Li-bearing, disordered Mg-rich tourmaline from a pegmatite-marble contact in the Austroalpine basement units (Styria, Austria)     

Andreas Ertl  Heinrich Mali  Ralf Schuster  Wilfried Körner  John M. Hughes  Franz Brandstätter  Ekkehart Tillmanns 《Mineralogy and Petrology》2010,99(1-2):89-104

Pale-blue to pale-green tourmalines from the contact zone of Permian pegmatites to mica schists and marbles from different localities of the Austroalpine basement units (Rappold Complex) in Styria, Austria, are characterized. All these Mg-rich tourmalines have small but significant Li contents, up to 0.29 wt% Li₂O, and can be characterized as dravite, with FeO contents of ?~?0.9–2.7 wt%. Their chemical composition varies from ^X (Na_0.67Ca_0.19?K_0.02?_0.12) ^Y (Mg_1.26Al_0.97Fe²⁺ _0.36Li_0.19Ti⁴⁺ _0.06Zn_0.01?_0.15) ^Z (Al_5.31?Mg_0.69) (BO₃)₃ Si₆O₁₈ ^V (OH)₃? ^W [F_0.66(OH)_0.34], with a?=?15.9220(3), c?=?7.1732(2) Å to ^X (Na_0.67Ca_0.24?K_0.02?_0.07) ^Y (Mg_1.83Al_0.88Fe²⁺ _0.20Li_0.08Zn_0.01Ti⁴⁺ _0.01?_0.09) ^Z (Al_5.25?Mg_0.75) (BO₃)₃ Si₆O₁₈ ^V (OH)₃? ^W [F_0.87(OH)_0.13], with a?=?15.9354(4), c?=?7.1934(4) Å, and they show a significant Al-Mg disorder between the Y and the Z sites (R1?=?0.013–0.015). There is a positive correlation between the Ca content and?<?Y-O?>?distance for all investigated tourmalines (r?≈?1.00), which may reflect short-range order configurations including Ca and Fe²⁺, Mg, and Li. The tourmalines have X_Mg (X_Mg?=?Mg/Mg?+?Fe_total) values in the range 0.84–0.95. The REE patterns show more or less pronounced negative Eu and positive Yb anomalies. In comparison to tourmalines from highly-evolved pegmatites, the tourmaline samples from the border zone of the pegmatites of the Rappold Complex contain relatively low amounts of total REE (~8–36 ppm) and Th (0.1–1.8 ppm) and have low La_N/Yb_N ratios. There is a positive correlation (r?≈?0.91) between MgO of the tourmalines and the MgO contents of the surrounding mica schists. We conclude that the pegmatites formed by anatectic melting of mica schists and paragneisses in Permian time. The tourmalines crystallized from the pegmatitic melt, influenced by the metacarbonate and metapelitic host rocks.  相似文献   

Nitrogen recycling in subducted oceanic lithosphere: The record in high- and ultrahigh-pressure metabasaltic rocks     

Ralf Halama  Gray E. Bebout  Volker Schenk 《Geochimica et cosmochimica acta》2010,74(5):1636-7521

