Geochemical and isotopic studies of aeolian sediments in China   总被引：5，自引：0，他引：5  

Masatoshi Honda  Sadayo Yabuki  Hiroshi Shimizu† 《Sedimentology》2004,51(2):211-230

The Sr and Nd isotopic, rare earth element (REE) and major element compositions, together with mineral and grain‐size proportions, are reported for aeolian loess deposits and desert sands from several Chinese localities. The study was carried out in order to examine regional variations in the isotopic and geochemical features of these aeolian sediments, and to constrain the provenance of Chinese loess. Samples include loesses from the Tarim and Junggar basins and desert sands from the Taklimakan desert in north‐west China, loess from the Ordos area and desert sands from the Tengger and Mu‐us deserts in north‐central China, as well as loess and desert sands from the Naiman area, north‐east China. REE distributions show minimal variation among the Chinese loess deposits, whereas those for the desert sands show regional variations. New isotopic data document a latitudinal variation in Sr and Nd isotopic features for the loesses and desert sands. The Naiman and Junggar loesses have distinctly lower ⁸⁷Sr/⁸⁶Sr ratios and higher ε_Nd(0) values than the loesses from the Tarim Basin, the Ordos area and the Loess Plateau. Among the desert sands, the Naiman samples have higher ε_Nd(0) values than the Taklimakan, Tengger and Mu‐us samples. Isotopic data suggest that loesses of the Loess Plateau were supplied from the Tarim Basin loesses and Taklimakan Desert sand, and that the Naiman loesses were supplied from the Junggar Basin loesses. The latitudinal variation in the loesses and desert sands may be partly explained by isotopic variations reported previously for moraines from the Tianshan and west Kunlun Mountains, which are possible sources for the loesses and desert sands. These inferences on the provenance of the loesses and desert sands are consistent with the dust transport pattern over East Asia.  相似文献   

Noble gases in submarine pillow basalt glasses from the Lau Basin: Detection of a solar component in backarc basin basalts     

Masahiko Honda  Desmond B. Patterson  Ian McDougall  Trevor J. Falloon 《Earth and Planetary Science Letters》1993,120(3-4):135-148

Noble gas elemental and isotopic abundances have been analysed in eight samples of youthful basaltic glass dredged from three different locations within the Lau Backarc Basin: (1) the King's Triple Junction, (2) the Central Lau Spreading Centre at 18°S and (3) the Eastern Lau Spreading Centre at 19°S. Samples from the Lau central and eastern spreading centres have MORB-like helium isotopic ratios of approximately 1.2 × 10⁻⁵ (8.5 R/R_A). In contrast, the samples from the King's Triple Junction yield helium isotopic ratios averaging 9.4 (±0.8) × 10⁻⁶ (6.7 ± 0.6 R/R_A), systematically lower than the MORB-like value, which may be reflecting the addition of radiogenic ⁴He released from the descending slab. Neon isotopic ratios are enriched in ²⁰Ne and ²¹Ne with respect to atmospheric ratios by as much as 23% and 62% respectively. These observations further confirm that non-atmospheric neon is a common characteristic of samples derived from the mantle. The helium and neon isotopic signatures in the samples can be explained by mixing of a primordial solar component, radiogenic and nucleogenic components produced by radioactive processes inside the Earth, and an atmospheric component. This reconnaissance survey of noble gases in a backarc basin indicates that current volcanism is dominated by magmas from the mantle wedge, a source similar to that from which MORBs are derived. The heavier noble gases (argon, krypton and xenon), however, show more atmosphere-like compositions, either indicating strong interaction of the magmas with the atmosphere or the presence of a recycled component derived from the underlying subducting slab.  相似文献   

Cosmogenic 21Ne exposure dating of young basaltic lava flows from the Newer Volcanic Province,western Victoria,Australia     

D. Gillen  M. Honda  A.R. Chivas  I. Yatsevich  D.B. Patterson  P.F. Carr 《Quaternary Geochronology》2010,5(1):1-9

Cosmogenic ²¹Ne was utilised to determine exposure ages of young subaerial basaltic lava flows from the Newer Volcanic Province, western Victoria, Australia. The ages (36–53 ka) determined from co-existing cosmogenic ²¹Ne and ³He in olivines separated from basalts are consistent within analytical uncertainties with ages previously determined by cosmogenic ³⁶Cl exposure dating. This paper illustrates the potential of cosmogenic neon exposure ages in studying the eruption, surface morphology, and erosion history of young volcanic rocks, which are difficult to date using other conventional methods, such as K-Ar or ⁴⁰Ar/³⁹Ar dating. The present study demonstrates that combined cosmogenic ³He and ²¹Ne dating, specifically measured cosmogenic ³He/²¹Ne ratios, on the same samples, is powerful for evaluating the validity of calculated cosmogenic ³He and ²¹Ne surface exposure ages.  相似文献   

Theoretical Evaluation of the Mechanical Behavior of Unsaturated Soils     

Michinori Honda  Shintaro Ohno  Atsushi Iizuka  Katsuyuki Kawai  Hideki Ohta 《Geotechnical and Geological Engineering》2011,29(2):171-180

