U-Pb dating of Ordovician felsic volcanism in the Schistose Domain of the Galicia-Trás-os-Montes Zone near Cabo Ortegal (NW Spain)

The northern termination of the Schistose Domain of the Galicia-Trás-os-Montes Zone is a tectonic slice named the Rio Baio Thrust Sheet, which is sandwiched between the Cabo Ortegal Complex and the Ollo de Sapo Domain of the Central-Iberian Zone. The Rio Baio Thrust Sheet is formed by two volcanosedimentary series, the Loiba and the Queiroga Series. The Loiba Series contains calc-alkaline dacite and rhyolite, while the overlying Queiroga Series has alkaline rhyolite. These series were considered to be in stratigraphically upwards continuity and believed to be Silurian in age. U-Pb dating of an alkaline rhyolite in the Queiroga Series provides an Arenig age of 475 ± 2 Ma. This age makes the Queiroga Series the oldest known stratigraphic unit in the Schistose Domain of the Galicia-Trás-os-Montes Zone, impeding correlation between the lithostratigraphic sequences of Ortegal and Central Galicia. As well as providing evidence of an unforeseen structural complexity within the Rio Baio Sheet, the new data supports the notion that the Schistose Domain is not parautochtonous, but a separate lithotectonic unit in thrust contact with the underlying Central-Iberian Zone

U–Pb Age of the Stanley Brook Granite, Grand Manan Island, New Brunswick

The Stanley Brook Granite on Grand Manan Island has yielded an Early Cambrian U-Pb zircon age of 535 ± 2 Ma. The granite was emplaced into sedimentary rocks of the Flagg Cove Formation of the Castalia Group, proving that the latter is no younger than Early Cambrian. Previous dating of detrital zircons from the Flagg Cove Formation limits its maximum depositional age to be no older than 574 ± 7 Ma. The intrusive age of the Stanley Brook Granite is essentially identical to the 539 ± 3 Ma age obtained previously from dacitic tuff of the Priest Cove Formation, suggesting a comagmatic relationship between the two. The contact between the Flagg Cove and Priest Cove formations is invariably faulted. However, the consanguineous relationship between the Priest Cove Formation and Stanley Brook Granite suggests that the Priest Cove Formation was deposited on the Flagg Cove Formation. This proposed stratigraphic relationship supports the interpretation that the tuffaceous and volcaniclastic sedimentary rocks of the Priest Cove Formation represent a distal facies of the mafic flows and fragmental volcanic rocks of the Ross Island Formation. The age of the Stanley Brook Granite is consistent with the interpretation that Mesoproterozoic (?) to Neoproterozoic platformal carbonate rocks of the Brookville terrane represent basement to Neoproterozoic volcanic rocks of the New River terrane. RÉSUMÉ L’âge U-Pb sur zircon du granite du ruisseau Stanley, sur l’île Grand Manan, se situerait à environ 535 ± 2 Ma et remonterait au début du Cambrien. Ce granite a été mis en place dans les roches sédimentaires de la Formation de Flagg Cove du groupe de Castalia, ce qui établirait que cette dernière formation date tout au plus du début du Cam-brien. Les travaux de datation précédents des zircons détritiques de la Formation de Flagg Cove ont fixé l’âge maximal de la sédimentation à 574 ± 7 Ma, tout au plus. Pour l’essentiel, l’âge de l’intrusion du granite du ruisseau Stanley correspond à l’âge de 539 ± 3 Ma déjà déterminé pour le tuf dacitique de la Formation de Priest Cove, ce qui donnerait à penser qu’il y a une relation comagmatique entre les deux. La zone de contact entre les formations de Flagg Cove et de Priest Cove est pratiquement toujours faillée. Toutefois, l’origine commune de la Formation de Priest Cove et du granite du ruisseau Stanley porte à croire que la sédimentation de la Formation de Priest Cove s’est superposée à la Formation de Flagg Cove. Ce lien au plan stratigraphique viendrait corroborer l’interprétation voulant que les roches sédimentaires tufacées et volcanoclastiques de la Formation de Priest Cove sont de fait un faciès éloigné des coulées mafiques et des roches volcanoclastiques de la Formation de Ross Island. L’âge établi pour le granite du ruisseau Stanley va dans le sens de l’interprétation voulant que les roches carbonatées dans la succession de plateformes du Mésoprotérozoïque (?) au Néoprotérozoïque du terrane de Brookville forment le socle des roches volcaniques du Néoprotérozoïque du terrane de New River. [Traduit par la redaction

