A case of successful soil geochemistry: the Rubiales Zn-Pb orebody (NW Spain)

The Rubiales Zn-Pb orebody (NW Spain) is a blind deposit developed in a vertical shear zone during the Variscan Orogenesis. It is about 1200 m long in a N-S direction, with an average thickness of 30 m, and is hosted by lower Cambrian limestones and slates, with some quartzite beds. The deposit has a large hydrothermal alteration aureole. The silicified halo contain sphalerite and galena disseminations, with grades between 0.2 and 3% Pb + Zn.The Rubiales orebody was discovered in the late 60s following a soil geochemical survey. In the regional phase of the survey, 28,622 samples were collected in 57 lines; two of the lines over the Rubiales zone yielded 1400 ppm Pb and 1550 ppm Zn. In a local phase, centred on the anomalous zone, 1716 samples were collected in 21 lines. This local survey defined the geochemical anomalies that were subsequent drill-hole targets. Based on 38 surface-holes, geological ore reserves of 18.6 million tons, with 8.6% Zn + Pb, were estimated.Residual soil geochemical anomalies of Zn and Pb were developed over the silicification zone. The Zn anomaly has a greater extent than the Pb anomaly, due to the greater Zn mobility in surficial environments. The Zn and Pb anomalies exhibit an asymmetrical morphology, with greater extent to the south, due to the down slope creep of residual anomalies. The main cross-faults present in the deposit also control the morphology of the anomalies, as a result of Zn and Pb mobilisation and transport by ground waters along the cross-faults. The Cu anomaly defines two maxima over the feeder zones to the orebody. The two feeder zones, also in the silicification zone, are extensively brecciated and contain the highest grades of the deposit (∗> 20% Zn + Pb) and disseminated chalcopyrite.     

Source mechanism of intermediate and deep earthquakes in southern Spain

Focal mechanisms of 10 intermediate-depth earthquakes (30相似文献   

Low-light and nutrient-rich coral assemblages in an Upper Aptian carbonate platform of the southern Maestrat Basin (Iberian Chain, eastern Spain)

A Lower Cretaceous (Aptian) succession of carbonate rocks in the southern Maestrat Basin (Iberian Chain, Spain) was analysed in terms of sedimentological and palaeontological criteria. The shallow marine sequence was deposited upon a homoclinal carbonate ramp. Five main facies types were distinguished: (A) peloidal and bioclastic grainstones and rudstones of the inner ramp shoals; (B) orbitolinid wackestones-packstones of the distal outer ramp; (C) peloid and Ostrea wackestones-packstones of the middle outer ramp; (D) coral-algal sheetstones of the proximal outer ramp; and (E) coral-algal platestones-domestones of the middle ramp. Coral-bearing facies types (D) and (E) showed similar major environmental factors: low energy hydrodynamism, low light intensity and apparently nutrient-rich water. Slight differences in these conditions are reflected in the different growth forms and coral assemblages. Coral-algal sheetstones are characterized by sheet-like and lamellar forms with a low coral diversity not clearly dominated by any taxon. Coral-algal platestones-domestones develop platy, tabular and irregular massive forms with a slightly higher coral diversity characterized by a Microsolenina-Faviina association. The coral fauna is revised taxonomically and yielded a total of 22 species in 18 genera (21 Scleractinia species, one Octocorallia species). Genera of the suborders Microsolenina and Faviina predominate, those of the suborders Stylinina, Fungiina, Rhipidogyrina and the order Coenothecalia are subordinate.     

