Phase transformations in ABO 4 type compounds under high pressure     

Osamu Fukunaga  Shinobu Yamaoka 《Physics and Chemistry of Minerals》1979,5(2):167-177

For ABO ₄ type ternary oxides, high pressure phase transformations known up to the present are reviewed, and an attempt is made to explain and predict crystal structures of their high pressure phases. When ABO ₄ type compounds are plotted based on the two variables, k=r _A /r _B and t=(r _A +r _B )/2r _O, where r _A , r _B , and r _O are the ionic radii of A and B cations and divalent oxygen, they can be classified into the major structure types. It is found empirically that a compound basically transforms to the structure type isostructural with a compound lying in a classified area with the same k and larger t values in the diagram.  相似文献   

Antarctic saline lakes—stable isotopic ratios,chemical compositions and evolution     

Osamu Matsubaya  Hitoshi Sakai  Tetsuya Torii  Harry Burton  Knowles Kerry 《Geochimica et cosmochimica acta》1979,43(1):7-25

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Under‐ice salinity and stable isotope distribution of Saroma‐ko Lagoon,Hokkaido, northern Japan     

Maki Morimoto  Kyoko Kawanobe  Osamu Abe  Takayoshi Kawai  Toshiyuki Kawamura  Kunio Shirasawa 《水文研究》2010,24(7):904-916

In winter, lakes and lagoons at high altitudes or high latitudes have interesting hydrological cycles that differ from those in other seasons or in other regions, because water surfaces are covered with ice. Hydrological balances of lakes and lagoons are complex dynamic systems, and to elucidate them, isotopic tracers of water have been used as effective tools along with observations of precipitation, evaporation, inflows, and outflows. Here, to understand hydrological processes during freezing periods in the brackish Saroma‐ko Lagoon, Hokkaido, northern Japan, we examined horizontal and vertical distributions of salinity and isotope compositions of lagoon water and ice in 2005 and 2006. Horizontal and vertical gradients of salinity and isotope compositions were observed from the river mouth to the sea channel, and factors determining these distributions were considered. The mixing of freshwater and seawater and a freezing effect were presumed to be factors in relationships between salinity and isotopes and in relationships between surface waters and ice just above the water. A simple box model for water balance was constructed based on these putative factors to reproduce the distributions of salinity and isotope compositions of surface waters and ice. An evaluation of the model revealed that this hydrological system is controlled primarily by horizontal advection of the epilimnion, freshwater influx, and the ice growth rate. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Distribution of <Emphasis Type="Italic">Nemopilema nomurai</Emphasis> in the southwestern Sea of Japan related to meandering of the Tsushima Warm Current     

Satoshi?KitajimaEmail author  Naoki?Iguchi  Naoto?Honda  Tatsuro?Watanabe  Osamu?Katoh 《Journal of Oceanography》2015,71(3):287-296

We investigated the horizontal distribution of Nemopilema nomurai medusae using a midwater trawl in the southwestern Sea of Japan from September to October of each year from 2006 to 2012. Numerous medusae of this species found in 2006, 2007, and 2009 were mainly distributed far (>40 km) from the mainland of Japan in the western part of the survey area, but were distributed in the stations closest (<25 km) to the mainland in the eastern part, particularly in 2006 and 2009. These distribution patterns were associated with the path of the second branch of the Tsushima Warm Current (TWC) that flows offshore to the west of Oki Islands and usually approaches the mainland of Japan to the east of Oki Islands. Differences in jellyfish distribution across the survey periods were related to the distribution of the second branch being associated with types, position and intensity of eddies in the eastern part of the survey area. Hence, the formations of eddies and consequent variation in the path of the TWC would be responsible for transporting medusae from offshore to near the mainland to the east of Oki Islands. Individuals with large bells accumulated in the northwestern part of the survey area, where a cyclonic eddy was present downstream of the third branch of the TWC. This variation in bell size distribution may be ascribed to differences in the physical and/or biological factors among the three branches of the TWC.  相似文献   

From an initial transient-state to a steady-state in metamorphic reactions: An experimental approach in the system dolomite-quartz-H₂O     

