P. Schmoldt, PhD - MTNet - DIAS

7. Geology of the Iberian Peninsula
crystalline rocks, whereas seismic and xenolith studies indicate that the middle and lower
crust consist of felsic intrusives and granulites, respectively. Since no seismic activity was
recorded below the middle crust, it is likely that the lower crust, is an incompetent, ductile
layer between the mantle and the other crustal layers.
Faults with an approximately N45W direction intersect the PICASSO Phase I profile
in the proximity of stations pic005, pic009, and pic013, potentially yielding a respective
geoelectric strike direction in MT data of shorter periods. Material interfaces at crustal
depth below the Tajo Basin, as interred from seismic studies, coincide with the borders
of the Betic Cordillera and the Iberian Range. The respective ENE-WSW and NW-SE
orientation of the interfaces indicate different geoelectric strike directions for the northern
and southern parts of the PICASSO Phase I profile (cf. Sec. 9.6.1). Furthermore, since the
low velocity feature, occurring slightly north of the Betic Cordillera, reaches down to at
least 200 km, whereas the anomaly associated with the Iberian Range cannot be observed
at depths greater than 53 km, it is likely that the geoelectric strike direction in the Tajo
Basin below the PICASSO Phase I profile will also change with depth.
Seismic tomography studies further derive low velocity structures at crustal depth beneath
Betic Cordillera and Alboran Sea, in the mid- and lower crust beneath in the Campo
de Montiel region, and an extensive low velocity region located approximately 50 km to
350 km beneath the Tajo Basin. Different settings could explain such decreases of velocity,
e.g. increased temperature, different chemistry, and the presence of partial melt or
fluids. Investigation of the electric conductivity distribution in this region will add further
constraints on this issue and might help to better understand the geological setting and the
related tectonic evolution.
In addition, results of the PICASSO Phase I investigation can help to reassess the
stratigraphy of Tajo Basin and Betic Cordillera as deduced from seismic reflection and
refraction studies. Formation of proposed Miocene folding and the depth extend of faults
in the Tajo Basin may also be evaluated using results of this study. Further, the currently
unknown eastward extent of the Iberian Massif beneath the Tajo Basin, in the region of
the Manchega Plain, can be investigated given the significantly higher resistivity of the
Iberian Massif.
At deeper regions, it can be tested whether an uppermost electric asthenosphere layer
with values of approximately 10 Ωm (proposed for the Betics region) is observable beneath
central Iberia, or whether a more resistive upper mantle (as suggested by laboratory
studies) satisfies the responses. If the location of the eLAB can be derived for the study
area, its relative position in respect to the estimates for sLAB and tLAB in the region
can be used to enhance knowledge about the local geological processes. Furthermore, by
contrasting results of MT, seismic, and thermal studies conclusions can be drawn about
composition and condition of the south-central Iberian Peninsula subsurface.
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