Petrochronologic histories across the para autochthon – allochthon boundary, Yukon-Tanana Terrane, eastern AK

The Yukon – Tanana Terrane is a the remnants of a multiply deformed accretionary margin that is bound in AK by the Tintina Fault on the north and Denali Fault to the south. The region has been divided into several important lithotectonic domains that broadly fit into reworked autochthonous crust and structurally overlaying allochthonous units interpreted to have been thrust onto the North American margin. However, the role of extensional deformation on the reactivation of this important boundary has added complexity to the structural history, and obscures the primary relationships between these two important crustal entities. Our recent work involves using petrochronologic techniques (in-situ monazite, zircon, apatite) in attempt to reconcile differing P-T-t paths across this important tectonic boundary. This work integrates mapping with the ADGGS (Alaska Dept of Geologic and Geophysical Surveys) and US Geological Survey.

modified from Dusel-Bacon et al. (2015)
Strain gradient into shear zone delineating the boundary between allochthonous Yukon-Tanana terrane and para autochthonous North America (Lake George Subterrane)
Mg K x-ray map of a full thin section from pelitic schist with monazite grains located and mapped at submicron resolution. In-situ geochronology provides the foundation for establishing direct relationships between petrologic process to time.

Current Students: Alec Wildland (MSc candidate). Thesis topic: Petrochronologic constraints on mid-crustal shear zone development in autochthonous North America, eastern AK