5:15 PM - 7:15 PM
[HCG20-P01] Data Collection and Organization on the Distribution of Volcanic Dikes
Keywords:Geological Disposal, Dike, Geological Map, GIS, Quaternary Volcano, Ancient Caldera / Cauldron
Background and Objectives: In the geological disposal project and safety regulations for HLW, one of the challenges in the investigation and evaluation technology for volcanic and igneous activity, which is important for site selection and safety assessment of geological disposal, is the sophistication of technology to grasp the range of influence of magma. In particular, there is a need to accumulate data on cases where the development of dikes extends beyond a radius of 15 km from the center of a Quaternary volcano; however, it is realistically difficult to grasp the distribution of vents hidden beneath existing volcanic bodies and the dikes branching off from them.
When conducting geological surveys in the field, it is possible to find outcrops containing small dike intrusions even in areas far from Quaternary volcanoes. Whether such dikes are related to nearby Quaternary volcanoes will be important in assessing the extent of the dikes. Therefore, we focused on the geological maps published by the AIST, extracted "dykes" from the maps, and attempted to evaluate their relationship with Quaternary volcanoes.
Details: The information collection targets were geological maps of 1:200,000, covering of the "Chugoku-Shikoku region" and "Hokuriku-Chubu and Kinki region,". For the data extraction process, the distribution of the dikes was digitally traced using GIS software, and GIS data such as Shape files were created and organized on a blank map. The following data was then extracted: "Location", "Size", "Orientation" "Age", "Rock type", etc. and organized on a spreadsheet software. Additionally, within the study area, there are ancient calderas and cauldrons. Their locations were converted into a GIS based on literature information, and the distances between them and dikes were also digitized.
Result: A total of 1,219 volcanic rock dikes and other structures were extracted. Information on 66 Quaternary volcanoes and 33 ancient calderas and cauldrons was also collated.
The major axis length of the dikes was less than 1 km for 637 dikes (more than half), and if less than 2 km was included, the total was 986 dikes (over 80%). The longest is 19,456m, and is the Kozagawa body, which is classified as a Kumano acidic dyke. Other dikes exceeding 10,000m in depth are also distributed around the periphery of the ancient calderas and cauldrons.
The ages of the dikes were: 16 Quaternary, 703 Neogene, 65 Paleogene, and 435 Cretaceous. The Quaternary dikes are broken down into 4 at Oki, 10 at Mt. Daisen, and 2 at Mt. Megan, and the distribution of Quaternary dikes exposed on the surface is limited to within 10 km of the Quaternary volcanoes. For dikes older than the Quaternary period, we examined the relationship between the distance between the Quaternary volcanoes and the dikes, and the angle between that direction and the dike's extension direction, and concluded that there is little relationship between dikes older than the Quaternary period and Quaternary volcanoes.
In the future, we plan to expand the range of data collection and use the organized data to determine the distance between ancient calderas and cauldrons and their nearby dikes, and to investigate whether the degree of dike development associated with volcanic activity was the same as that of Quaternary volcanoes in ancient volcanic activity.
Acknowledgments: This study was partly funded by the Ministry of Economy, Trade and Industry, Japan, as part of its R&D supporting program titled “Establishment of Technology for Comprehensive Evaluation of the Long-term Geosphere Stability on Geological Disposal Project of Radioactive Waste” (grant no. JPJ007597; fiscal year 2024).
When conducting geological surveys in the field, it is possible to find outcrops containing small dike intrusions even in areas far from Quaternary volcanoes. Whether such dikes are related to nearby Quaternary volcanoes will be important in assessing the extent of the dikes. Therefore, we focused on the geological maps published by the AIST, extracted "dykes" from the maps, and attempted to evaluate their relationship with Quaternary volcanoes.
Details: The information collection targets were geological maps of 1:200,000, covering of the "Chugoku-Shikoku region" and "Hokuriku-Chubu and Kinki region,". For the data extraction process, the distribution of the dikes was digitally traced using GIS software, and GIS data such as Shape files were created and organized on a blank map. The following data was then extracted: "Location", "Size", "Orientation" "Age", "Rock type", etc. and organized on a spreadsheet software. Additionally, within the study area, there are ancient calderas and cauldrons. Their locations were converted into a GIS based on literature information, and the distances between them and dikes were also digitized.
Result: A total of 1,219 volcanic rock dikes and other structures were extracted. Information on 66 Quaternary volcanoes and 33 ancient calderas and cauldrons was also collated.
The major axis length of the dikes was less than 1 km for 637 dikes (more than half), and if less than 2 km was included, the total was 986 dikes (over 80%). The longest is 19,456m, and is the Kozagawa body, which is classified as a Kumano acidic dyke. Other dikes exceeding 10,000m in depth are also distributed around the periphery of the ancient calderas and cauldrons.
The ages of the dikes were: 16 Quaternary, 703 Neogene, 65 Paleogene, and 435 Cretaceous. The Quaternary dikes are broken down into 4 at Oki, 10 at Mt. Daisen, and 2 at Mt. Megan, and the distribution of Quaternary dikes exposed on the surface is limited to within 10 km of the Quaternary volcanoes. For dikes older than the Quaternary period, we examined the relationship between the distance between the Quaternary volcanoes and the dikes, and the angle between that direction and the dike's extension direction, and concluded that there is little relationship between dikes older than the Quaternary period and Quaternary volcanoes.
In the future, we plan to expand the range of data collection and use the organized data to determine the distance between ancient calderas and cauldrons and their nearby dikes, and to investigate whether the degree of dike development associated with volcanic activity was the same as that of Quaternary volcanoes in ancient volcanic activity.
Acknowledgments: This study was partly funded by the Ministry of Economy, Trade and Industry, Japan, as part of its R&D supporting program titled “Establishment of Technology for Comprehensive Evaluation of the Long-term Geosphere Stability on Geological Disposal Project of Radioactive Waste” (grant no. JPJ007597; fiscal year 2024).