Shocked quartz/
Introduction
Shocked quartz is a form of quartz that has undergone a significant change in its structure due to the impact of a meteorite or other high-velocity impacts. This transformation is characterized by microscopic features called planar deformation features (PDFs), which are not found in normal quartz. The presence of shocked quartz is used as evidence of past impact events.
Formation
Shocked quartz is formed when quartz, a common mineral found in the Earth's crust, is subjected to extremely high pressures and temperatures. These conditions are typically caused by the impact of a meteorite or during a nuclear explosion. The pressure of the impact causes the quartz crystal structure to deform, creating planar deformation features (PDFs). These features are essentially planes of dislocation caused by the shock wave passing through the crystal.
Planar Deformation Features
Planar deformation features (PDFs) are the defining characteristic of shocked quartz. They are microscopic, parallel planes of deformation within the quartz crystal, typically only a few micrometers apart. PDFs are not found in any other form of quartz, making them a unique identifier of shocked quartz. The orientation and spacing of PDFs can provide information about the direction and intensity of the shock wave that created them.
Detection and Analysis
Shocked quartz is typically identified by the presence of PDFs, which can be observed under a microscope. However, because PDFs are so small and can be difficult to distinguish from other microscopic features in quartz, other methods of analysis are often used. These include Raman spectroscopy, which can detect the subtle changes in the quartz crystal structure caused by the shock, and electron backscatter diffraction (EBSD), which can map the orientation of the PDFs and provide more detailed information about the shock event.
Significance in Geology and Astrobiology
The presence of shocked quartz in a geological sample is a strong indicator of a past impact event, such as a meteorite strike. This makes it a valuable tool for geologists studying the history of the Earth. For example, shocked quartz was used as evidence of the Chicxulub impact event, which is believed to have caused the extinction of the dinosaurs.
In addition, the study of shocked quartz can provide insights into the conditions on other planets and moons. For example, shocked quartz has been found in meteorites from Mars, suggesting that the planet has experienced meteorite impacts in the past.