A non-cylindrical model of development of the Hercynian belt allochthonous terranes

[Resumen] Se propone un modelo no cilíndrico para el desarrollo del Cinturón Hercínico Europeo. Los terrenos alóctonos fuertemente trasladados que forman parte de él se componen de una mezcla de unidades catazonales y ofiolíticas, así como de fragmentos del margen continental de Gondwana. La disposición de estos terrenos y sus relaciones con la paleogeografía de Gondwana, así como las estructuras que muestran, sugieren que se emplazaron de manera oblícua, en una dirección que formaba un pequeño ángulo con el margen de este continente. El alóctono podría estar ligado al desarrollo de un arco de islas o de una subplaca con forma de cuña en la parte meridional de la placa Báltica. Con posterioridad a su emplazamiento, la convergencia entre Gondwana y Laurasia, que habría incluido movimientos transcurrentes esencialmente dextros, sería responsable de la complejidad actual del orógeno.[Abstract] A case is made for a non-cylindrical development of the European Hercynian belt. Far-travelled allochthonous terranes in it consits of a mixture of units including catazonal ones, ophiolites and units derived from the continental margin of Gondwana. Considerations upon the disposition of the terranes, their relationships with the paleogeography of the Gondwana realm and the structures in them, suggest that their emplacement took place in an oblique fashion at a small angle to the margin of this continent. The proposed allochthon could be related to the development of an island arc or a wedge-like subplate in the southern part of the Baltica plate. Later, convergence between Gondwana and Laurussia, involving transcurrent, mostly dextral movements, would account for the present complexity of the belt

Tectonothermal evolution associated with crustal escale extension: an hercynian example from the Tormes gneiss dome (NW Salamanca, Iberian Massif)

[Abstract] The tectonothermal Variscan evolution ofthe Tormes Gneiss Dome is controlled by a subhorizontal ductile shear zone of crustal scale and extensional characteristics, that induced a quick exhumation ofthe deep parts ofthe metamorphic complex during crustal thinning. The shearing affected a broad band of metamorphic rocks but, as the temperature decreased, became progressively concentrated in a low-grade ductile detachment that separates two distinct units, characterized by their lithology and different tectonothermal evolution. Kinematic indicators in non-coaxial fabrics show a displacement of the hangingwall to the SE, i. e., parallel to the trend of the foldbelt. The subhorizontal shearing is related to the extensional collapse ofthe variscan crust, previously thickened during the collision tectonics

El complejo de Órdenes: subdivisión, descripción y discusión sobre su origen.

[Resumen] El Complejo de Ordenes, el mayor de los macizos alóctonos con rocas máficas y ultramAficas de Galicia y el N de Portugal, se ha subdividido en cinco unidades en base, fundamentalmente, a las asociaciones litológicas: U. de Santiago, U. de Villa de Cruces, U. De la Sierra del Careón-Bazar, U. de SobradoMellid y U. de Betanzos-Arzúa. Todas ellas están separadas entre si por cabalgamientos y superpuestas tectónicamente. Para cada unidad, se realiza una descripción petrológica y se analizan las relaciones de las diferentes rocas entre si. ,Se efectúa, además, una revisión de los datos geoquimicos disponibles y, finalmente, se discute el origen probable de las distintas unidades[Abstract] The Ordenes Complex, the biggest OI the allochthonous massifs with mafic and ultramafic rocks in Galicia and northern Portugal, has been divided into five units according to the lithological associations: Santiago Unit, Villa de Cruces Unít, Sierra del Care6n-Bazar Unit, Sobrado-Mellid Unít and BetanzoS-Arzúa Unít. They are separated from each other by thrust faults and tectonically stacked. For each OI the units, a petrological description is given, explaining the relationships between the different rock types. Moreover, the geochemical data available are reviewed and the probable origin of the units is discusse

A Revision of the characteristics and clasification of the hercynian granitoids of Northern Galicia and Western Asturias (NW Spain)

