Pyroxenes from lherzolite inclusions of Itinome-gata,Japan     

Ken-Ichiro Aoki  Ikuko Shiba 《Lithos》1973,6(1):41-51

The lherzolites have recrystallized to plagioclase lherzolites consisting of olvine, pyroxenes, chromian spinel, plagioclase and pargasite at a depth of 20 to 25 km in the uppermost part of the mantle. It is believed that the garnet lherzolites and spinel lherzolites were originally derived from depths of 50–75 km and 30–50 km respectively. The clinopyroxenes contained about 10 mol. % of jadeite and Tschermak's molecules, respectively and the orthopyroxenes also included about 5–10% of Tschermak's component. Transported upward, the garnet was transformed through pyroxene-spinel symplectite to olivine, plagioclase and spinel aggregates, and most of the jadeite amd some Tschermak's components in the pyroxenes formed secondary pyroxenes and pargasite, and finally plagioclase under isochemical conditions.  相似文献   

Some clinopyroxenes from ultramafic inclusions in Dreiser Weiher,Eifel   总被引：6，自引：1，他引：6  

Ken -ichiro Aoki  Dr. Ikuo Kushiro 《Contributions to Mineralogy and Petrology》1968,18(4):326-337

Eight clinopyroxenes from wehrlites and clinopyroxenites and three clinopyroxenes of crystal lapilli in tuff of Dreiser Weiher in Eifel, Germany, have been separated and chemically analysed. One hornblende and two phlogopites from a wehrlite and clinopyroxenites have also been analysed. The rocks enclosing these inclusions are alkali basalts of basanite composition. The analysed clinopyroxenes contain considerable amounts of Al₂O₃ (3.87–10.84 wt%). The calculated Tschermak's component ranges from 5.9 to 18.4 mol per cent. All of the analysed clinopyroxenes are clearly different from chromian diopsides in lherzolite inclusions in basaltic rocks in Dreiser Weiher and other localities; the former has higher contents of total FeO, CaO and TiO₂ and lower contents of MgO and Cr₂O₃ than the latter. Two clinopyroxenes separated from apatite-bearing clinopyroxenites show high contents of Fe₂O₃ with about 2 per cent of Na₂O, indicating the presence of considerable amounts of acmite component in addition to Tschermak's component. The relative proportions of Al in the tetrahedral site and that in the octahedral site in the analysed clinopyroxenes are clearly different from those of the common igneous clinopyroxenes and eclogites, and similar to those of the clinopyroxenes from other inclusions in basaltic rocks and granulites. It is suggested that all the analysed clinopyroxenes and their host inclusions have crystallized from alkali basalt magmas in relatively deep levels of the continental crust.  相似文献   

A satellite cross-calibration experiment     

Nieke  J. Aoki  T. Tanikawa  T. Motoyoshi  H. Hori  M. 《Geoscience and Remote Sensing Letters, IEEE》2004,1(3):215-219

Recently, the Advanced Earth Observing Satellite 2 (ADEOS-2) was launched (December 14, 2002) successfully, and the Global Imager (GLI) onboard the ADEOS-2 satellite became operational in April 2003. In a first calibration checkup, the radiometric performance of GLI was compared relatively to that of other sensors on different satellites with different calibration backgrounds. As a calibration site, a large snowfield near Barrow, Alaska, was used, where space sensors in polar orbits view the same ground target on the same day with small differences in the local crossing times. This is why GLI, the Moderate Resolution Imaging Spectroradiometer (Terra, Aqua), the Sea-viewing Wide Field-of-view Sensor, the Advanced Very High Resolution Radiometer (N16, N17), the Medium Resolution Imaging Spectrometer, and the Advanced Along Track Scanning Radiometer datasets were selected for the following clear-sky condition days: April 14 and 26, 2003. At the same time, ground-truth experiments (e.g., measurements of ground reflectance, bidirectional reflectance distribution function, aerosol optical thickness) were carried out. Thereinafter, top-of-atmosphere (TOA) radiance/reflectance was forward calculated by means of radiative transfer code for each sensor, each band, and each day. Finally, the vicariously retrieved TOA signal was compared to TOA sensor Level 1B data. As a result, GLI's performance is encouraging at that time of the mission. GLI and the other seven sensors deliver similar sensor output in the range of about 5% to 7% around the expected vicariously calculated TOA signal.  相似文献   

