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International audience; Abstract. Back-arc extension superimposed on mountain belts leads to distributed normal faults and shear zones interacting with magma emplacement within the crust. The composition of granitic magmas emplaced at this stage often involves a large component of crustal melting. The Miocene Aegean granitoids were emplaced in metamorphic core complexes (MCCs) below crustal-scale low-angle normal faults and ductile shear zones. Intrusion processes interact with extension and shear along detachments, from the hot magmatic flow within the pluton root zone to the colder ductile and brittle deformation below and along the detachment. A comparison of the Aegean plutons with the island of Elba MCC in the back-arc region of the Apennine subduction shows that these processes are characteristic of pluton–detachment interactions in general. We discuss a conceptual emplacement model, 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. 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.

International audience; Although fundamental to the understanding of crustal dynamics in extensional setting, the relationships between the emplacement of granitic intrusions and activity of detachments still remain very elusive. Through a multi-scale approach, we here document a continuous deformation history between the monzogranitic intrusion of Naxos and the Naxos-Paros Detachment System (Cyclades, Greece). Field observations first show an early magmatic deformation followed by solid-state, ductile and then brittle deformation when approaching the detachment zone, as evidenced by the overprinting of mylonites by cataclastes and pseudotachylites. From these observations, we define six strain facies that characterize a positive strain gradient from core to rim of the Naxos monzogranite. Based on field pictures, X-ray tomography and Electron BackScatter Diffraction (EBSD) analyses along the strain gradient, we then quantify the intensity of mineralogical fabrics in 2D and 3D and better characterize the deformation mechanisms. Our measured shape variations of the strain ellipsoid corroborate the large-scale strain gradient, showing a good correlation between qualitative and quantitative studies. In addition, EBSD data indicate that dislocation creep was predominant during cooling from more than 500°C to temperature conditions of the ductile-to-brittle transition. However, 1) a weakening of quartz lattice preferred orientation with increasing strain and 2) evidence of numerous four-grain junctions in high-strain shear bands also indicate that grain boundary sliding significantly contributed to the deformation. Although the source of grain boundary sliding remains to be constrained, it provides a consistent approach to account for strain localization in Naxos.

International audience; Within deforming continental regions where metamorphic core complexes (MCCs) and synextensional granitoids are closely associated, deciphering the link between detachment faulting and magmatism often remains complex as (1) the rheological weakness of magma may stimulate mechanisms of strain localization, and conversely, (2) tectonic processes may open/close drains where magmas can intrude. Here we tackle this issue by focusing on the Cyclades with the comparison of five granitoid-cored MCCs (Tinos, Mykonos, Ikaria, Naxos, and Serifos) and their flanking detachment systems. In this region, granitoids were emplaced into the middle/upper crust over a relatively short time period (15–9 Ma), while metamorphic domes were largely exhumed after more than 10 Myr of extension. None of those intrusions thereby proves to be a real candidate for the genesis of MCCs but would rather be a consequence of a warmer regime during lithospheric thinning. However, all collected structural and kinematic data converge toward a regional scheme in which magmatic activity played a more pivotal role than previously postulated. Indeed, late evolution stages of MCCs were dynamically impacted by intrusions along which local and transient heterogeneities of the mechanical strength occurred, interfering with the sequential development of detachments. During their tectonically controlled emplacement, magmatic products intruded already formed detachments at depth, locally inhibiting their activity, associated with a contemporaneous upward migration of extensional deformation that tended to localize through time within intrusion roofs along rheological discontinuities. The newly formed detachments are expressed within granitoids through a continuum of deformation from comagmatic to ductile conditions, followed by cataclasis along detachments.

