Caracterización gravimétrica y magnética de controles estructurales en depósitos de Sn-W. Ejemplo del yacimiento de San Finx (A Coruña)

Critical raw materials are essential for the development of our society. However, most shallow ores have already been exploited and only deep targets remain unexplored. This work aims to apply indi-rect geophysical techniques to the San Finx Sn-W deposit (A Coruña) in order to get further constrains of its deep structure and geometry. Accordingly, a magnetic and a gravity survey have been carried out in the area (SE of Noia, A Coruña), at the southern part of the Mal-pica-Tui Complex. The resulting absolute magnetic anomaly and the relative gravity anomaly have been studied analytically and through 2-2.75D forward modeling. Results indicate that, the sampling inter-val (~1 km) is too high to characterize the anomalies related to the Sn-W mineralization. Contrarily, they show the potential field imprint of the regional Variscan tectonics. To better assess the relationship between the regional Variscan tectonics and the mineralization, a higher resolution survey should be acquired to detect this depositLas materias primas críticas son fundamentales para el desarro-llo de nuestra sociedad. Sin embargo, la mayoría de los yacimientos poco profundos ya han sido explotados, quedando únicamente sin explorar los objetivos profundos. En este trabajo se presentan los re-sultados de la aplicación de técnicas geofísicas indirectas al estudio del yacimiento de Sn-W de San Finx (A Coruña). Su objetivo es cons-treñir la geometría y estructura del yacimiento en profundidad. En este sentido, se ha realizado una campaña de adquisición de datos magnéticos y gravimétricos en dicha zona (SE de Noia, A Coruña) en la parte sur del Complejo Malpica-Tui. La anomalía magnética absoluta y la anomalía gravimétrica relativa resultante se han estu-diado analíticamente y mediante modelización directa 2-2,75D. Los resultados indican que el intervalo de muestreo usado (~1 km) es muy alto para individualizar la respuesta magnética y gravimétrica del yacimiento. Sin embargo, los mapas obtenidos muestran que la signatura de campos potenciales está ligada a la tectónica Varisca a gran escala. Encontrar la relación entre esta última y la mineraliza-ción y hacer un muestreo geofísico de alta resolución en la zona son la clave para entender este depósit

Lithospheric image of the Central Iberian Zone(Iberian Massif) using global-phase seismic interferometry

This paper presents the lithospheric structure of Central Iberia on the basis of seismic interferometry of teleseismic dat

Imaging the lithospheric structure of the Central Iberian Zone

[EN]This presentation includes an image of the structure of the crust and upper mantle in the Central Iberian Zone and across the Central Syste

El Perfil sísmico ALCUDIA: una imagen de la Zona Centroibérica (Varisco Ibérico meridional, España)

The 250 km long, vertical incidence seismic reflection profile ALCUDIA was acquired in spring 2007. It samples the Variscan Central Iberian Zone from Toledo to Fuenteovejuna. Its main goal was to continue the structure obtained for the crust and mantle from the IBERSEIS transect towards the N and NE. The acquisition parameters, similar to those used in the IBERSEIS profile have proven to be adequate to show a detailed image of the whole crust and upper mantle. After preliminary processing, the upper crust shows a moderate reflectivity that can be easily correlated with identifiable surface geologic features. The middle and lower part of the crust seems to be very reflective, laminated and afected by deformation, although to a different extent. The Moho is placed at approximately 10 s TWT and appears to be flat in the time section. The section can be divided into four domains of reflectivity that can be key to stablish different domains of crustal evolution. This new transect, together with the previous IBERSEIS profile, complete an almost 600 km long lithospheric section that crosses the southern half of the Iberian Variscides.El perfil sísmico de reflexión ALCUDIA , de 250 km de longitud, fue adquirido en la primavera del año 2007. Este perfil ha muestreado la Zona Centroibérica entre Toledo y Fuenteovejuna, y su objetivo principal ha sido continuar hacia el NE la estructura de corteza y manto ya obtenida mediante el perfil IBERSEIS. Los parámetros de adquisición, similares a los de IBERSEIS, han sido adecuados para mostrar una imagen detallada de toda la corteza y el manto superior. Una vez efectuado el procesado preliminar, la corteza superior presenta una reflectividad moderada que puede correlacionarse fácilmente con rasgos geológicos de superficie. Las partes media e inferior de la corteza son muy reflectivas, laminadas y afectadas por una deformación que varía a lo largo del perfil. La Moho se localiza a unos 10 s TWT y tiene geometría plana en la sección de tiempo. La variación en los patrones generales de reflectividad permite dividir el pefil sísmico en cuatro dominios, que corresponden a diferentes evoluciones corticales. Este nuevo perfil sísmico, unido al anterior perfil IBERSEIS, constituye una sección litosférica de casi 600 km de longitud, que atraviesa la parte meridional del Varisco Ibérico.Depto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasTRUEMinisterio de Ciencia e Innovación (MICINN)Generalitat de CatalunyaJunta de Comunidades de Castilla La Mancha.pu

