^1,2Toshimori Sekine,²Tsubasa Tobase,³Youjun Zhang,⁴Ginga Kitahara,⁴Akira Yoshiasa,⁵Tomoko Sato,⁶Takamichi Kobayashi,⁷Akihisa Mori
American Mineralogist 108, 686-694 Link to Article [http://www.minsocam.org/msa/ammin/toc/2023/Abstracts/AM108P0686.pdf]
¹Center for High Pressure Science and Technology Advanced Research, Shanghai 201203, China
²Graduate School of Engineering, Osaka University, Suita 565-0871, Japan
³Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China
⁴Graduate School of Science and Technology, Kumamoto University, Kumamoto 860-8555, Japan
⁵Department of Earth and Planetary Systems Science, Hiroshima University, Higashi-Hiroshima 739-8526, Japan
⁶National Institute for Materials Science, Tsukuba 305-0044, Japan
⁷Department of Mechanical Engineering, Sojo University, Kumamoto 860-0082, Japan
Copyright: The Mineralogical Society of America

Heavy meteorite impacts on Earth’s surface produce melt and vapor that are quenched rapidly and
scattered over wide areas as natural glasses with various shapes and characteristic chemistry, which
are known as tektites and impact glasses. Their detailed formation conditions have long been debated
using mineralogical and geochemical data and numerical simulations of impact melt formations. These
impact processes are also related to the formation and evolution of planets. To unravel the formation
conditions of impact-induced glasses, we performed shock recovery experiments on a tektite. Recovered samples were characterized by X-ray diffraction, Raman spectroscopy, and X-ray absorption fine
structure spectroscopy on the Ti K-edge. Results indicate that the densification by shock compression
is subjected to post-shock annealing that alters the density and silicate-framework structures but that
the local structures around octahedrally coordinated Ti ions remain in the quenched glass. The relationship between the average Ti-O distance and Ti K pre-edge centroid energy is found to distinguish the
valance state of Ti ions between Ti4+ and Ti3+ in the glass. This relationship is useful in understanding
the formation conditions of impact-derived natural glasses. The presence of Ti3+ in tektites constrains
the formation conditions at extremely high temperatures or reduced environments. However, impact
glasses collected near the impact sites do not display such conditions, but instead relatively mild and
oxidizing formation conditions. These different formation conditions are consistent with the previous
numerical results on the crater size dependence.