Occurrence of Samarskite-Y in the Mineralized Umm Lassifa Pegmatite, Central Eastern Desert, Egypt

Abstract

Samarskite-Y, with an average assay of about 43.23% Nb2O5 and 17.43% Y2O5 has been identified in the mineralized pegmatite bodies injected in Gabal Umm Lassifa monzogranite. The mineral is associated with columbite, zircon, monazite, cassiterite, ilmenite and rutile. The mineralogy and geochemistry of the studied samarskite variety were determined using microscopic examination and X-ray Diffraction (XRD) as well as quantitative analysis by both Field emission scanning electron microscope and electron microprobe analysis. Microscopic investigation revealed that the defined samarskite crystals are characteristically velvet-yellow brown to bloody red in color and having a characteristic pendent vitreous or resinous luster. Analytical data confirmed the presence of samarskite-Y whose composition corresponding to empirical formula: [(Y0.42, REE0.44, Th0.076, Si0.05, Ca0.007, U0.07, Fe0.077) Σ1.15 (Nb0.81, Ta0.014) Σ0.86 O4]. Accordingly, the mineralized Umm Lassifa pegmatite can be considered as a promising target ore for its rare-metal mineralization that includes mainly Nb, Ta, Y, REE and Zr together with U and Th.