Effect of silica concentration on the diopsidic pyroxenes in the system diopside-CaTiAl2O6SiO2     

Alok K. Gupta  Kosuke Onuma  Kenzo Yagi  Edward G. Lidiak 《Contributions to Mineralogy and Petrology》1973,41(4):333-344

The effect of silica concentration on the solubility of Al and Ti in diopsidic pyroxenes has been investigated at one atmosphere in the system diopside-CaTiAl₂O₆-SiO₂ at temperatures between 1150–1420° C. The composition of pyroxene in the system diopside-CaTiAl₂O₆-SiO₂ is influenced by the total SiO₂ content. Near the join diopside-CaTiAl₂O₆, the pyroxene forms a solid solution with the CaTiAl₂O₆ molecule, and co-exists with perovskite for compositions greater than 11 weight percent CaTiAl₂O₆. Anorthite is an accompanying phase. With increasing total SiO₂ content a series of mineralogical changes involving Ti-bearing phases occur. Sphene solid solution co-exists with diopside solid solution, anorthite, and perovskite in a small compositional range near the diopside-CaTiAl₂O₆ join. Additional total SiO₂ results in the elimination of perovskite and a decrease of solid solution in the pyroxenes. With further increase in SiO₂ content, tridymite appears and the pyroxene is approximately pure diopside. Rutile joins diopside, anorthite, sphene solid solution and tridymite over a broad compositional range in the Ti, Si-rich part of the system. These results demonstrate that increased silica concentration decreases the solubility of Al and Ti in diopsidic pyroxenes and controls the stability of co-existing Ti-bearing phases.  相似文献   

Types of quaternary volcanic activity in Northeastern Japan     

K. Yagi  Y. Kawano  K. Aoki 《Bulletin of Volcanology》1963,26(1):223-235

The northeastern Japan forms a typical arcuate structure with a remarkable zonal arrangement of many geologic features, including the distribution of Quaternary volcanoes. Thus two distinct zones of volcanoes are noted here: i. e., Nasu zone on the east and Tyokai zone on the west. Some of the volcanoes of Nasu zone are characterized by the presence of pumice flows or pumice falls, sometimes of very large scales. These pumice flows belong to the calc-alkali rock series. While pumice flows or falls are rare in the Tyokai zone, where they are present though on small scale. Migration of the center of activity is noted along linear fissures, running either from east to west, or north to south at some volcanoes of Nasu zone, and consequently large swarms of volcanoes are common in this zone. While central eruption with definite center is typical of the Tyokai zone. From the petrographical and petrochemical study on the lavas and pyroclastics the original magma of the Nasu zone is estimated to be tholeiitic, and that of the Tyokai zone high-alumina basaltic. Abundant calc-alkali rocks are derived from these parental magmas. Thus the difference in the volcanic activity should be ascribed to the different nature of the parental magmas or the magmas derived from them.  相似文献   

Dissolved organic carbon in a eutrophic lake; dynamics,biodegradability and origin   总被引：1，自引：0，他引：1  

Takehiko Fukushima  Je-chul Park  Akio Imai  Kazuo Matsushige 《Aquatic Sciences - Research Across Boundaries》1996,58(2):139-157

The seasonal and spatial changes in dissolved organic carbon (DOC) in Lake Kasumigaura, a shallow, eutrophic lake, were analyzed and the lability of DOC was tested by long-term incubations. There was a nearly 1 mgCl^–1 downstream increase in refractory DOC in the lake; at the center it fluctuated little seasonally. The characteristic UV-absorbance: DOC ratios were determined for samples from the influent rivers (pedogenic: used interchangeably with allochthonous) and outdoor experimental ponds (autochthonous) during incubations. These ratios were then used to calculate the proportion of total measured lake water DOC in each of four components: pedogenic-refractory (PR), pedogenic-labile (PL), autochthonous-refractory (AR) and autochthonous-labile (AL). PR was uniform (around 1.5 mgCl^–1) or diminished very slightly over time. AR increased from nearly zero at the station closest to an influent river to 1 mgCl^–1 at the lake center. PL declined downstream from 0.3 mgCl^–1 to zero. AL was virtually constant at 0.8 mgCl^–1 except at the station closest to the influent river. The constancy of the UV-absorbance: DOC ratio during the biodegradation process was confirmed for Lake Kasumigaura; hence a two-component model (pedogenic-autochthonous) could be applied here without consideration of DOC lability. However, this assumption is not always met for other water bodies, and therefore it should be checked before applying a two-component model elsewhere.  相似文献   

