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71.
G. J. MacPherson K. Nagashima A. N. Krot S. M. Kuehner A. J. Irving K. Ziegler L. Mallozzi C. Corrigan D. Pitt 《Meteoritics & planetary science》2023,58(1):135-157
Northwest Africa (NWA) 8418 is an unusual chondrite whose properties do not exactly match those of any other known chondrite. It has similarities to the CV (Vigarano group), CK (Karoonda group), and CL (Loongana group) chondrites, but its abundance of large calcium-aluminum-rich inclusions (CAIs) and the low NiO content (<0.2 wt%) of its matrix olivine ally it most closely with the CV group. The absence of grossular, monticellite, wollastonite, and sodalite from the alteration products of the CAIs; the magnesium-rich nature of the matrix olivines (Fa38) relative to that of the CV3 chondrites (~Fa50); and the presence of secondary Na-bearing plagioclase and chlorapatite indicate a metamorphic temperature >600 °C. NWA 8418 contains kamacite, taenite, and troilite, and lacks magnetite and pentlandite. We propose that NWA 8418 be reclassified as a reduced CV4 chondrite, which makes it the first CV chondrite of petrologic type 4. 相似文献
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M. J. Jamieson M. Finch R. S. Friedman A. Dalgarno 《Planetary and Space Science》1992,40(12):1719-1721
Pectroscopic data on the shifts and widths of the energy levels of molecular oxygen have been used in the empirical construction of a diabatic potential matrix that characterizes the interactions of the B3∑−u state with the 5Πu, 23∑+u, 3Πu and 1Πu states. The diabatic potential matrix is u theory formulation to calculate the cross-sections for the excitation of O(1D) atoms in collisions of two O(3P) atoms. Total cross-sections are obtained by adding the excitation from the 3Πg, channel. The rate coefficient for quenching of O(1D) by O(3P) is evaluated as a function of temperature. The values conflict with a recent analysis of the emission of the oxygen red line in the upper atmosphere. 相似文献
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S. Osterman J. Green C. Froning S. B��land E. Burgh K. France S. Penton T. Delker D. Ebbets D. Sahnow J. Bacinski R. Kimble J. Andrews E. Wilkinson J. McPhate O. Siegmund T. Ake A. Aloisi C. Biagetti R. Diaz W. Dixon S. Friedman P. Ghavamian P. Goudfrooij G. Hartig C. Keyes D. Lennon D. Massa S. Niemi C. Oliveira R. Osten C. Proffitt T. Smith D. Soderblom 《Astrophysics and Space Science》2011,335(1):257-265
The Cosmic Origins Spectrograph (COS) was installed in the Hubble Space Telescope in May, 2009 as part of Servicing Mission 4 to provide high sensitivity, medium and low resolution spectroscopy at far- and near-ultraviolet wavelengths (FUV, NUV). COS is the most sensitive FUV/NUV spectrograph flown to date, spanning the wavelength range from 900 Å to 3200 Å with peak effective area approaching 3000 cm2. This paper describes instrument design, the results of the Servicing Mission Orbital Verification (SMOV), and the ongoing performance monitoring program. 相似文献
76.
The major and trace element chemistry of phonolites containing spinel Iherzolite xenoliths from Bokkos (Nigeria), Phonolite Hill (northeastern Australia) and Heldburg (East Germany) is consistent with an origin by fractional crystallization of basanitic magmas at upper mantle pressures (10–15 kbar). At Bokkos, spatially associated lavas ranging from hawaiitic nepheline mugearite to nepheline benmoreite can be modeled very well by fractional crystallization of kaersutitic amphibole + olivine + Fe-Ti-spinel + apatite, a crystal extract consistent with experimentally-determined near-liquidus phase relationships for mugearitic liquids. Further fractional crystallization of aluminous clinopyroxene + mica + apatite will yield the phonolites. A similar model relating the unusual Iherzolite-bearing mafic nepheline benmoreite from Pigroot (New Zealand) to basanitic lavas of the East Otago province is not supported by major and trace element data. The Pigroot lava is possibly the product of melting of a mantle source region previously enriched in Sr and light rare earth elements, with subsequent minor fractional crystallization of olivine + kaersutite. Dynamic flow crystallization processes operating within conduit systems from mantle pressures are capable of yielding large volumes of evolved phonolitic liquids from primary basanitic liquids, if magma flow rates are appropriate. This mechanism may provide an explanation for the volumetric bias towards salic differentiates in some alkalic provinces. 相似文献
77.
Siderophile and chalcophile element abundances in shergottites: Implications for Martian core formation 下载免费PDF全文
Shuying Yang Munir Humayun Kevin Righter Gwendolyn Jefferson Dana Fields Anthony J. Irving 《Meteoritics & planetary science》2015,50(4):691-714
Elemental abundances for volatile siderophile and chalcophile elements for Mars inform us about processes of accretion and core formation. Such data are few for Martian meteorites, and are often lacking in the growing number of desert finds. In this study, we employed laser ablation inductively coupled plasma–mass spectrometry (LA‐ICP‐MS) to analyze polished slabs of 15 Martian meteorites for the abundances of about 70 elements. This technique has high sensitivity, excellent precision, and is generally accurate as determined by comparisons of elements for which literature abundances are known. However, in some meteorites, the analyzed surface is not representative of the bulk composition due to the over‐ or underrepresentation of a key host mineral, e.g., phosphate for rare earth elements (REE). For other meteorites, the range of variation in bulk rastered analyses of REE is within the range of variation reported among bulk REE analyses in the literature. An unexpected benefit has been the determination of the abundances of Ir and Os with a precision and accuracy comparable to the isotope dilution technique. Overall, the speed and small sample consumption afforded by this technique makes it an important tool widely applicable to small or rare meteorites for which a polished sample was prepared. The new volatile siderophile and chalcophile element abundances have been employed to determine Ge and Sb abundances, and revise Zn, As, and Bi abundances for the Martian mantle. The new estimates of Martian mantle composition support core formation at intermediate pressures (14 ± 3 GPa) in a magma ocean on Mars. 相似文献
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Irving Michelson 《Pure and Applied Geophysics》1966,65(1):164-167
Summary The Loitsyanskii theorem for turbulent fluid motion is presented in simplified form from the viewpoint of angular momentum conservation and extended by a normalization with respect to total mass. When the new parameter thus obtained is evaluated for a gas cloud of the size and mass of the present Sun-Earth system, and this is equated to the corresponding parameter for the Earth-Moon configuration, an accurate equation between independently determined astronomical constants is found. The Earth's rotational speed is expressed in terms of its mean orbital motion, the Sun-Earth mass ratio, the ratio of separation distances, and the Earth's radius. The most simple form of the algebraic relationship (10) is believed unique in linking planetary orbital dynamics to motion about the center of gravity. 相似文献