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Nagata, Mitsuhiro; Fukuda, Shoma; Sueoka, Shigeru; Nakajima, Toru; Yokoyama, Tatsunori; Wall, C. J.*; Danhara, Toru*; Iwano, Hideki*; Tagami, Takahiro*
Fuisshon, Torakku Nyusureta, (37), p.11 - 13, 2024/12
In recent years, advances in analytical technology have made it possible to measure the U-Th-Pb dating of young geological units (e.g. 
1 Ma). However, there are very few young standard samples available for evaluation. In this study, we attempted U-Pb dating using isotope dilution Thermal Ionization Mass Spectrometry (ID-TIMS) on young zircon samples (TRG04 and OGPK). As a result, we obtained preliminary U-Pb ages of 2.6654 
0.0016 Ma and 1.1266 0.0014 Ma, respectively.
Nakajima, Toru; Fukuda, Shoma; Sueoka, Shigeru; Niki, Sota*; Kawakami, Tetsuo*; Danhara, Toru*; Tagami, Takahiro*
Geochronology (Internet), 6(3), p.313 - 323, 2024/07
In this study, we explored the impacts of radiation damage and chemical composition on the etching time of fission tracks in monazite. Despite the potential of monazite fission-track (MFT) dating as an ultralow-temperature thermochronology, the comprehensive effects of radiation damage and non-formula elements, especially on the etching rate of MFTs, remain unexplored, and established analytical procedures are lacking. We quantified the degree of radiation damage (dFHWM) in Cretaceous to Quaternary monazites distributed in the Japan arc through Raman spectroscopy and chemical composition analyses. Subsequently, MFT etching was performed to examine the correlation between these parameters and the etching time. Estimation of the degree of radiation damage showed an increase in radiation damage corresponding to the cooling age of each geological unit. For example, the Toya ignimbrite (ca. 0.1 Ma) and the Kurobegawa granodiorite (0.8 Ma), both of which are types of monazite from Quaternary geological units, have dFHWM values of 0.27 and 0.55 cm
, respectively. In contrast, the Muro ignimbrite (ca. 15 Ma) has a dFHWM value of 4.01 cm, while the Kibe granite and the Sagawa granite, both of which are Cretaceous granitoids, yielded 7.35 and 6.31 cm, respectively. MFT etching of these samples according to the existing recipe (6M HCl at 90
C for 60-90 min) was completed at 1200, 860, 210, 120, and 90 min for the Toya ignimbrite, Kurobegawa granodiorite, Muro ignimbrite, Sagawa granite, and Kibe granite, respectively.
Sueoka, Shigeru; Iwano, Hideki*; Danhara, Toru*; Niwa, Masakazu; Kanno, Mizuho; Kohn, B. P.*; Kawamura, Makoto; Yokoyama, Tatsunori; Kagami, Saya; Ogita, Yasuhiro; et al.
Earth, Planets and Space (Internet), 75(1), p.177_1 - 177_24, 2023/12
Times Cited Count：0 Percentile：0.00(Geosciences, Multidisciplinary)Fluid-inclusion and thermochronometric analyses have been applied to hydrothermal alteration zones and their host rocks outcropping in the Hongu area of the Kii Peninsula, southwestern Japan in an attempt to detect thermal anomalies related to hydrothermal events and quantify the thermal effects on the host rocks. Hydrothermal events at ca 150 deg. C and ca 200 deg. C were identified by fluid-inclusion microthermometry of quartz veins in the alteration zones. For the host rocks and alteration zones, in the youngest population zircon yielded U-Pb dates ranging between ca 74.7-59.2 Ma, fission-track dates of ca 27.2-16.6 Ma, and (U-Th)/He single-grain dates of ca 23.6-8.7 Ma. Apatite yielded pooled fission-track ages of ca 14.9-9.0 Ma. The zircon U-Pb dates constrain the maximum depositional ages of the sedimentary samples. However, the fission-track and (U-Th)/He dates show no clear trend as a function of distance from the alteration zones. Hence, no thermal anomaly was detected in the surrounding host rocks based on the thermochronometric data patterns. The fission-track and (U-Th)/He dates are rather thought to record regional thermal and exhumation histories rather than a direct thermal imprint of fluid flow, probably because the duration of such activity was too short or because fluid flow occurred before regional cooling events and were later thermally overprinted. Apatite fission-track ages of ca 10 Ma may reflect regional mountain uplift and exhumation related to the obduction of the SW Japan lithospheric sliver onto the Shikoku Basin, or the rapid subduction of the Philippine Sea slab associated with the clockwise rotation of the Southwest Japan Arc.
