Non-coaxial deformation of elliptical particles     

Bernard Le Theoff 《Tectonophysics》1979,53(1-2)

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Volcanic plume thermal radiation: 1972 eruption of piton de la fournaise, Réunion Island     

F. Le Guern  P. Morel  H. Tazieff  C. Vavasseur 《Journal of Volcanology and Geothermal Research》1982,12(1-2)

Using an infrared radiometer, the authors measured the infrared radiation emitted by the plume during the 1972 Piton de la Fournaise (Réunion Island) eruption in the 9.1- to 11.9-μm range.Eight histograms summarize twenty hours of continuous measurements and show a flux between 0.557 and 1.279 W/cm² with an average of 0.88 W/cm². The greatest number of events correspond to the flux emitted by lava fountains, while the high and rare flux values (4–6 W/cm²) correspond to detonations of chemical explosions, probably of H₂ and O₂.After calibration in the laboratory on a reference black body and in the field by correlation with field observations, such a technique can be used to follow changes of volcanic activity in remote and dangerous spots. Information on the number of explosions, their magnitude, and the presence and relative significance of hot magma can be transmitted continuously to a safe place.  相似文献   

Quantitative evaluation of fractional crystallization in Bouvet Island lavas     

Anton P. Le Roex  A.J. Erlank 《Journal of Volcanology and Geothermal Research》1982,13(3-4)

Bouvet Island, situated near the southernmost end of the Mid-Atlantic Ridge, is characterized by lavas ranging in composition from hawaiite through mugearite and benmoreite to rhyolite. Major and trace elements vary systematically throughout the sequence, as do mineral compositions, and geochemical modelling indicates that the compositional variations observed in the differentiated lavas can be ascribed to extensive fractional crystallization of a parental hawaiite magma. Following this scheme the hawaiite parent magma experienced approximately 44% fractional crystallization of plagioclase + clinopyroxene + olivine + opaque oxides and minor apatite to give rise to the mugearite magma, which in turn experienced a further 69% fractional crystallization of the same phase assemblage (though with more evolved compositions) to give rise to the Bouvet Island rhyolite. Extensive fractional crystallization (64%), possibly separated in time, of the parental hawaiite gave rise to the benmoreite magma. In the latter scheme the fractionating phases are similar both in composition and proportion to those crystallizing in the passage from hawaiite to mugearite, suggesting that the Bouvet Island hawaiites correspond in composition to a six phase (plag + of + cpx + Fe-Ti oxide + ap+ lq) saturation surface and that the more differentiated lavas resulted from differing degrees of crystallization on this surface.  相似文献   

Scapolite phenocrysts in a latite dome,northwest Arizona,U.S.A.     

Fraser Goff  Barbara H. Arney  Andrea C. Eddy 《Earth and Planetary Science Letters》1982,60(1):86-92

A latite dome in northwest Arizona contains a rare occurrence of primary SO₄-rich scapolite phenocrysts. The total phenocryst assemblage consists of plagioclase (An₂₀?An₃₃), hornblende, biotite, and scapolite (Me₆₈). Microphenocrysts include allanite and oxidized low-Ti magnetite. Electron microprobe analyses show that the scapolite contains about 1.74 wt.% S, which indicates an atomic S/(S + C) of 0.58. Although scapolite occurs in xenoliths in volcanic rocks and diatremes, as well as a metamorphic mineral in granulites, its occurrence as a primary igneous mineral is extremely rare.Ca-rich scapolite has been crystallized experimentally by others from melts with a wide range of SiO₂, CaO, and Na₂O contents, at temperatures above 825°C and pressures ranging from 3 to 15 kbar. Comparison of scapolite from this latite with synthetic scapolite crystallized from nepheline syenite melt suggests that the Arizona phenocrysts crystallized under conditions of 850 to 900°C, 3–6 kbar total pressure, and unusually high ?_CO2 and ?_SO2. The rarity of scapolite as a phenocryst mineral suggests that high partial pressures of CO₂ and SO₂ are rare in the magmatic environment.  相似文献   

