Abstract
The Kurosegawa tectonic zone is a serpentinite melange zone in which various kinds of tectonic blocks occur. Muscovites coexisting with high-P minerals gave ages of 352-394 m.y. They indicate that so-called semischists were neither metamorphosed at the time of formation of the Kurosegawa tectonic zone, nor by the Sanbagawa metamorphism, but show a distinct metamorphic event older than Middle Carboniferous. This is the oldest radiometric age among glaucophane schists in Japan. Muscovites from the schist xenoliths of albite-epidote amphibolite facies grade were dated at 317 and 327 m.y. by the K/Ar method. Hornblende and barroisite are sometimes replaced by actinolite or riebeckite along their cleavages or irregular cracks. Muscovite is also deformed to show kink-band folding and is chloritized parallel to cleavage or along irregular cracks. Therefore, the values 317 and 327 m.y. may not show the time of albite-epidote amphibolite facies metamorphism, but are older than those of the Sanbagawa schists.-M.Ak.
Translated title of the contribution | Japanese with English abstract |
---|---|
Original language | Japanese |
Pages (from-to) | 230-233 |
Number of pages | 4 |
Journal | Journal of the Japanese Association of Mineralogists, Petrologists & Economic Geologists |
Volume | 75 |
Issue number | 7 |
Publication status | Published - Jan 1 1980 |
ASJC Scopus subject areas
- Environmental Science(all)
- Earth and Planetary Sciences(all)