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791.
David Völker Heidi Wehrmann Steffen Kutterolf Karthik Iyer Wolfgang Rabbel Jacob Geersen Kaj Hoernle 《International Journal of Earth Sciences》2014,103(7):2129-2153
In this paper, we constrain the input and output fluxes of H2O, Cl and S into the southern-central Chilean subduction zone (31°S–46°S). We determine the input flux by calculating the amounts of water, chlorine and sulfur that are carried into the subduction zone in subducted sediments, igneous crust and hydrated lithospheric mantle. The applied models take into account that latitudinal variations in the subducting Nazca plate impact the crustal porosity and the degree of upper mantle serpentinization and thus water storage in the crust and mantle. In another step, we constrain the output fluxes of the subduction zone both to the subcontinental lithospheric mantle and to the atmosphere–geosphere–ocean by the combined use of gas flux determinations at the volcanic arc, volume calculations of volcanic rocks and the combination of mineralogical and geothermal models of the subduction zone. The calculations indicate that about 68 Tg/m/Ma of water enters the subduction zone, as averaged over its total length of 1,480 km. The volcanic output on the other hand accounts for 2 Tg/m/Ma or 3 % of that input. We presume that a large fraction of the volatiles that are captured within the subducting sediments (which accounts for roughly one-third of the input) are cycled back into the ocean through the forearc. This assumption is however questioned by the present lack of evidence for major venting systems of the submarine forearc. The largest part of the water that is carried into the subduction zone in the crust and hydrated mantle (accounting for two-thirds of the input) appears to be transported beyond the volcanic arc. 相似文献
792.
David Völker Jacob Geersen Eduardo Contreras-Reyes Javier Sellanes Silvio Pantoja Wolfgang Rabbel Martin Thorwart Christian Reichert Martin Block Wilhelm Reimer Weinrebe 《International Journal of Earth Sciences》2014,103(7):1765-1787
The continental shelf and slope of southern Central Chile have been subject to a number of international as well as Chilean research campaigns over the last 30 years. This work summarizes the geologic setting of the southern Central Chilean Continental shelf (33°S–43°S) using recently published geophysical, seismological, sedimentological and bio-geochemical data. Additionally, unpublished data such as reflection seismic profiles, swath bathymetry and observations on biota that allow further insights into the evolution of this continental platform are integrated. The outcome is an overview of the current knowledge about the geology of the southern Central Chilean shelf and upper slope. We observe both patches of reduced as well as high recent sedimentation on the shelf and upper slope, due to local redistribution of fluvial input, mainly governed by bottom currents and submarine canyons and highly productive upwelling zones. Shelf basins show highly variable thickness of Oligocene-Quaternary sedimentary units that are dissected by the marine continuations of upper plate faults known from land. Seismic velocity studies indicate that a paleo-accretionary complex that is sandwiched between the present, relatively small active accretionary prism and the continental crust forms the bulk of the continental margin of southern Central Chile. 相似文献
793.
Abstract While beginning to establish a German Civil GPS Information and Observation Service in 1990, the actual and (near) future GPS market in Germany was analyzed. In addition, the feasibility of using GPS for water authority tasks has been studied during past years. Typical capabilities in this area are real‐time positioning for hydrographic surveying (kinematic application) and precise transfer of levels to tide gauges and verification at offshore positions. The article describes the user interests, the requirements, some of the test campaigns, and the derived concepts for future applications. 相似文献
794.
