Neutron diffraction study of aluminous hydroxide δ-AlOOD     

C. B. Vanpeteghem  A. Sano  K. Komatsu  E. Ohtani  A. Suzuki 《Physics and Chemistry of Minerals》2007,34(9):657-661

We have determined the position of deuterium atoms in δ-AlOOD by neutron powder diffraction at ambient pressure. As previously reported by theoretical and experimental studies, the deuterium atoms are located in the tunnel formed by the chains of AlO₆ octahedra. The data are best fit with the P2₁ nm structure, producing bond lengths of D–O1 of 1.552(2) Å, O2–D of 1.020(2) Å and O1–O2 of 2.571(2). This study confirms that the hydrogen bond is asymmetric at ambient conditions in agreement with recent single-crystal synchrotron study for δ-AlOOH.  相似文献   

High-temperature annealing of amoeboid olivine aggregates: Heating experiments on olivine–anorthite mixtures     

Mutsumi Komatsu  Takashi Mikouchi  Masamichi Miyamoto 《Polar Science》2009,3(1):31-55

Amoeboid olivine aggregates (AOAs) are composed of forsteritic olivine, Fe,Ni-metal, and Ca,Al-rich nodules consisting mainly of Al-diopside, spinel, and anorthite. Although the textures, shapes, and mineralogy of AOAs are consistent with their being aggregates of nebular condensates, some textures are in conflict with equilibrium condensation calculations, indicating that AOAs were not produced by a simple one-stage condensation. To examine the origin of the constituent minerals within AOAs and their textural relationships, we performed heating experiments using mineral mixtures analogous to those in AOAs. Isothermal and cooling experiments on forsterite + anorthite mixtures reveal that a high-Ca pyroxene phase forms via the incipient melting of the two minerals. Comparative studies of heating experiments performed using the mineralogy of AOAs suggest that Al-diopside in AOAs can be produced from a small degree of melting of forsterite and anorthite. The formation of Al-diopside in this way is consistent with the annealing textures observed in AOAs, and it may account for the discrepancy between the observed mineralogy of AOAs and the results of equilibrium condensation calculations, the occurrence of two types of diopside (Al,Ti-rich diopside and Al-diopside), and the variable Al₂O₃ content of Al-diopside.  相似文献   

Depositional age of the Himenoura Group on the Amakusa‐Kamishima area,Kyushu, southwest Japan: Using zircon U–Pb dating of the acidic tuffs          下载免费PDF全文

Yukiyasu Tsutsumi  Yuka Miyake  Toshifumi Komatsu 《Island Arc》2017,26(4)

The Upper Cretaceous Himenoura Group in the Amakusa‐Kamishima Island area, southwest Japan is subdivided into the Hinoshima and Amura Formations. In order to determine the numerical depositional age of the formations, zircon U–Pb ages were investigated using laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) for acidic tuff samples from the lower part of the Hinoshima Formation and the upper part of the Amura Formation. Although the two samples contain some accidental zircons, the samples have a definite youngest age cluster and their weighted mean ages are 85.4 ± 1.3 and 81.5 ± 1.1 Ma, respectively (errors are 95 % confidence interval). These age data indicate that the Himenoura Group in the Amakusa‐Kamishima Island area was deposited mainly in the early Santonian to early Campanian which is consistent with biostratigraphic ages. Additionally, zircon age distributions of the two tuff samples from the upper part of the Hinoshima Formation do not show a distinct youngest peak of eruption age but characteristics of detrital zircons suggestive of maximum depositional age of the host sediments. These results demonstrate that the mean age of the youngest zircon age cluster of a tuff sample does not always indicate depositional age of the tuff, and statistical evaluation of age data is effective to determine depositional age of a tuff bed using zircon U–Pb ages.  相似文献   

Chitinozoans and scolecodonts from the Silurian and Devonian of Japan     

Thijs R. A. Vandenbroucke  Olle Hints  Mark Williams  Simon Wallis  Jules Velleman  Toshiyuki Kurihara  Gengo Tanaka  Toshifumi Komatsu  Peep Mnnik  David J. Siveter  Tim de Backer 《Island Arc》2019,28(3)

