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Calcretos da regiĆ£o de Elvas : Estudo preliminar
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Advisor(s)
Abstract(s)
RESUMO: A construĆ§Ć£o de uma via-fĆ©rrea no Nordeste Alentejano atravessando a Zona de Ossa-Morena permitiu estudos detalhados focados nas unidades geolĆ³gicas e na estrutura da Ć”rea. Na regiĆ£o de Elvas, o MiocĆ©nico Ć© representado por um conglomerado coberto por lutitos, mais grosseiro perto da falha de Messejana, onde apresenta basculamento tectĆ³nico. Os sedimentos e as rochas do substrato estĆ£o fortemente afetados pela calichificaĆ§Ć£o ocorrida no MiocĆ©nico, com observaƧƵes de campo a indicarem a ocorrĆŖncia de pelo menos dois episĆ³dios. A caracterizaĆ§Ć£o quĆmica dos calcretos ao longo de perfis verticais foi feita com fluorescĆŖncia de raio-X portĆ”til e repetida com o equivalente equipamento de laboratĆ³rio para 41% das amostras. Os resultados preliminares da amostragem em perfil de calichificaĆ§Ć£o do granito e dos sedimentos miocĆ©nicos sĆ£o apresentados e discutidos. As correlaƧƵes dos resultados obtidos pelas duas metodologias adotadas nĆ£o evidenciaram diferenƧas significativas, demonstrando a eficiĆŖncia do equipamento de FRX portĆ”til como ferramenta de campo.
ABSTRACT: The construction of a new railway in NE Alentejo crossing the Ossa-Morena Zone allowed new detailed studies focused on the geological units and the structure of the area. In the Elvas region, the Miocene is represented by a coarse conglomerate covered by sandy mudstones. The conglomerate is coarser near the Messejana fault, where it is also tilted. Its deposition is probably related to the Alpine reactivation of the fault. The sediments and the basement rocks, represented by granites, are strongly affected by Miocene calcretization, with field observations indicating at least two episodes. A chemical characterization of calcrete along vertical profiles was done with portable x-ray fluorescence equipment. Furthermore, 41% of the results were compared with laboratory XRF equipment. The preliminary results from the analysed profiles are presented and discussed. Correlations between results obtained with portable and laboratory equipment have shown no significant differences, indicating that portable XRF is a good field allied on rock characterization.
ABSTRACT: The construction of a new railway in NE Alentejo crossing the Ossa-Morena Zone allowed new detailed studies focused on the geological units and the structure of the area. In the Elvas region, the Miocene is represented by a coarse conglomerate covered by sandy mudstones. The conglomerate is coarser near the Messejana fault, where it is also tilted. Its deposition is probably related to the Alpine reactivation of the fault. The sediments and the basement rocks, represented by granites, are strongly affected by Miocene calcretization, with field observations indicating at least two episodes. A chemical characterization of calcrete along vertical profiles was done with portable x-ray fluorescence equipment. Furthermore, 41% of the results were compared with laboratory XRF equipment. The preliminary results from the analysed profiles are presented and discussed. Correlations between results obtained with portable and laboratory equipment have shown no significant differences, indicating that portable XRF is a good field allied on rock characterization.
Description
Keywords
Calcretos CalichificaĆ§Ć£o Granito Conglomerados Bacia do Guadiana Calcrete Calcretization Granite Conglomerates Guadiana basin
Pedagogical Context
Citation
Soares, S., Dias, R., RessurreiĆ§Ć£o, R., Morais, I., Albardeiro, L., GonƧalves, P., SolĆ”, R. & Castro-Pina, M. (2025). Calcretos da regiĆ£o de Elvas : Estudo preliminar. In: ComunicaƧƵes GeolĆ³gicas, 2025, vol. 112, FascĆculo Especial I, pp. 385-390. https://doi.org/10.34637/j0s5-vd55
Publisher
LNEG - LaboratĆ³rio Nacional de Energia e Geologia