Partial amorphization of experimentally shocked plagioclase: A spectroscopic study

1,2Lidia Pittarello,3,4Joerg Fritz,1Julia Roszjar,5Christoph Lenz,5Chutimun Chanmuang N.,1,2Christian Koeberl
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13445]
1Natural History Museum Vienna, Burgring 7, A‐1010 Vienna, Austria
2Department of Lithospheric Research, University of Vienna, Althanstrasse 14, A‐1090 Vienna, Austria
3Saalbau Weltraum Projekt, Liebigstrasse 6, D‐64646 Heppenheim, Germany
4Zentrum für Rieskrater‐ und Impaktforschung Nördlingen (ZERIN), Vordere Gerbergasse 3, D‐86720 Nördlingen, Germany
5Institut für Mineralogie und Kristallographie, University of Vienna, Althanstrasse 14, A‐1090 Vienna, Austria
Published by arrangement with John Wiley & Sons

Shock amorphization of plagioclase, from partial to complete, has been used to evaluate the degree of shock in meteorites. Important information on the shock amplitude can be derived from the measurement of the refractive index in plagioclase, either from mineral separates or in petrographic thin sections. However, this technique is time‐consuming, and associated sample preparations are considered destructive and are not always possible for precious and rare meteorite samples. In addition, plagioclase amorphization is commonly inhomogeneous at the sample scale and a statistically meaningful number of grains must be considered. Here, we apply several nondestructive spectroscopic techniques, such as Raman spectroscopy, photoluminescence, and cathodoluminescence, to plagioclase experimentally shocked at 28 GPa, and thus in the transition regime between crystalline plagioclase and fully amorphous material. Most of the plagioclase was transformed into diaplectic glass at 28 GPa, yet some grains exhibit heterogeneously distributed crystalline domains. This confirms that intrinsic and extrinsic factors lead to local variations in the intensity of the shock pressure within individual plagioclase crystals of homogeneous composition. The amorphization of plagioclase can qualitatively (and potentially also quantitatively) be investigated by spectroscopic techniques, highlighting such local variations in the shock efficiency.

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