Scanning electron microscope‐cathodoluminescence (SEM‐CL) imaging of planar deformation features and tectonic deformation lamellae in quartz

Abstract

Abstract-Planar deformation features (PDFs) in quartz are essential proof for the correct identification of meteorite impact structures and related ejecta layers, but can be confused with tectonic deformation lamellae. The only completely reliable method to demonstrate the shock origin of suspected (sub-) planar microstructures, transmission electron microscope (TEM) observations, is costly and time consuming. We have used a cathodoluminescence (CL) detector attached to a scanning electron microscope (SEM) to image both PDFs and tectonic deformation lamellae in quartz to demonstrate the potential of a simple method to identify PDFs and define characteristics that allow their distinction from tectonic deformation lamellae. In both limited wavelength grayscale and composite color SEM-CL images, PDFs are easily identified. They are straight, narrow, well-defined features, whereas tectonic deformation lamellae are thicker, slightly curved, and there is often no clear boundary between lamella and host quartz. Composite color images reveal two types of CL behavior in PDFs: either they emit a red to infrared CL signal or they are nonluminescent. The color of the CL signal emitted by tectonic deformation lamellae ranges from blue to red. For comparison, we also imaged several shocked quartz grains at cryogenic temperature. In most cases, the PDF characteristics in cryo-CL images do not differ significantly from those in images recorded at room temperature. We conclude that SEM-CL imaging, especially when color composites are used, provides a promising, practical, low cost, and nondestructive method to distinguish between PDFs and tectonic lamellae, even when the simplest CL techniques available are used.

Evolution of intragranular stresses and dislocation densities during cyclic deformation of polycrystalline copper

“…[24], potential to scan large areas, easy access to complementary SEM imaging modes (e.g. electron channelling contrast image (ECCI) [25] and cathodoluminescence (CL) [26]), and the improvement in angular resolution makes HR-EBSD a powerful technique to study fatigue deformation process in polycrystalline materials. Considerable development of the method has been made such that the analysis generates rather comprehensive deformation information such as intragranular residual stresses (type III) [27], geometrically necessary dislocation (GND) density [28] and total dislocation density [29].…”

Scanning electron microscope cathodoluminescence imaging of subgrain boundaries, twins and planar deformation features in quartz

“…do not indicate precise specific CL emission wavelength), but indicate in which colour range the main CL emission of a feature in the sample is. See Hamers and Drury (2011) for a more detailed discussion of SEM-CL imaging.…”

“…A one-to-one correlation of SEM-CL and TEM showed that the non-luminescent shock features were amorphous PDFs, whereas the red CL type was healed PDFs or shock induced Brazil twins (Hamers et al 2016). Tectonic deformation lamellae show red to blue CL (Hamers and Drury 2011).…”

“…Cathodoluminescence (CL) is good for examining defects arising from differences in impurities associated with growth zones (Götze et al 1999(Götze et al , 2001Götze 2009) and deformation microstructures, such as fractures, deformation lamellae, PDFs and mechanical Brazil twins found in shocked quartz (Seyedolali et al 1997;Boggs et al 2001;Cavosie et al 2010;Hamers and Drury 2011;Hamers 2013;Hamers et al 2016). In particular, composite colour CL imaging in the scanning electron microscope (SEM), in which red, green and blue filters are used, is useful in distinguishing two types of PDFs, a nonluminescent type and a red to infrared CL type (Hamers and Drury 2011;Hamers et al 2016). A one-to-one correlation of SEM-CL and TEM showed that the non-luminescent shock features were amorphous PDFs, whereas the red CL type was healed PDFs or shock induced Brazil twins (Hamers et al 2016).…”

Geophysical anomalies and quartz deformation of the Warburton West structure, central Australia

“…3 Ferriere et al, 2009;French and Koeberl, 2010;Hamers and Drury, 2011;Glikson and Uysal, 2013). Duane and Reimold (1990) and Ordovician pelagic to shelf clastic sediments (Gatehouse et al, 1995;Gravestock and Gatehouse, 1995;Radke, 2009;Roberts et al, 1990;Sun, 1997Sun, , 1998Sun, , 1999Sun et al, 1994).…”