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101.
The Ohori ore deposit is one of the Cu–Pb–Zn deposits in the Green Tuff region, NE Japan, and consists of skarn‐type (Kaninomata) and vein‐type (Nakanomata) orebodies. The former has a unique origin because its original calcareous rocks were made by hydrothermal precipitation during Miocene submarine volcanism. Carbon and oxygen isotope ratios of skarn calcite and sulfur isotope ratios of sulfides were measured in and around the deposit. Carbon and oxygen isotope ratios of the skarn calcite are δ13C = ?15.51 to ?5.1‰, δ18O = +3.6 to +22.5‰. δ13C values are slightly lower than those of the Cretaceous skarn deposits in Japan. These isotope ratios of the Kaninomata skarn show that the original calcareous rocks resemble the present submarine hydrothermal carbonates at the CLAM Site, Okinawa Trough, than Cenozoic limestones, even though some isotopic shifts had occurred during later skarnization. δ34S ratios of the sulfide minerals from the Kaninomata and Nakanomata orebodies are mostly in a narrow range of +4.0 to +7.0‰ and they resemble each other, suggesting the same sulfur origin for the both deposits. The magnetite‐series Tertiary Kaninomatasawa granite is distributed just beneath the skarn layer and has δ34S ratios of +7.5 to 8.1‰. The heavy sulfur isotope ratio of the skarn sulfides may have been affected by the Kaninomatasawa granite. 相似文献
102.
Movement of deep-seated rainfall-induced landslide at Hsiaolin Village during Typhoon Morakot 总被引:1,自引:0,他引:1
Yu-Shu Kuo Yuan-Jung Tsai Yu-Shiu Chen Chjeng-Lun Shieh Kuniaki Miyamoto Takahiro Itoh 《Landslides》2013,10(2):191-202
This study analyzes the mechanism of the landslide event at Hsiaolin Village during Typhoon Morakot in 2009. This landslide event resulted in 400 deaths. The extremely high intensity and accumulative rainfall events may cause large-scale and complex landslide disasters. To study and understand a landslide event, a combination of field investigations and numerical models is used. The landslide area is determined by comparing topographic information from before and after the event. Physiographic parameters are determined from field investigations. These parameters are applied to a numerical model to simulate the landslide process. Due to the high intensity of the rainfall event, 1,675 mm during the 80 h before the landslide event, the water content of soil was rapidly increased causing a landslide to occur. According to the survivors, the total duration of the landslide run out was less than 3 min. Simulation results indicated that the total duration was about 150 s. After the landslide occurrence, the landslide mass separated into two parts by a spur at EL 590 in about 30 to 50 s. One part passed the spur in about 30 to 60 s. One part inundated the Hsiaolin Village and the other deposited at a local river channel and formed a landslide dam. The landslide dam had height between 50 and 60 m and length between 800 and 900 m. The simulation result shows that the proposed model can be used to evaluate the potential areas of landslides induced by extremely high intensity rainfall events. 相似文献
103.
104.
105.
We observed 3EG J1234-1318 with the CANGAROO-II telescope in March, 2002. This source is a steady unidentified EGRET gamma-ray
source at high Galactic latitude which has been associated with a dynamically merging clusters of galaxies, and is therefore
a candidate TeV source. TeV gamma-ray emission is also expected as a result of large-scale cosmological structure formation.
We here report the resulting upper limit on the TeV gamma-ray emission from 3EG J1234-1318.
For the CANGAROO Collaboration. 相似文献
106.
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108.
