Zircon U-Pb dating of lower crustal rocks from the G.ry Sowie Massif (Central Sudetes, SW Poland): new insights on the sedimentary origin and the tectono-thermal evolution

Devonian HP‒UHP lithotectonic associations represent pivotal element of Paleozoic evolution of European Variscan belt across the continent from Portugal to Poland. The Góry Sowie Massif (GSM), located in the Central Sudetes, represents one of the best preserved outcrops of lower crustal rocks that experienced protracted Devonian tectono-metamorphic history at the easternmost extremity of the belt. The area is surrounded by Devonian ophiolite remnants (c. 400 Ma; Kryza & Pin, 2010) and by Devonian and Silurian to Carboniferous sedimentary basins in the northern and southern part, respectively. The GSM is mainly composed of paragneisses and subordinate orthogneisses, metabasites and granulite. The dominantly sedimentary association and the overall geotectonic setting contrast with other km-scale granulite complexes in the Bohemian Massif that are dominated by felsic granulites and Late Cambrian orthogneisses that experienced 340 Ma HP metamorphism. Weak Carboniferous overprint makes the GSM a key locality to better understand Devonian stages of formation of HP granulites and provenance of the whole pre-Devonian lithological association. New U‒Pb analyses were carried out on zircons from 4 migmatitic paragneisses, 3 felsic biotite-poor granulites and two biotite-rich granulites in the northern part of the GSM, in order to constrain source provenance and tectono-thermal history of the area

Deciphering the nature and age of the protoliths and peak P−T conditions in retrogressed mafic eclogites from the Maures-Tannneron Massif (SE France) and implications for the southern European Variscides

We present new constraints on the age, nature, and tectonic setting of mafic eclogite protoliths from the Maures-Tanneron Massif, southern Variscan belt. Whole-rock major and trace element geochemistry was combined with zircon dating using 206Pb/238U by LA‒ICP‒MS to improve the understanding of this key-target of the European Southern Variscides. Geochemical data show that protoliths of the mafic eclogites are typical MORBs, while REE and HFSE patterns suggest an E-MORB affinity. However, the geochemical study shows several signs of crustal contamination that increases with the degree of retrogression. A comparison with Sardinian eclogites, which belong to the same Variscan microplate, namely, “MECS” (Maures-Estérel-Corsica-Sardinia), demonstrates that the eclogites are included in migmatites, which is the case for the studied samples, are the most contaminated. The Maures-Tanneron mafic eclogites represent the remnant of an oceanic basaltic crust. Zircon cores display homogeneous Th/U ratios (0.3–0.4), which are consistent with a magmatic origin, and define an age peak at 499.5 ± 2.9 Ma that is interpreted as the most likely emplacement age of the basaltic protolith. This age suggests that this protolith was part of an oceanic floor that was older than the Rheic Ocean and located to the north of the Gondwana active continental margin as predicted by recent unified full plate reconstruction models. Although the studied eclogites are retrogressed, the study of mineral inclusions trapped in garnets combined with thermodynamic modelling yields a P−T range of 17.2–18.5 kbar and 640–660 °C, which is consistent with the standard oceanic subduction palaeo-geotherm. These new data suggest that eclogites recognized in the “MECS” Variscan microplate represent the closure of oceanic domains of different ages (Cambrian or Ordovician)

Geochemistry, zircon U‒Pb and Hf isotopic compositions of lower crustal rocks from the Góry Sowie Massif (Central Sudetes, SW Poland): New insights on the sedimentary origin and tectono-thermal evolution

Devonian HP-UHP lithotectonic associations represent a pivotal element of Paleozoic evolution of the European Variscan belt across the continent from Portugal to Poland. The Góry Sowie Massif (GSM), located in the Central Sudetes, represents one of the best preserved outcrops of lower crustal rocks that experienced a protracted Devonian tectono-metamorphic history at the easternmost extremity of the belt. The area is surrounded by Devonian ophiolite remnants and Devonian to Carboniferous sedimentary basins in the northern and southern part, respectively. The GSM is mainly composed of paragneisses and subordinate orthogneisses, metabasites and granulite. The dominantly sedimentary association and the overall geotectonic setting contrast with the other km-scale granulite complexes in the Bohemian Massif that are dominated by felsic granulites and late Cambrian orthogneisses that experienced 340 Ma HP metamorphism. Weak Carboniferous overprint makes the GSM a key locality to better understand the Devonian stages of formation of HP granulites and provenance of the whole pre-Devonian lithological association. New U-Pb and Lu/Hf analyses were carried out on zircons from 4 migmatitic paragneisses, 3 felsic biotite-poor granulites and 2 biotite-rich granulites in the northern part of the GSM, and combined with geochemical analyses in order to constrain a source provenance and tectono-thermal history of the area. The paragneisses dominated by stromatic migmatite and felsic granulites occur as hundred meter-scale bodies associated with metric lenses of amphibolites, mafic and ultramafic rocks in the northern part of the massif

