广东长坑金、银矿床成矿模式

广东省长坑金、银矿床共存于同一层间蚀变构造破碎带,上金、下银分别构成独立的金、银矿床.金矿床具有沉积岩围岩型金矿床的全部特征,银矿床则有石英-硫化物脉型矿床的特征.在系统归纳金、银矿石及围岩的化学组成,微量元素、稀土元素、稳定同位素地球化学特征及同位素年代学,矿石矿物包裹体的温度、压力、成分,以及对三水裂谷盆地演化特征分析的基础上,提出金矿床是沉积盆地中的流体在大规模迁移过程中萃取地层中的金而形成的浅成低温热液交代型矿床,银矿床属于构造-岩浆叠加改造热液交代型矿床,金矿床形成在先,银矿床形成于后并改造了金矿床,金、银矿床均不是热水沉积型矿床或海底喷流-沉积型矿床.

METALLOGENIC MODEL OF CHANGKENG GOLD AND SILVER DEPOSIT IN GUANGDONG PROVINCE

Gold and silver deposits occur in the same inter-bedded tectonic crush belt, which are independent ore-bodies characterized with gold in the upper part and silver in the lower part. The gold deposit has all the features of sedimentary-rock-hosted gold deposit, but the silver deposit owns the characters of quartz-sulfide vein type deposit. Based on the systematic analysis on chemical compositions, trace-elements, rear earth elements, stable isotope and isotopic dating, temperatures, pressures and components of fluid inclusions inside gold and silver ores, and also the evolutional characters of Sanshui rift basin, this paper has proposed the different mineralization models for either gold or silver deposit respectively. Gold was deposited by the mineralization replacement of hypergene low-temperature hydrothermal when large-scale basin fluid migrated and dissoluted Au from stratigraphic strata. While silver was formed by replacement of the ore-bearing fluid mixed by tectonic-magma hydrothermal with construction water. It is found that gold deposit was formed earlier than silver. It is concluded that both gold and silver were not deposited under the sea floor by exhalation or hot-water sedimentation but hydrothermal replacement apparently.