Deep seismic exploration of the Iberian Microplate

[EN]This presentation was a key-note lecture at the International Symposium on Deep Exploration and Practices. It describes the acquisition of controlled source seismic data in the Iberian Peninsula during the last decade

Characterization of the shallow subsurface structure across the Carrascoy Fault System (SE Iberian Peninsula) using P-wave tomography and Multichannel Analysis of Surface Waves

The seismicity in the SE Iberian Peninsula is distributed parallel to the coast in a well-developed strike-slip fracture system known as the Eastern Betic Shear Zone (EBSZ). This work focuses on the characterization of the shallow subsurface structure of the Algezares-Casas Nuevas Fault, within the Carrascoy Fault System of the EBSZ. The Carrascoy Fault borders the Guadalentín Depression to the south, which is a densely populated area with extensive agricultural activity. Therefore, this faults system represents a seismic hazard with significant social and economic implications. We have constructed two velocity-depth models based on P-wave tomography and Multichannel Analysis of Surface Waves (MASW) acquired from seismic reflection data. The resulting velocity models have allowed us to interpret the first ~250m depth and have revealed: i) the thickness of the critical zone; ii) the geometry of the Algezares-Casas Nuevas Fault; iii) the depth of the Messinian/Tortonian contact and iv) the presence of blind thrusts and damage zones under the Guadalentín Depression. Our results have also helped us to estimate an apparent vertical slip rate of 0.66±0.06m/ky for the Algezares-Casas Nuevas Fault since 209.1±6.2ka. Our results provide a methodological and backflow protocol to study the shallow subsurface of active faults, complementing previous geological models based on paleoseismological trenches, and can be used to improve the seismic hazard assessment of tectonically active regions around the world

Geophysical Imaging of the Critical Zone along the Eastern Betic Shear Zone (EBSZ), SE Iberian Peninsula

The critical zone (CZ) represents the most-shallow subsurface, where the bio-, hydro-, and geospheres interact with anthropogenic activity. To characterize the thickness and lateral variations of the CZ, here we focus on the Eastern Betic Shear Zone (EBSZ), one of the most tectonically active regions in the Iberian Peninsula. Within the EBSZ, the Guadalentín Depression is a highly populated area with intensive agricultural activity, where the characterization of the CZ would provide valuable assets for land use management and seismic hazard assessments. To achieve this, we have conducted an interdisciplinary geophysical study along the eastern border of the Guadalentín Depression to characterize the CZ and the architecture of the shallow subsurface. The datasets used include Electrical Resistivity Tomography (ERT), first-arrival travel time seismic tomography, and multichannel analysis of surface waves (MASW). The geophysical datasets combined help to constrain the high-resolution structure of the subsurface and image active fault systems along four transects. The resulting geophysical models have allowed us to interpret the first ~150 m of the subsurface and has revealed: (i) the variable thickness of the CZ; (ii) the CZ relationship between the fault zone and topographic slope; and (iii) the differences in CZ thickness associated with the geological units. Our results provide a method for studying the shallow subsurface of active faults, complementing previous geological models based on paleo-seismological trenches, and can be used to improve the CZ assessment of tectonically active regions

Subduction and volcanism in the Iberia-North Africa collision zone from tomographic images of the upper mantle

New tomographic images of the upper mantle beneath the westernmost Mediterranean suggest that the evolution of the region experienced two subduction-related episodes. First subduction of oceanic and/or extended continental lithosphere, now located mainly beneath the Betics at depths greater than 400 km, took place on a NW-SE oriented subduction zone. This was followed by a slab-tear process that initiated in the east and propagated to the west, leading to westward slab rollback and possibly lower crustal delamination. The current position of the slab tear is located approximately at 4°W, and to the west of this location the subducted lithosphere is still attached to the surface along the Gibraltar Arc. Our new P-wave velocity model is able to image the attached subducted lithosphere as a narrow high-velocity body extending to shallow depths, coinciding with the region of maximum curvature of the Gibraltar Arc, the occurrence of intermediate-depth earthquakes, and anomalously thick crust. This thick crust has a large influence in the measured teleseismic travel time residuals and therefore in the obtained P-wave tomographic model. We show that removing the effects of the thick crust significantly improves the shallow images of the slab and therefore the interpretations based on the seismic structureThis is a contribution of the Team Consolider-Ingenio 2010 TOPO-IBERIA (CSD2006-00041). Additional fundingwas provided by the SIBERIA (CGL2006-01171), RIFSIS (CGL2009-09727) and ALERTES-RIM (CGL2013-45724-C3-3-R) projects.Peer reviewe