GEOCHEMICAL CONTRIBUTIONS OF REE'S BEARING PEGMATITES, WITHIN KADABORA GRANITIC PLUTON, CENTRAL EASTERN DESERT, EGYPT

Abstract

Pegmatitic bodies are encountered within the Kadabora granite to which they are spatially and genetically related. These bodies bearing REEs, U, Th, Y, Zr, Hf, Nb, Ta, and Cs. The mineralized pegmatites are characterized by high ΣREEs contents ranging from 3404 ppm to 15196 with an average of 7516ppm. The assemblage of the accessory minerals encountered in the mineralized pegmatites are zircon, allanite, fergusonite, uranothorite, betafite, samarskite, pyrochlore, bastnaesite, cerianite, rutile, euxenite and opaques. Each of these minerals is bearing certain trace elements ; zircon (Zr, Hf , Th); fergusonite (U, Th, Zr); uranothorite (Th, U); betafite (U, Nb, Ta); samarskite (Nb, Ta, U); pyrochlore (Nb, Ta); bastnaesite (REEs); cerianite (Ce, Th, Nb, Ta, Zr) and rutile (Ti). The REEs distribution pattern in the mineralized pegmatites reflects the role of these minerals as REEs accumulators e. g. betafite, bastnaesite and cerianite host LREEs while zircon, allanite and samarskite host HREEs. The REEs pattern is characterized by HREEs enrichment relative to LREEs with convex tetrad effect and a sharp negative Eu anomaly. This well demonstrated pattern reflects highly differentiated rocks associated with self strong hydrothermal interaction. It seems that parent magma has undergone extensive magmatic differentiation, during associated with syngenetic interaction of aqueous hydrothermal fluids resulted in the tetrad effect of REEs distribution forming highly mineralized pegmatites.