Abstract
Hydrothermal mineral-bearing volcanic products are produced by phreatic eruptions and are widely recognized in high-resolution volcano stratigraphy, as well as in studies on recent individual eruptions. Recent eruptions have revealed the close relationship between eruptions and subvolcanic hydrothermal systems. At volcanoes where the frequency of magmatic eruptions is low, volcanic products are rich in alteration minerals derived from the siliceous and advanced argillic alteration zones; at volcanoes where magmatic eruptions occur frequently, sulphur-bearing minerals are dominant, occurring as fallout tephra as well as in flow deposits. Phreatic eruptions include landslide-related and landslide-unrelated types. The compositions and input rates of magmas are closely related to the style and repeating pattern of phreatic eruptions.
