Geology, Geochemistry and Radioactivity of Wadi El- Morakh Basement RQcb, South Taba, Sinai, Egypt

Abstract

The present thesis deals with the geology, petrography, geochemistry and radioactivity of Wadi El-Morakh basement rocks which are located south Talia, along the western coast of the Gulf of Aqaba between 29°20' and 29°30' N, and longitudes 34°41' and 34°54' E. The studied area covers about 215 Km2 Detailed field work revealed that the investigated area is built up of

the following Precambrian rnetamorphic and igneous rocks (from old to young): 1) Metasediments (schists); 2) Metadiorites; 3) Paragneisses and Migmatites; 4) Foliated Granitoids; 5) Younger granites (phase II); 6) Volcanic rocks; 7) Younger granites (phase III); 8) Pegmatites as well as post-granitic dykes. The studied schists are derived, by metamorphism, from greywackes and petites or pelitic greywackes that were originally l 1 derived from felsic and intermediate igneous provenance and deposited in a

tectonic setting related to an active continental margin regime. The studied 1 I metadiorite is characterized by a subalkaline tholeiitic affinity and, based

on Meschede (1986) discrimination diagrams, is mainly developed in

"volcanic arc" tectonic environment.

In the study area, the gneisses comprise mainly paragneisses and migmatites, however, it is difficult to separate them into two separate mapple unitS. TwQ varieties of paragneisses were recorded (biotite-gneiss and staurolite-garnet-biotite gneiss). The sedimentary origin for these gneisses is indicated by the presence of aluminum-rich mineral assemblage such - as garnet and staurolite of the pelitic rocks (e.g. Wadi Tweiba paragneiss), the high percent of quartz and biotite and the presence of sedimentary structures. The migmatites are well recognized and the main