湖南仁里稀有金属矿床岩相学和矿物学特征及其地质意义--以5号脉ZK708号钻孔为例

Petrographic and mineralogical characteristics of Renli rare metal deposit in Hunan Province and their geological implications:A case study of drill hole ZK708 of the No.5 vein

仁里矿床是中国近年新发现的超大型花岗伟晶岩型稀有金属矿床,文章针对其稀有金属矿化富集规律、成岩成矿演化特征及找矿标志等问题,以5号主矿脉钻孔ZK708全孔岩芯及岩体内、外伟晶岩为研究对象,采用了电子探针、能谱仪分析和全岩地球化学分析等方法,开展了伟晶岩岩相学、矿物学及地球化学等方面的研究工作。研究结果表明:①仁里矿床伟晶岩岩性比较复杂,不同岩性伟晶岩相互穿插,为同期次不同阶段的结果,经历了多阶段的岩浆-热液活动,铌钽等稀有金属矿化与多阶段岩浆-热液活动密切相关,铌钽等稀有金属矿物主要赋存于粗-中粒、粗粒白云母钠长石伟晶岩中,随着伟晶岩粒度的增加,铌钽等稀有金属矿化具有逐渐增加的趋势;②仁里矿床伟晶岩为LCT(Li-Cs-Ta)型伟晶岩,经历了不同阶段的岩浆-热液活动,多阶段的热液活动(尤其是富P、F热液流体)为Li、Nb、Ta等稀有元素的进一步富集提供了热源和物质来源,促使Li、Nb、Ta等稀有元素的进一步释出和富集;不同世代矿物出现在伟晶岩熔体-溶液不同演化阶段。磷灰石和粒状、叶片状钠长石可做为本区铌钽等稀有金属矿产的重要找矿标志。

The Renli deposit is a newly discovered superlarge granite pegmatite-type Nb-Ta deposit in Hunan Province.For the purpose of revealing its rare metal mineralization and enrichment regularity,diagenetic and metallogenic evolution characteristics as well as prospecting indicators,the authors chose the core samples from drill hole ZK708 of the No.5 main orebody and the pegmatite inside and outside the rock mass as the research objects,and studied petrographic,mineralogical and geochemical characteristics of pegmatites by means of EPMA,EDS and whole rock geochemistry.Some conclusions have been reached:①The lithology of the pegmatites in the Renli deposit is relatively complex,with different lithologic pegmatites penetrating each other.This phenomenon might have resulted from evolution of different stages of the same period.It has experienced multi-stage magmatic-hy‐drothermal activities.The mineralization of rare metals was closely related to multi-stage magmatic hydrothermal activities.Nb,Ta and other rare metal minerals mainly occur in coarse-medium grained and coarse-grained mus‐covite albite pegmatite.With the increase of the particle size of the pegmatite,the mineralization of rare metals such as Nb and Ta tends gradually to increase;②The pegmatites in the Renli deposit are LCT(Li-Cs-Ta)pegma‐tites,which have undergone different stages of magmatic hydrothermal activities.The multi-stage hydrothermal activities(especially P and F-rich hydrothermal fluids)provided heat and material sources for the further enrich‐ment of Li,Nb,Ta and other rare elements,and promoted further release and enrichment of rare elements such as Li,Nb,and Ta.Minerals of different generations occurred in different evolution stages of pegmatite melt-solu‐tion.The apatite and granular and foliated albite can be used as important prospecting indicators in search for rare metal minerals such as Nb,Ta in this area.