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1

Buch

Program, abstracts : = Programm, Kurzfassungen (2012)

Stipp, Michael ; Behrmann, Jan Hinrich 1953- ; Berndt, Christian 1969- ; [weitere]

Kiel : The Future Ocean

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Schlagwort(e): Konferenzschrift

Materialart: Buch

Seiten: 119 S. , Ill., graph. Darst., Kt.

Serie: Tectonics, Structural Geology and Geology of Crystalline Rocks [1]

Sprache: Englisch , Deutsch

Anmerkung: Text teilw. engl., teilw. dt.

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Tectonics, Structural Geology and Geology of Crystalline Rocks : = Tektonik, Strukturgeologie und Kristallingeologie : 14. Symposium ; Kiel, 26.3. - 1.4.2012 (2012)

Stipp, Michael ; Behrmann, Jan Hinrich 1953- ; Berndt, Christian 1969- ; [weitere]

Kiel : The Future Ocean

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Schlagwort(e): Konferenzschrift ; Tektonik ; Geologie ; Geophysik ; Mineralogie

Materialart: Buch

Sprache: Englisch , Deutsch

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Extrapolation of bulk rock elastic moduli of different rock types to high pressure conditions and comparison with texture-derived elastic moduli (2018)

Ullemeyer, Klaus ; Lokajicek, Tomas ; Vasin, Roman N. ; [weitere]

Elsevier

In: Physics of the Earth and Planetary Interiors, 275 . pp. 32-43.

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Publikationsdatum: 2021-02-08

Beschreibung: Highlights • Bulk rock elastic moduli of gneiss, amphibolite and marble using different techniques. • Neutron diffraction texture analysis and modeling of rock physical properties. • Measurement of seismic velocity anisotropy under pressures of up to 600 MPa. • Extrapolation of experimental data to higher pressures of 1000 MPa (crack free rock). • Comparison of modeled, experimental and extrapolated elastic anisotropy data. Abstract In this study elastic moduli of three different rock types of simple (calcite marble) and more complex (amphibolite, micaschist) mineralogical compositions were determined by modeling of elastic moduli using texture (crystallographic preferred orientation; CPO) data, experimental investigation and extrapolation. 3D models were calculated using single crystal elastic moduli, and CPO measured using time-of-flight neutron diffraction at the SKAT diffractometer in Dubna (Russia) and subsequently analyzed using Rietveld Texture Analysis. To define extrinsic factors influencing elastic behaviour, P-wave and S-wave velocity anisotropies were experimentally determined at 200, 400 and 600 MPa confining pressure. Functions describing variations of the elastic moduli with confining pressure were then used to predict elastic properties at 1000 MPa, revealing anisotropies in a supposedly crack-free medium. In the calcite marble elastic anisotropy is dominated by the CPO. Velocities continuously increase, while anisotropies decrease from measured, over extrapolated to CPO derived data. Differences in velocity patterns with sample orientation suggest that the foliation forms an important mechanical anisotropy. The amphibolite sample shows similar magnitudes of extrapolated and CPO derived velocities, however the pattern of CPO derived velocity is closer to that measured at 200 MPa. Anisotropy decreases from the extrapolated to the CPO derived data. In the micaschist, velocities are higher and anisotropies are lower in the extrapolated data, in comparison to the data from measurements at lower pressures. Generally our results show that predictions for the elastic behavior of rocks at great depths are possible based on experimental data and those computed from CPO. The elastic properties of the lower crust can, thus, be characterized with an improved degree of confidence using extrapolations. Anisotropically distributed spherical micro-pores are likely to be preserved, affecting seismic velocity distributions. Compositional variations in the polyphase rock samples do not significantly change the velocity patterns, allowing the use of RTA-derived volume percentages for the modeling of elastic moduli.

Materialart: Article , PeerReviewed

Format: text

DOI: 10.1016/j.pepi.2018.01.001

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Potential of full pattern fit methods for the texture analysis of geological materials: implications from texture measurements at the recently upgraded neutron time-of-flight diffractometer SKAT (2014)

Keppler, Ruth ; Ullemeyer, Klaus ; Behrmann, Jan H. ; [weitere]

Wiley

In: Journal of Applied Crystallography, 47 (5). pp. 1520-1534.

