柴北缘赛坝沟金矿深部热液蚀变作用  

Deep Hydrothermal Alteration of the Saibagou Gold Deposit in the Northern Margin of the Qaidam Basin

作　　者：王炜晓 唐名鹰 丁正江 彭永和 华磊 吴洪彬 翟孝志 郑成龙 董振昆 WANG Weixiao;TANG Mingying;DING Zhengjiang;PENG Yonghe;HUA Lei;WU Hongbin;ZHAI Xiaozhi;ZHENG Chenglong;DONG Zhenkun(No.8 Institute of Geology and Mineral Resources Exploration of Shandong Province,Rizhao,Shandong 276826;Key Laboratory of Nonferrous Metal Ore Exploration and Resource Evaluation of Shandong Provincial Bureau of Geology and Mineral Resources,Rizhao,Shandong 276826;Shandong Provincial Engineering Laboratory of Application and Development of Big Data for Deep Gold Exploration,Weihai,Shandong 264209;No.6 Exploration Institute of Geology and Mineral Resources,Weihai,Shandong 264209)

机构地区：[1]山东省第八地质矿产勘查院,山东日照276826 [2]山东省地矿局有色金属找矿与资源评价重点实验室,山东日照276826 [3]山东省深部金矿探测大数据应用开发工程实验室,山东威海264209 [4]山东省第六地质矿产勘查院,山东威海264209

出　　处：《地质与勘探》2022年第5期917-928,共12页Geology and Exploration

基　　金：山东省深部金矿探测大数据应用开发工程实验室开放课题(编号:SDK202205);山东省地矿局局控地质勘查与科技创新项目(编号:202013)联合资助。

摘　　要：赛坝沟金矿是青海省柴北缘构造带东段重要的金矿床,矿体受NW-NNW向韧-脆性断裂构造组控制,主要赋存于奥陶系英云闪长岩中,矿化蚀变主要有硅化、黄铁矿化、绢英岩化、绿泥石化、绿帘石化和碳酸盐化等。本文在厘定赛坝沟金矿热液蚀变类型、矿物组合特征以及蚀变空间变化关系的基础上,选取Ⅳ-4主矿体在AZK3901钻孔深部见矿岩心及底板蚀变围岩进行研究,通过对蚀变岩及其原岩的地球化学分析,剖析热液蚀变作用过程与机理。研究结果表明,赛坝沟金矿床钻孔深部蚀变中,绿泥石化绿帘石化及强糜棱岩化岩石表现为主量元素K_(2)O、CaO的明显带入和Na_(2)O的带出,大离子亲石元素Pb、Ba、Sr的带出以及过渡族金属元素Bi、Co、Cr的带入;黄铁矿绢英岩化、硅化岩石中,主量元素K_(2)O、SiO_(2),大离子亲石元素Rb、Ba、Cs、Pb以及过渡族金属元素均表现出不同程度的带入;各蚀变岩石中稀土元素以及高场强元素并未表现变化,仅在近矿体处出现了轻重稀土的解耦以及高场强元素Zr元素的带入。综合研究认为,赛坝沟金矿强糜棱岩化绿泥石化英云闪长岩为强烈的韧性剪切和脆性断裂叠加改造作用的产物,对流体成矿物质的运移形成了一定的屏障,使得成矿物质大部分沉淀在硅化、绢英岩化带内,局部发育的方解石细脉与成矿晚期碳酸盐化作用相关。金的沉淀主要是由于含矿流体温度、压力的下降和氧逸度的升高,使得含矿流体与围岩强烈反应形成硅化、绢云母化,同时伴随成矿流体pH值的增大和H^(+)的减少,热液中含硫组分与Fe元素发生反应形成黄铁矿等硫化物,破坏了含金络合物的稳定性,导致金的大量沉淀。The Saibadou gold deposit is an important gold deposit in the eastern section of the northern Qaidam tectonic belt in Qinghai Province.The ore bodies are controlled by NW-NW trending ductile and brittle fractures,and mainly occur in the Ordovician dolomite.The mineralization alteration is dominated by silicification,pyritization,sericitization,chloritization,epidotization and carbonation.Based on the classification of hydrothermal alteration types,mineral assemblages and spatial variation of alteration in the Saibagou deposit,the work studied the cores and bottom altered surrounding rock of the drill hole AZK3901 penetrating the main ore bodyⅣ-4,and analyzed the process and mechanism of hydrothermal alteration through geochemical analysis of the altered rock and its proto-rock.Results show that the chloritic-epidotite and mylonitic rocks display significant enrichment of major elements K_(2)O and CaO and depletion of Na_(2)O,and the depletion of large-ion lithophile elements Pb,Ba and Sr,and enrichment of transition metal elements Bi,Co and Cr.The pyrite sericitized and silicified rocks show different enrichment of major elements K_(2)O,SiO_(2),large-ion lithophile elements Rb,Ba,Cs,Pb and transition metal elements.For altered rocks,rare earth elements and high field strength elements show no significant change,and just display decoupling of heavy and light rare earth elements and the enrichment of high field strength element Zr near ore bodies.The mylotic chloritic tonalite in the Saibaigou gold deposit resulted from superimposed strong ductile shear and brittle fracturing,which acts a certain barrier to the migration of ore fluids.As a result,most ore-forming materials precipitated in silicified and sericitization belts,and locally developed calcite veins were related to the carbonation in late mineralization.Gold precipitation was mainly attributed to the reduced temperature and pressure of ore fluids and the increase of oxygen fugacity.In consequent,the strong reaction of the ore fluids with wall rocks led

关 键 词：热液蚀变 质量平衡 成矿物质运移 韧性剪切 构造叠加 赛坝沟金矿 柴北缘 

分 类 号：P579[天文地球—矿物学] P618[天文地球—地质学]