An evaluation method for the mechanical behavior of unsaturated soils is studied in this paper. Although the mechanical behavior of unsaturated soils is complicated, a simple modeling is preferable in practice. This is because the soil properties are not homogeneous and ground data is limited when structures are being designed. In addition, in order to evaluate the reliability of the design, the physical meanings of the parameters applied in the prediction model should be clear. Firstly, the authors study the relationship between compaction curves and compression indexes in the unsaturated state that is used in the proposed constitutive model. Based on the constitutive model, the stress paths for constant volume shear tests are formulated under a constant void ratio condition and the stress paths for undrained shear tests are calculated under a constant water content condition. In the case of unsaturated specimens, the volume of these specimens changes with the shear deformation and the stress paths depend on the initial degree of saturation. The results of the calculation qualitatively describe the test results by considering the changes in effective confining pressure in the undrained condition and the water retention curves.  相似文献   

Seasonal Changes in Submarine Groundwater Discharge and Associated Nutrient Transport into a Tideless Semi-enclosed Embayment (Obama Bay,Japan)     

Ryo Sugimoto  Hisami Honda  Shiho Kobayashi  Yoshitake Takao  Daisuke Tahara  Osamu Tominaga  Makoto Taniguchi 《Estuaries and Coasts》2016,39(1):13-26

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40Ar/39Ar geochronology of mafic rocks from the granite—rhyolite terrane of southeastern Missouri     

Masahiko Honda  Paul J. Sylvester  Frank A. Podosek  Klaus J. Schulz 《Precambrian Research》1985,27(4):301-306

The predominant 1480 Ma granites and rhyolites of the St. Francois Mountains, southeastern Missouri, are intruded by mafic rocks. A ⁴⁰Ar—³⁹Ar study of some of these, the Skrainka Mafic Group, indicates an age of ～ 1240 Ma, significantly younger than the host rocks, significantly older than Grenville/Keweenawan age, and close to the age of similar rocks in Labrador.  相似文献   

⁴⁰Ar—³⁹Ar ages of guyots in the western Pacific and discussion of their evolution     

M. Ozima  Masahiko Honda  K. Saito 《Geophysical Journal International》1977,51(2):475-485

Summary. Six submarine rocks dredged from guyots in the western Pacific were dated by means of ⁴⁰Ar–³⁹Ar step heating dating technique. All ages show mid- to late-Cretaceous ages in accordance with the generally supposed age of the ocean crust estimated from the magnetic anomaly pattern.
The back-tracked paths were calculated for the guyots with the use of their absolute ages, for both the Pacific plate movements proposed by Morgan and by Clague & Jarrard. In both cases these show birth places for the guyots, which are located near the equator.
Fossil ages are nearly concordant with the ⁴⁰Ar–³⁹Ar ages for the guyots which are older than 95 Myr, whereas the fossil ages are considerably younger than the ⁴⁰Ar–³⁹Ar ages for the guyots younger than 90 Myr. This contrast may be due to the world-wide marine transgression, whose climax is believed to have occurred at about 85 Myr BP.  相似文献   

An interpretation of the Nusselt-Rayleigh number relationship for convection in a spherical shell     

Yasuyuki Iwase  Satoru Honda 《Geophysical Journal International》1997,130(3):801-804

Recent studies on the relationship between the Nusselt ( Nu ) and Rayleigh ( Ra ) numbers for base-heated convection in a spherical shell with a constant viscosity show that the power-law index is around 1/4, which is different from the value of 1/3 predicted by a simple boundary layer theory. We show that such a difference may be caused by the flow pattern due to the geometry. The flow pattern of the convection in a spherical shell at relatively low Ra , at least, less than 10⁶, is characterized by narrow upwelling and broad downwelling, which is similar to the opposite flow pattern of internally heated convection. Convection in the internally heated case predicts the power-law index of 1/4. We demonstrate this relationship based on the concept of 'local' Rayleigh ( Ra1 ) and Nusselt ( Nu1 ) numbers  相似文献   

Distribution of tungsten and molybdenum between metal,silicate, and sulphide phases of meteorites     

Keiko Imamura  Masatake Honda 《Geochimica et cosmochimica acta》1976,40(9):1073-1080

The concentrations of W, Mo, Co and Ni have been determined by neutron activation analysis in the separated metal, silicate and troilite of twelve chondrites—nine ordinary, two enstatite and one carbonaceous. Concentration ratios of W and Mo in silicate relative to metal are 0.03–0.6 and 0.05–0.55, respectively, and those of W in the troilite relative to the metal are 0.01–0.2. The contents of Mo in the troilite are nearly equal to those in the metal. Co and Ni are more depleted than W and Mo both in the silicate and troilite.Thermodynamic considerations have been made for determined concentration ratios. In some L-chondrites, W is depleted in the silicate by a factor of three to four of the value estimated from the correlation line between H- and LL-chondrites. This tendency seems to suggest a relatively higher temperature in the thermal history of these L-chondrites.  相似文献   

Parametrization of heat transport by non-Newtonian convection     

Y. Kawada  & S. Honda 《Geophysical Journal International》1999,137(2):441-448

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