Abstract

The rift-related Rapitan Group of the Mackenzie Mountains of northwestern Canada acquired several magnetizations due to pulses of hydrothermal activity. The first pulse, attributed to initiation of Rapitan rifting, produced a widespread overprint (P2) that may be reflected in the basal Mount Berg Formation. Two later pulses produced overprints similar to components found in an earlier study. Development of iron formation and hematite pigment in the overlying Sayunei Formation is attributed to the second pulse, represented by a paleopole (N = 10 sites; 334°E, 01°S; δp, δm = 4°, 9°) that coincides with poles of the Franklin igneous events of northern Canada. The Franklin episode, suggested on geological grounds to be coeval with Sayunei deposition, dates the Sayunei at ca. 725 Ma. This relation implies that rifting in Mackenzie Mountains could be related to rifting in northern Canada. A third pulse, reflected by a pole at 007°E, 16°N (N = 6 sites; δp, δm = 6°, 12°), is attributed to final rifting during deposition of the Shezal Formation at the top of the Rapitan. Overprints attributed to Sayunei and Shezal times indicate regional latitudes of 6 ± 4° and 4 ± 6° during the Sturtian glaciation. During Mount Berg time, the regional latitude could have exceeded 25°. All directions have been tilt corrected and some have been then rotated, based on comparisons with a P2 reference overprint.

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