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971.
Sulfur and O isotope analyses of dissolved SO4 were used to constrain a hydrogeological model for the area overlying the Gorleben–Rambow Salt Structure, Northern Germany. Samples were collected from 80 wells screened at different depth-intervals. The study area consists of a set of two vertically stacked aquifer systems. Generally, the isotope data show a good spatial correlation, outlining well-defined groundwater zones containing SO4 of characteristic isotopic composition. Highly saline waters from deeper parts of the lower aquifer system are characterized by rather constant SO4 isotopic compositions, which are typical of Permian Zechstein evaporites (δ34S=9.6–11.9‰; δ18O=9.5–12.1‰). Above this is a transition zone containing ground waters of intermediate salinity and slightly higher isotopic values (average δ34S=16.6‰; δ18O=15.3‰). The confined groundwater horizon on the top of the lower aquifer system below the low permeable Hamburg Clays is low in total dissolved solids and is characterized by an extreme 34S enrichment (average δ34S=39.1‰; δ18O=18.4‰), suggesting that bacterially mediated SO4 reduction is a dominant geochemical process in this zone. Two areas of distinct isotopic composition can be identified in the shallow ground water horizons of the upper hydrogeological system. Sulfate in groundwaters adjacent to the river Elbe and Löcknitz has a typical meteoric isotopic signature (δ34S=5.2‰; δ18O=8.2‰), whereas the central part of the area is characterized by more elevated isotopic ratios (δ34S=12.7‰; δ18O=15.6‰). The two major SO4 pools in the area are represented by Permian seawater SO4 and a SO4 of meteoric origin that has been mixed with SO4 resulting from the oxidation of pyrite. It is suggested that the S-isotope compositions observed reflect the nature of the SO4 source that have been modified to various extent by bacterial SO4 reduction. Groundwaters with transitional salinity have resulted from mixing between brines and low-mineralized waters affected by bacterial SO4 reduction. 相似文献
972.
The study of palynomorphs and calcareous nannofossils from the Albian–Campanian Napo Group in the Pungarayacu 30 well in the Subandean Zone of Ecuador has led to a new biostratigraphic framework revealing the existence of several hiatuses for this area. The palynological and palynofacies data are used together with other fossils and lithological evidence to define a sequence stratigraphic framework. The distribution of palynomorphs and palynofacies indicates a strong terrestrial input for the lower part of the Napo Group (Napo Basal and Lower Napo formations). In the upper part (Middle and Upper Napo formations), terrestrial input is reduced and a restricted marine environment with several dysoxic–anoxic intervals can be inferred. The hydrocarbons present in the well studied have traditionally been regarded as locally sourced. However, several lines of evidence (TAS, Tmax and VR) prove the immature stage of the source rock in this borehole as well as in a larger area. 相似文献
973.
In July 2000 the 15.5 km long fixed link across the Øresund was opened, connecting the Danish capital Copenhagen and the Swedish city of Malmö. With the decrease of the barrier an enlarged flow of shoppers was expected with Swedish customers availing themselves of the range of opportunities in the Copenhagen area and Danish customers making use of the much longer shop opening hours in Sweden. However, experience from other European border areas shows that customers tend to do their ordinary shopping in their home countries and that there must be significant differences in prices or ranges of goods to overcome the barrier of the border. Does the typical situation result from the rural nature of many border areas, and will matters be quite different in a metropolitan area? The purpose of the present paper is to describe the level and character of cross-border shopping by the residents of the Øresund region before and after the opening of the fixed link. Responses from about 4,000 people form the basis of the conclusion that a little less than a year after the opening of the fixed link the number of shopping trips across the Øresund had increased, but there was still no heavy flow of customers doing ordinary shopping in the neighbouring countries. In order to assess the level of cross-border shopping across the Øresund the findings are compared to those from surveys across the Danish-German land border. 相似文献
974.
In situ experiments and seismic analysis of existing buildings. Part II: Seismic integrity threshold
The interest of in situ measurements (presented in Part I paper) for a seismic assessment of existing buildings is analysed in this paper. It is shown that the experimental modal characteristics obtained on regular concrete structures are described successfully by suited Timoshenko beam modelling. For a given structure, taking into account the experimental data, the corresponding beam model, and choosing the maximum tensile strain of concrete as damage criterion for key structural elements, a maximum level of the ground acceleration can be determined. This so‐called seismic integrity threshold is directly related to the onset of structural damages. This new approach is illustrated on one of the studied buildings. The advantages of using ambient vibrations survey for the vulnerability assessment of existing buildings are discussed. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
975.
