Impact-induced phyllosilicate formation from olivine and water     

Yoshihiro Furukawa  Toshimori Sekine  Takeshi Kakegawa 《Geochimica et cosmochimica acta》2011,75(21):6461-6472

Shock-recovery experiments on mixtures of olivine and water with gas (air) were performed in a previous study to demonstrate water-mineral interactions during impact events (Furukawa et al., 2007). The products of these former experiments were investigated in the present study using transmission electron microscopy, scanning electron microscopy, and X-ray powder diffraction with the aim of finding evidence of aqueous alteration. Serpentine formed on the surface of shocked olivine with well-developed mosaicism. The yield of serpentine depended on the water/olivine ratio in the starting material, indicating progressive serpentinization under water-rich conditions. Comminution and mosaicism were developed in shocked olivine grains. The temperature and pressure changes of the samples during the experiments were estimated by constructing Hugoniots for mixtures of olivine and water, combined with the results of an additional fracturing experiment on a shocked container. Pressures and temperatures reached 4.6-7.2 GPa and at least 230-390 °C, respectively, for 0.7 μs during in-shock compression. Post-shock temperatures reached a maximum of ∼1300 °C, when the shock wave reached the gas in the sample cavity. The serpentine formed after the post-shock temperature maximum, most likely when temperatures dropped to between 200 and 400 °C. This is the first experiment to demonstrate the formation of phyllosilicates using heat supplied by an impact. The present results and estimations suggest that phyllosilicates could form as a result of impacts into oceans as well as by impacts on terrestrial and Martian crustal rocks, and on some asteroidal surfaces, where liquid or solid H₂O is available. A significant amount of phyllosilicates would have formed during the late heavy bombardment of meteorites on the Hadean Earth, and such phyllosilicates might have affected the prebiotic carbon cycle.  相似文献   

Impact of the winter North Atlantic Oscillation (NAO) on the Western Pacific (WP) pattern in the following winter through Arctic sea ice and ENSO. Part II: multi-model evaluation of the NAO–ENSO linkage     

Tetsu Nakamura  Masayuki Hara  Miki Oshika  Yoshihiro Tachibana 《Climate Dynamics》2015,45(11-12):3547-3562

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Water exchange and material exchange through a strait due to tidal flow     

Yoshihiro Mazda 《Journal of Oceanography》1984,40(1):19-28

The process of material transport through a strait due to tidal flow is modeled, and then the differences between various concepts of tidal exchange which have been used hitherto are pointed out using this model. In particular, the exchange of water itself and the exchange of material should be distinguished even in the case where the material of interest is carried by the water,i.e., the material and water move as one body. Further, the physical meaning of “tidal trapping” (Fischeret al., 1979) is discussed by using the model in this paper. The relationship between the exchange ratio for the water itself (r) and the phase lag (δ) of material concentration to the tidal stream in a section of the strait, which is an important factor in tidal trapping, is obtained as follows: $$\delta = \tan ^{ - 1} \left( {\tfrac{1}{r} - 1} \right)$$ Observational results at Lake Hamana (Shizuoka Pref) and at Kabira Cove (Okinawa Pref.) support the validity of the above relationship.  相似文献   

Japan-equator XBT sections in late November 1989 and in early December 1991     

Jiro Yoshida  Hideo Sudo  Masaji Matsuyama  Yoshihiro Kurita  Yuji Mine 《Journal of Oceanography》1993,49(1):121-129

A comparison between Japan-equator XBT sections along 150°E in late November 1989 and along 140°E in early December 1991 is made. The warmest surface water above 29°C diminished to the south of 2–4°N and the surface mixed layer noticeably decreased in thickness in the equatorial region in December 1991; besides, the North Equatorial Countercurrent was intensified. This is considered to be a manifestation of changes in the surface layer of the western equatorial Pacific in the mature phase of El Niño.  相似文献   

Numerical study of enhanced energy dissipation near a seamount     

Nobuyuki Iwamae  Toshiyuki Hibiya  Yoshihiro Niwa 《Journal of Oceanography》2006,62(6):851-858

Using a two-dimensional primitive equation model, we examine nonlinear responses of a semidiurnal tidal flow impinging on a seamount with a background Garrett-Munk-like (GM-like) internal wavefield. It is found that horizontally elongated pancake-like structures of high vertical wavenumber near-inertial current shear are created both in the near-field (the region over the slope of the seamount) and far-field (the region over the flat bottom of the ocean). An important distinction is that the high vertical wavenumber near-inertial current shear is amplified only at mid-latitudes in the far-field (owing to a parametric subharmonic instability (PSI)), whereas it is amplified both at mid-and high-latitudes (above the latitude where PSI can occur) in the near-field. In order to clarify the generating mechanism for the strong shear in the near-field, additional numerical experiments are carried out with the GM-like background internal waves removed. The experiments show that the strong shear is also created, indicating that it is not caused by the interaction between the background GM-like internal waves and the semidiurnal internal tides. One possible explanation is proposed for the amplification of high vertical wavenumber near-inertial current shear in the near-field where tide residual flow resulting from tide-topography interaction plays an important role in transferring energy from high-mode internal tides to near-inertial internal waves.  相似文献   

