Electrical conductivity structure of northern Chilean subduction zone at 23°S from 2D magnetotelluric inversion
Abstract
The Chilean margin has been subjected to active subduction since at least the Jurassic. This process is a major element of the geodynamic evolution of the Andean orogen. Nowadays it is widely accepted that subduction is a key element to understand the development of arc magmatism and highly seismogenical zones. Fluid influx to the asthenospheric wedge drives a series of metamorphic reactions which changes the petrophysical properties of the medium, allowing methods like magnetotellurics (MT) to image zones where these reactions are taking place.
Northern Chile is seismologically and volcanically active, being inserted in the Central Volcanic Zone (CVZ) with important active volcanic centers such as Lascar volcano, and numerous seismic events like the 2007 Tocopilla earthquake. In this context, a long period magnetototelluric (LMT) survey was carried out in northern Chile (23°S). Stations were located in the forearc and arc every 5 to 10 km, following an almost W-E direction. Even though previous MT surveys have taken place in the area, these measurements were collected 30 years ago or have been recorded at other latitudes. In order to complement the measured data some of this previous stations are considered in the processing. Dimensionality analysis and a 2D inversion are performed to elucidate the electrical structure of the subduction zone and surrounding areas. The electrical structure of northern Chile is described by taking into account the geological information available in the zone, the magmatic characteristics of the CVZ, and deep metasomatic processes occurring in the subducted slab and asthenospheric wedge. This allows a better comprehension of the cortical structure up to depths of approximately 50 km.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.T31H0401R
- Keywords:
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- 7240 Subduction zones;
- SEISMOLOGYDE: 8170 Subduction zone processes;
- TECTONOPHYSICSDE: 8185 Volcanic arcs;
- TECTONOPHYSICSDE: 8413 Subduction zone processes;
- VOLCANOLOGY