Silurian and Devonian chitinozoans and scolecodonts are recorded from strata of the Hida‐Gaien Terrane, central Honshu. Silurian chitinozoans include Eisenackitina, Bursachitina, and the species Angochitina elongata. The latter provides a precise biostratigraphical tie between the Japanese succession and the Type Ludlow Series of the Welsh Borderland, UK, and indicates a Ludlow age (Gorstian or early Ludfordian) for the upper member of the Yoshiki Formation in the Ichinotani Valley. Chitinozoans from other Yoshiki Formation localities contain other specimens of Lagenochitinidae. Scolecodonts are more common than chitinozoans in the palynological residues, but are mostly represented by fragments or minor apparatus elements with a low biostratigraphical value. However, material from the Yoshiki and Fukuji Formations includes several species of Mochtyella as well as representatives of Oenonites, Kettnerites, Lunoprionella, Vistulella? and possibly other placognath taxa. Scolecodonts are also present in the Silurian Middle Member of the Gionyama Formation, Kyushu, including a well‐preserved jaw of Pistoprion, and fragments of putative Kettnerites and Oenonites. These finds of scolecodonts suggest close similarity in assemblages between Paleozoic polychaete faunas of Japanese terranes and those of Baltica‐Laurentia.  相似文献   

Effects of slope gradient on runoff from bare-fallow purple soil in China under natural rainfall conditions     

Yoshitaka Komatsu  Hiroaki Kato  Bo Zhu  Tao Wang  Fan Yang  Randeep Rakwal  Yuichi Onda 《山地科学学报》2018,15(4):738-751

Purple soil is highly susceptible for overland flow and surface erosion, therefore understanding surface runoff and soil erosion processes in the purple soil region are important to mitigate flooding and erosion hazards. Slope angle is an important parameter that affects the magnitude of runoff and thus surface erosion in hilly landscapes or bare land area. However, the effect of slope on runoff generation remains unclear in many different soils including Chinese purple soil. The aim of this study was to investigate the relationship between different slope gradients and surface runoff for bare-fallow purple soil, using 5 m × 1.5 m experimental plots under natural rainfall conditions. Four experimental plots(10°, 16°, 20° and 26°) were established in theYanting Agro-ecological Experimental Station of Chinese Academy of Science in central Sichuan Basin. The plot was equipped with water storage tank to monitor water level change. Field monitoring from July 1 to October 31, 2012 observed 42 rainfall events which produced surface runoff from the experimental plots. These water level changes were converted to runoff. The representative eight rainfall events were selected for further analysis, the relationship between slope and runoff coefficient were determined using ANOVA, F-test, and z-score analysis. The results indicated a strong correlation between rainfall and runoff in cumulative amount basis. The mean value of the measured runoff coefficient for four experimental plots was around 0.1. However, no statistically significant relationship was found between slope and runoff coefficient. We reviewed the relationship between slope and runoff in many previous studiesand calculated z-score to compare with our experimental results. The results of z-score analysis indicated that both positive and negative effects of slope on runoff coefficient were obtained, however a moderate gradient(16°-20° in this study) could be a threshold of runoff generation for many different soils including the Chinese purple soil.  相似文献   

哈密盆地北缘活动断裂带微地貌     

柏美祥  罗福忠  李军  今泉俊文  宫内崇裕  原四强  麻勇 《内陆地震》1999,13(2):162-168

哈密盆地北线活动断裂带走向北西西,断续长180km。8条剖面的GPS测量结果显示,断坎坡度为15°～18°及31°～33°．单个断崖高3～10m。由年代学资料计算出该断裂带中全新世垂直活动速率为0．65±0．08mm／a,比晚更新世晚期垂直活动速率有所增大。  相似文献   

Enrichment of alkanes within a phytoplankton bloom during an in situ iron enrichment experiment in the western subarctic Pacific     

Sohiko Kameyama  Urumu Tsunogai  Fumiko Nakagawa  Motoki Sasakawa  Daisuke D. Komatsu  Akira Ijiri  Junko Yamaguchi  Takeo Horiguchi  Hiroshi Kawamura  Aika Yamaguchi  Atsushi Tsuda 《Marine Chemistry》2009,115(1-2):92-101

