Mineralogy and plasticity in clay sediments from north-east Tunisia

Journal of African Earth Sciences (Impact Factor: 1.38). 04/2010; 57(1/2):41-46. DOI: 10.1016/j.jafrearsci.2009.07.007


Several cross-sections carried out in the Bir M'Cherga area (northern Tunisia) provided a complete Trias-sic–Miocene stratigraphic sequence, rather representative of the whole Tunisian Ridge Field located in the northern Atlas. Mineralogical analysis revealed a predominance of illite in the Early Cretaceous, while smectite is dominant in the Late Cretaceous and Tertiary. In terms of Atterberg limits, the Bir M'Cherga samples can be divided into two groups: one of moderately plastic clay samples until the Early Creta-ceous, and another represented by the Late Cretaceous and Tertiary clays, which are the most plastic. As expected, the Atterberg limits increase with the amount of phyllosilicates present in the sample, which is dependent on the amount of smectite. This analysis was complemented by the use of the equiv-alent basal spacing (EBS) parameter, which gives a good correlation between the mineralogical character-istics of the clays and their plasticity. Using EBS, we can predict the mechanical/plastic behaviour of any clay sample according to its mineralogical composition.

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    • "According to literature, several factors have been suggested to be responsible for the plasticity behavior of soils and sediments, such as particle size distribution, clay content, clay mineral composition, the effect of diagenesis, presence of amorphous clay-size materials, and organic matter (Wan et al., 2002; de Oliveira Modesto and Bernardin, 2008; Hajjaji et al., 2010). Thus, identifying the respective influences of these parameters on the plasticity behavior of the sedimentary material is difficult. "
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    ABSTRACT: Seven samples (MB2 to MB8) collected from the clays and silty clays formations belonging to the Paleogene sedimentary series of the Plateau du Kik (Western High Atlas, Morocco) were characterized for granulometric analysis, mineral composition, clay composition and textures and for Atterberg limits. All the studied samples are classified asMH–OH type soils according to the ASTMinternational standard. Palygorskite usually constitutes themore abundantmineral phase in all the samples (35 to 64). The liquid limit for themost samples iswell above 50 indicating the highly plastic nature of the studied sediment. Thiswork clearly evidences that fibrous clay rich clayey materials having similar grain distribution and identicalmineral composition and contents can have very different plasticity behaviors. This suggests that the fibrous clay textures play a role of prime importance in the plasticity behavior of the studied materials.
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    • "Furthermore, the Tunisian clay formations have been the subject of several studies and geological researches (e.g. Agafonoff and Jouravsky, 1934; Jamoussi, 2001; Grabowska- Olszewska, 2003; Jamoussi et al., 2003; Felhi et al., 2008; Jeridi, 2008; Jeridi et al., 2008; Mahmoudi et al., 2008; Hajjaji et al., 2010; Mahmoudi et al., 2010). "
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    ABSTRACT: The geological study of Miocene clays from Gram area, North West of Tunisia shows an important series of clay materials to use them in the faience ceramic. Selected samples were studied with the objective of analyzing their chemical and mineralogical composition, morphology, particle size, plasticity, thermal analysis and their ceramic aptitude to be used in the faience ceramic. Raw materials are mainly composed of illite and kaolinite are the dominant clay minerals with minor quartz and dolomite. The plasticity indexes are lower than 15.40%, suggesting that these clays are not plastic. Technical characterization was carried out on one representative mixture of Miocene clay samples. The firing characteristics (shrinkage and water absorption) were measured. The optimum firing temperature of clay mixture (M) has been established. These clays could be used in the manufacture of ceramic pieces.
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    • "Determining the ceramic properties of a clay may involve a plethora of approaches, ranging from the characterisation of specific clayey outcrops (Dondi, 1999; Hajjaji et al., 2010; Marques et al., 2011; Montana et al., 2011; Nyakairu et al., 2002) to the evaluation of the effects of firing (e.g. Arsenović et al., 2012; Bauluz et al., 2003; Dondi, 1999; Mahmoudi et al., 2010; Manoharan et al., 2011; Monterio and Vieira, 2004; Ngun et al., 2011; Trindade et al., 2011). "
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    ABSTRACT: For the first time, the characterisation and the ceramic properties of thirty clays from southern Tuscany are discussed on the basis of their particle size distribution, Atterberg limits, geochemical (XRF) and mineralogical (XRD) composition and microfossils content. Very little information was available for the Albegna Basin, therefore, sampling included all outcroppings of Neogene–Quaternary clays. The results allowed the distinction of Miocene, Pleistocene and Holocene Ca-poor clays, suitable for the production of red stonewares and dense and frost resistant masonry materials, from Pliocene Ca-rich clays, used for the production not only of red earthenware but also of hard and porous masonry materials.
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