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1.
Cordula Gdaniec 《GeoJournal》1997,42(4):377-384
Reconstruction of the historic centre of Moscow and the construction of apartment blocks on the citys outskirts are the citys two main programmes within what must be regarded as its urban policy. With these priorities, the strategy of relying on a mixture of city and private investments, the city governments policies contribute to an increasing exclusiveness of the city centre. This process, which includes a process of gentrification, reflects the impact of the transition to a free-market economy. City planning and reconstruction projects are subject to the new, still chaotic, market opportunities and constraints while the soviet planning principles and organizations have not yet been replaced by efficient new ones. There is a lack of control and regulation, as well as a concentration of power in the mayoral cabinet on the one hand, but on the other hand, the finance strategies make large-scale regeneration possible. With entering the global economy, post-soviet Moscow is acquiring more traits of western, capitalist cities. These include marketing the centres historic character, subsidising private investment, and a new residential segregation based on capital.  相似文献   

2.
Ocean plate stratigraphy (OPS) is essential to understanding accretionary wedges and complexes along convergent plate margins. Mélanges within accretionary wedges and complexes are the products of fragmentation and mixing processes during and following OPS accretion. A new term, ‘OPS mélange’, is proposed here for mélanges composed mostly of blocks of OPS with an argillaceous matrix, and for a mixture of mélanges of multiple origins with either broken or coherent formations. An OPS mélange results from the fragmentation and disruption of OPS, without admixing of other components. Three major types of OPS mélange can be distinguished on the basis of their components: turbidite type, chert–turbidite type, and limestone–basalt type. These three types potentially form similar mélanges, but they are derived from different parts of the OPS, depending on the level of the decollement surface. The concept of ‘OPS mélange’ can be applied to most of the mélanges in accretionary prisms and complexes worldwide. In addition, this proposal recognizes a distinction between processes of fragmentation and mixing of OPS components, and mixing of ophiolite components, the latter of which results in serpentinite mélanges, not OPS mélanges. Mélanges composed of OPS sequences occur worldwide. The recognition of OPS mélanges is a key aspect of understanding tectonic processes at convergent margins, which result in mélange formation in orogenic belts globally.  相似文献   

3.
The Salvan-Dorénaz intramontane basin formed between ca. 308–293 Ma as an asymmetric graben along crustal-scale transtensional fracture zones within the Aiguilles-Rouges crystalline massif (Western Alps) and represents a feature of the post-collisional evolution of the Variscan orogens. It contains 1.5–1.7 km of continental clastic deposits which were eroded from granitic, volcanic, and metamorphic rocks. Textural and compositional immaturity of the sandstones, and the numerous lithic fragments with low chemical and physical stability suggest only short-range transport. 40Ar/39Ar analyses of detrital muscovite are interpreted to represent cooling of the crystalline basement below the respective closure temperatures. Ages from detrital muscovite range between ca. 280–330 Ma. 40Ar/39Ar white mica plateau ages from granitic boulders range between 301–312 Ma and suggest rapid cooling. The very short time interval recorded between the 40Ar/39Ar cooling ages and the stratigraphic age of the host sediment suggests that considerable portions of the upper crust were removed prior to the formation of the basin. Late Variscan granitic boulders document surface exposure and erosion of Late Carboniferous granites during early stages of the infilling of the basin. Therefore, unroofing of basement units, magmatic activity, and formation of the fault bounded Salvan-Dorénaz basin were acting concomitantly, and are highly suggestive of extensional tectonics. When compared with other orogens, this situation seems specific to the Variscan, especially the exclusively young ages of detrital material, however, modern analogous may exist.Electronic Supplementary Material Supplementary material is available for this article if you access the article at . A link in the frame on the left on that page takes you directly to the supplementary material.  相似文献   

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International Journal of Earth Sciences - New U–Pb dating on zircon yielded ca. 470 Ma ages for the granitoids from the Lévézou massif in the southern French Massif...  相似文献   

7.
The Qilian Mountains water conservation forest in Gansu province is an important ecological barrier surrounding the oasis in China’s Hexi Corridor. The water they provide is the basis for the existence and sustainable socioeconomic development of those oases. As a result of unsustainable use of the water conservation forest until the 1980s, the oasis ecosystems of the Hexi region were seriously damaged, and the oasis areas experienced deterioration of their ecological environment. In this paper, Landsat images were used to monitor the temporal and spatial changes in area of water conservation in Qilian Mountains of China’s Gansu province and to assess the effect on water conservation by analyzed relationship between water conservation forest area, climatic data and hydrological data. The results showed that the forest covered 15.1% of the study area in 2007 and has followed different trends during the study period. From 1978 to 1990, the forest area decreased; however, from 1990 to 2007, the forest area increased, with a faster rate of increase from 1990 to 2000, and the rate of increase averaged 2,733.89 ha per year since 1990. The water conservation forest appears to play an important role in flood control, runoff regulation, the prevention of soil erosion, and water conservation; and these benefits increase with an increasing area of forest.  相似文献   

