0000000000790732
AUTHOR
Werner Joswig
showing 4 related works from this author
Scolecite, Part I: Refinement of high-order data, separation of internal and external vibrational amplitudes from displacement parameters
1997
A single crystal of scolecite, CaAl2Si3O10· 3H2O, was studied by X-ray diffraction methods at room temperature. The intensities were measured with MoKα radiation (λ=0.71069 A) in a complete sphere of reflection up to sinθ/λ=0.9 A−1. The structure was refined in the pseudo-orthorhombic setting of space group F1d1 instead of the conventional setting Cc for better comparison with natrolite (Fdd2). The cell parameters are: a=18.502(1) A, b=18.974(2) A, c=6.525(1) A, β=90.615(7)°, V=2290.6(3) A3, Z=8. A refinement of high-order diffraction data yielded residuals of R(F)=0.9%, R w (F)=0.9%, GoF=1.73 for 1831 high-angle reflections (0.7≤sinθ/λ≤0.9 A−1) and R(F)=1.2%, R w (F)=1.4%, GoF=3.22 for all…
Prehnite: Structural similarity of the monoclinic and orthorhombic polymorphs and their Si/Al ordering
1990
Abstract Two modifications of the naturally occurring mineral prehnite, Ca 2 Al(Si 3 AlO 10 )(OH) 2 , are characterized by precise single crystal diffraction methods. The two forms are topologically identical. They differ only in the siting of one Al and one Si atom per unit cell: these switch their places in two of the tetrahedrally coordinated sites. This appears to be the only known case where a silicate occurs with two differently ordered tetrahedral distributions of Al and Si atoms. The two forms are not polytypes according to the current definition of polytypes. The two modifications are so similar to each other that they differ only in the eighth coordination sphere.
Detection of a Ca-rich lithology in the Earth's deep (>300 km) convecting mantle
2005
Earth's deep convecting upper mantle is believed to represent a rather homogenous geochemical reservoir of spinel or garnet lherzolite with primitive major element and moderately depleted trace element composition. Only where subduction occurs is this homogeneity disrupted by a suite of rocks ranging from eclogites/garnet pyroxenites (former oceanic crust) to residual harzburgites. In addition to these well documented peridotitic and metabasaltic rocks we have now discovered the presence of a chemically distinct reservoir in the deep convecting upper mantle. In situ structural analyses (micro X-ray diffraction and micro Raman spectroscopy) and three-dimensional trace element mapping (confoc…
CO2-recycling to the deep convecting mantle
2006
Institut fur Geowissenschaften, Johann Wolfgang Goethe-Universitat Frankfurt, 60054 Frankfurt, Germany (f.brenker@ em.uni-frankfurt.de) Max Planck Institute for Chemistry, Mainz, Germany (cvollmer@mpch-mainz.mpg.de) Ghent University, Department of Analytical Chemistry, Belgium (Laszlo.Vincze@UGent.be) University of Antwerp, Department of Chemistry, Belgium (bart.vekemans@ua.ac.be; koen.janssens@ua.ac.be) Institute of Experimental Physics, University of Debrecen, Hungary (szaloki@tigris.klte.hu) Institut fur Geowissenschaften, Johannes Gutenberg-Universitat, Mainz, Germany (nasdala@uni-mainz.de) KM Diamond Exploration Ltd., Vancouver, Canada (felixvkaminsky@cs.com)