MINERALOGY, CHEMISTRY AND RADIOACTIVITY OF THE ANOMALOUS QUARTZ VEIN ACCOMPANYING THE WESTERN SHEAR ZONE OF RAS ABDA GRANODIORITE, NORTH EASTERN DESERT, EGYPT

The quartz vein cutting the granodiorite of Ras Abda, along the western shear zone, exhibits high
radioactive potentiality (up to 3000 ppm for Th and 1600 ppm for U. The microscopic investigation of
the quartz vein revealed that it is composed mainly of quartz and iron oxides enclosing squadrons of
the accessory minerals. Granitic fragments are corroded and digested from the wall-rock affecting the
chemical composition of the studied rock. Chemically, it is characterized by low alumina and medium
potassium contents with peralkaline affinity. It is also characterized by high concentrations of the trace
elements (Zr >10000, Nb 3481, Y 8621, U 903 and Th 2340 ppm) and the total rare earth elements (up to
24246 ppm) specially the HREEs with very low degree of fractionation in the melt (0.014) and in turn,
high degree of fractionation in the accessory minerals.
The mineralogical investigation using ESEM and XRD techniques revealed the minerals are
responsible for the radioactivity in the anomalous rock such as zircon, thorite, uranothorite and Nb-Ta
minerals (columbite, euxenite and uranopolycrase).
Experimental work in this study agreed with the previous experiments and concluded that metamictization
is attributed to the heat of self-annealing that responsible for transformation of U-euxenite to metamictized
euxenite and transformation of Ti-U-euxenite to metamictized uranopolycrase.
The present study concluded that the studied quartz vein originated from silicic magma rich in the trace
and rare earth elements; hence it is considered as good hostile for the radioelements and possesses high
radioactive potentiality.