共查询到20条相似文献，搜索用时 46 毫秒
1.
The geothermal flow which emerges by convection at the springs in Aragón is evaluated, and compared with the theoretical heat flow which permeates the surface of the region by conduction. The geological materials through which the convection takes place are defined (geothermal formations), and the areas where thermal convection appears most intensely are related.
Resumen En el presente trabajo se evalúa el flujo geotérmico que emerge por convección en los principales manantiales de aguas termales de Aragón (España), comparándolo con el flujo geotérmico que penetra en la corteza terrestre por conducción. Se definen las formaciones geotérmicas y se estudian las áreas en las que se concentra de forma preferente ese flujo termal por convección.
Résumé Le flux géothermique qui émerge par convection à la source Aragon est évalué, et comparé avec le flux de chaleur théorique par conduction. Le matériel géologique dans lequel la convection prend place est défnit (formations géothermiques) et les zones qui manifestent les plus importantes convections thermiques sont relatés.相似文献
2.
Dawnika L. Blatter Ian S. E. Carmichael 《Contributions to Mineralogy and Petrology》1998,132(2):121-138
Approximately 150 km west of Mexico City in the central part of the Mexican Volcanic Belt (MVB) near Zitácuaro, Mexico, young
volcanism has produced shield volcanoes, large volume silicic deposits, and fault-related basalt and andesite lava flows and
cinder cones. This paper concerns a small cluster of Pleistocene andesite cones and flows which can be separated into two
distinct groups: high-magnesium andesites (>6% MgO, 57–59% SiO2), conveniently called basaltic andesites, with phenocrysts of orthopyroxene and augite, or augite and olivine; and andesites
(60–62% SiO2, <4.6% MgO), which have phenocrysts of orthopyroxene and augite, and ghosts of relict hornblende. Remarkably, plagioclase
phenocrysts are absent, and evenly distributed but sparse (0.5–3.5%) quartz xenocrysts are present in all the lavas. In order
to establish the conditions under which early crystallizing plagioclase is suppressed in these lavas, water saturated experiments
up to 3 kbars were performed on one of the basaltic andesites. The conditions required to reproduce the phenocryst assemblages
(either olivine + augite or opx + augite) are temperatures in excess of 1000 °C, with water saturated liquids (>3 wt%) at
pressures of about 1 kbar. Compared to basaltic andesites of western Mexico, the Zitácuaro basaltic andesites have ∼2 wt%
lower Al2O3 concentrations, which causes plagioclase to precipitate at significantly lower temperatures, and it therefore follows the
crystallization sequence: olivine, augite, and orthopyroxene. Based on ubiquitous quartz xenocrysts, with glassy rhyolitic
inclusions, a reasonable conclusion is that substantial mixing of a quartz-bearing rhyolitic magma with a parental basaltic
andesite has occurred at low pressure (shallow depth), and this would account for the low Al2O3 concentrations in the Zitácuaro basaltic andesites. Whatever the mechanism of incorporation, the quartz xenocrysts are evidence
of contamination of basaltic magma with more siliceous material, thus making it difficult to use these magmas as indicators
of mantle melting processes.
Received: 29 July 1997 / Accepted: 29 January 1998 相似文献
3.
