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91.
FABRIZIO INNOCENTI DAVID S. WESTERMAN SERGIO ROCCHI SONIA TONARINI 《Geological Journal》1997,32(2):131-151
The Montecristo monzogranite (MM) is a near-circular peraluminous monzogranite pluton occupying the entire 10 km2 of Montecristo Island. Outcrops of country rock are scarce, and are mainly roof pendants of metagabbros and calcsilicate hornfels of the Apenninic ophiolite sequence. Emplacement of the pluton (Rb–Sr age=7·1±0·2 Ma), following the early Miocene onset of continental collision, occurred during an extensional phase which migrated eastward via a combined process of subduction–delamination. The MM rocks are strongly porphyritic, the assemblage being composed of alkali-feldspar, quartz, plagioclase (all occurring as mega- or phenocrysts), biotite and minor cordierite. Accessory minerals include tourmaline, apatite, zircon, ilmenite, allanite, monazite, rutile and hellandite. Reconstructed crystallization histories for the mineral phases reveal a polybaric crystallization starting at about 5 kb. Textural variations of MM occur in sharp contact with each other; darker types often form globular masses containing fewer megacrysts and more abundant mafic microgranular enclaves. Geochemical, isotopic and petrographic data indicate that the MM magma was produced by anatectic melting of an intermediate to deep pelitic crustal source. On the basis of the geochemical and mineralogical characteristics of the enclaves, modification of their parent magma occurred by crystal fractionation coupled with mixing and mingling of components from the MM magma. The limited geochemical variation in MM is interpreted as due to crystal fractionation processes during the magma's ascent. Younger porphyritic dykes with more potassic and alkaline affinities cut the pluton; these dykes are concentrated in a major fracture zone and are associated with contemporaneous pseudotachylites. © 1997 John Wiley & Sons, Ltd. 相似文献
92.
DAVID F. SCOTT 《水文研究》1997,11(6):543-555
A wildfire in an afforested research catchment presented the rare opportunity to compare the hydrological effects of wildfire with the effects of clearfelling in the same catchment in the Jonkershoek Valley, in the south-western Western Cape Province of South Africa. The timber plantation, which occupies 57% of the 2 km2 catchment, had been clearfelled and re-planted to Pinus radiata roughly five years before the fire. The effects of the two treatments on total flow, storm-flow and quick-flow volumes, peak discharge and storm response ratio were determined by means of multiple regression analysis, employing the dummy variable method to test for the significance of treatments. Both clearfelling and wildfire caused significant increases in all the stream-flow variables analysed. But the clearfelling effect was dominated by large increases in total flow (96% over three years), of which storm-flow and quick-flow volumes formed only minor parts. After the wildfire, by contrast, increases in total flow were small (12%) but the storm flow increases were three- to four-fold in the first year and roughly double in the second year. The wildfire caused fire-induced water repellency in the soils which led to overland flow on mid-slope sites, where soil infiltrability normally far exceeds local rainfall intensities. It is argued that these results support the hypothesis that stream-flow generation processes were changed by the wildfire in that overland flow made a direct contribution to storm flows, but that clearfelling had no such effect. © 1997 by John Wiley & Sons, Ltd. 相似文献
93.
Regional dynamics in the globalising wine industry: the case of Marlborough, New Zealand 总被引:1,自引:0,他引:1
The rapid expansion of the New Zealand wine industry has rested largely on a specific wine commodity form, Marlborough Sauvignon Blanc. Global demand for a specialised product has provided the impetus for substantial development at the regional level, an increasingly complex industry structure, and for the intrusion of international capital. This paper explores the contests and relations within the industry through attention to the commodity's value-added chain, wherein recent developments are interpreted as a contest over the brand rents. The contemporary situation therefore may be explained through overlapping organisational and geographic framings of these relations: producer versus buyer-driven dynamics; regional–national and global interests; and inter- and intra-corporate strategies. The commercial contest for control of the region-varietal commodity reveals some paradoxical outcomes in which the region is reaffirmed as a site of investment in an evidently globalised industry, and the significance of who controls what fraction of the value chain is re-asserted. 相似文献
94.
Abstract This paper is a review of research themes in the field of geographical information systems, as identified from the evidence submitted to the Department of the Environment's Committee of Enquiry into the Handling of Geographic Information (the Chorley Committee) which reported in 1987, the papers and discussions at a workshop on research in GIS held in Edinburgh in 1987 and jointly sponsored by the Economic and Social Research Council in the United Kingdom and the National Science Foundation in the United States, and the proceedings of an international symposium on the research agenda for GIS, organized by the Association of American Geographers and held in Washington in 1987. The interpretation of and the emphases given to these themes are, however, the author's own 相似文献
95.
