Abstract

The Late Proterozoic rocks of the Wadi El-Imra district of the Central Eastern Desert, Egypt, comprise a metagabbro-diorite complex (oldest) and Older and Younger Granitoid complexes. Trace element characteristics show that the basic and granitoid rocks are of calc-alkaline affinity, but some of the Younger Granitoids grade into alkaline granites. The º_Nd values of the the basic and granitoid rocks range from +8.3 to +4.9, and Nd model ages are younger or rather similar to crystallization ages. These data suggest a predominant depleted mantle derivation, indicating formation by subduction in an oceanic setting. REE patterns of the granitoid rocks suggest different modes of petrogenesis. This, coupled with the occurrence of amphibolite xenoliths in the Older Granitoids, may indicate that some of these rocks represent partial melts from basic rocks that have been amphibolitized at deep crustal levels of the oceanic arc.