Sueoka, Shigeru; Iwano, Hideki*; Danhara, Toru*; Okamoto, Akira*; Tagami, Takahiro*
Fuisshon, Torakku Nyusureta, (35), p.1 - 4, 2022/12
no abstracts in English
Nakajima, Toru; Fukuda, Shoma; Nagata, Mitsuhiro; Danhara, Toru*; Iwano, Hideki*; Sueoka, Shigeru
Fuisshon, Torakku Nyusureta, (35), p.34 - 36, 2022/12
In this presentation, we report the results of fission-track etching experiments for the practical use of baddeleyite fission-track dating and a brief discussion of the results.
Fukuda, Shoma; Kohn, B. P.*; Sueoka, Shigeru; Danhara, Toru*; Iwano, Hideki*; Tagami, Takahiro*
Fuisshon, Torakku Nyusureta, (35), p.7 - 10, 2022/12
In order to establish the age standard of zircon (U-Th)/He method, we performed zircon (U-Th)/He (hereinafter, ZHe) dating on 4 zircon samples. In this presentation, the Nohi rhyolite and the Mt. Wasso moonstone rhyolite as domestic samples, and Mt. Dromedary and OD-3 were also adopted as age standard zircons of fission-track and U-Pb methods. Consequently, regarding the ZHe age of the Nohi rhyolite indicated younger, which possibly reflected secondary heating, while ones of the others indicated consistent with previous thermochronometric data. Integrated with previously obtained ZHe data about 7 samples, the Utaosa rhyolite in the previous study showed a small age dispersion in grain ages, which infers a suitable candidate for the ZHe age standard. As future prospects, we are planning to conduct geochemical analyses and structure observations of these zircons for exploring the causal factors in age dispersions.
Nakajima, Toru; Kawakami, Tetsuo*; Iwano, Hideki*; Danhara, Toru*; Sakai, Harutaka*
Journal of Geophysical Research; Solid Earth, 127(5), p.e2021JB023630_1 - e2021JB023630_33, 2022/05
Times Cited Count：3 Percentile：31.13(Geochemistry & Geophysics)The thermochronological methods were applied to the Higher Himalayan Crystalline (HHC) nappe and the underlying Lesser Himalayan sediments (LHS) to elucidate the denudation process of the middle- and upper-crust of eastern Nepal over the geological time scale. The thermochronological inverse analysis was undertaken for new results of fission-track (FT) age and FT length data of zircon and apatite in order to reconstruct the time-temperature (
) paths in the temperature range of 60-350 degree. Eight paths obtained along the across-strike section showed that the cooling process of the HHC nappe was characterized by following three aspects: (1) gradual cooling followed by rapid cooling and subsequent gradual cooling, (2) northward-younging of the timing of the rapid cooling, (3) gradual cooling followed by ca. 2 Myr rapid cooling in the frontmost part of the HHC nappe. The observed FT ages and paths were then compared with those predicted by forward thermokinematic modeling. The results of the thermokinematic modeling for the Flat-Ramp-Flat MHT model, in which the HHC and the underlying LHS are denudated accompanied with the movement of the Main Himalayan Thrust (MHT), well reproduced the observed paths and FT ages in eastern Nepal. This suggests that the observed FT ages and paths reflect a denudation process driven by the movement of the MHT showing the flat-ramp-flat geometry, and that the denudation rate and its spatial distribution have roughly been constant in eastern Nepal since ca. 9 Ma.
Sasao, Eiji; Danhara, Toru*; Yamashita, Toru*; Hayashi, Joji*
Mizunamishi Kaseki Hakubutsukan Kenkyu Hokoku, (48), p.9 - 19, 2021/05
Petrographic description of tuffs in the Miocene Mizunami Group has been made to offer basic data. This report includes the descriptions of 14 and 4 tuff beds in the Mizunami and Iwamura Groups, respectively. Followings are presented in this report; mineral and heavy mineral composition, shape of volcanic glass, and refractive indices of volcanic glass and plagioclase.
