2026-06-29T01:17:02Zhttps://docta.ucm.es/rest/oai/request

oai:docta.ucm.es:20.500.14352/1242292025-09-24T12:38:52Zcom_20.500.14352_14col_20.500.14352_15

00925njm 22002777a 4500 dc García Rivas, Javier author Dias, Maria Isabel author Paiva, Isabel author Fernandes, Paula G. author Marques, Rosa author García Romero, Emilia author Suárez, Mercedes author 2025-08-07 This work aims to perform a detailed mineralogical, crystal-chemical, and geochemical characterization of bentonites from the Benavila outcrop, the largest known deposit of bentonites in continental Portugal. Bulk samples and different size fractions were characterized through X-Ray Diffraction (XRD). Structural formulae of the smectites were fitted from point analyses acquired by analytical electron microscopy (AEM) with transmission electron microscopy (TEM). Smectites are the major component with variable amounts of calcite and minor amounts of quartz, feldspar, illite, and chlorite. Occasionally, amphiboles and dolomite have also been identified. The high content of carbonates in different parts of the sampling area is related to the circulation of carbonate-rich fluids. The smectites present high-layer charge, are intermediate terms of the montmorillonite–beidellite series, and also show an intermediate cisvacant–transvacant configuration. Major and trace elements concentrations were determined by ICP-MS. The geochemical analysis of the samples indicates an enrichment in SiO2 and Al2O3 and a depletion of the more clayey materials in REE, HFSE, and Y, among others. The calculation of the PIA and CIA alteration indices, along with other parameters observed, shows the possible alteration pathways of the Benavila deposit. Research to evaluate the ability of these bentonites to be used as engineering barrier systems (EBS) and sealing materials for radioactive waste repositories is ongoing. García-Rivas, J., Dias, M. I., Paiva, I., Fernandes, P. G., Marques, R., García-Romero, E., & Suárez, M. (2025). Mineralogical and geochemical characterization of the benavila (Portugal) bentonites. Minerals, 15(8), 836. https://doi.org/10.3390/min15080836 10.3390/min15080836 https://hdl.handle.net/20.500.14352/124229 2075-163X https://doi.org/10.3390/min15080836 https://openpolicyfinder.jisc.ac.uk/id/publication/18600 Mineralogical and geochemical characterization of the Benavila (Portugal) bentonites