Katsuro Anazawa

Chapter 6: Fluorine and Coexisting Volatiles in the Geosphere: The Role in Japanese Volcanic Rocks

Abstract Comprehensive knowledge of the volatile behavior in volcanic rocks is of great value to clarify the process of magma generation and differentiation. However, few studies on volatile elements, particularly the fluorine content in volcanic rocks, have been made because of the difficulties of the analytical technique. In the present research, two types of analytical techniques have been investigated. One is a progressed separation method of distillation with potentiometric determination and the other is a chromatographic method combined with cation-exchange pretreatment. Using the above techniques, fluorine was determined on the 113 volcanic rocks obtained from various parts of Japanese islands. In addition, the other volatile and major elements were also determined on 44 different samples. The analytical results were geochemically interpreted using multivariate analysis in the light of magma generation theory in the subduction zones. The geographical distribution of volatile elements showed that the chemical contents were more related to the source of the elements rather than the chemical property or ionic radius. The factor structure of volatile elements led to the following findings: (1) seawater components brought by subducting slab have a significant influence on the behavior of chlorine, bromine, boron, and arsenic; (2) fluorine and sulfur are mainly contributed by the mantle components.