Coroboration of magnetotelluric investigations with other geophysical anomalies for a case study located in North-West to central part of Romania

The results of the magnetoteluric investigations carried out along the profiles are presented in the form of sections in which the variations of the different parameters, the 2-D modeling, as well as the inversions.

The results of the geophysical researches (magnetotellurics, gravity, geomagnetics) obtained were aimed at obtaining a unitary image on the deep geological structure in the investigated area. A number of information was obtained regarding such as:

• Determination of the thickness of the package of formations belonging to the post-tectogenetic sedimentary cover of the Transylvanian Depression; sedimentary sedimentary cover, conductive, with a maximum thickness of approximately 4000 m in the Pannonian Depression;
• Contouring of the Tethysian Major Suture (near the town of Alba Iulia in the Transylvanian Basin), represented by the Transylvanian nappes system (ofiolitic complex and sedimentary formations), with resistivities of about 500 Ohm*m, which separates two blocks with continental crust of different thicknesses (22- 27 km for Internal Dacids and 32-36 km for Median Dacids);
• Highlighting the change of nappes systems belonging to the Transylvanians, with a wide development both to the north (Căpâlnas-Techereu nappes and the nappes of Groşi and Criş), as well as to the east (the ophiolite complex and sedimentary cover), over the Biharia nappes system, respectively Central-Eastern Carpathian nappes; extension of the Codru and Biharia - Arieşeni nappes, the last with higher resistivities (200 Ohm*m);
• Highlighting the transcrustal fault that marks the contact between the Inner Dacides and the Median ones;
• Individualization at the level of the lower crust of a transition zone; significant decrease of resistivity, as a consequence of the presence of the fluids in the transition zone, from the pressure in the pores from lithostatic type to the hydrostatic type (occurs at depths of 22 - 30 km and at temperatures of 350º - 400º C).

The electromagnetic data reflect the anomalies of electrical conductivity in a sensitive way, but due to the many causes that can generate them, a careful analysis of the particularities existing for each case, especially the superficial ones, was necessary.

The correlation of the all the information provided in sections (resistivity, phases, density, magnetic susceptibility), inversions, modeling, lead to the validation of the model.