Abstract A standard approach to the kinematic dynamo problem is that pioneered by Bullard and Gellman (1954), which utilizes the toroidal-poloidal separation and spherical harmonic expansion of the magnetic and velocity fields. In these studies, the velocity field is given as a combination of small number of toroidal and poloidal harmonics, with their radial dependences prescribed by some physical considerations. Starting from the original paper of Bullard and Gellman (1954), a number of authors repeated such analyses on different combination of velocity fields, including the most recent and comprehensive effort by Dudley and James (1989). In this paper, we re-examine the previous kinematic dynamo models, using the computer algebra approach initiated by Kono (1990). This method is particularly suited to this kind of research since different velocity fields can be treated by a single program. We used the distribution of magnetic energies in various harmonics to infer the convergence of the results. The numerical results obtained in this study for the models of Bullard and Gellman (1954), Lilley (1970), Gubbins (1973), Pekeris et al. (1973), Kumar and Roberts (1975), and Dudley and James (1989) are consistent with the previously reported results, in particular, with the extensive calculation of Dudley and James. In addition, we found that the combination of velocities used by Lilley can support the dynamo action if the radial dependence of the velocity is modified. We also examined the helicity distributions in these dynamo models, to see if there is any correlation between the helicity and the efficiency of dynamo action. A successful dynamo can result both from the cases in which the helicity distributions are symmetric or antisymmetric with respect to the equator. In both cases, it appears that the dynamo action is efficient if the volume integral of helicity over a hemisphere is large. 相似文献
109.
Takahiro Watanabe Toshio Nakamura Fumiko Watanabe Nara Takeshi Kakegawa Kazuho Horiuchi Ryoko Senda Takefumi Oda Mitsugu Nishimura Genki Inoue Matsumoto Takayoshi Kawai 《Quaternary International》2009,205(1-2):12
High-time resolution 14C dating of Lake Baikal sediment cores indicates negative and positive anomalies of calculated linear sedimentation rate (LSR; 1.1 and 35.6 cm/ka, respectively) during the period of climate transition from the last glacial to Holocene. The timing of the Lake Baikal apparent LSR anomalies is consistent with that of the changes in the atmospheric radiocarbon concentration (Δ14C) during Younger Dryas rapid cooling event. 14C dating of lipids in the Lake Baikal surface sediments revealed that the sources of sedimentary lipids were different in each basin. In the Northern Basin of Lake Baikal, the 14C age of total lipids from the surface sediment (4.0 14C ka) was found to be older than that of TOC (1.6 14C ka). By contrast, the 14C age of total lipids in the Southern Basin was younger than that of the TOC by ca. 0.7–3.0 ka.In the Lake Hovsgol sediment cores, ages of the main lithologic boundaries during the last glacial–interglacial transition were estimated based on new 14C data sets. TOC concentration in the cores started to rapidly increase at 13.8 ± 0.3 14C ka at the base of the basinwide finely laminated layer deposited during Bølling/Allerød. The base of the layer diatomaceous mud corresponds to the end of Younger Dryas event (10.6 ± 0.1 14C ka). 相似文献
110.
Effect of salt of various concentrations on liquid limit,and hydraulic conductivity of different soil-bentonite mixtures 总被引:1,自引:0,他引:1
Anil Kumar Mishra Masami Ohtsubo Loretta Y. Li Takahiro Higashi Junboum Park 《Environmental Geology》2009,57(5):1145-1153
Effect of the various concentrations of NaCl and CaCl2 on the four different soil-bentonite mixtures has been evaluated. The results show that the liquid limit of the mixtures
decreases with an increase in the salt concentration. Liquid limit decreased significantly with an increase in CaCl2 concentration from 0 to 0.1 N. However, a further increase in the concentration did not produce any significant decrease
in liquid limit. A quite opposite trend was observed for the NaCl solution. An increase in NaCl concentration from 0 to 0.1 N
did not produce any major decrease in the liquid limit, but a further increase in concentration from 0.1 to 1 N decreased
the liquid limit significantly. Consolidation tests were carried out on the mixtures to evaluate the effect of mineralogical
composition of the bentonite on the hydraulic conductivity (k) of the mixture in the presence of various salts concentrations. The k for any mixtures was found to be decreasing with decrease in the salt concentration. At relatively low concentration, Ca2+ had more effect on the k in comparison to the same concentration of Na+. However, at 1 N of NaCl and CaCl2 almost an equal value of k was observed. A comparison of the performance of four bentonites showed that the mixture with bentonite having highest exchangeable
sodium percentage (ESP) exhibited the lowest k when permeated with de-ionized (DI) water, however, k increased with an increase in the salt concentration. Similarly, mixture with a bentonite of lower ESP exhibited a higher
k with DI water but with the increase in the salt concentration alteration in the k, compared to all other mixtures, was relatively less. 相似文献