フィッション・トラック法からみた日高山脈の隆起時期

概要

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The Hidaka Mountains are located in the southern central Hokkaido. The area is underlain mainly by Tertiary metamorphic and plutonic rocks, and is called the Hidaka metamorphic belt. Systematic zircon and apatite fission-track analyses across the southern part of the mountains unraveled the uplift history of the Hidaka Mountains. In the main part of the mountains, zircon FT ages show rapid cooling, while apatite FT ages show slower cooling. These results may indicate early rapid uplift slower later uplift of the Hidaka Mountains. The early rapid cooling (12-17 Ma) of the main part of the mountains leads to the conclusion of an earlier uplift than formerly assumed (e.g. Miyasaka, 1987). On the other hand, FT ages, almost 40 Ma, in the eastern part of the mountains are consistent with the occurrence of Oligocene sediments in the Hidaka coastal range, which shows the possibility of old mountains existing before 30 Ma.