Abstract
This contribution presents an age equation and a multi-band calibration of the zircon Raman geochronometer. Raman and LA-ICP-MS measurements confirm the empirical relationship between the Raman bandwidths (Γ) and positions (ω), and the self-irradiation α-doses (Dα) of a set of volcanic zircons. The width (ΓER) of the external rotation (ER) Raman band (ωER ≈ 356 cm−1) is a sensitive and practical estimate of the damage in the zircon lattice. The dose to dose-rate ratio defines an unambiguous Raman date t = Dα/(dDα/dt). We derive an explicit age equation for calculating t from ΓER and an effective uranium concentration eU. The sample date of a population of same-age zircons is obtained from a linear isochron to the single-grain data in a plot of measured Dαvs. eU, from the pooled Raman and eU data, or as a weighted mean. The Raman date is an apparent age that must be interpreted, based on contextual data, as either an event age, the time of cooling through a specific closure temperature, or a meaningless mixed age.
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