Zircon U-Pb and Hf isotopic constraints on the genesis of a post-kinematic S-type Variscan tin granite: the Logrosán cupola (Central Iberian Zone)

The Variscan orogeny produced widespread granites along the European Variscan belt. In relation to crustal thickening, post-collisional multiple tin-bearing highly fractionated S-type leucogranites were emplaced. The Logrosán granite represents one of those granitic bodies and is a focus of this study. The Logrosán granite is located in the Central Extremadura Batholith (CEB), within the Central Iberian Zone (CIZ) and was emplaced during post kinematic stages of the Variscan orogeny at ca. 308 Ma, as determined by combined ID-TIMS U–Pb and LA-ICPMS geochronology. The granitic body intruded the metasedimentary Schist Greywacke Complex (SGC) of Neoproterozoic age. A moderately evolved medium- to coarse-grained two mica leucogranite (Main unit) and some highly evolved aplitic or microporphyritic units (evolved units) are distinguishable on the basis of their petrography and whole rock geochemistry.  Initial 87Sr/86Sr ratios vary from 0.7134 to 0.7311, whereas initial εNd shows a restricted range from -4.3 to -4.0 and εHf(t) ranges from  +2.0 to -4.6 for Variscan-age zircons. Inherited zircons exhibit mostly Neoproterozoic ages and juvenile Hf-isotope composition (eHf up to +14.6), analogous to that of zircons from the SGC metasediments. The available geological, geochronological, geochemical and isotopic data allow to propose the partial melting of heterogeneous Neoproterozoic metasedimentary material, similar to the outcropping SGC, for the genesis of the Logrosán granite.La orogenia Varisca produjo una gran cantidad de granitos a lo largo del Cinturón Varisco Europeo. En relación con el engrosamiento cortical se emplazaron tardíamente granitos de tipo-S, muy fraccionados y ricos en Sn. El presente estudio se centra en uno de esos cuerpos graníticos, el granito de Logrosán. El plutón de Logrosán forma parte del Batolito de Extremadura Central (BEC), en la Zona Centroibérica (ZCI), y se emplazó durante las etapas tardías de la orogenia Varisca, a los ca. 308 Ma, según los datos combinados de geocronología de U-Pb por ID-TIMS y por LA-ICPMS. El cuerpo granítico intruyó los metasedimentos del Complejo Esquisto Grauváquico (CEG) de edad fundamentalmente Neoproterozoica. En el plutón se distinguen, de acuerdo a la petrografía y a la geoquímica de roca total, un leucogranito de dos micas de tamaño de grano medio-grueso moderadamente evolucionado (Main Unit) y varias unidades aplíticas o microporfídicas altamente evolucionadas (Evolved Units). Las relaciones isotópicas iniciales de 87Sr/86Sr varían de 0.7125 a 0.7286, mientras que el εNd inicial muestra un rango restringido de -4.3 a -4.0 y el εHf(t) en circones variscos oscila de +5.7 a -10.5. Los circones heredados del granito de Logrosán muestran edades principalmente Neoproterozoicas y composiciones isotópicas de Hf juveniles (εHf > +14.7), análogas a las encontradas en los circones del CEG. Los datos geológicos, geoquímicos, geocronológicos e isotópicos de los que se dispone sugieren que el granito de Logrosán se originó por la fusión parcial de materiales metasedimentarios Neoproterozoicos similares a los del CEG

Reconstructing the Crustal Section of the Intra-Oceanic Caribbean Island Arc: Constraints From the Cumulate Layered Gabbronorites and Pyroxenites of the Rio Boba Plutonic Sequence, Northern Dominican Republic

