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17 results on '"Variscan Pyrenees"'

1. Polyphase magmatic pulses along the Northern Gondwana margin: U-Pb zircon geochronology from gneiss domes of the Pyrenees.

Author

Schnapperelle, S., Mezger, J.E., Stipp, M., Hofmann, M., Gärtner, A., and Linnemann, U.

Abstract

Alkaline granitic dikes intruding the metasedimentary mantle and orthogneiss cores of the Aston and Hospitalet domes of the Axial Zone of the Pyrenees are subjects of a laser ablation ICP-MS U-Pb zircon geochronology study. The age spectra recorded by detrital, magmatic xenocrystic and inherited zircons reveal a more complex, nearly continuous Paleozoic magmatic history of the Variscan basement of the Pyrenees than previously known. Inherited and detrital zircons of Mesoarchean, Paleoproterozoic to Ediacaran ages attest to the Peri-Gondwana location of the Cambrian sediments that later form the metamorphic core of the Variscan Pyrenees. The youngest magmatic zircon ages fall into the late Carboniferous and earliest Permian, ranging from ca. 306–297 Ma, and represent the emplacement ages of the dikes and small granite intrusions. The age spectra of magmatic xenocrystic zircons contain several maxima, middle (475–465 Ma) and late Ordovician (455–445 Ma), early (415–402 Ma) and late Devonian (385–383 Ma), early (356–351 Ma) and middle Carboniferous (ca. 328 Ma). Middle Ordovician and middle Carboniferous ages are obtained from xenocrystic zircons that were assimilated from the rocks the dikes intruded, the Aston and Hospitalet orthogneisses and the Soulcem granite. The presence of early-mid Carboniferous magmatic zircons in several samples lends further support to a wide-spread early Variscan magmatic activity in the central Pyrenees. The other age peaks do not have equivalent igneous or metaigneous rocks in the central Axial Zone, but are thought to be present in the Pyrenean crust, not exposed and yet to be identified. The diversity of Ordovician, Devonian and Carboniferous up to Permian magmatic ages indicates polyphase emplacement of intrusive bodies during pre-Variscan and Variscan orogenies. The source of the heat for the Devonian to early-mid Carboniferous magmatic activity remains elusive and may involve intracontinental subduction zone, lithospheric-scale shearing or a mantle plume (TUZO). Unlabelled Image • Carboniferous granite dikes within Pyrenean gneiss domes probe Variscan basement. • Zircon xenocrysts reveal near continuous Cambrian to early Permian magmatic activity. • First evidence for Devonian magmatism and confirmation of early Carboniferous pulse [ABSTRACT FROM AUTHOR]

Published
2020
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2. Anisotropy of magnetic susceptibility of the Pyrenean granites

Author

Manuel Porquet, Emilio L. Pueyo, Teresa Román-Berdiel, Philippe Olivier, Luis A. Longares, Julia Cuevas, Javier Ramajo, the Geokin3DPyr working group by alphabetical order, Borja Antolín, Aitor Aranguren, Jean Baptiste Auréjac, Jean-Luc Bouchez, Antonio M. Casas, Yoann Denèle, Gerard Gleizes, Asier Hilario, Esther Izquierdo-Llavall, Dennis Leblanc, Belén Oliva-Urcia, Vicente Santana, José M. Tubía, and Nestor Vegas

Subjects
AMS, Variscan Pyrenees, magnetic lineation, magnetic foliation, bulk susceptibility, granitoid, Maps, G3180-9980
Abstract

In this paper, we report on a compilation of more than 2200 sites (more than 10,000 individual measurements) where anisotropy of magnetic susceptibility (AMS) was studied in granites from the Variscan Pyrenees. The standardization and homogenization of this information has allowed us to produce three Main Maps that synthesize all the information related with the AMS of the Pyrenean granites. We also describe the problems found during the construction of the database (variable geo-positioning, different published information, etc.). The information derived from 21 granite bodies, the database, and the synthesis maps (magnetic susceptibility, Km, and the orientation of the magnetic foliation, plane perpendicular to k3, and of the magnetic lineation, k1) allow us to see for the first time a complete image of this important kinematic and petrographic indicator.

Published
2017
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3. Evolution of the middle crust of the Pyrenees during the Paleozoic: new data on the plutonic rocks from the North Pyrenean Agly Massif.

Author

Guille, B. Tournaire, Olivier, Ph., Paquette, J. -L., Bosse, V., and Guillaume, D.