øystein Hov Asgeir Sorteberg Norbert Schmidbauer Sverre Solberg Frode Stordal David Simpson Anne Lindskog Hans Areskoug Pedro Oyola Heikki Lättilä Niels Z. Heidam 《Journal of Atmospheric Chemistry》1997,28(1-3):173-193
Observations and model calculations of the concentration of hydrocarbonsat five Scandinavian rural sites during March–June 1993are reported.Decreasing concentrations from March to June are observedat all sites. The highest concentrations of hydrocarbons were found in air massescoming in from the southwest to southeast, indicating that long rangetransport fromcontinental Europe and the U.K. is important in pollution episodes. An episode of elevated concentrations of hydrocarbons observed at three of the sites in the middle of Marchis described and discussed in relation to the synoptic situation and thepresenceof other chemical compounds (NO2, PAN, total nitrate andozone).A Lagrangian numerical model is used to calculate the concentrations of theindividual hydrocarbons at the fivesites and comparison with observations is made.The calculated concentrations for nonmethane hydrocarbons with quite longchemicallifetimes agree well with the observations.For the sum of observed and calculated hydrocarbons the correlationcoefficientsare in the range of 0.65–0.88 for the five sitesand the ratio between calculated and measured concentrations was0.72–0.97, indicating thatthe European VOC emission inventory is quite well estimated. 相似文献
976.
U. Wiechert Dmitri A. Ionov Karl Hans Wedepohl 《Contributions to Mineralogy and Petrology》1997,126(4):345-364
Spinel peridotite xenoliths from the Atsagin-Dush volcanic centre, SE Mongolia range from fertile lherzolites to clinopyroxene(cpx)-bearing
harzburgites. The cpx-poor peridotites typically contain interstitial fine-grained material and silicate glass and abundant
fluid inclusions in minerals, some have large vesicular melt pockets that apparently formed after primary clinopyroxene and
spinel. No volatile-bearing minerals (amphibole, phlogopite, apatite, carbonate) have been found in any of the xenoliths.
Fifteen peridotite xenoliths have been analysed for major and trace elements; whole-rock Sr isotope compositions and O isotope
composition of all minerals were determined for 13 xenoliths. Trace element composition and Sr-Nd isotope compositions were
also determined in 11 clinopyroxene and melt pocket separates. Regular variations of major and moderately incompatible trace
elements (e.g. heavy-rare-earth elements) in the peridotite series are consistent with its formation as a result of variable
degrees of melt extraction from a fertile lherzolite protolith. The Nd isotope compositions of LREE (light-rare-earth elements)-depleted
clinopyroxenes indicate an old (≥ 1 billion years) depletion event. Clinopyroxene-rich lherzolites are commonly depleted in
LREE and other incompatible trace elements whereas cpx-poor peridotites show metasomatic enrichment that can be related to
the abundance of fine-grained interstitial material, glass and fluid inclusions in minerals. The absence of hydrous minerals,
ubiquitous CO2-rich microinclusions in the enriched samples and negative anomalies of Nb, Hf, Zr, and Ti in primitive mantle-normalized
trace element patterns of whole rocks and clinopyroxenes indicate that carbonate melts may have been responsible for the metasomatic
enrichment. Low Cu and S contents and high δ34S values in whole-rock peridotites could be explained by interaction with oxidized fluids that may have been derived from
subducted oceanic crust. The Sr-Nd isotope compositions of LREE-depleted clinopyroxenes plot either in the MORB (mid-ocean-ridge
basalt) field or to the right of the mantle array, the latter may be due to enrichment in radiogenic Sr. The LREE-enriched
clinopyroxenes and melt pockets plot in the ocean island-basalt field and have Sr-Nd isotope signatures consistent with derivation
from a mixture of the DMM (depleted MORB mantle) and EM (enriched mantle) II sources.
Received: 18 January 1996 / Accepted: 23 August 1996 相似文献
977.
Partial fusion of basic granulites at 5 to 15 kbar: implications for the origin of TTG magmas 总被引:24,自引:0,他引:24
Partial fusion experiments with basic granulites (S6, S37) believed to represent the lower crust beneath the Eifel region
(Germany) were performed at pressures from 5 to 15 kbar. Water-undersaturated experiments were carried out in the presence
of 1 wt% H2O plus 2.44 or 0.81 wt% CO2 equivalent to mole fractions of H2O/(H2O + CO2) of 0.5 and 0.75, respectively, of the volatile components added. At temperatures from 850 to 1100 °C the weight proportions
of melt range from 7 to 30 %. Melt compositions change from trondhjemitic over tonalitic to dioritic with increasing degree
of partial melting. Crystalline residua are plagioclase/pyroxene dominated at 5 kbar to garnet/pyroxene dominated at 15␣kbar.
Dehydration melting was studied in granulite S35 similar in composition to S6. The magmatic precursors of the granulite xenoliths
used in this study had geochemical characteristics of cumulate gabbro (metagabbro S37) and evolved melts (metabasalts S6,
S35), respectively. Melts from granulite S37 match the major element compositions of natural trondhjemites and tonalites.
