福建南平花岗伟晶岩型稀有金属矿田Nb-Ta-Sn地球化学研究

On Nb-Ta-Sn element geochemistry of the Nanping rare metal granitic pegmatite orefield

福建南平是我国重要的花岗伟晶岩型矿田之一,伟晶岩主要产出在中-新元古代变质岩系中。伟晶岩脉的形成和加里东期西芹花岗岩具有密切的成因联系。根据伟晶岩主要矿物成分和所含Nb、Ta、Sn等元素可分为白云母-钾长石-早期钠长石型(Ⅰ)、白云母-钠长石-钾长石型(Ⅱ)、白云母-钾长石-钠长石型(Ⅲ)和白云母-钠长石-锂辉石型(Ⅳ)。对矿田中的中-新元古代变质岩系、西芹花岗岩,花岗伟晶岩中的Nb、Ta、Sn地球化学做了详细研究。认为南平伟晶岩是在区域地层和相关花岗岩中Nb、Ta、Sn含量具有高背景值的环境中产生的。伟晶岩在形成过程中,Nb、Ta、Sn元素伴随伟晶熔体的分异、演化及交代作用,其含量向晚期趋于增高,在白云母-钠长石-锂辉石伟晶岩中,Nb、Ta、Sn构成了工业矿体,而且主要以独立矿物形式存在。

The Nanping is one of the important rare metal granitic pegmatite orefield in China. It s mainly occur in meso-late Proterozoic metamorphic rock series. There is a close genesis relationship between pegmatite formation and the Xiqin Caledonian granite. Acording to the mineral composition and rare element contents, pegmatite veins can be divided into four types： muscovite-orthoclase-early albite type （ 1 ） ; muscovite-albite-orthoclase type （ II ） ; muscovite-orthoclase-albite type （III） ; muscovite-- albite 5podumene type （IV）. In this paper, it was deep individually studied for the meso-late Proterozoic metamorphic rocks , Xiqin granite, granite pegmatite. Nanping pegmatite was produced in an inviroment of high contents of Nb-Ta-Sn element located in regional stratum and related granites. In the forma tion process of pegmatite , accompanied wich differentiation, evolution and metasomatism of pegmatite melt, the contents of Nb Ta Sn will be increased in later period. In the pegmatite of IV type, Nb-Ta -Sn formed industrial ore bodies. In the pegmatite of this type, Nb Ta-Sn element were chiefly occurred in independend minerals.