ROTATION OF THE OMAN OPHIOLITE AND INITIAL LOCATION OF THE RIDGE IN THE HOTSPOT REFERENCE FRAME

The volcanic units of the Oman ophiolite were paleomagnetically studied in order to better constrain the large rotation of the nappe during emplacement suggested by previous paleomagnetic results. The volcanic sequence, going from pillow basalts extruded at the mid-oceanic ridge up to submarine lavas extruded during the oceanic thrusting, before the end of the obduction, displays components of magnetization which were acquired at various stages during the movement of the nappe on the sea floor. Paleomagnetic Euler Pole analysis shows that the movement can be modeled by a single, large rotation of about 145-150-degrees around an Euler pole located close to the nappe (less than 200 km away). Combining plate tectonic concepts, a mantle-anchored hotspot reference frame and paleomagnetic data, we were able to determine the initial paleolatitude (around 10-degrees-N), the initial paleolongitude (around 45-degrees-E) as well as the paleorientation (NNW-SSE to N-S) of the ridge in hotspot coordinates. The linear velocity of the nappe between the period of accretion at the ridge and the end of the obduction onto the Arabian peninsula would have been slightly less than 2 cm per year.