マグマのダイナミクス : 同位体地球化学的アプローチ(<特集>火山学の『夢』を語る)

概要

論文の詳細を見る
The way to apply isotope geochemistry to reveal the dynamics of magmatic processes is discussed. One method is to reveal the isotopic disequilibrium in a magma. Most isotope studies have been applied to get the information of the magma sources, so samples which are less suffered by shallow magmatic processes, such as crustal contamination, assimilation, etc., are usually selected. However, such processes would be recorded as disequilibrium in a magma. Thus, geochemical disequilibrium between groundmass and phenocrysts, among phenocrysts and in a phenocryst, like zoning, would give the information of shallow magmatic processes. Data on major elements and some trace elements have been used for such purposes, but additional geochemical studies, especially noble gas isotopic studies, would be more powerful and reveal them clearer, because noble gases would be quite sensitive for magmatic processes. The other method is to apply geochemical data to constrain forward models. Geochemical data alone are far from establishing a physical image of the dynamic phenomena. However, they can be transferred through a model to model parameters which have more physical meanings ; melting degree, temperature of melt and size of magmatic bodies, for example. Then, geochemical study can be connected with the geophysical study, which would contribute the clarification of magma dynamics more.
1995-12-25