贵州低温热液型汞、锑、金矿床成矿谱系——以晴隆大厂、兴仁紫木凼和铜仁乱岩塘为例

摘要

Guizhou province is an very important area for epithermal type Hg,Sb and Au deposits in China.All a-long,there is considerable controversy about the mineralization age.In this study,Sm-Nd isotopic isochron age measurements were performed on the fluorites and calcites collected from the Dachang Sb deposit,the Zimudang Au deposit,and the Luanyantang Hg deposit.The results show that the fluorites and calcites from the Dachang Sb deposit were formed in Late Jurassic with the Sm-Nd isochron age measured as 148 ± 13 Ma and 142.3 ±7.9 Ma,with neodymium initial values of 0.512256 and 0.512151 respectively.The Sm-Nd isochron age of the calcites from the Zimudang Au deposit is 250 ± 14 Ma,a transition between Late Permian and Early Triassic,and its neodymium initial value is 0.511909.The Sm-Nd isochron age of the calcites from the Luanyantang Hg deposit is 364 ±24 Ma,which was formed in the Late Devonian,and the neodymium initial value is 0.511517.Combined with the previous studies,we infer that the mineralization of Hg,Sb and Au are not all formed in one period only (i.e.the Yans-hanian),but experienced a complex process from Caledonian to Hercynian-Indosinian,to early Yanshanian and late Yanshanian.Thus,they formed an epithermal-type mineralization pedigree with a long history of evolution.%贵州是我国低温热液型汞、锑、金矿的重要产区,但对其成矿时代一直存在不同看法.本次研究采用Sm-Nd同位素等时线法对晴隆大厂锑矿、兴仁紫木凼金矿和铜仁乱岩塘汞矿区的萤石、方解石分别进行了同位素年代学的研究,结果表明晴隆大厂锑矿中的方解石(Sm-Nd等时线年龄为148±13 Ma,钕初始值为0.512256)和萤石(Sm-Nd等时线年龄为142.3±7.9 Ma,钕初始值为0.512151)形成于晚侏罗世；紫木凼金矿中方解石(Sm-Nd等时线年龄为250±14 Ma,钕初始值为0.511909)形成于晚二叠世与早三叠世的过渡期；乱岩塘汞矿中的方解石(Sm-Nd等时线年龄为364±24 Ma,钕初始值为0.511517)则形成于晚泥盆世.结合前人其他资料,本文认为贵州的汞、锑、金矿床不是在燕山期一个时间段形成的,而是经历了从加里东期、海西-印支期到燕山早期和燕山晚期的复杂过程,从而形成了一个演化历史悠久的低温热液型成矿谱系.