Duluth Complex apatites: Age reference material for LA–ICP–MS‐based fission‐track dating

Iwano, Hideki; Danhara, Tohru; Yuguchi, Takashi; Hirata, Takafumi; Ogasawara, M.

doi:10.1111/ter.12393

Cited by 15 publications

(25 citation statements)

References 38 publications

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“…ZFT dating using laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) was performed based on a workflow that was developed by Iwano, Danhara, Yuguchi, Hirata, and Ogasawara (2019) and Iwano et al (in press). To separate zircon grains, approximately 300 g of each sample was crushed to disaggregate the rock sample into discrete mineral grains.…”

Section: Zft Analysismentioning

confidence: 99%

Northward cooling of the Kuncha nappe and downward heating of the Lesser Himalayan autochthon distributed to the south of Mt. Annapurna, western central Nepal

et al. 2020

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We investigated the tectonothermal history of the Lesser Himalayan sediments (LHS), which are tectonically overlain by the Higher Himalayan Crystalline. Fissiontrack dating and the track length measurement of detrital zircons obtained from the Kuncha nappe and the Lesser Himalayan autochthonous sediments in western central Nepal revealed northward cooling of the nappe and possible downward heating of the autochthon by the overlying hot nappe. Nine zircon fission-track (ZFT) ages of the nappe showed northward-younging linear distribution from 11.6 Ma in the front at Tamghas, 6 Ma in the central at Naudanda, and 1.6 Ma in the northernmost point at Tatopani. Thermochronological invert calculation of the ZFT length elucidated that the Kuncha nappe gradually cooled down (30 C/Myr) at the front and rapidly cooled down (120 C/Myr) at the root zone. In contrast, the ZFT age of the Chappani Formation, located just beneath the Kuncha nappe in the central part, demonstrated a totally reset age of 6.8 Ma, whereas the Virkot Formation, structurally far from the nappe, yielded a partially reset age of 457.3 Ma. This suggests that the LHS underwent downward heating, resulting in a thermal print on the upper part of the LHS; however, the thermal effect was not sufficient to anneal ZFT totally in the deeper part. Presently, the nappe cover is eroded and denuded from this area. Detrital zircons from the Chappani Formation in Tansen area to the south of the Bari Gad Fault did not show any evidence of annealing, suggesting that nappe never covered the LHS distributed to the south of the fault.

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Section: Zft Analysismentioning

confidence: 99%

Northward cooling of the Kuncha nappe and downward heating of the Lesser Himalayan autochthon distributed to the south of Mt. Annapurna, western central Nepal

et al. 2020

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“…ZFT dating using laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) was performed based on a workflow that was developed by Iwano, Danhara, Yuguchi, Hirata, and Ogasawara (2019) and Iwano et al (in press). Zircon grains were separated from the fragmented rock samples using heavy liquid as in Danhara, Iwano, Kasuya, and Yamashita (1992) and mounted on a Teflon sheet during 8 s at approximately 338 °C.…”

Section: Methodsmentioning

confidence: 99%

Northward younging zircon fission‐track ages from 13 to 2 Ma in the eastern extension of the Kathmandu nappe and underlying Lesser Himalayan sediments distributed to the south of Mt. Everest

