Exhumation processes of the high-P metamorphic rocks constrained by integrated radiogenic ages of zircon in the clasts of the Miocene conglomerates

采用不同的放射性成因测年方法（英云母K-Ar、锆石裂变径迹和锆石U-Pb），对四国和关东地区中新世和始新世砾岩的暴露片岩样品和碎屑进行了高压型变质岩（三巴川变质岩）的发掘过程进行了研究。我们的结果如下：(1)古始新世砾岩中碎屑的出土年龄比中新世砾岩中碎屑的出土年龄要大，甚至比目前暴露的片岩的出土年龄还要大，但在国国岛满托带始新世砾岩中除外。(2)三巴川变质岩的原岩年代为晚白垩世早期，因此与石曼托带的增生杂岩有关。(3)三巴川变质岩的发掘时间估计约为60万年，比以前的估计要长。

Exhumation processes of high pressure type metamorphic rocks (Sanbagawa metamorphics) was examined using various radiogenic dating method (phengite K-Ar, zircon fission-track and zircon U-Pb) for the schist samples from exposures and from the clasts of Miocene and Eocene conglomerates in Shikoku and Kanto. Our results are as follows; (1) The exhumation age of the clasts in the older (Eocene) conglomerate is older than those in the Miocene conglomerate and even than schists from current exposures, except the case of Eocene conglomerate in the Shimanto Belt in Shikoku. (2) Protolith of the Sanbagawa metamorphics dated is early Late Cretaceous, therefore is correlative with the accretionary complex of the Shimanto belt. (3) Duration time of the exhumation of the Sanbagawa metamorphics is estimated about 60 m.y., longer than previously estimated.