Electrical resistivity model of the crust and upper mantle from a magnetotelluric survey through the central Pyrenees

Abstract

SUMMARY An MT profile which roughly coincides with the south side of the ECORS-Pyrenees deep reflection seismic profile was made from the North Pyrenean zone through the central Pyrenees and Ebro basin. The periods recorded ranged from 0.0128s to 2000 s. Analysis of MT data shows a 2-D conductive structure. The strike direction of the structure is E-W, parallel to the Pyrenean chain. Interpretation of the data includes geomagnetic transfer functions and is constrained by some relevant geometric crustal features observed in seismic data. Accordingly, a 2-D resistivity cross-section has been obtained. The most striking results are: (1) detection of subvertical conductors in the upper crust coinciding with major fault zones; (2) detection of a deep, high-conductivity zohe at the contact between the Iberian and the European plates: (3) the fact that the European plate is thicker and more resistive than the Iberian one. Interpretation of the deep high conductivities suggests the existence of partial melting in the Pyrenees related to the subduction of the Iberian plate beneath Europe.