Subjects
*PALEOZOIC Era, *IGNEOUS intrusions, *CRUST of the earth, *GRANITE
Abstract

The Variscan middle crust of the eastern Pyrenees is represented by the Bélesta and Caramany gneissic units of the North Pyrenean Agly Massif. In this study, we date and reinterpret the orthogneisses and granites composing these units. We characterize a recurrent plutonic activity spanning all the Paleozoic in this part of the Pyrenean crust. The Bélesta unit (amphibolite facies) is mainly composed of sills of (Latest Ediacaran)-Earliest Cambrian (542 ± 4 and 540 ± 4 Ma) orthogneisses (70% of the series), almost unknown in the Pyrenees until now, and Latest Carboniferous-(Earliest Permian) (307 ± 3-298 ± 3 Ma time span) granites (15% of the series). These plutonic rocks were emplaced in probably Ediacaran aluminous pelites later transformed into paragneisses (15% of the series). The Caramany unit (granulite facies) is mainly composed of Precambrian aluminous paragneisses migmatized during the Latest Carboniferous-(Earliest Permian) (299 ± 4 Ma), sills of Earliest Cambrian (529 ± 5 Ma) orthogneisses and sills (about 30% of the series) of Late Carboniferous (308 ± 3-299 ± 3 Ma) opx-bearing and opx-free granodiorites, grt-bearing leucogranites and norites. Among these last rocks, the Ansignan charnockite, forming a 800 m-thick laccolith near the base of the Caramany unit, and previously dated at 314 ± 6/7 Ma (Respaut, Lancelot, Neues Jahrbuch Miner Abh 147-1:21-34, 1983), is refined at 307 ± 3 Ma. Our results confirm the importance of the Late Carboniferous plutonism in deep levels of the Pyrenean crust, which largely resulted from recycling of older para- and orthoderived rocks of this crust. The emplacement of hundreds of metres in thickness of granites and other plutonic rocks in the Variscan Pyrenees occurred in a rather short time both as sills in these deep levels and as large plutons in shallower levels, a fact which necessarily had consequences on the HT-LP Carboniferous metamorphism. [ABSTRACT FROM AUTHOR]

Published
2019
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4. Anisotropy of magnetic susceptibility of the Pyrenean granites.

Author

Porquet, Manuel, Pueyo, Emilio L., Román-Berdiel, Teresa, Olivier, Philippe, Longares, Luis A., Cuevas, Julia, Ramajo, Javier, Antolín, Borja, Aranguren, Aitor, Auréjac, Jean Baptiste, Bouchez, Jean-Luc, Casas, Antonio M., Denèle, Yoann, Gleizes, Gerard, Hilario, Asier, Izquierdo-Llavall, Esther, Leblanc, Dennis, Oliva-Urcia, Belén, Santana, Vicente, and Tubía, José M.

Subjects
GRANITE, MAGNETIC susceptibility, MOUNTAINS
Abstract

In this paper, we report on a compilation of more than 2200 sites (more than 10,000 individual measurements) where anisotropy of magnetic susceptibility (AMS) was studied in granites from the Variscan Pyrenees. The standardization and homogenization of this information has allowed us to produce threeMain Mapsthat synthesize all the information related with the AMS of the Pyrenean granites. We also describe the problems found during the construction of the database (variable geo-positioning, different published information, etc.). The information derived from 21 granite bodies, the database, and the synthesis maps (magnetic susceptibility, Km, and the orientation of the magnetic foliation, plane perpendicular to k3, and of the magnetic lineation, k1) allow us to see for the first time a complete image of this important kinematic and petrographic indicator. [ABSTRACT FROM PUBLISHER]

Published
2017
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5. Fluid-fluxed melting and melt loss in a syntectonic contact metamorphic aureole from the Variscan eastern Pyrenees.

Author

Aguilar, C., Liesa, M., Reche, J., and Powell, R.

Subjects
*METAMORPHISM (Geology), *MIGMATITE, *BIOTITE, *SEDIMENTARY rocks
Abstract

Open-system behaviour through fluid influx and melt loss can produce a variety of migmatite morphologies and mineral assemblages from the same protolith composition. This is shown by different types of granulite facies migmatite from the contact aureole of the Ceret gabbro-diorite stock in the Roc de Frausa Massif (eastern Pyrenees). Patch, stromatic and schollen migmatites are identified in the inner contact aureole, whereas schollen migmatites and residual melanosomes are found as xenoliths inside the gabbro-diorite. Patch and schollen migmatites record D1 and D2 structures in folded melanosome and mostly preserve the high- T D2 in granular or weakly foliated leucosome. Stromatic migmatites and residual melanosomes only preserve D2. The assemblage quartz-garnet-biotite-sillimanite-cordierite±K-feldspar-plagioclase is present in patch and schollen migmatites, whereas stromatic migmatites and residual melanosomes contain a sub-assemblage with no sillimanite and/or K-feldspar. A decrease in XFe (molar Fe/(Fe + Mg)) in garnet, biotite and cordierite is observed from patch migmatites through schollen and stromatic migmatites to residual melanosomes. Whole-rock compositions of patch, schollen and stromatic migmatites are similar to those of non-migmatitic rocks from the surrounding area. These metasedimentary rocks are interpreted as the protoliths of the migmatites. A decrease in the silica content of migmatites from 63 to 40 wt% SiO2 is accompanied by an increase in Al2O3 and MgO+FeO and by a depletion in alkalis. Thermodynamic modelling in the NCKFMASHTO system for the different types of migmatite provides peak metamorphic conditions ~7-8 kbar and 840 °C. A nearly isothermal decompression history down to 5.5 kbar was followed by isobaric cooling from 840 °C through 690 °C to lower temperatures. The preservation of granulite facies assemblages and the variation in mineral assemblages and chemical composition can be modelled by ongoing H2O-fluxed melting accompanied by melt loss. The fluids were probably released by the crystallizing gabbro-diorite, infiltrating the metasedimentary rocks and fluxing melting. Release of fluids and melt loss were probably favoured by coeval deformation (D2). The amount of melt remaining in the system varied considerably among the different types of migmatite. The whole-rock compositions of the samples, the modelled compositions of melts at the solidus at 5.5 kbar and the residues show a good correlation. [ABSTRACT FROM AUTHOR]

Published
2016
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6. Geochemistry and zircon U–Pb geochronology of the ultramafic and mafic rocks emplaced within the anatectic series of the Variscan Pyrenees: The example of the Gavarnie–Heas dome (France).

