共查询到20条相似文献，搜索用时 31 毫秒
1.
B.Sc. B. S. Morgan Ph.D. 《GeoJournal》1984,9(3):301-310
This paper adopts a positivist approach to social geography, which is viewed as a study of the two-way relationship between spatial structure and social structure. This relationship is examined in cities in contemporary Britain and the United States. The concept of social structure is discussed in the first section. It is suggested, after Blau, that social structure may be delineated by parameters which demarcate the lines of differentiation among people, created in their social interaction. Area of residence may be considered such a parameter. Social structure comprises a complex configuration of these parameters. In general, coinciding parameters limit social mobility and lead to an atomised society. The processes by which social structure takes on spatial expression are discussed in the second section. The salience of various parameters of social structure in a spatial setting is assessed first. Behaviouralist, managerialist and structuralist approaches to residential differentiation are reviewed. It is argued that most insight will come from studies of the interaction between groups of households and the major institutions of the housing market in the context of characteristics of the housing supply. The impact of neighbourhood on social structure is examined in the third section. The role of propinquity in social interaction is discussed along with the role of neighbourhood as a status symbol. Individuals may change their position along structural parameters as a consequence of their residential location. Residential segregation is also a means, through its role in circumscribing contacts, by which the continuation of the stratification system is ensured in the next generation. In conclusion, it is noted that the isolation of racial minorities in the disadvantaged parts of the city poses a danger to social stability. 相似文献
2.
A. Del Popolo 《Astronomy Reports》2007,51(3):169-196
This paper provides a review of the types of dark matter that are thought to be fundamental components of the Universe, and
their role in the origin and evolution of structures, together with some new original results concerning improvements to the
spherical collapse model. In particular, we show how the spherical collapse model is modified when dynamical friction and
tidal torques are taken into account.
Published in Russian in Astronomicheskiĭ Zhurnal, 2007, Vol. 84, No. 3, pp. 195–226.
The text was submitted by the author in English. 相似文献
3.
Clastic sediments may have a strong deterministic component to their permeability variation. This structure may be seen in the experimental semivariogram, but published geostatislical studies have not always exploited this feature during data analysis and covariance modeling. In this paper, we describe sedimentary organization, its importance for flow modeling, and how the semivariogram can be used for identification of structure. Clastic sedimentary structure occurs at several scales and is linked to the conditions of deposition. Lamination, bed, and bedset scales show repetitive and trend features that should be sampled carefully to assess the degree of organization and levels of heterogeneity. Interpretation of semivariograms is undertaken best with an appreciation of these geological units und how their features relate to the sampling program. Sampling at inappropriate intervals or with instruments having a large measurement volume, for example, may give misleading semivariograms. Flow simulations for models which include and ignore structure show that the repetitive features in permeability can change anisotropy and recovery performance significantly. If systematic variation is present, careful design of the permeability fields therefore is important particularly to preserve the structure effects. 相似文献
4.
A generalised crustal structure of Fiordland is proposed.Detailed mapping in part of Western Fiordland has led to the recognition of a basement granulite facies lower crustal material, probably Precambrian in age) separated by a regional thrust zone from a cover sequence (amphibolite facies gneisses, of Lower Paleozoic age). With the recognition of the basement—cover relationship and the aid of aeromagnetic anomalies Fiordland has been divided into four, generally north-northeast trending, regions. The Western Fiordland region is composed chiefly of basement rocks. The Central Fiordland and Southwestern Fiordland regions are made up predominantly of amphibolite and greenschist-facies metasediments and gneissic granodiorites of the cover sequence, which in Central Fiordland have a regional dip to the east, off the basement. The Eastern Fiordland region is characterised by a series of basic, intermediate and acid intrusive rocks. The