PETROCHEMISTRY AND RADIOACTIVITY OF GABAL ABU AQARIB ALKALI FELDSPAR GRANITE, CENTRAL EASTERN DESERT, EGYPT

Abstract

The present work deals with geology, geochemistry and radiometry of Gabal Abu Aqarib Alkali Granite, Central Eastern Desert, Egypt. Gabal Abu Aqarib about 136 km2, and represents a part of the late Precambrian Arabian Nubian Shield. It is of alkali feldspar granite composition and may be considered epeiorogenic uplifts granitoids. Geochemically, the granite rocks of G. Abu Aqarib were originated frommetaluminous calc-alkaline magmas that developed in volcanic arc post orogenic tectonic setting. The studied granite rocks of G. Abu Aqarib area were generated at depth of about 9-20 km equivalent to 4-6 kb and temperature ranging from 760oC to 840oC with multi-processes of both assimilation and fractional crystallization involving plagioclase, hornblende and Fe-Ti oxides from a partial melted lithospheric magma. The U and Th contents in the studied area are associated with hematitization and silicification. Also, the radioactivity are controlled by the presence of higher content of zircon as accessory minerals and iron oxides while iron oxide and hydroxides are known to absorb U from circulating fluids.