Microbialites and their Responsible Microbes Following the End-Permian Extinction in Sichuan, South China     

Yoichi Ezaki  Jianbo Liu  Natsuko Adachi 《Gondwana Research》2001,4(4):614

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Major and trace element abundances in volcanic glass shards in visible tephras in SG93 and SG06 drillcore samples from Lake Suigetsu,central Japan,obtained using femtosecond LA–ICP–MS     

Seiji Maruyama  Keiji Takemura  Takafumi Hirata  Tohru Yamashita  Tohru Danhara 《第四纪科学杂志》2020,35(1-2):66-80

The major and trace element concentrations of volcanic glass shards from visible tephra layers in the SG93 and SG06 cores from Lake Suigetsu, central Japan, were determined by femtosecond laser ablation–inductively coupled plasma–mass spectrometry. The glass-shard analyses, together with the petrographic properties of the tephra samples, allow the Suigetsu tephra layers to be broadly classified into tephras derived from calderas on Kyushu Island, and from Daisen and Sambe volcanoes in the Chugoku district of southwest Japan. The layers correlated with tephras from Kuju caldera and Daisen volcano, and with the younger Sambe tephras, have adakitic elemental features. A Suigetsu tephra sample correlated with the Sambe−Kisuki tephra based on petrographic properties has an elemental pattern similar to that of the Toya tephra from Hokkaido Island, northeast Japan. This match implies that tephras from northeast Japan, as well as Kyushu–Chugoku tephras, are possible correlatives of the Suigetsu tephra layers. Both petrographic properties and major–trace element data of volcanic glass shards are essential for robust tephra correlations, and hierarchical cluster analysis proved additionally useful in statistically evaluating relationships among the tephras.  相似文献   

Reconstruction of historical pressure patterns over Japan using two-point pressure–temperature datasets since the nineteenth century     

Masumi Zaiki  Gunther P. Können  Keiji Kimura  Takehiko Mikami  Togo Tsukahara 《Climatic change》2009,95(1-2):231-248

The temperature and pressure differences between Tokyo and Nagasaki were used to reconstruct past climate conditions. January and July in each available year since the 1820s were classified into several types with characteristic sea level atmospheric pressure patterns. This results in 18 years of pre-1881 data and a continuous series thereafter. The series indicate that the warming after 1900 (after the end of the so-called Little Ice Age) and again after 1960 can at least partly be attributed to an increase in the frequency of warm circulation pattern types at the expense of cold types. The difference in nature of the shifts in circulation types that occurred in the late nineteenth century compared with that in the late twentieth centuries suggests that the mechanism behind the warming in the late nineteenth century differs from that in the late twentieth century.  相似文献   

Accretion rates of planetesimals by protoplanets embedded in nebular gas     

Takayuki Tanigawa  Keiji Ohtsuki 《Icarus》2010,205(2):658-673

When protoplanets growing by accretion of planetesimals have atmospheres, small planetesimals approaching the protoplanets lose their energy by gas drag from the atmospheres, which leads them to be captured within the Hill sphere of the protoplanets. As a result, growth rates of the protoplanets are enhanced. In order to study the effect of an atmosphere on planetary growth rates, we performed numerical integration of orbits of planetesimals for a wide range of orbital elements and obtained the effective accretion rates of planetesimals onto planets that have atmospheres. Numerical results are obtained as a function of planetesimals’ eccentricity, inclination, planet’s radius, and non-dimensional gas-drag parameters which can be expressed by several physical quantities such as the radius of planetesimals and the mass of the protoplanet. Assuming that the radial distribution of the gas density near the surface can be approximated by a power-law, we performed analytic calculation for the loss of planetesimals’ kinetic energy due to gas drag, and confirmed agreement with numerical results. We confirmed that the above approximation of the power-law density distribution is reasonable for accretion rate of protoplanets with 1-10 Earth masses, unless the size of planetesimals is too small. We also calculated the accretion rates of planetesimals averaged over a Rayleigh distribution of eccentricities and inclinations, and derived a semi-analytical formula of accretion rates, which reproduces the numerical results very well. Using the obtained expression of the accretion rate, we examined the growth of protoplanets in nebular gas. We found that the effect of atmospheric gas drag can enhance the growth rate significantly, depending on the size of planetesimals.  相似文献   

Two-dimensional consolidation analysis using an elasto-viscoplastic constitutive equation     

F. Oka  T. Adachi  Y. Okano 《国际地质力学数值与分析法杂志》1986,10(1):1-16

A two-dimensional consolidation analysis of clay deposits was made with an elasto-viscoplastic constitutive model and Biot's consolidation theory. One- and two-dimensional consolidation problems were analysed numerically by the finite element and finite difference methods. Results show that the proposed method can describe the effect of sample thickness and aging on consolidation phenomena. The two-dimensional behaviour of a clay foundation during the construction of embankments also was simulated.  相似文献   

Thermal anomaly around the Nojima Fault as detected by fission-track analysis of Ogura 500 m borehole samples   总被引：1，自引：0，他引：1  

Takahiro Tagami  Noriko Hasebe  Hidenori Kamohara  Keiji Takemura 《Island Arc》2001,10(3-4):457-464

