Detrital chromites in metasediments of the East-Arabian continental marginin the Saih Hatat area: constraints for the palaeogeographic setting of the Hawasina and Semail basins (Oman Mountains)

In Oman, the convergence between Arabia and Eurasia resulted in the Late Cr etaceous overthrusting of oceanic crust and mantle lithosphere onto the Ara bian continental margin. During this compressional event, a part of the con tinental plate was subducted to a depth of more than 60 km (0.5 GPa, 250-35 0 degrees C to more than 2.0 GPa, 550 degrees C) resulting in progressive m etamorphism of the continental margin sediments, well exposed in the Saih H atat tectonic window, northeastern Oman Mountains. We attempt to constrain the possibility of one continuous history of extension (starting along the east Arabian continental margin in the Permian) that was followed by one co ntinuous history of convergence starting at 90 Ma near a dead oceanic ridge . This compression resulted in the observed progressive metamorphism by oph iolite overthrusting onto the continental margin. Constraining arguments ar e the palaeogeographic setting before ophiolite obduction of the As Sifah u nits and the Hawasina Complex near Ghurba. Detrital chromites in the Triass ic-Cretaceous metasediments of the Hawasina Complex are compared with magma tic Semail chromites, and the whole-rock chemistry of these metasediments a nd associated metabasites are investigated. In contrast to former hypothese s, differences in the chemical composition between detrital and magmatic ch romites, and the probable origin of all detrital chromites in the Hawasina Basin from Permian age oceanic rocks, suggest that the high-pressure metamo rphic sediments of As Sifah can be considered as part of the basal deposits of the Hawasina Basin.