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61.
Hydration of rhyolitic glass during weathering as characterized by IR microspectroscopy 总被引:1,自引:0,他引:1
Tadashi Yokoyama Satoshi Okumura Satoru Nakashima 《Geochimica et cosmochimica acta》2008,72(1):117-125
The mechanism and rate of hydration of rhyolitic glass during weathering were studied. Doubly polished thin sections of two rhyolites with different duration of weathering (Ohsawa lava: 26,000 yr, Awanomikoto lava: 52,000 yr) were prepared. Optical microscope observation showed that altered layers had developed along the glass surfaces. IR spectral line profile analysis was conducted on the glass sections from the surface to the interior for a length of 250 μm and the contents of molecular H2O (H2Om), OH species (OH) and total water (H2Ot) were determined. The diffusion profile of H2Om in Ohsawa lava extends beyond the layer observed by optical microscope. The content of H2Om in the hydrated region is much higher than that of OH species. Thus, the reaction from H2Om to OH appears to be little and H2Om is the dominant water species moving into the glass during weathering. Based on the concentration profiles, the diffusion coefficients of H2Om(DH2Om) and H2Ot(DH2Ot) were determined to be 2.8 × 10−10 and 3.4 × 10−10 μm2 s−1 for Ohsawa lava, and 5.2 × 10−11 and 4.1 × 10−11 μm2 s−1 for Awanomikoto lava, respectively. The obtained DH2Om during weathering are more than 2-3 orders of magnitude larger than the diffusion coefficient at ∼20 °C that is extrapolated from the diffusivity data for >400 °C. This might suggest that the mechanism of water transport is different at weathering conditions and >400 °C. 相似文献
62.
Stable isotope exchange processes between solid and liquid phases of a natural melting snowpack are investigated in detail by separating the liquid water from snow grains at different depths of the snowpack and collecting the bottom discharge using a lysimeter. In the melting–freezing mass exchange process between the two phases, the theoretical slope of the δD? δ18O line for newly refrozen ice is calculated to be nearly that of pore water. However, based on observations of the isotopic evolution and snow grain coarsening of the snowpack, it is demonstrated that the slope of the δD? δ18O line for newly refrozen ice is equal to that of the original ice. This is proved to be due to preferential water flow in the snowpack, which leads to relatively more deuterium and less oxygen‐18 in the mobile water than the immobile water because of the kinetic effect. Higher mass exchange rate in the mobile water region results in excess deuterium in the bulk refrozen ice, compared with the fractionation of uniform fractionation factors and exchange rate. This effect, which is termed the ‘preferential exchange rate effect of isotopic fractionation’, is shown to be larger in the lower part than the upper part of the snowpack. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
63.
64.
Dehydration behavior of muscovite flake was investigated at 760–860°C by using in situ high-temperature IR microspectroscopy
for the OH absorption band around 3,620 cm−1. Isothermal kinetic heating experiments at each temperature gave detailed decrease curves of the OH band area with time.
These curves have been simulated by the first and second order reactions or mono- and two-dimensional diffusion processes.
The mono-dimensional diffusion was found to give the best fit to the experimental data and apparent diffusion coefficients
D were determined at 760–860°C with the activation energy of 290 ± 20 kJ/mol. The apparent diffusion coefficients D varied with the sample thickness L. This variation can be explained by an m layers model with a unit length of L′ with a constant diffusion coefficient D′. Therefore, the dehydration process might be rate-limited by mono-dimensional diffusion through tetrahedral silicate sheet
perpendicular to (001) planes of muscovite with a unit length of L′. 相似文献
65.
Masaya Masayoshi Saito Kiyotaka Tanikawa 《Celestial Mechanics and Dynamical Astronomy》2007,98(2):95-120
The dynamical structure of phase space of gravitational Newtonian three bodies which lie on a line (rectilinear three-body
system) is studied. We take an initial value plane and classify the points on the plane according to the fate of the orbits
starting from the points, using symbol sequences. The structure appearing on the initial value plane with this classification
was well studied for the equal-mass case (Tanikawa and Mikkola 2000, Chaos 10, 649–657). In this paper, we follow and clarify the changes of this structure with the mass ratio of three particles. 相似文献
66.
Masayoshi Oka 《Transactions in GIS》2011,15(1):109-123
This article demonstrates a way to model the urban microclimate using a combination of statistical analysis and a geographic information system (GIS). Field measurements of ambient temperature and relative humidity were collected in various urban settings at ground level over two surface materials and at two different times of the day. A panel autoregressive (PAR) model was created to conduct a regression analysis capable of accounting for the spatial autocorrelation. With the PAR analyses, selected urban street characteristics showed varying effects over the different surface materials and at different times of the day. The overall influences were consistent with previous findings. PAR models were then applied in GIS to create thermal prediction maps for the study area to determine the hot and cool spots. Since GIS is the most commonly used technology among a wide range of researchers and professionals, this article provides a means to improve the synthesis, integration, and sharing of information to understand the relationship between the heat‐vulnerable population and heat stress within the urban environment. This methodology will be useful in the effort to reduce the heat‐related morbidity and mortality, which are expected to increase with projected global warming. 相似文献
67.
