Abstract
To analyze the process of subduction of the Nazca and South American plates in the area of the Southern Andes, and its relationship with the tectonic and volcanic regime of the place, magnetotelluric measurements were made through a transversal profile of the Chilean continental margin. The data-processing stage included the analysis of dimensional parameters, which as first results showed a three-dimensional environment for periods less than 1 s and two-dimensional for periods greater than 10 s. In addition, through the geomagnetic transfer function (tipper), the presence of structural electrical anisotropy was identified in the data. After the dimensional analysis, a deep electrical resistivity image was obtained by inverting a 2D and a 3D model. Surface conductive anomalies were obtained beneath the central depression related to the early dehydration of the slab and the serpentinization process of the mantle that coincides in location with a discontinuity in the electrical resistivity of a regional body that we identified as the Nazca plate. A shallow conductive body was located around the Calbuco volcano and was correlated with a magmatic chamber or reservoir which in turn appears to be connected to the Liquiñe Ofqui fault system and the Andean Transverse Fault system. In addition to the serpentinization process, when the oceanic crust reaches a depth of 80–100 km, the ascending fluids produced by the dehydration and phase changes of the minerals present in the oceanic plate produce basaltic melts in the wedge of the subcontinental mantle that give rise to an eclogitization process and this explains a large conductivity anomaly present beneath the main mountain range.
Highlights
The Southern Andes constitute an orogenic mountain belt developed on an active continental margin, with subduction between the Nazca and South American tectonic plates as the main cause of the magmatic and tectonic processes in the area (Hervé, 1994)
The area of study is framed in the Southern Volcanic Zone of the Andes (SVZ), in this zone, the complex interaction between tectonic and magmatic processes is evident in the architecture and geochemical signature of the volcanic systems, and Cembrano and Lara (2009) relate this spatial distribution of plutons, dikes and volcanic cones, with the lithospheric stress generated by the Liquiñe Ofqui Fault System
The South of Chile represents an attractive place for a volcano-tectonic study; since it is located in an orogenic margin, with an important system of faults dominating the terrestrial crust and active volcanic centers, it appears as a favorable environment for the development of natural disasters related to volcanoes and earthquakes
Summary
The Southern Andes constitute an orogenic mountain belt developed on an active continental margin, with subduction between the Nazca and South American tectonic plates as the main cause of the magmatic and tectonic processes in the area (Hervé, 1994). The area of study is framed in the Southern Volcanic Zone of the Andes (SVZ), in this zone, the complex interaction between tectonic and magmatic processes is evident in the architecture and geochemical signature of the volcanic systems, and Cembrano and Lara (2009) relate this spatial distribution of plutons, dikes and volcanic cones, with the lithospheric stress generated by the Liquiñe Ofqui Fault System. The South of Chile represents an attractive place for a volcano-tectonic study; since it is located in an orogenic margin, with an important system of faults dominating the terrestrial crust and active volcanic centers, it appears as a favorable environment for the development of natural disasters related to volcanoes and earthquakes.
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