The thermoelastic parameters of synthetic Ca3Al2Si3O12 grossular garnet were examined in situ at high-pressure and high-temperature by energy dispersive X-ray diffraction, using
a Kawai-type multi-anvil press apparatus coupled with synchrotron radiation. Measurements have been conducted at pressures
up to 20 GPa and temperatures up to 1,650 K: this P, T range covered the entire high-P, T stability field of grossular garnet. The analysis of room temperature data yielded V0,300 = 1,664 ± 2 ?3 and K0 = 166 ± 3 GPa for K¢0 K^{\prime}_{0} fixed to 4.0. Fitting of our P–V–T data by means of the high-temperature third order Birch–Murnaghan or the Mie–Grüneisen–Debye thermal equations of state,
gives the thermoelastic parameters: (∂K0,T/∂T)P = −0.019 ± 0.001 GPa K−1 and α0,T = 2.62 ± 0.23 × 10−5 K−1, or γ0 = 1.21 for fixed values q0 = 1.0 and θ0 = 823 (Isaak et al. Phys Chem Min19:106–120, 1992). From the comparison of fits from two different approaches, we propose to constrain the bulk modulus of grossular garnet
and its pressure derivative to KT0 = 166 GPa and K¢T0 K^{\prime}_{T0} = 4.03–4.35. Present results are compared with previously determined thermoelastic properties of grossular-rich garnets. 相似文献
The thermoelastic parameters of the CAS phase (CaAl4Si2O11) were examined by in situ high-pressure (up to 23.7 GPa) and high-temperature (up to 2,100 K) synchrotron X-ray diffraction, using a Kawai-type multi-anvil press. P–V data at room temperature fitted to a third-order Birch–Murnaghan equation of state (BM EOS) yielded: V0,300 = 324.2 ± 0.2 Å3 and K0,300 = 164 ± 6 GPa for K′0,300 = 6.2 ± 0.8. With K′0,300 fixed to 4.0, we obtained: V0,300 = 324.0 ± 0.1 Å3 and K0,300 = 180 ± 1 GPa. Fitting our P–V–T data with a modified high-temperature BM EOS, we obtained: V0,300 = 324.2 ± 0.1 Å3, K0,300 = 171 ± 5 GPa, K′0,300 = 5.1 ± 0.6 (?K0,T/?T)P = ?0.023 ± 0.006 GPa K?1, and α0,T = 3.09 ± 0.25 × 10?5 K?1. Using the equation of state parameters of the CAS phase determined in the present study, we calculated a density profile of a hypothetical continental crust that would contain ~10 vol% of CaAl4Si2O11. Because of the higher density compared with the coexisting minerals, the CAS phase is expected to be a plunging agent for continental crust subducted in the transition zone. On the other hand, because of the lower density compared with lower mantle minerals, the CAS phase is expected to remain buoyant in the lowermost part of the transition zone. 相似文献
A comprehensive study was performed to characterize, for the first time, the mud, water, and gases released from onshore mud volcanoes located in the southern margin of the Junggar Basin, northwestern China. Chemical compositions of mud, along with the geology of the basin, suggest that a source of the mud is Mesozoic or Cenozoic shale. Oxygen and H isotope compositions of the released water suggest a local meteoric origin. Combined with the positive Eu anomalies of the water, a large 18O shift of the water suggests extensive interaction with rocks. Gases discharged from the mud volcanoes are predominantly thermogenic hydrocarbons, and the high δ13C values (>+20‰ VPDB) for CO2 gases and dissolved carbonate in muddy water suggest secondary methanogenesis with CO2 reduction after oil biodegradation.The enrichments of Eu and 18O in water and the low thermal gradient of the area suggest that the water-rock interactions possibly occur deeper than 3670 ± 200 m. On the other hand, considering the relationship to the petroleum reservoir around the mud volcanoes, the depth of the gases can be derived from about 3600 m, a depth that is greater than that generally estimated for reservoirs whose gas is characterized by 13C-enriched CO2. Oil biodegradation with CO2 reduction likely occurs at a shallower depth along the seepage system of the mud volcano. The results contribute to the worldwide data set of gas genesis in mud volcanoes. Moreover, they further support the concept that most terrestrial mud volcanoes release thermogenic gas produced in very deep sediments and may be early indicators of oil biodegradation, an important problem in the petroleum industry. 相似文献
