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Hanazono Valley

Saimaru, Sekimoto village, Kita-Ibaraki city, Ibaraki pref., Japan


Abyssal pegmatite

Pegmatite associated with granite of the Late Cretaceous (100 Ma) Tabito Pluton intruded in gneiss of the Takanuki metamorphic rocks, a member of the metamorphosed Early Jurassic (180 Ma) accretionary complex. The Takanuki metamorphic rocks have been subjected to Amphibolite to Granulite facies metamorphism by the medium-P Takanuki metamorphism in the Early Cretaceous (110 Ma). The granite of Tabito Pluton is S-type (Ilmenite-series), and its origin is considered as migmatite formed by partial melting of the Takanuki metamorphic rocks. 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.

Hanazono Valley

Outcrop of granitic pegmatite of the Tabito Pluton. Gray grains with a vitreous luster are quartz, and pale brown parts are feldspar. Black spots are cross section of prismatic schorl. This pegmatite is approximately 1.0 m in width and traverses schistosity of the host biotite gneiss of the Takenuki Metamorphic Rocks.

Reported Minerals

  • Schorl
  • Almandine
  • Biotite

Mineral Assemblages

  • Quartz - Feldspar - Biotite - Schorl
  • Quartz - Feldspar - Biotite - Almandine
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