CHIME zircon age of garnet-granite from the Naguri Fault Zone, Kanto Mountains, central Japan

Abstract

The Chichibu Composite Terrane hereafter, Chichibu Terrane consists of the North and South Chichibu Belts with the Kurosegawa Terrane in between. The Kurosegawa Terrane represents typically a serpentinite mélange zone containing peculiar rocks which are exotic to the Jurassic to Early Cretaceous Chichibu accretionary complex hereafter, Chichibu Complex and is characteristically associated with the Cretaceous forearc basin deposits. In the Kanto Mountains Fig. 1 , the Sanchu Graben is generally accepted as the eastern extension of the Kurosegawa Terrane based on the following two facts; 1 the Cretaceous forearc basin deposits are trapped, and 2 serpentinites occur along a part of its southern boundary fault Fig. 1. The Sanchu Graben is interrupted by the Miocene Chichibu Basin on the east. On this account, the Chichibu Terrane in the western half of the Kanto Mountains is demarcated into the North and South Chichibu Belts by the Sanchu Graben e.g., Hisada and Kishida, 1986; Iwasaki et al., 1989. Whereas, in the eastern half, subdivision of the Chichibu Terrane is provisional Fig. 1 and isolated patch-like areas within the South Chichibu Belt are assigned to the Kurosegawa Terrane The Conveners of the Paleo-Mesozoic Symposium of the Annual Meeting in Saitama, 1995. Rocks found in several areas of the Kanto Mountains are correlated with the constituent of the Kurosegawa Terrane hereafter, Kurosegawa-rocks. 1 Serpentinites