The magmatism of the Vosges mountains : consequence of the paleozoic subductions (dating, petrology, geochemistry, AMS)

Les Vosges sont caractérisées par la présence de nombreuses intrusions et extrusions magmatiques d’affinités variées. Elles constituent donc un excellent site d’étude pour contraindre, par la datation et la géochimie, l’évolution des évènements de ce segment de l’orogène Varisque. Ce travail révèle ainsi deux successions d’évènements magmatiques identiques, décalées dans le temps, caractérisent les domaines Moldanubien (360 à 320 Ma) et Saxothuringien (335 à 295 Ma). Ces successions d’évènements magmatiques résultent de deux processus majeurs. L’avancée des croûtes continentales subduites et sous-plaquées au niveau du Moho sous les blocs continentaux permet le passage du magmatisme calco-alcalin au magmatisme calco-alcalin riche en potassium. L’apport de chaleur par désintégration des éléments radiogéniques (K, U et Th) présents dans ces croûtes continentales subduites permet, dans un premier temps, la formation du magmatisme magnésio-potassique en profondeur. Dans un second temps, elle permet la formation du magmatisme d’origine crustale par l’intrusion du magmatisme magnésio-potassique, riche en K, U et Th, à la limite croûte moyenne - croûte supérieure. Ces successions d’évènements magmatiques et particulièrement, la présence des granites magnésio-potassiques, relient clairement les Vosges à la partie Est de l’orogène Varisque (Forêt Noire, Massif de Bohème, Alpes et Corse-Sardaigne).The Vosges Mountains are characterized by the presence of numerous magmatic intrusions and extrusions of varied affinities. Accordingly, they constitute the best site to investigate, by dating and geochemistry, the evolution of the events affecting this segment of the Variscan orogeny. Two successions of identical magmatic events, shifted in the time, are identified, characterizing both Moldanubian (360 to 320 Ma) and the Saxothuringian (335 to 295 Ma) domains. These successions of magmatic events result of two major process. The progress of subducted and underplated continental crusts at Moho depth under continental blocks permits to shift from calc-alkaline to high potassic calc-alkaline magmatism. The radiogenic heat production from latter underplated continental crusts, in a first time, permits to generate magnesio-potassic magmas at depth. Then, this radiogenic heat permits to generate crustal magmas by intrusion of magnesio-potassic magmas rich in K, U and Th at mid-upper crust boundarie. These successions of magmatic events and particularly, the presence of the magnesio-potassic granites, imply a strong link between the Vosges Mts. and the eastern part of the Variscan orogeny (Black Forest, Bohemian Massif, the Alps and Corsica Batholith)

The magmatism of the Vosges mountains : consequence of the paleozoic subductions (dating, petrology, geochemistry, AMS)

