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[EN] The Cambrian Atlas – Ossa–Morena – North Armorican Rift extended along West Gondwana from the end of the Pan-African and Cadomian orogenies until the diachronous beginning of drift conditions related to the opening of the Rheic Ocean. The along-axis rift cross-cut the western parts of the Anti-Atlas, High Atlas and Coastal Meseta, which were linked to the Ossa–Morena Zone and the North Armorican Domain, whereas several joint tectonic branches connected with off-axis rift transects of the Central Iberian, West Asturian–Leonese and Cantabrian zones (Iberian Massif), the Central and South Armorican domains, the Occitan Domain, the Pyrenees, and southern Sardinia. The pre-rift unconformity, post-dating the orogenic collapse, is characterized by initial (half-)graben development and subsequent infill, with slope-related breccias and conglomerates controlled by the denudation of surrounding uplands. Synrift pulses show regional extension and are distinctly identifiable on the top of rift shoulders, recording episodes of carbonate production due to their association with karst and hydrothermal processes. The break-up unconformity ranges from volcanic-free angular discordances and paraconformities to generalized uplift and denudation of subaerially exposed areas, associated with the onset of granite-dominant large igneous provinces (LIPs). The Furongian–Tremadocian (Toledanian) and Ordovician (Sardic) phases have been interpreted as due to: (i) Andean-type subduction magmatism reaching the crust in an arc–back-arc setting; (ii) post-collisional decompression melting without significant mantle involvement; and (iii) partial melting of the lower continental crust affected by the underplating of hot mafic magmas linked to superplumes.

Geochemical data of the Variscan gneisses derived from pre-Variscan intrusives and late-Variscan granitoids in the Pyrenees and the Catalan Coastal Ranges were obtained from two main sources: (1) individually mined from published articles and unpublished PhD theses (Autran et al., 1970; Guitard, 1970; Enrique, 1989; Soler and Enrique, 1989; Enrique, 1990; Soler, 1990; Gleizes, 1992; Debon et al., 1996; Arranz, 1997; Guitard et al., 1998b, 1998b; Roberts et al., 2000; Vilà et al., 2005; Casas et al., 2010; Navidad et al., 2010; Druguet et al., 2014; Laumonier et al., 2015; Navidad et al., 2018; Lemirre et al., 2019; Álvaro et al., 2021; Liesa et al., 2021; Casas et al., 2024), and (2) the GEOROC Database (Geochemistry of Rocks of the Oceans and Continents, Göttingen University, https://georoc.eu/; last access: 03/2024; Lehnert et al., 2000). Other Findable, Accessible, Interoperable, and Reusable (FAIR; Wilkinson et al., 2016) databases were searched using geographic and lithogeochemical constrains, yielding no results. The mined data were curated and classified based on the analysed rock types, ages, regional tectonic setting, and mode of occurrence in outcrop, resulting in more than 600 entries that are associated with up to 66 data fields. Associated with each entry are generic, descriptive and informative fields (Sample ID, Unit/Massif, Rock category, Rock details, Outcrop description, and References), major element oxide abundances (SiO2, Al2O3, FeOT, Fe2O3T, MnO, MgO, CaO, Na2O, K2O, TiO2, P2O5, and LOI), and trace element concentrations (Ag, As, Ba, Be, Bi, Co, Cr, Cs, Cu, Ga, Ge, Hf, In, Mo, Nb, Ni, Pb, Rb, Sb, Sc, Sn, Sr, Ta, Th, Tl, U, V, W, Y, Zn, Zr, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu). The resulting database, named NEIGRA (North-East Iberian GRAnitoids), represents the first Open-Access compilation of granite and orthogneiss geochemical data in the Pyrenees and the Catalan Coastal Ranges.

