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1.
Dendritic cordierite occurs in argillaceous hornfels from the Toki area, Gifu Prefecture, Japan. The cordierite crystal consists of c-arms elongated parallel to the c-axes and a-arms perpendicular to the c-axis. The latter arms could be divided into six kinds of untwinned a-arms with different growth directions elongated parallel to the respective a-axis and twinned a-arms elongated parallel to the (110) twin plane. A-arms branch out from c-arms or other a-arms with different growth directions and c-arms sometimes branch out from a-arms, leading to a tree-like structure. Each of the c-arms contains three kinds of domains related by a three-fold axis about the c-axis. These domains are irregularly distributed without any relation to the shape of the c-arm and the domain boundaries are of zigzag shape. This domain arrangement suggests that c-arms grew as hexagonal cordierite and were later transformed into orthorhombic cordierite. The fact that each untwinned a-arm has a fixed growth direction to its orientation suggests that the a-arms grew as an orthorhombic cordierite. From the growth directions of c- and a-arms, orthorhombic and hexagonal phases are considered to grow preferentially along the c- and a-axes, respectively. The branching of a new arm is explained by nucleation on an old arm with a different preferred growth direction. The preferential growth is discussed in terms of a significant chemical potential gradient of the cordierite component. This has been preserved in the mineral zoning observed in the matrix around the cordierite porphyroblast.  相似文献   

2.
To explain both origin and outcome of disasters (natural, technical, and war-borne), as well as social action during disasters proper, a macrosociological model of internal causation is introduced (PERDUE). It consists of six stages of possible, and of most likely paths of social change between these six (Peace is founded, Everyday routine, Rising class struggle, Disasters strike, Unconditional surrender of collective defence, and Evaporation of common values). The stages are developed by making use of three dimensions of social change (rapidity, radicality, and rituality), and described.  相似文献   

3.
The vein-type gold deposits of middle to late Archean age constitute one of the major sources of gold production in the world. These deposits are highly diverse in character, but are invariably found in proximity to mafic and ultramafic volcanic rocks, and closely associated with tectonically disturbed zones, or breaks, in the ancient crust. Using the Larder Lake break of northern Ontario and Quebec as a model, a general theory of genesis for such deposits is proposed.The Larder Lake break is of linear configuration, up to four miles wide, and extending over a distance of approximately 150 miles. Many rich and extensive vein-type gold deposits are associated with it. This break is recognized as a highly folded and faulted, dominantly sedimentary stratigraphic unit, formed as part of the development of the Blake River geosyncline of the Abitibi greenstone belt. Faulting is pervasive within the break but it is non-continuous.Under an oxygen-poor, somewhat acidic weathering regime believed extant in Archean time, gold and associated constituents, derived as weathering products from mafic and ultramafic volcanics, appear to have been concentrated as solutions and sols in muddy surficial accumulations along a paleo-continental margin. On transfer to a shallow marine environment, the gold-bearing solutions became concentrated mainly as cherty and pyritic evaporitic residues. These residues, infolded and variably metamorphosed and remobilized during ensuing geosynclinal development, formed the numerous and apparently heterogeneous gold deposits of the Larder Lake break.Mode of redistribution of gold-bearing residues and metamorphism of their host rocks varies widely. In mild form, little vein development is present and original sedimentary features of the host rock are often preserved. In more extreme cases, true hydrothermal veining is evident and complete recrystallization of the host rock has taken place, sometimes to the extent of formation of a melt with intrusive capabilities. In any case, the gold and related vein constituents remain closely associated with the primary host material and alteration effects are largely derived from the recrystallization of original host rock constituents.The suggested mode of genesis clarifies the relationship between various types of break-related, vein-type gold deposits and offers an explanation of the complex stratigraphy and structure of the break environment. It also suggests a penecontemporaneous relationship between the Larder Lake break and other auriferous breaks, of varying configuration, within the Superior Province of the Canadian Shield. The concept can be used advantageously in exploration for new breaks and new deposits.  相似文献   

4.
Defining the urban   总被引：1，自引：0，他引：1  
A. Sayer Dr. 《GeoJournal》1984,9(3):279-284
In everyday discourse, the term urban causes few problems, but it certainly has for social theory. While the paper accepts the recent consensus that the term no longer serves to refer to a distinct object in capatalist societies, it argues that the familiar arguments have been confused by inadequate approaches to the problem of definition and inadequate concepts of space and ideology. Clarification of such definitions is a prime task of social theory and different methods of definition are discussed. The paper ends with a commentary on what is probably the best attempt at defining the urban — Raymond Williams The Country and the City.  相似文献   

