共查询到20条相似文献，搜索用时 93 毫秒
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Rodríguez-Cañero Rosario Jabaloy-Sánchez Antonio Navas-Parejo Pilar Martín-Algarra Agustín 《International Journal of Earth Sciences》2018,107(5):1791-1806
International Journal of Earth Sciences - Graphite-rich metamorphic limestones included within low-grade black schists of the lowest Nevado-Filábride tectonic unit in the Sierra de Baza... 相似文献
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The spatial–temporal patterns of cloud-to-ground (CG) lightning covering the period 2010–2015 over the northwest Iberian Peninsula were investigated. The analysis conducted employed three main methods: the circulation weather types developed by Jenkinson and Collison, the fit of a generalized additive model (GAM) for geographic variables, and the use of a concentration index for the ratio of lightning strikes and thunderstorm days. The main activity in the summer months can be attributed to situations with eastern or anticyclonic flow due to convection by insolation. In winter, lightning proves to have a frontal origin and is mainly associated with western or cyclonic flow situations which occur with advections of air masses of maritime origin. The largest number of CG discharges occurs under eastern flow and their hybrids with anticyclonic situations. Thunderstorms with greater CG lightning activity, highlighted by a higher concentration index, are located in areas with a higher density of lightning strikes, above all in mountainous areas away from the sea. The modeling of lightning density with geographic variables shows the positive influence of altitude and, particularly, distance to the sea, with nonlinear relationships due to the complex orography of the region. Likewise, areas with convex topography receive more lightning strikes than concave ones, a relation which has been demonstrated for the first time from a GAM. 相似文献
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F. Barroso-Barcenilla O. Cambra-Moo F. Escaso F. Ortega A. Pascual A. Pérez-García J. Rodríguez-Lázaro J.L. Sanz M. Segura A. Torices 《Cretaceous Research》2009,30(5):1268-1278
The palaeontological site of “Lo Hueco” was discovered in Cuenca, Spain, in 2007. It includes a stratigraphic interval in “Garumn” facies belonging to the upper part of the Villalba de la Sierra Formation. A succession of versicolor marly mudstone levels (V, G1, R1, G2, R2 and M) can be observed at the site studied. This succession is partially modified by a sandy channel structure (C) and by a sulphated interval (S). The C structure and the G1, G2 and R2 (lower part) levels have an extremely rich and varied fossil concentration and have provided to date more than 8500 macroremains. These are mainly from vertebrates, but also from plants and invertebrates. In general, vertebrates are represented by mineralized bones with an early infilling of gypsum, a ferruginous crust, and a secondary precipitation of gypsum; invertebrates by internal moulds; and plants by carbonized remains. Among the vertebrates, titanosaur dinosaurs (some of them with partially articulated skeletons) are by far the most common representatives, although lepisosteid fishes, bothremydid turtles, squamate lizards, eusuchian crocodiles, and ornithischian and theropod dinosaurs are also well represented. The relative stratigraphic position and the palaeontological content of this site allow to attribute it to the upper Campanian-lower Maastrichtian. Interpretation of its materials suggests a near coast muddy flood plain crossed by distributary sandy channels environment, exposed to brackish to fresh water aquatic influence. 相似文献
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Tomás Martín-Crespo Cristina De Ignacio-San José David Gómez-Ortiz Silvia Martín-Velázquez Javier Lillo-Ramos 《Environmental Earth Sciences》2010,59(6):1275-1284
Mining of massive (Cu, Pb and Zn) sulphide bodies in the Iberian Pyrite Belt (SW Spain) has generated a great number of abandoned
waste deposits such as mine ponds. These represent large accumulations of reactive minerals and subsequently, emission sources
of trace elements and formation of acid drainage. Even if they have been restored, monitoring studies are required to evaluate
the corrective effects and how they may change over time. This work presents the results of a monitoring study carried out
at Mine Concepción mine pond, based on mineralogical (XRD), geochemical (INAA, X-ray fluorescence, ICP-MS) and geophysical
(electrical resistivity tomography) techniques. In it, a series of relevant parameters have been well delimited, such as the
infilling thickness and its variation and, the position, geometry and absence of water leakages through the base of the mine
pond. Additionally, the existence of an internal, remnant flow of acid waters that tends to come out through the pond dyke
has been identified. Chemistry of these waters indicates that oxidation processes affecting the Mina Concepción mine tailings
are generating acid drainage waters which could potentially release substantial amounts of trace elements to the river Odiel.
