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Journal of Iberian Geology

, Volume 43, Issue 1, pp 3–12 | Cite as

3-D distribution of the radioelements in the granitic rocks of northern and central Portugal and geothermal implications

  • R. Lamas
  • M. M. MirandaEmail author
  • A. J. S. C. Pereira
  • L. J. P. F. Neves
  • N. Ferreira
  • N. V. Rodrigues
Research Article
First Online:

Abstract

Purpose

The main purpose of this work is to study the distribution of radioelements in both horizontal and vertical directions within the main granitic units outcropping in northern and central Portugal in order to assess the main target for geothermal energy feasibility studies.

Methods

For that, a total of 314 samples collected in the surface as well as in the subsurface were analysed by gamma-ray spectrometry techniques.

Results

The results show that the older granitic units studied (syn-orogenic pre-D3) reveal smaller concentrations of both uranium (U = 4.5 mg/kg) and thorium (Th = 9.1 mg/kg) than the youngest units (late- to post-orogenic/post-D3). This last group presents an average concentration of 7.1 mg/kg for uranium and 21.0 mg/kg for thorium. The subsurface samples belong to the youngest granitic group that was studied, and present higher uranium concentration (U = 14.3 mg/kg) but a decrease in thorium concentration (Th = 17.5 mg/kg) in comparison with the surface samples of the same lithology. Within 1000 m in depth the concentration of radioelements has a remarkably constant pattern suggesting that the distribution of radioelements is not a function of depth.

Conclusions

Based on the results, it can be concluded that the late- to post-tectonic porphyritic, biotite or biotite-muscovite granite (e.g., Beiras Granitic Batholith) is the highest radiothermal granitic group in the studied area, which makes it the main target for more detailed studies regarding its potential for geothermal energy, for power production and others exploitation options in Central Portugal.

Keywords

Radioelements Granites Geothermal energy Central Iberian Zone Portugal 

Resumen

Objetivo

El objetivo principal de este trabajo es estudiar la distribución de radioelementos tanto en dirección horizontal como vertical dentro de las principales unidades graníticas aflorantes en el norte y centro de Portugal para evaluar cuál de ellas tiene más potencial para estudios de viabilidad de energía geotérmica.

Métodos

Para eso, un total de 314 muestras recogidas en la superficie así como en el subsuelo se analizaron mediante técnicas de espectrometría de rayos gamma.

Resultados

Los resultados muestran que las unidades graníticas más antiguas estudiadas revelan concentraciones más bajas de ambos, uranio (U = 4,5 mg/kg) y torio (Th = 9,1 mg/kg) que las unidades más recientes. Este último grupo se presenta con una concentración media de 7,1 mg/kg de uranio y 21,0 mg/kg para el torio. Las muestras de subsuelo pertenecen al grupo granítico más reciente y presentan un aumento en la concentración de uranio (U = 14,3 mg/kg), pero una disminución de torio (Th = 17,5 mg/kg) en comparación con las muestras superficiales de la misma litología. Hasta los 1000 m de profundidad la concentración de radioelementos tiene un padrón notablemente constante lo que sugiere que la distribución de los radioelementos no es una función de la profundidad.

Conclusiones

Con base en los resultados, se puede concluir que el granito profiroide, biotitico o biotitico-muscovitico tarde- a post-tectónico (e.g., Batolito Granítico das Beiras) es el grupo granítico más radiotérmico del área estudiada, lo que lo hace el principal objetivo de estudios más detallados sobre su potencial para la energía geotérmica, para la producción de energía y otras opciones de explotación en el centro de Portugal.

Palabras clave

Radioelementos granitos energía geotérmica Zona Centroibérica Portugal 
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Notes

Acknowledgements

This work has been framed under the Initiative Energy for Sustainability of the University of Coimbra and supported by the Energy and Mobility for Sustainable Regions Project (CENTRO-07-0224-FEDER-002004), co-funded by the European Regional Development Fund (ERDF) through the «Programa Operacional Regional do Centro 2007–2013 (PORC)», in the framework of the «Sistema de Apoio a Entidades do Sistema Científico e Tecnológico Nacional», and by the «Fundação para a Ciência e Tecnologia». The authors would like to acknowledge Prof. José António Simões Cortez and Câmara Municipal de Almeida for allowing the study of the borehole core, and Jorge Carvalho e Inês Pereira for their help in improving the manuscript.