Growth of twinned magnetic crystals in talc and talc-magnesite rock at Torika,Nagasaki Prefecture,Japan     

Reiko Iwasaki  Yoshikazu Aoki 《Lithos》1983,16(2):125-133

Spinel-type twins of magnetite in a talc rock and a talk-magnesite rock at Torika, Nagasaki Prefecture, Japan have been studied by means of optical microscopy, differential interference microscopy, microprobe analysis and size distribution analysis. The growth processes are discussed in detail. The number of magnetite twins in the talc-magnesite rock is larger than in the talc rock, and the percentage of the frequency number increases rapidly with increase in grain size. It is suggested that magnetite crystals in the talc-magnesite rock have grown by rapid crystallization in the earlier stage and by a layer-growth mechanism in the later stage in the carbonation-dehydration reaction that occurred within the rock. As large number of twin nuclei formed by rapid crystallization in the earlier stage of magnetite formation. As the dehydration reaction proceeded, the number of twin nuclei gradually decreased with the lowering of supersaturation by addition of some water. Magnetite crystals in the talc rock formed after talc crystallization by silicification and dehydration reactions in the process of steatitization. The twin nuclei here must have formed with difficulty, governed by the distribution of talc which crystallized before the magnetite and at relatively low supersaturation.  相似文献   

Geostatistical Evaluation of the Mechanical Properties of Rock Mass for TBM Tunnelling by Seismic Reflection Method     

K. Aoki  Y. Mito  T. Yamamoto  S. Shirasagi 《Rock Mechanics and Rock Engineering》2007,40(6):591-602

Summary. The evaluation of the rock mass mechanical properties by the seismic reflection method and TBM driving is proposed for TBM tunnelling. The relationship between the reflection number derived from the three-dimensional seismic reflection method and the rock strength index (RSI) derived from TBM driving data is examined, and the methodology of conversion from the reflection number to the RSI is proposed. Furthermore a geostatistical prediction methodology to provide a three-dimensional geotechnical profile ahead of the tunnel face is proposed. The performance of this prediction method is verified by actual field data.  相似文献   

A new technique for non‐destructive field measurement of rock‐surface strength: an application of the Equotip hardness tester to weathering studies     

Hisashi Aoki  Yukinori Matsukura 《地球表面变化过程与地形》2007,32(12):1759-1769

Tafone‐like depressions have developed on the Aoshima sandstone blocks used for a masonry bridge pier in the coastal spray zone. A thin layer of partial granular disintegration was found on the surface in depressions. To evaluate quantitatively the strength of the thin weathered layer, the hardness was measured at the surface of the sandstone blocks using both an Equotip hardness tester and an L‐type Schmidt hammer. Comparison of the two testing results indicates that the Equotip hardness value is more sensitive in evaluating the strength of a thin layer of weathered surface rock than the Schmidt hardness value. By applying two methods, i.e. both the repeated impact method and the single impact method, the Equotip tester can evaluate the strengths of fresh internal and weathered surficial portions of rocks having a thin weathering layer. Comparison of the two strengths enables evaluation of strength reduction due to weathering. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Surface lowering rates of uplifted limestone terraces estimated from the height of pedestals on a subtropical island of Japan     

Yukinori Matsukura  Akira Maekado  Hisashi Aoki  Tetsuya Kogure  Yoshihiko Kitano 《地球表面变化过程与地形》2007,32(7):1110-1115

In Kikai‐jima, south‐western Japan, many pedestal rocks have developed on the surface of Holocene raised coral‐reef terraces with known dates of emergence. Pedestals are formed just under boulders, which are considered to have been transported by tsunami and settled on a reef flat before emergence. On the assumption that boulders protect the underlying limestone terrace from rainfall solution, the rate of surface lowering of these limestone terraces was evaluated from the height of pedestals and the period of their formation. The result showed that the mean lowering rate over 6000 years is 205 mm/ky. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Formation of density inhomogeneity in laser produced plasmas for?a?test bed of magnetic field amplification in supernova remnants     

