Cathodoluminescence microcharacterization of ballen silica in impactites

Okumura, T. and Gucsik, Arnold and Nishido, H. and Ninagawa, K. and Toyoda, S. (2009) Cathodoluminescence microcharacterization of ballen silica in impactites. In: Micro-Raman Spectroscopy and Luminescence Studies in the Earth and Planetary Sciences. Proceedings of the International Conference Spectroscopy 2009 (1163). American Institute of Physics, New York, pp. 148-155. ISBN 978-0-7354-0700-8

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Abstract

The ballen silica shows fairly weak (faint) CL with homogeneous feature in its grain exhibiting almost same spectral pattern with two broad band peaks at around 390 and 650 nm, which might be assigned to self-trapped excitons (STE) or an intrinsic and nonbridging oxygen hole centers (NBOHC), respectively, recognized in amorphous and crystalline silica. In addition, ballen silica from Lappajärvi crater shows bright and heterogeneous CL with a broad band centered at around 410 nm, presumably attributed to [AlO4/M+]0 centers or self-trapped excitons (STE). Micro-Raman and micro-XRD analyses show that fairly homogeneous CL part is alpha-quartz and heterogeneous CL part is composed of alpha-cristobalite and alpha-quartz. These indicate that ballen silica could be formed in the quenching process from relatively high temperature.

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