A combined structural, petrological, and anisotropy of magnetic susceptibility (AMS) study of the Cisuralian (285 ± 2 Ma) Cerro Redondo dacitic intrusion (Iberian Chain, NE Spain) has been conducted to reconstruct its emplacement kinematics and determine its 3D geometry at the outcrop scale. This small igneous body, covering only 0.17 km2, displays a well-defined magmatic foliation that is affected by asymmetrical, steeply plunging folds at different scales. Our multidisciplinary analysis suggests that the Cerro Redondo intrusion formed through the emplacement of successive magma pulses, during which the original magmatic foliations were passively folded. Detailed AMS data reveal a superposition of three kinematic processes recorded in the magnetic fabric, all occurring prior to complete crystallization: the development of an early planar magmatic fabric, localized simple shear deformation, and subsequent folding of the magmatic foliation. This integrated structural, petrological, and AMS study indicates that the Cerro Redondo intrusion is a sub-vertical, asymmetric subvolcanic body, emplaced at upper crustal levels under the control of extensional (or transtensional) movements of the late-Variscan Pardos Fault.

The Herrera Unit of the Iberian Chain (Cantabrian Zone, Iberian Massif) exhibits hundreds of outcrops of calc-alkaline igneous rocks that have been classically attributed to the Upper Carboniferous and the Lower Permian, although only two absolute radiometric ages have been reported. This work, with six new zircon LA-ICP-MS ages obtained from some of the most representative outcrops, provides the most complete age repository for the calc-alkaline magmatism of the prolongation of the Cantabrian Zone within the Iberian Chain. The obtained ages range between 294 and 288 Ma (Cisuralian Epoch) and show a well-defined peak at 290 Ma, which can be attributed to a main magmatic activity stage. This result allows us to correlate and integrate this magmatism within the widespread SW European calc-alkaline magmatism province developed under strike-slip tectonics. Therefore, the Iberian Chain magmatism and its age can be considered as a good temporal marker for the upper limit of the compressive tectonics associated with the Variscan orogeny and the onset of the extensional tectonics linked to Permo-Triassic rifting. Supplementary material: https://doi.org/10.6084/m9.figshare.c.6843778

Studying the magnetic fabric in volcanic edifices, particularly lava flows from recent eruptions, allows us to understand the orientation distribution of the minerals related to the flow direction and properly characterize older and/or eroded flows. In this work, the magnetic fabric from recent (Quaternary) lava flows (slightly inclined in seven sites and plateau lavas in two sites), pyroclastic deposits (two sites from a scoria cone) and volcanic cones, domes and plugs (three sites) from Penguin and Bridgeman islands, located in the Bransfield backarc basin, are presented. The volcanism in the two islands is related to rifting occurring due to the opening of the Bransfield Strait, between the South Shetlands archipelago and the Antarctic Peninsula. The direction of flow of magmatic material is unknown. Rock magnetic analyses, low temperature measurements and electron microscope observations (back-scattered electron imaging and Energy Dispersive X-ray analyses) reveal a Ti-poor magnetite (and maghemite) as the main carrier of the magnetic fabric. Hematite may be present in some samples. Samples from the centre of the lavas reveal a magnetic lineation either parallel or imbricated with respect to the flow plane, whereas in the plateau lavas the magnetic lineation is contained within the subhorizontal plane except in vesicle-rich samples, where imbrication occurs. The magnetic lineation indicates a varied flow direction in Bridgeman Island with respect to the spreading Bransfield Basin axis. The flow direction in the plateau lavas on Penguin Island is deduced from the imbrication of the magnetic fabric in the more vesicular parts, suggesting a SE–NW flow. The volcanic domes are also imbricated with respect to an upward flow, and the bombs show scattered distribution.

