Assessment of Chaves Low-Temperature CO2-Rich Geothermal System (N-Portugal) Using an Interdisciplinary Geosciences Approach
This paper reviews the results of a multi- and interdisciplinary approach, including geological, geomorphological, tectonic, geochemical, isotopic, and geophysical studies, on the assessment of a Chaves low-temperature (77°C) CO2-rich geothermal system, occurring in the northern part of the Portugue...
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Wiley
2019-01-01
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| Series: | Geofluids |
| Online Access: | http://dx.doi.org/10.1155/2019/1379093 |
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| author | J. M. Marques P. M. Carreira L. A. Aires-Barros F. A. Monteiro Santos M. Antunes da Silva P. Represas |
| author_facet | J. M. Marques P. M. Carreira L. A. Aires-Barros F. A. Monteiro Santos M. Antunes da Silva P. Represas |
| author_sort | J. M. Marques |
| collection | DOAJ |
| description | This paper reviews the results of a multi- and interdisciplinary approach, including geological, geomorphological, tectonic, geochemical, isotopic, and geophysical studies, on the assessment of a Chaves low-temperature (77°C) CO2-rich geothermal system, occurring in the northern part of the Portuguese mainland. This low-temperature geothermal system is ascribed to an important NNE-trending fault, and the geomorphology is dominated by the “Chaves Depression,” a graben whose axis is oriented NNE-SSW. The study region is situated in the tectonic unit of the Middle Galicia/Trás-os-Montes subzone of the Central Iberian Zone of the Hesperic Massif comprising mainly Variscan granites and Paleozoic metasediments. Chaves low-temperature CO2-rich geothermal waters belong to the Na-HCO3-CO2-rich-type waters, with pH≈7. Total dissolved solids range between 1600 and 1850 mg/L. Free CO2 is of about 500 mg/L. The results of SiO2 and K2/Mg geothermometers give estimations of reservoir temperature around 120°C. δ18O and δ2H values of Chaves low-temperature CO2-rich geothermal waters indicate a meteoric origin for these waters. No significant 18O-shift was observed, consistent with the results from the chemical geothermometry. δ13CCO2 values vary between −7.2 and −5.1‰ vs. V-PDB, and CO2/3He ratios range from 1×108 to 1×109, indicating a deep (upper mantle) source for the CO2. 3He/4He ratios are of about 0.9 (R/Ra). The Chaves low-temperature CO2-rich geothermal waters present similar 87Sr/86Sr ratios (between 0.728035 and 0.716713) to those of the plagioclases from granitic rocks (between 0.72087 and 0.71261) suggesting that water mineralization is strongly ascribed to Na-plagioclase hydrolysis. Geophysical methods (e.g., resistivity and AMT soundings) detected conductive zones concentrated in the central part of the Chaves graben as a result of temperature combined with the salinity of the Chaves low-temperature CO2-rich geothermal waters in fractured and permeable rock formations. This paper demonstrates the added value of an integrated and multi- and interdisciplinary approach for a given geothermal site characterization, which could be useful for other case studies linking the assessment of low-temperature CO2-rich geothermal waters and cold CO2-rich mineral waters emerging in a same region. |
| format | Article |
| id | doaj-art-5af9465c6f8d48b1be89b6c40a650ce3 |
| institution | Kabale University |
| issn | 1468-8115 1468-8123 |
