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91.
Zusammenfassung Bleiglanzproben aus verschiedenen Lagerstätten der Sierra de Cartagena wurden auf ihre Blei-Isotopen-Verhältnisse untersucht. Auffallend ist deren völlig identische Pb-Isotopen-Zusammensetzung, aus der sich nach dem Houtermans-Modell ein Modell-Alter von 30 Millionen Jahren errechnen läßt. Die Blei-Mineralisation im Erzdistrikt von Cartagena steht daher in einem sicheren Zusammenhang mit der Tätigkeit jungtertiärer subvulkanischer Magmenherde. Das Alter der Andesite wurde mittels Rb/Sr-Methode an einem Biotit des Atalaya-Andesites mit 44±27 m.y. bestimmt. Dieser Wert stimmt sehr gut mit einer Altersbestimmung an einem leukogranitischen Gang aus der Sierra Cabrera überein (50±3 m.y.). Die Ergebnisse der Spurenelement-bestimmung an Bleiglanzproben werden im Zusammenhang mit schon früher mitgeteilten Schwefel-Isotopen-Daten diskutiert.
Lead isotope ratios have been determined in galena samples from the Sierra de Cartagena (Spain). The range of the Pb-isotopes is extremely narrow within the ore district, which contains different types of ore deposits. The age of the galena bearing ore deposits has been determined by using the Houtermansmodel: 30 million years. The lead minertalisation in the district therefore may be linked to the subvolcanic activity of Tertiary age. Ascribing the mineralisation to three volcanic episodes of Palaeozoic, Miocene and Pliocene ages and two periodes of supergene processes is not possible. Rb/Sr ratios have been determined in a biotite sample from the Atalaya andesite. The mica age is 44±27 m.y. which is in closest agreement with the age given for rocks in the Sierra Cabrera (50±3 m.y.). The results of trace element analyses are discussed in connection with previously studied sulphur isotope composition.相似文献
92.
The search for exoelectron emission from Apollo 12 materials usually produced negative results, suggesting that the concentration of naturally occurring traps is very low. Weak exoelectron activity was found scattered inhomogeneously within a pigeonite basalt rock and in a deep core tube sample. Its erratic appearance and intensity makes any interpretation of radiation history most difficult and is attributed to the activity being carried by only a few scattered crystals. The thermally stimulated emission of exoelectrons is judged an unsuitable technique for tracing the radiation histories of these samples. 相似文献
93.
94.
Stefan L. Hastenrath 《Pure and Applied Geophysics》1969,75(1):268-277
Summary Vertical profiles of the content of sensible heat, potential energy, and latent heat in the atmosphere between 1000 and 100 mb, during January and July, are derived for the latitude circles 0, 10, 20, 30, 40, 50, and 60°N. Contrasts between oceans and continents are found to vary significantly with latitude and season.
Zusammenfassung Vertikalprofile des Gehalts an fühlbarer Wärme, potentieller Energie und latenter Wärme in der Atmosphäre zwischen 1000 and 100 mb werden für Januar und Juli und die Breitenkreise 0, 10, 20, 30, 40, 50, und 60°N abgeleitet. Gegensätze zwischen Land und See ändern sich mit geographischer Breite und Jahreszeit.相似文献
95.
Isaac Larbi Emmanuel Obuobie Anne Verhoef Stefan Julich Karl-Henz Feger Aymar Yaovi Bossa 《水文科学杂志》2020,65(13):2196-2209
ABSTRACT The need for a detailed investigation of the Vea catchment water balance components cannot be overemphasized due to its accelerated land-cover dynamics and the associated impacts on the hydrological processes. This study assessed the possible consequences of land-use change scenarios (i.e. business as usual, BAU, and afforestation for the year 2025) compared to the 2016 baseline on the Vea catchment’s water balance components using the Soil and Water Assessment Tool (SWAT) model. The data used include daily climate and discharge, soil and land use/land cover maps. The results indicate that the mean annual water yield may increase by 9.1% under the BAU scenario but decrease by 2.7% under the afforestation scenario; actual evapotranspiration would decrease under BAU but increase under afforestation; and groundwater recharge may increase under both scenarios but would be more pronounced under the afforestation scenario. These outcomes highlight the significance of land-cover dynamics in water resource management and planning at the catchment. 相似文献
96.