Sueoka, Shigeru; Shimada, Koji; Terusawa, Shuji*; Iwano, Hideki*; Danhara, Toru*; Ogita, Yasuhiro; Hirata, Takafumi*
Chishitsugaku Zasshi, 127(1), p.25 - 39, 2021/01
no abstracts in English
Takahashi, Hiroshi*; Mikoshiba, Masumi*; Shimura, Toshiaki*; Nagata, Mitsuhiro; Iwano, Hideki*; Danhara, Toru*; Hirata, Takafumi*
Island Arc, 30(1), p.e12393_1 - e12393_15, 2021/01
Times Cited Count：3 Percentile：16.35(Geosciences, Multidisciplinary)The Hidaka metamorphic belt is an excellent example of island-arc-type crust, and in this belt the metamorphic grade increases westwards from unmetamorphosed sediment up to the granulite facies. The metamorphic age of the belt had previously been considered to be ca. 55 Ma. However, zircons from the granulites in the lower sequence have given U-Pb ages of ca. 21-19 Ma and a preliminary report on zircons from pelitic gneiss in the upper sequence gave a U-Pb age of ca. 40 Ma. In this paper we provide new U-Pb ages for zircons from the pelitic gneisses in the upper sequence in order to assess the metamorphic age and also the maximum depositional age of the sedimentary protolith. The weighted mean 
Pb/
U ages and 2 sigma errors for zircons from biotite gneiss in the central area of the belt are 39.6 0.9 Ma for metamorphic overgrowth rims and 53.1 0.9 Ma for the youngest inherited detrital cores. The ages of zircons from cordierite-biotite gneiss in the southern area are 35.9 0.7 Ma for overgrowth rims and 46.5 2.8 Ma for the youngest detrital cores. These results indicate that the metamorphism of the upper sequence took place at ca. 40-36 Ma, and that the sedimentary protolith was deposited after ca. 53-47 Ma. These metamorphic ages are consistent with the reported ages of ca. 37-36 Ma plutonic rocks in the upper sequence, but contrast with the ca. 21-19 Ma ages of metamorphic and plutonic rocks in the lower sequence. Therefore, we conclude, that the upper and lower metamorphic sequences developed independently but became coupled before ca. 19 Ma as a result of dextral reverse tectonic movements, as indicated by the intrusion of ca. 19-18 Ma magmas, possibly generated in the lower sequence, into the upper sequence.
Niwa, Masakazu; Amamiya, Hiroki*; Yonaga, Yusuke; Ogita, Yasuhiro; Yasue, Kenichi*; Iwano, Hideki*; Danhara, Toru*; Hirata, Takafumi*
Chishitsugaku Zasshi, 126(5), p.267 - 283, 2020/05
U-Pb and fission-track (FT) ages from single zircon grain were measured for three tephra samples (TKB3, TKB6, and TKB7) intercalated in Neogene to Quaternary in Horonobe area, Hokkaido, to understand their depositional ages. In TKB3 and TKB6, weighed average U-Pb and FT ages for zircon grains within the youngest age range are coincident within a range of error 2 
each other, which suggest that their ages correspond to the eruption ages. In TKB7, FT ages for most zircons are reset to their U-Pb ages or younger. The weighed average FT age for all analyzed zircons and weighed average U-Pb age for zircon grains within the youngest age range are coincident within a range of error 2 each other. Thus, their ages could also show the eruption age.
Ueki, Tadamasa; Niwa, Masakazu; Iwano, Hideki*; Danhara, Toru*; Hirata, Takafumi*
Chishitsugaku Zasshi, 125(3), p.227 - 236, 2019/03
no abstracts in English
Yuguchi, Takashi*; Sueoka, Shigeru; Iwano, Hideki*; Izumino, Yuya*; Ishibashi, Masayuki; Danhara, Toru*; Sasao, Eiji; Hirata, Takafumi*; Nishiyama, Tadao*
Journal of Asian Earth Sciences, 169, p.47 - 66, 2019/01
Times Cited Count：18 Percentile：62.22(Geosciences, Multidisciplinary)This study presents position-by-position 
paths within a granitic pluton based on thermochronological data, and describes their constraints and their relationship with fracture frequency, as an example from the Toki granite, central Japan. The cooling paths have position-specific characteristics; a single path does not represent the cooling behavior of the entire pluton. Such position-specific paths enable us to evaluate three-dimensional thermal evolution within the granitic pluton, and thus can clarify the detailed formation history of the entire pluton after the incipient intrusion of the granitic magma into the shallow crust. This study reveals the relationship between position-specific paths and fracture frequency, and thus provides a criterion for evaluating the fracture population in terms of thermal stress.
