The process of formation of rare metal-bearing phosphates by hydrothermal alteration.

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The studied materials were collected from Yamaguchi Prefecture, Shimane prefecture, Saga Prefecture, and Kagoshima Prefecture. Many phosphate minerals are recognized from the Hinomaru-Nako mine, Abu-cho, Yamaguchi Prefecture. Among them, trolleite, gorceixite and goyazite are firstly found in Japan. They are closely associated and barium and minor strontium are concentrated in gorceixite, only strontium is in goyazite. Though both minerals are isostructural, no complite solidsolution exists between them under the condition of hydrothermal alteration. Gorceixite and goyazite do not include REE in spite of their close association with isostructural florencite- (Ce). REE-bearing crandallite and woodhouseite are found in alunite rock from the alteration rigion around Makurazaki, Kagoshima Prefecture and Ugusu, Shizuoka Prefecture. The sequence of concentration of rare metal and assemblage of anions during the hydrothermal alteration is recognized under the chemical analyzes and observatoin of back-scattered electron images. For example, the assemblage of anions is (PO_4) (PO_4), (PO_4) (SO_4) and (SO_4) (SO_4) in order of stage of formation.