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1.
Summary The granulite terrane of the Czech part of the Gf?hl unit includes numerous small bodies of mantle derived peridotite, some
of which contain layers or lenses of eclogite and garnet pyroxenite. These eclogitic rocks have generally been considered
to be high-pressure crystal cumulates formed in the upper mantle. We present new analyses of whole-rock major and trace element
contents for three kynanite-quartz eclogite samples taken from the Nové Dvory garnet peridotite body. Integrating these data
with previously published analyses from the literature on eclogitic rocks from this terrane, we demonstrate that a magnesian
group of eclogites, including these three new samples, were originally formed as cumulus gabbros, which were later transformed
to eclogites in the mantle. A gabbroic origin for some mafic layers (Type II) has been advocated for other orogenic peridotites,
such as Beni Bousera (Morocco), Ronda (Spain), and Horoman (Japan). By comparing these sets of data with those from the Bohemian
Massif, we propose a simple method of identifying groups of metagabbros by utilizing MgO-normalization in oxide ratio plots
for whole-rock major element analyses. 相似文献
2.
Dissolved and particulate concentrations of silver in Tokyo Bay estuarine waters and Japanese rivers were determined in this
study. The dissolved silver concentrations in the surface water of Tokyo Bay range from 5.9 to 15.1 pmol kg−1, which is comparable to those in the surface water of the Japan Sea, but two or three times higher than those in the surface
water of the open ocean. However, elevated concentrations of dissolved silver are not found in Tokyo Bay compared with those
in other highly urbanized estuaries, such as San Francisco Bay (20∼243 pmol kg−1). In the Tokyo Bay estuary, silver typically exhibits non-conservative mixing behavior, which is a common feature in the
other estuaries reported previously. Dissolved silver concentrations decrease with salinity from the rivers to the mouth of
Tokyo Bay. Silver is efficiently scavenged by suspended particulates, as evidenced by the high conditional distribution coefficients
for silver throughout the estuary (log Kd > 5.0 ± 0.6). The silver fluxes into Tokyo Bay via inflowing rivers and atmospheric deposition were estimated as 83 kg y−1 and 15 kg y−1, respectively. A simple budget calculation shows that the silver supplied from rivers and atmosphere must be rapidly scavenged
within the Tokyo Bay estuary. 相似文献
3.
Hirokazu Ozaki Hajime Obata Mikio Naganobu Toshitaka Gamo 《Journal of Oceanography》2009,65(2):235-244
We measured potential temperature, salinity, and dissolved oxygen profiles from the surface to the bottom at two locations
in the north Ross Sea (65.2°S, 174.2°E and 67.2°S, 172.7°W) in December 2004. Comparison of our data with previous results
from the same region reveals an increase in potential temperature and decreases in salinity and dissolved oxygen concentration
in the bottom layer (deeper than 3000 m) over the past four decades. The changes were significantly different from the analytical
precisions. Detailed investigation of the temperature, salinity, dissolved oxygen and σ
3 value distributions and the bottom water flow in the north Ross Sea suggests a long-term change in water mass mixing balance.
That is to say, it is speculated that the influence of cool, saline, high-oxygen bottom water (high-salinity Ross Sea Bottom
Water) formed in the southwestern Ross Sea has possibly been decreased, while the influences of relatively warmer and fresher
bottom water (low-salinity Ross Sea Bottom Water) and the Adélie Land Bottom Water coming from the Australia-Antarctic Basin
have increased. The possible impact of global warming on ocean circulation needs much more investigation. 相似文献
4.
Hajime Obata Jun Nishioka Taejin Kim Kazuhiro Norisuye Shigenobu Takeda Yohei Wakuta Toshitaka Gamo 《Journal of Oceanography》2017,73(3):333-344
Using a clean seawater sampling system for trace metals onboard the R. V. Shinsei-Maru, newly launched in 2013, we investigated the vertical distributions of dissolved iron and zinc in Sagami Bay and the Izu-Ogasawara Trench. We applied appropriate clean sampling and filtering processes for trace metals, so that uncontaminated seawater samples were successfully collected. The distribution of zinc in the trench area was similar to that of silicate and the same as that previously reported in the subtropical North Pacific. There were spatial variations in the iron (Fe) distribution in the trench areas. We used previously reported information about biogeochemical cycling in the trench area, and found that Fe has a residence time of 29 years in the water column. The short residence time of Fe (29 years) corresponds to the vertical variations of dissolved Fe in the water column. 相似文献
5.
6.
Masaaki Obata Kazuhito Ozawa Kosuke Naemura Akira Miyake 《Mineralogy and Petrology》2013,107(6):881-895
An isochemical kelyphite (orthopyroxene+spinel+plagioclase) that has nearly the same bulk chemical composition as the precursor garnet was found within a matrix of ordinary kelyphites (orthopyroxene+clinopyroxene+spinel±amphibole) in garnet peridotites from the Czech part of the Moldanubian Zone. It was shown that the kelyphitization of garnet took place in three stages: (1) the garnet-olivine reaction, accompanied by a long-range material transfer across the reaction zone, and (2) the isochemical breakdown of garnet, essentially in a chemically-closed system, and finally, (3) an open-system hydration reaction producing a thin hydrous zone (amphibole+spinel+plagioclase), which is located between the isochemical kelyphite and relict garnet. The presence of relict garnet suggests that this breakdown reaction of the second stage did not proceed to a completion probably being hindered by the formation of the hydrous zone at the reaction front. It was found by electron back-scattered diffraction method that orthopyroxene and spinel do not show any topotaxic relationship in the first type of kelyphite; whereas they show locally topotaxic relationship in the isochemical kelyphite. The transition from the first type to the second type of kelyphite is discussed on the basis of the detailed observations in the transition zone between the two kelyphites. More widespread occurrence of isochemical kelyphite is expected to occur in orogenic peridotites as well as from xenoliths brought by volcanics. 相似文献
7.
