Tectonic control of pyrrhotite phase distribution studied on a fold structure     

Lutz Kübler  Bengt Lindqvist 《Lithos》1979,12(3):241-249

A fold structure within a pyrite ore specimen has been analysed with respect to the amount and distribution of pyrrhotite modifications present. The relative distribution of the two types of pyrrhotite, hexagonal 5C and monoclinic 4C, was found to be strongly dependent upon the stress distribution. Within very short distances the hexagonal fraction of the total amount of pyrrhotite varied from nearly zero up to 0.65 giving steep and structurally well defined gradients. The monoclinic phase was preferably located to regions deformed by intense shearing. It is suggested that the influence of anisotropic stresses accelerated the conversion of hexagonal to monoclinic pyrrhotite. Variations in the distribution of the total amount of pyrrhotite were also observed and partly ascribed to migration of pyrrhotite.  相似文献   

Deformation mechanisms in experimentally deformed single crystals of pyrrhotite,Fe1−xS     

Lutz Kübler 《Physics and Chemistry of Minerals》1985,12(6):353-362

Single crystals of hexagonal and monoclinic pyrrhotite, Fe_1?xS, have been experimentally deformed by uniaxial compression at 300 MPa confining pressure, and at a strain rate of 1 × 10^?5 s^?1 in the temperature range from 200° C to 400° C. Very high anisotropy characterizes the mechanical behaviour of the crystal structure. During compression parallel to thec-axis, when no slip system may be activated, the maximum strength is observed. One or two degrees of non-parallelism between [c] and σ₁ results in slip on the basal plane, illustrating the very low resistance of the lattice against shear in this plane. At σ₁ Λ(0001)=45°, i.e. when maximum resolved shear stress is attained on the basal plane, the strength reaches a minimum. Thecritical resolved shear stress (CRSS) increases from less than 4.7 MPa at 400° C to 52 MPa at 200° C. A new slip system, \((10\overline 1 0)\parallel \left\langle {1\overline 2 10} \right\rangle \) prism slip, is described. It is activated only at high angles (>70°) between σ₁ and [c]. The CRSS of the prism slip ranges from 7 MPa (400° C) to 115 MPa (200° C). Twinning on \((10\overline 1 2)[(10\overline 1 2):(1\overline 2 10)]\) , earlier reported by several authors, has been produced only at the highest temperature either as secondary feature during pressure release (compression ‖[c]) or in heterogeneously strained areas (compression ⊥[c]). As twinning and prism slip attain their maximum values of the Schmidt factor under nearly equal stress conditions it is postulated that the former of the two deformation modes has the higher shear resistance.  相似文献   

Direct determination of geostrophic drag coefficients at sea     

Lutz Hasse  Michael Dunckel 《Boundary-Layer Meteorology》1974,7(3):323-329

Geostrophic drag coefficients are obtained from direct measurements of the momentum flux and from an objective analysis of the synoptic pressure field by the method of least squares. At a site in the Kiel Bight, a mean geostrophic drag coefficient c _g = 0.0223 was obtained with near neutral/ slightly unstable conditions and a surface Rossby Number of 1.2 × 10⁹.Contribution of the sonderforschungsbereich Meeresforschung Hamburg der Deutschen Forschungsgemeinschaft, Hamburg, F.R.G.  相似文献   

Zur Geologie von Libyen     

Prof. Dr. Franz Hecht  Dr. Manfred Fürst  Dr. Eberhard Klitzsch 《International Journal of Earth Sciences》1964,53(2):413-470

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The baltic sea ferry guidance and information system (BAFEGIS)     

Horst Hecht 《Ocean Dynamics》1997,49(4):511-517

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Shock-induced growth and metastability of stishovite and coesite in lithic clasts from suevite of the Ries impact crater (Germany)     

Volker Stähle  Rainer Altherr  Mario Koch  Lutz Nasdala 《Contributions to Mineralogy and Petrology》2008,155(4):457-472

The microtextures of stishovite and coesite in shocked non-porous lithic clasts from suevite of the Ries impact structure were studied in transmitted light and under the scanning electron microscope. Both high-pressure silica phases were identified in situ by laser-Raman spectroscopy. They formed from silica melt as well as by solid-state transformation. In weakly shocked rocks (stage I), fine-grained stishovite (≤1.8 μm) occurs in thin pseudotachylite veins of quartz-rich rocks, where it obviously nucleated from high-pressure frictional melts. Generally no stishovite was found in planar deformation features (PDFs) within grains of rock-forming quartz. The single exception is a highly shocked quartz grain, trapped between a pseudotachylite vein and a large ilmenite grain, in which stishovite occurs within two sets of lamellae. It is assumed that in this case the small stishovite grains formed by the interplay of conductive heating and shock reverberation. In strongly shocked rocks (stages Ib–III, above ∼30 GPa), grains of former quartz typically contain abundant and variably sized stishovite (<6 μm) embedded within a dense amorphous silica phase in the interstices between PDFs. The formation of transparent diaplectic glass in adjacent domains results from the breakdown of stishovite and the transformation of the dense amorphous phase and PDFs to diaplectic glass in the solid state. Coesite formed during unloading occurs in two textural varieties. Granular micrometre-sized coesite occurs embedded in silica melt glass along former fractures and grain boundaries. These former high-pressure melt pockets are surrounded by diaplectic glass or by domains consisting of microcrystalline coesite and earlier formed stishovite. The latter is mostly replaced by amorphous silica.  相似文献   

