Stream sediment geochemical survey of rare elements in an arid region of the Hamadat area, central Eastern Desert, Egypt

Abstract

The present work deals with the possibility of conducting orientated geochemical survey exploration in an arid area using stream sediments. These sediments were drained from the Neoproterozoic metavolcanic and granitic rocks of the Hamadat area, Egypt. The fine size fraction of <63 µm, which is most appropriate for the exploration in the arid desert conditions, has been considered. Fourty four samples, including 35 clay and silt fractions and three size fractions of three samples, were analyzed by ICP-MS for major and trace elements. The heavy mineral content was separated from the stream sediments and identified. Based on the geochemical and mineralogical features, the catchment area of the studied stream sediments is split into two primary domains: namely first and second. The first domain drains monzogranite and associated pegmatite and quartz veins, whereas the second domain drains a metasomatized riebeckite granite. The stream sediments of the first domain are enriched in LREE (and ΣREE), Th, Zr and Hf, whereas the second domain has a clear signature of Nb, Ta, Th, U, Y and HREE. These rare metals are predominantly accommodated in the structure of detrital minerals representative of the clastic aureole around the source rocks and are absorbed to a lesser extent. The obtained data are utilized for constructing high-resolution geochemical maps to show the distribution of different rare metals. The anomaly aureoles have been delineated for Y, Yb, Nb, Th and U on a base map of the catchment area. The distribution maps propose possible potential mineralization of rare metals, especially REE, Nb, Ta, Zr, and Hf, in the study area. The HREE + Y appear to be prospective in the second domain, whereas Th, Zr and LREE are possible resources in the first domain. Further studies to authenticate the potentiality of these resources are strongly recommended.