[Resumen] Este trabajo resume parte de los resultados obtenidos en el desarrollo del proyecto «Caracterización y correlación petrológica, geoquímica y geocronológica de las rocas graníticas de Galicia (A Coruña-Lugo)>>, realizado por el 1. ~G. M. E. El estudio sistemático de los distintos plutones graníticos de esta región ha puesto de manifiesto que los criterios de clasificación tradicionalmente utilizados en este ámbito geológico, presentan una serie de limitaciones debidas por una parte a la rigidez de los grupos establecidos y por otra, a las características transicionales de algunas unidades plutónicas. Estos hechos permiten suponer que las relaciones entre los «granitoides alcalinos y alumínicos de dos micas» y los «granitoides de tendencia calcoalcalina» no son tan independientes como se ha venido considerando en los modelos preexistentes. En función de la profundidad y etapa de emplazamiento y de las características petrológicas, las distintas unidades se han agrupado en las siguientes familias: - Granitoides sincinemáticos de emplazamiento relativamente profundo. - Granitoides sincinemáticos de emplazamiento somero. - Granitoides postcinemáticos de emplazamiento somero. Asimismo se detectan unidades plutónicas complejas, constituidas por varios granitos, a los cuales les corresponderían génesis diferentes, si se siguiesen los criterios previamente vigentes.[Abstract] This article summarizes part of the results of the project «Petrological, geochemical and geochronological caracterization and correlation of the granitic rocks of Galicia (provinces of A Coruña-Lugo)>>, executed on behalf of the Spanish Institute of Geology and Mining (1. G. M. E.). The Systematic investigation of the different granite plutons of the area evidences that the application of the criteria traditionally used for the classification of the granitic rocks in Galicia meets with serious difficulties. These are due to the rigidity of the established groups on the one hand and the transitional character of a number of plutonic units on the other hand. The study suggests that the relationship among the {<a1caline and aluminous two-mica granites» and the granitoids of the «ca1c-a1caline tendency is less independent than assumed in the hitherto used classification schemes and petrogenetical models. As a function of the depth and time of their emplacement and their petrological features, the different plutonic units are grouped into the following families: - Synkinematic, relatively deep-seated granitoid bodies. - Synkinematic, shallow-level granitoid bodies. - Postkinematic, shallow-level granitoid bodies. Attention is drawn to the occurrence of complex plutonic units whose constituent members would, according to the criteria of the pre-existing classification schemes, be petrogenetically unrelated or poorly related

Tectonic evolution of the Eastern Moroccan Meseta: from Late Devonian fore‐arc sedimentation to Early Carboniferous collision of an Avalonian promontory

This study was founded by the Ministerio de Economia y Competitividad (MINECO) of Spain through the project PANGEATOR (CGL2015-71692-P) and the Doctoral scholarship BES-2016-078168. GeoHistory Facility instruments were funded via an Australian Geophysical Observing System grant provided to AuScope Pty Ltd. by the AQ44 Australian Education Investment Fund program. The NPII multicollector was obtained via funding from the Australian Research Council LIEF program (LE150100013). The authors want to express their gratitude to Dr. Manuel Francisco Pereira (University of Evora, Portugal) and Dr. Michel Villeneuve (Centre Europeen de Recherche et d'Enseignement des Geosciences de l'Environnement, France) for their constructive reviews that helped to improve the quality of the original manuscript. Special thanks to Brad McDonald (Curtin University, Australia) for technical assistance regarding LA-ICPMS and Hf analyses, Profs. Abdelfatah Tahiri (University Mohammed V of Rabat, Morocco) and Hassan El Hadi (University Hassan II of Casablanca, Morocco) for their support during field work, Prof. Yvette Kuiper (Colorado School of Mines, USA) for her precious hints about the interpretation of Hf data, and Dr. Lorenzo Valetti for proofreading the manuscript. Supporting information can be obtained in Mendeley Data: https://doi.org/10.17632/b8fdbykmbx.1 (https://data.mendeley.com/datasets/b8fdbykmbx/draft?a=eaae2da0-8e224056-861b-4824984f1c10).The deformed Paleozoic succession of the Eastern Moroccan Meseta crops out in relativelysmall and isolated inliers surrounded by Mesozoic and Cenozoic rocks. Two of the largest inliers(Mekkam and Debdou) are characterized by a monotonous succession of slates and greywackes affected bypolyphasic folding that occurred at low‐to very low grade metamorphic conditions. New U‐Pb ages ondetrital zircon grains from the Debdou‐Mekkam metasediments constrain the maximal depositional age asLate Devonian, interpreted to be close to the true sedimentation age. Furthermore, theεHfvalues of theDevonian detrital zircons, together with the presence of a series of scattered zircon grains with ages betweenc. 0.9 and c. 1.9 Ga, suggest provenance from a subduction‐related magmatic arc located on the Avalonianmargin. The Debdou‐Mekkam massif is characterized by an Early Carboniferousfirst deformationalevent (D1), which gave way to a pervasive cleavage (S1) associated with plurikilometric‐scale, tight toisoclinal, overturned to recumbent folds. Later events (Dc) occurred at Late Carboniferous time andgenerated variably developed crenulation cleavages (Sc) associated with variously oriented metric‐tokilometric‐scale folds, which complicate the pattern of both D1 intersection lineations (L1) and axial traces.The restoration of this pronounced curved pattern yields originally SW‐NE‐oriented D1 fold axes withregional SE‐vergence. This important Early Carboniferous shortening and SE‐directed tectonic transport canbe explained by closure of the Rheic Ocean and thefirst phases of the collision between the northern passivemargin of Gondwana and an Avalonian promontory.Ministerio de Economia y Competitividad (MINECO) of Spain CGL2015-71692-P BES-2016-078168Australian Geophysical Observing SystemAustralian Education Investment Fund program AQ44Australian Research Council LE15010001

