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GEOREF RECORD

Precambrian coesite from northern Mali; first record and implications for plate tectonics in the trans-Saharan segment of the Pan-African belt

Renaud Caby
Precambrian coesite from northern Mali; first record and implications for plate tectonics in the trans-Saharan segment of the Pan-African belt
European Journal of Mineralogy (April 1994) 6 (2): 235-244

Abstract

Coesite occurs as inclusions in omphacite in an impure marble from the late Proterozoic internal nappes of the frontal part of the Pan-African belt in the Gourma area of N Mali. Possible pseudomorphs after coesite are also found in garnets from the surrounding eclogitic metasediments. These eclogitic mica schists are slightly overprinted mineral assemblages with kyanite, garnet (Py (sub 32-40) Alm (sub 41-52) Gro (sub 15-18) ), jadeite-rich clinopyroxene (Jd (sub 48-68) ), phengite (Si (sub 3.35-3.40) ) and rutile. Provisional P-T estimates (> 27 kbar, 700-750 degrees C) for this metamorphism suggest that large parts of the palaeo-West African plate were subducted to depths > 90 km. It is suggested that the coesite-bearing unit was exhumed from depths along low- angle migrating thrusts, in the form of a fast extrusive slice pushed up above a low-angle sole thrust.


ISSN: 0935-1221
Serial Title: European Journal of Mineralogy
Serial Volume: 6
Serial Issue: 2
Title: Precambrian coesite from northern Mali; first record and implications for plate tectonics in the trans-Saharan segment of the Pan-African belt
Author(s): Caby, Renaud
Affiliation: Universite Montpellier II, Unite C.N.R.S., Montpellier, France
Pages: 235-244
Published: 199404
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 37
Accession Number: 1994-025771
Categories: Solid-earth geophysics
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table, geol. sketch map
N16°00'00" - N16°00'00", E02°30'00" - E02°30'00"
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom
Update Code: 199412
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