Non-mafic rocks in the greenschist, blueschist and eclogite facies

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doi: 10.1016/0009-2541(85)90109-3
Authors:Koons, Peter O.; Thompson, Alan B.
Author Affiliations:Primary:
Eidg. Tech. Hochsch., Dep. Erdwiss., Zurich, Switzerland
Tech. Univ. Berlin, Inst. Angew. Geophys., Petrol. und Lagerstättenforsch., Federal Republic of Germany
Eidg. Tech. Hochsch. Zentrum, Inst. Kristall. und Petrogr., Switzerland
Volume Title:Chemistry and petrology of eclogites
Volume Authors:Smith, David C., editor; Franz, Gerhard; Gebauer, Dieter
Source:Chemical Geology, 50(1-3), p.3-30; First international eclogite conference, Clermont-Ferrand, France, Aug. 31-Sept. 2, 1982, edited by David C. Smith, Gerhard Franz and Dieter Gebauer. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0009-2541
Publication Date:1985
Note:In English
Summary:High-P pelitic rocks occurring in rocks of the blueschist and eclogite facies differ from their lower-P equivalents primarily in the presence of the mixed felsic-mafic phases, Na-amphibole and Na-pyroxene. Several three-phase assemblages (e.g. chloritoid + talc + staurolite, chlorite + talc + chloritoid, with muscovite and quartz) are indicative of P and T of equilibration, but the presence of a single AFM phase is not necessarily useful in determining physical conditions of equilibration. Several continuous reactions are potentially useful as geobarometers, but most are highly dependent upon the assemblage present and therefore compositional variation due to the pertinent exchange must be evaluated for each assemblage. The whole-rock reaction may cause compositional shifts at variance with those predicted by an examination of sub-assemblages in simple systems because of vector coupling. The H2O-conserving reactions must be considered prior to the assignment of an assemblage to a given set of physical conditions of formation. Retrogression of rocks of pelitic composition in the tectonic regime accompanying uplift occurs more readily than retrogression of associated mafic rocks due to both equilibration and non-equilibrium processes. This paper and alongwith 19 additional abstracts constitute an issue of Chemical Geology devoted to the chemistry and petrology of eclogites, representing some of the papers presented at the First International Eclogite Conference, Clermont-Ferrand, 1982. [J.M.H.]
Subjects:Blueschist facies; Composition; Eclogite facies; Facies; Greenschist facies; Metamorphic rocks; Metamorphism; Mineral assemblages; P-T conditions; Regional metamorphism; Terrains; Whole rock
Abstract Numbers:86M/2511
Record ID:1985067136
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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