11:00 AM - 1:00 PM
[SCG42-P04] Interpretation of thermochronological date in the Kitakami Mountains
Keywords:Kitakami Mountains, Thermochronology
The tectonic mechanisms in fore-arc regions of an arc-trench system, such as uplift and subsidence, are considered to be strongly affected by the plate subduction. However, on the fore-arc side of the Northeastern Japan Arc, where Neogene and Quaternary sediments are found in limited areas, only a few quantitative discussions of the uplift/subsidence histories (especially in 106 yr time scale) were carried out. This study aims for estimating the uplift/denudation history in the Kitakami Mountains on the fore-arc side of the Northeastern Japan Arc based on thermochronological data (zircon U-Pb, apatite fission-track (AFT) and apatite helium (AHe) ages).
For the Cretaceous granitoids exposed in the Kitakami Mountains, zircon U-Pb ages were previously reported between approximately 135 and 120 Ma (e.g., Osozawa et al., 2019); AFT ages between roughly 130 and 70 Ma (Goto, 2001; Fukuda et al., unpublished; Kajita et al., 2021); AHe ages between around 80 and 30 Ma (Fukuda et al., 2020; Kajita et al., 2021). AFT ages get older to the east side, whereas AHe ages are spatially uniform except for the older ages at the westernmost localities. These age-trends in the east-west direction are not associated with the rock formation ages, but with the spatial difference in the cooling processes, considering the uniform zircon U-Pb ages. This differential cooling can be attributed to: (1) heterogeneous thermal structure related to migration of the volcanic front or adakitic magmatism including the Jodogahama rhyolites and (2) spatially different uplift/denudation rates driven by underplating (Menant et al., 2020). These factors will be discussed in detail with geological information and thermal inversion data utilizing distributions of FT lengths at the poster presentation on that day.
The future prospects are (1) to increase localities to perform thermal inversion, (2) to adopt more integrated tectonic simulations, and (3) to apply ultra-low-temperature thermochronology (e.g., electron spin resonance dating).
Acknowledgements: This study was funded by the Ministry of Economy, Trade and Industry (METI), Japan as part of its R&D supporting program titled “Establishment of Advanced Technology for Evaluating the Long-term Geosphere Stability on Geological Disposal Project of Radioactive Waste (Fiscal Years 2018 to 2021), Grant Number JPJ007597”. This study was also supported by the Grant-in-Aid for Scientific Research on Innovative Areas (KAKENHI No. 26109003) from the Ministry of Education, Culture, Sports, Science and Technology (MEXT).
For the Cretaceous granitoids exposed in the Kitakami Mountains, zircon U-Pb ages were previously reported between approximately 135 and 120 Ma (e.g., Osozawa et al., 2019); AFT ages between roughly 130 and 70 Ma (Goto, 2001; Fukuda et al., unpublished; Kajita et al., 2021); AHe ages between around 80 and 30 Ma (Fukuda et al., 2020; Kajita et al., 2021). AFT ages get older to the east side, whereas AHe ages are spatially uniform except for the older ages at the westernmost localities. These age-trends in the east-west direction are not associated with the rock formation ages, but with the spatial difference in the cooling processes, considering the uniform zircon U-Pb ages. This differential cooling can be attributed to: (1) heterogeneous thermal structure related to migration of the volcanic front or adakitic magmatism including the Jodogahama rhyolites and (2) spatially different uplift/denudation rates driven by underplating (Menant et al., 2020). These factors will be discussed in detail with geological information and thermal inversion data utilizing distributions of FT lengths at the poster presentation on that day.
The future prospects are (1) to increase localities to perform thermal inversion, (2) to adopt more integrated tectonic simulations, and (3) to apply ultra-low-temperature thermochronology (e.g., electron spin resonance dating).
Acknowledgements: This study was funded by the Ministry of Economy, Trade and Industry (METI), Japan as part of its R&D supporting program titled “Establishment of Advanced Technology for Evaluating the Long-term Geosphere Stability on Geological Disposal Project of Radioactive Waste (Fiscal Years 2018 to 2021), Grant Number JPJ007597”. This study was also supported by the Grant-in-Aid for Scientific Research on Innovative Areas (KAKENHI No. 26109003) from the Ministry of Education, Culture, Sports, Science and Technology (MEXT).