Thus, giving that not complete sealing is accomplished by the restoration capping and rainfall water infiltrates into the
pond materials, at least the sealing of the dyke through which leakages occur should be revised. 相似文献
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A geochronology and Hf isotope study, using laser ablation-ICP-MS analysis of zircon grains, has been conducted to date felsic volcanic rocks from the Portuguese sector of the Iberian Pyrite Belt and to establish possible sources for these rocks. The ages obtained range from the Famennian to the Tournaisian, with the oldest ages reported in the Belt so far being identified in its southwestern part (Cercal area). Results also indicate that within each area, volcanism may have extended for significant periods of time. This suggests that caution is needed in interpreting possible migration trends for the volcanism, as the exact stratigraphic position of the sampled rocks is not always clear. Despite of this, the new data, coupled with previously reported information, suggests that volcanism migrated within the basin from the southwest to the northeast (present day coordinates). Projection from initial zircon ?Hf values towards the depleted mantle evolution curve, via an intermediate reservoir, allows the calculation of Hf protolith model ages that are predominantly Meso-Proterozoic. This is compatible with acid magmas resulting from the fusion of Phyllite–Quartzite (PQ) Formation metasedimentary rocks, which are beneath the volcanic rocks. This is because zircon grains from one PQ Formation sample provided Late Neo-Proterozoic ages and Paleo-Proterozoic to Late Archean U–Pb ages, and the Hf isotope signatures of these zircons can be expected to mix during fusion and result in protolith model ages that would be intermediate between the two U–Pb age populations, as recorded. Further supporting this source for the magmas, the distribution of U–Pb ages of (pre-Variscan) inherited zircon grains in the volcanic rocks is very similar to that shown by the detrital zircon grains from a PQ sample. 相似文献
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A. Pesquera P. P. Gil-Crespo J. Torres-Ruiz E. Roda-Robles 《International Geology Review》2018,60(2):157-187
The Jálama pluton (JP) is a Variscan peraluminous granitoid that intruded into low-grade metasediments from the Central Iberian Zone (CIZ). It comprises a sillimanite-bearing two-mica monzogranite in the inner zone, followed by a tourmaline-bearing two-mica monzogranite, and a marginal tourmaline-muscovite leucogranite in the northern half of the pluton. Microgranitoid enclaves and metasedimentary xenoliths occur locally in monzogranites. The change in rock type from the central monzogranite to the marginal leucogranite corresponds to decreasing TiO2, MgO, FeO, CaO, Sr, Ba, Zr, and ΣREE, and increasing SiO2, Na2O, P2O5, Rb, Li, Cs, Ta, Sn, and W. Fe/(Fe+Mg) ratios in biotite, muscovite and tourmaline increase with increasing Fe/(Fe+Mg) in bulk rock, suggesting an important control of the bulk-rock composition on mineral chemistry. The high peraluminosity, the low CaO and high P contents, as well as the similarity of ε(Nd)300 values in both the granites and metasediments of the southern CIZ constitute strong evidences for a crustal origin of the granite suite, probably by melting of these metasedimentary rocks. Field and petrographic observations, together with mineralogical and geochemical data, suggest that assimilation and mingling/mixing acted in concert with fractional crystallization during the formation of the JP. These processes may also have been important in the evolution of other granitoids from this region. 相似文献
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《Geodinamica Acta》2013,26(2):115-129
