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Las Palmas de Gran Canaria, Spain

Vila M.,Institute Geologic Of Catalonia | Fernandez M.,CSIC - Institute of Earth Sciences Jaume Almera | Jimenez-Munt I.,CSIC - Institute of Earth Sciences Jaume Almera
Tectonophysics | Year: 2010

Determining the temperature distribution within the lithosphere requires the knowledge of the radiogenic heat production (RHP) distribution within the crust and the lithospheric mantle. RHP of crustal rocks varies considerably at different scales as a result of the petrogenetic processes responsible for their formation and therefore RHP depends on the considered lithologies. In this work we address RHP variability of some common lithological groups from a compilation of a total of 2188 representative U, Th and K concentrations of different worldwide rock types derived from 102 published studies. To optimize the use of the generated RHP database we have classified and renamed the rock-type denominations of the original works following a petrologic classification scheme with a hierarchical structure. The RHP data of each lithological group is presented in cumulative distribution plots, and we report a table with the mean, the standard deviation, the minimum and maximum values, and the significant percentiles of these lithological groups. We discuss the reported RHP distribution for the different igneous, sedimentary and metamorphic lithological groups from a petrogenetic viewpoint and give some useful guidelines to assign RHP values to lithospheric thermal modeling. © 2010. Source

Vila M.,Institute Geologic Of Catalonia | Martinez-Llado X.,Center Tecnologic Of Manresa
Journal of Geochemical Exploration | Year: 2015

Geochemical reference levels are necessary preliminary steps for appropriate environmental legislation, especially in the assessment of management of soil pollution and protection measures. The problem of establishing reference levels in areas with variable basic geology and anthropogenic pressure is addressed by characterising the geochemistry of 82 representative samples of the geologic materials of the Congost River basin (NE Iberia). The samples have been grouped in a system of 12 operative geochemical units comprising the entire area of the basin. The 'total' and 'partial' concentrations of 54 chemical elements have been determined. The geochemical variability has been discussed by means of statistical methodologies, diagrams and GIS techniques.The analysed samples reveal that the composition of the Congost catchment is highly varied. The differences between the 'total' and 'partial' concentrations define complex patterns reflecting the mineralogy of samples. The results indicate that bedrock geology is the most important factor influencing the major and trace element distributions in the basin. Pb and Zn were observed to be enriched in units more exposed to pollution than their parent materials. In general, the defined operative geologic units are characterised by different major and trace element compositional ranges as a consequence of their lithological diversity. The fact that the samples have been linked to a system of regional geological units allows the geochemical comparison of materials from the Congost River basin with other reference materials from neighbouring areas, or worldwide. For such an approach, we have focused on the geochemistry of the Pleistocene detritic sediments. We close the study by proposing that a good way of expressing the geographic distribution of the geochemical variability of a region could be to apply geologic extrapolation of three representative statistics, an average value (the 50th percentile), a low value (the 25th percentile) and a high value (the 75th percentile). As an example, we present the Th maps, which permit the clear discussion of the Th distribution in the basin. © 2014 Elsevier B.V. Source

Liesa M.,University of Barcelona | Carreras J.,Autonomous University of Barcelona | Castineiras P.,Complutense University of Madrid | Casas J.M.,University of Barcelona | And 2 more authors.
Geologica Acta | Year: 2011

New geochronological data from the Albera Massif confirm the presence of an Early - Mid Ordovician igneous event (472 - 465Ma) recorded in the pre-Variscan rocks of the Pyrenees. This event resulted in the emplacement of a large granitic body in the lower part of the pre-Upper Ordovician metasedimentary succession and in the intrusion of a series of metric sized dykes in the middle and upper parts of it. The two types of igneous rocks were gneissified during subsequent Variscan deformation. The geochronological data confirm the occurrence of the gneiss as having derived from an Ordovician intrusive sheet, as in other Pyrenean massifs. The dykes are considered to be the subvolcanic equivalent of the intrusive sheet. The data also provide insight into the age of the metasedimentary series of the massif and enable us to correlate the dated rocks with other gneissic and subvolcanic bodies of the Variscan massifs of the Pyrenees and Iberia. Source

Falgas E.,University of Barcelona | Ledo J.,University of Barcelona | Benjumea B.,Institute Geologic Of Catalonia | Queralt P.,University of Barcelona | And 3 more authors.
Surveys in Geophysics | Year: 2011

Groundwater management needs detailed aquifer characterization, especially in semiarid costal aquifer systems that are under hydrological pressure. Our study area is in the Tordera delta, northeastern coast of Spain, where a detrital fluvio-deltaic aquifer system has been developed above granitic basement. The main purpose of this study is to characterize the complex lithological structure and the seawater intrusion state by combining hydrological information, audiomagnetotelluric (AMT) and seismic reflection and refraction models. This allowed us to provide spatially continuous information about aquifer properties and processes. Thus, we have determined the thickness and continuity of the aquifer units, as well as the morphology and depth to the basement. The models revealed that the main seawater intrusion main path is found in the western deltaic area that coincides with an existing buried paleochannel. This new result explains the anomalously high chlorine concentrations observed in the deep semiconfined aquifer more than 1,500 m inland. © 2011 Springer Science+Business Media B.V. Source

Goded T.,Complutense University of Madrid | Goded T.,Institute of Geological & Nuclear Sciences | Irizarry J.,Institute Geologic Of Catalonia | Buforn E.,Complutense University of Madrid
Bulletin of Earthquake Engineering | Year: 2012

A vulnerability analysis of some historical and monumental buildings in the city of Málaga is presented in this paper. More than twenty of these monuments were severely damaged or completely destroyed due to the large earthquake (I max = VIII-IX) occurred in the Málaga region in October 1680. The vulnerability index methodology has been used in this paper. This technique is based on statistical data from seismic damage caused to Italian monuments for the past 30 years. For each building, vulnerability curves have been obtained and damage grades have been estimated. A comparison has been carried out between the expected damage grades and the damage observed from past earthquakes, in order to check the feasibility of applying this methodology to Spanish monuments. This comparison has been possible due to the fact that detailed seismic damage information exists for monuments in the city of Málaga that still exist today, which is a very uncommon case in Spain. Results show a good consistency between expected and observed damage, especially for the churches type. Two seismic scenarios have been proposed for the city centre, one deterministic and one probabilistic, where 54 historical and modern buildings have been analyzed. Both scenarios show worrying results, especially for the types of churches, chapels and towers, where expected high probabilities of suffering very heavy damage or even collapse have been obtained. It is highly recommended to take the necessary measures, in the hope of trying to avoid the possible damage that can be expected from future earthquakes. © Springer Science+Business Media B.V. 2011. Source

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