Minor and Trace Elements and Refractive Indices of Volcanic Glasses of Tuffs

Abstract

From the point of view of the stratigraphy of the oil or gas fields in Japan, it is very important to establish the methods of identifying or distinguishing vitric tuff beds which are intercalated in the Neogene formations and serve as horizon-markers. For the above purpose, we carried out spectrochemical analysis of many tuff samples from the Maego district, Akita Prefecture, and also measured refractive indices of volcanis glasses in them. Through this preliminary study we have come to the following conclusions: (1) Such elements as V, Zr, Pb, Co, Ni, and B, and refractive indices of volcanic glasses clearly characterize some tuff beds of similar lithology. (2) Because of the irregularity of the distribution of the elements in any tuff bed, which is partly due to impurities and alteration, sampling tuffs and treating the samples must be carefully conducted.