This paper provides the first measurements of the nitrogen (N) concentrations and isotopic compositions of high- and ultrahigh-pressure mafic eclogites, aimed at characterizing the subduction input flux of N in deeply subducting altered oceanic crust (AOC). The samples that were studied are from the Raspas Complex (Ecuador), Lago di Cignana (Italy), the Zambezi Belt (Zambia) and Cabo Ortegal (Spain), together representing subduction to 50-90 km depths. The eclogites contain 2-20 ppm N with δ¹⁵N_air values ranging from −1 to +8‰. These values overlap those of altered oceanic crust, but are distinct from values for fresh MORB (for the latter, ∼1.1 ppm N and δ¹⁵N_air ∼ −4‰). Based on N data in combination with other trace element data, the eclogite suites can be subdivided into those that are indistinguishable from their likely protolith, AOC, with or without superimposed effects of devolatilization (Lago di Cignana, Cabo Ortegal), and those that have experienced metasomatic additions during subduction-zone metamorphism (Zambezi Belt, Raspas). For the former group, the lack of a detectable loss of N in the eclogites, compared to various altered MORB compositions, suggests the retention of N in deeply subducted oceanic crust. The metasomatic effects affecting the latter group can be best explained by mixing with a (meta)sedimentary component, resulting in correlated enrichments of N and other trace elements (in particular, Ba and Pb) thought to be mobilized during HP/UHP metamorphism. Serpentinized and high-pressure metamorphosed peridotites, associated with the eclogites at Raspas and Cabo Ortegal, contain 3-15 ppm N with δ¹⁵N_air values ranging from +3 to +6‰, significantly higher than the generally accepted values for the MORB mantle (δ¹⁵N_air ∼ −5‰). Based on their relatively high N contents and their homogeneous and positive δ¹⁵N values, admixing of sedimentary N is also indicated for the serpentinized peridotites.One possible pathway for the addition of sediment-derived N into eclogites and peridotites involves mixing with fluids along the slab-mantle wedge interface. Alternatively, sedimentary N could be incorporated into peridotites during serpentinization at bending-related faults at the outer rise and, during later deserpentinization, released into fluids that then infiltrate overlying rocks. Deep retention of N in subducting oceanic crust should be considered in any attempt to balance subduction inputs with outputs in the form of arc volcanic gases. If materials such as these eclogites and serpentinized peridotites are eventually subducted to beyond sub-arc depths into the deeper mantle, containing some fraction of their forearc-subarc N inventory (documented here), they could deliver isotopically heavy N into the mantle to potentially be sampled by plume-related magmas.  相似文献   

The role of the Kupferschiefer in the formation of hydrothermal base metal mineralization in the Spessart ore district, Germany: insight from detailed sulfur isotope studies     

Thomas Wagner  Martin Okrusch  Stefan Weyer  Joachim Lorenz  Yann Lahaye  Heiner Taubald  Ralf T. Schmitt 《Mineralium Deposita》2010,45(3):217-239

The Spessart district (SW Germany), located at the southwestern margin of the Permian Kupferschiefer basin in Central Europe, hosts abundant stratabound and structurally controlled base metal mineralization. The mineralization styles identified are (1) stratabound Cu-Pb-Zn-(Ag) ores in Zechstein sedimentary rocks, (2) structurally controlled Cu-As-(Ag) ores in Zechstein sedimentary rocks, (3) crosscutting Co-Ni-(Bi)-As and Cu-Fe-As veins, (4) stratabound metasomatic Fe-Mn carbonate ores in Zechstein dolomite, (5) barren barite veins, and (6) Fe-Mn-As veins in Permian rhyolites. Building on previous work that involved mineralogical, textural, and chemical characterization of the major mineralization types, we have performed a comprehensive sulfur isotope study that applied both conventional and novel laser-ablation multi-collector inductively coupled plasma mass spectrometry techniques. The δ³⁴S values of sulfide minerals from the different ore types are consistently negative and highly variable, in the range between −44.5‰ and −3.9‰, whereas the δ³⁴S values of barite are all positive in the range between 4.7‰ and 18.9‰. Remarkably, stratabound and structurally controlled mineralization in Zechstein sedimentary rocks has the least negative δ³⁴S values, whereas vein-type deposits have consistently more negative δ³⁴S values. The observed pattern of sulfide δ³⁴S values can be best interpreted in terms of fluid mixing at the basement-cover interface. Hydrothermal fluids originating from the crystalline basement migrated upward along subvertical fault zones and were periodically injected into groundwaters that were flowing in the post-Variscan sedimentary cover. These groundwaters had interacted with the Zechstein sedimentary rocks, resulting in fluids characterized by elevated concentrations of reduced sulfur (with negative δ³⁴S values) and alkaline pH. Repeated mixing between both chemically contrasting fluids caused rapid and efficient precipitation of sulfide ore minerals in hydrothermal veins with highly variable but distinctly negative δ³⁴S values.  相似文献   