5.
Zusammenfassung Im NW-Karakorum, einem Innensegment der großen zentralasiatischen Faltengebirgsscharung, überschneiden sich die Einflüsse der variskisch schon weitgehend konsolidierten Pamirischen Scharung und der jungalpidisch noch hochaktiven Himalaya-Syntaxis, wobei die zone axiale des NW-Karakorum die paläogeographische und tektogenetische Schnittlinie darstellt.Die in den einzelnen Baueinheiten (Zonen I bis V) spezifischen Formungspläne, deren relative Altersfolge (b1-b2-B3-B4) durch eine tektonische Gefügeanalyse ermittelt ist, werden von einem jüngsten B5-Plan (dem heute vorherrschenden WNW-ESE-Generalstreichen des Gebirges) überprägt. Im Verlaufe dieser letzten radialen Einengung fanden steile, nord- und südvergente Auschiebungen statt. Weiträumige Deckenüberschiebungen sind diesem Baustil fremd!
Summary The geological exploration of the NW-Karakoram, carried out by the author during the German-Austrian Himalaya-Karakoram Expedition in 1954, allows an insight into the complicated development of the Alpine type mountain building within the syntaxial bend of Central Asia.The zone axiale of the NW-Karakoram (Batura Muztagh), with its synorogenetic young cretaceous evolution of different granodioritic rocks, seems to mark a boundary-line of influences between the mainly Variscan consolidated Pamir Culmination, and the Alpine activated Himalaya Syntaxis. Contrasting to the northern part of the NW-Karakoram (the Tethys-Karakoram, see Abb. 2 and 4 / Zones V-Va), which in all its paleogeography and tectonic features belongs to the southern extremity of the Pamirs, the southern part (Zones I–III) on the other hand shows clear relations to the record of the Himalaya System. Especially the Tertiary (about Oligocene) synorogenetic regeneration (granitization) of the Nanga Parbat Dome at the end of the Jhelum-Wedge, has extended its influences, mainly as dynamometamorphism, up to the zone axiale and its crystalline schistose mantle-rocks (Zones III–IV).The results of a tectonic analysis of the different zones of the actual NW-Karakoram (II–V) show that each zone has its special B-tectonic structure of older deformation (see Abb. 3 and Taf. 15: b1-b2, B3, B4). Later the entire region was exposed to an unique pressure of a younger act of deformation (B5), which caused the present actual general striking (WNW-ESE) of the zones. This B-tectonics are succeeded by huge elevations, mainly as different bloc-movement, of the mountain arcs. Contrasting to the synkinematic evolution of the granodioritic axis, distinct dykes of different igneous rocks of acid as well as basic composition, appearing in the zones III-IV-V, are younger than the B-tectonics.Sections across the NW-Karakoram (Abb. 4) show the change in vergency within the zone axiale, without a remarkable nappe structure in the whole area.

Als Habilitationsschrift der Naturwissenschaftlichen Fakultät der Universität München am 26. Juni 1957 eingereicht.  相似文献   

6.
Summary A proposal is under consideration to construct a dam on an experimental basis by a cast (or directional) blasting technique, DBT. The dam site is located at Bharari Khad, a tributary of the Sutlaz river in Himachal Pradesh. Site investigations have been completed and a large scale blast has been designed for construction of the experimental dam.The paper describes the basic design concept of DBT and application of throw and caving methods for construction of dams. The preliminary tests required to design the blasting pattern are detailed. The technique has a great potential because it reduces construction cost and time particularly in inaccessible mountain regions.  相似文献   

7.
The volcanic stratigraphy and petrogenesis of the Oman ophiolite complex   总被引：12，自引：0，他引：12  
The volcanic stratigraphy and trace element geochemistry of the Oman ophiolite complex indicate a multistage magmatic origin comprising: (1) magmatism due to sea-floor spreading in a marginal basin; (2) magmatism associated with discrete submarine volcanic centres or seamounts; (3) magmatism associated with crustal uplift and rifting; and (4) magmatism associated with continent-arc collision.Trace element petrogenetic modelling is used to investigate the nature of the mantle source region and the partial melting and fractional crystallization history for each magmatic event. The petrogenetic pathway for the sea-floor spreading lavas requires a high degree of melting of a mantle that was depleted in incompatible elements prior to subduction but subsequently selectively enriched in certain elements (mostly LIL elements and H2O) from an underlying subduction zone; it also requires magma mixing in an open system magma chamber prior to eruption. The seamount lavas were probably derived by a similar degree of partial melting of a similar source, but fractional crystallization was restricted to smaller high-level magma chambers. The rifting lavas were derived from a mantle source that was more depleted than the seamount lavas prior to subduction but which was later modified by a larger subduction zone component. The syn-collision lavas were however derived from an enriched mantle source, which probably underlay the passive continental margin rather than the marginal basin complex. Results such as these may provide considerable insight into the petrogenetic changes accompanying the transitions from spreading to arc volcanism in a supra-subduction zone setting.  相似文献   