Impact of agricultural activity and geologic controls on groundwater quality of the alluvial aquifer of the Guadalquivir River (province of Jaén,Spain): a case study

The alluvial aquifer of the Alto Guadalquivir River is one of the most important shallow aquifers in Jaén, Spain. It is located in the central-eastern part of the province, and its groundwater resources are used mainly for crop irrigation in an agriculture-dominated area. Hydrochemical and water-quality data obtained through a 2-year sampling (2004–2006) and analysis program indicate that nitrate pollution is a serious problem affecting groundwater due to the use of nitrogen (N)-fertilizers in agriculture. During the study, 231 water samples were collected from wells and springs to determine water chemistry and the extent of nitrate pollution. The concentration of nitrate in groundwater ranged from 1.25 to 320.88 mg/l. Considerable seasonal fluctuations in groundwater quality were observed as a consequence of agricultural practices and other factors such as annual rainfall distribution and the Guadalquivir River flow regime. The chemical composition of the water is not only influenced by agricultural practices, but also by interaction with the alluvial sediments. The dissolution of evaporites accounts for part of the Na⁺, K⁺, Cl⁻, SO₄ ²⁻, Mg²⁺, and Ca²⁺, but other processes, such as calcite precipitation and dedolomitization, also contribute to groundwater chemistry.     

Numerical modelling of surfacewater/groundwater flows for freshwater/saltwater hydrology: the case of the alluvial coastal aquifer of the Low Guadalhorce River, Malaga, Spain

This applied research deals with the numerical modelling and transient simulation of the joint surfacewater/groundwater flows that characterize the freshwater/saltwater hydrology of the coastal alluvial valley of the Low Guadalhorce River, Malaga, Spain. The MELEF model used was mainly adapted and calibrated for a simulation period of two hydrological years 1989/1990–1990/1991, before the current channelling of the river, where floods and low precipitations have been recorded. The model calibration process was performed with the aid of phreatic levels measured in numerous wells and piezometers, as well as recharges from precipitation and irrigation on the alluvial surface, which was also assessed by the hydrologic model SSMA-2. The present numerical approach can predict the forthcoming hydrology of the coastal alluvial of the Guadalhorce River after its final channelling.     

Factors Affecting Domestic Water Consumption on the Spanish Mediterranean Coastline

During the last decades on the Spanish Mediterranean coastline there has been a great development of low-density urban areas, as well as a change in the sociodemographic structures, especially in the municipalities that have developed a residential tourism model. Likewise, urban and tourist development have stressed the balance between the availability of water resources and urban water demands, generating situations of scarcity that might be aggravated by climate change. This study identifies the determinants of water consumption on the Spanish Mediterranean coastline, focusing on the variables related to urban land uses and socioeconomic and sociodemographic variables at the municipal level using an ordinary least square (OLS) and a geographically weighted regression (GWR) model. The GWR model results substantially improved the results of the OLS model, explaining 88.27 percent of the variance in domestic water consumption and solving the spatial autocorrelation problem of some independent variables. The most influential variables include the percentage of second homes or the percentage of residential properties with swimming pools at the municipal level. These characteristics must be considered to develop demand management policies and an updated hydrological planning to ensure urban supply in a future with less available water resources.     

Geological records of the pacific plate subduction in the northeast asian continental margin; An overview北大核心CSCD

The Paleo-Pacific Ocean was originated from the Panthalassa, which was a vast global ocean surrounding the Pangea Supercontinent. With the breakup of the Pangea and the closure of the Paleo-Tethyan Ocean, the Paleo-Pacific, Atlantic, Arctic and Indian Oceanic plates were in turn formed. About 190 Ma, the Pacific Plate was initially generated at the junction of the oceanic rift among the Izanagi, Karallon and Pheonix plates. Although most geologists considered a coherent genetic relationship between Meso-Cenozoic tectonic evolution of NE Asian continental margin and subduction of the Pacific Plate, there still exist some key problems. The main issues include; ( I ) the formation, motion trait and evolution paths of the Pacific Plate, especially the Izanagi Plate which subducted beneath the NE Asian continental margin at least since early Jurassic; ( 2) the beginning time of the Pacific Plate subduction; (3) the identification of subduction-related magmatisni; and(4) physical conditions of subduction processes. Based on the recent research progress of the above issues, this paper synthesizes that the subduction of the Paleo-Pacific Plate( or Izanagi Plate) beneath the NE Asian continent started in the early Jurassic. The subduction zone was gradually migrated eastward and constituted anarchipelagic oceanic framework with the involvement of old microblocks or foreign massifs.     

