Micro-Raman spectroscopy and electron microscopy of shock veins in metaquartzites from the Vredefort impact structure: controls on coesite and stishovite genesis

Introduction: In this work, we report on the results of a combined scanning electron microscopy and micro-Raman spectroscopy investigation of stishovite and coesite in shocked Hospital Hill quartzite from the Vredefort impact structure of South Africa. Sanples have investigated using optical microscopy and under the scanning electron microscope, using energy dispersive x-ray spectrometry (EDS), and electron back-scattered diffraction (EBSD). Both highpressure silica phases were identified by micro-Raman spectrometery. The conditions of their formation and distribution related to shock-induced high pressure metamorphism are discussed in order to better understand the response of planetary materials to shock metamorphism.