Late Carboniferous porphyry copper mineralization at La Voluntad,Neuquén,Argentina: Constraints from Re–Os molybdenite dating     

Mirta Garrido  Fernando Barra  Eduardo Domínguez  Joaquin Ruiz  Victor A. Valencia 《Mineralium Deposita》2008,43(5):591-597

The La Voluntad porphyry Cu–Mo deposit in Neuquén, Argentina, is one of several poorly known porphyry-type deposits of Paleozoic to Early Jurassic age in the central and southern Andes. Mineralization at La Voluntad is related to a tonalite porphyry from the Chachil Plutonic Complex that intruded metasedimentary units of the Piedra Santa Complex. Five new Re–Os molybdenite ages from four samples representing three different vein types (i.e., quartz–molybdenite, quartz–sericite–molybdenite and quartz–sericite–molybdenite ± chalcopyrite–pyrite) are identical within error and were formed between ~312 to ~316 Ma. Rhenium and Os concentrations range between 34 to 183 ppm and 112 to 599 ppb, respectively. The new Re–Os ages indicate that the main mineralization event at La Voluntad, associated to sericitic alteration, was emplaced during a time span of 1.7 ± 3.2 Ma and that the deposit is Carboniferous in age, not Permian as previously thought. La Voluntad is the oldest porphyry copper deposit so far recognized in the Andes and indicates the presence of an active magmatic arc, with associated porphyry style mineralization, at the proto-Pacific margin of Gondwana during the Early Pennsylvanian.  相似文献   

Guidelines for navigation and overflight in the exclusive economic zone     

Mark J. Valencia  Kazumine Akimoto 《Marine Policy》2006,30(6):704-711

Several significant international incidents in Asian exclusive economic zones (EEZs) have underscored the ambiguity and lack of agreement regarding the regime governing foreign military activities in coastal States’ EEZs. A group of senior officials and analysts participated in their personal capacities in a dialogue from 2002–2005 that discussed the issues with a view to improving mutual understanding of the regime and finding areas of agreement. The Tokyo meeting in September 2005 reached consensus on some voluntary, non-binding guidelines that are presented here. The guidelines are based selectively on the 1982 UNCLOS, State practice and emerging ‘soft’ law, and attempt to balance the interests of coastal States and user States. It is hoped that they may serve as the basis for discussion and eventual agreements between governments.  相似文献   

Phosphate adsorption and desorption in a tropical estuary (Maracaibo system)     

D. López-Hernández  T. Herrera  F. Rotondo 《Marine environmental research》1980,4(2):153-163

The Maracaibo Estuary is of particular interest because of its location in the tropics, its large size (over 12,000 km²), the economic importance of its underlying hydrocarbon deposits and its increasing rate of pollution. Sediments from this estuary were studied in order to characterise their capacity to adsorb and desorb phosphorus. Considerable variability in capacity for phosphate sorption was found among the seventeen samples studied. This variability can be attributed first to the differences among the samples in total P content and, secondly, to their differences in free iron content. Also, it appears that P retention contributes to the control of P concentration in the water and therefore the sediments serve as a buffer in controlling P eutrophication in the estuary.  相似文献   

Zooplankton variability and climatic anomalies from 1994 to 2001 in the Balearic Sea (Western Mediterranean)     

Fernandez de Puelles  M. Luz; Valencia  Joaquin; Vicente  Laura 《ICES Journal of Marine Science》2004,61(4):492-500

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Flotation of oxidized minerals of copper using a new synthetic chelating reagent as collector     

M. Barbaro  R. Herrera Urbina  C. Cozza  D. Fuerstenau  A. Marabini 《International Journal of Mineral Processing》1997,50(4):275-287

A new synthetic reagent containing a mixed aliphatic-aromatic structure, with a hydrocarbon chain and an aminothiophenol chelating group, has proven to be an effective collector for the flotation of chrysocolla minerals. The flotation is optimum in the narrow pH range of 5.5 to 6, falls sharply at pH 5, and is moderate in the pH range 7 to 11. Infrared spectra indicate that copper aminothiophenolate chelates are formed on the surface of the chrysocolla under the conditions of maximum flotation.  相似文献   

Modélisation morphodynamique cross-shore d'un estran vaseux     

Benoı̂t Waeles  Pierre Le Hir  Ricardo Silva Jacinto 《Comptes Rendus Geoscience》2004,336(11):1025-1033

Numerical experiments were performed to simulate the profile evolution of an intertidal mudflat with a 1D cross-shore morphodynamical model. First, the hydrodynamical forcing is a cross-shore tidal current due to semi-diurnal variations of the free surface elevation at the open boundary. Further, considering the conservation of the action density of surface gravity waves, a wave height (and resulting bottom shear stress) calculation is added to the morphodynamical model. Results of the numerical experiments show that the shape of the profile reaches equilibrium. The mudflat progrades continually when the forcing is tide only, whereas it can be steady under the simultaneous action of tide and waves. To cite this article: B. Waeles et al., C. R. Geoscience 336 (2004).  相似文献   

Daily precipitation statistics in a EURO-CORDEX RCM ensemble: added value of raw and bias-corrected high-resolution simulations     

