The petrography, mineral chemistry and petrogenesis of a sample from the Weissenstein eclogite, Bavaria, Germany, has been investigated. The total mineral assemblage comprises garnet, clinopyroxeneI+II, quartz, amphiboleI+II, rutile, phengite, epidote/allanite, plagioclase, biotite, apatite, pumpellyite, titanite (sphene), zircon, alkali feldspar and calcite. Textural observations combined with geothermobarometry (Fe/Mg distribution between clinopyroxene/garnet and phengite/garnet; jadeite-content of omphacite, Si-content of phengite, and An-content of plagioclase) provide indications of two different stages in the metamorphic evolution of the rock. The main phengitequartz-eclogite mineral equilibration occurred at minimum P=13–17kbar, minimum T=620±50° C; the retrograde symplectite stage (clinopyroxeneII, amphiboleII, biotite, plagioclase) occurred at Ptotal between 12 and 8.5 kbar. Reactions of the symplectite stage are:
The phengite decomposition produces H2O, whereas the clinopyroxene decomposition consumes H2O. The estimated P-T-conditions for the Weissenstein eclogite are in the same order of magnitude as those for other eclogite bodies from the Alps and Caledonides believed to be related to subduction processes. 相似文献
Petrologic data on the paragenesis of (I) kyanite-zoisite marbles and (II) garnet-chloritoid quartz-mica schists are presented with the goal of providing constraints on the pressure-temperature evolution of the Eclogite Zone, Tauern Window, Austria. The peak metamorphic assemblages in the two rock types are: (I) kyanite + zoisite + dolomite + quartz; zoisite + muscovite + dolomite + calcite + quartz; and (II) garnet + chloritoid + kyanite + muscovite + quartz + epidote ± dolomite ± Zn-staurolite. The estimated peak metamorphic conditions are 19 ± 2 kbar, 590 ± 20°C.
Secondary alteration of the kyanite-zoisite marbles was accomplished in two stages. The early stage resulted in the production of margarite, paragonite, secondary muscovite and chlorite and the later stage resulted in the formation of sudoite (a di/trioctahedral Mg---Al layer silicate) and kaolinite. The early alteration is bracketed at conditions between 3 and 10 kbar, 450–550°C and the later alteration between 200 and 350°C, P 3 kbar.
The P-T path is characterized by maximum burial to approximately 19 kbar (60–70 km) (at≈590°C), followed by nearly isothermal decompression to approximately 10 kbar (30 km), and then more gradual decompression with cooling to approximately 3 kbar (10 km). Alteration was apparently accomplished by the influx of H2O-rich fluids, with the composition of the fluid locally buffered by the mineral assemblage. 相似文献
An improved laboratory respiration fermentor construction for batchwise operations by which permeations of gases through connecting rubber tubings could be avoided is described. From the registration of curves for oxygen consumption during batchwise treatment of waste water from coal gasification at 37°C a decrease of the COD reduction rate is observed when the dissolved oxygen concentration decreased to below 0,7 mg/l. At dissolved oxygen concentrations above 0,7 mg/l, biokinetic data were determined which on account of the improved respiratory fermenter construction diverge strongly from the values formerly given \documentclass{article}\pagestyle{empty}\begin{document}$({\rm \mu = 0,24 h}^{{\rm - 1}};Y_{\frac{x}{{{\rm O}_2 }}} = 0,57{\rm g\; OBTSZ/g O}_{\rm 2};Y_{\frac{x}{s}} = 0,32{\rm g\; OBTSZ/g\; COD}) $\end{document}. Investigations performed in the thermophilic range (55°C) led at dissolved oxygen concentration of 1,5 mg/l to significant slower COD-reduction rates whereas at dissolved oxygen concentration of 1,5 mg/l the efficiency of COD-reduction was significantly higher than in the mesophilic range. The results obtained at different dissolved oxygen concentrations and different treating temperatures are discussed. 相似文献
Zusammenfassung An Hand einer Reihe von konkreten Wetterlagen wird die Größenordnung der durch eine ausgeglichene Topographie der Alpen erzeugten Vertikalbewegung, der Divergenz, des vertikalen Vorticitytransportes und des Twisting-Termes (Vertikalschwenkungseffektes) im 500- und 700 mb-Niveau abgeschätzt. Es zeigt sich hiebei, daß Divergenz und Vertikaltransport von gleicher Größenordnung sind, während der Twisting-Term um eine Größenordnung kleiner ausfällt. Unter gewissen Voraussetzungen wird im Hinblick auf die graphische Integration der Vorticitygleichung im orographischen Störbereich die Bedeutung des Vertikaltransportes quantitativ ermittelt. Hieraus ergeben sich gewisse Rückschlüsse auf die Enwirkung der Struktur des Temperaturfeldes auf mögliche orographische, zyklogenetische und antizyklogenetische Effekte in den entsprechenden Geopotentialflächen.
Summary Using a number of actual weather situations an estimate is made of vertical movement, divergence, vertical vorticity transport, and twisting term, in the 500 mb and 700 mb levels, caused by the (idealized) topography of the Alps. It turns out that divergence and vertical transport are of the same magnitude, whereas the twisting term is one order of magnitude smaller. Under certain assumptions, the importance of vertical transport for the graphical integration of the vorticity equation in regions of topographic disturbances is quantitatively evaluated. Some conclusions can be drawn about the influence of the temperature field on orographic, cyclogenetic, and anticyclogenetic effects in the corresponding geopotential levels.
