[SVC47-01] Variation of hydrothermal mineral associations and characteristics of volcanic activity at Ponmachineshiri Volcano during the last 1000 years, Meakan volcanic group, Eastern Hokkaido, Japan
Keywords:Meakan volcano, Hydrothermal system, Phreatomagmatic eruption, Hydrothermal eruption, Advanced Argillic Alteration
To assess the contribution from the sub-volcanic hydrothermal system for the eruptions, we determined hydrothermal mineral associations within the Pon-1, Pon-2, Pon-3, and Pon-4 deposits and intercalated eruptive products. The mineral associations can be divided into three types based on their equivalent temperature as; (1) Silica minerals + pyrophyllite + Kaolin group minerals indicative of relatively high temperature; (2) Silica minerals + Kaolin group minerals indicative of moderate temperature; and (3) Silica mineral ± smectite indicative of relatively lower temperature. Mineral associations of Pon-1, Pon-2, Pon-3, and Pon-4 deposits and intercalated eruptive products show several trends, such as the appearance of the lower temperature mineral association (3) in the (phreato-)magmatic eruption products and subsequent phreatic eruptive deposits. Alternatively, the higher temperature mineral association (1) appears in the proximal phreatic eruption products that preceded magmatic events. Following the intense magmatic activity of Pon-2, the hydrothermal mineral association changed from lower temperature to higher temperature, which indicates that the hydrothermal system related to these eruptions became a higher temperature system. The decreasing proportion of juvenile material in eruptive deposits over the last 1000 years is consistent with a reduced magma contribution and indicates that the hydrothermal system is likely to play an important role in future eruption scenarios.
This work was supported by MEXT "Integrated Program for Next Generation Volcano Research and Human Resource Development.