This case-study examines correlations in the continental-marine sedimentary record for the Late Triassic Carnian Humid Episode in the western Tethys domain of present-day E Spain and islands of Majorca and Minorca.The study area was divided into five sectors from west to east. Sectors 1 to 3 comprise the continental sedimentary record of this humid episode in eastern Iberia, which is represented by the three subunits (K-2.1, K-2.2 and K-2.3) of the K-2 Fm or Manuel Fm; each subunit records a fluvial episode with marine intercalations in distal areas. Sector 4 corresponds to Majorca Island and represents volcaniclastic input into a marginal continental marine transitional environment. Finally, sector 5 on Minorca Island comprises a karst surface developed on middle ramp deposits of the Arenal d'en Castell Fm, and separating this formation from the overlying Fontanelles Fm. Based on the ages of the units, estimated through palynomorph assemblages and ammonites, the Carnian Humid Episode was located in both the continental and marine sedimentary records.A detailed sedimentary study focused on fades analysis identified allogenic controls on both continental and marine records. Hence, in continental areas influenced by sea-level fluctuations, fluvial deposits appear integrated within standard lowstand, transgressive and highstand system tracts. This connection based on sedimentary sequences and unit ages indicates that subunits K-2.1 and K-2.2 are represented by a karst surface on the subaerially exposed shallow marine deposits, while subunit K-2.3 already reflects a return to the normal Late Triassic semi-arid to arid conditions that laterally correspond to the transgressive stage represented by the Fontanelles Fm in sector 5.Late Triassic tectonics activated previously developed N.NE-S" SW and NW-SE conjugate fault lineaments in eastern Iberia. This rifting episode controlled sedimentation in sectors 1 to 3, allowing volcanic activity at the fault lineaments junction in sector 4, and configuring a palaeogeography of elevated and subsiding blocks, which controlled both continental and marine sedimentation in the study area. 2016 Elsevier B.V. All rights reserved.

Deception Island shows a volcanism related to the Phoenix Plate subduction and roll-back under South Shetland Block in the present times. The development of the island is related to the evolution and collapse of a volcanic caldera, and this study is focused on the petrology, mineralogy and geochemistry of the post-caldera rocks. We have made a study of the lava flows, dikes and the youngest historic eruption in 1970. These rocks range from dacite to rhyolite and have a microporphyritic texture with olivine and minor clinopyroxene. A pre-caldera basaltic andesite has also been studied. It has a microporphyritic texture with clinopyroxene. The intermediate and acid compositions alternating in the volcanostratigraphic sequence suggest either mafic recharge events or melt extraction from different levels in the deep magmatic system. All the studied compositions share a subduction-related signature similar to other magmatics from the Bransfield Basin. However, compositional differences between pre-caldera and post-caldera rocks indicate a different magma source and depth of crystallisation. According to the geothermobarometric calculations the pre-caldera magmas started to crystallise at deeper levels (13.5–15 km) than the post-caldera magmas (6.2–7.8 km). Specifically, the postcaldera magmas indicate a smaller influence of the subducting slab in the southwestern part of the Bransfield Basin in respect to the available data from other sectors as well as the involvement of crustal contamination in the genesis of the magmas.

We have carried out a complete study of the Upper-Triassic alkaline magmatism on the northwestern margin of the Iberian Chain. This magmatism is composed of mafic sills, which intrude the Keuper facies in two geographic sectors: the Cameros Massif (NW) and the Moncayo Massif (SE). In both of these sectors, the rocks are characterised by an intense alteration (spilitisation). The field relationships point to an Upper Triassic age for the studied sills, given that: 1) interactions are recognised between the magma and wet, unconsolidated host sediments, suggesting that the magma was emplaced during or shortly after the deposition of the Keuper facies; 2) in the Moncayo sector a conglomerate bed that includes igneous clasts overlaies the sills and passes upwards to the Norian-Rhaetian Imon Fm. According to the petrological and geochemical features of the sills, an internal differentiation can be recognised inwards, with the developments of three zones: chilled margins, central facies and pegmatoid facies. The rocks are porphyritic and are mainly composed of phenocrysts of pseudomorphed olivine and microcrysts of plagioclase, opaque minerals and minor clinopyroxene. Vesicles and xenoliths of the host sedimentary rocks are also recognised, especially at the chilled margins. The mineral assemblage is constant across the sills but the mineral proportions vary among the different zones. The sills are basic to intermediate rocks. They are classified as basalts to dacites with an alkaline geochemical affinity. According to the trace element contents, this magmatism is related to an enriched sub-lithospheric mantle source affected by crustal contamination. Considering the Upper Triassic magmatisms from southwestern Europe, two types can be distinguished. On the one hand, the magmatisms in the Catalonian Coastal Ranges and SE France are paleogeographically located in the inner platform and are related to deep, astenospheric mantle sources with no evidence of crustal contamination. On the other hand, the magmatisms in the NW Iberian Chain –this study-, the External Betics and the Brescian Prealps are situated in a more litoral position and are related to a shallower, lithospheric mantle with evidence of crustal contamination. These differences could be related to the thickness of the continental crust, which might be thinner in the inner areas of the platform.