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| spelling | doaj-art-5af9465c6f8d48b1be89b6c40a650ce32025-02-03T05:45:04ZengWileyGeofluids1468-81151468-81232019-01-01201910.1155/2019/13790931379093Assessment of Chaves Low-Temperature CO2-Rich Geothermal System (N-Portugal) Using an Interdisciplinary Geosciences ApproachJ. M. Marques0P. M. Carreira1L. A. Aires-Barros2F. A. Monteiro Santos3M. Antunes da Silva4P. Represas5Instituto Superior Tecnico (CERENA/IST), Universidade de Lisboa, Av. Rovisco Pais 1049-001 Lisboa, PortugalCentro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico (C2TN/IST), Universidade de Lisboa, Estrada Nacional 10, ao km 139, 7 2695-066 Bobadela LRS, PortugalInstituto Superior Tecnico (CERENA/IST), Universidade de Lisboa, Av. Rovisco Pais 1049-001 Lisboa, PortugalUniversidade de Lisboa-DEGGE-IDL, Campo Grande Ed. C8, 1749-016 Lisboa, PortugalSuper Bock Group, Apartado 1044, 4466-955 S. Mamede de Infesta, PortugalLaboratório Nacional de Energia e Geologia, Estrada da Portela, Bairro do Zambujal, Apartado 7586-Alfragide 2610-999 Amadora, PortugalThis paper reviews the results of a multi- and interdisciplinary approach, including geological, geomorphological, tectonic, geochemical, isotopic, and geophysical studies, on the assessment of a Chaves low-temperature (77°C) CO2-rich geothermal system, occurring in the northern part of the Portuguese mainland. This low-temperature geothermal system is ascribed to an important NNE-trending fault, and the geomorphology is dominated by the “Chaves Depression,” a graben whose axis is oriented NNE-SSW. The study region is situated in the tectonic unit of the Middle Galicia/Trás-os-Montes subzone of the Central Iberian Zone of the Hesperic Massif comprising mainly Variscan granites and Paleozoic metasediments. Chaves low-temperature CO2-rich geothermal waters belong to the Na-HCO3-CO2-rich-type waters, with pH≈7. Total dissolved solids range between 1600 and 1850 mg/L. Free CO2 is of about 500 mg/L. The results of SiO2 and K2/Mg geothermometers give estimations of reservoir temperature around 120°C. δ18O and δ2H values of Chaves low-temperature CO2-rich geothermal waters indicate a meteoric origin for these waters. No significant 18O-shift was observed, consistent with the results from the chemical geothermometry. δ13CCO2 values vary between −7.2 and −5.1‰ vs. V-PDB, and CO2/3He ratios range from 1×108 to 1×109, indicating a deep (upper mantle) source for the CO2. 3He/4He ratios are of about 0.9 (R/Ra). The Chaves low-temperature CO2-rich geothermal waters present similar 87Sr/86Sr ratios (between 0.728035 and 0.716713) to those of the plagioclases from granitic rocks (between 0.72087 and 0.71261) suggesting that water mineralization is strongly ascribed to Na-plagioclase hydrolysis. Geophysical methods (e.g., resistivity and AMT soundings) detected conductive zones concentrated in the central part of the Chaves graben as a result of temperature combined with the salinity of the Chaves low-temperature CO2-rich geothermal waters in fractured and permeable rock formations. This paper demonstrates the added value of an integrated and multi- and interdisciplinary approach for a given geothermal site characterization, which could be useful for other case studies linking the assessment of low-temperature CO2-rich geothermal waters and cold CO2-rich mineral waters emerging in a same region.http://dx.doi.org/10.1155/2019/1379093 |
| spellingShingle | J. M. Marques P. M. Carreira L. A. Aires-Barros F. A. Monteiro Santos M. Antunes da Silva P. Represas Assessment of Chaves Low-Temperature CO2-Rich Geothermal System (N-Portugal) Using an Interdisciplinary Geosciences Approach Geofluids |
| title | Assessment of Chaves Low-Temperature CO2-Rich Geothermal System (N-Portugal) Using an Interdisciplinary Geosciences Approach |
| title_full | Assessment of Chaves Low-Temperature CO2-Rich Geothermal System (N-Portugal) Using an Interdisciplinary Geosciences Approach |
| title_fullStr | Assessment of Chaves Low-Temperature CO2-Rich Geothermal System (N-Portugal) Using an Interdisciplinary Geosciences Approach |
| title_full_unstemmed | Assessment of Chaves Low-Temperature CO2-Rich Geothermal System (N-Portugal) Using an Interdisciplinary Geosciences Approach |
| title_short | Assessment of Chaves Low-Temperature CO2-Rich Geothermal System (N-Portugal) Using an Interdisciplinary Geosciences Approach |
| title_sort | assessment of chaves low temperature co2 rich geothermal system n portugal using an interdisciplinary geosciences approach |
| url | http://dx.doi.org/10.1155/2019/1379093 |
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