Geochemical and geochronological constraints on the origin and emplacement of the Shimo-ondori diorites in Shikoku,Southwest Japan     

Shogo Aoki  Kazumasa Aoki  Mayuko Fukuyama  Masatsugu Ogasawara  Yuta Tsuchiya 《Island Arc》2021,30(1):e12420

In this study, the LA-ICP-MS zircon U–Pb dating of the Shimo-ondori diorites in the Shimanto accretionary complex of SW Japan provides ~130 Ma, representing the timing of their crystallization ages. Combined with the geological occurrence, that age clearly indicates that the diorites occur as blocks, not as intrusive rocks as suggested by previous studies. Moreover, the ages of the Shimo-ondori diorites are suggesstive that they could be influential for the estimate of the early-Cretaceous tectonic evolution for the eastern Asian margin. Their whole-rock chemical compositions show high MgO, Ni and Cr contents, and low total FeO/MgO ratios, indicating that they were crystallized from high magnesian andesite (HMA) magmas. Moreover, their TiO₂ and REE compositions suggest that they were formed by the same processes as the sanukites. And, the zircon Hf isotopic ratios (ε_Hf [~130 Ma] = +9.9 − +17.5), which is close to or slightly lower than that of the ~130 Ma depleted mantle, suggest that the wedge-mantle materials were predominantly involved in the formation of the dioritic magmas. Their geochronological and geochemical similarities of the Shimo-ondori diorites with the early Cretaceous adakites and HMAs in the eastern Asian margin suggest that they might have been formed possibly by the same slab rollback of the Izanagi plate at the early Cretaceous. After the crystallization of the Shimo-ondori diorites, they were delivered and deposited as blocks in a trench site with the surrounding sedimentary rocks of the Shimanto accretionary complex.  相似文献   

Magma discharge variations during the 2011 eruptions of Shinmoe-dake volcano, Japan, revealed by geodetic and satellite observations     

Tomofumi Kozono  Hideki Ueda  Taku Ozawa  Takehiro Koyaguchi  Eisuke Fujita  Akihiko Tomiya  Yujiro J Suzuki 《Bulletin of Volcanology》2013,75(3):1-13

We present precise geodetic and satellite observation-based estimations of the erupted volume and discharge rate of magma during the 2011 eruptions of Kirishima-Shinmoe-dake volcano, Japan. During these events, the type and intensity of eruption drastically changed within a week, with three major sub-Plinian eruptions on January 26 and 27, and a continuous lava extrusion from January 29 to 31. In response to each eruptive event, borehole-type tiltmeters detected deflation of a magma chamber caused by migration of magma to the surface. These measurements enabled us to estimate the geodetic volume change in the magma chamber caused by each eruptive event. Erupted volumes and discharge rates were constrained during lava extrusion using synthetic aperture radar satellite imaging of lava accumulation inside the summit crater. Combining the geodetic volume change and the volume of lava extrusion enabled the determination of the erupted volume and discharge rate during each sub-Plinian event. These precise estimates provide important information about magma storage conditions in magma chambers and eruption column dynamics, and indicate that the Shinmoe-dake eruptions occurred in a critical state between explosive and effusive eruption.  相似文献   

Occurrence and source characteristics of the high-latitude components of Jovian broadband kilometric radiation     

Tomoki Kimura  Fuminori Tsuchiya  Akira Morioka 《Planetary and Space Science》2008,56(8):1155-1168

Ulysses had a “distant encounter” with Jupiter when it was within 0.8 AU of the planet during February, 2004. The passage of the spacecraft was from north to south, and observations of the Jovian radio waves were carried out for a few months from high to low latitudes (+80° to +10°) of Jupiter. The statistical study performed during this “distant encounter” event provided the occurrence characteristics of the Jovian broadband kilometric radiation (bKOM), including the high-latitude component as follows: (1) the emission intensity of bKOM was found to have a sinusoidal dependence with respect to the central meridian longitude (CML), showing a broad peak at ∼180°, (2) bKOM was preferably observed in the magnetic latitudinal range from ∼+30° to +90°, and the emission intensities at the high latitudes were found to be two times larger than that at the equatorial region, and (3) the emission intensity was controlled possibly by the sub solar longitude (SSL) of Jupiter. The intensity had a sharp peak around SSL ∼210°. A 3D ray tracing approach was applied to the bKOM in order to examine the source distribution. It was suggested that: (1) the R-X mode waves generated through the Cyclotron Maser Instability process would be unable to reproduce the intense high-latitude component of the bKOM, (2) the L-O mode, which was assumed to be generated at frequencies near the local plasma frequency, was considered to be the dominant mode for past and present observations at mid- and high-latitudinal regions, and (3) the high-latitude component of bKOM was found to have a source altitude of 0.9-1.5 Rj (Rj: Jovian radii), and to be distributed along magnetic field lines having L>10.  相似文献   

