The Narcea Antiform Structure and its relation to the Western Cantabrian Zone thrust sheets. Part II: The Eastern Sector

In the eastern part of the Narcea Antiform, the Narcea Tectonic Window, only one cleavage developes, which is axial plane to vertical hinge folds. This foliation does not continue into the overlying unconformable Herrería Formation, Cambrian in age. The contact between these two formations is a fault running along the unconformity plane, which may produce spaced foliations in the hangingwall rocks at high angle with precambrian rocks cleavage.Both, fault and cleavage are due to a variscan deformation event, partition of the deformation occurs at the unconformity, revealing different theological behaviours and different original orientations. The limit between these western and the eastern units is a major thrust./nThe Somiedo Unit, the westernmost of the allochton ones in the Cantabrian Zone, has been known for long. It is formed by four main units, developed during the so called first thrust generation, which has a basal thrust, showing staircase trajectories, below the Láncara formation, except in the westernmost part of the unit where it deepens into the precambrian rocks, being the only part of the Cantabrian Zone where the rooting of this units can be seen. This ramp produces a culmination over it and causes the antiform. Another generation of thrusts can be seen, the second one, which crosscuts the first ones and affects not only Somiedo Unit but Narcea Antiform as well. The second generation ones do not depict staircase trajectories, listric ones are common, and have much less displacement than the first generation ones. These listric reverse faults modify the first generation pattern, and causes Narcea Antiform re-folding./nThe relations between all these units are complex, and a tentative correlation between the two deformation phases at the WALZ, and the first thrust generation, at the CZ, has been done. The second thrusting stage is responsible for the final disposition of structures at the CZ and the WALZ.En el sector oriental del Antiforme del Narcea, denominado Ventana Tectónica del Narcea, existe una foliación que es de plano axial de pliegues con ejes verticales. Esta foliación no se continúa en la formación suprayacente, la Formación Herrería El contacto entre estas dos formaciones es un despegue que discurre por el plano de discordancia y que puede producir foliación espaciada en la parte baja de la Formación Herrería, formando un elevado ángulo con la foliación existente en las rocas precámbricas. Tanto el despegue como las foliaciones en este sector, están asociadas auna deformación varisca que pone de manifiesto el contraste de competencias y la diferente orientación original entre las rocas implicadas./nLa Unidad de Somiedo es la más occidental de las unidades alóctonas de la Zona Cantábrica, y se conoce desde Ios años 50. Está formada por cuatro escamas principales, emplazadas durante la denominada primera generación de cabalgamientos, que tienen una geometría en escalera el cabalgamiento basal se encuentra por debajo de la Formación Láncara, excepto en el sector más occidental, donde profundiza hasta las rocas precámbricas, siendo el único lugar de la ZC donde se observa el enraizamiento de estas unidades. Esta rampa produce una culminación y es la causa del Antiforme. Se observa otra generación de cabalgamientos, que corta a los previos y afecta no sólo a la Unidad de Somiedo, sino también a su autóctono aflorante en la Ventana Tectónica del Narcea. Estos cabalgamientos no muestran trayectorias en escalera, sino geometrías lístncas, tienen desplazamientos pequeños, y modifican el patrón generado durante la primera fase de deformación y amplifican el Antiforme del Narcea./nLas relaciones entre todas las unidades son complejas; se ha realizado una correlación interpretativa entre las dos fases de deformación de la ZAOL y la primera fase de cabalgamientos de la ZC. La segunda fase de deformación sería la respondable de la disposición final de las estructuras de la ZC y la ZAOL

The Ediacaran-early Palaeozoic Cadomian zircon province fringing Northwest Gondwana

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The importance of along-margin terrane transport in northern Gondwana: insights from detrital zircon parentage in Neoproterozoic rocks from Iberia and Brittany

Detrital zircons from late Neoproterozoic rocks of the peri-Gondwanan Cadomian belt of SW Iberia and north Armorican Domain of Brittany record Neoproterozoic (ca. 860-550 Ma), Palaeoproterozoic (ca. 2300-1800) and Archaean (ca 3300-2600 Ma) U-Pb ages. The absence of Mesoproterozoic zircons suggests that these terranes evolved in a peri-W African realm. This is in contrast to other western European terranes that preserve Mesoproterozoic zircons and are likely to have evolved in a peri-Amazonian realm. Such a contrast in detrital zircon populations, coupled with the presence of Mesoproterozoic zircons in the Ordovician Armorican quartzite, deposited in a peri-African platform, is interpreted to record along-margin terrane transport. The change in provenance suggests that subduction was replaced by transform faults that juxtaposed Amazonia-derived terranes against W Africa-derived terranes to form the Avalonia and Armorica microcontinents. Subsequent extension along the margin resulted in the birth of the Rheic Ocean and the outboard drift of Avalonia