Magma intrusions within the lithosphere are often considered as thermomechanical instabilities capable to locally and transiently stimulate strain localization. With the aim of testing this model and determining possible mechanisms that govern the initiation of localized deformation at the contact and within magmatic bodies, this thesis combine a fieldwork with an experimental approach. The Cyclades (Aegean Sea, Greece) form a highly extended continental domain in which five metamorphic core complexes (MCCs) were intruded by magmatic complexes, themselves capped by detachment systems. All collected structural and kinematic data, combined with previous investigations, converge toward a regional scheme in which magmatic bodies dynamically impacted the late evolution of the Cycladic MCCs. Granitoids were emplaced in relatively short time period (15-9 Ma) while metamorphic domes were largely exhumed after more than 10 Myrs of extension. None of those intrusions thereby proves to be a real candidate for the genesis of MCCs. However, continuums of deformation recorded within granitoids (magmatic to ductile/brittle states) as well as geometrical relationships with detachments suggest a pivotal role of magmatic complexes in redistribution and localization processes of the deformation, with in particular the sequential development of detachments. Precursors of strain localization within partially cristallized magmas have been concurrently deciphered by an experimental study. The investigation of the structural behavior of magmas, chemically and texturally similar to natural systems, corroborates that strain localization is efficiently activated along interfaces with contrasting rheology such as in the vicinity of synplutonic dikes. It has been also shown that the initial presence of textural inhomogeneities (e.g. like clusters) in medium-crystallized magmas can drastically influence the degree of strain localization during subsequent cooling stages.; Les intrusions magmatiques au sein d’une lithosphère soumise aux contraintes tectoniques sont souvent considérées comme des instabilités thermomécaniques à même de stimuler transitoirement et localement la localisation de la déformation. Dans le but de tester ce modèle et de déterminer les possibles mécanismes gouvernant l’initiation d’une déformation localisée au contact et au sein de corps magmatiques en cours de consolidation, ce travail de thèse se propose de coupler une étude de terrain à une approche expérimentale. Les Cyclades (Mer Égée, Grèce) constituent un domaine de croûte continentale en extension dans lequel se sont mises en place au cœur de cinq dômes métamorphiques extensifs (MCCs) des intrusions magmatiques, elles-mêmes coiffées par des systèmes de détachements. Les diverses campagnes de terrain, combinées aux données de la bibliographie, ont permis de proposer un modèle d’interaction régional dans lequel ces corps magmatiques impactent l’évolution tardive de MCCs cycladiques. Au vu des âges de mise en place des intrusions (15-9 Ma), soit plusieurs millions d’années après le début de l’extension et les premiers stades d’exhumation de roches métamorphiques, le magmatisme dans les Cyclades ne peut être considéré comme un candidat réel pour la genèse de MCCs. Néanmoins, les continuums de la déformation enregistrés en bordure des intrusions (depuis l’état magmatique jusqu’aux conditions ductile/cassant) et les relations géométriques avec les détachements laissent supposer un rôle majeur des complexes magmatiques dans les processus de redistribution et de localisation de la déformation, notamment sur le développement séquentiel de détachements. Les vecteurs de localisation de la déformation au sein de magmas partiellement cristallisés ont été en parallèle recherchés par la voie expérimentale. L’étude du comportement structural de magmas, chimiquement et texturalement proches de systèmes naturels, a permis d’une part de confirmer que la déformation se localise préférentiellement le long d’interfaces à rhéologie contrastée tels aux abords de filons syn-plutoniques. Il est d’autre part montré que la présence initiale d’inhomogénéités texturales (e.g. concentration de cristaux en amas) au sein de magmas moyennement cristallisés peut de manière drastique influencer le degré de localisation de la déformation au cours des stades de refroidissement ultérieurs.

