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81.
Urs Neu 《Boundary-Layer Meteorology》1995,73(1-2):189-193
The reduction of ozone in the nocturnal residual layer by vertical mixing to the surface was investigated for several summer smog episodes on the Swiss plateau in the years 1990 and 1991. Using a limited data set of SODAR measurements and surface ozone concentrations, a parameterization of the ozone depletion in the nocturnal residual layer due to vertical mixing to the ground is proposed. This model is not intended to be physically complete but is rather simple with limited input information required. The nocturnal ozone reduction within the whole planetary boundary layer (nocturnal boundary layer plus residual layer) over the complex terrain of the Swiss plateau for the days investigated is between 20 and 50%. 相似文献
82.
Chemical and geochemical studies of Lake Biel 总被引:1,自引:0,他引:1
Urs P. Nyffeler Paul W. Schindler Urban E. Wirz Dieter M. Imboden 《Aquatic Sciences - Research Across Boundaries》1983,45(1):45-61
The mixing and transport processes in Lake Biel have been studied using the heat and excess Rn-222 as natural tracers. The
mixing parameters were established in terms of coefficients of eddy diffusion in a two-dimensional box model. To account for
observed transient Rn-222 distribution, transport by advection had to be included in the model calculations.
Part I: Peter W. Santschi and Paul W. Schindler: A mass balance for Lake Biel and its implications for the rates of erosion
of the drainage area. Schweiz. Z. Hydrol.39, 182–200 (1977). 相似文献
83.
To elucidate the age and origin of seamounts in the eastern North Atlantic, 54 titanite and 10 zircon fractions were dated by the U-Pb chronometer, and initial Pb, Sr, and Hf isotope ratios were measured in feldspars and zircon, respectively. Rocks analyzed are essentially trachy-andesites and trachytes dredged during the “Tore Madeira” cruise of the Atalante in 2001. The ages reveal different pulses of alkaline magmatism occurring at 104.4 ± 1.4 (2σ) Ma and 102.8 ± 0.7 Ma on the Sponge Bob seamount, at 96.3 ± 1.0 Ma on Ashton seamount, at 92.3 ± 3.8 Ma on the Gago Coutinho seamount, at 89.3 ± 2.3 Ma and 86.5 ± 3.4 Ma on the Jo Sister volcanic complex, and at 88.3 ± 3.3 Ma, 88.2 ± 3.9, and 80.5 ± 0.9 Ma on the Tore locality. No space-time correlation is observed for alkaline volcanism in the northern section of the Tore-Madeira Rise, which occurred 20-30 m.y. after opening of the eastern North Atlantic. Initial isotope signatures are: 19.139-19.620 for 206Pb/204Pb, 15.544-15.828 for 207Pb/204Pb, 38.750-39.936 for 208Pb/204Pb, 0.70231-0.70340 for 87Sr/86Sr, and +6.9 to +12.9 for initial epsilon Hf. These signatures are different from Atlantic MORB, the Madeira Archipelago and the Azores, but they lie in the field of worldwide OIB. The Cretaceous seamounts therefore seem to be generated by melts from a OIB-type source that interact with continental lithospheric mantle lying formerly beneath Iberia and presently within the ocean-continent transition zone. Inheritance in zircon and high 207Pb of initial Pb substantiate the presence of very minor amounts of continental material in the lithospheric mantle. A long-lived thermal anomaly is the most plausible explanation for alkaline magmatism since 104 Ma and it could well be that the same anomaly is still the driving force for tertiary and quaternary alkaline magmatism in the eastern North Atlantic region. This hypothesis is agreement with the plate-tectonic position of the region since Cretaceous time, including an about 30° anti-clockwise rotation of Iberia. 相似文献
84.
Beda A. HOFMANN Silvio LORENZETTI Otto EUGSTER Urs KRÄHENBÜHL Gregory HERZOG Feride SEREFIDDIN Edwin GNOS Manuel EGGIMANN John T. WASSON 《Meteoritics & planetary science》2009,44(2):187-199
Abstract— The original mass (15915 g) of the Twannberg IIG (low Ni‐, high P) iron was found in 1984. Five additional masses (12 to 2488 g) were recovered between 2000 and 2007 in the area. The different masses show identical mineralogy consisting of kamacite single crystals with inclusions of three types of schreibersite crystals: cm‐sized skeletal (10.5% Ni), lamellar (17.2% Ni), and 1–3 × 10 μm‐sized microprismatic (23.9% Ni). Masses I and II were compared in detail and have virtually identical microstructure, hardness, chemical composition, cosmic‐ray exposure (CRE) ages, and 10Be and 26Al activities. Bulk concentrations of 5.2% Ni and 2.0% P were calculated. The preatmospheric mass is estimated to have been at least 11,000 kg. The average CRE age for the different Twannberg samples is 230 ± 50 Ma. Detrital terrestrial mineral grains in the oxide rinds of the three larger masses indicate that they oxidized while they were incorporated in a glacial till deposited by the Rhône glacier during the last glaciation (Würm). The find location of mass I is located at the limit of glaciation where the meteorite may have deposited after transport by the glacier over considerable distance. All evidence indicates pairing of the six masses, which may be part of a larger shower as is indicated by the large inferred pre‐atmospheric mass. 相似文献
85.
