The Equatorial Ring Current as a Part of a Coupled System

The equatorial ring current is the symmetrical plasmaspheric drift current of energetic plasma trapped by the geomagnetic field. Assuming that, during a geomagnetic storm, the ring can exchange energy with other regions of the magnetosphere, a second-order differential equation must be considered as its dynamical expression, and contributions other than the solely solar-wind-induced electric field must express the forced input. The decay parameters of the recovery phase of the storm must be determined considering periods with Bz(IMF) Bz(IMF) 0.     

Vulkanismus und Graben-Bildung im Roten Meer

Zusammenfassung Von Vulkanit-Proben derValdivia-Kampagnen 1971/72 werden die Ergebnisse petrographischer und chemischer Untersuchungen dargestellt. Im zentralen Graben des Roten Meeres sind Olivin-Tholeiit-Baselte ohne modalen Pyroxen verbreitet. Außerhalb des zentralen Grabens treten neben vorwiegend holokristallinen Pyroxen-führenden Olivin-Tholeiit-Basalten Alkali-Basalte sowie basaltische Tuffe und Hyaloklastite auf. Vergleichsweise wurden Basalte und deren saure Differentiate aus dem Hinterland von Djibouti untersucht. Kristallisations- und Differentiationsgrad der Gesteine sind Abbild eines diapirartig aufgestiegenen Asthenolithen. Die Aufwölbung der Asthenosphäre wird durch die Einsenkung eines Scheitelgrabens kompensiert. Eine Trennung der kontinentalen Kruste betrifft nur den Bereich des zentralen Grabens.

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During theValdivia cruise 1971/72 volcanic fragments were raised from the bottom of the Red Sea, especially from the axial through. Data on petrography and chemistry are represented. The axial trough is floored with olivine-tholeiitic basalts without modal pyroxene. According to the rapid ascent from relatively shallow depth olivinetholeiitic magma reached the sea-floor before any substantial differentiation took place. Beyond the axial trough alkali-basalts, basaltic tuffs, hyaloklastites are distributed as well as olivine-tholeiitic basalts with modal pyroxene. For comparison basalts and their acid differentiates from the hinterland of Djibouti have been analyzed and discussed. The grade of crystallisation and fractionation of the melt is in a direct connection with the diapiric upwelling of the asthenosphere. The upwarped asthenosphere is compensated by normal faulting and rifting of the axial trough. The attenuation and separation of the continental crust is restricted to the axial trough.

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Résumé Pendant les campagnes de laValdivia en 1971/72, des échantillons de volcanites ont été prélevés au fond de la Mer Rouge, à des fins d'analyses pétrographiques et chimiques. Dans le fossé central il y a des basaltes tholéiitiques à olivine sans pyroxène modal. En dehors du fossé central apparaissent des basaltes alcalins, des tufs basaltiques et des hyaloclastites ainsi que des basaltes tholéiitiques à olivine et pyroxène modal prédominemment holocristallins. A titre de comparaison, des basaltes et leurs différenciats acides, prélevés dans le hinterland de Djibouti, ont été analysés. Le degré de cristallisation et de différenciation des roches est en relation avec l'asténolite monté par voie diapirique. Le bombement de l'asténosphère est compensé par l'enfoncement du fossé. La séparation de la croûte continentale est restreinte au fossé axial.

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, 1971/1972 . - . , - , , . . . . .

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Herrn Dr. H.Bäcker von derPreussag AG, Hannover, danken wir für dieÜberlassung des Proben-Materials und für das Einverständnis zur Publikation. Wir danken unseren Kollegen A.Baumann, Braunschweig, und H.Raschka, BfB Hannover, für die Bestimmung der Schwermetall- und Spurenelement-Gehalte sowie den Herren H.Pichler, Tübingen, und A.Schneider, Göttingen, für die Norm-Berechnungen.     

Chemistry and genesis of garnets in metamorphic rocks

250 analyses of garnets in metamorphic pelitic, arkosic, and pyroclastic rocks from the Stavanger area have been made by means of a microprobe (ARL-EMX). The relations between chemistry and metamorphic grade are discussed. The dependence of the Mn content upon temperature, pressure, chemistry of the parent rocks and oxygen fugacity is a very sophisticated one.It is shown that the Mn content of the garnets depends on the oxygen fugacity of the system and that the oxygen fugacity is strongly linked to the behaviour of graphite during increasing metamorphism.Examples described by Miyashiro (1953) and Engel and Engel (1960) are in agreement with the model presented here.Some observations show an influence of primary sedimentary enrichments of manganese upon the first occurrence of garnets in the course of metamorphism.     

Computer modelling of clouds at Kleiner Feldberg

The airflow, cloud microphysics and gas- and aqueous-phase chemistry on Kleiner Feldberg have been modelled for the case study of the evening of 1 November 1990, in order to calculate parameters that are not easily measured in the cloud and thus to aid the interpretation of the GCE experimental data-set. An airflow model has been used to produce the updraught over complex terrain for the cloud model, with some care required to ensure realistic modelling of the strong stable stratification of the atmosphere. An extensive set of measurements has been made self-consistent and used to calculate gas and aerosol input parameters for the model. A typical run of the cloud model has calculated a peak supersaturation of 0.55% which occurs about 20 s after entering cloud where the updraught is 0.6 m s^–1. This figure has been used to calculate the efficiency with which aerosol particles were scavenged; it is higher than that calculated by other methods, and produces a cloud with slightly too many droplets. A broad cloud droplet size spectrum has been produced by varying the model inputs to simulate turbulent mixing and fluctuations in cloud parameters in space and time, and the ability of mixing processes near cloud-base to produce a lower peak supersaturation is discussed. The scavenging of soluble gases by cloud droplets has been observed and departures from Henry's Law in bulk cloud-water samples seen to be caused by variation of pH across the droplet spectrum and the inability of diffusion to adjust initial distributions of highly soluble substances across the spectrum in the time available. Aqueous-phase chemistry has been found to play a minor role in the cloud as modelled, but circumstances in which these processes would be more important are identified.     