Les Vosges sont caractérisées par la présence de nombreuses intrusions et extrusions magmatiques d’affinités variées. Elles constituent donc un excellent site d’étude pour contraindre, par la datation et la géochimie, l’évolution des évènements de ce segment de l’orogène Varisque. Ce travail révèle ainsi deux successions d’évènements magmatiques identiques, décalées dans le temps, caractérisent les domaines Moldanubien (360 à 320 Ma) et Saxothuringien (335 à 295 Ma). Ces successions d’évènements magmatiques résultent de deux processus majeurs. L’avancée des croûtes continentales subduites et sous-plaquées au niveau du Moho sous les blocs continentaux permet le passage du magmatisme calco-alcalin au magmatisme calco-alcalin riche en potassium. L’apport de chaleur par désintégration des éléments radiogéniques (K, U et Th) présents dans ces croûtes continentales subduites permet, dans un premier temps, la formation du magmatisme magnésio-potassique en profondeur. Dans un second temps, elle permet la formation du magmatisme d’origine crustale par l’intrusion du magmatisme magnésio-potassique, riche en K, U et Th, à la limite croûte moyenne - croûte supérieure. Ces successions d’évènements magmatiques et particulièrement, la présence des granites magnésio-potassiques, relient clairement les Vosges à la partie Est de l’orogène Varisque (Forêt Noire, Massif de Bohème, Alpes et Corse-Sardaigne).The Vosges Mountains are characterized by the presence of numerous magmatic intrusions and extrusions of varied affinities. Accordingly, they constitute the best site to investigate, by dating and geochemistry, the evolution of the events affecting this segment of the Variscan orogeny. Two successions of identical magmatic events, shifted in the time, are identified, characterizing both Moldanubian (360 to 320 Ma) and the Saxothuringian (335 to 295 Ma) domains. These successions of magmatic events result of two major process. The progress of subducted and underplated continental crusts at Moho depth under continental blocks permits to shift from calc-alkaline to high potassic calc-alkaline magmatism. The radiogenic heat production from latter underplated continental crusts, in a first time, permits to generate magnesio-potassic magmas at depth. Then, this radiogenic heat permits to generate crustal magmas by intrusion of magnesio-potassic magmas rich in K, U and Th at mid-upper crust boundarie. These successions of magmatic events and particularly, the presence of the magnesio-potassic granites, imply a strong link between the Vosges Mts. and the eastern part of the Variscan orogeny (Black Forest, Bohemian Massif, the Alps and Corsica Batholith)

Le magmatisme des Vosges : conséquence des subductions paléozoïques (datation, pétrologie, géochimie, ASM)

The Vosges Mountains are characterized by the presence of numerous magmatic intrusions and extrusions of varied affinities. Accordingly, they constitute the best site to investigate, by dating and geochemistry, the evolution of the events affecting this segment of the Variscan orogeny. Two successions of identical magmatic events, shifted in the time, are identified, characterizing both Moldanubian (360 to 320 Ma) and the Saxothuringian (335 to 295 Ma) domains. These successions of magmatic events result of two major process. The progress of subducted and underplated continental crusts at Moho depth under continental blocks permits to shift from calc-alkaline to high potassic calc-alkaline magmatism. The radiogenic heat production from latter underplated continental crusts, in a first time, permits to generate magnesio-potassic magmas at depth. Then, this radiogenic heat permits to generate crustal magmas by intrusion of magnesio-potassic magmas rich in K, U and Th at mid-upper crust boundarie. These successions of magmatic events and particularly, the presence of the magnesio-potassic granites, imply a strong link between the Vosges Mts. and the eastern part of the Variscan orogeny (Black Forest, Bohemian Massif, the Alps and Corsica Batholith).Les Vosges sont caractérisées par la présence de nombreuses intrusions et extrusions magmatiques d’affinités variées. Elles constituent donc un excellent site d’étude pour contraindre, par la datation et la géochimie, l’évolution des évènements de ce segment de l’orogène Varisque. Ce travail révèle ainsi deux successions d’évènements magmatiques identiques, décalées dans le temps, caractérisent les domaines Moldanubien (360 à 320 Ma) et Saxothuringien (335 à 295 Ma). Ces successions d’évènements magmatiques résultent de deux processus majeurs. L’avancée des croûtes continentales subduites et sous-plaquées au niveau du Moho sous les blocs continentaux permet le passage du magmatisme calco-alcalin au magmatisme calco-alcalin riche en potassium. L’apport de chaleur par désintégration des éléments radiogéniques (K, U et Th) présents dans ces croûtes continentales subduites permet, dans un premier temps, la formation du magmatisme magnésio-potassique en profondeur. Dans un second temps, elle permet la formation du magmatisme d’origine crustale par l’intrusion du magmatisme magnésio-potassique, riche en K, U et Th, à la limite croûte moyenne - croûte supérieure. Ces successions d’évènements magmatiques et particulièrement, la présence des granites magnésio-potassiques, relient clairement les Vosges à la partie Est de l’orogène Varisque (Forêt Noire, Massif de Bohème, Alpes et Corse-Sardaigne)

Le magmatisme des Vosges (conséquence des subductions paléozoïques (datation, pétrologie, géochimie, ASM))