Author

Kilzi, Mohammad A., Grégoire, Michel, Bosse, Valérie, Benoît, Mathieu, Driouch, Youssef, de Saint Blanquat, Michel, and Debat, Pierre

Subjects
*GEOCHEMISTRY, *ZIRCON, *GEOLOGICAL time scales, *ULTRABASIC rocks, *MAFIC rocks, *PLAGIOCLASE, *HERCYNIAN orogeny
Abstract

The origin and evolution of ultramafic (UM), mafic (M) and intermediate rocks emplaced within the metamorphic and anatectic series of the middle crust of the Variscan segment of the Pyrenees are defined in the light of new isotopic data U–Pb zircon ages, and Sr, Nd isotopic ratios. In the Gavarnie–Heas dome (central Pyrenees), ultramafic, mafic and intermediate rocks form three massifs several kilometers in size emplaced within the anatectic series: (i) the Gloriettes massif, which mostly consists of norites with enclaves of ultramafic rocks; (ii) the Troumouse massif, which comprises intermediate rocks (gabbro-diorite and diorite) with norite enclaves, and (iii) the Aguila massif, which consists of intermediate rocks with hornblendite enclaves. U–Pb zircon geochronology (first data for these rock types in the Axial Zone of the Pyrenees) revealed an age of 294 Ma for the diorite crystallization and correlatively for the crystallization of the anatectic granite. This new radiometric age allows us to suggest that the Variscan orogeny continued at least until the Early Permian and spread over around 30 Ma. The Nd and Sr isotopic compositions of all UM and M samples plot within the field of the continental crust. Two scenarios can explain the genesis and the emplacement of the components of the magmatic suite: i) evolution of mantle melts and contamination (AFC); ii) evolution of melts originating from a heterogeneous source (mantle + crust) at the local or regional scale. The strong crustal affinity of all UM and M rock types from Gavarnie–Heas leads us to favor the second scenario. [ABSTRACT FROM AUTHOR]

Published
2016
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7. Early Variscan (Visean) granites in the core of central Pyrenean gneiss domes: implications from laser ablation U-Pb and Th-Pb studies.

Author

Mezger, Jochen E. and Gerdes, Axel

Abstract

Laser ablation U-Pb and Th-Pb single zircon and monazite geochronology was applied to seven samples from two Variscan gneiss domes in the central Pyrenean Axial Zone. Detrital zircon ages obtained from a paragneiss in the western Aston dome range from Neoarchean (ca. 2.57 Ga) to Late Neoproterozoic (ca. 560 Ma), suggesting that late Ediacaran sediments were deposited along the northern margin of Gondwana. Cadomian magmatism is recorded for the first time in the central Pyrenees from a biotite metagranite (ca. 545 Ma) in the central Aston dome. A second sample of an orthogneiss from the Aston dome yields a Middle Ordovician protolith age (ca. 467 Ma), similar in age to other dated orthogneisses of the Axial Zone. Three samples from granite stocks situated in the core of the Aston and Bossòst domes have crystallization ages of ca. 339–337 Ma, providing the first evidence of Visean igneous activity in the Axial Zone. In contrast to the larger and significantly younger (ca. 312–305 Ma) granite plutons along the margins of the gneiss domes, Visean magmatism caused LP-HT contact metamorphism (M 2 ). Migmatization throughout the Aston dome, though less well-constrained by overgrowth ages on zircon (ca. 331 Ma) and monazite ages (ca. 340–320 Ma), is likely to be related to Visean intrusions. The main S 2 schistosity in the Aston and Bossòst domes is coeval with the Visean intrusions. Inclusion trails in porphyroblasts nucleating in the contact aureoles document the continuous development of S 2 related to local extension. Crystal-plastic deformation of the granites indicates that the D 2 deformation event continued after their crystallization. Visean magmatism played a crucial role in early stages of dome formation by thermally weakening the metasedimentary mantle, and to a certain degree the orthogneiss as well, enhancing the development of orogen-parallel shear zones in an overall N–S compressive setting. [ABSTRACT FROM AUTHOR]

Published
2016
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8. P- T- t- d evolution of orogenic middle crust of the Roc de Frausa Massif (Eastern Pyrenees): a result of horizontal crustal flow and Carboniferous doming?

Author

Aguilar, C., Liesa, M., Štípská, P., Schulmann, K., Muñoz, J. A., and Casas, J. M.

