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21.
Lamprophyric dikes, mainly of camptonite/monchiquite affinities occur in the Wiedemanns Fjord area. One example contains a complex assemblage of olivine-orthopyroxene-chrome spinel nodules, megacrysts of kaersutite, diopside, strongly reverse-zoned green salite and various spinel phases. Microprobe analyses are presented for all these phases and for the lilac-coloured titansalites and strongly-coloured kaersutites of the groundmass. It is concluded that these minerals record evolution under various P, T and oxidation regimes during the formation of a lamprophyric parent magma. The nodules provide evidence for deep fractures in this area supposedly associated with early rifting in the North Atlantic. 相似文献
22.
Sedimentology and kinematics of a large, retrogressive growth-fault system in Upper Carboniferous deltaic sediments, western Ireland 总被引:2,自引:0,他引:2
Growth faulting is a common feature of many deltaic environments and is vital in determining local sediment dispersal and accumulation, and hence in controlling the resultant sedimentary facies distribution and architecture. Growth faults occur on a range of scales, from a few centimetres to hundreds of metres, with the largest growth faults frequently being under‐represented in outcrops that are often smaller than the scale of feature under investigation. This paper presents data from the exceptionally large outcrops of the Cliffs of Moher, western Ireland, where a growth‐fault complex affects strata up to 60 m in thickness and extends laterally for ≈ 3 km. Study of this Namurian (Upper Carboniferous) growth‐fault system enables the relationship between growth faulting and sedimentation to be detailed and permits reconstruction of the kinematic history of faulting. Growth faulting was initiated with the onset of sandstone deposition on a succession of silty mudstones that overlie a thin, marine shale. The decollement horizon developed at the top of the marine shale contact for the first nine faults, by which time aggradation in the hangingwall exceeded 60 m in thickness. After this time, failure planes developed at higher stratigraphic levels and were associated with smaller scale faults. The fault complex shows a dominantly landward retrogressive movement, in which only one fault was largely active at any one time. There is no evidence of compressional features at the base of the growth faults, thus suggesting open‐ended slides, and the faults display both disintegrative and non‐disintegrative structure. Thin‐bedded, distal mouth bar facies dominate the hangingwall stratigraphy and, in the final stages of growth‐fault movement, erosion of the crests of rollover structures resulted in the highest strata being restricted to the proximity of the fault. These upper erosion surfaces on the fault scarp developed erosive chutes that were cut parallel to flow and are downlapped by the distal hangingwall strata of younger growth faults. 相似文献
23.
Simone Carr-Cornish Peta Ashworth John Gardner Stephen J. Fraser 《Climatic change》2011,107(3-4):549-565
There is a large body of research and development into the low emission energy technologies that has the potential to assist developed and developing countries transition to more sustainable energy systems. It has long been recognised that public perceptions can have a fundamental effect on the market for technology and this issue raises questions about the role society will play in developing a low emissions energy future. Understanding how the public will respond to the range of low emission energy technologies as part of a climate change mitigation package is therefore critical for researchers, policy makers and industry stakeholders. In the current research, we investigated the Australian public’s likely acceptance of a range of low emission energy technologies by assessing the diverse ‘orientations’ that have emerged in response to low emission energy technologies. In a survey of two Australian states we measured the support for, and knowledge of, a range of low emission energy technologies. Using self-organising maps, a relatively new approach for segmenting response profiles, we identified that at least four distinct ‘orientations’ have emerged toward the issue and are characterising the likely acceptance of these technologies: ‘Disengaged’, ‘Nuclear Oriented’, ‘Renewables Oriented’, and ‘Engaged’. The implications of these multiple public viewpoints are described for climate change mitigation policy and for future research into the social acceptance of alternative energy technologies. 相似文献
24.
The groundwater response of coastal aquifers to tidal forcing is described by Laplace's equation coupled with the nonlinear phreatic-free surface boundary condition. Here we describe fluctuations in the water table using two small parameters, extending previous work by proposing an ansatz to compute higher order, semi-analytical solutions. The new solutions are compared with known lower order solutions. The relative difference between the linear solution and higher order solutions can reach up to 30% of the linear solution for shallow beaches. The new solutions exhibit a reduction in the over height of the groundwater fluctuations compared with the lower order solutions. In addition, the super elevation of the water table, both near shore and as the aquifer tends landward, is examined with the inclusion of higher order terms. 相似文献
25.
26.
Discard mitigation - what we can learn from waste minimization practices in other natural resources?
Solutions to the problem of discarding in fisheries have been debated for decades. Despite this attention, measures to ameliorate discarding have had limited success. Regulators, researchers, and industry continue to struggle with fisheries management and foregone yield in the face of the continued wastage of valuable resources due to discarding.Waste minimization and by-product utilization are powerful imperatives in other sectors that are also reliant on the harvest of natural resources. This paper considers the performance of these sectors in waste minimization and by-product utilization, with the aim of identifying practices and processes that may be applied to ameliorate discarding in fisheries.This paper describes the handling, utilization, and mitigation of discards and waste in the livestock farming, agriculture, mining, and waste management industries, and in particular, in forestry. In terms of biological impact, economic objectives, and management approaches the harvesting of trees has substantial similarities to industrialized fishing. However, the forestry sector has found ways to utilize almost 100% of the natural product harvest by establishing markets and new products. Analogous developments within the fishing industry could substantially improve sustainability through reduced levels of discarding and wastage. Based on the experiences of these sectors it is suggested that evaluations of potential Management Strategies are developed to specifically examine discard mitigation approaches on a broader scale than previously conducted. 相似文献
27.
