Effect of layering on brittle deformation: results from hypervelocity impact experiments on gneiss

This study explores the effects of grain size, mineralogy, and pervasive layering on brittle deformation during high-strain rate events such as blasting and hypervelocity impact. Two hypervelocity (6.9 and 7.2 km/s) impact experiments were carried out. The findings reveal that the layering significantly affects shock wave led brittle damage in the subsurface of the crater. For example, vertical layering results in deeper and more widespread damage, while horizontal layering increases the density of fractures close to the crater surface and decreases the fracture intensity in the subsurface of the crater. These subsurface damage variations and fracture distributions dictate the final crater morphology and hydrothermal activity. Our observations agree well with a recent study on the Lonar crater, India. The experiments further reveal significant differences between the fracturing of biotite and feldspar grains, suggesting that weaker biotite layers can shield stronger feldspar layers from shock waves. These findings underscore the importance of layer orientation and the presence of weaker layers when predicting the mechanical behavior of rocks under extreme conditions, which has implications for various fields, including mining, construction, and planetary science.