Preprints
https://doi.org/10.5194/se-2021-11
https://doi.org/10.5194/se-2021-11

  16 Feb 2021

16 Feb 2021

Review status: this preprint is currently under review for the journal SE.

Interactions of plutons and detachments, comparison of Aegean and Tyrrhenian granitoids

Laurent Jolivet1, Laurent Arbaret2,3,4, Laetitia Le Pourhiet1, Florent Cheval-Garabedian2,3,4, Vincent Roche1, Aurélien Rabillard2,3,4, and Loïc Labrousse1 Laurent Jolivet et al.
  • 1Sorbonne Université, CNRS-INSU, Institut des Sciences de la Terre Paris, ISTeP UMR 7193, F-75005 Paris, France
  • 2Université d’Orléans, ISTO, UMR 7327, 45071, Orléans, France
  • 3CNRS/INSU, ISTO, UMR 7327, 45071 Orléans, France
  • 4BRGM, ISTO, UMR 7327, BP 36009, 45060 Orléans, France

Abstract. Back-arc extension superimposed on mountain belts leads to distributed normal faults and shear zones, interacting with magma emplacement in the crust. The composition of granitic magmas emplaced at this stage often involves a component of crustal melting. The Miocene Aegean granitoids were emplaced in metamorphic core complexes (MCC) below crustal-scale low-angle extensional shear zones and normal faults. Intrusion in such contexts interacts with extension and shear along detachments, from the hot magmatic flow within the pluton root zone to the colder ductile and brittle deformation along the detachment. A comparison of the Aegean plutons with the Elba Island MCC in the back-arc region of the Apennines subduction shows that these processes are characteristic of pluton-detachment interactions in general and we discuss a conceptual emplacement scenario, tested by numerical models. Mafic injections within the partially molten lower crust above the hot asthenosphere trigger the ascent within the core of the MCC of felsic magmas, controlled by the strain localization on persistent crustal scale shear zones at the top that guide the ascent until the brittle ductile transition is reached during exhumation. Once the system definitely enters the brittle regime, the detachment and the upper crust are intruded while new detachments migrate upward and in the direction of shearing. Numerical models reproduce the geometry and the kinematic evolution deduced from field observations.

Laurent Jolivet et al.

Status: open (until 07 Apr 2021)

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  • RC1: 'Comment on se-2021-11', Antonio Castro, 05 Mar 2021 reply

Laurent Jolivet et al.

Laurent Jolivet et al.

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Short summary
Although viscosity of the crust largely exceeds that of magmas, we show, based on the Aegean and Tyrrhenian Miocene syn-kinematic plutons, how the intrusion of granites in extensional contexts is controlled by crustal deformation, from magmatic stage to cold mylonites. We show that a simple numerical setup with partial melting in the lower crust in an extensional context leads to the formation of metamorphic core complexes and low-angle detachments reproducing the observed evolution of plutons.