Iron, manganese and aluminum in upper waters of the western South Pacific Ocean and its adjacent seas 总被引：1，自引：0，他引：1
Hajime Obata Kiminori Shitashima Kenji Isshiki Eiichiro Nakayama 《Journal of Oceanography》2008,64(2):233-245
Total dissolvable iron, manganese and aluminum distributions in upper waters were determined in the western South Pacific,
Solomon Sea, Coral Sea, and Tasman Sea. In these oceanic regions, the surface aluminum distributions well reflect the atmospheric
deposition pattern of mineral dust in the western South Pacific reported previously. Surface manganese distributions derive
mainly from lateral transportation from the coastal sediments of western tropical islands. Compared to Mn and Al, the Fe distributions
reflect the nutrient cycle in upper waters. Iron limitation over the vast South Pacific, as revealed by physiological features
of phytoplankton, seems to be caused by low atmospheric dust deposition and low Fe:N ratios in deep waters. In the western
South Pacific, with its unique geographic and oceanographic settings, the local sources of trace metals might considerably
affect their biogeochemical cycles. 相似文献
8.
9.
Yayoi Hongo Hajime Obata Dia Sotto Alibo Yoshiyuki Nozaki 《Journal of Oceanography》2006,62(4):441-455
The concentration of dissolved rare earth elements (REE) were determined at 47 stations in the North Pacific surface waters.
Combining with other previous data, we present the surface REE distribution in the North Pacific and discuss the controlling
factors. The surface concentrations increase toward the high latitude and continental margin (e.g. [Nd] > 10 pmol kg−1) from the central North Pacific (e.g. [Nd] < 5 pmol kg−1). The North Pacific Deep Water-normalized REE patterns are varied, indicating that two or more factors contribute to the
REE distribution. We examined four factors making the regional variation of surface REE concentrations mainly; a) particle
scavenging, b) atmospheric dust input, c) vertical mixing and d) lateral transport from the coastal region. Flux calculations
for Nd showed that the influence of atmospheric dust was less significant than the vertical input even in the western upwelling
zone. Moreover, the longitudinal and latitudinal transitions of surface REE seem to reflect the lateral supply from the coastal
areas. We constructed the diagram of surface Er/Lu and Er/Yb molar ratios in order to assess the origin and the input processes
of the surface REE. Both molar ratios showed increasing trend toward PEW (Er/Lu (>10.5) and Er/Yb (>1.4)) from PSUW (Er/Lu
(>7) and Er/Yb (>1.2)). The high Er/Lu and Er/Yb ratios in PEW indicate that the lateral supply of terrestrial materials from
the coastal area is possibly the important factor in PEW, because only weathering and dissolution of rocks can explain such
high Er/Lu and Er/Yb ratios to our knowledge. 相似文献
10.
Hajime Obata Yoshiyuki Nozaki Yoshiyuki Yamamoto 《Geochimica et cosmochimica acta》2004,68(5):1035-1048
To carry out comparative geochemical investigation of refractory and reactive metals in different oceanic settings covering different θ-S characteristics, productivity, dissolved oxygen profiles, water and sediment discharge, etc., we have determined the vertical profiles of dissolved (<0.04 μm) Al, In and Ce, as well as 210Pb and 210Po in the eastern Indian Ocean (from 40°S in the Southern Ocean to 8°N in the Bay of Bengal) and the Southeast Asian Seas. In the Antarctic Circumpolar Region, the concentrations of these refractory metals are very low, presumably due to very low the atmospheric input and intensified scavenging. Resemblance in the vertical profiles of these metals is often seen in some other stations. However, there are also significant differences among their distributions, for example, in the magnitude of surface enrichment caused by the external input from eolian and fluvial-coastal sources. Comparison of Al distributions in surface waters with those of atmospherically derived 210Pb suggests the relative importance of eolian input over fluvial-coastal sources. Fluvial and coastal input appears to be insignificant for dissolved In, but may be important for Ce. The mean residence time of Al in the surface mixed layer was estimated to be ∼2 years which is similar to that of 210Pb.In the intermediate and deep waters, the concentrations of each element vary with depth and location. The range of variation is in the order of Al>Ce>In, depending upon particle reactivity. Although dissolved Al decreases along the water trajectory by particle scavenging, variations of dissolved In and Ce are relatively small which may be due to less scavenging for both elements. Compared with significantly high (>4 pM) dissolved Ce throughout the water column in the Bay of Bengal, dissolved Al concentration remains low, suggesting that it has higher affinity to particles and hence is scavenged by sinking particulate matter. This is consistent with the observation that the dissolved Al in the Antarctic Intermediate Water (AAIW) decreases from 4 to 6 nM in the 30°S Perth Basin to <0.7 nM in the 10°S West Australia Basin along its trajectory. Using the chlorofluorocarbons (CFCs) ventilation age of AAIW (Fine, 1993), the mean residence time of Al in the intermediate and deep waters in the eastern Indian Ocean is estimated to be <17 yr, approximately the same as that of 210Pb (10-15 yr). In the semiclosed basins of Southeast Asia, the distributions of Al, In and Ce are also very unique. In the South China Sea, there is a strong sediment source for dissolved In and Ce during the deepwater passage through the Luzon Strait. 相似文献