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11.
Segregation of incompatible elements at grain interfaces may have considerable influence on the physical and chemical properties of mantle rocks. Using a recently developed predictive model to estimate the interface enrichment of elements based on their mineral/melt partitioning (Hiraga and Kohlstedt, companion paper), we consider interface enrichment for a simplified model peridotite consisting of olivine, orthopyroxene, and clinopyroxene. Our calculated results reveal the following: (1) Significant amounts of heavy alkali elements and rare gases likely reside at grain-grain interfaces, whereas interface concentrations of less incompatible are less pronounced. (2) The contribution of the chemical components stored at interfaces to whole-rock chemistry strongly depends on mineral mode and, most importantly, on grain size. (3) Grain size reduction resulting from dynamic recrystallization can increase the total storage of highly incompatible elements on grain interfaces and thereby will diminish their concentration in mineral grains. (4) Analysis of Cs concentrations in mantle clinopyroxenes potentially provides estimates of the grain size of mantle rocks. (5) Transport through peridotite will be dominated by diffusion along interfaces rather than through grain interiors for elements less compatible than Lu. 相似文献
12.
The system CaMgSi2O6CaAl2SiO6CaFeAlSiO6 has been studied in air at 1 atm. The phase assemblage at subsolidus temperatures in the CaMgSi2O6-rich portion is Cpx + An + Mel and that in the CaMgSi2O6-poor portion Cpx + An + Mel + Sp. At subsolidus temperatures the sigle-phase field of clinopyroxene increases with an increase in the CaFeAlSiO6 component of the system. The Al2O3 content of clinopyroxene, however, continues to increase beyond the single-phase field and attains at least 16.04 wt.% Al2O3 with 3.9 wt.% Fe2O3. The stability field of fassaite in the system over a range of pressures and oxygen fugacities has been estimated from data in the literature as well as the present data. The CaFeAlSiO6 content of fassaite is dependent on oxygen fugacity, but is not influenced by pressure. The stability field is strongly influenced by oxygen fugacity at low and high pressure, and decreases with decreasing oxygen fugacity. Clinopyroxenes in both volcanic and metamorphic rocks from various localities, when plotted on the CaMgSi2O6CaAl2SiO6CaFeAlSiO6 triangle, show that there is no compositional gap between diopside and fassaitic pyroxene in metamorphic rocks, and that the fassaitic pyroxene in alkalic rocks becomes richer in both CaAl2SiO6 and CaFeAlSiO5 components as crystallization proceeds. These results agree with those obtained in the experimental study. 相似文献
13.
Bulletin of Volcanology - The possibility of formation of nephelinite magma from picrite magma by separation of eclogitic fraction is discussed from experimental results on some picritic rocks.... 相似文献
14.
Takehiko Yagi Yoshiaki Ida Yosiko Sato Syun-Iti Akimoto 《Physics of the Earth and Planetary Interiors》1975,10(4):348-354
The pressure dependence of the three lattice parameters and unit cell volume of fayalite (Fe2SiO4 olivine) was determined by X-ray diffraction under hydrostatic pressures up to 70 kbar. In order to eliminate stress inhomogeneity within a composite material consisting of a specimen mixed with an internal-pressure standard, a liquid (1 : 1 mixture of ethanol and methanol) was used as a pressure-transmitting medium. The isothermal bulk modulus calculated on the basis of the second-order Birch-Murnaghan equation of state gives the values K0 = 1.19 ± 0.10 Mbar and K0′ = 7 ± 4, and if we assume K0′ = 5: K0 = 1.24 ± 0.02 Mbar. Three axes of fayalite were found to be compressible in the following order, b >c >a. Comparisons with the results obtained under non-hydrostatic compression are made. 相似文献
15.