Tadao  Nishiyama  Aiko  Tominaga  Hiroshi  Isobe 《Island Arc》2007,16(1):16-27

Abstract We carried out hydrothermal experiments in the system dolomite‐quartz‐H₂O to track the temporal change in reaction rates of simultaneous reactions during the development of reaction zones. Two types of configurations for the starting materials were prepared: dolomite single crystals + quartz powder + water and quartz single crystals + dolomite powder + water, both sealed separately in gold capsules. Runs at 0.1GPa and 600°C with cold seal pressure vessels gave the following results. (i) In short duration (45–71 h) runs metastable layer sequences involving wollastonite and talc occur in the reaction zone, whereas they disappear in longer duration (168–336 h) runs. (ii) The layer sequence of the reaction zones in short duration runs differs from place to place on the dolomite crystal even in the same run. (iii) The diversity of layer sequences in the short duration runs merges into a unique layer sequence in the longer duration runs. (iv) The reaction zone develops locally on the dolomite crystal, but no reaction zone was observed on the quartz crystal in any of the runs. The lines of evidence (i)–(iii) show that the system evolves from an initial transient‐ to a steady‐state and that the kinetic effect is important in the development of reaction zones. A steady diffusion model for the unique layer sequence Qtz/Di/Fo + Cal/Dol + Cal/Dol shows that the Dol + Cal layer cannot be formed by diffusion‐controlled process and that the stability of the layer sequence Qtz/Di/Fo + Cal/Dol depends not only on L‐ratios (a = /L_CaOCaO and b = /L_MgOMgO) but also on the relative rate P = (−2ξ₁ − ξ₂)/(–ξ₁ − 2ξ₂) of competing reactions: Dol + 2Qtz = Di + 2CO₂ (ξ₁) and 2Dol + Qtz = Fo + 2Cal + 2CO₂ (ξ₂). For smaller P the stability field will shift to higher values of a and b. The steady diffusion model also shows that the apparent‐non‐reactivity on the quartz surface can be attributed to void formation in a large volume fraction in the diopside layer.  相似文献   

Determining the O/O ratio of water using a water-CO₂ equilibration method: Application to glacial-interglacial changes in O-excess from the Dome Fuji ice core, Antarctica     

Ryu Uemura  Osamu Abe 《Geochimica et cosmochimica acta》2010,74(17):4919-7445

Recent studies show that oxygen three isotope measurement (¹⁶O, ¹⁷O, and ¹⁸O) of water provides additional information for investigating the hydrological cycle and paleoclimate. For determining the ¹⁸O/¹⁶O value of water, a conventional CO₂-water equilibration method involves measurement of the ratios of CO₂ isotopologues which were equilibrated with water. However, this long-established technique was not intended to measure the ¹⁷O/¹⁶O ratio, primarily because the historic ion correction scheme does not allow for possible deviations from a fixed (and mass-dependent) relationship between ¹⁷O/¹⁶O and ¹⁸O/¹⁶O isotope ratios. Here, we propose an improved method for obtaining the ¹⁷O/¹⁶O isotope ratio of fresh water by the equilibration method and measurement of the 45/44 CO₂ ion abundance ratio. Equations which we formulated for ¹⁷O/¹⁶O measurement have two features: first, instead of absolute isotope ratio (R), all equations are formulated in δ values, measured by isotope ratio mass spectrometry. Second, we include two “assigned” δ values of water standards in the equations, because the δ¹⁸O are commonly measured against two working standards to normalize the span of the δ scale. This approach clarifies that the contribution from ¹⁷O (¹²C¹⁶O¹⁷O⁺) to the molecular ion current at mass-to-charge ratio m/z 45 signal depends not on the absolute ¹³C/¹²C ratio, but on the relative δ¹³C differences between the working standards and the sample. The pH value of water affects δ¹⁷O estimation because δ¹³C of CO₂ was changed in the water-CO₂ system. We reevaluated this effect using a set of equations, which explicitly includes CO₂ partial pressure effect on pH value. Our new estimation of pH effect is significantly smaller than previously reported value, but it does not alter the main conclusions in the previous study. The method was verified by δ¹⁷O measurements of an international standard reference water (GISP) provided by the IAEA. We applied the method to investigate ¹⁷O-excess of the ice core drilled at the Dome Fuji station, Antarctica. A total of 1320 samples from a 130 m section around Marine Isotope Stage 9.3 (∼330,000 years before present) were measured. The error of a measurement for δ¹⁷O is 0.175‰ and that of ¹⁷O-excess is 184 per meg. Although these analytical uncertainties hampered accurate estimation of the changes in ¹⁷O-excess, the averaged data indicate that ¹⁷O-excess around MIS 9.3 was higher than during the subsequent glacial period. This approach can be applied only to fresh water samples, and additional improvements will be needed to measure samples which contains significant amount of carbonate minerals.  相似文献   

Characteristics of Triassic epithermal Au mineralization at the Q prospect,Chatree mining area,Central Thailand     

Ladda Tangwattananukul  Daizo Ishiyama  Osamu Matsubaya  Toshio Mizuta  Punya Charusiri  Hinako Sato  Koichiro Sera 《Resource Geology》2014,64(2):167-181

