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More than twenty years after the last mining operations were completed in the Hiendelaencina Mining District, it is necessary to carry out a geochemical characterisation of the tailings stored in two contiguous mine ponds. Both have significant amounts of quartz, siderite, barite and muscovite and show significant contents of As, Ba, Pb, Sb and Zn. The tailings show alkaline pH and low electrical conductivity values, which support the visual observation that rules out acid drainage into the environment. The comparison of the National Topographic Map of 1954 with LiDAR data from 2014 has allowed estimating the volume of abandoned waste. Based on the volume of slurry and its average density, the total tonnage of pollutants has been estimated at 279 ± 9 t stored in Pond North and 466 ± 11 t stored in Pond South. Although these are significant quantities that pose a risk to the environment and nearby populations, they are lower than those present in other Spanish districts, such as the Iberian Pyrite Belt or Cartagena-La Unión. The combined use of LiDAR data, aerial imagery and geochemical methods has proven to be very useful for the estimation of the volume of pollutants stored in mine ponds., Comunidad de Madrid, Universidad Rey Juan Carlos, Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

This study used spatiotemporal land gravity data to investigate the 2021 eruption that occurred in the Cumbre Vieja volcano (La Palma, Canary Islands). First, we produced a density model by inverting the local gravity field using data collected in July 2005 and July 2021. This model revealed a low-density body beneath the western flank of the volcano that explains a highly fractured and altered structure related to the active hydrothermal system. Then, we retrieved changes in gravity and GNSS vertical displacements from repeated measurements made in a local network before (July 2021) and after (January 2022) the eruption. After correcting the vertical surface displacements, the gravity changes produced by mass variation during the eruptive process were used to build a forward model of the magmatic feeding system consisting of dikes and sills based on an initial model defined by the paths of the earthquake hypocenters preceding the eruption. Our study provides a final model of the magma plumbing system, which establishes a spatiotemporal framework tracing the path of magma ascent from the crust–mantle boundary to the surface from 11–19 September 2021, where the shallowest magma path was strongly influenced by the low-density body identified in the inversion process., Ministerio de Ciencia e Innovación (MICINN), Universidad Complutense de Madrid (UCM), Sección Departamental de Física de la Tierra y Astrofísica (Ciencias Matemáticas), Fac. de Ciencias Matemáticas, TRUE, pub

Timanfaya National Park is a volcanic area located in the southwest of Lanzarote Island (Canary Islands, Spain). Several lava tubes have been found in the lava flows but many others remain unknown. Its location and identification are important to mitigate collapse hazards in this touristic area. We present a new study about the location of recent lava tubes by the analysis and joint interpretation of around penetrating radar (GPR), microgravity and electromagnetic induction (EMI) data along the same profile over an area not previously surveyed. GPR data display a complex pattern of reflections up to ~10 m depth. The strongest hyperbolic reflections can be grouped in four different areas. Visual inspections carried out in the field allow confirming the occurrence of lava tubes at two of them. These reflections have been interpreted as the effect of the roof and bottom interfaces of several lava tubes. The microgravity survey defines a wide gravity low with several over-imposed minor highs and lows. Using the GPR data, a 2.5D gravity model has been obtained revealing four lava tubes. EMI data have been used to obtain an inverted resistivity model that displays four high resistivity areas that closely match the locations of the lava tubes derived from the previous methods. This resistivity model exhibits the lower resolution although reaches a deeper investigation depth (~20 m). The comparison of the results has revealed that joint interpretation of GPR, microgravity and EMI methods provides reliable models useful for the detection of unknown shallow lava tubes, Organismo Autonomo Parques Nacionales, Unidad Deptal. de Astronomía y Geodesia, Fac. de Ciencias Matemáticas, TRUE, pub