Les Vosges sont caractérisées par la présence de nombreuses intrusions et extrusions magmatiques d affinités variées. Elles constituent donc un excellent site d étude pour contraindre, par la datation et la géochimie, l évolution des évènements de ce segment de l orogène Varisque. Ce travail révèle ainsi deux successions d évènements magmatiques identiques, décalées dans le temps, caractérisent les domaines Moldanubien (360 à 320 Ma) et Saxothuringien (335 à 295 Ma). Ces successions d évènements magmatiques résultent de deux processus majeurs. L avancée des croûtes continentales subduites et sous-plaquées au niveau du Moho sous les blocs continentaux permet le passage du magmatisme calco-alcalin au magmatisme calco-alcalin riche en potassium. L apport de chaleur par désintégration des éléments radiogéniques (K, U et Th) présents dans ces croûtes continentales subduites permet, dans un premier temps, la formation du magmatisme magnésio-potassique en profondeur. Dans un second temps, elle permet la formation du magmatisme d origine crustale par l intrusion du magmatisme magnésio-potassique, riche en K, U et Th, à la limite croûte moyenne - croûte supérieure. Ces successions d évènements magmatiques et particulièrement, la présence des granites magnésio-potassiques, relient clairement les Vosges à la partie Est de l orogène Varisque (Forêt Noire, Massif de Bohème, Alpes et Corse-Sardaigne).The Vosges Mountains are characterized by the presence of numerous magmatic intrusions and extrusions of varied affinities. Accordingly, they constitute the best site to investigate, by dating and geochemistry, the evolution of the events affecting this segment of the Variscan orogeny. Two successions of identical magmatic events, shifted in the time, are identified, characterizing both Moldanubian (360 to 320 Ma) and the Saxothuringian (335 to 295 Ma) domains. These successions of magmatic events result of two major process. The progress of subducted and underplated continental crusts at Moho depth under continental blocks permits to shift from calc-alkaline to high potassic calc-alkaline magmatism. The radiogenic heat production from latter underplated continental crusts, in a first time, permits to generate magnesio-potassic magmas at depth. Then, this radiogenic heat permits to generate crustal magmas by intrusion of magnesio-potassic magmas rich in K, U and Th at mid-upper crust boundarie. These successions of magmatic events and particularly, the presence of the magnesio-potassic granites, imply a strong link between the Vosges Mts. and the eastern part of the Variscan orogeny (Black Forest, Bohemian Massif, the Alps and Corsica Batholith).STRASBOURG-Bib.electronique 063 (674829902) / SudocSudocFranceF

Paleozoic evolution of the Variscan Vosges mountains. In: Schulmann, K., Martínez Catalán, J. R., Lardeaux, J. M., Janoušek, V. & Oggiano, G. (eds) The Variscan Orogeny: Extent, Timescale and the Formation of the European Crust.

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Microstructural evidences for mineralogical inheritance in partially molten rocks: example from the Vosges Mts

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AMS record of brittle dilation, viscous-stretching and gravity-driven magma ascent in area of magma-rich crustal extension (Vosges Mts., NE France)

International audienceOrogenic compression-related fabrics (similar to 340-335 Ma) were reworked during regional extensional deformation (similar to 328-325 Ma) in a large anatectic crustal domain of the Central Vosges (NE France). The extension was first accommodated by brittle dilation affecting vertically anisotropic high-grade rocks associated with emplacement of subvertical granitic sheets. The AMS fabric of granitoids is consistent with highly partitioned transtensional deformation marked by alternations of flat and steep foliations and development of orthogonal lineations. This deformation passes to top-to-the-southwest ductile shearing expressed in southerly migmatitic middle crust. The AMS fabric revealed moderately west-dipping foliations bearing subhorizontal NNW-SSE-trending lineations and predominantly plane strain to prolate shapes. This fabric pattern is interpreted as a viscous response of stretched partially molten crust during continuous ductile extension. Vertical ascent of voluminous granites and stoping of the upper crust occurs further south. This gravity ascent triggered by extension leads to development of south-dipping AMS foliations, south-plunging lineations and oblate fabrics in various crustal granites. Vertical shortening related to ascent of these (similar to 325 Ma) granitoids and persistent N-S stretching is responsible for reworking and remelting of originally vertical compression-related fabric in roof supracrustal granites (similar to 340 Ma) and development of highly prolate fabrics in these rocks. This work shows that the finite shape of AMS fabric ellipsoid is highly sensitive to both strain regime and superpositions of orthogonal deformation events