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71.
Sources of fluids and gases expelled at cold seeps offshore Georgia, eastern Black Sea 总被引:1,自引:0,他引:1
Anja Reitz Thomas Pape Mark Schmidt Florian Scholz Giovanni Aloisi Stephan M. Weise 《Geochimica et cosmochimica acta》2011,75(11):3250-46
Four seep sites located within an ∼20 km2 area offshore Georgia (Batumi seep area, Pechori Mound, Iberia Mound, and Colkheti Seep) show characteristic differences with respect to element concentrations, and oxygen, hydrogen, strontium, and chlorine isotope signatures in pore waters, as well as impregnation of sediments with petroleum and hydrocarbon potential. All seep sites have active gas seepage, near surface authigenic carbonates and gas hydrates. Cokheti Seep, Iberia Mound, and Pechori Mound are characterized by oil-stained sediments and gas seepage decoupled from deep fluid advection and bottom water intrusion induced by gas bubble release. Pechori Mound is further characterized by deep fluid advection of lower salinity pore fluids. The Pechori Mound pore fluids are altered by mineral/water reactions at elevated temperatures (between 60 and 110 °C) indicated by heavier oxygen and lighter chlorine isotope values, distinct Li and B enrichment, and K depletion. Strontium isotope ratios indicate that fluids originate from late Oligocene strata. This finding is supported by the occurrence of hydrocarbon impregnations within the sediments. Furthermore, light hydrocarbons and high molecular weight impregnates indicate a predominant thermogenic origin for the gas and oil at Pechori Mound, Iberia Mound, and Colkheti Seep. C15+ hydrocarbons at the oil seeps are allochtonous, whereas those at the Batumi seep area are autochthonous. The presence of oleanane, an angiosperm biomarker, suggests that the hydrocarbon source rocks belong to the Maikopian Formation. In summary, all investigated seep sites show a high hydrocarbon potential and hydrocarbons of Iberia Mound, Colkheti Seep, and Pechori Mound are predominantly of thermogenic origin. However, only at the latter seep site advection of deep pore fluids is indicated. 相似文献
72.
Experimental Study of the Brittle Behavior of Clay shale in Rapid Unconfined Compression 总被引:6,自引:3,他引:3
Florian Amann Edward Alan Button Keith Frederick Evans Valentin Samuel Gischig Manfred Blümel 《Rock Mechanics and Rock Engineering》2011,44(4):415-430
The mechanical behavior of clay shales is of great interest in many branches of geo-engineering, including nuclear waste disposal,
underground excavations, and deep well drilling. Observations from test galleries (Mont Terri, Switzerland and Bure, France)
in these materials have shown that the rock mass response near the excavation is associated with brittle failure processes
combined with bedding parallel shearing. To investigate the brittle failure characteristics of the Opalinus Clay recovered
from the Mont Terri Underground Research Laboratory, a series of 19 unconfined uniaxial compression tests were performed utilizing
servo-controlled testing procedures. All specimens were tested at their natural water content with loading approximately normal
to the bedding. Acoustic emission (AE) measurements were utilized to help quantify stress levels associated with crack initiation
and propagation. The unconfined compression strength of the tested specimens averaged 6.9 MPa. The crack initiation threshold
occurred at approximately 30% of the rupture stress based on analyzing both the acoustic emission measurements and the stress–strain
behavior. The crack damage threshold showed large variability and occurred at approximately 70% of the rupture stress. 相似文献
73.
Florian Kobierska Tobias Jonas Jan Magnusson Massimiliano Zappa Mathias Bavay Thomas Bosshard Frank Paul Stefano M. Bernasconi 《Applied Geochemistry》2011
A comprehensive hydrological modeling study in the drainage area of a hydropower reservoir in central Switzerland is presented. Two models were tested to reproduce the measured discharge dynamics: (1) a detailed energy-balance model (ALPINE3D) primarily designed for snow simulations; (2) a conceptual runoff model system (PREVAH), including a distributed temperature-index snow and ice melt model. Considerable effort was put into distributing available meteorological station data to the model grids as forcing data. The recent EU regional climate modeling initiative ENSEMBLES provided up-to-date climate predictions for two 30-a periods in mid and late 21st century. These were used to estimate evolutions in the water supply of the hydropower reservoir in response to expected climate changes. The simulations suggest a shift of spring peak-flow by almost two months for the end of the century. Warmer winter temperatures will cause higher winter base-flow. Due to glacier retreat, late-summer flow will decrease at the end of the century. 相似文献
74.