Magma intrusions within the lithosphere are often considered as thermomechanical instabilities capable to locally and transiently stimulate strain localization. With the aim of testing this model and determining possible mechanisms that govern the initiation of localized deformation at the contact and within magmatic bodies, this thesis combine a fieldwork with an experimental approach. The Cyclades (Aegean Sea, Greece) form a highly extended continental domain in which five metamorphic core complexes (MCCs) were intruded by magmatic complexes, themselves capped by detachment systems. All collected structural and kinematic data, combined with previous investigations, converge toward a regional scheme in which magmatic bodies dynamically impacted the late evolution of the Cycladic MCCs. Granitoids were emplaced in relatively short time period (15-9 Ma) while metamorphic domes were largely exhumed after more than 10 Myrs of extension. None of those intrusions thereby proves to be a real candidate for the genesis of MCCs. However, continuums of deformation recorded within granitoids (magmatic to ductile/brittle states) as well as geometrical relationships with detachments suggest a pivotal role of magmatic complexes in redistribution and localization processes of the deformation, with in particular the sequential development of detachments. Precursors of strain localization within partially cristallized magmas have been concurrently deciphered by an experimental study. The investigation of the structural behavior of magmas, chemically and texturally similar to natural systems, corroborates that strain localization is efficiently activated along interfaces with contrasting rheology such as in the vicinity of synplutonic dikes. It has been also shown that the initial presence of textural inhomogeneities (e.g. like clusters) in medium-crystallized magmas can drastically influence the degree of strain localization during subsequent cooling stages., Les intrusions magmatiques au sein d’une lithosphère soumise aux contraintes tectoniques sont souvent considérées comme des instabilités thermomécaniques à même de stimuler transitoirement et localement la localisation de la déformation. Dans le but de tester ce modèle et de déterminer les possibles mécanismes gouvernant l’initiation d’une déformation localisée au contact et au sein de corps magmatiques en cours de consolidation, ce travail de thèse se propose de coupler une étude de terrain à une approche expérimentale. Les Cyclades (Mer Égée, Grèce) constituent un domaine de croûte continentale en extension dans lequel se sont mises en place au cœur de cinq dômes métamorphiques extensifs (MCCs) des intrusions magmatiques, elles-mêmes coiffées par des systèmes de détachements. Les diverses campagnes de terrain, combinées aux données de la bibliographie, ont permis de proposer un modèle d’interaction régional dans lequel ces corps magmatiques impactent l’évolution tardive de MCCs cycladiques. Au vu des âges de mise en place des intrusions (15-9 Ma), soit plusieurs millions d’années après le début de l’extension et les premiers stades d’exhumation de roches métamorphiques, le magmatisme dans les Cyclades ne peut être considéré comme un candidat réel pour la genèse de MCCs. Néanmoins, les continuums de la déformation enregistrés en bordure des intrusions (depuis l’état magmatique jusqu’aux conditions ductile/cassant) et les relations géométriques avec les détachements laissent supposer un rôle majeur des complexes magmatiques dans les processus de redistribution et de localisation de la déformation, notamment sur le développement séquentiel de détachements. Les vecteurs de localisation de la déformation au sein de magmas partiellement cristallisés ont été en parallèle recherchés par la voie expérimentale. L’étude du comportement structural de magmas, chimiquement et texturalement proches de systèmes naturels, a permis d’une part de confirmer que la déformation se localise préférentiellement le long d’interfaces à rhéologie contrastée tels aux abords de filons syn-plutoniques. Il est d’autre part montré que la présence initiale d’inhomogénéités texturales (e.g. concentration de cristaux en amas) au sein de magmas moyennement cristallisés peut de manière drastique influencer le degré de localisation de la déformation au cours des stades de refroidissement ultérieurs.

International audience; In order to better understand the interactions between plutonic activity and strain localization during metamorphic core complexes formation the Miocene granodioritic pluton of Serifos (Cyclades, Greece) is studied. This pluton (11.6-9.5 Ma) intruded the Cycladic Blueschists during thinning of the Aegean domain along a system of low-angle normal faults belonging to the south-dipping West Cycladic Detachment System (WCDS). Based on structural fieldwork, together with microstructural observations and anisotropy of magnetic susceptibility (AMS), we recognize a continuum of deformation from magmatic to brittle conditions within the magmatic body. This succession of deformation events is kinematically compatible with the development of the WCDS. The architecture of the pluton shows a marked asymmetry resulting from its interaction with the detachments. We propose a tectonic scenario for the emplacement of Serifos pluton and its subsequent cooling during the Aegean extension. (1) A first stage corresponds to the metamorphic core complex initiation and associated southwestward shearing along the Meghàlo Livadhi detachment. (2) In a second stage the Serifos pluton has intruded the dome at shallow crustal level, piercing through the ductile/brittle Meghàlo Livadhi detachment. Southwest-directed extensional deformation was contemporaneously transferred upward in the crust along the more localized Kàvos Kiklopas detachment. (3) A third stage was marked by syn-magmatic extensional deformation and strain localization at the contact between the pluton and the host rocks resulting in narrow shear zones nucleation which (4) continued to develop after the pluton solidification.