References

  1. Basham, I. R., & Matos Dias, J. M. (1986). Uranium veins in Portugal. In International Atomic Energy Agency (Ed.), Vein type uranium deposits (pp. 181–191). Austria: International Atomic Energy Agency Technical Document.Google Scholar
  2. Boyle, R. W. (1982). Geochemical prospecting for thorium and uranium deposits. Amsterdam: Elsevier.Google Scholar
  3. Cabral Pinto, M. M. S., Silva, M. M. V. G., & Neiva, A. M. R. (2014). Release, migration, sorption and (re)precipitation of U during a granite alteration under oxidizing conditions. Procedia Earth and Planetary Science, 8, 28–32.CrossRefGoogle Scholar
  4. Chiozzi, P., Pasquale, V., & Verdoya, M. (2002). Heat from radioactive elements in young volcanics by γ-ray spectrometry. Journal of Volcanology and Geothermal Research, 119, 205–214.CrossRefGoogle Scholar
  5. Clauser, C. (2006). Geothermal energy. In K. Heinlot (Ed.), Energy technologies, subvolume C: Renewable energy. Numerical data and functional relationships in science and technology, group VIII: Advanced materials and technologies volume 3 (pp. 493–604). Berlin: Landolt-Börnstein, Springer.Google Scholar
  6. Dias, G., Leterrier, J., Mendes, A., Simões, P. P., & Bertrand, J. M. (1998). U–Pb zircon and monazite geochronology of post-collisional Hercynian granitoids from the Central Iberian Zone (Northern Portugal). Lithos, 45, 349–369.CrossRefGoogle Scholar
  7. Ferreira, N., Iglesias, M., Noronha, F., Pereira, E., Ribeiro, A., & Ribeiro, M. L. (1987). Granitoides da Zona Centro Iberica e seu enquadramento geodinâmico. In F. Bea, A. Carnicero, J. C. Gonzalo, M. López Plaza, & M. D. Rodríguez Alonso (Eds.), Geologia de los granitoides y rocas associadas del Macizo Hesperico (pp. 37–51). Madrid: Editorial Rueda.Google Scholar
  8. Ferreira, J. A., Ribeiro, M. A., & Martins, H. C. B. (2014). The Pedregal granite (Portugal): Petrographic and geochemical characterization of a peculiar granitoid. Estudios Geológicos, 70(2), 1–9.CrossRefGoogle Scholar
  9. Godinho, M. M., Pereira, A. J. S. C., & Neves, L. J. P. F. (1991). Potencial térmico das rochas graníticas num segmento do Maciço Hespérico (Portugal Central). Memórias e Notícias, 112, 469–483. (Publ. Mus. Lab. Mineral. Geol Univ. Coimbra).Google Scholar
  10. Jaupart, C., & Mareschal, J.-C. (2003). Constraints on crustal heat production from heat flow data. In R. Rudnick (Ed.), Treatise of geochemistry. The crust (Vol. 3, pp. 65–84). New York: Elsevier.CrossRefGoogle Scholar
  11. Jiménez-Díaz, A., Ruiz, J., Villaseca, C., Tejero, R., & Capote, R. (2012). The thermal state and strength of the lithosphere in the Spanish Central System and Tajo Basin from crustal heat production and thermal isostasy. Journal of Geodynamics, 58, 29–37.CrossRefGoogle Scholar
  12. Lachenbruch, A. H. (1970). Crustal temperature and heat production: Implications of the linear heat-flow relation. Journal of Geophysical Research, 75, 3291–3300.CrossRefGoogle Scholar
  13. LNEG. (2010). Carta Geológica de Portugal à escala 1:1000,000. ISBN: 978-989-675005-3.Google Scholar
  14. Martins, L., Gomes, E., Neves, L., Sousa, L., & Oliveira, A. (2010). Dados preliminares da radioactividade natural na região de Amarante (Norte de Portugal). VIII Congresso Nacional de Geologia, 13(14), 1–4.Google Scholar
  15. Mateus, A., & Noronha, F. (2010). Sistemas mineralizantes epigenéticos na Zona Centro-Ibérica; expressão da estruturação orogénica Meso- a Tardi-Varisca. In J. M. Cotelo Neiva, A. Ribeiro, M. Victor, F. Noronha, & M. Ramalho (Eds.), Geologia Aplicada. Ciências Geológicas: Ensino, Investigação e sua História (Vol. 2, pp. 47–61). Porto: Universidade do Porto.Google Scholar
  16. Pasquale, V., Verdoya, M., & Chiozzi, P. (2014). Geothermics: Heat flow in the lithosphere. Springer briefs in earth sciences. Berlin: Springer.CrossRefGoogle Scholar
  17. Pérez-Soba, C., Villaseca, C., Orejana, D., & Jeffries, T. (2014). Uranium-rich accessory minerals in the peraluminous and perphosphorous Belvís de Monroy pluton (Iberian Variscan belt). Contributions to Mineralogy and Petrology, 167(1008), 1–25.Google Scholar
  18. Plant, J. A., Reeder, S., Salminem, R., Smith, D. B., Tarvainen, T., De Vivo, B., et al. (2003). The distribution of uranium over Europe: Geological and environmental significance. Applied Earth Sciences, 112, 221–238.CrossRefGoogle Scholar
  19. Sams, M. S., & Thomas-Betts, A. (1988). 3-D numerical modelling of the conductive heat flow of SW England. Geophysical Journal, 92, 323–334.CrossRefGoogle Scholar
  20. Stober, I., & Bucher, K. (2013). Geothermal energy: From theoretical models to exploration and development. Berlin: Springer.CrossRefGoogle Scholar
  21. Tammemagi, H. Y., & Smith, N. L. (1975). A radiogeologic study of the granites of SW. England. Journal of the Geological Society of London, 131, 415–427.CrossRefGoogle Scholar
  22. Taylor, S. R., & McLennan, S. M. (1985). The continental crust: Its composition and evolution. Oxford: Blackwell Scientific Publishing.Google Scholar
  23. Teixeira, R. J. S., Gomes, M. E. P., Martins, L. M. O., Pereira, A. J. S. C., & Neves, L. J. P. J. (2014). Natural radiation and geochemistry of the Lamas de Olo biotite granite, northern Portugal. Goldschmidt Abstracts, 2014, 2458.Google Scholar
  24. Wheildon, J., Francis, M. F., Ellis, J. R. L., & Thomas-Betts, A. (1981). Investigation of the S.W. England thermal anomaly zone. Commission of the European Communities.Google Scholar

Copyright information

© Springer International Publishing Switzerland 2017

Authors and Affiliations

  1. 1.CEMMPRE – Centre of Mechanical Engineering Materials and Processes, Faculty of SciencesUniversity of PortoPortoPortugal
  2. 2.Department of Earth Sciences, CEMMPRE – Centre of Mechanical Engineering Materials and Processes, IMAR-Institute of Marine ResearchUniversity of CoimbraCoimbraPortugal
  3. 3.LNEG – Laboratório Nacional de Energia e GeologiaS. Mamede de InfestaPortugal

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