《Journal of South American Earth Sciences》2000,13(1-2):147-156
Four magnetotelluric soundings were carried out in 1993 in the region of the Copahue active volcano located at the border between Chile and Argentina (37°45′S, 71°18′W). Three soundings were located inside the caldera of the ancient stratovolcano (east of Copahue) and the fourth outside it. The soundings inside the caldera were situated at about 6, 11, and 14 km from the volcano. Digital data were obtained covering the range of periods from 1 sec to 10,000 sec using induction coils and a flux-gate magnetometer to obtain the magnetic data and Cu-SO4Cu electrodes for electric field measurements. The apparent resistivity curves corresponding to principal directions were analyzed in conjunction with the geological background in order to eliminate distortion — which is very important in this hot volcanic region. Then, 1D modellings were performed using the “normal” curves — i.e., curves without distortions. Using the apparent resistivity curves with distortions, 2D modelling was also performed along a profile perpendicular to the regional tectonic trend suggested by MT soundings into the caldera. Results show low resistivity values of about 3-15 Ωm between 9 km to 20 km depth in the crust, suggesting high temperatures, with minimum values of about 700°C with partially melted zones in the upper crust between 9 km to 20 km depth under the caldera. The presence of a possible sulphide-carbonaceous layer (SC layer) in the upper basement could play an important role in lowering the electrical resistivities because of its high electronic conductivity. 相似文献
4.
5.
Australia’s Jurassic vertebrate fossil record remains extremely sparse with only two dinosaur taxa and two temnospondyl amphibians identified to date. Of these, the spectacular and extremely well-preserved giant amphibian, Siderops kehli, and the only known pre-Cretaceous sauropod in Australia, Rhoetosaurus brownei, are perhaps the most important. The age of both specimens, and the stratigraphic context of Rhoetosaurus brownei, are weakly constrained and imprecisely defined, limiting our understanding of their evolutionary relationships within a broader Gondwanan context. To clarify and contextualise the evolutionary relationships and ages of these two iconic Jurassic taxa, we used UPb detrital zircon geochronology to date the sandstone matrix from around the bones of the historic museum specimens. The robust maximum depositional age for Siderops was calculated at 176.6 Ma ± 2 Ma, indicating that it is no older than late Toarcian, which refines existing biostratigraphic estimates. The Rhoetosaurus maximum depositional age was determined to be 162.6 ± 1.1 Ma, no older than early Oxfordian, demonstrating that the fossils are younger than expected, and definitely recovered from the Walloon Coal Measures. 相似文献
6.
The Ordovician Ponón Trehué Formation is the only early Palaeozoic sedimentary sequence known to record a primary contact with the Grenvillian-age basement of the Argentinean Cuyania terrane, in its southwards extension named the San Rafael block. Petrographic and geochemical data indicate contributions from a dominantly upper continental crustal component and a subordinated depleted component. Nd isotopes indicate εNd of ? 4.6, ?Sm/Nd ? 0.36 and TDM 1.47 Ga in average. Pb-isotope ratios display average values for 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb of 19.15, 15.69 and 38.94 respectively. U–Pb detrital zircon ages from the Ponón Trehué Formation cluster around values of 1.2 Ga, indicating a main derivation from a local basement source (Cerro La Ventana Formation). The Upper Ordovician Pavón Formation records a younger episode of clastic sedimentation within the San Rafael block, and it shows a more complex detrital zircon age population (peaks at 1.1 and 1.4 Ga as well as Palaeoproterozoic and Neoproterozoic detrital grains). Detailed comparison between the two Ordovician clastic units indicates a shift with time in provenance from localized basement to more regional sources. Middle to early Upper Ordovician age is inferred for accretion of the Cuyania terrane to the proto-Andean margin of Gondwana. 相似文献
7.
8.
9.
L. Fuks I. Herdzik-Koniecko L. Maskalchuk T. Leontieva 《International Journal of Environmental Science and Technology》2018,15(10):2047-2058
Results of sorption of caesium(I), strontium(II), europium(III) and americium(III) ions on the aluminosilicates separated from the clay-salt slimes (CSS) depending on the contact time, pH, initial metal concentration are presented. CSS 1A and CSS 1B sorbents appear to be sufficiently chemically and radiation stable for practical application in treatment of the radioactive wastewaters. 相似文献
10.
