Abstract

The Otto Stock consists mainly of syenite. Except for some mafic phases the syenites are magnetically unstable, but late-stage lamprophyre dikes and basic rocks in the contact aureole contain abundant stable material. Their mean direction of magnetization is 330°, +71 °(18 sites, 84 samples, α95 = 3°) with a corresponding pole at 69°N, 133°W (A95 = 5°). A subordinate later magnetization also occurs in three lamprophyre dikes. Using these and previous results a path of apparent polar wander for Laurentia for the interval 2200 to 1800 m.y. of simple form is constructed. The fact that a single simple polar path can be constructed, which is consistent with data from localities spread widely over the Laurentian Shield, indicates that the Hudsoni orogeny may not have been accompanied by very large relative motions of the bordering Archean cratons.

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