Calcium isotope record of Phanerozoic oceans: Implications for chemical evolution of seawater and its causative mechanisms 总被引:1,自引:0,他引:1
Juraj Farkaš Florian Böhm John Blenkinsop Robert van Geldern Silke Voigt 《Geochimica et cosmochimica acta》2007,71(21):5117-5134
A total of 280 brachiopods of Ordovician to Cretaceous age, complemented by published data from belemnites and planktonic foraminifera, are used to reconstruct the evolution of calcium isotope composition of seawater (δ44/40CaSW) over the Phanerozoic. The compiled δ44/40CaSW record shows a general increase from ∼1.3‰ (NIST SRM 915a) at the beginning of the Ordovician to ∼2‰ at present. Superimposed on this trend is a major long-term positive excursion from the Early Carboniferous to Early Permian as well as several short-term, mostly negative, oscillations.A numerical model of the global cycles of calcium, carbon, magnesium and strontium was used to estimate whether the recorded δ44/40CaSW variations can be explained by varying magnitudes of input and output fluxes of calcium to the oceans. The model uses the record of marine 87Sr/86Sr ratios as proxy for seafloor spreading rates, a record of oceanic Mg/Ca ratios to estimate rates of dolomite formation, and reconstructed atmospheric CO2, discharge and erosion rates to estimate continental weathering fluxes.The model results indicate that varying magnitudes of the calcium input and output fluxes cannot explain the observed δ44/40CaSW trends, suggesting that the isotope signatures of these fluxes must also have changed. As a possible mechanism we suggest variable isotope fractionation in the sedimentary output flux controlled by the dominant mineralogy in marine carbonate deposits, i.e. the oscillating ‘calcite-aragonite seas’. The ultimate control of the calcium isotope budget of the Phanerozoic oceans appears to have been tectonic processes, specifically variable rates of oceanic crust production that modulated the hydrothermal calcium flux and the oceanic Mg/Ca ratio, which in turn controlled the dominant mineralogy of marine carbonates, hence the δ44/40CaSW. As to the causes of the short-term oscillations recorded in the secular δ44/40CaSW trend, we tentatively propose that these are related to variable rates of dolomite formation and/or to changing chemical composition of the riverine flux, in particular and ratios, induced by variable proportions of silicate vs. carbonate weathering rates on the continents. 相似文献
75.
76.
Martin Thullner Florian CentlerHans-Hermann Richnow Anko Fischer 《Organic Geochemistry》2012,42(12):1440-1460
Compound specific stable isotope analysis (CSIA) has been established as a viable tool for proving, characterizing and assessing degradation of organic pollutants within contaminated aquifers. The fractionation of stable isotopes during contaminant degradation leads to observable shifts in stable isotope ratios which can serve as an indicator for in situ pollutant degradation and allow for a quantitative assessment by means of the so-called Rayleigh (distillation) equation.This review highlights the recent developments of the Rayleigh equation approach for quantifying in situ degradation of organic pollutants in contaminated aquifers. The advantages and limitations of the Rayleigh equation approach are discussed and suggestions for improvements are given. Concepts are provided to estimate the uncertainty due to errors or variability of input parameters and how to deal with such uncertainty. Moreover, the applicability of the Rayleigh equation approach is evaluated regarding the heterogeneity and complexity of groundwater systems. For such systems, the review discusses the relevance of non-destructive processes, which affect the concentration (e.g., dispersive mixing) and potentially also the stable isotope ratio of contaminants (e.g., sorption, volatilization), and the resulting implications for the Rayleigh equation approach. 相似文献
77.
