Zur Petrogenese intermediärer effusiver Magmen

Zusammenfassung Die intermediären effusiven Magmen gehen auf ein einziges, auf das olivinbasaltische Magma zurück. Bei dessen langwährendem Eruptionsprozeß aus dem oberen Erdmantel durch die Sialkruste bis zur Oberfläche findet durch Reaktion mit den wall rocks des Grund- und Deckgebirges eine (z.T. selektive) Einschmelzung statt, die zur völligen Syntexis führt. Durch Zunahme von Si, Al und Alkalien aus dem kristallinen Grundgebirge entstehen die übersättigten Vulkanite. Die Desilifizierung der foidführenden Alkaligesteine wird nachDaly undShand durch Assimilation von Kalk, Dolomit und Mergel herbeigeführt.Ungeklärt bleibt hierbei jedoch die Zunahme des Kalis; denn dies war mit seiner Menge dem basischen Ausgangsmagma fremd. An Hand untersuchter Vorkommen in der Rhön und im Kaiserstuhl/Deutschland, im Monzoni-Gebiet/Oberitalien und in der Roccamonfina NW Neapel wird gezeigt, daß es komplexe Vorgänge sind, die die Kali-betonten Alkali-Effusivmagmen schufen. Bereits vor der Syntexis durch Karbonatgesteine waren sie schon einmal gründlich verändert worden durch Assimilation von Alkalisilikatgesteinen des durchbrochenen Grundgebirgssockels.

---

The intermediate effusive magmas originate in only one, the olivine basalt magma. During its continuous eruption-process out of the upper mantle through the sial crust to the earth's surface there takes place a (partly selective) assimilation by reaction with the wall rocks of the basement and the sedimentary covering, that leads to a complete syntexis. By increase of silica, alumina and alcalis of the crystalline basement the oversaturated vulcanites are formed. AfterDaly andShand the assimilation of lime, dolomite and marl causes the desilication of the feldspathoid-bearing alcali rocks.Nevertheless the increase of the potassium is indefinite, because it was not in accordance the basic primary magma with regarding its amount. With the aid of investigated rocks of Rhön, Monzoni-district/Upper Italy, Roccamonfina nw. Naples, and Kaiserstuhl there is shown, that complex processes created the potassium-rich alcali-effusive magmas. Already befor syntexis by limestones they were fundamentally transformed by assimilation of alcali-silicate rocks of the broken through basement platform.

---

Résumé Les magmas effusives intermédiaires peuvent être ramenés à un seul, le magma olivine-basaltique. Pendant le procès d'éruption lente de celui-ci par l'écorce sialique à la surface il se produit une réaction avec les « wall rocks » du cristallin et du manteau sédimentaire. Cette réaction produit par assimilation des matériaux une syntexis complète. Par augmentation de Si, Al, et des éléments alcalins du socle cristallin se développent les roches volcaniques sursaturées. La désilification des roches alcalines avec feldspathoides se produit d'aprèsDaly etShand par assimilation de calcaires, dolomites et marnes.L'augmentation du potassium reste à expliquer; la grande quantité de potassium n'existe pas dans le magma original basique. Nous avons pu démontrer par la recherche des roches volcaniques de la « Rhön », de « Monzoni » (Italie), de « Roccamonfina » (Naples) et du « Kaiserstuhl » que les réactions, qui produisent les magmas basiques alcalins avec dominance de potassium, sont d'un type très complexe. Ces magmas ont été modifiés à fond avant la syntexis par les roches carbonatiques au cours de l'assimilation des roches alcalo-siliciques du socle cristallin surmonté.

---

, - . ( ) . , . (Rhö n, Kaiserstuhl) (Monzoni, Roccamonfina) , .