A direct numerical approach to the Chandrasekhar'sH-functions for arbitrary characteristic functions     

Kiyoshi Kawabata  Takehiko Satoh  Sueo Ueno 《Astrophysics and Space Science》1991,182(2):249-260

The purpose of this paper is to present a numerical technique to directly compute the Chandrasekhar'sH ()-function for anisotropic scattering in terms of the roots of the characteristic equations as well as the quadrature points of a certain degreen employed to approximate the definite integral involved in the basic equation. The principal feature of the algorithm proposed here is a compact computer code to enumerate _n C _m combinations ofn distinct integers {1,...,n} takenm at a time. With these quantities available, the coefficients of the polynomial equation of the characteristics equation can be readily computed for any given characteristic function, so that a standard technique such as the Laguerre method can be applied to find all the roots.It is shown that the results obtained for some representativeH()-functions using the present technique with relatively low-order formula (e.g.,n=7) are sufficiently accurate for all practical purposes.  相似文献   

The ZnSiO3 clinopyroxene-ilmenite transition: Heat capacity,enthalpy of transition,and phase equilibria     

M. Akaogi  H. Yusa  E. Ito  T. Yagi  K. Suito  J. T. Iiyama 《Physics and Chemistry of Minerals》1990,17(1):17-23

ZnSiO₃ clinopyroxene stable above 3 GPa transforms to ilmenite at 10–12 GPa, which further decomposes into ZnO (rock salt) plus stishovite at 20–30 GPa. The enthalpy of the clinopyroxene-ilmenite transition was measured by high-temperature solution calorimetry, giving ΔH⁰=51.71 ±3.18 kJ/mol at 298 K. The heat capacities of clinopyroxene and ilmenite were measured by differential scanning calorimetry at 343–733 and 343–633 K, respectively. The C _p of ilmenite is 3–5% smaller than that of clinopyroxene. The entropy of transition was calculated using the measured enthalpy and the free energy calculated from the phase equilibrium data. The enthalpy, entropy and volume changes of the pyroxene-ilmenite transition in ZnSiO₃ are similar in magnitude to those in MgSiO₃. The present thermochemical data are used to calculate the phase boundary of the ZnSiO₃ clinopyroxene-ilmenite transition. The calculated boundary,