桂林唐家湾剖面中—上泥盆统碳酸盐岩沉积相和成岩作用

本文的工作区域是按中国地矿部和德国下萨克森州科学和艺术部之间科学台作协议而提供的。在唐家湾地区的中上泥盆统碳酸盐岩中可以见到以下8种微相类型:泥岩、具纹层球粒-颗粒岩/泥粒岩、无纹层球粒-颗粒岩/泥粒岩、介形虫-颗粒岩/泥粒岩、枝状层孔虫-粒泥岩、枝状层孔虫-棘皮类-粒泥岩、生物碎屑-粒泥岩和骨架岩。这些微相类型可指示不同的能量指数及水深。同欧文(Irwin,1965)浅水碳酸盐沉积模式对比,唐家湾泥盆纪(吉维特期和弗拉斯期)属于Y带和Z带沉积,并可分出发育生物丘-生物层的正常海环境、局限浅水沉积环境和潮坪沉积环境。最大水深估计为10m—20m。唐家湾剖面碳酸盐岩经历了三种早成岩环境:海水成岩环境、大气水成岩环境和混合水成岩环境。其后又经历了晚成岩阶段的压溶、重结晶和交代作用。白云石化部分为混合水成因,部分为晚成岩期交代成因。     

The application of Tb/Ca-Tb/La abundance ratios to problems of fluorspar genesis

A comprehensive review of the authors' and their co-workers' results on the fractionation of Rare Earth Elements (REE) during the crystallization and/or recrystallization of Fluorspar is given. The fractionation can be explained as the result of REE complexation in the ore forming solution and systematic changes in distribution coefficients of REE. It is shown that the Tb/Ca and Tb/La ratios are sufficient to characterize pegmatitic (pneumatolytic), hydrothermal and sedimentary fluorspar. This has been confirmed by numerous investigations on various types of deposits.     

The friction and deformation behaviour of rock joints

SummaryThe Friction and Deformation Behaviour of Rock Joints The present investigation deals with the influence of joint roughness and material strength on the friction and deformation behaviour of rough indented joints. Besides the analytical determination of the joint roughness by the dilatation behaviour of the joint, friction tests on models with natural joint morphology and rock samples have been conducted.A material law is developed, describing the friction resistance and the dilatation behaviour at large deformations in their dependence on normal stress and material strength.

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ZusammenfassungDas Reibungs- und Verformungsverhalten von Klüften Die vorliegende Untersuchung war dem Einfluß der Kluftflächenunebenheit und der Materialfestigkeit auf das Reibungs- und Verformungsverhalten rauher, verzahnter Kluftflächen gewidmet.Neben der analytischen Bestimmung der Kluftflächenunebenheit anhand des Dilatationsverhaltens der Kluftfuge wurden Reibungsversuche an Modellkörpern mit natürlicher Kluftmorphologie und an Gesteinen durchgeführt. Es wird ein Stoffgesetz entwickelt, mit welchem der Reibungswiderstand und das Dilatationsverhalten in Abhängigkeit von der Normalspannung und der Materialfestigkeit bei längeren Gleitwegen beschrieben werden kann.

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RésuméLe comportement des fissures au frottement et aux déformations La présente étude traite de l'influence de la rugosité d'une diaclase et de la résistance de la roche sur le comportement au frottement et aux déformations d'une fissure âpre et endentée. La rugosité de la fissure a été déterminée d'après la dilatation maximale. Des éssais de frottement ont été exécutés à l'aide de modèles ayant une surface de fissure naturelle et à l'aide d'échantillons de roche. Une loi a été développée qui décrit la resistancé au frottement et le comportement à la dilatation de la fissure pour de grandes déformations en fonction de la contrainte normale et de la résistance des matériaux.

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List of Symbols h dilatation - i deviation angle, dilatation angle - s shear deformation - residual friction angle - normal stress - _F tensile strength - shear stress With 15 Figures     

Deformation of shock-loaded andalusite studied with X-ray diffraction techniques

The structural deformation of an andalusite single crystal, shockloaded up to 400 kb with shock wave direction approximately parallel to c, was investigated by means of X-ray powder (Guinier) and single crystal techniques (Weissenberg, precession). Exposure to the dynamic pressure revealed a fracturing of the crystal into lattice blocks, with a mean size >1,000 Å. No change of the lattice constants could be observed after pressure release. From the streaks of X-ray reflection spots measured within the hk0, h0l, 0kl, and hhl planes the shock-induced lattice deformation is interpreted in terms of rotational gliding and/or microfracturing. The distortion mode is highly structure controlled. It follows preferrably two different structural motion systems: (1) Gliding parallel to (001) occurs, which produces lamellae parallel to (001), mainly arranged in two sublattices with common c-axis. The stacking sequence of lamellae along c is irregular. The lamellae-type structure may also result from an orientated transformation into a high pressure phase of lower symmetry and subsequent inversion into the original phase after pressure release. (2) Gliding parallel to (100) occurs. In this case the deformation mode is asymmetrical with respect to the undistorted crystal. The common direction b of the (001) and (100) deformation planes is probably the main direction of the shock-induced lattice deformation.     

Neue Bücher und Zeitschriften

Ohne ZusammenfassungDie Transkription der Autorennamen und der geographischen Namen erfolgte nach den Richtlinien der Zentralstelle für wissenschaftliche Literatur, Berlin NW 7, vom 7. Dezember 1955.