This study used spatiotemporal land gravity data to investigate the 2021 eruption that occurred in the Cumbre Vieja volcano (La Palma, Canary Islands). First, we produced a density model by inverting the local gravity field using data collected in July 2005 and July 2021. This model revealed a low-density body beneath the western flank of the volcano that explains a highly fractured and altered structure related to the active hydrothermal system. Then, we retrieved changes in gravity and GNSS vertical displacements from repeated measurements made in a local network before (July 2021) and after (January 2022) the eruption. After correcting the vertical surface displacements, the gravity changes produced by mass variation during the eruptive process were used to build a forward model of the magmatic feeding system consisting of dikes and sills based on an initial model defined by the paths of the earthquake hypocenters preceding the eruption. Our study provides a final model of the magma plumbing system, which establishes a spatiotemporal framework tracing the path of magma ascent from the crust–mantle boundary to the surface from 11–19 September 2021, where the shallowest magma path was strongly influenced by the low-density body identified in the inversion process.

[EN] Colomera is the Spanish meteorite (IIE) that has aroused the greatest interest among the international scientific community. Until now, the story of the find was only partially known and certain data are incorrect. The amazing journey of this meteorite has been recounted in this work. It reveals unpublished information derived from local archives, and testimonies from the descendants of the family that found the meteorite in 1913, and from the inhabitants of Colomera (Granada, Spain). We also document the story after its discovery, which culminated in a 2015 court ruling demanding the return of the largest part the mass (120.34 kg) to the heirs of the Spanish family that discovered the meteorite. Some of the material initially extracted in Spain (305 g) is currently housed in the Natural History Museum (121.3 g; London, UK). Nine kilograms of fragments remains in the United States after returning the meteorite to Spain in 1969. Of these, we have only located slightly more than 4 kg in several American institutions. Recently, 235 g has been returned to Spain: two fragments in private collections and two fragments in the Museo Geominero, Spanish Geological and Mining Institute (Spanish acronym: IGME).

The Hiendelaencina district in Spain was the most important silver producer in Europe during 1844–1925. At the end of the 20th century, with mines having closed, some waste rock dumps were reprocessed, and the sludge from the flotation process was stored in two tailings ponds. When this activity ceased, the residues began to be eroded and disperse. In this study, the state of degradation of both deposits was evaluated using historical mapping and light detection and ranging (LiDAR) data, incorporated into a Geographic Information System. In the aerial images (1946–2018), mine tailings and their main erosive and sedimentary forms were mapped. Geoforms linked to hydrological (channels, gullies, alluvial cones), wind (eolian mantles), hydric–gravitational (colluvium) and anthropic (motorbike tracks) processes which move sludge into the surrounding areas were identified. A net loss of 8849 m3 of sludge, a release of 10.3 t of potentially polluting substances and a high erosion rate of 346 t/ha*year were calculated based on LiDAR data from 2009 and 2014. The ponds show a current high degree of erosion that could increase due to both human activity and the growing frequency of drought and torrential rain periods if stabilization measures are not undertaken., Universidad Rey Juan Carlos, Comunidad de Madrid, Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

En este trabajo se ha realizado un estudio del estado ambiental de los suelos en un radio de 250 m alrededor de los lodos resultantes de procesar sulfuros y sulfosales de Ag de las minas de Hiendelaencina. Los suelos muestreados corresponden a distintos tipos: desarrollados sobre raña, sobre el ortogneis Ollo de Sapo y en un caso, sobre una antigua escombrera. Son suelos en general de poco desarrollo, casi todos con perfiles A-C y en general con poca materia orgánica. Los análisis de contenidos totales de metales indican que son suelos con concentraciones importantes de SiO2, Al2O3, Fe2O3 (hierro total) y K2O, derivadas de la mineralogía base determinada mediante DRX (cuarzo, feldespatos, moscovita, biotita-clorita y magnetita-ilmenita-rutilo). En cuanto a elementos traza, son suelos con alta cantidad de Ba, debido a la abundancia de baritina, que es uno de los principales minerales de la ganga, y con contenidos igualmente importantes de As, Pb y Zn. Estos tres elementos más el Fe, fueron seleccionados para realizar un estudio preliminar de especiación, a través de tres procedimientos de ataque químico en laboratorio (extracciones simples) para determinar en qué tipo de fracción mineral del suelo se alojan en cada caso. Los resultados de estas extracciones revelaron por una parte que el As se encuentra fuertemente ligado a la fracción reducible, probablemente por su adsorción en óxidos/hidróxidos de Fe, y por tanto es un elemento considerado como inmóvil, a pesar de que sus concentraciones pueden ser extremas (600 ppm) en suelos desarrollados sobre escombreras. Por otra parte, Pb y Zn resultan más móviles al estar asociados tanto a la fracción oxidable (restos de sulfuros de la mineralización) como a la fracción extraíble en ácido (ligados a siderita, que consiste en el otro mineral principal de la ganga junto con la baritina). En global, pese a que los porcentajes de metales movilizados son muy bajos y por tanto no parece que exista un gran riesgo ambiental, las gr

