Variscan eclogites from the Argentera–Mercantour Massif (External Crystalline Massifs, SW Alps): a dismembered cryptic suture zone

We document structural, geochemical, petrological and 40 Ar/ 39 Ar geochronological data performed on Variscan eclogites from the Argentera–Mercantour Massif, southwestern Alps. Based on the high-resolution field mapping, we present new eclogite occurrences and discuss the relationships between eclo...

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Bibliographic Details
Published in:International journal of earth sciences : Geologische Rundschau 2020-06, Vol.109 (4), p.1273-1294
Main Authors: Jouffray, Fabrice, Spalla, Maria Iole, Lardeaux, Jean Marc, Filippi, Marco, Rebay, Gisella, Corsini, Michel, Zanoni, Davide, Zucali, Michele, Gosso, Guido
Format: Article
Language:English
Subjects:
Amphiboles
Amphibolite facies
Amphibolites
Argon
Continental crust
Earth and Environmental Science
Earth Sciences
Eclogite
Geochemistry
Geochronology
Geology
Geophysics/Geodesy
Isotopes
Magma
Mapping
Massifs
Mesozoic
Mineral Resources
Oceanic crust
Original Paper
Radiometric dating
Sciences of the Universe
Sedimentology
Structural Geology
Subduction
Subduction (geology)
Tectonics
Thermodynamic models
Trace elements
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Summary:We document structural, geochemical, petrological and 40 Ar/ 39 Ar geochronological data performed on Variscan eclogites from the Argentera–Mercantour Massif, southwestern Alps. Based on the high-resolution field mapping, we present new eclogite occurrences and discuss the relationships between eclogites and surrounding migmatites. We recognized for the first time preserved eclogite facies assemblages. Trace elements and REE patterns establish that eclogites protoliths are MORBs contaminated by continental crust. Standard thermobarometry and thermodynamic modeling are consistent with P – T values of 640–740 °C for 1.5 ± 0.25 GPa, coherent with paleo-geotherms predicted for warm subduction of oceanic crust. We interpret these eclogites as a dismembered cryptic suture zone. 40 Ar/ 39 Ar dating on amphiboles yields an age of 339.7 ± 12 Ma for eclogite retrogression under amphibolite facies conditions. All these data are combined to link the Argentera–Mercantour Massif in the tectonic framework of both pre-Mesozoic Alpine basement and European southern Variscides.
ISSN:1437-3254
1437-3262
DOI:10.1007/s00531-020-01848-2