8.
Anton Gosar 《GeoJournal》2000,52(2):107-117
Europe in general is in a great state of change. States uniting with difficulty, states collapsing in pain, newly freed states struggling for new political, economic, and social identities - it is a region in a true transition. The paper is focussing primarily on the European Shatter Belt, formerly known as Eastern Europe. This is in fact a subset of new and old nation-states in the region of Central and Eastern Europe or, to use an older, but increasingly popular term, Mitteleuropa (Ruppert, 1997). Mitteleuropa is reemerging from the commotion resulting from the collapse of the old political order - communism. Our focus in this presentation is on personal experiences and observations. We will note the progress and positive dimensions of the change (transition) in the light of Europe's and NATO expansion. We will address the issues at two scales- at the international/national level and then, at the level of a Slovenian case study. This will enable us to discuss the natural system of the process of enlargement and incorporate supporting material of geographical, historical and social nature as envisioned by Hartshorne. Since the collapse of communism, the region has experienced some serious traumas that vary in intensity across the region. Probably the greatest pain has been experienced in the former Yugoslavia - an estimated 150,000 have perished and about 2.5 millions have been displaced within and outside the country. Chaos still exists despite the protectorate arrangement in Bosnia. The hot spot Kosovo has yet to be calmed down. In parts of the region economic pain has been considerable. Every state of Mitteleuropa experienced absolute economic decline from 1990–1995; high inflation rates, increased economic inequality, high levels of poverty, increase of crime and more. Economic and psychological stress effect demographic processes. Things have partly changed to the better in the most recent years. The adoption of capitalism and a democratic political system has been painful, disorienting, and is still in progress. The democratization process varies considerably across the region and in some states is in jeopardy. Reformed communist parties had staged a restoration in nearly all of the states - in some winning the control of the government, in others gaining strong and influential positions, or both. But, two major processes promise future democracy, rule of law, wealth and stability in general. This is the decision of the member states of the European Union and NATO to incorporate some/several states of the Shatter Belt into their own zone of protection and/or federation. Nation-states of the region tend to follow the EU Agenda 2000 rules with Slovenia one of the first!  相似文献   

9.
Object of study is the insight of traditional herbalists in the landscape-ecological factors wich control the growth of the plants they use for healing their patients. The extent of this insight determines their capacity to adapt to environmental changes such as deforestation and soil degradation. This paper deals with the landscape-ecological perception of herbalists who live in an area with sharp landscape contrasts and drastic changes in landuse: the Keiyo Escarpment in the Rift which links the cool and humid Uasin Gishu Plateau at a level of more than 2600 m above sea level, with the warm and semi-arid Kerio Valley at 1250 m. The landuse changes of the last 50 years are caused by growing population density, loss of traditional attitudes towards the value of the land, and changes in forest cover. Data on local knowledge are acquired through interviews and field visits. The corresponding western knowledge is derived from aerial photographs and existing reports and maps. Six landscape-ecological zones are recognized. They are named after topography (wareng, mosop, soin), vegetation (teguming, korget) or landuse (tumdo). These zones coincide with the units of the agro-climatic map of Kenya. Apart from geology, all the factors of the hierarchical model used in western-based landscape ecology (climate, geology, relief, water, soil, vegetation and fauna) are included in the indigenous perception of the landscape, but the hierarchical order is not necessarily the same: e.g. the herbalists assume that rock grows in the soil instead of the other way around, and that forests attract rain. From the herbalists' point of view, deforestation and the establishment of small-holder agriculture is less serious for their trade than the replacement of indigenous trees by plantations with exotic species. They adapt to the loss of the forest by travelling to areas with comparable landscape-ecological conditions or, especially in the case of women and older male herbalists, by planting the required species in the garden. According to the herbalists, good climate and fertile soil stimulate species diversity, but best medicinal performance give plants on soils which are periodically dry.  相似文献   

