Li abundances in eclogite minerals: a clue to a crustal or mantle origin?     

Alan B. Woodland  Hans-Michael Seitz  Rainer Altherr  Horst Marschall  Bettina Olker  Thomas Ludwig 《Contributions to Mineralogy and Petrology》2002,143(5):587-601

The mineral phases of 33 eclogite and garnet clinopyroxenite samples from various tectonic settings were analysed for Li by secondary ion mass spectrometry (SIMS). In all samples, Li is preferentially incorporated into clinopyroxene (0.4 to 80 µg/g), whereas co-existing garnet contains only minor amounts of Li (0.01 to 3.7 µg/g). When present, glaucophane shows Li abundances which are similar to those of clinopyroxene, but phengite contains significantly less Li than clinopyroxene. Additional phases, such as amphibole, quartz, clinozoisite and kyanite, have low Li concentrations (<1 µg/g). No correlation is apparent between the Li contents and major-element compositions of clinopyroxene or garnet. On the basis of both measured Li concentrations in clinopyroxene and estimated Li abundances in the whole rocks, the investigated samples can be subdivided into high-Li and low-Li groups. These groups coincide with the mode of origin of the rocks. Metabasaltic (metagabbroic) eclogites from high-pressure terranes belong to the high-Li group whereas, except for one eclogite, all kimberlite- and basanite-hosted xenoliths have low Li contents. Samples from eclogites and garnet clinopyroxenites associated with orogenic peridotites fall into both groups. It is suggested that the high-Li eclogites originated from basaltic oceanic crust whereby the notable Li enrichment of some samples was probably caused by low-temperature hydrothermal alteration prior to subduction. Furthermore, the low-Li eclogites and garnet clinopyroxenites may represent high-pressure cumulates from mafic melts percolating through the mantle.  相似文献   

Facies interfingering and synsedimentary tectonics on late Ladinian-early Carnian carbonate platforms (Dolomites, Italy)     

Lorenz Keim  Rainer Brandner 《International Journal of Earth Sciences》2002,91(3):555-556

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An experimental study of B-, P- and F-rich synthetic granite pegmatite at 0.1 and 0.2 GPa   总被引：1，自引：0，他引：1  

Ilya V. Veksler  Rainer Thomas 《Contributions to Mineralogy and Petrology》2002,143(6):673-683

Extreme enrichment in H₂O, B, P and F is characteristic of many evolved granites and pegmatites. We report experimental phase relations of a synthetic peraluminous pegmatite spiked with P₂O₅, B₂O₃ and F (5 wt% of each), Rb₂O, Cs₂O (1 wt% of each) and Li₂O (0.5 wt%). Experiments were carried out in H₂O-saturated conditions in cold-seal rapid-quench pressure vessels at 0.1-0.2 GPa. Crystallisation starts at about 820 °C with berlinite and topaz. Quartz appears at 700-750 °C. Topaz is replaced by muscovite at about 600 °C. At near-solidus temperatures (450-500 °C) amblygonite, lacroixite and a Cs-bearing aluminosilicate crystallise. In all charges aluminosilicate melt coexists with low-density hydrous fluid and hydrosaline melt. The latter is strongly enriched in Na₃AlF₆ and H₃BO₃ components. Experimental evidence of the liquid immiscibility and mineral reactions documented in our study offers new explanations of many enigmatic features of natural pegmatites.  相似文献   

Iodine Chemistry and its Role in Halogen Activation and Ozone Loss in the Marine Boundary Layer: A Model Study   总被引：6，自引：0，他引：6  

Rainer Vogt  Rolf Sander  Roland von Glasow  Paul J. Crutzen 《Journal of Atmospheric Chemistry》1999,32(3):375-395

