Structural geology of the eastern Nadaleen trend, Yukon Territory, Canada: Implications for recently discovered sedimentary rock-hosted gold

- Complex local structures include S-, E-, W-, and SE-plunging folds, an E-striking strike-slip fault, and a N-trending reverse fault.
- Gold zones are hosted in separate S-plunging anticlines close to faults and not in folds in other orientations.
- An E-striking triangle zone across the eastern Nadaleen trend probably influenced Au-rich ore fluid migration.
- Local structures and the triangle zone may have been influenced by the subsurface ancestral Dawson fault.
- The eastern Nadaleen trend gold zones are structurally similar to Carlin-type deposits in Nevada.

Recently discovered gold-rich mineral deposits in the eastern Nadaleen trend of northeastern Yukon Territory occur in unmetamorphosed Neoproterozoic carbonate and siliciclastic rocks and their location is partly controlled by structures. Regional deformation largely resulted from mid-Cretaceous NNE-vergent, thin-skinned fold-thrust activity. However, structures in the eastern Nadaleen trend are more complex and include strike-slip and reverse faults, and SSW-, W-, and E-plunging folds. Local structures are cospatial with regional geologic features, including (1) an E-striking structural triangle zone defined by oppositely dipping reverse faults that verge toward the eastern Nadaleen trend, (2) a transition zone between Paleozoic Ogilvie platform rocks in the north to Selwyn basin rocks in the south, and (3) a change in regional deformation character from west to east, whereby to the west, rocks in the south are more deformed than rocks in the north, whereas to the east, rocks show no obvious change in deformation style. The structural complexity within the eastern Nadaleen trend probably resulted from these regional geological features and was further complicated by local competency contrasts between rock units. The cospatial location of the regional geological features may have been caused by a pre-existing, W-trending subsurface basement structure. Reverse faults bounding the E-striking triangle zone may have acted as low permeability aquitards that directed mineralizing fluids up-dip into reactive carbonate stratigraphy in the eastern Nadaleen trend. Gold-rich mineral deposits in the eastern Nadaleen trend occur preferentially in SSW-plunging anticlines and near faults, both of which probably influenced the migration of mineralizing fluid.