Critical shear stress for mechanical twinning of jadeite—an experimental study |
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Authors: | Jens Orzol Claudia A Trepmann Bernhard Stckhert Guanghai Shi |
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Institution: | a Institute of Geology, Mineralogy and Geophysics, Ruhr-University Bochum, Bochum, Germany;b Institute of Geology and Geophysics, Chinese Academy of Science, Beijing, China |
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Abstract: | Coarse-grained natural jadeitite samples from Myanmar were experimentally deformed in a Griggs-type solid-medium apparatus at strain rates of 2·10−5 and 5·10−6 s−1 and temperatures of 900 and 1000 °C. The microfabrics of the deformed samples are investigated by scanning electron microscopy (SEM) using the electron backscatter diffraction (EBSD) technique. The critical shear stress for twinning in the (100) 001] system is derived from the orientation distribution of jadeite crystals with and without mechanical twins. The results indicate a homogeneous stress field within the sample and a critical shear stress of 150±25 MPa, which compares well to that determined by Kollé and Blacic J. Geophys. Res. 87 (1982) 4019] for mechanical twinning of other clinopyroxenes. With the critical shear stress known, mechanical twinning of jadeite can be used as a paleopiezometer for high stress tectonic environments. |
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Keywords: | Deformation experiments Mechanical twinning Jadeite Paleopiezometry |
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