The Variscides of Iberia have a bilateral symmetry with east vergence in the eastern branch and west vergence in the western, on both sides of a Centro-Iberian Zone (CIZ), with predominant steep axial planes. All the structures curve around the Ibero-Armorican Arc (IAA). Unconformities in the sedimentary sequences of Cambrian to Early Ordovician age were ascribed to “Sardic phase” by correlation with similar tectonosedimentary events in Sardinia. Recent studies showed diachronism between these events in Sardinia and Iberia but migration of major geodynamic regime in time may be due to regional variation of major events at plate tectonic scale. We studied in detail two critical areas in the CIZ, the Marão anticline in the NE and the Amêndoa-Carvoeiro synform in the SW. Two unconformities can be put in evidence, as elsewhere in CIZ. A stronger lower unconformity of a Volcano-Sedimentary Complex of Lower Arenig (and Tremadocian?) age on top of a Cambrian clastic sequence with flysch characteristics; and a milder upper unconformity of Armorican Quartzite of Arenig age on both the Volcano-Sedimentary Complex and the Cambrian sequences. The lithostratigraphy of the studied areas is described and correlated with other areas in Iberia. The Volcano-Sedimentary Complex and coeval magmatic bodies with bimodal composition are briefly described. The Sardic event corresponds to folds with steep axial planes at high angles to Variscan structures that produce the penetrative cleavage that cut across the unconformity surfaces. Sardic thrusts are also present and can be explained by thin-skinned compressive tectonics. Sardic folds and thrusts suggest a brief period of transient inversion between a major extensional regime from Cambrian to Devonian. The obliquity of Sardic structures to Variscan compression suggests a component of transpression during the Sardic tectonic event, corresponding to a tectonically enhanced unconformity near the Cambro-Ordovician boundary. The transient Sardic inversion is interpreted in terms of a break-up unconformity related to the migration of an intracratonic rift; in the Ordovician this rift moves into the SW of Ossa Morena Zone (OMZ) and since then become the SW Iberia suture during the Variscan Wilson cycle. This migration induced transient compression and dextral strike-slip in the major boundary between CIZ and OMZ due to presence of incipient primary curvature in this segment of IAA. 相似文献
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The magnitudes of early instrumentally recorded earthquakes in the Iberian region (1912–1962) have been studied through processing of digitized seismograms of Wiechert seismograph and analysis of macroseismic information. A magnitude system based on instrumental registrations and macroseismic observations has been proposed. It consists of two compatible magnitude formulae depending on the total duration of seismic oscillations and on the maximum ground amplitude/period ratio of surface waves and includes correspondent intensity–magnitude relationships. 相似文献
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Koroteev V. A. Chervyakovskiy V. S. Zaitseva M. V. Volchek E. N. Necheukhin V. M. 《Doklady Earth Sciences》2019,487(1):756-760
Doklady Earth Sciences - This paper reports on the first U–Pb dating of zircons from dacites of the volcanic paleo-edifice of the andesite–dacite complex of the Eastern Zone of the... 相似文献
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The first results on current movements are presented for the western part of the Dzhugdzhur–Stanovoi Terrane based on GPS geodesy of a geodynamic survey area of the Upper Amur region. Processing of the GPS data resulted in a vector field of the displacement rates of points of the geodynamic survey area with zones of intense deformations. It was concluded from a comprehensive analysis of geological–geophysical data and estimates of the displacement rates that the terrane is characterized by kinematic integrity and was subjected to a complex of tectonic factors related to the evolution of the eastern segment of Baikal Rift Zone in the area of transpression interaction of the Eurasian and Amur plates. 相似文献
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López-Moro F. J. López-Plaza M. Gutiérrez-Alonso G. Fernández-Suárez J. López-Carmona A. Hofmann M. Romer R. L. 《International Journal of Earth Sciences》2018,107(3):985-1004
International Journal of Earth Sciences - In this study, we report U–Pb Laser Ablation ICP-MS zircon and ID-TIMS monazite ages for peraluminous granitoid plutons... 相似文献
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I. Subías I. Fanlo E. Mateo K. Billström C. Recio 《Chemie der Erde / Geochemistry》2010,70(2):149-158
