STRUCTURAL GEOLOGY OF THE MOHO AND SURROUNDING PART OF THE OMAN OPHIOLITE

Extensive flow and shear structures including mylonite, thrust faults, and folds were mapped and structurally analyzed in the Bat area on Wadi Zabin and its southern extension areas, Northern Oman Mountains.

Mylonitized and serpentinized peridotite are largely exposed at the bottom of the dome at Bat bounded by faults to W, and covered with massive and layered gabbro to E. Each rock body except for the later stage intrusive bodies is always associated with strong shear zones.

The mylonite and schist of ultramafic composition are developed in various fashions mostly parallel to the surrounding large structures. Small-scale isoclinal folds asymmetric folds and thrusts characterize the deformation both in the mylonite and shear zones.

NW structural trends are dominant, parallel to the spreading direction. The vergences of those structures are both towards SW and NE. Consideration of those structural characters, attitude and vergences indicate that the flow and shear structures occur at several stages, first under high temperature conditions to form ductile deformations, and later semi brittle deformations.

Those tendencies may indicate the early phase during spreading and later large stage converging tectonics, possibly at the obduction stage. However, there are more stages of oblique NE and E-W trending shear zones with dextral or sinistral slip. Such converging, or oblique shears are remarkable around the Moho horizon in the Northern Oman Ophiolite.

Key wards: Northern Oman Ophiolite, Moho, mylonite, shear zones ductile deformations, brittle deformations.