Water content of primitive low-K tholeiitic basalt magma from Iwate Volcano,NE Japan arc: implications for differentiation mechanism of frontal-arc basalt magmas     

Takeshi Kuritani  Takeyoshi Yoshida  Jun-Ichi Kimura  Yuka Hirahara  Toshiro Takahashi 《Mineralogy and Petrology》2014,108(1):1-11

The water content of low-K tholeiitic basalt magma from Iwate volcano, which is located on the volcanic front of the NE Japan arc, was estimated using multi-component thermodynamic models. The Iwate lavas are moderately porphyritic, consisting of ~8 vol.% olivine and ~20 vol.% plagioclase phenocrysts. The olivine and plagioclase phenocrysts show significant compositional variations, and the Mg# of olivine phenocrysts (Mg#78–85) correlates positively with the An content of coexisting plagioclase phenocrysts (An_85–92). The olivine phenocrysts with Mg# > ~82 do not form crystal aggregates with plagioclase phenocrysts. It is inferred from these observations that the phenocrysts with variable compositions were primarily derived from mushy boundary layers along the walls of a magma chamber. By using thermodynamic calculations with the observed petrological features of the lavas, the water content of the Iwate magma was estimated to be 4–5 wt.%. The high water content of the magma supports the recent consensus that frontal-arc magmas are remarkably hydrous. Using the estimated water content of the Iwate magma, the water content and temperature of the source mantle were estimated. Given that the Iwate magma was derived from a primary magma solely by olivine fractionation, the water content and temperature were estimated to be ~0.7 wt.% and ~1,310 °C, respectively. Differentiation mechanisms of low-K frontal-arc basalt magmas were also examined by application of a thermodynamics-based mass balance model to the Iwate magma. It is suggested that magmatic differentiation proceeds primarily through fractionation of crystals from the main molten part of a magma chamber when it is located at <~200 MPa, whereas magma evolves through a convective melt exchange between the main magma and mushy boundary layers when the magma body is located at >~200 MPa.  相似文献   

An empirical model for landslide travel distance prediction in Wenchuan earthquake area   总被引：2，自引：1，他引：1  

Deping Guo  Masanori Hamada  Chuan He  Yufeng Wang  Yulin Zou 《Landslides》2014,11(2):281-291

Sliding mass of landslides highly endangered the area along travel path, especially landslides with long travel distance. It is necessary to develop an effective prediction model for preliminarily evaluating landslide travel distance so as to improve disaster prevention and relocation. This paper collected 54 landslides with 347–4,170 m travel distance triggered by the 2008 Wenchuan earthquake to discuss the effectiveness of various influential factors on landslide travel distance and obtained an empirical model for its prediction. The results revealed that rock type, sliding source volume, and slope transition angle were the predominant factors on landslide travel distance. The validity of proposed model was verified by the satisfactory agreement between observations and predictions. Therefore, this model might be practically applicable in Wenchuan earthquake area and other similar geomorphological and geological regions.  相似文献   

The evolution of baryon density fluctuations in multicomponent cosmological simulations     

Naoki Yoshida  Naoshi Sugiyama  Lars Hernquist 《Monthly notices of the Royal Astronomical Society》2003,344(2):481-491

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Gas cooling in simulations of the formation of the galaxy population     

Naoki Yoshida  Felix Stoehr  Volker Springel  Simon D. M. White 《Monthly notices of the Royal Astronomical Society》2002,335(3):762-772

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The first generation of stars in the Λ cold dark matter cosmology     

L. Gao  N. Yoshida  T. Abel  C. S. Frenk  A. Jenkins  V. Springel 《Monthly notices of the Royal Astronomical Society》2007,378(2):449-468

We have performed a large set of high-resolution cosmological simulations using smoothed particle hydrodynamics to study the formation of the first luminous objects in the Lambda cold dark matter cosmology. We follow the collapse of primordial gas clouds in eight early structures and document the scatter in the properties of the first star-forming clouds. Our first objects span formation redshifts from   z ∼ 10  to ∼50 and cover an order of magnitude in halo mass. We find that the physical properties of the central star-forming clouds are very similar in all of the simulated objects despite significant differences in formation redshift and environment. This suggests that the formation path of the first stars is largely independent of the collapse redshift; the physical properties of the clouds have little correlation with spin, mass or assembly history of the host halo. The collapse of protostellar objects at higher redshifts progresses much more rapidly due to the higher densities, which accelerates the formation of molecular hydrogen, enhances initial cooling and shortens the dynamical time-scales. The mass of the star-forming clouds cover a broad range, from a few hundred to a few thousand solar masses, and exhibit various morphologies: some have disc-like structures which are nearly rotational supported; others form flattened spheroids; still others form bars. All of them develop a single protostellar 'seed' which does not fragment into multiple objects up to the moment that the central gas becomes optically thick to H₂ cooling lines. At this time, the instantaneous mass accretion rate on to the centre varies significantly from object to object, with disc-like structures having the smallest mass accretion rates. The formation epoch and properties of the star-forming clouds are sensitive to the values of cosmological parameters.  相似文献   

