Water and sediment outbursts from advanced Franz Josef Glacier,New Zealand   总被引：1，自引：0，他引：1  

Timothy R. H. Davies  Chris C. Smart  Jill M. Turnbull 《地球表面变化过程与地形》2003,28(10):1081-1096

The Franz Josef Glacier, Westland, New Zealand, has a history of catastrophic sediment‐laden outburst ?oods associated with extreme rainfall events when the glacier toe is advanced over its own sediments. Consideration of these events and inspection of recent sediment deposits suggest that there are three distinct modes of outburst. The ?rst is associated with fans fed by over?ow along the glacier margin. As the glacier has advanced across its own fore?eld gravels, it is inferred that the primary drainage conduit has developed a reach of negative slope. In high ?ows massive boulders can block the conduit, trapping lesser clasts. The resulting backup of water causes over?ows through marginal moulins, producing the fan type of deposit. The second type of outburst deposits massive imbricated boulders at a greater or lesser distance from the glacier portal. In this case, pressure buildup drives the blockage out of the portal where the boulders deposit. Smaller materials are generally carried away. The third type consists of very shallow ?ows, and produces massive gravel deposits of uncertain provenance. In this condition, the excess pressure in the conduit results in slight uplift of the glacier and widespread discharge of water and sediment below the glacier snout; gravels and smaller sediments are laid down in a massive deposit across the fore?eld. The massive, boulder‐veneered deposit from the December 1995 outburst is interpreted in the light of the above mechanisms as a hyperconcentrated ?ow deposit from hydraulic jacking, overlain by boulders emplaced by a subsequent conduit outburst. A possible association of outbursts with the present advanced position of the glacier is suggested. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Classification of artificial (man-made) ground   总被引：1，自引：0，他引：1  

M. S. Rosenbaum  A. A. McMillan  J. H. Powell  A. H. Cooper  M. G. Culshaw  K. J. Northmore 《Engineering Geology》2003,69(3-4):399-409

The legacy inherited from anthropogenic processes needs to be addressed in order to provide reliable and up-to-date ground information relevant to development and regeneration in the urban environment. The legacy includes voids as well as anthropogenic deposits (artificial ground). Their characteristics derive from former quarrying and mining activities industrial processes creating derelict ground, variably consolidated made ground, and contaminated groundwater and soils. All need to be systematically assessed to inform the planning process and provide the basis for engineering solutions. Site-specific investigation needs to be conducted on the back of good quality geoscientific data. This comes from ‘field’ survey, remotely sensed data interpretation, historical maps, soil geochemical sampling, and geotechnical investigation. Three-dimensional and, in the future, four dimensional, characterization of superficial deposits is required to reach an understanding of the potential spatial lithological variability of artificial ground and the geometry of important surfaces, i.e. the boundary conditions. The classification scheme for artificial ground outlined in this paper and adopted by the British Geological Survey, will help in achieving this understanding.  相似文献   

An experimental investigation of LNAPL migration in an unsaturated/saturated sand   总被引：4，自引：0，他引：4  

Radhey S. Sharma  Mostafa H. A. Mohamed 《Engineering Geology》2003,70(3-4):305-313

Accidental spills of hydrocarbons, such as Light Non-Aqueous Phase Liquids (LNAPLs), are one of the most common sources of subsurface contamination. Migration of LNAPL in a porous medium is influenced by various factors such as the number of fluids present in the unsaturated/saturated zones and the proportion of pores occupied by each fluid. The results for relationship between matric suction and degree of saturation are presented in this paper for water–air, water–LNAPL and LNAPL–air systems in a sand. A simple and reliable setup using Buchner funnel was designed to obtain these relations. It was found that the relationship between matric suction head and degree of saturation is hysteretic for all the fluid systems (water–air, water–LNAPL and LNAPL–air). Furthermore, the amount of hysteresis depended upon the fluid system, with the maximum hysteresis occurring for water–air system. The results suggest that the amount of trapped air depends upon the reversal degree of saturation from drying to wetting.  相似文献   

