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441.
The distribution of megablocks in the Ries crater,Germany: Remote sensing,field investigation,and statistical analyses 下载免费PDF全文
Sebastian Sturm Thomas Kenkmann Malte Willmes Gisela Pösges Harald Hiesinger 《Meteoritics & planetary science》2015,50(1):141-171
The Ries crater is a well‐preserved, complex impact crater that has been extensively used in the study of impact crater formation processes across the solar system. However, its geologic structure, especially the megablock zone, still poses questions regarding crater formation mechanics. The megablock zone, located between the inner crystalline ring and outer, morphologic crater rim, consists of allochthonous crystalline and sedimentary blocks, Bunte Breccia deposits, patches of suevite, and parautochthonous sedimentary blocks that slumped into the crater during crater modification. Our remote sensing detection method in combination with a shallow drilling campaign and geoelectric measurements at two selected megablocks proved successful in finding new megablock structures (>25 m mean diameter) within the upper approximately 1.5 m of the subsurface in the megablock zone. We analyzed 1777 megablocks of the megablock zone, 81 of which are new discoveries. In our statistical analysis, we also included 2318 ejecta blocks >25 m beyond the crater rim. Parautochthonous megablocks show an increase in total area and size toward the final crater rim. The sizes of allochthonous megablocks generally decrease with increasing radial range, but inside the megablock zone, the coverage with postimpact sediments obscures this trend. The size‐frequency distribution of all megablocks obeys a power‐law distribution with an exponent between approximately ?1.7 and ?2.3. We estimated a total volume of 95 km3 of Bunte Breccia and 47 km3 of megablocks. Ejecta volume calculations and a palinspastic restoration of the extension within the megablock zone indicate that the transient cavity diameter was probably 14–15 km. 相似文献
442.
Sanaz Salati Frank J.A. van Ruitenbeek Freek D. van der Meer Majid Hashemi Tangestani Harald van der Werff 《International Journal of Applied Earth Observation and Geoinformation》2011
Lithological boundaries provide information useful for activities such as mineral and hydrocarbon exploration, water resource surveys, and natural hazard evaluation. Automated detection of lithological boundaries reduces bias inherent in expert interpretation of boundaries and thus improves the reliability of lithological mapping. The Rotation Variant Template Matching (RTM) algorithm was applied to ASTER imagery to detect pre-defined lithological boundaries. Templates incorporating the mineral combinations gypsum–calcite and calcite–illite were designed to detect boundaries between evaporites, marly limestone, and sandstone. The RTM algorithm successfully detected lithological boundaries by rotating the templates over the ASTER imagery. The accuracy of the detected boundaries was spatially assessed using fuzzy set theory. Boundaries from a published geological map and boundaries interpreted from a stereo pair of aerial photos by five experts were used as references for assessing the accuracy. A confidence region unifying spatial errors was defined for the geological map and stereo-pair interpretation to provide boundary zones from these references. The correspondence between detected boundaries and the boundary zones of the aerial photo was better than between detected boundaries and boundary zones of the geological map. 相似文献
443.
High-resolution atmospheric angular momentum functions related to Earth rotation parameters during CONT08 总被引:1,自引:1,他引:0
Michael Schindelegger Johannes Böhm David Salstein Harald Schuh 《Journal of Geodesy》2011,85(7):425-433
Due to the temporal resolution of available numerical weather analyses, the effect of the atmosphere on Earth rotation at
daily and sub-daily periods is usually investigated using 6-hourly atmospheric angular momentum (AAM) functions. During the
period of CONT08, however, atmospheric analysis data were provided by the European Centre for Medium-Range Weather Forecasts
(ECMWF) also on an hourly basis. In this paper, we, therefore, determine two sets of AAM functions from ECMWF data—one for
CONT08 with hourly resolution and one for the year 2008 with 6-hourly resolution. The comparisons of the AAM functions to
high-resolution Earth rotation parameters (ERP) from VLBI and GPS observations are carried out in the frequency domain. Special
attention is paid to the preparation of the high-resolution data sets for the geodetic purposes, as there are jump discontinuities
at 12 h intervals. Hence, the hourly AAM functions need to be concatenated. The revised functions yield much smaller amplitudes
than their 6-hourly counterparts, as can be seen from the equatorial and the axial frequency spectra of atmospheric excitation
in Earth rotation. This decrease of spectral power in the hourly AAM functions is found to be associated with a strong counteraction
of pressure and wind terms, which originates from atmospheric circulation on short time scales. The results are compared to
previous findings published by Brzeziński and Petrov (IERS Tech Note 28:53–60, 2000) based on the data from the U.S. National Centers for Environmental Prediction (NCEP). 相似文献
444.
