Clay Material of an Eocene Deposit (Khanguet Rheouis, Tunisia): Identification Using Geochemical and Mineralogical Characterization

Abstract

AbstractDespite the numerous studies on geomaterials in Tunisia, quite a few clay varieties are not yet well defined. In fact no detailed geological, mineralogical, or geochemical characterizations of Tunisian palygorskite deposits have been carried out to date. The purpose of the present work was to study the continental Eocene clay deposit at the southern end of the Tunisian North axis, between Jebel Rheouis and Jebel Boudinar, to determine its potential as a clay reserve. Nine samples were collected from the Cherahil formation representing the lower, middle, and upper levels. The analytical results obtained using several techniques (chemical analysis, X-ray diffraction, specific surface area measurements, Fourier-Transform infrared spectroscopy, scanning electron microscopy) revealed that palygorskite is the dominant clay mineral. Dolomite and quartz are present as associated minerals. Chemical analysis of sample AR9 showed a smaller potassium content compared to other samples. Sample AR9 consists essentially of dolomite associated with palygorskite and quartz. Other samples (AR5, AR6, and AR7) collected from the same Cherahil formation contained palygorskite as the main phyllosilicate mineral (80%). The important reserve of palygorskite was found in the middle of the Cherahil formation. Dolomite and quartz associated with palygorskite reduced the length and crystallinity of the fibrous clay morphology. Analysis by scanning electron microscopy proved that the crystallinity of palygorskite was less in the lower and upper parts of the Cherahil formation. The central palygorskite deposit may be of interest for pharmaceutical (adsorbent drug) and other applications. The two other levels of Cherahil formation are mineralogically heterogeneous and considered economically less important than the middle level, which is rich in palygorskite.