EVALUATING A NEW, RAPID ZIRCON AND TITANITE DISSOLUTION METHOD FOR (U-TH)/HE THERMOCHRONOLOGY
This contribution evaluates a new method that uses ammonium fluoride to dissolve whole zircon and titanite crystals for (U-Th)/He dating. Instead of the 1.5 weeks needed to dissolve grains using standard acid-vapor dissolution methods, this new technique can completely dissolve grains in ~4 hours. In addition, it does not require pressure vessels, and instead uses screw-top Teflon vials, greatly increasing sample throughput. Finally, this method reduces the amount of ultra-pure reagents needed for dissolution (specifically ultra-pure HF), further decreasing the cost of analysis.
Zircons from the fish canyon tuff standard dissolved with the new method yield a date of 28.9 ± 1.7 Ma (n=10), indistinguishable from grains analyzed using the standard acid-vapor dissolution method (28.7 ± 1.8 Ma, n=178). Dates for 3 other zircon samples, as well as 1 titanite sample, are similarly indistinguishable between the new and conventional methods. These data strongly suggest that this new, higher-throughput method completely dissolves zircon and titanite and can be employed regularly in (U-Th)/He thermochronology.