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101.
Jon M Friedrich John C Bridges Ming-Sheng Wang 《Geochimica et cosmochimica acta》2004,68(13):2889-2904
To study compositional trends associated with open and closed system metamorphism and/or shock-induced heating of the L4-6 chondrite parent(s), we used ICPMS and RNAA to quantify 51 trace elements in 48 chemically representative fall samples. With these data, we used graphic and two multivariate statistical methods for examining evidence for compositional differences with respect to petrographic type and degree of shock loading. Comparisons of mildly shocked (S1-S3) L5 and L6 suites (9 and 8 chondrites, respectively) yield no convincing statistical evidence for a difference in trace element content. Our multivariate comparisons show a difference on a model-dependent basis, but yield indeterminate results on a model-independent basis. Compositionally, suites of strongly shocked (S4-S6) and mildly shocked L4-6 chondrites (26 and 19 samples, respectively) can be distinguished at statistically significant levels on both model-dependent and -independent bases. In the strongly shocked suite, contents of refractory lithophiles are higher, and siderophiles and volatiles are lower than those of the mildly shocked suite at moderately (p ≤ 0.05) to highly significant (p ≤ 0.01) levels. Our studies suggest that chemical differences from vaporization and loss of volatiles along with metal/silicate partitioning are present from extended cooling of shock-heated bodies produced by intermittent impacts, especially the massive impact(s) that disrupted the L chondrite parent(s) ∼500 Ma ago. 相似文献
102.
FriedrichAckermann 《地球空间信息科学学报》1998,(1)
A geo-reference is a global or regional geographical or geodetic coor-dinate system to which sensors or spatial object data are related.Hence,geo-ref-erencing is close to the well known photogrammetric concept of exterior or abso-lute orientation,the common execution of which is indirect,via the use of groundcontrol point.GPS and INS technologies have changed the situation,permittingdirect measurement of position and attitude parameters and making exterior orien-tation feasible without ground control at all,in principle.The analysis of accuracyand reliability performance discloses,however,that especially INS does not yetmeet the high demands of photogrammetry.Moreover,control of systematic er-rors,the problem of datum transformation,and reliability conditions make theuse of some ground control points still mandatory,at least for any high perfor-mance geo-referencing. 相似文献
103.
After World War II Saudi Arabia has experienced spectacular changes. Based on huge oil and gas revenues a particularly rapid
growth of population and a spectacular urbanization took place. One of the most booming cities in the desert environment of
the arabian peninsula is the Kingdoms capital city of Riyadh. With a built-up area of 3.5 km2 only before 1950 the city's present-day expansion reaches more than 500 km2. During the same period of time the population of Riyadh grew from less than 50,000 in 1945 to more than 1.4 Mio. in 1985.
Such an explosive development can be documented best by a satellite image. In this paper the process of urbanization of Riyadh
is presented by the interpretation of a MOMS image taken in 1984, documenting the geographic situation, urban structures,
and the city's development. 相似文献
104.
105.
Helmut Schäfer Wolfgang Friedrich Müller Ulrich Hornemann 《Physics and Chemistry of Minerals》1984,10(3):121-124
Shock recovery experiments on melilite samples in the pressure range from 11 to 50.5 GPa have been performed in order to examine the effects of shock waves on this material. The shocked samples were subsequently studied in the transmission electron microscope. All samples displayed the shock-induced amorphous areas, known as diaplectic glass. The amount of diaplectic melilite glass increased from a few percent at 11 GPa to about 85 percent at 50.5 GPa shock pressure. The shock waves also caused deformational effects as planar faults parallel to (001) and dislocations with a density in the order of 1010 cm?2. Regarding the present discussion on the origin and nature of diaplectic glass, diaplectic melilite glass is assumed to be the reversion product of a high-density phase produced in the shock front. Deformed melilites in Ca-Al-rich inclusions from chondritic meteorites studied so far do not contain diaplectic glass. It is assumed that the meteoritic melilites were hot (>1,000° C) and thus plastically deformable by shock waves of rather low amplitudes. 相似文献
106.
Cation ordering in omphacite and effect on deformation mechanism and lattice preferred orientation (LPO) 总被引:1,自引:0,他引:1
We present microstructural data and lattice preferred orientations (LPOs) of omphacites from a suite of eclogites, from the Adula/Cima Lunga nappe (Central Alps). Our work shows a surprisingly strong correlation between the measured LPO and the ordering state of cations in omphacite. Estimates of deformation temperature from metamorphic petrology, together with measured omphacite compositions and LPOs, determine the field (ordering state), on the omphacite phase diagram, into which each sample falls. LPOs dominated by L-type and S-type signatures are developed in samples that fall in the P2/n field (ordered structure) and C2/c field (disordered structure), respectively.Dislocations with b=1/2−110 or b=[001] are observed in the transmission electron microscope (TEM) in all samples. The former change from a perfect dislocation in the C2/c structure to a partial in P2/n. Any movement of a partial dislocation requires the formation or growth of a stacking fault. Furthermore, in order to pass an obstacle a partial dislocation has to constrict to a unit dislocation. The energy to form a constriction is high in omphacite due to the large separation width. Thus, the activity of the b=1/2−110 dislocation is hindered in the P2/n structure relative to the C2/c structure, which change the balance between the two and might give rise to the different LPOs. 相似文献
107.
