排序方式: 共有33条查询结果,搜索用时 15 毫秒
21.
太行山和华北其它地区中生代岩浆作用的锆石U-Pb年代学和地球化学特征及其岩浆成因和地球动力学意义 总被引:31,自引:20,他引:31
华北克拉通东部中生代岩浆岩的主要特征是岩石类型复杂(从辉长质到二长花岗质),显示高钾钙碱性、高Sr—Ba、高Sr/Y和La/Yb比值和高度富集的Sr-Nd同位素成分。锆石SHRIMP定年表明,太行山地区岩浆作用发生在138—127Ma之间。该年代结果与东亚其它地区已经发表的锆石年代数据揭示了中生代岩浆作用的发展具有从日本岛(和朝鲜半岛;210Ma),到胶辽半岛(180Ma),再到大别山-太行山(138Ma)的年轻化趋势。这暗示华北中生代岩浆作用可能与古太平洋板块的俯冲有关。但华北中生代岩浆岩似乎没有明显的向内陆方向的成分变化极性,可能与古太平洋板块在地幔过渡带的水平俯冲有关。地球化学数据表明,华北中生代岩浆岩可能主要形成于壳幔岩浆混合作用和随后的分离结晶过程.而不是形成于基性下地壳部分熔融作用。 相似文献
22.
Seiichiro Ioka Toshiaki Sakai Toshifumi Igarashi Yoji Ishijima 《Environmental Earth Sciences》2011,64(1):143-149
The in situ redox potential (Eh) in anoxic groundwater with high methane and iron contents (approximately 12.3 and 28.4 mg/L,
respectively) was potentiometrically measured to identify the processes that control Eh. The measured Eh ranged from −213
to −187 mV; it had an inverse correlation with the concentration of methane and no correlation with that of iron. The saturation
indices indicate that goethite and amorphous FeS were nearly at solubility equilibrium. A comparison of the measured Eh with
those calculated for the particular redox pairs indicates that either Fe2+/FeOOH or CH4/CO2, but not sulfur redox pairs, controlled the measured Eh. The inverse relationship between measured Eh and methane concentration
suggests possible control of the redox conditions by the CH4/CO2 redox pair. Furthermore, the equilibrium solubility state of goethite, which has higher crystallinity and lower solubility
than Fe(OH)3 indicates that the iron reaction was electrochemically irreversible. This further supports the contribution of the CH4/CO2 pair to controlling the measured Eh of groundwater. 相似文献
23.
Unmanned mobile robots for surface exploration of the Moon or planets have been extensively studied and developed. A lunar
rover is expected to travel safely in a wide area and explore in detail. Japanese lunar robotics exploration is under study
to conduct an unmanned geological survey in the vicinity of central peaks of impact craters for investigation of the sub-surface
materials. This will give us the key information to study the lunar inner structure and understand the Moon’s origin and evolution
as well as to investigate the evolution of magma ocean and later igneous processes. To carry out the geological exploration
in the central peak, lander and rover co-operative exploration is proposed. The working group has been conducting feasibility
study of advance technologies. This paper addresses an overview of lunar exploration with lander and rover and also enumerates
future technologies to be established.
The rover R&D group has developed an innovative science micro rover with a new mobility system and a lightweight manipulator.
The design and implementation of a science rover for the near future lunar missions requiring long traverses and scientific
observations are described and some experimental results are presented. 相似文献
24.
Taku Kitajima Yoji Kobayashi Ryuji Ikeda Yoshihisa Iio Kentaro Omura 《Island Arc》2001,10(3-4):318-325
Abstract Terrestrial heat flow at Hirabayashi in Awaji Island, south-west Japan, was investigated using the deep borehole penetrating through the Nojima Fault, which was activated during the 1995 Hyogo-ken Nanbu earthquake, by measuring the thermal conductivity of basement rocks. Using the temperature logging data, the value of terrestrial heat flow in Hirabayashi was found to be 56.6 ± 5.2 mW/m2 . The relationship between cut-off depth of aftershocks of the Hyogo-ken Nanbu earthquake in Hirabayashi and terrestrial heat flow are discussed. The cut-off depth roughly corresponds to isotherms of 300°C. 相似文献
25.
