Fluid and Melt Pathways in the Central Chilean Subduction Zone Near the 2010 Maule Earthquake (35–36°S) as Inferred From Magnetotelluric Data

Abstract

©2019. American Geophysical Union. All Rights Reserved.The subduction zone of central Chile (36°S) has produced some of the world's largest earthquakes and significant volcanic eruptions. Understanding the fluid fluxes and structure of the subducting slab and overriding plate can provide insight into the tectonic processes responsible for both seismicity and magmatism. Broadband and long-period magnetotelluric data were collected along a 350-km profile in central Chile and Argentina and show a regional geoelectric strike of 15 ± 19° east of north. The preferred two-dimensional inversion model included the geometry of the subducting Nazca plate as a constraint. On the upper surface of the Nazca plate, conductors were interpreted as fluids expelled from the downgoing slab via compaction at shallow depth (C1) and metamorphic reactions at depths of 40–90 km (C2 and C3). At greater depths (130 km), a conductor (C7) is interpreted as a region of partial melt related to deserpentinization in