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131.
Robert A. Watson Pedro Carreira Kieran Cleary Rod D. Davies Richard J. Davis Clive Dickinson Keith Grainge † Carlos M. Gutiérrez Michael P. Hobson Michael E. Jones Rüdiger Kneissl Anthony Lasenby Klaus Maisinger Guy G. Pooley Rafael Rebolo José Alberto Rubiño-Martin ‡ Ben Rusholme § Richard D. E. Saunders Richard Savage Paul F. Scott Ane Slosar Pedro J. Sosa Molina Angela C. Taylor David Titterington Elizabeth Waldram Althea Wilkinson 《Monthly notices of the Royal Astronomical Society》2003,341(4):1057-1065
132.
Alan E. Rubin Angeline Rehfeldt Eric Peterson Klaus Keil Eugene Jarosewich 《Meteoritics & planetary science》1983,18(3):179-196
Our survey of type 4–6 ordinary chondrites indicates that gas-poor, melt-rock and/or exotic clast-bearing fragmental breccias constitute 5%, 22% and 23%, respectively, of H, L and LL chondrites. These abundances contrast with the percentages of solar-gas-rich regolith breccias among ordinary chondrites: H (14%), L (3%) and LL (8%) (Crabb and Schultz, 1981). Petrologic study of several melt-rock-clast-bearing fragmental breccias indicates that some acquired their clasts prior to breccia metamorphism and others acquired them after metamorphism of host material. In general, the melt-rock clasts in gas-poor H chondrite fragmental breccias were acquired after breccia metamorphism and were probably formed by impacts into boulders or exposed outcrops of H4-6 material in the H chondrite parent body regolith. In contrast, most of the melt-rock clasts in gas-poor L and LL fragmental breccias were acquired prior to breccia metamorphism. The low abundance of regolith breccias among L chondrites and evidence that at least two-thirds of the L chondrites suffered a major shock event 0.5 Gyr ago, suggest that the L parent body may have been disrupted by a major collision at that time and that the remaining parent body fragments were too small to develop substantial regoliths (e.g., Heymann, 1967; Crabb and Schultz, 1981). Such a disruption would have exposed a large amount of L chondrite bedrock, some of which would consist of fragmental breccias that acquired melt-rock clasts very early in solar system history, prior to metamorphism. The exposed bedrock would serve as a potential target for sporadic meteoroid impacts to produce a few fragmental breccias with unmetamorphosed melt-rock clasts. The high proportion of genomict brecciated LL chondrites reflects a complex collisional history, probably including several episodes of parent body disruption and gravitational reassembly. Differences in the abundances of different kinds of breccias among the ordinary chondrite groups are probably due to the stochastic nature of major asteroidal collisions. 相似文献
133.
Everett K. Gibson David E. Lange Klaus Keil Terry E. Schmidt J. Michael Rhodes 《Meteoritics & planetary science》1977,12(2):95-107
The Kramer Creek, Colorado, chondrite was found in 1966 and identified as a meteorite in 1972. Bulk chemical analysis, particularly the total iron content (20.36%) and the ratio of Fetotal/SiO2 (0.52), as well as the compositions of olivine (Fa21.7) and orthopyroxene (Fs18.3) place the meteorite into the L-group of chondrites. The well-defined chondritic texture of the meteorite, the presence of igneous glass in the chondrules and of low-Ca clinopyroxene, as well as the slight variations in FeO contents of olivine (2.4% MD) and orthopyroxene (5.6% MD) indicate that the chondrite belongs to the type 4 petrologic class. 相似文献
134.
Summary The unprecedented quality of the IRAS data prompted a series of papers reinvestigating the origin of the galactic infrared/submillimeter radiation and the nature of the heating sources of the interstellar dust. The scope of this paper is to review the main results of these new studies. Sect. 1 contains a general introduction to the subject and an overview of the earlier work. In Sect. 2 and 3, we summarize our current knowledge on dust properties and on the interstellar radiation field. Then, we present the recent interpretations of the infrared emission of our Galaxy, which are based on the IRAS data: in Sect. 4 we present the results from the galactic disk; Sect. 5 covers the question of the contribution from small dust particles, and in Sect. 6 we describe the infrared radiation from the galactic center. The nature of the heating sources and the origin of the galactic infrared radiation is then discussed in Sect. 7. Finally, Sect. 8 presents a comparison of our Galaxy with external galaxies 相似文献
135.
