Structural modelling, refinement and possible formation mechanism of a 4M.sub.3./sub. non-MDO ferriphlogopite (Ruiz Peak volcano)

0367120 - FZÚ 2012 RIV DE eng J - Journal Article
Pignatelli, I. - Dušek, Michal - De Titta, G. - Nespolo, M.
Structural modelling, refinement and possible formation mechanism of a 4M₃ non-MDO ferriphlogopite (Ruiz Peak volcano).
European Journal of Mineralogy. Roč. 23, č. 1 (2011), s. 73-84. ISSN 0935-1221. E-ISSN 1617-4011
Grant - others:AV ČR(CZ) AP0701
Program: Akademická prémie - Praemium Academiae
Institutional research plan: CEZ:AV0Z10100521
Keywords : mica polytypism * ferriphlogopite * non-MDO polytype * PID analysis * OD character * structural refinement * charge distribution
Subject RIV: BM - Solid Matter Physics ; Magnetism
Impact factor: 1.486, year: 2011

The first reliable structural refinement of a non-MDO mica polytype from single-crystal X-ray diffraction data is presented. The sample is a 4-layer ferriphlogopite from the Ruiz Peak volcano, New Mexico. Structural refinement in the space group C2/c converges to R(obs)=6.3%. The formation of this polytype by spiral growth can be interpreted either as the result of the occurrence of a stacking fault in the exposed ledge of a 3T polytype or as a cell-twin formed by two 2M1 substructures. The formation of a non-MDO polytype from two substructures corresponding to MDO polytypes explains why the second and fourth layers of the polytype are meso-octahedral even if the space-group symmetry does not force the cis sites to be equivalent.
Permanent Link: http://hdl.handle.net/11104/0201896