Fine structure of the lower oceanic crust on the Cocos Plate

摘要: Abstract From seismic refraction data on the Northern Cocos Plate, it is found that crust thickens with age. Assuming processes of crustal formation have remained constant over at least past 10 m.y., indicate thickening caused by a gradual transformation top 2 km upper mantle into material having crustal-like velocities. Serpentinization possible mechanism. The also suggest crust—mantle interface may be laterally variable, in some places being relatively sharp and others gradational. Upper anisotropy appears to decrease from about 0.6 km/sec near rise axis 0.3 m.y.