Cathodoluminescence Microscopy and Spectroscopy of Planar Deformation Features of Shocked Zircon from the Vredefort Impact Structure, South Africa

Thorough understanding of the shock metamorphic signatures of zircon will provide a basis for the application of this mineral as a powerful tool for the study of terrestrial impact structures and formations. This paper of the cathodoluminescence (CL) spectroscopic signatures of naturally shocked zircon crystals from the Vredefort Dome, South Africa contributes to the understanding of the formation of microdeformation in zircon under very high pressures. All investigated shocked samples shows an inverse relationship between the brightness of the backscattered electron (BSE) signal and the corresponding cathodoluminescence intensity of the zonation patterns. The CL spectra of samples are characterised by narrow emission lines and broad bands in the region of visible light and in the near-ultraviolet range. The emission lines result from rare earth element activators and the broad bands are associated with lattice defects. The results show a clear relationship between the CL properties of zircon and shock pressure, which confirm the possible use of these methods as shock indicators

Micro-Raman study of the Allende meteoritic nanodiamonds: Supernova-driven shock wave origin is revisited

Abstract I have studied the Raman spectroscopic signatures of nanodiamonds from the Allende meteorite, in which some portions must be of presolar origin as indicated by the isotopic compositions of various trace elements. The spectra of the meteoritic nanodiamonds show a narrow peak at 1326 cm−1 and a broad band at 1590 cm−1. Compared to the intensities of these peaks, the background fluorescence is relatively high. A significant frequency shift from 1332 to 1326 cm−1, peak broadening, and appearance of a new peak at 1590 cm−1 might be due to shock effects during formation of the diamond grains. Such changes may have several origins: an increase in bond length, a change in the electron density function or charge transfer, or a combination of these factors. However, Raman spectroscopy alone does not allow distinguishing between a shock origin of the nanodiamonds and formation by a CVD process, as is favored by most workers

New impact fragments of Fe-Ni-Si spherules at Takamatsu Crater, Japan

Fe-Ni-Si grains trapped in vacant regions formed by impact events on granitic rock are found in spherules included in glassy blocks on the surface of the buried Takamatsu crater, Japan

Grains formed by impact reaction found at spherules of various impact craters, meteorite showers and geological boundaries

New types of impact-related grains of Fe-Ni-Si or Fe-Si in composition found in spherules are collected at various impact craters, meteorite showers and geological boundaries