Sueoka, Shigeru; Shimada, Koji; Ishimaru, Tsuneari; Danhara, Toru*; Iwano, Hideki*; Yagi, Koshi*
Chigaku Zasshi, 127(6), p.795 - 803, 2018/12
no abstracts in English
Yokoyama, Tatsunori; Kimura, Junichi*; Mitsuguchi, Takehiro; Danhara, Toru*; Hirata, Takafumi*; Sakata, Shuhei*; Iwano, Hideki*; Maruyama, Seiji*; Chang, Q.*; Miyazaki, Takashi*; et al.
Geochemical Journal, 52(6), p.531 - 540, 2018/12
Times Cited Count：17 Percentile：59.29(Geochemistry & Geophysics)Sasao, Eiji; Danhara, Toru*; Iwano, Hideki*; Hirata, Takafumi*
Chishitsugaku Zasshi, 124(2), p.141 - 150, 2018/02
Here U-Pb and reassessed fission track (FT) ages are presented for samples from the Miocene Mizunami and Iwamura groups in the southeastern Gifu Prefecture, central Japan. The U-Pb ages of three tuff samples coincide with the reassessed FT ages within the error range. These new U-Pb and reassessed FT ages are consistent with those reported in previous microfossil and paleomagnetic studies, which indicate the following depositional history: The Hongo and Akeyo formations of the Mizunami Group were deposited at ~19-18 Ma and ca. 18 Ma, respectively, and the lower part of the Toyama Formation of the Iwamura Group was deposited ca. 18 Ma.
Yuguchi, Takashi*; Sueoka, Shigeru; Iwano, Hideki*; Danhara, Toru*; Ishibashi, Masayuki; Sasao, Eiji; Nishiyama, Tadao*
Island Arc, 26(6), p.e12219_1 - e12219_15, 2017/11
Times Cited Count：12 Percentile：37.41(Geosciences, Multidisciplinary)The spatial distribution of AFT age in the granitic body is a favorable key to reveal a cooling behavior of the whole pluton. The cooling behavior is attributable to the regional exhumation of the Toki granite related to the regional denudation of the Tono district. Combination of the AERs and AFT inverse model applying to the granite is a powerful procedure for evaluating the cooling and exhumation history of the granitic pluton and thus denudation history of the tectonic region that surrounded the rock body.
Sueoka, Shigeru; Shimada, Koji; Ishimaru, Tsuneari; Niwa, Masakazu; Yasue, Kenichi; Umeda, Koji*; Danhara, Toru*; Iwano, Hideki*
Journal of Geophysical Research; Solid Earth, 122(3), p.1848 - 1859, 2017/03
no abstracts in English
Sueoka, Shigeru; Shimada, Koji; Ishimaru, Tsuneari; Niwa, Masakazu; Yasue, Kenichi; Umeda, Koji*; Danhara, Toru*; Iwano, Hideki*
Fuisshon, Torakku Nyusureta, (29), p.5 - 7, 2016/12
no abstracts in English
Sueoka, Shigeru; Umeda, Koji; Yasue, Kenichi; Niwa, Masakazu; Shimada, Koji; Ishimaru, Tsuneari; Danhara, Toru*; Iwano, Hideki*; Yagi, Koshi*
Chigaku Zasshi, 125(2), p.201 - 219, 2016/04
We applied multi-system thermochronology to the Tsuruga body of the Kojaku granite to constrain the cooling/denudation history of the Tsuruga area. Based on the thermochronometric results and other data, we reconstructed the cooling and denudation histories of the Tsuruga body as below: (1) the Tsuruga body intruded at c.a. 68 Ma at the depth of 4-5 km, (2) rapidly cooled down to c.a. 200C by heat conduction within a few million years or less, and (3) slowly cooled due to peneplanation during the Cenozoic. This cooling/denudation history is consistent with the observations that cataclasite and fault gouge are dominant in the crush zones of the Tsuruga body, that similar slow cooling histories over the Cenozoic are estimated in the surrounding areas based on thermochronometric ages, and that the amount of denudation in the last few million years in the Tsuruga area is inferred at less than several hundred meters from the elevations of the uplifted peneplains.