The Iberian Range contains abundant Pb–Zn–(Ag)– and Ba-dominated low temperature veins, mostly formed during the Mesozoic. The hydrothermal activity was related to the extensional regime occurring throughout the Variscan basement of Europe, North Africa and the Appalachians. A stable and radiogenic isotopic study of these veins has identified the reservoir/s of mineralizing components involved in the ore-forming processes. Sulphur isotope ratios indicate that the source of mineralizing components for the base metals veins was a mixture of the Palaeozoic country rocks and Variscan ore deposits. In contrast, either Mesozoic seawater or evaporites supplied most of the sulphur for Ba veins, although a minor contribution of isotopically heavy sulphur derived from the basement is envisaged. The lead isotopic data of galenas define a linear trend in the thorogenic diagram, interpreted in terms of mixing of lead from different reservoirs. The main source is related to local sedimentary country rocks, but a minor contribution from igneous rocks cannot be ruled out. Sr isotope ratios of barites also suggest that most of the components were leached from the basement sequence. When the veins are hosted by carbonate rocks, however, a local source of metals is also available. 相似文献
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Martin J.S. Rudwick 《《幕》》2008,31(3):363-366
Bursting the Limits of Time by the distin- guished historian of geology Martin Rudwick is a massive, two-part book. The first part contains what he calls a synchronous history of what eventually became historical geology in western Europe between the time of de Sans- sure＇s epoch-making ascent of Mont Blanc in 1787 and the discovery of the Kirkdale hyaena cave by Buckland in the winter of 1821-1822, 相似文献
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Analysis of the degree of contamination and evolution in the last 100 years of the composition of the bed sediments of the Anllóns Basin 总被引：3，自引：2，他引：1
Rosa Devesa-Rey M. T. Barral J.-M. Jouanneau F. Díaz-Fierros 《Environmental Earth Sciences》2010,61(7):1401-1417
In this study, five cores of the Anllóns River bed sediments were analyzed in order to evaluate the downcore and downstream
variations in their chemical composition. The first step was the evaluation of the metal distribution in the bulk (<2 mm)
and fine fractions (<63 μm). The analysis revealed that most of the metals followed the same trend in both fractions, although
the fine fraction presented usually higher concentrations. However, the concentration of both fractions tended to equalize
with increasing contamination. No general increase was observed in the metal concentrations toward the surface which could
be attributed to recent anthropogenic contributions. Instead, the distributions were homogeneous or peaked at various depths
downcore. The most important historical feature was observed at the mouth of the river, at 96-cm depth, corresponding to the
end of the eighteenth century. Upcore increased metal concentrations in parallel with increased fine fraction occurred from
this depth, which were attributed to a bridge construction and consequent changes in sediment dynamics. As the metal concentrations
can be influenced by variations in texture or other sediment characteristics, the second step was to evaluate the efficiency
of several normalized indexes in the assessment of the degree of contamination, by calculating the enrichment factor (EF),
the geoaccumulation index (I
GEO) and the pollution load index (PLI). The EFs obtained were <10, thus revealing little anthropogenic inputs to the basin.
The I
GEO produced higher values when compared with the EFs. Instead of absolute EF or I
GEO absolute values, the use of cumulative probability plots allowed identifying more accurately potential outliers indicating
contamination. Only one population was identified for Zn and Pb, with a reduced number of outliers at the highest concentrations
for Pb. As shown, a more complex plot with the outliers identified at C4 and C5. Finally, the PLI allowed determining the
absence of a significant contamination in the bed sediments. The bioavailable and non-geogenic fractions contribute up to
a 90% of the total concentrations in the case of As and Cu, and showed similar (dissimilar) profiles in comparison with total
metals. Also, the quality guidelines were surpassed, so the high solubility of As, Zn, Pb and Ni in the sediments revealed
the need to monitor the bed sediment quality of the Anllóns River. 相似文献
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Doklady Earth Sciences - The influence of the temperature and moisture content of the near-surface soil layer on variations of the barodeformation interaction of the boundary layer of the... 相似文献