Abstract
The Daiichi-Kashima Seamount is situated near the junction area of the Japan and Izu-Bonin Trenches and characterized by the presence of the upper, eastern flat summit (about 3, 600 to 4, 000 m in water depth) and the lower, western terrace (about 5, 100 to 5, 500 m in water depth).
From the geological, mineralogical, and geochemical points of view, the present writers have obtained the following conclusions:
1) The Daiichi-Kashima Seamount is characterized mainly by the presence of alkaline rock series with or without alkali minerals such as anorthoclase and arfvedsonite.
2) Its present geomorphological feature is likely to be secondary in origin. This means that the tectonic movement of fault-making was responsible for the formation of two flat terraces of the Daiichi-Kashima Seamount.
3) The present water depth of the Daiichi-Kashima Seamount (Guyot) was produced not by the global eustatic change of sea-level, but by the tectonic sinking of the Daiichi-Kashima Seamount.
