U-Pb and 40Ar-39Ar geochronology of plutonic rocks from the Teslin suture zone, Yukon Territory

Abstract

An isotopic dating study was undertaken in the Teslin suture zone of south-central Yukon in order to constrain; 1) the protolith ages of rock units that took part in Teslin suture deformation and, 2) the timing of deformation and uplift of Teslin suture zone rocks. Three bodies of deformed metatonalite to quartz diorite from the study area give Early Mississippian U-Pb zircon ages. These are interpreted as crystallization ages and provide a minimum depositional age for siliciclastic metasedimentary units that they intrude. A massive hornblende-bearing tonalite to quartz diorite pluton gives Early Jurassic U-Pb zircon (÷188 Ma), 40Ar/39Ar biotite (182 +/- 2 Ma), and 40Ar/39Ar hornblende (179 +/- 2 Ma) ages. The U-Pb zircon age is interpreted as a minimum crystallization age and places a local minimum age for deformation of Teslin suture zone rocks in the study area. The 40Ar/39Ar ages are interpreted as uplift/cooling ages and are younger than previously reported cooling ages (184-195 Ma) for rocks of the zone.