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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可可西里库赛湖揭示的青藏高原北部近4000年来的干湿变化   总被引：3，自引：0，他引：3  

王永波  刘兴起  羊向东  张恩楼  Ryo Matsumoto 《湖泊科学》2008,20(5):605-612

通过青藏高原北部可可西里库赛湖KS-2006孔(深637cm)沉积岩芯总有机碳、总氮含量及沉积物粒度变化的研究,恢复了该地区近4000年来的干湿变化历史.结果表明,该地区近4000年来经历了显著的干湿变化,干旱时段出现在3900-3590cal aBP、3320-2630cal aBP、1720-1420cal aBP及1100-840cal aBP期间:湿润时段出现在3590-3320cal aBP、2630-1720cal aBP、1420-1100cal aBP以及840cal aBP之后小冰期有效降水升高的相对湿润时期.区域对比分析表明库赛湖地区近4000年来的干湿变化受亚洲季风影响;同时,该地区存在明显的中世纪暖期及小冰期的三次降温事件记录.  相似文献   

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   

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   

Particle Image Velocimetry Measurements of Turbulent Flow Within Outdoor and Indoor Urban Scale Models and Flushing Motions in Urban Canopy Layers     

Hiroshi Takimoto  Ayumu Sato  Janet F. Barlow  Ryo Moriwaki  Atsushi Inagaki  Shiho Onomura  Manabu Kanda 《Boundary-Layer Meteorology》2011,140(2):295-314

We investigate the spatial characteristics of urban-like canopy flow by applying particle image velocimetry (PIV) to atmospheric turbulence. The study site was a Comprehensive Outdoor Scale MOdel (COSMO) experiment for urban climate in Japan. The PIV system captured the two-dimensional flow field within the canopy layer continuously for an hour with a sampling frequency of 30 Hz, thereby providing reliable outdoor turbulence statistics. PIV measurements in a wind-tunnel facility using similar roughness geometry, but with a lower sampling frequency of 4 Hz, were also done for comparison. The turbulent momentum flux from COSMO, and the wind tunnel showed similar values and distributions when scaled using friction velocity. Some different characteristics between outdoor and indoor flow fields were mainly caused by the larger fluctuations in wind direction for the atmospheric turbulence. The focus of the analysis is on a variety of instantaneous turbulent flow structures. One remarkable flow structure is termed ‘flushing’, that is, a large-scale upward motion prevailing across the whole vertical cross-section of a building gap. This is observed intermittently, whereby tracer particles are flushed vertically out from the canopy layer. Flushing phenomena are also observed in the wind tunnel where there is neither thermal stratification nor outer-layer turbulence. It is suggested that flushing phenomena are correlated with the passing of large-scale low-momentum regions above the canopy.  相似文献   

Holocene vegetational and climatic variation in westerly-dominated areas of Central Asia inferred from the Sayram Lake in northern Xinjiang,China   总被引：2，自引：0，他引：2  

JIANG QingFeng  JI JunFeng  SHEN Ji  Ryo MATSUMOTO  TONG GuoBang  QIAN Peng  REN XueMei  YAN DeZhi 《中国科学:地球科学(英文版)》2013,(3):339-353

Changes in the vegetation and climate of the westerly-dominated areas in Central Asia during the Holocene were interpreted using pollen-assemblages and charcoal data from a 300-cm-long sediment core of the Sayram Lake,northern Xinjiang.Accele-rator Mass Spectrometry(AMS) radiocarbon dating methods were applied to bulk organic matter of the samples.Artemisia spp./Chenopodiaceae ratios and results from principal component analysis were used to infer that the lake basin was dominated by desert vegetation before ca.9.6 cal.ka BP,which suggests a warm and dry climate in the early Holocene.Desert steppe/steppe expanded during 9.6-5.5 cal.ka BP,indicating a remarkable increase both in the precipitation and temperature during the mid-Holocene.Desert vegetation dominated between 6.5 and 5.5 cal.ka BP,marking an extreme warmer and drier interval.The steppe/meadow steppe recovered,and temperatures decreased from 5.5 cal.ka BP in the late Holocene,as indicated by the increased abundance of Artemisia and the development of meadows.Holocene temperatures and moisture variations in the Sayram Lake areas were similar to those of adjacent areas.This consistency implies that solar radiation was the main driving factor for regional temperature changes,and that the effect of temperature variations was significant on regional changes in humidity.The evolution of climate and environment in the Sayram Lake areas,which were characterized as dry in the early Holocene and relatively humid in the middle-late Holocene,are clearly different from those in monsoonal areas.Dry conditions in the early Holocene in the Sayram Lake areas were closely related to decreased water vapor advection.These conditions were a result of reduced westerly wind speeds and less evaporation upstream,which in turn were caused by seasonal changes in solar radiation superimposed by strong evaporation following warming and drying local climate.  相似文献   

Correlating biostratigraphy and palaeoceanographic changes during late Quaternary at cold seeps with gas hydrate‐free areas of the Japan Sea using foraminifera paleoecology          下载免费PDF全文

Mahsa Saeidi Ortakand  Shiro Hasegawa  Ryo Matsumoto  Hiroki Matsuda 《Island Arc》2016,25(1):55-71

Late Quaternary foraminifera assemblages have been examined in two sediment cores (MD179‐3296 and MD179‐3317) from cold seep areas in the eastern margin of the Japan Sea, off Joetsu, Niigata Prefecture. Foraminifera assemblages in core MD179‐3296, which was located at the center of a pockmark on the Umitake Spur, show no evidence of methane flux and, especially in its upper portion, share the same paleo‐environmental history as other free gas hydrate areas of the Japan Sea. In comparison, in the core MD179‐3317 at the center of a pockmark at Joetsu Knoll, foraminiferal distributions were strongly affected by methane activities and, in the main part of the core, were deposited under local conditions. Three horizons were identified in this core, which are characterized by the high abundance value of Thalmannammina parkerae and might be related to methane flux due to sea level fall especially through late marine isotope stage (MIS) 3 and MIS 2.  相似文献