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The late Proterozoic magmatic province of the Ras Gharib district, northern Egyptian Shield, includes wide surface areas of granitoid rocks, that occur in the form of separate plutons and large batholiths. Based on petrographic and geochemical characteristics, the granitoid rocks can be divided into three main suites, namely: a calc-alkaline suite of granodiorite, monzogranite and syenogranite, a trondhjemite suite, and an alkali granite suite. The granodiorite-monzogranite-syenogranite suite (63-76 % SiO2) is peraluminous (A/CNK = 1-1.35) with small negative Eu anomalies (Eu/Eu* = 0.65-0.8), and shows moderate enrichment in the light rare earth elements (LREE) (La-N/Yb-N = 10-22), and the large ion lithophile elements (LILE). It displays chemical characteristics of volcanic are granites. The trondhjemite suite is more silicic, muscovite-bearing, strongly peraluminous (A/CNK = 1.2-1.4), and has very low concentrations of REE (Sigma 14 REE = 29 ppm), Fe2O3* (0.96-1.3 %), MgO (0.19-0.45 %), Rb (50-65 ppm), and Zr (28-35 ppm). The alkali granite suite is depleted in Al2O3, MgO and enriched in Fe2O3*. It shows a more pronounced Eu anomaly (Eu/Eu* = 0.08) and high REE (Sigma 14 REE = 383 ppm) and HFSE contents and therefore chemically resembles A-type granites.

Geochemical modelling suggests that the granodiorite-monzogranite-syenogranite suite was formed by 35 % dehydration melting of amphibolitic lower crust having REE contents of the exposed gabbro-diorite complex. The trondhjemitic rocks represent a higher degree of partial melting of the same source but were generated under higher f(H2O). The alkali granites were derived by partial melting of the early granodiorite, and further affected by fluid metasomatism during and after their emplacement. The metasomatic effect contributes to enrichment in REE and HFSE as well as in rising their initial Sr-87/Sr-86 ratio. Although the alkali granites show the characteristic features of A-type granites, they are not related to a true rifting event in the Nubian Shield, but most probably to a partial melting process along major shear zones.