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81.
Yasuhito Sekine Kenya Kodama Takamichi Kobayashi Seiji Obata Yu Chang Nanako O. Ogawa Yoshinori Takano Naohiko Ohkouchi Koichiro Saiki Toshimori Sekine 《Meteoritics & planetary science》2018,53(6):1267-1282
The present study systematically investigates shock-induced alteration of organic simulants of planetary bodies (OSPBs) as a function of peak shock pressure and temperature by impact experiments. Our results show that the composition and structure of OSPBs are unchanged upon impacts at peak pressures ≤~5 GPa and temperatures ≤~350 °C. On the other hand, these are dramatically changed upon impacts at >7–8 GPa and > ~400 °C, through loss of hydrogen-related bonds and concurrent carbonization, regardless of the initial compositions of OSPBs. Compared with previous results on static heating of organic matter, we suggest that shock-induced alteration cannot be distinguished from static heating only by Raman and infrared spectroscopy. Our experimental results would provide a proxy indicator for assessing degree of shock-induced alteration of organic matter contained in carbonaceous chondrites. We suggest that a remote-sensing signature of the 3.3–3.6 μm absorption due to hydrogen-related bonds on the surface of small bodies would be a promising indicator for the presence of less-thermally-altered (i.e., <350 °C) organic matter there, which will be a target for landing to collect primordial samples in sample-return spacecraft missions, such as Hayabusa2 and OSIRIS-REx. 相似文献
82.
High‐pressure polymorphs in Yamato‐790729 L6 chondrite and their significance for collisional conditions 下载免费PDF全文
Yukako Kato Toshimori Sekine Masahiko Kayama Masaaki Miyahara Akira Yamaguchi 《Meteoritics & planetary science》2017,52(12):2570-2585
Shock pressure recorded in Yamato (Y)‐790729, classified as L6 type ordinary chondrite, was evaluated based on high‐pressure polymorph assemblages and cathodoluminescence (CL) spectra of maskelynite. The host‐rock of Y‐790729 consists mainly of olivine, low‐Ca pyroxene, plagioclase, metallic Fe‐Ni, and iron‐sulfide with minor amounts of phosphate and chromite. A shock‐melt vein was observed in the hostrock. Ringwoodite, majorite, akimotoite, lingunite, tuite, and xieite occurred in and around the shock‐melt vein. The shock pressure in the shock‐melt vein is about 14–23 GPa based on the phase equilibrium diagrams of high‐pressure polymorphs. Some plagioclase portions in the host‐rock occurred as maskelynite. Sixteen different CL spectra of maskelynite portions were deconvolved using three assigned emission components (centered at 2.95, 3.26, and 3.88 eV). The intensity of emission component at 2.95 eV was selected as a calibrated barometer to estimate shock pressure, and the results indicate pressures of about 11–19 GPa. The difference in pressure between the shock‐melt vein and host‐rock might suggest heterogeneous shock conditions. Assuming an average shock pressure of 18 GPa, the impact velocity of the parent‐body of Y‐790729 is calculated to be ~1.90 km s?1. The parent‐body would be at least ~10 km in size based on the incoherent formation mechanism of ringwoodite in Y‐790729. 相似文献
83.
Kelyphite is a reaction product between garnet and olivine, which was formed by subsolidus reactions upon decompression during the ascent of mantle peridotite. We studied crystallographic relationships among constituent (product) phases of kelyphite ?C orthopyroxene, clinopyroxene, spinel and reactant phases, garnet and olivine, using EBSD and found that, for a relatively high temperature sample (from Czech Moldanubian), spinel and pyroxenes are in a topotaxic relationship in such a way that spinel {111} coincides with pyroxene (100) and spinel {110} coincides with pyroxene (010); while the topotaxy is incomplete or non for a lower-temperature sample (from western Norway). On the basis of the observed microstructural and crystallographic relationships, we propose a hypothesis that the topotaxic relationship may be established at nucleation stages of the onset of the kelyphitization and that the degree of topotaxy may be related to the transformation temperature and the degree of supersaturation of the reaction. The lower the temperature, the higher the supersaturation and, therefore, more rapid the nucleation becomes, resulting in a more disordered state in topotaxic relationship. 相似文献
84.