Martin Sudmanns Dirk Tiede Stefan Lang Helena Bergstedt Georg Trost Hannah Augustin 《International Journal of Digital Earth》2020,13(7):832-850
ABSTRACT Turning Earth observation (EO) data consistently and systematically into valuable global information layers is an ongoing challenge for the EO community. Recently, the term ‘big Earth data’ emerged to describe massive EO datasets that confronts analysts and their traditional workflows with a range of challenges. We argue that the altered circumstances must be actively intercepted by an evolution of EO to revolutionise their application in various domains. The disruptive element is that analysts and end-users increasingly rely on Web-based workflows. In this contribution we study selected systems and portals, put them in the context of challenges and opportunities and highlight selected shortcomings and possible future developments that we consider relevant for the imminent uptake of big Earth data. 相似文献
97.
Using a sample of 57 VLT FORS spectra in the redshift range 1.37< z < 3.40 and a comparison sample with 36 IUE spectra of local (
) starburst galaxies we derive CIV equivalent width values and estimate metallicities of starburst galaxies as a function
of redshift. Assuming that a calibration of the CIV equivalent widths in terms of the metallicity based on the local sample
of starburst galaxies is applicable to high-z objects, we find a significant increase of the average metallicities from about 0.16 Z
⊙ at the cosmic epoch corresponding to z ≈ 3.2 to about 0.42 Z
⊙ at z ≈ 2.3. A significant further increase in metallicity during later epochs cannot be detected in our data. Compared to the
local starburst galaxies our high-redshift objects tend to be overluminous for a given metallicity.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
98.
Davis JA May MD Greenfield BK Fairey R Roberts C Ichikawa G Stoelting MS Becker JS Tjeerdema RS 《Marine pollution bulletin》2002,44(10):1117-1129
In 1997, seven sport fish species were sampled from seven popular fishing areas in San Francisco Bay. Mercury exceeded a human health screening value in 44 of 84 (52%) samples. All collected samples of leopard shark and striped bass exceeded the mercury screening value of 0.23 microg/g wet weight. PCBs exceeded the screening value in 51 of 72 (71%) samples. DDT, chlordane, and dieldrin, had lower numbers of samples above screening values: 16 of 72 (22%) for DDT, 11 of 72 (15%) for chlordanes, and 27 of 72 (37%) for dieldrin. Concentrations of PCBs and other trace organics were highest in white croaker and shiner surfperch, the two species with the highest fat content in their muscle tissue. Fish from one location, Oakland Harbor, had significantly elevated wet weight concentrations of mercury, PCBs, DDTs, and chlordanes compared to other locations. Removal of skin from white croaker fillets reduced lipid concentrations by 27-49% and concentrations of trace organics by 33-40%. 相似文献
99.
Mitigating the Rate and Extent of Global Warming 总被引:1,自引:0,他引:1
Editorial Introduction
Mitigating the Rate and Extent of Global Warming 相似文献100.
Harald Geiger Ian Barnes Karl H. Becker Birger Bohn Theo Brauers Birgit Donner Hans-Peter Dorn Manfred Elend Carlos M. Freitas Dinis Dirk Grossmann Heinz Hass Holger Hein Axel Hoffmann Lars Hoppe Frank Hülsemann Dieter Kley Björn Klotz Hans G. Libuda Tobias Maurer Djuro Mihelcic Geert K. Moortgat Romeo Olariu Peter Neeb Dirk Poppe Lars Ruppert Claudia G. Sauer Oleg Shestakov Holger Somnitz William R. Stockwell Lars P. Thüner Andreas Wahner Peter Wiesen Friedhelm Zabel Reinhard Zellner Cornelius Zetzsch 《Journal of Atmospheric Chemistry》2002,42(1):323-357
Within the German Tropospheric Research Programme (TFS) numerous kinetic and mechanistic studies on the tropospheric reaction/degradation of the following reactants were carried out: oxygenated VOC, aromatic VOC, biogenic VOC, short-lived intermediates, such as alkoxy and alkylperoxy radicals.At the conception of the projects these selected groups were classes of VOC or intermediates for which the atmospheric oxidation mechanisms were either poorly characterised or totally unknown. The motivation for these studies was the attainment of significant improvements in our understanding of the atmospheric chemical oxidation processes of these compounds, particularly with respect to their involvement in photooxidant formation in the troposphere. In the present paper the types of experimental investigations performed and the results obtained within the various projects are briefly summarised. The major achievements are highlighted and discussed in terms of their contribution to improving our understanding of the chemical processes controlling photosmog formation in the troposphere. 相似文献