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711.
The volcano-sedimentary sequence at the Raul mine, central Peru, consists of andesitic volcanics, graywackes, and siltstones, and has been metamorphosed to the upper greenschist-lower amphibolite facies at temperatures of 400–500°C. Isotopic data (O and H) have been collected from: (a) quartz and magnetite from stratiform ores, (b) amphiboles from amphibolite units that host stratiform ores, (c) calcite from late veins, (d) detrital quartz from graywackes, and (e) whole rocks.Interunit differences in quartz and magnetite δ18O values suggest that these minerals have resisted isotopic exchange during metamorphism, and that quartz-magnetite isotopic temperatures (380–414°C) represent primary formational temperatures. Calculated δ18O values of water in equilibrium with quartz and magnetite range from 9.1 to 12.6%..Amphibole δ18O and δD values show no interunit differences and suggest that the amphiboles have exchanged isotopes with a large metamorphic fluid reservoir. Calculated δ18OH2O and δDH2O values range from 8 to 12%. and ?3 to +42%., respectively.δ18OH2O values calculated from δ18O calcite and fluid inclusion filling temperatures range from 7.5 to 10%.. Water extracted from fluid inclusions in calcite has a δD value of ?20%..δ18O values of metamorphosed graywackes and volcanic sediments are not atypical, but andesitic lavas are 18O-rich (8–10%.) compared to normal andesites.Waters involved in ore deposition, metamorphism, and late vein formation at Raul are all thought to have a common source, principally seawater. The δ18OH2O and δDH2O values could be produced by evaporation of seawater, shale ultrafiltration, and isotopic exchange with host rocks during deep circulation through the volcano-sedimentary pile.A model is proposed whereby coastal ocean water is restricted from the open sea by volcanic island arcs, and subsequently undergoes evaporation. Circulation of this water is initiated by heat associated with seafloor volcanism. 18O-enrichment in andesites may be produced by isotopic exchange with high 18O waters at elevated temperatures and sufficiently high water/rock ratios. 相似文献
712.
Masaki Akaogi Nanami Horiuchi Takayuki Ishii Hiroshi Kojitani 《Physics and Chemistry of Minerals》2012,39(10):797-802
Phase relations in the system TiO2–ZrO2 were examined in the pressure range of 3.5–12?GPa at 1,800?°C, using multianvil apparatus. At 1,800?°C, TiO2 rutile transforms to αPbO2 structure at 10?GPa, and the αPbO2-type solid solution is stable in compositional range between TiO2 and about (Ti0.6, Zr0.4)O2 at 3.5–12?GPa. Combination of the present results with the published data at 0–3?GPa demonstrates that continuous solid solution with the αPbO2-type structure is stable between TiO2 and (Ti1?x , Zr x )O2 (x?≈?0.6) at 0–12?GPa. This indicates that both the αPbO2-type TiO2 and srilankite Ti2ZrO6 with the same structure belong to the continuous solid solution system though the two phases have been regarded as different minerals. With increasing ZrO2 content, lattice parameters of a- and c-axes of the αPbO2-type solid solution increase, but b-axis is almost constant or slightly decreases. At higher pressure, the αPbO2-type solid solution dissociates into two phases, αPbO2-type phase and tetragonal zirconia. Srilankite with more TiO2-rich composition than Ti2ZrO6 might be found in natural rocks derived from the deep upper mantle. 相似文献
713.
Zonghu Liao Yang Hong Jun Wang Hiroshi Fukuoka Kyoji Sassa Dwikorita Karnawati Faisal Fathani 《Landslides》2010,7(3):317-324
An early warning system has been developed to predict rainfall-induced shallow landslides over Java Island, Indonesia. The
prototyped early warning system integrates three major components: (1) a susceptibility mapping and hotspot identification
component based on a land surface geospatial database (topographical information, maps of soil properties, and local landslide
inventory, etc.); (2) a satellite-based precipitation monitoring system () and a precipitation forecasting model (i.e., Weather Research Forecast); and (3) a physically based, rainfall-induced landslide
prediction model SLIDE. The system utilizes the modified physical model to calculate a factor of safety that accounts for
the contribution of rainfall infiltration and partial saturation to the shear strength of the soil in topographically complex
terrains. In use, the land-surface “where” information will be integrated with the “when” rainfall triggers by the landslide
prediction model to predict potential slope failures as a function of time and location. In this system, geomorphologic data
are primarily based on 30-m Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data, digital elevation
model (DEM), and 1-km soil maps. Precipitation forcing comes from both satellite-based, real-time National Aeronautics and
Space Administration (NASA) Tropical Rainfall Measuring Mission (TRMM), and Weather Research Forecasting (WRF) model forecasts.
