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11.
Hidetoshi Asanuma Eiji Ohtani Takeshi Sakai Hidenori Terasaki Seiji Kamada Tadashi Kondo Takumi Kikegawa 《Physics and Chemistry of Minerals》2010,37(6):353-359
The melting temperature of Fe–18 wt% Si alloy was determined up to 119 GPa based on a change of laser heating efficiency and
the texture of the recovered samples in the laser-heated diamond anvil cell experiments. We have also investigated the subsolidus
phase relations of Fe–18 wt% Si alloy by the in-situ X-ray diffraction method and confirmed that the bcc phase is stable at
least up to 57 GPa and high temperature. The melting curve of the alloy was fitted by the Simon’s equation, P(GPa)/a = (T
m(K)/T
0)
c
, with parameters, T
0 = 1,473 K, a = 3.5 ± 1.1 GPa, and c = 4.5 ± 0.4. The melting temperature of bcc Fe–18 wt% Si alloy is comparable with that of pure iron in the pressure range
of this work. The melting temperature of Fe–18 wt% Si alloy is estimated to be 3,300–3,500 K at 135 GPa, and 4,000–4,200 K
at around 330 GPa, which may provide the lower bound of the temperatures at the core–mantle boundary and the inner core–outer
core boundary if the light element in the core is silicon. 相似文献
12.
Survival of a proto-atmosphere through the stage of giant impacts: the mechanical aspects 总被引：2，自引：0，他引：2
When a giant impact occurs, atmosphere loss may occur due to global ground motion excited by a strong shock wave traveling in the planetary interior. Here, the relations between the ground motion and the amount of the lost atmosphere are systematically investigated through calculations of a spherically one-dimensional atmospheric motion for various initial atmospheric conditions. The fraction of the lost atmosphere to the total mass of the atmosphere is found to be controlled only by the ground velocity and, insensitive to the initial atmospheric conditions. Unlike the previous studies (Ahrens, 1990, Origin of the Earth, H.E. Newson, J.H. Jones (Eds.), pp. 211-227; Ahrens, 1993, Annu. Rev. Earth Planet. Sci. 21, 525-555; Chen and Ahrens, 1997, Phys. Earth Planet. Inter. 100, 21-26); the estimated loss fraction for the giant impact is only 20%. Significant escape occurs only when the ground velocity is close to the escape velocity. Thus, most of the atmosphere should survive the giant impact. The cause of the difference from previous estimates is discussed from energetic and dynamic points of view. Moreover, if our estimates are applied to the atmosphere of the impactor planet, a significant fraction of it is carried to the target planet. Survival of the proto-atmosphere has very important effects on the origin and evolution of the terrestrial planets' volatile budget. 相似文献
13.
Yuki Shibazaki Eiji Ohtani Hidenori Terasaki Ryuji Tateyama Tatsuya Sakamaki Taku Tsuchiya Ken-ichi Funakoshi 《Earth and Planetary Science Letters》2011,301(1-2):153-158
We have carried out in situ X-ray diffraction experiments on the FeS–H system up to 16.5 GPa and 1723 K using a Kawai-type multianvil high-pressure apparatus employing synchrotron X-ray radiation. Hydrogen was supplied to FeS from the thermal decomposition of LiAlH4, and FeSHx was formed at high pressures and temperatures. The melting temperature and phase relationships of FeSHx were determined based on in situ powder X-ray diffraction data. The melting temperature of FeSHx was reduced by 150–250 K comparing with that of pure FeS. The hydrogen concentration in FeSHx was determined to be x = 0.2–0.4 just before melting occurred between 3.0 and 16.5 GPa. It is considered that sulfur is the major light element in the core of Ganymede, one of the Galilean satellites of Jupiter. Although the interior of Ganymede is differentiated today, the silicate rock and the iron alloy mixed with H2O, and the iron alloy could react with H2O (as ice or water) or the hydrous silicate before the differentiation occurred in an early period, resulting in a formation of iron hydride. Therefore, Ganymede's core may be composed of an Fe–S–H system. According to our results, hydrogen dissolved in Ganymede's core lowers the melting temperature of the core composition, and so today, the core could have solid FeSHx inner core and liquid FeHx–FeSHx outer core and the present core temperature is considered to be relatively low. 相似文献
14.
In order to determine the maintenance mechanisms of the currents of the global ocean, this study investigates the budget of
the annual mean kinetic energy (KE) in a high-resolution (0.1° × 0.1°) semi-global ocean simulation. The analysis is based
on a separation of the mean KE using the barotropic (i.e., depth-averaged) and baroclinic (the residual) components of velocity.
