PLANAR LAMELLAR SUBSTRUCTURES IN QUARTZ

Both single and multiple sets of lamellar features in quartz grains ca n be produced in shock experiments and are observed at known impact si tes; they can also be produced in static, constant strain-rate experim ents and are observed at known tectonic and explosive volcanic sites. The former are strictly planar and parallel and generally conform to r ational crystallographic orientations in the quartz crystal structure. The latter can also be planar and parallel but sometimes show slight to moderate curvature with lamellar bifurcations and variable lamellar widths. Their orientations show a variety of forms with, in general, a broader angular distribution than that of the impact-generated lamel lae. Deductions of physical conditions of deformation from optical mor phology, spacing, multiplicity and orientation information alone remai n somewhat conjectural; full characterization by transmission electron microscopy (TEM) appears to be necessary.