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751.
Lindsay P. Keller James C. Clark Charles F. Lewis Carleton B. Moore 《Meteoritics & planetary science》1992,27(1):87-91
Abstract— The Maralinga meteorite was found near the village of Maralinga, South Australia (30°18′S, 131°16′E) in 1974, but was not recognized as a meteorite until 1989. One weathered individual was recovered with a total mass of 3.38 kg. The bulk composition and petrography of Maralinga indicate that it is a metamorphosed (petrographic type 4) carbonaceous chondrite with major similarities to the Vigarano-subtype. However, recent trace element data from the literature suggest that Maralinga should be included with the CK (Karoonda-type) carbonaceous chondrites. We classify Maralinga as an anomalous CK4 chondrite because of its abundant chondrules and refractory inclusions relative to other known members of the CK group. Maralinga contains homogeneous silicates, including Ni-bearing olivines (Fa34), high-Ca clinopyroxene, and rare orthopyroxene. Plagioclase is chemically heterogeneous and falls into two distinct compositional groups one of ~ An20 and an ~ An80 group. Highly oxidizing conditions during metamorphism of Maralinga are indicated by the abundance of magnetite and the paucity of Fe-Ni metal. 相似文献
752.
753.
J. Casares G. Dubus T. Shahbaz C. Zurita P.A. Charles 《Monthly notices of the Royal Astronomical Society》2002,329(1):29-36
We present Very Large Telescope (VLT) low-resolution spectroscopy of the neutron star X-ray transient XTE J2123−058 during its quiescent state. Our data reveal the presence of a K7V companion which contributes 77 per cent to the total flux at λ 6300 and orbits the neutron star at . Contrary to other soft X-ray transients (SXTs), the H α emission is almost exactly in antiphase with the velocity curve of the optical companion. Using the light-centre technique we obtain and hence This, combined with a previous determination of the inclination angle yields and . M 2 agrees well with the observed spectral type. Doppler tomography of the H α emission shows a non-symmetric accretion disc distribution mimicking that seen in SW Sex stars. Although we find a large systemic velocity of − this value is consistent with the galactic rotation velocity at the position of J2123−058, and hence a halo origin. The formation scenario of J2123−058 is still unresolved. 相似文献
754.
755.
Reference samples of three prominent pumice units of Glacier Peak tephra collected east of the volcano within a distance of 100 km are similar petrographically to units described by earlier workers. Glass shards isolated from these samples were analyzed by electron microprobe to determine the content of Ca, Fe, and K. Resulting data, plus those published for two other references samples, provide a basis for attributing certain outlying tephra layers from 14 locations in eastern Washington, Idaho, Wyoming, and Montana to eruptions of Glacier Peak. Ten of the samples have properties of both Glacier Peak tephra and Mount St. Helens set J tephra, but proportions of Ca:Fe:K in glass shards indicate that 9 of the 10 outlying samples came from Glacier Peak, whereas one is assigned to Mount St. Helens set J. The remaining six outlying samples, all from southeastern Washington, contain cummingtonite phenocrysts and are chemically similar to some parts of Mount St. Helens tephra sets that are older than 12,000 BP. 相似文献
756.
吉塞尔斯地震活动可能是因蒸汽开发引起的.水在一个承受很高构造剪应力和应变的大范围破裂体中汽化为蒸汽。 汽田地震震源机制解与区域构造应变场几乎一致,并且在该区域范围内汽田地震与别的构造地震不易区分。观测中注意到地震活动与注液历史无关,这表明孔隙水压力增高与注液不可能是吉塞尔斯诱发地震的成因。 相反,所有证据都表明诱发地震与孔隙水压力及温度降低有关。形成机制有两种最大可能:其一,是裂隙排水(汽)导致局部剪应力增加所致,其二,是由稳定滑动转化为不稳定滑动(粘滑)。没有其它记载的诱发地震机制与吉塞尔斯汽田条件相符。 相似文献
757.
David C. Palmer Russell J. Hemley Charles T. Prewitt 《Physics and Chemistry of Minerals》1994,21(8):481-488
The pressure dependence of the cristobalite Raman spectrum has been investigated to 22 GPa at room temperature, using single-crystal Raman spectroscopy with a diamond-anvil cell. We observe a rapid, first-order phase transition on increasing pressure, consistent with the cristobalite I?II transition revealed in previous x-ray diffraction experiments. The phase transition has been bracketed at 1.2±0.1 GPa on increasing pressure and 0.2±0.1 GPa on decreasing pressure. The pressure shifts II) of 11 Raman bands in the high-pressure phase (cristobalite have been measured. Evidence for an unusual hybridization of modes at 490–500 cm?1 is found. Changes in the Raman spectra also reveal an additional phase transition to a new phase at P ≈ 11 GPa, which remains to be fully characterized. 相似文献
758.
Qin Huanhuan Andrews Charles B. Tian Fang Cao Guoliang Luo Yong Liu Jiurong Zheng Chunmiao 《Hydrogeology Journal》2018,26(4):1061-1081
Hydrogeology Journal - Beijing, in the North China plain, is one of the few megacities that uses groundwater as its main source of water supply. Groundwater accounts for about two-thirds of the... 相似文献
759.
Fluid inclusions and geological relationships indicate that rodingite formation in the Asbestos ophiolite, Québec, occurred
in two, or possibly three, separate episodes during thrusting of the ophiolite onto the Laurentian margin, and that it involved
three fluids. The first episode of rodingitization, which affected diorite, occurred at temperatures of between 290 and 360°C
and pressures of 2.5 to 4.5 kbar, and the second episode, which affected granite and slate, occurred at temperatures of between
325 and 400°C and pressures less than 3 kbar. The fluids responsible for these episodes of alteration were moderately to strongly
saline (~1.5 to 6.3 m eq. NaCl), rich in divalent cations and contained appreciable methane. A possible third episode of alteration is suggested
by primary fluid inclusions in vesuvianite-rich bodies and secondary inclusions in other types of rodingite, with significantly
lower trapping temperatures, salinity and methane content. The association of the aqueous fluids with hydrocarbon-rich fluids
containing CH4 and higher order alkanes, but no CO2, suggests strongly that the former originated from the serpentinites. The similarities in the composition of the fluids in
all rock types indicate that the ophiolite had already been thrust onto the slates when rodingitization occurred. 相似文献
760.
The location of new homes defines the urban–rural fringe and determines many facets of the urban–rural interaction set in
motion by construction of new homes in previously rural areas. Home, neighborhood and school district characteristics play
a crucial role in determining the spatial location of new residential construction, which in turn defines the boundary and
spatial extent of the urban–rural fringe. We develop and apply a spatial hedonic variant of the Blinder (J Hum Resour 8:436–455,
1973) and Oaxaca (Int Econ Rev 9:693–709, 1973) price decomposition to newer versus older home sales in the Columbus, Ohio metropolitan area during the year 2000. The preferences
of buyers of newer homes are compared to those who purchased the nearest neighboring older home located in the same census
block group, during the same year. Use of the nearest older home purchased in the same location represents a methodology to
control for various neighborhood, social–economic-demographic and school district characteristics that influence home prices.
Since newer homes reflect current preferences for home characteristics while older homes reflect past preferences for these
characteristics, we use the price differentials between newer and older home sales in the Blinder–Oaxaca decomposition to
assess the relative significance of various house characteristics to home buyers.
相似文献
Joni S. CharlesEmail: |