Fe²⁺-Mg fractionation between orthopyroxene and spinel: experimental calibration in the system FeO-MgO-Al₂O₃-Cr₂O₃-SiO₂, and applications     

H. P. Liermann  J. Ganguly 《Contributions to Mineralogy and Petrology》2003,145(2):217-227

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Radio identification and continuum spectra of decameter-wavelength sources     

O. V. Verkhodanov  N. V. Verkhodanova  H. Andernach 《Astronomy Reports》2003,47(2):110-118

The paper describes a method for the radio identification of decameter-wavelength sources based on their continuum spectra and analysis of their coordinates in relatively large error boxes surrounding a specified position on the sky. The distribution of continuum spectra and identifications in other wavelength ranges are analyzed for the resulting radio catalog. Using identifications with the FIRST and NVSS surveys, the statistics of the spectral index-size and spectral index-flux density distributions for steep-spectrum sources have been studied, and a catalog of ultrasteep-spectrum (α相似文献   

Changes in physical and chemical properties of three soil types in India as a result of amendment with fly ash and sewage sludge   总被引：6，自引：0，他引：6  

H. Veeresh  S. Tripathy  D. Chaudhuri  B. Ghosh  B. Hart  M. Powell 《Environmental Geology》2003,43(5):513-520

The use of coal fly ash and domestic sewage sludge in agriculture is being considered as one of the methods for recycling of these wastes in an environmental beneficial manner. Mixtures with soil were prepared at different proportions of fly ash and sludge, either alone or in combination at a maximum application rate of 52 t ha^-1. The changes in the selected properties and heavy metal contents of three soil types in India were studied after incubating the respective mixtures for 90 days at near field capacity moisture level. Sewage sludge, due to its acidic and saline nature, high organic matter and heavy metals content, had more impact on soil properties than the fly ash. Sludge application produced several changes including an increase in available nitrogen, organic carbon, salinity and water-holding capacity of the soils. The concentrations of major cations and heavy metals also increased because of the sludge application and the pH was decreased. However, the levels of individual metal concentrations in all the mixture types were below the allowable limits prescribed by several environmental agencies. Using fly ash either alone or in equal quantity with sewage sludge had little influence on soil properties and heavy metal content. The relative availability (RA) of heavy metals in three soils amended with 52 t ha^-1 of sewage sludge was observed to be highest in oxisol, followed by alfisol and vertisol.  相似文献   

Mercury-bearing black shales and human Hg intake in eastern Finland: impact and mechanisms   总被引：1，自引：0，他引：1  

K. Loukola-Ruskeeniemi  M. Kantola  T. Halonen  K. Seppänen  P. Henttonen  E. Kallio  P. Kurki  H. Savolainen 《Environmental Geology》2003,43(3):283-297

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Capture of Helium and Other Volatiles during the Growth of Olivine Phenocrysts in Picritic Basalts from the Juan Fernandez Islands   总被引：1，自引：0，他引：1  

NATLAND  JAMES H. 《Journal of Petrology》2003,44(3):421-456

Olivine crystals in basalt contain helium that can be extractedfor isotopic analysis. Helium-bearing olivine phenocrysts inpicritic tholeiites from the Juan Fernandez Islands, SE Pacific,crystallized from moderately differentiated liquids. None arexenocrysts of mantle peridotite. The helium occurs in cavitiesor bubbles in inclusions best seen at high magnification inthe olivine. The olivine grew around spinel, sulfide, and bubblesthat preferentially nucleated on crystal surfaces. Inclusionswithin these phases range from large cavities to tiny, facetedpits arranged in rows. Many crystals contain curving trainsof inclusions along annealed features. The inclusions formedduring mixing between cooler differentiated magma and hotterolivine-charged magma, which accelerated vesiculation. Bubblesnucleated on the olivine as they do on ice when stirred in carbonatedwater. Mixing also induced thermal stress fracturing, like thecracking of ice dropped into water. Cracking, irregular extinction,and subgrain formation occurred when faceted crystals collidedwith each other or with conduit walls. Boundary layer meltsand bubbles were drawn quickly into the fractures. Thus fewinclusions contain equilibrium proportions of minerals and vapor.Mantle-derived helium clearly permeated into shallow storagereservoirs, including rift zones where magmatic differentiation,mixing, and vapor exsolution were fairly extensive. KEY WORDS: Juan Fernandez; volatiles; inclusions; olivine; picrite  相似文献   

