Magmatism and metamorphism in the Ladakh Himalayas (the Indus-Tsangpo suture zone)

Ladakh (India) provides a complete geological section through the northwestern part of the Himalayas from Kashmir to Tibet. Within this section the magmatic, metamorphic and geotectonic evolution of the northern Himalayan orogeny has been studied using petrographic, geochemical and isotope analytical techniques.The beginning of the Himalayan cycle was marked by large basaltic extrusions (Panjal Trap) of Permian to Lower Triassic age at the “northern” margin of the Gondwana continent (Indian Shield). These continental type tholeiitic basalts were followed by a more alkaline volcanism within the Triassic to Jurassic Lamayuru unit of the Gondwana continental margin.Lower Jurassic to Cretaceous oceanic crust and sediments (ophiolitic mélange s.s.) accompany the Triassic to Cretaceous flysch deposits within the Indus-Tsangpo suture zone, the major structural divide between the Indian Shield (High Himalaya) and the Tibetan Platform. So far, no relic of Paleozoic oceanic crust has been found.Subduction of the Tethyan oceanic crust during Upper Jurassic and Cretaceous time produced an island arc represented by tholeiitic and calc-alkaline volcanic rock series (Dras volcanics) and related intrusives accompanied by volcaniclastic flysch deposits towards the Tibetan continental margin.Subsequent to the subduction of oceanic crust, large volumes of calc-alkaline plutons (Trans-Himalayan or Kangdese plutons) intruded the Tibetan continental margin over a distance of 2000 km and partly the Dras island arc in the Ladakh region.The collision of the Indian Shield and Tibetan Platform started during the middle to upper Eocene and caused large-scale, still active intracrustal thrusting as well as the piling up of the Himalayan nappes. The tectonically highest of these nappes is built up of oceanic crust and huge slices of peridotitic oceanic mantle (Spongtang klippe).In the High Himalayas the tectonic activity was accompanied and outlasted by a Barrovian-type metamorphism that affected Triassic sediments of the Kashmir-Nun-Kun synclinorium up to kyanite/staurolite grade and the deeper-seated units up to sillimanite grade. Cooling ages of micas are around 20 m.y. (muscovite) and 13 m.y. (biotite). Towards the Indus-Tsangpo suture zone metamorphism decreases with no obvious discontinuity through greenschist, prehnite-pumpellyite to zeolite grade. Remnants of possibly an Eo-Himalayan blueschist metamorphism have been found within thrust zones accompanying ophiolitic mélange in the suture zone.     

Kohlenwasserstoffgenese in Sedimentgesteinen: Untersuchungen über den thermischen Abbau von Kerogen unter besonderer Berücksichtigung der n-Paraffinbildung

Zusammenfassung Proben eines limnischen Ölschiefers eozänen Alters wurden, nachdem die löslichen Kohlenwasserstoffe durch Extraktion entfernt worden waren, in einem Autoklaven während fünf Stunden auf Temperaturen zwischen 190–490° C erhitzt. Dabei bildete sich aus dem unlöslichen Kerogen neues, extrahierbares Material, das vergleichbar ist mit den Extrakten aus tiefversenktem Sedimentgestein. Der ursprüngliche Extrakt des Ölschiefers zeigte eine starke Bevorzugung der höheren, ungeradzahligen n-Paraffine. Die durch den thermischen Abbau neu gebildeten n-Paraffine zeigten ebenfalls eine Bevorzugung, die jedoch mit steigender Versuchstemperatur abnimmt und bei Temperaturen über 300° C erlischt. Der Verlust der Bevorzugung ist auf einen Verdünnungseffekt zurückzuführen.

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Summary Samples of non marine oil shale of Eocene age have been extracted and the extract-free samples were heated for 5 hours in an autoclave at temperatures between 190°–490° C. By the temperature treatment new extractable matter has been formed, that is comparable to extracts of sediments which suffered great depth of burial. The original extract of the oil shale showed a strong predominance of the odd — numbered high molecular n-paraffins. The n-paraffins which were formed by the temperature treatment also showed an odd —predominance. This predominance, however, decreased with increasing temperature of the autoclave and disappeared above 300° C. The disappearance of the odd-predominance can be explained by a diluting effect.

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Résumé Nous avons chauffé des échantillons de schistes petrolifères limnigues de l'éocène pentant 5 heures à des temperatures entre 190°–490° C après avoir eliminés les hydrocarbones solubles par extraction. Nous avons reçu du kérogène insoluble, un materiel de nouveau extractible. Ce materiel est comparable à des extraits de sédiments d'une grande profondeur. L'extrait primaire des schistes petrolifères montrait une préfération des n-paraffines impaires de haute séquence. Les paraffines développés par la dégradation thermique montraient de même une préfération. Mais elle diminue en montant les temperatures et disparait au dessus de 300° C. La perte de cette préfération est explicable par un effet de dilution.

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190° 490° , . .

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Der Gewerkschaft Elwerath in Hannover, im besonderen Herrn Direktor Dr. A.Roll danke ich herzlich für die finanzielle Unterstützung, durch die die Anschaffung eines Gaschromatographen ermöglicht wurde, und für die Überlassung von Probenmaterial aus dem Gifhorner Trog.Der Deutschen Forschungsgemeinschaft bin ich für ihre großzügige personelle und finanzielle Hilfe ebenfalls zu großem Dank verpflichtet.Schließlich möchte ich mich noch bei meinen Mitarbeitern Frau U.Grütze und Herrn cand. geol. H.Wehhner bedanken, die einen großen Teil der Laboratoriumsarbeiten durchführten.     

