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Aeromagnetic anomalies in mainland Portugal and their tectonic implications

1989; Elsevier BV; Volume: 95; Issue: 1-2 Linguagem: Inglês

10.1016/0012-821x(89)90174-x

1385-013X

J. M. Miranda, A. Galdéano, J. C. Rossignol, L. A. Mendes Victor,

Geological and Geochemical Analysis

The aeromagnetic anomaly map for mainland Portugal shows a clear zonation correlated with the main structural units of the Hercynian foldbelt. Four zones can be distinguished from south to north: the South Portuguese Zone (SPZ) marked by small-amplitude negative anomalies of medium to large wavelength, the Ossa Morena Zone (OMZ) with medium positive amplitudes (about 100 nT) of short wavelength, the Centro Iberian Zone (CIZ) with low magnetic anomalies and, finally, the Galicia-Trás-os-Montes Subzone (GTS) corresponding to a negative regional anomaly. The limits of these zones are in agreement with those described by geologists except for the western border of the CIZ which does not have any magnetic signature in this new survey. The good correlation between neotectonics and magnetic anomalies confirms the role of Hercynian tectonics in understanding recent movements. The lack of magnetic response of the supposed great shear along the Odemira-Avila fault is noticeable. Last, the isolated anomalies associated with Cretaceous volcanism underline the southwest limit of the Iberian peninsula.