Located in northern Dominican Republic, the Early Cretaceous Rio Boba mafic-ultramafic plutonic sequence constitutes a lower crust section of the Caribbean island arc, made up by gabbroic rocks and subordinate pyroxenite. Modal compositions, mineral chemistry, whole-rock compositions and thermobarometric calculations indicate that pyroxenites and gabbronorites represent a cumulate sequence formed by fractionation of tholeiitic magmas with initially very low H2O content in the lower crust of the arc (0.6–0.8 GPa). Melts evolved along a simplified crystallization sequence of olivine → pyroxenes → plagioclase → Fe-Ti oxides. The magmatic evolution of the Rio Boba sequence and associated supra-crustal Puerca Gorda metavolcanic rocks is multi-stage and involves the generation of magmas from melting of different sources in a supra-subduction zone setting. The first stage included the formation of a highly depleted substrate as result of decompressional melting of a refractory mantle source, represented by a cumulate sequence of LREE-depleted island arc tholeiitic (IAT) and boninitic gabbronorites and pyroxenites. The second stage involved volumetrically subordinate cumulate troctolites and gabbros, which are not penetratively deformed. The mantle source was refractory and enriched by a LILE-rich hydrous fluid derived from a subducting slab and/or overlying sediments, and possibly by a LREE-rich melt. The third stage is recorded in the upper crust of the arc by the Puerca Gorda “normal” IAT protoliths, which are derived from an N-MORB mantle source enriched with a strong subduction component. This magmatic evolution has implications for unraveling the processes responsible for subduction initiation and subsequent building of the Caribbean island arc.This research was funded through CGL2012-33669/BTE and PID2019-105625RB-C22 of the MCIN/AEI/10.13039/501100011033 projects and PRX18/00055 stay grant to the J. Escuder-Viruete of the Ministerio de Ciencia e Innovación of the Spanish Government

Insights on high-grade deformation in quartzo-feldspathic gneisses during the early Variscan exhumation of the Cabo Ortegal nappe, NW Iberia

High-grade, highly deformed gneisses crop out continuously along the Masanteo peninsula and constitute the upper part of the lower crustal section in the Cabo Ortegal nappe (NW Spain). The rock sequence formed by migmatitic quartzo-feldspathic (qz-fsp) gneisses and mafic rocks records the early Ordovician (ca. 480–488 Ma) injection of felsic dioritic/granodioritic dykes at the base of the qz-fsp gneisses, and Devonian eclogitization (ca. 390.4 ± 1.2 Ma), prior to its exhumation. A SE-vergent ductile thrust constitutes the base of quartzo-feldspathic gneissic unit, incorporating mafic eclogite blocks within migmatitic gneisses. A NW-vergent detachment displaced metasedimentary qz-fsp gneisses over the migmatites. A difference in metamorphic pressure of ca. 0.5 GPa is estimated between both gneissic units. The tectono-metamorphic relationships of the basal ductile thrust and the normal detachment bounding the top of the migmatites indicate that both discrete mechanical contacts were active before the recumbent folding affecting the sequence of gneisses during their final emplacement. The progressive tectonic exhumation from eclogite to greenschist facies conditions occurred over ca. 10 Ma and involved bulk thinning of the high-grade rock sequence in the high pressure and high temperature (HP–HT) Cabo Ortegal nappe. The necessary strain was accommodated by the development of a widespread main foliation, dominated by flattening, that subsequently localized to a network of anastomosing shear bands that evolved to planar shear zones. Qz-fsp gneisses and neighbouring mafic granulites were exhumed at > 3 mm yr−1 , and the exhumation path involved a cooling of ∼ 20 ◦C/100 MPa, These figures are comparable to currently active subduction zones, although exhumation P–T trajectory and ascent rates are at the hotter and slower end in comparison with currently active similar settings, suggesting an extremely ductile deformation environment during the exhumation of qz-fsp gneisses within a coherent Cabo Ortegal nappe

Insights on high-grade deformation in quartzo-feldspathic gneisses during the early Variscan exhumation of the Cabo Ortegal nappe, NW Iberia

