Clays and Clay Minerals, Vol. 54, No. 6, 653–666, 2006.
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Authors
Christidis, George E.
Mitsis, Ioannis
Issue Date
2006-11
Type
Article
Language
en_US
Keywords
Periodicals , Geology , Greece , Metastability , Ni-rich Stevensite , Octahedral Vacancy , Othrys Ophiolite Complex , PVP , Serpentine , Supergene Alteration , Talc , XRD
Alternative Title
A New Ni-Rich Stevensite from the Ophiolite Complex of Othrys, Central Greece
Abstract
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 250ºC for 90 min. Total conversion to talc is observed at 550ºC. 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 750ºC.
Description
Citation
Clays and Clay Minerals, Vol. 54, No. 6, 653–666, 2006.
Publisher
The Clay Minerals Society
License
Copyright © 2006-2018.