Samples from the Cap de Creus shear zone network were investigated to constrain the timing of the basement's polycyclic evolution by combining structural and microstructural analyses, electron imaging chemical investigations, and laser ablation mass spectrometry in situ RbSr and Th-U-Pb geochronology. Two generations of muscovite (Ms I and Ms. II) yield in situ RbSr isochron ages of 290–270 Ma and 60–50 Ma, consistent with UPb ages of c. 290 Ma in monazite cores and 50–30 Ma rims. Microstructure study shows that Ms. II grew during dynamic recovery of quartz ribbon precursors (Qz I). Fe-enrichment in Ms. II, localized in mica fish tails and C′ shear planes, along with Fe-rich veins marking Qz II grain boundaries, evidence that the RbSr system in muscovite recorded an episode of dynamic fabric recovery of quartz in presence of fluids. We thus demonstrate that rocks fabrics were annealed during late Variscan HT-LP metamorphism and deformation in the Early Permian, followed by ductile-plastic reactivation of the shear zones during the Eocene. This reactivation was facilitated by external fluid influx, drained by Ms. II neocrystallization and Qz II boundary migration. The Cap de Creus shear zones, usually interpreted as Variscan, also record a major Eocene reactivation during the formation of the Pyrenean orogenic prism through underthrusting of basement slices. These zones acted as early accommodation structures for crustal shortening. This study highlights the critical role of fluid-induced rheological softening in ductile reactivation of polycyclic basements and provides a context-dependent framework for interpreting the behavior of the RbSr geochronometer in muscovite during deformation.

Samples from the Cap de Creus shear zone network were investigated to constrain the timing of the basement's polycyclic evolution by combining structural and microstructural analyses, electron imaging chemical investigations, and laser ablation mass spectrometry in situ Rb-Sr and Th-U-Pb geochronology. Two generations of muscovite (Ms I and Ms. II) yield in situ Rb-Sr isochron ages of 290-270 Ma and 60-50 Ma, consistent with U-Pb ages of c. 290 Ma in monazite cores and 50-30 Ma rims. Microstructure study shows that Ms. II grew during dynamic recovery of quartz ribbon precursors (Qz I). Fe-enrichment in Ms. II, localized in mica fish tails and C ' shear planes, along with Fe-rich veins marking Qz II grain boundaries, evidence that the Rb-Sr system in muscovite recorded an episode of dynamic fabric recovery of quartz in presence of fluids. We thus demonstrate that rocks fabrics were annealed during late Variscan HT-LP metamorphism and deformation in the Early Permian, followed by ductile-plastic reactivation of the shear zones during the Eocene. This reactivation was facilitated by external fluid influx, drained by Ms. II neocrystallization and Qz II boundary migration. The Cap de Creus shear zones, usually interpreted as Variscan, also record a major Eocene reactivation during the formation of the Pyrenean orogenic prism through underthrusting of basement slices. These zones acted as early accommodation structures for crustal shortening. This study highlights the critical role of fluid-induced rheological softening in ductile reactivation of polycyclic basements and provides a context-dependent framework for interpreting the behavior of the Rb-Sr geochronometer in muscovite during deformation.