Deception Island is the most active volcano in the South Shetland Islands (Antarctica) with more than 20 explosive eruptive events registered over the past few centuries. The most recent eruption (August 1970) was severely violent with a volcanic explosivity index (VEI) of 3. The column height reached 10 km at its maximum, the estimated bulk eruptive volume was > 0.1 km3 and tephra fallout was reported as far as in King George Island (> 150 km distance). In this work, we perform a compositional and textural analysis of the 1970 tephra layers found at Livingston Island¿s glaciers (between 25 and 40 km distance from Deception IsIand). Results obtained are then compared to the in situ pyroclastic deposits of the diverse vents active during this eruption. The objective is to establish a correlation between the eruptive phases occurred during the 1970 event and the physicochemical features observed in the tephra deposits. This will be used as a starting point for future studies of tephra layers found in glaciers and marine/lacustrine sediment cores outside the island, improving our capacity to reconstruct the eruptive dynamics of past eruptions. These results are fundamental to: (i) determine the size and explosiveness of past eruptive events; (ii) assess the extent of their related hazards (e.g., ash fall out); (iii) complete the eruption record of the island; and (iv) consequently, perform more accurate hazard assessments at the island. This is of special concern, since the South Shetland Islands are an important tourist destination and host numerous year-round and seasonal scientific stations and base camps.

This study presents a new geochemical, petrological, and geochronological U–Pb dataset from Ediacaran metabasites of the Canigó and Cap de Creus massifs, Eastern Pyrenees. The rocks are composed of calcic amphibole + plagioclase + chlorite + epidote ± quartz plus titanite + apatite + ilmenite ± biotite ± rutile as accessory phases and show relict igneous textures. Peak pressure-temperature determinations share common conditions, ranging 452–482ºC and 5.2–7.7kbar. These intermediate P-T conditions suggest Barrovian-type metamorphism, most likely related to a collisional setting. The metabasites correspond to evolved basaltic rocks (Mg#<0.55) with moderate TiO2 content (up to 2.08wt.%) and relatively low Cr (43–416ppm). The rocks are moderately enriched in light rare earth elements (LREE) relative to heavy rare earth elements (HREE) (average (La/Lu)n of 2.7) and the N-MORB normalized multi-element patterns show negative slopes, with prominent negative Nb anomalies ((Nb/La)NMORB=0.33–0.78). These variations are akin to island arc tholeiites generated in back-arc basins and to other metabasites described in the Eastern Pyrenees with a putative Ediacaran age, and they differ from the Ordovician tholeiitic metabasites from the Canigó massif, which derived from a contaminated E-MORB source. The positive ƐNd(T) values (0.82–3.05) of the studied metabasites preclude a notable contribution from an older continental crust. U-Pb dating (LA-ICP-MS) of one chlorite-rich schist sample in contact with the metabasites from the Canigó massif yielded a main peak at ca. 632Ma. We argue that the Cadomian metabasites from the Pyrenees formed during back-arc extension in the continental margin of Gondwana and were later affected by (probably early Variscan) medium-P metamorphism before the HT-LP metamorphism classically described in the Pyrenees

Various models have been proposed to explain the formation of the Ibero-Armorican Arc (IAA) as either primary or secondary (rotational). Models for secondary arc formation require significant rotation around a vertical axis at the end of the Variscan orogeny. Estimates for the amount of north–south (present coordinates) contraction (horizontal shortening) required for these rotations range from 54 at the core to 91% at the SE tip of the arc, near to the present day Mediterranean coast. These estimates are compared with coeval deformational structures developed in three areas of the orogen: (1) in the autochthonous hinterland in the southern branch of the arc; (2) in the Cantabrian Zone foreland fold–thrust belt in the core of the arc; and (3) in the SE continuation of the southern branch of the IAA in the present day Iberian Chain. From this analysis it follows that the contraction associated with late Variscan deformation is much less than that needed to explain the formation of the IAA from a formerly linear orogen via rotation around a vertical axis. We therefore propose that the geometry of the arc should be re-evaluated. We discuss the palaeomagnetic data purported to support the secondary origin, as well as the role of late Variscan regional strike-slip faults in modifying the geometry of the Iberian and Armorican massifs. Our analysis suggests that the IAA formed mainly from a primary non-rotational margin-controlled curvature, slightly modified by c. 5–20% of superposed contraction during late Carboniferous and/or Alpine times.

