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11.
fil. dr. HARALD SVENSSON 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(1):8-12
Svensson, Harald, 1976; Relict ice-wedge polygons revealed on aerial photographs from Kaltenkirchen, northern Germany. Geografisk Tidsskrift 75: 8–12. København, juni 1, 1976. On aerial photographs polygonal patterns are detected in cultivated fields due to vegetational contrasts. In a section through the ground the structure and composition of the material were studied. The outline of the ice-wedge cast is very faint, hut the existing structure and soil qualities are sufficient to make the polygonal network show on the ground surface. The season of the year and the external conditions at the time of photographing are of great importance for a distinct reproduction of the pattern in the aerial photograph. 相似文献
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ARNE HASSEL HEIN RUNE SKJOLDAL HARALD GJØSÆTER HARALD LOENG LENA OMLI 《Polar research》1991,10(2):371-388
The distribution of capelin was mapped in the area east of Hopen. Zooplankton was sampled with Juday net and 1 m2 MOCNESS sampler, and analysed with respect to hydrography and capelin abundance. The capelin "front" coincided more or less with the physical Polar Front, and this complicated the interpretation of the results. Strong indications for a grazing impact by capelin on zooplankton were nevertheless obtained. The zooplankton biomass was significantly lower in the area with high abundance of capelin than in the area with no capelin. This effect was due to a lower biomass of relatively large zooplankton (> 1 mm size fraction) and seen most clearly in data obtained with the MOCNESS. The biomass of zooplankton in the upper 100 m was very low where capelin was present, suggesting rapid depletion of the major prey items. The biomass (m −2 ) of capelin in the capelin front area was about three times higher than the biomass of zooplankton in areas without capelin. The capelin front would therefore have the potential to graze down the available prey in 3-4 days. Light seems to be an important factor for the predation impact by capelin, resulting in strong interactions between capelin predation and zooplankton vertical distribution. 相似文献
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Experimental Petrology of the 1991-1995 Unzen Dacite, Japan. Part I: Phase Relations, Phase Composition and Pre-eruptive Conditions 总被引：2，自引：0，他引：2
HOLTZ FRANCOIS; SATO HIROAKI; LEWIS JARED; BEHRENS HARALD; NAKADA SETSUYA 《Journal of Petrology》2005,46(2):319-337
Crystallization experiments were conducted on dry glasses fromthe Unzen 1992 dacite at 100–300 MPa, 775–875°C,various water activities, and fO2 buffered by the Ni–NiObuffer. The compositions of the experimental products and naturalphases are used to constrain the temperature and water contentsof the low-temperature and high-temperature magmas prior tothe magma mixing event leading to the 1991–1995 eruption.A temperature of 1050 ± 75°C is determined for thehigh-temperature magma based on two-pyroxene thermometry. Theinvestigation of glass inclusions suggests that the water contentof the rhyolitic low-temperature magma could be as high as 8wt % H2O. The phase relations at 300 MPa and in the temperaturerange 870–900°C, which are conditions assumed to berepresentative of the main magma chamber after mixing, showthat the main phenocrysts (orthopyroxene, plagioclase, hornblende)coexist only at reduced water activity; the water content ofthe post-mixing dacitic melt is estimated to be 6 ± 1wt % H2O. Quartz and biotite, also present as phenocrysts inthe dacite, are observed only at low temperature (below 800–775°C).It is concluded that the erupted dacitic magma resulted fromthe mixing of c. 35 wt % of an almost aphyric pyroxene-bearingandesitic magma (1050 ± 75°C; 4 ± 1 wt % H2Oin the melt) with 65 wt % of a phenocryst-rich low-temperaturemagma (760–780°C) in which the melt phase was rhyolitic,containing up to 8 ± 1 wt % H2O. The proportions of rhyoliticmelt and phenocrysts in the low-temperature magma are estimatedto be 65% and 35%, respectively. It is emphasized that the strongvariations of phenocryst compositions, especially plagioclase,can be explained only if there were variations of temperatureand/or water activity (in time and/or space) in the low-temperaturemagma. KEY WORDS: Unzen volcano; magma mixing; experimental study 相似文献
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Platinum-Group Elements (PGE) in Basalts of the Seaward-Dipping Reflector Sequence, SE Greenland Coast 总被引：8，自引：1，他引：8
The rift-related, seaward-dipping reflector sequence (SDRS)SE of Greenland consists of basaltic lavas that exhibit variabledegrees of magmatic differentiation, derived from a heterogeneousmantle source. Platinum-group elements (PGE) are used to provideinsights into the petrogenetic evolution of the SDRS, and tocharacterize the magma sources. Noble metal concentrations correlatewell with indicators for magmatic differentiation (mg-number,MgO), exhibiting two distinct trends. Concentrations of Ir,Ru and Rh tend to decrease with progressive differentiation,indicating compatible behaviour of these elements during fractionalcrystallization processes. The variation of Pt and Pd showssegmented trends. In primitive magmas, Pt and Pd are incompatibleand become enriched in the melt. The primitive magma is S undersaturated,despite derivation from a depleted mid-ocean ridge basalt sourceat a moderate degree of melting, reflecting enhanced S solubilityin the melt caused by high Fe content and elevated temperature.In the more evolved lavas, Pt and Pd decrease with decreasingMgO and mg-number. This indicates that S saturation had occurredwith Pt and Pd being incorporated in sulphides, which probablysegregated during ascent. Bulk partition coefficients for thePGE during partial melting are calculated based on data froma primitive basaltic unit with MgO 相似文献
15.