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Publikationsdatum: 2018-06-08

Beschreibung: The application of Rietveld texture analysis (RTA) to time-of-flight (TOF) neutron diffraction data allows complex materials with many diffraction peaks to be investigated, for example, rocks composed of different minerals. At the recently upgraded SKAT texture diffractometer at the JINR in Dubna (Russia), which provides three alternative multidetector systems, resolution and accessible range of lattice d spacings can be adapted to sample requirements. In order to infer the optimum experimental setup and the reliability of texture estimates from complicated TOF patterns, the influence of counting statistics and various spectral resolutions on texture deconvolution was investigated. Comparing the results obtained at different resolutions and from different sections of the d patterns indicates that the textures of a four-phase sample can be determined, but using a section at small d spacings with a larger number of peak overlaps leads to smoother textures. A complex seven-phase sample shows orientation differences in addition to the smoothing effect. Weak textures and textures of the minor rock constituents are inaccurate owing to multiple peak overlaps. Consequently, good resolution is essential for RTA on such samples. Grid thinning tests confirmed that no more than 150 diffraction spectra are needed to characterize the texture of a monomineralic sample, and approximately 350 spectra are sufficient for a four-phase sample. The irregular grid point arrangement caused by the SKAT geometry has no negative consequences.

Materialart: Article , PeerReviewed

Format: text

DOI: 10.1107/S1600576714015830

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Crystallographic preferred orientations of exhumed subduction channel rocks from the Eclogite Zone of the Tauern Window (Eastern Alps, Austria), and implications on rock elastic anisotropies at great depths (2015)

Keppler, Ruth ; Ullemeyer, Klaus ; Behrmann, Jan H. ; [weitere]

Elsevier

In: Tectonophysics, 647 . pp. 89-104.

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Publikationsdatum: 2017-04-13

Beschreibung: Highlights • Analysis of crystallographic preferred orientations of high-pressure polymineralic rocks by time-of-flight neutron diffraction • Elastic properties of a complete set of subduction channel rocks calculated from their crystallographic preferred orientation • Vp/Vs ratio and P-wave anisotropy of eclogites and metasediments • Influence of eclogite retrogression during exhumation on their elastic properties • Evaluation of the seismic signature of both clastic and carbonate sediments in subduction channels Abstract Crystallographic preferred orientations (CPO) of rocks from an exhumed subduction channel of the Alpine orogen were determined using time-of-flight neutron diffraction. This method allows the investigation of large polymineralic samples and, more importantly, the application of full pattern fit methods to constrain CPOs of mineralogically complex rocks. Samples studied include intensely deformed fresh and retrogressed eclogites, as well as metasediments, which are interleaved with the eclogites in the subduction channel. From the CPO, seismic properties of the samples were calculated. P- wave anisotropies of the eclogite samples are fairly low, with an average of about 1.5%, and mainly constrained by pronounced omphacite CPO. Growth and deformation of retrograde amphibole in the eclogites also led to a pronounced CPO, which has a large impact on seismic anisotropies by raising them to up to 3.7% and changing the orientations of velocity maxima. Elastic anisotropies of the subducted metasediments are higher (up to 7.4%) and constrained by quartz and mica CPO in clastics and by calcite CPO in marble. VP/VS ratios may help to distinguish fresh eclogites from retrogressed ones, and both rock types from mantle peridotites of downgoing lithospheric slabs in seismic imaging. Our data also indicate that subducted terrigenous sediments are not only strongly anisotropic, but also have low VP/VS ratios. This way there may be potential to image them by seismic tomography at depth in active subduction channels.

Materialart: Article , PeerReviewed

Format: text

DOI: 10.1016/j.tecto.2015.02.011

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Bulk rock elastic moduli at high pressures, derived from the mineral textures and from extrapolated laboratory data (2015)

Ullemeyer, Klaus ; Lokajíček, T. ; Keppler, Ruth ; [weitere]

IOP Publishing

In: IOP Conference Series: Materials Science and Engineering, 82 (1). 012093.

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Publikationsdatum: 2019-01-15

Beschreibung: The elastic anisotropy of bulk rock depends on the mineral textures, the crack fabric and external parameters like, e.g., confining pressure. The texture-related contribution to elastic anisotropy can be predicted from the mineral textures, the largely sample-dependent contribution of the other parameters must be determined experimentally. Laboratory measurements of the elastic wave velocities are mostly limited to pressures of the intermediate crust. We describe a method, how the elastic wave velocity trends and, by this means, the elastic constants can be extrapolated to the pressure conditions of the lower crust. The extrapolated elastic constants are compared to the texture-derived ones. Pronounced elastic anisotropy is evident for phyllosilicate minerals, hence, the approach is demonstrated for two phyllosilicate-rich gneisses with approximately identical volume fractions of the phyllosilicates but different texture types.

