北海道神居古潭変成岩類班渓幌内ユニットからの新たなジルコンU-Pb年代

抄録

The Pankehoronai Unit occupies the lowest part of the Cretaceous Kamuikotan high-P metamorphic rocks in central Hokkaido, Northeast Japan, and consists mainly of pelitic and mafic schists. Detrital zircon grains from the pelitic schist of the Pankehoronai Unit along the Kamuidaiyonsengawa River, in the west of Asahikawa, have the youngest age cluster with the weighted mean of the ²⁰⁶Pb/²³⁸U ages of 81.45±0.99 Ma (95% confidence; Campanian). This result indicates that the pelitic protolith of the Pankehoronai Unit was deposited in the Campanian (latest Cretaceous) or later, which is the youngest record of the depositional age from the Kamuikotan metamorphic rocks.