胶东三山岛金矿床黄铁矿As富集机制及其对金成矿作用的指示  

Enrichment mechanisms of arsenic in pyrite from Sanshandao gold deposit(Jiaodong Peninsula,China)and implications for gold metallogenesis

作　　者：许杨 蓝廷广[1,2] 舒磊 胡换龙 陈应华 王洪 XU Yang;LAN TingGuang;SHU Lei;HU HuanLong;CHEN YingHua;WANG Hong(State Key Laboratory of Ore Deposit Geochemistry,Institute of Geochemistry,Chinese Academy of Sciences,Guiyang 550081,Guizhou,China;College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China;MNR Key Laboratory of Gold Mineralization Processes and Resources Utilization,Shandong Institute of Geological Sciences,Jinan 250013,Shandong,China)

机构地区：[1]中国科学院地球化学研究所,矿床地球化学国家重点实验室,贵州贵阳550081 [2]中国科学院大学地球与行星科学学院,北京100049 [3]山东省地质科学研究院,国土资源部金矿成矿过程与资源利用重点实验室,山东省金属矿产成矿地质过程与资源利用重点实验室,山东济南250013

出　　处：《矿床地质》2021年第3期419-431,共13页Mineral Deposits

基　　金：国家自然科学基金(编号:41873048);国家重点研发计划(编号:2016YFC0600105)联合资助。

摘　　要：胶东是中国最大的金矿集区,其金矿成因目前还存在较大争议。作为最重要的载金矿物,黄铁矿显微结构及元素-同位素组成能够很好地示踪成矿物质来源和成矿过程。利用SEM、EPMA和LA-ICP-MS微区原位分析方法对胶东代表性蚀变岩型金矿—三山岛金矿的黄铁矿开展详细的BSE显微结构以及As含量和S同位素耦合关系研究,发现矿区至少存在3种不同结构和As含量的黄铁矿:①含金石英-黄铁矿细脉中具交代残余结构的低As黄铁矿(Py-1),在BSE图像中显示暗色的核部(Py-1a)和亮色的边部(Py-1b),Py-1a和Py-1b的w(As)分别为48×10^(-6)~524×10^(-6)和183×10^(-6)~1134×10^(-6),δ^(34)S值分别为10.4‰~10.8‰和11.6‰~11.9‰;②含金石英-黄铁矿细脉中具韵律环带结构的高As黄铁矿(Py-2),在BSE图像中显示富含矿物包裹体并多孔的核部(Py-2a)以及很少含矿物包裹体的"干净"边部(Py-2b),Py-2a和Py-2b的w(As)分别为0.14%~0.31%和0.47%~0.97%;③含金石英-多金属硫化物细脉中具核边结构且As含量变化大的黄铁矿(Py-3),其核部Py-3a富含黄铜矿、闪锌矿等矿物包裹体并贫As,w(As)仅为1×10^(-6)~10×10^(-6),δ^(34)S值为4.2%~5.8‰,边部Py-3b几乎不含矿物包裹体但富As,w(As)为8877×10^(-6)~17839×10^(-6),δ^(34)S值为7.7%~10.1‰。上述黄铁矿中,从Py-1a到Py-1b,w(As)和δ^(34)S值缓慢升高,可能主要受水岩相互作用的控制;Py-2具韵律环带且核部多孔、多矿物包裹体,指示了较为剧烈的流体沸腾作用;Py-3a和Py-3b具有截然不同的w(As)和δ^(34)S值,指示了外来富As流体的加入。这些过程有利于As和Au的进一步富集,多种形式的富As和Au机制表明胶东金矿存在复杂的矿化过程和物质来源,特别是流体在迁移过程中萃取围岩中的成矿物质不可忽视。Jiaodong Peninsula is the largest gold Province in China.How the huge amounts of gold were accumulated in such an area is still controversial.Pyrite is the most important Au-carrier mineral,the elemental and isotopic compositions of which,coupled with its microtexture,can well record the specific ore-forming processes and the origin of Au.In this study,SEM,EPMA and LA-(MC)-ICP-MS analyses were conducted on microtextures as well as As contents and S isotopic compositions of pyrite from the giant Sanshandong gold deposit.The results show that at least three types of pyrite occur:①Low-As pyrite(Py-1)in the Au-bearing quartz-pyrite vein,which shows metasomatic relict texture.Under the BSE imaging,a dark relict core(Py-1a)is surrounded by a grey rim(Py-1b).The Py-1a has As contents of 48×10^(-6)~524×10^(-6)and δ^(34)S values of 10.4‰~10.8‰while the Py-1b has As contents of 183×10^(-6)~1134×10^(-6)and δ^(34)S values of 11.6‰~11.9‰;②High-As pyrite(Py-2)in the Au-bearing quartz-pyrite vein,which shows rhythmic zoning texture.Under the BSE imaging,the pyrite has a dark porous core containing abundant mineral inclusions(Py-2a)and a bright clean rim(Py-2b).The Py-2a and Py-2b have As contents of 0.14%~0.31%and 0.47%~0.97%,respectively;③Pyrite in the Au-bearing quartz-polymetallic sulfide vein(Py-3).This pyrite is characterized by core-rim texture,showing a dark As-poor core(Py-3a)and a grey As-rich rim(Py-3b).The Py-3a and Py-3b have As contents of 1×10^(-6)~10×10^(-6)and 8877×10^(-6)~17839×10^(-6),δ^(34)S values of 4.2‰~5.8‰and 7.7‰~10.1‰,respectively.The slight increase of As and δ^(34)S from Py-1a and Py-1b was most likely induced by fluid-rock interaction.The rhythmic zoning texture of Py-2,coupled with its mineral inclusion-bearing and porous core,likely suggests a fluid boiling.The contrasted As and δ^(34)S values between the Py-3a and Py-3b indicate the injection of another As-rich fluid.The above processes facilitate the As and Au to be further enriched,implying that complex ore-fo

关 键 词：地球化学 黄铁矿原位分析 显微结构 富As机制 S同位素 三山岛金矿 胶东 

分 类 号：P618.51[天文地球—矿床学]