Discrimination between unaltered and altered volcanic products based on Cu and Fe isotopic measurements

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K16372
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Natural disaster / Disaster prevention science
• Research Institution: University of Tsukuba
• Principal Investigator: IKEHATA KEI 筑波大学, 生命環境系, 助教 (70622017)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: 火山噴出物 / マグマ水蒸気爆発 / 水蒸気爆発

Outline of Final Research Achievements

Chemical compositions of tiny primary copper minerals in volcanic products of phreatic and phreatomagmatic eruptions are similar to those in volcanic products of a magmatic eruption. In contrast, Cu isotopic compositions for the tiny primary copper minerals in the volcanic products of phreatic and phreatomagmatic eruptions are different from those (primary magmatic values) in the volcanic products of a magmatic eruption. This suggests that these primary copper minerals in the volcanic products of phreatic and phreatomagmatic eruptions were affected by hydrothermal alteration or weathering.

Free Research Field

火成岩岩石学・鉱床学・地球化学

Academic Significance and Societal Importance of the Research Achievements

本研究の結果から、火山噴出物に含まれる銅鉱物の銅同位体比は、噴出物の変質の程度を評価する指標になり得ると考えられる。火山噴火の様式の一つであるマグマ噴火の噴出物は、主に未変質な火山ガラスや造岩鉱物からなる。マグマ噴火の前駆現象として、変質噴出物を含む水蒸気爆発やマグマ水蒸気爆発が発生することがある。従って、火山噴出物の変質の程度を把握することができれば、火山噴火推移予測に役に立つことが期待される。