Evidence of upper-mantle processes related to continental rifting versus oceanic crust in the Gulf of California

摘要

Receiver functions from teleseismic events, recorded by stations around the Gulf of California,udare used to map the upper-mantle seismic discontinuities. We observe a mean transition zoneudthickness comparable to the global average for most of the region. A low-velocity layer isuddetected above the 410 discontinuity that varies in thickness along the Gulf of California. Theud660 discontinuity shows complex waveforms south of latitude 30◦N as a result of the phaseudchange of garnet to perovskite. Within the transition zone, a complex behaviour of the receiverudfunctions is observed mainly at the southern end of the Gulf. The north–south variations ofudthis zone are likely associated with a slab window at the northern Gulf, resulting from theudcessation of subduction of the Farallon plate 12 Ma, and the subduction of the Guadalupe andudMagdalena microplates at the southern end, resulting in a hydrated upper mantle. Our resultsudsuggest that change in rifting styles occurring along the Gulf of California mirrors deeperudprocesses in the upper mantle.