正The papers in this issue stem from the 13th International Symposium on River Sedimentation held in September 2016 at the University of Stuttgart,Germany.The Symposiums on River Sedimentation aim to provide a platform for scientists and engineers for fruitful and in-depth knowledge exchange.The objectives are to develop sustainable revitalization and management strategies that address the ongoing negative effects of anthropogenic activities,whilst improving river systems toward a healthy ecological status.The fundamental research and understanding of interactive 相似文献
108.
V. V. Adushkin B. B. Chen S. I. Popel A. Yu. Dubinskii P. G. Weidler F. Friedrich 《Izvestiya Physics of the Solid Earth》2018,54(2):330-335
An experimental study of small-scale mineral particles in the atmosphere over Kyrgyzstan is carried out. It is shown that the substance of the studied particles corresponds to quartz-enriched minerals, feldspars, layered silicates, minerals containing lime carbonate, etc. Overall, there is a definite correspondence between the mineral particle compositions in the atmosphere of Kyrgyzstan and in the other regions of Central Asia. The constructed size-distribution functions of the particles agree with the results of studying the dust aerosol properties in the deserts of Central Asia obtained in the southwestern part of Tajikistan in 1989. 相似文献
109.
Climate change effects on hydrological system conditions influencing generation of storm runoff in small Alpine catchments 总被引:1,自引:0,他引:1 下载免费PDF全文
Gertraud Meißl Herbert Formayer Klaus Klebinder Florian Kerl Friedrich Schöberl Clemens Geitner Gerhard Markart David Leidinger Axel Bronstert 《水文研究》2017,31(6):1314-1330
Floods and debris flows in small Alpine torrent catchments (<10 km2) arise from a combination of critical antecedent system state conditions and mostly convective precipitation events with high precipitation intensities. Thus, climate change may influence the magnitude–frequency relationship of extreme events twofold: by a modification of the occurrence probabilities of critical hydrological system conditions and by a change of event precipitation characteristics. Three small Alpine catchments in different altitudes in Western Austria (Ruggbach, Brixenbach and Längentalbach catchment) were investigated by both field experiments and process‐based simulation. Rainfall–runoff model (HQsim) runs driven by localized climate scenarios (CNRM‐RM4.5/ARPEGE, MPI‐REMO/ECHAM5 and ICTP‐RegCM3/ECHAM5) were used in order to estimate future frequencies of stormflow triggering system state conditions. According to the differing altitudes of the study catchments, two effects of climate change on the hydrological systems can be observed. On one hand, the seasonal system state conditions of medium altitude catchments are most strongly affected by air temperature‐controlled processes such as the development of the winter snow cover as well as evapotranspiration. On the other hand, the unglaciated high‐altitude catchment is less sensitive to climate change‐induced shifts regarding days with critical antecedent soil moisture and desiccated litter layer due to its elevation‐related small proportion of sensitive areas. For the period 2071–2100, the number of days with critical antecedent soil moisture content will be significantly reduced to about 60% or even less in summer in all catchments. In contrast, the number of days with dried‐out litter layers causing hydrophobic effects will increase by up to 8%–11% of the days in the two lower altitude catchments. The intensity analyses of heavy precipitation events indicate a clear increase in rain intensities of up to 10%. 相似文献
110.
Elena I. Virina Friedrich Heller Stanislav S. Faustov Nathalia S. Bolikhovskaya Robert V. Krasnenkov Tatyana Gendler Ernie A. Hailwood Jozeph Hus 《第四纪科学杂志》2000,15(5):487-499
Until now, palaeoclimatic reconstructions for the major stages in the development of the Quaternary loess–palaeosol sequence on the Russian Plain have been based on pedological, palynological and faunal (vertebrates and molluscs) analyses. In order to demonstrate the palaeoclimatic influence on the magnetic properties of this sequence, the magnetic susceptibility signature of the Strelitsa type section in the Upper Don basin is compared with a detailed landscape – climate reconstruction of loess and soil from palynological data. Large amplitude fluctuations of palaeoclimate and palaeoenvironment are reflected clearly in the lithology and in the rock magnetic properties, which usually are enhanced in wet and warm interglacial periods, but stay at low levels during cold glacial epochs. Palynological climate zonation, however, is sometimes in conflict with the pedologic–magnetic record. Strong climate fluctuations, as indicated by changing pollen assemblages, are not always paralleled by corresponding changes in lithology and/or rock magnetic properties. Alternatively, light coloured illuvial horizons with low magnetic signal sometimes appear to have formed during early stages of interglacials, and the top parts of some palaeosols apparently formed during glacial stages. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献