The system’s prediction performance has been evaluated using a local landslide inventory, and results show that the system
successfully predicted landslides in correspondence to the time of occurrence of the real landslide events. Integration of
spatially distributed remote sensing precipitation products and in-situ datasets in this prototype system enables us to further
develop a regional, early warning tool in the future for predicting rainfall-induced landslides in Indonesia. 相似文献
714.
The distribution and dynamics of water molecules and monovalent cations (Li+, Na+, K+, Cs+, and H3O+) on muscovite surfaces were investigated by molecular dynamics (MD) simulations. The direct comparison of calculated X-ray reflectivity profiles and electron density profiles with experiments revealed the precise structure at the aqueous monovalent electrolyte solutions/muscovite interface. To explain the experimentally observed electron density profiles for the CsCl solution-muscovite interface, the co-adsorption of Cs+ and Cl− ion pairs would be necessary. Two types of inner-sphere complexes and one type of outer-sphere complex were observed for hydrated Li+ ions near the muscovite surface. For Na+, K+, Cs+, and H3O+ ions, the inner-sphere complexes were stable on the muscovite surface. The density oscillation of water molecules was observed to approximately 1.5 nm from the muscovite surface. The number of peaks and the locations for the density of water oxygen atoms were almost similar among the water molecules coordinated to Li+, Na+, K+, and H3O+ ions adsorbed on the muscovite surfaces. The water molecules around Cs+ ions that were adsorbed to muscovite surfaces seemed to avoid coordinating with Cs+ ions on the surface, and the density of water oxygen near the muscovite surface decreased relative to that in a bulk state. There was no significant difference in self-diffusion, viscosity, retention time, and reorientation time of water molecules among different cations adsorbed to muscovite surfaces. These translational and rotational motions of water molecules located at less than 1 nm from the muscovite surfaces were slower than those in a bulk state. A significant difference was observed for the exchange times of water molecules around monovalent cations. The exchange time of water molecules was long around Li+ ions and decreased with an increase in the ionic radius. 相似文献
715.
Hiroshi Nagasawa Douglas P. Blanchard Hiroshi Shimizu Akimasa Masuda 《Geochimica et cosmochimica acta》1982,46(9):1669-1673
Concentrations of rare-earth elements (REE), Sc, Fe, Co, Cr, Na and Ir in the bulk sample and mineral separates of the isotopically unique Allende inclusion, EK 1-4-1, were determined by instrumental neutron activation analysis. REE concentrations were also determined by mass-spectrometric isotope dilution for two density separates.The inclusion showed enrichment of light REE over heavy REE with a positive Yb anomaly, thus showing a tendency to resemble group II fine-grained inclusions in REE abundances, although EK 1-4-1 is a coarse-grained inclusion. High Cr concentrations also indicate group II affinity. However, high Ir (6 ppm) and Sc (105 ppm), and low FeO (1.80%), and Co (13.8 ppm) concentrations in the bulk sample and low Na concentrations in mineral separates show group I affinity.Between melilite and pyroxene fractions, the same samples in which mass-fractionated O isotope ratios were observed (Clayton and Mayeda, 1977), REE, Sc, Co and Fe showed distributions which are substantially different from those observed for “ordinary” Allende type B inclusions. These two minerals do not appear to be in equilibrium with respect to trace element distributions.The results indicate that the isotopically unique EK 1-4-1 is also unusual in its elemental abundances and distributions. 相似文献
716.
Air-Sea Interaction, Coastal Circulation and Primary Production in the Eastern Arabian Sea: A Review
Air-sea interaction, coastal circulation and primary production exhibit an annual cycle in the eastern Arabian Sea (AS). During
June to September, strong southwesterly winds (4∼9 m s−1) promote sea surface cooling through surface heat loss and vertical mixing in the central AS and force the West India Coastal
Current equatorward. Positive wind stress curl induced by the Findlater jet facilitates Ekman pumping in the northern AS,
and equatorward-directed alongshore wind stress induces upwelling which lowers sea surface temperature by about 2.5°C (compared
to the offshore value) along the southwestern shelf of India and enhances phytoplankton concentration by more than 70% as
compared to that in the central AS. During winter monsoon, from November to March, dry and weak northeasterly winds (2–6 m
s−1) from the Indo-China continent enhance convective cooling of the upper ocean and deepen the mixed layer by more than 80 m,
thereby increasing the vertical flux of nutrients in the photic layer which promotes wintertime phytoplankton blooms in the
northern AS. The primary production rate integrated for photic layer and surface chlorophyll-a estimated from the Coastal
Zone Color Scanner, both averaged for the entire western India shelf, increases from winter to summer monsoon from 24 to 70
g C m−2month and from 9 to 24 mg m−2, respectively. Remotely-forced coastal Kelvin waves from the Bay of Bengal propagate into the coastal AS, which modulate
circulation pattern along the western India shelf; these Kelvin waves in turn radiate Rossby waves which reverse the circulation
in the Lakshadweep Sea semiannually. This review leads us to the conclusion that seasonal monsoon forcing and remotely forced
waves modulate the circulation and primary production in the eastern AS.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
717.
