Publication Date:
2018-09-14
Description:
Twins in zircon are increasingly being used as an indicator of shock metamorphism on Earth and other planetary bodies, yet the conditions of their formation have not been quantified. We modeled the shear stress involved with homogeneous nucleation of the most common zircon twin (112)(Formula presented.). This stress is between 1.7 to 2.6 GPa for the range of crystal sizes common to the crust, stresses that are restricted to impact deformation regimes as opposed to tectonism. The twin nucleation stress is largely pressure independent, and it is likely that twins can form over a much larger range of shock pressures than is currently appreciated. This prediction is validated by the occurrence of twins in shocked zircon from distal regions of the 2.02 Ga Vredefort impact structure. ©2018. American Geophysical Union. All Rights Reserved.
Print ISSN:
0094-8276
Electronic ISSN:
1944-8007
Topics:
Geosciences
,
Physics
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