Post-collisional batholiths do contribute to continental growth

This work was supported through the Spanish Research Agency (AEI) Grant N◦ PGC2018-096534-B-I00 (Proyecto IBERCRUST). We acknowledge the support received from the Instituto Andaluz de Ciencias de la Tierra (CSIC - UGR) and its staff for the installa- tion of a high-pressure laboratory. We are particularly grateful to Taras Gerya and Mike Fowler for their positive and constructive feedback. We also want to thank Rosemary Hickey-Vargas for her handling of this manuscript.Supplementary material related to this article can be found on- line at https://doi.org/10.1016/j.epsl.2022.117978Post-collisional voluminous silicic magmatism is represented in most orogens across the world in the form of large granodiorite batholiths and minor intermediate and mafic intrusions, postdating 5-30 Ma the age of the collisional paroxysm responsible of the main mountain building events. Post-collisional mafic intrusions are acknowledged as a mechanism that contributes to long-term yet minor continental growth. The silicic magmas forming the large batholiths, however, have been dismissed from the crustal growth discussion due to bias in the conception that they always generate by recycling older lower crustal igneous rocks. Contrary to this, geochemical and isotopic relations together with new experimental data provided in this paper suggest that the post-collisional signature can be reproduced without the implication of a crustal component, supporting a potential common origin for the two suites, intermediate and silicic. That is, both suites can be derived from a metasomatized mantle source, thus representing the injection of largely juvenile material to produce new continental crust. This inference is contextualized within the supercontinent cycle, showing that the timing of post-collisional magmatism accounts for the generation and preservation rates predicted by the existing models, since both reach maximum values in the amalgamation-collisional stage of the supercontinent cycle, rather than in the subduction stage. All together these inferences lead to think that post-Archean, post-collisional magmatism has been significantly underestimated when computing continental crustal growth through time.Spanish Government PGC2018-096534-B-I0

Direct synthesis of β-ketophosphonates and vinyl phosphonates from alkenes or alkynes catalyzed by CuNPs/ZnO

Copper nanoparticles (CuNPs) supported on ZnO have been shown to effectively catalyze the direct synthesis of β-ketophosphonates from alkenes or alkynes, and that of vinyl phosphonates from alkynes and diethylphosphite, under air and in the absence of any additive or ligand. When using alkynes as starting materials, the selectivity proved to be dependent on the nature of the alkyne. Thus, alkynes conjugated with an aromatic ring or a carbon–carbon double bond gave β-ketophosphonates as the main reaction products, whereas aliphatic alkynes or alkynes conjugated with a carbonyl group led to the formation of the corresponding vinyl phosphonates.This work was generously supported by the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Agencia Nacional de Promoción Científica y Tecnológica (ANPCyT) and Universidad Nacional del Sur (UNS) from Argentina. V. G. thanks the CONICET for a postdoctoral fellowship

New ideas on the Proterozoic-Early Palaeozoic evolution of NW Iberia: insights from U–Pb detrital zircon ages

U–Pb ages were obtained on single detrital zircon grains separated from six samples of Neoproterozoic and Lower Palaeozoic sedimentary and volcanosedimentary rocks from NW Iberia using the laser ablation microprobe-inductively coupled plasma mass spectrometry (LAM-ICP-MS) method. Precambrian greywackes yielded abundant zircons with Neoproterozoic (800–640 Ma) and Mesoproterozoic (0.9–1.2 Ga) ages, and a smaller proportion of Palaeoproterozoic (1.8–2 Ga) and Archaean zircons. Palaeozoic samples (Lower Cambrian and Ordovician) yielded abundant zircons with younger Neoproterozoic (ca. 550 and 620 Ma) and Mesoproterozoic (0.9–1.2 Ga) ages. Palaeoproterozoic (1.8–2 Ga) and Archaean zircons were also found. This data set, used in conjuction with previous paleogeographic and isotopic studies sheds new light on the Precambrian-early Palaeozoic evolution of NW Iberia and is consistent with the following sequence of events: (1) Early Cadomian-Avalonian subduction and arc construction (ca. 800–640 Ma). This magmatic episode created the main arc edifice (Avalonia); (2) full development of a back arc basin upon which the Neoproterozoic sediments were deposited (ca. 640–640 Ma). The combined U–Pb ages of detrital zircons and Nd isotopic features of these sedimenary rocks suggest that they were mostly shed from the main magmatic arc. On the basis of the presence of Grenvillian age detrital zircons with short waterborne transport before incorporation in the sediment, we propose that the basin was possibly located in a peri-Amazonian realm close to West Avalonian terranes. These basins were developed upon a cratonic basement that possibly involved both Grenvillian (ca. 0.9–1.2 Ga) and Transamazonian (ca. 1.9–2.1) igneous rocks. The reported zircon ages suggest a long-lived subduction, starting at ca. 800 Ma and terminated by ca. 580–570 Ma with no geological record of a final collision event; (3) the continuation of extension gave rise to the undocking of Avalonia from the back-arc. Detrital zircon ages in Lowermost Cambrian strata suggest that the main arc edifice had drifted away by ca. 550–540 Ma and was no longer shedding detritus into the back-arc basin. (4) During the Lower Ordovician, further extension of an already thinned crust gave rise to the Lower Ordovician ‘Ollo de Sapo’ magmatic event (ca. 480 Ma). Coeval volcanism in neighbouring areas displaying within-plate geochemical signatures is consistent with an extensional setting for the generation of the Lower Ordovician igneous and sedimentary rocks. Detrital zircon ages and Nd isotopic features of the Ordovician greywackes reflect both an increase in the contribution from older crustal components and the addition of newly accreted crust. A progressively thinning crust is a likely scenario that would explain the simultaneous exhumation of lower crustal (Grenvillian+Transamazonian/Icartian) material and the generation of coeval magmatism. This latter scenario is consistent with models proposed for other circum-North Atlantic Avalonian-Cadomian terranes where repeated episodes of melting occurred in response to subduction and subsequent rifting events