Basement structure of the Hontomín CO2 Geological storage facility (Burgos, Spain): integration of microgravity & 3D seismic reflection data

The structure of the Hontomín CO2 geological storage research facility has been addressed combining 3D seismic reflection data, borehole information and microgravity data. The integrated interpretation constrains the basement structural setting geometry and that of the sedimentary succession. The study unravels the deep structure and topography of the basement and quantifies the thickness of the Triassic Keuper evaporites. We describe a half-graben setting filled with Keuper evaporites (up to 2000 m) forming an extensional forced fold. Three set of faults are identified with two main fault systems compartmentalizing the area into three differentiated blocks. These faults have been interpreted to be reactivated normal faults that have led to the formation of the Hontomín dome.The datasets in this work have been funded by Fundación Ciudad de la Energía (Spanish Government, www.ciuden.es) and by the European Union through the “European Energy Programme for Recovery” and the Compostilla OXYCFB300 project. Dr. Juan Alcalde is currently funded by NERC grant NE/M007251/1.Peer Reviewe

Basement structure of the Hontomín CO2 Geological storage facility (Burgos, Spain): integration of microgravity & 3D seismic reflection data

The structure of the Hontomín CO2 geological storage research facility has been addressed combining 3D seismic reflection data, borehole information and microgravity data. The integrated interpretation constrains the basement structural setting geometry and that of the sedimentary succession. The study unravels the deep structure and topography of the basement and quantifies the thickness of the Triassic Keuper evaporites. We describe a half-grabensetting filled with Keuper evaporites (up to 2000 m) forming an extensional forced fold. Three set of faults are identified with two main fault systems compartmentalizing the area into three differentiated blocks. These faults have been interpreted to be reactivated normal faults that have led to the formation of the Hontomín dome.The datasets in this work have been funded by Fundación Ciudad de la Energía (Spanish Government, www.ciuden.es) and by the European Union throughthe “European Energy Programme for Recovery” and the Compostilla OXYCFB300 project. Dr. Juan Alcalde is currently funded by NERC grant NE/M007251/1.Peer Reviewe

