Remnant of the ancient Farallon Plate breakup: A low-velocity body in the lower oceanic crust off Nicoya Peninsula, Costa Rica - evidence from wide-angle seismics - art. no. 1939

摘要

1] A seismic wide-angle section offshore Costa Rica is presented across the boundary between oceanic crust generated at the East Pacific rise (EPR) and at the Galapagos spreading center (GSC) as indicated by magnetic anomalies. This suture, where the Farallon plate broke up similar to 23 Ma ago, is marked by pronounced velocity variations throughout the crust including a low-velocity body in the lower crust. This body is well constrained by refracted waves above the inversion zone and by strong Pm P reflections from its lower boundary. The distinctness of this body and the local gravity field point to an igneous intrusion rather than serpentinized rock. Typical oceanic crust is found adjacent to the suture zone. [References: 11