河南破山银矿床地质地球化学特征及成因研究

Geological and geochemical characteristics and genesis of the Poshan silver deposit,Henan Province

破山特大型银矿床位于桐柏围山城金银多金属矿带的西端。矿床赋存在新元古界歪头山组上部的炭质绢云石英片岩中,矿体产出受地层和褶皱构造双重控制,多呈似层状、脉状和透镜状,矿石以蚀变岩型矿石为主。成矿流体属于中温、低盐度、低密度、富CO2的K+-SO24-型流体,成矿早中阶段以变质流体为主,晚阶段逐渐演化为以大气水为主。成矿物质主要来自于歪头山组地层。热液绢云母和云煌岩脉的钾氩年龄分别为103.6Ma和134Ma,指示矿床形成于早白垩世,即秦岭-桐柏地区的构造环境从挤压向伸展转变的构造背景下。

The Poshan superlarge silver deposit is located in the western end of the Weishancheng Au-Ag- dominated poly-metallic ore belt in Tongbai Mountains. The orebodies hosted in the horizons of carbonaceous sericite schist of the upper part of Neoproterozoic Waitoushan Formation （Pt3w3）. Strictly controlled by the hosting strata and the Heqianzhuang anticline, the occurrences of orebodies are mainly shaped as stratiform, lode or lens. The dominated ore-type is altered tectonite. The ore-fluid belongs to the mesothermal, low salinity, low density, CO2 rich and K＋-SO4^2- type fluid system. The ore-forming fluids were metamorphic in origin and generally evolved into meteoric water-sourced fluid in late metallogenic stage. The ore-forming elements including S and Pb must be mainly sourced from the Waitoushan Formation. The K-Ar isotopic ages of hydrothermal sericite and minette dyke are 103.6 Ma and 134 Ma, respectively, indicating the metallogenesis of the Poshan silver deposit formed in Early Cretaceous, when a tectonic setting changed from collisional compression to extension in Qinling-Tongbai orogen belt.