Major and trace-element composition and pressure–temperature evolution of rock-buffered fluids in low-grade accretionary-wedge metasediments, Central Alps

The chemical composition of fluid inclusions in quartz crystals from Alpine fissure veins was determined by combination of microthermometry, Raman spectroscopy, and LA-ICPMS analysis. The veins are hosted in carbonate-bearing, organic-rich, low-grade metamorphic metapelites of the Bündnerschiefer of the eastern Central Alps (Switzerland). This strongly deformed tectonic unit is interpreted as a partly subducted accretionary wedge, on the basis of widespread carpholite assemblages that were later overprinted by lower greenschist facies metamorphism. Veins and their host rocks from two locations were studied to compare several indicators for the conditions during metamorphism, including illite crystallinity, graphite thermometry, stability of mineral assemblages, chlorite thermometry, fluid inclusion solute thermometry, and fluid inclusion isochores. Fluid inclusions are aqueous two-phase with 3.7–4.0 wt% equivalent NaCl at Thusis and 1.6–1.7 wt% at Schiers. Reproducible concentrations of Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, B, Al, Mn, Cu, Zn, Pb, As, Sb, Cl, Br, and S could be determined for 97 fluid inclusion assemblages. Fluid and mineral geothermometry consistently indicate temperatures of 320 ± 20 °C for the host rocks at Thusis and of 250 ± 30 °C at Schiers. Combining fluid inclusion isochores with independent geothermometers results in pressure estimates of 2.8–3.8 kbar for Thusis, and of 3.3–3.4 kbar for Schiers. Pressure–temperature estimates are confirmed by pseudosection modeling. Fluid compositions and petrological modeling consistently demonstrate that chemical fluid-rock equilibrium was attained during vein formation, indicating that the fluids originated locally by metamorphic dehydration during near-isothermal decompression in a rock-buffered system.     

The Rolling Pig or How does a surveyor creep through a pipeline?

The inspection of a pipeline from the inside becomes more and more widespread. An inspection tool, called Geometry Pig, carries a variety of sensors, among which a strapdown inertial system provides essential geometric information on the pipeline. In this paper the inspection pig is described as a surveying tool, which delivers information on centre line, shape and features of the pipe. After some background information it is explained, why the inertial system is the optimal instrument to deliver some structural parameters of the pipeline. The interaction between data evaluation and measurement procedure is discussed in view of the very few possibilities to vary the procedure. One of them is a forced rotation about the forward axis. Analogies are shown to traditional surveying procedures. Finally some results of actual surveys are presented. A positioning accuracy of 1:2500 is achieved with respect to tie points.     

Grundschicht und Nullschicht der Atmosphäre

Zusammenfassung NachdemSchneider-Carius die von ihm in mehreren Untersuchungen behandelte und von ihm so bezeichnete «Grundschicht» als das Hauptausgleichniveau für die Druckgegensätze zwischen Hoch und Tief in den unteren Luftschichten nachgewiesen hat, entstand naturgemäß die Frage, wie und in welcher Höhensicht der notwendige Massenfluß vom Tief zum Hoch erfolgt. Ohne denselben würden sich die Druckgebilde wegen der ageostrophischen Windkomponente vom Hoch zum Tief in der Grundschicht binnen kürzester Zeit auflösen.H. Faust fand diese Schicht über Mitteleuropa in 10 km Höhe. Sie ist identisch mit dem Sitz des hochtroposphärischen Windmaximums und weist das Maximum des ageostrophischen Massenflusses vom Tief zum Hoch auf. Da in ihr die für das Wettergeschehen so fundamental wichtigen Vertikalbewegungen Null sind, nannteFaust die Schicht «Nullschicht». In der Grundschicht und der Nullschicht sind somit zwei atmosphärische Schichten gefunden, die in polarer Wechselwirkung miteinander für die Dynamik der Wettervorgänge von entscheidender Bedeutung sind.

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Summary Especially whenSchneider-Carius had shown in several papers the ground layer to be the main levelling layer of pressure contrasts, the question arose where the seat of mass transport from low to high pressure is located. ThenFaust found a layer 10 kms above Central Europe, where vertical motion in highreaching cyclones and anticyclones averages zero. Because of the fundamental significance of vertical motion, he called it the «zero layer». This zero layer, which is identical with the wind maximum in the upper troposphere, turned out to be the principal seat of ageostrophic mass transport from low to high pressure. Also, the angle between true and geostrophic wind (the ageostrophic component) has its maximum in the zero layer. As the processes in the zero layer produce and/or increase pressure contrasts, it is the direct counterpart of the ground layer. It is shown that both layers are exercising reciprocal effects upon each other, with action in one layer producing the appropriate reaction in the other layer. As both layers are the principal seat of ageostrophic mass transport between areas of high and low pressure, their mutual action proves to be of basic importance for the dynamics of the whole weather trend.