K. Schmidt D. Garbe-Schönberg A. Koschinsky H. Strauss C.L. Jost V. Klevenz P. Königer 《Chemical Geology》2011,280(1-2):1-18
Depending on the geological setting, the interaction of submarine hydrothermal fluids with the host rock leads to distinct energy and mass transfers between the lithosphere and the hydrosphere. The Nibelungen hydrothermal field is located at 8°18′S, about 9 km off-axis of the Mid-Atlantic Ridge (MAR). At 3000 m water depth, 372 °C hot, acidic fluids emanate directly from the bottom, without visible sulfide chimney formation. Hydrothermal fluids obtained in 2009 are characterized by low H2S concentrations (1.1 mM), a depletion of B (192 μM) relative to seawater, lower Si (13.7 mM) and Li (391 μM) concentrations relative to basaltic-hosted hydrothermal systems and a large positive Eu anomaly, and display a distinct stable isotope signature of hydrogen (?2HH2O = 7.6–8.7‰) and of oxygen (?18OH2O = 2.2–2.4‰).The heavy hydrogen isotopic signature of the Nibelungen fluids is a specific feature of ultramafic-hosted hydrothermal systems and is mainly controlled by the formation of OH-bearing alteration minerals like serpentine, brucite, and tremolite during pervasive serpentinization. New isotopic data obtained for the ultramafic-hosted Logatchev I field at 14°45′N, MAR (?2HH2O = 3.8–4.2‰) display a similar trend, being clearly distinguished from other, mafic-hosted hydrothermal systems at the MAR.The fluid geochemistry at Nibelungen kept stable since the first sampling campaign in 2006 and is evident for a hybrid alteration of mafic and ultramafic rocks in the subseafloor. Whereas the ultramafic-fingerprint parameters Si, Li, B, Eu anomaly and ?2HH2O distinguish the Nibelungen field from other hydrothermal systems venting in basaltic settings at similar physico-chemical conditions and are related to the interaction with mantle rocks, the relatively high concentrations of trace alkali elements, Pb, and Tl can only be attributed to the alteration of melt-derived gabbroic rocks. The elemental and isotopic composition of the fluid suggest a multi-step alteration sequence: (1) low- to medium-temperature alteration of gabbroic rocks, (2) pervasive serpentinization at moderate to high temperatures, and (3) limited high-temperature interaction with basaltic rocks during final ascent of the fluid. The integrated water/rock ratio for the Nibelungen hydrothermal system is about 0.5.The fluid compositional fingerprint at Nibelungen is similar to the ultramafic-hosted Logatchev I fluids with respect to key parameters. Some compositional differences can be ascribed to different alteration temperatures and other fluid pathways involving a variety of source rocks, higher water/rock ratios, and sulfide precipitation in the sub-seafloor at Logatchev I. 相似文献
445.