Nobuyoshi Miyajima Tommaso Mandolini Florian Heidelbach Caroline Bollinger 《Comptes Rendus Geoscience》2019,351(2-3):295-301
Dislocation microstructures in experimentally deformed single-crystal pyrope-rich garnet, (Mg,Fe)3(Al,Cr)3Si3O12, and polycrystalline forsterite, Mg2SiO4, were investigated by using electron channeling contrast imaging (ECCI) and transmission electron microscopy (TEM) combined with a focused ion beam (FIB)-microsampling. In the orientation-optimized ECCI method, we successfully observed individual dislocations across subgrain boundaries in a low-atomic-number mineral, pyrope-rich garnet (averaged Z-numbers, AZs ~ 10). Dislocations in a deformed forsterite (iron-free olivine) were also visible in the ECCI. In the ECCI on the single-crystal garnet, deformation bands consisting of dislocations, unusual contrasts in stripes and inhomogeneous distributions of sub-micrometer-sized pores were found. Further site-specific TEM observation on the deformation band revealed a high density of partial dislocations and stacking fault ribbons. The site-specific characterizations from ECCI to TEM, with assistance of FIB, can provide a new approach to investigate dislocation microstructures of deformed materials at high pressure and high temperature. 相似文献
78.
A multi‐method field experiment to determine local groundwater flow in a glacier forefield 下载免费PDF全文
Florian Kobierska Tobias Jonas Nena Griessinger Christian Hauck Stephan Huxol Stefano M. Bernasconi 《水文研究》2015,29(6):817-827
We implemented multiple independent field techniques to determine the direction and velocity of groundwater flow at a specific stream reach in a glacier forefield. Time‐lapse experiments were conducted using two electrical resistivity tomography (ERT) lines installed in a cross pattern. A circular array of groundwater tubes was also installed to monitor groundwater flow via discrete salt injections. Both inter‐borehole and ERT results confirmed this stream section as a losing reach and enabled quantification of the flow direction. Both techniques yielded advection velocities varying between 5.7 and 21.8 m/day. Estimates of groundwater flow direction and velocity indicated that groundwater infiltrates from the stream nearby and not from the adjacent lateral moraine. Groundwater age estimated from radon concentration measurements supported this hypothesis. Despite uncertainties inherent to each of the methods deployed, the combination of multiple field techniques allowed drawing consistent conclusions about local groundwater flow. We thus regard our multi‐method approach as a reliable way to characterize the two‐dimensional groundwater flow at sites where more invasive groundwater investigation techniques are difficult to carry out and local heterogeneities can make single measurements unreliable. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
79.
Uranyl Retention on Quartz—New Experimental Data and Blind Prediction Using an Existing Surface Complexation Model 总被引:1,自引:0,他引:1
The adsorption behaviour of uranyl onto seven different samples of quartz was studied in batch experiments. Sea-sand (0.1–0.3 mm),
Fil-Pro 12/20 (1–2 mm) and five Min-U-Sil samples with smaller particle sizes (5, 10, 15, 30 and 40 μm) were used. The uptake
curves show “pH adsorption edges” in the range of pH 4–5. A good agreement of the new data with literature data was found
when plotting surface-normalised distribution coefficients versus pH. Differences in the adsorption behaviour for pre-treated
and untreated sea-sand samples were detectable resulting in a shift of the pH edge to higher pH values after treatment. A
literature surface complexation model was applied for blind predictions of the experimental results. The simulations described
the experimental observations quite well for the Min-U-Sil samples. For the two coarser quartz samples, the calculated over-predictions
were explained by the larger-than-expected measured specific surface area and measurable amounts of associated minerals, for
Fil-Pro 12/20 and sea-sand, respectively. Dissolution of the samples was studied as a function of pH. After 5 days, the measured
Si concentrations were all higher than equilibrium quartz solubilities, but lower than those of amorphous silica. With increasing
pH, dissolved silica increased. This strongly suggests that formation of dissolved uranyl–silicato complexes have to be considered
based on measured silica concentrations. 相似文献
80.
Nicolas Deichmann John Clinton Stephan Husen Florian Haslinger Donat Fäh Domenico Giardini Philipp Kästli Urs Kradolfer Iris Marschall Stefan Wiemer 《Swiss Journal of Geoscience》2009,102(3):505-514
This report of the Swiss Seismological Service summarizes the seismic activity in Switzerland and surrounding regions during
2008. During this period, 451 earthquakes and 75 quarry blasts were detected and located in the region under consideration.
The three strongest events occurred in the Valais, near Lac des Toules (ML 3.6), and in Graubünden, near Ilanz (ML 3.7) and Paspels (ML 4.0). Although felt by the population, they were not reported to have caused any damage. However, with a total of only 15
events with ML ≥ 2.5, the seismic activity in the year 2008 was far below the average over the previous 33 years. 相似文献