Subjects
*OROGENIC belts, *CARBONIFEROUS Period, *SILLIMANITE, *BIOTITE, *GARNET
Abstract

Structural, petrological and textural studies are combined with phase equilibria modelling of metapelites from different structural levels of the Roc de Frausa Massif in the Eastern Pyrenees. The pre-Variscan lithological succession is divided into the Upper, Intermediate and Lower series by two orthogneiss sheets and intruded by Variscan igneous rocks. Structural analysis reveals two phases of Variscan deformation. D1 is marked by tight to isoclinal small-scale folds and an associated flat-lying foliation (S1) that affects the whole crustal section. D2 structures are characterized by tight upright folds facing to the NW with steep NE- SW axial planes. D2 heterogeneously reworks the D1 fabrics, leading to an almost complete transposition into a sub-vertical foliation (S2) in the high-grade metamorphic domain. All structures are affected by late open to tight, steeply inclined south-verging NW- SE folds (F3) compatible with steep greenschist facies dextral shear zones of probable Alpine age. In the micaschists of the Upper series, andalusite and sillimanite grew during the formation of the S1 foliation indicating heating from 580 to 640 °C associated with an increase in pressure. Subsequent static growth of cordierite points to post-D1 decompression. In the Intermediate series, a sillimanite-biotite-muscovite-bearing assemblage that is parallel to the S1 fabric is statically overgrown by cordierite and K-feldspar. This sequence points to ~1 kbar of post-D1 decompression at 630-650 °C. The Intermediate series is intruded by a gabbro-diorite stock that has an aureole marked by widespread migmatization. In the aureole, the migmatitic S1 foliation is defined by the assemblage biotite-sillimanite-K-feldspar-garnet. The microstructural relationships and garnet zoning are compatible with the D1 pressure peak at ~7.5 kbar and ~750 °C. Late- to post-S2 cordierite growth implies that F2 folds and the associated S2 axial planar leucosomes developed during nearly isothermal decompression to <5 kbar. The Lower series migmatites form a composite S1-S2 fabric; the garnet-bearing assemblage suggests peak P-T conditions of >5 kbar at suprasolidus conditions. Almost complete consumption of garnet and late cordierite growth points to post-D2 equilibration at <4 kbar and <750 °C. The early metamorphic history associated with the S1 fabric is interpreted as a result of horizontal middle crustal flow associated with progressive heating and possible burial. The upright F2 folding and S2 foliation are associated with a pressure decrease coeval with the intrusion of mafic magma at mid-crustal levels. The D2 tectono-metamorphic evolution may be explained by a crustal-scale doming associated with emplacement of mafic magmas into the core of the dome. [ABSTRACT FROM AUTHOR]

Published
2015
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9. Metastable staurolite–cordierite assemblage of the Bossòst dome: Late Variscan decompression and polyphase metamorphism in the Axial Zone of the central Pyrenees

Author

Mezger, Jochen E., Passchier, Cees W., and Régnier, Jean-Luc

Subjects
*SILICATE minerals, *ANDALUSITE, *GARNET, *METAMORPHISM (Geology)
Abstract

A kilometre-scale shear zone is recognized in the Cambro–Ordovician schist of the Bossòst dome, a Variscan metamorphic and structural dome in the Axial Zone of the central Pyrenees. Non-coaxial deformation is recorded by rotated garnet and staurolite porphyroblasts following regional metamorphism M1, while coaxial conditions prevailed during later contact metamorphic M2 growth of andalusite and cordierite. Mineral compositions and bulk rock analyses show that garnet–staurolite–andalusite–cordierite assemblages are significantly enriched in Mg and Mn over the garnet–staurolite assemblage, which lacks sufficient Mg for cordierite to form. The garnet–staurolite assemblage preserves conditions during M1, estimated by AFM diagrams and P–T pseudosections to be 5.5 kbar and 580 °C, respectively. Pseudosections also indicate that staurolite is not a stable phase in cordierite–andalusite assemblages of M2, suggesting polyphase metamorphism and decompression along a clockwise P–T path for the staurolite–cordierite–andalusite assemblages. This concurs with proposed extensional tectonics along the regional shear zone. To cite this article: J.E. Mezger et al., C. R. Geoscience 336 (2004). [Copyright &y& Elsevier]

Published
2004
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10. Origin of Cap de Creus pegmatites : integrated field approach, petrology and geochemistry

Author

Serrano, Julien, Géosciences Environnement Toulouse (GET), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD), Université Paul Sabatier - Toulouse III, Marieke Van Lichtervelde, Michel de Saint-Blanquat, Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), and Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)

Subjects
Geochemistry, Origin of pegmatites, Granite, Tectonique, Géochimie, Variscan Pyrenees, Origine des pegmatites, Tectonic, Pyrénées Varisque, [SDU.STU.AG]Sciences of the Universe [physics]/Earth Sciences/Applied geology, Migmatite, Cap de Creus
Abstract

