The lacustrine facies from two sections (Candasnos and Fraga) ofthe Oligocene-Miocene Torrente de Cinca lithostratigraphic Unit in thecentral part of the Ebro Basin (Spain) have been analysed to determine theinfluence of orbital parameters in lacustrine sedimentation. The unit ispredominantly composed of limestones and marls, and represents a shallowlacustrine freshwater system. The sedimentological features of the faciesstudied demonstrate that the lower part of the Candasnos section representsoffshore lacustrine subenvironments whereas the upper part, and the whole ofthe Fraga section, characterise marginal lacustrine areas. Series of stratalthickness variations of limestone, marl, and limestone/marl couplets fromboth sections have been analysed using spectral analysis. This shows thatinformation corresponding to periodic cycles only appears in the offshorefacies, that is to say, in the lower part of Candasnos section, and disappearsin the marginal facies where non-periodic cycles exist. Furthermore, thespectral analysis of the offshore facies highlights the existence of a peak inthe power spectrum with a period of around 7 (6.8 to 7.8) that can berecognised in the field as shallowing-upward lacustrine sequences.Magnetostratigraphic data from the Candasnos section allow us to establish atime span of 2,808 years for the limestone/marl couplet from the lower partof this section, and between 19,000 and 22,000 years for the periodic cycleidentified, thus representing the climatic precession cycle. Shallowingsequences from marginal areas do not correspond with any periodiccycle. 相似文献
In this study, the methodology of geochemical prospecting has been applied to the study of cadmium, lead, copper and zinc dispersion in the fine sediments of the upper course of the Huerva River (Iberian Range, NE Spain). The survey was organised in two stages: (1) general sampling along the river and its tributary channels, aimed at selecting the sections with the highest contents of the target elements, and (2) detailed study of those sections, aimed at an interpretation of possible positive geochemical anomalies and identification of their sources. The results of this study prove the existence of multiple and complex sources, with a significant influence of sources related to anthropogenic activity. However, the system shows a good ability to depurate itself under current conditions. 相似文献
A procedure for validating landslide susceptibility maps wasapplied in a study area in northern Spain and the results obtained compared. Validationwas used to carry out sensitivity analysis for individual variables and combinationsof variables. The validity of different map-making methods was tested, as well as theutility of different types of Favourability Functions. The results obtained show thatvalidation is essential to determine the predictive value of susceptibility maps. Italso helps to better select the most suitable function and significant variables, thus improving the efficiency of the mapping process. Validation based on a temporal strategy makes it possible to derive hazard maps from susceptibility maps. 相似文献
Major volcanogenic structures within the Marifil Formation allowed to determine the location of a claderas field that spreads along 400 kilometers. This field has at least three large calderas with diameters near to 100 kilometers, recognizable by regional distribution of associated dikes and rhyolite lava flows present at the caldera border that separates a monotonous ignimbritic plateau from a depressed (150 meters) inner volcanic collapsed caldera. The Marifil ignimbritic plateau cover more than 50,000 square kilometers with thicknesses that reach 800 meters. Associated with these plateau ignimbrites there is an important fluorite mineralization. 相似文献
Magmatic
iron meteorites are thought to be samples of the central metallic cores
of asteroid-sized parent bodies. Sulfur is believed to have been an
important constituent of these parental cores, but due to the low
solubility of S in solid metal, initial S-contents for the magmatic
groups cannot be determined through direct measurements of the iron
meteorites. However, experimental solid metal-liquid metal partition
coefficients show a strong dependence on the S-content of the metallic
liquid. Thus, by using the experimental partition coefficients to model
the fractional crystallization trends within magmatic iron meteorite
groups, the S-contents of the parental cores can be indirectly
estimated. Modeling the Au, Ga, Ge, and Ir fractionations in four of
the largest magmatic iron meteorite groups leads to best estimates for
the S-contents of the parental cores of 12 ± 1.5 wt% for
the IIIAB group, 17 ± 1.5 wt% for the IIAB group, and 1
± 1 wt% for the IVB group. The IVA elemental
fractionations are not adequately fit by a simple fractional
crystallization model with a unique initial S-content. These S-content
estimates are much higher than those recently inferred from
crystallization models involving trapped melt. The discrepancy is due
largely to the different partition coefficients that are used by the
two models. When only partition coefficients that are consistent with
the experimental data are used, the trapped melt model, and the low
S-contents it advocates, cannot match the Ge and Ir fractionations that
are observed in IIIAB iron
meteorites. 相似文献
