Mineral chemistry aspects of radioactive mineralization associated with Zr-, Nb-, and REE-bearing minerals from felsic dikes at Abu Hawis, North Eastern Desert, Egypt

Abstract

The exposed rocks in Abu Hawis area, North Eastern Desert (NED), Egypt, consist of tonalite-granodiorite and monzogranite, dissected by post-granite felsic (microgranite and rhyolite) and mafic (basaltic-andesite) dikes. The investigated radioactive minerals and Zr-, Nb-, and REE-bearing minerals were restricted to felsic dikes having E–W and NE–SW trends. Uraninite, uranothorite, and thorite occur as the main radioactive minerals in microgranite dikes, while thorite is represent in rhyolite dikes. Y2O3 and HREE are recorded in zircon crystals from rhyolite dikes whereas HREEs in zircon grains from microgranite dikes are below detection limit. Zircon crystals from microgranite dikes contain high values of HfO2 with up to 9.08 wt % owing to the effect of hydrothermal activity. Columbite from microgranite dikes has Ta/(Ta + Nb) and Mn/(Mn + Fe) ratios ranging between 0.0052–0.0164 and 0.0549–0.7010, respectively, which point to manganocolumbite composition, except for two spots that show a ferrocolumbite composition. Fergusonite is recorded in microgranite dikes, with average values of Nb2O5, Y2O3, and HREE2O3 reaching 50.3, 22.93, and 17.68 wt%, respectively. Monazite is recorded in both microgranite and rhyolite dikes, with marked enrichment of ThO2, which reaches up to 12.52 wt% in the first one, while the total ΣLREE2O3 reached up to 68.5 wt% in the latter. Parisite and chevkinite are confined to rhyolite dikes with clear enrichment in LREE with averages ranging between 53.53 and 43.75 wt% ΣLREE2O3, respectively.