《Applied Geochemistry》2002,17(8):961-973
Legal regulation of heavy metal contents is an important issue in many European countries, where laws still do not exist establishing the heavy metal levels permitted in soils. As a first step to determine the reference levels of heavy metals, it is necessary to know their contents in soils under natural conditions. To achieve this goal in the Autonomous Community of Aragón, a total of 133 sites have been sampled. A balanced allotment of the sampling sites, according to soil spatial distribution in the region, has been carried out by selecting 9 soil types that represent 97.5% of its surface area. Fifteen elements (Cr, Cu, Ba, As, Sb, Hg, Sn, Mn, Fe, Al, Zn, Ni, Co, Cd and Pb) have been analysed by (ICP–AES) after a partial acid extraction. The content of analysed elements has been correlated to some soil parameters such as organic matter, pH, and granulometric fractions. Results of the statistical analyses have shown a large variety and complexity in some of these relationships. The main factors for variation in the heavy metal contents are both the soil type and the lithology. Gypsisols and Calcisols developed on sedimentary rocks have the lowest contents while Leptosols overlying metamorphic and igneous rocks have the highest contents. The spatial distribution of heavy metal contents shows a large variability with the highest contents in the mountain ranges (Iberian and Pyrenees) and the lowest in the plains of the central Ebro valley. 相似文献
11.
12.
Gargouri-Ben Ayed Z. Souissi R. Soussi M. Abdeljaouad S. and Zouari K. Laboratoire de radio-analyses et environnement Ecole Nationale d’Ingénieurs de Sfax BP W Sfax Tunisie Université Tunis El Manar Faculté des Sciences de Tunis Département de géologie Tunis Tunisie 《中国地球化学学报》2007,26(3):244-251
The tidal flat of Nakta is located in the northern part of the gulf of Gabes and in the southern coast of Sfax. It corresponds to a flat reef protected from less topography, with a slope ranging between 2° and 4°, which borders the Gargour Wadi. The study sector is renowned to have moderate hydrodynamics which lasts almost for two millenary (14C isotopic dating). The sedimentological study of the Nakta tidal flat revealed different facies: fine-grained sand in the intertidal zone and carbonated muddy sand in the infratidal zone. Equilibrium state of the Nakta ecosystem depends entirely on tide currents, which mainly inhibit drift currents. The Nakta tidal flat is characterized by a variety of faunal species (Cerastoderma glaucum, Arca noe, Cardita antiquatus, Chlamys varied, Ruditapes deccussatus, Tapes rhomboids, Pinctada radiate, etc.) and floristic diversities (Halocnemum strobilacum, Halimione portulacoides, Enteromorpha linza, Ulva rigida, Cymodocea nodosa, Posidonia oceanica). The species are abundant in the infratidal zone, while in its intertidal zone, faunal species remain little diversified and are dominated by limivorous diggering. The paleogeographic study of the Nakta tidal flat showed the alternation of regression and transgression periods. 相似文献
13.
Mihaela Constantin Aurelian C. Trandafir Marta C. Jurchescu Daniel Ciupitu 《Environmental Earth Sciences》2010,59(7):1569-1578
The May–August 2005 heavy rainstorm events in Romania triggered a large number of geomorphic hazards of great magnitude, consisting
of primarily floods and landslides. Some of the most affected regions were the Curvature Carpathians and Subcarpathians. This
paper addresses the effects of rainfall on slopes, especially in the middle sector of the Sibiciu basin (the Buzău Carpathians)
outlining the significant landslide damage along the road connecting the Colţi and Aluniş villages. The landslides are analyzed
in terms of geologic, geomorphic and engineering geologic features, focusing on the Colţi–Aluniş landslide which had the greatest
impact on the road displacement. The related environmental and social impacts are also discussed. 相似文献
14.