A multiple basic to intermediate sill is reported for the first time in the south-eastern Iberian Ranges. It is composed of several tabular to irregular levels intercalated within the fluvial sediments of the Alcotas Formation (Middle-Upper Permian). The sill could represent the youngest Paleozoic subvolcanic intrusion in the Iberian Ranges. The igneous rocks are classified as basaltic andesites. They show a subophitic microstructure constituted by plagioclase (An62 – An6), augite (En48Wo44Fs7 –En46Wo39Fs15), pseudomorphosed olivine, minor amounts of oxides (magnetite and ilmenite)and accessory F-apatite. According to the mineralogy and whole-rock composition, their geochemical affinity is transitional from subalkaline to alkaline. Radiometric dating of the sill is not feasible due to its significant alteration. Field criteria, however, suggest an emplacement coeval to the deposition of the Alcotas Formation (Middle-Upper Permian). This hypothesis is supported by the transitional affinity of these rocks, similar to other Middle-Upper Permian magmatisms in the western Tethys, e.g., from the Pyrenees. Taking into account their isotopic signature (eSr: -6.8 to -9.2; eNd:+1.7 to +8.3), an enriched mantle source with the involvement of a HIMU component has been identified. This interpretation is supported by the trace element contents. Some of these HIMU characteristics have been recognised in the Middle-Upper Permian magmatisms of the Central Pyrenees (Anayet Basin) and the High Atlas (Argana Basin). However, none of these source features are shared with other Middle-Upper Permian magmatisms of the western Tethys (Catalonian Coastal Ranges, Corsica-Sardinia and southern France), nor with the Lower Permian magmatism of the Iberian Ranges. These differences support the presence of a heterogeneous mantle in the western Tethys during the Permian.

The effects of different petrological processes on the rock fabric of a folded sill from the Albarracin Massif (southeastern Iberian Chain, Spain) were studied by means of the anisotropy of magnetic susceptibility (AMS) technique. The most outstanding feature of the sill at outcrop-scale is a network of joints linked to thermal contraction, which define polygonal columns. The analysis of the magnetic fabric, taking the orientation of sill walls and column axes as a reference and using the ‘restored’ directional data corresponding to the whole of K3 susceptibility axes, has revealed magnetic fabrics related to two processes: (a) magma flow with a SW-trending flow vector characterized by a curved geometry of the magma foliations and (b) thermal contraction coeval to lava cooling. Early magnetite crystals, grown in a relatively high viscosity calc-alkaline magma, are the main carriers involved in the AMS fabric. Passive rotation of the early magnetic mineralogy within a medium-viscosity magma explains the magnetic fabric linked to both magma flow and near-solidus thermal contraction of the magma. Late-Variscan folding of the sill produced the rigid-body reorientation of the magnetic fabric.

Recent studies have confirmed the important role played by magmatism during the Late Carboniferous–Permian transition. In this report, we describe the characteristics of this magmatism in the Central Iberian realm (Iberian Ranges and eastern Spanish Central System) and discuss its palaeoenvironmental impact. In the studied area, the late-Variscan transtensional to extensional tectonic regime favoured the emplacement of a calc-alkaline magmatism during the Late Stephanian–Permian. This magmatism is expressed both as pyroclastic rocks filling small half-graben basins and hypabyssal intrusions (sills and dykes). Pyroxenic- and amphibolic-andesites are the main rock compositions, while basalt, dacite and rhyolite are less represented. The available K/Ar isotopic data suggests a Lower Permian age for this magmatism, also supported by its complete macro- and microflora content and by features related to its emplacement (hypabyssal intrusions crosscut Stephanian rocks and are in turn overlain by late Permian–Triassic sediments). Frequent xenoliths of middle and lower crustal levels indicate considerable magma–crust interaction. This interaction may have led to substantial crustal assimilation during the first emplacement stages in conditions of a low extension rate. Crustal contamination barely affected the final magmatic products emplaced under conditions of greater extension. The palaeoecological effects of explosive manifestations of this volcanism are expressed in the varied macroflora record in volcaniclastic basins. The number and volume of hypabyssal intrusions suggest that the original geological record of explosive activity in these basins was much greater and was reduced by subsequent erosion processes.