MICHAEL F. WORBOYS HILARY M. HEARNSHAW DAVID J. MAGUIRE 《International journal of geographical information science》2013,27(4):369-383
Data modelling is a critical stage of database design. Recent research has focused upon object-oriented data models, which appear more appropriate for certain applications than either the traditional relational model or the entity-relationship approach. The object-oriented approach has proved to be especially fruitful in application areas, such as the design of geographical information systems which have a richly structured knowledge domain and are associated with multimedia databases. This article discusses the key concepts in object-oriented modelling and demonstrates the applicability of an object-oriented design methodology to the design of geographical information systems. In order to show more clearly how this methodology may be applied, the paper considers the specific object-oriented data model IFO. Standard cartographic primitives are represented using IFO, which are then used in the modelling of some standard administrative units in the United Kingdom. The paper concludes by discussing current research issues and directions in this area. 相似文献
96.
ANDREW K. SKIDMORE PHILIP J. RYAN WARWICK DAWES DAVID SHORT EMMETT O'LOUGHLIN 《International journal of geographical information science》2013,27(4):431-445
Abstract Mapping forest soils using conventional methods is time consuming and expensive. An expert system is described and applied to the mapping of five forest soil-landscape units formed on a single granitoid parent material. Three thematic maps were considered important in influencing the distribution of soils. The first showed the distribution of nine classes of native eucalypt forests, and the second and third were derived from a digital elevation model and represented slope gradient and a soil wetness index combined with topographical position. These layers were input to a raster based geographical information system (GIS) and then geometrically co-registered to a regular 30 m grid. From a knowledge of soil distributions, the relationships between the soil-landscape units and the three data layers were quantified by an experienced soil scientist and used as rules in a rule based expert system. The thematic layers accessed from the GIS provided data for the expert system to infer the forest soil-landscape unit most likely to occur at any given pixel. The soil-landscape map output by the expert system compared favourably with a conventional soil-landscape map generated using interpretation of aerial photographs. 相似文献
97.
98.
99.
DAVID HOOSON 《The Geographical journal》2004,170(4):377-379
100.
DANYUSHEVSKY LEONID V.; EGGINS STEPHEN M.; FALLOON TREVOR J.; CHRISTIE DAVID M. 《Journal of Petrology》2000,41(8):1329-1364
The H2O contents and trace-element abundances are presentedfor two well-studied suites of mid-ocean ridge basalt (MORB)glasses from the Northern East Pacific Rise (EPR, 911°N)and the South East Indian Ridge (SEIR, 127129°E).Exactly the same region of the glass samples has been analysedfor these components using microbeam techniques. Our data allowexamination of the fine details of H2O geochemical behaviourduring MORB genesis. We demonstrate that relative H2O contents[i.e. H2O/(another incompatible element)] vary systematicallywith increasing (La/Sm)N in MORB glasses from both the EPR andSEIR. This indicates that H2O behaves like other incompatible(in peridotite mineralogies) elements during MORB petrogenesis,and is primarily controlled by solidmelt partitioning.However, the relative H2O contents of MORB glasses from theSEIR are higher than in glasses from the EPR at a given (La/Sm)N,demonstrating global variations in the H2O contents of MORB.Despite regional differences in relative H2O contents, the incompatiblebehaviour of H2O is similar in both studied regions. The relativeincompatibility of H2O varies systematically with increasing(La/Sm)N: in depleted MORB, H2O is similar to La whereas inEMORB, H2O is similar to Ce. Similar patterns of varying relativeincompatibility (to REE) are displayed by Zr, Hf, and P. Ourdata are best explained if H2O is stored in the mantle in thesame phase with LREE (clinopyroxene?) at sub-solidus. Regionalvariations in relative H2O contents in EMORB that have moreradiogenic Sr, Nd and Pb isotopes might be explained by differencesin the nature of enriched components recycled via subductionprocesses. However, when EMORB have the same radiogenic isotopecompositions as NMORB within a segment, relative H2O contentsin EMORB probably reflect local processes that lead to enrichmentin incompatible elements. Regional differences in relative H2Ocontents of NMORB may reflect either initial variations in theEarths mantle or inhomogeneities left after formationof the continental crust. KEY WORDS: glass; geochemistry; H2O; MORB; petrology 相似文献