M. Tajuddin Sikder Yusuke Kihara Masaomi Yasuda Yustiawati Yoshihiro Mihara Shunitz Tanaka Dalkhjav Odgerel Badamtsetseg Mijiddorj Suhaemi M. Syawal Toshiyuki Hosokawa Takeshi Saito Masaaki Kurasaki 《洁净——土壤、空气、水》2013,41(1):60-68
To compare water quality in rivers of developed and developing countries, a study based on physicochemical parameters and dissolved metals levels was conducted. Water samples were collected from selected sites in Dhaka, Bangladesh; Hokkaido and Osaka, Japan; Erdenet, Mongolia and West Java, Indonesia. Analysis of least significant differences revealed that most water quality parameters were within comparable low levels in both developed and developing countries. The dissolved metals concentrations were found to be similar and below those of water standards except for manganese and cadmium at every sampling point, and lead in Erdenet, Mongolia. Some metals showed high enrichment factors in the rivers of Osaka, Japan and Erdenet, Mongolia, indicating accumulation possibility of metals in the river‐bed sediments. High concentrations of dissolved organic carbon, Escherichia coli and dissolved metals suggested greater water pollution in some rivers of developing countries than in the rivers of Japan. Principal component analysis showed strong correlations between “dissolved organic carbon and chemical oxygen demand” and “conductivity and total dissolved solids” at each sampling point, and E. coli, nitrate (NO), nitrite (NO), and pH levels were found to be higher in the rivers of Dhaka and Erdenet. In addition, there were high levels of Al and Zn in West Java, Pb in Erdenet, and Mn, Fe, and Cr in the rivers of Dhaka and Japan. Based on pressures and impacts, it is evident that dissolved metal, organic, and fecal pollution in the rivers of developing countries are in somewhat dreadful condition in comparison with the rivers of developed country. 相似文献
85.
Amphibole and chlorite in mafic and ultramafic rocks in the lower crust and upper mantle 总被引:4,自引:0,他引:4
Stabilities of amphibole and chlorite in mafic and ultramafic compositions have been considered in the model system CaO+MgO+Al2O3+SiO2+H2O. From topological arguments two petrogenetic grids have been constructed. Although available experimental data in CMASH are compatible with the grid in which amphibole reacts out before chlorite in model ultramafic compositions for the pressure range 6 to 15 kbar, naturally observed mineral assemblages and some experimental data in more complex systems favour the other grid in which chlorite reacts out before amphibole at all pressures. This discrepancy between natural and model systems is due to differential movement of the dehydration equilibria of the two hydrates reflecting the variation of activity of H2O or of components other than CMASH. 相似文献
86.
Kay I. Ohshima Genta Mizuta Motoyo Itoh Yasushi Fukamachi Tatsuro Watanabe Yasushi Nabae Koukichi Suehiro Masaaki Wakatsuchi 《Journal of Oceanography》2001,57(4):451-460
In the southwestern part of the Okhotsk Sea, oceanographic and sea-ice observations on board the icebreaker Soya were carried out in February 1997. A mixed layer of uniform temperature nearly at the freezing point extending down to a
depth of about 300 m was observed. This is much deeper than has previously been reported. It is suggested that this deep mixed
layer originated from the north (off East Sakhalin), being advected along the shelf slope via the East Sakhalin Current, accompanied
with the thick first-year ice (average thickness 0.6 m). This vertically uniform winter water, through mixing with the surrounding
water, makes the surface water more saline (losing a characteristic of East Sakhalin Current Water) and the water in the 100–300
m depth zone less saline, colder, and richer in oxygen (a characteristic of the intermediate Okhotsk Sea water). The oceanographic
structure and a heat budget analysis suggest that new ice zone, which often appears at ice edges, can be formed through preconditioning
of thick ice advection and subsequent cooling by the latent heat release due to its melting.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
87.
Takayuki Ishikawa Jinro Ukita Kay I. Ohshima Masaaki Wakatsuchi Takashi Yamanouchi Nobuo Ono 《Journal of Oceanography》1996,52(3):389-398
Coastal polynyas off East Queen Maud Land in Antarctica are examined using NOAA AVHRR infrared data. From image analyses, two locations of coastal polynyas in this region are identified; one in Breid Bay and the other along the shelf break. The areal coverage of the Breid Bay polynya is significantly related to the strength of katabatic winds, which maintain their strength over the coastal sea due to land topography favoring for their confluence, thereby being capable of removing newly formed ice. Land fast ice in the eastern part of the bay also plays an additional role in the formation mechanism. It is also found that the areal coverage of coastal polynyas in this region fluctuate coherently. Moreover, these fluctuations correspond to the synoptic index, which measures the strength of the offshore wind, with their peaks closely associated with the areal peaks. These facts strongly suggest the influence of synoptic scale weather on the formation and maintenance of polynyas in this region. 相似文献
88.