On the efficiency of vertical array aeolian field traps 总被引：10，自引：0，他引：10
The efficiency of three vertical array field traps for measuring the distribution of aeolian mass transport with height was compared with measurements with an isokinetic trap. The vertical traps seem to work adequately (efficiency > 80%) at heights greater than ≈15 mm above the bed. Closer to the bed, however, the open array trap catches about 70%, the two continuous arrays only about 50%. Because most of the transport takes place close to the surface, the overall efficiency of the field traps ranges from 50 to 70%.
Based on these wind tunnel tests, we have developed a low single-compartment wedge-shaped trap. Its shape, in combination with flow straighteners at the entrance, minimizes stagnation effects, so that the efficiency is ≈80%. Our data indicate that with the wedge trap used in combination with the vertical array Aberdeen trap, we can sample mass transport in the field during periods with unidirectional winds with an overall efficiency of the order of 80%. 相似文献
Based on these wind tunnel tests, we have developed a low single-compartment wedge-shaped trap. Its shape, in combination with flow straighteners at the entrance, minimizes stagnation effects, so that the efficiency is ≈80%. Our data indicate that with the wedge trap used in combination with the vertical array Aberdeen trap, we can sample mass transport in the field during periods with unidirectional winds with an overall efficiency of the order of 80%. 相似文献
16.
Forty-four components in six bottles of BHVO-1 have been determined using wet chemical, atomic absorption, X-ray fluorescence, ion sensitive electrodes, and neutron activation techniques. No indications for systematic inhomogeneity were found, but the average ferrous iron contents of two bottles are lower than the averages of the other four. 相似文献
17.
Authigenic pyrite grains from a section of the Lower Toarcian Posidonia Shale were analysed for their trace‐element contents and sulphur‐isotope compositions. The resulting data are used to evaluate the relationship between depositional conditions and pyrite trace‐element composition. By using factor analysis, trace‐elements in pyrite may be assigned to four groups: (i) heavy metals (including Cu, Ni, Co, Pb, Bi and Tl); (ii) oxyanionic elements (As, Mo and Sb); (iii) elements partitioned in sub‐microscopic sphalerite inclusions (Zn and Cd); and (iv) elements related to organic or silicate impurities (Ga and V). Results indicate that trace‐element contents in pyrite depend on the site and mechanism of pyrite formation, with characteristic features being observed for diagenetic and syngenetic pyrites. Diagenetic pyrite formed within anoxic sediments generally has a high heavy metals content, and the degree of pyritization of these elements increases with increasing oxygen deficiency, similar to the degree of pyritization of reactive Fe. The highest gradient in the increase of the degree of trace element pyritization with bottom‐water oxygenation was found for the elements Ni < Cu < Mo = As < Tl. In contrast, syngenetic pyrite formed within a euxinic water column typically is enriched in As, Mo and Sb, but is low in heavy metals, and the geochemical variation reflects changes in sea water composition. 相似文献
18.
Flood Basalts of Vestfjella: Jurassic Magmatism Across an Archaean-Proterozoic Lithospheric Boundary in Dronning Maud Land, Antarctica 总被引：2，自引：1，他引：1
Continental flood basalts (CFBs) of Jurassic age make up theVestfjella mountains of western Dronning Maud Land and demonstratean Antarctic extension of the Karoo large igneous province.A detailed geochemical study of the 120-km-long Vestfjella rangeshows the CFB suite to consist mainly of three intercalatedbasaltic rock types designated CT1, CT2 and CT3 (chemical types1, 2 and 3) that exhibit different incompatible trace elementratios. CT1 and CT2 of north Vestfjella record wide ranges ofNd and Sr isotopic compositions with initial 相似文献
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During 1975–1977, the USGS reference rocks GSP-1, BCR-1 and from 1977 onwards AGV-1 have been systematically analysed in routine INAA as test samples. The results are given for up to 26 elements per sample and the reliability of our setup is demonstrated. For further 17 geochemical reference samples, new results are presented and compared with available data. 相似文献