Since several decades, the debate on the origin of pegmatite formation has led to the development of two models, a granitic model and an anatectic model. Although these models are commonly accepted by the scientific community, they rely mainly on geochemical and/or petrological criteria, occasionally on geochronological datas, and rarely on structural criteria. The aim of my thesis is to study and to determine the origin -granitic vs anatectic- of the Cap de Creus pegmatites (Spain) by combining structural and geochemical studies. In-situ analyses (microprobe, LA-ICPMS) combined with different structural works and microstructural observations, both in pegmatites and their host rock, allowed me to establish a relative chronology of pegmatite emplacement, but also to replace the origin of the Cap de Creus pegmatites in a regional geodynamic model, thus highlighting two pegmatite fields of different origins.; Depuis plusieurs décennies, le débat sur l'origine de formation des pegmatites a conduit à l'élaboration de deux modèles, un modèle granitique et un modèle anatectique. Bien que ces modèles soient communément admis par la communauté scientifique, ils s'appuient majoritairement sur des critères géochimiques et/ou pétrologiques, occasionnellement sur des critères géochronologiques, et rarement sur des critères structuraux. Le but de ma thèse est d'étudier et de déterminer l'origine -granitique vs anatectique- des pegmatites du Cap de Creus (Espagne) en combinant travaux structuraux et géochimiques. Les analyses in-situ (microsonde, LA-ICPMS) combinées aux différentes mesures structurales et observations microstructurales, à la fois dans les pegmatites et leurs encaissants, m'ont permis non seulement d'établir une chronologie relative de mise en place des pegmatites, mais également de replacer l'origine des pegmatites du Cap de Creus dans un modèle géodynamique régional, mettant ainsi en évidence deux champs de pegmatites d'origines différentes.

Published
2019

11. Thermal peak detected in gold-bearing shear zones by a thermo-structural study: a new tool to retrieve fluid flow?

Author

Gaétan Link, Olivier Vanderhaeghe, Didier Béziat, Michel de Saint Blanquat, Margot Munoz, Guillaume Estrade, Laurent Guillou-Frottier, Eric Gloaguen, Abdeltif Lahfid, Jérémie Melleton, Géosciences Environnement Toulouse (GET), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), Institut des Sciences de la Terre d'Orléans - UMR7327 (ISTO), Bureau de Recherches Géologiques et Minières (BRGM) (BRGM)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Géodynamique - UMR7327, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Bureau de Recherches Géologiques et Minières (BRGM) (BRGM)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Référentiel Géologique de la France (RGF) - chantier Pyrénées, BRGM, Society for Geology Applied to Mineral Deposits, Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD), Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Bureau de Recherches Géologiques et Minières (BRGM) (BRGM)-Institut des Sciences de la Terre d'Orléans - UMR7327 (ISTO), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Bureau de Recherches Géologiques et Minières (BRGM) (BRGM)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, and Link, Gaétan

Subjects
[SDU] Sciences of the Universe [physics], [SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics, Fluid flow, [SDU]Sciences of the Universe [physics], [SDU.STU.TE] Sciences of the Universe [physics]/Earth Sciences/Tectonics, [SDU.STU] Sciences of the Universe [physics]/Earth Sciences, [SDU.STU.PE]Sciences of the Universe [physics]/Earth Sciences/Petrography, [SDU.STU.PE] Sciences of the Universe [physics]/Earth Sciences/Petrography, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Thermal Convection, Variscan Pyrenees, Gold deposits
Abstract

International audience; Gold mineralizations of the northern part of the Canigou massif (Eastern Pyrenees, France) are localized along regional-scale shear zones. These structures connect the upper metapelitic greenschist facies unit (suprastructure) to the lower migmatitic unit (infrastructure) and are attributed to the late-Variscan tectonic evolution transposing earlier structures. Raman spectroscopy of carbonaceous materials (RSCM) approach documents thermal anomalies in these shear zones with a temperature peak [20-100 °C] above the host rocks values. These thermal anomalies are interpreted as recording the upward circulation of a hot fluid. These data point to gold mobilization and transfer controlled by localized deformation and fluid flow at the end of the Variscan orogeny. The nature and origin of the mineralizing fluids, the source(s) of gold, and the mechanisms of ore mobilization-transfer-deposition remain to be determined.

Published
2019

12. Two‐stage Variscan metamorphism in the Canigou massif: evidence for crustal thickening in the Pyrenees

Author

Jean Van Den Driessche, Luc de Hoÿm de Marien, Florence Cagnard, Marc Poujol, Pavel Pitra, Benjamin Le Bayon, Géosciences Rennes (GR), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Centre National de la Recherche Scientifique (CNRS), Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), Česká geologická služba, 'Référentiel Géologique de la France' programme, Bureau de Recherches Géologiques et Minières, Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), and Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS)

Subjects
geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Geochemistry, [SDU.STU.PE]Sciences of the Universe [physics]/Earth Sciences/Petrography, Metamorphism, Geology, Massif, 15. Life on land, 010502 geochemistry & geophysics, 01 natural sciences, Geochemistry and Petrology, Stage (stratigraphy), B arrovia n metamorphism, crustal thickening, Variscan Pyrenees, Thickening, pseudosections, polyphase P–T path, 0105 earth and related environmental sciences
Abstract

