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  • 1995-1999  (1)
  • 1990-1994  (6)
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  • 1
    Electronic Resource
    Electronic Resource
    Calculation of elastic properties in lower part of the Kola borehole from bulk chemical compositions of core samples (1994)
    Springer
    Surveys in geophysics 15 (1994), S. 545-573 
    Details
    ISSN: 1573-0956
    Keywords: Petrophysical modeling ; deep boreholes ; elastic properties ; cracks ; anisotropy ; rock fabric
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract In-situ elastic properties in deep boreholes are controlled by several factors, mainly by lithology, petrofabric, fluid-filled cracks and pores. In order to separate the effects of different factors it is useful to extract lithology-controlled part from observedin-situ velocities. For that purpose we calculated mineralogical composition and isotropic crack-free elastic properties in the lower part of the Kola borehole from bulk chemical compositions of core samples. We use a new technique of petrophysical modeling based on thermodynamic approach. The reasonable accuracy of the modeling is confirmed by comparison with the observations of mineralogical composition and laboratory measurements of density and elastic wave velocities in upper crustal crystalline rocks at high confining pressure. Calculations were carried out for 896 core samples from the depth segment of 6840–10535m. Using these results we estimate density and crack-free isotropic elastic properties of 554 lithology-defined layers composing this depth segment. Average synthetic P- wave velocity appears to be 2.7% higher than the velocity from Vertical Seismic Profiling (VSP), and 5% higher than sonic log velocity. Average synthetic S-wave velocity is 1.4 % higher than that from VSP. These differences can be explained by superposition of effects of fabric-related anisotropy, cracks aligned parallel to the foliation plain, and randomly oriented cracks, with the effect of cracks being the predominant control. Low sonic log velocities are likely caused by drilling-induced cracking (hydrofractures) in the borehole walls. The calculated synthetic density and velocity cross-sections can be used for much more detailed interpretations, for which, however, new, more detailed and reliable seismic data are required.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00690174
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    Paper (German National Licenses)
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  • 2
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    Calculation of elastic properties in lower part of the Kola borehole from bulk chemical compositions of core samples (1994)
    Springer
    Details
    Publication Date: 1994-09-01
    Print ISSN: 0169-3298
    Electronic ISSN: 1573-0956
    Topics: Geosciences , Physics
    Published by Springer
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    PAPER CURRENT
  • 3
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    Calculation of phase equilibria and elastic properties of magmatic rocks (1994)
    In:  Izvestiya - Physics of the Solid Earth
    Details
    Publication Date: 2020-02-12
    Description: We propose a new method of petrologic modeling allowing equilibrium mineral compositions, densities, and elastic properties of rocks to be calculated from their bulk chemical compositions and pressure-temperature (P-T equilibrium conditions. To calculate the mineral composition of a rock, the method of direct minimization of the Gibbs free energy is used applying to the eight-component (SiO2 - Al2O3 - Fe2O3 - FeO - MgO - CaO - Na2O - K2O) multiphase closed thermodynamic system. The density of rock, the isotropic VP, VS, and their P-T derivatives are computed on the actual mineral compositions, with the use of available experimental data on elastic moduli of minerals. Good accuracy of the computations is supported by comparison with experiments on the phase transitions gabbro/eclogite in rocks and with high-precision laboratory measurements of elastic wave velocities in samples of magmatic and metamorphic rocks. The calculated phase diagrams are given together with isolines of density, elastic wave velocities, and their pressure and temperature derivatives for some abundant anhydrous magmatic rocks ranging from granite to lherzolite. The density and elastic wave velocities noticeably increase with formation pressure of rock due to proceeding several mineral reactions resulting in the appearance and growth of garnet and disappearance of plagioclase. Character of the pressure dependence of VP and VS is determined by the bulk chemical composition of rock and can essentially be nonlinear. Rocks of different bulk compositions are well-distinguished on the plots of VP - VP/VS density. Such diagrams together with phase diagrams can be employed as efficient means for petrological interpretation of seismic data.
