JpGU-AGU Joint Meeting 2020

Presentation information

[E] Poster

S (Solid Earth Sciences ) » S-MP Mineralogy & Petrology

[S-MP36] Physics and Chemistry of Minerals

convener:Seiji Kamada(Frontier Research Institute for Interdisciplinary Sciences, Tohoku University), Masahiro KAYAMA(Department of General Systems Studies, Graduate School of Arts and Sciences, The University of Tokyo)

[SMP36-P10] Twinning in wadsleyite

Nobuyoshi Miyajima1, Johannes Buchen1,2, *Takaaki Kawazoe1,3 (1.Bayerisches Geoinstitut, University of Bayreuth, 2.Division of Geological and Planetary Sciences, California Institute of Technology, 3.Department of Earth and Planetary Systems Science, Hiroshima University)

Keywords:mantle transition zone, wadsleyite, twinning, twin, twin boundary, high pressure

Twinning was discovered in wadsleyite, which is the most abundant mineral at the upper part of the mantle transition zone. Wadsleyite crystals were synthesized from a powder of San Carlos olivine with distilled water at a pressure of 15 GPa and a temperature of 1670 K for 3 h using a multi-anvil apparatus. The wadsleyite twin was found based on change in color at a twin boundary due to strong pleochroism of wadsleyite by observing a thin section of the twin by optical microscopy. A thin foil perpendicular to the twin boundary was cut by focused iron beam (FIB) and was observed by transmission electron microscopy (TEM). The TEM observation revealed that twin domains make a 180° rotation about an axis perpendicular to the {101} plane in the pseudo-cubic system (cf. ringwoodite). Moreover, the composition plane of the twin domains is the {101} plane in the pseudo-cubic system. The wadsleyite twinning may be important in phase transformation, growth and deformation.