Elastic anisotropy of Tambo gneiss from Promontogno, Switzerland: a comparison of crystal orientation and microstructure-based modelling and experimental measurements

0480056 - GLÚ 2018 RIV GB eng J - Journal Article
Vasin, R. N. - Kern, H. - Lokajíček, Tomáš - Svitek, Tomáš - Lehmann, E. - Mannes, D. C. - Chaouche, M. - Wenk, H.-R.
Elastic anisotropy of Tambo gneiss from Promontogno, Switzerland: a comparison of crystal orientation and microstructure-based modelling and experimental measurements.
Geophysical Journal International. Roč. 209, č. 1 (2017), s. 1-20. ISSN 0956-540X. E-ISSN 1365-246X
R&D Projects: GA MŠMT LH13102; GA ČR GA13-13967S; GA ČR(CZ) GA16-03950S
Institutional support: RVO:67985831
Keywords : numerical solutions * microstructures * elasticity and anelasticity * seismic anisotropy * acoustic properties
OECD category: Geology
Impact factor: 2.528, year: 2017

Felsic and mafic gneisses constitute large proportions of the upper and lower continental crust. Gneisses often display high anisotropy of elastic properties associated with preferred orientations of sheet silicates. Here we study the elastic anisotropy of a sample of Tambo gneiss from Promontogno in the Central Alps. We apply optical microscopy, time-of-flight neutron diffraction, neutron and X-ray tomography to quantify mineral composition and microstructures and use them to construct self-consistent models of elastic properties. They are compared to results of ultrasonic measurements on a cube sample in a multi-anvil apparatus and on a spherical sample in an apparatus that can measure velocities in multiple directions. Both methods provide similar results. It is shown that models of microstructure-derived elastic properties provide a good match with ultrasonic experiment results at pressures above 100 MPa. At a pressure of 0.1 MPa the correspondence between the model and the experiment is worse. This may be caused by an oversimplification of the model with respect to microfractures or uncertainties in the experimental determination of S-wave velocities and elastic tensor inversion. The study provides a basis to determine anisotropic elastic properties of rocks either by ultrasonic experiments or quantitative models based on microstructures. This information can then be used for interpretation of seismic data of the crust.
Permanent Link: http://hdl.handle.net/11104/0275975