Wolfgang Siebel Horst P. Hann Martin Danišík Cosmas K. Shang Christoph Berthold Johann Rohrmüller Klaus Wemmer Noreen J. Evans 《International Journal of Earth Sciences》2010,99(6):1187-1197
Movement within the Earth’s upper crust is commonly accommodated by faults or shear zones, ranging in scale from micro-displacements
to regional tectonic lineaments. Since faults are active on different time scales and can be repeatedly reactivated, their
displacement chronology is difficult to reconstruct. This study represents a multi-geochronological approach to unravel the
evolution of an intracontinental fault zone locality along the Danube Fault, central Europe. At the investigated fault locality,
ancient motion has produced a cataclastic deformation zone in which the cataclastic material was subjected to hydrothermal
alteration and K-feldspar was almost completely replaced by illite and other phyllosilicates. Five different geochronological
techniques (zircon Pb-evaporation, K–Ar and Rb–Sr illite, apatite fission track and fluorite (U-Th)/He) have been applied
to explore the temporal fault activity. The upper time limit for initiation of faulting is constrained by the crystallization
age of the primary rock type (known as “Kristallgranit”) at 325 ± 7 Ma, whereas the K–Ar and Rb–Sr ages of two illite fractions
<2 μm (266–255 Ma) are interpreted to date fluid infiltration events during the final stage of the cataclastic deformation
period. During this time, the “Kristallgranit” was already at or near the Earth’s surface as indicated by the sedimentary
record and thermal modelling results of apatite fission track data. (U–Th)/He thermochronology of two single fluorite grains
from a fluorite–quartz vein within the fault zone yield Cretaceous ages that clearly postdate their Late-Variscan mineralization
age. We propose that later reactivation of the fault caused loss of helium in the fluorites. This assertion is supported by
geological evidence, i.e. offsets of Jurassic and Cretaceous sediments along the fault and apatite fission track thermal modelling
results are consistent with the prevalence of elevated temperatures (50–80°C) in the fault zone during the Cretaceous. 相似文献
795.
Pavla Kováříková Wolfgang Siebel Emil Jelínek Miroslav Štemprok Václav Kachlík František V. Holub Vratislav Blecha 《International Journal of Earth Sciences》2010,99(3):545-565
Mafic and intermediate intrusions occur in the Slavkovsky les as dykes, sills and minor tabular bodies emplaced in metamorphic
rocks or enclosed in late Variscan granites near the SW contact of the Western Krušné hory/Erzgebirge granite pluton. They
are similar in composition and textures to the redwitzites defined in NE Bavaria. Single zircon Pb-evaporation analyses constrain
the age of a quartz monzodiorite at 323.4 ± 4.4 Ma and of a granodiorite at 326.1 ± 5.6 Ma. The P–T range of magma crystallization is estimated at ~1.4–2.2 kbar and ~730–870°C and it accords with a shallow intrusion level
of late Variscan granites but provides lower crystallization temperatures compared to the Bavarian redwitzites. We explain
the heterogeneous composition of dioritic intrusions in the Slavkovsky les by mixing between mafic and felsic magmas with
a minor effect of fractional crystallization. Increased K, Ba, Rb, Sr and REE contents compared to tholeiitic basalts suggest
that the parental mafic magma was probably produced by melting of a metasomatised mantle, the melts being close to lamprophyre
or alkali basalt composition. Diorites and granodiorites originated from mixed magmas derived by addition of about 25–35 and
50 vol.%, respectively, of the acid end-member (granite) to lamprophyre or alkali-basalt magma. Our data stress an important
role of mafic magmas in the origin of late Variscan granitoids in NW Bohemian Massif and emphasize the effect of mantle metasomatism
on the origin of K-rich mafic igneous rocks. 相似文献
796.
Wolfgang Schirmer 《Central European Journal of Geosciences》2010,2(1):32-40
All younger Pleistocene interglacials form interglacial complexes. The term interglacial complex is a short term for a tight complex of interglacials, interstadials and breviglacials, separating a complex of warm periods from the long glacial periods (euglacials). In the terrestric environment the interglacial complexes are represented by soil clusters (solcomplexes). Therein which occur interglacial and interstadial soils of different types in the loess environment separated by thin beds of loess or loess derivates (breviglacials). This article considers the mutilation and simulation of solcomplexes. Frequently, fossil solcomplexes present themselves as diminished to a few soils or to one single soil. This mutilation of solcomplexes can be due to soil convergence (soils of different warm periods — interglacials, interstadials — merge to form optically one soil), syn-solcomplex erosion or post-solcomplex erosion and sometimes to soil disguise. Conversely solcomplexes may be simulated by narrowing of soils which belong to different interglacial complexes and moreover by soil divergence (splitting of a soil of one single warm period by an interlayer of rock) or by reworked soil sediment. 相似文献
797.
