Zircon Raman thermochronology in practice: first results and implications

Zircon Raman dating rests on measurements of (1) self-irradiation damage in the zircon lattice from the Raman bandwidth (FWHM), and (2) the U and Th concentrations in the same volume. Ages are calculated from the ratio of the dose-equivalent damage estimate and the effective uranium content (eU). As the lattice damage anneals at high temperatures, zircon Raman dating is a thermochronological method, whose results are interpreted in terms of the thermal history of a zircon with respect to the method’s closure temperature (Tc). Tc estimates based on laboratory annealing experiments span a range from 260 to 370 °C for various Raman bands and kinetic models.

We dated zircon samples from igneous and metamorphic rocks with a known thermal history, combining Raman spectroscopy with SIMS and EPMA, to test (1) the general applicability of zircon Raman dating, and (2) whether the experimental estimates of the closure temperature match the closure temperature determined on natural samples.