5:15 PM - 6:30 PM
[SVC30-P05] Construction of Geochemical database of Kikai Caldera magmas for understanding the magmatic evolution prior to caldera-forming eruptions
Keywords:Kikai Caldera, Caldera-forming eruption, Wide-spread tephra, Database, Analytical Technique, Magma genesis
The Kikai Caldera, located in southern Kyushu, experienced a caldera-forming eruption at 7.3 ka, which was the youngest and largest one on Earth during the Holocene, and caused voluminous deposits of pyroclastic flow and tephra (known as the Akahoya ash). In order to evaluate such past supereruptions and prepare for future eruptions, we compile a database that integrates available geochemical data from throughout the eruptive history of the Kikai Caldera. Based on the database, we will discuss the evolution and diversity of magmas responsible for past activities of the Kikai Caldera.
To track and correlate the widespread tephra from past Kikai eruptions, it is necessary to collate and compare information on volcanic ash collected from various parts of Japan. Recent advances in analytical techniques have allowed us to conduct microanalyses of various major and trace elements and multiple isotope ratios of glass and minerals in volcanic ash. To date, geochemical data of eruption products derived from the Kikai Caldera are; (1) whole-rock analytical data of proximal lavas and pyroclastic flows around the Kikai Caldera, such as those on Satsuma-Iwojima and Takeshima islands, using wet analysis or XRF, and (2) microanalytical data of volcanic glass of widespread tephra such as Kikai-Akahoya from a wide area ranging from Kyushu to Kanto, using EPMA and LA-ICP-MS. The former covers a wide range of ages, from pre-caldera activities to the eruptions during 1934-1935 that formed Showa-Iwojima, although available data are limited to major elements and specific trace elements. On the other hand, detailed geochemical data of eruption products including multiple trace element data for the widespread tephra from the Kikai Caldera, have been reported and become available over the past decade.
We will introduce the outline of the constructed database and the characteristics of available geochemical data related to the Kikai Caldera. Based on analysis using the database, the compositional variation of magmas throughout the period of Kikai Caldera activity will be evaluated. The database will be provided on a publicly available website.
To track and correlate the widespread tephra from past Kikai eruptions, it is necessary to collate and compare information on volcanic ash collected from various parts of Japan. Recent advances in analytical techniques have allowed us to conduct microanalyses of various major and trace elements and multiple isotope ratios of glass and minerals in volcanic ash. To date, geochemical data of eruption products derived from the Kikai Caldera are; (1) whole-rock analytical data of proximal lavas and pyroclastic flows around the Kikai Caldera, such as those on Satsuma-Iwojima and Takeshima islands, using wet analysis or XRF, and (2) microanalytical data of volcanic glass of widespread tephra such as Kikai-Akahoya from a wide area ranging from Kyushu to Kanto, using EPMA and LA-ICP-MS. The former covers a wide range of ages, from pre-caldera activities to the eruptions during 1934-1935 that formed Showa-Iwojima, although available data are limited to major elements and specific trace elements. On the other hand, detailed geochemical data of eruption products including multiple trace element data for the widespread tephra from the Kikai Caldera, have been reported and become available over the past decade.
We will introduce the outline of the constructed database and the characteristics of available geochemical data related to the Kikai Caldera. Based on analysis using the database, the compositional variation of magmas throughout the period of Kikai Caldera activity will be evaluated. The database will be provided on a publicly available website.