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Fluid and melt pathways in the central Chilean subduction zone near the 2010 Maule Earthquake (35–36°S) as inferred from magnetotelluric data

Fluid and melt pathways in the central Chilean subduction zone near the 2010 Maule Earthquake (35–36°S) as inferred from magnetotelluric data
Fluid and melt pathways in the central Chilean subduction zone near the 2010 Maule Earthquake (35–36°S) as inferred from magnetotelluric data

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 the backarc. 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 coseismic slip behavior of large megathrust earthquakes at this latitude. Correlations with seismicity suggest slab fluids alter the forearc mantle and define the downdip 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.

Chile, fluid flux, magnetotellurics, Maule earthquake, subduction zone, volcanism
1525-2027
Cordell, Darcy
45b4eb9c-3dbb-44b0-b3dc-2e1ceff38f19
Unsworth, Martyn J.
204f6ab9-260e-4203-8261-305473cce130
Diaz, Daniel
62d55e9d-8f13-4544-bd25-d39b3afb1591
Reyes-Wagner, Valentina
201fa0ad-450c-46f8-ac0b-a1e430373a54
Currie, Claire A.
43cbddfd-04df-4caf-a9da-53353229d878
Hicks, Stephen P.
036d1b3b-bb7a-4a22-b2ce-71618a1723a3
Cordell, Darcy
45b4eb9c-3dbb-44b0-b3dc-2e1ceff38f19
Unsworth, Martyn J.
204f6ab9-260e-4203-8261-305473cce130
Diaz, Daniel
62d55e9d-8f13-4544-bd25-d39b3afb1591
Reyes-Wagner, Valentina
201fa0ad-450c-46f8-ac0b-a1e430373a54
Currie, Claire A.
43cbddfd-04df-4caf-a9da-53353229d878
Hicks, Stephen P.
036d1b3b-bb7a-4a22-b2ce-71618a1723a3

Cordell, Darcy, Unsworth, Martyn J., Diaz, Daniel, Reyes-Wagner, Valentina, Currie, Claire A. and Hicks, Stephen P. (2019) Fluid and melt pathways in the central Chilean subduction zone near the 2010 Maule Earthquake (35–36°S) as inferred from magnetotelluric data. Geochemistry, Geophysics, Geosystems. (doi:10.1029/2018GC008167).

Record type: 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 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 the backarc. 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 coseismic slip behavior of large megathrust earthquakes at this latitude. Correlations with seismicity suggest slab fluids alter the forearc mantle and define the downdip 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.

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Accepted/In Press date: 27 March 2019
e-pub ahead of print date: 1 April 2019
Keywords: Chile, fluid flux, magnetotellurics, Maule earthquake, subduction zone, volcanism

Identifiers

Local EPrints ID: 431058
URI: https://eprints.soton.ac.uk/id/eprint/431058
ISSN: 1525-2027
PURE UUID: 986930d1-5a7a-48ac-a646-5ad88288a272
ORCID for Stephen P. Hicks: ORCID iD orcid.org/0000-0002-7476-3284

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Date deposited: 22 May 2019 16:30
Last modified: 02 Oct 2019 04:01

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Contributors

Author: Darcy Cordell
Author: Martyn J. Unsworth
Author: Daniel Diaz
Author: Valentina Reyes-Wagner
Author: Claire A. Currie
Author: Stephen P. Hicks ORCID iD

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