Lukáš Ackerman Martina Krňanská Wolfgang Siebel Ladislav Strnad 《Mineralogy and Petrology》2010,99(3-4):185-199
In western Bohemia, the Drahotín (gabbro-diorite) and Mutěnín (gabbronorite-diorite-syenite) intrusions show different origins and patterns of geochemical evolution. Parental magmas of the Drahotín intrusion were derived predominantly from enriched mantle sources, and the melts have undergone a significant degree of assimilation-fractional crystallization (AFC) during their ascent and/or emplacement into the crust. In contrast, the compositional variation of the complex Mutěnín intrusion cannot be explained by simple AFC processes, but more likely reflects the involvement of several parental magmas. The gabbronorite was derived from a depleted mantle source, whereas the diorite/syenite stem from a mixed mantle-crust reservoir. The contrasting evolution of the Drahotín and Mutěnín intrusions may be due to their melt derivation and magma emplacement under different tectonothermal regimes at different times. 相似文献
798.
Amateur decision-making in avalanche terrain with and without a decision aid: a stated choice survey
Avalanches pose a serious threat to recreational backcountry travelers in mountainous terrain. This study explores how the
three main amateur user groups of avalanche terrain in western Canada (backcountry skiers, out-of-bound skiers, and snowmobile
riders) balance recreational goals with safety concerns when choosing backcountry destinations under varying avalanche conditions.
Using a discrete choice experiment (DCE), a stated preference technique, the study first examines the strengths and weaknesses
in the decision process of the three amateur groups by comparing their responses with the choice patterns of professional
mountain guides. The results show that the decision-making strategies employed by the respective amateur groups vary considerably
in their level of complexity and the degree to which avalanche safety considerations are incorporated. Second, we examine
the effects of a decision aid that preprocesses the most crucial pieces of avalanche hazard information on the decision preferences
of the amateur groups in the DCE. The results show that a relatively simple decision aid can influence the decision-making
process considerably and steer users towards more avalanche hazard sensitive behaviour. 相似文献
799.
800.
Gert Finger Frank Eisenhauer Reinhard Genzel Christopher Mandla Ian Baker Domingo Alvarez Antonio Amorim Wolfgang Brandner Christophe Dupuy Casey Deen Derek Ives Leander Mehrgan Manfred Meyer Karin Perraut Guy Perrin Jörg Stegmeier Christian Straubmeier Harald J. Weller Vincent Isgar 《Astronomische Nachrichten》2023,344(8-9):e20230069
Near-infrared adaptive optics as well as fringe tracking for coherent beam combination in optical interferometry require the development of high-speed sensors. Because of the high speed, a large analog bandwidth is required. The short exposure times result in small signal levels which require noiseless detection. Both requirements cannot be met by state-of-the-art conventional CMOS technology of near-infrared arrays as has been attempted previously. A total of five near-infrared SAPHIRA 320 × 256 pixel HgCdTe e−APD arrays have been deployed in the wavefront sensors and in the fringe tracker of the VLTI instrument GRAVITY. The current limiting magnitude for coherent exposures with GRAVITY is mk = 19, which is made possible with ADP technology. New avalanche photo-diode array (APD) developments since GRAVITY include the extension of the spectral sensitivity to the wavelength range from 0.8 to 2.5 μm. After GRAVITY a larger format array with 512 × 512 pixels has been developed for both AO applications at the ELT and for long integration times. Since dark currents of <10−3 e−/s have been demonstrated with 1Kx1K e−APD arrays and 2Kx2K e−APD arrays have already been developed, the possibilities and adaptations of e−APD technology to provide noiseless large-format science-grade arrays for long integration times are also discussed. 相似文献