He,Ne and Ar in peridotitic and eclogitic paragenesis diamonds from the Jwaneng kimberlite,Botswana—Implications for mantle evolution and diamond formation ages     

Masahiko Honda  David Phillips  Jeff W. Harris  Takuya Matsumoto 《Earth and Planetary Science Letters》2011,301(1-2):43-51

We have undertaken helium, neon and argon step-heating, isotopic analyses of eleven polycrystalline diamonds of known peridotite/eclogite paragenesis from the Jwaneng kimberlite pipe, Botswana. In contrast to the findings of crustal noble gases in framesites from the same kimberlite pipe (Honda et al., 2004. Unusual noble gas compositions in polycrystalline diamonds: preliminary results from the Jwaneng kimberlite, Botswana. Chem. Geol. 203, 347–358.), the Jwaneng polycrystalline diamonds appear to contain similar noble gas isotopic compositions (particularly Ne) to those representing a mantle source for MORBs. This implies that the Jwaneng polycrystalline diamonds may have formed in recent times, possibly close to the time of kimberlite emplacement at ~ 235 Ma. In contrast, Jwaneng framesites could be as old as gem diamonds (mineral inclusion ages of ~ 2.9 Ga). Furthermore, the data indicate that the sub-continental mantle lithosphere in the region has heterogeneous Ne isotopic compositions, or that these compositions changed over time from crustal Ne (as observed in the framesites) to MORB-like (as observed in the polycrystalline diamonds).  相似文献   

Formation age of the lunar crater Giordano Bruno     

Tomokatsu Morota  Junichi Haruyama  Hideaki Miyamoto  Chikatoshi Honda  Makiko Ohtake  Yasuhiro Yokota  Tsuneo Matsunaga  Naru Hirata  Hirohide Demura  Hiroshi Takeda  Yoshiko Ogawa  Jun Kimura 《Meteoritics & planetary science》2009,44(8):1115-1120

Abstract— Using the Terrain Camera onboard the Japanese lunar explorer, SELENE (Kaguya), we obtained new high‐resolution images of the 22‐kilometer‐diameter lunar crater Giordano Bruno. Based on crater size‐frequency measurements of small craters (<200 m in diameter) superposed on its continuous ejecta, the formation age of Giordano Bruno is estimated to be 1 to 10 Ma. This is constructive evidence against the crater's medieval age formation hypothesis.  相似文献   

Sea water weathering effect on K-Ar age of submarine basalts     

Minoru Ozima  Kazuo Saito  Masahiko Honda  Sigeo Aramaki 《Geochimica et cosmochimica acta》1977,41(4):453-461

K-Ar dating and ⁴⁰Ar-³⁹Ar step heating experiments have been done for successive zones from the surface to the interior in two, altered dredged submarine basalts (16-2-6 and Aries V-23). The K contents show a systematic decrease (surface to the interior), whereas the K-Ar ages show a similar decrease in one sample (16-2-6) and almost no change in the other (Aries V-23).A simple diffusion model suggests that the K content decreases systematically from the surface to the interior, whereas the K-Ar age decreases or remains almost constant, depending on whether the times of solidification and of commencement of K-diffusion are close to each other or differ significantly. Comparison of the observed K content and K-Ar age variations within the rocks with the theoretical model then suggests that the solidification age of the sample Aries V-23 is much older than the commencement of the potassium-diffusion, the latter age perhaps being represented by the Eocene planktonic foraminifera on this sample. The ⁴⁰Ar-³⁹Ar isochron age obtained for the freshest specimen of Aries V-23 is 86.6 ± 3.7 m.y., supporting the above conclusion.The mathematical simulation indicates that an apparent concordance of the K-Ar age observed in some submarine basalts may be an artifact, only reflecting the significant gap between the solidification age and the time of the commencement of the K-diffusion in the rocks. Microprobe examination reveals that the potassium enrichment in the outer margin, is mainly due to K feldspar, which is an alteration product of plagioclase.  相似文献   

Trapping of rare gases during the condensation of solids     

Masahiko Honda  M. Ozima  Y. Nakada  T. Onaka 《Earth and Planetary Science Letters》1979,43(2):197-200

Rare gas trapping during crystallization from vapor phases of (1) CdTe, (2) Zn, (3) Mg and (4) Fe₃O₄ has been studied. Samples were deposited as very fine crystals (about several hundred angströms) in ambient Ar atmospheres of various pressures. It was found that the amount of Ar trapped in the samples was proportional to the ambient Ar pressure. Stepheating degassing of the crystals showed that Ar was rather loosely trapped and released at relatively low temperatures. However, on a simple mechanical compaction of the crystal powder the retentivity of Ar was considerably enhanced.  相似文献   

Age characteristics of walleye pollock school echoes     

Kang  Myounghee; Honda  Satoshi; Oshima  Tatsuki 《ICES Journal of Marine Science》2006,63(8):1465-1476

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Bifurcation current along the southwest coast of the Kii Peninsula   总被引：1，自引：0，他引：1  

Junichi Takeuchi  Naoto Honda  Yoshitaka Morikawa  Takashi Koike  Yutaka Nagata 《Journal of Oceanography》1998,54(1):45-52

