Studies on Propylitization (5th Report)

Abstract

Refractive indices and chemical compositions of chlorites and plagioclases in propylites from the Izu Peninsula and the Northeast district of Japan were determined by Winchell's net and Hartmann's net. In consequence, the propylites were divided into two types, namely, lava type and intrusive type propylites. Especially, the plagioclases in the former have compositions between anorthite and andeclase, while those in the intrusive type were between albiclase and albite.
In this respect, the intrusive type propylite has been related to ore deposition and rock alteration, and controlled the structure of hydrothermal deposits in these districts of Japan.