Earth's youngest exposed granite and its tectonic implications: The 10-0.8 Ma Kurobegawa Granite

Abstract

Although the quest for Earth's oldest rock is of great importance, identifying the youngest exposed pluton on Earth is also of interest. A pluton is a body of intrusive igneous rock that crystallized from slowly cooling magma at depths of several kilometers beneath the surface of the Earth. Therefore, the youngest exposed pluton represents the most recent tectonic uplift and highest exhumation. The youngest exposed pluton reported to date is the Takidani Granodiorite (∼ 1.4 Ma) in the Hida Mountain Range of central Japan. Using LA-ICP-MS and SHRIMP U-Pb zircon dating methods, this study demonstrates that the Kurobegawa Granite, also situated in the Hida Mountain Range, is as young as ∼ 0.8 Ma. In addition, data indicate multiple intrusion episodes in this pluton since 10 Ma with a ∼ 2-million-year period of quiescence; hence, a future intrusion event is likely within 1 million years.