Mo-related Adakitic Granitoids from Non-island-arc Setting: Jecheon Pluton of South Korea   总被引：2，自引：0，他引：2  

Shunso Ishihara    Myung Shik Jin  Shigeru Terashima 《Resource Geology》2005,55(4):385-396

Abstract. The Jecheon granitoids, having an elongated shape of NE-SW 27 km and NW-SE 13 km (190 km²), are composed mostly of magnetite-series hornblende-biotite granodiorite and biotite granite, which intrude into the Neoproterozoic metamor-phic and Paleozoic sedimentary rocks of the Ogcheon Belt. The granitoids have Triassic-Jurassic age of 202.7 ±1.9 Ma with very high ⁸⁷Sr/⁸⁶Sr initial ratio of 0.7140. The granodiorite has 63–69 % SiO₂, 15.1–17.3 % Al₂O₃, <1.6 % MgO, 6–15 ppm Y and Sr/Y ratios of 24–76, and is depleted in HREE. Biotite granite together, the Jecheon pluton has adakitic characteristics, which are unique in a continental tectonic setting. The granitoids may have been generated by partial melting of an older adakitic granitoid of I-type basement, or by separation of early crystallized garnet and hornblende from an anatectic melt.  相似文献   

Historical change in lake sedimentation in Lake Takkobu, Kushiro Mire, northern Japan over the last 300 years   总被引：1，自引：0，他引：1  

Young Sang Ahn  Shigeru Mizugaki  Futoshi Nakamura  Yugo Nakamura 《Geomorphology》2006,78(3-4):321-334

Environmental degradation, including shallowing, deterioration of aquatic habitat and water pollution, has arisen from the inflow of fine sediment to Lake Takkobu in northern Japan. The lake has experienced gradual environmental degradation due to agricultural development, which has introduced both fine sediment and sediment-associated nutrients into the lake. We have reconstructed the history of sediment yield to Lake Takkobu in Kushiro Mire over the last 300 years and have examined trends with reference to land-use development. Fifteen lake sediment core samples were obtained, and various physical variables of lake sediments were analyzed and dated using ¹³⁷Cs and tephrochronology. The physical variables showed that all points contained mainly silt, except for two points close to the river mouths, where the mean diameter was < 35 μm. The peaks were defined as a “signal” when the physical variables were synchronous in a profile. These were created by floods and engineering works constructing drainage systems. The signal of canal construction in 1898 was detected in all core points. Lake Takkobu core samples contained two tephra layers. From the refractive indices of dehydrated glasses, the lower tephra layer was identified as Ko-c2 (1694) and the upper tephra layer as Ta-a (1739). A clear peak in the ¹³⁷Cs concentration was detected at all the sampling points, except for the site close to the Takkobu River. This site showed two peaks in the ¹³⁷Cs concentration, which was attributed to perturbation from flood events and a drainage project. The maximum ¹³⁷Cs concentration was identified as the sediment surface from 1963, enveloped by the 1962 and 1964 signals. The sediment yield averaged over the last 300 years for Lake Takkobu was reconstructed for four periods using the signal, tephra and ¹³⁷Cs as marker layers. The sediment yield under the natural erosion condition for the first two periods was 226 tons/year from 1694 to 1739 and 196 tons/year from 1739 to 1898. The development of the Takkobu watershed started in 1880s with partial deforestation and channelization in 1898, 1959, and 1962 leading to an increased sedimentation yield of 1016 tons/year from 1898 to 1963. Continued deforestation, channelization works in 1964, road construction in 1980–1990s, as well as agriculture development caused a further increase to 1354 tons/year from 1963 to 2004. Compared to the averaged natural sedimentation yield of 206 tons/year until 1898, initial land-use development in a catchment accelerated lake sedimentation, indicated by the 5-fold sediment yield. With increasing agricultural development since 1960s, sedimentation yields were highest for 1963–2004; a 7-fold increase compared with pre-impact conditions. To reduce sediment yield, riparian buffers along the rivers should be preserved or rebuilt, and sluices may function effectively during short-term periods of flooding. Environmental management policy and laws restricting uncontrolled and inappropriate land-use might help in addition to ensure longer-term environmental health by reducing the sedimentation rate.  相似文献   

ELEMENTAL CONCENTRATIONS IN NINE NEW JAPANESE ROCK REFERENCE SAMPLES     

Shigeru TERASHIMA  Atsushi ANDO 《Geostandards and Geoanalytical Research》1987,11(1):75-77

Twenty-eight major, minor and trace elements in nine new rock reference samples of Geological Survey of Japan (GSJ), JA-2, JA-3 JB-1a, JG-1a, JG-2, JG-3, JF-1, JF-2 and JP-1 have been determined using atomic absorption spectrometry, flame emission spectrometry and wet chemical techniques.  相似文献   

Mineral chemistry of MUSES‐C Regio inferred from analysis of dust particles collected from the first‐ and second‐touchdown sites on asteroid Itokawa     