Pegmatites and aplites enriched in P, Be, Nb, Ta and Li occur in the high-temperature metamorphic lithological units of the NE Bavarian Basement, SE Germany. They are accompanied by Ba mineralization, in vein-type deposits in the basement as well as in its foreland. Locally, Ba minerals are encountered in the late Variscan pegmatites and aplites too. The shallow discordant stock-like pegmatites (Hagendorf-type) are barren as to Ba, but in the tabular, concordant aplites and pegmatites Ba was concentrated (Plössberg-type). These concordant pegmatites and aplites are supposed to be the root zone of the intrusive pegmatites. In the rare case of low sulfur fugacity, Ba forms Ba–Zr–K–Sc phosphates/silicates in the pegmatites (transition of magmatic into the hydrothermal stages I/II). Under high sulfur fugacity, Ba is accommodated within the same stages in the structure of baryte. Barium is not accommodated in the lattice of phosphates during or in the immediate aftermaths of the emplacement of these Be–P–Nb–Ta pegmatites (stage III). This element shows up again in APS minerals during supergene alteration under acidic conditions (stage IV). Considering the host rocks of baryte mineralization, the Sr contents of baryte increased from the early Paleozoic to the Late Triassic. The Sr contents of baryte are a function of the depth below ground in the vein-type deposits and in the shear-zones bounding the tabular concordant pegmatites. Beryl is not only a marker mineral for the shear-zone-hosted pegmatites but can also be used as a tool for the geodynamic positioning of these pegmatites using its oxygen isotopes. A subdivision of the pegmatites into intrusive and shear-zone hosted may be achieved by its REE and minor elements. 相似文献
446.
The Idrija mine was the second largest Hg mine in the world surpassed only by the Almaden mine in Spain. It has been estimated that almost 145,000 tons of Hg was produced during operation (1490-1995) of the mine. In the first decade of Hg mining in Idrija the ore was roasted in piles; after that it was roasted for 150 years, until 1652, in earthen vessels at various sites in the woods around Idrija. Pšenk is one out of 21 localities of ancient roasting sites established on the hills surrounding Idrija and one of the largest localities of roasting vessel fragments. The unique way of roasting very rich Hg ore at this site has resulted in soil contamination and considerable amounts of waste material that potentially leach Hg into the surrounding environment. The main aim of this study was to determine the distribution and the forms of Hg in contaminated soils in order to evaluate potential environmental risk. Detailed soil sampling was performed on 37,800 m2 area to establish the extent of Hg pollution and to investigate Hg transformations and transport characteristics through the 400 a-long period. A total of 156 soil (0-15 cm and 15-30 cm) and SOM (soil organic matter) samples were collected from 73 sampling points. Three soil profiles were sampled to determine vertical distribution of Hg. The main Hg phases were determined by the Hg-thermo-desorption technique. The measured Hg contents in soil samples in the study area vary from 5.5 to almost 9000 mg/kg with a median of 200 mg/kg. In SOM, Hg contents range from 1.4 to 4200 mg/kg with a median of 20 mg/kg. Extremely high Hg contents were found in soil profiles where the metal reaches 37,020 mg/kg. In general, Hg concentrations in all three profiles show a gradual decrease with depth with the minimum values between 140 mg/kg and 1080 mg/kg. The Hg-thermo-desorption curves indicate the presence of Hg in the form of cinnabar and that of Hg bound to organic or mineral soil matter. The distribution of Hg species in soil and SOM samples show almost equal distribution of cinnabar and non-cinnabar Hg compounds. The non-cinnabar fraction shows a little increase with depth, but cinnabar represents a high portion of total Hg (about 40%). Large amounts of potentially mobile and transformable non-cinnabar Hg compounds exist at the roasting site, which are potentially bioavailable. 相似文献
447.
Divergent growth trajectories in China’s chemical industry: the case of the newly developed industrial parks in Shanghai,Nanjing and Ningbo 总被引:1,自引:0,他引:1
In the late 1990’s, the “new-economy” industries in China proved to be relatively vulnerable and were strongly hit by the
financial crisis in Asia. As a result, a new economic support policy was introduced in China’s Yangtze Delta region, which
put greater emphasis on the support of traditional industrial sectors, including the chemical industry. This paper investigates
the effects of the growth of this industry, as well as the potential and current problems emerging from new growth paths.
