Three‐dimensional microstructure of samples recovered from asteroid 25143 Itokawa: Comparison with LL5 and LL6 chondrite particles     

Akira Tsuchiyama  Masayuki Uesugi  Kentaro Uesugi  Tsukasa Nakano  Ryo Noguchi  Toru Matsumoto  Junya Matsuno  Takashi Nagano  Yuta Imai  Akira Shimada  Akihisa Takeuchi  Yoshio Suzuki  Tomoki Nakamura  Takaaki Noguchi  Masanao Abe  Toru Yada  Akio Fujimura 《Meteoritics & planetary science》2014,49(2):172-187

In this study, the three‐dimensional (3‐D) microstructure of 48 Itokawa regolith particles was examined by synchrotron microtomography at SPring‐8 during the preliminary examination of Hayabusa samples. Moreover, the 3‐D microstructure of particles collected from two LL6 chondrites (Ensisheim and Kilabo meteorites) and an LL5 chondrite (Tuxtuac meteorite) was investigated by the same method for comparison. The modal abundances of minerals, especially olivine, bulk density, porosity, and grain size are similar in all samples, including voids and cracks. These results show that the Itokawa particles, which are surface materials from the S‐type asteroid Itokawa, are consistent with the LL chondrite materials in terms of not only elemental and isotopic composition of the minerals but also 3‐D microstructure. However, we could not determine whether the Itokawa particles are purely LL5, LL6, or a mixture of the two. No difference between the particles collected from Rooms A and B of the sample chamber, corresponding to the sampling sequence of the spacecraft's second and first touchdowns, respectively, was detected because of the statistically small amount of particles from Room B.  相似文献   

A 16 ka climate record deduced from δ13C and C/N ratio in Qinghai Lake sediments, northeastern Tibetan Plateau     

SHEN Ji  WANG Yong  LIU Xingqi  Ryo Matsumoto 《中国海洋湖沼学报》2006,24(2)

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Trace-element zoning patterns in porphyroblastic garnets in low-T eclogites: Parameter optimization of the diffusion-limited REE-uptake model     

Ryo Fukushima  Tatsuki Tsujimori  Shogo Aoki  Kazumasa Aoki 《Island Arc》2021,30(1):e12394

Compositional zoning patterns of the major elements and REEs in prograde-zoned garnets whose Mg/(Mg + Fe) atomic ratios increase rimward have been widely used to understand the metamorphic P–T–t trajectories, and the diffusion-limited REE-uptake model is a promising way to interpret their growth rates and the REE diffusion kinetics in the low-temperature eclogite. In order to elucidate their growth kinetics with Skora et al.'s (2006) diffusion-limited REE uptake model for prograde-zoned garnets, we examine the trace-element zoning patterns of two prograde-zoned porphyroblastic garnets (~6 mm in size) in low-temperature eclogites from two different localities. Core-to-rim trace-element profiles in a garnet (prp_5–9alm_61–67sps_1–3grs_24–30) of a glaucophane-bearing epidote eclogite of Syros (Cyclades, Greece) are characterized by the presence of Y + HREE peaks in the mantle, which might be attributed to a continuous breakdown of the titanite to form rutile during the garnet growth. In contrast, those in a garnet (prp_4–7alm_61–68sps_3–10grs_23–24) extracted from a lawsonite-eclogite of the South Motagua Mélange (SMM) (Guatemala) have prominent central peaks of Y + HREEs. Although the REE profiles of both the garnets can be explained by the diffusion-limited uptake, their Mn profiles suggest that their growth-rate laws are different: i.e., diffusion-controlled (Syros) and interface-controlled (SMM). Prior to the model application, we optimize the number of the parameters as the garnet grows with the interface-controlled processes based on the growth Péclet number. In particular, we propose the ratio of the REE diffusivity in the eclogitic matrix to the garnet growth rate as the new parameter. Visualizing the values of the new parameters allows to readily understand the relationship between the REE profiles and the REE-diffusion/garnet-growth kinetics in low-T eclogite. Our model refinement leads to the simple quantitative characterization of core-to-rim REE profiles in garnet in low-temperature eclogites.  相似文献   

The effect of wind on long-term summer water temperature trends in Tokyo Bay,Japan   总被引：1，自引：1，他引：0  

Li-Feng Lu  Ryo Onishi  Keiko Takahashi 《Ocean Dynamics》2015,65(6):919-930

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Fission–track Ages and Magnetic Susceptibility of Cretaceous to Paleogene Volcanic Rocks in Southeastern Sikhote Alin, Far East Russia     

Takaaki MaTSUDA  Tohru SAKIYAMA  Ryo ENAMI  Yo–ichiro OTOFUJI  Vladimir G. SAKHNO  Anatoly P. MATUNIN  Ruslan G. KULINICH  Petr S. ZIMIN 《Resource Geology》1998,48(4):285-290

Abstract: Seven zircon fission-track ages and 30 magnetic susceptibilities were measured on welded pyroclastic rocks from the Bogopol and Sijanov Groups of the Cretaceous to Paleogene volcanic rocks in the southeastern part of the eastern Sikhote Alin volcano-plutonic belt, Far East Russia. The fission-track ages range from 42. 7 Ma to 64. O Ma which indicate that both the groups are of Early Paleogene time. Two thirds of the samples from the Bogopol Group have high magnetic susceptibility values, more than 3 A- 10^-3 SI unit, which imply that they are of the magnetite–series, whereas the samples from the Sijanov Group show 3 A- 10^-3 to 8 A- 10^-5 SI unit which suggest this group of probably the ilmenite-series.
The Paleogene age and high magnetic susceptibility of the Bogopol Group are quite similar to the Paleogene igneous rocks of the San'in belt, Southwest Japan. This suggests, taking accounts of the opening of the Japan Sea, that the eastern Sikhote Alin volcano-plutonic belt continued to the San'in Belt, and that the Paleogene igneous rocks along the Japan Sea coast of Northeast Japan were situated along the volcanic front of the eastern Sikhote Alin volcano-plutonic belt.  相似文献   

