POST-(?)TRANS-HUDSONIAN FOLDING IN THE FOXE FOLD BELT, MELVILLE PENINSULA, NUNAVUT, CANADA

The Paleoproterozoic Foxe Fold Belt (FFB) of Melville Peninsula is an ENE-trending fold belt along the northern margin of the Trans-Hudson Orogen (THO). It interfolds the Paleoproterozoic Penrhyn Group with Archean Prince Albert Group gneisses of the Rae Province. We investigated the kinematics and timing of folding in the FFB of Melville Peninsula in order to elucidate its role in the formation of supercontinent Columbia (Nuna). Previously, a WSW orogen-parallel transport direction was inferred from sheath folds, which is inconsistent with north-verging folds and thrust faults in the FFB of Baffin Island.

Results from detailed structural mapping of key areas indicate that the FFB is dominated by large-scale, shallowly plunging, ~250°-trending, NNW-verging (F₂) folds that tighten toward the WSW. Small-scale isoclinal folds are typically parallel or sub-parallel to the orientation of these larger scale folds. Along F₂ fold hinges, rare evidence exists of ~260°-trending isoclinal F₁ folds. These results suggest the general transport direction in the FFB of Melville Peninsula was toward ~340° with possible earlier transport toward ~350°. Our results are consistent with the interpreted northerly transport direction in the FFB of Baffin Island.

Four samples were analyzed by U-Pb CA-TIMS methods to constrain the age of deformation. F₁ and F₂ folding in the central FFB occurred between 1827 Ma, the age of a pre-F₁ pegmatite, and 1775 Ma, the age of a crosscutting pegmatite. A pre-F₁ pegmatite in the southern FFB is 1746 Ma, suggesting that some major folding occurred after 1746 Ma. In the northeastern FFB, an apparently undeformed 1718 Ma pegmatite/aplite contains an open fold with a quartz-feldspar axial planar cleavage, indicating that the latest folding in the FFB occurred after 1718 Ma. Deformation outlasted ~1.83-1.80 Ga convergence between the Superior Province and the Reindeer Zone of the THO, which is thought to represent the final stages of assembly of Columbia. The late folding in the FFB may be a result of (1) late adjustment as a result of convergence between the Superior Province and the Reindeer Zone, (2) collapse of the central THO resulting in shortening along its margins, (3) a separate unknown event related to convergence between the Rae Province and an unknown terrane that may have existed to the NW.