8.
The second half of the Ediacaran period began with a large impact e the Acraman impact in South Australia, which was accompanied by a negative d13Ccarb anomaly and an extinction-radiation event involvi...  相似文献   

9.
A three-dimensional geomechanical model of Southern California, including mountain relief, fault tectonics, and characteristic internal borders, such as the roof of the consolidated crust and Moho surface, was created. The initial stress state of the model is determined by the gravitational force and horizontal tectonic movement, established on basis of GPS observations. Monitoring of variations in the stress state of the Earth’s crust and lithosphere, which are generated by seismic processes, has shown that the model enables us to predict an increase of seismic activity in a region and to mark the places in which average earthquakes can occur in the following two weeks.  相似文献   

10.
 Field and laboratory structural studies show that the Devonian–Dinantian units of the northeast French Massif Central experienced a complex and contrasting tectonic–metamorphic evolution during the Hercynian orogeny. The structural analysis of the pre-Middle Visean Brévenne–Violay–Beaujolais rocks, in the Loire area, shows a polyphase tectonic evolution associated with greenschist to amphibolite facies metamorphism. The first event, D1, probably occurred in Early Tournaisian or Latest Devonian times. It is responsible for the flat-lying regional foliation and the NW/SE- to N/S-trending lineation. It is well observed in the Violay group and corresponds to the NW-vergent emplacement of the Late Devonian units upon their gneissic basement, represented by the Affoux gneisses. The second event, D2, is responsible for the NE/SW- to E/W-trending lineation. To the south, D2 deformation is locally reworked by the Grand-Chemin dextral wrench fault, around 345–350 Ma ago. This polyphase deformation is also found in several Devonian–Dinantian areas of the NE Massif Central, but not in Morvan. This tectonics corresponds to the Tournaisian closure, by northward thrusting and subsequent intracontinental deformation, of the oceanic Brévenne–Violay–Beaujolais rift which opened in Devonian times in a back-arc setting. Received: 4 September 1998 / Accepted: 27 May 1999  相似文献   

11.
INTRODUCTIONMany experi mental results have indicated thatthe deterioration process of concrete can be dividedinto two stages—the nondestructive stage (stage 1)and the destructive stage (stage 2) ,as shownin Fig.1 ( Wu, 2002 ; Rostam, 1993) . When concrete issubjected to environmental actions ,the inner energyit gains is al most balanced by the released energywhen crackingin stage 1 , while in stage 2 the innerenergy is greater than that released. There are fewremarkable degradation phe…  相似文献   

12.
Colin Flint 《GeoJournal》2000,51(3):145-156
This paper makes two contributions towards making a theoretically driven electoral geography a vital component of geography. First, a theoretical framework for the empirical analysis of elections is proposed that views elections as one component of the social construction of space while simultaneously illustrating how space structures electoral behavior. Second, the concepts of a geographic theory of voter mobilization need to be operationalized in such a way that space is an integral component of statistical analysis. The statistical concepts of spatial dependence and spatial heterogeneity are used to include electoral locales and the regionalization of voter mobilization in the analysis. The theoretical framework and statistical operationalization proposed are illustrated by a statistical analysis of the growth of the Nazi party vote in Baden between 1924 and 1932.  相似文献   

13.
Background: Radiographic signs of Pneumoconiosis found in farming Ladakhi despite absences of mines and industries were believed to be due to exposure to frequent dust storms and domestic fire pollutions. Seasonal Koilonychia (spoon nail) occurring predominantly in farming women in absences of iron deficiency anaemia was thought to arise from exposure to water made alkaline by weathering of hornblende minerals. The relation of these health conditions to environmental geohydrochemistry is postulated as the source of irrigation water in the affected population originates from glaciers in trans-Himalaya range of sedimentary geology and steep landscape favouring flushing of silica/silicate containing silts. Methods and results: Survey in two central Ladakh villages revealed radiographic evidence of silicosis in all middle aged women and half in middle aged men. In a large-scale study of 3105 subjects aged over 30 years from three villages; 101 (22.5%) of the 449 radiographed showed signs of pneumoconiosis (ILO 1980 criteria) including eggshell calcification of hilar gland and progressive massive fibrosis. Indoor dust analyzed using Philips 400T electron microscope with energy dispersive analysis system attached showed SiO2 levels upto 53.27% with particle size of 0.5 to 5.0 microns and the concentration during cooking period in the worst affected area was 7.495 mg/m^3. Microscopy and histopathology from the subject was characteristic of pneumoconiosis. Analysis of the inorganic dust in the lung showed 40.2% muscovite, 37.3% quartz with the extracted dust wt 147.9 mg/gm of dry tissue. Prevalence of chronic cough with chronic phlegm and percentage of villagers with FEV1/FVC ratio of less than 65% rose with age. Of 70 subjects studied 19 women and 2 men had Koilonychia with incidence being highest in summer. Absence of seasonal Koilonychia in villages fed by water derived from northern mountain range glaciers with mainly igneous geology supports our hypothesis.  相似文献   

