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In two companion papers, we report the detailed geological and mineralogical study of two emblematic serpentinized ultramafic bodies of the western North Pyrenean Zone (NPZ), the Urdach massif (this paper) and the Saraille massif (paper 2). The peridotites have been exhumed to lower crustal levels during the Cretaceous rifting period in the future NPZ. They are associated with Mesozoic pre-rift metamorphic sediments and small units of thinned Paleozoic basement that were deformed during the mantle exhumation event. Based on detailed geological cross-sections and microprobe mineralogical analyses, we describe the lithology of the two major extensional fault zones that accommodated: (i) the progressive exhumation of the lherzolites along the Cretaceous basin axis; (ii) the lateral extraction of the continental crust beneath the rift shoulders and; (iii) the decoupling of the pre-rift cover along the Upper Triassic (Keuper) evaporites and clays, allowing its gliding and conservation in the basin center. These two fault zones are the (lower) crust-mantle detachment and the (upper) cover decollement located respectively at the crust-mantle boundary and at the base of the detached pre-rift cover. The Urdach peridotites were exposed to the seafloor during the Late Albian and underwent local pervasive carbonation and crystallization of calcite in a network of orthogonal veins (ophicalcites). The carbonated serpentinized peridotites were partly covered by debris-flows carrying fragments of both the ultramafics and Paleozoic crustal rocks now forming the polymictic Urdach breccia. The mantle rocks are involved in a Pyrenean overturned fold together with thin units of crustal mylonites. Continent-derived and mantle-derived fluids that circulated along the Urdach crust-mantle detachment led to the crystallization of abundant metasomatic rocks containing quartz, calcite, Cr-rich chlorites, Cr-rich white micas and pyrite. Two samples of metasomatized material from the crust-mantle detachment yielded in situ zircon U/Pb ages of 112.9 +/- 1.6 Ma and 109.4 +/- 1.2 Ma, thus confirming the Late Albian age of the metasomatic event. The cover decollement is a 30-m thick fault zone which also includes metasomatic rocks of greenschist facies, such as serpentinecalcite association and listvenites, indicating large-scale fluid-rock interactions implying both ultramafic and continental material. The lowermost pre-rift cover is generally missing along the cover decollement due to tectonic disruption during mantle exhumation and continental crust elision. Locally, metasomatized and strongly tectonized Triassic remnants are found as witnesses of the sole at the base of the detached pre-rift cover. We also report the discovery of a spherulitic alkaline lava flow emplaced over the exhumed mantle. These data collectively allow to propose a reconstruction of the architecture and fluid-rock interaction history of the distal domain of the upper Cretaceous northern Iberia margin now inverted in the NPZ.

Keban metamorphites located at the orogenic belt of the Eastern Taurides is an allochtonous union metamorphized at the greenschist facies comprised of several nappes. Contrary to the massives around it, the aging of the union is not quite satisfactory due to the lack of fossil data. Permo-Triassic/Permo-Carboniferous ages have been used until now for the age of the metamorphites that are stated to be located only at a single location, the species of which have not been determined and which are based on two fossil data. However, for the first time in this study, “ microgastropods ” have been found at Early Triassic age related with The Great Dying at the end of the Permian inside the clastic limestones at the base levels of the Nimri Formation which is one of the lower nappes of the Keban metamorphites. Again, trace fossils Planolites , Rhizocorallium , Thalassinoides , Helminthopsis and (?)Protovirgularia have been determined for the first time in the layered crystallized limestones at the medium levels of the Nimri Formation. This ichnofabric is frequently observed in the Middle Triassic aged limestones at Germany, Poland, Austria, Italy and the Taurides and is known as the “vermicular limestone facies”. The ages of Keban marble, Delimehmet and Suleymanli Formations, tectonically located on the Nimri Formation, are evaluated by regional correlations as Middle-Late Devonian, Late Devonian and Early Carboniferous, respectively. In addition, probably pre-Triassic aged, dark green colored metadiabase dykes have been inserted in the Delimehmet formation in relation with the Variscan Orogeny. Regional correlations with other units and massives indicate that the Keban metamorphites that have deposited at the farthest north of the south branch of the Neo-Tethys ocean paleogeographically may be the continuation of the Bolkardagi Union at the east rather than the Alanya and Geyikdagi Unions.