MAPPING THE SPAIN´S EXCLUSIVE ECONOMIC ZONE IN THE GALICIAN MARGIN

MAPPING THE SPAIN´S EXCLUSIVE ECONOMIC ZONE IN THE GALICIAN MARGIN Gómez Ballesteros, M.1(*), González-Aller, J-D. 2, Martín Dávila, J. 3, Carbó, A., 4, Somoza, L. 5, Druet, M. 1, Martínez-Espinosa, S. 2, Catalán, M. 3, Muñoz, A. 4, León, R 5 1 Instituto Español de Oceanografía / C/. Corazón de María, 8, 28020 Madrid 2 Instituto Hidrográfico de la Marina / Pl. San Severiano, 3, 11007 Cádiz 3 Real Observatorio de la Armada, C/. Cecilio Pujazón s/n 11100Cádiz 4 Universidad Complutense de Madrid / Av Séneca, 2, 28040 Madrid 5 Instituto Geológico y Minero de España, Calle de Ríos Rosas, 23, 28003 Madrid (*)Corresponding Author: [email protected] In the context of the Hydrographic and Oceanographic Research of the Spain´s Exclusive Economic program (ZEEE), operated jointly by Instituto Hidrográfico de la Marina (IHM) and Real Observatorio de la Armada (ROA) working in close collaboration with the Instituto Español de Oceanografía (IEO), Universidad Complutense de Madrid (UCM) and Instituto Geológico y Minero de España (IGME) have conducted seven oceanographic cruises in Galician waters (EEZ -01 -02 ZEE , ZEE -03, ZEE -06 -07 ZEE , ZEE- ZEE- 08 and 09). The main objective of the Spain´s Exclusive Economic Zone project is mapping the seafloor, carrying out a systematic bathymetric survey of the 200 miles that comprise this area. In addition, as secondary objectives were performed acquiring that complement other geophysical parameters characterizing the seafloor and seabed from the knowledge of other variables such as the Terrestrial Magnetic Field , Terrestrial Gravity field, sound velocity and seabed internal structure. For the acquisition of detailed and accurate information during these cruises, carried on board the BIO Hespérides, high-resolution geophysical techniques were used to compile the data and the bathymetry of the region was mapped using a multibeam system during which 100 per cent coverage was obtained. At the same time high-resolution parametric seismic reflection profiles, as well as gravity and magnetic, were also recorded in the survey areas. These systems provide data on bathymetry, quality seafloor, acoustics backscatter , gravimetry, magnetometry and subsurface structure and require the use of precise positioning techniques, so were used in conjunction with GPSD and inertial navigation systems. As a result of these oceanographic researches and post-processing, analysis and interpretation of the whole acquired data, a synthesis of 6 maps were published with 1:500.000 scale and corresponding to Bathymetric map, Geomorphology map, Geomagnetic Anomaly map, Bouguer and Free Air Anomaly maps and backscatter map. REFERENCIAS J. Martín Davila, M. Catalán, M. Larrán, Sección de Hidrografía del IHM, A. Carbó, A. Muñoz-Martín, JL Granja, P. Llanes, L. Somoza, R. León, F.J. Gonzalez, M. Gómez-Ballesteros, M. Druet, and J. Acosta, 2014: Zona Económica Exclusiva Española (ZEEE): Margen Continental Gallego. Mapas Generales de batimetría, de anomalías Geomagnéticas, Graviméwtricas de Aire Libre y Bpouguer, Geomorfológico y Mosaico de Imágenes de Reflectividad (E. 1:500.000). Ministerio de Defensa. Secretaria General Técnica, NIPO: 083-12-230-3, DL: M-39518-201

Seismic structure of the northern continental margin of Spain from ESCIN deep seismic profiles

By the end of the Carboniferous, the crust of the continental shelf in northwestern Spain was made up of deeply rooted structures related to the Variscan collision. From Permian to Triassic times the tectonic setting had changed to mainly extensional and the northern Iberian continental margin underwent rifting during Late Jurassic-Early Cretaceous times, along with sea-floor spreading and the opening of the Bay of Biscay until the Late Cretaceous. Subsequently, the northern Iberian margin was active during the north-south convergence of Eurasia and Iberia in the Tertiary. A multichannel seismic experiment, consisting of two profiles, one north-south (ESCIN-4) crossing the platform margin offshore Asturias, and another (ESCIN-3) crossing the platform margin to the northwest of Galicia, was designed to study the structure of the northern Iberian margin. The ESCIN-4 stacked section reveals inverted structures in the upper crust within the Le Danois Basin. North of the steep continental slope, ESCIN-4 shows a thick sedimentary package from 6 to 9.5 s, two-way travel time (TWT). Within this latter package, a 40-km-long, north-tapering wedge of inclined, mainly south-dipping reflections is thought to represent a buried, Alpine-age accretionary prism. In the north western part of the ESCIN-3 (ESCIN-3-1) stacked section, horizontal reflections from 6.5 to 8.5 s correspond to an undisturbed package of sediments lying above oceanic-type basement. In this part of the line, a few kilometres long, strong horizontal reflection at 11.2 s within the basement may represent an oceanic Moho reflection. Also, a band of reflections dips gently towards the southeast, from the base of the gently dipping continental slope. The part of ESCIN-3 line that runs parallel to the NW-Galicia coast (ESCIN-3-2), is characterized by bright, continuous lower crustal reflections from 8 to 10 s. Beneath the lower crustal reflectivity, a band of strong reflections dips gently toward the southwest from 10 to 13.5 s. The part of ESCIN-3 that parallels the northern margin (ESCIN 3-3), shows good reflectivity in all levels. Upper crustal reflections image the sedimentary fill of probable Mesozoic to recent basins. Mid-crustal reflectivity is characterized by dipping reflections until 8 s that are probably related to compressional Variscan features. The lower crustal level shows 'layered' reflections between 8 and 12 s. Dipping reflections are found below the continental Moho.J. Alvarez-Marrón held a post-doc research grant from the Ministry of Education and Science of Spain. The ESCI-N program was sponsored by the Spanish agencies CICYT (project GEO 90-0660) and FICYT, and STRIDE Program of the EU.Peer Reviewe