U-Th-Pb LA-ICPMS (Laser Ablation - Inductively Coupled Plasma Mass Spectrometry) has the power to elucidate the timing of metamorphism, deformation, migmatization, and plutonism. The Montagne Noire Variscan gneiss dome (southern French Massif Central) has been extensively studied, but interpretations of geochronology data remain highly debated. In tribute to Jean-Louis Paquette’s work, we first present the results of the last 10 years of reflection on our knowledge of the Montagne Noire dome, highlighting the various contributions of LA-ICPMS U-Th-Pb geochronology. Then, based on new structural, petrological and U-Th-Pb data obtained in the southeastern part of the Montagne Noire Axial Zone (MNAZ), in 'Les Gorges d'Héric” valley, we provide new insight into the structure and strain partitioning in this region and propose the existence of a crustal-scale dextral shear zone that we name the “Gorges d’Héric Shear Zone” (GHSZ). The LA-ICPMS U-Th-Pb age on monazite, obtained on a pegmatite cross-cutting vertical structures on the southern margin of the GHSZ, constrains that the end of ductile deformation at ca. 295 Ma. Further north, a localized deformation corridor is accompanied by significant metasomatism recorded in retrogressed eclogite lenses. U-Th-Pb results obtained on zircon from this metasomatized metamafic rock highlight a long and complex geological history, including inherited components with a magmatic protolith emplacement linked to early Paleozoic event(s) and the existence of a high-grade metamorphic event dated at ca. 315 Ma. The 315 Ma event triggered the formation of eclogites in the core of the Variscan belt and, at the same time, the early stage of low-pressure – high-temperature metamorphism associated with the emplacement of the dome. Most of the zircon U-Pb data give a concordia age of 280.6 ± 2.5 Ma, interpreted as the age of zircon (re)crystallization during localized deformation and fluid circulation along E-W trending shear zones within the GHSZ, probably related to the well-known early Permian regional volcanic episode. Within the GHSZ, the geochronological dataset spans the period from 320 Ma to 280 Ma, suggesting that this is a significant structure that progressively accommodated the transition between the Variscan and Alpine cycles.

U-Th-Pb LA-ICPMS (Laser Ablation − Inductively Coupled Plasma Mass Spectrometry) has the power to elucidate the timing of metamorphism, deformation, migmatization, and plutonism. The Montagne Noire Variscan gneiss dome (southern French Massif Central) has been extensively studied, but interpretations of geochronology data remain highly debated. In tribute to Jean-Louis Paquette’s work, we first present the results of the last 10 yr of reflection on our knowledge of the Montagne Noire dome, highlighting the various contributions of LA-ICPMS U-Th-Pb geochronology. Then, based on new structural, petrological and U-Th-Pb data obtained in the southeastern part of the Montagne Noire Axial Zone (MNAZ), in “Les Gorges d’Héric” valley, we provide new insight into the structure and strain partitioning in this region and propose the existence of a crustal-scale dextral shear zone that we name the “Gorges d’Héric Shear Zone” (GHSZ). The LA-ICPMS U-Th-Pb age on monazite, obtained on a pegmatite cross-cutting vertical structures on the southern margin of the GHSZ, constrains the end of ductile deformation at ca. 295 Ma in that part of the shear zone. Further north, a localized deformation corridor is accompanied by significant fluid circulation recorded in retrogressed metamafic lenses. Petrographic observations reveal a complex mineralogical evolution characterised by the formation of garnet, amphibole, orthopyroxene, and secondary spinel, interpreted as the product of fluid-driven mineral reactions. Potassium metasomatism is responsible for the development of syn-kinematic biotite. The final retrograde stage is marked by the development of amphibole + chlorite assemblages and late serpentinization reactions. U-Th-Pb results obtained on zircon grains highlight a long and complex geological history. Three age populations have been identified and associated with: (1) the magmatic protolith emplacement likely to be linked to early Paleozoic event(s), (2) the existence of a ca. 315 Ma event interpreted as a high-grade metamorphic imprint and (3) a last corresponding to most of the zircon U-Pb data gives a concordia age of 280.6 ± 2.5 Ma, interpreted as the age of zircon (re)crystallization during localized deformation and aqueous fluid circulation along the GHSZ, probably related to the well-known early Permian regional volcanic episode. Within the GHSZ, the geochronological dataset spans the period from 320 Ma to 280 Ma, suggesting that this is a significant structure.