International audience; The Aegean domain has been characterized since the Oligocene by extensional tectonics caused by the southward retreat of the African slab subducting beneath Eurasia. Structures and associated kinematics relative to this extensional tectonics are well constrained in the western Cyclades and the Menderes massif of western Turkey. Major extensional detachments such as the North Cycladic Detachment System (NCDS) or the Simav Detachment have accommodated the exhumation of a series of metamorphic core complexes (MCC) from Andros-Tinos-Mykonos in the west to the northern Menderes massif in the east. However, the transition between the NCDS and the Simav Detachment is currently not understood. This transition is located above a large-scale tear in the Aegean slab and its effects on the kinematics of deformation and P-T-t evolution of the overlying thinned crust are not known. The geology of Ikaria Island, located in this region, remains poorly known and the few existing studies are strikingly conflicting. This work attempts to clarify the geology of Ikaria by a new geological mapping and structural field study coupled with a thermometric study by Raman spectrometry of carbonaceous material (RSCM). Foliation over the whole island defines a structural dome, lately intruded by intrusive granitic bodies. Lineation shows a ca. N-S ductile stretching associated with an overall top-to-the-North sense of shear. Final exhumation of the dome was thus completed by a system of two top-to-the-North detachments, operating in the ductile and then the brittle fields. The proposed tectono-metamorphic evolution of the dome is consistent with the evolution of the northern Aegean area, suggesting that Ikaria belongs to the Aegean MCC and that the NCDS continues eastward. Besides, the distribution of RSCM temperatures within the dome and the presence of migmatites in the western part of the island comply with the description of migmatite-cored MCC such as Naxos or Mykonos. A better comprehension of the geology of the island also permits to discuss the correlations of tectonic events and nappes between the Cyclades and the neighboring Menderes massif in western Turkey.

International audience; Back-arc extension in the Aegean Sea has been accommodated by several large-scale detachments such as the West Cycladic Detachment System (WCDS) in the Oligocene and Miocene. The WCDS is associated on Serifos island (Cyclades) with a synkinematic granodioritic intrusion. Serifos is also well known for its skarn deposit and a rich mineralogy as well as colder Fe-Ba ore deposits that were exploited until 1963. The geometrical and kinematic relations between the detachments and ore bodies have so far been little studied. Different types of skarn can be observed (1) massive garnet endoskarns, (2) garnet-pyroxene endoskarns in the granodiorite, (3) garnet-pyroxene cracks exoskarns, (4) brecciated pyroxene +/- ilvaite skarn within the Meghàlo Livadhi and Kavos Kiklopas detachments.Fields observations show that the formation of the skarn is intimately associated with the detachments and the deformation of the intrusion in the footwall. Endo and exo-skarn deposits formed before, during and after the ductile and brittle structures resulting from the activity of the WCDS. They are represented by echelon veins, veins with antithetic shear and boudinaged veins wrapped within sheath folds, with a shearing movement top SSW or SW compatible with the regional tectonics, deformation in host-rock and the emplacement of the syn-tectonic granodioritic intrusion. Skarnified breccias formed within the two main detachments attesting for the intense circulation of fluids at a certain distance from the main intrusion. These skarn parageneses were deposited by hydrothermal fluids associated with the intrusion, mixed with meteoric or oceanic fluids forming at the regional level of pyroxene. The two detachments acted as preferential crustal-scale drains during footwall exhumation. This example illustrates the potential of detachments to channelize large amount of fluids in the crust during extension.

International audience; Over the past thirty years, intense research has been devoted to interrelations of plutons emplacement and shear zones localization and development in various tectonic settings, from strike-slip, extensional to compressional. Within deforming continental regions, especially regions where Metamorphic Core Complexes (MCC) developed, emplacement of plutons interacts with processes of shear localization in the crust, and shear zones nucleation and their subsequent propagation are often coeval with the crystallization of magmas in plutonic bodies. Despite existing interest, the question of how and why plutons interact with extensional shear zones is still poorly understood. It is thus essential to recognize localizing events during emplacement and cooling of magmatic bodies, measure their kinematic and temporal indicators and evaluate their ability to localize deformation at the local and regional-scale. The Cyclades (Aegean Sea, Greece) form a well-suited area to study this relationship as the development of crustal-scale structures, metamorphism and emplacement of magmatic bodies are shown to be synchronous. The Cycladic granitoids (17-8Ma) intruded the middle/upper crust during thinning of the Aegean domain. They were all emplaced in close interaction with Miocene high-temperature metamorphic domes and associated crustal-scale detachments. Integrating existing data and our new observations performed on Serifos, Mykonos, Naxos and Ikaria Islands, we describe (1) the geometrical relationships between the granitoids, the host rocks and the crustal-scale detachments (2) kinematic indicators inside and outside the granitoids (3) distribution, localization and evolution of deformation within each pluton during emplacement and cooling. Intrusion, cooling and internal deformation of all granitoids were coeval and kinematically compatible with the development of detachments. One can indeed recognize a continuum of deformation from late-magmatic to brittle conditions within magmatic bodies during their emplacement and cooling, consistent with shearing recorded within host rocks. Plutons have an influence on the activity of detachments: in several examples the intrusion of a plutonic body makes the detachment migrate upward in the crust, progressively inactivating the deep branches of detachments (Mykonos, Tinos and Serifos). On the other hand the distribution and evolution of deformation in plutons show that their emplacements were largely tectonically controlled by active detachments and that the deformation tends to localize through time at the contact between granitoids and host rocks during their cooling. While the system of detachments exerts a control on the shape and final location of intrusions, the Serifos pluton recorded within a short time span strain localization resulting in shear zone nucleation and growth during its cooling. This study emphasizes once more the importance of regional tectonics and particularly that of detachments system in the control of granitic plutons emplacement, and introduces some additional constraints on the relationship between MCC formation, detachments and pluton emplacement in the Aegean Sea.