     

New safety issues when moving from liquid fuels to natural gas

Natural gas (NG) is produced whenever organic matter is decomposed in the absence of oxygen. The main constituent of natural gas is methane. In contrast to liquid fuels, methane has a boiling point far below normal ambient temperatures. Even the critical temperature is well below ambient. Therefore natural gas must be stored either as compressed natural gas (CNG) at very high pressures at ambient temperatures, or as liquefied natural gas (LNG) at very low temperatures. The basic safety issues are caused by loss of confinement of either CNG or LNG. In both cases the issues are: global greenhouse effects of natural gas (methane); local fire and explosion hazards; and local asphyxiation hazard due to reduced oxygen content in the atmosphere breathed when air is mixed with methane.     

Time of maximum Late Wisconsin glaciation, West Coast of Canada

New data from a deep-sea core in the eastern North Pacific Ocean indicate that the western margin of the Late Wisconsin Cordilleran Ice Sheet began to retreat from its maximum position after 15,600 yr B.P. Ice-rafted detritus is present in the core below the 15,600 yr B.P. level and was deposited while lobes of the Cordilleran Ice Sheet advanced across the continental shelf in Queen Charlotte Sound, Hecate Strait, and Dixon Entrance. The core data are complemented by stratigraphic evidence and radiocarbon ages from Quaternary exposures bordering Hecate Strait and Dixon Entrance. These indicate that piedmont lobes reached the east and north shores of Graham Island (part of the Queen Charlotte Islands) between about 23,000 and 21,000 yr B.P. Sometime thereafter, but before 15,000–16,000 yr B.P., these glaciers achieved their greatest Late Wisconsin extent. Radiocarbon ages of late-glacial and postglacial sediments from Queen Charlotte Sound, Hecate Strait, and adjacent land areas show that deglaciation began in these areas before 15,000 yr B.P. and that the shelf was completely free of ice by 13,000 yr B.P.     

I. Erdöl Ergebnisse der erdölgeologischen Erforschung Nordwestdeutschlands 1932–1947, ein Überblick

Ohne Zusammenfassung     

Chemical aspects of quick-clay formation

In connection with the systematical examination of the slope stability in the Go¨ta River Valley in Sweden it was impossible to get a satisfactory explanation of the cause of the high sensitivity of quick clays which could be used in the continued examination as a basis for geotechnical investigations.

It was concluded that the quick-clay problem must be regarded as a problem of colloid chemical nature. Many of the results obtained pointed out the fact that the surface properties of the grains will play an important role, and in this connection the problem with the possible existence of surface-active agents (dispersing agents) in natural quick clays has been studied.

Systematic isolations of dispersing agents have been made by different methods, and the subsequent extracts have been analysed chromatographically. It is found to be easy to isolate dispersing substances by most of the methods tested, but it is very difficult to find any substances with a known composition. Instead, this part of the examination will approach the humic problem. In one case it has been possible to break up the complexes into individual components of known composition, i.e., in the case of fatty acids and soaps. Quick clay contains homologuous series of normal saturated fatty acids and for this reason soaps seem to be components which contribute to the quick-clay formation.     

Crustal structure between the Knipovich Ridge and the Van Mijenfjorden (Svalbard)

Marine Geophysical Research - The Alfred Wegener Institute of Polar and Marine Research, the University of Bergen and Hokkaido University acquired new seismic refraction data along a transect from...     

Comparison of Earth’s magnetospheric magnetic field models in the context of cosmic ray physics

Over the last two decades, models of the Earth’s magnetospheric magnetic field have been continuously improved to describe more precisely the different magnetospheric current systems (magnetopause current, symmetric and partial ring currents, tail currents and field aligned currents). In this paper we compare the different Tsyganenko models and the Alexeev and Feldstein model in the context of cosmic ray physics. We compare the vertical cutoff rigidity and asymptotic direction of vertical incidence obtained with these models for the January 20, 2005, ground level enhancement and for the big magnetic storm of April 6, 2000. For the event of January 20, 2005, we study the impact of the differences in asymptotic direction obtained with the models on the radiation dose computation at aircraft altitude. For the magnetic storm of April 6, 2000, we discuss the importance of the different magnetospheric current systems in causing cutoff rigidity variations. Finally we summarise the advantages and drawbacks of the different models in the context of space weather.