A number of seismoacoustic T-wave events were observed between January 2003 and January 2004 by broadband ocean-bottom seismometers installed on the French Polynesia seafloor at depths of 4,000?C5,000?m, well below the conjugate depth of the SOFAR channel. Using T-wave arrival times, we located 89 T-wave events along the Pacific-Antarctic Ridge. Among these, 63 events were not detected by land-based seismic observations of the United States Geological Survey (USGS), which was nearly twice the number of earthquakes reported by the USGS in the area during the observation period. We used a simple method to estimate earthquake magnitude from T-wave energy. The magnitudes of the events unidentified by the USGS ranged from 2.3 to 5.5, whereas magnitudes of the earthquakes reported by the USGS ranged from 4.1 to 6.2. Our study suggests that T-wave observations with abyssal ocean-bottom seismometers can improve the detection of small earthquakes and help our understanding of the seismotectonics of remote oceanic areas. 相似文献
Thermal expansion of single-crystal fayalite has been measured by a dilatometric method at temperatures between 25 °C and 850 °C. The results show the presence of anomalous expansion in the b axis, which is correlated to the anomalous variation of elastic moduli with temperature. Grüneisen's parameter is 1.10 and the thermal Debye temperature is 565 K, which is close to the acoustic Debye temperature of 511 K. 相似文献
Particulate matter plays an important role in the removal of metal ions from water in natural aquifers. Some of the most important of these materials consist of associations of inorganic particles (clay minerals, oxides) with humic substances, associations that can form readily in such an environment due to the strong affinity between inorganic particles and humic substances. These associations are referred to in this paper as organic-inorganic hybrids. However, it is not clear whether the sorbed species of metal ions in such organic-inorganic hybrids are organic or inorganic species because of the complexity of such hybrids and the lack of appropriate methods for characterizing the trace metal ions incorporated in them. In this study, laser-induced fluorescence spectroscopy (LIF) was used successfully to characterize the Cm(III) species on an FA(fulvic acid)-montmorillonite hybrid, an example of such organic-inorganic hybrids. The LIF clearly showed that Cm(III) can be sorbed as Cm(III)-fulvate complex in the FA-montmorillonite hybrid. These results were consistent with those of experiments of solid-water partitioning of Cm(III) (or Eu(III) used as an analogue) and speciation calculations based on the stability constants of Cm(III)-fulvate complexes determined in this study. The results of LIF and the partitioning experiments showed that the solid-water distribution of humic substances governed that of Cm(III) under our experimental conditions. The Cm(III) preference for forming Cm(III)-fulvate complexes was also evident under a condition that would be found in a natural aquifer with a fairly low concentration of organic matter in freshwater (dissolved organic carbon: 2 mg/dm3), as determined by our speciation calculations. These findings on the importance of humic substances in the migration of Cm(III) indicate that the clarification of the environmental behavior of humic substances is necessary to understand fully the behavior of Cm(III), or actinide(III) and lanthanide(III) ions, in natural aquifers. 相似文献
To reconstruct the pattern of past climate change in central Japan during the last 140 kyr, total planktonic diatom valve concentrations (valves g–1) and fluxes (valves cm–2 year–1) of total planktonic diatoms flux (PVF) and individual species were examined using a 140-m core taken from Lake Biwa, Shiga Prefecture. Most records had a sample resolution between approximately 150 and 300 yr. Based on characteristics of past and modern diatom responses to possible climate variables, we interpreted changes in Stephanodiscus suzukii flux (SVF) to reflect changes in phosphorus levels, which reflect, in turn, summer precipitation levels; changes in Aulacoseiva nipponica flux (AVF) reflect winter vertical lake-water mixing induced by winter temperatures and snowfall levels. Thus, changes in total planktonic diatom flux reflect a combination of summer precipitation, winter temperature, and snowfall values. During the 140–101 ka interval, changes in S. suzukii productivity at a millennial timescale may correspond