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1.
Cu-bearing pyroxene, Mg(Cu.56,Mg.44)Si2O6, has been synthesized by a flux method and crystal structure refinement has been performed by single crystal X-ray diffraction. It is found that the crystal structure is orthorhombic (space group Pbca) with unit cell dimensions of a=18.221(4), b=8.890(1), c=5.2260(7)Å and the cell volume of 846.5( )3Å3. In the M2-site one of the M-O bonds(M-O3B) is extremely expanded from 2.444(2) in enstatite to 2.732(2), thus the coordination polyhedron around M2-site is regarded as square pyramidal rather than square planar or octahedral. It is also found that the M1-site in the pyroxene structure is occupied almost exclusively by Mg, while the M2-site is almost evenly occupied by Mg and Cu. The observed extreme site preference shown by Cu2+ is unusual among the divalent cations with similar ionic sizes. 相似文献
2.
Toshihiko Yajima Hideo Higuchi Hiroshi Nagasawa 《Contributions to Mineralogy and Petrology》1972,35(3):235-244
The abundances of rare earth elements in 5 each of aphyric volcanic rocks of pigeonitic and hypersthenic rock series from Izu-Hakone region have been determined by neutron activation analysis. Pigeonitic rock series show rare earth patterns with relative depletion of lighter rare earths (low lanthanum type) and large increase in rare earth abundances with differentiation. Hypersthenic rock series show higher lanthanum abundances (high lanthanum type) compared with pigeonitic rock series. The differences in rare earth patterns between two rock series are compatible with the theory of independent magmatic generation of these two series. Variation of rare earth patterns in both series have been examined by a model of magmatic differentiation based on the observed rare earth partition coefficients. 相似文献
3.
Diffusion coefficients of Co2+ and Ni2+ in synthetic single crystal forsterite along the c-axis were determined in the temperature ranges, 700–1200?°C and 800–1300?°C, respectively. The synthesized forsterite specimens were coated with thin evaporated films of CoO and NiO on the c-surface and annealed for diffusion experiments. The short penetration distance of diffusing ions in forsterite was measured by secondary ion mass spectrometry using the depth profile method. The diffusion coefficients of Co (700–1200?°C) and Ni (800–1300?°C) are given by: and The observed diffusion coefficient values show good linear relationships in Arrhenius plots and the activation energy values obtained agree well with the previous values, although the diffusion coefficient values observed at the high temperature end of the experimental range deviate from the previous values. These results indicate that Co and Ni diffuse in olivine with a single mechanism within the temperature range observed, possibly with an extrinsic in nature as in the case of Mg tracer diffusion observed by Chakraborty et?al. 1994 and of Fe-Mg interdiffusion by Chakraborty. 相似文献
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Hiroshi Nagasawa Douglas P Blanchard Jeffrey W Jacobs Joyce C Brannon John A Philpotts Naoki Onuma 《Geochimica et cosmochimica acta》1977,41(11):1587-1600
Concentrations of the REE, Sc, Co, Fe, Zn, Ir, Na and Cr were determined by instrumental neutron activation and mass spectrometric isotope dilution analysis for mineral separates of the coarseand fine-grained types (group I and II of Martin and Mason's classification) of the Allende inclusions.These data, combined with data on mineral/liquid partition coefficients, oxygen isotope distributions and diffusion calculations, suggest the following: (1) Minerals in the coarse-grained inclusions (group I) crystallized in a closed system with respect to refractory elements. On the other hand, differences in oxygen isotope distributions among minerals preclude a totally molten stage in the history of the inclusion. Group I inclusions were formed by rapid condensation (either to liquid or solid) in a supercooled solar nebula; extrasolar pyroxene and spinel dust were included but not melted in the condensing inclusions, thus preserving their extrasolar oxygen isotope composition. REE were distributed by diffusion during the subsequent heating at subsolidus temperatures; because oxygen diffuses much more slowly at these temperatures, the oxygen isotope anomalies were preserved. (2) The fine-grained (group II) inclusions were also formed by condensation from a super-cooled nebular gas; however, REE-rich clinopyroxene and spinel were formed early and REE-poor sodalite and nepheline were formed later and mechanically mixed with clinopyroxene and spinel to form the inclusions. The REE patterns of the bulk inclusions and the mineral separates are fractionated, indicating that REE abundances in the gaseous phase were already fractionated at the time of condensation of the minerals. (3) Pre-existing Mg isotope anomalies in the coarse-grained inclusions must have been erased during the heating stage thus resetting the 26Al-26Mg chronometer. 相似文献
8.
