The origins of hot spring water in and around the northern Kanto Mountains

Abstract

This study examined the origins of hot spring water in and around the northern Kanto Mountains, by using multi-tracers such as chemical characteristics and noble gas isotopes. The mixing of slab-derived fluid was suggested in the hot springs for the entire study area. A significant contribution of slab-derived fluid was confirmed in both the south-west area of Gunma Prefecture, composed of igneous rocks, and in the area south of the Median Tectonic Line where metamorphic rocks predominate. The significant contribution of slab-derived fluid around the Median Tectonic Line is in accordance with the previous studies carried out in the south-west Japan. In the central part of Gunma Prefecture where thick marine sediments deposit, it is likely that fossil seawater and diagenetic dehydrated fluid play an important role in the formation of hot spring water.