Model of nucleation and growth of crystals in cooling magmas   总被引：4，自引：0，他引：4  

Atsushi Toramaru 《Contributions to Mineralogy and Petrology》1991,108(1-2):106-117

The nucleation and growth of liquidus phases in cooling magmas at constant rates are modeled taking into account homogeneous nucleation, diffusion-limited growth, and depletion of crystallizing component from melt, and the temperature-dependent diffusivity. The formulation of governing equations shows that four dimensionless parameters, whose physical meanings are the nucleation difficulty, the fusion enthalpy, the ratio of the growth rate to the cooling rate, and the activation energy of diffusion, control the crystallization phenomena. The nucleation behavior with time (or temperature) is determined primarily by the competition between increasing nucleation rate with cooling and the reduced supersaturation with depletion by progressive growth of crystals previously nucleated. The maximum nucleation rate and the number density of crystals increase with decreasing interfacial tension and diffusivity, and with increasing fusion enthalpy and cooling rate. Quantitative expressions of the time or temperature interval for which the nucleation remains appreciable, the peak nucleation rate, the number density of crystals and the mean crystal radius are derived as functions of controlling parameters, and can be used to estimate the cooling rate or other unknown parameters from the number density of crystals of a rock.  相似文献   

Preface     

Atsushi Tsuda  Kazuhiro Kogure  Shuichi Watanabe 《Journal of Oceanography》2016,72(1):1-2

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Evaluation of tsunami impacts on shallow marine sediments: An example from the tsunami caused by the 2003 Tokachi-oki earthquake, northern Japan     

Atsushi Noda  Hajime Katayama  Tsumoru Sagayama  Kazuya Suga  Yasuhito Uchida  Kenji Satake  Kohei Abe  Yukinobu Okamura 《Sedimentary Geology》2007,200(3-4):314-327

A combined approach of field geology and numerical simulation was conducted for evaluating the tsunami impacts on the shelf sediments. The 2003 Tokachi-oki earthquake, M 8.0, that occurred on 25 September 2003 off southeastern Hokkaido, northern Japan, generated a locally destructive tsunami. Maximum run-up height of the tsunami waves reached 4 m above sea level. In order to estimate the tsunami impacts on shallow marine sediments, we compared pre- and post-tsunami marine sediments in water depths of 38–112 m in terms of grain size, sedimentary structure, and microfossil content. Decreases of fine fractions, especially finer than very fine sand, which led to coarsen the mean grain size, were detected in the inner shelf of the northern part of the study area. Foraminiferal assemblages also changed in the coarsened sediments. On the other hand, the other shelf sediments largely unchanged or slightly fined. We also simulated the tsunami wave velocity and direction, and grain size entrained by the modeled tsunami. The numerical simulation resulted in that the 2003 tsunami could transport very fine sand in water depths shallower than 45–95 m at the northern part of the study area. This is comparable with the actual grain-size changes after the tsunami had passed. However, some storms and tidal currents might also be possible to stir the surface sediments after the pre-tsunami survey, so we could not conclude that the grain-size changes had been caused only by the tsunami. Nevertheless, a combined approach of sampling and modeling was powerful for estimating the tsunami impacts under the sea.  相似文献   

Secular change of permeability in the fracture zone near the Nojima fault estimated using strain changes due to water injection experiments     

Atsushi Mukai  Kunio Fujimori   《Tectonophysics》2007,443(3-4):193

Water injection experiments were performed in 1997, 2000 and 2003 at the 1800 m borehole near the fracture zone of the 1995 Hyogo-ken Nanbu earthquake. During these experiments, a contraction of about 10^− 8–10^− 7 was observed with three-component strainmeters at a bottom of the 800 m borehole, 70 m southwest of the 1800 m borehole. We estimated hydraulic properties of the fracture zone near the Nojima fault by using the strain data to investigate a healing of the fault during the postseismic stage. We calculated pore pressure changes due to the water injection using Darcy's equation and obtained strain changes due to the pore pressure changes as elastic deformations of the crust. The calculated strain changes have a nearly agreement with the observed strain changes. Hydraulic conductivity in 1997, 2000 and 2003 was determined to be 0.9 ± 0.2 × 10^− 6, 0.8 ± 0.2 × 10^− 6 and 0.4 ± 0.1 × 10^− 6 m/s, respectively. The reduced hydraulic conductivities in 2000 and 2003 suggest that the fractures had been healing.  相似文献   

