Radioactivity and geochemical characteristics of post collision granites, west Wadi Murrah area, South Eastern Desert, Egypt

摘要

Wadi Murrah area is located in the southern Eastern Desert of Egypt comprising four distinct lithological groups: Ophiolitic assemblage (dismembered ophiolitic rocks and ophiolitic mélange), arc assemblage (metavolcanics, metagabbros and older granites), post-collision granites (monzogranite, syenogranite and alkali feldspar granite), dykes and quartz veins. The post collision granites are originated from metaluminous, subalkaline magma in extensional suite. They were developed in within plate tectonic setting and have A2-type character which means that these granites were generated from apparent crustal source via fractional crystallization. The similar chondrite-normalized REEs distribution patterns of these granites reveal that they may be derived from the same source magma. Uranium and thorium were mainly controlled by primary magmatic processes. They are mainly present in accessory minerals such as allanite, zircon, sphene and apatite.