START — the road from Bellagio

The START initiative (co-sponsored by IGBP, WCRP and HDP) has as its primary objective development of regional frameworks to support regional research related to global change, associated capacity building and synthesis scientific assessments related to policy development. START now has six regional networks under development in South-East Asia, Northern Africa, East Asia, South Asia, the Meditteranean, and Southern Africa. Issues before START include the coordination of regional activities with that of sponsoring programmes, the need for a more elaborated HDP, and the development of thematic programming that will secure multi-donor, multi-year support.     

Recently formed elastic anisotropy and petrological models for the continental subcrustal lithosphere in southern Germany

This paper advances new evidence for elastic anisotropy in the continental subcrustal lithosphere in southern Germany. The range of petrological models compatible with the observed azimuthal variation of seismic P-wave velocity is explored. The azimuthal distribution of amplitudes of mantle phases and the observed increase of P velocity with depth both indicate a continuation of anisotropy with depth together with an increase of preferred orientation. Even depletion of the upper mantle in basaltic components, as suggested by mantle xenoliths from various parts of Germany, cannot explain the velocity-depth and azimuthal amplitude observations without an increase of anisotropy with depth.Preferred orientation of olivine is the most likely mechanism for the observed phenomena. Its fast a-axis at the Moho level is directed towards N22.5°E. The b-axis is also required to be horizontal; i.e., the b-plane, one of the preferred glide planes of olivine, is vertical, with a strike of N22.5°E. Therefore, this preferred glide plane of olivine practically coincides with the plane of maximum horizontal shear stress deduced from fault-plane solutions of earthquakes in western Germany. This is a strong indication that the preferred orientation of olivine is formed in the recent West European crustal stress field leaking into the upper mantle. The distribution of velocities to a depth of at least 50 km requires slight horizontal rotation of the a-axis with depth by ～ 10° towards N32°E, and a change in the modal composition towards a depletion increasing with depth compatible with the composition of mantle xenoliths from western Germany. Further experiments are needed to substantiate this suggestion, which could lead to a better understanding of the interaction of crustal and upper-mantle stress-strain fields.     

Calcium-aluminum-rich inclusions in the Allende meteorite: evidence for a liquid origin

We have made a detailed examination of the mineralogy, textures and assemblages of six calcium-aluminum-rich inclusions (CAI) in the Allende meteorite. They can be classified into four types—hibonite-bearing, fassaite- and olivine-bearing, feldspathoid-bearing and fassaite-bearing CAI that are hibonite and olivine free. Examples of each type appear to have crystallized from a liquid rather than by agglomeration of solid nebular condensates. Some lines of evidence for a liquid origin are (1) the presence of spherical and ovoid shapes, (2) rims containing minerals (e.g. hibonite, perovskite) that are more refractory than minerals inside the inclusion, (3) eutectic and poikilitic textures, (4) minerals that are completely enclosed by more refractory minerals and (5) glass and fine-grained grossular stringers.Thermodynamic calculations and comparisons with liquidus phase diagrams indicate that the CAI could have been produced by direct condensation to metastable subcooled liquids that subsequently crystallized (blander and Katz, 1967) or by remelting of an equilibrium high-temperature condensate by impact. The diopside rims in some hibonite-bearing CAI and the paucity of metal in fassaite-olivinebearing CAI are more consistent with direct condensation of a liquid. The sluggishness of solid-solid reactions at the relatively high temperatures at which the CAI formed argues against assuming equilibrium in calculations at lower temperatures.     

Crustal structure of the Rhinegraben area

Numerous ge ological and geophysical investigations within the past decades have shown that the Rhinegraben is the most pronounced segment of an extended continental rift system in Europe. The structure of the upper and lower crust is significantly different from the structure of the adjacent “normal” continental crust.

Two crustal cross-sections across the central and southern part of the Rhinegraben have been constructed based on a new evaluation of seismic refraction and reflection measurements. The most striking features of the structure derived are the existence of a well-developed velocity reversal in the upper crust and of a characteristic cushion-like layer with a compressional velocity of 7.6–7.7 km/sec in the lower crust above a normal mantle with 8.2 km/sec. Immediately below the sialic low-velocity zone in the middle part of the crust, an intermediate layer with lamellar structure and of presumably basic composition could be mapped.

It is interesting to note that the asymmetry of the sedimentary fill in the central Rhinegraben seems to extend down deeper into the upper crust as indicated by the focal depths of earthquakes. The top of the rift “cushion” shows a marked relief which has no obvious relation to the crustal structure above it or the visible rift at the surface.     

