Clay mineralogy, chemical and geotechnical characterization of bentonite from Beni Bou Ifrour Massif (the Eastern Rif, Morocco) H. Ait Hmeid 1 *, M. Akodad 1 , M. Aalaoul 2 , M. Baghour 1 , A. Moumen 1 , A. Skalli 1 , A. Anjjar 3 , P. Conti 4 , A. Sfalanga 4 , F. Ryazi Khyabani 4 , S. Minucci 5 and L. Daoudi 6 1 Laboratory Observatory of the Marchica Lagoon of Nador and Limiting Regions, Multidisciplinary Faculty of Nador, Mohamed 1st University, 60700 Nador, Morocco 2 Laboratory of Applied Geosciences, Faculty of Sciences of Oujda, Mohamed 1st University, 60000 Oujda, Morocco 3 Laboratory Géosciences and Environment, Faculty of Science and Technology, Sidi Mohmed Ben Abdellah University, BP2202, Fès-Atlas, Morocco 4 Laboratory of Prove, the Center of Geotechnology, University of Siena, Via Vetri Vecchi, 34-52027 San Giovanni Valdarno (AR), Italy 5 Department of Chemical and Geological Science, University of Cagliari, Cagliari, Italy 6 Laboratory of Geosciences and Environment, Department of Geology, Faculty of Science and Technology, University Cadi Ayyad, Marrakech, Morocco HAH, 0000-0002-4941-4373; AA, 0000-0002-1598-4204; PC, 0000-0001-5280-3460 *Correspondence: hanane.aithmeid@gmail.com Abstract: Bentonite clay mineral is widely present in the Gourougou Volcanic Massif and its satellites located in NE Morocco. It originated from the alteration of pyroclastic flows in shallow marine water in a lagoon lake environment (Ibourhardayn deposit). All studied samples were collected from that area and analysed accord- ingly in order to characterize and identify their components. Experimental techniques used included X-ray dif- fraction, Fourier transform infrared spectroscopy, X-ray fluorescence and the geotechnical characterization of the clay fraction and Atterberg limits. Granulometric analysis exhibited the presence of a clay fraction (,2 μm) ranging from 9.2 to 32.4%. The geotechnical study showed that the bentonites studied were generally very plas- tic, with plasticity index values ranging from 19.4 to 46.6%, and are also characterized by very high liquidity limits of 37.3–67%. A high water retention capacity with water contents ranging from 8.2 to 40.7% indicated that Ibourhardayn bentonites have important swelling properties. Mineralogical results showed that all speci- mens were mostly composed of montmorillonite alongside other clay minerals. Some crystalline impurities were also detected by X-ray diffraction and Fourier transform infrared spectra. Clay and clay minerals are considered as some of the oldest materials used by humans. In the modern world they are necessary for the manufacture of materials such as drilling fluids, ligands on casting moulds and precursor materials of organophilic clays, as well as for applications in vegetal and min- eral oil decolouration and deodorization (Mannu et al. 2019). Owing to their low cost, abundance, high sorption properties and ion exchange potential, clays are good candidates as pollutant adsorbents. The classification of clay and clay minerals is based on the differences in their layered structures (smectites, illites, kaolinites and such like; Reeves et al. 2006; Mannu et al. 2019). Bentonites consist essentially of a smectite clay mineral, which is composed of two silica sheets and one aluminium sheet (Fig. 1). The smectite mineral is divided into two subgroups: trioctahedra (hectorite, saponite and stevensite) and dioctahedra (montmorillonite, beidellite and nontronite). This particular group of minerals is characterized by the substitution of Si 4+ by Al 3+ , leaving uncompensated negative charges which are balanced by exchange- able interlayer cations (Na + , Ca 2+ , Mg 2+ ,H + , etc.). Depending on the dominant exchangeable cat- ions present, the clay may be referred to as calcium bentonite or sodium bentonite. Most bentonites are formed by the alteration of vitreous and pyroclastic ash flows, which are linked to explosive volcanism (Christidis and Scott 1997). Different bentonites are distinguished according to their mode of geo- logical formation, chemical and mineralogical com- position, grain size distribution, swelling and absorption rate, and geotechnical and textural From: Aïfa, T. (eds) 2020. Mineralization and Sustainable Development in the West African Craton: From Field Observations to Modelling. Geological Society, London, Special Publications, 502, https://doi.org/10.1144/SP502-2019-25 © 2020 The Author(s). Published by The Geological Society of London. All rights reserved. For permissions: http://www.geolsoc.org.uk/permissions. Publishing disclaimer: www.geolsoc.org.uk/pub_ethics by guest on March 21, 2020 http://sp.lyellcollection.org/ Downloaded from