焦家深部金矿床成矿流体来源:来自黄铁矿微量元素及S-He-Ar同位素的约束  

Source of ore-forming fluids of the Jiaojia deeplyseated gold deposit: Evidences from trace elements and sulfur-helium-argon isotopes of pyrite

作　　者：李杰[1,2,3] 宋明春 梁金龙 姜梦瑶[2] 李世勇 丁正江 苏菲 LI Jie;SONG MingChun;LIANG JinLong;JIANG MengYao;LI ShiYong;DING ZhengJiang;SU Fei(Center of Deep Sea Research,Key Laboratory of Marine Geology and Environment,Institute of Oceanology,Chinese Academy of Sciences,Qingdao 266071,China;School of Resources,Hebei GEO University,Shijiazhuang 050031,China;Laboratory for Marine Mineral Resources,Qingdao National Laboratory for Marine Science and Technology,Qingdao 266237,China;Shandong Provincial No6 Exploration Institute of Geology and Mineral Resources,Weihai 264209,China;College of Earth Sciences,Chengdu University of Technology,Chengdu 610059,China;Shandong Institute of Geophysical and Geochemical Exploration,Jinan 250013,China;Shandong Bureau of Geology and Mineral Resources Exploration and Development,Jinan 250013,China;Key Laboratory of Earth and Planetary Physics,Chinese Academy of Sciences,Beijing 100029,China)

机构地区：[1]中国科学院海洋研究所深海研究中心,海洋地质与环境重点实验室,青岛266071 [2]河北地质大学资源学院,石家庄050031 [3]青岛海洋科学与技术试点国家实验室海洋矿产资源评价与探测技术功能实验室,青岛266237 [4]山东省地质矿产勘查开发局第六地质大队,威海264209 [5]成都理工大学地球科学学院,成都610059 [6]山东省物化探勘查院,济南250013 [7]山东省地质矿产勘查开发局,济南250013 [8]中国科学院地球与行星物理重点实验室,北京100029

出　　处：《岩石学报》2020年第1期297-313,共17页Acta Petrologica Sinica

基　　金：山东省自然科学基金项目(ZR2016DM01);国家重点研发计划“深地资源勘查开采”重点专项(2016YFC0600408);山东省重点研发计划(2017CXGC1604);泰山学者建设工程专项(ts201511076、ts201712075);山东省地矿局科研项目(KY201014、KY2016011);青岛海洋科学与技术试点国家实验室“鳌山人才”卓越科学家计划项目(2017ASTCP-OS07)联合资助

摘　　要：焦家金矿是胶东蚀变岩型金矿的典型代表,金储量超过200t。矿体受焦家主干断裂控制,呈脉状产出,发育钾化、绢英岩化、硅化和碳酸盐化等蚀变,矿石中主要载金矿物为黄铁矿。热液成矿期主要可分为四个阶段:黄铁矿-石英阶段(i)、金-石英-黄铁矿阶段(ii)、金-石英-多金属硫化物阶段(iii)和石英-碳酸盐阶段(iv)。本文选取焦家金矿床深部I号主矿体为研究对象,采集了不同标高(-600^-1100m)的钻孔岩心样品,分析了黄铁矿的微量元素和S-He-Ar同位素组成,以此讨论成矿流体的组成、性质及来源。研究发现:焦家深部I号矿体黄铁矿呈浅黄色,强金属光泽,自形-半自形粒状结构,粒度50~1000μm,呈浸染状-细脉状分布于黄铁绢英岩化碎裂岩中,为第ii成矿阶段的产物。黄铁矿的稀土元素含量较低,ΣREE为3.27×10^-6~38.5×10^-6,富集轻稀土元素,δCe值为0.81~1.05,δEu值为0.67~1.43,Th/La、Nb/La比值均小于1,指示成矿流体为富Cl的还原性流体。Co/Ni比值介于0.54~1.57之间,平均值为0.99,与变质流体相近;Y/Ho比值在21.9~35.5之间,与地幔值(25~30)和中国东部大陆地壳值(20~35)接近,指示成矿流体与壳-幔相互作用有关。Y/Ho值、Zr/Hf值和Nb/Ta值变化范围较大,表明成矿热液体系发生了交代作用或有外来热液加入。与大陆地壳相比,黄铁矿富集Cu、Pb、Zn、Cd、Co、Ni等亲硫、铁族元素,亏损高场强元素。焦家深部金矿床黄铁矿的δ^34 S值介于7.5‰~9.8‰之间,平均值为8.7‰,低于浅部矿床δ^34 S值,呈现出由浅到深δ^34 S值逐渐降低的特点。胶东金矿硫同位素组成整体一致,绝大多数矿床δ^34 S值均为正值,变化范围主要集中在6‰~12‰,其来源与古老的变质基底岩系、中生代花岗岩以及幔源流体具有继承演化关系。δ^34 S值整体呈现出:石英脉型<硫化物石英脉型<蚀变岩型的变化规律,说明矿化类型的差异是造成硫同位素组成�The Jiaojia gold deposit is a typical representative altered rock type gold deposit in the Jiaodong Peninsula,with a gold reserve of more than 200 tons.The distribution of the vein-like orebodies is controlled by the Jiaojia Fault.The potash feldspathization,beresitization,silicification and carbonization are well developed in the country rock.Pyrite is the main gold-bearing mineral in the ore.The hydrothermal metallogenic period can be divided into four stages:(i)pyrite-quartz stage;(ii)gold-quartz-pyrite stage;(iii)gold-quartz-polymetallic sulfide stage;and(iv)quartz-carbonate stage.In this paper,we collected nine pieces of drilling hole samples at different depths(-600^-1100m)from the No.I orebody of Jiaojia deeply-seated gold deposit.The trace elements and S-He-Ar isotopic compositions of the pyrites in these samples are analyzed,and the compositions,properties and sources of their ore-forming fluids are discussed.It is found that the pyrites of the No.I orebody are light yellow,with strong metallic luster,euhedral-granular or hypidiomorphic-granular textures,and they ocuured as disseminated grains with sizes of 50~1000μm or veined assemblages in sericitized cataclastic rocks,which are taken as minerals of the gold-quartz-pyrite metallogenic stage(ii).The contents of their REE are relatively low and enriched in LREE,with ΣREE of 3.27×10^-6~38.5×10^-6,δCe values of 0.81~1.05,δEu values of 0.67~1.43 and the ratios of Th/La,Nb/La less than 1,indicating the ore-forming fluids might be Cl-rich reduced fluids.The Co/Ni ratios of the pyrites range from 0.54 to 1.57,with an average value of 0.99,these ratios are close to average values of those from metamorphic-hydrothermal type gold deposit.The Y/Ho ratios range from 21.9 to 35.5,coincident with the mantle(25~30)and the continental crust of eastern China(20~35),indicating that the ore-forming fluids were related to the crust-mantle interaction.The Y/Ho,Zr/HF and Nb/Ta values vary in a wide range,indicating that the metasomatism or the addition of external hydr

关 键 词：焦家金矿床 黄铁矿 氦-氩同位素 硫同位素 成矿流体 微量元素 

分 类 号：P578.292[天文地球—矿物学] P597[天文地球—地质学]