Geocronología y geoquímica isotópica (Sr, Nd) de los granitoides de Pola de Allande (Asturias): ¿Relictos de un arco magmático cadomiense en la Zona Asturoccidental Leonesa?

[ES] Los granitoides pre-Variscos de Pola de Allande se sitúan en el Antiforme del Narcea, en el límite entre las zonas Cantábrica y Asturoccidental Leonesa de la cadena Varisca Ibérica. Estos granitoides, formados por tonalitas y granodioritas con afinidades geoquímicas de arco magmático, intruyeron en sedimentos siliciclásticos Neoproterozoicos y fueron posteriormente afectados por la deformación tangencial Varisca. La datación U-Pb de circones de dos intrusiones por el método de Ablación Láser ICP-MS proporcionó edades concordantes de intrusión de 605±5 y 580±15 Ma. En conocimiento de los autores, ésta es la primera edad U-Pb Cadomiense obtenida en esta zona de la cadena Varisca Ibérica. Estas intrusiones son contemporáneas con el principal episodio de magmatismo dominantemente calcoalcalino relacionado con la subducción Cadomiense. Los granitoides estudiados presentan características geoquímicas asimilables a las de otros granitoides de la misma edad en otras áreas del cinturón Cadomiense/Avaloniense. La composición isotópica (Sr y Nd) de los granitoides indica que éstos se originaron, bien por mezcla de fundidos mantélicos Cadomienses con un basamento enriquecido de edad en torno a 2 Ga (Icartiense), o bien por fusión parcial de un protolito máfico infracortical extraído del manto a 1,2 Ma (basamento Grenville).[EN] The Pola de Allande pre-Variscan tonalite-granodiorite plutons are located in the Narcea Antiform, at the boundary zone between the Cantabrian and West- Asturian Leonese zones of the Iberian Variscan belt. These granitoids were intruded into a Neoproterozoic siliciclastic sedimentary sequence with subordinate volcanic intercalations and were subsequently overprinted by Variscan thrust related shear deformation. U-Pb Laser Ablation ICP-MS dating of zircons from two plutons yielded concordant ages of intrusion of 605±10 and 580+15 Ma. To the authors' knowledge, this is the first reported U-Pb Cadomian-Avalonian age for igneous rocks in this section of the Iberian Variscan belt. These intrusions are coeval with the main episode of dominantly calc-alkaline magmatic activity related to Cadomian-Avalonian event. Major and trace element composition of the granitoids is characteristic of I-type high-K calc-alkaline granitoids, and are comparable to those of coeval granitoids in other areas of the Cadomian-Avalonian belt. Sr and Nd isotopic signatures indicate tha the genesis of the Pola de Allande granitoids involved either mixing of mantle melts of Cadomian extraction with an older enriched crust (Eburnean-Icarthian) or melting of a mafic infracrustal protolith with a Gren ville age (ca. 1,2 Ga) mantle extraction

LiDAR Datasets Applied to Roman Gold Mining Studies in NW Iberia. Response to Paper: Roman Gold Mining at “Las Miédolas” (NW Spain): Lidar and Photo Interpretation in the Analysis of “Peines”

.Early LiDAR datasets in Spain are available since 2014 (5-m resolution), when the first works were carried out by our team (Fernández-Lozano and Gutiérrez-Alonso Mapping 167:22–29, 2014; Fernández-Lozano et al. J Archaeol Sci 2014:356–373, 2015). The implementation of LiDAR to 1-m resolution was subsequently used and compared by Fernández-Lozano and Gutiérrez-Alonso (J Archaeol Sci 5:509–520, 2016) in combination with UAV-derived (Unmanned Aerial Vehicles) photogrammetry. These works showed different Roman gold mining scenarios that were modeled providing outstanding results even with the poorest resolution LiDAR datasets. Moreover, the implementation of visual enhancement tools, widely used in different fields of archeology, geomorphology, and geology, such as Sky-View, Multi-hillside, Slope, LRM, Openness, and Principal Components have improved notably the interpretation of results in both mining and archeological works. This paper discusses the potential and insights provided by our methodological approach and shows that the results of its application to the study area of Las Miédolas can provide better results than those obtained by Matías and Llamas (Geoheritage 13(2):1–22, 2021).SIPublicación en abierto financiada por el Consorcio de Bibliotecas Universitarias de Castilla y León (BUCLE), con cargo al Programa Operativo 2014ES16RFOP009 FEDER 2014-2020 DE CASTILLA Y LEÓN, Actuación:20007-CL - Apoyo Consorcio BUCL