International audience; The Aegean domain is an ideal place to investigate the development of Metamorphic Core Complex (MCC) and to study the role of syn-tectonic granites on their development. MCCs of the Aegean domain are dynamically associated with a few major detachments, especially the North Cycladic Detachment System (NCDS) and the West Cycladic Detachment System (WCDS), which have accommodated a large part of the crustal thinning during the Oligocene and Miocene. The NCDS extends toward the East within the Simav Detachment that has exhumed the northern high-temperature part of the Menderes massif. The transition between the NCDS and the Simav Detachments is located above a major tear in the Aegean slab whose effects on lithospheric deformation are far from understood. The Aegean granitoids were emplaced during the Middle Miocene within a zone of high-temperature during the episode of slab tearing and recorded increments of extensional tectonics within this complex zone. Ikaria Island (Cyclades, Greece) is a metamorphic dome intruded by three Miocene granitoid plutons (one I-type intrusion, two S-type ones) including the largest pluton of the Aegean domain. However, geometry, structures and kinematics are still debated with several recent yet conflicting studies. We have reconsidered the geology of Ikaria to settle the geological and structural context of these plutons. The intrusion depth of the Raches granite has been estimated at 10-15 km by the Al-in-hornblende barometer. Our field study has led to the identification of two major structures: the Gialiskari and Kalamos detachments, which we interpret as belonging to the NCDS. A study of deformation in the granites has highlighted a continuum during cooling that can be described in three stages: i) magmatic deformation, ii) high-temperature ductile deformation from late magmatic stage until complete crystallization of the granite, iii) low-temperature brittle deformation. Throughout this evolution, the same top-to-the-NE shearing deformation was active below the Gialiskari and Kalamos detachments with a progressive localization of strain. A scenario of this deformation continuum below the Gialiskari-Kalamos detachments through the ductile-brittle transition is proposed. The granites were emplaced while the exhumation of the Ikaria high-temperature metamorphic dome was already underway. We conclude that the crustal-scale detachment has controlled the localization of the intrusion and not the opposite.

International audience; The Cycladic granitoids (Ikaria, Mykonos, Naxos, Kos, Lavrion, Serifos, Tinos) intruded the Aegean crust during a rather short period (17-10 Ma) compared to the much longer Oligo-Miocene crustal thinning phase (35 Ma to the Present). Their geochemical characteristics show that their sources have changed through time and space, with a progressive decreasing component of continental crust contamination with time and from east to west. They all interacted with large-scale detachments, namely the North Cycladic Detachment System (NCDS) in the north and the West Cycladic Detachment System (WCDS) in the south. In Mykonos, Naxos, Serifos and Ikaria the plutons are also associated with a high-temperature metamorphic dome of Miocene age. Their intrusion period roughly covers the same time window as the fast clockwise rotation of the western Aegean evidenced by paleomagnetic measurements and they are contemporaneous with a surge of alkaline volcanism in the eastern Aegean that can be related to a slab tear imaged below western Anatolia. The continental crust component in the Middle Miocene Cycladic plutons is not found in the early Miocene plutons of the northern Aegean, like in Kavala and Vrondou. They thus probably record a quite sudden thermal event in the Cyclades that led to the partial melting of the extending deep crust. We propose a model involving slab tear starting at ~17 Ma, fast retreat of the slab west of the tear and southwestward influx of hot asthenospheric material below the Aegean crust, leading to melting of the lower crust. Partial melting of the whole lower crust above the hot asthenospheric flow could explain the flat Moho observed below the Cyclades. The close proximity of plutons with the detachments suggests that their ascent toward the upper crust is favoured by the extreme extension at work there. The first granitoids in the region of the tear (Ikaria) are the richest in crustal component and this component decreases while the crust thins more and more, the youngest plutons being more purely derived from the mantle as for instance Kos and the granitic dyke swarm of Samos.