Aegean extension began during Eocene-Oligocene times and led to the thinning of the upper plate into a retreating slab system. The style of extension during the Miocene remains controversial, with a majority of studies arguing for extension accommodated by low-angle extensional brittle-ductile faults, called detachments. In other hands, the present-day active seismic faults in the Aegean Sea are only high-angle normal faults and dextral strike-slips. We aim to constrain and date the style of faulting in central Greece by combining analysis of 19 offshore seismic lines with onshore structural observations on Syros Island and LA-ICP-MS U-Pb dating of calcite sampled in two major fault zones of Syros (Palos and Fabrika faults). Three main sets of faults have been identified in the Central Cyclades: NW-SE trending normal faults, NNW-SSE oblique (sinistral)-normal faults, and NNE-SSW trending dextral strike-slip faults. High-angle normal faults define regularly spaced horsts and grabens, suggesting a wide rifting-type of extension. Dextral strike-slip faults occur at Syros, mainly offshore, and are kinematically compatible with normal faults. U-Pb dating of calcite crystallizing in normal fault planes at Syros yields ages at c.a. 10 Ma for high-angle normal faults activity. On these bases, we propose that wide rifting with high-angle normal faults accommodated Aegean extension when trench retreat accelerated in the middle to late Miocene. At this time, dextral strike-slip faults formed as a response of the onset of Anatolia lateral extrusion.

This study investigates the P–T–t–D evolution of two metapelitic samples from the middle crust exposed in the Aiguilles Rouges Massif. Garnet compositional mapping, phase equilibrium modelling, zirconium-in-rutile thermometry, trace element geochemistry of garnet and monazite, and U-Pb LA-ICP-MS dating on monazite were used to better understand the tectonic and thermal history of the variscan External Crystalline Massifs. In the sample representing the upper-middle crust (AR736, southwestern part of the massif), using the preserved mineral assemblage in garnet inclusion (Grt + St + Bt + Ms + Qz + Pl + Rt) and garnet compositions, the prograde P–T path was constrained from ∼0.5–0.6 GPa and 550–625 °C to ∼0.76–0.82 GPa and 600–640 °C. The P–T conditions at the onset of this prograde evolution suggest a high geothermal gradient (∼30–35 °C/km) prior to the onset of crustal thickening. In the sample representing the lower-middle crust (AR14, central part of the massif), using the preserved mineral assemblage in garnet inclusion (Grt + Bt + Ms + Qz + Pl + Rt), the occurrence of sillimanite and ilmenite in the matrix and garnet compositions, a β-shaped P–T path characterised by a late temperature increase during exhumation was identified. Both samples recorded a retrograde P–T stage at ∼0.4 GPa and 545 °C, dated at 315–305 Ma. Microstructural analysis indicates dextral transcurrent deformation from the late crustal thickening stage to the exhumation phase. Comparison with previously published P–T paths from eclogitic lenses highlights the juxtaposition of middle and lower crustal domains during dextral transcurrent deformation. We propose a tectonic model in which the formation of supra-subduction volcano-sedimentary basins (∼350 Ma) is followed by crustal thickening between 350 and 340 Ma under a thermal gradient of ∼5–15 °C/km. The exhumation of the lower and middle crust took place in a transcurrent regime between 340 and 305 Ma. This prolonged transcurrent tectonic activity suggests that the numerous transcurrent shear zones in the Variscan belt are not merely late orogenic structures but played a significant role in the geodynamic evolution, particularly in the exhumation of the orogenic crust, from the end of continental collision to the closure of the Variscan orogeny.

A striking feature of the Imilchil alkaline province, in the Moroccan Central High Atlas, is the close association of magmatic intrusions with Triassic sediments exhumed by diapirism. This study reports field, petrographic, geochemical and Sr-Nd isotopic data, as well as new U-Pb zircon ages, which allow us to constrain the timing of the intrusions and to discuss their relationship to diapiric structures and the magmatic and hydrothermal processes. Our results indicate a restricted range of Late Jurassic ages (ca. 163 +/- 1-ca. 149 +/- 2 Ma) for the paroxysm of magmatic activity and confirm the diachronicity between diapirism and magmatism, albeit with a short interval of only a few My between the end of diapirism and the magmatic paroxysm. Deep-seated faults associated with transtensional tectonics, accommodating the increasing spreading rate of the Central Atlantic during the Jurassic, played a key role in the close association of magmatic intrusions with diapirs. The faults first triggered active diapirism in the Early- Jurassic and then guided OIB-type partial melts formed by local decompression melting of the mantle. At shallower depths, the diapiric structures acted as corridors for magma migration, probably using evaporites as preferential pathways. Magmas underwent fractional crystallization and interacted with evaporites to produce pervasive Na-rich hydrothermal fluids.