Massimo Chiaradia Jean Vallance Lluis Fontboté Holly Stein Urs Schaltegger Joshua Coder Jeremy Richards Mike Villeneuve Ian Gendall 《Mineralium Deposita》2009,44(4):371-387
New U–Pb, Re–Os, and 40Ar/39Ar dates are presented for magmatic and hydrothermal mineral phases in skarn- and porphyry-related ores from the Nambija and
Pangui districts of the Subandean zone, southeastern Ecuador. Nambija has been one of the main gold-producing centers of Ecuador
since the 1980s due to exceptionally high-grade ores (average 15 g/t, but frequently up to 300 g/t Au). Pangui is a recently
discovered porphyry Cu–Mo district. The geology of the Subandean zone in southeastern Ecuador is dominated by the I-type,
subduction-related, Jurassic Zamora batholith, which intrudes Triassic volcanosedimentary rocks. The Zamora batholith is in
turn cut by porphyritic stocks, which are commonly associated with skarn formation and/or porphyry-style mineralization. High
precision U–Pb and Re–Os ages for porphyritic stocks (U–Pb, zircon), associated prograde skarn (U–Pb, hydrothermal titanite),
and retrograde stage skarn (Re–Os, molybdenite from veins postdating gold deposition) of the Nambija district are all indistinguishable
from each other within error (145 Ma) and indicate a Late Jurassic age for the gold mineralization. Previously, gold mineralization
at Nambija was considered to be Early Tertiary based on K–Ar ages obtained on various hydrothermal minerals. The new Jurassic
age for the Nambija district is slightly younger than the 40Ar/39Ar and Re–Os ages for magmatic–hydrothermal minerals from the Pangui district, which range between 157 and 152 Ma. Mineralization
at Nambija and Pangui is associated with porphyritic stocks that represent the last known episodes of a long-lived Jurassic
arc magmatism (∼190 to 145 Ma). A Jurassic age for mineralization at Nambija and Pangui suggests that the Northern Andean
Jurassic metallogenic belt, which starts in Colombia at 3° N, extends down to 5° S in Ecuador. It also adds a new mineralization
style (Au-skarn) to the metal endowment of this belt.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
86.
John W Morgan Urs Krähenbühl R Ganapathy Edward Anders 《Geochimica et cosmochimica acta》1973,37(4):953-961
Luna 20 soil is remarkably similar to Apollo 16 soil, in its content of 17 mainly volatile or siderophile elements: Ag, Au, Bi, Br, Cd, Cs, Ge, In, Ir, Rb, Re, Sb, Se, Te, Tl, U, and Zn. Like other highland soils, it seems to contain an ancient meteoritic component of fractionated, volatile-poor composition. The bulk soil has a high ratio (9.4 × 10?2), similar to that in Apollo 16 soils (5.4 × 10?2), but higher than that in samples from other sites (1.1 × 10?2). It is severely contaminated with Ag, Cd, Re, and Sb, judging from a comparison with a 1.7 mg soil breccia sample from the coarse fraction of the soil. 相似文献
87.
Florian Gallien Aberra Mogessie Ernesto Bjerg Sergio Delpino Brigida Castro de Machuca Martin Thöni Urs Klötzli 《Lithos》2010,114(1-2):229-252
Migmatitic paragneisses of the Valle Fértil–La Huerta Ranges at the Western margin of the Sierras Pampeanas are composed of garnet–cordierite–plagioclase–biotite–quartz-bearing units that experienced peak metamorphic conditions of ca. 800 °C at 6–7 kbar. Based on petrological studies, pseudosection modeling and petrographic observations, an anticlockwise P–T path with a small pressure increment is proposed. Rare earth element LA-ICP-MS patterns acquired from rutile bearing garnets suggest a single stage of garnet growth at high-T at pressures above the ilmenite–rutile transition. U–Pb dating of zircon rims from the migmatites indicates two distinct metamorphic U–Pb ages of 525 ± 9 Ma and 478 ± 9 Ma. The older age is suggested to record an amphibolite facies event of the Pampean orogeny. The younger metamorphic age is contemporary with igneous zircons from metatonalites and pegmatites that yield 478 ± 4 Ma. We suggest that the prograde high-T metamorphic Famatinian event is associated with the emplacement of large magmatic bodies in which large-scale magmatic activity gave rise to an increased geothermal gradient of about 35 °C/km. Sm–Nd garnet ages of 447 ± 3 Ma indicate a time span of around 30 Ma for which temperatures above the garnet closure temperature prevailed. Using U–Pb, Sm–Nd and Rb–Sr isotope systems, a cooling rate of 3 to 6 °C/Myr is inferred. 相似文献
88.
