Eine gerichtete Kontaktbreccie am Basaltstock der kleinen Schneegrube im Riesengebirge

Zusammenfassung Die vulkanische Tätigkeit an der kleinen Schneegrube im schlesischen Riesengebirge kam hoch an den gut ausgebildeten S-Klüften des Granits. Explosionen begannen. Sie wahrscheinlich verwandelten den Granit auf kleinem Raum in eine schalige Feinbreccie, die aus parallelen Granittäfelchen von loser, aber streng paralleler Packung aufgebaut ist. Noch zähe Schlackenbomben wurden ihr ein- und zwischengelagert. Grobe und mächtige Schlackenagglomerate folgten. Zum Schluß drang Basaltschmelze empor und verzweigte sich in und zwischen den umgebenden Gesteinen zu einem länglichen, steilen Stock. Scherben der granitischen Feinbreccie wurden von ihr umschlossen und mit Mineralneubildungen (Opal und Zeolithen) zementiert. Die Breccie selbst wurde gestaucht und gefaltet.Die Zertrümmerung des Granits ging an einem ungleichwertigrechtwinkligen Rißsystem vor sich, das in zwei Hauptebenen der elastischen Beanspruchung lag, und unterscheidet sich insofern von den bekannteren Beispielen einer natürlichen Verformung unter Bruch.     

On time scales and causes of abrupt paleoclimatic events

During the last 7 × 10⁵ years the occurrence of abrupt climatic variations, of an intensity probably reaching 5°C/50 yr and with a duration of the order of several centuries can be demonstrated; their frequency is of the order 10^?4 (sometimes even 10^?3) per year. Most impressive examples are sudden coolings in earlier interglacials; in some periods the variability of past climates was obviously much greater than now. Due to the effective spatial coherence of the atmospheric and oceanic circulation their extension, not necessarily of similar intensity, is probably hemispheric or even global. They are modified by feedback mechanisms within the geophysical climatic system; orbital changes play a selective role leading either to suppression or to growth. Any physical interpretation of such abrupt paleoclimatic events remain as yet speculative. One of the most attractive models is the occurrence of clusters of major volcanic eruptions which is more frequent than expected in random series. This is similar to the clustering of severe earthquakes in recent years; both events are probably interrelated responses to the (apparently discontinuous) motions of tectonic plates.     

Zur Kenntnis des Klimas der Freien Atmosphäre über Sizilien

Zusammenfassung Auf Grund einer 21 Monate (Oktober 1941–Juli 1943) umfassenden Messreihe von deutschen Radiosonden und Höhenwindmessungen in Catania werden die mittleren Temperatur- und Druckverhältnisse bis 20 (bzw. 22) km Höhe über Sizilien abgeleitet. Die Bearbeitung der Höhenwinde nach Häufigkeit, Richtung und Geschwindigkeit beschränkt sich auf die orographisch nicht mehr gestörte Troposphäre zwischen 3 und 12 km. Vergleichende Betrachtungen beziehen sich auf die Temperaturunterschiede in meridionaler und zonaler Richtung, sowie auf die Windverhältnisse in Mittelmeergebiet.

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Summary On the base of german radio-soundings and pilot-balloons during a 21-month-period (1941, October to 1943, July) at Catania the average temperatures and pressures over Sicily up to 20 (or 22) km were derived. The discussion of upper wind deals with frequence, direction and velocity in the orographically undisturbed troposphere between 3 and 12 km, comparing the meridional and zonal differences of temperature and the distribution of wind in the Mediterranean area.

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Riassunto Nei 21 mesi dall'Ottobre 1941 al Luglio 1943 il Servizio Meteorologico Tedesco eseguì a Catania radio-sondaggi e misure del vento in quota, dalle quali è possibile deduree le condizioni termiche e bariche medie regnanti sulla Sicilia fino all'altezza di 20 (o 22) km. L'elaborazione dei venti in quota, secondo la frequenza, la direzione e la velocità si limita a quella parte della troposfera orograficamente non perturbata fra 3 e 12 km d'altezza. L'analisi comparativa dei risultati riguarda particolarmente le differenze di temperatura nella direzione meridionale e zonale, nonchè le condizioni anemologiche dominanti nel Mediterraneo.

     

Niederschlagsstrukturen von Zyklonen in Nordamerika

Zusammenfassung Durch Auswertung der stündlichen Niederschlagsmessungen von 1500 Stationen in den USA werden die Ausbreitungsformen und die zeitlichen Intensitätsvariationen der Niederschläge von 32 nordamerikanischen Zyklonen während der Jahre 1949 und 1950 untersucht. Es ergibt sich, daß im Durchschnitt die Niederschlagsgebiete dieser Zyklonen ihre größere Fläche und Ergiebigkeit links von der Zugbahn des Zentrums haben. Ein geschlossener Ausläufer des Niederschlagsgebietes wird auf der linken Seite des Tiefs herumgeführt. Die Fronten und ihre Niederschläge haben keinen verbindlichen Zusammenhang mit dem eigentlichen Niederschlagsgebiet der Zyklone.Es wird der Aufbau des Zyklonenteils links von der Zugbahn des Zentrums diskutiert und zur Deutung werden für die Luftmassen in diesem Teil erhebliche Aufgleitvorgänge gefordert. Durch theoretische Betrachtungen und den Nachweis der Wahrscheinlichkeit anderer Hebungsursachen in diesem Teil der Zyklone wird diese Vorstellung unterstützt.Die Niederschlagsintensität erfährt bei Durchzug des Zyklonenkerns starke Variationen mit charakteristischen Merkmalen, die zum Teil ausgeprägte Erhaltungstendenz zeigen. Zur Deutung dieser Ergebnisse wird die Existenz von Wellenzügen innerhalb der Grenzfläche als wahrscheinlich angesehen.

