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Walther E. Petrascheck Jr. 《International Journal of Earth Sciences》1959,48(1):205-217
Zusammenfassung Der Widerspruch, welcher sich aus der hohen Schmelztemperatur ultrabasischer Magmen und der geringen Kontaktmetamorphose ergibt, ist allgemein weder durch den kühlen Kristallbrei noch durch die tektonische Einschuppung von Bruchstücken der Peridoditschale lösbar. Die Platznahme der Ultrabasite erfolgte teils tief intrusiv, teils seicht intrusiv im Bereich der Geosynklinalböden, teils submarin extrusiv. Sedimentogene Serpentine sind sehr selten. Das Alter der Serpentine im alpinmediteranen Raum reicht vom Altpaläozoikum bis in die oberste Kreide. 相似文献
134.
Conclusion The status of various results on the determination of the appropriate family of theoretical wave spectra to describe wind generated seas and the status of various wave forecasting methods have been reviewed. The spectra of Neumann appear to describe the sea more accurately than other theoretical spectra and the wave forecasting methods of Pierson, Neumann and James appear to be the most nearly correct for the widest variety of possible wave and weather situations. 相似文献
135.
The manned Apollo 11, 12, 14 and 15 and the automated Luna 16 lunar missions have provided us with lunar rock and regolith (soil) samples from a number of geologically distinct sites. The mare regions were sampled by Apollo 11, 12 and Luna 16, whereas Apollo 14 landed on a terrain with more relief, the Fra Mauro Formation which represents an ejecta blanket from the Imbrian Basin, and Apollo 15 touched down near the lunar highlands. The samples collected consist of a mixture, mainly of basalt, breccia and regolith (soil-particulate matter, generally < 1 cm in size). The basalts show considerable variation in texture, mineralogy and chemistry and probably represent fragments from various parts of relatively thin and extensive lava flows in the maria. The breccias represent regolith material which was indurated to varying degrees by impact events. The regolith is a product of the breakdown, again by impact, of coherent rock masses of basalt and breccia. 相似文献
136.
The olivine phenocrysts of four basalts (12004, 12008, 12009 and 12022) are concentrically zoned and have core compositions about as magnesian as experimentally produced liquidas olivines, features which suggest fractional crystallization and absence of Fe-Mg reequilibration. In the magnesium- and olivine-rich granular basalt 12035, the olivines are either unzoned or are zoned toward adjacent grains and have compositions more iron-rich than either cumulus olivines or liquidus olivines (should the rock represent the composition of a melt), features which suggest extensive Fe-Mg re-equilibration. 相似文献
137.
A. F. Wickersham Jr. 《Pure and Applied Geophysics》1970,80(1):271-287
Summary Propagating acoustic-like disturbances generated by nuclear explosions have been observed to split in the lower ionosphere. The resulting two disturbances propagate vertically into the upper ionosphere at different speeds, the slower at ordinary sound speed in a neutral medium and the faster at almost twice the speed of sound.The faster disturbance travels at the speed of an ion-acoustic wave in the ionic fluid. Such identification is prohibited theoretically by the large damping, or coupling, of the ionic mode to the neutral particle medium through ion-neutral elastic collisions; however, if inelastic collisions are included in the theory, the principal exothermic charge-exchange and charge-transfer reactions in the ionosphere provide enough additional coherent momentum in the charged particles to offset the losses through elastic collisions. It is shown quantitatively that in some regions of the ionosphere ionacoustic wave propagation can occur almost losslessly.It is possible that under some conditions the ionosphere approaches an unstable chemical equilibrium that is relieved by the spontaneous generation of ion-acoustic wavelets. Various ionospheric observations are examined in which there is some evidence of the effects of ionospheric ionacoustic disturbances. 相似文献
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139.
Five lizardite-chrysotile type serpentinites from California, Guatemala and the Dominican Republic show oxygen isotope fractionations of 15.1 to 12.9 per mil between coexisting serpentine and magnetite (O18 magnetite=–7.6 to –4.6 per mil relative to SMOW). Nine antigorites (mainly from Vermont and S. E. Pennsylvania) show distinctly smaller fractionations of 8.7 to 4.8 per mil (O18 magnetite=–2.6 to +1.7 per mil). Two lizardite and chrysotile serpentinites dredged from the Mid-Atlantic Ridge exhibit fractionations of 10.0 and 12.4 per mil (O18 magnetite=–6.8 and –7.9 per mil, respectively), whereas an oceanic antigorite shows a value of 8.2 per mil (O18 magnetite=–6.2). These data all clearly indicate that the antigorites formed at higher temperatures than the chrysotilelizardites. Electron microprobe analyses of magnetites from the above samples show that they are chemically homogeneous and essentially pure Fe3O2. However, some magnetites from certain other samples that show a wide variation of Cr content also give very erratic oxygen isotopic results, suggesting non-equilibrium. An approximate serpentine-magnetite geothermometer curve was constructed by (1) extrapolation of observed O18 fractionations between coexisting chlorites and Fe-Ti oxides in low-grade pelitic schists whose isotopic temperatures are known from the quartz-muscovite O18 geothermometer, and (2) estimates of the O18 fractionation factor between chlorite and serpentine (assumed to be equal to unity). This serpentine-magnetite geothermometer suggests approximate equilibrium temperatures as follows: continental lizardite-chrysotile, 85° to 115° C; oceanic lizardite and chrysotile, 130° C and 185° C, respectively; oceanic antigorite, 235° C; and continental antigorites, 220° to 460° C.Contribution No. 2029 of the Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91109. 相似文献
140.
Na2O contents were determined by electron microprobe analysis in 124 garnets from diamonds, xenoliths of peridotites, eclogites from kimberlitic pipes and metamorphic complexes. Na2O content ranges between 0.01 and 0.22% with the limit of detection at about 0.01%. In the garnets of diamond-bearing eclogites and orange garnets from diamonds a regular increase in the Na2O content has been established, varying from 0.09 to 0.22, as compared to garnets from eclogites of metamorphic complexes (range 0.01 to 0.06). It is assumed that the increased Na2O content in the garnets of eclogites is mainly connected with higher pressure, whereas isomorphism of sodium is connected with the initial stages of the transition from Si4 to Si6 in the garnet structure: CaAlNaSi.The study of the sodium content of garnets has shown that all the orange-coloured garnets from diamonds so far studied are related to eclogite assemblage. Determination of the Na2O content of individual inclusions of chrome pyropes from diamonds permits a conclusion on the type of assemblage (with or without clinopyroxene). Proceeding from these data, the importance of garnet-olivine paragenesis within the stability field of diamond has been revealed.Some clear distinctions in the sodium content of the garnets from xenoliths of the kyanite eclogites from the Zagadochnaya pipe in Yakutia and the Roberts Victor mine in South Africa confirm the relation of these eclogites to different subfacies.A conclusion is drawn as to the possibility of utilizing the Na/Na+Ca distribution in the garnets and pyroxenes of eclogites of especially deep-seated origin as a pressure indicator and to the necessity for experimental testing of the dependence of the distribution of these elements in garnets and pyroxenes on pressure, presumably in the range of 30–100 kbars. 相似文献