Ore-forming epoch of gold deposits in northeastern Hunan
Ore-forming epoch of gold deposits in northeastern Hunan
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作者：
H. Feng
湘东北地区金矿主要产于中元古界冷家溪群浅变质碎屑岩中。前人认为金矿化发生在加里东期或燕山期，但没有高质量的年龄资料支持。本文利用石英包裹体Rb-Sr等时线测定了金矿的成矿时代。黄金洞、金矿床、金万古和团山背金矿床的成矿时代为（462±18）Ma（MSWD=1.6），（425±33）Ma（MSWD=0.14）和（222.4±9.4）Ma（MSWD=2.6），（87 Sr/86 Sr）i为（0.7589±0.0005），（0.7517±0.0004）和（0.7335±0.0009）。测年结果表明，湘东北金矿化主要发生在加里东期，另外，湘西和湘东北金矿成矿期可能集中在加里东期和印支期，表明加里东期和印支期是江南地体的两个主要成矿期。
Gold deposits in northeastern Hunan are mainly hosted in epimetamorphic clastic rocks of Middle Proterozoic Lengjiaxi Group.It was thought by some earlier researchers that gold mineralization took place in Caledonian or Yanshanian epoch,which,however,was not supported by high-quality age data.In this paper, the Rb-Sr isochron of fluid inclusions trapped in quartz was used to date the ore-forming epochs of gold deposits.The Huangjindong,Wangu and Tuanshanbei gold deposits are dated at(462±18) Ma(MSWD=1.6),(425±33) Ma(MSWD=0.14) and(222.4±9.4) Ma(MSWD=2.6) respectively,with(87Sr/86Sr)i being(0.7589±0.0005),(0.7517±0.0004) and(0.7335±0.0009).Dating results show that gold mineralization in northeastern Hunan mainly occurred in Caledonian,with Indosinian probably being the other metallogenic epoch.In addition,gold ore-forming epochs of western Hunan and northeastern Hunan were likely concentrated in Caledonian and Indosinian,implying that Caledonian and Indosinian were the two main ore-forming epochs in Jiangnan terrain.