Shock metamorphism in plagioclase and selective amorphizationOPEN ACCESS 

· by · in , , ,

Lidia Pittarello, Luke Daly, Annemarie E. Pickersgill, Ludovic Ferrière, Martin R. Lee

Meteoritics & Planetary Science
Version of Record online:30 May 2020

LINK (OPEN ACCESS)
PDF (OPEN ACCESS)

“Plagioclase feldspar is one of the most common rock‐forming minerals on the surfaces of the Earth and other terrestrial planetary bodies, where it has been exposed to the ubiquitous process of hypervelocity impact. However, the response of plagioclase to shock metamorphism remains poorly understood. In particular, constraining the initiation and progression of shock‐induced amorphization in plagioclase (i.e., conversion to diaplectic glass) would improve our knowledge of how shock progressively deforms plagioclase. In turn, this information would enable plagioclase to be used to evaluate the shock stage of meteorites and terrestrial impactites, whenever they lack traditionally used shock indicator minerals, such as olivine and quartz. Here, we report on an electron backscatter diffraction (EBSD) study of shocked plagioclase grains in a metagranite shatter cone from the central uplift of the Manicouagan impact structure, Canada. Our study suggests that, in plagioclase, shock amorphization is initially localized either within pre‐existing twins or along lamellae, with similar characteristics to planar deformation features (PDFs) but that resemble twins in their periodicity. These lamellae likely represent specific crystallographic planes that undergo preferential structural failure under shock conditions. The orientation of preexisting twin sets that are preferentially amorphized and that of amorphous lamellae is likely favorable with respect to scattering of the local shock wave and corresponds to the “weakest” orientation for a specific shock pressure value. This observation supports a universal formation mechanism for PDFs in silicate minerals.”

Related posts (automatically generated):

  1. Ultrafast structural response of shock-compressed plagioclaseOPEN ACCESS 
  2. Formation, preservation and extinction of high-pressure minerals in meteorites: temperature effects in shock metamorphism and shock classificationOPEN ACCESS 
  3. Stress and strain during shock metamorphism
  4. Direct evidence of ancient shock metamorphism at the site of the 1908 Tunguska event
  5. Shock metamorphism of planetary silicate rocks and sediments: Proposal for an updated classification system.
  6. Raman Spectroscopy Studies of Equilibrated Ordinary Chondrites with H and L Group and Shock Metamorphism DegreesOPEN ACCESS 
  7. Shock stage distribution of 2280 ordinary chondrites—Can bulk chondrites with a shock stage of S6 exist as individual rocks?
  8. Shock Effects in NWA 8159: A Martian Plagioclase-Augite Basalt
  9. Shock‐induced phase transformation of anorthitic plagioclase in the eucrite meteorite Northwest Africa 2650
  10. Investigation of the shocked Viñales ordinary chondrite (L6) meteorite fall – Implications for shock classification, fragmentation, and collision dynamics
Tags: , , , ,