Abstract

Paleomagnetic poles from the Upper Proterozoic Mackenzie Mountains supergroup (MMs) of northwestern Canada define an apparent polar wander path lying to the west of the Grenville Loop. This path is suggested from an analysis of the quartzitic Katherine Group, whose probable primary pole lies at the beginning of the sequence, near the younger end of the Grenville Track (0.88 Ga). The end of the apparent polar wander (APW) sequence may be defined by a primary pole from sills intruding the Tsezotene Formation below the Katherine. We relate the sills, dated at about 0.77 Ga, to the rifting event that led to "Copper cycle" and Rapitan sediments above the MMs, and we suggest that the exposed part of the MMs has an age between 0.88 and 0.77 Ga. The APW path is apparently not affected by rotations: pole evidence indicates little if any relative rotation between thrust sheets of the fold belt or between the fold belt and the craton.Paleomagnetic analysis of the Katherine Group data, obtained by alternating field, thermal, and chemical methods, revealed three magnetizations. The probable primary remanence, KA, carried by mainly detrital hematite grains, has a direction of D, I = 267°, +21 °(N = 13 specimens, k = 33, α95 = 7°) and a pole at 9°N, 210°W (δp, δm = 4°, 8°). A secondary component, KB, carried by hematite pigment, has a direction of D, I = 258°, +42 °(N = 4 sites, k = 326, α95 = 5°) and a pole at 17°N, 196°W (δp, δm = 4°, 6°). It documents further a pervasive overprint magnetization found in most MMs rocks. A similar hematite magnetization is probably primary in the overlying Copper cycle rocks. The youngest component, KC, is found partly in a second, probably largely post-folding pigment phase (post-Late Cretaceous or Paleocene) and has a direction of D, I = 007°, +84 °(N = 9 sites, k = 77, α95 = 6°) and a pole at 77°N, 122°W (δp, δm = 11°, 12°).

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