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Crystallochemical characterization of the palygorskite and sepiolite from the Allou Kagne deposit, Senegal



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García Romero, Emilia and Súarez Barrios, Mercedes and Santarén Rome, Julio and Álvarez Berenguer, Antonio (2007) Crystallochemical characterization of the palygorskite and sepiolite from the Allou Kagne deposit, Senegal. Clays and clay minerals, 55 (6). pp. 606-617. ISSN 0009-8604

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The Allou Kagne (Senegal) deposit consists of different proportions of palygorskite and
sepiolite, and these are associated with small quantities of quartz and X-ray amorphous silica as impurities.
No pure palygorskite or sepiolite has been recognized by X-ray diffraction. Textural and microtextural
features indicate that fibrous clay minerals of the Allou Kagne deposit were formed by direct precipitation
from solution. Crystal-chemistry data obtained by analytical/transmission electron microscopy (AEM/
TEM) analyses of isolated fibers show that the chemical composition of the particles varies over a wide
range, from a composition corresponding to palygorskite to a composition intermediate between that of
sepiolite and palygorskite, but particles with a composition corresponding to sepiolite have not been found.
Taking into account the results from selected area electron diffraction and AEM-TEM, fibers of pure
palygorskite and sepiolite have been found but it cannot be confirmed that all of the particles analyzed
correspond to pure palygorskite or pure sepiolite because both minerals can occur together at the crystallite
scale. In addition, the presence of Mg-rich palygorskite and very Al-rich sepiolite can be deduced.
It is infrequent in nature that palygorskite and sepiolite appear together because the conditions for
simultaneous formation of the two minerals are very restricted. The chemical composition of the solution
controls the formation of the Allou Kagne sepiolite and palygorskite. The wide compositional variation
appears as a consequence of temporary variations of the chemical composition of the solution.

Item Type:Article
Uncontrolled Keywords:AEM-TEM, Allou-Kagne Deposits, Crystal Chemistry, Palygorskite, SAED, Senegal, Sepiolite
Subjects:Sciences > Geology > Mineralogy
ID Code:13453
Deposited On:21 Oct 2011 09:10
Last Modified:11 Dec 2018 08:46

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