¹Junya Matsuno, ¹Akira Tsuchiyama, ¹Akira Miyake, ²Ryo Noguchi, ³Satoshi Ichikawa
¹Department of Geology and Mineralogy, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwake, Sakyo-ku, Kyoto 606-8502, Japan
²Department of Earth and Space Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
³Institute for Nano-science Design, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan

Glass with embedded metal and sulfides (GEMS) are amorphous silicates included in anhydrous interplanetary dust particles (IDPs) and can provide information about material evolution in our early solar system. Several formation processes for GEMS have been proposed so far, but these theories are still being debated. To investigate a possible GEMS origin by reduction of interstellar silicates, we synthesized amorphous silicates with a mean GEMS composition and performed heating experiments in a reducing atmosphere. FeO-bearing amorphous silicates were heated at 923 K and 973 K for 3 hr, and at 1023 K for 1-48 hr at ambient pressure in a reducing atmosphere. Fe grains formed at the interface between the silicate and the reducing gas through a reduction. In contrast, TEM observations of natural GEMS show that metallic grains are uniformly embedded in amorphous silicates. Therefore, the present study suggests that metallic inclusions in GEMS could not form as reduction products and that other formation process such as condensation or irradiation are more likely.

Reference
Matsuno J, Tsuchiyama A, Miyake A, Noguchi R, Ichikawa S (2014) Reduction Experiment of FeO-bearing Amorphous Silicate: Application to Origin of Metallic Iron in Gems. The Astrophysical Journal 792 (in Press)
Link to Article [doi:10.1088/0004-637X/792/2/136]