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221.
Weibiao HSU Aicheng ZHANG Rainer BARTOSCHEWITZ Yunbin GUAN Takayuki USHIKUBO Urs KRÄHENBÜHL Rainer NIEDERGESAESS Rudolf PEPELNIK Ulrich REUS Thomas KURTZ Paul KURTZ 《Meteoritics & planetary science》2008,43(8):1363-1381
Abstract— We report here the petrography, mineralogy, and geochemistry of lunar meteorite Sayh al Uhaymir 300 (SaU 300). SaU 300 is dominated by a fine‐grained crystalline matrix surrounding mineral fragments (plagioclase, pyroxene, olivine, and ilmenite) and lithic clasts (mainly feldspathic to noritic). Mare basalt and KREEPy rocks are absent. Glass melt veins and impact melts are present, indicating that the rock has been subjected to a second impact event. FeNi metal and troilite grains were observed in the matrix. Major element concentrations of SaU 300 (Al2O3 21.6 wt% and FeO 8.16 wt%) are very similar to those of two basalt‐bearing feldspathic regolith breccias: Calcalong Creek and Yamato (Y‐) 983885. However, the rare earth element (REE) abundances and pattern of SaU 300 resemble the patterns of feldspathic highlands meteorites (e.g., Queen Alexandra Range (QUE) 93069 and Dar al Gani (DaG) 400), and the average lunar highlands crust. It has a relatively LREE‐enriched (7 to 10 x CI) pattern with a positive Eu anomaly (?11 x CI). Values of Fe/Mn ratios of olivine, pyroxene, and the bulk sample are essentially consistent with a lunar origin. SaU 300 also contains high siderophile abundances with a chondritic Ni/Ir ratio. SaU 300 has experienced moderate terrestrial weathering as its bulk Sr concentration is elevated compared to other lunar meteorites and Apollo and Luna samples. Mineral chemistry and trace element abundances of SaU 300 fall within the ranges of lunar feldspathic meteorites and FAN rocks. SaU 300 is a feldspathic impact‐melt breccia predominantly composed of feldspathic highlands rocks with a small amount of mafic component. With a bulk Mg# of 0.67, it is the most mafic of the feldspathic meteorites and represents a lunar surface composition distinct from any other known lunar meteorites. On the basis of its low Th concentration (0.46 ppm) and its lack of KREEPy and mare basaltic components, the source region of SaU 300 could have been within a highland terrain, a great distance from the Imbrium impact basin, probably on the far side of the Moon. 相似文献
222.
Abstract— A series of experiments carried out by Koscheev et al. (1998, 2001, 2004, 2005) showed that the bimodal release of heavy noble gases from meteoritic nanodiamonds can be reproduced by a single implanted component. This paper investigates the implications of this result for interpreting the noble gas compositions of meteoritic nanodiamonds and for their origin and history. If the bimodal release exhibited by meteorite diamonds reflects release of the P3 noble gas component, then the composition inferred for the pure Xe‐HL end member changes slightly, the excesses of heavy krypton isotopes that define Kr‐H become less extreme, evidence appears for a Kr‐L component, and the nucleosynthetic contribution to argon becomes much smaller. After correction for cosmogenic neon inherited from the host meteorites, the neon in presolar diamonds shows evidence for pre‐irradiation, perhaps in interstellar space, and a nucleosynthetic component perhaps consistent with a supernova source. After a similar correction, helium also shows evidence for presolar irradiation and/or a nucleosynthetic component. For the case of presolar irradiation, due to the small size of the diamonds, a large entity must have been irradiated and recoiling product nuclei collected by the nanodiamonds. The high 3He/21Ne ratio (?43) calls for a target with a (C + O)/heavier‐element ratio higher than in chondritic abundances. Bulk gas + dust (cosmic abundances) meet this criteria, as would solids enriched in carbonaceous material. The long recoil range of cosmogenic 3He argues against a specific phase. The excess 3He in presolar diamonds may represent trapped cosmic rays rather than cosmogenic 3He produced in the vicinity of the diamond crystals. 相似文献
223.
