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Titolo:
METAMORPHIC COOKEITE IN ALPINE METAPELITES FROM RIF, NORTHERN MOROCCO, AND THE BETIC CHAIN, SOUTHERN SPAIN
Autore:
GOFFE B; AZANON JM; BOUYBAOUENE ML; JULLIEN M;
Indirizzi:
ECOLE NORMALE SUPER,URA 1316 CNRS,GEOL LAB,24 RUE LHOMOND F-75005 PARIS FRANCE UNIV GRANADA,DEPT GEODINAM E-18071 GRANADA SPAIN UNIV MOHAMMED 5,FAC SCI,DEPT GEOL RABAT MOROCCO
Titolo Testata:
European journal of mineralogy
fascicolo: 2, volume: 8, anno: 1996,
pagine: 335 - 348
SICI:
0935-1221(1996)8:2<335:MCIAMF>2.0.ZU;2-9
Fonte:
ISI
Lingua:
ENG
Soggetto:
LOW-TEMPERATURE METAMORPHISM; HIGH-PRESSURE; CORDILLERAS; SYSTEM; ALPS;
Keywords:
COOKEITE; CRYSTAL CHEMISTRY; METAMORPHISM; SEBTIDES-ALPUJARRIDES; MOROCCO; SPAIN; TEM;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
38
Recensione:
Indirizzi per estratti:
Citazione:
B. Goffe et al., "METAMORPHIC COOKEITE IN ALPINE METAPELITES FROM RIF, NORTHERN MOROCCO, AND THE BETIC CHAIN, SOUTHERN SPAIN", European journal of mineralogy, 8(2), 1996, pp. 335-348

Abstract

Cookeite, LiAl4[AlSi3O10](OH)(8) is reported for the first time from Permo-Triassic metapelites of the Sebtides and Alpujarrides nappes in the Rif and Betic mountains. Cookeite occurs in low-pressure, low-temperature as well as high-pressure, low-temperature metamorphic terranes. In the Rif chain, it occurs in the upper (Tizgarine) and lower (BeniMzala) units of the Beni Mzala window. In the Betic chain its occurrences are widespread in the lower Alpujarrides units (Escalate and Salobrena units) between Granada and Almeria. Cookeite is associated with pyrophyllite in the lowest-grade units and is essentially a product ofkyanite alteration in the highest-grade units. Electron and ion microprobe analyses show large compositional variations: Si ranges from 3 to 3.76 atoms per formula unit, Al from 4.51 to 5 and R(2+) (= Fe + Mg Mn) from 0.03 to 0.87 while the Li2O content varies from 1.95 to 2.70 wt%. These variations are interpreted as the combination of intergrowth of pyrophyllite with cookeite, of partial alteration to kaolinite and of the R(2+)SiAl(-2) (Tschermak) and LiAlR(-2)(2+) (cookeite-sudoite) substitutions. The substitution toward the sudoite end-member reaches 30 mole %. The structural and compositional variations revealed byTEM observations could be related to the metamorphic variations. Under low-grade, low-pressure metamorphic conditions, cookeite is expectedto be highly substituted and structurally disordered while it is nearend-member and highly ordered under high-pressure and low-temperatureconditions.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 01/12/20 alle ore 16:19:00