Tomoki Nakamura  Aiko Nakato  Hatsumi Ishida  Shigeru Wakita  Takaaki Noguchi  Michael E. Zolensky  Masahiko Tanaka  Makoto Kimura  Akira Tshuchiyama  Toshihiro Ogami  Takahito Hashimoto  Mitsuru Konno  Masayuki Uesugi  Toru Yada  Kei Shirai  Akio Fujimura  Ryuji Okazaki  Scott. A. Sandford  Yukihiro Ishibashi  Masanao Abe  Tatsuaki Okada  Munetaka Ueno  Junichiro Kawaguchi 《Meteoritics & planetary science》2014,49(2):215-227

The mineralogy and mineral chemistry of Itokawa dust particles captured during the first and second touchdowns on the MUSES‐C Regio were characterized by synchrotron‐radiation X‐ray diffraction and field‐emission electron microprobe analysis. Olivine and low‐ and high‐Ca pyroxene, plagioclase, and merrillite compositions of the first‐touchdown particles are similar to those of the second‐touchdown particles. The two touchdown sites are separated by approximately 100 meters and therefore the similarity suggests that MUSES‐C Regio is covered with dust particles of uniform mineral chemistry of LL chondrites. Quantitative compositional properties of 48 dust particles, including both first‐ and second‐touchdown samples, indicate that dust particles of MUSES‐C Regio have experienced prolonged thermal metamorphism, but they are not fully equilibrated in terms of chemical composition. This suggests that MUSES‐C particles were heated in a single asteroid at different temperatures. During slow cooling from a peak temperature of approximately 800 °C, chemical compositions of plagioclase and K‐feldspar seem to have been modified: Ab and Or contents changed during cooling, but An did not. This compositional modification is reproduced by a numerical simulation that modeled the cooling process of a 50 km sized Itokawa parent asteroid. After cooling, some particles have been heavily impacted and heated, which resulted in heterogeneous distributions of Na and K within plagioclase crystals. Impact‐induced chemical modification of plagioclase was verified by a comparison to a shock vein in the Kilabo LL6 ordinary chondrite where Na‐K distributions of plagioclase have been disturbed.  相似文献   

1998 Compilation of Analytical Data for Five GSJ Geochemical Reference Samples: The "Instrumental Analysis Series"   总被引：1，自引：0，他引：1  

Noboru Imai  Shigeru Terashima  Shiro Itoh  Atsushi Ando 《Geostandards and Geoanalytical Research》1999,23(2):223-250

Analytical data for five GSJ (Geological Survey of Japan) reference samples, the "Instrumental analysis series" received by October 1998, are compiled. The data reported in publications and personal communications were evaluated statistically, taking into account the analytical method and sample preparation. Based on the selected available data, recommended and preferred values for fourteen major and fifty one minor and trace elements are proposed.  相似文献   

Evolution of the velocity dispersion of self-gravitating particles in disc potentials     

Kouji Shiidsuka  Shigeru Ida 《Monthly notices of the Royal Astronomical Society》1999,307(4):737-749

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Low cyclic fatigue and hysteretic behavior of U‐shaped steel dampers for seismically isolated buildings under dynamic cyclic loadings          下载免费PDF全文

Yu Jiao  Shoichi Kishiki  Satoshi Yamada  Diana Ene  Yoshinao Konishi  Yuuma Hoashi  Masao Terashima 《地震工程与结构动力学》2015,44(10):1523-1538

Energy dissipation devices are necessary for base‐isolated buildings to control the deformation in the isolation system and to dissipate the earthquake‐induced energy. U‐shaped steel dampers (also known as U‐dampers) dissipate energy through plastic deformation of specially designed U‐shaped steel elements. This type of device can be installed at several locations in the isolation system. U‐dampers have been widely used in Japan for different types of isolated structures, such as hospitals, plants and residential buildings, since the 1995 Kobe Earthquake. Previous research has used static tests to estimate the performance of U‐dampers. However, the ultimate plastic deformation capacities and hysteretic behaviors of full‐scale U‐dampers under dynamic excitations still remain unclear. In addition, it is unclear whether the initial temperature has an effect on the hysteretic behavior and plastic deformation capacity of U‐dampers. In this paper, two series of dynamic loading tests of U‐dampers were conducted to evaluate the issues described earlier. The major findings of the study are (i) the loading speed has little effect on the plastic deformation capacity of U‐dampers; (ii) method to evaluate the ultimate plastic deformation capacities of U‐shaped steel dampers of different sizes is established using a Manson–Coffin relation‐based equation that is based on the peak‐to‐peak horizontal shear angle γ_t, which is defined as the lateral deformation amplitude (peak‐to‐peak amplitude) divided by the height of the dampers; (iii) the loading rate and the initial temperature have a minimal effect on the hysteretic behavior of the U‐dampers; and (iv) a bilinear model is proposed to simulate the force‐deformation relationships of the U‐dampers. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献