Meteoric hydrothermal origin of calcites in “Green Tuff” formations,Miocene age,Japan     

Keiko Hattori  Hitoshi Sakai 《Contributions to Mineralogy and Petrology》1980,73(2):145-150

Oxygen and carbon isotope compositions were determined for calcites from the Green Tuff formations of Miocene age in Japan. Values of ¹⁸O from 24 calcites in altered rocks from 5 districts range from –2 to +16_SMOW, in most cases from 0 to +8_SMOW. The low ¹⁸O values rule out the possibility of their low-temperature origin or any significant contribution of magmatic fluid in the calcite precipitation. These values, coupled with their mineral assemblages, suggest that the calcites formed from meteoric hydrothermal solutions which caused propylitic alteration after the submarine strata became emergent.Values of ¹³C from the calcites show a wide variation from –17 to 0_PDB. Calcites from different districts have different ranges of ¹³C values, indicating that there was no homogeneous reservoir of carbon at the time the calcite formed, and that the carbon had local sources. Carbon isotopic compositions of calcite within ore deposits in the Green Tuff formations range from –19 to 0_PDB, similar to those of calcite in the altered rocks in the same district, suggesting that the carbon in ore calcites was likely supplied from the surrounding rocks through activity of meteoric hydrothermal solutions.  相似文献   

Oxygen isotope study of metamorphic and granitic rocks of the Yanai district in the Ryoke belt,Japan     

Hiroji Honma  Hitoshi Sakai 《Contributions to Mineralogy and Petrology》1975,52(2):107-120

¹⁸O/¹⁶O ratios have been obtained for 134 whole-rocks and minerals from metamorphic and granitic rocks of the Yanai district in the Ryoke belt, Southwest Japan. The ¹⁸O/¹⁶O ratios of pelitic rocks of the marginal metamorphic zone decrease progressively with increasing metamorphic grade. In the gneiss-granite complex (zone of migmatite [1]), the most characteristic feature of the rocks is that oxygen isotopic homogenization proceeds on both local and regional scales in parallel with “granitization” or chemical homogenization. Granitic rocks of various origin are fairly uniform in isotopic composition with δ ¹⁸O of quartz of 12 to 14‰ (SMOW) and δ ¹⁸O of biotite of 7 to 9‰ and are about 3 to 4‰ enriched in ¹⁸O compared to other Cretaceous granites of non-metamorphic terranes in Japan. The high ¹⁸O/¹⁶O ratios of granitic rocks of this district were discussed in relation to the ¹⁸O-depletion in metasediments. Oxygen isotopic fractionations among coexisting minerals from various rock-types of the gneiss-granite complex indicate that these minerals were formed under near isotopic equilibrium at a temperature of about 600 to 700° C. Some abnormal fractionations of quartz-biotite pairs also were obtained for rocks which had undergone a progressive ¹⁸O-depletion or ¹⁸O-enrichment. This is due to high resistivity of quartz and contrastive susceptibility of biotite to isotopic exchange during metamorphism and “granitization”.  相似文献   

Hydrogen isotopic fractionation factor between brucite and water in the temperature range from 100° to 510° C     

Satake  Hiroshi  Matsuo  Sadao 《Contributions to Mineralogy and Petrology》1984,86(1):19-24

The hydrogen isotopic fractionation factor between brucite and water has been determined in the temperature range of 100°–510° C. Brucite is always depleted in deuterium relative to the coexisting water, and the degree of depletion becomes larger with decreasing temperature. The fractionation factor changes smoothly in the temperature range of 144°–510° C and its temperature dependence was obtained by the method of least square fit in the following form: 10³In=8.72×10⁶ T ^–2–3.86×10⁴ T ^–1+14.5However, a marked decrease of about 5 was observed at 100°–144° C. The D/H fractionation factor for the brucite-water system is not similar to that for serpentine-water system presented by Sakai and Tsutsumi (1978), though all the hydroxyl ions coordinate to magnesium ion in both minerals. This discrepancy cannot be attributed to hydrogen bonding but to distortion of Mg-octahedron of serpentine, in which the Mg-OH bonding length is shorter than the sum of ionic radius of Mg²⁺ and O^2– and there is no distortion in brucite. It is indicated that aside from hydrogen bonding, the structure effect also controls the D/H fractionation between hydrous mineral and water.  相似文献   

Turbulent Airflow and Wave-Induced Stress Over the Ocean     

Hitoshi Tamura  William M. Drennan  Clarence O. CollinsIII  Hans C. Graber 《Boundary-Layer Meteorology》2018,169(1):47-66

We examine the structure of turbulent airflow over ocean waves. Based on an analysis of wind and wave observations derived from a moored and floating Air–Sea Interaction Spar buoy during the Shoaling Waves Experiment field campaign, we show that the cospectra of momentum flux for wind–sea conditions follow established universal scaling laws. Under swell-dominant conditions, the wave boundary layer is extended and the universal cospectral scaling breaks down, as demonstrated previously. On the other hand, the use of peak wave frequency to reproduce the universal cospectra successfully explains the structure of the turbulent flow field. We quantify the wave-coherent component of the airflow and this clarifies how ocean waves affect momentum transfer through the wave boundary layer. In fact, the estimated wave-induced stresses for swell-dominant conditions explain the anomalous cospectral shapes observed near the peak wave frequency.  相似文献   

Seasonal variation of bromocarbons at Hateruma Island,Japan: implications for global sources     

Yoko Yokouchi  Takuya Saito  Jiye Zeng  Hitoshi Mukai  Stephen Montzka 《Journal of Atmospheric Chemistry》2017,74(2):171-185