Ilia Louban Nicole Bobrowski Dmitri Rouwet Salvatore Inguaggiato Ulrich Platt 《Bulletin of Volcanology》2009,71(7):753-765
The simultaneous quantitative determination of two-dimensional bromine monoxide (BrO) and sulphur dioxide (SO2) distributions in volcanic gas plumes is described. Measurements at the fumarolic field on the island Vulcano (autumn 2004)
and in the plume of Mt. Etna volcano (spring 2005) were carried out with an Imaging DOAS instrument. The SO2 fluxes of several fumaroles were estimated from two-dimensional distributions of SO2. Additionally, the first two-dimensional distributions of BrO within a volcanic plume were successfully retrieved. Slant
column densities of up to 2.6 × 1014 molecules per square centimetre were detected in the plume of Mt. Etna. The investigation of the BrO/SO2 ratio, calculated from the two-dimensional distributions of SO2 and BrO, shows an increase from the centre to the edge of the volcanic plume. These results have significance for the involvement
of ozone during BrO formation processes in volcanic emissions. 相似文献
224.
Bohdan Kříbek Karel Žák Petr Dobeš Jaromír Leichmann Marta Pudilová Miloš René Bohdan Scharm Marta Scharmová Antonín Hájek Daniel Holeczy Ulrich F. Hein Bernd Lehmann 《Mineralium Deposita》2009,44(1):99-128
Three major mineralization events are recorded at the Rožná uranium deposit (total mine production of 23,000 t U, average
grade of 0.24% U): (1) pre-uranium quartz-sulfide and carbonate-sulfide mineralization, (2) uranium, and (3) post-uranium
quartz-carbonate-sulfide mineralization. (1) K–Ar ages for white mica from wall rock alteration of the pre-uranium mineralization
style range from 304.5 ± 5.8 to 307.6 ± 6.0 Ma coinciding with the post-orogenic exhumation of the Moldanubian orogenic root
and retrograde-metamorphic equilibration of the high-grade metamorphic host rocks. The fluid inclusion record consists of
low-salinity aqueous inclusions, together with H2O-CO2-CH4, CO2-CH4, and pure CH4 inclusions. The fluid inclusion, paragenetic, and isotope data suggest that the pre-uranium mineralization formed from a
reduced low-salinity aqueous fluid at temperatures close to 300°C. (2) The uraniferous hydrothermal event is subdivided into
the pre-ore, ore, and post-ore substages. K–Ar ages of pre-ore authigenic K-feldspar range from 296.3 ± 7.5 to 281.0 ± 5.4 Ma
and coincide with the transcurrent reorganization of crustal blocks of the Bohemian Massif and with Late Stephanian to Early
Permian rifting. Massive hematitization, albitization, and desilicification of the pre-ore altered rocks indicate an influx
of oxidized basinal fluids to the crystalline rocks of the Moldanubian domain. The wide range of salinities of fluid inclusions
is interpreted as a result of the large-scale mixing of basinal brines with meteoric water. The cationic composition of these
fluids indicates extensive interaction with crystalline rocks. Chlorite thermometry yielded temperatures of 260°C to 310°C.
During this substage, uranium was probably leached from the Moldanubian crystalline rocks. The hydrothermal alteration of
the ore substage followed, or partly overlapped in time, the pre-ore substage alteration. K–Ar ages of illite from ore substage
alteration range from 277.2 ± 5.5 to 264.0 ± 4.3 Ma and roughly correspond with the results of chemical U–Pb dating of authigenic
monazite (268 ± 50 Ma). The uranium ore deposition was accompanied by large-scale decomposition of biotite and pre-ore chlorite
to Fe-rich illite and iron hydrooxides. Therefore, it is proposed that the deposition of uranium ore was mostly in response
to the reduction of the ore-bearing fluid by interaction with ferrous iron-bearing silicates (biotite and pre-ore chlorite).
