The nature of subslab slow velocity anomalies beneath South America. Issue 10 (21st May 2017)

• Record Type: Journal Article
• Authors: Portner, Daniel Evan; Beck, Susan; Zandt, George; Scire, Alissa
• Is Part Of: Geophysical research letters. Volume 44:Issue 10(2017)
• Page Start: 4747
• Page End: 4755
• Publication Date: 2017-05-21
• Subjects: tomography -- hot spots -- subduction -- South America; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1002/2017GL073106
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Slow seismic velocity anomalies are commonly imaged beneath subducting slabs in tomographic studies, yet a unifying explanation for their distribution has not been agreed upon. In South America two such anomalies have been imaged associated with subduction of the Nazca Ridge in Peru and the Juan Fernández Ridge in Chile. Here we present new seismic images of the subslab slow velocity anomaly beneath Chile, which give a unique view of the nature of such anomalies. Slow seismic velocities within a large hole in the subducted Nazca slab connect with a subslab slow anomaly that appears correlated with the extent of the subducted Juan Fernández Ridge. The hole in the slab may allow the subslab material to rise into the mantle wedge, revealing the positive buoyancy of the slow material. We propose a new model for subslab slow velocity anomalies beneath the Nazca slab related to the entrainment of hot spot material. Key Points: A new regional P wave tomography model beneath Chile/Argentina shows a subslab slow velocity anomaly near the Pampean flat slab A hole in the slab reveals physical constraint on the nature of the imaged subslab slow velocity anomaly Correlation across South America between subducted hot spot ridges and subslab slows suggests a hot spot origin for the anomalies