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Titolo:
ORDERING OF THE STACKING-SEQUENCE IN COOKEITE WITH INCREASING PRESSURE - AN HRTEM STUDY
Autore:
JULLIEN M; BARONNET A; GOFFE B;
Indirizzi:
ECOLE NORMALE SUPER,URA 1316 CNRS,GEOL LAB,24 RUE LHOMOND F-75231 PARIS 05 FRANCE CNRS,CTR RECH MECANISMES CROISSANCE CRISTALLINE F-13288 MARSEILLE 09 FRANCE
Titolo Testata:
The American mineralogist
fascicolo: 1-2, volume: 81, anno: 1996,
pagine: 67 - 78
SICI:
0003-004X(1996)81:1-2<67:OOTSIC>2.0.ZU;2-C
Fonte:
ISI
Lingua:
ENG
Soggetto:
FRENCH ALPS; CHLORITE; METAMORPHISM; PYROPHYLLITE; CHEMISTRY; DISORDER; SUDOITE; FRANCE; SYSTEM;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Science Citation Index Expanded
Citazioni:
57
Recensione:
Indirizzi per estratti:
Citazione:
M. Jullien et al., "ORDERING OF THE STACKING-SEQUENCE IN COOKEITE WITH INCREASING PRESSURE - AN HRTEM STUDY", The American mineralogist, 81(1-2), 1996, pp. 67-78

Abstract

To explore the effect of pressure on the stacking-sequence of the chlorite cookeite, a systematic TEM study of stacking microstructures hasbeen conducted on natural samples from pegmatitic and metamorphic environments representing a large pressure field over a relatively narrowtemperature range. The low-P and low-T conditions (1-5 kbar, 280-350 degrees C) are represented by late-crystallized cookeite from pegmatites and by cookeite from low-temperature metapelites. For the high-P conditions (5-16 kbar, 280-430 degrees C), cookeite samples from metapelites and metabauxites were selected. Combining selected-area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM) imaging shows that the polytypes evolve from a fully semirandom type to fully ordered types under increasing total pressure. For both polytypes the repeat distance (from one to five layers) of the basic structures and the diversity of repeats increase with pressure. Above 10 kbar, long-period polytypes (LPP), up to at least a 14-layer repeat, coexist with perfectly ordered basic structures. Neither the unique type of intralayer stacking (Ia) nor the single-layer subcell volume measurements improve understanding of the role of pressure on the ordering process. Clearly, the regular polytypes of cookeite behave as polymorphs that are remarkably sensitive to total pressure.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 04/12/20 alle ore 19:21:54