Subduction of the Chile Ridge: Upper mantle structure and flow

Abstract

Arrival times for the P waves were determined via a multi-channel cross-correlation procedure that makes use of the duplicate information obtained by cross-correlating all possible pairs of waveforms (VanDecar and Crosson, 1990; VanDecar et al., 2003). This procedure produces both

Tomographic evidence for a slab tear induced by fossil ridge subduction at Manila Trench, South China Sea

“…Based on body-wave travel-time tomography, the P-wave structure of the subducted Chile Ridge between the Nazca and Antarctic plates shows a distinct low-velocity zone relative to surrounding asthenospheric mantle. It is inferred as being filled by unusually warm asthenosphere, consistent with subduction of the Chile Ridge (Russo et al 2010). In addition, aseismic ridge subduction has been linked with other considerable changes in the geometry and kinematics of both the subducting and overriding plates, such as reduction of the slab dip or a gap in arc volcanism (Rosenbaum and Mo 2011;Martinod et al 2013).…”

“…Usually, the occurrence of ridge subduction is associated with interpretations of slab tear or the formation of a slab window (e.g. Thorkelson and Taylor 1989;Madson et al 2006;Zandt and Humphreys 2008;Russo et al 2010). Based on body-wave travel-time tomography, the P-wave structure of the subducted Chile Ridge between the Nazca and Antarctic plates shows a distinct low-velocity zone relative to surrounding asthenospheric mantle.…”

Trace element indiscrimination diagrams

“…The ages of samples of CFB and OPB vary from Permian to Cretaceous. We excluded several suites of samples: Columbia River flood basalts in the western United States because subduction processes may have played a critical role in their genesis (e.g., Liu and Stegman, 2012;Cabato et al, 2015); samples from the Azores, Galápagos and Iceland because a plume may have interacted with the ridge at these locations (e.g., Shorttle et al, 2010;and A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT 5 samples from the Chile and Mendocino triple junction areas because their compositions may have been affected by ridge subduction (e.g., Russo et al, 2010;Thorkelson et al, 2011). The selected samples are further divided into two series, alkaline and subalkaline, using the classification of MacDonald and Katsura (1964).…”

Seismicity distribution in the vicinity of the Chile Triple Junction, Aysén Region, southern Chile

“…Using teleseismic arrivals of S-waves radiated from six of the largest events of the 2007 Aysén seismic sequence, Russo et al (2010b) studied shear wave splitting and upper mantle flow of this region. Their results show a transition from the generally NeStrending fast shear wave azimuths north of the CTJ, to ENE-trending azimuths in the area of the asthenospheric slab window mentioned before.…”