Materialart: Article , PeerReviewed

Format: text

DOI: 10.1088/1757-899X/82/1/012093

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Evaluation of intrinsic velocity-pressure trends from low-pressure P-wave velocity measurements in rocks containing microcracks (2011)

Ullemeyer, Klaus ; Nikolayev, Dmitry I. ; Christensen, Nikolas I. ; [weitere]

Wiley

In: Geophysical Journal International, 185 (3). pp. 1312-1320.

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Publikationsdatum: 2018-07-10

Beschreibung: Dependent on the ‘intrinsic’ effects on the crystal lattice of the rock constituents and the diminishing ‘extrinsic’ effects of pores and microcracks, elastic wave velocity versus pressure trends in cracked rocks are characterized by non-linear velocity increase at low pressure. At high pressure the ‘extrinsic’ influence vanishes and the velocity increase becomes approximately linear. Usually, the transition between non-linear and linear behaviour, the ‘crack closure pressure’, is not accessible in an experiment, because actual equipment is limited to lower pressure. For this reason, several model functions for describing velocity—pressure trends were proposed in the literature to extrapolate low-pressure P-wave velocity measurements to high pressures and, in part, to evaluate the ‘intrinsic’ velocity—pressure trend from low-pressure data. Knowing the ‘intrinsic’ velocity trend is of particular importance for the quantification of the crack influence at low pressure, at high pressure, the ‘intrinsic’ trend describes the velocity trend as a whole sufficiently well. Checking frequently used model functions for suitability led to the conclusion that all relations are unsuitable for the extrapolation and, if applicable, the estimation of the ‘intrinsic’ velocity trend. However, it can be shown that the ‘intrinsic’ parameters determined by means of a suitable model function, the zero pressure velocity and the pressure gradient depend on maximum experimental pressure in a non-linear way. Our approach intends to obtain better estimates of particular parameters from observed non-linear behaviour. A converging exponential function is used to approximate particular trends, assuming that the point of convergence of the function represents a better estimate of the zero pressure velocity and the pressure gradient, respectively. Whether the refined ‘intrinsic’ velocity trend meets the ‘true intrinsic’ velocity trend within acceptable errors cannot be proven directly due to missing experimental data at very high pressure. We, therefore, conclude that our approach cannot ensure absolutely certain ‘intrinsic’ velocity trends, however, it can be shown that the optimized trends approximate the ‘true intrinsic’ velocity trend better as all the other relations do.

Materialart: Article , PeerReviewed

Format: text

DOI: 10.1111/j.1365-246X.2011.05008.x

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New approaches in rock deformation and recrystallisaton analysis at POWTEX Neutron Diffractometer, FRM II Germany (2012)

Walter, Jens M. ; Stipp, Michael ; Ullemeyer, Klaus ; [weitere]

The Future Ocean

In: [Poster] In: 14. Symposium on Tectonics, Structural Geology and Geology of Crystalline Rocks (TSK 14), 28.03.-30.03.2012, Kiel . 14. Symposium: Tectonics, Structural Geology and Geology of Crystalline Rocks = Tektonik, Strukturgeologie und Kristallingeologie : Kiel 26.3.-1.4.2012 ; program, abstracts ; p. 107 .

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Publikationsdatum: 2019-09-23

Materialart: Conference or Workshop Item , NonPeerReviewed

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Evaluation of crystallographic preferred orientations applying whole pattern deconvolution method (2012)

Vasin, Roman ; Ullemeyer, Klaus

The Future Ocean

In: [Poster] In: 14. Symposium on Tectonics, Structural Geology and Geology of Crystalline Rocks (TSK 14), 28.03.-30.03.2012, Kiel . 14. Symposium: Tectonics, Structural Geology and Geology of Crystalline Rocks = Tektonik, Strukturgeologie und Kristallingeologie : Kiel 26.3.-1.4.2012 ; program, abstracts ; p. 103 .

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Publikationsdatum: 2012-07-18

Materialart: Conference or Workshop Item , NonPeerReviewed

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Monitoring the Deformation or Recrystallisation Path at POWTEX Neutron Diffractometer at FRM II Garching, Germany – New Experimental Perspectives in Geoscience (2014)

Walter, J. ; Randau, C. ; Stipp, Michael ; [weitere]

In: [Poster] In: Deutsche Tagung für Forschung mit Synchrotronstrahlung, Neutronen und Ionenstrahlen an Großgeräten 2014, 21.-23.09.2014, Bonn .

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Publikationsdatum: 2014-11-12

Materialart: Conference or Workshop Item , NonPeerReviewed

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