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Pure and Applied Geophysics

, Volume 175, Issue 6, pp 2153–2165 | Cite as

Three-Dimensional Electrical Resistivity Image of the Volcanic Arc in Northern Chile—An Appraisal of Early Magnetotelluric Data

  • Christine Kühn
  • Heinrich Brasse
  • Gerhard Schwarz
Article

Abstract

Magnetotelluric investigations were carried out in the late 1980s across all morphological units of the South American subduction zone with the aim to observe lithosphere structures and subduction-induced processes in northern Chile, southwestern Bolivia, and northwestern Argentina at ~ 22°S. Earlier two-dimensional forward modeling yielded a complex picture of the lower crust and upper mantle, with strong variations between the individual morphological units as well as between forearc and backarc. The principal result was a highly conductive zone beneath the volcanic arc of the Western Cordillera starting at ~ 25 km depth. Goal of this work is to extend the existing 2-D results using three-dimensional modeling techniques at least for the volcanic arc and forearc region between 22°S and 23°S in Northern Chile. Dimensionality analysis indicates strong 3-D effects along the volcanic arc at the transition zone to the Altiplano, in the Preandean Depression and around the Precordillera Fault System at ~ 22°S. In general, the new 3-D models corroborate previous findings, but also enable a clearer image of lateral resistivity variations. The magmatic arc conductor emerges now as a trench-parallel, N–S elongated structure slightly shifted to the east of the volcanic front. The forearc appears highly resistive except of some conductive structures associated with younger sedimentary infill or young magmatic record beneath the Precordillera and Preandean Depression. The most prominent conductor in the whole Central Andes beneath the Altiplano and Puna is also modeled here; it is, however, outside the station array and thus poorly resolved in this study.

Keywords

Magnetotellurics 3-D inversion Volcanic arc Central Andes Subduction zones 

Notes

Acknowledgements

We are grateful to Gary Egbert, Anna Kelbert, and Naser Meqbel for providing the freely available ModEM software and Naser Meqbel for his grid and data editor (3D\(\_\)Grid academic). Comments by two anonymous reviewers helped to improve the manuscript.

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Copyright information

© Springer International Publishing AG, part of Springer Nature 2017

Authors and Affiliations

  1. 1.Freie Universität Berlin, Fachrichtung GeophysikBerlinGermany
  2. 2.Geological Survey of SwedenUppsalaSweden

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