Submarine hydrothermal activity in the Izu-Ogasawara Arc, Western Pacific

Abstract

The Geological Survey of Japan has been conducting a study on submarine hydrothermal activity in the Izu-Ogasawara (or Bonin) Arc and the northernmost part of the Mariana Arc since 1984. Hydrothermal products, both unequivocal and inferred, are divided into three categories: 1) manganese or iron enriched sediments, and Mn-Fe hydroxide and silica deposits (chimneys) in the back-arc basin area; 2) manganese and/or iron oxide deposits occurring in the mountainous areas of both the back-arc and the volcanic front areas; and 3) a veinlet of iron-copper-zinc sulfides in hydothermally altered andesite on a wall of a submarine caldera along the volcanic front. This paper outlines these products as well as related geological, geophysical and geochemical data in the area.