     

Systematics of the isotopic composition of sulfur in the oceans during the Phanerozoic and its implications for atmospheric oxygen

Past treatments of the variation of δS³⁴ in marine evaporites have either assumed a steady-state ocean or have invoked rather simplified ocean input-output models. This paper derives more completely the relationships between the parameters that influence the time variation of δS³⁴ in ocean water and the relationship between δS³⁴ in ocean water and net gains and losses of atmospheric oxygen due to the operation of the sulfur cycle. The lower and mid-Paleozoic are shown to have been periods of net gain of atmospheric oxygen by the operation of the sulfur cycle; the upper Paleozoic, particularly the Permian, a period of oxygen loss. It is difficult to relate these oxygen gains and losses to variations in the oxygen content of the atmosphere, because the oxygen flux due to the operation of the carbon cycle is approximately twice as large as the flux due to the operation of the sulfur cycle. Data for the organic carbon and sulfide content of sedimentary rocks of the Russian Platform suggest that a decrease in sulfide from the Paleozoic to the Mesozoic and Cenozoic Era was roughly balanced by an increase in the proportion of organic carbon; however, such data are insufficient to define the abundance of atmospheric oxygen during the Phanerozoic. Biologic data and a better understanding of controls on atmospheric P_o2 are more likely to produce convincing evidence regarding variations of atmospheric oxygen in the past.     

Interaction of genetic processes in holocene reefs off North Eleuthera Island,Bahamas

The inner shelf platform off North Eleuthera consists of a series of terraces at 6 m, 8 m, 20 m, and 35 m depth, respectively. The boundary between 6 and 8 m terraces is marked by a near continuous reef ridge, landward and seaward of which isolated reef structures are found. Reefs are aggregates of pillar structures, which in turn are composed of columnar, club-shaped or mushroom-shaped pillars of corals. The dominant primary framebuilder above 3 m depth isAcropora palmata; below corals of the generaMontastrea andDiploria, Porites astreoides andP. porites also contribute to the frame, as does the hydrozoanMillepora. The secondary framebuilders start developing and changing the shape of the frame as soon as they find suitable substrates; most important are coralline red algae, which encrust internal and external surfaces, but also may fuse the components of the frame; other organisms just add to the frame. In contrast boring and rasping organisms destroy the frame. Constructing or destructing organisms were found living on every surface, external or internal, accreting or diminishing.The composite nature of the reef structure, fabrics of skeletal material, and borings of organisms provide numerous cavities of mm to m size. These are subject to syngenetic sedimentation and cementation, which help maintain the frame, but change composition, fabrics, and facies. Thus rates of organism growth and destruction, of sedimentation, cementation, and mechanical breakdown and the dynamic changes of these rates determine final shape and preservation of the reef.Recognition of the relationship between these processes should help interpret fossil reef remnants.

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Zusammenfassung Die Schelfplattform vor North Eleuthera gliedert sich in mehrere Terrassenstufen, deren Ränder bei 6 m, 8 m, 20 m und 35 m Wassertiefe liegen. Der 6-m-Terrassenstufe folgt über 25 km ein nahezu ununterbrochener Korallenriffrücken; seewärts und landwärts von diesem Rücken hegen isolierte Riffstrukturen. Die Riffe setzen sich aus Pfeilern zusammen, die ihrerseits wieder säulige, keulenförmige oder pilzartige Korallenstöcke als kleinere Bauelemente aufweisen.Bis in 3 m Wassertiefe istAcropora palmata der wichtigste Riffbildner, tiefer herrschenMontastrea- undDiploria-Arten vor.Porites astreoides, P. porites und die HydrozoeMillepora tragen ebenfalls zur Gerüstbildung bei. Sobald geeignetes Substrat angeboten wird, beginnen die sekundären Riffbildner mit der Ausgestaltung des Riffgerüstes; hierbei beteiligen sich in erster Linie die Rotalgen, die alle externen und internen Oberflächen überkrusten, darüber hinaus aber auch das Riffgerüst fester zusammenfügen; die anderen sekundären Riffbildner fügen dem Gerüst Material hinzu. Im Gegensatz dazu zerstören bohrende und raspelnde Organismen das Riffgerüst. Aufbauende und zerstörende Organismen leben auf und unter jeder Oberfläche des Riffes, sei sie extern oder intern.Der komplexe Aufbau der Riffstrukturen, das Wachstum des organischen Gerüstes und die Tätigkeit bohrender Organismen führen zur Bildung zahlreicher Hohlräume von mm-bis m-Größe. In diesen Hohlräumen erfolgen syngenetische Sedimentation und Zementation, die zur Erhaltung des Gerüstes beitragen, wobei jedoch die Zusammensetzung, das Gefüge und die Lithofazies des ursprünglichen Gerüstes weitgehend umgewandelt werden. So wird die endgültige Form und Erhaltung des Riffes von den jeweiligen Geschwindigkeiten bzw. dem dynamischen Wechsel der Geschwindigkeiten des Aufbaues und der Zerstörung durch Organismen, der Sedimentation und Zementation sowie der mechanischen Zerstörung bestimmt. Die Kenntnis vom Zusammenspiel dieser Prozesse führt zum besseren Verständnis der Vorgänge, die am Aufbau der fossilen Riffe beteiligt waren.

