2013

Pegmatites  occurrence  of Gabal El urf AREA, Central Eastern Desert, Egypt

Asran, M.H.*, El-Mansi, M.M.**, Ibrahim, M.E**. and Abdel Ghani, I.M.**

* Geology Dept., Fac. Sci., Sohag University.

** Nuclear Materials Authority, Cairo, Egypt.

Radioactive minerals in two zoned pegmatite bodies (30×40m and 50×70m across) associated with granitic rocks are commonly encountered, at Gabal El-Urf area, Central Eastern desert of Egypt and display rounded, elongated, lensoidal and irregular shapes. They are either hosted by perthitic leucogranite, granodiorite, and quartz- diorite or occurred along the contact between them. Field observations and petrography display three mineral sequence zones from outside to inward: 1) wall zone (muscovite/ or phlogopite + biotite); 2) intermediate zone (microcline + orthoclase perthite ± sodic plagioclase) and 3) core quartz.

The two pegmatite bodies are  characterized by their high U and Th contents compared to the host granitic rocks.

The two zoned pegmatites show variation in average  eU (from 344 to 1271 ppm) and eTh (from 1101 to 719 ppm) content as reflected from the presence of radioactive and accessory minerals. Thorianite and uranophane in association with columbite, allanite, fluorite and magnetite are common in the small pegmatite body whereas the big one is characterized by uranium oxides (euxenite, betafite, ashanite and yetteroclumbite) as well as uranium silicates (uranophane) together with galena, zircon, rutile and hematite.

Key words:  radioactive; allanite; zircon; pegmatites; El Urf; Eastern Desert; Egypt

Corresponding author: email:asran_58@yahoo.com