Shock deformation of alpha quartz: laboratory experiments and TEM investigation
Tattevin, Hélène; Syono, Yasuhiko; Kikuchi, Masae; Kusaba, Keiji; Velde, Bruce
European Journal of Mineralogy Volume 2 Number 2 (1990), p. 227 - 234
published: Apr 17, 1990
manuscript accepted: Nov 17, 1989
manuscript received: Apr 17, 1989
ArtNo. ESP147050202008, Price: 29.00 €
Abstract 13 shock experiments were performed on oriented single-crystal quartz samples at pressures of 30-38 GPa, above the Hugoniot elastic limit. The change from crystalline to amorphous material in the post-shock samples was observed by X-ray diffraction and TEM. The glassy lamellae show a relationship between shock direction and crystal lattice which suggests that planes of weakness in the crystal could be more important than stress forces in producing shear zones under shock conditions. A model is proposed for the production of diaplectic glass in quartz. During the compression stage under elastic or visco-plastic shear deformation conditions, shear planes create small disordered glassy zones, which can be denser than the crystalline quartz. Increased pressure amplifies the density contrast between these zones and quartz. As a result, the adjacent material becomes glassy at the crystal-glass contact. Post-shock release creates a great difference in density this time positive between glass and crystal, with the production of spindle-shaped glass zones with shear zones penetrating into the quartz.