The behaviour of tetrahedrally coordinated and octahedrally coordinated Cr3+ ions in diopside is discussed from the study on the join CaMg-Si2O6-CaCrCrSiO6. The molecule CaCrCrSiO6 decomposes into uvarovite+eskolaite and its maximum solubility in diopside is 6.7 wt percent at 940 ° C. Crystalline phases are diopside ss (ss is abbreviation of solid solution), uvarovite ss, wollastonite ss, spinel and eskolaite. The diopside ss is blue in colour. Its optical spectra were measured in the wavelenght range of 325–2600 nm, and assigned after tetrahedral configuration Td and octahedral configuration Oh. It is estimated that octahedral Cr3+ ions are in high spin state, while tetrahedral Cr3+ ions may be probably in low spin state. The t and B are 10,300–10,370 cm–1 and 429–432 cm–1. The CFSE for tetrahedral low spin Cr3+ ions is nearly the same as that for octahedral high spin Cr3+ ions. The ionic radii of tetrahedral low spin Cr3+ ions calculated are 0.47–0.53 Å, shrinked from the radius of octahedral high spin Cr3+ ion (0.615 Å) as much as 14–24 percent. Petrologic implications of the result are also discussed.The first half of the D. Sc. dissertation of K. Ikeda presented to Hokkaido University in June, 1976 相似文献
16.
Sanae Koizumi Takehiko Hiraga Chihiro Tachibana Miki Tasaka Tomonori Miyazaki Tamio Kobayashi Asako Takamasa Naoki Ohashi Satoru Sano 《Physics and Chemistry of Minerals》2010,37(8):505-518
Synthesized mineral powders with particle size of <100 nm are vacuum sintered to obtain highly dense and fine-grained polycrystalline
mantle composites: single phase aggregates of forsterite (iron-free), olivine (iron containing), enstatite and diopside; two-phase
composites of forsterite + spinel and forsterite + periclase; and, three-phase composites of forsterite + enstatite + diopside.
Nano-sized powders of colloidal SiO2 and highly dispersed Mg(OH)2 with particle size of ≤50 nm are used as chemical sources for MgO and SiO2, which are common components for all of the aggregates. These powders are mixed with powders of CaCO3, MgAl2O4, and Fe(CO2CH3)2 to introduce mineral phases of diopside, spinel, and olivine to the aggregates, respectively. To synthesize highly dense
composites through pressureless sintering, we find that calcined powders should be composed of particles that have: (1) fully
or partially reacted to the desired minerals, (2) a size of <100 nm and (3) less propensity to coalesce. Such calcined powders
are cold isostatically pressed and then vacuum sintered. The temperature and duration of the sintering process are tuned to
achieve a balance between high density and fine grain size. Highly dense (i.e., porosity ≤1 vol%) polycrystalline mantle mineral
composites with grain size of 0.3–1.1 μm are successfully synthesized with this method. 相似文献
17.
Geochemical study of arsenic and other trace elements in groundwater and sediments of the Old Brahmaputra River Plain,Bangladesh 总被引:1,自引:1,他引:0
Faruque Ahmed M. Hawa Bibi Hiroaki Ishiga Takehiko Fukushima Teruyuki Maruoka 《Environmental Earth Sciences》2010,60(6):1303-1316
The geochemical study of groundwaters and core sediments from the Old Brahmaputra plain of Bangladesh was conducted to investigate
the distribution of arsenic and related trace elements. Groundwaters from tube wells are characterized by pH of 6.4–7.4, dissolved
oxygen (DO) of 0.8–1.8 mg/l, Ca contents of 5–50 mg/l, and Fe contents of 0.2–12.9 mg/l. Arsenic concentrations ranged from
8 to 251 μg/l, with an average value of 63 μg/l. A strong positive correlation exists between As and Fe (r
2 = 0.802; p = 0.001) concentrations in groundwater. The stratigraphic sequences in the cores consist of yellowish silty clays at top,
passing downward into grayish to yellowish clays and sands. The uppermost 3 m and lower parts (from 13 to 31 m) of the core
sediments are oxidized (average oxidation reduction potential (ORP) +170 and +220 mV, respectively), and the ORP values gradually
become negative from 3 to 13 m depths (−35 to −180 mV), indicating that anoxic conditions prevail in the shallow aquifers
of the Brahmaputra plain. Age determinations suggest that clay horizons at ~10 m depth were deposited at around 2,000 and
5,000 years BP (14C ages) during the transgressive phase of sea-level change. Elevated concentrations of As, Pb, Zn, Cu, Ni, Cr, and V are present
in the silts and clays, probably due to adsorption onto clay particles. Significant concentrations of As occur in black peat
and peaty sediments at depths between 9 and 13 m. A strong positive correlation between As and Fe was found in the sediments,
indicating As may be adsorbed onto Fe oxides in aquifer sediments. 相似文献
18.
