GEOLOGY OF OCEANOGRAPHER FRACTURE ZONE - MODEL FOR FRACTURE ZONES

An unreversed refraction experiment located 325 km west of the center of the Oceanographer transform and aligned along the axis of the fracture zone yielded information on the velocity structure of the crust within the fracture zone axis. A layer 2 km thick having a compressional wave velocity of 4. 4 km/s overlies a layer with a compressional wave velocity of 6. 5 km/s. The thickness of the lower layer is not precisely determined but is probably of the order of 4 km thick. It is suggested that the geology within fracture zones, especially large offset ones, is complex. As a function of changes in the pole of relative motion with time, there can be igneous intrusive contacts of varying ages and compositions, the zone of strain can change width and intensity, and metamorphic and structural contacts can be varied.