Atomistic simulation of the structure and elastic properties of pyrite (FeS2) as a function of pressure     

Sithole  H.M.  Ngoepe  P.E.  Wright  K. 《Physics and Chemistry of Minerals》2003,30(10):615-619

Interatomic potential parameters have been derived at simulated temperatures of 0 K and 300 K to model pyrite FeS₂. The predicted pyrite structures are within 1% of those determined experimentally, while the calculated bulk modulus is within 7%. The model is also able to simulate the properties of marcasite, even though no data for this phase were included in the fitting procedure. There is almost no difference in results obtained for pyrite using the two potential sets; however, when used to model FeS₂ marcasite, the potential fitted at 0 K performs better. The potentials have also been used to study the high-pressure behaviour of pyrite up to 44 GPa. The calculated equation of state gives good agreement with experiment and shows that the Fe–S bonds shorten more rapidly that the S–S dimer bonds. The behaviour of marcasite at high pressure is found to be similar to that of pyrite.  相似文献   

Metamorphic petrology and zircon geochronology of high-grade rocks from the central Mozambique Belt of Tanzania: crustal recycling of Archean and Palaeoproterozoic material during the Pan-African orogeny   总被引：7，自引：0，他引：7  

H. Sommer  A. Kröner  C. Hauzenberger  S. Muhongo  M. T. D. Wingate 《Journal of Metamorphic Geology》2003,21(9):915-934

New data on the metamorphic petrology and zircon geochronology of high‐grade rocks in the central Mozambique Belt (MB) of Tanzania show that this part of the orogen consists of Archean and Palaeoproterozoic material that was structurally reworked during the Pan‐African event. The metamorphic rocks are characterized by a clockwise P–T path, followed by strong decompression, and the time of peak granulite facies metamorphism is similar to other granulite terranes in Tanzania. The predominant rock types are mafic to intermediate granulites, migmatites, granitoid orthogneisses and kyanite/sillimanite‐bearing metapelites. The meta‐granitoid rocks are of calc‐alkaline composition, range in age from late Archean to Neoproterozoic, and their protoliths were probably derived from magmatic arcs during collisional processes. Mafic to intermediate granulites consist of the mineral assemblage garnet–clinopyroxene–plagioclase–quartz–biotite–amphibole ± K‐feldspar ± orthopyroxene ± oxides. Metapelites are composed of garnet‐biotite‐plagioclase ± K‐feldspar ± kyanite/sillimanite ± oxides. Estimated values for peak granulite facies metamorphism are 12–13 kbar and 750–800 °C. Pressures of 5–8 kbar and temperatures of 550–700 °C characterize subsequent retrogression to amphibolite facies conditions. Evidence for a clockwise P–T path is provided by late growth of sillimanite after kyanite in metapelites. Zircon ages indicate that most of the central part of the MB in Tanzania consists of reworked ancient crust as shown by Archean (c. 2970–2500 Ma) and Palaeoproterozoic (c. 2124–1837 Ma) protolith ages. Metamorphic zircon from metapelites and granitoid orthogneisses yielded ages of c. 640 Ma which are considered to date peak regional granulite facies metamorphism during the Pan‐African orogenic event. However, the available zircon ages for the entire MB in East Africa and Madagascar also document that peak metamorphic conditions were reached at different times in different places. Large parts of the MB in central Tanzania consist of Archean and Palaeoproterozoic material that was reworked during the Pan‐African event and that may have been part of the Tanzania Craton and Usagaran domain farther to the west.  相似文献