High-grade, highly deformed gneisses crop out continuously along the Masanteo peninsula and constitute the upper part of the lower crustal section in the Cabo Ortegal nappe (NW Spain). The rock sequence formed by migmatitic quartzo-feldspathic (qz-fsp) gneisses and mafic rocks records the early Ordovician (ca. 480–488 Ma) injection of felsic dioritic/granodioritic dykes at the base of the qz-fsp gneisses, and Devonian eclogitization (ca. 390.4 ± 1.2 Ma), prior to its exhumation. A SE-vergent ductile thrust constitutes the base of quartzo-feldspathic gneissic unit, incorporating mafic eclogite blocks within migmatitic gneisses. A NW-vergent detachment displaced metasedimentary qz-fsp gneisses over the migmatites. A difference in metamorphic pressure of ca. 0.5 GPa is estimated between both gneissic units. The tectono-metamorphic relationships of the basal ductile thrust and the normal detachment bounding the top of the migmatites indicate that both discrete mechanical contacts were active before the recumbent folding affecting the sequence of gneisses during their final emplacement. The progressive tectonic exhumation from eclogite to greenschist facies conditions occurred over ca. 10 Ma and involved bulk thinning of the high-grade rock sequence in the high pressure and high temperature (HP–HT) Cabo Ortegal nappe. The necessary strain was accommodated by the development of a widespread main foliation, dominated by flattening, that subsequently localized to a network of anastomosing shear bands that evolved to planar shear zones. Qz-fsp gneisses and neighbouring mafic granulites were exhumed at > 3 mm yr−1 , and the exhumation path involved a cooling of ∼ 20 ◦C/100 MPa, These figures are comparable to currently active subduction zones, although exhumation P–T trajectory and ascent rates are at the hotter and slower end in comparison with currently active similar settings, suggesting an extremely ductile deformation environment during the exhumation of qz-fsp gneisses within a coherent Cabo Ortegal nappe

The interaction of fluorinated glycomimetics with DC-SIGN: multiple binding modes disentangled by the combination of NMR methods and MD simulations

Fluorinated glycomimetics are frequently employed to study and eventually modulate protein–glycan interactions. However, complex glycans and their glycomimetics may display multiple binding epitopes that enormously complicate the access to a complete picture of the protein–ligand complexes. We herein present a new methodology based on the synergic combination of experimental 19F-based saturation transfer difference (STD) NMR data with computational protocols, applied to analyze the interaction between DC-SIGN, a key lectin involved in inflammation and infection events with the trifluorinated glycomimetic of the trimannoside core, ubiquitous in human glycoproteins. A novel 2D-STD-TOCSYreF NMR experiment was employed to obtain the experimental STD NMR intensities, while the Complete Relaxation Matrix Analysis (CORCEMA-ST) was used to predict that expected for an ensemble of geometries extracted from extensive MD simulations. Then, an in-house built computer program was devised to find the ensemble of structures that provide the best fit between the theoretical and the observed STD data. Remarkably, the experimental STD profiles obtained for the ligand/DC-SIGN complex could not be satisfactorily explained by a single binding mode, but rather with a combination of different modes coexisting in solution. Therefore, the method provides a precise view of those ligand–receptor complexes present in solution.We thank Agencia Estatal de Investigación (Spain) for grants RTI2018-094751-B-C21 and B-C22, CTQ2015-68756-R, and for FPI and FPU fellowships to J.D.M. and P.V., respectively, and for the Severo Ochoa Excellence Accreditation (SEV-2016-0644). J.J.-B. also thanks to the European Research Council (RECGLYCANMR, Advanced Grant no. 788143). S.O. thanks the SFI Award 13/IA/1959Peer reviewe

Minimizing the entropy penalty for ligand binding: lessons from the molecular recognition of the histo blood-group antigens by human galectin-3

6 p.-5 fig.-2 tab.Ligand conformational entropy plays an important role in carbohydrate recognition events. Glycans are characterized by intrinsic flexibility around the glycosidic linkages, thus in most cases, loss of conformational entropy of the sugar upon complex formation strongly affects the entropy of the binding process. By employing a multidisciplinary approach combining structural, conformational, binding energy, and kinetic information, we investigated the role of conformational entropy in the recognition of the histo blood‐group antigens A and B by human galectin‐3, a lectin of biomedical interest. We show that these rigid natural antigens are pre‐organized ligands for hGal‐3, and that restriction of the conformational flexibility by the branched fucose (Fuc) residue modulates the thermodynamics and kinetics of the binding process. These results highlight the importance of glycan flexibility and provide inspiration for the design of high‐affinity ligands as antagonists for lectins.We thank Agencia Estatal de Investigacion and ISCIII of Spain and the European Research Council for financial support.Peer reviewe

Mapa Geológico de España E 1:200000, hoja 69, Pozoblanco

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