Defying traditional plate tectonics, the Alice Springs Orogeny (ASO) developed between 450 to 300 Ma deep within the interior of the Australian continent, at significant distances from any plate boundaries. The region NE of the Amadeus basin presents a surprising geological association of the Entia gneiss dome, exhuming high-grade Paleoproterozoic gneisses alongside a nappe complex comprising high-grade rocks of the Harts Range Metamorphic Complex and Paradise Nappes and their lower-grade Neoproterozoic covers. These isoclinally folded nappes were thrust onto the lower-grade Ruby Gap duplex and White Range duplex, which consist of Amadeus basin sequences, overlapping the Amadeus basin. Collectively, these nappes constitute the Arltunga Nappe Complex. Understanding of the regional geology took a transformative turn when detrital zircon data revealed that the HRMC, into which the Entia dome was emplaced, did not belong to the Paleoproterozoic basement. Instead, these gneisses are the metamorphic equivalent of Neoproterozoic to Palaeozoic marine siliciclastic and limestone sediments of the Amadeus Basin. A transect from the Entia Dome to the Ruby Gap duplex reveals conformable structures that juxtapose a high-grade extensional domain (the Entia dome), and a low-grade contractional domain (the Ruby Gap and White Range duplexes), across a transitional zone containing the Bruna décollement zone and the Illogwa shear zone. Exhumation of the Entia Dome and shearing and thrusting of the Arltunga Nappe Complex are age-bracketed between ~345 and ~310 Ma. The structural continuity and geochronology suggest that these features are synchronous and interrelated. Numerical experiments support a tectonic model in which the dome and nappe complex formed synchronously because of the convergent gravitational collapse of the Paleozoic Harts Range Rift basin. In this model, the Entia dome was emplaced into the 30-40 km deep Harts Range Rift basin, the base of which reached granulite facies metamorphism and melting at ~470 Ma. The density contrast between the Neoproterozoic to Paleozoic sedimentary basin infill and the metamorphic Paleoproterozoic basement created a strong horizontal pressure gradient, leading to significant gravitational stresses acting laterally towards the basin. As the geotherm in the basin reached melting conditions, these gravitational forces may have overcome viscous strength to drive centripetal flow, forcing the exhumation of the Entia Dome and the development of gravity nappes at the Earth’s surface.

In central Australia, an apparently coeval gneiss dome (Entia Dome) developed adjacent to a thrust belt (Arltunga Nappe Complex) within an intracratonic setting. Here we employ a combination of fieldwork, geochronology, and numerical modeling to investigate the structure and tectonic evolution of these features. We present a structural model linking an extensional domain comprising the Entia Dome, across a transitional zone containing the Bruna decollement zone and the Illogwa shear zone, into a contractional zone comprising thrusts and duplexes of the Arltunga Nappe Complex. Supported by numerical modeling, we propose a tectonic model in which the dome and nappe complex formed synchronously because of the convergent gravitational collapse of the 30-40-km-deep Paleozoic Harts Range rift.

