Resumen

AKINTOLA, O. F.  y  ADEKEYE, J. I. D.. MINERALIZATION POTENTIALS OF PEGMATITES IN THE NASARAWA AREA OF CENTRAL NIGERIA. Earth Sci. Res. J. [online]. 2008, vol.12, n.2, pp.213-234. ISSN 1794-6190.

Pegmatites in Nasarawa area of Central Nigeria lie within a fracture-controlled east-north-east trending rare metal pegmatite belt closely associated with late Pan African peraluminous granites in Nigeria. Trace elements of feldspars andmuscovites of pegmatites in Nasarawa area of CentralNigeriawere analyzed to determine the raremetalsmineralization potentials of the pegmatites. The minerals show fractionation even within units of complex mineralized pegmatites 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 elements are enriched along lateNa-rich raremetalmineralizing fluids. The rare alkalis Rb 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. In the 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 versus Cs 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 complex mineralized pegmatites. While the Be-, and Li-Be-types are highly prospective for gem tourmaline, beryl and columbite; themost evolved pegmatites in this area are good candidates for tantalite, amblygonite-montebrasite, and probably pollucite prospecting/mining.

Palabras clave : Rare metals; Pegmatites; Muscovites; Feldspars; Mineralization; Correlations.

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