A detailed set of reactions treating the gas and aqueous phase chemistry of the most important iodine species in the marine boundary layer (MBL) has been added to a box model which describes Br and Cl chemistry in the MBL. While Br and Cl originate from seasalt, the I compounds are largely derived photochemically from several biogenic alkyl iodides, in particular CH2I2, CH2ClI, C2H5I, C3H7I, or CH3I which are released from the sea. Their photodissociation produces some inorganic iodine gases which can rapidly react in the gas and aqueous phase with other halogen compounds. Scavenging of the iodine species HI, HOI, INO2, and IONO2 by aerosol particles is not a permanent sink as assumed in previous modeling studies. Aqueous-phase chemical reactions can produce the compounds IBr, ICl, and I2, which will be released back into the gas phase due to their low solubility. Our study, although highly theoretical, suggests that almost all particulate iodine is in the chemical form of IO-3. Other aqueous-phase species are only temporary reservoirs and can be re-activated to yield gas phase iodine. Assuming release rates of the organic iodine compounds which yield atmospheric concentrations similar to some measurements, we calculate significant concentrations of reactive halogen gases. The addition of iodine chemistry to our reaction scheme has the effect of accelerating photochemical Br and Cl release from the seasalt. This causes an enhancement in ozone destruction rates in the MBL over that arising from the well established reactions O(1D) + H2O 2OH, HO2 + O3 OH + 2O2, and OH + O3 HO2 + O2. The given reaction scheme accounts for the formation of particulate iodine which is preferably accumulated in the smaller sulfate aerosol particles.  相似文献   

Composition of soluble organic matter in coals: relation to rank and liptinite fluorescence     

Matthias Radke  Rainer G. Schaefer  Detlev Leythaeuser  Marlies Teichmüller 《Geochimica et cosmochimica acta》1980,44(11):1787-1800

Study of a series of twenty-six German high volatile bituminous B to low volatile bituminous coals of Upper Carboniferous age by recently refined analytical methods (‘flow-blending’ extraction, medium pressure liquid chromatography, HPLC, glass capillary gas chromatography and spectral fluorescence microscopy) reveals that yield and composition of soluble organic matter are strongly controlled by rank. In particular, the following points of inflection are noted in rank trends around 0.9% vitrinite reflectance: a maximum in yields of total soluble organic matter, aromatic hydrocarbons and n-alkanes; the most pronounced change in aromatic hydrocarbon composition; a trend reversal for pristane/ phytane ratios; a gradient change in the odd/even-predominance of long chain n-alkanes; appearance of a bimodal n-alkane distribution; and a sharp drop in concentration of individual n-, and isoprenoid alkanes. This discontinuity in rank trends around 0.9% Rm is interpreted to reflect a major change in reaction types, i.e. a shift from predominantly hydrocarbon generating to predominantly fragmentation reactions. Rank trends of maceral fluorescence exhibit the following pronounced changes over a similar but broader rank range: Different types of the maceral sporinite show a relatively abrupt shift of the fluorescence colour from yellow towards red between 0.8–0.9% Rm while up to about 1.0% Rm a sharp increase is recorded in the proportion of fluorescent vitrinite. This coincidence at a near-equal rank stage suggests a common cause for changes in yield and composition of the soluble organic matter and the maceral fluorescence of these coals.  相似文献   

Organic and inorganic geochemistry of some coastal plain rivers of the southeastern United States   总被引：1，自引：0，他引：1  

K.C. Beck  J.H. Reuter  E.M. Perdue 《Geochimica et cosmochimica acta》1974,38(3):341-364

In a comprehensive study of the distribution of organic and inorganic constituents in natural waters, the chemical compositions of several rivers flowing through the Coastal Plain of southeast Georgia (the Satilla River, in particular) have been investigated. These streams are generally characterized by low suspended load, low ionic strength, low pH values, and a predominance of organic over inorganic constituents. The dominance of sodium and chloride among inorganic ions indicates that rainfall is a major factor in determining the distribution of major elements in these waters. The low pH values and the relatively high concentrations of iron and aluminum appear to result from the high concentrations of organic matter. Chemical analysis (total acidity, carboxyl groups, amino acid residues, and CHN analysis) and spectroscopic analysis (i.r. and NMR) indicate that river water organic matter is chemically similar to soil fulvic acids.The dominance of organic matter over inorganic constituents and the resultant low pH values of these waters are in direct contrast with the chemical compositions of most of the rivers of the world which have been previously studied. Many large tributaries draining from the low relief tropical basins of the Amazon and other tropical rivers are expected to show similar characteristics; however, none of these has been studied extensively.  相似文献   

Zur graphischen Integration der Wirbelgleichung mit Berücksichtigung orographischer Effekte     

