贵州竹林沟锗锌矿床碳酸盐矿物学和矿物化学特征及其地质意义  

Mineralogy and mineral chemistry of carbonates from the Zhulingou Ge-Zn deposit in Guizhou Province and its geological significance

作　　者：杨智谋 周家喜 罗开 杨德智[4] 余杰[4] 周发朝 YANG ZhiMou;ZHOU JiaXi;LUO Kai;YANG DeZhi;YU Jie;ZHOU FaChao(School of Earth Sciences,Yunnan University,Kunming 650500,China;Key Laboratory of Critical Minerals Metallogeny in Universities of Yunnan Province,Kunming 650500,China;MNR Key Laboratory of Sanjiang Metallogeny and Resources Exploration&Utilization,Kunming 650500,China;Institute of Geophysical and Geochemical Prospecting,Bureau of Geology and Mineral Exploration and Development of Guizhou Province,Guiyang 550018,China;The Xiaoxiban Antimonu Co.,Ltd.,Wenshan 663502,China)

机构地区：[1]云南大学地球科学学院,昆明650500 [2]云南省高校关键矿产成矿学重点实验室,昆明650500 [3]自然资源部三江成矿作用及资源勘查利用重点实验室,昆明650500 [4]贵州省地质矿产勘查开发局地球物理地球化学勘查院,贵阳550018 [5]西畴县小锡板锑业有限公司,文山663502

出　　处：《岩石学报》2021年第9期2743-2760,共18页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(41872095、42172082、U1812402);云南大学科研启动项目(YJRC4201804);云南省科技厅重点项目(2019FY003029);云南大学研究生科研创新基金项目(2020Z45)联合资助.

摘　　要：以碳酸盐岩为容矿岩石的后生热液铅锌矿床(Mississippi Valley-type,MVT矿床)是世界上一种重要的铅锌矿床类型,也是锗的重要工业来源之一。热液碳酸盐矿物是MVT矿床中最主要的脉石矿物,其形成贯穿整个MVT矿床成矿过程。因此,碳酸盐矿物携带丰富的成矿信息,是认识MVT矿床成因的重要补充。位于贵州省贵定县境内的竹林沟锗锌矿床,是近年来新发现的富锗锌矿床(平均品位97.9×10^(-6) Ge,6.54%Zn),赋存于泥盆系碳酸盐岩中。本次工作发现该矿床不同期次热液白云石的矿物学和微量元素地球化学特征存在明显差异:成矿期前白云石(Dol1)主要呈细脉状穿插围岩,被成矿期白云石和硫化物脉穿插,部分呈细粒状被后期白云石包裹;成矿早期白云石(Dol2)主要呈粗粒状,与闪锌矿共生;主成矿期白云石(Dol3)主要呈脉状、团块状,与闪锌矿和黄铁矿共生;成矿晚期白云石(Dol4)呈团块状充填于闪锌矿矿石或者围岩中;成矿期后白云石(Dol5)呈脉状穿插或包裹其它期次白云石/闪锌矿-黄铁矿条带。C-O同位素研究表明,成矿期白云石主要来源于碳酸盐围岩的溶解,成矿流体中的C来源于围岩,而较低的δ18 O值可能是亏损18 O的成矿流体和围岩间水/岩反应过程中O同位素发生交换的结果。激光剥蚀电感耦合等离子体质谱(LA-ICPMS)白云石原位微量元素分析结果表明,Dol2-Dol4的Y/Ho比值相对稳定(30.5~47.9),结合区域成矿特征,认为形成成矿期白云石的流体主要为盆地卤水,与该矿床属于MVT矿床事实吻合。Dol1和Dol5具有相对较低的稀土总量(∑REE=3.97×10^(-6)~29.7×10^(-6)),很可能与白云岩围岩(∑REE=25.2×10^(-6)~61.3×10^(-6))溶解作用有关,直接继承围岩的稀土元素组成特征;成矿期Dol2-Dol4的∑REE较高(∑REE=39.2×10^(-6)~117×10^(-6)),暗示成矿流体本身也携带了部分稀土元素。成矿各期次白云石均具有明显的Eu负异常(δEu=0.38Carbonate-hosted epigenetic hydrothermal Pb-Zn deposits,i.e.Mississippi Valley-type(MVT)deposits,are important lead-zinc resources in the world and a major industrial source of germanium(Ge).Wherein hydrothermal carbonates are the most important gangue minerals and their formation runs through the whole metallogenic process of MVT deposits.Therefore,hydrothermal carbonates contain rich mineralization information and are an important supplement for understanding the genesis of MVT deposits.The Devonian carbonate-hosted Zhulingou Ge-Zn deposit(97.9×10^(-6) Ge,6.54%Zn)located in Guiding County,Guizhou Province,is newly discovered in recent years.The hydrothermal dolomite of the Zhulingou deposit have various mineralogical features:the pre-ore dolomite(Dol1)occurs mainly as veinlets or interspersed in host rocks and cross-cut by ore-stage dolomite and sulfides,or occurs as fine crystals enclosed by the late dolomite;the early ore-stage dolomite(Dol2)is mainly coarse-grained and coexists with sphalerite;the main ore-stage dolomite(Dol3)is mainly vein-like or clumpy,coexisting with sphalerite and pyrite;the late ore-stage dolomite(Dol4)fills into sphalerite or host rocks in the form of clumps;the post-ore dolomite(Dol5)crosscuts/encloses early stages of dolomite/sphalerite-pyrite bands.The C and O isotopic data show that the formation of Dol2-Dol4 is likely related to the dissolution of the carbonate host rocks,and the C in the ore-forming fluid derives from the country rocks,the lowerδ18 O may be contributed to the isotope exchange between the host rock and the ore-forming fluid with 18 O depletion.The laser ablation inductively coupled plasma mass spectrometry(LA-ICPMS)in situ analytical results show that the Y/Ho ratios of Dol2-Dol4 are relatively constant(30.5~47.9).This indicates that the fluids formed metallogenic dolomite are basin brine,which is supported by the MVT genesis of the Zhulingou deposit.Dol1 and Dol5 with lower∑REE values(3.97×10^(-6)~29.7×10^(-6))may be related to the dissolution of the host

关 键 词：碳酸盐矿物 微量和稀土元素 C-O同位素 成矿流体来源与演化 竹林沟锗锌矿床 

分 类 号：P571[天文地球—矿物学] P595[天文地球—地质学]