Radiation characteristics of quasi-periodic radio bursts in the Jovian high-latitude region     

Tomoki Kimura  Fuminori Tsuchiya  Akira Morioka 《Planetary and Space Science》2008,56(15):1967-1976

Ulysses had a “distant encounter” with Jupiter in February 2004. The spacecraft passed from north to south, and it observed Jovian radio waves from high to low latitudes (from +80° to +10°) for few months during its encounter. In this study, we present a statistical investigation of the occurrence characteristics of Jovian quasi-periodic bursts, using spectral data from the unified radio and plasma wave experiment (URAP) onboard Ulysses. The latitudinal distribution of quasi-periodic bursts is derived for the first time. The analysis suggested that the bursts can be roughly categorized into two types: one having periods shorter than 30 min and one with periods longer than 30 min, which is consistent with the results of the previous analysis of data from Ulysses’ first Jovian flyby [MacDowall, R.J., Kaiser, M.L., Desch, M.D., Farrell, W.M., Hess, R.A., Stone, R.G., 1993. Quasi-periodic Jovian radio bursts: observations from the Ulysses radio and plasma wave. Experiment. Planet. Space Sci. 41, 1059-1072]. It is also suggested that the groups of quasi-periodic bursts showed a dependence on the Jovian longitude of the sub-solar point, which means that these burst groups are triggered during a particular rotational phase of the planet. Maps of the occurrence probability of these quasi-periodic bursts also showed a unique CML/MLAT dependence. We performed a 3D ray tracing analysis of the quasi-periodic burst emission to learn more about the source distribution. The results suggest that the longitudinal distribution of the occurrence probability depends on the rotational phase. The source region of quasi-periodic bursts seems to be located at an altitude between 0.4 and 1.4 Rj above the polar cap region (L>30).  相似文献   

The large-scale landslide on the flank of caldera in South Sulawesi, Indonesia   总被引：1，自引：0，他引：1  

Satoshi Tsuchiya  K. Sasahara  S. Shuin  S. Ozono 《Landslides》2009,6(1):83-88

An extraordinarily large-scale landslide with a volume of about 200 million m³, a width of about 1,600 m, and a height of about 750 m occurred on 2004 March 26, 13:45 local time, on a steep caldera wall on the northwest flank of Mt. Bawakaraeng (2,830 m) at the headwater of the Jeneberang River in South Sulawesi, Indonesia. The debris avalanche extended about 7 km from the headwater and buried the river valley, causing devastating damage. There are a great many calderas in the world, notably Japan. If a large-scale sector collapse were to occur in a heavily populated area, it would be a devastating disaster for the people living in the area. The aim of this paper is to outline such a landslide and explain its mechanism of occurrence. We evaluated the stability of the original slope before the landslide using the limit equilibrium method and the finite-element-based shear strength reduction method (SSRFEM) with the strength reduction factor. The limit equilibrium method showed that a rise in the groundwater level caused the landslide. Although the critical slip surface predicted by the SSRFEM was shallower than that of the actual slip surface, the end positions of the actual and predicted slip surfaces were almost the same. Moreover, the end position of the critical slip surface before the landslide—the headwater of the Jeneberang River—was a knick point at which the slope inclination became steeper. SSRFEM analysis may be useful for evaluating the slope stability of large-scale landslides, because the critical slip surface predicted by it was close to the actual surface, even though we assumed homogenous conditions without information on the degree of weathering or ground properties. As the knick point formed at the end of the critical slip surface and is equivalent to the end of the actual slip surface, we assume such topographic features to be a primary geomorphologic cause of the landslide.  相似文献   

<Emphasis Type="Italic">Landslides</Emphasis>: a review of achievements in the first 5 years (2004–2009)     

Kyoji Sassa  Satoshi Tsuchiya  Keizo Ugai  Akihiko Wakai  Taro Uchimura 《Landslides》2009,6(4):275

The international journal Landslides was initiated in April 2004. It is the core project (IPL-C100) of the International Programme on Landslides, a joint initiative of the International Consortium on Landslides and the United Nations and other global organizations. The aims of Landslides are to promote landslide sciences, technology, and capacity building and strengthen global cooperation for landslide risk reduction within the United Nations International Strategy for Disaster Reduction. This paper presents an analysis of the first 5 years of Landslides, the study methods employed, the types and major causes of landslides, the number of different contributors per country, and the “times cited” per issue and most frequently cited papers and briefly discusses some of these. Strategies for future development of the journal involve obtaining input and suggestion from researchers and readers worldwide.  相似文献   

Quantitative mapping of a precursory seismic quiescence to the Izu–Oshima 1990 (M6.5) earthquake, Japan     

Max Wyss  Kunihiko Shimazaki  Taku Urabe 《Geophysical Journal International》1996,127(3):735-743

