Signatures of Impacts in Quartz (Microstructures and Formation Mechanisms)
The impact on the Earth surface of high velocity meteorite generates a high dynamic compression (up to several tens of GPa) during a very short time (10−6 to 1 s depending on the size of the impactor). It is accompanied by a severe temperature increase which can induce phase transitions toward high pressure polymorphs and local melting or even vaporization. Specific lattice defects are also produced in the shocked minerals which are considered as impact signatures. In quartz such specific defects are thin lamellae of mechanical twins and planar deformation features (PDF). These later ones are very straight and narrow bands of dense amorphous silica.
KeywordsShock Wave Differential Stress Mechanical Twin Meteorite Impact Crystalline Quartz
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