This study presents a new geochemical, petrological, and geochronological U–Pb dataset from Ediacaran metabasites of the Canigó and Cap de Creus massifs, Eastern Pyrenees. The rocks are composed of calcic amphibole + plagioclase + chlorite + epidote ± quartz plus titanite + apatite + ilmenite ± biotite ± rutile as accessory phases and show relict igneous textures. Peak pressure-temperature determinations share common conditions, ranging 452–482ºC and 5.2–7.7kbar. These intermediate P-T conditions suggest Barrovian-type metamorphism, most likely related to a collisional setting. The metabasites correspond to evolved basaltic rocks (Mg#<0.55) with moderate TiO2 content (up to 2.08wt.%) and relatively low Cr (43–416ppm). The rocks are moderately enriched in light rare earth elements (LREE) relative to heavy rare earth elements (HREE) (average (La/Lu)n of 2.7) and the N-MORB normalized multi-element patterns show negative slopes, with prominent negative Nb anomalies ((Nb/La)NMORB=0.33–0.78). These variations are akin to island arc tholeiites generated in back-arc basins and to other metabasites described in the Eastern Pyrenees with a putative Ediacaran age, and they differ from the Ordovician tholeiitic metabasites from the Canigó massif, which derived from a contaminated E-MORB source. The positive ƐNd(T) values (0.82–3.05) of the studied metabasites preclude a notable contribution from an older continental crust. U-Pb dating (LA-ICP-MS) of one chlorite-rich schist sample in contact with the metabasites from the Canigó massif yielded a main peak at ca. 632Ma. We argue that the Cadomian metabasites from the Pyrenees formed during back-arc extension in the continental margin of Gondwana and were later affected by (probably early Variscan) medium-P metamorphism before the HT-LP metamorphism classically described in the Pyrenees.

This study presents a new geochemical, petrological, and geochronological U-Pb dataset from Ediacaran metabasites and associated rocks of the Canigó and Cap de Creus massifs, Eastern Pyrenees. Metabasites are composed of calcic amphibole + plagioclase + chlorite + epidote ± quartz plus titanite + apatite + ilmenite ± biotite ± rutile as accessory phases and show relict igneous textures. Peak pressure-temperature determinations share common conditions, ranging 452-482ºC and 5.2-7.7kbar, which suggest Barrovian-type metamorphism, most likely related to a collisional setting. The metabasites correspond to evolved basaltic rocks (Mg#<0.55) with moderate TiO content (up to 2.08wt.%) and relatively low Cr (43-416ppm). The rocks are moderately enriched in Light Rare Earth Elements (LREE) relative to Heavy Rare Earth Elements (HREE) (average (La/Lu) of 2.7) and the N-MORB normalized multi-element patterns show negative slopes, with prominent negative Nb anomalies ((Nb/La)=0.33–0.78). These variations are akin to island arc tholeiites generated in back-arc basins and to other metabasites described in the Eastern Pyrenees with a putative Ediacaran age, and they differ from the Ordovician tholeiitic metabasites from the Canigó massif, which derived from a contaminated E-MORB source. The positive Ɛ values (0.82-3.05) of the studied metabasites preclude a notable contribution from an older continental crust. Detrital zircon U-Pb dating Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) of one chlorite-rich schist sample in contact with the metabasites from the Canigó massif yielded a main peak at ca. 632Ma and apparent maximum age of deposition at ca. 550Ma. We argue that the Cadomian metabasites from the Pyrenees formed during back-arc extension in the continental margin of Gondwana and were later affected by (probably early Variscan) medium-P metamorphism before the Low-Pressure High-Temperature (LP-HT) metamorphism classically described in the Pyrenees.

Detailed geological mapping of the La Cerdanya area (Canigó unit, Eastern Pyrenees) provides new data characterizing the different structural styles exhibited by Cambrian–Lower Ordovician (Jujols Group) and Upper Ordovician successions. Their unconformable contact, related to the Sardic Phase, ranges from 0° (paraconformity) to 90° (angular discordance). The Jujols Group rocks topped by the unconformity are affected by Sardic foliation-free open folds. The pre-Sardic succession, the Sardic Unconformity and the lower part of the post-Sardic succession (Rabassa Conglomerate and Cava formations) are cut and offset by several Late Ordovician NNE–SSW-trending synsedimentary extensional faults associated with hydrothermal activity, which dramatically affected the thickness of the lower part of the Upper Ordovician succession. We relate (1) the Mid-Ordovician Sardic uplift and erosion, and (2) a Mid-to Late-Ordovician upward propagating extensional fault system bounding the outline of half-grabens, subsequently infilled by alluvial deposits, to a thermal doming event (about 475– 450 Ma) that led to the uplift and stretching of the Ordovician lithosphere. Thermal doming may be caused by mafic magma underplating and responsible for the coeval calc-alkaline magmatic activity broadly developed in the Eastern Pyrenees. We discuss the similarities between the Mid-Ordovician Sardic Unconformity and other Early Paleozoic unconformities described in neighbouring areas. Finally, we suggest a geodynamic scenario in which a regional-scale thermal event was related to the opening of the Rheic Ocean that led to the drift of Avalonia from the SW European margin of Gondwana.

