Nihon Kessho Gakkaishi
Online ISSN : 1884-5576
Print ISSN : 0369-4585
Part 1. Microtexture in Minerals and Crystallography
Order-Disorder Transition in Majorite Garnet in Shocked Meteorites and Deep Earth's Interior
Naotaka TOMIOKA
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2018 Volume 60 Issue 1 Pages 2-8

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Abstract

Microstructures and symmetries of synthetic and natural(Mg, Fe)SiO3 garnet(majorite)have been investigated by transmission electron microscopy. Modulated and twin structures commonly observed in the synthetic majorite suggest a cubic-tetragonal phase transition due to cation ordering in its octahedral sites during quenching. Natural tetragonal majorite, which was newly discovered in a shock meteorite, has less-ordered octahedral cations than those in the synthetic samples. The order-disorder state of majorite provides important constraints not only on shock metamorphism of meteorites, but also on the deep Earth's mineralogy.

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© 2018 The Crystallographic Society of Japan
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