Gemma Mitjanas, researcher from the University of Barcelona and member of the PIXIL project, gave a talk in the European Geosciences Union General Assembly (EGU) which took place from 19 to 30 April this year.
Under the title Multiscale fracture analysis of the Vallès fault zone in La Garriga-Samalús geotermal system, Gemma Mitjanas presented a study based on the analysis of the geothermal system in La Garriga-Samalús zone, located in the Catalan Coastal Ranges (CCR) (NE Spain). The analysis combines satellite pictures, field studies and laboratory measurements of both field and borehole samples.
In order to characterize fractures in depth, the samples have been digitized via photogrammetry method allowing the identification and characterization of the fractures sets at greater depths. The permeability differences between the fault core and the damage zone can be also identified in the borehole samples. Moreover, the presence of centimetric open fractures, cavities, and hydrothermal minerals, confirm the circulation of thermal fluids. Meanwhile, other samples within the fault trace are compact rocks, with slickensides and high-pressure alteration minerals.
These results have been also correlated with a previous 2D magnetotelluric (MT) model which shows the Vallès fault zone as a low resistivity unit (Mitjanas et al., 2021a). The fault zone may give a low resistivity value only if it is permeable and water saturated. Therefore, our results identify the damage zone of the Vallès fault as the potential reservoir of La Garriga-Samalús geothermal system.
More information about the study
a G. Mitjanas, J. Ledo, A. Macau, G. Alías, P. Queralt, F. Bellmunt, Ll. Rivero, A. Gabàs, A. Marcuello, B. Benjumea, A. Martí, S. Figueras (2021). Integrated seismic ambient noise, magnetotellurics and gravity data for the 2D interpretation of the Vallès basin structure in the geothermal system of La Garriga-Samalús (NE Spain). Geothermics, V 93, (2021), 102067. https://doi.org/10.1016/j.geothermics.2021.102067.