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In the framework of a quasilinear theory we examine the interaction between thermal electrons and ion-cyclotron waves (ICW) in the outer plasmasphere of the earth. For this type of wave-particle interaction, a simplification of the quasilinear diffusion integral in a magneto-active plasma under plasmaspheric conditions is given. Under the assumption of a Maxwellian distribution of electrons we have calculated the collision frequency and the heating source as the electrons are scattered by ICW. The obtained values of intrinsic parameters of the outer plasmasphere may exceed greatly, accordingly, the Coulomb frequency of collisions and the heating source due to suprathermal electrons. ICW-heating causes the ionosphereward thermal flux to increase, and this must lead to an increase in electron temperature in lower-lying plasmaspheric regions and in the subauroral ionosphere. A quantitative estimation of the electron temperature for the hot zone, made in this paper, is consistent with available experimental data. 相似文献
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Mafic orthopyroxene monzodiorite (jøtunite) lithologies are exposed in the St. Urbain plutonic suite as a marginal facies to quartz mangerite and massif anorthosite intrusive bodies and as dikes within a variety of host rocks. High concentrations of Ti, Fe, P, K, Ba, Nb, La, Ce, Zn, Ga, Zr and Y characterize these rocks and are distinctive of many mafic lithologies associated with anorthosite massifs worldwide. Characteristically low concentrations of Ni and Cr, in conjuction with low Mg numbers, have been used by previous investigators as evidence for either partial melting of mafic granulitic lower crust or extensive fractional crystallization of a mantle-derived magma. In an attempt to distinguish between these competing models, we note that jøtunite display many features that bear a strong resemblance to continental tholeiitic flood basalts, including chemical signatures on normalized multi-element (‘spider’) diagrams. Ratios of incompatible trace elements and patterns on rare earth and ‘spider’ diagrams collectively indicate that the jøtunite rocks were derived from an enriched, rather than depleted, mantle source. Enrichment may have occured by subduction-derived fluids or by mixture with a plume component prior to partial melting so that isotopic and trace-element compositions are decoupled. Small amounts of partial melting of mafic granulite has been advanced as an alternative model; we show, however, that the experimental data on which this model is built are not applicable. Our preferred model begins with partial melting of a trace-element enriched mantle source that fractionates olivine at high to moderate pressures. Increasing concentrations of P (and Ti) eventually caused a contraction of the olivine stability field in favor of orthopyroxene. Fractional crystallization may yield the series of rocks from anorthosite, leuconorite, oxide-apatite gabbronorite, to jøtunite. Mafic magmas emplaced into continental crust are typically attributed to incipient rifting or mantle upwelling, which are features common to many models for the genesis of anorthosite and related rocks. 相似文献
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Nicolas D. Greber Christopher Siebert Thomas F. Nägler Thomas Pettke 《Geostandards and Geoanalytical Research》2012,36(3):291-300
Molybdenum concentration and δ98/95Mo values for NIST SRM 610 and 612 (solid glass), NIST SRM 3134 (lot 891307; liquid) and IAPSO seawater reference material are presented based on comparative measurements by MC‐ICP‐MS performed in laboratories at the Universities of Bern and Oxford. NIST SRM 3134 and NIST SRM 610 and 612 were found to have identical and homogeneous 98Mo/95Mo ratios at a test portion mass of 0.02 g. We suggest, therefore, that NIST SRM 3134 should be used as reference for the δ–Mo notation and to employ NIST SRM 610 or 612 as solid silicate secondary measurement standards, in the absence of an isotopically homogeneous solid geological reference material for Mo. The δ98/95MoJMC Bern composition (Johnson Matthey ICP standard solution, lot 602332B as reference) of NIST SRM 3134 was 0.25 ± 0.09‰ (2s). Based on five new values, we determined more precisely the mean open ocean δ98/95MoSRM 3134 value of 2.09 ± 0.07‰, which equals the value of δ98/95MoJMC Bern of 2.34 ± 0.07‰. We also refined the Mo concentration data for NIST SRM 610 to 412 ± 9 μg g?1 (2s) and NIST SRM 612 to 6.4 ± 0.7 μg g?1 by isotope dilution. We propose these concentration data as new working values, which allow for more accurate in situ Mo determination using laser ablation ICP‐MS or SIMS. 相似文献
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实地科考,广博查询,长期探索,坚韧追求,人类首次、全面解开世界海拔8 000m以上雪山之迷:海拔8 000m级雪山地有17处(其中3处山地为新发现),面积共11.95414km2,海拔8 000m以上独立山峰39座.世界海拔8 000m级山地和山峰地貌形态、相互关系,己在即将出版的"世界八千米雪山地图集"中得到表示.该图集比例尺1∶100000,等高距40m,幅面550mm×790mm.该图集由序言、7幅地图和后记组成,是世界第一部关于海拔8 000m级雪山地图集. 相似文献
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川西地区中三叠统雷口坡组岩相古地理 总被引:2,自引:0,他引:2
川西地区中三叠世雷口坡期位于威西蒸发海盆的西南部.盆地边缘及相邻地区主要发育潮坪相碳酸盐岩及少量的蒸发岩类,向盆地内部,除晚期部分地区发育碳酸盐岩外,硬石膏岩、石盐岩、杂卤石岩等蒸发岩类不断增多.区域上,岩相的垂向和平面相变明显。不同古地理位置的白天岩碳、氧同位素分析结果表明,盆地边缘的沉积作用和白云石化作用受到来自古陆方向的淡水影响。 相似文献