International audience; Plutons emplacement often interacts with the processes of shear localization in the continental crust, as well as the evolution of deformation from the magmatic stage to the sub-solidus stage in granitic magmas. Shear zones nucleation and their propagation are often coeval with the crystallization of magma. This interaction can be in both ways. On the one hand, shear zones can create a space for pluton emplacement. On the other hand, the partially crystallized magmatic bodies represent rheological heterogeneities that may trigger strain localization and shear zones nucleation that can become potential sources of high velocity displacements. In order to evaluate the potential strain localization at different scales from the magmatic stage to the sub-solidus stage in granitic bodies, a study of the Serifos granodiorite was undertaken. Serifos Island, located in the western part of the Cyclades Archipelago (Greece), is a structural dome whose core is dominated by an I-type granitoid. This Miocene pluton (10Ma) intruded the Cycladic Blueschists during thinning of the Aegean Sea below a crustal-scale low-angle normal fault system, namely the West Cycladic Detachment System (WCDS). Thermo-chronological data suggest that metamorphism related to the ductile extension was active during Miocene. Based on a field study and petrological and AMS data, we describe (1) the geometrical relationships between the pluton, the host rocks and the large-scale detachments (2) kinematic indicators inside and outside the pluton (3) distribution and evolution of deformation in the pluton during emplacement and cooling. Based on our field observations, we propose a cross section of Serifos Island, where the pluton shows a clear asymmetry related to the top-to-the South shear sense along the West Cycladic Detachment system. The large-scale structure of the pluton is entirely controlled by the top-to-the-south shearing associated with the WCDS and the shearing is distributed through the whole plutonic body while it is still soft and it tends to localize along narrow shear zones during cooling. One can indeed recognize a continuum of deformation from late-magmatic to brittle conditions within the magmatic body. This succession of deformation events from magmatic to sub-solidus is entirely kinematically compatible and coeval with the development of the WCDS. We finally propose a model of pluton emplacement during crustal extension in interaction with extensional shear zones.

Back-arc extension in the Aegean Sea has been accommodated by several large-scale detachments such as the West Cycladic Detachment System (WCDS) in the Oligocene and Miocene. The WCDS is associated on Serifos island (Cyclades) with a synkinematic granodioritic intrusion. Serifos is also well known for its skarn deposit and a rich mineralogy as well as colder Fe-Ba ore deposits that were exploited until 1963. The geometrical and kinematic relations between the detachments and ore bodies have so far been little studied. Different types of skarn can be observed (1) massive garnet endoskarns, (2) garnet-pyroxene endoskarns in the granodiorite, (3) garnet-pyroxene cracks exoskarns, (4) brecciated pyroxene +/- ilvaite skarn within the Meghàlo Livadhi and Kavos Kiklopas detachments. Fields observations show that the formation of the skarn is intimately associated with the detachments and the deformation of the intrusion in the footwall. Endo and exo-skarn deposits formed before, during and after the ductile and brittle structures resulting from the activity of the WCDS. They are represented by echelon veins, veins with antithetic shear and boudinaged veins wrapped within sheath folds, with a shearing movement top SSW or SW compatible with the regional tectonics, deformation in host-rock and the emplacement of the syn-tectonic granodioritic intrusion. Skarnified breccias formed within the two main detachments attesting for the intense circulation of fluids at a certain distance from the main intrusion. These skarn parageneses were deposited by hydrothermal fluids associated with the intrusion, mixed with meteoric or oceanic fluids forming at the regional level of pyroxene. The two detachments acted as preferential crustal-scale drains during footwall exhumation. This example illustrates the potential of detachments to channelize large amount of fluids in the crust during extension.