A. Casanueva  S. Kotlarski  S. Herrera  J. Fernández  J. M. Gutiérrez  F. Boberg  A. Colette  O. B. Christensen  K. Goergen  D. Jacob  K. Keuler  G. Nikulin  C. Teichmann  R. Vautard 《Climate Dynamics》2016,47(3-4):719-737

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Comparison of water-level,extensometric, DInSAR and simulation data for quantification of subsidence in Murcia City (SE Spain)     

S. Tessitore  J. A. Fernández-Merodo  G. Herrera  R. Tomás  M. Sanabria  J. Duro  J. Mulas  D. Calcaterra 《Hydrogeology Journal》2016,24(3):727-747

Subsidence due to groundwater overexploitation has been recognized in the metropolitan area of Murcia (25 km²) in south-eastern Spain since the early 1990s. Previous published works have focused their attention on land subsidence that occurred during the drought period between 1995 and 2008. This work first analyzes the groundwater recovery that has occurred since 2008 and then determines the kind of associated ground deformation detected by the new extensometric data. Subsequently, subsidence time series are computed on 24 geotechnical boreholes scattered throughout the study area by means of a hydro-mechanical finite element code and a linear-elastic constitutive law. A spatio-temporal interpolation of the numerically modeled surface displacements is performed over the whole domain and compared with extensometers and DInSAR-derived displacement maps in two different periods: the drought period from 2004 to 2008, and the recovery period from 2008 to 2012. In spite of the limited information on the geomechanical parameters characterizing the modelled geological formations, the proposed approach is able to discriminate areas where the soils have an elastic behavior (small differences in the comparisons) or an elasto-plastic behavior (large differences in the comparisons). This zonation enhances the understanding of the subsidence phenomenon in Murcia City and could prevent, from a quantitatively point of view, future severe subsidence due to aquifer overexploitation.  相似文献   

Hydrogeology and sustainable future groundwater abstraction from the Agua Verde aquifer in the Atacama Desert,northern Chile   总被引：1，自引：0，他引：1  

Javier Urrutia  Jorge Jódar  Agustín Medina  Christian Herrera  Guillermo Chong  Harry Urqueta  José A. Luque 《Hydrogeology Journal》2018,26(6):1989-2007

The hyper-arid conditions prevailing in Agua Verde aquifer in northern Chile make this system the most important water source for nearby towns and mining industries. Due to the growing demand for water in this region, recharge is investigated along with the impact of intense pumping activity in this aquifer. A conceptual model of the hydrogeological system is developed and implemented into a two-dimensional groundwater-flow numerical model. To assess the impact of climate change and groundwater extraction, several scenarios are simulated considering variations in both aquifer recharge and withdrawals. The estimated average groundwater lateral recharge from Precordillera (pre-mountain range) is about 4,482 m³/day. The scenarios that consider an increase of water withdrawal show a non-sustainable groundwater consumption leading to an over-exploitation of the resource, because the outflows surpasses inflows, causing storage depletion. The greater the depletion, the larger the impact of recharge reduction caused by the considered future climate change. This result indicates that the combined effects of such factors may have a severe impact on groundwater availability as found in other groundwater-dependent regions located in arid environments. Furthermore, the scenarios that consider a reduction of the extraction flow rate show that it may be possible to partially alleviate the damage already caused to the aquifer by the continuous extractions since 1974, and it can partially counteract climate change impacts on future groundwater availability caused by a decrease in precipitation (and so in recharge), if the desalination plant in Taltal increases its capacity.  相似文献   

Site scale modeling of slow-moving landslides,a 3D viscoplastic finite element modeling approach     

G. Bru  J.A. Fernández-Merodo  J.C. García-Davalillo  G. Herrera  J. Fernández 《Landslides》2018,15(2):257-272

This paper presents an advanced 3D numerical methodology to reproduce the kinematics of slow active landslides, more precisely, to reproduce the nearly constant strain rate (secondary creep) and the acceleration/deceleration of the moving mass due to hydrological changes. For this purpose, finite element analyses are performed in a large area covering a long time-span (12 years), in order to exhibit different interacting slope movements. First, we perform a stability analysis using the shear strength reduction (SSR) technique with a Mohr-Coulomb failure criteria. It is done in order to compute factors of safety (FS) and to identify two different scenarios, the first one being stable (FS > 1) and the second one being unstable (FS < 1). In the studied test case, the Portalet landslide (Central Spanish Pyrenees), the first scenario corresponds to an initial stable configuration of the slope and the second one to an unstable excavated configuration. Second, taking the first scenario as an initial condition, a time-dependent analysis is performed using a coupled formulation to model solid skeleton and pore fluids interaction, and a simplified ground water model that takes into account daily rainfall intensity. In this case, a viscoplastic constitutive model based on Perzyna’s theory is applied to reproduce soil viscous behavior and the delayed creep deformation due to the excavation. The fluidity parameter is calibrated to reproduce displacements measured by the monitoring systems. Our results demonstrate that 3D analyses are preferable to 2D ones for reproducing in a more realistic way the slide behavior. After calibration, the proposed model is able to simulate successfully short- and medium-term predictions during stages of primary and secondary creep.  相似文献