more prominent magnetic anomalies in Eastern Fiordland, Southwestern Fiordland, and a large anomaly off the coast of Western Fiordland, are all considered to be caused by intrusive bodies. The presence of a positive gravity anomaly over Western Fiordland, coupled with a gravity low offshore, is consistent with the lower crust being uplifted and exposed in this area. Continuing shallow and intermediate-depth seismic activity beneath Fiordland, as well as the large size of the gravity anomaly, suggest that tectonic forces are currently acting to maintain Western Fiordland at its unusually high level.Fiordland thus displays a cross-section of continental crust: Precambrian(?) metaigneous granulites in the lower crust; Lower Paleozoic metasedimentary amphibolitefacies gneisses and melted equivalents in the middle crust; Mesozoic intrusives, and overlying Cretaceous and Tertiary sediments in the upper crust. 相似文献
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Based upon the deep seismic sounding profiles carried out in the Tengchong Volcano-Geothermal Area (TVGA), western Yunnan Province of China, a 2-D crustal P velocity structure is obtained by use of finite-difference inversion and forward travel-time fitting method. The crustal model shows that a low-velocity anomaly zone exists in the upper crust, which is related to geothermal activity. Two faults, the Longling–Ruili Fault and Tengchong Fault, on the profile extend from surface to the lower crust and the Tengchong Fault likely penetrates the Moho. Moreover, based on teleseismic receiver functions on a temporary seismic network, S-wave velocity structures beneath the geothermal field show low S-wave velocity in the upper crust. From results of geophysical survey, the crust of TVGA is characterized by low P-wave and S-wave velocities, low resistivity, high heat-flow value and low Q. The upper mantle P-wave velocity is also low. This suggests presence of magma in the crust derived from the upper mantle. The low-velocity anomaly in upper crust may be related to the magma differentiation. The Tengchong volcanic area is located on the northeast edge of the Indian–Eurasian plate collision zone, away from the eastern boundary of the Indian plate by about 450 km. Based on the results of this paper and related studies, the Tengchong volcanoes can be classified as plate boundary volcanoes. 相似文献
7.
澳大利亚西部Pilbara(皮尔巴拉)克拉通的金矿化多与岩浆作用及构造形变事件有关。位于Pilbara克拉通中部的Mallina(马利纳)盆地是该区金矿化最为丰富的地区之一,其构造以强烈褶皱及横贯盆地的Mallina剪切带为主要特征,盆地内最大的金矿床Withnell（威思奈尔）矿床位于Mallina剪切带北侧,是典型的赋存于浊积岩中的构造控矿脉型金矿床。通过细致研究地表露头及岩芯特征,使用DIPS软件处理构造数据,揭示区内典型金矿化构造控矿要素,确立在剪切带变形控制下,金矿体的有利赋存构造位置为褶劈理S3发育较好、向南陡倾的剪切构造区,目标矿脉为近直立、向南陡倾的含黄铁矿石英方解石脉,为下一步找矿工作提出新的方向。 相似文献
8.
The stratigraphy of the highly deformed and overthrust supracrustal rocks of the Akjoujt area consists of two sequences separated by an angular unconformity. A new stratigraphic framework has been proposed that is virtually the reverse of previously published schemes. The oldest recognisable supracrustal sequence consists of metabasalts overlain by banded iron formations and semipelitic and quartz-rich metasedimentary schists, for which the name Eizzene group has been proposed. This is overlain with angular unconformity by orthoquartzite followed by a suite of siliciclastic rocks, mafic to felsic volcaniclastic rocks, flows and banded iron formations. This well-layered sequence is overlain by poorly layered monotonous submarine metabasalts and coeval dolerites. All the rocks above the unconformity have been assigned to the newly created Oumachoueı̈ma group. The supracrustal rocks of the Akjoujt area are preserved as a complex system of overlapping thrust sheets, representing the disjointed limbs of a large-scale recumbent syncline. Igneous and metamorphic basement, with basal Oumachoueı̈ma group metasedimentary rocks attached, has been overthrust and is preserved in synformal remnants within the supracrustal domain. These are the erosional remnants of refolding by later, upright events. The main tectonic episodes consisted essentially of two periods of thrusting and recumbent folding followed by two episodes of thin-skinned upright folding above the sole thrust. Overthrusting of the suite onto the Archaean Amsaga basement to the northeast along the sole thrust is believed to be a late-stage event. The idiosyncratic Fe–Cu–Au–Mg carbonate mineralisation style of the Akjoujt area shows evidence of having been generated more than once during the evolution of the host rocks. Starting with pre to syn-early thrusting events, the carbonate-rich mineralisation recurred at least until the upright folding. There is strong field evidence for a genetic link to carbonate-rich iron formations by remobilisation, but no evidence of a synvolcanic or synsedimentary mineralising event. 相似文献
9.
