Detrital zircon U-Pb and ΕHf signature of the Yukon-Tanana terrane in Yukon, Canada

The mountain ranges of the northern Cordillera of North America are comprised of multiple tectonic entities known as terranes. The basement of the Yukon-Tanana terrane (YTT) was once an outlying portion of the Laurentian passive margin, known as the Snowcap assemblage. During the Devonian, a volcanic arc was built upon this Laurentian substrate. Coeval arc magmatism and back-arc rifting provided a plethora of new detritus to basins that would eventually form the upper two assemblages of the YTT: the Finlayson and the Klinkit. These two assemblages record magmatism from the Devonian to the Permian. Back-arc rifting associated with the Yukon-Tanana volcanic arc created what is known as the Slide Mountain Ocean. This ocean basin separated the Yukon-Tanana arc from the rest of the continent and was later accreted back onto the continent in the Mesozoic. The purpose of this study was to determine if what has been defined as Yukon-Tanana terrane-south (YTTs) in southeastern Alaska is truly equivalent to YTT-north (YTTn) in Yukon. The mineral zircon was used to understand the provenance and tectonic history of metasedimentary rocks of YTTn. Previous work characterized YTTs as having magmatism ca. 350-400 Ma. This study found that magmatism was not prevalent in YTTn until ca. 365 Ma. Magmatism also continued in YTTn until ca. 330 Ma later than in YTTs. This suggests that the two tectonic bodies were not one cohesive terrane that was later separated.