Hiroshi Takeda 《Journal of Oceanography》1984,40(5):349-366
General characteristics of topographically trapped subinertia waves are discussed from the viewpoint of an eigenvalue problem and ray theory. Special attention is paid to the slope parameterS(x) (=(dh/dx)/h, wherex denotes the coordinate perpendicular to the shoreline, increasing seaward, andh(x) is the depth) which is a measure of the strength of the restoring force of the waves. Three cases for theS distribution are considered, in whichS is assumed to be positive at the coast and to tend to zero far from the coast. The first is whereS(x) decreases monotonically towards the open ocean. It is found in this case that waves are trapped near the coast. The second is whereS(x) does not decrease monotonically, but has a maximum. It is concluded that this case may contain two types of waves, i.e., those trapped near the coast and those trapped near the maximum, and the dispersion curves corresponding to different types may nearly intersect, namely, result in “kissing”. The third is whereS(x) has a negative region (corresponding to the presence of a trench). It is found in this case that an infinite sequence of waves is trapped in the negativeS region which propagate with the coast to their left (right) in the northern (southern) hemisphere besides the waves trapped near the coast. The topography in the second case corresponds to a typical continental shelf and a typical continental slope. It is shown by model calculation that trapped waves are present over the continental slope as well as over the continental shelf. Almost the same results are obtained for superinertia waves ifS is replaced by 1/h which is a measure of the restoring force of superinertia waves. 相似文献
718.
Shi Xiaoyong Wang Xiulin Han Xiurong Jiang Yu Zhu Mingyuan Chen Shang Koshikawa Hiroshi 《海洋学报(英文版)》2001,20(2):231-240
~IOXWith economic development and consumer demand, oil pollutants have been one of themain marine pollutants in the coastal regal Of China. The oil-contaminated area incrsharply to 69% in 1995 and its average criterion index reached up to 2. 17 in the ChangjiangEstuary (NBEP, 1996). TO assess the influences Of the oil POllutants on the marine ~tern, it is neceSSary to develOP a mathematical kinetic model of the tranSport, distribution andfate in the marine ~teln, espeCially to esthate … 相似文献
719.
Spatial Heterogeneity in Distributions of Chlorophyll a Derivatives in the Subarctic North Pacific during Summer 总被引:1,自引:1,他引:1
The distribution of chlorophyll a derivatives was examined in samples collected from the subarctic North Pacific during July to September 1997. Pheophorbide a, pheophytin a and pyropheophorbide a as determined by high performance liquid chromatography (HPLC) were the major derivatives recorded. The distribution patterns of chlorophyll a and its derivatives showed a strong vertical and horizontal heterogeneity. Patches with high concentration of derivatives seemed to be associated with high concentration of chlorophyll a. A clear east-west gradient was observed in both chlorophyll a and pheophorbide a integrated from the surface to 100 m depth with significantly higher amounts of both the pigments in the Western Subarctic Gyre and in the Bering Sea than in the Alaskan Gyre. In contrast, no apparent gradient was observed in the integrated pyropheophorbide a and pheophytin a. Grazing experiments conducted with the copepod (Neocalanus cristatus) and salp (Cyclosalpa bakeri) fed on five species of phytoplankton cultures, showed a marked difference in the composition of the derivatives in their fecal pellets. Pyropheophorbide a was dominant in the copepod fecal pellet regardless of the phytoplankton species fed on. In the salp, however, pheophytin a and pheophorbide a were found in the fecal pellets, the relative concentrations varying with the algal food. Spatial heterogeneity in the distribution of the derivatives is considered to reflect local variations in dominant herbivorous processes. 相似文献
720.
Jianyu Hu Hiroshi Kawamura Huasheng Hong Fumiaki Kobashi Dongxiao Wang 《Journal of Oceanography》2001,57(1):69-78
Sea surface height (SSH) variations with a period of 36 months (SSH36 variations) in the South China Sea (SCS) and its adjacent ocean are intensively investigated using six years of TOPEX/POSEIDON-derived SSH data. The results show that there appears higher energy of SSH36 variations in the east of the Luzon Strait and in some areas of the SCS, both of which are correlated with each other. The SSH36 variations usually propagate westward in the subtropical region of the northern Pacific Ocean and turn northward in the east of the Luzon Strait while they sometimes propagate into the SCS through the Luzon Strait with the phase speed of about 11–12 cm/s, which may be considered as Rossby waves. It can be inferred that the SSH36 variations are strongly associated with current structures and eddies in the SCS because of their significant intensiveness. The SSH variations with the period of 6 months are more dominant than those with the other periods in the SCS. 相似文献