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31.
Summary A chemical analysis of rhodizite from Manjaka, Madagascar, establishes the new formula CsAl4Be4B11(OH)4O25. Space group P43m; a0 7.317±0.001 Å; density 3.44±0.01 (meas.), 3.47 (calc.); Z=1. The index of refraction, 1.693±0.001 (Na), and the unit cell dimension are identical within the limits state for material from lithia-pegmatites at Manjaka, Antsongombato, Antandrokomby and Ambalalehifotsy, in Madagascar. Hardness 81/2.
Dedicated to ProfessorF. Machatschki on the occasion of his 70th birthday. 相似文献
Zusammenfassung Eine chemische Analyse von Rhodizit an Material von Manjaka, Madagaskar, liefert die neue Formel CsAl4Be4B11(OH)4O25. Raumgruppe P43m, a0=7,317±0,001 Å; Dichte 3,44±0,01 (exp.), 3,47 (ber.); Z=1. Der Brechungsindex, 1,693±0,001 (Na), und die Gitterkonstante sind innerhalb der angegebenen Grenzen für Material von den Lithium-Pegmatiten bei Manjaka, Antsongombato, Antandrokomby und Ambalalehifotsy auf Madagaskar gleich. Härte 81/2.
Dedicated to ProfessorF. Machatschki on the occasion of his 70th birthday. 相似文献
32.
We present a new experimental result of fragment spin-rate in impact disruption, using a thin glass plate. A cylindrical projectile impacts on a side (edge) of the plate. Dispersed fragments are observed using a high-speed camera and the spin rates of fragments are measured. We find that the measured fragment spin-rate decreases with increasing size. Assuming that the rotational energy of fragments is supplied from the residual stress, the spin rate ω decreases with increasing fragment size r as ω∼r−1, which explains the above experimental results. This size-dependence is similar to that of the observed spin rates of small fast-rotating asteroids. Our results suggest that spin rates of fragments of small asteroids immediately after disruption may have a similar size-dependence, and can provide constraints on the subsequent spin-state evolution of small asteroids due to thermal torques. 相似文献
33.
Hiromi Hayashi Eiji Ohtani Hidenori Terasaki Yoshinori Ito 《Geochimica et cosmochimica acta》2009,73(16):4836-4475
Coupled 186Os/188Os and 187Os/188Os enrichments of plume-derived lavas have been suggested to reflect contributions of materials from the outer core (Brandon et al., 1998). This hypothesis is based on the assumption that the Earth’s liquid outer core has high Pt/Os and slightly high Re/Os ratios as a result of the crystallization of the solid inner core, and shows coupled enrichments in the 186Os/188Os and 187Os/188Os ratios, reflecting the decay of 190Pt and 187Re to 186Os and 187Os, respectively. Partitioning experiments of Pt-Re-Os between solid and liquid metal were performed at 5-20 GPa and 1250-1400 °C, to examine the effects of pressure in the Fe-Ni-S system. The ratios (DOs/DPt, DOs/DRe) of measured partition coefficients of Pt, Re and Os are almost constant with increasing pressure. DOs/DPt increases significantly, whereas DOs/DRe decreases, with increasing sulphur content in the liquid metal. On the basis of the present experimental results, it is unlikely that the required Pt-Re-Os fractionation is generated during inner core crystallization, assuming that the light element in the Earth’s core is sulphur. 相似文献
34.