10.
The Lluta collapse of northern Chile is one of the oldest recognizable landslides (>2.5 Ma) in a hyperarid continental setting. This paper develops a conceptual landscape evolution model of the Lluta collapse and analyzes the controls of mass wasting and erosion/sediment transport in channels on the topographic development. The data presented here imply that high relief along a topographic scarp, surface fracturing, elevated groundwater table during a more humid climate and an aquitard underlying permeable ignimbrites are preparatory causal factors for landsliding >2.5 Ma ago. A strong seismic event then possibly resulted in the displacement of ca. 26 km3 of mass. Subsequent modification of the landslide scar occurred by backward erosion, resulting in the establishment of a dendritic drainage network and the removal of an additional ca. 24 km3 of material. It appears that this mass was produced by mass wasting in the headwaters, and exported by high-concentrated debris flows in channels. In addition, morphometric information suggest that whereas the geometrical development of the Lluta collapse has been controlled by gravitational mass wasting, the rates of the development of this geomorphic unit have been limited by the export rates of mass and hence by the transport capacity of the flows.  相似文献   

11.
Summary A criterion for determining normal stress levels of shear failure of rock masses is developed, then the shear resistance of the rock mass, based upon the geometric model of en-echelon jointed rock masses, can be evaluated for low normal stress levels or high normal stress levels respectively by using the method proposed in this paper. Finally, a procedure generating joint patterns which are described with individual joint geometry parameter or multi-joint geometry parameter is discussed.  相似文献   

12.
IPCCs statement in its 1995 report (IPCC 1996) that a human influence was discernible in global climate has been widely quoted but often misunderstood. The character of the evidence underpinning this detection statement is explained so that its strengths and weaknesses can be better understood and the subtleties of its message better appreciated. To demonstrate the close linkage between the government-approved summary and the underlying chapters of the IPCC report the detailed evolution of the detection statement from first draft through to the form finally approved by the IPCC is described.  相似文献   

13.
The introduction of roofbolting in the UK coal mining industry has been well documented and is an example of reinforcement design utilizing a design by measurement or observational approach. This has involved detailed monitoring of rock strata movements and rockbolt loads at a large number of sites. Analysis of roadway deformation monitoring information from across the Selby coalfield provided an ideal opportunity of assessing how geological and stress variations affect the stability of reinforced coal mine roadways. Statistical analysis of this data has confirmed the detrimental effects of maximum horizontal stress direction and relatively weak roof geology on the magnitude of roof deformation. Further analysis has led to the development of a roof lithology index for assessing the quality of the immediate roof geology and the use of geological hazard analysis for providing useful information for the development of a stability index for assessing support requirements of existing and future roadways. This investigation has also verified previous observations regarding mechanisms controlling roadway deformational behaviour and highlights the importance of the site-specific nature of reinforcement design.  相似文献   

14.
The object of the paper is to analyze changes in modal and port allocation of general cargo flows in Sweden's foreign trade between 1960 and 1976. It summarizes some results of a forthcoming report on the project Tendencies in Liner Shipping financed by the Transport Research Delegation, Stockholm.  相似文献   

15.
J. Eyles Dr. 《GeoJournal》1984,9(3):247-253
Social geography is seen as part of an integrated social science, being important for its emphasis on people and its maintenance of the importance of the spatial in social theory. The paper proceeds by looking at the problems of definition, concluding that most definitions are time-specific. Despite this fact, they remain influential and also enable the three main strands of social geographical development to be identified, these being the empirical, the theoretical and the practical. These themes are elaborated in turn as are the relationships between them. While the empirical has tended towards empiricism, the theoretical is perhaps only just beginning to ground itself in the study of the real world. But the practical — or policy element — is seen as being underdeveloped. The conclusion addresses the possible fusion of the three strands.  相似文献   

16.
Conclusion This paper has described some of the changes that have occurred in the geography of the UK's coal industry in a period when decline was the keynote, and attempted to illustrate some of the developments that are occurring in the late 1970s with implementation of the Plan for Coal. Launched at a time when the complete collapse of European energy supply seemed a distinct possibility, that Plan is encountering many problems in its implementation, and its unmodified completion must remain in doubt. The Plan 1974 and its successor embody a fundamental change of direction for the coal industry — from contraction to expansion.But although there is a change of direction at the national scale, at the inter- and intra-regional scales the direction remains largely the same. The dominance of the central coalfields is likely to increase further, while within these areas the trend towards large-scale deep mines in the concealed sections remains strong. Indeed achievement of the new desired direction at the national level, based as it must be on an industry that is price-competitive with other energy sources, may be dependent upon an intensification of these regional trends towards concentration of investment in areas where mining conditions are favourable and high-productivity, low-cost production can be achieved. It is also being recognized that removal of the burden of high-cost inefficient collieries in less favoured, mainly peripheral fields may also be vital to the competitive position:-the overall competitiveness of the industry is ... at present adversely affected by a small proportion of capacity where productivity is low and costs are high, mainly as a result of difficult working conditions. Closure of uneconomic pits as they became worked out will improve the industry's ability to compete with other fuels, (Secretary of State for Energy 1978).It thus appears that in the last quarter of the twentieth century the coal industry in the UK will become more and more focused on especially favoured areas in the central parts of the country, through the twin process of shedding loss-making activities in less favoured peripheral fields, and investing in the ample resources that underline the English lowlands.  相似文献   