Akira Yamaguchi Takehiko Setoyanagi Mitsuru Ebihara 《Meteoritics & planetary science》2006,41(6):863-874
Abstract— We studied the texture, mineralogy, and bulk chemical composition of Dhofar 007, a basaltic achondrite. Dhofar 007 is a polymict breccia that is mostly composed of coarse‐grained granular (CG) clasts with a minor amount of xenolithic components, such as a fragment of Mg‐rich pyroxene. The coarse‐grained, relict gabbroic texture, mineral chemistry, and bulk chemical data of the coarse‐grained clast indicate that the CG clasts were originally a cumulate rock crystallized in a crust of the parent body. However, in contrast to monomict eucrites, the siderophile elements are highly enriched and could have been introduced by impact events. Dhofar 007 appears to have experienced a two‐stage postcrystallization thermal history: rapid cooling at high temperatures and slow cooling at lower temperatures. The presence of pigeonite with closely spaced, fine augite lamellae suggests that this rock was cooled rapidly from higher temperatures (>0.5 °C/yr at ˜1000 °C) than typical cumulate eucrites. However, the presence of the cloudy zone in taenite and the Ni profile across the kamacite‐taenite boundaries indicates that the cooling rate was very slow at lower temperatures (˜1–10 °C/Myr at <600–700 °C). The slow cooling rate is comparable to those in mesosiderites and pallasites. The two‐stage thermal history and the relative abundance of siderophile elements similar to those for metallic portions in mesosiderites suggest that Dhofar 007 is a large inclusion of mesosiderite. However, we cannot rule out a possibility that Dhofar 007 is an anomalous eucrite. 相似文献
19.
Asami Sano-Furukawa Takehiko Yagi Taku Okada Hirotada Gotou Takumi Kikegawa 《Physics and Chemistry of Minerals》2012,39(5):375-383
X-ray diffraction measurements of distorted rutile-type oxyhydroxides β-GaOOH, InOOH, β-CrOOH, and β-CrOOD were taken at a
maximum pressure of up to 35 GPa under quasi-hydrostatic conditions, at ambient temperature. Anomalies in the evolution of
the relative lattice constants and the axial ratios of β-GaOOH, InOOH, and β-CrOOD suggest anisotropic stiffening along the
a- and/or b-axes where the hydrogen bond is formed. The changes were observed at 15 GPa in β-GaOOH and InOOH and at 4 GPa in β-CrOOD.
The pressures were higher in oxyhydroxides that have longer O…O distances of the hydrogen bond at ambient pressure. In contrast,
such stiffening behavior was not observed in CrOOH, which has a significant short O…O distance and strong hydrogen bond. The
stiffening behaviors observed in the present study can be attributed to the symmetrization of the hydrogen bonds in oxyhydroxides,
as was previously found in δ-AlOOH(D). 相似文献
20.
Ken?NiwaEmail author Takehiko?Yagi Kenya?Ohgushi 《Physics and Chemistry of Minerals》2011,38(1):21-31
Compression behaviors of CaIrO3 with perovskite (Pv) and post-perovskite (pPv) structures have been investigated up to 31.0(1.0) and 35.3(1) GPa at room
temperature, respectively, in a diamond-anvil cell with hydrostatic pressure media. CaIrO3 Pv and pPv phases were compressed with the axial compressibility of β
a > β
c > β
b and β
b > β
a > β
c, respectively and no phase transition was observed in both phases up to the highest pressure in the present study. The order
of axial compressibility for pPv phase is consistent with the crystallographic consideration for layer structured materials
and previous experimental results. On the other hand, Pv phase shows anomalous compression behavior in b axis, which exhibit constant or slightly expanded above 13 GPa, although the applied pressure remained hydrostatic. Volume
difference between Pv and pPv phases was gradually decreased with increasing pressure and this is consistent with the results
of theoretical study based on the ab initio calculation. Present results, combined with theoretical study, suggest that these
complicate compression behaviors in CaIrO3 under high pressure might be caused by the partially filled electron of Ir4+. Special attention must be paid in case of using CaIrO3 as analog materials to MgSiO3, although CaIrO3 exhibits interesting physical properties under high pressure. 相似文献