During the Subarctic Pacific Iron Experiment for Ecosystem Dynamics Study ΙΙ (SEEDS-II), we monitored variations in the concentrations of non-methane hydrocarbons (NMHCs), CH₃Cl, N₂O, and CH₄ within a phytoplankton bloom. Stable isotopic compositions were also determined to evaluate the sources of the variations. Although there was little variation in either the concentrations or the stable isotopic compositions of alkenes, CH₃Cl, N₂O, and CH₄ during the 23-day observation period, alkane concentrations increased substantially as the phytoplankton bloomed. The column-integrated quantities of alkanes increased to 3 times pre-bloom levels for C₂H₆, 5 times for C₃H₈, and 20 times for n-C₄H₁₀. The δ¹³C values of both C₂H₆ and C₃H₈ remained almost constant while concentrations increased, whereas that of n-C₄H₁₀ increased by about 12‰. To evaluate the sources of the alkanes produced during the bloom, we compared their δ¹³C values with those of alkanes produced in axenic phytoplankton cultures in our laboratory. We concluded that during the SEEDS-ΙΙ experiment the major portions of C₂H₆ and C₃H₈ were produced during the autolysis of diatoms cells, whereas n-C₄H₁₀ was produced during autolysis of other phytoplankton cells such as cryptophytes and dinoflagellates.  相似文献   

Spreading of river water in Suruga Bay     

Kiyoshi Tanaka  Yutaka Michida  Teruhisa Komatsu  Kenji Ishigami 《Journal of Oceanography》2009,65(2):165-177

We have investigated the spreading of river water in Suruga Bay by performing numerical experiments and conducting field surveys with drifting buoys. There are clear seasonal variations in the large river discharges into the bay: increased discharge in the rainy summer season and decreased discharge in the dry winter season. The numerical model reproduces the main feature that has been observed in the actual sea: the river water extends gradually from the northwestern to the southeastern regions in the bay, especially in summer. The river water spreading is greatly influenced by the bottom topography of the bay: the Fuji River water spreads over a deep continental slope as a surface-advected plume and extends well offshore, since a large bulge (anticyclonic eddy at the river mouth) extends well offshore and effectively transports the river water offshore. On the other hand, the Oi River water tends to flow parallel to isobaths (along a coastline) on a shallow continental shelf as a bottomadvected plume. Moreover, the influences of seasonal variations in the stratification and a bay-scale, wind-driven circulation are also investigated. Trajectories of the drifting buoys, which were released around the Fuji River mouth, certainly suggest that the bulge exists there.  相似文献   

Numerical experiments on wind-driven circulations and associated transport processes in Suruga Bay     

Kiyoshi Tanaka  Yutaka Michida  Teruhisa Komatsu 《Journal of Oceanography》2008,64(1):93-102

The dynamics of the wind-driven circulations and surface transport processes in Suruga Bay have been examined by performing numerical experiments. While strong winds exist outside the bay, the winds inside the bays are greatly reduced, which generates a strong wind stress curl in winter and autumn. In particular, in winter, a strong positive curl region is located across the bay mouth, and a strong surface circulation with counterclockwise rotation is generated beneath it. The circulation is nearly geostrophic, but is not affected by the bottom topography in the deep bay. It is suggested that intense surface water exchange through the bay mouth occurs in winter, whereas it is not active in the other seasons when no significant vorticity is supplied on the bay mouth from the atmosphere. Moreover, we propose a hypothesis that the atmospheric wind stress curl will cause the frequent appearance of the counterclockwise circulation in winter in the real ocean.  相似文献   

Spirits of Yokokurayama: shrine of the Japanese trilobites     

Christopher Stocker  Mark Williams  Tatsuo Oji  Gengo Tanaka  Toshifumi Komatsu  Simon Wallis 《Geology Today》2019,35(1):15-19

‘We are such stuff as dreams are made on, and our little life is rounded with a sleep’. So sleep the trilobites of Yokokurayama, a sacred mountain hidden within the beautiful landscape of Japan’s Shikoku’s island. And though Prospero may have been speaking to his daughter and her fiancé (in William Shakespeare’s The Tempest), he might well have been contemplating the magnificent trilobite fossils of Yokokurayama. Japan may be better known for its sweeping volcanic landscapes, majestic castles, Shinto shrines and bullet trains, but it is also home to important collections of Silurian and Devonian trilobites.  相似文献