A high-resolution climatic change since the Late Glacial Age inferred from multi-proxy of sediments in Qinghai Lake   总被引：12，自引：3，他引：9  

Ryo Matsumoto 《中国科学D辑(英文版)》2005,48(6):742-751

The study of climatic changes since the Late Glacial Age has become one of the hotspots of the PAGES in recent years.Deep-sea cores from the high-latitude area show that the climate was very unstable during the transitional period from the Late Glacial Age to the Holocene[1,2],which has also been testified by the geological records from ocean sediments,ice cores and terrestrial sections in different latitudes of the earth[3—8].What’s more,climatic instability also ex-isted in the Holoce…  相似文献   

Nutritional condition of first-feeding larvae of Japanese sardine in the coastal and oceanic waters along the Kuroshio Current     

Kimura  Ryo; Watanabe  Yoshiro; Zenitani  Hiromu 《ICES Journal of Marine Science》2000,57(2):240-248

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A 3600 YEARS PALEOCLIMATIC CHANGE INFERRED FROM ORGANIC δ~(13)C AND TOC/TN OF THE GUCHENG LAKE SEDIMENTS, SOUTHEAST CHINA   总被引：1，自引：0，他引：1  

沈吉  王苏民 《中国海洋湖沼学报》1997,(3)

Im0DUrmNItiswellknownthatpabodbotechangeamrdedbyisotopesinlakesedimentScanbeobtainedbymcasuringthebl0andb'3CofauthigeniccarbonateSpeudsonetal.,l989),orbyrmsuringtheblbandb'tofmoiluscanshellsopntZetal.,l987)togetpabolaketeInPeratme.ButitisdiffictiltsoInebotodistinguishthegenetictypeofthecarbonatesfoedinoroutSidethelake.Furthennre,thepaservationof6'Dasapaleotemeraturerecordcanbeahabypostdepositionisotopicexchangecausedbydi-agnosesandotherfactorssuchas"vitalefTtal'(Marshall,l992).Itisdimcul…  相似文献   

The high-pressure phase relation of the MgSO₄-H₂O system and its implication for the internal structure of Ganymede     

Ryo Nakamura  Eiji Ohtani 《Icarus》2011,211(1):648-654

We have determined the phase relation of the MgSO₄-H₂O binary system using an externally heated diamond anvil cell in the compositional range of 0-30 wt.% MgSO₄, and under temperature and pressure conditions from 298 to 500 K and up to 4.5 GPa. Using our experimental results, we were able to estimate the composition of the ice mantle of the large icy satellites of Jupiter, such as Ganymede.In our experiments, we identified the following phases in the MgSO₄-H₂O system up to 4 GPa at 298 K: Ices VI and VII, magnesium heptahydrate, MgSO₄·7H₂O, and a liquid phase. The present phase relations suggest that there may be a deep internal ocean down to a depth about 800 km in the interior of Ganymede.  相似文献   

Fine-scale chemostratigraphy of cross-sectioned hydrogenous ferromanganese nodules from the western North Pacific     

Shiki Machida  Kentaro Nakamura  Tetsu Kogiso  Ryo Shimomura  Koichi Horinouchi  Kyoko Okino  Yasuhiro Kato 《Island Arc》2021,30(1):e12395

A broad area densely covered by ferromanganese nodules was recently discovered around Minamitorishima (Marcus) Island, representing a high-potential metal resource, particularly for Co, Ni, Mo, and W. We studied 16 nodule samples from nodule fields around Minamitorishima Island. To define the fine-scale chemostratigraphy of the nodules, polished cross-sections of the samples were analyzed by microfocus X-ray fluorescence. Our results show that a general pattern of compositional variation was common throughout the growth history of the nodules in all the regions we studied. Chemical mapping clarified changes in the chemical signature and proportion of five lithological components throughout the growth history: Mn represented columnar δ-MnO₂; Fe represented layered amorphous FeOOH*xH₂O; Ti represented TiO₂*2H₂O intergrown with an amorphous FeOOH phase; P, Ca and Y represented particles of biogenic calcium phosphate; and Si, Al, K, Cu, and Ni represented pelagic sediment infills. We proposed a method for a creating a multi-dimensional compositional map of the fine-scale chemostratigraphy observed in the ferromanganese oxide layers on the basis of merging the mapped Mn, Fe, Ti, P, Si and Cu intensities. Multi-dimensional compositional mapping of the sampled nodules from the western North Pacific revealed two fundamental findings: (1) previously recognized first-order Fe–Mn layers, L0, L1, and L2, were further divided into two, three, and four sublayers, respectively, and (2) a delayed supply of material to be nuclei of nodule or a growth hiatus of Fe–Mn layer(s), leading to missing sublayers in the layers L0 and L2, regulated the nodule size. In contrast, layer L1, which does not have any missing sublayers, was commonly observed in the samples for this study and has been reported in studies of other regions in the western Pacific. We propose, therefore, that the layer L1 is a key facies for examining chemostratigraphic correlations with other areas of seafloor.  相似文献