Electromagnetic imaging of a transpressional tectonics in SW Iberia

Forty-one magnetotelluric soundings are carried out along a 200 kin-long pr ofile (approximately NNE-SSW) across the three major geotectonic units in S W Iberia. A model obtained from two-dimensional inversion of the magnetotel luric data set reveals high conductivity zones in the middle-lower crust (1 0-30 km). TWO Of these zones correspond to the transition between the main geotectonic units: one between the South Portuguese Zone and the Ossa Moren a Zone, interpreted as having been caused by metasediments, and the other b etween the Ossa Morena Zone and the Central Iberia Zone associated with a s hear zone and metasediments. Another high conductivity anomaly related to b lack shales with major graphite impregnation was detected within thr: Ossa Morena Zone. The resistive features, located preferentially in the upper cr ust (1-10 km), coincide with gabbroic and granitic complexes.