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Modelling phase-assemblage diagrams for magnesian metapelites in the system K2O – FeO – MgO – Al2O3 – SiO2 – H2O: geodynamic consequences for the Monte Rosa nappe, Western Alps. R. Le Bayon 1 , C. de Capitani and M. Frey 2 1 TU Darmstadt and 2 University of Basel, CH Magnesian metamorphic rocks with metapelitic mineral assemblages and composition are of great interest in metamorphic petrology for their ability to constrain P-T conditions in terranes where metamorphism is not easily visible. Phase-assemblages diagrams for natural and modal magnesian metapelites in the system KFMASH are presented to document how phase relationships respond to water activity, bulk composition, pressure and temperature. The phase assemblage displayed on these phase diagrams are consistent with natural mineral assemblages occurring in magnesian metapelites. It is shown that the equilibrium assemblages at high pressure conditions are very sensitive to a(H2O). Specifically, the appearance of the characteristic HP assemblage chloritoidtalc-phengite-quartz (with excess H2O) in the magnesian metapelites of the Monte Rosa nappe (Western Alps) is due to reduction of a(H2O). Furthermore, the mineral assemblages are determined by the whole-rock FeO/(FeO+MgO) ratio and effective Al content XA as well as P and T. The predicted mineral association for the low- and high –XA model bulk compositions of magnesian metapelites at high pressure are not dependent on the XA variations as they show a similar sequence of mineral assemblages. Above 20 kbar, the prograde sequence of assemblages associated with phengite (with excess SiO2 and H2O) for low- and high-XA bulk compositions of magnesian metapelites is: carpholite-chlorite –» chlorite-chloritoid –» chloritoid-talc –» chloritoid-talc-kyanite –» talc-garnet-kyanite –» garnet-kyanite ± biotite. At low to medium P-T conditions, a low-XA stabilises the phengite-bearing assemblages associated with chlorite, chlorite + K-feldspar and chlorite + biotite while a high-XA results in the chlorite-phengite bearing assemblages associated with pyrophyllite, andalusite, kyanite and carpholite. At high-XA magnesian metapelites with nearly iron-free content stabilises the talc-kyanite-phengite assemblage at moderate to high P-T conditions. Taking into account the effective bulk composition and a(H2O) involved in the metamorphic history, the calculated phase-assemblage diagrams may be applied to all magnesian metapelites that have compositions within the system KFMASH and therefore may contribute to gaining insights into the metamorphic evolution of deep buried structural units. As an example, the magnesian metapelites of the Monte Rosa nappe have been investigated, and an exhumation path (following Alpine continental collision of the subdued delaminated Monte Rosa nappe) with P-T conditions for the western roof of the Monte Rosa nappe has been derived for the first time. The exhumation shows first a near-isothermal decompression from the Alpine eclogite peak conditions around 24 kbar and 505°C down to approximately 8 kbar and 475°C followed by a second decompression with concomitant cooling. - 158 -
Chemical composition and mineralogical composition of Saharan mineral dust over south east Morocco K. Kandler 1 , C. Deutscher 2 , M. Ebert 1 , H. Hofmann 1 , S. Jäckel 1 , A. Petzold 3 , L. Schütz 2 , S. Weinbruch 1 , B. Weinzierl 3 , S. Zorn 2 1 Institute of Applied Geosciences, Darmstadt University of Technology, Darmstadt 2 Institute for Physics of the Atmosphere, Johannes-Gutenberg-University, Mainz 3 Institute of Atmospheric Physics, German Aerospace Center, Wessling The Saharan Mineral Dust Experiment (SAMUM) is dedicated to the understanding of the radiative effects of mineral dust. A joint field campaign focussed on the source-near investigation of Saharan dust was carried out in southern Morocco. Ground based measurements were a performed near Tinfou and at the Ouarzazate airport; airborne measurements were carried out onboard a Falcon and a Partenvia aircraft. Together th th with Satellite observations, these measurements ranged from May 13 to June 7 , 2006. Airborne as well as ground based samples were collected with a miniature impactor system on carbon coated substrates and carbon foils; additionally, filter samples were collected, of which the aerosol mass concentration was determined. The size-resolved particle aspect ratio and chemical composition is determined by means of electronmicroscopical single particle analysis. The mineralogical composition of the filter samples is determined by x-ray diffraction. Additional information on single particles will be collected by transmission electron microscopy. The bulk mineralogical composition was found to be dominated by major compounds like quartz, calcite, feldspars (plagioclase and K-spars), and clay minerals (illite/muscovite, kaoline, and chlorite) and minor compounds like hematite. relative fraction 1.0 0.8 0.6 0.4 0.2 n=50 n=361 n=1276 n=1329 n=209 n=13 0.0 1 10 particle diameter, µm other carbonaceous sulfates mixtures silicates quartz halite gypsum other calcium rich carbonates titanium rich iron rich Fig. 1: Relative abundance of particles classes as function of particle diameter for a sample collected at 100 m altitude above the valley east of Ouarzazate, Morocco - 159 -
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ANNUAL REPORT 2 0 0 6 FACULTY OF MA
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Annual Report 2006 Faculty 11 Mater
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Preface The year 2006 of the Depart
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difference of numerical and analyti
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Institute of Materials Science Phys
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Research Projects Bulk Amorphous Al
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el Dsoki, C.; Landersheim, V. ; Kau
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Das, J.; Kim, K. B.; Xu, W.; Wei, B
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Staff Members Head Prof. Dr. Jürge
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Zhou L.; Rixecker G.; Aldinger F.;
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concerned with the synthesis and ch
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Publications Fleissner, A.; Schmid,
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• Surface analysis The UHV-surfac
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T. Mayer, U. Weiler, E. Mankel and
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Thin films The Thin Film division w
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Berky, W.; Gottschalk, S.; Elliman,
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Guest Scientists Research Projects
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Hesse, S.; Zimmermann, J.; von Segg
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Structure Research The research in
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Research Projects Functional Advanc
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Dincer, I.; Elerman, Y.; Elmali, A;
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hexakis(imidazole)nickel(II)bis(for
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Chemical Analytics The chemical ana
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Collaborations The above mentioned
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Hoffmann, P.; Non-Invasive Identifi
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Ferroelectrics For this class of ma
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Materials Modelling The research ac
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Materials for Renewable Energies In
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Joint Research Laboratory Nanomater
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Collaborative Research Center (SFB)
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B7 P.I.: Prof. H. v. Seggern / Dr.
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The glass transition temperature (T
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transition allows to investigate at
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Relative density 1.00 0.95 0.90 0.8
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Fig. 2 shows the time dependencies
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Dielectric interface trap engineeri
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∆V C q th eff 12 −2 p ( VGS = 0
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Fig. 3: Schematic of the photovolta
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synthesis and analysis of interface
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Fig. 2: Resistivity vs temperature
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Fig. 2: X-ray appearance near-edge
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Capacity [mAhg -1 ] 700 600 500 400
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Texture investigations and field em
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screening effects. Gold coating of
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Figure 2 shows a selected region of
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The spectrum shows that apart from
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The effect of crystallinity on the
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Electrochemical investigation and c
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This phenomenon can be understood c
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∆ = 0 − exhibiting dominance of
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constituents. The requirement of va
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In order to assess the influence of
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In this study, we have therefore de
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Fig. 1: Proposed models for a) Pt,
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