太阳十厘米射电流量与太阳运动     

郑乐平  董士仑 《紫金山天文台台刊》1999,18(2):176-178

本文利用１９４７ ～１９９０ 年加拿大Ｏｔｔａｗａ 的２８００ ＭＨｚ 太阳射电流量与太阳绕太阳系质心运动的角动量变化率ｄＬ／ｄｔ 做线性相关,当迟滞时间τ～３ 年得相关系数为０ ．８２２ ,线性相关置信水平远大于９９ ．９ ％ 。本文还用同期的太阳黑子相对数与太阳角动量变化率ｄＬ／ｄｔ 做线性相关,当迟滞时间τ～２ － ３ 年得相关系数为０ ．８２９ ,其置信水平亦远大于９９ ．９ ％ ,证实了董士仑在１９９７ 年在天体物理学报发表的结果（１９００ － １９８０ 年,τ～２ 年,相关系数为０ ．８１）  相似文献   

The chemistry of magmatic gases from Erta'Ale,Ethiopia     

Werner F Giggenbach  Francois Le Guern 《Geochimica et cosmochimica acta》1976,40(1):25-30

The chemical composition of the gases emitted from a hornito close to the active lava lake of Erta'Ale, Ethiopia, as derived from chemical analyses on 18 samples collected on 23 January 1974, was found to be (in mol-%): H₂O: 79.4, CO₂: 10.4, total S: 7.36, HCl: 0.42, H₂: 1.49, N₂: 0.18, Ar: 0.001, CO: 0.46, and COS: 0.009. Thermodynamic considerations, based on the equilibria CO₂ + H₂ ? CO + H₂O and CO₂ + 3H₂ + SO₂ ? COS + 3H₂O show that the analytical values represent the equilibrium composition of a gas mixture at the measured temperature of around 1130°C under close to the surface pressure conditions. Comparison of the Erta'Ale gas emissions with those from other volcanoes suggests a close similarity in their chemical composition. This similarity is considered to be due to common processes governing the release of gaseous species from a magma.  相似文献   

Zoned Cr,Fe-spinel from the La Perouse layered gabbro,Fairweather Range,Alaska     

Gerald K. Czamanske  Glen R. Himmelberg  Fraser E. Goff 《Earth and Planetary Science Letters》1976,33(1):111-118

Zoned spinel of unusual composition and morphology has been found in massive pyrrhotite-chalcopyrite-pent-landite ore from the La Perouse layered gabbro intrusion in the Fairweather Range, southeastern Alaska. The spinel grains show continuous zoning from cores with up to 53 wt.% Cr₂O₃ to rims with less than 11 wt.% Cr₂O₃. Their composition is exceptional because they contain less than 0.32 wt.% MgO and less than 0.10 wt.% Al₂O₃ and TiO₂. Also notable are the concentrations of MnO and V₂O₃, which reach 4.73 and 4.50 wt.%, respectively, in the cores. The spinel is thought to have crystallized at low oxygen fugacity and at temperatures above 900°C, directly from a sulfide melt that separated by immiscibility from the gabbroic parental magma.  相似文献   

The effect of prolonged X-ray irradiation on lithium tetraborate glass discs as used in X.R.F. analyses     

Roger W. Le Maitre  Maunu T. Haukka 《Geochimica et cosmochimica acta》1973,37(3):708-710

Prolonged irradiation by X-rays of lithium tetraborate glass discs causes significant changes in countrates for certain elements e.g. Na and Mg decrease while Al, Si and P increase. This effect is probably due to surface diffusion in the glass as grinding away about 10 μm of the surface of the disc restores the countrates to their original levels. Although no change in countrates will ever be noticed on individual glass discs undergoing routine analyses, where irradiation time is only a minute or so, a close watch must be kept on any specimens that have been irradiated for more than a few tens of hours.  相似文献   

Preface     

F. Le Guern 《Bulletin of Volcanology》1982,45(3):157-157

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Heat Flow at Broken Hill, New South Wales     

J. H. Sass  A. E. Le Marne 《Geophysical Journal International》1963,7(4):477-489

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