Suchergebnisse

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. ; 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. ; Spanish Government CGL2004-04623/BTE CGL2007-63101/BTE CGL2011-24101 CSD2006-00041 ; Spanish Government ; European Commission BEGAL 18/00090 ; Universidad de Salamanca BEGAL 18/00090 ; European Commission grant Marie Curie Actions 264517-TOPOMOD-FP7-PEOPLE-2010-ITN

This study was found by the Ministerio de Economia y Competitividad (MINECO) of Spain through the project PANGEATOR (CGL2015-71692) and the Pre-Doctoral scholarship BES-2016-078168. We are indebted to Mike Hall and Brad McDonald for their assistance and technical support on sample preparation and the LA-ICPMS, respectively. The CL imaging was carried out on the Curtin University's Microscopy & Microanalysis Facility, whose instrumentation has been partially funded by the University, State and Commonwealth Governments, and the Scanning Electron Microscope (SEM) Facility at the University of Edinburgh. Analysis in the SHRIMP and GeoHistory Facilities, JdLC, Curtin University were enabled by AuScope (auscope.org.au) and the Australian Government via the National Collaborative Research Infrastructure Strategy (NCRIS) and an Australian Geophysical Observing System grant provided to AuScope Pty Ltd. by the AQ44 Australian Education Investment Fund program, respectively. The NPII multi-collector was obtained via funding from the Australian Research Council LIEF program (LE150100013). The SIMS analyses were performed at the NERC Ion Microprobe Facility of the University of Edinburgh (UK). Comments from two anonymous reviewers and editorial handling by Prof. Victoria Pease are acknowledged. Funding for open access charge: YUniversidad de Granada / CBUA. ; The systematic acquisition of U–Pb geochronological data from detrital zircon grains has become an essential tool in tectonic studies focused on reconstructing the pre–Variscan geography of the northern Gondwanan passive margin. New detrital zircon ages for 16 samples from the Cambrian–Lower Devonian succession of the Moroccan Mesetas (northern Morocco) are reported here. The results, combined with previously published data, reassert the strong West African Craton affinity of the Paleozoic sedimentary rocks, characterized by dominant Cadomian/Pan–African (c. 850–540 Ma) and Eburnean (c. 2.2–1.9 Ga) detrital zircon populations and a minor Leonian/Liberian (c. 2.5 Ga) population. Primary sources of these zircon grains are well established as the West African Craton located just to the south, but also in the Precambrian basement that locally crops out in the Moroccan Mesetas themselves. During the Cambrian–Early Ordovician, erosion preferentially dismantled Cadomian (c. 590–540 Ma) arc–derived rocks of the Gondwanan continental margin, while later, the slightly older Pan–African (c. 650–600 Ma) basement became the main sediment source. In the studied samples, irregularly present minor detrital zircon populations suggest additional sediment provenance from secondary sources such as: (i) remote northeastern African cratons (e.g., Saharan Metacraton and/or Arabian–Nubian Shield) that likely could have provided the c. 1.1–0.9 Ga and, possibly, the c. 1.9–1.7 Ga zircon grains, and (ii) rift–related Cambrian–Early Ordovician volcanic centers in the Moroccan Mesetas that supplied heterogeneously distributed – although locally dominant in small areas – sedimentary detritus before rift abortion and burial underneath the overlying passive margin sedimentary succession. ; Ministerio de Economia y Competitividad (MINECO) of Spain through the project PANGEATOR CGL2015-71692 ; Scanning Electron Microscope (SEM) Facility at the University of Edinburgh ; Australian Geophysical Observing System grant by AQ44 Australian Education Investment Fund program ; Australian Research Council LE150100013 ; Universidad de Granada / CBUA BES-2016-078168

[EN]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 Geológico y Minero de España 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. The data used in this work is accessible at the DIGITAL.CSIC repository (DeFelipe et al., 2021) at http://dx.doi.org/10.20350/digitalCSIC/9061.