The Reid Lakes batholith (RLB) in southwestern McQuesten map area (115P) has previously been tentatively assigned a mid-Cretaceous age, although two K-Ar ages from the northwestern part of the batholith indicated that at least part of the body must be late Paleozoic or older. U-Pb dating of two lithologically distinct samples from the southeastern part of the RLB yields Early Mississippian crystallization ages (341.5 ± 0.7 Ma and 355.7 ± 0.9 Ma). A sample of the Moose Creek pluton, which is on the northeast side of the Tintina fault zone, but was previously interpreted to be part of the RLB, yielded a U-Pb age of 92.0 ± 0.3 Ma. The Moose Creek pluton is therefore correlated with the mainly 95-93 Ma South Lansing plutonic suite which intrudes rock units of Ancestral North America, whereas the RLB is a multi-phase, Early Mississippian intrusion into metamorphic rocks of the Yukon-Tanana terrane.
