Origin and tectonic setting of granitoids from Eastern desert of Egypt : major elements constraints

الملخص EN

The complete chemical analyses of 118 granitic samples are compiled, of which 84 new analyses are presented.

These granitic rocks be¬long to the Older Granitoids, Younger Granitoids and post-orogenic Alkali Granites.

Among the Younger Granitoids, three granitic phases are distin¬guished, based on field relations.

The origin and tectonic setting of the granitoid rocks are discussed using field relations, multivariate statistics of the chemical data, and several major element parameters.

TJhe mineralogical and chemical similarities dis¬played by the Older and Younger Granitoids phase-I indicatelhat these two calc-alkaline rock suites probably evolved in the same tectonic environ¬ment, which is interpreted here as subduction related.

On the other hand, it is argued that the Younger Granitoids phase-II (calc-alkaline to alkaline) evolved during the gradual stabilization of the area during Pan-African time.

The alkaline granites of phase-III were possibly formed after the com¬plete cratonization of the Arabian-Nubian Shield, probably associated with incipient rifting.

The post-orogenic Alkali Granites were probably formed as intraplate anorogenic granites.