International audience; The Variscan metamorphism in the Pyrenees is dominantly of the low-pressure-high-temperature (LP-HT) type. The relics of an earlier, Barrovian-type, metamorphism that could be related to orogenic crustal thickening are unclear and insufficiently constrained. A microstructural and petrological study of micaschists underlying an Ordovician augen orthogneiss in the core of the Canigou massif (Eastern Pyrenees, France) reveal the presence of two syntectonic metamorphic stages characterized by the crystallization of staurolite (M1) and andalusite (M2), respectively. Garnet is stable during the two metamorphic stages with a period of resorption between M1 and M2. The metamorphic assemblages M1 and M2 record similar peak temperatures of 580 °C at different pressure conditions of 5.5 kbar and 3 kbar, respectively. Using chemical zoning of garnet and calculated P–T pseudosections, a prograde P–T path is constrained with a peak pressure at ~6.5 kbar and 550 °C. This P–T path, syntectonic with respect to the first foliation S1, corresponds to a cold gradient (of ~9 °C/km), suggestive of crustal thickening. Resorption of garnet between M1 and M2 can be interpreted either in terms of a simple clockwise P–T path or a polymetamorphic two stage evolution. We argue in favour of the latter, where the medium‐pressure (Barrovian) metamorphism is followed by a period of significant erosion and crustal thinning leading to decompression and cooling. Subsequent advection of heat, probably from the mantle, lead to a new increase in temperature, coeval with the development of the main regional fabric S2. LA‐ICP‐MS U‐Th‐Pb dating of monazite yields a well‐defined date at c. 300 Ma. Petrological evidence indicates that monazite crystallization took place close to the M1 peak‐pressure conditions. However, the similarity between this age and that of the extensive magmatic event well documented in the eastern Pyrenees suggests that it probably corresponds to the age of monazite recrystallization during the M2 LP–HT event. This article is protected by copyright. All rights reserved.

Published
2019
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13. Evolution of the middle crust of the Pyrenees during the Paleozoic: new data on the plutonic rocks from the North Pyrenean Agly Massif

Author

Ph. Olivier, Damien Guillaume, Valérie Bosse, Jean-Louis Paquette, B. Tournaire Guille, Laboratoire des Mécanismes et Transfert en Géologie (LMTG), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Magmas et Volcans (LMV), Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet [Saint-Étienne] (UJM)-Institut de Recherche pour le Développement et la société-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Institut national des sciences de l'Univers (INSU - CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS), Cyclotron ARRONAX, GIP, Institut des Sciences de la Terre de Paris (iSTeP), Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Institut national des sciences de l'Univers (INSU - CNRS), Géosciences Environnement Toulouse (GET), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD), Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Recherche pour le Développement et la société-Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne (UCA)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne (UCA), Université Jean Monnet [Saint-Étienne] (UJM), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), and Université Jean Monnet - Saint-Étienne (UJM)

Subjects
Late Carboniferous, 010504 meteorology & atmospheric sciences, Paleozoic, Granite, Geochemistry, Metamorphism, Partial melting, 010502 geochemistry & geophysics, 01 natural sciences, Precambrian, Ediacaran, Orthogneiss, [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, Carboniferous, Variscan Pyrenees, Metamorphic facies, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, geography, geography.geographical_feature_category, Massif, Granulite, Plutonism, North Pyrenean Agly Massif, Earliest Cambrian, Crust recycling, General Earth and Planetary Sciences, [SDU.OTHER]Sciences of the Universe [physics]/Other, Geology
Abstract

International audience; The Variscan middle crust of the eastern Pyrenees is represented by the Bélesta and Caramany gneissic units of the North Pyrenean Agly Massif. In this study, we date and reinterpret the orthogneisses and granites composing these units. We characterize a recurrent plutonic activity spanning all the Paleozoic in this part of the Pyrenean crust. The Bélesta unit (amphibolite facies) is mainly composed of sills of (Latest Ediacaran)–Earliest Cambrian (542 ± 4 and 540 ± 4 Ma) orthogneisses (70% of the series), almost unknown in the Pyrenees until now, and Latest Carboniferous–(Earliest Permian) (307 ± 3–298 ± 3 Ma time span) granites (15% of the series). These plutonic rocks were emplaced in probably Ediacaran aluminous pelites later transformed into paragneisses (15% of the series). The Caramany unit (granulite facies) is mainly composed of Precambrian aluminous paragneisses migmatized during the Latest Carboniferous–(Earliest Permian) (299 ± 4 Ma), sills of Earliest Cambrian (529 ± 5 Ma) orthogneisses and sills (about 30% of the series) of Late Carboniferous (308 ± 3–299 ± 3 Ma) opxbearing and opx-free granodiorites, grt-bearing leucogranites and norites. Among these last rocks, the Ansignan charnockite, forming a 800 m-thick laccolith near the base of the Caramany unit, and previously dated at 314 ± 6/7 Ma (Respaut, Lancelot, Neues Jahrbuch Miner Abh 147-1:21–34, 1983), is refined at 307 ± 3 Ma. Our results confirm the importance of the Late Carboniferous plutonism in deep levels of the Pyrenean crust, which largely resulted from recycling of older para- and orthoderived rocks of this crust. The emplacement of hundreds of metres in thickness of granites and other plutonic rocks in the Variscan Pyrenees occurred in a rather short time both as sills in these deep levels and as large plutons in shallower levels, a fact which necessarily had consequences on the HT–LP Carboniferous metamorphism.