to changes in summer rainfall in central Japan. The disappearance of A. nipponica during the same period could indicate weaker vertical mixing, possibly caused by increased temperatures and decreased snowfall levels in winter. During the 101–70 ka interval, the AVF record shows levels near or above those observed in present times, indicating that winter water temperatures fell within the optimal range for A. nipponica to prosper. Generally low AVF values during the 70–7 ka interval indicate weak winter vertical mixing and cold winters. The many intervals with low PVF values during the same period suggest decreased summer precipitation levels. Between 7 and 0 ka, PVF, SVF, and AVF records show levels near or above those of the present, suggesting winter temperatures favorable for A. nipponica growth, and snowfall and summer precipitation levels probably similar to or above those currently recorded. 相似文献
A dynamic effective stress analysis with the finite element method has long been recommended to predict the liquefaction phenomena of sandy soil by authors and Zienkiewicz et al. as well as the similar approaches by the others. Our approach of the analysis is summarized in the first.
Until recently, however, these approaches has not commonly been used as the means of design, although its capability of prediction is appreciated by geotechnicians. This method has been neglected because of the lack of verification studies of soil models of sand and mathematical formulation for boundary problems of liquefaction phenomena. Therefore the verification of the numerical method to evaluate liquefaction potential are urgent requirement of the recent engineering practice. To respond this requirement, extensive numerical studies on the liquefation simulations are performed by DIANA program for shaking table tests which have been conducted by the authors. The test models are soil-structure type models with combination of homogenous ground and partially improved ground by compaction.
The good performance of our approach is proved by the results of numerical simulation showing good agreement with experimental data in terms of response acceleration, excess pore pressure, and deformation profile. It is also demonstrated that the numerical results can provide substantial information to understand the mechanisms of soil ground behavior which is not easily obtained by experiments.
The procedure to identify soil constants for the reflecting surface model is also reported in details. 相似文献
A method of body-wave inversion is developed in an attempt to extract the information about asperities or barriers in a fault zone. A sequence of point sources, each being characterized with the seismic moment, the onset time and the location, are iteratively derived from observed records at multi-stations, where the two-dimensional extent of the source location is taken into account. A modification is made of the iterative method of Kikuchi and Kanamori on the formulation of inversion procedure to facilitate the computation.Using this method, we analyse long period P waves of the Tokachi-Oki earthquake of 1968 (Mw = 8.2) and obtain several significant subevents with time durations of ~ 10 s. Their spatio-temporal distribution shows that the rupture process consists of three characteristic stages: (A) a stage of introductory rupture, (B) a stage of main rupture and (C) a stage of aftershocks. The main rupture takes place in the form of clustering around a few sites of the fault plane. The largest subevent occurs in the northwestern corner. The stress drop associated with this event is estimated to be ~ 200 bars, one order of magnitude higher than the stress drop averaged over the entire fault plane. The sum of the seismic moments of the individual subevents amounts to 2.3 × 1028 dyn. cm which approximately coincides with the one estimated from the analysis of long-period surface waves. This implies that the source of the Tokachi-Oki earthquake consists of several major subevents with time durations of ~ 10 s in addition to other minor subevents. 相似文献
Elastic moduli of forsterite were measured between 300 and 1,200 K (? 1.6 times the Debye temperature) by the Rectangular Parallelepiped Resonance method. All the moduli decrease regularly with temperature. A summary of the results is as follows: