[SVC50-P20] Raman spectroscopy applied to reveal the oxidation state of the “Red” obsidian from Shirataki, Hokkaido, Japan
Keywords:obsidian, Raman spectroscopy, textural analysis, Shirataki
At the Akaishiyama obsidian lava on Shirataki, northern Hokkaido, Japan, we can observe the red-colored oxidized obsidian mingled with black-colored obsidian. The mingled shows various contrasts and distributions on the hand specimen, and we can consider that such a various oxidation texture reflect the different mechanisms of outgassing process during the eruption. In this study, we used the microRaman spectroscopy to characterize the oxidation state in the obsidian, using a JASCO NRS-7100 Laser Raman Spectrometer with 514 nm excitation at Kobe University Research Facility Center for Science and Technology, Japan. We obtained the 2 types of Raman spectra of oxide microlites in red and black obsidians, respectively. Compared with referential spectra, we identified captured spectrum as magnetite and hematite. Based on the analytical results of microRaman Spectrometer and distribution pattern of oxidation texture, we can discuss the formation process of heterogeneous oxidation textures during the eruption.