Abstract Permian magmatism in the Pyrenees is characterized by two compositionally different and temporally consecutive magmatic episodes: a calc-alkaline-transitional phase (andesites) and a midly alkaline phase (basalts and dolerites). These two magmatic episodes were related to the attenuation of late Variscan transtensional tectonics and the onset of extension related to regional rifting. The strike-slip fault systems that affected the Pyrenees in late Variscan times initially controlled the development and morphology of the sedimentary basins. These were periodically affected by phases of extension, which controlled the subsidence of the basins, and, in addition, the emplacement of magmas. The whole-rock trace-element and isotopic signature of the andesites suggests that they were derived from the upper mantle and variably hybridized with late orogenic crustal melts, whereas the alkali basalts could have been derived from a lithospheric mantle source, enriched as a consequence of Variscan subduction processes with the contribution, in some areas, of an enriched (asthenospheric) component.

Abstract Late Variscan magmatism in the Iberian Chain (Central Spain) is recorded by the presence of both pyroclastic units and high-level intrusions (sills and dykes). This magmatism encompasses a variety of subalkaline igneous rocks, from basalt to rhyolite; andesitic rocks are, however, dominant. The pyroclastic units contain plant fossils and pollen that suggest an Autunian age, which is consistent with the available K-Ar radiometric age data (283–292 Ma) obtained for the hypabyssal intrusions. Earlier amphibole-rich andesite, rich in crustal xenoliths (metapelite, granitoid and quartzite fragments) and xenocrysts (e.g. garnet) suggest the occurrence of significant crustal assimilation in the petrogenesis of the intermediate magmas, whereas later intrusions (pyroxene-rich andesites, basalts and some rhyolites) lack any crustal xenoliths or xenocrysts. Crustal assimilation is also suggested by the radiogenic 87Sr/86Sr290 and negative ɛNd290 values for all the studied rocks. The cross-cutting relationships between the different rock types provide evidence for a multi-stage magmatic evolution, coeval with the post-orogenic transtensive evolution of the southern Variscan belt in Europe. A significant hiatus, covering the Middle Permian and most of the Upper Permian, separates this Lower Permian magmatism from the subsequent Triassic and Jurassic alkaline magmatism that represents different rifting events that affected the Iberian Chain, progressively thinning the Variscan crust as the Alpine cycle began.

A detailed mineral composition study (EMP) of three different textural types of scapolite porphyroblasts in calc-silicate and microdiorite samples from the Maladeta Plutonic Complex (Central Pyrenees) is presented, Additionally, a scapolite mineral separate was characterised by XRD, TGA and IR spectrometry, in order to obtain reliable CO2 and SO3 estimates and crystallographic parameters. Many of the obtained compositions are Cl-rich and seem to be related, in their genesis, to the composition of the fluid phase. According to textural and chemical criteria, these scapolite porphyroblasts postdate the main contact metamorphism. The genesis of scapolite is interpreted as a result of the replacement of either metamorphic or igneous plagioclase. related to flow of NaCl- and CaCO3-rich hydrothermal solutions around the intrusive complex. Other minerals (biotite) also seem to be involved in the replacement process affecting plagioclase in microdiorite. Reaction schemes are proposed for the genesis of scapolite in the different compositional groups considered in this paper. The growth of scapolite porphyroblasts N as followed by the precipitation of hydrothermal scapolite as vein fillings. in optical and chemical continuity with previous crystals.

The shallow intrusive bodies and lava flows emplaced within the Permian upper red unit in the Anayet Massif, represent a magmatic episode that occurred about 255 Ma (Saxonian) in the Pyrenean Axial Zone (northern Spain). Anisotropy of magnetic susceptibility (AMS) measurements, in both igneous bodies and their host rocks, allow us to infer the existence of magnetic fabrics of tectonic origin linked to the main cleavage-related folding episode. The relationship between the susceptibility axes and the field structures is the criterion that permits to differentiate normal from inverse magnetic fabrics in the igneous samples. The structural interpretation of all AMS data taken from the igneous bodies and sedimentary host rocks, is in accordance with a folding model which include: (i) flattening associated with cleavage formation during fold amplification in incompetent layers (host pelites), responsible for a magnetic lineation at high angles with respect to the regional folding axis and (ii) buckling in competent (conglomerates and igneous bodies) levels, responsible for a magnetic lineation parallel to the regional fold axes.