Abstract. Zircon Raman dating based on irradiation damage is a debated concept but not an established geo-/thermochronological method. One issue is the temperature range of radiation-damage annealing over geological timescales. We conducted isochronal and isothermal annealing experiments on radiation-damaged zircons between 500 and 1000 ∘C for durations between 10 min and 5 d to describe the annealing kinetics. We measured the widths (Γ) and positions (ω) of the ν1(SiO4), ν2(SiO4), and ν3(SiO4) internal Raman bands, and the external rotation Raman band at ∼974, 438, 1008, and 356 cm−1 after each annealing step. We fitted a Johnson–Mehl–Avrami–Kolmogorov and a distributed activation energy model to the fractional annealing data, calculated from the widths of the ν2(SiO4), ν3(SiO4), and external rotation bands. From the kinetic models, we determined closure temperatures Tc for damage accumulation for each Raman band. Tc ranges from 330 to 370 ∘C for the internal ν2(SiO4) and ν3(SiO4) bands; the external rotation band is more sensitive to thermal annealing (Tc∼260 to 310 ∘C). Our estimates are in general agreement with previous ones, but more geological evidence is needed to validate the results. The Tc difference for the different Raman bands offers the prospect of a multi-closure-temperature zircon Raman thermochronometer.

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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

Abstract. We conducted isochronal and isothermal annealing experiments on radiation-damaged zircons between 500 and 1000 °C for durations between ten minutes and five days. We measured the widths (Γ) and positions (ω) of the internal ν1(SiO4), ν2(SiO4), ν3(SiO4), and external rotation Raman bands at ~ 974, 438, 1008, and 356 cm−1. We fitted a Johnson-Mehl-Avrami-Kolmogorov and a distributed activation energy model to the fractional annealing data, calculated from the widths of the ν2(SiO4), ν3(SiO4), and external rotation bands. From the kinetic models, we determined closure temperatures Tc for damage accumulation for each Raman band. Tc range from 330 to 370 °C for the internal ν2(SiO4) and ν3(SiO4) bands; the external rotation band is more sensitive to thermal annealing (Tc ~ 260 to 310 °C). Our estimates are in general agreement with previous ones, but more geological evidence is needed to validate the results. The Tc difference for the different Raman bands offers the prospect of a multi-closure-temperature zircon Raman thermochronometer.

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