Christoph THALMANN Otto EUGSTER Gregory F. HERZOG Suizhou XUE Jeffrey KLEIN Urs KRHENBÜHL Stephan VOGT 《Meteoritics & planetary science》1996,31(6):857-868
Abstract— We investigated the characteristics and history of lunar meteorites Queen Alexandra Range 93069, Yamato 793169 and Asuka 881757 based on the abundances of all stable noble gas isotopes, the concentrations of the radionuclides 10Be, 26Al, 36Cl, and 81Kr, and the abundances of Mg, Al, K, Ca, Fe, Cl, Sr, Y, Zr, Ba, and La. Based on the solar wind and cosmic-ray irradiations, QUE 93069 is the most mature lunar meteorite studied up to now. The 40Ar/36Ar ratio of the trapped component is 1.87 ± 0.16. This ratio corresponds to a time when the material was exposed to solar and lunar atmospheric volatiles ~400 Ma ago. On the other hand, Yamato 793169 and Asuka 881757 contain very little or no solar noble gases, which indicates that these materials resided in the top layer of the lunar regolith only briefly or not at all. For all lunar meteorites, we observe a positive correlation of the concentrations of cosmic-ray produced with trapped solar noble gases. The duration of lunar regolith residence for the lunar meteorites was calculated based on cosmic-ray produced 21Ne, 38Ar, 78Kr, 83Kr, and 126Xe and appropriate production rates that were derived based on the target element abundances and the shielding indicator 131Xe/126Xe. For QUE 93069, Yamato 793169, and Asuka 881757, we obtained 1000 ± 400 Ma, 50 ± 10 Ma, and <1 Ma, respectively. Both Asuka 881757 and Yamato 793169 show losses of radiogenic 4He from U and Th decay and Yamato 793169 also 40Ar loss from K-decay. For Asuka 881757, we calculate a K-Ar gas retention age of 3100 ± 600 Ma and a 244Pu-136Xe fission age of 4240 ± 170 Ma. This age is one of the oldest formation ages ever observed for a lunar basalt. The exposure history of QUE 93069 after ejection from the Moon was derived from the radionuclide concentrations: ejection 0.16 ± 0.03 Ma ago, duration of Moon-Earth transit 0.15 ± 0.02 Ma and fall on Earth <0.015 Ma ago. This ejection event is distinguished temporally from those which produced the other lunar meteorites. We conclude that six to eight events are necessary to eject all the known lunar meteorites. 相似文献
89.
90.
Survey and monitoring of landslide displacements by means of L-band satellite SAR interferometry 总被引:2,自引:2,他引:2
Tazio Strozzi Paolo Farina Alessandro Corsini Christian Ambrosi Manfred Thüring Johannes Zilger Andreas Wiesmann Urs Wegmüller Charles Werner 《Landslides》2005,2(3):193-201
This paper illustrates the capabilities of L-band satellite SAR interferometry for the investigation of landslide displacements.
SAR data acquired by the L-band JERS satellite over the Italian and Swiss Alps have been analyzed together with C-band ERS-1/2
SAR data and in situ information. The use of L-band SAR data with a wavelength larger than the usual C-band, generally considered
for ground motion measurements, reduces some of the limitations of differential SAR interferometry, in particular, signal
decorrelation induced by vegetation cover and rapid displacements. The sites of the Alta Val Badia region in South Tyrol (Italy),
Ruinon in Lombardia (Italy), Saas Grund in Valais (Switzerland) and Campo Vallemaggia in Ticino (Switzerland), representing
a comprehensive set of different mass wasting phenomena in various environments, are considered. The landslides in the Alta
Val Badia region are good examples for presenting the improved performance of L-band in comparison to C-band for vegetated
areas, in particular concerning open forest. The landslides of Ruinon, Saas Grund, and Campo Vallemaggia demonstrate the strength
of L-band in observing moderately fast displacements in comparison to C-band. This work, performed with historical SAR data
from a satellite which operated until 1998, demonstrates the capabilities of future planned L-band SAR missions, like ALOS
and TerraSAR-L, for landslide studies. 相似文献