Published
2018
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14. Geochemistry and zircon U–Pb geochronology of the ultramafic and mafic rocks emplaced within the anatectic series of the Variscan Pyrenees: The example of the Gavarnie–Heas dome (France)

Author

Youssef Driouch, Mathieu Benoit, Pierre Debat, Mohammad Kilzi, Valérie Bosse, Michel de Saint Blanquat, Michel Grégoire, Géosciences Environnement Toulouse (GET), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Laboratoire Magmas et Volcans (LMV), Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS), Domaines Océaniques (LDO), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Observatoire des Sciences de l'Univers-Institut d'écologie et environnement-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Mécanismes et Transfert en Géologie (LMTG), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Observatoire Midi-Pyrénées (OMP), Géosciences Environnement Toulouse ( GET ), Institut de Recherche pour le Développement ( IRD ) -Université Paul Sabatier - Toulouse 3 ( UPS ) -Observatoire Midi-Pyrénées ( OMP ) -Centre National de la Recherche Scientifique ( CNRS ), Laboratoire Magmas et Volcans ( LMV ), Université Blaise Pascal - Clermont-Ferrand 2 ( UBP ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Université Jean Monnet [Saint-Étienne] ( UJM ) -Centre National de la Recherche Scientifique ( CNRS ), Domaines Océaniques ( LDO ), Institut national des sciences de l'Univers ( INSU - CNRS ) -Université de Brest ( UBO ) -Observatoire des Sciences de l'Univers-Institut d'écologie et environnement-Centre National de la Recherche Scientifique ( CNRS ), Laboratoire des Mécanismes et Transfert en Géologie ( LMTG ), Université Paul Sabatier - Toulouse 3 ( UPS ) -Observatoire Midi-Pyrénées ( OMP ) -Centre National de la Recherche Scientifique ( CNRS ), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet [Saint-Étienne] (UJM)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), and Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
010504 meteorology & atmospheric sciences, Geochronology, Geochemistry, Earth and Planetary Sciences(all), Gavarnie–Heas dome, 010502 geochemistry & geophysics, 01 natural sciences, Ultramafic rock, [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, Ultramafic rocks, Variscan Pyrenees, Petrology, 0105 earth and related environmental sciences, Global and Planetary Change, geography, geography.geographical_feature_category, Continental crust, Massif, 15. Life on land, [ SDU.STU.GC ] Sciences of the Universe [physics]/Earth Sciences/Geochemistry, Mafic to intermediate rocks, Diorite, Early Permian, General Earth and Planetary Sciences, Mafic, Norite, Geology, Zircon
Abstract

International audience; The origin and evolution of ultramafic (UM), mafic (M) and intermediate rocks emplaced within the metamorphic and anatectic series of the middle crust of the Variscan segment of the Pyrenees are defined in the light of new isotopic data U–Pb zircon ages, and Sr, Nd isotopic ratios. In the Gavarnie–Heas dome (central Pyrenees), ultramafic, mafic and intermediate rocks form three massifs several kilometers in size emplaced within the anatectic series: (i) the Gloriettes massif, which mostly consists of norites with enclaves of ultramafic rocks; (ii) the Troumouse massif, which comprises intermediate rocks (gabbro-diorite and diorite) with norite enclaves, and (iii) the Aguila massif, which consists of intermediate rocks with hornblendite enclaves. U–Pb zircon geochronology (first data for these rock types in the Axial Zone of the Pyrenees) revealed an age of 294 Ma for the diorite crystallization and correlatively for the crystallization of the anatectic granite. This new radiometric age allows us to suggest that the Variscan orogeny continued at least until the Early Permian and spread over around 30 Ma. The Nd and Sr isotopic compositions of all UM and M samples plot within the field of the continental crust. Two scenarios can explain the genesis and the emplacement of the components of the magmatic suite: i) evolution of mantle melts and contamination (AFC); ii) evolution of melts originating from a heterogeneous source (mantle + crust) at the local or regional scale. The strong crustal affinity of all UM and M rock types from Gavarnie–Heas leads us to favor the second scenario.

Published
2016
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15. Anisotropy of magnetic susceptibility of the Pyrenean granites

Author

Porquet Pardina, Manuel, Pueyo Morer, Emilio Luis, Román Berdiel, Teresa, Olivier, Philippe, Longares, Luis A., Cuevas, Julia, Ramajo, Javier, Antolín, Borja, Aranguren, Aitor, Auréjac, Jean Baptiste, Bouchez, Jean-Luc, Casas-Sainz, Antonio M., Denèle, Yoann, Gleizes, Gerard, Hilario, Asier, Izquierdo Llavall, Esther, Leblanc, Dennis, Oliva-Urcia, Belén, Santana, Vicente, Tubía, José M., Vegas, Néstor, Porquet Pardina, Manuel, Pueyo Morer, Emilio Luis, Román Berdiel, Teresa, Olivier, Philippe, Longares, Luis A., Cuevas, Julia, Ramajo, Javier, Antolín, Borja, Aranguren, Aitor, Auréjac, Jean Baptiste, Bouchez, Jean-Luc, Casas-Sainz, Antonio M., Denèle, Yoann, Gleizes, Gerard, Hilario, Asier, Izquierdo Llavall, Esther, Leblanc, Dennis, Oliva-Urcia, Belén, Santana, Vicente, Tubía, José M., and Vegas, Néstor

Abstract

In this paper, we report on a compilation of more than 2200 sites (more than 10,000 individual measurements) where anisotropy of magnetic susceptibility (AMS) was studied in granites from the Variscan Pyrenees. The standardization and homogenization of this information has allowed us to produce three Main Maps that synthesize all the information related with the AMS of the Pyrenean granites. We also describe the problems found during the construction of the database (variable geo-positioning, different published information, etc.). The information derived from 21 granite bodies, the database, and the synthesis maps (magnetic susceptibility, Km, and the orientation of the magnetic foliation, plane perpendicular to k3, and of the magnetic lineation, k1) allow us to see for the first time a complete image of this important kinematic and petrographic indicator.