Abstract To better understand heat generation and transfer along earthquake faults, this paper presents preliminary zircon fission-track (FT) length data from the Nojima Fault, Awaji Island, Japan, which was activated during the 1995 Kobe earthquake (Hyogo-ken Nanbu earthquake). Samples were collected of Cretaceous granitic rocks from the Ogura 500 m borehole as well as at outcrops adjacent to the borehole site. The Nojima Fault plane was drilled at a depth of 389.4 m (borehole apparent depth). Fission-track lengths in zircons from localities > 60 m distance from the fault plane, as well as those from outcrops, are characterized by the mean values of ≈10–11 μm and unimodal distributions with positive skewness, which show no signs of an appreciable reduction in FT length. In contrast, those from nearby the fault at depths show significantly reduced mean track lengths of ≈6–8 μm and distributions having a peak around 6–7 μm with rather negative skewness. In conjunction with other geological constraints, these results are best interpreted by a recent thermal anomaly around the fault, which is attributable to heat transfer via focused fluids from the deep interior of the crust and/or heat dispersion via fluids associated with frictional heating by fault motion.  相似文献   

RbSr whole-rock ages of Precambrian metamorphic rocks in the Kamiaso conglomerate from central Japan     

Ken Shibata  Mamoru Adachi 《Earth and Planetary Science Letters》1974,21(3):277-287

Whole-rock samples of metamorphic and granitic cobbles and boulders from the Kamiaso conglomerate in central Japan yield well-defined RbSr isochron ages of 1985 ± 25 my and 1820 ± 40 my. These ages are the oldest yet obtained for rocks in the Japanese Islands, and provide key evidence for the middle Precambrian metamorphic and igneous events in the provenance of these rocks. The age of 1985 my defined by six samples of quartzo-feldspathic gneiss may be the time of emplacement of the original granitic rocks. The 1820 my age indicates the time of extensive regional metamorphism and igneous activity. Precambrian episodes in the provenance of the Kamiaso conglomerate are summarized as follows: (1) 2000 my — formation of granitic rocks, (2) 1800–1600 my — high grade metamorphism accompanied by igneous activity, (3) 1200–1000 my — some significant thermal event.Judging from rock types and geochronological data, it can be said that metamorphic rocks in the Kamiaso conglomerate are remarkably similar to those of the Matenrei and Nangnim systems in North Korea. The Precambrian complex from which the metamorphic and granitic rocks were derived, was exposed to the north not far from the present site of the Kamiaso conglomerate in the late Paleozoic time, and it was probably a part of the large Precambrian continent in East Asia.  相似文献   

Displacement behavior of CH4 adsorbed on coals by injecting pure CO2, N2, and CO2–N2 mixture     

Sohei Shimada  Huoyin Li  Yoshito Oshima  Kazuhide Adachi 《Environmental Geology》2005,49(1):44-52

Gas adsorption isotherms of Akabira coals were established for pure carbon dioxide (CO₂), methane (CH₄), and nitrogen (N₂). Experimental data fit well into the Langmuir model. The ratio of sorption capacity of CO₂, CH₄, and N₂ is 8.5:3.5:1 at a lower pressure (1.2 MPa) regime and becomes 5.5:2:1 when gas pressure increases to 6.0 MPa. The difference in sorption capacity of these three gases is explained by differences in the density of the three gases with increasing pressure. A coal–methane system partially saturated with CH₄ at 2.4 MPa adsorption pressure was experimentally studied. Desorption behavior of CH₄ by injecting pure CO₂ (at 3.0, 4.0, 5.0, and 6.0 MPa), and by injecting the CO₂–N₂ mixture and pure N₂ (at 3.0 and 6.0 MPa) were evaluated. Results indicate that the preferential sorption property of coal for CO₂ is significantly higher than that for CH₄ or N₂. CO₂ injection can displace almost all of the CH₄ adsorbed on coal. When modeling the CH₄–CO₂ binary and CH₂–CO₂–N₂ ternary adsorption system by using the extended Langmuir (EL) equation, the EL model always over-predicted the sorbed CO₂ value with a lower error, while under-predicting the sorbed CH₄ with a higher error. A part of CO₂ may dissolve into the solid organic structure of coal, besides its competitive adsorption with other gases. According to this explanation, the EL coefficients of CO₂ in EL equation were revised. The revised EL model proved to be very accurate in predicting sorbed ratio of multi-component gases on coals.  相似文献   

Polarized infrared absorbance spectra of an optically anisotropic crystal: Application to the orientation of the OH- dipole in quartz     

Keiji Shinoda  Nobuvuki Aikawa 《Physics and Chemistry of Minerals》1993,20(5):308-314

The polarized infrared (IR) absorbance spectrum was formulated for an optically anisotropic crystal under the conditions of Fourier transform microspectroscopy. The adequacy of this formulation was confirmed by comparison of calculated interference fringes with those observed in polarized absorbance spectra of optically anisotropic crystal. In accordance with the formulated absorbance, an experimental constraint for the correct measurement of polarized IR absorbance spectrum of optically anisotropic crystal is proposed. Under this experimental constraint, polarized IR absorbance spectra of quartz from Arkansas were measured. They show that the orientation of OH^- dipole which compensates the charge balance coupled with Al³⁺ in quartz is highly polarized perpendicular to the c-axis.  相似文献   

Underground oil storage facilities in Japan     

Toshiaki Makita  Yoshiharu Miyanaga  Keiji Iguchi  Teruyoshi Hatano 《Engineering Geology》1993,35(3-4):191-198

In Japan, three underground crude-oil storage facilities with a total capacity of 5 million kl are under construction as a chain of the national oil storage project. Because the NATM method was used in this project, we applied a systematic work control system, consisting ofin situ measurements and engineering geological observations, including an original rock-mass classification system. The classification system used can be slightly modified depending upon site-specific geological conditions and the purposes of the facilities such as, i.e., an artificial water sealing system.  相似文献