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Monazite-epidote reaction in amphibolite grade blackwall rocks

Rodney Grapes, Kurt Bucher and Paul W. O. Hoskin
Monazite-epidote reaction in amphibolite grade blackwall rocks
European Journal of Mineralogy (August 2005) 17 (4): 553-566


Composite monazite-epidote grains in a staurolite schist protolith have reacted to form apatite, chlorite + thorite, with REE enrichment of the epidote, during amphibolite-facies hydrothermal conditions of blackwall formation at Kvesjoeen, east-central Norway. The simplified breakdown reaction is 1.8 monazite + 1.5 epidote + 11.1 H (sub 2) O + 6 Fe (sub aq) = 0.6 apatite +1.5 chlorite + 1.8 REE (sub aq) + 11.1 H (super +) with additional thorite (and a possible Y-oxide phase). EPMA results are given for epidote, chlorite, apatite and monazite. This breakdown reaction is explained in terms of the destructioin of the monazite phosphate structure in relation to coupled substitutions with removal of REE by a fluid boundary layer. REEs, Y, Th and U remained within the boundaries of the original composite monazite-epidote grains. Decrease in bulk rock Ca and enrichment in Al during blackwall development favoured preservation of epidote rather than monazite, and inhibited growth of new epidote.

ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 17
Serial Issue: 4
Title: Monazite-epidote reaction in amphibolite grade blackwall rocks
Affiliation: Universitaet Freiburg, Institut fuer Mineralogie, Petrologie und Geochemie, Freiburg, Federal Republic of Germany
Pages: 553-566
Published: 200508
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 55
Accession Number: 2006-013169
Categories: Mineralogy of silicatesIgneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom
Update Code: 200607
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