[SMP32-P20] 3D microstructural analyses of fault rocks using CT and μCT scanning techniques
Keywords:computed tomography, fault rocks, microstructure
In this study, the CT and µCT imaging techniques are exploited to observe the 3D internal structures of a series of representative fault rocks: 1) pseudotachylytes of different origins (melting and crushing), and 2) cataclasitic rocks including fault gouge, fault breccia and cataclasite, by utilizing two types of scanning apparatuses (Bruker microCT, 2014): 1) μCT flat panel (FP), and 2) μCT charge coupled device (CCD). The samples of pseudotachylyte are from Fuyun, NW China (Lin, 1994), Ohsumi, Japan (Fabbri et al., 2000), and Musgrave Mt, Australia (Lin et al., 2005), respectively. The samples of fault gouge were acquired from two typical active fault zones in Japan: The Nojima Fault and Arima-Takatsuki Tectonic Line, SW Japan (Lin and Nishiwaki, 2019). The FP analysis shows that 1) the flow structures within the melting-origin pseudotachylytes are denoted by parallel colored glassy matrix layers with numerous rounded quartz clasts and quartz-filled amygdules which are oriented along the flow layers, and 2) chilled margins are characterized by fine-grained microlites orientated parallel to the margins. The 3D scanning images show that the layering structures developed within the fault gouge and fault breccia zones which are marked by sharp colored boundaries, oriented clasts and fine-grained matrixes. Our results demonstrate that 1) the CCD imaging makes it possible to observe sub-micron and even nano-scale 3D microsturctures fault rocks without destruction, and 2) µCT imaging can be further combined with traditional methods (such as optical microscope and SEM observation) to determine the spatial variations for both the meso- and microstructures and chemical compositions of fault rocks.
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