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

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(Ge⁴⁺→Si⁴⁺)和补偿替代(Al³⁺+Li⁺/Na⁺/K⁺→Si⁴⁺)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...

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

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. Stage Ⅰ quartz is fine-grained and subhedral, associated with fine-grained pyrite and sphalerite; stage Ⅱ quartz is medium-coarse-grained and subhedral, associated with coarse-grained sphalerite and galena; and stage Ⅲ quartz 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 (Ge4+→Si4+) and compensatory substitution (Al3+ +Li+/Na+/K+→Si4+). 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 Stages Ⅰ to Ⅱ and decrease from Stages Ⅱ to Ⅲ, 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.