Abstract
Caryopilite, Mn^<2+> -rich serpentine group mineral, is a major constituent of the manganese ores in the North Chichibu belt in the Shikoku region, SW Japan. The North Chichibu belt is the Jurassic accretionary complex containing abundant chert beds of Permian-Triassic age and has been subjected to low-grade metamorphism of the prehnite-pumpellyite to pumpellyite-actinolite facies. Caryopilite close to Mn end-member in composition and having 1M polytype commonly occur in the chert-hosted manganese deposits. Greenalite, the Fe^<2+> analogue of caryopilite, has 1T polytype and rarely occurs in some chert-hosted deposits. Fe-rich caryopilite having intermediate composition between caryopilite and greenalite and having 1M polytype occurs in an iron-manganese deposit and a manganese deposit associated with basalt. Manganoan chlorites also occur in these deposits.
