Abstract
Granitic pegmatites formed during middle Miocene are observed in Okueyama, Miyazaki Prefecture. Various REE minerals are found at this area but there are a few studies of these minerals. The aim of this study is to investigate the mineralogical features of fergusonite from Okueyama and compare with fergusonite from Naegi, Gifu Prefecture. Samples from Naegi were also recrystallized. XRD patterns of fergusonite from Okueyama are T-phase and characteristically not metamict while samples from Naegi are heavily metamict. In recrystallization experiment, several peaks (T'-phase) appeard at 650 degrees and peaks of T-phase were observed at 1300 degrees. When samples were cooling, T-phase transformed to M-phase at 500 degrees. These factor are revealed that natural fergusonite crystallized as T-phase may not transform M-phase.