The HYPER-MUCHFUSS project—target selection and analysis     

A. Tillich  S. Geier  U. Heber  H. Hirsch  P. F. L. Maxted  T. Marsh  B. Gänsicke  R. Napiwotzki  R. Østensen  R.-D. Scholz 《Astrophysics and Space Science》2010,329(1-2):63-68

The HYPER-MUCHFUSS project targets a population of high velocity subluminous B stars to discover either close binaries with massive unseen companions or hyper-velocity stars. Our starting point is the enormous database of SDSS. We preselected sdO/B candidates by colour and classified them by visual inspection of their spectra. We measured the radial velocity from the coadded SDSS spectra, which serves as first epoch measurement. Stars with high Galactic rest-frame velocities were selected and second epoch observations were obtained starting in 2007 at several sites. For the brighter targets we also included the SDSS individual spectra as additional information. In the course of our survey we observed 88 out of 265 stars from our target list. We discovered 39 HVS candidates as well as 49 close binaries. In addition we analysed all single spectra of sdBs from SDSS and found 120 close binaries. For the targets with constant RVs we performed a proper motion analysis with the highest possible accuracy from the available digitised photographic plates. Together with the analysed spectra and the calculation of the spectroscopic distance, we calculated complete trajectories and deduced the origins of these stars. Targets with high RV variability on short timescales were selected for follow-up. Numerical simulations based on the period and companion mass distribution of the known sdB binary sample were carried out to optimise the target selection and single out candidate binaries with massive companions. The follow-up campaign using WHT/ISIS and CAHA-3.5m/TWIN started in 2009.  相似文献   

The HYPER-MUCHFUSS project—the constant high-velocity population     

A. Tillich  S. Geier  U. Heber  H. Hirsch  P. F. L. Maxted  T. Marsh  B. Gänsicke  R. Napiwotzki  R. Østensen  R.-D. Scholz 《Astrophysics and Space Science》2010,329(1-2):69-76

The HYPER-MUCHFUSS (HYPER-velocity stars or Massive Unseen Companions of Hot Faint Underluminous Stars from SDSS) project targets a population of high-velocity subluminous B stars to discover either close binaries with massive unseen companions or hyper-velocity stars. We re-observed high-velocity subdwarf selected candidates from the SDSS spectroscopic Data Release 6. Starting in 2007 we used several instruments and have now reached a completion level of 33% (from 265 targets), whereas we found at least 16 close binaries. Here we present results for two of our 39 hyper-velocity star candidates. From the available Digitized Sky Surveys photographic plates we measured a significant proper motion for 14 stars. Combining this information with a detailed spectroscopic analysis allows for the first time a complete determination of the 3D-trajectories for a high-velocity sample. We present our preliminary results for the two subdwarfs J1644+4523 and J1211+1437. Assuming the Standard Allen and Santillan (Rev. Mex. Astron. Astrofis. 22:255, 1991) potential the first one is bound and originates in the central region of the Galaxy. The subdwarf B star J1211+1437 is possibly unbound and seems to originate in the Galactic rim. We also performed numerical kinematical experiments with increased dark matter halo mass. and found that the origin of J1644+4523 in the central region is not changed but the time-of-flight is drastically shortened. J1211+1437 would be bound and probably belongs to population II.  相似文献   

A study to explain the emission of nitric oxide from a marsh soil   总被引：1，自引：0，他引：1  

Armin Remde  Jörg Ludwig  Franz X. Meixner  Ralf Conrad 《Journal of Atmospheric Chemistry》1993,17(3):249-275