At 5 kbar, their Al2O3 is relatively low, similar to tonalites from ophiolites. At 15 kbar, Al2O3 in the melts is high due to the near absence of plagioclase in the crystalline residua. The Al2O3 concentrations in 15 kbar melts from S6 (˜20 wt%) are higher than in natural tonalites. Depth constraints on the formation
of tonalitic magmas in the continental crust are provided by REE (rare earth element) patterns of the synthetic melts calculated
from the known REE abundances in metagabbro S37 and metabasalt S6 assuming batch melting and using partition coefficients
from the literature. The REE patterns of tonalites from active continental margins and Archean trondhjemite-tonalite-granodiorite␣associations
low in REE with LaN (chondrite normalised) from 10 to 30 and YbN from 1 to 2 are reproduced at pressures of 10 and 12.5 kbar from metagabbro S37 which displays a slightly L(light)REE enriched
pattern with LaN = 8 and YbN = 3. Natural tonalites with LaN from 30 to 100 require a source richer in REE than granulite S37. At 15 kbar, H(heavy)REEN in melts from granulite S37 are depressed below the level observed in natural tonalites due to the high proportion of garnet
(>30 wt%) in the residue. Melts from metabasalt S6 (enriched in REE with LaN = 38 and YbN = 16) do not match the REE characteristics of natural tonalites under any conditions.
Received: 1 July 1994 / Accepted: 11 September 1996 相似文献
978.
Columbite solubility in granitic melts: consequences for the enrichment and fractionation of Nb and Ta in the Earth's crust 总被引:13,自引:0,他引:13
The behaviour of niobium and tantalum in magmatic processes has been investigated by conducting MnNb2O6 and MnTa2O6 solubility experiments in nominally dry to water-saturated peralkaline (aluminium saturation index, A.S.I. 0.64) to peraluminous
(A.S.I. 1.22) granitic melts at 800 to 1035 °C and 800 to 5000 bars. The attainment of equilibrium is demonstrated by the
concurrence of the solubility products from dissolution, crystallization, Mn-doped and Nb- or Ta-doped experiments at the
same pressure and temperature. The solubility products of MnNb2O6 (Ksp
Nb) and MnTa2O6 (Ksp
Ta) at 800 °C and 2 kbar both increase dramatically with alkali contents in water-saturated peralkaline melts. They range from
1.2 × 10−4 and 2.6 × 10−4 mol2/kg2, respectively, in subaluminous melt (A.S.I. 1.02) to 202 × 10−4 and 255 × 10−4 mol2/kg2, respectively, in peralkaline melt (A.S.I. 0.64). This increase from the subaluminous composition can be explained by five
non-bridging oxygens being required for each excess atom of Nb5+ or Ta5+ that is dissolved into the melt. The Ksp
Nb and Ksp
Ta also increase weakly with Al content in peraluminous melts, ranging up to 1.7 × 10−4 and 4.6 × 10−4 mol2/kg2, respectively, in the A.S.I. 1.22 composition. Columbite-tantalite solubilities in subaluminous and peraluminous melts (A.S.I.
1.02 and 1.22) are strongly temperature dependent, increasing by a factor of 10 to 20 from 800 to 1035 °C. By contrast columbite-tantalite
solubility in the peralkaline composition (A.S.I. 0.64) is only weakly temperature dependent, increasing by a factor of less
than 3 over the same temperature range. Similarly, Ksp
Nb and Ksp
Ta increase by more than two orders of magnitude with the first 3 wt% H2O added to the A.S.I. 1.02 and 1.22 compositions, whereas there is no detectable change in solubility for the A.S.I. 0.64
composition over the same range of water contents. Solubilities are only slightly dependent on pressure over the range 800
to 5000 bars. The data for water-saturated sub- and peraluminous granites have been extrapolated to 600 °C, conditions at
which pegmatites and highly evolved granites may crystallize. Using a melt concentration of 0.05 wt% MnO, 70 to 100 ppm Nb
or 500 to 1400 ppm Ta are required for manganocolumbite and manganotantalite saturation, respectively. The solubility data
are also used to model the fractionation of Nb and Ta between rutile and silicate melts. Predicted rutile/melt partition coefficients
increase by about two orders of magnitude from peralkaline to peraluminous granitic compositions. It is demonstrated that
the γNb2O5/γTa2O5 activity coefficient ratio in the melt phase depends on melt composition. This ratio is estimated to decrease by a factor
of 4 to 5 from andesitic to peraluminous granitic melt compositions. Accordingly, all the relevant accessory phases in subaluminous
to peraluminous granites are predicted to incorporate Nb preferentially over Ta. This explains the enrichment of Ta over Nb
observed in highly fractionated granitic rocks, and in the continental crust in general.
Received: 9 August 1996 / Accepted: 26 February 1997 相似文献
979.
Knowledge about new technology is a main determinant of the competitiveness of cities and regions nowadays. It reduces the amount of uncertainty of companies in their daily operations. In addition, it is a basis for the establishment of new companies and the restructuring of old ones. The availability and use of knowledge has thus a major influence on the development of urban and regional economies. An amazingly small amount of research has been done on the knowledge capacity of cities to date, i.e. urban potentials to generate, store, transfer and use knowledge. This article explores therefore, the urban knowledge capacity in a theoretical and empirical sense. Attention will be given to essential urban knowledge activities, and to the comprehensive and complex nature of the phenomena involved. In addition, various planning tools aimed at knowledge-based economic growth will be considered, with a focus on differences between the actors involved, and opportunities and constraints for success. In the empirical part, the city of Delft in the Netherlands will serve as an example, particularly regarding local policies for knowledge-based growth. Delft is an interesting case given the abundant availability of new technology and the relatively low level of local new firm formation. 相似文献
980.