山西繁峙县义兴寨金矿床地质特征及成因探讨

Metallogenic characteristics and genesis analysis of Yixingzhai gold deposit in the Fanshi County of Shanxi,China

山西省繁峙县义兴寨金矿床位于恒山山脉东段南麓,是五台山—恒山金矿集区内典型的金矿床。近年来在矿区河湾斑岩体的深部发现了多个蚀变斑岩型金矿体,同时发育石英脉型金矿体。关于该斑岩型矿体成因的相关研究欠缺,制约了对矿区深部及外围勘探工作的开展。调查研究显示,金矿体分布受近SN向及NW向断层和赋存于角砾岩筒的晚燕山期中酸性次火山岩控制。脉型和斑岩型金矿体中的绢云母^(40)Ar/^(39)Ar年代学分析显示,其成矿年龄为(138.94±1.38)Ma~(139.16±1.37)Ma,属于早白垩世早期成矿阶段;主成矿阶段标志性矿物温度测试获得石英脉型金矿体主成矿温度集中在270℃~350℃,斑岩型金矿体的成矿温度在270℃~330℃;石英中流体包裹体的H-O同位素分析和电气石硼同位素LA-MC-ICP-MS分析显示,斑岩金矿体和石英脉状金矿体的成矿流体主要来自岩浆流体,成矿晚阶段混入有大气降水;成矿物质主要来自于岩浆,均主要受控于同期同源的岩浆活动。矿床成因类型为中低温斑岩型金矿—热液充填石英脉型金多金属矿床,具“多位一体”成矿特征。

Yixingzhai gold deposit in Fanshi County,Shanxi Province is located at the southern foot of the eastern section of the Hengshan Mountains.It is the most typical gold deposit in the Wutaishan-Hengshan gold ore concentration area.In recent years,many altered porphyry-type gold orebodies have been discovered in the deep exploration process of the Hewan porphyry body in the mining area,while quartz vein-type gold ore bodies also developed.There is still a lack of relevant research on the genesis of the porphyry orebodies,which restrict the development of deep and peripheral exploration of the deposit.Investigation and research have found that the distribution of orebodies is controlled by SN and NW striking faults and also controlled by the late Yanshanian intermediate-acid subvolcanic rocks that are hosted in the breccia pipes.sericite ^(40)Ar/^(39)Ar geochronology analysis for the porphyry-type gold orebody shows that the metallogenic age of Yixingzhai gold deposit is(138.94±1.38)Ma-(139.16±1.37)Ma,which belongs to the early stage of Early Cretaceous mineralization.The mineral thermometry of the characteristic minerals in the main metallogenic stage shows the metallogenic temperature of the quartz vein-type gold ore bodies and the porphyry gold ore bodies are concentrated in 270℃-350℃and 270℃-330℃,respectively.H-O isotope analysis of fluid inclusions in quartz and tourmaline boron isotope LA-MC-ICP-MS analysis shows that the ore-forming fluids of porphyry gold orebodies and quartz vein-type gold orebodies both mainly came from magmatic fluids,and were mixed with a certain amount of meteotic water in the late stage of mineralization.The ore-forming materials also mainly come from magma,which are mainly controlled by the same period of homologous magmatic activities.The genetic type of the deposit is a medium-low temperature porphyry-type gold deposithydrothermal quartz vein filling-type gold polymetallic deposit,with the metallogenic characteristics of"All in one".