贵州五指山那雍枝铅锌矿床矿石组构特征及矿床成因初探

摘要

五指山矿集区分布有那润、新麦等众多中小型铅锌矿床，其中那雍枝铅锌矿床是迄今川滇黔地区贵州境内近年来勘查发现的大型铅锌矿床。相对本区的地质勘查程度而言，其地质科学研究极为薄弱。有鉴于此，本文通过大量野外地质工作和室内光薄片鉴定，详细研究了该矿床矿石组构特征及矿化期次，以期为扬子台缘铅锌矿床成因提供可靠的地质依据。研究认为：该矿床典型矿石的主要结构包括结晶结构、交代结构、固溶体分离结构、压碎角砾状结构、揉皱结构以及放射状结构等；其主要构造包括浸染状构造、块状构造、脉状构造、角砾状构造及条带状构造等。上述矿石组构特征表明成矿作用具有多期多阶段的特点，并指示出沉积成矿兼有后期热液改造成矿的组构特征。结合野外地质观察和矿床地质特征分析认为，那雍枝铅锌矿床的形成经历了同生沉积与后期热液改造过程。%Among Narun and Xinmai medium-small-sized Pb-Zn deposits,Nayongzhi Pb-Zn deposit is located in Wuzhishan ore-concentrated area and is a large-sized Pb-Zn deposit which is newly discovered in Guizhou. Compared with geological exploration activities,few geological scientific research are conducted in this re-gion.In light of this situation,this paper examined the ore-fabric characteristics and mineralization stages of the deposit in detail based on a large amount of filed geological survey works and laboratory investigation of polished thin sections,so as to provide reliable geological basis for the argument on the genesis of lead-zinc deposits at the edge of Yangtze Platform.The research indicates that:the primary textures of the typical ores of the deposit include crystalline texture,metasomatic texture,unmixing texture of solid solution,cata-clastic-brecciated texture,corrugation texture and radial texture;and the ores predominantly occur as dis-seminated,massive,veined,brecciated and branding in form.The above-mentioned ore-fabric characteristics suggest that the mineralization is characterized by multiple stages and periods,and it is also pointed out that the sedimentary mineralization has the fabric characteristics of late hydrothermal reworking mineralization. Combined with field geological observation and analysis on geological characteristics of the deposit,Nayong-zhi Pb-Zn deposit is formed through syndepositional stage and late hydrothermal reworking process.