In situ Rb-Sr and <SUP>40</SUP>Ar-<SUP>39</SUP>Ar dating of distinct mica generations in the exhumed subduction complex of the Western Alps - INSU - Institut national des sciences de l'Univers Accéder directement au contenu
Article Dans Une Revue Contributions to Mineralogy and Petrology Année : 2023

In situ Rb-Sr and 40Ar-39Ar dating of distinct mica generations in the exhumed subduction complex of the Western Alps

Résumé

Dating specific pressure-temperature-time-deformation-fluid (P-T-t-d-f) events is a major petrological issue, particularly for polymetamorphic assemblages. In order to better assess such events using mica populations, this study uses a combined in situ Rb-Sr and Ar-Ar dating approach coupled with chemical mapping, with application to an exhumed subduction complex (Schistes Lustrés, Western Alps). Geochronological investigation of the most Si-rich (Tschermak substitution) mica population allows us to investigate the (near-)peak burial ages of the various tectonometamorphic units of this high-pressure/low-temperature subduction complex. In the blueschist-facies units, a wide range of ages between ∼36 (younger than previously obtained peak ages) and ~ 52 Ma suggests a diachronous slicing of units with different initial paleogeography and/or a long residence time at near-peak conditions. The combined use of Ar-Ar and Rb-Sr isochron ages reveals the existence of some excess argon in the studied metamorphic rocks, interpreted as the result of (i) heterogeneous contamination from an argon-rich fluid in the higher grade eclogite-facies units and (ii) partial removal, during pseudomorphic recrystallization, of argon inherited from earlier stages of metamorphism in the lower grade blueschist-facies units.
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insu-04188117 , version 1 (25-08-2023)

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Thomas Gyomlai, Philippe Agard, Clément Herviou, Laurent Jolivet, Patrick Monié, et al.. In situ Rb-Sr and 40Ar-39Ar dating of distinct mica generations in the exhumed subduction complex of the Western Alps. Contributions to Mineralogy and Petrology, 2023, 178, ⟨10.1007/s00410-023-02042-8⟩. ⟨insu-04188117⟩
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