The Chatree deposit is located in the Loei‐Phetchabun‐Nakhon Nayok volcanic belt that extends from Laos in the north through central and eastern Thailand into Cambodia. Gold‐bearing quartz veins at the Q prospect of the Chatree deposit are hosted within polymictic andesitic breccia and volcanic sedimentary breccia. The orebodies of the Chatree deposit consist of veins, veinlets and stockwork. Gold‐bearing quartz veins are composed mainly of quartz, calcite and illite with small amounts of adularia, chlorite and sulfide minerals. The gold‐bearing quartz veins were divided into five stages based on the cross‐cutting relationship and mineral assemblage. Intense gold mineralization occurred in Stages I and IV. The mineral assemblage of Stages I and IV is characterized by quartz–calcite–illite–laumontite–adularia–chlorite–sulfide minerals and electrum. Quartz textures of Stages I and IV are also characterized by microcrystalline and flamboyant textures, respectively. Coexistence of laumontite, illite and chlorite in the gold‐bearing quartz vein of Stage IV suggests that the gold‐bearing quartz veins were formed at approximately 200°C. The flamboyant and brecciated textures of the gold‐bearing quartz vein of Stage IV suggest that gold precipitated with silica minerals from a hydrothermal solution that was supersaturated by boiling. The δ¹⁸O values of quartz in Stages I to V range from +10.4 to +11.6‰ except for the δ¹⁸O value of quartz in Stage IV (+15.0‰). The increase in δ¹⁸O values of quartz at Stage IV is explained by boiling. P_H2O is estimated to be 16 bars at 200°C. The f_CO2 value is estimated to be 1 bar based on the presence of calcite in the mineral assemblage of Stage IV. The total pressure of the hydrothermal solution is approximately 20 bars at 200°C, suggesting that the gold‐bearing quartz veins of the Q prospect formed about 200 m below the paleosurface.  相似文献   

Coronal Mass Ejections Observed at the Total Solar Eclipse on 13 November 2012     

Yoichiro Hanaoka  Jun Nakazawa  Osamu Ohgoe  Yoshiaki Sakai  Kazuo Shiota 《Solar physics》2014,289(7):2587-2599

White-light observations of the total solar eclipse on 13 November 2012 were made at two sites, where the totality occurred 35 min apart. The structure of the corona from the solar limb to a couple of solar radii was observed with a wide dynamic range and a high signal-to-noise ratio. An ongoing coronal mass ejection (CME) and a pre-CME loop structure just before the eruption were observed in the height range between 1?–?2 R_⊙. The source region of CMEs was revealed to be in this height range, where the material and the magnetic field of CMEs were located before the eruption. This height range includes the gap between the extreme ultraviolet observations of the low corona and the spaceborne white-light observations of the high corona, but the eclipse observation shows that this height range is essential for the study of CME initiation. The eclipse observation is basically just a snapshot of CMEs, but it indicates the importance of a continuous coverage of CME observations in this height range in the future.  相似文献   

Finite vertical oscillation of fluid parcel in a heterogeneous,incompressible sea water—Part II     

Masahide Tominaga 《Journal of Oceanography》1970,26(5):267-270

Observations of temperature fluctuations and simultaneous observations of temperature and salinity fluctuations conducted in the sea are carefully analyzed on the theoretical basis developed in Part I. Observed remarkable fluctuations of about 10 minutes period are considered to agree with the unstable oscillations obtained from the theory. Actual oscillations observed in the sea are regarded to have small wave length such that they satisfy the condition (F) described in the Section 1 of Part I.  相似文献   

Paleomagnetic and rock magnetic results from lower crustal rocks of IODP Site U1309: Implication for thermal and accretion history of the Atlantis Massif     

Xixi Zhao  Masako Tominaga   《Tectonophysics》2009,474(3-4):435-448

Integrated Ocean Drilling Program (IODP) Expeditions 304/305 recovered a total of 1.4 km sequence of lower crustal gabbroic and minor ultramafic rocks from the Atlantis Massif oceanic core complex on the western flank of the Mid Atlantic Ridge (MAR) at 30°N. We conducted an integrated paleomagnetic and rock magnetic study on this sequence to help address the interplay between magmatism and detachment faulting. Detailed thermal and alternating-field demagnetization results demonstrate that stable components of magnetization of mainly reversed polarity with unblocking temperatures below the Curie temperature of magnetite are retained in gabbroic rocks at IODP Site U1309. Several samples also contain multicomponent remanences of both normal and reversed polarities that were acquired over sharply defined blocking temperature intervals, providing evidence for localized reheating of some intervals during both normal and reversed polarity periods. Results from a series of rock magnetic measurements corroborate the demagnetization behavior and show that titanomagnetites are the main magnetic carrier rocks recovered at Site U1309D. The overall magnetic inclination of Hole U1309D is -35°, implying significant (up to ~ 50° counterclockwise, viewed to the north) rotation of the footwall around a horizontal axis parallel to the rift axis (010°) may have occurred. The tectonic rotations inferred by the paleomagnetic data suggest that the original fault orientation dipped relative steeply toward the spreading axis and subsequently rotated to a shallower angle. Coupled with the newly published U–Pb zircon ages for Hole U1309D rocks [Grimes, C.B., John, B.E., Wooden, J.L., 2008. Protracted construction of gabbroic crust at a slow-spreading ridge: Constraints from ²⁰⁶Pb/²³⁸U zircon ages from Atlantis Massif and IODP Hole 1309D, (30°N, MAR). Geochem. Geophys. Geosyst. 9, Q08012. doi:1029/2008GC002063], the new paleomagnetic data provide temporal and thermal constraints on the accretion history of the Atlantis Massif.  相似文献