中国地方における低度変成岩のK-Ar全岩年代

K-Ar whole-rock ages of low-grade metamorphic rocks in Chugoku, Southwest Japan

Oho Yukimasa

Hirayama Yasuyuki

Kawamoto Naomi

Suzuki Mineo

広島大学大学院総合科学研究科紀要. II, 環境科学研究

Bulletin of the Graduate School of Integrated Arts and Sciences, Hiroshima University. II, Studies in environmental sciences

K-Ar whole-rock ages are obtained from the low-grade metamorphic rocks of the Misumi Group, the Jurassic Chizu Formation, the Jurassic Tsunotani Formation and the Permian Maizuru Group. The low-grade metamorphic rocks are distributed adjacent to the high P/T Sangun metamorphic rocks in the Chugoku district. There are quite differences in small-scale structures between the low-grade metamorphic rocks and the Sangun metamorphic rocks. In the low-grade metamorphic rocks, two generations of penetrative foliation and associated structures can be recognized: slaty cleavage and crenulation cleavage. On the other hand, three generations of foliation are developed in the Sangun metamorphic rocks: schistosity and two stages of crenulation cleavage. Obtained K-Ar whole-rock ages are nearly 170-190 Ma. This indicates that slaty cleavage in the low-grade metamorphic rocks have been formed in Middle Jurassic time, and that the Sangun memtamorphic rock has been formed before 170-190 Ma.

Earth sciences. Geology [ 450 ]

jpn

広島大学大学院総合科学研究科

Copyright (c) 2006 by Graduate School of Integrated Arts and Sciences, Hiroshima University. All rights reserved

[ISSN] 1881-7696

[NCID] AA12198658