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Calcretos da região de Elvas : Estudo preliminar
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Advisor(s)
Abstract(s)
RESUMO: A construção de uma via-férrea no Nordeste Alentejano atravessando a Zona de Ossa-Morena permitiu estudos detalhados focados nas unidades geológicas e na estrutura da área. Na região de Elvas, o Miocénico é representado por um conglomerado coberto por lutitos, mais grosseiro perto da falha de Messejana, onde apresenta basculamento tectónico. Os sedimentos e as rochas do substrato estão fortemente afetados pela calichificação ocorrida no Miocénico, com observações de campo a indicarem a ocorrência de pelo menos dois episódios. A caracterização química dos calcretos ao longo de perfis verticais foi feita com fluorescência de raio-X portátil e repetida com o equivalente equipamento de laboratório para 41% das amostras. Os resultados preliminares da amostragem em perfil de calichificação do granito e dos sedimentos miocénicos são apresentados e discutidos. As correlações dos resultados obtidos pelas duas metodologias adotadas não evidenciaram diferenças significativas, demonstrando a eficiência do equipamento de FRX portátil 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 Calichificação Granito Conglomerados Bacia do Guadiana Calcrete Calcretization Granite Conglomerates Guadiana basin
Pedagogical Context
Citation
Soares, S., Dias, R., Ressurreição, R., Morais, I., Albardeiro, L., Gonçalves, P., Solá, R. & Castro-Pina, M. (2025). Calcretos da região de Elvas : Estudo preliminar. In: Comunicações Geológicas, 2025, vol. 112, Fascículo Especial I, pp. 385-390. https://doi.org/10.34637/j0s5-vd55
Publisher
LNEG - Laboratório Nacional de Energia e Geologia