Metamorphic evolution of the Kamuikotan high-pressure and low- temperature metamorphic rocks in central Hokkaido, Japan

The Kamuikotan complex in the Sorachi-Yezo belt has been extensively subjected to subduction-related high-pressure and low-temperature metamorphism. On the basis of geological, petrological, and geochronological data, the coherent metamorphic rocks are divided into six units which can be classified into the following three baric types: high-pressure 1, high-pressure 2, and high-pressure intermediate. The results, together with the previously published K-Ar and ⁴⁰Ar-³⁹Ar ages, suggest that the Kamuikotan metamorphic rocks gradually decreased in pressure during the Cretaceous. This tendency indicates an increase in the Kamuikotan subduction geotherm during Early Cretaceous to early Eocene time. -from Authors