Yoji Arakawa Mie Kurosawa Kaori Takahashi Yoji Kobayashi Masashi Tsukui Hiroshi Amakawa 《Journal of Volcanology and Geothermal Research》1998,80(3-4)
Sr and Nd isotope and geochemical investigations were performed on a remarkably homogeneous, high-silica rhyolite magma reservoir of the Aira pyroclastic eruption (22,000 years ago), southern Kyushu, Japan. The Aira caldera was formed by this eruption with four flow units (Osumi pumice fall, Tsumaya pryoclastic flow, Kamewarizaka breccia and Ito pyroclastic flow). Quite narrow chemical compositions (e.g., 74.0–76.5 wt% of SiO2) and Sr and Nd isotopic values (87Sr/86Sr=0.70584–0.70599 and Nd=−5.62 to −4.10) were detected for silicic pumices from the four units, with the exception of minor amounts of dark pumices in the units. The high Sr isotope ratios (0.7065–0.7076) for the dark pumices clearly suggest a different origin from the silicic pumices. Andesite to basalt lavas in pre-caldera (0.37–0.93 Ma) and post-caldera (historical) eruptions show lower 87Sr/86Sr (0.70465–0.70540) and higher Nd (−1.03 to +0.96) values than those of the Aira silicic and dark pumices. Both andesites of pre- and post-caldera stages are very similar in major- and trace-element characteristics and isotope ratios, suggesting that the both andesites had a same source and experienced the same process of magma generation (magma mixing between basaltic and dacitic magmas). Elemental and isotopic signatures deny direct genetic relationships between the Aira pumices and pre- and post-caldera lavas. Relatively upper levels of crust (middle–upper crust) are assumed to have been involved for magma generation for the Aira silicic and dark pumices. The Aira silicic magma was derived by partial melting of a separate crust which had homogeneous chemistry and limited isotope compositions, while the magma for the Aira dark pumice was generated by AFC mixing process between the basement sedimentary rocks and basaltic parental magma, or by partial melting of crustal materials which underlay the basement sediments. The silicic magma did not occupy an upper part of a large magma body with strong compositional zonation, but formed an independent magma body within the crust. The input and mixing of the magma for dark pumices to the base of the Aira silicic magma reservoir might trigger the eruptions in the upper part of the magma body and could produce a slight Sr isotope gradient in the reservoir. An extremely high thermal structure within the crust, which was caused by the uprise and accumulation of the basaltic magma, is presumed to have formed the large volume of silicic magma of the Aira stage. 相似文献
26.
In order to examine the relationship between anomalous crustal deformations and subsequent large earthquakes, we compiled and examined data on preseismic anomalous crustal deformations for two earthquakes that occurred in and around the Japanese Islands in recent years. We found that the slip on a downward extension of a seismogenic fault accelerates before the main shock and that the average slip velocity is inversely proportional to the time remaining until the main shock occurs. 相似文献
27.
28.
Log-irradiance fluctuations of He-Ne laser light were simultaneously measured at three different points in the receiving plane. The cumulative probability distributions of log-irradiance show excellent agreement with the Rice-Nakagami distribution in the region of weak fluctuations. The irradiance distributions strongly depend upon the locations of the observing points with respect to the center of the beam, as expected from recent theory. 相似文献
29.
Yoji Ogawa 《Applied Ocean Research》1984,6(3):140-147
The integrated equations of deep sea mooring lines in static equilibrium under consideration of gravity force and line elongation are obtained. The most useful forms of the equations for designing deep sea mooring system are those in which horizontal displacement and horizontal and vertical components of tension are obtained as functions of line length, water depth, critical tension and unit weight of line.When the dynamic simulation of a buoy system is carried out, line tensions acting on the buoy should be represented as a linear function of displacement. Therefore the linearisation method is introduced by use of linearisation coefficient matrix. Translation formulae for the matrix from two to three dimensions is also presented.The influence of line elongation on the horizontal component of tension in a taut mooring condition is important, therefore the elongation of stretched deep sea mooring line must be considered carefully. Also, the scaling law under consideration of line elongation in static equilibrium, which is necessary in estimation from a small sized experiment, is discussed. 相似文献
30.
We compared the cutoff depth of seismicity in and around the Nojima fault broken by the 1995 Kobe earthquake occurring in intraplate Japan with the brittle–ductile transition depth of the widely accepted strength profile model of the crust. We successfully determined the temperature profile from borehole measurements, since almost the same geothermal gradients were observed at two boreholes located about 4 km apart from each other, and the thermal conductivity and heat production were also measured by taking numerous core samples. We found that the cutoff depth was much deeper than the transition depth under the assumption that wet granite is deformed at a strain rate of 3×10−15 s−1. This small strain rate implies, however, that plastic flow is uniformly distributed below the seismogenic region. When the strain rate is assumed to be greater than 10−13 s−1, the cutoff depth can be attributed to the transition depth. This suggests that deformation is localized in a narrow fault zone below the seismogenic region, even in the intraplate region. 相似文献