The barotropic and baroclinic KEs dominate in higher and lower latitudes, respectively, with their global average being comparable
to each other. The working rates of wind forcing on the barotropic and baroclinic circulations in the global ocean are 243
and 747 gigawatts, respectively. This study presents at least three new results for the budget of the barotropic KE. Firstly,
an energy diagram is rederived to show that the work of the barotropic component of the horizontal pressure gradient (HPG)
is connected to the work related to the joint effect of baroclinicity and bottom relief (JEBAR), and then to the budget of
potential energy (PE). Secondly, the model analysis shows that the globally averaged work of the barotropic HPG (which is
connected to the work related to JEBAR and then to the budget of the PE) is nearly zero. This indicates that the wind- and
buoyancy-induced barotropic circulations in the global ocean are of the same strength with opposite sign. Thirdly, it is found
that the work of the wind forcing on the barotropic component of the simulated Antarctic Circumpolar Current (ACC) is canceled
by the combined effect, in equal measure, of the work of the barotropic HPG and the work of dissipative processes for mean
KE. This result makes a significant contribution to the discussion on the depth-integrated momentum balance of the ACC. The
barotropic KE is dissipated by the effects of bottom frictional stress, lateral frictional stress, and the Reynolds stress,
of which more than half is attributed to an unexpectedly large contribution from biharmonic horizontal friction. Future studies
should pay more attention to the role of biharmonic friction used in high-resolution numerical models. 相似文献
15.
Ryuji Tateyama Eiji Ohtani Hidenori Terasaki Keisuke Nishida Yuki Shibazaki Akio Suzuki Takumi Kikegawa 《Physics and Chemistry of Minerals》2011,38(10):801-807
The compositional dependence on the density of liquid Fe alloys under high pressure is important for estimating the amount
of light elements in the Earth’s outer core. Here, we report on the density of liquid Fe–Si at 4 GPa and 1,923 K measured
using the sink–float method and our investigation on the effect of the Si content on the density of the liquid. Our experiments
show that the density of liquid Fe–Si decreases from 7.43 to 2.71 g/cm3 non-linearly with increasing Si content (0–100 at%). The molar volume of liquid Fe–Si calculated from the measured density
gradually decreases in the compositional range 0–50 at% Si, and increases in the range 50–100 at% Si. It should be noted that
the estimated molar volume of the alloys shows a negative volume of mixing between Fe and Si. This behaviour is similar to
Fe–S liquid (Nishida et al. in Phys Chem Miner 35:417–423, 2008). However, the excess molar volume of mixing for the liquid Fe–Si is smaller than that of liquid Fe–S. The light element
contents in the outer core estimated previously may be an underestimation if we take into account the possible negative value
of the excess mixing volume of iron–light element alloys in the outer core. 相似文献
16.
Abstract We study the formation of lenses of the ocean's intermediate water using a 2.5-layerβ-plane primitive equation model with localized injection of water mass. For the injecting rate of 1.0 Sv, we have observed that strong vortices are shed regularly. These vortices propagate westward much faster than the second baroclinic long Rossby wave. They are totally isolated from each other and show strong baroclinicity as well. Moreover, they remain stable over a sufficiently long period of time. Regular formation of such strong vortices in the intermediate layer has not been reported previously. The translation speed is explained using the Euler's momentum integral theorem for the nonlinear baroclinic vortex on the β-plane. We have demonstrated that coupling between the primary motion in the intermediate layer and the secondary motion in the upper layer with a meridional shift is crucial to the fast westward translation of the intense vortices. A simple dispersion formula relating the zonal translation speed with the vortex radius is also derived under the assumption of quasi-geostrophy. It has turned out that the analytical relation explains the numerical results surprisingly well despite the limitation of its derivation. 相似文献
17.
Thermal anomaly around the Nojima Fault as detected by fission-track analysis of Ogura 500 m borehole samples 总被引：1，自引：0，他引：1
Abstract To better understand heat generation and transfer along earthquake faults, this paper presents preliminary zircon fission-track (FT) length data from the Nojima Fault, Awaji Island, Japan, which was activated during the 1995 Kobe earthquake (Hyogo-ken Nanbu earthquake). Samples were collected of Cretaceous granitic rocks from the Ogura 500 m borehole as well as at outcrops adjacent to the borehole site. The Nojima Fault plane was drilled at a depth of 389.4 m (borehole apparent depth). Fission-track lengths in zircons from localities > 60 m distance from the fault plane, as well as those from outcrops, are characterized by the mean values of ≈10–11 μm and unimodal distributions with positive skewness, which show no signs of an appreciable reduction in FT length. In contrast, those from nearby the fault at depths show significantly reduced mean track lengths of ≈6–8 μm and distributions having a peak around 6–7 μm with rather negative skewness. In conjunction with other geological constraints, these results are best interpreted by a recent thermal anomaly around the fault, which is attributable to heat transfer via focused fluids from the deep interior of the crust and/or heat dispersion via fluids associated with frictional heating by fault motion. 相似文献
18.