Across-shelf variations in thickness, grain size, and frequency of sandstone beds in a transgressive outer-shelf succession were investigated from the Middle Pleistocene (ca. 0.7 Ma) Kakinokidai Formation on the Boso Peninsula, Japan. The transgressive deposits are generally muddy and contain slumps and slump scars. The intercalated sandstone beds are interpreted to have been formed from turbidity currents as a response to erosion and resuspension of sandridge-complex deposits in the southwestern upslope area during storm events. Mapping of volcanic ash beds and a transgressive surface in the base of the formation permits detailed bed-by-bed correlation of the outer-shelf sandstone beds. Although, overall, thickness, grain size, and frequency of sandstone beds decrease in the downslope direction, some sandstone beds locally thin out and coarsen in association with slump scars in the surrounding muddy deposits. These sandstone beds subsequently thicken and fine, and finally thin out in the farther downslope area. In addition to the local thinning of sandstone beds, the frequency of sandstone beds first decreases and then increases in the farther offshore direction. From this evidence, we concluded that these non-uniform patterns of across-outer-shelf variations in thickness, grain size, and frequency of sandstone beds were caused by the local increases in flow speeds and subsequent expansion and reduced speeds of turbidity currents, along with a local increase in the seafloor gradient that was induced by the development of slump scars in the transgressive outer-shelf floor. These physiographic features in the outer shelf are interpreted not to have permitted monotonous downslope thinning and fining of sandstone beds, compared with the bed-shape models of depletive turbidity currents and with the proximality trend of shelf sandstones from modern and ancient highstand-stage shelf systems. 相似文献
35.
The geochemistry of ostracode shells and bulk carbonates in a 19-meter sediment core documents at century-scale resolution the evolution of water chemistry in Coldwater Lake, North Dakota, providing a continuous paleohydrologic record of Holocene climate change in the northern Great Plains. A combination of 18O, 13C, Mg/Ca and Sr/Ca in ostracode calcite aided by Sr/Ca in bulk carbonates are used to constrain the paleoclimatic reconstructions. A fresh-water phase in the early Holocene, indicated by the absence of Candona rawsoni and low concentrations of Sr/Ca in bulk carbonate, was followed by a sharp increase in salinity between 10800 and 8900 yr B.P. The climate was predominately dry during the late part of the early Holocene and most of the middle Holocene (8900–5000 yr B.P.), when the lake was very sensitive and recorded a series of dry and wet oscillations. Maximum salinity occurred around 5500 yr B.P. and was followed by a gradual decrease between 5000 and 2400 yr B.P. From 2400 yr B.P. the 18O, Mg/Ca, and Sr/Ca in the ostracodes indicate generally wet conditions interrupted by a series of lesser salinity and temperature oscillations lasting until 600 yr B.P. Ostracode geochemistry indicates that a warm and dry climate returned at about the time of the Little Ice Age (600–150 yr B.P.). Ostracode 13C shows a ong-term increasing trend during the Holocene, which suggests that lake productivity and atmospheric CO2 exchange made greater contributions to the hypolimnetic carbon pool as the lake became shallower with time. 相似文献
36.
Contaminations in sediments by polycyclic aromatic hydrocarbons (PAHs) and alkylated PAHs were investigated at 44 sites in Osaka Bay, Japan. Concentrations of total PAHs and alkylated PAHs were in the range 6.40–7800 ng/g dry weights and 13.7–1700 ng/g dry weights, respectively. The PAH concentrations tended to be higher along the shoreline in the vicinities of big ports, industrialized areas, and densely populated regions such as the cities of Osaka and Kobe. The major sources appeared to be pyrogenic or both pyrogenic and petrogenic at most of the sites. PAH concentrations were remarkably high at a site near Kobe, where the concentrations of dibenzo(a,h)anthracene and benzo(g,h,i)perylene exceeded the effects-range-medium concentration and eight PAHs were above the corresponding effects-range-low concentrations. Those PAHs may have been derived from the great fire associated with the large earthquake in 1995. 相似文献
37.
