Preferred orientation distribution of shock‐induced planar microstructures in quartz and feldspar
| Autor: | Ludovic Ferrière, Jean-Guillaume Feignon, Christian Koeberl, Gordon R. Osinski, Lidia Pittarello |
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| Rok vydání: | 2020 |
| Předmět: |
Shock wave
Geometry Articles 010502 geochemistry & geophysics 01 natural sciences Article Shock (mechanics) Core (optical fiber) Shock metamorphism Geophysics Space and Planetary Science 0103 physical sciences Planar deformation features Shocked quartz 010303 astronomy & astrophysics Joint (geology) Striation Geology 0105 earth and related environmental sciences |
| Zdroj: | Meteoritics & Planetary Science |
| ISSN: | 1945-5100 1086-9379 |
| Popis: | Shocked quartz and feldspar grains commonly exhibit planar microstructures, such as planar fractures, planar deformation features, and possibly microtwins, which are considered to have formed by shock metamorphism. Their orientation and frequency are typically reported to be randomly distributed across a sample. The goal of this study is to investigate whether such microstructures are completely random within a given sample, or whether their orientation might also retain information on the direction of the local shock wave propagation. For this work, we selected samples of shatter cones, which were cut normal to the striated surface and the striation direction, from three impact structures (Keurusselkä, Finland, and Charlevoix and Manicouagan, Canada). These samples show different stages of pre‐impact tectonic deformation. Additionally, we investigated several shocked granite samples, selected at different depths along the drill core recovered during the joint IODP‐ICDP Chicxulub Expedition 364 (Mexico). In this case, thin sections were cut along two orthogonal directions, one parallel and one normal to the drill core axis. All the results refer to optical microscopy and universal‐stage analyses performed on petrographic thin sections. Our results show that such shock‐related microstructures do have a preferred orientation, but also that relating their orientation with the possible shock wave propagation is quite challenging and potentially impossible. This is largely due to the lack of dedicated experiments to provide a key to interpret the observed preferred orientation and to the lack of information on postimpact orientation modifications, especially in the case of the drill core samples. |
| Databáze: | OpenAIRE |
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