Geostatistical simulation aims at reproducing the variability of the real underlying phenomena. When nonlinear features or large-range connectivity is present, the traditional variogram-based simulation approaches do not provide good reproduction of those features. Connectivity of high and low values is often critical for grades in a mineral deposit. Multiple-point statistics can help to characterize these features. The use of multiple-point statistics in geostatistical simulation was proposed more than 10 years ago, on the basis of the use of training images to extract the statistics. This paper proposes the use of multiple-point statistics extracted from actual data. A method is developed to simulate continuous variables. The indicator kriging probabilities used in sequential indicator simulation are modified by probabilities extracted from multiple-point configurations. The correction is done under the assumption of conditional independence. The practical implementation of the method is illustrated with data from a porphyry copper mine. 相似文献
Abstract Spatial and temporal variations in radiative fluxes influence glacier mass‐balance in mountain areas. The primary goal of this study was to assess differences in solar radiation on three glacial cirques located in the Maladeta Mountain massif (Central Spanish Pyrenees), and analyse their implications on glacier development and morphology. A quantitative approach is adopted to obtain the values of solar radiation (direct, diffuse and global radiation), combining several field data parameters (measured at 55 control‐points) with the solar radiation modelling package Ecosim. The data obtained confirm that the morphologies of the glacial bodies developed in the three cirques have a good correlation with the spatial variation on solar radiation inputs, favouring also the conservation (Aneto and Coronas cirques) or total vanishing (Llosás cirque) of the glacial remnants analysed here. The study shows how strongly in this Alpine‐Mediterranean context solar radiation — firstly as a function of latitude and time of year, and locally as a function of topographic slope, aspect and shadowing — controls the mass‐balance and the spatial distribution of melting in small glaciers, having an effect on the development of their morphologies. 相似文献
The objective of this work is to assess the concentrations of three factions of air particles (settable particles, TSP and PM10) and the levels of several toxic elements in a clay atomisation industry through aerosol sampling at several points inside an industrial plant. Mechanical activities, which produce diffuse emissions, are the main process of discharge of particles in both indoor and outdoor workplace environments in the atomisation plant. The levels of As, Cd, Pb, Zn, Ba and Ni increase in the zones with higher concentrations of particles and lower ventilation. The concentrations of As and F are not influenced by the recycling processes. The levels of Cd and Pb do not show great enrichment in air particles collected inside the atomisation plant although the content of both elements is associated with ceramic muck recycling. Finally, the content of B in waste water is mainly transferred in gaseous phase to the atmosphere during the process of drying by atomisation. 相似文献
Zoned quartz and feldspar phenocrysts of the Upper Carboniferous eastern Erzgebirge volcano-plutonic complex were studied by cathodoluminescence and minor and trace element profiling. The results verify the suitability of quartz and feldspar phenocrysts as recorders of differentiation trends, magma mixing and recharge events, and suggest that much heterogeneity in plutonic systems may be overlooked on a whole-rock scale. Multiple resorption surfaces and zones, element concentration steps in zoned quartz (Ti) and feldspar phenocrysts (anorthite content, Ba, Sr), and plagioclase-mantled K-feldspars etc. indicate mixing of silicic magma with a more mafic magma for several magmatic phases of the eastern Erzgebirge volcano-plutonic complex. Generally, feldspar appears to be sensitive to the physicochemical changes of the melt, whereas quartz phenocrysts are more stable and can survive a longer period of evolution and final effusion of silicic magmas. The regional distribution of mixing-compatible textures suggests that magma mingling and mixing was a major process in the evolution of these late-Variscan granites and associated volcanic rocks.
Quartz phenocrysts from 14 magmatic phases of the eastern Erzgebirge volcano-plutonic complex provide information on the relative timing of different mixing processes, storage and recharge, allowing a model for the distribution of magma reservoirs in space and time. At least two levels of magma storage are envisioned: deep reservoirs between 24 and 17 km (the crystallisation level of quartz phenocrysts) and subvolcanic reservoirs between 13 and 6 km. Deflation of the shallow reservoirs during the extrusion of the Teplice rhyolites triggered the formation of the Altenberg-Teplice caldera above the eastern Erzgebirge volcano-plutonic complex. The deep magma reservoir of the Teplice rhyolite also has a genetic relationship to the younger mineralised A-type granites, as indicated by quartz phenocryst populations. The pre-caldera biotite granites and the rhyodacitic Schönfeld volcanic rocks represent temporally and spatially separate magma sources. However, the deep magma reservoir of both is assumed to have been at a depth of 24–17 km. The drastic chemical contrast between the pre-caldera Schönfeld (Westfalian B–C) and the syn-caldera Teplice (Westfalian C–D) volcanic rocks is related to the change from late-orogenic geotectonic environment to post-orogenic faulting, and is considered an important chronostratigraphic marker. 相似文献