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Résumé La plate-forme continentale au large de North Eleuthera est formée de plusieurs terrasses en gradins dont les rebords se situent à des profondeurs d'eau de 6 m, 8 m, 20 m et 35 m. Le premier rebord (6 m) suit pendant plus de 25 km une crête récifale presque ininterrompue de part et d'autre de laquelle se trouvent des structures de récif isolées. Les récifs se composent de pinacles, qui à leur tour présentent des amas coralliens en forme de massue et de champignon.Jusqu'à 3 m de profondeur, l'Acroporapalmata est le plus important bâtisseur primaire; plus en profondeur, prédominent les espècesMontastrea etDiploria. LesPontes astreoides, P. porites et les hydrozoairesMillepora contribuent aussi à la formation de la charpente. Les constructeurs secondaires commencent à développer et à modifier la forme du bâtis dès qu'ils trouvent un substrat approprié; les algues rouges y participent en première ligne; elles s'incrustent sur les surfaces internes et externes; par ailleurs, elles cimentent plus solidement les éléments de la charpente du récif. Les bâtisseurs secondaires contribuent aux matériaux de charpente; en contre partie, des organismes perforants et râpeurs la détruisent. Les organismes constructeurs et destructeurs vivent au-dessus et en dessous de chaque surface du récif, qu'elles soient externes ou internes.La construction complexe des structures du récif, la croissance de la charpente organique et l'action des organismes perforants conduisent à la formation de nombreuses cavités de grandeurs comprises entre le mm et le m. Sédimentation et cimentation syngénétiques se produisent dans ces cavités; elles contribuent à la formation du bâtis mais en changent la composition, la structure et les microfaciès. Ainsi, la forme définitive et la conservation du récif sont déterminées par les vitesses de croissance organique et de destruction biologique, de sédimentation, de cimentation et de destruction mécanique ainsi que par des changements dynamiques de ces vitesses respectives. La connaissance des relations entre ces processus conduit à une meilleure compréhension des phénomènes qui prirent part à la construction des récifs fossiles.

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Eleuthera , 6, 8, 20 35 . ; cyme . , , , . 3 Acropora palmata, — Montastrea Diploria. Porites astreoides, P. porites Hydrozoa Millepora. , . ; . . .., , , . - . , . . . , , .

     

Flow computations for ship safety problems

A number of ship safety problems involve flow computations. Most of them do not require involved CFD calculations, but can be solved by relatively simple means which, nonetheless, are not state of the art. The problems discussed here are, in order of increasing sophistication: cross-flooding of damaged compartments; evacuation of persons on board a ship; sinking of a damaged ship in still water; accelerations and loads on free-fall lifeboats and damaged ship survival time in a seaway.     

Energieakkumulation in Grundschicht und Nullschicht

Zusammenfassung Grundschicht und Nullschicht wurden bereits früher als zwei Schichten erkannt, die in bezug auf den Massenhaushalt der hochreichenden Hoch — und Tiefdruckgebiete von polar entgegengesetzter Bedeutung sind: In der Grundschicht erfolgt ein ageostrophischer Massenfluss vom hohen zum tiefen Druck, in der Nulischicht ein solcher vom tiefen zum hohen Druck. Beide Schichten weisen aber auch Gemeinsamkeiten auf. Sie liegen unter den markantesten Inversionen der Troposph?re (Peplopause bzw. Tropopause). Da eine Inversion als Sperrschicht des nach oben gerichteten Flusses der kinetischen Energie wirkt, kommt es unter ihr zu einem Stau kinetischer Energie, der eine ageostrophische Erh?hung der Windgeschwindigkeit gegenüber den vertikal benachbarten Schichten mit sich bringt. Anhaltspunkte für eine derartige Erh?hung der Windgeschwindigkeit unterhalb der Peplopause liegen vor.