Pre-Variscan basement rocks from the Pyrenees provide evidence of several magmatic episodes with complex geodynamic histories from late Neoproterozoic to Palaeozoic times. One of the most significant episodes, consisting of several granitic and granodioritic bodies and volcanic rocks, mostly pyroclastic in nature, dates from the Late Ordovician period. In the Eastern Pyrenees, this magmatism is well represented in the Ribes de Freser and Núria areas; here, the Núria orthogneiss and the Ribes granophyre, both dated at c. 457-460 Ma, seem to form a calc-alkaline plutonic suite emplaced at different crustal levels. The presence of numerous pyroclastic deposits and lavas interbedded with Upper Ordovician (Sandbian-lower Katian, formerly Caradoc) sediments, intruded by the Ribes granophyre, suggests that this magmatic episode also generated significant volcanism. Moreover, the area hosts an important volume of rhyolitic ignimbrites and andesitic lavas affected by Alpine deformation. These volcanic rocks were previously attributed to late Variscan volcanism, extensively represented in other areas of the Pyrenees. Here we present the first five laser-ablation U-Pb zircon dates for this ignimbritic succession and two new ages for the Ribes granophyre. The ages of the ignimbrites, overlapping within error, are all 460 Ma, suggesting a genetic relationship between the plutonic and volcanic rocks and indicating that the Sandbian-Katian magmatism is much more voluminous than reported in previous studies, and possibly includes mega-eruptions linked to the formation of collapse calderas. © Cambridge University Press 2019.

During Ordovician times, the northwestern margin of Gondwana, in a transect linking the Anti-Atlas, the western and eastern branches of the Ibero-Armorican Arc and the Alps, recorded a stepwise succession of stratigraphic gaps, in some cases linked to magmatism, extensional tectonics, uplift and erosion. The Furongian (Toledanian) and Mid–Ordovician (Sardic) Phases are distinctly separated in time, but share the calc-alkaline-dominant affinities of their involved magmatism and the absence of some typical deformation properties, such as cleavage and metamorphism. The stratigraphic gaps related to uplift events and denudation have been interpreted as break-up (or rift/drift) unconformities, subduction-related orogenies or transpressive-transtensive events associated with hypothetical terranes that have not yet been found amalgamated to other orogens. This geodynamic framework is used to introduce the contributions of this special volume.

The Ribes de Freser area of the Eastern Pyrenees is characterized by an Alpine antiformal stack that comprises the so-called El Baell and Bruguera tectonostratigraphic units. This work presents detailed geological mapping and stratigraphic and facies analyses of these units, in order to improve the understanding of the Mid–Late Ordovician paleogeographical features of this sector of the Pyrenean margin of North Gondwana, subsequently affected by the Sardic Phase and the Variscan Orogeny. The Katian El Baell Formation, which crops out in the homonymous unit, is revised, formally erected and proposed as a lateral equivalent of the Estana Formation. The El Baell Formation consists of shale/limestone alternations where the carbonate production was controlled by development of pelmatozoan–bryozoan meadows and mud-mounds with plano-convex geometries and preservation of ramose bryozoans in life position. The thicker limestone levels, marking the top of shallowing-upward sedimentary cycles, contain fissure networks occluded with Pb–Zn–As ore mineralizations, whose clast counterparts occur forming overlying lags. The El Baell/Ansovell contact is marked by karstic clayey byproducts. Both the drastic changes in thickness and facies of the El Baell and Estana formations, and the presence of contemporaneous epithermal and fissuring episodes in the former, point to the onset of Katian (Late Ordovician) extensional tectonics, which may have controlled sharp modifications in accommodation space. Finally, the internal structure of the El Baell and Bruguera units are different, pointing to the record of a pre-Variscan (Mid Ordovician) deformational episode responsible for the dispersion of Variscan mesostructures in pre-Upper Ordovician rocks.