New data on the K-white micas from the Sanbagawa Metamorphic Belt, and their petrologic significace.

New b0 values were measured for 123 K-white mica specimens from the Sanbagawa Metamorphic Belt. The rather high b0 values have been obtained on 43 specimens from the quartzose schists and metabasites and the values are considered to be related to the bulk rock compositions. On 80 b0 values which has been obtained from the petapelites, we obtained the following remarks: i) the b0 values decrease significantly with increasing metamorphic temperature; ii) the physical conditions during the Sanbagawa metamorphic processes has been changed significantly. It has become evident that the metamorphic temperature probably increased under substantially unchanged pressure conditions during the metamorphism.