RARE ELEMENTS DISTRIBUTION AND MINERALIZATION POTENTIALITY OF PEGMATITES IN GABAL ABU SAMYUK GRANITE, NORTH EASTERN DESERT, EGYPT

Abstract

Numerous pegmatite bodies are hosted by Gabal Abu Samyuk perthitic granite, which constituting part of the Late Neoproterozoic Gattar granites in the North Eastern Desert of Egypt. The pegmatite bodies have in most cases lenticular and irregular outlines within the host granite. They range in size from few meters to 25m length and their width usually less than 7m, although small pockets are also present. Most of the pegmatites display simple zoning structure that consists of feldspar-rich outer zone and internal quartz core. The gamma-ray measurements over these pegmatites indicated that some bodies are radiometrically anomalous, dominantly in the feldspar-rich outer zones. The radioactive zones were sampled with the aim to study the mineralogical compositions, distribution of trace elements and assessment of the mineralization potentiality of these pegmatites. The mineralogical data of the mineral separates revealed that the rare metals primarily comprised zircon, fergusonite-(Y), columbite-(Fe) and xenotime-(Y). Trace and rare earth elements are extremely variable with different degrees of enrichment in Zr, Th, U, Nb, Ta, Y and REE. The studied pegmatites show a NYF-type mineralogical and geochemical signature, whereas the enrichment of rare element can be explained by high degrees of fractional crystallization of a suite of volatile-rich magmas.