RAMAN AND CATHODOLUMINESCENCE SPECTROSCOPICAL MICROCHARACTERIZATION OF PLANAR DEFORMATION FEATURES IN SHOCKED QUARTZ FROM RIES IMPACT CRATER (GERMANY)

Naturally shocked quartz grains with microstructures such as Planar Fractures (PFs) and Planar Deformation Features (PDFs) were characterized using Secondary Electron Microscopy-Cathodoluminescence (SEM-CL) and micro-Raman spectroscopy. PFs in quartz grain are observed as non-luminescent straight lines, which are ~3 µm wide and spaced 15-20 µm, whereas PDFs are shown dark luminescent straight lines, which are <1 µm wide and spaced 1~5 µm. In the secondary electron imaging of PFs, they are observed as cracks and PDFs are unrecognizable. PDFs and the remaining part except planar microstructures in quartz grain in CL spectroscopy were revealed two main bands at ~385 nm and ~650 nm. CL spectrum of PDFs in quartz suffered high shock show no emission band around 385 nm, whereas an emission band with maxima near 650 nm is observed independent of shock pressure. Thus, the ~385 nm intensity in shocked quartz demonstrates a tendency of decrease with increasing in shocked stage. The result implies that emission band at ~385 nm are related to an amorphization or a deformed structure of quartz by shock metamorphism. Raman intensities of PDFs were considerably lower than that of the remaining parts. Raman maps of shocked quartz grain showing distribution patterns of the integrated intensity of A₁ Raman band at 459 cm^–1 may reveal the difference of crystallinity in shocked quartz grain. The result might show that CL emission at 385 nm falls off due to a partial destruction of Si-O-Si bond in quartz (SiO₄ tetrahedral cluster-type structure) and a partial distinction of luminescence centers with distortion by shock metamorphism. Therefore, SEM-CL analysis techniques provide structural information and an easy method for detecting shocked-induced microstructures in shocked quartz.