Chromium and phosphorus enrichment in the metal of type II (C2) carbonaceous chondrites

Electron microprobe analyses of metal grains in nine C2 meteorites show consistently high Cr and P contents, with large grain to grain variations within individual meteorites. Cr ranges from 0.16 to 1.0 wt.% (average 0.6 per cent for 43 analyses). P ranges from 0.00 to 3.2 wt.% (average 0.42 per cent). In addition, metal grains in seven C3 meteorites show a lesser enrichment of Cr, 0.00 to 0.7 per cent (average 0.13 per cent for 59 analyses), with no P present. Both of these elements, Cr and P, are generally below detection in the metal of other chondrite groups, equilibrated and unequilibrated. C2 metal grains occur typically as spherical to ovate blebs contained within single, euhedral forsterite crystals or crystal fragments that are either isolated in the black C2 matrix or are in clusters making up white inclusions. Metal is rare within true chondrules. Calculations of the expected Cr contents in metal condensing directly from a solar nebular gas agree remarkably well with the observed values. Unfortunately, no calculation is possible for P because of insufficient data at the present time. The composition and the textural relationships indicate this Cr, P rich metal, and the enclosing forsterite are direct condensates from a cooling solar nebula. Cr and P, in the quantities reported here, characterize C2 metal.     

Tektonische Untersuchungen in dem zentralindischen Manganerz-Gürtel des südlichen Bawanthari-Fluß-Gebietes

Zusammenfassung Das Gebiet des südlichen Bawanthari-Flusses wurde in zwei Jahren geologisch neu aufgenommen, wobei in dem vorliegenden Bericht die Ergebnisse der tektonischen Bearbeitung dargelegt werden.In dem gesamten Arbeitsgebiet ist immer nur eine Hauptschieferung S₁, S₂, S_x) erkennbar, die aber in den untersehiedlichen Gesteinstypen und in Abhängigkeit von deren Deformationsgrad (und Metamorphose) verschiedenartige Trennflächen darstellt. Im Süden herrscht eine hauptsächlich der ursprünglichen Schichtung folgende (S₁=SS) und dem metamorphen S entsprechende Schieferung vor. Nördlich daran anschließend wird das Schieferungsgefüge vor allem durch eine Achsenebenenschieferung (S₂) geprägt, die gewöhnlich nicht vom metamorphen S (S₁) getrennt werden kann. Die Trennflächen S_x in den Gneisen sind uneinheitlicher ausgebildet und verlaufen meist parallel zu einer ausgeprägten Bänderung.Zwei Faltengenerationen sind erkennbar. Der Verlauf der Falten der ersten Generation ist prinzipiell West-Ost. Der Faltenstil ändert sich jedoch von Süden nach Norden. Im Süden herrschen Biegefalten vor. Nördlich davon gehen diese zuerst in eng zusammengepreßte, nach Norden überkippte isoklinale Scherfalten über, die schon teilweise den Charakter von Fließfalten haben. Die Falten der zweiten Generation sind stets Querfalten (B B), fallen nach Süden ein und sind fast ausschließlich liegende Fließfalten. Letztere sind etwas jünger als die Falten der ersten Generation.Der regionale Faltenbau verhält sich wie der im Handstückbereich. Die regional entwickelten Syn- und Antiklinen sind jedoch keine einheitlich verlaufenden Großfalten, sondern Faltensysteme, die sich in der Art von en-échelon-Falten, aus mehreren, immer mehr nach Norden verschobenen Einzelfalten zusammensetzen. Neben diesem Faltenbau der ersten Generation, der im ganzen Gebiet verfolgt werden kann, bilden die Großfalten der zweiten Generation nur im Norden zwei unregelmäßige Antiklinen aus.Abweichend von der Auffassung früherer Bearbeiter kann das Untersuchungsgebiet nicht in mehrere, durch regional verfolgbare Störungszonen getrennte Faltengürtel gegliedert werden. Es wird der Nachweis erbracht, daß eine kontinuierliche Intensivierung der Verformung (parallel der ansteigenden Metamorphose) von Süden nach Norden festzustellen ist.

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In a period of 2 years the area of the Southern Bawanthari River has been mapped. In the following paper the results concerning the structure are presented.In the mapped area only one trend of foliation has been recognised, of which only locally, depending on the type of rock, degree of deformation (and degree of metamorphism), different types (S₁, S₂, S_x) can be distinguished. In the south the foliation (S₁) is usually parallel to the original bedding (S₁ = SS). To the north this foliation gradually changes to a typical axial plane foliation (S₂) and S₁ disappears competely. Further north this schistosity becomes a typical gneissic lamination (S_x).Two generations of folds have been recognised. The general trend of the first generation folds is west-east, but their style changed from south to north. In the south similar folds dominate, which further north gradually change to concentric isoclinal shear folds. These are first slightly and then more and more overturned to the north. The overturned, lying isoclinal folds resemble flow folds. The folds of the second generation are cross folds (B B); they plunge to the south and generally are flow folds. They are slightly younger than the folds of the first generation.The macroscopic fold pattern is identical to the pattern observed in hand specimens. The macroscopic synclines and anticlines show no regular synclinorium, but a system of folds, which follow each other to the north in an en échelon fashion. In contrast to the fold structures of the first generation, which can be recognised every where in the area studied, the macroscopic folds of the second generation are developed only in the northern part of the area, where they form two irregular anticlines.In contrast to the opinion of earlier workers the mapped area cannot be divided into different fold belts along major fault zones. It is shown that a gradual increase of deformation to the north exists, which parallels the increase of metamorphism.

