A new Ni-rich stevensite from the ophiolite complex of Othrys, Central Greece
Christidis, George E. (Technical University of Crete. Department of Mineral Resources Engineering)
Mitsis, Ioannis (Univerity of Athens. Section of Geochemistry and Economic Geology. Department of Geology)

Fecha:	2006
Resumen:	The first occurrence of Ni-rich stevensite found in the ophiolite complex of Othrys, Central Greece is described. The stevensite, which develops in cracks in a host serpentinite, formed at the expense of serpentine. Two varieties of stevensite have been described: a Mg-rich, Ni-poorer variety with 0. 4-1. 2 octahedral Ni atoms per half formula unit (p. h. f. u. ) and a Ni-rich variety with >2 Ni atoms p. h. f. u. The layer charge in both varieties is -0. 24 p. h. f. u. . Stevensite layers are completely separated when dispersed in dilute polyvinylpyrrolidone (PVP) solutions and begin to convert to talc after heating at 250°C for 90 min. Total conversion to talc is observed at 550°C. Formation of Ni-rich stevensite took place at ambient temperature during supergene processes. The scarcity of Ni-rich stevensite occurrences in nature is attributed to the metastability of smectite and to the analytical procedures used in previous studies. Stevensite is considered a phase containing domains with variable numbers of octahedral vacancies. A new experimental protocol is proposed for the determination of Ni-rich stevensite, based on a combination of XRD after solvation with various organic liquids and subsequent heating at 750°C.
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Lengua:	Anglès
Documento:	Article ; recerca ; Versió publicada
Materia:	Greece ; Metastability ; Ni-rich Stevensite ; Octahedral Vacancy ; Othrys Ophiolite Complex ; PVP ; Serpentine ; Supergene Alteration ; Talc ; XRD
Publicado en:	Clays and Clay Minerals, Vol. 54, Núm. 6 (2006) , p. 653-666, ISSN 1552-8367

DOI: 10.1346/CCMN.2006.0540601

14 p, 1.9 MB  Acceso restringido a la UAB

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