M.C. Oncescu 《Tectonophysics》1982,90(1-2)
A set of 26 earthquakes recorded by a newly installed telemetered network was used for a simultaneous inversion of hypocenters and velocities. The travel-times and their partial derivatives were computed for flat-lying layers of constant velocity gradients.After a velocity model was found and the 26 foci relocated, three different velocity models for three different zones covered by the network were succesfully inverted (with the foci kept fixed).The procedure was applied for first arriving P-waves and also tried for S-wave arrivals. Two low-velocity zones were put into evidence. 相似文献
10.
B. Mysen 《Contributions to Mineralogy and Petrology》1997,127(1-2):104-118
The anionic structure of aluminosilicate melts of intermediate degree of polymerization (NBO/T = 0.5) and with along the composition join (LS4-LA4) has been examined in-situ to ˜1480 °C, and compared with recent data for melts along the analog composition join
and with less polymerized melts along the join and O_5. With , the anionic equilibrium, (1) , adequately describes the structure. With , a second expression, (2) , is required because an additional structural unit, Q1, is stabilized in the melts. The enthalpy, , of reaction (1) increases from − 36 ±4 kJ/mol in the absence of aluminum to 34± 5 kJ/mol at and 64 ± 4 kJ/mol at Al/(Al + Si) = 0.45. Similar trends are reported for other alkali aluminosilicate melts. Least-squares
fitting of abundance of structural units as a function of temperature and bulk composition has been conducted. The unit abundance
is dominantly a function of temperature, Al/(Al +Si), and bulk melt polymerization. Configurational entropy and heat capacity
of mixing of melts above their glass transition temperatures have been calculated with the aid of the least-squares fitted
equations. The values of these parameters indicate that as the ionization potential of the metal cations increases, configurational
heat capacity of alkali aluminosilicate melts becomes temperature dependent. As a result, transport properties (viscosity,
diffusivity, and conductivity) of such melts will not show Arrhenian behavior even in the high-temperature range. Further,
discontinuous changes in entropy and heat capacity of mixing results from temperature-induced changes in types of structural
units in the melts. Such discontinuous changes would also be reflected in discontinuous changes of temperature-dependent transport
properties.
Received: 26 September 1996 / Accepted: 18 October 1996 相似文献
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Summary The crystal structure of scotlandite —a=4.505(2),b=5.333(2),c=6.405(6) Å, =106.24(3)o; space groupP21/m; cell content 2 {PbSO3} — was determined from singlecrystal X-ray diffractometer data. Scotlandite is isotypic with molybdomenite, PbSeO3. Lead is coordinated to nine oxygen atoms with Pb-Oav=2.75 Å, and possibly further to one sulphur atom with Pb–S=3.46 Å. The average S–O distance in the pyramidal SO3 group is 1.52 Å. The structural relationships to cerussite, PbCO3, are discussed.
With 2 Figures 相似文献
Die Kristallstruktur des Scotlandits, PbSO3
Zusammenfassung Die Kristallstruktur des Scotlandits —a=4,505(2),b=5,333(2),c=6,405(6) Å, =106,24(3)o; RaumgruppeP21/m; Zellinhalt 2 {PbSO3} — wurde aus Einkristall-Röntgendiffraktometerdaten bestimmt. Scotlandit ist mit Molybdomenit, PbSeO3, isotyp. Blei wird von neun Sauerstoffatomen mit Pb–Oav=2,75 Å und möglicherweise zusätzlich von einem Schwefelatom mit Pb–S=3,46 Å koordiniert. Der durchschnittliche S–O-Abstand in der pyramidalen SO3-Gruppe mißt 1,52 Å. Die strukturellen Beziehungen zu Cerussit, PbCO3, werden diskutiert.
With 2 Figures 相似文献
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14.