Lake-level changes during the past 100,000 years at Lake Baikal, southern Siberia   总被引：1，自引：0，他引：1  

Atsushi Urabe  Masaaki Tateishi  Hirokazu Matsuoka  Alexsander Dmytriev 《Quaternary Research》2004,62(2):214-222

Lake-level changes inferred from seismic surveying and core sampling of the floor of Lake Baikal near the Selenga River delta can be used to constrain regional climatic history and appear to be correlated to global climate changes represented by marine oxygen isotope stages (MIS). The reflection pattern and correlation to the isotope stages indicate that the topset and progradational foreset sediments of the deltas formed during periods of stable lake levels and warm climatic conditions. During warm stages, the lake level was high, and during cold stages it was low. The drop in the lake level due to cooling from MIS 5 through MIS 4 is estimated to be 33-38 m; from MIS 3 through MIS 2, it fell an additional 11-15 m. Because the lake level is chiefly controlled by evaporation and river input, we infer that more water was supplied to Lake Baikal during warm stages.  相似文献   

High pressure transitions in the system KAlSi3O8-NaAlSi3O8     

Atsushi Yagi  Toshihiro Suzuki  Masaki Akaogi 《Physics and Chemistry of Minerals》1994,21(1-2):12-17

Phase relations in the system KAlSi₃O₈-NaAlSi ₃O₈ have been examined at pressures of 5–23 GPa and temperatures of 700–1200° C. KAlSi₃O₈ sanidine first dissociates into a mixture of wadeite-type K₂Si₄O₉, kyanite and coesite at 6–7 GPa, which further recombines into KAlSi₃O₈ hollandite at 9–10 GPa. In contrast, NaAlSi₃O₈ hollandite is not stable at 800–1200° C near 23 GPa, where the mixture of jadeite plus stishovite directly changes into the assemblage of calcium ferrite-type NaAlSiO₄ plus stishovite. Phase relations in the system KAlSi₃O₈-NaAlSi₃O₈ at 1000° C show that NaAlSi₃O₈ component gradually dissolves into hollandite with increasing pressure. The maximum solubility of NaAlSi₃O₈ in hollandite at 1000° C was about 40 mol% at 22.5 GPa, above which it decreases with pressure. Unit cell volume of the hollandite solid solution decreases with increasing NaAlSi₃O₈ component. The hollandite solid solution in this system may be an important candidate as a host mineral of K and Na in the uppermost lower mantle  相似文献   

1992 compilation of analytical data for rare-earth elements, scandium, yttrium, zirconium and hafnium in twenty-six GSJ reference samples     

Shiro ITOH  Shigeru TERASHIMA  Noboru IMAI  Hikari KAMIOKA  Naoki MITA  Atsushi ANDO 《Geostandards and Geoanalytical Research》1993,17(1):5-79

Abstract: Analytical data for fourteen rare-earth elements, scandium, yttrium, zirconium and hafnium, received by May 1992, have been compiled on twenty-six GSJ (Geological Survey of Japan) reference samples. Seventeen of them are 'Igneous rock series' and nine are "Sedimentary rock series". The reported data including personal communication were evaluated under the consideration on analytical methods and geochemical evidences. No significant difference has been observed between the values obtained by the different analytical methods. Based on the selected available data, 1992 compilation values were tabulated.  相似文献   

Trace-element characteristics of east–west mantle geochemical hemispheres     

Hikaru Iwamori  Hitomi Nakamura  Masaki Yoshida  Takashi Nakagawa  Kenta Ueki  Atsushi Nakao  Tatsuji Nishizawa  Satoru Haraguchi 《Comptes Rendus Geoscience》2019,351(2-3):209-220

Recent statistical analyses on the isotopic compositions of oceanic, arc, and continental basalts have revealed that the Earth's mantle is broadly divided into eastern and western hemispheres. The present study aimed to characterize the isotopically defined east–west geochemical hemispheres using trace-element concentrations. Basalt data with Rb, Sr, Nd, Sm, Pb, Th, and U in addition to the isotopic ratios ⁸⁷Sr/⁸⁶Sr, ¹⁴³Nd/¹⁴⁴Nd, ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, and ²⁰⁸Pb/²⁰⁴Pb were selected mostly from the GEOROC and PetDB databases. A total of 4787 samples were used to investigate the global geochemical variations. The results show that the wide trace-element variations are broadly explained by the melting of melt-metasomatized and fluid-metasomatized mantle sources. The larger amount of the fluid component derived from subducted plates in the eastern hemisphere than that in the western hemisphere is inferred from the basalts. These characteristics support the hypothesis that focused subduction towards the supercontinent created the mantle geochemical hemispheres.  相似文献   