It compares the growth of three newly developed chemical industry parks in Shanghai, Nanjing and Ningbo. The paper is based
on an institutional perspective of clustering processes arguing that regional industrialization is subject to formal and informal
institutions which shape the growth paths and contribute to divergent regional trajectories. Although these industrial parks
all benefit from the general economic upswing in China, their development is influenced by different business models, economic
contexts, goals and strategies, leaving room for divergence and specialization. Due to the existing structure of operations,
these parks have a great deal of potential but also face substantial challenges, such as the establishment of internal networks
and close customer linkages. It is argued that this might limit their innovative capability in the future. Furthermore, their
growth prospects differ depending on future government policies. 相似文献
448.
A systems dynamics model was developed to assess the planetary boundary for P supply in relation to use by human society. It is concluded that present day use rates and poor recycling rates of P are unsustainable at timescales beyond 100+ a. The predictions made suggest that P will become a scarce and expensive material in the future. The study shows clearly that market mechanisms alone will not be able to secure an efficient use before a large part of the resource will have been allowed to dissipate into the natural environment. It is suggested that population size management and effective recycling measures must be planned long term to avoid unpleasant consequences of hunger and necessary corrections imposed on society by mass balance and thermodynamics. 相似文献
449.
Harald Milsch Ronny Giese Mathias Poser Stefan Kranz Elvira Feldbusch Simona Regenspurg 《Environmental Earth Sciences》2013,70(8):3459-3463
A versatile fluid–chemical monitoring unit has been developed in the framework of the geothermal research platform Groß Schönebeck, Germany. It enables selective online and in situ measurements of various physico-chemical parameters at different surface locations of a geothermal fluid loop. Sensors are provided for pressure, temperature, volumetric flow rate, density, pH-value, redox potential, oxygen content, and electrical conductivity. In addition, the apparatus features two fluid samplers to manually collect fluid under in situ conditions and ultimately analyze the solution composition. All devices are mounted on a rack allowing easy transfer of the apparatus to other geothermal plants. The maximum operating pressure and temperature of the unit are 15 bar and 150 °C, respectively. The scientific and technical purpose of the system is to monitor a compositional variability of the produced fluid and chemical processes potentially occurring within the plant. These may result from reactions between the fluid and the surrounding materials, e.g., corrosion. Also, mineral precipitation as a consequence of temperature and/or pressure decrease or oxygen contamination may occur. This information is of paramount importance as so induced reactions might lead to failure of plant components or may damage the geothermal reservoir upon fluid reinjection and thus decrease injectivity. 相似文献
450.
Steven F. DiMarco Josiah Strauss Nelson May Ruth L. Mullins-Perry Ethan L. Grossman David Shormann 《Aquatic Geochemistry》2012,18(2):159-181
Hypoxic conditions in the coastal waters off Texas (USA) were observed since the late 1970s, but little is known about the
causes of stratification that contribute to hypoxia formation. Typically, this hypoxia is attributed to downcoast (southwestward)
advection of waters from the Mississippi–Atchafalaya River system. Here, we present evidence for a hypoxic event on the inner
shelf of Texas coincident with the presence of freshwater linked to high flow of the Brazos River in Texas. These conclusions
are based on hydrographic observations and isotopic measurements of waters on the inner shelf near the Brazos River mouth.
These data characterize the development, breakdown, and dispersal of a hypoxic event lasting from June through September 2007
off the Texas coast. Oxygen isotope compositions of shelf water indicate that (1) discharge from the Brazos River was the
principal source of freshwater and water column stratification during the 2007 event, and (2) during low Brazos River discharge
in 2008, freshwater on the Texas shelf was derived mainly from the Mississippi–Atchafalaya River System. Based on these findings,
we conclude that the Mississippi–Atchafalaya River System is not the sole cause of hypoxia in the northern Gulf of Mexico;
however, more data are needed to determine the relative influence of the Texas versus Mississippi rivers during normal and
low flow conditions of Texas rivers. 相似文献