In this contribution, we investigate the spatial and temporal evolution of mid-crustal flow in the Agly Massif (North Pyrenean Zone) that represents the southern foreland of the Variscan orogenic plateau. In the Agly Massif, the middle crust is represented by an Ediacarian–Devonian series of metasedimentary rocks that recorded high-grade metamorphism synchronously with crustal thinning (D2) and dextral wrenching (D3) during Carboniferous. D2 crustal thinning formed a penetrative S2 flat-lying foliation and localized C2 extensional shear zones with a top-to-the-North kinematics. D2 planar fabrics are deformed by a D3 dextral transpression localized into a two-kilometer wide high-strain zone. We performed LA-ICPMS U–Th–Pb dating on zircon and monazite from small magmatic bodies and from metamorphic rocks showing strain features relative to D2 and/or D3. Our results, compiled with published data, argue that the middle crust of the Agly Massif reached high-temperature and suprasolidus conditions at ca. 325–320 Ma and was partially molten until ca. 300 Ma. They also indicate that the D2 thinning and top-to-the north shearing was active from ca. 325–290 Ma. D2 extension and D3 transpression were synchronous from ca. 308–290 Ma. Making a comparison with the Pyrenean Axial Zone, the Montagne Noire and the French Central Massif, we propose a two-step tectonic model for the mid-crustal flow with a horizontal flow towards South in both the orogenic plateau and the southern forelands between ca. 325 and 310 Ma and locally reoriented into an E–W longitudinal flow between 310 and 300 Ma in high-strain dextral strike-slip shearing domains.

In exhumed orogens, refractory mafic rocks have the potential to preserve a record of petrogenesis and high-pressure (HP) metamorphism that is commonly obliterated in quartzofeldspathic rocks owing to re -equilibration at high-temperature, low-pressure (LP-HT) conditions. In the Montagne Noire (France) migma-tite dome, located in the foreland of the Variscan orogen, eclogite is exposed in both the core and margin of the dome. In this study, we combine in situ U-Pb petrochronology and oxygen-isotope analyses of key eclogite phases to demonstrate that eclogites from the two distinct domains had different protoliths and source regions, traveled relatively variable distances in the deep crust, and differentially interacted with surrounding migmatite prior to exhumation. Dome-margin eclogite zircons are small (-40 mu m) with well-preserved inherited cores and thin (<15 mu m) rims, compared to larger (40-120 mu m) neo-and recrystallized dome-core zircons with small relict cores and wide (15-30 mu m) recrystallized rims. Protolith and HP metamorphism ages were determined using in situ zircon and rutile petrochronology (LASS-ICP-MS). Both eclogites formed in a continental setting; dome margin protolith zircon cores formed at 442.5 +/- 3.4 Ma (steep HREE slope, no Eu-anomaly) whereas zircon cores of the dome-core eclogites yielded scattered dates suggesting protolith crystallization between-500-400 Ma (steep HREE slope, pronounced Eu-anomaly). Both eclogites experienced HP metamorphism at c. 320-310 Ma in garnet-stable, plagioclase-absent conditions. Most analyzed rutile yielded dates of 307-304 Ma associated with cooling. The record of HP fluid conditions was determined by O-isotope (SIMS) analyses of garnet and zircon. Dome-margin zircon cores and rims have 818O of-8.2-8.5 %o, indistinguishable within uncertainty, in isotopic equilibrium with isotopically unzoned garnet (818O -8.0-8.2 %o). In contrast, zircons in dome-core eclogites have systematically lower zircon-core 818O values compared to their rims and neocrystallized grains, and zircon cores were in equilibrium with major-cation zoned garnet with respect to oxygen. The two dome-core eclogite samples yielded zircon and garnet 818O values of-8.6-9.5 %o and -9.7-10.5 %o. Based on these results and existing HP fabric data for these eclogites, we propose that (1) gabbro protoliths for the two eclogites were emplaced at different depths in a Cambro-Ordovician continental crustal package; and (2) dome-core eclogites interacted extensively with surrounding gneiss during burial and foreland-vergent crustal flow, whereas the dome-margin eclogite was sourced proximally to the dome-emplacement location and had minimal chemical interaction with surrounding gneiss. At least parts of the Montagne Noire migmatite dome were deeply sourced, but rocks exhumed in the core had a more extensive and protracted history of deep-crustal flow than deep-crustal rocks exhumed at the margin.