H. Pichler  H. Reuter 《Meteorology and Atmospheric Physics》1960,11(4):413-426

Zusammenfassung Es wird eine Methode angegeben, die gestattet, die Wirbelgleichung unter Berücksichtigung orographischer Effekte graphisch zu integrieren; dabei werden barokline thermodynamische Prozesse nicht berücksichtigt. der Arbeit liegt folgende Vorstellung zu Grunde: Ein jedes Luftquantum, das einen Gebirgskamm überquert, erhält eine zusätzliche Vorticity. Demnach müssen alle diejenigen Teile des Wirbelfeldes, die zu Beginn der graphischen Integration stromaufwärts vom Gebirgskamm liegen-und zwar bis zur Entfernung, die dem Windweg des zur graphischen Integration verwendeten Zeitschrittes (24 Stunden) entspricht —, eine Korrektur erfahren. Mit Hilfe von Angaben vonKüttner über das durchschnittliche Verhalten der Vertikalgeschwindigkeit bei orographischer Beeinflussung gelingt es, die oben geforderten Korrekturen zu berechnen. Dadurch ist man in der Lage, die im Lee eines Gebirges bei Strömungsübersetzung auftretende Niveausenkung der 500 mb-Fläche zwanglos zu erklären.An einem Beispiel wird die Methode veranschaulicht. Der Alpenkamm und der Karpathenbogen werden von einer kräftigen Nordwestströmung überquert. Im Lee der Gebirge — Raum Italien-Griechenland—tritt innerhalb von 24 Stunden eine maximale Niveausenkung von 20 gpdm ein. Mittels der graphischen Integration der barotropen Wirbelgleichung kann man nur 10 bis 20%, mit Hilfe der hier angeführten Methode dagegen nahezu 100% der Senkung der 500 mg-Fläche arklären.

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Summary A procedure is developed for graphical integration of the vorticity equation incorporating orographic influences. Baroclinic effects due to thermodynamic processes are not considered. The investigation is based upon the following idea: Each air particle crossing the mountain range receives additional vorticity. Hence those parts of the vorticity distribution lying streamupwards from the mountain range up to a distance corresponding to the movement of the air particle during the timestep used for the integration have to be corrected. The magnitude of these corrections is evaluated usingKüttners results for the average changes of vertical velocity by orographic features. Thus it is possible to explain the decrease of height of the 500 mb surface in the lee of the mountain range.The method is illustrated by an actual example: The Alps and the Carpathians are crossed by a strong north-westerly flow. In the lee of the mountain range (Italy and Greece) a maximum decrease of height of the 500 mb surface of 20 gpdm within 24 hours is observed. The graphical integration of the barotropic vorticity equation explains only 10 to 20% of the depression, while the present method renders a result in almost complete agreement with the observations.

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Résumé L'auteur expose une méthode permettant d'intégrer graphiquement l'équation de tourbillon en tenant compte d'effets orographiques, mais en excluant des processus thermodynamiques barocliniques. Chaque quantum d'air franchissant une montagne reçoit une vorticity supplémentaire, de sorte que les parties du champ tourbillonnaire situées en amont d'une chaîne montagneuse, à une distance de 24 h. de chemin, doivent subir une correction. Celle-ci se calcule à l'aide de données deKüttner qui a établi l'allure moyenne de la composante verticale de vitesse au-dessus d'un obstache. On se trouve ainsi à même d'expliquer l'abaissement de la surface de 500 mb à l'aval d'une chaîne de montagnes.Un exemple illustre la méthode décrite. Par fort vent de Nord-Ouest au-dessus des Alpes et des Carpathes, il se produit sous le vent, dans la région Italie/Grèce, un abaissement maximum de 200 gpm de la surface de 500 mb. L'intégration graphique de l'équation barotrope de tourbillon rend compte de 10 à 20% seulement de cet abaissement, mais la méthode ici décrite l'explique entièrement.

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Cretaceous synsedimentary tectonics in the Atlas system of Central Morocco     

Rainer Ensslin 《International Journal of Earth Sciences》1992,81(1):91-104

Cretaceous sediments in Central Morocco were deposited in various depositional environments and comprise an undetermined Lower Cretaceous base up to Maastrichtian. The sedimentary columns show a similar facies evolution. Basal unconformities, conglomeratic layers and significant differences in thicknesses reflect pre- and synsedimentary vertical tectonic movements. These tectonic movements took place along large NE/SW striking fault systems, one of the major features of the present tectonic framework. Permanent displacement of the subsidince maxima in time and space indicate the development of small tectonic blocks which were tilted and/or compressed between the fault zones. High sedimentation rates in areas of strong subsidence, however, prevented the evolution of intraplatformbasins. Although tectonic influence was important, eustatic sea level changes ruled the whole sedimentary regime.

