Fluid and melt pathways in the central Chilean subduction zone near the 2010 Maule earthquake (35° ‐ 36° S) as inferred from magnetotelluric data
File(s)
Accepted version
Author(s)
Type
Journal Article
Abstract
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 over‐riding 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 down‐going 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 de‐serpentinization in the back‐arc. A resistor on the slab interface (R1) is coincident with a high‐velocity anomaly which was interpreted as a strong asperity which may affect the co‐seismic slip behavior of large megathrust earthquakes at this latitude. Correlations with seismicity suggest slab fluids alter the forearc mantle and define the down‐dip limit of the seismogenic zone. Beneath the volcanic arc, several upper crustal conductors (C4 and C5) represent partial melt beneath the Tatara‐San Pedro Volcano and the Laguna del Maule Volcanic Field. A deeper lower‐crustal conductor (C6) underlies both volcanoes and suggests a connected network of melt in a thermally‐mature lower crust.
Date Issued
2019-04-01
Date Acceptance
2019-03-27
Citation
Geochemistry, Geophysics, Geosystems, 2019, 20 (4), pp.1818-1835
ISSN
1525-2027
Publisher
American Geophysical Union (AGU)
Start Page
1818
End Page
1835
Journal / Book Title
Geochemistry, Geophysics, Geosystems
Volume
20
Issue
4
Copyright Statement
© 2019 American Geophysical Union. All rights reserved.
Subjects
Science & Technology
Physical Sciences
Geochemistry & Geophysics
SOUTHERN VOLCANIC ZONE
ARC MAGMATISM
FIELD
MEGATHRUST
ANDES
EVOLUTION
BENEATH
COMPLEX
SLAB
CONSEQUENCES
Geochemistry & Geophysics
04 Earth Sciences
02 Physical Sciences
Publication Status
Published
Date Publish Online
2019-04-01