Juan Alcalde has been supported by the Natural Environment Research Council (grant no. NE/M007251/1) and the H2020 European Institute of Innovation and Technology (SIT4ME (grant no. 17024)). Clare E. Bond is currently funded through a Royal Society of Edinburgh research sabbatical on uncertainty in seismic image interpretation. Gareth Johnson is funded by the University of Strathclyde Faculty of Engineering. Oriol Ferrer has been supported by the SALCONBELT Project (grant no. CGL2017-85532-P), the Geomodels Research Institute and the Grup de Geodinàmica i Anàlisi de Conques (grant no. 2017SGR-596). Puy Ayarza is funded by the Regional Government of Castile and León (project SA065P17). The seismic image used in the experiment is available on the Virtual Seismic Atlas (https://www.seismicatlas.org, last access: 30 September 2019). The questionnaire presented to the participants is available in the Supplement. Interpretations and statistical analyses are available upon request. ; Peer reviewed ; Publisher PDF
Acknowledgments The authors sincerely thank the Guest Editor Irina Artemieva and the two anonymous reviewers for their useful comments. Funding for this Project has been partially provided by the Spanish Ministry of Industry, Tourism and Trade, through the CIUDEN-CSIC-Inst. Jaume Almera agreement (ALM-09-027: Characterization, Development and Validation of Seismic Techniques applied to CO2 Geological Storage Sites) and by the European Union through the Technology Demonstration Plant of Compostilla OXYCFB300 Project (European Energy Programme for Recovery). Additional support has been provided by Spanish Ministry of Education Science (CSD2006-00041), Generalitat de Catalunya (2009SGR006) and CSIC JAE-Doc postdoctoral research contract (E.S.). The sole responsibility of this publication lies with the authors. The European Union is not responsible for any use that may be made of the information contained herein. Juan Alcalde is being currently supported by the Fundación Ciudad de la Energía (CIUDEN) Research training program. The authors would like to sincerely thank Javier Elío for his kind help with the capacity estimation calculations, Institut Geològic de Catalunya for their useful work with the GWs, GEMODELS/UB and to all the people involved directly or indirectly in the elaboration of this work. ; Peer reviewed ; Postprint
The nature of the crust beneath central Iberia was estimated by a wide-angle seismic reflection/refraction transect, ALCUDIA-WA, which sampled the southern half of the Variscan Central Iberian Zone, covered in the north by the Cenozoic Tajo Basin. The shot gathers recorded by vertical component sensors revealed well defined P- and S-wave phases. These arrivals were modeled by an iterative forward approach providing 2D crustal models showing variations in the velocity distribution with upper crustal P- and S-wave velocities increasing northwards. The lower crust P-wave velocities are homogeneous along the profile while the S-wave velocities slightly increase northwards. The Moho is placed at 32 km depth in the southern edge of the profile, deepening northward down to 35 km beneath the Tajo Basin. The Poisson's ratio, calculated from P- and S-wave velocities, varies along the profile at upper crustal depths. The highest values are located below the Mora and Pedroches batholiths. These resulting physical properties can serve to constrain the crustal composition by comparing them with laboratory measurements on rock samples. Our results suggest that the upper crust in the southern and central segments of the ALCUDIA profile is made up of low-grade metasedimentary rocks, while the northern segment is dominated by igneous rocks, in agreement with the surface geology. Separated by a sharp boundary located between 12 km (south) and 18 km (north) depth, the lower crust is more homogeneous and shows low Poisson' ratios compatible with a rather felsic composition. However, outstanding lamination described in coincident vertical incidence data indicates some degree of intercalation with mafic components. ; The authors thank the Associated Editor and the anonymous reviewers for their thoroughly valuable suggestions and comments that improved the manuscript. Seismic data were collected in 2012 with funding provided by the Spanish Ministry of Science and Innovation (grants: CGL2004-04623/BTE, CGL2007-63101/BTE, CGL2011-24101, CSD2006-00041). Instrumentation was provided by the IRIS-PASSCAL instrument center, Socorro, New Mexico, USA. The seismic data, including experiment geometry are stored in the IRIS-PASSCAL facilities and can be accessed through the IRIS-PASSCAL data management center. I.P. is funded by the Spanish Government and the Universidad de Salamanca with a Beatriz Galindo grant (BEGAL 18/00090). S.A. Ehsan is funded by the European Commission grant Marie Curie Actions (264517-TOPOMOD-FP7-PEOPLE-2010-ITN). We thank Instituto Geologico y Minero de Espana for providing the logistic help and an academic crew for data acquisition. GMT was used to prepare some of the figures shown in the paper. ; Peer reviewed
The Eastern Galicia Magnetic Anomaly is the best studied anomaly of the Central Iberian Arc. This is due to its location, on the Lugo-Sanabria gneiss dome, and to the fact that its source rocks crop out in the Xistral Tectonic Window. Multiple studies of this anomaly have been carried out, but still, new results keep on shedding light on its understanding. This paper presents the first results on rock magnetic analyses, natural remanent magnetization, anisotropy of the magnetic susceptibility, X-ray diffraction, and stable isotopes geochemistry carried out on the source rocks of this anomaly. Results suggest that magnetization responds to the increase in oxygen fugacity underwent by rocks affected by late Variscan (330-300 Ma) extensional tectonics. Extensional detachments were the pathways that allowed the entrance of fluids that led to syntectonic crystallization of magnetite and hematite in metasediments and inhomogeneous S-Type granitoids derived from their partial melting. Accordingly, magnetization is not linked to lithologies, but to extensional structures developed in the late Carboniferous/earliest Permian, during the Kiaman reverse superchron. Systematic reverse magnetic remanence exhibited by hematite-bearing samples confirms the age of the magnetization and adds complexity to the interpretation of the anomaly. Understanding the EGMA contributes to the interpretation of other anomalies existing in the CIA, also located on thermal domes. The observed extension-related magnetization probably affected most of the NW Iberian Massif, thus hindering the study of previous tectonics by paleomagnetic techniques. This work aims to provide new hints to interpret magnetic anomalies located in extensional tectonic contexts worldwide. ; Projects SA065P17 and BU235P18, funded by the Regional Castilla-León Government, (2) Salamanca University through different lines of funding related to its support to research groups program, (3) projects CGL2016-78560-P and CGL2016-77560 of the Spanish Ministry of Economy, Industry and Competitiveness, and (4) project PID2019-108753GB-C21/AECI/10.13039/501100011033 of the Agencia Estatal de Investigación.
We dedicate this paper to the memory of Prof. Andres Perez Estaún, who was a great and committed scientist, wonderful colleague and even better friend. 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 15 for Recovery" and the Compostilla OXYCFB300 project. Dr. Juan Alcalde is currently funded by NERC grant NE/M007251/1. Simon Campbell and Samuel Cheyney are acknowledged for thoughtful comments on gravity inversion ; Peer reviewed ; Publisher PDF
