河北平山县秋卜洞银矿角砾岩体特征与成矿过程元素迁移规律  

Study on breccia body characteristics and element migration during the metallogenetic process of Qiubudong silver deposit in Pingshan County,Hebei Province

作　　者：孙文燕[1] 杨成栋[2] 薛建玲[3] 李胜荣[4] 张学义 SUN Wenyan;YANG Chengdong;XUE Jianling;LI Shengrong;ZHANG Xueyi(Chinese Academy of Geological Sciences,Beijing 100037,China;Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037,China;Development and Research Center,China Geological Survey,Beijing 100037,China;School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China;China Metallurgical Geology Bureau,Beijing 100025,China)

机构地区：[1]中国地质科学院,北京100037 [2]中国地质科学院矿产资源研究所,北京100037 [3]中国地质调查局发展研究中心,北京100037 [4]中国地质大学(北京)地球科学与资源学院,北京100083 [5]中国冶金地质总局,北京100025

出　　处：《地质通报》2023年第6期1013-1034,共22页Geological Bulletin of China

基　　金：国家重点研发计划项目《华北克拉通成矿系统的深部过程与成矿机理》(编号:2016YFC0600106);横向项目《中国世界地质公园申报与建设技术支撑》(编号:HX202101);中国地质调查局项目《我国边疆地区世界地质公园潜力区筛选示范》(编号:DD20230550)。

摘　　要：河北平山县秋卜洞银矿为隐爆角砾岩型矿床,为寻找近矿标志,对该矿区的角砾岩体特征及围岩蚀变元素地球化学特征进行了研究。对角砾岩的地质、岩性、角砾特征(形态、大小、成分)、胶结物特征进行统计分析,结果发现:①由浅部到深部角砾形态为棱角状→次棱角状→次圆状;②角砾大小在浅部呈现由边部向中心减小的趋势,钻孔中角砾大小空间变化不明显;③角砾成分由浅到深从以浅粒岩为主,转变为以石英斑岩为主,中部角砾成分稍复杂;这种特征指示角砾岩体的形成依次受控于气爆(岩粉胶结)、液爆(金属硫化物胶结)与浆爆(岩浆胶结)作用。围岩蚀变过程中元素地球化学特征表明,该过程带入的组分为SiO_(2)、CaO、MgO等,迁出的组分为K_(2)O、Na_(2)O、Al_(2)O_(3)、Fe_(2)O_(3)、FeO、Sr、Ba等,成矿元素Au、Ag、Cu、Zn、Sb、Pb等含量明显增加,鉴于Fe、Cu、Pb、Zn等以硫化物形式存在,稀土元素特征显示成矿环境由氧化条件逐渐转变为还原条件。综合研究揭示,该矿床形成经历了至少3个阶段流体沸腾作用,银卸载成矿在隐爆角砾岩形成的基础上,绢英岩化(带)与黄铁矿化叠加形成,因此,这2种蚀变的出现是靠近矿体的有利标志。The Qiubudong silver deposit is a cryptoexplosive breccia type deposit.In order to find the indicators of proximity to the ore body,the characteristics of the breccia body and the geochemical characteristics of alteration elements in the host rock are studied in this paper.The statistical analyses of the geology and lithology of the breccia body,characteristics of the breccia(e.g.,shape,size,composition)and cement indicate that:①the shape of breccia changes from angular to subangular to subcircular as the depth increases;②the size of breccia decreases from the edge to the center in the surface,and the spatial change of breccia size is not obvious in the borehole;③the composition of breccia changes from leptite to quartz porphyry,and then become complicated as the depth increases,which indicates that the formation processes of breccia body are dominated by gas explosion(rock powder cementation),liquid explosion(polymetallic sulfide cementation)and magmatic explosion(magma cementation)from the surface to the depth.The geochemical characteristics of elements in the alteration process of host rocks indicate that the introduced components are SiO_(2),CaO,MgO,and the migrated components are K_(2)O,Na_(2)O,Al_(2)O_(3),Fe_(2)O_(3),FeO,Sr,Ba,etc.The contents of ore-forming elements such as Au,Ag,Cu,Zn,Sb and Pb increased significantly.Considering that Fe,Cu,Pb and Zn existed in the sulfide,REEs showed that the ore forming environment gradually changed from oxidation condition to reduction condition.The comprehensive characteristics reveal that the deposit has undergone at least three stages of fluid boiling processes,and silver unloading mineralization occurs on the basis of sericitization as well as pyritization based on cryptoexplosive breccia formation.Therefore,the occurrence of these two types of alteration is a favorable indicator of proximity to the ore body.

关 键 词：银矿 角砾岩 围岩蚀变 元素迁移规律 秋卜洞 矿产勘查工程 河北省 

分 类 号：P618.52[天文地球—矿床学]