Silica-undersaturated sapphirine, spinel and kornerupine granulite facies rocks, NE Strangways Range, Central Australia 总被引:6,自引:0,他引:6
B. GOSCOMBE 《Journal of Metamorphic Geology》1992,10(2):181-201
Small pods of silica-undersaturated Al-rich and Mg-rich granulite facies rocks containing sapphirine, pleonastic spinel, kornerupine, cordierite, orthopyroxene, corundum, sillimanite and gedrite are scattered throughout the NE Strangways Range, Central Australia. These are divided into four distinct rock types, namely orthopyroxene-rich aluminous granofels and metapelitic gneisses containing sapphirine, spinel or kornerupine. Two granulite facies metamorphic events are recognized, of which only the first (M1) is considered in this paper. Peak metamorphic mineral parageneses indicate that the M1 thermal maximum occurred at approximately 900–950 °C and 8–9 kbar. All samples are characterized by profuse and diverse coronitic and symplectic reaction textures. These are interpreted as evidence for the sequential crossing of the following reactions in the system FMAS: cordierite + spinel + corundum = sapphirine + sillimanite, cordierite + spinel = orthopyroxene + sapphirine + sillimanite, sapphirine + spinel + sillimanite = orthopyroxene + corundum, sapphirine + sillimanite = cordierite + orthopyroxene + corundum. Phase stability relationships in FMAS and MASH indicate an anticlockwise P–T path terminated by isobaric cooling. Such a path is exemplified by early low-P mineral parageneses containing spinel, corundum and gedrite and the occurrence of both prograde and retrograde corundum. Reaction textures preserve evidence for an increase in aH2O and aB2O3 with progressive isobaric cooling. This hydrous retrogression resulted from crystallization of intimately associated M1 partial melt segregations. There is no evidence for voluminous magmatic accretion giving rise to the high M1 thermal gradient. The M1 P–T path may be the result of either lithospheric thinning after both crustal thickening and burial of the supracrustal terrane, or concomitant crustal thickening and mantle lithosphere thinning. 相似文献
28.
Koushik Sen Ruchika Sharma B. R. Arora Vikram Gupta 《Journal of the Geological Society of India》2010,76(5):322-330
Anisotropy of Magnetic Susceptibility (AMS) and seismic wave velocity studies of some paramagnetic Himalayan granitoids show
good correlation between magnetic fabric anisotropy and P wave velocity (Vp). Vp shows strong positive correlation with magnetic
lineation (L) and degree of magnetic anisotropy (P′) having correlation coefficient (r) values of 0.93 and 0.89 respectively.
Both Vp and Vs show positive correlation with the SiO2 content of Proterozoic and Paleozoic granitoids. Velocity of S wave (Vs) shows negative correlation with mean magnetic susceptibility
(Km) having ‘r’ value of 0.86. The correlation between Vs-Km, Vp-P′, Vp-L also shows >95% probability in Spearman’s rank correlation. Based on the results from the present sample size it is suggested
that, in paramagnetic granites, Vp is proportional to intensity of deformation and preferred orientation of minerals as well as the mineralogy. On the other
hand, Vs is more dependent on the mineralogy alone. 相似文献
29.
Besides Pb and U loss and mixing of crystals of different age, U gain is considered a possible cause of discordant U-Pb ages of zircons. However, whether U gain without new zircon growth occurs in nature had not been proven, so far. In order to test this possibility, two detrital zircon populations were studied for which the absence of later zircon overgrowth after deposition could be demonstrated. The samples were separated from a metaquartzite near a large pegmatite body and from metaquartzite inclusions found in the pegmatite (Martell Valley, Italian Alps). The distribution of neutron-induced fission tracks reveals distinct accumulation of U in the rims of more than 90% of the zircon grains of the inclusions (total U in the crystals: 540–850 ppm), whereas in the country rock only some of the grains show similar but weaker patterns (total U: 155–320 ppm). From the isotopic data and from additional U-Pb and Rb-Sr analyses of minerals and whole-rock samples of the pegmatite, the marginal accumulation and the higher concentration of U in the zircon grains of the inclusions are interpreted as the result of episodic U gain during the intrusion of the pegmatite and/or during a later metamorphism. From the concentration levels of common Pb, an addition of Pb - and possibly other elements - to the zircon grains is inferred. 相似文献
30.
B. I. Nazarov S. F. Abdullaev V. A. Maslov 《Izvestiya Atmospheric and Oceanic Physics》2010,46(4):475-481
We studied the temperature variations of the lower air layer caused by dust content using a dust storm in Dushanbe in November
2007 as an example. Quantitative estimates of air cooling and a decrease in the diurnal temperature difference due to a diminishing
horizontal visibility range are given. Observations of air temperature variations due to the dust content of the atmosphere
in an arid zone are presented. The critical value of aerosol concentration for toggling between the greenhouse and antigreenhouse
effects is determined. The long-term effect of dust aerosol on climate is analyzed. 相似文献