The role of H3O+ in the crystal structure of illite
Nieto, Fernando (Universidad de Granada. Departamento de Mineralogía y Petrología)
Mellini, Marcello (Universita di Siena. Dipartimento di Scienze della Terra)
Abad, Isabel (Universidad de Jaén. Departamento de Geología)

Data:	2010
Resum:	In spite of decades of research on the subject, the crystal structure of illite is still poorly understood. The purpose of this study was to address this problem by investigating the nature of the interlayer content in illite IMt-2 from Silver Hill, Montana, using analytical transmission electron microscopy (ATEM), thermogravimetry (TG), and X-ray powder diffraction (XRPD) analyses. The ATEM data, together with literature and TG results, yieldedthe formula KNa(HO) (AlFe Fe Mg)(SiAl)O(OH) or, assuming the presence of HO, KNa(HO) (AlFe Fe Mg)(SiAl)O(OH). The first formula indicates surplus interlayer andoctahedral species, whereas the secondshows no excess. The XRPD data were refinedby Rietveldte chniques, down to an Rp factor of 10. 48-13. 8%. The mineral composition consists largely of illite-2M1, illite-1M, andminor quartz. Although the refinement accuracy is limitedby the intrinsic poor quality diffraction of the illites, the partially refined model is consistent with the chemical composition; in particular, attempts to introduce octahedral cations in excess of 2 were fruitless. All the results support the simple structural model, by which the illite structure strictly corresponds to a dioctahedral mica with HO replacing K. As a consequence, the crystalchemical formula of illites should be calculated on the basis of six tetrahedral plus octahedral cations.
Nota:	Altres ajuts: Junta de Andalucía (GL 2007-66744, RNM-179, RNM-325)
Drets:	Tots els drets reservats.
Llengua:	Anglès
Document:	Article ; recerca ; Versió publicada
Matèria:	Composition ; Hydronium ; Illite ; Water
Publicat a:	Clays and Clay Minerals, Vol. 58, Núm. 2 (2010) , p. 238-246, ISSN 1552-8367

DOI: 10.1346/CCMN.2010.0580208

9 p, 584.8 KB  Accés restringit a la UAB

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