Plagioclases in different types of lunar highland rocks (all highly feldspathic) are twinned according to different laws and in different styles. Carlsbad and Carlsbad-albite twins, presumed to be growth twins, occur mainly in rocks which show igneous texture, and which have not been severely brecciated. These two twin laws appear to be absent from cataclastic rocks, including cataclastic anorthosite, possibly because the original twins were preferentially broken up in cataclasis (the composition plane being a plane of weakness). Pericline and lamellar albite twins, presumed to be deformation twins (except for some albite growth twins) occur in all types of rocks, and obvious deformation features, such as bending of lamellae, are well shown in many cataclastic rocks. Surprisingly, some Carlsbad and Carlsbad-albite twins are found in rocks with granoblastic texture, which presumably recrystallized in the solid state. This contrasts with previous observations on terrestrial metamorphic rocks, in which such growth twins are scarce or absent. The difference may be due to a higher rate of temperature change in the shock-heated lunar rocks. Further study of plagioclase twin laws in lunar rocks may assist in deciphering the complicated history of the highlands. 相似文献
136.
A total of 150 samples were collected at a 10-days' anchor station in the Bornholm basin (55° 31.1′N, 15° 32.1′E) and analyzed for dissolved (< 0.4 μm) and particulate trace metals. For dissolved Mn, large gradients have been found in the vertical distribution with minimum concentrations (< 0.2 μgl?1) in the halocline zone and considerably higher values in the deep waters (up to 50 μgl?1). Ultrafiltration studies indicate that dissolved Mn is probably present as Mn2+ in the oxygenated bottom layer. The primary production process was not evident in the particulate Mn profile; the suspended particulate material (SPM), however, shows a considerable enrichment with depth, apparently due to Mn-oxide precipitation.The distribution of dissolved Fe was rather homogeneous, with average concentrations throughout the water column between 0.86 and 1.1 μgl?1, indicating that the oxidation of Fe2+ ions released from the sediments must already be complete in the very near oxidation boundary layer. Relatively high concentrations of particulate Fe were actually measured in the bottom layer, with the maximum mean of 11.2 μgl?1 at 72 m. Similarly to Mn, the profile of particulate Fe does not reflect the SPM curve of the eutrophic layer. On average, about 70% of the total Fe in surface waters was found to be particulate.The average concentrations of dissolved Zn, Cd and Cu were found to be rather homogeneous in the water column but showed a relatively high variability with time. A simplified model on trace-metal uptake by phytoplankton indicates no significant change in dissolved metal concentrations during the period of investigation. On average, only 1.7% Zn, 3.3% Cd and 9.8% Cu of the total metal concentrations were found in particulate form. SPM analyses showed significant correlations of Zn, Cd and Cu with Fe, indicating that particulate iron is an important carrier for particulate trace metals in Baltic waters. 相似文献
137.
Abstract— Based on optical microscopy and electron microprobe analysis of mafic minerals, Ingella Station, a new meteorite find from the area of the Tenham strewnfield, Queensland, Australia, is classified as an H5a chondrite. 相似文献
138.