Motoo Ito Hiroshi Nagasawa Hisayoshi Yurimoto 《Meteoritics & planetary science》2006,41(12):1871-1881
Abstract— The measurements of magnesium and potassium isotopic compositions of refractory minerals in Allende calcium‐aluminum‐rich inclusions (CAIs), 7R‐19–1, HN3–1, and EGG3 were taken by secondary ion mass spectrometry (SIMS). The 7R‐19–1 contains 16O‐rich and 16O‐poor melilite grains and define a single isochron corresponding to an initial 26Al/27Al ratio of (6.6 ± 1.3) × 10?5. The Al‐Mg isochron, O isotope measurements and petrography of melilite in 7R‐19–1 indicate that 16O‐poor melilite crystallized within 0.4 Myr after crystallization of 16O‐rich melilite, suggesting that oxygen isotopic composition of the CAI‐forming region changed from 16O‐rich to 16O‐poor within this time interval. The 16O‐poor melilite is highly depleted in K compared to the adjacent 16O‐rich melilite, indicating evaporation during remelting of 7R‐19–1. We determined the isochron for 41Ca‐41K isotopic systematics in EGG3 pyroxene with (4.1 ± 2.0) × 10?9 (2s?) as an initial ratio of 41Ca/40Ca, which is at least two times smaller than the previous result (Sahijipal et al. 2000). The ratio of 41Ca/40Ca in the EGG3 pyroxene grain agrees within error with the value obtained by Hutcheon et al. (1984). No evidence for the presence of 41K excess (decay product of a short‐lived radionuclide 41Ca) was found in 7R‐19–1 and HN3–1. We infer that the CAI had at least an order of magnitude lower than canonical 41Ca/40Ca ratio at the time of the CAI formation. 相似文献
9.
The aim of this study was to evaluate total mercury concentration and its lithogenic and exogenic fractions in some calcareous soils of western Iran, where water contamination and bioaccumulation of mercury have been reported in the bottomland’s reservoir. In particular, we investigated soil physico-chemical properties and weathering conditions related to lithogenic and exogenic fractions of mercury for two groups of calcareous soils with a known comparative pedological evolution and weathering condition that was evident in the presence or absence of underlying layers of accumulated clay. Our results showed that the total mercury content of the studied soils ranged from 45.40 to 830.36 with a mean of 486.81 μg kg?1. Furthermore, calculation of mercury fractions revealed that lithogenic and exogenic fractions vary slightly according to the three reference elements (Fe, U and Nb) used in the calculations for the two groups of studied soils. The results also illustrated that most of the mercury content is of exogenic origin; therefore, total mercury variations are closely related to the content of exogenic mercury, while the lithogenic fraction exhibited no relationship with total mercury concentration. Moreover, application of the weathering indexes of Parker and the CaO/ZrO2 molar ratio supported the dependence of lithogenic mercury accumulation on weathering intensity in the studied calcareous soils. However, the significance of this relationship is stronger for more weathered calcareous soils; in such cases, fine-particle fractions are more developed, which encourages carrier phases such as organic materials and iron oxyhydroxides to become involved in more efficient fixation of mercury. Nevertheless, the formation of underlying layers of accumulated clay, i.e. argillic horizons, may restrain fixation of exogenic mercury by limiting its atmospheric input. 相似文献
10.
Masaji Matsuyama Makiko Wadaka Taizo Abe Masaaki Aota Yoshio Koike 《Journal of Oceanography》2006,62(2):197-205
ADCP, CTD and XBT observations were conducted to investigate the current structure and temperature, salinity and density distributions
in the Soya Warm Current (SWC) in August, 1998 and July, 2000. The ADCP observations clearly revealed the SWC along the Hokkaido
coast, with a width of 30–35 km and an axis of maximum speed of 1.0 to 1.3 ms−1, located at 20–25 km from the coast. The current speed gradually increased from the coast to a maximum and steeply decreased
in the offshore direction. The SWC consisted of both barotropic and baroclinic components, and the existence of the baroclinic
component was confirmed by both the density front near the current axis and vertical shear of the alongshore current. The
baroclinic component strengthened the barotropic component in the upper layer near the axis of the SWC. The volume transport
of the SWC was 1.2–1.3 SV in August, 1998 and about 1.5 SV and July, 2000, respectively. Of the total transport, 13 to 15%
was taken up by the baroclinic component. A weak southeastward current was found off the SWC. It had barotropic characteristics,
and is surmised to be a part of the East Sakhalin Current. 相似文献