Chemical characteristics of chromian spinel in plutonic rocks: Implications for deep magma processes and discrimination of tectonic setting   总被引：2，自引：0，他引：2  

Shoji Arai  Hidenobu Okamura  Kazuyuki Kadoshima  Chima Tanaka  Kenji Suzuki  Satoko Ishimaru 《Island Arc》2011,20(1):125-137

We summarize chemical characteristics of chromian spinels from ultramafic to mafic plutonic rocks (lherzolites, harzburgites, dunites, wehrlites, troctolites, olivine gabbros) with regard to three tectonic settings (mid‐ocean ridge, arc, oceanic hotspot). The chemical range of spinels is distinguishable between the three settings in terms of Cr# (= Cr/(Cr + Al) atomic ratio) and Ti content. The relationships are almost parallel with those of chromian spinels in volcanic rocks, but the Ti content is slightly lower in plutonics than in volcanics at a given tectonic environment. The Cr# of spinels in plutonic rocks is highly diverse; its ranges overlap between the three settings, but extend to higher values (up to 0.8) in arc and oceanic hotspot environments. The Ti content of spinels in plutonics increases, for a given lithology, from the arc to oceanic hotspot settings by mid‐ocean ridge on average. This chemical diversity is consistent with that of erupted magmas from the three settings. If we systematically know the chemistry of chromian spinels from a series of plutonic rocks, we can estimate their tectonic environments of formation. The spinel chemistry is especially useful in dunitic rocks, in which chromian spinel is the only discriminating mineral. Applying this, discordant dunites cutting mantle peridotites were possibly precipitated from arc‐related magmas in the Oman ophiolite, and from an intraplate tholeiite in the Lizard ophiolite, Cornwall.  相似文献   

Assessment of carbon- and fluorescence-based primary productivity in Ariake Bay,southwestern Japan     

S.C. Tripathy  J. Ishizaka  T. Fujiki  T. Shibata  K. Okamura  T. Hosaka  T. Saino 《Estuarine, Coastal and Shelf Science》2010

A comparative account of primary productivity (PP), in the characteristically turbid and highly dynamic waters of Ariake Bay, measured by ¹³C uptake and fast repetition rate fluorometer (FRRF) was conducted to ensure compatibility between the two methods. Estimates from both methods depicted strong linearity for both short-term (r² > 0.90) and daily (r² = 0.42–0.93) measurements, except in the near-surface (∼0 m) layer. ¹³C-based short-term (1 h; in situ) PP estimates showed similar magnitudes and trend with the instantaneous PP measured by FRRF concurrently. Whereas, unlike short-term measurements, the daily PP estimates from both methods showed large difference, with FRRF-based time integrated daily PP resulting in 1.09–1.82 times higher than the carbon-based daily (24 h; simulated in situ) PP. This difference between daily PP estimates was mainly due to: (1) the temporal variation of water column chlorophyll a (Chl a) because of frequent moving of water mass, and (2) the dissimilarity in ambient light field conditions between the two methods. Results revealed that considering the above two environmental factors invariable over a daylength, fairly close approximation of daily PP, compared to ¹³C-based daily PP, could be obtained from FRRF. Hence, FRRF-based daily PP can be considered as more realistic in this highly dynamic water body like Ariake Bay where water column parameters are subjected to strong temporal variation. The relationship between Chl a-specific photosynthetic rate (P^B) and the corresponding photosynthetically active radiation (PAR) in the water column (PAR–P^B relationship) was found to be linear for FRRF and curvilinear for ¹³C-based measurements in the near-surface layer, for the same intensities of incident PAR, and this is thought to be the primary basis for the higher difference in PP estimates at the near-surface layer. Considering the minor variations in FRRF-based time series of PAR–P^B relationships, a combined and/or instantaneous PAR–P^B relationship in combination with incubation Chl a and light field condition was used to obtain fairly close estimates of daily water column integrated PP from FRRF.  相似文献   

Lower Cd/P ratio in settling particles than in surface seawater in the Okinawa Trough     

Kazuo Abe  Kazuo Iseki  Kazumaro Okamura  Yoko Kiyomoto 《Journal of Oceanography》2006,62(5):745-752

The characteristics of the ratios between cadmium (Cd) and phosphorus (P) in settling particles collected from the Okinawa Trough in the East China Sea were examined using a sediment trap, moored at a depth of 811 m for one year. The Cd/P ratios varied within a narrow range throughout the year, in spite of the large seasonal change in the total dry mass, Cd, and P fluxes. The average Cd/P ratio of settling particles was 0.062 (nmol/μmol), which was obviously lower than that of surface seawater around the study site (0.16). This lower ratio in the Okinawa Trough particles collected using the 811 m-moored trap certainly reflected the mixture of biologically produced organic matter around the study site and other components that were mainly transported as lateral flux from the shelf edge and slope area of the East China Sea.  相似文献   

Ocean Color Satellite Imagery and Shipboard Measurements of Chlorophyll a and Suspended Particulate Matter Distribution in the East China Sea   总被引：1，自引：0，他引：1  

Yoko Kiyomoto  Kazuo Iseki  Kazumaro Okamura 《Journal of Oceanography》2001,57(1):37-45

