MINERALIZATION POTENTIALS OF PEGMATITES IN THE NASARAWA AREA OF CENTRAL NIGERIA

Pegmatites in Nasarawa area of Central Nigeria lie within a fracture-controlled east-north-east trending rare metal pegmatite belt closely associatedwith late PanAfrican peraluminous granites inNigeria. Trace elements of feldspars andmuscovites of pegmatites inNasarawa area of CentralNigeriawere analyzed to determine the raremetalsmineralization potentials of the pegmatites. The minerals show fractionation even within units of complex mineralizedpegmatites as indicated by the wide ranges of K/Rb in Na-feldspars (albites), muscovites and K-feldspars and the wide range of K/Tl in the latter two minerals. Cs, Rb and Tl and the rare earth elements (REEs) Ce, La, Pr and Y are enriched in the K-bearing muscovites and K-feldspars; K-feldspars have the highest average values of Tl, Ce, La, Pr and Y while the muscovites have the highest average values of Sn, Nb, Ga, F and Zn. Average values of Ta, Sr, Ba,Wand Zr are highest in the albites,which also have the lowest averageNb/Ta ratio. This is an indication that these elementsare enriched along lateNa-rich raremetalmineralizing fluids. The rare alkalisRb and Cs and Tl are positively correlated with the rare lithophile elements (Ta, REEs, Pb, Bi and Y), in both the pegmatite K-feldspars and muscovites, strongly positively correlated with Sn in the muscovites but negatively correlated with Nb in the minerals. Inthe pegmatitic albites, Nb has very strong positive correlations with Ta (0.868) and Zr (0.847), which is indicative of the incorporations/substitution of these elements in the crystal lattice of the ore minerals. There is a general enrichment of the rare elements towards themiddle and inner zones of the complexmineralized pegmatites. Fluorine, phosphorus and boron-rich fluids played significant roles in the magmatic complexation/fractionation and concentration of Sn-Ta-Li-Cs-Be in the albitized zones of the highly evolved pagmatites.K/Rb versusCs in theK-feldspars classify the pegmatites into barren, Be-, Li-Be, and Li-Cs-Be-Ta types. Comparably low Nb/Ta ratios in the late albites and amblygonites indicate the paragenesis of theseminerals with the tantalumores in themiddle/inner zones of the complexmineralized pegmatites. While the Be-, and Li-Be-types are highly prospective for gem tourmaline, beryl and 213 Accepted for publication: November 4th, 2008. columbite; themost evolved pegmatites in this area are good candidates for tantalite, amblygonite-montebrasite, and probably pollucite prospecting/mining.