Futatsu-dake Peak of Mount Haruna
Ikaho, Ikaho village, Shibukawa city, Gunma pref., Japan
Occurrence
Minerals in andesitic pumice of the Futatsudake 2nd Pyroclastic Flow erupted from the Futatsudake peak of Mount Haruna in middle 6th century (1460 years ago, 1.46 ka). The Futatsudake 2nd Pyroclastic Flow is a part of the Haruna-Ikaho Tephra, the most recent eruption of Mount Haruna associated with the Futatsudake Lava Dome. Mount Haruna had been active since the Middle Pleistocene (0.4 Ma) to middle 6th century (1.46 ka).
Outcrop of an andesitic pumice bed of the Futatsudake 2nd Pyroclastic Flow. The white lapilli bigger than the scale coin are pumice. There are some light gray pebbles of hornblende-bearing andesite. Reddish-brown pebbles are bedrock subjected to contact metamorphism by magma.
Reported Minerals
- Hypersthene
- Hornblende
- Anorthite
- Beta-Quartz
Mineral Assemblages
- Pumice(Host) - Hypersthene - Hornblende
- Andesite(Host) - Hornblende - Anorthite
- Bedrock(Host) - Beta-Quartz
Localities
- Shishiiwa (Volcanic tuff)
- Goroku (Volcanic tuff)
- Mount Haruna (Pumice)
- Iwo Jima (Crystal lapilli)
- Daikokuten (Crystal lapilli)