Structural geology of a Sickle outlier near Notigi Lake, Manitoba

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Ziehlke, Daniel V.
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The area of study is located thirty-five miles northwest of Nelson House, Manitoba, and is underlain by a meta-arkose to diatexite gneiss outlier, of Sickle-type rocks, approximately 25 square miles in area. The Sickle rocks differ considerably from the underlying Wasekwan-type gneisses which constitute the predominant rock type around the Sickle outlier. The deformational history of the outlier is based on ground attitude measurements backed up by detailed air-photo interpretation, and interpreted stratigraphy. The rocks have undergone at least three, and probably four, folding events, plus two periods of brittle deformation: folding of original sediments into isoclinal folds (f1); weak open folds developed perpendicular to f1 axial planes (f2); refolding of f1 and f2 axial planes by f3 isoclinal folding; refolding of f1, f2 and f3 axial planes about a north-south axial plane (f4) to produce the present configuration of the Sickle outlier. Extensive amphibolite grade metamorphism accompanied f3 folding, resulting in partial anatexis and flow in less competent layers. Late brittle deformation consisted of early jointing (D5), along which pegmatite later intruded. This was followed by a period of jointing (D6). Two periods of post-f4 faulting occurred with the earlier northeast striking faults offset by a north-south striking late period of faults.