Geoelectrical Classification of Gypsum Rocks     

Ander Guinea  Elisabet Playà  Lluís Rivero  Mahjoub Himi  Ricard Bosch 《Surveys in Geophysics》2010,31(6):557-580

Gypsum rocks are widely exploited in the world as industrial minerals. The purity of the gypsum rocks (percentage in gypsum mineral in the whole rock) is a critical factor to evaluate the potential exploitability of a gypsum deposit. It is considered than purities higher than 80% in gypsum are required to be economically profitable. Gypsum deposits have been studied with geoelectrical methods; a direct relationship between the electrical resistivity values of the gypsum rocks and its lithological composition has been established, with the presence of lutites being the main controlling factor in the geoelectrical response of the deposit. This phenomenon has been quantified in the present study, by means of a combination of theoretical calculations, laboratory measurements and field data acquisition. Direct modelling has been performed; the data have been inverted to obtain the mean electrical resistivity of the models. The laboratory measurements have been obtained from artificial gypsum-clay mixture pills, and the electrical resistivity has been measured using a simple electrical circuit with direct current power supply. Finally, electrical resistivity tomography data have been acquired in different evaporite Tertiary basins located in North East Spain; the selected gypsum deposits have different gypsum compositions. The geoelectrical response of gypsum rocks has been determined by comparing the resistivity values obtained from theoretical models, laboratory tests and field examples. A geoelectrical classification of gypsum rocks defining three types of gypsum rocks has been elaborated: (a) Pure Gypsum Rocks (>75% of gypsum content), (b) Transitional Gypsum Rocks (75–55%), and (c) Lutites and Gypsum-rich Lutites (<55%). From the economic point of view, the Pure Gypsum Rocks, displaying a resistivity value of >800 ohm.m, can be exploited as industrial rocks. The methodology used could be applied in other geoelectrical rock studies, given that this relationship between the resistive particles embedded within a conductive matrix depends on the connectivity of the matrix particles.  相似文献   

POC export from ocean surface waters by means of Th/U and Po/Pb disequilibria: A review of the use of two radiotracer pairs     

Elisabet Verdeny  Pere Masqu  Jordi Garcia-Orellana  Claudia Hanfland  J. Kirk Cochran  Gillian M. Stewart 《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(18):11

²³⁴Th (T_1/2=24.1 d) and ²¹⁰Po (T_1/2=138.4 d) are particle reactive radioisotopes that are used as tracers for particle cycling in the upper ocean. Particulate organic carbon (POC) export has frequently been estimated using ²³⁴Th/²³⁸U disequilibrium. Recent evidence suggests that ²¹⁰Po/²¹⁰Pb disequilibrium may be used as an additional tool to examine particle export, given the direct biological uptake of ²¹⁰Po into cellular material. Differences in these two radioisotope pairs with regard to their half-lives, particle reactivity and scavenging affinity in seawater should provide complementary information to be obtained on the processes occurring in the water column. Here, we review eight different studies that have simultaneously used both approaches to estimate POC export fluxes from the surface ocean. Our aim is to provide a complete “dataset” of all the existing POC flux data derived from the coupled use of both ²³⁴Th and ²¹⁰Po and to evaluate the advantages and limitations of each tracer pair. Our analysis suggests that the simultaneous use of both radiotracers provides more useful comparative data than can be derived from the use of a single tracer alone. The difference in half-lives of ²³⁴Th and ²¹⁰Po enables the study of export production rates over different time scales. In addition, their different biogeochemical behaviour and preferred affinity for specific types of particles leads to the conclusion that ²³⁴Th is a better tracer of total mass flux, whereas ²¹⁰Po tracks POC export more specifically. The synthesis presented here is also intended to provide a basis for planning future sampling strategies and promoting further work in this field to help reveal the more specific application of each tracer under specific water column biogeochemistries.  相似文献   

Ground-shaking scenarios and urban risk evaluation of Barcelona using the Risk-UE capacity spectrum based method   总被引：1，自引：0，他引：1  

J. Irizarry  N. Lantada  L.G. Pujades  A.H. Barbat  X. Goula  T. Susagna  A. Roca 《Bulletin of Earthquake Engineering》2011,9(2):441-466

The Capacity Spectrum Based Method developed in the framework of the European project Risk-UE has been applied to evaluate the seismic risk for the city of Barcelona, Spain. Accordingly, four damage states are defined for the buildings, the action is expressed in terms of spectral values and the seismic quality of the buildings, that is, their vulnerability, is evaluated by means of capacity spectra. The probabilities of the damage states are obtained considering a lognormal probability distribution. The most relevant seismic risk evaluation results obtained for Barcelona, Spain, are given in the article as scenarios of expected losses.  相似文献   

Naturally and anthropogenically produced bromoform in the Kattegatt,a semi-enclosed oceanic basin     

Elisabet Fogelqvist  Mikael Krysell 《Journal of Atmospheric Chemistry》1991,13(4):315-324

