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January 22, 2021

Poirierite, a New Mineral Discovered in Meteorites:
A Major Key toward Uncovering the Asteroid Collision Process and the deep Earth’s Dynamics

1. Overview

A research group led by Dr. Naotaka Tomioka, Senior Researcher at the Kochi Institute for Core Sample Research of the Japan Agency for Marine-Earth Science and Technology (KOCHI JAMSTEC) gave the mineral name “poirierite” to a high-pressure phase with the chemical composition of olivine that was found in shocked meteorites. Poirierite has now been officially approved as a new mineral species by the International Mineralogical Association.

Olivine (peridot) is abundantly found not just in the Earth's upper mantle, but also in stony meteorites. Using a high-resolution electron microscope, the research group examined a meteorite that have been exposed to high-temperature and high-pressure environments caused by a mutual collision of asteroids. As a result, the research group made the world’s first discovery of a high-pressure phase of olivine called the “epsilon phase” in 2017 (more information can be found in the explanatory article). The research group has since discovered “epsilon phase” in two more different stony meteorites and has investigated their structures and chemical compositions by experimental and theoretical methods. Based on this detailed data, the research group proposed to call the epsilon phase “poirierite”—a new mineral (Figures 1 and 2).

Poirierite possibly exists in oceanic plates subducting into the deep Earth interior. Therefore, not only is poirierite a possible key to understanding early solar system processes such as asteroid collisions; it could also shed light on mineral transformations occurring in tectonic plates. The research group is further planning to conduct transmission electron microscopy on both, meteorite and high-pressure synthetic samples, and also in-situ X-ray diffraction measurements of olivine under experimental shock compression. The aim is to elucidate the formation conditions of poirierite and to understand transformation behaviors of minerals, that have the chemical composition of olivine, under high temperature and high-pressure conditions. Moreover, the researchers plan to conduct similar analytical techniques on the samples recently obtained by the Asteroid Explorer Hayabusa2. This is expected to shed light on the mineral compositions and the formation history of the asteroid 162173 Ryugu.

These results have been reported in the British scientific journal Communications Earth & Environment in the issue of January 22, 2021 (Japan time). This study was funded by the JSPS Grants-in-Aid for Scientific Research 15H03750JP and 17H01172JP.

Poirierite, a dense metastable polymorph of magnesium iron silicate in shocked meteorites
Naotaka Tomioka1, Luca Bindi2, Takuo Okuchi3, Masaaki Miyahara4, Toshiaki Iitaka5, Zhi Li6, Tsutomu Kawatsu7, Xiande Xie8, Narangoo Purevjav9, Riho Tani1,10, Yu Kodama11
2. Dipartimento di Scienze della Terra, Università degli Studi di Firenze
3. Institute for Integrated Radiation and Nuclear Science, Kyoto University
4. Graduate School of Advanced Science and Engineering, Hiroshima University
5. Discrete Event Simulation Research Team, RIKEN Center for Computational Science
6. School of Materials Science and Engineering, Nanjing University of Science and Technology
7. Institute for Solid State Physics, University of Tokyo(At the time of research: Head Office for Information Systems and Cybersecurity (ISC), RIKEN)
8. Guangzhou Institute of Geochemistry, Chinese Academy of Sciences
9. Bayerisches Geoinstitut, University of Bayreuth
10. Graduate School of Science, Hiroshima University
11. Marine Works Japan Ltd..

Figure 1. Transmission electron microscope image of the ringwoodite sample from the Tenham meteorite (left). Lattice fringes and weak diffraction spots unique to the poirierite structure were observed in the ultrahigh-resolution image (lattice image) (top right) and the electron diffraction pattern (bottom right), respectively.


Figure 2. Transmission electron microscope image of the wadsleyite sample from the Miami meteorite (left) and electron diffraction patterns from its zones “A” and “B” (right). The pattern from zone B (the center of the sample) shows weak diffraction spots (dotted circles) in addition to the diffraction spots of wadsleyite, indicating the presence of poirierite.


(For this study)
Naotaka Tomioka, Senior Researcher, Institute for Extra-cutting-edge Science and Technology Avant-garde Research (X-star), Kochi Institute for Core Sample Research (KOCHI), Isotope Geochemistry Research Group, JAMSTEC
(For press release)
Public Relations Section, Marine Science and Technology Strategy Department, JAMSTEC
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