胶西北新城金矿床热液蚀变作用  

Hydrothermal alteration of the Xincheng gold deposit,northwestern Jiaodong,China

作　　者：张潮[1,2] 黄涛[2,3] 刘向东[2,4] 刘育[2] 赵海 王旭东 

机构地区：[1]中国地质调查局发展研究中心,北京100037 [2]中国地质大学地质过程与矿产资源国家重点实验室,北京100083 [3]江苏长江地质勘查院,南京210046 [4]山东省第六地质矿产勘查院,威海264209 [5]山东黄金矿业股份有限公司新城金矿,莱州261438

出　　处：《岩石学报》2016年第8期2433-2450,共18页Acta Petrologica Sinica

基　　金：国家自然科学基金重点项目(41230311;41572069);国家科技支撑计划课题(2011BAB04B09);国家重点研发计划(2016YFC0600100);高等学校学科创新引智计划(B07011)联合资助

摘　　要：新城金矿床是胶西北金矿集区中典型的破碎带蚀变岩型金矿床,其矿体受控于NE-NNE向焦家断裂及其次级断裂系统,主要赋存于断裂下盘(黄铁)绢英岩与红化花岗岩体中。焦家断裂下盘分带性明显,自主断裂面向外依此发育主断裂面和断层泥、挤压片理带、构造透镜体带、密集节理带和稀疏节理带。其中,主断裂面和断层泥发育粘土化蚀变;挤压片理带发育面状黄铁绢英岩化蚀变,其内赋存黄铁绢英岩型矿体;构造透镜体带发育脉型(黄铁)绢英岩化、面状绢英岩化和硅化蚀变,其次级断裂内赋存石英硫化物脉型矿体;节理带(包括密集节理带和稀疏节理带)主要发育成红化和细脉型(黄铁)绢英岩化,沿节理面赋存细脉型矿体。碳酸盐化蚀变叠加于上述热液蚀变之上。焦家断裂带表现为以水平为主的蚀变-矿化特征,(黄铁)绢英岩化蚀变与金成矿关系最为密切。论文在厘定断裂构造分带与蚀变-矿化分带空间关系的基础上,通过对各类蚀变岩与新鲜新城花岗岩体元素地球化学分析,剖析了热液蚀变作用过程及其机制。选取TiO_2作为不活动组分,质量平衡计算表明,成矿前新城花岗岩体发生红化作用时,带入组分有Fe_2O_3、K_2O、Al_2O_3以及少量Au、Ag、Cu、Pb、Zn、Sb和Bi等,而被带出组分有SiO_2、CaO和Na_2O等;成矿期红化花岗岩体蚀变为(黄铁)绢英岩过程中,明显带入组分有SiO_2、Fe_2O_3、FeO、Al_2O_3、Mg O、K_2O、Au、Ag、As、Cu、Pb、Zn、Sb和Bi等,而被带出组分为Na_2O。稀土元素地球化学特征与REE球粒陨石标准化配分模式曲线表明,红化和(黄铁)绢英岩化热液蚀变作用影响REE迁移。REE分别在红化和(黄铁)绢英岩化蚀变中带入和带出;Eu在红化过程中呈显著带入,表现为显著Eu正异常(δ_(Eu)=1.34),而在(黄铁)绢英岩化蚀变中活化带出,表现出Eu负异常(0.89~0.95)。成矿期发生(黄铁)绢英岩化蚀变时,Eu从The Xincheng gold deposit, located at the Zhaoyuan-Laizhou goldfield in the northwestern Jiaodong, is one of the most typical altered-type gold deposits. The gold mineralization is controlled by Jiaojia fault with NE-NNE strikes and its secondary faults and facture system. The ores are mainly hosted in （pyrite）-sericite-quartz and red colouration granite of Xincheng in the footwall. Distinct structural zonation is recognized vertically with the fault plane and the fault gouge zone, extruded schistosity zone, tectonic lens zone, dense joints zone and sparse joints zone. The fault plane and the fault gouge zone develop clay alteration. The types of hydrothermal alteration in the extruded schistosity zone mainly are sericitization and sulfuration, with the pyrite-sericite-quartz type ore bodies. The hydrothermal alterations in the tectonic lens zone are signified by the veins of （pyrite）-sericite-quartz, sericite-quartz and silicification, and being as the quartz-sulfide vein type ore bodies. The alterations in the joint zone are the veins of （pyrite）-sericite-quartz and red colouration, and changed into the fine ore veins ore bodies along the joint surface. Carbonatization mostly overlaps all of the alterations. Horizontal zonation of mineralization-alteration is the main signature for the ore-controlling mechanism in Xincheng gold deposit, and the （pyrite）-sericite-quartz alteration is critical for gold mineralization. The alteration process and mechanism have been studied based on the spatial relationship between the distinct structural zonation, the alterations and mineralizations, and along with the geochemical analysis of the altered rocks and the unaltered Xincheng granite. TiO2 is selected as an inactive component to perform the mass balance calculations. Based on the results, Fe2O3, K2O, Al2O3, Au, Ag, Cu, Pb, Zn, Sb and Bi were brought in, contrary with SiO2, CaO and Na2O during red colouration process, While during （pyrite）-sericite-quartz alteration, SiO2, Fe2O3, FeO, Al2O3, MgO, K2O,

关 键 词：热液蚀变 质量平衡 断裂带结构 新城金矿床 胶西北 

分 类 号：P618.51[天文地球—矿床学]