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Titolo:
TEM evidence for high-temperature (300 degrees C) smectite in multistage clay-mineral pseudomorphs in pelitic rocks (Rif, Morocco)
Autore:
Agard, P; Jullien, M; Goffe, B; Baronnet, A; Bouybaouene, M;
Indirizzi:
Ecole Normale Super, CNRS, UMR 8538, Geol Lab, F-75231 Paris 05, France Ecole Normale Super Paris France 05 , Geol Lab, F-75231 Paris 05, France CEA Saclay, DCC, DESD, SESD,LMGS, F-91191 Gif Sur Yvette, France CEA Saclay Gif Sur Yvette France F-91191 F-91191 Gif Sur Yvette, France CNRS, CRMC2, F-13288 Marseille 09, France CNRS Marseille France 09CNRS, CRMC2, F-13288 Marseille 09, France Univ Mohamed V, Fac Sci, Rabat, Morocco Univ Mohamed V Rabat MoroccoUniv Mohamed V, Fac Sci, Rabat, Morocco
Titolo Testata:
EUROPEAN JOURNAL OF MINERALOGY
fascicolo: 4, volume: 11, anno: 1999,
pagine: 655 - 668
SICI:
0935-1221(199907/08)11:4<655:TEFH(D>2.0.ZU;2-4
Fonte:
ISI
Lingua:
ENG
Soggetto:
DORA-MAIRA MASSIF; WESTERN ALPS; HIGH-PRESSURE; CHLORITE; METAPELITES; BLUESCHISTS; AEM; PHYLLOSILICATES; TRANSFORMATION; TRANSMISSION;
Keywords:
pseudomorph; clay minerals; smectite; high-pressure low-temperature metamorphism; magnesiochloritoid;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
58
Recensione:
Indirizzi per estratti:
Indirizzo: Agard, P Ecole Normale Super, CNRS, UMR 8538, Geol Lab, 24 Rue Lhomond, F-75231 Paris 05, France Ecole Normale Super 24 Rue Lhomond Paris France 05 is 05, France
Citazione:
P. Agard et al., "TEM evidence for high-temperature (300 degrees C) smectite in multistage clay-mineral pseudomorphs in pelitic rocks (Rif, Morocco)", EUR J MINER, 11(4), 1999, pp. 655-668

Abstract

Optically homogeneous pseudomorphs occur in high-pressure metapelites fromthe Alpine Rif chain, Morocco, along with talc and kyanite. Further characterization using optical microscopy, electron microprobe, single-crystal X-ray diffraction, and HRTEM reveals a complex metamorphic replacement sequence of a previous high-pressure metamorphic mineral, possibly magnesiochloritoid. Within the pseudomorphs, three zones are recognized based on the occurrence of distinct layer silicates, which crystallized under different P-T conditions along the retrograde metamorphic P-T path. These layer silicates are,from core to rim: (I) a relic mixture of margarite and chlorite, (2) oriented chlorite-smectite intergrowths +/- pyrophyllite, and (3) chlorite and abundant smectite (at the periphery of the pseudomorph). These pseudomorphs represent an uncommon record of the retrograde metamorphic P-T path because the earliest smectite formed while the rocks still experienced P-T conditions in the stability field of pyrophyllite. This observation suggests that clay minerals may crystallize as regional metamorphic products, and that their stability field might not be restricted to late shallow-depth alteration.

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Documento generato il 28/11/20 alle ore 12:58:34