Michiyo Sawai Ikuo Katayama Arisa Hamada Makoto Maeda Satoru Nakashima 《Physics and Chemistry of Minerals》2013,40(4):319-330
The dehydration kinetics of serpentine was investigated using in situ high-temperature infrared microspectroscopy. The analyzed antigorite samples at room temperature show relatively sharp bands at around 3,655–3,660 cm?1 (band 1), 3,570–3,595 cm?1 (band 2), and 3,450–3,510 cm?1 (band 3). Band 1 corresponds to the Mg–OH bond, and bands 2 and 3 correspond to OH associated with the substitution of Al for Si. Isothermal kinetic heating experiments at temperatures ranging from 625 to 700 °C showed a systematic decrease of the OH band absorbance with heating duration. The one-dimensional diffusion was found to provide the best fit to the experimental data, and diffusion coefficients were determined with activation energies of 219 ± 37 kJ mol?1 for the total water band area, 245 ± 46 kJ mol?1 for band 1, 243 ± 57 kJ mol?1 for band 2, and 256 ± 53 kJ mol?1 for band 3. The results indicate that the dehydration process is controlled by one-dimensional diffusion through the tetrahedral geometry of serpentine. Fluid production rates during antigorite dehydration were calculated from kinetic data and range from 3 × 10?4 to 3 × 10?5 $ {\text{m}}_{\text{fluid}}^{ 3} \,{\text{m}}_{\text{rock}}^{ - 3} \,{\text{s}}^{ - 1} $ . The rates are high enough to provoke hydraulic rupture, since the relaxation rates of rocks are much lower than these values. The results suggest that the rapid dehydration of antigorite can trigger an intermediate-depth earthquake associated with a subducting slab. 相似文献
68.
Kaul Gena Hitoshi Chiba Katsuo Kase Kazuo Nakashima Daizo Ishiyama 《Resource Geology》2013,63(4):360-370
A sulfide chimney ore sampled from the flank of the active Tiger vent area in the Yonaguni Knoll IV hydrothermal field, south Okinawa trough, consists of anhydrite, pyrite, sphalerite, galena, chalcopyrite and bismuthinite. Electron microprobe analysis indicates that the chalcopyrite contains up to 2.4 wt% Sn, whereas bismuthinite contains up to 1.7 wt% Pt, 0.8 wt% Cu and 0.5 wt% Fe. The Sn‐rich chalcopyrite and Pt–Cu–Fe‐bearing bismuthinite are the first reported occurrence of such minerals in an active submarine hydrothermal system. The results confirm that Sn enters the chalcopyrite as a solid solution towards stannite by the coupled substitution of Sn4+Fe2+ for Fe3+Fe3+, whereas Pt, Cu and Fe enter the bismuthinite structure as a solid solution during rapid nucleation. The fluid inclusions homogenization temperatures in anhydrite (220–310°C) and measured end‐member temperature of the vent fluids on‐site (325°C) indicate that Sn‐bearing chalcopyrite and Pt–Cu–Fe‐bearing bismuthinite express the original composition of the minerals that precipitated as metastable phases at a temperature above 300°C. The result observed in this study implies that sulfides in ancient volcanogenic massive sulfide deposits have similar trace element distribution during nucleation but it is remobilised during diagenesis, metamorphism or supergene enrichment processes. 相似文献
69.
Noriko T. Kita Kees C. Welten John W. Valley Michael J. Spicuzza Daisuke Nakashima Travis J. Tenner Takayuki Ushikubo Glenn J. MacPherson Linda Welzenbach Philipp R. Heck Andrew M. Davis Matthias M. M. Meier Rainer Wieler Marc W. Caffee Matthias Laubenstein Kunihiko Nishiizumi 《Meteoritics & planetary science》2013,48(4):641-655
The Mifflin meteorite fell on the night of April 14, 2010, in southwestern Wisconsin. A bright fireball was observed throughout a wide area of the midwestern United States. The petrography, mineral compositions, and oxygen isotope ratios indicate that the meteorite is a L5 chondrite fragmental breccia with light/dark structure. The meteorite shows a low shock stage of S2, although some shock‐melted veins are present. The U,Th‐He age is 0.7 Ga, and the K‐Ar age is 1.8 Ga, indicating that Mifflin might have been heated at the time of the 470 Ma L‐chondrite parent body breakup and that U, Th‐He, and K‐Ar ages were partially reset. The cosmogenic radionuclide data indicate that Mifflin was exposed to cosmic rays while its radius was 30–65 cm. Assuming this exposure geometry, a cosmic‐ray exposure age of 25 ± 3 Ma is calculated from cosmogenic noble gas concentrations. The low 22Ne/21Ne ratio may, however, indicate a two‐stage exposure with a longer first‐stage exposure at high shielding. Mifflin is unusual in having a low radiogenic gas content combined with a low shock stage and no evidence of late stage annealing; this inconsistency remains unexplained. 相似文献
70.
Masayoshi Nakashima 《地震工程与工程振动(英文版)》2012,11(1):11-21
Steel fiber reinforced cementitous composites(SFRCC)is a promising material with high strength in both compression and tension compared with normal concrete.The ductility is also greatly improved because of 6%volume portion of straight steel fibers.A steel beam-column connection with Steel fiber reinforced cementitous composites(SFRCC) slab diaphragms is proposed to overcome the damage caused by the weld.The push-out test results suggested that the application of SFRCC promises larger shear forces transferred through headed studs allocated in a small area in the slab. Finite element models were developed to simulate the behavior of headed studs.The failure mechanism of the grouped arrangement is further discussed based on a series of parametric analysis.In the proposed connection,the SFRCC slab is designed as an exterior diaphragm to transfer the beam flange load to the column face.The headed studs are densely arranged on the beam flange to connect the SFRCC slab diaphragms and steel beams.The seismic performance and failure mechanism of the SFRCC slab diaphragm beam-column connection were investigated based on the cyclic loading test.Beam hinge mechanism was achieved at the end of the SFRCC slab diaphragm by using sufficient studs and appropriate rebars in the SFRCC slab. 相似文献