ORCID Profile
0000-0003-4081-7798
Current Organisation
University of Queensland
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Publisher: Elsevier BV
Date: 10-2023
Publisher: Copernicus GmbH
Date: 04-03-2021
DOI: 10.5194/EGUSPHERE-EGU21-9940
Abstract: & & La Garriga-Samal& #250 s geothermal system is located in the Catalan Coastal Ranges (CCR) (NE Spain). The CCR is a NE-SW horst and graben system with two lifted mountain chains, the Precoastal (PR) and Coastal ranges (CR), separated by the Vall& #232 s basin. An Hercynian highly fractured granodiorite thrusts the Paleozoic metamorphic units in the northern part of the PR. Towards the south, the intrusive unit is in contact with the Miocene rocks of the Vall& #232 s basin by a major Neogene normal fault, the Vall& #232 s fault.& & & & Previous works in this area showed that the fractured zone associated to the Vall& #232 s normal fault, located in the Hercynian granodiorite, could act as the geothermal reservoir as well as the fast-ascending path for the hot fluids. Although some geophysical prospections and exploration boreholes have been made in La Garriga-Samal& #250 s area, it is still necessary to understand and model the fracture network.& & & & This study presents a multiscale fracture analysis of the granodiorite from outcrops and boreholes s les. This multiscale analysis combines satellite pictures, field studies and laboratory measurements of both field and borehole s les.& & & & The fracture data collection has allowed the identification of 3 major fracture sets related to the main tectonic events of the CCR, in addition to 7 other minor fracture groups. Through the variation of fracture density in the footwall, a 10 meters fault core, and an asymmetric damage zone of approximately 300 m, have been identified. The damage zone shows an increasing fracture density towards the northern and southern limits of the granodiorite, which are an alpine thrust and the Vall& #232 s fault, respectively. In the fault core, the presence of cemented rocks like cataclasites with hydrothermal sealed fractures result in low porosity and permeability. Contrary, the damage zone consists of minor faults and related fractures which may enhance fault permeability with respect the core and its protolith.& & & & In order to characterize fractures in depth, the borehole s les have been digitized via photogrammetry method. The study of the point cloud related to this s les have allowed the identification and characterization of some 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 s les. The presence of centimetric open fractures, cavities, and hydrothermal minerals, confirm the circulation of thermal fluids. Meanwhile, other s les within the fault trace are compact rocks, with slickensides and high-pressure alteration minerals.& & & & These fracture results have been also correlated with a previous 2D magnetotelluric (MT) model which shows the Vall& #232 s fault zone as a low resistivity unit. 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 Vall& #232 s fault as the potential reservoir of La Garriga-Samal& #250 s geothermal system.& &
Publisher: Elsevier BV
Date: 06-2021
Publisher: Elsevier BV
Date: 2023
DOI: 10.2139/SSRN.4379484
Publisher: Elsevier BV
Date: 2024
Publisher: Instituto Geologico y Minero de Espana
Date: 09-2023
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-6769
Abstract: & & The Vall& #232 s geothermal system is located in the Catalan Coastal Ranges (CCR) (NE Spain). The CCR are formed by horst and graben structures limited by NE-SW and ENE-WSW striking normal faults, developed during the opening of the Valencia Trough (northwestern Mediterranean) (Gaspar-Escribano et al., 2004). In the Vall& #232 s Basin area, the thermal anomaly is located in the northeastern horst-graben limit, where a highly fractured Hercynian granodiorite is in contact with Miocene rocks by a major normal fault. This main structure seems to control the heat and the hot-water flow, nevertheless, the geological structure of this area, as well as the role of the Vall& #232 s normal fault, is poorly understood.& & & & Magnetotellurics and gravity methods together with a detailed geological map have been applied in this area to understand the main structure. Although the geophysical part makes up most of the study, we are also elaborating a detailed geological map of the area, making a fractures study at different scales. We are working with DEM alignments analysis, and fractures study from outcrops and thin sections.& & & & Our preliminary results in gravity show a strong gravity gradient in the NE-SW Vall& #232 s half-graben system and the recent MT profiles image the main fault of that system (Vall& #232 s normal fault). These results show a basin geometry with the major thickness of the basin towards the depocenter, disagreeing with the roll-over geometry assumed in previous works.& & & & Interpretations of the fractures study, together with geophysical data and models, have allowed a preliminary characterization of damage zones associated with the fault system, which are directly related to the fluid flow and the hot springs. The nature of this damage zones could be related to relay r s, commonly regarded as efficient conduits for fluid flow (Fossen and Rotevatn, 2016).& &
Location: Spain
No related grants have been discovered for Gemma Mitjanas.