赣南淘锡坑钨矿床流体包裹体特征及其地质意义

淘锡坑钨矿是赣南一个重要的大型石英脉型钨多金属矿床。矿床主要矿化阶段含矿石英脉中石英和黄玉中的流体包裹体类型有单一水溶液相H2O-NaCl(Ⅰa型)、富液L+V两相H2O-NaCl(Ⅰb型)、两相H2O-NaCl-CO2体系包裹体(Ⅱa型)和三相H2O-NaCl-CO2包裹体(Ⅱb型)。Ⅰb型包裹体均一温度范围为80~370℃,具有多峰态分布特征,可识别出140~190℃,200~250℃和340~360℃几个峰。成矿流体的盐度相对较低,一般<8w(NaCleq)%。用流体包裹体组合的方法获得四组包体的相关参数,结果表明同一包体组合内不同包体的盐度、均一温度及密度基本一致,而不同包体组合中包体的盐度、均一温度及密度则相差较大,显示出不同包体组合所捕获的流体存在较大的差异。Ⅰb型包裹体均一温度分别分布在329~355℃,214~240℃和141~189℃三个温度区间,经压力校正后的捕获温度分别为400~425℃,275~300℃,210~260℃。这些特征表明,淘锡坑钨矿至少存在三期热液流动,其中前两期为成矿期的热液活动,第三期(次生包体)为成矿后的热液活动。根据Ⅱ型包裹体的CO2部分均一温度与最终均一温度计算出成矿流体的捕获压力67.3~97.8 Mpa,平均压力74.8 Mpa,按静岩压力换算成成矿深度为2.59~3.77 km,平均为2.88 km。

Fluid Inclusion Characteristic and Its geological Implication of the Taoxikeng Tungsten Deposit,Southern Jiangxi Province

Taoxikeng tungsten deposit is one of the most important quartz-vein type of W-polymetallic deposit in Southern Jiangxi Province,China.Four main types of fluid inclusions： single aqueous phase H2O-NaCl（Ⅰa type）,rich liquid L＋V two-phase H2O-NaCl（Ⅰb type）,two phase H2O-NaCl-CO2（Ⅱa type） and three phase H2O-NaCl-CO2（Ⅱb type） have been recognized in all samples from the wolframite-bearing quartz and topaz of the major mineralizing stage.The Ⅰb type homogenization temperatures are widely from 80℃ to 370℃ with multi-peaks distribution,mainly in 140 ~ 190℃,200 ~ 250℃ and 340~360℃.Ore-forming fluids has the characteristic of low salinity,generally 8 w（NaCleq） %.We obtained four related groups parameters by the means of ＂fluid inclusion assemblage＂.The results are indicated that different fluid inclusions parameters are generally belongs to the same range in the same fluid inclusion assemblage,such as salinities,homogenization temperatures and densities,while those parameters are quite different in different fluid inclusion assemblages,showing trapped fluids are diversity in different fluid inclusion assemblages.There are three ranges of the four fluid inclusion assemblages homogenization temperatures： 329 ~ 355 ℃,214 ~ 240 ℃ and 141 ~ 189 ℃,which can be adjusted to trapping temperature： 400 ~ 425 ℃,275 ~ 300 ℃ and 210 ~ 260 ℃ by pressure.All of these presented that there are existing at least three hydrothermal flow in Taoxikeng tungsten deposit,of which the first two periods are ore-forming hydrothermal activity,and the third period is a hydrothermal activity after diagenesis.According to CO2 homogenization temperatures and final homogenization temperatures of type Ⅱ fluid inclusions,this paper got trapping pressures 67.3 ~ 97.8 Mpa of ore-forming fluid,an average of 74.8 Mpa,converted into ore-forming depth of 2.59 ~ 3.77 km by lithostatic pressure,an average of 2.88 km.