Raman study of radiation-damaged zircon under hydrostatic compression     

Lutz Nasdala  Ronald Miletich  Katja Ruschel  Tamás Váczi 《Physics and Chemistry of Minerals》2008,35(10):597-602

Pressure-induced changes of Raman band parameters of four natural, gem-quality zircon samples with different degrees of self-irradiation damage, and synthetic ZrSiO₄ without radiation damage, have been studied under hydrostatic compression in a diamond anvil cell up to ~10 GPa. Radiation-damaged zircon shows similar up-shifts of internal SiO₄ stretching modes at elevated pressures as non-damaged ZrSiO₄. Only minor changes of band-widths were observed in all cases. This makes it possible to estimate the degree of radiation damage from the width of the ν₃(SiO₄) band of zircon inclusions in situ, almost independent from potential “fossilized pressures” or compressive strain acting on the inclusions. An application is the non-destructive analysis of gemstones such as corundum or spinel: broadened Raman bands are a reliable indicator of self-irradiation damage in zircon inclusions, whose presence allows one to exclude artificial color enhancement by high-temperature treatment of the specimen.  相似文献   

Mass-transport deposits and reservoir quality of Upper Cretaceous Chalk within the German Central Graben,North Sea     

Jashar Arfai  Rüdiger Lutz  Dieter Franke  Christoph Gaedicke  Jonas Kley 《International Journal of Earth Sciences》2016,105(3):797-818

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Erratum to: Impact of the arc length on GNSS analysis results     

Simon Lutz  Michael Meindl  Peter Steigenberger  Gerhard Beutler  Krzysztof Sośnica  Stefan Schaer  Rolf Dach  Daniel Arnold  Daniela Thaller  Adrian Jäggi 《Journal of Geodesy》2016,90(5):501-501

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Occurrence and distribution of “moganite” in agate/chalcedony: a combined micro-Raman, Rietveld, and cathodoluminescence study     

Jens Götze  Lutz Nasdala  Reinhard Kleeberg  Marita Wenzel 《Contributions to Mineralogy and Petrology》1998,133(1-2):96-105

Agate/chalcedony samples of different origin were investigated by performing Raman, X-ray diffraction (using Rietveld refinement), and cathodoluminescence measurements. These analyses were performed to measure the content and spatial distribution of the silica polymorph moganite, which is considered to represent periodic Brazil-law twinning of α-quartz at the unit-cell scale in agate/chalcedonies. Homogeneous standard samples including the nearly α-quartz free moganite type material from Gran Canaria were analysed in order to compare results of the X-ray diffractometry and Raman spectroscopy techniques and to provide a calibration curve for the Raman results. However, due to the different length scales analysed by the two techniques, the “moganite content” in microcrystalline SiO₂ samples measured by Raman spectroscopy (short-range order) was found to be considerably higher than the “moganite content” measured by X-ray diffractometry (long-range order). The difference is explained by the presence of moganite nanocrystals, nano-range moganite lamellae, and single Brazil-law twin-planes that are detected by vibrational spectroscopy but that are not large enough (in the sense of coherently scattering lattice domains) to be detected by X-ray diffractometry. High resolution Raman analysis provides a measure of the moganite content and its spatial variation in microcrystalline silica samples with a lateral resolution in the μm-range. Variations in the moganite-to-quartz ratio are revealed by varying intensity ratios of the main symmetric stretching-bending vibrations (A₁ modes) of α-quartz (465 cm⁻¹) and moganite (502 cm⁻¹), respectively. Traces of Raman microprobe analyses perpendicular to the rhythmic zoning of agates revealed that the moganite-to-quartz ratio is often not uniform but shows a cyclic pattern that correlates with the observed cathodoluminescence pattern (colour and intensity). Data obtained from an agate sample from a fluorite deposit near Okorusu, Namibia and from a volcanic agate from Los Indios, Cuba were selected for detailed presentation. Variations of cathodoluminescence and Raman data between single bands in agates suggest alternating formation of fine-grained, highly defective chalcedony intergrown with moganite, and coarse-grained low-defect quartz. Multiple zones indicate dynamic internal growth during a self-organizational crystallization process from silica-rich fluids. Received: 4 December 1997 / Accepted 19 June 1998  相似文献