胶东台上金矿床成矿流体演化:载金黄铁矿稀土元素和微量元素组成约束  

Evolution of ore fluid of the Taishang gold deposit Jiaodong: Constraints on REE and trace element component of auriferous pyrite

作　　者：陈炳翰 王中亮[1] 李海林[1] 李金奎 李京濂 王国强[1] 

机构地区：[1]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 [2]山东中矿集团有限公司玲南金矿,招远265401

出　　处：《岩石学报》2014年第9期2518-2532,共15页Acta Petrologica Sinica

基　　金：国家自然科学基金重点项目(41230311);国家科技支撑计划课题(2011BAB04B09);地质过程与矿产资源国家重点实验室开放课题(GPMR201307)联合资助

摘　　要：胶西北金资源量占胶东地区的90%,台上金矿床是胶西北最大的断裂带招平断裂带内重要的＂焦家式＂金矿床矿体严格受破头青断裂及其下盘的次级断裂控制;蚀变主要有钾长石化、绢英岩化、硅化和碳酸盐化蚀变;矿化类型划分为破碎带蚀变岩型和石英脉型。矿石矿物主要为黄铁矿,其次是黄铜矿和方铅矿。根据野外蚀变、矿化发育情况,手标本及镜下鉴定,将成矿期划分为4个阶段：即黄铁矿-石英-绢云母阶段（Ⅰ）;石英-黄铁矿阶段（Ⅱ）;石英-多金属硫化物阶段（Ⅲ）;石英-碳酸盐阶段（Ⅳ）。本研究在不同中段内系统采集了不同成矿阶段的蚀变岩型和脉型矿石样品,利用电感耦合等离子体质谱（ICP-MS）方法分析样品内黄铁矿微量元素、稀土元素,以此反映成矿流体演化。与碳质球粒陨石相比,各阶段黄铁矿的LREE比HREE更富集,Hf/Sm、Nb/La和Th/La值均小于1,表明成矿流体中富Cl-,F-含量低。与大陆地壳相比,黄铁矿微量元素特征表明成矿流体富集亲硫元素Cu、Zn、Cd、Pb和铁族元素Co、Ni。各阶段黄铁矿Ce异常较弱（δCe值0.86~1.03）,表明在成矿过程中物理化学条件为还原环境。Eu2＋易于在高温条件下存在,形成正异常,黄铁矿内Eu主要为负异常,Ⅰ、Ⅱ成矿阶段δEu值0.26~1.06,变化范围较大,个别样品δEu值大于1,Ⅲ、Ⅳ阶段δEu值0.45~0.61,变化范围减小,分布在0.5左右,δEu值变化特征表明成矿前期流体温度总体较低,有较高温度的热液混入,成矿后期流体温度较低。同一热液体系中Y/Ho、Zr/Hf和Nb/Ta比值稳定,台上金矿床各成矿阶段Y/Ho值、Zr/Hf值和Nb/Ta值变化范围较大,表明成矿各阶段热液体系可能受到干扰,发生了交代作用或有外来热液加入。黄铁矿Y/Ho范围与中国东部大陆地壳Y/Ho范围重合最多,表明成矿流体与地壳关系密切。Jiaodong Peninsula is the largest gold province in China, the proven gold reserve in northwestern Jiaodong Peninsula occupies 90% of that of Jiaodong PeninsULa. Zhaoping fault belt is the largest fault belt in northwestern Jiaodong Peninsula. Taishang gold deposit is an important Jiaojia-type gold deposit in the northern part of Zhaoping fault belt. The orebodies are controlled by Potouqing fault and its secondary faults. Alteration type includes potash-feldspathization, sericitization, silication and carbonatation. Mineralizatian includes fractured belt-alteration rock type and vein type, pyrite, chalcopyrite, galena and sphalerite are the most common metallic minerals. According to the characteristics of alteration and mineralization in the field, hand specimen, petrography and ore microscopy observation, the mineralization stages are divided into the pyrite-quartz-sericite stage （ I ）, the quartz-pyrite stage （ II ）, the quartz-polysulfide stage （ IU ） and the quartz-carbonate stage （ 1V ）. We collect samples of fractured belt-alteratian rock type and vein-type at different levels, and divide these samples into different mineralization stages. With the method of inductively coupled plasma mass spectrometry （ICP-MS）, trace dement and rare earth dement of the pyrites in the samples are tested to inflect characteristics of ore fluids evolution. Compared to CI chondrite, LREE is more enriched than HREE in pyrites, Hf/Sm, Nb/La and Th/La are all less than 1, which indicates C1^- was enriched in the ore fluids while F^- was lacking. Compared to continental crust, thiophil elements including Cu, Zn, Cd, Pb and iron group dements including Co, Ni were enriched in ore fluid. In each stage, pyrites show a weak Ce anomaly （δCe ranges from 0. 86 to 1.03 ）, which indicates a reducing condition during the mineralization process. Eu^2＋ is apt to stay in the high temperature condition which leads to the normal anomaly, while Eu in the pyrite shows a negative anomaly. During the I and II stage, 8Eu r

关 键 词：黄铁矿 稀土元素 微量元素 成矿流体 台上金矿床 胶东 

分 类 号：P595[天文地球—地球化学] P618.51[天文地球—地质学]