International audience; In two companion papers, we report the detailed geological and mineralogical study of two emblematic serpentinized ultramafic bodies of the western North Pyrenean Zone (NPZ), the Urdach massif (this paper) and the Saraillé massif (paper 2). The peridotites have been exhumed to lower crustal levels during the Cretaceous rifting period in the future NPZ. They are associated with Mesozoic pre-rift metamorphic sediments and small units of thinned Paleozoic basement that were deformed during the mantle exhumation event. Based on detailed geological cross-sections and microprobe mineralogical analyses, we describe the lithology of the two major extensional fault zones that accommodated: (i) the progressive exhumation of the lherzolites along the Cretaceous basin axis; (ii) the lateral extraction of the continental crust beneath the rift shoulders and; (iii) the decoupling of the pre-rift cover along the Upper Triassic (Keuper) evaporites and clays, allowing its gliding and conservation in the basin center. These two fault zones are the (lower) crust-mantle detachment and the (upper) cover décollement located respectively at the crust-mantle boundary and at the base of the detached pre-rift cover. The Urdach peridotites were exposed to the seafloor during the Late Albian and underwent local pervasive carbonation and crystallization of calcite in a network of orthogonal veins (ophicalcites). The carbonated serpentinized peridotites were partly covered by debris-flows carrying fragments of both the ultramafics and Paleozoic crustal rocks now forming the polymictic Urdach breccia. The mantle rocks are involved in a Pyrenean overturned fold together with thin units of crustal mylonites. Continent-derived and mantle-derived fluids that circulated along the Urdach crust-mantle detachment led to the crystallization of abundant metasomatic rocks containing quartz, calcite, Cr-rich chlorites, Cr-rich white micas and pyrite. Two samples of metasomatized material from the crust-mantle detachment yielded in situ zircon U/Pb ages of 112.9 ± 1.6 Ma and 109.4 ± 1.2 Ma, thus confirming the Late Albian age of the metasomatic event. The cover décollement is a 30-m thick fault zone which also includes metasomatic rocks of greenschist facies, such as serpentine-calcite association and listvenites, indicating large-scale fluid-rock interactions implying both ultramafic and continental material. The lowermost pre-rift cover is generally missing along the cover décollement due to tectonic disruption during mantle exhumation and continental crust elision. Locally, metasomatized and strongly tectonized Triassic remnants are found as witnesses of the sole at the base of the detached pre-rift cover. We also report the discovery of a spherulitic alkaline lava flow emplaced over the exhumed mantle. These data collectively allow to propose a reconstruction of the architecture and fluid-rock interaction history of the distal domain of the upper Cretaceous northern Iberia margin now inverted in the NPZ.; Dans deux articles compagnons, nous décrivons la géologie et la minéralogie de deux massifs de péridotites serpentinisées représentatifs de la Zone Nord-Pyrénéenne (ZNP) occidentale, le massif d’Urdach (cet article) et le massif du Saraillé (article 2). Les péridotites ont été portées vers les niveaux crustaux supérieurs durant l’épisode de rifting pyrénéen crétacé qui a affecté la future ZNP. Elles sont associées à des sédiments métamorphiques pré-rift et à des lambeaux de croûte Paléozoïque déformée durant l’exhumation. En s’appuyant sur des descriptions de coupes géologiques et des analyses de minéraux à la microsonde, nous précisons la lithologie de deux failles extensives majeures qui ont permis : (i) la remontée des lherzolites sous l’axe du bassin ; (ii) l’extraction latérale de la croûte continentale sous les bordures du rift et ; (iii) le découplage et le glissement de la couverture pré-rift le long des évaporites et argiles du Keuper. Ces deux zones de faille sont le détachement croûte-manteau (inférieur) et le décollement de couverture (supérieur) situés respectivement à la limite croûte-manteau et à la base de de la série pré-rift glissée. Les péridotites d’Urdach ont été mises à l’affleurement sur le fond marin où elles ont subi une carbonatation interne partielle accompagnée de cristallisation de calcite dans un réseau de veines orthogonales (ophicalcites). Les serpentinites ont été recouvertes partiellement par la brèche d’Urdach formée d’écoulements de débris ultramafiques et paléozoïques. Les roches du manteau sont engagées avec de minces lentilles de mylonites crustales dans un pli deversé vers l’ouest. Des fluides d’origine mantellique et continentale ont circulé le long du détachement croûte-manteau et ont permis la cristallisation de roches métasomatiques renfermant : quartz, calcite, chlorite et mica riches en Cr, et pyrite. Deux échantillons de ces roches métasomatiques ont fourni des âges U/Pb in situ sur zircons de 112.9 ± 1.6 Ma et 109.4 ± 1.2 Ma confirmant ainsi l’âge Albien supérieur de cet événement métasomatique. Le décollement de couverture renferme aussi des roches métasomatiques (associations calcite-serpentine et listvénites), témoignant d’échanges fluide-roche à grande échelle à partir de matériel mantellique et crustal. La base de la couverture pré-rift a subi une troncature basale lors de l’exhumation du manteau et des résidus triasiques très déformés sont présents à la base de la série pré-rift décollée. Nous avons également découvert une coulée de lave sphérulitique alcaline mise en place sur le manteau exhumé. Cet ensemble de données sur le massif d’Urdach permet de proposer une reconstitution au Crétacé supérieur de l’histoire des fluides et de l’architecture du domaine distal de la marge nord ibérique aujourd’hui inversée dans la ZNP.

The tectonic boundary of between the Lyngen magmatic complex and the underlaying Nordmannvik have been examined for kinematic indicators. This boundary is characterised by an amphibole facies garnet-mica-kyanite gneiss overlain by a greenschist facies amphibolite/meta-gabbro succession separated by heavily foliated and lineated garnet-mica schist, phyllites and quartzites. Two main populations of lineation were identified: A West verging and a NW verging. Field observations and thin section analyses indicate an overall top to the WNW sense of shear. Not all kinematic indicators show emplacement in this direction; a cluster of indicators located in a synform NE of Nordkjosbotn showed a consistently top to the SE sense of shear. Top to the WNW kinematic indicators were also found on the East side of Storfjorden, 8 km to the east of the Lyngen nappe/Nordmannvik boundary. The emplacement is interpreted to have happened in greenschist facies conditions based on the presence of chlorite in schist and phyllites. Quartz CPO indicate that the temperatures were high enough that rhomb and prism a-slip was dominant with grain boundary migration as the dominant recrystallization mechanism. A top WNW sense of shear indicate that the Lyngen nappe could have been displaced due to extensional collapse or possibly extrusion wedging.