Résumé Se basant sur une série de situations météorologiques concrètes, l'auteur estime, aux niveaux de 500 et 700 mb, l'ordre de grandeur du mouvement vertical, de la divergence, de la modification verticale de la «Vorticity» ainsi que du «twisting-term» (effet de changement vertical de direction) provoqué par une topographie égalisée des Alpes. Il en conclut que la divergence et le mouvement vertical sont du même ordre de grandeur tandis que le «twisting-term» est d'une puissance de 10 inférieur. Il calcule, dans certaines conditions, l'importance de l'effet vertical en vue de l'intégration graphique de l'équation de «vorticity» dans les zones perturbées par le relief. Il en découle certaines répercussions sur l'influence que peut avoir la structure du champ des températures sur des effets orographiques, cyclogénétiques et anticyclogénétiques possibles aux niveaux géopotentiels considérés.
Zoisite-bearing high-pressure pegmatites from the MünchbergMassif, Germany, provide an excellent example of the characteristicsof the onset of metabasite melting at eclogite-facies conditions.The pegmatites were derived by partial melting of a mid-oceanridge basalt (MORB)-like eclogite at T 680°C/2·3GPa to 750°C/3·1 GPa, which produced small amountsof tonalitic to trondhjemitic melt. The melt concentrated locallyin isolated, small melt pockets and crystallized primary zoisiteas liquidus phase at P 2·3 GPa/680°C to 2·1GPa/750°C. Compositional zoning of pegmatite zoisite recordsan ensuing multi-stage uplift history with successive, discretecrystallization events at 1·4 ± 0·2 GPa/650700°Cand 1·0 ± 0·1 GPa/620650°C.Resorption textures indicate reheating and thermal perturbationof the whole system prior to each successive crystallizationevent. Final solidification of zoisite-pegmatites occurred at0·9 ± 0·1 GPa/620650°C. Thedata suggest that isolated melt + zoisite crystal mush pocketsformed an integral part of the eclogite throughout uplift frommelt formation at T 680°C/2·3 GPa to 750°C/3·1GPa to final solidification at 0·9 GPa/620630°C;that is, over a depth range of 4560 km. The entire pegmatite-formingprocess was probably fluid conserving: fluid present duringmelt formation was trapped by fully or nearly water-saturatedsiliceous melts, whereas fluid liberated during pegmatite crystallizationinteracted with dehydrated eclogite-facies assemblages to formamphibolite-facies hydrous minerals. A set of empirical Dmelt/eclogitevalues based on mean zoisite-pegmatite and eclogite compositionwere used to model the onset of partial high-pressure meltingof metabasites. KEY WORDS: adakite; high-pressure melting; pegmatite; trondhjemite; zoisite相似文献
The internal organization of plankton communities plays a key role in biogeochemical cycles and in the functioning of aquatic ecosystems. In this study, the structure of a marine plankton community (including both unicellular and multicellular organisms) was inferred by applying an ecological network approach to species abundances observed weekly at the long‐term ecological research station MareChiara (LTER‐MC) in the Gulf of Naples (Tyrrhenian Sea, Mediterranean Sea) in the summers of 2002–2009. Two distinct conditions, characterized by different combination of salinity and chlorophyll values, alternated at the site: one influenced by coastal waters, herein named ‘green’, and the other reflecting more offshore conditions, named ‘blue’. The green and blue ‘phases’ showed different keystone biological elements: namely, large diatoms and small‐sized flagellates, respectively. Several correlations amongst species belonging to different trophic groups were found in both phases (connectance ~0.30). In the green phase, several links between phytoplankton and mesozooplankton and within the latter were detected, suggesting matter flow from microbes up to carnivorous zooplankton. A microbial‐loop‐like sub‐web, including mixo‐ and heterotrophic dinoflagellates and ciliates, was present in the green phase, but it was relatively more important in the blue phase. The latter observation suggests a more intense cycling of matter at the microbial trophic level in the blue phase. These results show that different modes of ecological organization can emerge from relatively small changes in the composition of aquatic communities coping with environmental variability. This highlights a significant plasticity in the internal structure of plankton webs, which should be taken into account in predictions of the potential effects of climatic oscillations on aquatic ecosystems and biogeochemical cycles therein. 相似文献
The Jurassic succession of Gangta Bet in the Kachchh basin of western India comprises around 130 m of mostly siliciclastic rocks. The strata belong to the Gangta Member of the Gadhada Formation and are herein sub-divided into four units: the Gangta sandstone beds, the lower silty sandstone beds, the upper silty sandstone beds, and the Gangta ammonite beds. These units can be separated by three marker horizons: the Brachiopod bed, the Gangta Conglomerate Bed, and the Gervillella Bed. Ammonites indicate an Oxfordian age for the upper half of the succession, but the scarcity of identifiable fossils in its basal part so far prevented precise biostratigraphic assignments. The shallow-water sediments can be interpreted as parasequences as a result of minor sea-level changes. Deposition took place close to the palaeo-coastline at water depths around the fair-weather wave-base. 相似文献