    Keywords: 550 - Earth sciences
    Type: info:eu-repo/semantics/article
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  • 4
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    Modelling of mineralogical composition, density and elastic wave velocities in the unhydrous rocks (1994)
    In:  Surveys in Geophysics
    Details
    Publication Date: 2020-02-12
    Description: We use the technique of direct minimization of the Gibbs free energy of the 8-component (K2O-Na2O-Fe2O3-FeO-CaO-MgO-Al2O3-SiO2) multiphase system in order to determine the equilibrium mineral assemblages of rocks of different bulk chemical compositions equilibrated at various P-T conditions. The calculated modal compositions of rocks and experimental data on elastic moduli of single crystals are then used to calculate densities and isotropic elastic wave velocities of rocks together with their pressure and temperature derivatives. Sufficient accuracy of the calculations is confirmed by comparison with experimental data on the gabbro-eclogite transformation and precise ultrasonic measurements of elastic wave velocities in a number of magmatic and metamorphic rocks. We present calculated phase diagrams with isolines of density, elastic wave velocities, and their pressure and temperature derivatives for several anhydrous magmatic rocks, from granite to Iherzolite. Density and elastic properties of rocks are controlled by their chemical compositions, especially the SiO2 content, and by P-T of equilibration, and they increase with pressure due to mineral reactions changing mineral assemblages from plagioclase-bearing and garnet-free to garnet-bearing and plagioclase-free. The V-p-density correlation is high, and shows two clear trends: one for iron-poor ultramafic rocks and another for all the other rocks considered. Mineral reactions, which occur at high pressures, change V-p, and density of anhydrous magmatic rocks following the well-known Birch (or a similar) law. Felsic, intermediate and mafic rocks can be well distinguished in the V-p-V-p/V-S- diagram, although their values of V-p can be close to one another. The V-p-V-p/V-S-density diagrams together with calculated phase diagrams can serve as efficient instruments for petrologic interpretation of seismic velocities.
    Keywords: 550 - Earth sciences
    Type: info:eu-repo/semantics/article
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  • 5
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    Calculation of elastic properties in lower part of the Kola borehole from bulk chemical compositions of core samples (1994)
    In:  Surveys in Geophysics
    Details
    Publication Date: 2020-02-12
    Description: In-situ elastic properties in deep boreholes are controlled by several factors, mainly by lithology, petrofabric, fluid-filled cracks and pores. In order to separate the effects of different factors it is useful to extract lithology-controlled part from observedin-situ velocities. For that purpose we calculated mineralogical composition and isotropic crack-free elastic properties in the lower part of the Kola borehole from bulk chemical compositions of core samples. We use a new technique of petrophysical modeling based on thermodynamic approach. The reasonable accuracy of the modeling is confirmed by comparison with the observations of mineralogical composition and laboratory measurements of density and elastic wave velocities in upper crustal crystalline rocks at high confining pressure. Calculations were carried out for 896 core samples from the depth segment of 6840–10535m. Using these results we estimate density and crack-free isotropic elastic properties of 554 lithology-defined layers composing this depth segment. Average synthetic P- wave velocity appears to be 2.7% higher than the velocity from Vertical Seismic Profiling (VSP), and 5% higher than sonic log velocity. Average synthetic S-wave velocity is 1.4 % higher than that from VSP. These differences can be explained by superposition of effects of fabric-related anisotropy, cracks aligned parallel to the foliation plain, and randomly oriented cracks, with the effect of cracks being the predominant control. Low sonic log velocities are likely caused by drilling-induced cracking (hydrofractures) in the borehole walls. The calculated synthetic density and velocity cross-sections can be used for much more detailed interpretations, for which, however, new, more detailed and reliable seismic data are required.
    Keywords: 550 - Earth sciences
    Type: info:eu-repo/semantics/article
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  • 6
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    Temperature and dynamics of the upper mantle beneath the French Massif Central (1997)
    In:  Upper Mantle Heterogeneities from Active and Passive Seismology | NATO ASI series : Series 1, Disarmament technologies ; 17
    Details
    Publication Date: 2020-02-12
    Description: We introduce a new technique for the dynamic interpretation of high resolution tomographic image and apply it to the French Massif Central. Using petrological and mineral physics data, we convert an upper mantle tomographic model into a 3-D temperature distribution which is then used as input for the dynamic model. Calculated dynamic topography and geoid agree well with observations. This provides further credibility to the upper mantle temperature model which suggests the existence of the hot body (plume?) in the asthenosphere below the Massif Central.
    Keywords: 550 - Earth sciences
    Type: info:eu-repo/semantics/bookPart
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  • 7
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    Modelling of density and elastic wave velocities in the KTB pilot borehole (1994)
    In:  Contributions to the 7. Annual KTB-Colloquium : geoscientific results ; Giessen 1.-2. June 1994
    Details
    Publication Date: 2023-11-30
    Language: English
    Type: info:eu-repo/semantics/bookPart
    Format: application/pdf
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