滇东北麻栗坪铅锌矿床石英原位微量元素特征及其地质意义  

Characteristics of in-situ trace elements in quartz and their geological implications for the Maliping Pb-Zn deposit,Northeast Yunnan Province,SW China

作　　者：罗开 岳正鹏 张宵 李丽清 周家喜 黄智龙[3] 张伟[1,2] LUO Kai;YUE Zheng-peng;ZHANG Xiao;LI Li-qing;ZHOU Jia-xi;HUANG Zhi-long;ZHANG Wei(School of Earth Sciences,Yunnan University,Kunming 650500,Yunnan,China;Key Laboratory of Critical Minerals Metallogeny in Universities of Yunnan Province,Kunming 650500,Yunnan,China;State Key Laboratory of Ore Deposit Geochemistry,Institute of Geochemistry,Chinese Academy of Sciences,Guiyang 550081,Guizhou,China)

机构地区：[1]云南大学地球科学学院,云南昆明650500 [2]云南省高校关键矿产成矿学重点实验室,云南昆明650500 [3]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

出　　处：《云南大学学报（自然科学版）》2023年第2期390-398,共9页Journal of Yunnan University(Natural Sciences Edition)

基　　金：国家自然科学基金(92162218,41872095);云南省科技厅重点项目(2019FY003029).

摘　　要：麻栗坪大型铅锌矿床(~6.0 Mt@13.4%Pb+Zn)赋存于下寒武统梅树村组硅质白云岩中,是滇东北铅锌成矿带的代表性矿床之一.石英是麻栗坪矿床主要的脉石矿物,其形成贯穿整个成矿期.详细的矿物学研究表明,麻栗坪矿床发育3期石英.Ⅰ期石英呈细粒半自形,与细粒黄铁矿、闪锌矿共生,Ⅱ期石英呈中−粗粒半自形,与粗粒闪锌矿、方铅矿共生,Ⅲ期石英较纯.总体上,Ⅰ期至Ⅲ期石英的阴极发光(Cathodoluminescene,CL)强度先增大后减小,与Al、Ge、Li、Na、K含量呈协同变化趋势,暗示微量元素对CL强度的控制作用.元素含量相关性研究显示,微量元素主要以单原子替代(Ge^(4+)→Si^(4+))和补偿替代(Al^(3+)+Li^(+)/Na^(+)/K^(+)→Si^(4+))方式进入石英晶格.麻栗坪矿床石英中Ti含量极低,而Al含量变化范围较大,与岩浆热液矿床显著不同,显示其具有低温热液矿床的特点.Ⅰ期至Ⅲ期石英中Al含量呈先升高后降低的总体趋势,反映Al溶解度先增大后减小,暗示矿化形成于流体酸碱度(pH)先减小后增大的过程.因此,石英原位微量元素组成有助于认识热液矿床成因和成矿流体演化过程.The Maliping large-scale Pb-Zn deposit(~6.0Mt@13.4%Pb+Zn)is hosted in siliceous dolomite of the Lower Cambrian Meishucun Formation,which is one of the representative deposits of the Pb-Zn metallogenic district in Northeast Yunnan Province,China.Quartz is the major gangue mineral of the Maliping deposit,and its formation has lasted throughout the whole age of the mineral formation.Detailed mineral researches demonstrate that quartz of three stages was found in Maliping.StageⅠquartz is fine-grained and subhedral,associated with fine-grained pyrite and sphalerite;stageⅡquartz is medium-coarse-grained and subhedral,associated with coarsegrained sphalerite and galena;and stageⅢquartz is relatively pure.In general,the variation of quartz cathodoluminescene intensities from early to late stages of the Maliping deposit is closely related to the variation trends of Al,Ge,Li,Na and K contents,which implies the controlling effects of the trace elements over quartz cathodoluminescene intensities.The correlation among the elements suggests that trace elements in quartz enter the lattice mainly as single-atom substitution(Ge^(4+)→Si^(4+))and compensatory substitution(Al^(3+)+Li^(+)/Na^(+)/K^(+)→Si^(4+)).In addition,the large amount of Al and extremely small amount of Ti in the quartz from the Maliping deposit are characteristic of low-temperature hydrothermal deposits,which differs from those of the magmatic-related hydrothermal deposits.The variation of Al concentration in quartz has a general trend of increase from StagesⅠtoⅡand decrease from StagesⅡtoⅢ,which reflects that the solubility of Al increases first and decreases afterwards,and which also implies that the mineralization is formed during the processes with fluid pH decreasing first and increasing later.Hence,the in-situ trace element composition of quartz is helpful to understand the genesis of hydrothermal deposits and the evolution of ore-forming fluids.

关 键 词：石英微量元素 麻栗坪铅锌矿床 成矿过程 滇东北 

分 类 号：P618.4[天文地球—矿床学]