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Metamorphic cookeite in Alpine metapelites from Rif, northern Morocco, and the Betic Chain, southern Spain

Bruno Goffe, Jose Miguel Azanon, Mohamed Larbi Bouybaouene and Michel Jullien
Metamorphic cookeite in Alpine metapelites from Rif, northern Morocco, and the Betic Chain, southern Spain
European Journal of Mineralogy (April 1996) 8 (2): 335-348

Abstract

Cookeite is reported from low-T, low-P and from low-T, high-P Permo-Triassic metapelites of the Sebtides and Alpujarrides nappes in the Rif and Betic mountains. It occurs associated with pyrophyllite in the lowest-grade units and is essentially a product of kyanite alteration in the highest-grade units. EPMA and ion microprobe analyses show large compositional variations: Si ranges from 3 to 3.76 atoms pfu, Al from 5.51 to 5, and R (super 2+) from 0.03 to 0.87, while Li (sub 2) O ranges 1.95-2.70 wt.%. These variations are interpreted as a combination of the intergrowth of pyrophyllite with cookeite, partial alteration to kaolinite and the R (super 2+) SiAl (sub -2) (Tschermak) and LiAlR (super 2+) (sub -2) (cookeite-sudoite) substitutions; the substitution towards the sudoite end-member reaches 30 mole %. The structural and compositional variations revealed by TEM could be related to metamorphic variations; under low-grade, low-P metamorphic conditions, cookeite is expected to be highly substituted and structurally disordered whereas it is near end-member composition and highly ordered under high-P, low-T conditions.


ISSN: 0935-1221
Serial Title: European Journal of Mineralogy
Serial Volume: 8
Serial Issue: 2
Title: Metamorphic cookeite in Alpine metapelites from Rif, northern Morocco, and the Betic Chain, southern Spain
Affiliation: Ecole Normale Superieure, CNRS, Paris, France
Pages: 335-348
Published: 199604
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 38
Accession Number: 1996-044106
Categories: Igneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables, geol. sketch maps
N02°00'00" - N03°30'00", W37°00'00" - W37°00'00"
Secondary Affiliation: Universidad de Granada, ESP, SpainUniversite Mohammed V, MAR, Morocco
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom
Update Code: 199615
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