Near-Infrared Colors of the Binary Kuiper Belt Object 1998 WW 31     

Takato  Naruhisa  Fuse  Tetsuharu  Gaessler  Wolfgang  Goto  Miwa  Kanzawa  Tomio  Kobayashi  Naoto  Minowa  Yosuke  Oya  Shin  Pyo  Tae-Soo  Saint-Jacque  D.  Takami  Hideki  Terada  Hiroshi  Hayano  Yutaka  Iye  Masanori  Kamata  Yukiko  Tokunaga  A. T. 《Earth, Moon, and Planets》2003,92(1-4):183-191

We have measured near-infrared colorsof the binary Kuiper Belt object (KBO)1998 WW₃₁ using the Subaru Telescope withadaptive optics. The satellite was detectednear its perigee and apogee(0.18“ and 1.2” apart from the primary).The primary and the satellite have similar H–Kcolors, while the satellite is redder thanthe primary in J–H. Combined with the Rband magnitude previously published byVeillet et al., 2002, the color of the primaryis consistent with that of optically red KBOs. Thesatellite's R-, J-, H-colors suggest thepresence of ～1 μm absorption band dueto rock-forming minerals. If the surface of thesatellite is mainly composed by olivine, thesatellite's albedo is higher value than the canonicallyassumed value of 4%.  相似文献   

Global adjustment of star positions for the compilation of independent catalogs     

Masanori Yoshizawa  Shunsaku Suzuki 《Astrophysics and Space Science》1991,177(1-2):471-473

Presented is a method of global adjustment of stars' right ascensions for the compilation of an independent catalog obtained with a meridian circle. The concept of the problem is shown first, in which corrections to the catalog positions of observed stars can be determined directly by solving a set of observation equations constructed over many of nights. Some parameters such as clock correction, azimuth of artificial azimuth marks, and the correction to an adopted value of the latitude are assumed to vary regularly over the observation period. The present method is applied to the determination of the absolute azimuth of the Tokyo PMC by using upper and lower transits of azimuth stars.  相似文献   

Self-similar collapse with cooling and heating in an expanding universe     

Shuji Uchida  Tatsuo Yoshida 《Monthly notices of the Royal Astronomical Society》2004,348(1):89-99

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Miocene provenance change in Himalayan foreland basin and Bengal Fan sediments,with special reference to detrital garnet chemistry     

Kohki Yoshida  Toru Nakajima  Yuki Matsumoto  Ai Osaki  Lalit Kumar Rai  Jarrett W. Cruz  Harutaka Sakai 《Island Arc》2021,30(1):e12408

Bengal Fan Miocene sediments were collected during International Ocean Discovery Program Expedition 354 and investigated using petrographic and detrital garnet chemistry analyses. The Miocene Siwalik Group, which is composed of sediments deposited in the Himalayan foreland basin, was also analyzed for comparison with the Bengal Fan data for the provenance change during the Miocene. Our petrographic analyses revealed that the Miocene sediments of the Bengal Fan and Siwalik Group consist predominantly of Higher Himalayan Crystalline (HHC)-derived detritus such as chloritoid, staurolite, sillimanite, and/or kyanite, which appear among the accessory minerals. The chemistry of the detrital garnet varies across the stratigraphy; most of the garnet is rich in almandine and poor in spessartine and pyrope. However, pyrope-rich garnet, which is considered to originate from the HHC core (granulite facies), was found in the lower to upper Miocene deposits. The deposition of HHC-derived detrital garnet began before the Middle Miocene (15 Ma) and before the Late Miocene (10–9 Ma) in the Siwalik Group. The Bengal Fan data, by contrast, indicated that pyrope-rich garnet appeared in the Early Miocene (17.3 Ma) and Late Miocene (8.5–6.5 Ma). We conclude that the Bengal Fan sediments record the erosion of the HHC zone since the Early Miocene that appears in the Siwalik sediments. Furthermore, we found that the HHC-derived inputs decreased from the late Middle Miocene (12 Ma) to the early Middle Miocene (10 Ma) in both the Nepal Himalaya foreland basin and the Bengal Fan. The disappearance of the HHC-derived detritus is probably the result of dilution by Lesser Himalayan detritus, which suggests that the Lesser Himalayan zone, which is composed of metamorphosed and unmetamorphosed sedimentary rocks, was uplifted.  相似文献   

Precambrian Central India and its role in the Gondwanaland-Rodinia Context     

M. Yoshida  R.S. Divi  M. Santosh 《Gondwana Research》2001,4(2):208

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