This study presents the results of the geoenvironmental characterization of La Matildes riverbed, affected by mine tailings in the Cartagena–La Unión district, Murcia (southeast Spain). Soils and riverbeds in this area are highly polluted. Two Electrical Resistivity Imaging (ERI) profiles were carried out to obtain information about the thickness of the deposits and their internal structure. For the mine tailings deposits of La Murla, a tributary of the El Miedo riverbed, the geophysical method imaged two different units: the upper one characterized by low resistivity values and 5–8 m thickness, correlated with the mine tailings deposits; and the lower more resistive unit corresponding to the Paleozoic metasediments bedrock. The ERI profile transverse to the Las Matildes dry riverbed revealed the existence of three different units. The uppermost one has the lowest resistivity values and corresponds to the tailings deposits discharged to the riverbeds. An intermediate unit, with intermediate resistivity values, corresponds to the riverbed sediments before the mining operations. The lower unit is more resistive and corresponds to the bedrock. Significant amounts of pyrite, sphalerite, and galena were found both in tailings and riverbed sediments. The geochemical composition of borehole samples from the riverbed materials shows significantly high contents of As, Cd, Cu, Fe, Pb, and Zn being released to the environment. Mining works have modified the natural landscape near La Unión town. Surface extraction in three open-pit mines have changed the summits of Sierra de Cartagena–La Unión. Rock and metallurgical wastes have altered the drainage pattern and buried the headwaters of ephemeral channels. The environmental hazards require remediation to minimize the environmental impact on the Mar Menor coastal lagoon, one of the most touristic areas in SE Spain., Comunidad de Madrid, Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

This study presents the results of the geoenvironmental characterization of La Matildes riverbed, affected by mine tailings in the Cartagena–La Unión district, Murcia (southeast Spain). Soils and riverbeds in this area are highly polluted. Two Electrical Resistivity Imaging (ERI) profiles were carried out to obtain information about the thickness of the deposits and their internal structure. For the mine tailings deposits of La Murla, a tributary of the El Miedo riverbed, the geophysical method imaged two different units: the upper one characterized by low resistivity values and 5–8 m thickness, correlated with the mine tailings deposits; and the lower more resistive unit corresponding to the Paleozoic metasediments bedrock. The ERI profile transverse to the Las Matildes dry riverbed revealed the existence of three different units. The uppermost one has the lowest resistivity values and corresponds to the tailings deposits discharged to the riverbeds. An intermediate unit, with intermediate resistivity values, corresponds to the riverbed sediments before the mining operations. The lower unit is more resistive and corresponds to the bedrock. Significant amounts of pyrite, sphalerite, and galena were found both in tailings and riverbed sediments. The geochemical composition of borehole samples from the riverbed materials shows significantly high contents of As, Cd, Cu, Fe, Pb, and Zn being released to the environment. Mining works have modified the natural landscape near La Unión town. Surface extraction in three open-pit mines have changed the summits of Sierra de Cartagena–La Unión. Rock and metallurgical wastes have altered the drainage pattern and buried the headwaters of ephemeral channels. The environmental hazards require remediation to minimize the environmental impact on the Mar Menor coastal lagoon, one of the most touristic areas in SE Spain.

