(U–Th)/He thermochronometric mapping across the northeast Japan Arc: towards understanding mountain building in an island-arc setting

Abstract

Topographic relief in arc-trench systems is thought to be formed by plate subduction; however, few quantitative investigations have so far been reported, with respect to the related mountain building process. This study applies apatite and zircon (U-Th)/He thermochronometry (AHe, ZHe, respectively) to Cretaceous granite rocks in the north part of the northeast (NE) Japan Arc to reveal its cooling/denudation history. Weighted mean AHe ages ranging from 88.6 to 0.9 Ma and ZHe ages from 83.9 to 7.4 Ma were determined for 10 rock samples. Using the AHe data, denudation rates were obtained for each sample. On the fore-arc side, denudation rates of < 0.05 mm/year were calculated, indicating a slow denudation process since the Paleogene. However, in the Ou Backbone Range and on the back-arc side, denudation rates at > 0.1-1.0 mm/year were computed, probably reflecting a recent uplift event since ~ 3-2 Ma. These data indicate a clear contrast in thermal and denudation histories between the tectonic units in this study area, similar to that previously reported from the southern part of NE Japan Arc. A comparison of the thermal/denudation histories between the N-and S-traverses, revealed the arc-parallel trend, the uplift model of the volcanic arc, and some minor variations of thermal/denudation histories in each tectonic unit. This study offers some further insights into the understanding of tectonic processes in an island-arc setting.

Late Cretaceous–Paleogene terrestrial sequence in the northern Kitakami Mountains, Northeast Japan: Depositional ages, clay mineral contents, and vitrinite reflectance

“…(b) Condition 2: S I = 160 m/Myr. Dashed black lines ( E m ) in (a) and (b) indicate the mean exhumation rate in the Kitakami Mountains (∼50 m/Myr, Fukuda et al, 2020). (c and d) Relationship between the geothermal gradient and the maximum burial depth that explains the measured vitrinite reflectance (0.37 ± 0.03 ≤ VR r ≤0.53 ± 0.03).…”

“…We used a part of the code developed by Kaneki and Because the timing of basin inversion is unknown, it is difficult to estimate the exhumation rate in the Kado district. However, it may have been higher than the mean exhumation rate of the Kitakami Mountains since the Paleogene (E m < 50 m/Myr; Fukuda et al, 2020) if ΔK is >30 K/km (Figure 20).…”

Exhumation of the Coastal Metamorphic Belt Above the Subduction‐to‐Transform Transition, in the Southeast Caribbean Plate Corner

“…For dispersed aliquots with possible size or eU age controls, the range of single grain ages is reported for a sample (Ault et al., 2019; Flowers et al., 2009). We calculated the arithmetic mean (U‐Th)/He age only for samples with more than two reproducible single grain ages (e.g., Fukuda et al., 2020).…”

Special issue "Crustal dynamics: toward integrated view of island arc seismogenesis"

“…However, inelastic deformation is also essential to understand the topography and stress concentration, both of which are strongly related to earthquakes. Fukuda et al (2020) investigated cooling/denudation history in the northern part of the northeastern Japan arc using thermochronometry. The results indicate slow denudation rates in the fore-arc side and high rates in the Ou Backbone Range and on the back-arc side, similar to the southern part of the arc.…”