Tourmaline 40Ar/39Ar petrochronology as a timing constraint on ore formation

Recent experimental work has demonstrated that tourmaline (tur) can serve as a relatively high-temperature (400−600 °C) 40Ar/39Ar geochronometer. Incremental heating of tur from two mineralized localities in the Yukon (Canada), the Casino Cu-Au-Mo porphyry (74.8 ± 0.74 Ma) and Seagull Batholith (96.9 ± 0.14 Ma), yield 40Ar/39Ar plateau ages that overlap with zircon U-Pb ages from the host plutons, indicating rapid development of hydrothermal mineralization following regional magmatism. However, differences in K contents between Casino and Seagull tur and differing crystallization textures between successful (age plateaus) and unsuccessful (discordant) heating experiments illustrate that crystallochemical features (e.g., partial replacement) exert a strong control on geochronology. A petrochronologic approach integrating tur texture, chemistry, and 40Ar/39Ar ages can contribute insights into the formation conditions of tur-bearing mineralized systems.