Published
2017

16. Anisotropy of magnetic susceptibility of the Pyrenean granites

Author

Ministerio de Asuntos Económicos y Transformación Digital (España), CSIC - Instituto Geológico y Minero de España (IGME), Gobierno de Aragón, Porquet Pardina, Manuel, Pueyo Morer, Emilio Luis, Román-Berdiel, T., Olivier, Philippe, Longares Aladrén, Luis Alberto, Cuevas, Julia, Ramajo, Javier, Antolín, Borja, Aranguren, Aitor, Auréjac, Jean Baptiste, Bouchez, Jean-Luc, Casas-Sainz, Antonio M., Denèle, Yoann, Gleizes, Gerard, Hilario, Asier, Izquierdo Llavall, Esther, Leblanc, Dennis, Oliva-Urcia, Belén, Santana, Vicente, Tubía, José M., Vegas, Néstor, Ministerio de Asuntos Económicos y Transformación Digital (España), CSIC - Instituto Geológico y Minero de España (IGME), Gobierno de Aragón, Porquet Pardina, Manuel, Pueyo Morer, Emilio Luis, Román-Berdiel, T., Olivier, Philippe, Longares Aladrén, Luis Alberto, Cuevas, Julia, Ramajo, Javier, Antolín, Borja, Aranguren, Aitor, Auréjac, Jean Baptiste, Bouchez, Jean-Luc, Casas-Sainz, Antonio M., Denèle, Yoann, Gleizes, Gerard, Hilario, Asier, Izquierdo Llavall, Esther, Leblanc, Dennis, Oliva-Urcia, Belén, Santana, Vicente, Tubía, José M., and Vegas, Néstor

Abstract

In this paper, we report on a compilation of more than 2200 sites (more than 10,000 individual measurements) where anisotropy of magnetic susceptibility (AMS) was studied in granites from the Variscan Pyrenees. The standardization and homogenization of this information has allowed us to produce three Main Maps that synthesize all the information related with the AMS of the Pyrenean granites. We also describe the problems found during the construction of the database (variable geo-positioning, different published information, etc.). The information derived from 21 granite bodies, the database, and the synthesis maps (magnetic susceptibility, Km, and the orientation of the magnetic foliation, plane perpendicular to k3, and of the magnetic lineation, k1) allow us to see for the first time a complete image of this important kinematic and petrographic indicator.

Published
2017

17. Structure, age and mode of emplacement of the Hercynian Bordères-Louron pluton (Central Pyrenees, France)

Author

Gérard Crevon, Pierre Barbey, Asfawossen Asrat, Gérard Gleizes, Laboratoire des Mécanismes et Transfert en Géologie (LMTG), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Centre de Recherches Pétrographiques et Géochimiques (CRPG), and Institut national des sciences de l'Univers (INSU - CNRS)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)

Subjects
geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Pluton, Geochemistry, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Silicic, engineering.material, 010502 geochemistry & geophysics, 01 natural sciences, Bordères-Louron, Devonian, Granite emplacement, Zircon U-Pb age, Sill, Carboniferous, Anisotropy of magnetic susceptibility, engineering, General Earth and Planetary Sciences, Variscan Pyrenees, Mafic, Geology, Biotite, 0105 earth and related environmental sciences, Zircon
Abstract

International audience; The Hercynian Bordères-Louron pluton (20 km2) in the Central Pyrenees intrudes Devonian and Carboniferous metasediments. It shows a concentric zoning and consists of a significant proportion of (quartz) gabbros in its periphery, and of granodiorites, biotite monzogranites and biotite-muscovite monzogranites in its core. AMS study shows that the pluton corresponds to an elongated dome with a N100°E-trending axis. The anisotropy intensity Ppara% is high in the south and in the core of the pluton, whereas it is low in the north. The shape parameter T indicates that the fabric is strongly planar in a large central band oriented NW-SE, whereas it is strongly linear in the western and eastern tips of the pluton. These characteristics suggest that the Bordères-Louron pluton emplaced in two episodes: (1) intrusion of mafic magmas along a N100°E sill parallel to the regional foliation of the host metasediments; and (2) injection of three successive silicic batches (granodiorite, biotite monzogranite, two-micas monzogranite) which pushed aside the early mafic injections. In situ U-Pb dating of zircon grains indicates that the emplacement age of the biotite monzogranite is 309 ± 4 Ma, synchronous with the D 2 dextral transpressive event and close to the ages of the eastern Pyrenean plutons, may be slightly older.

Published
2006
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