Hanazono Cave
Hanazono, Hanakawa village, Kita-Ibaraki city, Ibaraki pref., Japan
Occurrence
Limestone block of the Gozaisho metamorphic rocks, a member of the metamorphosed Early Jurassic (180 Ma) accretionary complex. The limestone block has been subjected to metamorphism twice: Greenschist facies metamorphism by the medium-P Abukuma metamorphism before Early Cretaceous (120 Ma) and contact metamorphism by the S-type (Ilmenite-series) granitic rocks of the Late Cretaceous (100 Ma) Tabito pluton. The age of the limestone block has not been determined. Ages of sedimentary rocks were determined by radiolarians, the Abukuma metamorphism by U-Pb SHRIMP dating of zircon, and the Tabito pluton by K-Ar radiometric dating of hornblende and biotite.
Outcrop of crystalline limestone of the Gozaisho Metamorphic Rocks. This outcrop is composed of crystalline limestone only. Its surface turns gray by weathering but fresh surface is white. The surface of the outcrop is smooth as it was weathered.
Reported Minerals
- Calcite
- Strontian Calcite
- Graphite
- Strontianite?
Mineral Assemblages
- Calcite - Strontian Calcite
- Calcite - Graphite
Localities
- Shiroishi (Sanbagawa belt, High-P)
- Daioin (Hitachi-Takanuki belt, Medium-P)
- Hanazono Cave (Hitachi-Takanuki belt, Medium-P)