17.
Government policies for the use of publicly owned environmental resources in Australia are often justified as being for the economic good of the nation. Yet there has been little enquiry about how Australians perceive economic good in the context of the use of environmental resources. The residents of five State government electorates of Perth and one in regional south west Western Australia were surveyed. Their perceptions of economics, the environment and resources in relation to public policy were assessed. The differences in the responses were greater between the different electorates, than between the different socio-economic strata within the same electorate. This paper examines the spatial variability of the results and raises the possibility of developing a socio-locational indicator of attitudes which could provide a tool for policy implementation.  相似文献   

18.
Two orthogneiss suites dominate the Silvretta nappe. Primary crystallization of the larger suite (younger orthogneisses) is assumed to be Ordovician in age. The second, adjacent magmatic suite consists of older, alkaline to calc-alkaline, ultrabasic, basic to intermediate and granitic rocks known as older orthogneisses. U-Pb data of multigrain zircon fractions, as well as single zircon stepwise evaporation 207Pb/206Pb results suggest a latest Proterozoic to early Cambrian intrusion age for the protoliths of the older orthogneisses as both dating methods yield early Cambrian crystallization ages of 526±7 and 519±7 Ma for an alkaline granite gneiss; similar results were obtained for two neighbouring calc-alkaline orthogneisses (207Pb/206Pb ages of 533 ± 4 and 568 ± 6 Ma, respectively). The crystal habitus corresponds to P5, S19 and S9 zircons of magmatic origin. Whole-rock initial Sr isotope ratios indicate a primitive source. The igneous protoliths of these older orthogneisses represent a fragment of a Cadomian (Pan-African) crust found in places within the basement of the European Hercynides.  相似文献   

19.
A technique has been developed and tested to analyse 207Pb/206Pb apparent ages by thermal evaporation of radiogenic lead directly from untreated whole zircon grains (0.3 mm). The evaporation analyses are performed in the double-filament arrangement of a thermal ion mass spectrometer (ThIMS). The method is a powerful tool to distinguish between different lead components occurring in the same grain because differing activation energies of the competing lead components cause their sequential evaporation from the zircons. The evaporation of test samples results in 207Pb/206Pb apparent ages in good agreement with U/Pb ages known from literature: single zircons from a granite of the Marble Mountains/California yield an age of crystallization of 1,410±30 Ma; Ceylon zircons from heavy-mineral bearing gravels yield 560± 40 Ma as age of crystallization of the pegmatitic gravel sources; individuals from a heterogeneous zircon population of a diatexite from the Southern Schwarzwald/SW-Germany indicate metamorphic zircon formation around 500 Ma and the existence of Middle-Proterozoic relics (1.95±0.05 Ga).The evaporation analyses revealed closed-system U/Pb evolution of the crystalline domains of all investigated zircons irrespective of discordancy-trends documented by U/Pb analyses on related zircon concentrates. Therefore the majority of discordia-lines derived from U/Pb isotope distributions of zircon samples are supposed to be due to phase mixing. Lead components from the crystalline domains are concordant end members of the mixing arrays. Open-system behaviour and U/Pb fractionation should be attributed only to phases with low Pb activation energies eg. metamict zircon domains or intergrown non-zircon minerals.  相似文献   

20.
This paper studies the basis and nature of the long-term factors that may have influenced the electoral behavior of St. Petersburgers between 1989 and 1995 from the perspective of geography. Our analysis shows two distinct periods in St. Petersburgs recent electoral history marked by differing behavioral motivations of voters in the city. The first period was marked by only one ideological cleavage between marketers and hard-liners. In 1993 protest motivation managed to erode the predominance of ideology as the determining variable in voting behavior, and began to act as a new independent variable. This marked the beginning of the second period. Four major groupings of St. Petersburg electorate are described in terms of the basic ideological cleavages, party affiliations and geographical gravity centers.  相似文献   

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