Atsuki Shinbori Tomoaki Hori Yoshimasa Tanaka Yukinobu Koyama Takashi Kikuchi Tsutomu Nagatsuma 《极地研究(英文版)》2013,(4):296-314
To investigate temporal and spatial evolution of global geomagnetic field variations from high-latitude to the equator during geomagnetic storms, we analyzed ground geomagnetic field disturbances from high latitudes to the magnetic equator. The daytime ionospheric equivalent current during the storm main phase showed that twin-vortex ionospheric currents driven by the Region 1 field-aligned currents (R1 FACs) are intensified significantly and expand to the low-latitude region of-30~ magnetic latitude. Centers of the currents were located around 70~ and 65~ in the morning and afternoon, respectively. Corresponding to intensification of the R1 FACs, an enhancement of the eastward/westward equatorial electrojet occurred at the daytime/nighttime dip equator. This signature suggests that the enhanced convection electric field penetrates to both the daytime and nighttime equa- tor. During the recovery phase, the daytime equivalent current showed that two new pairs of twin vortices, which are different from two-cell ionospheric currents driven by the R1 FACs, appear in the polar cap and mid latitude. The former led to enhanced north- ward Bz (NBZ) FACs driven by lobe reconnection tailward of the cusps, owing to the northward interplanetary magnetic field (IMF). The latter was generated by enhanced Region 2 field-aligned currents (R2 FACs). Associated with these magnetic field variations in the mid-latitudes and polar cap, the equatorial magnetic field variation showed a strongly negative signature, produced by the westward equatorial electrojet current caused by the dusk-to-dawn electric field. 相似文献
38.
39.
The main objective of this paper was to investigate the dewatering behaviour of a clayey uranium ore slurry. The slurry (containing 28% clay size) exhibited moderate water adsorption (w l = 83% and w p = 30%). Primarily composed of muscovite (46%) and quartz (30%), the clay minerals included illite (8%), chlorite (5%) and kaolinite (2%) alongside a CEC of 41 (cmol(+)/kg) with Ca2+ and Mg2+ as the dominant cations. Likewise, the high EC (17,600 μS/cm) and ionic strength (1.15 mol/L) indicated a flocculated microstructure due to the presence of SO4 2? (22,600 mg/L) and Mg2+ (1340 mg/L) in the slurry water. Settling included sedimentation and consolidation at low initial solids condition (25–35%) whereas only consolidation was observed at high initial solids contents (40–50%). The average k reduced from 1.2 × 10?6 m/s (initial s = 25%) to 5.3 × 10?8 m/s (initial s = 50%) along with a void ratio reduction from 7.4 to 2.6. Due to thixotropic strength, volume compressibility during consolidation showed apparent pre-consolidation at low effective stress (0.3–2 kPa) with a reduction in void ratio from 2.6 to 2.5. The e s was found to be 2.46 at σ′ = 2 kPa and was followed by a steeper slope with the void ratio reducing to 2.1 at σ′ = 31 kPa. Likewise, the hydraulic conductivity during consolidation decreased from 2.6 × 10?9 m/s (at e = 2.6) to 2.0 × 10?10 m/s (at e = 2.1). 相似文献
40.
This paper examined sequence‐stratigraphic features of a gravelly fluvial system of the Iwaki Formation, which developed in a forearc‐basin setting in Northeast Japan during the Eocene through Oligocene. On the basis of three‐dimensional architectural element analysis, we discriminated three major cycles of channel complexes, which contain ten component channel deposits in total in the fluvial succession. Component channel deposits in the uppermost part of each cycle are sandier and associated with overbank muddy deposits and coal beds as compared with those in the lower part of the cycle. Mean clast‐size also decreases upsection in the entire gravelly fluvial deposits. The fluvial succession is interpreted to have been deposited in response to an overall rise in relative sea level that was superimposed by three short‐term relative sea‐level rises on the basis of vertical stacking patterns and component lithofacies features of channel deposits, and of correlation of the fluvial succession with an age‐equivalent marine succession in an area about 50 km offshore. However, geometry and stacking patterns of the channel complexes do not exhibit any distinct temporal variation and amalgamated channel and bar deposits are dominant throughout the transgressive fluvial succession. On the other hand, an overall fining‐upward pattern of the entire Iwaki Formation fluvial deposits in association with three component fining‐upward patterns is distinct, and is interpreted to be consistent with the tenet of the standard fluvial sequence‐stratigraphic models. This indicates that the present example represents one type of variation in the standard fluvial sequence‐stratigraphic models, possibly reflecting the forearc‐basin setting, which is generally represented by higher valley slope, higher shedding of coarse‐grained sediments, and shorter longitudinal profiles to the coastal area as compared with a passive‐continental‐margin setting. 相似文献