Nakajima

Sakai

Iwano³

et al. 2020

Island Arc

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This study is concerned with the tectono-thermal history of the Kathmandu nappe and the underlying Lesser Himalayan sediments (LHS) that are distributed in eastern Nepal. We carried out zircon fission-track(ZFT) dating and obtained 16 ZFT ages from the eastern extension of the Kathmandu nappe, the Higher Himalayan Crystalline, Kuncha nappe, and the Main Central Thrust (MCT) zone. The ZFT ages of the frontal part of the Kathmandu nappe range from 13.0 ±0.8 Ma to 10.7 ±0.7 Ma and exhibit a northward-younging tendency. These Middle Miocene ZFT ages indicate that the frontal part of the Kathmandu nappe remained at a temperature above 240 C until the termination of its southward emplacement at 12-11 Ma. The ZFT ages of the LHS range from 11.1 ±0.9 Ma in the southern part of the Okhaldhunga Window to 2.4 ±0.3 Ma of the augen gneiss in the northern margin and also exhibit a northward-younging age distribution. The ZFT ages show the northward-younging linear distribution pattern (−0.16 Ma/km) along the across-strikesection from the frontal part of the Kathmandu nappe to the root zone, without a significant age gap. This distribution pattern indicates that the Kathmandu nappe, the underlying MCT zone, and the Kuncha nappe cooled from the frontal zone to the root zone as a thermally united geologic body at a temperature below 240 C. An older ZFT age (456.3 ±24.3 Ma), which was partially reset at the axial part of the Midland anticlinorium in the central part of the Okhaldhunga Window, was explained by downward heating from the "hot" Kathmandu nappe. The above evidence supported a model that southward emplacement of the hot Kathmandu nappe resulted in a thermal imprint on the upper part of the LHS; however, the lower part did not reach 240 C.

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“…For comparison, we also studied zircons from the Neoproterozoic Duluth Complex anorthosites, Minnesota (FC1; Figure 1e; CA-ID-TIMS zircon 207 Pb/ 206 Pb age: 1,099.0 ± 0.6 Ma, Paces and Miller, 1993). These are homogeneous in CL, show no reaction textures, span a broad range of radiation damage (Marillo-Sialer et al, 2016), and did not experience reheating after initial cooling according to apatite fission track data (Iwano et al, 2019). We thus expect them to show neither artifactual band broadening nor annealing.…”

Section: Samplesmentioning

confidence: 99%

Multi‐Band Raman Analysis of Radiation Damage in Zircon for Thermochronology: Partial Annealing and Mixed Signals

Härtel

Jonckheere

Ratschbacher

2022

Geochem Geophys Geosyst

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Thermochronology studies the timing and rates of geologic phenomena based on the radioactive processes occurring within natural minerals. At the same time, these processes damage the mineral, changing its properties over time. Measurements of self-irradiation damage are thus an important part of thermochronologic studies. Such measurements broke ground for: (a) zircon Raman dating, in which the self-irradiation damage itself is a measure of the age of the sample (Härtel, Jonckheere, Wauschkuhn, Hofmann, et al., 2021;Pidgeon, 2014); (b) the refinement of thermochronometers, whose results are influenced by self-irradiation damage, for example, (U-Th)/ He dating (Anderson et al., 2020;Guenthner et al., 2013); and (c) the applicability of provenance studies, using Raman characteristics of detrital zircons to distinguish thermal histories (Garver & Davidson, 2015;Resentini et al., 2020).Zircon (ZrSiO 4 ) substitutes U and Th for Zr in its structure. Disintegration of 238 U, 235 U, 232 Th, and their daughters damages the lattice by the emission of α-particles and the recoil of the daughter nuclei (Bohr, 1948;Joly, 1907;Mügge, 1922). An α-particle displaces ∼10 2 atoms toward the end of its ∼10-20 μm trajectory through the

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Duluth Complex apatites: Age reference material for LA–ICP–MS‐based fission‐track dating

Cited by 15 publications

References 38 publications

Northward cooling of the Kuncha nappe and downward heating of the Lesser Himalayan autochthon distributed to the south of Mt. Annapurna, western central Nepal

Northward cooling of the Kuncha nappe and downward heating of the Lesser Himalayan autochthon distributed to the south of Mt. Annapurna, western central Nepal

Northward younging zircon fission‐track ages from 13 to 2 Ma in the eastern extension of the Kathmandu nappe and underlying Lesser Himalayan sediments distributed to the south of Mt. Everest

Multi‐Band Raman Analysis of Radiation Damage in Zircon for Thermochronology: Partial Annealing and Mixed Signals

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