Abstract:
The Rankin Inlet area, on the west shore of Hudson Bay
in the Northwest Territories, is in the Churchill Structural
Province. Metamorphosed volcanic and sedimentary rocks,
previously mapped as Archean and part of the Kaminak Group,
underlie most of the area. The Rankin Inlet Group consists
of greywacke, with minor conglomeratic greywacke, quartzite
and dolomite, overlain by massive and pillowed basaltic flows.
Gabbro sills intrude the sediments near the base of the volcanic
sequence and three serpentinite sills outcrop at the base of
the volcanic sequence. The sediments are in fault-contact with
quartz monzonite to the south and were intruded by granitic
rocks to the northwest. Two periods of folding were defined by
the mapping. The first generation folds are recumbent isoclinal
folds, with northwest-trending and northeast-dipping axial
planes, formed through gravitational sliding. The second
generation folds are symmetrically disposed about the axis of
the granitic intrusion and have east-southeast trending and
nearly vertical axial planes. Whole-rock analysis of 64 rock
samples indicates that metasomatic alteration accompanied the
intrusion of both the granitic rocks and the serpentinite. The
volcanic rocks, gabbro and serpentinite were derived from a
magma of oceanic tholeiitic affinities. The stratigraphic
sequence and chemistry of the volcanic rocks of the Rankin Inlet
Group indicate that this assemblage is correlative with the
Hurwitz Group rather than the Kaminak Group and is therefore
Aphebian in age.