The origin of bromoform in seawater and atmosphere, as well as possible sinks and breakdown mechanisms, is discussed. A bromoform budget is calculated for the Kattegatt area between Sweden and Denmark, where the input of bromoform from a power plant is significant. Both anthropogenically (250×10⁶ g yr^-1) and biogenically (350×10⁶ g yr^-1, 0.016 g m^-2 yr^-1) produced bromoform is likely to have a great impact locally on the inventory and the release to the atmosphere. Using measured surface concentrations of bromoform, the total annual release from the Kattegatt to the atmosphere is estimated to 550×10⁶ g (0.025 g m^-2 yr^-1).  相似文献   

Deep electrical resistivity structure of the northern Gibraltar Arc (western Mediterranean): evidence of lithospheric slab break‐off     

Oriol Rosell  Anna Martí  Àlex Marcuello  Juanjo Ledo  Pilar Queralt  Eduard Roca  Joan Campanyà 《地学学报》2011,23(3):179-186

  相似文献   

Introduction     

A. Roca  C. Oliveira 《Pure and Applied Geophysics》2001,158(12):2291-2294

  相似文献   

Evaluation of perfluoromethyldecalin as a deliberate tracer for the study of water mixing processes     

Elisabet Fogelqvist  Mikael Krysell  Peder hman 《Marine Chemistry》1989,26(4)

A deliberate tracer experiment has been carried out in an enclosed lagoon in a coastal area. The tracer used was a perfluorocarbon, perfluoro- -methyldecalin (PMD), analysed using liquid-liquid extraction and electron capture gas chromatography. The results show good recovery of the tracer, indicating that adsorption and volatilization did not occur to an appreciable extent over the short time period of the experiment. A mathematical model, PHOENICS, developed for simulation of flow systems, was used to simulate the experiment.  相似文献   

Dike intrusion under shear stress: Effects on magnetic and vesicle fabrics in dikes from rift zones of Tenerife (Canary Islands)     

Carles Soriano Clemente  Elisabet Beamud Amors  Miguel Garcs Crespo 《Journal of Structural Geology》2007,29(12):1931-1942

A theoretical model predicting how anisotropy of magnetic susceptibility (AMS) and vesicle fabrics are modified by shear stress resolved on the dike walls prior to the final cooling of magma is developed for vertical dikes. The resulting fabrics are asymmetric with respect to initial fabrics assumed to be symmetric. Application of this model together with collected data on magma flow direction, dike propagation direction and mechanism, and shear sense, allow us to interpret dike fabrics in terms of shear resolved on the dike walls during intrusion (en echelon arrangement, offsetting, and dike curvature). The interpretation of AMS and vesicle fabrics of the margins of four dikes shows a reasonable agreement with the proposed theoretical models, suggesting that asymmetric fabrics can be used to infer magma flow and may provide valuable information on the shear resolved on the dike walls during intrusion.  相似文献   

A Simplified Method for Vulnerability Assessment of Dwelling Buildings and Estimation of Damage Scenarios in Catalonia, Spain   总被引：1，自引：1，他引：1  

A. Roca  X. Goula  T. Susagna  J. Chávez  M. González  E. Reinoso 《Bulletin of Earthquake Engineering》2006,4(2):141-158

A simplified method for vulnerability assessment of dwelling buildings with a statistical approach at a regional scale based on the EMS’98 is proposed. It is presented some applications of this methodology in Catalonia, Spain: (i) tools for generation of damage scenarios for preventive purposes; (ii) simulation of damages of historical earthquakes if they would occur today; and (iii) territory zonation to establish the criteria for activating the different levels of earthquake emergency actions.  相似文献   

Coupling of latent heat flux and the greenhouse effect by large-scale tropical/subtropical dynamics diagnosed in a set of observations and model simulations     

A. Gershunov  R. Roca 《Climate Dynamics》2004,22(2-3):205-222

Coupled variability of the greenhouse effect (GH) and latent heat flux (LHF) over the tropical – subtropical oceans is described, summarized and compared in observations and a coupled ocean-atmosphere general circulation model (CGCM). Coupled seasonal and interannual modes account for much of the total variability in both GH and LHF. In both observations and model, seasonal coupled variability is locally 180° out-of-phase throughout the tropics. Moisture is brought into convergent/convective regions from remote source areas located partly in the opposite, non-convective hemisphere. On interannual time scales, the tropical Pacific GH in the ENSO region of largest interannual variance is 180° out of phase with local LHF in observations but in phase in the model. A local source of moisture is thus present in the model on interannual time scales while in observations, moisture is mostly advected from remote source regions. The latent cooling and radiative heating of the surface as manifested in the interplay of LHF and GH is an important determinant of the current climate. Moreover, the hydrodynamic processes involved in the GH–LHF interplay determine in large part the climate response to external perturbations mainly through influencing the water vapor feedback but also through their intimate connection to the hydrological cycle. The diagnostic process proposed here can be performed on other CGCMs. Similarly, it should be repeated using a number of observational latent heat flux datasets to account for the variability in the different satellite retrievals. A realistic CGCM could be used to further study these coupled dynamics in natural and anthropogenically altered climate conditions.  相似文献