Condensation of cometary silicate dust using an induction thermal plasma system

I. Enstatite and CI chondritic composition^★

¹ Department of Chemical Engineering, Wonkwang University, 460 Iksan-daero, Iksan 54538, Republic of Korea
e-mail: taehee928@wku.ac.kr
² Department of Earth and Planetary Science, The University of Tokyo, Tokyo 113-0033, Japan
e-mail: takigawa@eps.s.u-tokyo.ac.jp
³ Research Organization of Science and Technology, Ritsumeikan University, Shiga 525-8577, Japan
⁴ CAS Key Laboratory of Mineralogy and Metallogeny/Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences (CAS), Guangzhou 510640, PR China
⁵ CAS Center for Excellence in Deep Earth Science, Guangzhou 510640, PR China
⁶ The Kyoto University Museum, Kyoto University, Kyoto 606-8502, Japan
⁷ Division of Earth and Planetary Sciences, Kyoto University, Kyoto 606-8502, Japan
⁸ JEOL Ltd., Tokyo 196-8558, Japan

Received: 30 April 2021
Accepted: 12 October 2021

Abstract

Glass with embedded metal and sulfides (GEMS) is a major component of chondritic porous interplanetary dust particles. Although GEMS is one of the most primitive components in the Solar System, its formation process and conditions have not been constrained. We performed condensation experiments of gases in the system of Mg–Si–O (MgSiO₃ composition) and of the S-free CI chondritic composition (Si–Mg–Fe–Na–Al–Ca–Ni–O system) in induction thermal plasma equipment. Amorphous Mg-silicate particles condensed in the experiments of the Mg–Si–O system, and their grain size distribution depended on the experimental conditions (mainly partial pressure of SiO). In the CI chondritic composition experiments, irregularly shaped amorphous silicate particles of less than a few hundred nanometers embedded with multiple Fe–Ni nanoparticles of ≤20 nm were successfully synthesized. These characteristics are very similar to those of GEMS, except for the presence of FeSi instead of sulfide grains. We propose that the condensation of amorphous silicate grains smaller than a few tens of nanometers and with metallic cores, followed by coagulation, could be the precursor material that forms GEMS prior to sulfidation.