Project description

The voluminous Pan‐African calc‐alkaline granitic suite of the Ras Gharib crustal segment in northeastern Eygpt provides a typical example of orogenic magmatism. The 552 ± 7 Ma‐old granodiorite–adamellite and leucogranite suite is compositionally broad (58 to 77 wt.% SiO2) and exhibits calc‐alkaline geochemical trends and trace‐element characteristics typical of the volcanic‐arc granites. The rocks contain oligoclase, albite, K‐feldspar, calcic amphibole, biotite, titanite, zircon, and magnetite. The suite exhibits typical features characteristic of I‐type granites.

We contend that the magma was formed by partial melting of a modified oceanic crust at an active continental margin during the late stage of the Pan‐African orogeny. The process may have involved assimilation of Early Pan‐African dioritic country rocks. The more felsic units were produced by progressive fractionation of that magma. The petrological–geochemical evidence suggest that the Pan‐African crust in northeastern Egypt did not develop in an extensional tectonic regime, as proposed recently.

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