Suguru Takahashi Eiji Ohtani Hidenori Terasaki Yoshinori Ito Yuki Shibazaki Miho Ishii Ken-ichi Funakoshi Yuji Higo 《Physics and Chemistry of Minerals》2013,40(8):647-657
The phase and melting relations of the C-saturated C–Mg–Fe–Si–O system were investigated at high pressure and temperature to understand the role of carbon in the structure of the Earth, terrestrial planets, and carbon-enriched extraterrestrial planets. The phase relations were studied using two types of experiments at 4 GPa: analyses of recovered samples and in situ X-ray diffractions. Our experiments revealed that the composition of metallic iron melts changes from a C-rich composition with up to about 5 wt.% C under oxidizing conditions (ΔIW = ?1.7 to ?1.2, where ΔIW is the deviation of the oxygen fugacity (fO2) from an iron-wüstite (IW) buffer) to a C-depleted composition with 21 wt.% Si under reducing conditions (ΔIW < ?3.3) at 4 GPa and 1,873 K. SiC grains also coexisted with the Fe–Si melt under the most reducing conditions. The solubility of C in liquid Fe increased with increasing fO2, whereas the solubility of Si decreased with increasing fO2. The carbon-bearing phases were graphite, Fe3C, SiC, and Fe alloy melt (Fe–C or Fe–Si–C melts) under the redox conditions applied at 4 GPa, but carbonate was not observed under our experimental conditions. The phase relations observed in this study can be applicable to the Earth and other planets. In hypothetical reducing carbon planets (ΔIW < ?6.2), graphite/diamond and/or SiC exist in the mantle, whereas the core would be an Fe–Si alloy containing very small amount of C even in the carbon-enriched planets. The mutually exclusive nature of C and Si may be important also for considering the light elements of the Earth’s core. 相似文献
19.
We report systematic noble gas variation within a regional scale in an area that is well separated from all hotspots surrounding a remarkable ridge-ridge-ridge type triple junction—the Rodriguez Triple Junction of the Indian Ocean. We applied a newly established technique to select basaltic glass samples from the Mid-Oceanic Ridge Basalt (MORB) suite from the studied area. Samples were selected to create regular spacing along the ridge axis for investigating the magma system beneath the ridge axis. All samples show a typical isotope signature as MORB regardless of moderate contributions of an atmospheric component. Remarkably, uniform isotope ratios were found even for Ne and Ar in each segment. Such ratios had not been recognized in any magmatic system in Mid-Oceanic Ridges. Elemental abundances of samples are controlled both by mixing with the atmospheric component and by degassing. Contribution of atmospheric components is controlled strongly by a high temperature reaction caused by equilibration of dissolved noble gases between magma and seawater. Of the three models of the magma system around the Rodriguez Triple Junction, controlled contamination without mechanical mixing in a magma chamber presents the most likely scenario. 相似文献
20.
Properties of the soil surface layer, the temporal pattern of the microclimate variables as well as crop condition were combined to analyze the characteristics of the evapotranspiration from winter wheat fields in a saline soil area. In order to accomplish this analysis, evapotranspiration was divided into evaporation from the soil and transpiration from wheat. Moreover, the effect of soil salinity on evapotranspiration was evaluated through the relationship between actual evapotranspiration and potential evapotranspiration (Ea/Eo) and the total soil water potential (y) was divided into two components: matric potential (yM) and osmotic potential (yo). Two sites with different salinity levels were chosen for this study, located in Hebei Province, China. Measurements were conducted in April-May 1997 and May 1998. The Bowen ratio method was used to estimate the actual evapotranspiration (Ea), whereas potential evapotranspiration (Eo) was estimated using Penman’s equation. Measurements of soil evaporation (Es) were obtained with micro-lysimeters, and transpiration was calculated from the difference between Ea and Es. The results show that transpiration comprised on average almost 80 % of total evapotranspiration. Evaporation from the soil differed slightly between years, but this variation was dominated by the leaf area index (LAI), which ranged from 4 to 5 during the study period of 1997 and 1998. Soil electric conductivity (EC), which is directly related to osmotic potential, ranged from 1.9 to 3.5 mS cm-1 in 1997 and was negligible in 1998. Our results indicate that lower osmotic potential decreases the total soil water potential, thus affecting plant transpiration. Hence, it is possible to say that soil salinity actually decreases evapotranspiration from winter wheat fields. 相似文献