The Th data on primary, mostly aqueous, inclusions trapped in carbonates of the ore substage range between 152°C and 174°C
and total salinity ranges over a relatively wide interval of 3.1 to 23.1 wt% NaCl eq. Gradual reduction of the fluid system
during the post-ore substage is manifested by the appearance of a new generation of authigenic chlorite and pyrite. Chlorite
thermometry yielded temperatures of 150°C to 170°C. Solid bitumens that post-date uranium mineralization indicate radiolytic
polymerization of gaseous and liquid hydrocarbons and their derivatives. The origin of the organic compounds can be related
to the diagenetic and catagenetic transformation of organic matter in Upper Stephanian and Permian sediments. (3) K–Ar ages
on illite from post-uranium quartz-carbonate-sulfide mineralization range from 233.7 ± 4.7 to 227.5 ± 4.6 Ma and are consistent
with the early Tethys-Central Atlantic rifting and tectonic reactivation of the Variscan structures of the Bohemian Massif.
A minor part of the late Variscan uranium mineralization was remobilized during this hydrothermal event. 相似文献
225.
Sourabh Bal Semjon Schimanke Thomas Spangehl Ulrich Cubasch 《Journal of Earth System Science》2017,126(2):19
Sudden stratospheric warming (SSW) events are identified to investigate their influence on the equatorial tropospheric climate. Composite analysis of warming events from Era-Interim (1979–2013) record a cooling of the tropical lower stratosphere with corresponding changes in the mean meridional stratospheric circulation. A cooling of the upper troposphere induces enhanced convective activity near the equatorial region of the Southern Hemisphere and suppressed convective activity in the off-equatorial Northern Hemisphere. After selecting vortex splits, the see-saw pattern of convective activity in the troposphere grows prominent and robust. 相似文献
226.
Rabbia Osvaldo M. Correa Karen J. Hernández Laura B. Ulrich Thomas 《International Journal of Earth Sciences》2017,106(8):2687-2711
International Journal of Earth Sciences - The El Abra porphyry copper deposit belongs to the Late Eocene—Early Oligocene metallogenic belt of northern Chile, which host several world-class... 相似文献
227.
Juan Carlos Afonso Giorgio Ranalli Manel Fernàndez William L. Griffin Suzanne Y. O'Reilly Ulrich Faul 《Earth and Planetary Science Letters》2010,289(3-4):606-618
We use thermodynamically self-consistent and hybrid methods to analyze the correlation of important physical parameters (e.g. bulk density, elastic moduli) with bulk Mg# and modal composition in mantle peridotites at upper mantle conditions. Temperature (anharmonic and anelastic), pressure and compositional derivatives for all these parameters are evaluated. The results show that the widely used correlations between Vp/Vs and Mg# in peridotites are strictly valid only for garnet-bearing assemblages at temperatures < 900 °C. The correlation breaks down when: i) spinel is the stable Al-rich phase in the assemblage and ii) when anelastic attenuation of seismic velocities becomes important (T ? 900 °C). This implies that the range of applicability of published Vp/Vs–Mg# correlations for the upper mantle is limited to a depth interval between the spinel–garnet phase transition and the 900 °C isotherm. We use numerical simulations to show that this depth interval is virtually nonexistent in lithospheres thinner than ~ 140 km and can comprise up to ~ 50% of the lithospheric mantle in thick (> 220 km) lithospheric domains. In addition, we show that for most of the upper mantle the expected Δ(Vp/Vs) values associated with compositional variations are smaller than the resolution limit of current seismological methods. All these considerations suggest that the Vp/Vs ratio is not a reliable measure of compositional variations and that for large parts of the upper mantle compositional anomalies cannot be separated from thermal anomalies on the basis of seismological studies only. We further confirm that the only reliable indicator of compositional anomalies in a peridotitic mantle is the ratio of density to shear wave velocities (ρ/Vs). Our results demonstrate that geophysical–petrological models (forward or inverse) that model these two fields (i.e. density and Vs) self-consistently within a robust thermodynamic framework are necessary for characterizing the small-scale thermal and compositional structure of the lithosphere and sublithospheric upper mantle. 相似文献
228.
