Dias, María IsabelSuárez Barrios, M.Prates, S.2014-10-282014-10-282003http://hdl.handle.net/10272/9003The igneous massif of Benavila (Portugal) is constituted by rocks of granitoid nature, especially granodiorites associated to quartzdiorites, partially covered with palaeogenic sediments. A chemical, mineralógicaI and textural characterisation of clay materials deriving from weathering of those rocks has been done. Clays resulting of the weathered granodiorites of Benavila, are very rich in smectites. The X-ray diffraction (XRD) results of the bulk sample enhance the clayey characteristics of those materials, mainly associated to calcite, and traces of quartz and feldspars. A monomineralic clay sample has been chosen for a more detailed study. The clay fraction XRD results enhance the presence of only smectite, that is well crystallized and dioctahedral. A structural formula for this smectite of Benavila is proposed. The chemical analysis points to a Tatatila smectite type, relatively enriched in iron. The exchange cation capacity has been calculated in the bulk sample and in the < 2 pm fraction. The Specific Surface area has been evaluated in the 77°K nitrogen adsorption-desorption isotherms, applying the BET method. A porosity study has also been made through the t-curves. The results obtained with all those analyses are lower than the usually presented in literaturespaAtribución-NoComercial-SinDerivadas 3.0 Españahttp://creativecommons.org/licenses/by-nc-nd/3.0/es/GeochemistryMineralogySmectite,BeidellitePortugalStructural formulaXRDIR-spectroscopySpecific surface areajournal articleopen access