High-frequency measurements of dibromomethane (CH₂Br₂) and bromoform (CHBr₃) at Hateruma Island, in the subtropical East China Sea, were performed using automated preconcentration gas chromatography/mass spectrometry. Their baseline concentrations, found in air masses from the Pacific Ocean, were 0.65 and 0.26 ppt, respectively, in summer and 1.08 and 0.87 ppt, respectively, in winter. Air masses transported from Southeast Asia were rich in bromocarbons, suggesting strong emissions in this area. The passage of cold fronts from the Asian continent was associated with sharp increases in observed concentrations of bromocarbons derived from coastal regions of the continent. Comparison of the relationships between [CH₂Br₂]/[CHBr₃] and [CHBr₃] in the Hateruma Island data with those in monthly mean data from 14 globally distributed U.S. National Oceanic and Atmospheric Administration ground stations suggested that these gases are produced primarily from a common process on a global scale.  相似文献   

Factors influencing maintenance and decline of a diatom bloom in the Yatsushiro Sea,Japan     

Goh Onitsuka  Tomoyuki Shikata  Saho Kitatsuji  Kazuo Abe  Takeshi Yamamoto  Hiroki Ochiai  Hitoshi Matsuo 《Journal of Oceanography》2016,72(4):617-627

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Frequency-dependence of velocity and attenuation of elastic waves in granite under uniaxial compression     

Hitoshi Oda  Osamu Nishizawa  Kin'ichiro Kusunose  Takayuki Hirata 《Pure and Applied Geophysics》1990,133(1):73-85

Velocity as well as attenuation factorQ ^–1 ofP-wave in a dry granitic rock sample under uniaxial compressions were measured in the range of frequency between 100 kHz and 710 kHz by using the pulse transmission technique. Above the stress of 0.5 _f , where _f is the fracture stress, theP-wave velocity decreases with increasing axial stress, whereasQ ^–1 increases. Particularly, the change ofQ ^–1 is greater for high frequency than for low frequency. At a given stress level, the higher the frequency, the higher theP-wave velocity and the largerQ ^–1. This result means that the velocity decrease with increasing stress is smaller for higher frequency. Because of this frequency-dependence of velocity decrease, theP-wave in the rock under dilatant state shows dispersion. The body wave dispersion is more remarkable at higher stress, and is not found in a homogeneous material with no cracks. Thus the disperison is attributed to the generation of cracks. When the frequency-dependence ofQ ^–1 is approximated asf ⁿ in the present frequency range, the exponentn takes a value from 0.63 to 0.77.  相似文献   

Wind-dependent formation of phytoplankton spring bloom in Otsuchi Bay,a ria in Sanriku,Japan     

Ken Furuya  Koji Takahashi  Hitoshi Iizumi 《Journal of Oceanography》1993,49(4):459-475

Spring blooms of phytoplankton composed of centric diatoms developed in late February, March, and April in Otsuchi Bay on Sanriku ria coast, Japan. During this period, associated with prolonged seasonal west wind (>1 day), intense exchange of waters occurred between inside and outside the bay: outflow of nearsurface brackish water over inflow of oceanic water at depth. This circulation interrupted formation of the blooms, and transported phytoplankton populations seaward. By such water movements, a significant amount of nutrients in the bay was carried out, otherwise replenished into the bay, depending on water masses located outside the bay. Owing to irregular features of wind events, a bloom lasted from several days to a week. From February to April, supply of nutrients seemed to be replete except for the latter half of the bloom period, and estimates of the critical depth exceeded the depth of the bottom consistently. Thus, net growth of phytoplankton was expected throughout the observation period, and potentially blooms could be formed. However, the blooms were only formed under calm weather. We hypothesize that the exchange of waters dilutes populations in the bay, and that formation of the bloom, that is, accumulation of biomass depends on a balance between the growth of phytoplankton and the dilution of bay water.  相似文献   

Seagrasses from the Nansei Islands, Southern Japanese Archipelago: species composition, distribution and biogeography     

John Kuo  Ziyusei Kanamoto  Hitoshi Iizumi  Keiko Aioi  & Hiroshi Mukai 《Marine Ecology》2006,27(4):290-298

The Nansei Islands in the southern Japanese Archipelago have 15 taxa of seagrasses from seven genera within three families. Seagrasses in this region grow on coral sands or coral debris in shallow reefs and on sandy or muddy substrata in the shallow areas of bays and inlets. Certain Halophila species grow in deep water off some islands. Enhalus acoroides only reaches to Ishigaki I. with winter sea water temperature (WST) at 23 °C, while Okinawa I. (WST at 21.6 °C) is the northern biogeographic limit for Halophila decipiens, H. okinawensis, H. major and H. gaudichaudii. Amami‐oshima I. (WST at 20.7 °C) is the northern border for Thalassia hemprichii, H. minor, H. ovalis, Cymodocea serrulata, Cymodocea rotundata, Syringodium isoetifolium, Halodule uninervis and Halodule pinifolia. Halophila mikii the sole seagrass collected from Yakushima I. (WST at 19.3 °C), is of volcanic origin. The distribution of tropical seagrasses in the Nansei Islands is clearly associated with the warm Kuroshio Current, WST and habitat availability. Zostera japonica is the only temperate species occurring in the region. Meadows of Z. japonica, H. ovalis and Halodule pinifolia have disappeared from certain localities in the Archipelago, due probably to human activities and natural siltation.  相似文献   

Coupling simulation of microbially induced carbonate precipitation and bacterial growth using reaction–diffusion and homogenisation systems     

Nishimura  Ibuki  Matsubara  Hitoshi 《Acta Geotechnica》2021,16(5):1315-1330

Acta Geotechnica - Soil improvement techniques have been developed experimentally and empirically from various geotechnical standpoints based on physical, chemical, and biological findings. The...  相似文献