Masaaki Murano 《Journal of Oceanography》1970,26(3):137-150
A list of the 21 species represented in the collection by the bottom-net is given. Of these, 5 are impossible to be identified
with the already known species, especially 2 are reserved as their genera are undecided. It is found that there are 2 races
inHolmesiella affinis
Ii, the large-sized and the small-sized, as like as the most related species,H. anomala
Ortmann. As to a species,Pteromysis amemiyai
Ii, the development of the marsupium is discussed on the basis of an adult female collected by the ORI-net. The occurrence of
2 species,Petalophthalmus oculatus
Illig andPseudomma calloplura
Holt andTattersall, is a new record in the Pacific. For the former species, moreover, an ecological property of the habitat is discussed. 相似文献
89.
Kazuya Ono Kay I. Ohshima Tokihiro Kono Motoyo Itoh Katsuro Katsumata Yuri N. Volkov Masaaki Wakatsuchi 《Journal of Oceanography》2007,63(2):281-291
Intensive CTD observations that resolve the mean and tidal components were done with a total of 129 casts in summer of 2001
at Bussol’ Strait. Based on these data and all the available historical data, we have revealed the outflow from Bussol’ Strait
to the Pacific and the significant diapycnal mixing in the strait. In the range 27.0−27.3σ
θ
, the water property in Bussol’ Strait is almost identical to that of the Kuril Basin Water (KBW). The KBW out of Bussol’
Strait forms a water mass front with the East Kamchatka Current Water (EKCW). This front also corresponds to the front of
the Oyashio Current. In the lower part of the intermediate layer (27.3−27.6σ
θ
), part of the water in the strait is characterized by lower temperature, lower salinity, and higher dissolved oxygen than
that of KBW and EKCW, which can be explained only by the diapycnal mixing. The strong diapycnal mixing in the strait can also
be shown by the density inversion, occurrence frequency of which corresponds well to the amplitude distribution of the diurnal
current. In the density range 26.7−26.8σ
θ
, the water in Bussol’ Strait has the lowest potential vorticity, suggesting that it is a source region of the low potential
vorticity water. Seasonal change of the water can reach up to a density of 26.8σ
θ
around Bussol’ Strait. This leads us to propose that the combination of winter convection and local tidal mixing leads to
effective ventilation of the intermediate layer. 相似文献
90.
Masaaki Okuda Hiroomi Nakazato Norio Miyoshi Takeshi Nakagawa Hiroko Okazaki Saneatsu Saito Asahiko Taira 《Island Arc》2006,15(3):338-354
Abstract The 250-m Choshi core (CHOSHI-1), drilled from hemipelagic muds of the Inubo Group, has been physically, geochemically and tephrochronologically analyzed back to 1 Ma. We provide pollen results for the 19–169 m section of the core (400–780 ka) bracketed by the marker tephra Ty1 (equivalent to J4) and the Brunhes–Matuyama paleomagnetic boundary. The results show good agreement with the corresponding oxygen isotope (δ18 O) profile, with high δ18 O intervals dominated by boreal conifers Picea , Abies , Pinus (subgen. Haploxylon ) and Tsuga ( diversifolia ), whereas low δ18 O intervals are dominated by temperate conifers Cryptomeria , Taxaceae-Cephalotaxaceae-Cupressaceae and Sciadopitys . In order to confirm pollen-climate relations for the relevant taxa, a modern surface pollen dataset for the Japanese archipelago was consulted. In this analysis, the ratios of Cryptomeria / Picea and temperate/boreal conifers serve as proxies for the 100-kyr glacial/interglacial cycle during the Middle Pleistocene. Distinct signals for marine isotope stages (MIS) 11, 12, 13–15, 16, 17 and 18–19 are recognized in accordance with the tephrochronology and δ18 O of the same core. Application of the criteria to an independent pollen record from Lake Biwa provides an integrated pollen stratigraphy for mid-latitude Japan during the past 800 ky. Some degree of uncertainty remains in the chronology of the MIS13–15 interval, relating to the uncertainty in the eruption age of widespread tephra Ks11. 相似文献