Carry-over effects of the membrane interface probe

The membrane interface probe (MIP) is widely used to characterize the subsurface distribution of volatile organic compounds (VOCs). One problem that arises during MIP application is that disproportionately high MIP signals are obtained after passing source zones which contain mobile or residual phases. This serious problem occurs because of a carry-over effect, in particular caused by compound-specific retention times in the conventional unheated transfer line, commonly used during such an investigation. The objective of this study was to perform a qualitative methodical field evaluation of the carry-over effect of a conventional MIP system with a conventional unheated transfer line. This was achieved by coupling a mobile mass spectrometer to the MIP device. Results obtained were then further compared with those achieved using a laser induced fluorescence (LIF) system. Because of this coupling, time- and depth-dependent signals for different substances became known. Field evaluation data obtained showed complex superpositions of compounds with MIP system results. As a result of this superposition, MIP signals from the saturated zone beneath the source zone (zone with free and/or residual phase) are blurred and are therefore not representative of particular depths. However, utilizing multidirectional probing alongside conventional MIP probing (forwards and backwards), it was possible to detect the upper and lower phase boundary of the source zone. These MIP results correlated excellently with the LIF results. An important conclusion that can be drawn from the field investigation is that coupling a mobile mass spectrometer to the MIP system enables advanced MIP signal interpretation to be successfully achieved.     

Die Porositäten toniger Keuper- und Jura-Sedimente Südwestdeutschlands

After a short review of the basic principles governing compaction of clayey sediments, investigations of the porosities of Mesozoic shales from southwestern Germany are reported. The results reveal the influence of grain size, mineral content, temperature, and organic matter on the porosity of shales. All these and other factors have to be considered when evaluating primary porosities of shales at the time of deposition.     

Permian radiolarians,chert and basalt from the Daxinshan Formation in Lancangjiang belt of southwestern Yunnan,China

The stratigraphical sequences composed of chert and basalt were found in the Daxinshan area of Simao and the Manbie area of Jinghong, southwestern Yunnan. The Middle Permian to ealiest Late Permian radiolarians, such as Follicucullus and Pseudoalbaillella, have been identified from the chert. The chert from the Manbie area of Jinghong is characterized by high SiO₂content (over 92%), large ratios of MnO/TiO₂ (2.15) and low ratios of Al/(Al+Fe+Mn) (≤0.1) and Ce/Ce*(0.4), which indicate that the chert was deposited in pelagic basin. The chert from the Daxinshan area of Simao, however, is characterized by low SiO₂ content, low ratios of MnO/TiO₂ (0.27) and high ratios of Al/(Al+Fe+Mn) (0.49) and Ce/Ce*(0.88), which imply that the chert was deposited in continental margin basin. The basalts from the both areas belong to tholeiite series, and the chemical compositions of their major, rare earth and trace elements show the characteristics of MORB. These results evidence that there are volcanic rocks and chert sequences representing pelagic basin and oceanic basin near continent. These sequences and the formerly reported island-arc volcanic rock sequences imply that the Daxinshan Formation in the Lancangjiang belt represents a sedimentary assemblage formed in active continental margin basin.     

The operational weather radar of Fossalon di Grado (Gorizia, Italy): accuracy of reflectivity and differential reflectivity measurements

Summary The error structure of radar measurements should be accurately known in order to provide reliable estimates for a number of quantitative meteorological applications, from rainfall rate estimation to cloud microphysics. The aim of this paper is to give a detailed characterization of Z _H and Z _DR measurements obtained by the weather radar of Fossalon di Grado (Gorizia, Italy). Vertical-looking observations are used to determine the system bias on differential reflectivity and to estimate the measurement error on both Z _H and Z _DR in the rain medium. It is estimated that no bias is affecting Z _DR and the accuracy of Z _H and Z _DR is 0.8 and 0.1 dB, respectively. A similar evaluation is done in the rain medium at larger ranges with the antenna pointing at low elevation angles. The long time stability of the absolute reflectivity calibration is also established by radar-rain gage inter-comparison over almost 200 hours of precipitation data collected during nearly two years. Received June 21, 2001 Revised November 13, 2001     

Rapid crustal uplift in Patagonia due to enhanced ice loss

A vertical crustal uplift rate of 39 mm yr^? 1 is measured between 2003 and 2006 using Global Positioning System (GPS) measurements at the northeastern edge of the Southern Patagonia Icefield (SPI). This is the largest present-day glacial isostatic rate ever recorded. The combination of SPI's rapid melting and the unique regional slab-window tectonics that promotes a relatively low viscosity, is central to our interpretation of the observations. The two effects lead to a strong interaction of short relaxation times with ice loads that change on a comparable time scale. The profile of GPS observations link ice loss to the soft viscoelastic isostatic flow response over the time scale of the Little Ice Age (LIA), including ice loss in the period of observation. The agreement of the results with our model predictions strongly suggests the large crustal uplift in Patagonia is due an accelerated glacier wasting since the termination of the LIA and that the effective regional mantle viscosity is near 4.0–8.0 × 10¹⁸ Pa s. A century-long diminution of the icefields, at rates that are about 1/4 – 1/2 the contemporary loss rates, is consistent with multidecadal-scale temperature trends estimated for the past 50–100 years and is, in fact, a key feature in any model capable of explaining the uplift data.     

欧洲和远东第四纪陆相堆积的生物地层对比(哺乳动物)

在晚第三纪晚期和第四纪时,欧亚大陆古动物群的面貌受两个陆桥的影响很大,在尽西边有一个复合陆桥,即非洲与欧洲相连,与亚洲沿着非洲西边—伊比利亚半岛连接;中间的非洲—西西里岛陆桥和一个东地中海陆桥(非洲—阿拉伯半岛)连接。     

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