The closure temperature(s) of zircon Raman dating

Härtel, Birk; Jonckheere, Raymond; Wauschkuhn, Bastian; Ratschbacher, Lothar

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 inline-formulaC for durations between 10 min and 5 d to describe the annealing kinetics. We measured the widths (inline-formulaΓ) and positions (inline-formulaω) of the inline-formulaν1(SiOinline-formula4), inline-formulaν2(SiOinline-formula4), and inline-formulaν3(SiOinline-formula4) internal Raman bands, and the external rotation Raman band at inline-formula∼974, 438, 1008, and 356 cminline-formula−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 inline-formulaν2(SiOinline-formula4), inline-formulaν3(SiOinline-formula4), and external rotation bands. From the kinetic models, we determined closure temperatures inline-formulaTc for damage accumulation for each Raman band. inline-formulaTc ranges from 330 to 370 inline-formulaC for the internal inline-formulaν2(SiOinline-formula4) and inline-formulaν3(SiOinline-formula4) bands; the external rotation band is more sensitive to thermal annealing (inline-formulaTc∼260 to 310 inline-formulaC). Our estimates are in general agreement with previous ones, but more geological evidence is needed to validate the results. The inline-formulaTc difference for the different Raman bands offers the prospect of a multi-closure-temperature zircon Raman thermochronometer.

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Härtel, Birk / Jonckheere, Raymond / Wauschkuhn, Bastian / et al: The closure temperature(s) of zircon Raman dating. 2021. Copernicus Publications.

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