Roberto E. San Juan-Farfán Lkhamsuren Bayarjargal Björn Winkler Eiken Haussühl Miguel Avalos-Borja Keith Refson Victor Milman 《Physics and Chemistry of Minerals》2011,38(9):693-700
We have measured the pressure-induced change in the lattice dynamics of diaspore, α-AlO(OH), by in situ Raman spectroscopy
up to 25 GPa. The spectra are evaluated by density functional perturbation theory-based atomistic model calculations. The
assignment of calculated to experimentally observed Raman bands is based on the calculation of Raman intensities. We discuss
the accuracy of the approach employed for these calculations and explain the relative magnitudes of mode Grüneisen parameters. 相似文献
15.
This paper provides the first palynological data from four Upper Cretaceous localities from the Islands of Hvar and Šćedro (southern Croatia), in the central part of the Adriatic Carbonate Platform. Studied material represents palynomorphs produced by coastal vegetation and transported to the shallow marine platform areas. Determined vegetation includes diverse hygrophilous, understory vegetation, range of evergreen needle trees attributable to Pinaceae and Podocarpaceae, as well as Araucarian conifers; ginkgo, cycads and/or bennettites. Flowering plants were likely represented by herbaceous forms. The palynoflora is generally indicative of a temperate, warm and humid climate. The occurrence of the Normapolles group with the presence of Plicapollis sp. and Pseudoculopollis sp. point to Turonian or probable Turonian–Coniacian age, and represent the southernmost record of occurrence within the Normapolles palynological province. Dominance of angiosperms and low abundance of ferns suggests an early-Late Cretaceous age. These findings are supported by the micropaleontological analyses and previously determined age of the sauropod dinosaur footprints described on the Island of Hvar. Based on the paleobotanical and palynological data, the dinosaur diet probably included araucarian conifers, ginkgo and angiosperms, and ferns to a lesser extent. 相似文献
16.
The equilibrium phase relations of two volcanic rocks from thesubduction-related Mexican Volcanic Belt have been determinedwith an argon-pressurized internally heated vessel. One rockis the trachyandesite erupted from El Chich?n Volcano in 1982;the other is a primitive basalt erupted from Jorullo Volcanoin 1759. A simplified synthetic equivalent to the trachyandesitewas also investigated in lesser detail. All charges were saturatedwith hydrous vapor and a sulfur-bearing mineral. Temperatureranged from 800 to 1000?C, pressure from 1 to 4 kb, and fo2was controlled by four different solid oxygen buffers in a doublegold capsule configuration: fayalite-magnetite-quartz (FMQ),Ni-NiO (NNO), manganosite-hausmanite (MNH), and magnetite-hematite(MTH). Pyrrhotite was the only sulfur-bearing mineral observed in chargesbuffered under FMQ and NNO, whereas anhydrite crystallized underthe more oxidizing MNH or MTH; both of these observations areconsistent with those of earlier workers. With increasing temperatureand pressure, SiO2 and K2O decreased in the experimental melts,whereas Al2O3 and CaO increased. Sulfur solubility in silicatemelts was low (<0?1 wt% equivalent SOt3) for pyrrhotite-saturatedcharges, but significantly greater (to 1?3 wt.% SOt3) when anhydritewas present. Sulfur solubility in anhydrite-saturated meltsshowed strong positive dependence on both temperature and Pvapor. Sulfur amounted to some 2?5 wt.% (SOt3) of the total ejectaduring the 1982 El Chich?n eruptions, and the original magmaticsulfur content was in the range 1?25–2–5 wt% SOt3.Extrapolations of experimental temperature and pressure dependencesfor sulfur solubility indicate that such concentrations couldbe contained in a hydrous, oxidized, basaltic parent melt generatedunder Benioff zone conditions. During ascent through the uppermantle and crust, the sulfur solubility limit of the melt wouldcontinuously decrease; in response, most of the sulfur wouldbe transferred from the melt to anhydrite crystals and a separategas phase. Trachyandesite pumices erupted from El Chich?n in1982 contained both pyrrhotite and anhydrite at a temperatureof 800?C. The composition of the natural pyrrhotite yieldedan fo2 estimate 1 log unit above the NNO buffer. Based on compositionalvariations in the experimental melts with temperature and pressure,the composition of the matrix glass in the 1982 pumices indicatesequilibration of the magmatic liquid at about Ptotal=Pvapor=2kb just before eruption. At that time, sulfur in El Chich?ntrachyandesite was about equally partitioned between anhydritemicrophenocrysts and some 20 vol.% gas phase in which H2S wasprobably the dominant sulfur-bearing species. The melt thencontained only 0?05 wt.% SOt3, consistent with experimentalsolubility limits at 800?C and Pvapor=2 kb. 相似文献
17.