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Summary By evaluating the hourly measurements of the precipitations of 1500 stations in the USA, the forms of extension and the time variations of intensity of the precipitations of 32 North American cyclones during the years 1949 and 1950 are examined. It results that on an average the precipitation areas of these cyclones have their larger surface and yield to the left of the way of the centres. A closed spur of the precipitation area is led around to the left of the low pressure. The fronts and their precipitations have no direct connection to the real precipitation area of the cyclones.The structure of the cyclone part left to the way of the centre is discussed, and for the explanation considerable upslide phenomenons are requested for the air masses in this part. By theoretic consideration and the proof of probability of other elevation moments in this part of the cyclones this conception is supported.The precipitation intensity gets, when the cyclone core passes, strong variations with characteristics partly showing a pronounced tendency of persistence. For the explanation of these results the existence of wave trains within the boundary surface of the air masses is considered to be probable.

     

Melt- versus fluid-induced metasomatism in spinel to garnet wedge peridotites (Ulten Zone, Eastern Italian Alps): clues from trace element and Li abundances

The peridotite bodies of the Ulten Zone (Upper Austroalpine, Italian Eastern Alps) are enclosed in Variscan migmatites and derive from a mantle wedge environment. They display the progressive transformation of porphyroclastic spinel peridotites (T=1,200°C; P=1.5 GPa) into fine-grained garnet–amphibole peridotites (T=850°C; P=3 GPa). Detailed bulk-rock and mineral trace element analyses of a sample suite documenting the entire metamorphic evolution of the peridotites revealed several stages of metasomatism. The spinel peridotites derive from a depleted mantle that became enriched in some large ion lithophile element (LILE) and light rare earth elements (LREE). The same signature pertains to clinopyroxene and orthopyroxene, indicating that this metasomatic signature was acquired at the recorded temperature of 1,200°C. Such a temperature is considerably above the wet peridotite solidus and hence the metasomatic agent must have been a hydrous melt. Moreover, the Li-enrichment of the spinel-facies pyroxenes (up to 24 ppm Li) reflects disequilibrium distribution after exchange with a presumably mafic melt. ^cpx/opx D _Li=3–7 and ^cpx/ol D _Li=2.7–8 indicate that the spinel-facies clinopyroxene hosts higher Li amounts than the coexisting minerals. LREE fractionation, variable LREE enrichment, LILE enrichment with respect to HFSE (average clinopyroxene Pb _N /Nb _N =16–90) in spinel lherzolites can be related to chromatographic effects of porous melt flow. The significant enrichment of pyroxenes from the spinel lherzolites in Pb, U and Li indicates that the metasomatic melt was subduction-related. All these features suggest that the spinel lherzolites formed a mantle wedge layer percolated by melts carrying recycled crustal components and rising from a deeper source of subduction magmas. The garnet + amphibole peridotites equilibrated at temperatures well below the wet solidus in the presence of an aqueous fluid. Bulk-rock trace element patterns display pronounced positive anomalies in Cs, Ba, Pb and U and moderate enrichment in Li, indicating addition of a crustal component to the mantle rocks. Amphibole hosts most of these trace elements. Clinopyroxene displays high LILE/HFSE (Pb _N /Nb _N =300–600), low Ce/Pb (1.4–2.7 in garnet-facies clinopyroxene compared with 2.6–24.5 in the spinel-facies one) and variable LILE and LREE enrichments. The coupled increase of modal amphibole, Sr and Pb, together with positive Pb–Sr and Pb–U correlations, further indicate that incompatible element influx in these samples was fluid-mediated. In the garnet-facies samples, amphibole and, interestingly, olivine have similarly high Li concentrations as clinopyroxene, leading to ^cpx/amph D _Li=0.7 and ^cpx/ol D _Li=0.7–0.8, the latter being up to ten times lower than in the spinel-facies rocks. Due to its high modal abundance, olivine is the main host of Li in the garnet–amphibole peridotites. The observed metasomatic features provide evidence for the infiltration of an aqueous fluid in the mantle wedge above a subducting slab. This fluid most likely derived from subducted crustal rocks that underwent partial melting. Successive retrograde re-equilibration during exhumation of the garnet peridotite is accompanied by garnet and clinopyroxene breakdown and amphibole formation. This process produced minor changes, such as an increase of HREE and Li in amphibole, and an increase of Li in olivine. The general trace element signature remains essentially unchanged during retrogression and further hydration, indicating that fluids with a similar composition to the one present at the garnet–amphibole peridotite formation, were responsible for increased amphibole formation. The combined evidence from the metamorphic and metasomatic evolution indicates that the peridotites experienced first corner flow in a mantle wedge, followed by subduction and finally entrapment and exhumation within a crustal slab. During their entire history the Ulten peridotites were percolated first by melts and then by aqueous fluids, which added recycled crustal components to the mantle wedge.     

On M-Theory

This contribution gives a personal view on recent attempts to find a unified framework for non-perturbative string theories, with special emphasis on the hidden symmetries of supergravity and their possible role in this endeavor. A reformulation ofd = 11 supergravity with enlarged tangent space symmetry SO(1, 2) × SO(16) is discussed from this perspective, as well as an ansatz to construct yet further versions with SO(1, 1) × SO(16)^∞ and possibly even SO(1, 1)₊ × ISO(16)^∞ tangent space symmetry. It is suggested that upon “third quantization”, dimensionally reduced maximal supergravity may have an equally important role to play in this unification as the dimensionally reduced maximally supersymmetricSU(∞) Yang Mills theory.