Obsidian is a consolidated material from volcanic magma, thus, its occurrence is spatially restricted to the volcanic area. It is well known that obsidian has abundant microlites of ㎛ size. Although the chemical composition of the obsidians and microlites therein have been studied using XRF, EPMA, ICP-MS etc., the detailed morphology of the microlites using high resolution electron microscope has seldom been studied so far. This study aims to understand the cause of the contrasting morphology and chemical composition of microlites from the obsidians of the Mt. Baekdu and Kyushu areas. Furthermore, the condition of microlite formation was considered through the tectonic environment of obsidian occurrence, and finally the contrasting parameters for discriminating the obsidian sources were deduced using the obsidians from the Mt. Baekdu, Kyushu and Hokkaido, Japan, and Lipari Island, Italy.
The microlites from the Mt. Baekdu obsidian generally show the Arculite and radial type Asteroidal shapes, which show pokilitic texture of clinopyroxene and magnetite microlites. The microlites from the Kyushu obsidian usually represent Furculite and Scopulite shapes of dendritic texture, and Arculite shape of clinopyroxene-magnetite intergrowth texture. The microlites from the Hokkaido obsidian has characteristic feature of Crenulite and/or Scopulitic growth of dendritic shape of Fe-olivine. The microlites from the Lipari Island show Bacillite shape of magnetite-clinopyroxene intergrowth texture. Euhedral microlites of ilmenite composition are observed in the obsidians from the Kyushu and Hokkaido, Japan, and Lipari Island, Italy. In conclusion, it is well understood that the microlites of the obsidians from four different areas have distinct shapes due to the different tectonic and cooling condition of obsidian magmas.