Satellite-derived ocean color data of Coastal Zone Color Scanner (CZCS) on board the Nimbus-7 and Ocean Color and Temperature Scanner (OCTS) on board the Advanced Earth Observing Satellite (ADEOS) are jointly used with historical in situ data to examine seasonal and spatial distributions of chlorophyll a (Chl-a) and suspended particulate matter (SPM) concentrations in the East China Sea. Ocean color imagery showed that Chl-a concentrations on the continental shelf were higher than those of the Kuroshio area throughout the year. Satellite-derived Chl-a concentrations are generally in good accordance with historical in situ values during spring through autumn (although no shipboard in situ measurement was conducted at nearshore areas). In contrast, ocean color imagery in winter indicated high Chl-a concentrations (4–10 mg m^–3) on the continental shelf where bottom depth was less than 50 m when surface water was turbid (2–72 g m^–3 of SPM at surface), while historical in situ values were usually less than 1 mg m^–3. This suggests that resuspended bottom sediment due to wind-driven mixing and winter cooling is responsible for the noticeable overestimation of satellite-derived Chl-a concentrations. The algorithm for ocean color needs to be improved urgently for turbid water.  相似文献   

In-situ survey of nanomolar manganese in seawater using an autonomous underwater vehicle around a volcanic crater at Teishi Knoll,Sagami Bay,Japan     

Takashi Doi  Michiaki Takano  Kei Okamura  Tamaki Ura  Toshitaka Gamo 《Journal of Oceanography》2008,64(3):471-477

We present the results of a chemical survey at a submarine volcano, Teishi Knoll, obtained using a submersible in-situ Mn analyzer (GAMOS) mounted on an autonomous underwater vehicle (AUV) platform. During this survey, high-resolution data of dissolved Mn were obtained in three dimensions in nearly real time. The AUV enabled continuous detailed observations along a preprogrammed pathway, which could not have been performed with conventional CTD hydrocasts. During this observation, anomalously high dissolved Mn concentrations were obtained within the crater, corresponding to high water temperatures. The anomalies might be a hydrothermal signature due to volcanic activity from the crater.  相似文献   

Dependence of the build-up of the colour–magnitude relation on cluster richness at z∼ 0.8     

Yusei Koyama  Tadayuki Kodama  Masayuki Tanaka  Kazuhiro Shimasaku  Sadanori Okamura 《Monthly notices of the Royal Astronomical Society》2007,382(4):1719-1728

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The surface photometry of NGC 3379     

F. X. Hu  M. Hamabe  S. Okamura  H. J. Su 《Astrophysics and Space Science》1989,158(1):43-55

Surface photometry is carried out for the photometric standard galaxy NGC 3379 on the basis of two plates in the blue band taken with the Bejing Schmidt telescope. The results, including luminosity profiles, photometric parameters, integrated luminosity distribution, ellipticity and position angle variation, are presented in various forms of figures and tables. Especially our geometric profiles, i.e., ellipticity and position angle variations reach up to 5, much fainter region than that any previous study did. The accuracy of the present data is checked by comparing them with the surface photometry in the literature. We find the zero-point 0.12 mag brighter than the calibration of de Vaucouleurs and Capaccioli (1979), which agrees with the values 0.10–0.15 mag difference claimed by recent observations. The systematic differences is found to be less than 0.1 mag.  相似文献   

Orientation of Galaxies in the Local Supercluster: A Review     

F. X. Hu  G. X. Wu  G. X. Song  Q. R. Yuan  S. Okamura 《Astrophysics and Space Science》2006,302(1-4):43-59

The progress of the studies on the orientation of galaxies in the Local Supercluster (LSC) is reviewed and a summary of recent results is given. Following a brief introduction of the LSC, we describe the results of early studies based on two-dimensional analysis, which were mostly not conclusive. We describe next the three-dimensional analysis, which is used widely today. Difficulties and systematic effects are explained and the importance of selection effects is described. Then, results based on the new method and modern databases are given, which are summarized as follows. When the LSC is seen as a whole, galaxy planes tend to align perpendicular to the LSC plane with lenticulars showing the most pronounced tendency. Projections onto the LSC plane of the spin vectors of Virgo cluster member galaxies, and to some extent, those of the total LSC galaxies, tend to point to the Virgo cluster center. This tendency is more pronounced for lenticulars than for spirals. It is suggested that ‘field’ galaxies, i.e., those which do not belong to groups with more than three members, may be better objects than other galaxies to probe the information at the early epoch of the LSC formation through the analysis of galaxy orientations. Field lenticulars show a pronounced anisotropic distribution of spin vectors in the sense that they lay their spin vectors parallel to the LSC plane while field spirals show an isotropic spin-vector distribution.  相似文献   

Evaluation of ionic pollutants in cloud droplets at a mountain ridge in northern Japan using constrained oblique rotational factor analysis     

Nobuaki Ogawa  Ryoei Kikuchi  Tomoko Okamura  Junko Inotsume  Tetsuya Adzuhata  Toru Ozeki  Masahiro Kajikawa 《Atmospheric Research》2000,54(4)

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Stratigraphy of multiple piston-core sediments for the last 30,000 years from Lake Biwa, Japan     

Keiji Takemura  Akira Hayashida  Makoto Okamura  Hiromi Matsuoka  Mohammed Ali  Mohammed Ali  Yoshiki Kuniko  Masayuki Torii  Masayuki Torii 《Journal of Paleolimnology》2000,23(2):185-199

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