The Abu Tobil pluton is one of the alkaline, post-tectonic intrusions making up the eastern parts of El-Tor granitic mountains of Sinai. It comprises two phases: 1) an older granodiorite phase and 2) a younger leucogranite phase pertaining to YG-I and YG-III of Egyptian Younger Granites. The data of microprobe analysis of feldspars and micas indicate that the feldspars were formed at about 650 to 720˚C and 1 Kbar pressure while biotite and muscovite crystallized at about 480 to 550˚C. The granites are potassium-rich, metaluminous-peraluminous, with flat REE patterns and negative Eu anomalies, formed in post-collisional regime. In general, the YG-I is a less differentiated, calc-alkaline granodiorite, probably exhibits the features of I-type granite, and was formed from upper mantle wedge, contaminated by continental crust materials. On the other hand, the YG-III is strongly alkaline leucogranite, analogous to the A-type granite, and was formed by melting of lower crustal materials. The study reveals that both phases were emplaced in different environments.The leucogranites of YG-III are more alkaline, enriched in Rb, Ba, Th, U, Nb, Zr and light REE and depleted in Sc, Sr, Eu and heavy REE compared with granodiorite of YG-I, suggesting a separation (or less melting) of plagioclase feldspars. The field and geochemical peculiarities reveal that two phases are genetically unrelated.