Geology and age model of the Lower Pleistocene Nojima,Ofuna, and Koshiba Formations of the middle Kazusa Group,a forearc basin‐fill sequence on the Miura Peninsula,the Pacific side of central Japan     

Atsushi Nozaki  Ryuichi Majima  Koji Kameo  Saburo Sakai  Atsuro Kouda  Shungo Kawagata  Hideki Wada  Hiroshi Kitazato 《Island Arc》2014,23(2):157-179

We present field and core observations, nannofossil biostratigraphy, and stable oxygen isotope fluctuations in foraminiferal tests to describe the geology and to construct an age model of the Lower Pleistocene Nojima, Ofuna, and Koshiba Formations (in ascending order) of the middle Kazusa Group, a forearc basin‐fill succession, exposed on the northern Miura Peninsula on the Pacific side of central Japan. In the study area, the Nojima Formation is composed of sandy mudstone and alternating sandy mudstone and mudstone, the Ofuna Formation of massive mudstone, and the Koshiba Formation of sandy mudstone, muddy sandstone, and sandstone. The Kazusa Group contains many tuff beds that are characteristic of forearc deposits. Thirty‐six of those tuff beds have characteristic lithologies and stratigraphic positions that allow them to be traced over considerable distances. Examination of calcareous nannofossils revealed three nannofossil datum planes in the sequences: datum 10 (first appearance of large Gephyrocapsa), datum 11 (first appearance of Gephyrocapsa oceanica), and datum 12 (first appearance of Gephyrocapsa caribbeanica). Stable oxygen isotope data from the tests of the planktonic foraminifer Globorotalia inflata extracted from cores were measured to identify the stratigraphic fluctuations of oxygen isotope ratios that are controlled by glacial–interglacial cycles. The observed fluctuations were assigned to marine isotope stages (MISs) 49–61 on the basis of correlations of the fluctuations with nannofossil datum planes. Using the age model obtained, we estimated the ages of 24 tuff beds. Among these, the SKT‐11 and SKT‐12 tuff beds have been correlated with the Kd25 and Kd24 tuff beds, respectively, of the Kiwada Formation on the Boso Peninsula. The Kd25 and Kd24 tuff beds are widely recognized in Pleistocene strata in Japan. We used our age model to date SKT‐11 at 1573 ka and SKT‐12 at 1543 ka.  相似文献   

Oxygen and carbon isotope records of cultured freshwater pearl mussel <Emphasis Type="Italic">Hyriopsis</Emphasis> sp. shell from Lake Kasumigaura,Japan     

Toshihiro Yoshimura  Rei Nakashima  Atsushi Suzuki  Noriko Tomioka  Hodaka Kawahata 《Journal of Paleolimnology》2010,43(3):437-448

We present oxygen and carbon isotope ratios and the morphological structure of the cultured freshwater pearl mussel (Hyriopsis sp., Unionidae) shell and pearl. The number of first-order fluctuations of δ¹⁸O of the outer shell layer along the maximum growth axis was consistent with the number of cultured years. The dominant factor controlling annual δ¹⁸O fluctuations was water temperature with a minor contribution from the variation in δ¹⁸O of ambient water, especially during the rainy season. The δ¹³C values were approximately constant throughout the life of the mussel, suggesting that the contributions of body size to δ¹³C of the shell were minor. We observed nine distinct disturbance rings on the outer surface of the shell. Five rings coincided with the five winter peaks of the δ¹⁸O profile, indicating winter growth cessation below approximately 10°C, probably because of either inactive growth at low water temperatures or reproduction. Summer disturbance rings were not observed in all years. Moreover, some summer rings showed discontinuity in the inner structure. These findings suggest that summer growth cessation may be caused by occasional events such as heavy rains, as the decrease of dissolved oxygen concentration. The δ¹⁸O profile and shell structures indicated that shell aragonite was precipitated at close to equilibrium conditions with respect to the oxygen isotope composition of the ambient water. Hyriopsis sp. shells can potentially be used for reconstruction of past hydrologic conditions. The δ¹⁸O of a pearl indicated that calcification occurred over a temperature range of at least 13–23°C. The optimal temperature for pearl calcification in this species is lower than that for marine pearl calcification.  相似文献