In the period 18–21 September 1989, soil NO emission was studied at Halvergate Marshes, Norfolk (U.K.) within the framework of the BIATEX-LOVENOX joint field experiment. Using a dynamic chamber technique, 186 measurements at four plots were performed showing a net NO flux of 7.2–14.6×10^–12 kgN m^–2 s^–1. Soil samples from a soil profile (1.0 m) at a representative site and from the uppermost layer (0.1 m) of each of the four plots were sent to the laboratory for (a) detailed physical and chemical soil analysis, (b) determination of NO production rates, NO uptake rate constants, and NO compensation mixing ratios, and (c) characterization of the microbial processes involved. A diffusive model (Galbally and Johansson, 1989) was applied to the laboratory results to infer NO fluxes of the individual soil samples. When we compared these fluxes with those measured in the field, we found agreement within a factor 2–4. Furthermore, laboratory studies showed, that NO was produced and consumed only in the upper soil layer (0–0.1 m depth) and that the NO production and consumption activities observed in the Halvergate marsh soil were most probably due to the anaerobic metabolism of denitrifying bacteria operating in anaerobic microniches within the generally aerobic soil.  相似文献   

Parametric study of vertical vibrations of circular flexible foundations on layered media     

Nenad Gucunski  Ralf Peek 《地震工程与结构动力学》1993,22(8):685-694

The paper presents results of a parametric study of vertical oscillations of a flexible circular plate on the surface of an elastic half-space and an elastic layered system. The solution of the problem is based on the ‘ring method’. Vertical oscillations have been analysed to determine the displacement and soil reaction distributions at the soil-plate interface and the impedance functions. Parameters of the study include material and geometrical properties of a soil system and a plate and the load distribution on the plate. The results indicate significantly different behaviour of a flexible plate from that of a rigid one. Based on the observed behaviour, a classification of plates has been suggested.  相似文献   

The z=2.72 galaxy cB58: a gravitational fold arc lensed by the cluster MS 1512+36     

Stella Seitz  R. P. Saglia  Ralf Bender  Ulrich Hopp  Paola Belloni  & Bodo Ziegler 《Monthly notices of the Royal Astronomical Society》1998,298(4):945-965

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Emission of nitrous oxide from temperate forest soils into the atmosphere   总被引：5，自引：0，他引：5  

Joachim Schmidt  Wolfgang Seiler  Ralf Conrad 《Journal of Atmospheric Chemistry》1988,6(1-2):95-115

N₂O emission rates were measured during a 13-month period from July 1981 till August 1982 with a frequency of once every two weeks at six different forest sites in the vicinity of Mainz, Germany. The sites were selected on the basis of soil types typical for many of the Central European forest ecosystems. The individual N₂O emission rates showed a high degree of temporal and spatial variabilities which, however, were not significantly correlated to variabilities in soil moisture content or soil temperatures. However, the N₂O emission rates followed a general seasonal trend with relatively high values during spring and fall. These maxima coincided with relatively high soil moisture contents, but may also have been influenced by the leaf fall in autumn. In addition, there was a brief episode of relatively high N₂O emission rates immediately after thawing of the winter snow. The individual N₂O emission rates measured during the whole season ranged between 1 and 92 g N₂O-N m^–2 h^–1. The average values were in the range of 3–11 g N₂O-N m^–2 h^–1 and those with a 50% probability were in the range of 2–8 g N₂O-N m^–2 h^–1. The total source strength of temperate forest soils for atmospheric N₂O may be in the range of 0.7–1.5 Tg N yr^–1.  相似文献   

Comparative organic petrology of interlayered sandstones,siltstones, mudstones and coals in the Upper Carboniferous Ruhr basin,Northwest Germany,and their thermal history and methane generation     

Dr. Günter Scheidt  Dr. Ralf Littke 《International Journal of Earth Sciences》1989,78(1):375-390