Y. Kuramitsu  Y. Sakawa  T. Morita  S. Dono  H. Aoki  H. Tanji  C. D. Gregory  J. N. Waugh  B. Loupias  M. Koenig  N. Woolsey  T. Ide  T. Sano  H. Takabe 《Astrophysics and Space Science》2011,336(1):269-272

Density inhomogeneities for a test bed of magnetic field amplification in supernova remnants (SNRs) were created in laser produced plasmas. The density inhomogeneity is considered to be essential to the large magnetic field amplification to account for the very fast cosmic ray acceleration. In order to model the density variations about an order of magnitude in an interstellar medium, we performed three types of experiments using a high-power laser system: (1) irradiating a plastic (CH) plane with a single focal spot beams, (2) the same target with spatial separation of laser focal spots, and (3) irradiating a striped target of thin and thick CH plane. By irradiating a CH plane target with a single focal spot laser beams, a plasma plume was produced with the large density range. On the other hand, when the several laser beams with displacements of the focal spots, bumpy structures of electron density were produced. Making thin stripes on a CH plane target, density and velocity inhomogeneities were produced by irradiating the striped target with the laser beams. In the all methods the density variations were very large, which can be used for a model experiment of the magnetic field amplification.  相似文献   

Occurrence and chemical composition of the Eoarchean carbonate rocks of the Nulliak supracrustal rocks in the Saglek Block of northeastern Labrador,Canada     

Satoshi Yoshida  Akira Ishikawa  Shogo Aoki  Tsuyoshi Komiya 《Island Arc》2021,30(1):e12381

The Eoarchean Nulliak supracrustal rocks in the Saglek Block of northeastern Labrador, Canada, contain some of the world's oldest carbonate rocks. This work attempted to reveal the origin of the carbonate rocks and estimate the surface environmental conditions of the early Earth based on their occurrence and geochemistry. They occur together with mafic and ultramafic rocks in Pangertok Inlet and St. John's Harbour South, whereas they are interlayered with pelitic rock layers with quartzofeldspathic mineral assemblages in St. John's Harbour East and Big Island. The geological occurrence suggests that the formers were formed around hydrothermal fields, whereas the latters were deposited near a continental margin. Some carbonate rocks have high SiO₂, Al₂O₃, and Zr contents, indicating that the silicification and involvement of detrital materials influenced their composition; thus, pure carbonate rocks were selected using a combined filter of the SiO₂, TiO_2, Al₂O₃, Zr, and Ba contents. The selected carbonate rocks have positive La, Eu, Gd, Y, U, Pb, and Sr anomalies, negative Nb, Zr, and Hf anomalies, and relatively small enrichment in heavy rare earth elements (HREEs). The La and Y anomalies suggest that they originated from chemical sediments precipitated from seawater. On the other hand, the small HREE-enrichment suggests that REEs were mainly dissolved as REE-carbonate complexes in seawater or that the riverine influxes were dominated by the detritus of Eoarchean continental crusts, presumably composed of HREE-depleted TTG. The U anomaly suggests that uranium was more dissolved than Th as U-bearing carbonate complexes in seawater. The Nulliak carbonate rocks also show a positive correlation between Y and Eu anomaly values, suggesting that the precipitation of iron-oxyhydroxide causing the Y anomaly was more significant near the hydrothermal fields than the continental margin, consistent with an alkaline hydrothermal model.  相似文献   

Bidirectional loading hybrid tests of square cross‐sections of steel bridge piers     

Ji Dang  Tetsuhiko Aoki 《地震工程与结构动力学》2013,42(8):1111-1130

Steel rectangular section columns with stiffened plates are commonly used for elevated highway bridges in the urban areas of Japan. The seismic design of bridge piers is usually performed by dynamic analysis in the horizontal direction using various independent directional seismic acceleration data. However, this simple treatment does not reflect the effect of bilateral loading as a structural response to inelastic interaction. In this study, unidirectional and bidirectional loading hybrid tests were conducted to examine the seismic response and performance of square cross‐sections of steel bridge piers subjected to bidirectional seismic accelerations. Comparison of the results of unidirectional and bidirectional loading tests revealed that the maximum load is the same as the average of unidirectional loading in the NS and EW directions; however, the maximum response displacement and residual displacement increase in proportion with hard to soft ground types. Moreover, a modified seismic design is proposed considering these bidirectional loading effects. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献