Life habit of vesicomyid clam,Calyptogena soyoae,and hydrogen sulfide concentration in interstitial waters in Sagami Bay,Japan     

Jun Hashimoto  Suguru Ohta  Katsunori Fujikura  Yoshihiro Fujiwara  Shunji Sukizaki 《Journal of Oceanography》1995,51(3):341-350

In and around the beds of vesicomyid clam (Calytogena soyoae) located off Hatsushima Island in Sagami Bay, central Japan, hydrogen sulfide concentration in bottom water and interstitial water was measured every 10 cm from just above seafloor to 40 cm deep usingin situ separative dialysis bags. While hydrogen sulfide over 0.01 mmol/kg was not measured from the seawater just above the dense clam beds, the concentration of hydrogen sulfide increased rapidly below 10 cm deep. The results indicate that the habit of the clam is correlated with high concentration of hydrogen sulfide contained in pore waters of sediments between depths of 10 and 20 cm from the bottom surface. Concentrations of hydrogen sulfide ranging from approximately 0.05 mmol/kg to 0.6 mmol/kg might be suitable requirement for the habitat ofC. soyoae.  相似文献   

A small-scale energy release observed on the limb     

Ichiro Kawaguchi  Kap-Sung Kim  Yoshihiro Nakai 《Solar physics》1986,106(1):47-65

The D3 emission lines observed on the emerging flux loops and mound prominences above the limb were locally found to consist of two components, i.e., the main and the broadened components. A number of Doppler shifted emission lines, separated distinctly from the main body of the emission lines were also detected, which we call the separated components. On the sequential spectrograms, the lifetimes of these broadened and separated components were obtained and their histograms were made.We present the results of fitting the observed emission lines with the sum of two gaussian profiles in two simple cases under two different assumptions. In each assumption, it is found that the line-of-sight velocities of the broadened components with lifetimes shorter than 10 min monotonously increase with time and we attribute this behaviour to a single ejection of mass from the parent structures. In the broadened components with lifetimes longer than 10 min, the acceleration turns on and off alternately, each with a duration of several minutes. We attribute this behaviour to multiple ejections of mass.Finally, it is shown that the corona over the active region is supplied with enough mass for the formation of a coronal condensation if the ejected mass diffuses out high into the corona and some heating mechanisms for the mass switch on.Contributions from the Kwasan and Hida Observatories, University of Kyoto, No. 269.  相似文献   

The role of heterogenetic mantle in the genesis of adakites northeast of Sanandaj,northwestern Iran     

Hossein Azizi  Yoshihiro Asahara  Motohiro Tsuboi  Kento Takemura  Saman Razyani 《Chemie der Erde / Geochemistry》2014

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The use of microstructures for discriminating turbiditic and hemipelagic muds and mudstones          下载免费PDF全文

Yoshihiro Kase  Makoto Ito  Ken Ikehara  Shigeru Takizawa 《Sedimentology》2016,63(7):2066-2086

The microstructures of turbiditic and hemipelagic muds and mudstones were investigated using a scanning electron microscope to determine whether there are microstructural features that can differentiate turbiditic from hemipelagic sedimentary processes. Both types of muddy deposits are, in general, characterized by randomly‐oriented clay particles. However, turbiditic muds and mudstones also characteristically contain aggregates of ‘edge‐to‐face’ contacts between clay particles with long‐axis lengths of up to 30 μm. Based on observations of the clay fabric of the experimentally‐formed muds settled from previously agitated muddy fluids, these types of aggregates, hereafter referred to as ‘aggregates of clay particles’, are interpreted as having been formed by the collision of component flocs in turbulent fluids. Furthermore, some aggregates of clay particles have ‘face‐to‐face’ contacts between clay particles; this is similar to face‐to‐face aggregates characteristically developed in fluid‐mud deposits that are commonly recognized only in turbiditic mudstones, indicating the possibility of a final stage of deposition under highly‐dense conditions, such as temporary fluid muds. In conjunction with earlier proposed lithofacies‐based and ichnofacies‐based criteria, aggregates of clay particles should be useful for the differentiation of turbiditic and hemipelagic muddy deposits, particularly with limited volumes of non‐oriented samples from deep‐water successions.  相似文献   

Sorption behavior of the Pt(II) complex anion on manganese dioxide (δ-MnO2): a model reaction to elucidate the mechanism by which Pt is concentrated into a marine ferromanganese crust     

Mamiko Yamashita Maeno  Hironori Ohashi  Kotaro Yonezu  Akane Miyazaki  Yoshihiro Okaue  Koichiro Watanabe  Tamao Ishida  Makoto Tokunaga  Takushi Yokoyama 《Mineralium Deposita》2016,51(2):211-218

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