In the coal-mining Ruhr-area, Upper Carboniferous rocks (ca. 4000 m) consist of interlayered sandstones, siltstones, mudstones and coals. They were deposited in a tropical, paralic environment where alternating fluvial sedimentation, occasional marine ingressions, and swamp growth resulted in an irregular cyclic succession. The total sedimentary package contains on an average 6 Vol.-% of organic matter. About 70 Vol.-% of the organic matter occurs in coal seams, the rest as dispersed organic matter in clastic rocks. The organic matter is autochthonous in the coals and allochthonous in associated sandstones and siltstones. It consists of about 70% vitrinite, 20% inertinite, and 10% liptinite. The overall maceral group composition is the same for coals and dispersed organic matter. This surprising similarity is caused by a nearly exclusive input of land-plant derived organic matter to swamps and fluvial systems and a similar degree of preservation. Highest average liptinite contents (% of total macerals) were found in unrooted mudstones, highest average inertinite contents in coarse-grained siltstones and highest average vitrinite percentages in sandstones.Maturities of the sediments studied are well within the hydrocarbon generation window, e. g. vitrinite reflectivities range from 0.6% to 1.6%. Reflectivities measured on dispersed particles in clastic rocks are similar to those measured in coal seams. Calculations of the amount of methane generated indicate that coal seams contributed more to the total hydrocarbon generation than dispersed organic matter.

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Zusammenfassung Das Oberkarbon des Ruhrgebietes besteht aus ca. 4000 Metern wechsellagernder Sandsteine, Siltsteine und Kohleflöze. Der Ablagerungsraum der Sedimente war eine Region mit tropischem Klima, genauer ein paralisches Environment mit unregelmäßig alternierenden Folgen von fluviatilen Sedimenten, marinen Transgressionen und verbreiteten Sumpfablagerungen. Der Anteil organischer Substanzen an der gesamten Sedimentmenge beträgt durchschnittlich 6%. 70% dieser organischen Masse ist in Kohleflözen angereichert, der Rest liegt verteilt in den klastischen Gesteinen vor. Die Herkunft der organischen Substanz in den Kohleflözen ist autochthon, die in den benachbarten Sand- und Siltsteinen allochton. Die Zusammensetzung des organischen Materials ist 70% Vitrinit, 20% Inertinit und 10% Liptinit. Die allgemeine Zusammensetzung nach Mazeral-Gruppen ist für die Kohleflöze und das verteilte Material in den Nachbargesteinen identisch. Diese Ähnlichkeit beruht auf der gemeinsamen Herkunft der organischen Substanz in Sümpfen und Flußsystemen, die fast ausschließlich von Landpflanzen bestimmt wird, und einer sich entsprechenden Konservierung.Der Reifegrad der analysierten Sedimente liegt innerhalb des Kohlenwasserstoff-Bildungsbereiches (die Vitrinit-Reflexionen reichen von 0,6–1,6%). Dabei entsprechen die in den klastischen Gesteinen beobachteten Reflexionswerte weitgehend denen der Kohleflöze. Anhand der Menge des erzeugten Methans läßt sich erkennen, daß der Anteil der Kohleflöze an der Kohlenwasserstoff-Produktion höher ist als der Anteil, den disperse organische Substanzen der Klastika beisteuern.

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Résumé Dans la région minière de la Ruhr, le Carbonifère supérieur constitue une succession, épaisse de 4.000 m environ, de grès, de siltites et de charbon. Leur dépôt, dans un milieu paralique tropical, a été marqué par des alternances de sédimentation fluiviale, de transgressions marines occasionnelles, et d'épisodes marécageux; il en résulte une disposition cyclique irrégulière. La série sédimentaire contient dans l'ensemble 6% de matière organique en moyenne. Environ 70% de cette matière organique se trouve dans les couches de charbon où elle est autochtone; le reste est allochtone et dispersé dans les grès et siltites. La matière organique se répartit approximativement en 70% de vitrinite, 20% d'inertinite et 10% de liptinite. La composition moyenne du groupe «macéral» est la même pour les charbons et la matière organique dispersée. Cette identité surprenante est l'expression d'une alimentation provenant exclusivement de plantes terrestres et d'un même degré de conservation.La maturité des sédiments étudiés se situe à l'intérieur du domaine de genèse des hydrocarbures: le pouvoir réflecteur de la vitrinite s'échelonne entre 0,6% et 1,6%. Les gradients du pouvoir réflecteur observés dans les roches détritiques et dans les couches de charbon sont analogues. Le calcul de la quantité de méthane engendré indique que la contribution des couches de charbon à la production totale d'hydrocarbure est supérieur à celle de la matière organique dispersée.

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