Along the southwest coast of the Kii Peninsula, a bifurcation current is regularly observed. By using ADCP data taken on board the R/V Wakayama of the Wakayama Prefectural Fisheries Experimental Station, characteristics of this bifurcation current are analyzed. The occurrence frequency of the bifurcation current reaches about 70% in the period from 1988 to 1996. The bifurcation point appears to be changeable and occurs almost evenly between Cape Ichie and Cape Shionomisaki. The current divergence in the alongshore direction was also investigated. Positive divergence values dominated in the whole analyzed area, and an onshore current appears to be dominant along the southwest coast of the Kii Peninsula, except in 1990 when the Kuroshio flowed in a large meandering path.  相似文献   

Abundances of 23 field RR Lyrae stars     

Shu Liu  Gang Zhao  Yu-Qin Chen  Yoichi Takeda  Satoshi Honda 《天文和天体物理学研究(英文版)》2013,(11):1307-1329

We present stellar parameters and abundances of 15 elements （Na, Mg, A1, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Ni, Cu, Y and Ba） for 23 field RR Lyrae variables based on high-resolution （R ~ 60 000） and high signal-to-noise （S/N~ 200） spectra obtained using the High Dispersion Spectrograph on the Subaru Telescope. Six stars in the sample have more than one spectrum observed at different pulsation phases. The derived abundance ratios of [X/Fe] for 14 elements （except for Ba） do not vary during the pulsation cycle. An interesting curve of [Ba/Fe] versus phase is detected for the first time and it shows decreasing [Ba/Fe] with increasing temperature at a given metallicity. Combining with data in the literature, abundances of most RR Lyrae stars as a function of [Fe/H] follow the same trends as those of dwarf stars, but [Sc/Fe] and [Y/Fe] ratios of RR Lyrae stars at solar metallicity are lower than those of dwarf stars. The kinematics of RR Lyrae stars indicate that three comparatively metal-rich RR Lyrae stars might originate from the thick disk and they show higher [a/Fe] ratios than RR Lyrae stars with thin disk kinematics. Among 23 RR Lyrae stars, two special objects are found with abnormal abundances; TV Lib has high [a/Fe], [Sc/Fe], [Y/Fe] and [Ba/Fe] ratios while TW Her has solar [a/Fe] but significantly lower [Sc/Fe], [Y/Fe] and [Ba/Fe] ratios as compared with other RR Lyrae stars.  相似文献   

Impact of mesoscale eddies on particulate organic carbon flux in the western subarctic North Pacific     

Dobashi  Ryo  Ueno  Hiromichi  Matsudera  Nozomi  Fujita  Isao  Fujiki  Tetsuichi  Honda  Makio C.  Harada  Naomi 《Journal of Oceanography》2022,78(1):1-14

The mechanism that controls particulate organic carbon (POC) flux in the deep sea differs depending on the season and sea. The POC produced in the western subarctic North Pacific are known to be transported to the deep sea efficiently, but the direct relationship between the POC flux and physical processes is still unclear. In this study, we evaluated the effect of mesoscale eddies on POC flux in the western subarctic North Pacific. The seasonal and interannual variabilities of POC flux were investigated using data from a time-series sediment trap deployed at 4810 m at station K2 (47°N, 160°E) from 2005 to 2018. POC flux was high during May–November, appearing to reflect spring and fall blooms at the ocean surface. POC flux also showed interannual variability, with twelve peaks that were mostly affected by enhanced bloom just before the peak. Nine peaks of the twelve peaks were affected by mesoscale eddies, which enhanced bloom around K2 by extending the area with a high chlorophyll-a concentration along the coastal region into the offshore region, suggesting that mesoscale eddies strongly impact the interannual variability of POC flux at K2.

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POC fluxes estimated from 234Th in late spring–early summer in the western subarctic North Pacific     

Hajime Kawakami  Makio C. Honda  Kazuhiko Matsumoto  Masahide Wakita  Minoru Kitamura  Tetsuichi Fujiki  Shuichi Watanabe 《Journal of Oceanography》2015,71(3):311-324

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Tributyltin in blood of marine fish collected from a coastal area of northern Kyushu, Japan     

Miki S  Ikeda K  Oba Y  Satone H  Honda M  Shimasaki Y  Onikura N  Arakawa O  Oshima Y 《Marine pollution bulletin》2011,62(11):2533-2536

We investigated levels of the pollutant tributyltin (TBT) in blood of pufferfishes (six species), Japanese sea perch, red sea bream, Japanese common goby, Japanese flounder, rockfish, conger eel, and sea mullet collected off the coast of northern Kyushu, Japan. We found considerable levels of TBT (1.4-190 ng/mL) accumulated in the blood of these fish. Blood TBT concentrations were 1.3-22.5 times liver concentrations and 4.9-78 times muscle concentrations, except in conger eel and mullet. We detected TBT (16-111 ng/mL-blood) in the plasma of the fine-patterned puffer (Takifugupoecilonotus) year-round, without any apparent seasonal trend. These results suggest that fish inhabiting coastal areas of Kyushu, Japan, continue to be contaminated with TBT.  相似文献