Monika?HuraiováEmail author Jean?Dubessy Patrik?Kone?ny Klaus?Simon Ján?Král’ Grzegorz?Zielinski Jozef?Lipka Vratislav?Hurai 《Contributions to Mineralogy and Petrology》2005,148(5):615-633
Glassy orthopyroxene granodiorite-tonalite (named pincinite after type locality) was described from basaltic lapilli tuffs of the Pliocene maar near Pinciná village in the Slovakian part of the Pannonian Basin. Two pincinite types exhibit a qualitatively similar mineral composition (quartz, An20–55 plagioclase, intergranular silicic glass with orthopyroxene and ilmenite, ±K-feldspar), but strongly different redox potential and formation PT conditions. Peraluminous pincinite is reduced (6–7% of total iron as Fe3+ in corundum-normative intergranular dacitic glass) and contains ilmenite with 8–10 mol% Fe2O3 and orthopyroxene dominated by ferrosilite. High-density (up to 0.85 g/cm3) primary CO2 inclusions with minor H2, CH4, H2S, CO and N2 (<2 mol% total) are present in Qtz and Plg. Equilibrium PT conditions inferred from the intergranular Opx–Ilm–Glass assemblage and fluid density correspond to 1,170±50°C, 5.6±0.4 kbar, respectively. Metaluminous pincinite is more oxidised (25–27% of total iron as Fe3+ in diopside-normative intergranular glass of rhyolite–trachyte–dacite composition) and contains Fe2O3-rich ilmenite (17–29 mol%) associated with enstatite. Fluid inclusions are composed of CO2–H2O mixtures with up to 38 mol% H2O. Raman spectroscopy revealed H2S along with dominant CO2 in the carbonic phase. Equilibrium PT parameters for the intergranular Opx–Ilm–Glass assemblage correspond to 740±15°C, 2.8±0.1 kbar, respectively. Reducing gas species (<2 mol% total) in the CO2-inclusions of the peraluminous pincinite resulted from hydrogen diffusion due to fH2 gradient imposed during decrease of redox potential from the log fO2 values near QFM during Qtz + Plg growth, to QFM-2 incidental to the superimposed Opx + Ilm assemblage in the intergranular melt. The decrease in oxygen fugacity was recorded also in the metaluminous pincinite, where log fO2 values changed from ~QFM + 2.6 to QFM + 0.4, but hydrogen diffusion did not occur. Absence of OH-bearing minerals, major and trace element abundances (e.g. REE 300–320, Nb 55–57, Th 4–31, Zr 240–300 ppm, FeOtot/MgO up to 11), and Sr–O isotope ratios in the pincinites are diagnostic of high-temperature anorogenic magmas originated by dehydration melting of biotite in quartz-feldspathoid crust (87Sr/86Sr>0.705–0.706, 18O>9 V-SMOW) around alkali basalt reservoir in depths between 17 and 20 km, and around late stage derivatives of the basalt fractionation, intruding the crust up to depths of 10–11 km. Low water activity in the pincinite parental melt was caused by CO2-flux from the Tertiary basaltic reservoirs and intrusions. The anatexis leads to generation of a melt-depleted granulitic crust beneath the Pannonian Basin, and the pincinites are interpreted as equivalents of igneous charnockites and enderbites quenched at temperatures above solidus and unaffected by sub-solidus re-equilibration and metamorphic overprint. 相似文献
139.
C++ and Java code for recursion formulas in mathematical geodesy 总被引:2,自引:0,他引:2
Klaus Hehl 《GPS Solutions》2005,9(1):51-58
140.
Carbon Sequestration in Arable Soils is Likely to Increase Nitrous Oxide Emissions,Offsetting Reductions in Climate Radiative Forcing 总被引:5,自引:0,他引:5
Strategies for mitigating the increasing concentration of carbon dioxide (CO2) in the atmosphere include sequestering carbon (C) in soils and vegetation of terrestrial ecosystems. Carbon and nitrogen
(N) move through terrestrial ecosystems in coupled biogeochemical cycles, and increasing C stocks in soils and vegetation
will have an impact on the N cycle. We conducted simulations with a biogeochemical model to evaluate the impact of different
cropland management strategies on the coupled cycles of C and N, with special emphasis on C-sequestration and emission of
the greenhouse gases methane (CH4) and nitrous oxide (N2O). Reduced tillage, enhanced crop residue incorporation, and farmyard manure application each increased soil C-sequestration,
increased N2O emissions, and had little effect on CH4 uptake. Over 20 years, increases in N2O emissions, which were converted into CO2-equivalent emissions with 100-year global warming potential multipliers, offset 75–310% of the carbon sequestered, depending
on the scenario. Quantification of these types of biogeochemical interactions must be incorporated into assessment frameworks
and trading mechanisms to accurately evaluate the value of agricultural systems in strategies for climate protection. 相似文献