A new titanosaur (Dinosauria,Sauropoda) from the Upper Cretaceous of Lo Hueco (Cuenca,Spain)

The upper Campanian-lower Maastrichtian site of Lo Hueco (Cuenca, Spain) has provided a set of well-preserved partial skeletons in anatomical connection or with a low dispersion of their skeletal elements. One partial skeleton is herein described and a new titanosaurian sauropod is established, Lohuecotitan pandafilandi. This titanosaur is diagnosed by eight autapomorphic features: dorsally and ventrally widened or bifurcated posterior centrodiapophyseal lamina in anterior and middle dorsal vertebrae; short postspinal lamina with a transversely expanded distal end represented by smooth scars in the dorsal vertebrae; anteriormost caudals with the medial spinoprezygapophyseal and medial spinopostzygapophyseal laminae ventrally connected with the prespinal and postspinal laminae, respectively; anterior caudal neural spines with a dorsal projection of the prespinal and postspinal laminae; anterior caudal neural spines bears a “greek-cross”-like cross-section; middle caudal centra having two round and rough structures in the dorsal edge of the posterior articulation, which extends to the dorsal surface of the centrum; the articular ends of the rami of the haemal arches are divided in two articular surfaces; and tuberosity between the anterior and the lateral trochanter of the fibula. The herein performed phylogenetic analysis considered L. pandafilandi as a member of Lithostrotia more derived than Malawisaurus. The known palaeodiversity of the Late Cretaceous Ibero-Armorican titanosaurs is increasing, and further analyses focused on this group will be necessary to better understand the evolutionary history of European titanosaurs and to clarify their relationships within Titanosauria.     

A diatom-conductivity transfer function for Spanish salt lakes

Diatom-salinity transfer functions for interpretation of palaeosalinity and palaeoclimate change have been developed successfully for parts of North America and North and East Africa, but there is a need for data-sets in other saline lake regions of the world. A data-set of 74 modern diatom samples and associated water chemistry data is described from Spain. The influence of conductivity and other environmental variables on diatom distribution is explored using canonical correspondence analysis (CCA) and partial CCAs. A transfer function is derived for conductivity (70 samples) whose apparent predictive ability is high (apparent r² = 0.91). Performance under jackknifing is poor due to the heterogeneous nature of the data-set and poor coverage of the freshwater end of the salinity gradient. There is a lack of suitable low-salinity sites in Spain, and the accuracy of estimated salinity optima and tolerance ranges may be improved by merging this data-set with those of other regions. The Spanish transfer function has strong affinities with the African data-set and contributes important ecological data for diatom taxa which are absent or poorly represented in the modern flora of African lakes, and for which, in fossil material, there were previously no good modern analogues.     

Caledonian terranes along the southwestern border of the East European platform — Evidence,speculation and open questions

Summary According to the terrane model used for the interpretation of the heterogeneities in the Lower Palaeozoic development along the southwestern border of the East European platform (Baltica) several suspect terranes have been accreted to the passive platform margin during the closure of the postulated Tornquist Sea in Ordovician and Silurian times. Their final docking and partly overthrusting onto the platform are of Scandian (Early Devonian) age. A matter of dispute is the provenance of the various terranes. There are lithofacies, structural, palaeobiogeographical and palaeomagnetic constraints for relations both to Baltica and East Avalonia. Specific similarities can be observed between the Southern Jylland, Pomerania, ysogóry (including Radom-Krasik), and Rawa Russkaja terranes. After their accretion and amalgamation they may form a more or less continuous Caledonian marginal thrust belt along the platform border. On the other hand, more significant differences exist between the latter and the so far recognized Southern North Sea, Maopolska, Cracovides, Upper Silesian, Sudeten, Kochanowka, and Dobrogean terranes. The position of any Tornquist Sea suture zone(s) is still completely enigmatic.