are more scatteredexcept 2/3 data that are similar to those of granite. Part of the data points are similar to those of volcanic rocks and fall on the mantle lead evolution line or are distributed in the extending direction along this evolution line, the other part of data are apparentlyhigher than those of granite. The lead of the skarn-type was derived mainly from the granite, and part of it from the strata, which indicates the skarn-type ore deposits are directly related to Yanshanian granites.As for the interbeddedsulfide-type, there are three ore-forming material sources: Indosinian hydrothermal sedimentary mineralization,strata, and Yanshanina magmatic hydrothermal solusions.We think the Gejiu tin-polymetallic deposit resulted from multi-mineralization.