14.
The investigation of the environmental properties of minerals, i.e., environmental mineralogy, is a branch of science dealing with interactions between natural minerals and spheres of the Earth surface as well as a reflection of global change, prevention of ecological destruction, participation in biomineralogy, and remediation of environmental pollution. Pollutant treatment by natural minerals is based on the natural law and reflects natural self-purification functions in the inorganic world, similar to that of the organic world - a biological treatment. A series of case studies related to natural self-purification, which were mostly completed by our group, are discussed in this paper. In natural cryptomelane there is a larger pseudotetragonal tunnel than that formed by [MnO6] octahedral double chains, with an aperture of 0.462-0.466 nm2, filled with K cations. Cryptomelane might be a real naturally-occurring mineral of the active octahedral molecular sieve (OMS-2). CrⅥ-bearing wastewater can be treate  相似文献   

15.
The pyroxenite bands in spinel Iherzolites from three high-temperature peridotite massifs (Lherz, Freychinéde and Prades) in Ariège (French Pyrénées) have geochemical features including distributions of Mg, Ca, K, Ti, Zr and REE typical of cumulates derived by high PT crystal segregation. However, these features of the whole-rocks are not reflected in the element distribution among the minerals which was partially modified during subsequent recrystallization. In addition, samples from the margins of the pyroxenite bands were affected by secondary processes such as metasomatism or subsolidus re-equilibration. Unlike pyroxenite xenoliths from basalts which are usually assumed to be derived from alkalic basaltic magmas, the pyroxenite layers are related to tholeiitic magmas similar to the parental liquids of the Triassic dolentes encountered throughout the Pyrénées. The data show that high PT fractionation significantly affected the ascending tholeiitic magma and suggest that the continental tholeiites could have been derived from an upper mantle source with a chondrite shaped REE pattern.  相似文献   

16.
The Larderello geothermal field is generally accepted to have been produced by a granite intrusion at 4–9 km depth. Hydrothermal parageneses and fluid inclusions always formed at temperatures greater than or equal to the current ones, which implies that the field has always undergone a roughly monotonic cooling history (fluctuations < 40 K) since intrusion of the granite at 4 Ma. The heat required to maintain the thermal anomaly over such a long period is supplied by a seismically anomalous body of 32000 km3 rooted in the mantle. Borehole minerals from Larderello are thus a unique well-calibrated natural example of thermally induced Ar and Sr loss under geological conditions and time spans. The observations (biotites retain Ar above 450°C) agree well with other, albeit less precise, geological determinations, but contrast with laboratory determinations of diffusivity from the literature. We therefore performed a hydrothermal experiment on two Larderello biotites and derived a diffusivity D Lab(370°C)=5.3·10-18 cm2s-1, in agreement with published estimates of diffusivity in annite. From D Lab and the rejuvenation of the K/Ar ages we calculate maximum survival times at the present in-hole temperatures. They trend smoothly over almost two orders of magnitude from 352 ka to 5.3 ka, anticorrelating with depth: laboratory diffusivities are inconsistent not only with geological facts, but also among themselves. From the geologically constrained lifetime of the thermal anomaly we derive a diffusivity D G(370°C)=3.81·1021 cm2s-1, 3±1 orders of magnitude lower than D Lab. The cause of these discrepancies must be sought among various laboratory artefacts: overstepping of a critical temperature T *; enhanced diffusivities in wet experiments; presence of fast pathway (dislocation and pipe) diffusion, and of dissolution/reprecipitation reactions, which we imaged by scanning electron microscopy. These phenomena are minor in geological settings: in the absence of mineral transformation reactions, complete or near-complete resetting is achieved only by volume diffusion. Therefore, laboratory determinations will necessarily result in apparent diffusivities that are too high compared to those actually effecting the resetting of natural geochronometers.This word is dedicated to the memory of Aldo Valori (1958–1991)  相似文献   

