Deep TDEM Study for Structural and Mining Purposes: A Case Study of the Barbastro Saline-Evaporitic Formation, Spain

The objective of this study was to obtain the deep subsurface structure of a saline-evaporitic formation affected by an anticlinal structure, defining the position and thickness for its future exploitation (potassium salts). To improve this knowledge, geophysical methods can be applied to establish detailed information on geological structures at depth. This work analyzes the results of a deep time domain electromagnetic (TDEM) survey acquired over the southern flank of the Barbastro-Balaguer Anticline present in the Ebro Basin in the vicinity of Graus (Huesca, Spain), that controls the geometry of the Barbastro saline-evaporitic formation, of interest from the mining point of view. A deep time domain electromagnetic system (TDEM) is used, providing a penetration capability down to 3.0 km depth. A parametric constrained inversion over a lithological known borehole (Monzón-1) is used to obtain a resistivity model and then applied to the rest of the survey points. The applied methodology contributes to improving the geological knowledge, revealing a new detailed geological structure of the Barbastro saline-evaporitic formation affected by the Barbastro-Balaguer Anticline. The survey shows that the Barbastro saline-evaporitic formation presents a structure with a ramp hanging wall and close to flat footwall, generally dipping to the SW, with a decreasing thickness from 1103 m to 601 m, in concordance with the previous accepted geological structural model. The new geophysical study provides essential data, allowing design and drilling optimization in future mining exploitations.