18.
Rock fall is a common natural hazard causing significant damage to infrastructure and loss of life and property. This paper describes selection of prevention method, construction processes and the results of a rockfall hazard assessment for the village of Sarica (Gürün region, Turkey) based on an engineering-geological model. The study area is located on the lower parts of an area with very steep cliffs and 40-500 slopes with fractured sedimentary and volcanic rocks. Detailed studies have been conducted in the region to prevent the risk of any rockfalls. Maps and charts are prepared including the rock blocks that are likely to fall and the related housing area under the risk. It was found that block sizes reached 3 m3. Rockfall analyses were performed along the selected profiles using the Rocfall V.5.0 software. Kinetic energy, bounce height, horizontal location of rock end-points and velocity of the rocks along each section were evaluated separately for each profile. This data was used to select design and construction of rockfall preventing system. In this study professional type rock fall barrier (catchment fence) was used. This method was chosen because it was cheaper, more practical and reliable than others. 相似文献
19.
The siliciclastic sediments of the Itapecuru Formation occur in a large area of the Parnaíba Basin and its deposits crop out along the Itapecuru River, in Maranhão State, northern Brazil. The palynological analysis of the Igarapé Ipiranga and Querru 1 outcrops strata yields a rich and diversified data. The presence of index-palynofloras in assemblages allows the identification of the Complicatisaccus cearensis Zone, of Late Aptian-Early Albian age. Terrestrial palynomorphs are abundant in the assemblages, being represented by bryophytes and pteridophytes, especially perisporate trilete spores (Crybelosporites and Perotrilites), and gymnosperms and angiosperms (Afropollis and Elaterosporites). The composition of palynological assemblages suggests the presence of moist soils for both outcrops. Acritarchs were recovered in the Querru 1 outcrop, which suggest a marine setting supporting a tidal flat environment indicated by facies associations. Furthermore, reworked Paleozoic palynomorphs were observed in the Querru 1 outcrop. The microflora from Igarapé Ipiranga outcrop suggests terrestrial environment corroborating with floodplain environment indicated by facies association. 相似文献
20.
The Ordovician stratigraphy of southern-central Xizang (Tibet) has been revised based on new conodont data recovered from 43 samples in four stratigraphic units and their integration with existing nautiloid and graptolite data. The Histiodella holodentata and Pygodus serra biozones have been identified respectively in the Alai and Jiaqu formations of the Chiatsun Group exposed near Alai village in Nyalam County within the Himalayan terrane, and the Yangtzeplacognathus foliaceus Subbiozone (lower part of the Pygodus serra Biozone) in the Sangqu Formation exposed at the Guyu section within Zayu County in the Lhasa terrane. Recognition of these biozones has increased the precision of correlation of the middle-upper Darriwilian strata in the region. Regional reassessment of the Ordovician stratigraphy permitted by new biostratigraphic data has allowed revised definitions for the Chiatsun and Keerduo groups and the Sangqu and Xainza formations. The Chiatsun Group is defined herein to include three lithologically distinctive formations in descending order, the Jiaqu, the Alai and the Adang formations. The stratigraphic age for the Jiaqu and Alai formations in the type area ranges from the middle Darriwilian (Histiodella holodentata Biozone) to middle Katian (Hamarodus brevirameus Biozone), but the age of the Adang Formation remains less certain. 相似文献