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Zusammenfassung Im Mittleren Atlas und der Haute Moulouya reichen die Kreidesedimente von nicht genauer datierbarer Unterkreide bis ins Maastricht. Sie entstanden unter ständig wechselnden Ablagerungsbedingungen. Die einzelnen Sedimentsäulen weisen jeweils große Ähnlichkeiten in ihrer Faziesentwicklung auf, welche hauptsächlich den eustatischen Meeresspiegelschwankungen folgten. Basale Diskordanzen, Konglomeratlagen und signifikante Unterschiede in den Sedimentmächtigkeiten zeigen ständige synsedimentäre Vertikalbewegungen an. Diese erfolgten hauptsächlich an ausgedehnten, NE-SW streichenden Störungssystemen. Die ständigen, sowohl räumlichen als auch zeitlichen Verschiebungen der Subsidenzmaxima deuten auf die Entstehung von kleinräumigen tektonischen Blöcken hin, die zwischen den Störungszonen entweder gefaltet oder gekippt wurden. Dabei verhinderten die hohen Sedimentationsraten und die geringe räumliche Ausdehnung der Subsidenzzonen die Entstehung von tieferen Becken. Trotz der permanenten tektonischen Bewegungen waren eustatische Meeresspiegelschwankungen bestimmend für die Faziesentwicklung im gesamten Sedimentationsraum.

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Résumé Dans le Moyen Atlas et la Haute Moulouya, la sédimentation crétacée s'est effectuée dans des environnements variables depuis l'Eo-Crétacé jusqu'au Maastrichtien. Les colonnes sédimentaires dans les différentes localités sont caractérisées par une grande analogie d'évolution de faciès. Les discordances basales, les niveaux conglomératiques et la différence des épaisseurs d'une localité à une autre traduisent les mouvements verticaux pré- et synsédimentaires; ceci est surtout clair le long des failles de direction NE-SW qui ont constamment influencé la sédimentation. Les variations de la subsidence dans le temps et dans l'espace trouvent leur explication dans un modèle de basculement ou de plissement de petits blocs entre les zones de failles. Dans les zones à subsidence élevée, le taux de sédimentation était également élevé, ce qui a empêché la formation de bassins profonds. Ainsi, en dépit de l'action tectonique, les changements eustatiques du niveau de la mer ont déterminé tout le régime sédimentaire.

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Age constraints on Pleistocene megafauna at Tight Entrance Cave in southwestern Australia     

Linda K. Ayliffe  Gavin J. Prideaux  Michael I. Bird  Rainer Grün  Richard G. Roberts  Grant A. Gully  Rhys Jones  L. Keith Fifield  Richard G. Cresswell   《Quaternary Science Reviews》2008,27(17-18):1784-1788

A well-stratified succession of fossiliferous sediments occurs in Tight Entrance Cave, southwestern Australia. These infill deposits contain the remains of megafauna and have accumulated intermittently since the Middle Pleistocene: >137, 137–119 and 50–29 ka, according to the results of ¹⁴C, U–Th, ESR and OSL dating techniques. Megafaunal species richness was highest in the latest part of the penultimate glacial maximum and during the subsequent last interglacial (137–119 ka), but remains are less abundant following an apparent 70 ka depositional hiatus in the sequence. Most megafaunal specimens from the upper (<44 ka) units are fragmentary, and reworking from older strata cannot yet be ruled out. However, one specimen of Simosthenurus occidentalis (a large extinct kangaroo), a pair of articulated dentaries showing no signs of secondary transportation, was found within a sedimentary layer deposited between 48 and 50 ka. This represents one of the youngest demonstrably in situ occurrences of an Australian megafaunal taxon.  相似文献   

Buchbesprechungen     

F. Steinhauser  H. Reuter 《Meteorology and Atmospheric Physics》1960,12(1):134-150

Ohne Zusammenfassung  相似文献