Convective hydrothermal systems have been extensively studied using electrical and electromagnetic methods given the strong correlation between low conductivity anomalies associated with hydrothermal brines and high temperature areas. However, studies addressing the application of similar geophysical methods to hot dry rock geothermal systems are very limited in the literature. The Timanfaya volcanic area, located on Lanzarote Island (Canary Islands), comprises one of these hot dry rock systems, where ground temperatures ranging from 250 to 605 °C have been recorded in pyroclastic deposits at shallow (<70 m) depths. With the aim of characterizing the geophysical signature of the high ground temperature areas, three different geophysical techniques (ground penetrating radar, electromagnetic induction and magnetic prospecting) were applied in a well-known geothermal area located inside Timanfaya National Park. The area with the highest ground temperatures was correlated with the location that exhibited strong ground penetrating radar reflections, high resistivity values and low magnetic anomalies. Moreover, the high ground temperature imaging results depicted a shallow, bowl-shaped body that narrowed and deepened vertically to a depth greater than 45 m. The ground penetrating radar survey was repeated three years later and exhibited subtle variations of the signal reflection patterns, or signatures, suggesting a certain temporal variation of the ground temperature. By identifying similar areas with the same geophysical signature, up to four additional geothermal areas were revealed. We conclude that the combined use of ground penetrating radar, electromagnetic induction and magnetic methods constitutes a valuable tool to locate and study both the geometry at depth and seasonal variability of geothermal areas associated with hot dry rock systems.

En este Proyecto INNOVA-DOCENCIA “Modelado 3D de fenómenos geológicos en Islandia. Nueva contribución al Canal Geología-Historia” se ha realizado una nueva contribución al Canal de Vídeo "Geología e Historia (G&H)" con la película "Islandia: Naturaleza Extrema". En ella se muestra la Geología de Islandia y la explicación del fenómeno óptico de la doble refracción que presenta el Espato de Islandia, probable brújula solar que utilizaban los Vikingos para la navegación en días nublados. Este nuevo recurso docente incorporado al Canal Geología e Historia tiene la aportación de un modelado 3D que facilita la compresión de los fenómenos geológicos y ópticos.

The Timanfaya National Park is a volcanic area in the southwest of Lanzarote Island (Canary Archipelago, Spain) resulting from the 1730-1736 eruption period. Several active geothermal anomalies have been identified from 1970’s. Their location is important to prevent hazards in this restricted touristic area of the park. Presently, only some regional geophysical studies based on gravity, magnetic and seismic data have been undertaken to model the crustal structure of Lanzarote Island. This work presents a new study about the geothermal anomalies in the Timanfaya National Park by the analysis and joint interpretation of electrical resistivity tomography (ERT), magnetic anomalies and electromag netic induction data (EMI). All analyzed data have been obtained over areas which had not been surveyed before. The studied geothermal field is located at the Islote de Hilario visitor’s centre.

Memoria del PIMCD Nº 66 (2014): "Geohistoria: Recursos educativos para una enseñanza interdisciplinar". El Proyecto ha puesto a punto el Canal de Video “Geología e Historia” (Open Access), en el que se han reunido todos los vídeos realizados a lo largo de los cinco últimos años por el Grupo de Trabajo, constituido por los arriba firmantes. Estos recursos están orientados a una Enseñanza transversal a la Geología, Mineralogía, Gemología, Química, Historia, Arte y Arqueología y en su realización han participado profesores e investigadores de esas disciplinas. En este repositorio se ha depositado la Memoria, los vídeos realizados durante este PIMCD 2014 y durante los dos PIMCD, que disfrutó el Equipo Interdisciplinar en los años 2009 y 2013. Así mismo, se recogen dos mini-vídeos, que han sido premiados en dos Concursos de Divulgación Científica de la UCM.

—A ground penetrating radar survey is presented over a recent lava flow at the volcanic area of Timanfaya National Park (Canary Island, Spain). The purpose was to locate lava tubes into the lava flow through the combination of field and simulated data. Different modelling strategies were used for the analysis and knowledge of the signal behaviour. Finite-difference time-domain algorithm was considered for simulations, and the pattern of reflections generated from previously known volcanic structures were characterized. After the characterization of the radar-wave response, the interpretation achieved was applied over the field data acquired at other non-studied area in which different lava tubes were recognized.