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101.
Diffusive reequilibration of quartz-hosted silicate melt and fluid inclusions: Are all metal concentrations unmodified? 总被引:1,自引:0,他引:1
Zoltan Zajacz Jacob J. Hanley Werner E. Halter 《Geochimica et cosmochimica acta》2009,73(10):3013-2827
Experiments were conducted to determine the extent and mechanism by which the composition of quartz-hosted silicate melt inclusions (SMI) and aqueous fluid inclusions (FI) can undergo post-entrapment modification via diffusion. Quartz slabs containing assemblages of SMI and FI were reacted with synthetic HCl bearing and metalliferous aqueous fluids at T = 500-720 °C and P = 150-200 MPa. SMI from the single inclusion assemblages were analyzed by laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) and electron probe microanalysis (EPMA) before and after the experiments. Analyses revealed that rapid diffusion of the univalent cations Na+, Li+, Ag+, Cu+ and H+ occurred through the quartz from the surroundings, resulting in significant changes in the concentrations of these elements in the inclusions. Concentrations of other elements with an effective ionic radius larger than that of Ag+, or multiple valence states were not modified in the inclusions during the experiments. Our results warn inclusion‘‘ researchers that the interpretation of Na, Li, Cu and Ag concentrations from quartz-hosted SMI and FI should be treated critically. 相似文献
102.
Werner Singer Ralph Latteck Luis Federico Millan Nick J. Mitchell Jens Fiedler 《Earth, Moon, and Planets》2008,102(1-4):403-409
Many meteoroids burn up between about 120 km and 70 km, deposit metals and dust and form ionized trails which are detected
by radars. Model studies about the influence of neutral or positively charged background dust on the ambipolar diffusion indicate
that significant smaller decay times should be observed for weak meteor echoes compared to strong meteor echoes which can
affect the estimation of temperatures. The variation of meteor decay times in dependence on echo strength, height, and season
was studied using radar observations at 69° N, 22° S, and 67° S. Significantly reduced decay times were found for weak echoes
below about 88 km at low latitudes throughout the year, and at high latitudes with the exception of summer. In summer at high
latitudes, decreasing decay times of weak and strong meteors are observed at altitudes below about 85 km during the appearance
of noctilucent clouds. The impact of reduced decay times on the estimation of neutral temperatures from decay times is discussed. 相似文献
103.
Hamed Ketabchi Davood Mahmoodzadeh Behzad Ataie‐Ashtiani Adrian D. Werner Craig T. Simmons 《水文研究》2014,28(24):5938-5953
The fresh groundwater lenses (FGLs) of small islands can be highly vulnerable to climate change impacts, including sea‐level rise (SLR). Many real cases of atoll or sandy islands involve two‐layer hydrogeological conceptualizations. In this paper, the influential factors that affect FGLs in two‐layer small islands subject to SLR are investigated. An analytical solution describing FGLs in circular islands, composed of two geological layers, is developed for the simplified case of steady‐state and sharp‐interface conditions. An application of the developed model is demonstrated to estimate the FGL thickness of some real‐world islands by comparison with existing FGL thickness data. Furthermore, numerical modelling is applied to extend the analysis to consider dispersion effects and to confirm comparable results for both cases. Sensitivity analyses are used to assess the importance of land‐surface inundation caused by SLR, relative to other parameters (i.e. thickness of aquifer layers, hydraulic conductivity, recharge rate and land‐surface slope) that influence the FGL. Dimensionless parameters are used to generalize the findings. The results demonstrate that land‐surface inundation has a considerable impact on a FGL influenced by SLR, as expected, although the FGL volume is more sensitive to recharge, aquifer thickness and hydraulic conductivity than SLR impacts, considering typical parameter ranges. The methodology presented in this study provides water resource managers with a rapid‐assessment tool for evaluating the likely impacts of SLR and accompanying LSI on FGLs. 相似文献
104.
Werner Brückner 《International Journal of Earth Sciences》1951,39(1):196-212
Ohne Zusammenfassung 相似文献
105.
Summary Semi-monthly mean sea-level pressure maps for the Mediterranean and adjacent areas are presented. Isobars have been drawn at 1-millibar intervals. The most significant features on the maps and the advantages of the mode of presentation are discussed briefly.
With 25 Figures.
The work reported in this paper has been supported by the Geophysics Research Division of the Air Force Cambridge Research Center, under Contract AF 19 (122)-466. 相似文献
Zusammenfassung Es werden auf das Meeresniveau bezogene halbmonatliche mittlere Luftdruckkarten für das Mittelmeergebiet und die anstoßenden Länder vorgelegt. Die Isobaren wurden für Millibarabstände gezeichnet. Die wichtigsten Resultate der Karten und die Vorzüge der Darstellungsweise werden kurz besprochen.
Résumé Présentation de cartes de la pression moyenne semi-mensuelle, réduite au niveau de la mer, de la région méditerranéenne et des contrées voisines. Les isobares sont tracées de millibar en millibar. Brève discussion des traits principaux des cartes et des avantages de la méthode de représentation.
With 25 Figures.
The work reported in this paper has been supported by the Geophysics Research Division of the Air Force Cambridge Research Center, under Contract AF 19 (122)-466. 相似文献
106.