相似文献    86. Structure of the strong tidal jet in the naruto strait      Yoshio Takasugi  Tateki Fujiwara  Takehiko Higo 《Journal of Oceanography》1990,46(3):69-83 In order to clarify the structure of the strong tidal current at the Naruto Strait in the Seto Inland Sea of Japan, the sea-level values were observed in the strait and the current measurements were made with an Acoustic Doppler Current Profiler (ADCP).The tidal volume transports for M2 and S2 tides were about 74×103 and 26×103 m3 sec–1, respectively. The horizontal profile of the velocity at the phase of the strong tidal current compares favorably with a theoretical profile of the two-dimensional steady turbulent jet except for the side parts of the profile. Moreover, the entrainment rate of the surrounding water into the strong tidal jet was estimated from the difference of mass flux between two cross-sections at the strait, the entrainment rate and entrainment constant for both the northward and southward flows being about 1.3–2.5×10–4m–1 and about 0.03–0.05, respectively.  相似文献    87. Citrate-dithionite-bicarbonate extractable phosphorus (CDB-P) pool in the suspended and surface sediments of the tidal flat area in inner Ariake Bay,Japan      Katsuhisa Tanaka  Kazumaro Okamura  Katsunori Kimoto  Hiroshi Yagi  Masashi Kodama 《Journal of Oceanography》2007,63(1):143-148 CDB-P (phosphorus extractable by the citrate-dithionite-bicarbonate extraction procedure) was used as the indicator of bio-available inorganic P in the suspended and surface sediments in the inner part of Ariake Bay. The CDB-P pool of suspended and surface sediments in the tidal flat area was estimated to be 10 ton and 90 ton, respectively (total of 100 ton), which corresponds to 1.5 times the average dissolved inorganic phosphorus standing stock. During the summer periods of hypoxia, the CDB-P concentration in the surface sediments decreased with the decline of Eh, losing 43–47% of the CDB-P observed in April. These results suggest that the phosphorus dynamics have been affected by the decrease of resuspended sediment concentrations brought about by the reduction of the tidal currents and phosphate release from the surface sediments during frequently occurring summer hypoxia events.  相似文献    88. Some regular patterns in the distribution of sediment contamination in the coastal waters along Japan      Yasushi Hiraizumi  Takehiko Manabe  Hajime Nishimura 《Journal of Oceanography》1978,34(5):222-232 Observations of sediment contamination along the coast of Japan were analyzed. When the pollutant concentration is divided by the fine particle fraction in the sediment, a regular pattern is observed in the quantitative relationship among the degree and the area of contamination and the discharge rate of pollutant released continuously into the water along the coast. This regularity was observed with respect to COD,n-hexane soluble substances and heavy metals, and could be expressed by a formula.Polluted particles were supposed to disperse through suspension in the bottom water layer, and thus their distribution in the surface sediment is expected to become similar to effluent dispersion in the surface water.  相似文献    89. Topographic and geologic controls on landslides induced by the 2015 Gorkha earthquake and its aftershocks: an example from the Trishuli Valley,central Nepal   总被引：1，自引：0，他引：1   Ching-Ying Tsou  Masahiro Chigira  Daisuke Higaki  Go Sato  Hiroshi Yagi  Hiroshi P. Sato  Akihiko Wakai  Vishnu Dangol  Shanmukhesh C. Amatya  Akiyo Yatagai 《Landslides》2018,15(5):953-965 The devastating Gorkha earthquake (M w 7.8) on April 25, 2015 and its aftershocks triggered numerous landslides across the Lesser and Higher Himalayas of central Nepal. This study aims to characterize these landslides, based on the local topography and geology, and to develop data for landslide hazard zoning. This study focused on a mountainous catchment of the Trishuli River, where a digital elevation model was used to examine hilllslope and river profiles, aerial photos were used to identify 155 coherent landslides, and satellite images were used to map 912 earthquake-induced landslides. The topography of this area is mainly characterized by incised V-shaped inner gorges and steep (> 35°) SW-facing scarp slopes. Although most of the coherent landslides were not reactivated by the earthquakes, the Gogane landslide was affected by the earthquake and partly failed. A majority of the earthquake-induced landslides (91%) were new landslides, while the others were enlarged old landslides. The earthquake-induced landslides occurred mainly on the steep slopes of V-shaped inner gorges and scarp slopes, in gneiss and quartzite strata of the Lesser Himalayas, and they were primarily associated with fractured rock masses. This analysis provides a framework for zoning areas vulnerable to earthquake-induced landslides.  相似文献    90. Composition and pressure dependence of lattice thermal conductivity of (Mg,Fe)O solid solutions      Akira Hasegawa  Kenji Ohta  Takashi Yagi  Kei Hirose  Yoshiyuki Okuda  Tadashi Kondo 《Comptes Rendus Geoscience》2019,351(2-3):229-235 We measured the lattice thermal conductivities of Fe0.98O wüstite and iron-rich (Mg,Fe)O magnesiowüstite using the pulsed light heating thermoreflectance technique with a diamond anvil cell up to 61 GPa at 300 K. We found that the thermal conductivity of wüstite does not show a monotonic increase as a function of pressure, contrary to that of MgO periclase. Rocksalt (B1) to rhombohedral B1 transition is likely to induce an abnormal pressure response in the conductivity of wüstite. Our results also show that magnesiowüstite has a lower conductivity than that of MgO and FeO endmembers due to a strong iron impurity effect, which is well reproduced by a model considering phonon-impurity scattering in a binary solid solution.  相似文献    [首页] « 上一页 [4] [5] [6] [7] [8] 9 [10] [11] [12] [13] 下一页 » 末  页»