Raman microprobe (RMP) spectra were made of naturally shocked (27--32 GPa) microline from Lake Mistastin which showed the optical characteristics common to shocked minerals, i.e. loss of birefringence, strongly deformed twin planes in still birefringent material, etc. A detailed study of the optical properties of this material has been previously made. RMP spectra of different portions of shocked microline grains show a progressive change from crystalline organization to a structure which maintains the tetrahedral configurations common to feldspars but lost the overall long-range order of the crystalline state. The spectra obtained on shocked material are compared with those for thermal glass produced at various pressures and with feldspars containing three types of structural order in the tetrahedral positions (microcline, orthoclase, and sanidine). It is evident that the structure of shocked minerals and their amorphous shock products (diaplectic glass) differ from those of normal minerals and glasses. While there appears to be a preservation of the energetic and structural configuration of silica tetrahedra, there is total disorganization of the arrangement of these tetrahedra. This specific structural state can be used to explain the unusual characteristic of shocked minerals such as density crystals and high-density amorphous material. |