Abstract

The Takidani Granodiorite is a pluton (13 x 4 km) situated along a major axis of the Japan Alps that was intruded into late Pliocene age (2.4 Ma) volcanic rocks. Rb-Sr, K-Ar, and fission-track dates on coexisting minerals from the pluton are 1.9-0.8 Ma. Geology and mineral dates for the Takidani Granodiorite indicate that emplacement and cooling of the pluton occurred from late Pliocene to Quaternary time, making the Takidani Granodiorite the youngest granitoid pluton exposed on Earth's surface. Mineral ages give a nearly straight path on a temperature-time (T-t) diagram according to the closure temperature of the minerals. The linearity of the T-t path indicates high thermal input from deeper levels in the early stage and cooling through rapid uplift in the late stage. The rapid exposure of the Takidani Granodiorite resulted from more than 2000 m of Quaternary uplift along the major axis of the Japan Alps.

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