Mafic eclogites are found in many orogens as lenses embedded in quartzofeldspathic migmatites. These high-pressure relics are interpreted either as remnants of ancient sutures and thus formed during oceanic subduction or as fragments of lower crust exhumed from the root of orogenic thickened crust. It is critical to distinguish between these two endmember scenarios as the resulting palaeogeographic and geodynamic reconstructions may significantly differ. In this contribution, we investigated eclogite relics from Lac Cornu in the Aiguilles-Rouges massif, one of the External Crystalline Massifs of the Western Alps. Phase equilibrium modelling suggests that these mafic rocks were buried along a prograde path (M1) from similar to 600 degrees C/1.2 to 1.6 GPa to peak conditions of similar to 630-775 degrees C and >1.6 GPa. Zircon rims, with a rare earth element signature typical of eclogite facies zircon (no Eu anomalies, flat HREE spectrum), and rutile were dated by U-Th-Pb laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) at c. 335-330 Ma. Prograde deformation has not been identified in the field and is only recognized thanks to the crystallographic preferred orientation (CPO) of inclusions of omphacite and rutile in garnet. Peak pressure conditions were followed by a decompression stage (M2) from similar to 760 degrees C/1.4 GPa to similar to 600-650 degrees C/0.9 GPa supported by the breakdown of omphacite into plagioclase-clinopyroxene symplectite and the crystallization of plagioclase-amphibole corona around garnet. The M2 retrogression stage is associated with the development of a main sub-horizontal planar fabric and the CPO of minerals composing symplectite. This deformation stage is interpreted as the result of horizontal lower crustal flow. The final stage of exhumation (M3) is characterized by the replacement of symplectite and garnet by plagioclase and large euhedral amphibole and by the breakdown of rutile and ilmenite into titanite dated at c. 300 Ma. The CPO of titanite and amphibole are consistent with the development of vertical dextral shear zone in a transpressive regime. The combination of field observations and petrological, microtextural and geochemical analyses suggests that the mafic eclogites preserved in migmatitic rocks of the Aiguilles-Rouges massif are remnants of a continental lower crust exhumed and juxtaposed with lower-grade migmatites in crustal-scale vertical transpressive shear zones.

The Variscan basement of the Aiguilles-Rouges massif (Western Alps) exposes the Servoz syncline which consists of a metavolcano-sedimentary sequence composed of (i) a volcanic unit of unknown age and origin, (ii) Early Carboniferous sedimentary series affected by the Variscan orogeny and intruded by the Montées-Pélissier pluton, and (iii) a Late Carboniferous late-orogenic sedimentary sequence. We combined field investigations, Raman Spectroscopy on Carbonaceous Material geothermometry, and LA-ICPMS U-Th-Pb geochronology on zircon in order to reappraise the sedimentary sequence of the Servoz syncline. Our results allow us to identify three distinct sedimentary formations (F1, F2 and F3). The F1 formation is composed of metagreywackes, bimodal volcanic and magmatic rocks formed during basin opening at an early rifting stage (370–350 Ma) within a back-arc geodynamic setting. This extensional regime was responsible for a high thermal event recorded by a ca. 115 °C/km apparent geothermal gradient. Local anatexis of the basement rocks under the basin is dated at 351 ± 5 Ma. Basin inversion occurred between 350 and 330 Ma in response to oblique collision, with the development of large-scale dextral shear zones and syn-kinematic 340–330 Ma granite intrusions. Subsequent dextral transtension was responsible for the opening of a pull-apart basin between ca. 330 and 310 Ma with the deposition of the F2 phyllite formation that was later deformed by the ongoing dextral transcurrent Variscan tectonics at temperatures between 200 and 350 °C. Finally, the F3 terrigenous sedimentary rocks deposited at ca. 310–290 Ma in a late-orogenic extensional basin. The Alpine-related tectonic event overprinted all the temperatures below 350 °C. Although similar basins have been recognized in other External Crystalline Massifs of the Alps, the Servoz syncline is the first example that allows a major part of the polyphase tectonic evolution, since the early stages of the Devonian, to be recognized. Comparison with similar back-arc basins from the French Central massif, the Vosges massif and the Bohemian massif suggests that the External Crystalline Massifs initially belonged to the Moldanubian hinterlands of the Variscan belt.

