High-temperature volcanic sublimates from Iwodake volcano, Satsuma-Iwojima, Kyushu, Southwestern Japan

High temperature volcanic sublimates including so-called “molybdenum blue” sampled around the high-temperature fumaroles at Iwodake volcano, Satsuma-Iwojima, Kyushu, Southwestern Japan, were characterized by X-ray powder diffraction, X-ray micro-diffraction, Raman micro-scattering, electron microprobe and X-ray photoelectron spectroscopic analyses. The identified minerals are molybdenite, sphalerite, tugarinovite, molybdite, hematite, halite, sylvite, anglesite, wulfenite, quartz, tridymite, cristbalite and potassium alum. Occurrences of both tugarinovite and molybdite are observed in Kudriavy volcano, too, and the coexistence of their minerals is characteristic of high-temperature volcanic sublimates. The molybdenite and sphalerite from Iwodake are exceedingly rich in Re (up to 0.77 wt%) and In (up to 1.69 wt%), respectively, distinguished from those of a different origin by chemical composition. The molybdenite consists of both of 3R and 2H1 polytypes. Sublimates from Iwodake and Kudriavy volcanoes are similar in mineralogy. Although the difference in the host rock arises between the Iwodake (rhyolite) and the Kudriavy (basaltic andesite) volcanoes, their volcanic gases resemble each other in F and Cl contents. This resemblance might cause the similarity in sublimate mineralogy between these volcanoes.