Abstract
Myokenzan is located in the southern part of the Abukuma metamorphic belt, and consists of dioritic to gabbroic rocks of late Cretaceous intruded in the upper Paleozoic metamorphic members.
The pegmatite body, which is dike or lens in shape, is originated in the gabbroic rock, and is composed of quartz, albite, microcline, muscovite and tourmaline (indigolite). In the central part of the pegmatite body, fine-grained massive lepidolite vein is cutting through, and is associated with elbaite, beryl (Cs-bearing), pollucite, montebrasite and spodumene which is the first discovery in Japan. Spodumene occurs as light grey to grey translucent tabular crystals up to 10cm long and 5mm in thickness, and sometimes forms pseudomorph of hydromuscovite.
Other associated minerals are small amounts of cassiterite (Nb2O5; about 11 wt. %) and mangantantalite.
14 chemical analyses and 16 X-ray powder diffraction data are tabulated.