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Summary Ground layer and zero layer were recognized in the past already as two layers that are of directly opposite relevance to the mass exchange in high-reaching high and low pressure areas; taking place in the ground layer is an ageostrophic mass transport in the direction high to low pressure, while in the zero layer the opposite motion is accurring, i.e., from low to high pressure. Yet, the two layers have some communities too. They are located below the most significant inversions of the troposphere (Peplopause and/or Tropopause). Since an inversion will act upon the flow upward of kinetic energy as an intercepting layer, a congestion of kinetic energy will be produced below it, involving an ageostrophic increase in the wind speed, as compared with vertically adjoining layers. There are a number of clues for such an increase of wind speed actually occurring below the peplopause.

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Prof. Dr.Karl Schneider-Carius,Bad Kissingen Erhardstr. 3.

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Dr.Heinrich Faust, Deutscher Wetterdienst,Frankfurt a.M., Taunusanlage 18.     

Compositions of magmatic hydrothermal fluids determined by LA-ICP-MS of fluid inclusions from the porphyry copper–molybdenum deposit at Butte, MT

We analyzed 85 fluid inclusions from seven samples from the porphyry Cu–Mo deposit in Butte, MT, using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). The Butte deposit formed at unusually great depth relative to most porphyry deposits, and fluid inclusions in deep veins trapped a low-salinity, CO₂-bearing, magmatically derived, supercritical fluid as a single aqueous phase. This fluid is interpreted to be the parent fluid that cooled, decompressed, unmixed, and reacted with wall rock to form the gigantic porphyry Cu deposit at Butte. Few previous analyses of such fluids exist.Low-salinity, aqueous fluids from the earliest veins at Butte are trapped in deep veins with biotite-rich alteration envelopes (EDM veins). These veins, and the Butte quartz monzonite surrounding them, host much of the Butte porphyry Cu mineralization. Twenty fluid inclusions in one EDM quartz vein are dominated by Na, K, Fe (from 0.1 to 1 wt.%) and contain up to 1.3 wt.% Cu. These inclusions contain only small amounts (tens of ppm) of Pb, Zn, and Mn, and typically contain Li, B, Ca, As, Mo, Ag, Sn, Sb, Ba, and W in less than detectable quantities. The abundance of Cu in early fluids indicates that a low-salinity, Cu-rich, aqueous ore fluid can be directly produced by aqueous fluid separation from a granitic magma. Similar inclusions (eight) in an early deep quartz–molybdenite vein with a K-feldspar selvage have similar compositions but contain significantly less Cu than most inclusions in the biotite-altered vein. Analyzed inclusions in both veins contain less than detectable concentrations of Mo even though one is molybdenite-bearing.Low-salinity, CO₂-bearing aqueous fluids are also trapped in pyrite–quartz veins with sericitic selvages. These veins cut both of the above vein types and contain inclusions that were trapped at lower pressure and temperature. Thirty-nine inclusions in two such veins have compositions similar to early fluids, but are enriched by up to a factor of 10 in Mn, Pb, and Zn relative to early fluids, and are slightly depleted in Fe. Many of these inclusions contain as much or more Cu than early fluids, although little chalcopyrite is found in or around pyrite–quartz veins.Eighteen halite-bearing inclusions from three veins from both chalcopyrite-bearing and barren veins with both K-silicate and sericitic selvages were analyzed as well. Halite-saturated inclusions are dominated by Na, K, Fe, and in some inclusions Ca. Whereas these inclusions are significantly enriched in Ca, Mn, Fe, Zn, and Pb, fluids in all three veins contain significantly less Cu than early, high temperature, low-salinity inclusions.Analyses of all inclusion types show that whereas bulk-salinity of the hydrothermal fluid must be largely controlled by the magma, fluid–rock interactions have a significant role in controlling fluid compositions and metal ratios. Cu concentrations range over an order of magnitude, more than any other element, in all four samples containing low-salinity inclusions. We infer that variations are the result of fluid trapping after different amounts of fluid–rock reaction and chalcopyrite precipitation. Enrichment, relative to early fluids, of Mn, Pb, and Zn in fluids related to sericitic alteration is also likely the result of fluid–rock reaction, whereby these elements are released from biotite and feldspars as they alter to sericite. In halite-bearing inclusions, concentrations of Sr, Ca, Pb, and Ba are elevated in inclusions from the pyrite–quartz vein with sericitic alteration relative to halite-bearing inclusions from unaltered and potassically altered samples. Such enrichment is likely caused by the breakdown of plagioclase and K-feldspar in the alteration envelope, releasing Sr, Ca, Pb, and Ba.