Layering in gabbroid rocks from semail ophiolit, United Arab Emirates : characterization, tectonic control on origin and orientation

الملخص EN

Layering is well pronounced in several exposures of gabbroid rocks within certain zones, subzones and horizons of the Semail ophiolite (Late-Cretaceous).

From Khor Kalba Horizon-Wadi Hatta Zone, southward to Khor Fakkan Zone, and northward passing through Bathnah Zone (Al-Fujairah-Masafi road), most layered gabbros appear to have formed with their layering steeply inclined to vertical ; horizontal layering is rarely observed.

It is probably formed in situ on cooling walls or plated onto the walls by density or convection currents (current deposition).

This mechanism, may however, not be responsible for the formation of all types of layering found in the present work.

Preferred orientations of magmatic flow structure "layering" are compatible to a large extent with the major structural trends identified in the United Arab Emirates.

The NW orientation (Hatta Zone-Wadi Ham trend), the NE orientation (Dibba Zone trend) and NS orientation (overthrusted Semail ophiolite nappe) are consistent with the major tectonic trends identified in the UAE.

This may lead to a better understanding of the orientation of layering that has been controlled by the regional tectonism and may be the dynamics of magma chambers at oceanic spreading center.