A highly significant seismic quiescence with a standard deviate Z = 10.1. corresponding to a 99 per cent confidence level, lasted from 1987.7 up to the 1990 February 20 Izu-Oshima M 6.5 earthquake. The quiescent volume had dimensions of 30 km N-S and 10 km E-W and was centred below 14 km depth. Within the recently upgraded seismograph network of the Earthquake Research Institute (ERI), this main shock was the only one with a magnitude M > 5.8 in the upper 30 km of the crust for which the precursory quiescence hypothesis could be tested. Within a radius of 50 km, and during the observation period (1983.5–1995.9), there were no other 1.5 yr or longer periods of quiescence that were rated Z > 6.5 in the declustered earthquake catalogue, except one that was associated with volcanic activity. The total space-time covered by alarms, including the volcanic one, was less than 1 per cent at the Z = 6.5 level. The rarity of highly significant episodes of quiescence, and the correlation in space and time suggest that a precursory seismic quiescence started 2.5 yr before the Izu-Oshima 1990 earthquake in its source volume and to the north of it, and that it can be recognized with an alarm level of Z = 6.0, generating no false alarms. During the 1.5 yr quiescence window, only 10 earthquakes occurred in the quiet volume, whereas 50 events were expected based on the rate seen at other times. In randomly selected volumes containing 50, 100 and 200 events, the anomaly scored Z = 6.1 to 10.1. On the basis of the data from May 1983 to 1995, there is no highly significant quiescence currently present in the Izu-Oshima area.  相似文献   

The paradox of smooth and abrupt bends in two-dimensional in-plane shear-crack mechanics     

Taku Tada  Teruo Yamashita 《Geophysical Journal International》1996,127(3):795-800

It is pointed out, in the context of the boundary integral equation method (BIEM), that, in the mechanics of 2-D curved in-plane shear cracks, a smooth curve, along which the crack orientation changes continuously, and an abrupt kink, across which it changes discontinuously, are not equivalent to each other. The discrepancy is illustrated by numerical results, and a set of conceptual models is used to demonstrate analytically how the equations that govern the crack mechanics have inherently distinct forms depending on whether the crack orientation changes continuously or abruptly across a bend, as long as one abides by the principles of linear elasticity theory. This has serious implications for the numerical treatment of a curved crack, which can be modelled as a chain of finite elements that are connected either smoothly or at abrupt kinks, the two methods producing different numerical outcomes. No similar paradox arises in the cases of anti-plane shear or open in-plane cracks.  相似文献   

Microbial mutualism in leaching of Cu−Ni sulfide concentrate     

N.C Trivedi  H.M Tsuchiya 《International Journal of Mineral Processing》1975,2(1):1-14

With tightening legislations on air pollution and decreasing grades of Cu and Ni ores, the mineral processing industry will have to find an alternative to smelting. One such hydrometallurgical alternative is bacterial leaching; it utilizes the action of Thiobacillus ferrooxidans on sulfide minerals converting them to metal sulfates which can be leached by acid produced by the bacteria. The metal is recovered by cementation, solvent extraction or electrowinning. In the present paper, the authors report their test work with a Cu-Ni sulfide concentrate and show that the mutualistic association of T. ferrooxidans with nitrogen-fixing bacteria Beijerinckia lacticogenes helps leach more metal faster in a leaching medium devoid of any added carbon or nitrogen source. Use of intentionally mixed bacterial culture in ore leaching has not been previously reported.  相似文献   

Essential cellular modules for the proliferation of the primitive cell     

Koichi Higashi  Yoshikazu Kawai  Tomoya Baba  Ken Kurokawa  Taku Oshima 《地学前缘(英文版)》2018,9(4):1155-1161

Bacteria appeared early in the evolution of cellular life on planet Earth, and therefore the universally essential genes or biological pathways found across bacterial domains may represent fundamental genetic or cellular systems used in early life. The essential genes and the minimal gene set required to support bacterial life have recently been experimentally and computationally identified. It is, however,still hard to estimate the ancient genes present in primitive cells compared to the essential genes in contemporary bacteria, because we do not know how ancestral primitive cells lived and proliferated, and therefore cannot directly evaluate the essentiality of the genes in ancestral primitive cells. The cell wall is normally essential for bacterial proliferation and cellular division of walled bacterial cells is normally highly controlled by the essential FtsZ cell division machinery. But, bacteria are capable of reverting to their cell wall deficient ancestral form, called the "L-form". Unlike "normal" cells, L-forms divide by a simple physical mechanism based on the effects of membrane dynamics, suggesting a mode of primitive proliferation before the appearance of the cell wall. In this review, we summarize the experimental and computational investigations of minimal gene sets and discuss the minimal cellular modules required to support the proliferation of primitive cells, based on L-form proliferation.  相似文献