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Résumé La géologie de la région située au sud du fleuve Bawanthari a été étudiée de nouveau au cours de deux années. C'est dans ce résumé que les résultats des recherches structurales seront présentés.Dans la région en question, on peut toujours observer un clivage principal qui représente toute fois selon les types différents de roche, leur dégré de déformation (et leur dégré de métamorphisme) des plans de séparation différents: au sud, le clivage est en général parallèle à la stratification originale (S₁=SS). Vers le nord, le clivage (S₁) est transformé en un clivage de plan axial (S₂=schistosité) tandis que (S₁) disparaÎt entièrement. Plus au nord, enfin, la schistosité se développe en une structure rubanée gneissique (S_x).On peut constater deux générations de plissements: la direction des plissements de la lère génération est ouest-est tandis que le style de plissement varie du sud au nord. Au sud, les plissements véritables dominent. Plus au nord, les plis se transforment d'abord en plis de cisaillement qui sont fort comprimés et déversés, adoptant en partie le caractère de plis de fluage. Les plis de la 2ème génération sont toujours des plis repliés (B B) qui plongent vers le sud et qui sont presque sans exception des plis de fluage couchants. Ceux-ci sont un peu plus jeunes que les plis de la lère génération.Le type de plissement macroscopique ressemble au type mésoscopique. Les synclinaux et anticlinaux macroscopiques ne sont toutefois pas des synclinoriums régulièrement formés, mais des systemes de plis qui, à la manière de plis »en échelon«, se composent de plusieurs plis particuliers. Outre ce type de plissement de la lère génération développé dans toute la région, les plis macroscopiques de la 2ème génération ne forment au nord que deux anticlinaux irréguliers. à l'opposé des opinions d'autres auteurs, la région étudiée ne peut Être divisée en zones de plissement séparées par des zones de faille de caractère régional. Le résultat de ces recherches montre que, du sud vers le nord, une augmentation continuelle de déformation est accompagnée d'un métamorphisme intensifié.

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- , . — S₁, S₂, SS_× —, . , — S₁ = SS — S · , S₂, S (S1). . — : , : , , , . , . — , . , , , , , . , , . — , , . , , , .

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Den Herren Prof. R.Thienhaus , Prof. H.Borchert (beide Clausthal) und Prof. K.Schmidt, Münster, möchte ich hiermit für die anregenden Diskussionen und das Interesse an dieser Arbeit danken. Für die finanzielle Unterstützung bei der Geländearbeit danke ich dem Deutschen Akademischen Auslandsdienst (DAAD), Bad Godesberg.     

Massif Central (France): new constraints on the geodynamical evolution from teleseismic tomography

The Massif Central, the most significant geomorphological unit of the Hercynian belt in France, is characterized by graben structures which are part of the European Cenozoic Rift System (ECRIS) and also by distinct volcanic episodes, the most recent dated at 20 Ma to 4000 years BP. In order to study the lithosphere-asthenosphere system beneath this volcanic area, we performed a teleseismic field experiment.
During a six-month period, a joint French-German team operated a network of 79 mobile short-period seismic stations in addition to the 14 permanent stations. Inversion of P -wave traveltime residuals of teleseismic events recorded by this dense array yielded a detailed image of the 3-D velocity structure beneath the Massif Central down to 180 km depth. The upper 60 km of the lithosphere displays strong lateral heterogeneities and shows a remarkable correlation between the volcanic provinces and the negative velocity perturbations. The 3-D model reveals two channels of low velocities, interpreted as the remaining thermal signature of magma ascent following large lithospheric fractures inherited from Hercynian time and reactivated during Oligocene times. The teleseismic inversion model yields no indication of a low-velocity zone in the mantle associated with the graben structures proper. The observation of smaller velocity perturbations and a change in the shape of the velocity pattern in the 60–100 km depth range indicates a smooth transition from the lithosphere to the asthenosphere, thus giving an idea of the lithosphere thickness. A broad volume of low velocities having a diameter of about 200 km from 100 km depth to the bottom of the model is present beneath the Massif Central. This body is likely to be the source responsible for the volcanism. It could be interpreted as the top of a plume-type structure which is now in its cooling phase.     

Application of Hydrophobic Interaction Chromatography (HIC) in Water Analysis Anwendung der Hydrophobizitätschromatographie (HIC) in der Wasseranalytik

Dissolved high molecular weight organic substances, like humic substances, can be characterized with regard to their molecular weight distribution using gel filtration chromatography (GFC). In addition, the adsorption properties, for example on activated carbon, can be described, if the substances are separated by hydrophobic interaction chromatography (HIC) in different fractions using a chromatographic column with a hydrophobic matrix. The retention time (Rt) of single chemical substances in this column can be used to characterize the hydrophobicity or hydrophility of each compound as well as of the high molecular weight organic matter. The hydrophobic interaction between the matrix of the column and the dissolved chemical compounds also depends on the hydrophobicity of the gel and the composition of the eluent. Relations between retention times, log P-coefficients (octanol/water partition) and K-values of isotherms on activated carbon (Freundlich equation) were found.