[S-CG44] Rheology, fracture and friction in Earth and planetary sciences

[SCG44-15] Detailed Occurrence of Feather Features in Quartz in Experimentally Shocked Granite

*Toshihiro Tada¹, Kosuke Kurosawa^2,3, Naotaka Tomioka⁴, Takayoshi Nagaya^5,6, Junko Isa³, Christopher Hamann⁷, Haruka Oono⁸, Takafumi Niihara⁹, Takaya Okamoto³, Takafumi Matsui^1,3 (1.Chiba Institute of Technology, Institute for Geo-Cosmology, 2.Department of Human Environmental Science, Graduate School of Human Development and Environment, Kobe University, 3.Chiba Institute of Technology, Planetary Exploration Research Center, 4.Kochi Institute for Core Sample Research, X-star , Japan Agency for Marine-Earth Science and Technology, 5.Department of Environmental Science, Tokyo Gakgei University, 6.Department of Earth and Planetary Science, The University of Tokyo, 7.Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, 8.Research Organization of Science and Technology , Ritsumeikan University, 9.Department of Applied Science, Okayama University of Science)

Keywords:Feather Features, Shock deformation features

Evidence of impacts on planetary bodies is recorded in minerals as shock deformation features. In particular, shock deformation features of quartz have been used as shock indicators on Earth because of the nature of quartz, such as its abundance, resistance to chemical and physical alternation, and tendency to develop striking and unique shock deformation features.
Feather features (FFs) are one of the shock deformation features in quartz, composed of a PF and a set of lamellae (FF lamellae: FFL) extending in one direction from the PF. Although FFs have been reported from various natural impact structures, the often-quoted threshold peak pressure of 7–10 GPa required to generate FFs has been based on only one shot in the laboratory experiment by Poelchau and Kenkmann (2011). Further experimental confirmation is required to establish a shock barometer based on FFs.
To investigate the nature of FFs, including the threshold peak pressure required for the formation of FFs, the relationship between the orientation of FFs and the direction of shock-wave propagation, and the detailed structure of FFs, we have conducted shock recovery experiments of granite using the recently developed technique with decaying compressive pulses (Hamman et al., 2023; Kurosawa et al., 2022; Ono et al., 2023). The peak pressure distributions and the direction of shock-wave propagation in the targets were estimated with shock physics modeling. The FFs formed in the recovered targets were observed with an optical microscope equipped with a universal stage, SEM-EBSD, and TEM.
We found that FFs are formed at a wide range of peak pressures (~2–18 GPa) and that the characteristics of FFs, such as crystallographic orientations of PFs and FFL, the angles between PFs and FFL, the relationship with the direction of shock-wave propagation, and the structure of FFL, depend on the peak pressure. Based on these characteristics, FFs can be classified into three types (Type-I–Type-III). The threshold peak pressures for producing three types of FFs were estimated to be <~12 GPa, ~12–14 GPa, and >~16 GPa. The variation in the characteristics of FFs with peak pressure indicates that FFs in natural samples may serve as a new shock barometer.