湘东北幕阜山岩体南部稀有金属伟晶岩分带特征研究

On Zonation of Rare-Metal Pegmatite in the South of the Mufushan Granite Intrusive in Northeast Hunan

湘东北幕阜山岩体南部是近年来我省新发现的一处重要花岗伟晶岩型稀有金属矿产地。该区舌状岩体内外接触带分布有众多花岗伟晶岩脉,形成了仁里超大型铌钽矿、传梓源中型锂铌钽矿等多个铌钽锂矿床(点)。本文对该区密集发育的伟晶岩脉水平分带及结构分带进行研究,从花岗岩体内至外接触带随岩浆分异演化程度不断增强,依次划分出微斜长石伟晶岩带→二云母微斜长石钠长石伟晶岩带→白云母微斜长石钠长石伟晶岩带→白云母锂辉石钠长石伟晶岩带→白云母钠长石伟晶岩带等较为完整演化序列的水平分带;不同分带伟晶岩矿物组合及地球化学特征具有一定差异,对应形成了较完整的稀有金属演化序列:Be→Be+Nb→Be+Nb+Ta→Be+Nb+Ta+Li+Cs。区内稀有金属伟晶岩可分为早晚两期,稀有金属伟晶岩类型由低至高,成矿时代由老至新,早期稀有金属伟晶岩以Be矿化为主,晚期稀有金属以Li、Be、Nb、Ta等矿化组合为主。不同期次、类型、结构分带伟晶岩应注意不同稀有金属的找矿。

Many granitic pegmatite dykes occur in contact zone of the Mufushan granite intrusive in northeast Hunan.The superlarge Renli Nb-Ta deposit,Chuanziyuan medium-sized Li-Nb-Ta deposit and so on are confined to the granitic pegmatite dykes.This paper has a discussion on horizontal zonation of the granitic pegmatite dykes and divides them into microcline pegmatite zone,two-mica-microcline-albite pegmatite zone,muscovite-microcline-albite pegmatite zone,microcline-spodumene-albite pegmatite zone and muscovite-albite pegmatite zone and relevant metallic evolutionary series Be-Be+Nb-Be+Nb+Ta-Be+Nb+Ta+Li+Cs from the intrusive to endocontact and exocontact.