P. Wilh Werner Dr.-techn. h. c. 《Pure and Applied Geophysics》1952,23(1):36-42
Summary The present paper is a continuation of a previous study by the author(1), dealing with expansion waves in fluids. Relating to hydro-dynamic effects due to harmonic vibrations, with special reference to earthquakes, it contains solutions for some rigid-walled vessels of geometrically determined shape. A salient feature of the problem is that the motion is assumed discontinuous in the sense that it starts from the initial condition of rest. 相似文献
107.
Professor Dr. Werner Borchert 《Contributions to Mineralogy and Petrology》1952,3(2):124-130
Ohne ZusammenfassungHerrn Professor Dr. O. H.Erdmannsdörffer zur Vollendung seines 75. Lebensjahres in Dankbarkeit gewidmet. 相似文献
108.
Considerations of mineral resource availability and depletion form part of a diverse array of sustainable development-oriented studies, across domains such as resource criticality, life cycle assessment and material flow analysis. Given the multidisciplinary nature of these studies, it is important that a common understanding of the complexity and nuances of mineral supply chains be developed. In this paper, we provide a brief overview of these assessment approaches and expand on several areas that are conceptually difficult to account for in these studies. These include the dynamic nature of relationships between reserves, resources, cut-off grades and ore grades; the ability to account for local economic, social and environmental factors when performing global assessments; and the role that technology improvements play in increasing the availability of economically extractable mineral resources. Advancing knowledge in these areas may further enhance the sophistication and interpretation of studies that assess mineral resource depletion or availability. 相似文献
109.
Ines Bamberger Brian Oney Dominik Brunner Stephan Henne Markus Leuenberger Nina Buchmann Werner Eugster 《Boundary-Layer Meteorology》2017,164(1):135-159
Mountain-top observations of greenhouse gas mixing ratios may be an alternative to tall-tower measurements for regional scale source and sink estimation. To investigate the equivalence or limitations of a mountain-top site as compared to a tall-tower site, we used the unique opportunity of comparing in situ measurements of methane (\(\hbox {CH}_{4}\)) and carbon dioxide (\(\hbox {CO}_{2}\)) mixing ratios at a mountain top (986 m above sea level, a.s.l.) with measurements from a nearby (distance 28.4 km) tall tower, sampled at almost the same elevation (1009 m a.s.l.). Special attention was given to, (i) how local wind statistics and greenhouse gas sources and sinks at the mountain top influence the observations, and (ii) whether mountain-top observations can be used as for those from a tall tower for constraining regional greenhouse gas emissions. Wind statistics at the mountain-top site are clearly more influenced by local flow systems than those at the tall-tower site. Differences in temporal patterns of the greenhouse gas mixing ratios observed at the two sites are mostly related to the influence of local sources and sinks at the mountain-top site. Major influences of local sources can be removed by applying a statistical filter (\(5{\mathrm{th}}\) percentile) or a filter that removes periods with unfavourable flow conditions. In the best case, the bias in mixing ratios between the mountain-top and the tall-tower sites after the application of the wind filter was \({-}0.0005\pm 0.0010\) ppm for methane (September, 0000–0400 UTC) and \(0.11\pm 0.18\) ppm for \(\hbox {CO}_{2}\) (February, 1200–1600 UTC). Temporal fluctuations of atmospheric \(\hbox {CH}_{4}\) and \(\hbox {CO}_{2}\) mixing ratios at both stations also showed good agreement (apart from \(\hbox {CO}_{2}\) during summertime) as determined by moving bi-weekly Pearson correlation coefficients (up to 0.96 for \(\hbox {CO}_{2}\) and 0.97 for \(\hbox {CH}_{4}\)). When only comparing mixing ratios minimally influenced by local sources (low bias and high correlation coefficients), our measurements indicate that mountain-top observations are comparable to tall-tower observations. 相似文献
110.
James H. Churchill James L. Hench Richard A. Luettich Jackson O. Blanton Francisco E. Werner 《Estuaries and Coasts》1999,22(4):1057-1070
Drifter tracks and shipboard CTD observations have revealed a number of distinct features of the flood tide circulation carrying water through Beaufort Inlet, North Carolina. One of the most noteworthy of these features is a nearshore jet in the flow carrying water to the inlet on a flood tide. Characterized by a shoreward increase in longshore flow, the jet produces a narrow coastal zone over which water is carried into the inlet. The jet appears to be principally a tidal phenomenon, as it is closely reproduced by a tidally-driven barotropic numerical model. The model results also indicate the jet may be a near-inlet feature. Model simulations of spring tide conditions show the jet confined to within 4 km of the inlet mouth. Another observed phenomenon, which is reproduced by the tidal model, is a distinct splitting of the flow entering the inlet, in which water passing through a particular inlet segment tends to move up-estuary along a well-defined path. An observed flow feature not reproduced by the tidal model is an eastward skew of the region over which water is drawn into the inlet on a flood tide. This asymmetry is unrelated to the local wind. Modeling results from a previous study suggest it may be due to convergent flow at the edge of the low salinity plume issuing from the inlet. Taken together, the results of this and other recent studies in the Beaufort Inlet region reveal the importance of nearshore currents on the eastern side of the inlet in delivering oceanic-spawned larvae to the estuarine system connected to the inlet. 相似文献