The Aiguilles-Rouges and Mont-Blanc massifs represent a segment of a crustal-scale transpressional shear zone named the East Variscan Shear Zone (EVSZ) along which two plutonic pulses occurred during Early and Late Carboniferous times. The aim of this study is to constrain the relationships between the dynamics of the crustalscale shear zone, the mechanisms of pluton emplacement at different structural levels within the crust and the magma sources. A detailed structural analysis of the whole massif highlights the crustal-scale anastomosed network of the EVSZ. Microstructural observations and LA-ICPMS U-Th-Pb zircon ages from large plutons constrain the beginning of the transpression at ca. 340 Ma. From 340 to 305 Ma, the EVSZ broadened and formed a 25 km-wide dextral S-C-C' anastomosed shear zone network with dilation zones acting as preferential pathways for melt migration and pluton growths. Moreover, LA-ICPMS U-Th-Pb zircon ages from small magmatic bodies (i.e. pegmatite, aplite and microgranite) indicate an Ordovician-age inheritance component. Field evidences and zircon inheritance indicate that Late Carboniferous granitic melts are mainly derived from waterfluxed melting of Ordovician orthogneiss with the input of mantle-source derived magmas. Over time, the growth of the dextral anastomosed network enhanced water transfer through the shear zones and water-fluxed melting to produce more anatectic melts.

In orogens, pinpointing the timing of mineralization is often complex due to superimposition of magmatic, metamorphic and tectonic events. Unravelling the tectono-metamorphic evolution of deformed terranes is essential for understanding the formation of orogenic mineralization. In the Boss`ost dome of the Pyrenean Axial Zone, undated stratabound Pb-Zn mineralization previously considered to be SEDEX-like and devoid of evidence for significant remobilization/deformation, was recently interpreted as orogenic mineralization and structurally -controlled by Variscan tectonics. However, relations with the poly-magmatic and metamorphic events reported in the Pyrenean Axial Zone are still poorly constrained. In the Boss`ost dome, laser-ablation inductively coupled plasma mass spectrometry (LA-ICPMS) U-Th-Pb dating was performed on zircon to constrain the formation ages of two undeformed granitic dykes, and on monazite to identify both the metamorphic imprint recorded by two metapelites and the formation of stratabound Pb-Zn mineralization in the Bentaillou deposit. late-Carboniferous - early-Permian magmatic zircon ages (315-280 Ma) are commonly found in these undeformed dykes (307.4 +/- 4.7 Ma and 283 +/- 15 Ma), consistent with the main magmatic event, extensively recorded in the Pyrenean Axial Zone. Monazite crystals with co-genetic textural relationships with stratabound sphalerite from Bentaillou were dated at 309 +/- 11 Ma. We propose that the stratabound mineralization is formed during one main Variscan remobilization event associated with the first Variscan deformation event (D1) and probable metamorphic fluid circulation in pre-existing metal-rich Ordovician sedimentary levels. Moreover, monazite ages in metapelite rocks (289.1 +/- 5.9 Ma and 290.0 +/- 3.8 Ma) probably date both the end of high T - low P metamorphism and late fluid circulation in the Variscan tectonothermal event. Visean-Serpukhovian ages (340-325 Ma) are found in one inherited zircon and in two monazites included in garnet and staurolite, which probably record the end of the first Variscan magmatic-metamorphic event, mainly recorded in the core of the Pyrenean Axial Zone. Based on our ages and a regional synthesis, we propose a new tectono-metamorphic model for the Boss`ost dome and the related formation of Pb-Zn mineralization.