Metamorphic evolution and significance of a serpentinized peridotite slice within the eclogitic micaschist complex of the Sesia-Zone (Western Alps, Italy)

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Authors:Ferraris, Cristiano; Compagnoni, Roberto
Author Affiliations:Primary:
University of Siena, Department of Earth Sciences, Siena, Italy
University of Torino, Italy
Volume Title:Schweizerische Mineralogische und Petrographische Mitteilungen Bulletin Suisse de Minéralogie et Pétrographie
Source:Schweizerische Mineralogische und Petrographische Mitteilungen = Bulletin Suisse de Minéralogie et Pétrographie, 83(1), p.3-13. Publisher: Stäubli Verlag AG, Zurich, Switzerland. ISSN: 0036-7699
Publication Date:2003
Note:In English. 41 refs.
Summary:The petrography, mineral chemistry, and metamorphic evolution of a serpentinized peridotite slice, which occurs within the Eclogitic Micaschist Complex of the Sesia-Lanzo zone, W Alps (Italy), are described and possible tectonic implications are discussed. The ultramafics are mainly foliated serpentinites that preserve, in the central portion, relics of the peridotitic protolith. The relic peridotite includes both orthopyroxene- and olivine-rich layers and consists of olivine, diopsidic clinopyroxene, Cr-bearing chlorite and orthopyroxene porphyroclasts. The latter include olivine, amphibole, and orange-brownish Cr-Mg-Al-rich spinel aggregates, whose spatial arrangement indicates pseudomorphism after a mineral with a perfect cleavage set, most likely chlorite. Based on this interpretation, arisen from both the composition and geometric arrangement of spinel droplets, the host peridotite preserves evidence of a prograde metamorphism from the chlorite- to the spinel-peridotite field, which predates the Alpine polyphase evolution. These data may indicate that the Eclogitic Micaschist Complex, usually considered as a coherent fragment of Variscan continental crust, is in fact a unit with a more complex internal tectonic setting. [G.L.B.]
Subsections:Metamorphism: regional, dynamic
Subjects:Chemical composition; Concentration; Eclogite facies; Electron probe data; Facies; Foliation; Gabbros; Geochemistry; High pressure; High-grade metamorphism; Igneous rocks; Lherzolite; Mantle; Metaigneous rocks; Metamorphic rocks; Metamorphism; Metasomatic rocks; Metasomatism; Mineral composition; Peridotites; Petrography; Plutonic rocks; Pressure; Protoliths; Rodingite; Serpentinite; Serpentinization; Ultramafics; Alps; Europe; Italy; Piemonte Italy; Sesia Zone; Sesia-Lanzo Zone; Southern Europe; Western Alps
Abstract Numbers:04M/712
Record ID:2007021541
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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