Evaluation of seismic hazard for the assessment of historical elements at risk: description of input and selection of intensity measures 总被引:1,自引:1,他引:0
229.
Kay-Christian Emeis Ulrich Struck Thomas Leipe Timothy G. Ferdelman 《International Journal of Earth Sciences》2009,98(2):309-326
The coastal upwelling system offshore Namibia is ideally suited to address a focal question of the Integrated Marine Biogeochemistry and Ecosystem Research Programme: what are the mechanisms that drive long-term changes in ecosystems? Considerable interannual variability in climatic forcing is indicated by long time series of meteorological and remote sensing observation; these accompany considerable interannual to interdecadal changes in the upwelling intensity over the last 100 years, as well as a centennial trend. On longer time scales, the only archives available are sediment records spanning the late Holocene. To decipher the sediment record, we mapped surface-sediment patterns of proxies for physical (sea surface temperature/SST from alkenone unsaturation indexes) and nutrient (δ15N on bulk sedimentary N) variables. Their present-day surface-sediment patterns outline the coastal upwelling cells and filaments and associated high productivity area. Analysed in an array of dated sediment cores, the spatial patterns of SST suggest long-term (>100 years) variability in the location and intensity of individual upwelling cells. The patterns of δ15N outline an area of intense denitrification near the coast, and advection of water with low-oxygen concentrations in the undercurrent from the North. δ15N exhibits considerable downcore variability, in particular over the last 50 years. The variability appears to be governed by differences in extent of denitrification and thus of the shelf oxygen balance, which appears to have deteriorated in the last 50 years. Together, the data suggest that SST and denitrification conditions have remained in the narrow bounds outlined by today’s patterns in surface sediments, but that spatially small variability in upwelling intensity and make-up of upwelling feed waters induced considerable changes in the lower trophic levels of the coastal upwelling ecosystem over the last 6,000 years. Attempts to correlate proxy records from sediments with observational time series and regional climate reconstructions were not successful, possibly because annual to interannual environmental signals are erased in the process of sediment formation. 相似文献
230.
In order to advance our understanding of the long-term stability of subsurface ice, the diurnal martian water cycle, and implications for liquid water, we determined diffusion coefficients and adsorption kinetics for the water vapor produced by the sublimation of ice buried beneath various layers of fine-grained (<63, 63-125, and 125-250 μm) basaltic powder under simulated martian conditions. Sublimation rates at shallower depths, <10 mm, were determined to be affected by mass transfer through the atmosphere in addition to the basalt layer. For greater depths, the measured diffusion coefficients for water vapor moving through basalt grains were 1.56±0.53×10−4, 2.05±0.82×10−4, and for the <63, 63-125, and 125-250 μm basaltic layers, respectively. Through the Brunauer, Emmett and Teller (BET) isotherm, which assumes multiple molecular layers of adsorbed water, we determined the adsorption constants of 52.6±8.3 at 270 K for <63 μm, 39.0±6.4 at 267 K for 63-125 μm, and 54.3±9.3 at 266 K for 125-250 μm, resulting in surface areas of 2.6±0.1×104, 1.7±0.3×104, , respectively. These results suggest that while diffusion is too rapid to explain the purported diurnal cycle in water content of the atmosphere, adsorption is efficient and rapid, and does provide an effective mechanism to explain such a cycle. The present diffusion data suggest that very thin, <50 pr μm, shallow, 10 mm, ice deposits would last for >10 h at ∼224 K, just above the freezing point of saturated CaCl2. Temperatures can remain above ∼224 K over most of the planet, which means that water, even as saturated brine, will sublimate before the freezing point is reached and liquid could be formed. On the other hand, 1 m ice layers below 1 m of fine-grained basaltic regolith at 235 K and 10 Pa of atmospheric water could last 600 to 1300 years. At deeper depths and lower temperatures, ice could last since the last major obliquity change 400,000 years ago. 相似文献