Takuo Tamura Akira Yoshiasa Kazuaki Iishi Setsuo Takeno Hironobu Maeda Shuichi Emura Kichiro Koto 《Physics and Chemistry of Minerals》1996,23(2):81-88
The local structure around Co, Zn and Sr atoms in incommensurately modulated, melilite-type X2T1 T 2 2 O7 (X=Ca and Sr, T1=Mg, Co and Zn, T2=Si) solid-solutions has been investigated by EXAFS analyses. The modulated structure was confirmed in Ca2-xSrxCoSi2O7 solid-solutions with X=0.0 to 0.6 and for both Ca2Mg1-YCoYSi2O7 and Ca2Mg1-YZnYSi2O7 solid-solutions over the whole compositional range at room temperature. The actual bond-distances determined by the EXAFS method for the T1 site (Co-, Zn-O) in the modulated structure are longer than the mean bond-distances obtained from the X-ray diffraction method. This is attributable to the libration of the T1 tetrahedra. In the Ca1-XSrXCoSi2O7 solid-solution both the Sr-O and Co-O distances by the EXAFS method for the X-site increase from Ca end-member to Sr end-member. These increases are respectively 0.8% and 0.6%. This means the local expansions of the tetrahedral sheets and of the XO polyhedra are well matched. In the modulated Ca2Co1-YMgYSi2O7 and Ca2Zn1-YMgYSi2O7 solid-solutions, the actual Co-O and Zn-O distances for the T1-sites are nearly constant in the whole compositional range. The compositional variations of the local structure around the cations in the solid-solution are different for the X and T1 sites. It is concluded that the local geometric restriction for the size of substituted cation in X site is larger than that in T1 site. The dimension of the tetrahedral sheet puts restriction on the size of the cations situated at the interlayer X sites. In other words, the different behavior of the local geometric restriction between the X and T1 sites is an important feature of the melilite structure and is also related to the modulated structure. 相似文献
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Deception Island is an active volcano with a large structural collapse caldera that has been interpreted by several investigators as having been generated by different processes. The general stratigraphy and structural study of the volcano is presented, with special emphasis on the distribution and structural disposition of the different stratigraphic units. The rocks of Deception Island have traditionally been divided into pre- and post-caldera products. A subdivision of the pre-caldera deposits, called ‘pre- and syn-caldera deposits,’ has been observed in two main units. Bulk magnetic susceptibility analyses are used to support the field stratigraphy presented. The localization and distribution of dikes is used to assign the central collapse of the volcano to rifting induced by tensional tectonics occurring in the Bransfield Strait and the presence of transcurrent faults around the island. 相似文献
17.
R. Elsdon 《Geological Journal》1986,21(2):151-168
The Rough Point sill, which is one of the thickest of a large number of sills intruded into the Appin Group metasediments of the Dalradian sequence in north Donegal, contains a number of internal features including mafic:felsic banding, pegmatite bands and significant variations in grain size. There are also appreciable variations in mineralogy, particularly the proportions of plagioclase and amphibole, and in the major and trace element chemistry. Together these features indicate that the sill is, like the metasediments which it intrudes, inverted, and is therefore older than the Caledonian F2 structures which caused the inversion. Disruption of the sediments at the sill contact is also earlier than the F2 event. The timing of the basic magmatic episode together with the geochemistry of the sill invite comparison with the metadolerites of the southwest Highlands of Scotland. 相似文献
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广东凡口铅锌矿床控矿构造型式 总被引：4，自引：1，他引：4
文章通过对现有凡口矿区地质资料的研究与分析,结合矿区成矿地质条件及其矿床地质特征,认为凡口矿区的控矿构造型式为逆冲推覆构造体系,从而理顺了矿区内各组断裂构造间的相互关系。F203是区内Ⅰ级断裂构造,在以F203为主推滑面的逆冲推覆构造应力作用下,其推覆体中往往同期形成次一级的叠瓦式逆冲断层组,为区内Ⅱ级断裂构造。在Ⅱ级断裂构造之间,又有一组近NE向的断裂组,为区内Ⅲ级断裂构造。上述3个不同级次的构造是逆冲推覆构造演化过程中逐次形成的,时间上略有先后。其成生的力学机制相同,即共同处于一个构造应力场之下。岩层在逆冲断层扩展时发生应变,在软弱部位引起褶皱或小褶曲,常形成一定的扩容空间,当矿液沿断裂主通道(主滑面)向上运移时,易于在此部位聚集淀积成为矿体。根据其逆冲推覆构造体系控矿的规律性,指出凡口矿区寻找隐伏矿床的有利部位。 相似文献
20.
Summary The objective of this study is to determine the parameters which influence coal's mechanical behaviour. The two coals examined (HBL, Simon, France and Barro Banco, Brazil) structurally originated from different deposits. The differences are readily explained by the contrasting composition of vitrain, clarain, durain and fusain. Their mechanical behaviour is linked to their petrographical composition. The Lorrainain coal behavioural pattern was evaluated. It is elastobrittle or elastoplastic with progressive failure. Brazilian coal behaves according to a pattern of elastoplastic with progressive failure or perfect elastoplastic. 相似文献