地形学者のための熱年代学入門; 特にフィッション・トラック法と(U-Th)/He法を中心に

Introduction to thermochronology for geomorphologists; With a focus on fission-track and (U-Th)/He thermochronometries

末岡 茂   ; 福田 将眞   ; 中嶋 徹   ; 田上 高広*

Sueoka, Shigeru; Fukuda, Shoma; Nakajima, Toru; Tagami, Takahiro*

This paper aims at introducing thermochronology for geomorphologists, who are potentially involved in thermochronology as a user or collaborator. Thermochronology is a subdiscipline of geochronology, dealing with time-temperature histories of rocks/minerals based on radiometric dating methods. For certain radiometric dating systems, daughter nuclides are not stably retained in the rock/mineral at a temperature higher than their closure temperature. This phenomenon enables reconstruction of time-temperature histories, e.g., timing, rate, and temperature of cooling/heating which the rock/mineral experienced. Thermochronometries with a relatively low closure temperature, e.g., (U-Th)/He and fission-track methods, are useful for geomorphological investigations, such as, for constraining exhumation histories related to mountain formation, dating of fault slips, and determining eruption ages of tephra. This paper reviews their basic principles, geomorphological applications, target materials, analytical procedures, notes on use, future prospects, and accessibilities in Japan.