17.
As a part of the inevitable process of industrialization, urbanization and its associated spatial forms generally have a substantial effect on sustainability. This paper considers the spatial form and sustainability of urbanization by evaluating the interaction between land-use planning, urban regimes and the fragmented structure of land ownership. This paper conceptualizes the structure of landownership as an institution that affects the form of spatial development and thereby determines the spatial implications of urban sprawl on sustainability. With reference to the Ilan experience of urbanizing Taiwan, it shows that the development of spatial form and sustainability is the product of planning institution and urban regime mobilization, and it reflects the institutional impact of a fragmented landownership structure. The conclusion also discusses policy implications.  相似文献   

18.
A natural Ca-poor pigeonite (Wo6En76Fs18) from the ureilite meteorite sample PCA82506-3, free of exsolved augite, was studied by in situ high-temperature single-crystal X-ray diffraction. The sample, monoclinic P21/c, was annealed up to 1,093°C to induce a phase transition from P21/c to C2/c symmetry. The variation with increasing temperature of the lattice parameters and of the intensity of the b-type reflections (h + k = 2n + 1, present only in the P21/c phase) showed a displacive phase transition P21/c to C2/c at a transition temperature T Tr = 944°C, first order in character. The Fe–Mg exchange kinetics was studied by ex situ single-crystal X-ray diffraction in a range of temperatures between the closure temperature of the Fe–Mg exchange reaction and the transition temperature. Isothermal disordering annealing experiments, using the IW buffer, were performed on three crystals at 790, 840 and 865°C. Linear regression of ln k D versus 1/T yielded the following equation: ln k\textD = - 3717( ±416)/T(K) + 1.290( ±0.378);    (R2 = 0.988) \ln \,k_{\text{D}} = - 3717( \pm 416)/T(K) + 1.290( \pm 0.378);\quad (R^{2} = 0.988) . The closure temperature (T c) calculated using this equation was ∼740(±30)°C. Analysis of the kinetic data carried out taking into account the e.s.d.'s of the atomic fractions used to define the Fe–Mg degree of order, performed according to Mueller’s model, allowed us to retrieve the disordering rate constants C 0 K dis+ for all three temperatures yielding the following Arrhenius relation: ln( C0 K\textdis + ) = ln K0 - Q/(RT) = 20.99( ±3.74) - 26406( ±4165)/T(K);    (R2 = 0.988) \ln \left( {C_{0} K_{\text{dis}}^{ + } } \right) = \ln \,K_{0} - Q/(RT) = 20.99( \pm 3.74) - 26406( \pm 4165)/T(K);\quad (R^{2} = 0.988) . An activation energy of 52.5(±4) kcal/mol for the Fe–Mg exchange process was obtained. The above relation was used to calculate the following Arrhenius relation modified as a function of X Fe (in the range of X Fe = 0.20–0.50): ln( C0 K\textdis + ) = (21.185 - 1.47X\textFe ) - \frac(27267 - 4170X\textFe )T(K) \ln \left( {C_{0} K_{\text{dis}}^{ + } } \right) = (21.185 - 1.47X_{\text{Fe}} ) - {\frac{{(27267 - 4170X_{\text{Fe}} )}}{T(K)}} . The cooling time constant, η = 6 × 10−1 K−1 year−1 calculated on the PCA82506-3 sample, provided a cooling rate of the order of 1°C/min consistent with the extremely fast late cooling history of the ureilite parent body after impact excavation.  相似文献   

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A new coexisting amphibole pair was recently found in the Jianshan iron deposit, Loufan of Shanxi Province, China. Electron microprobe analysis shows that the coexisting pair is composed of grünerite K0.001 (Na0.027 Ca0.073 Mn0.031 Fe 1.801 2+ )1.932 (Fe 2.948 2+ Mg1.964 Ti0.002 Al0.087)5Si8.069 O22.10(OH)2 and ferropargasite (K0.135 Na0.461)0.596 (Na0.088 Ca1.853 Mn0.005 Fe 0.072 2+ )2(Mn0.005Fe 2.789 2+ Mg0.875Ti0.021Fe 0.499 3+ Al0.812)5(Si6.103Al1.897)8O22.00(OH)2. The two kinds of amphiboles occur in amphibole schist not only as separate phenocrysts, but also are combined to form “single-crystal” phenocrysts in the form of topotactic intergrowths with the common c- and b-axes. The boundary between topotactic grünerite and ferropargasite is optically and chemically sharp. In comparison with the coexisting ferromagnesian amphibole and calcic amphibole pair discovered by predecessors, the newly discovered pair has lower Mg/Fe ratios and wider miscibility gaps.  相似文献   

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