Paleomagnetism of the Paleoproterozoic hematitic breccia and paleosol at Ville-Marie, Québec: further evidence for the low paleolatitude of Huronian glaciation

The paleomagnetism of a saprolitic paleosol developed on Archean granite and of an overlying hematitic breccia in the basal Lorrain Formation of the Cobalt Group (Huronian Supergroup, ∼2.4–2.3 Ga) near Ville-Marie, Quebec, has been investigated to further constrain the paleolatitude of the Lorrain Formation and the subjacent glaciogenic Gowganda Formation. Only the breccia, whose hematite may be a product of weathering prior to or shortly after deposition, yielded useable results with stepwise thermal demagnetization. A stable component A (maximum unblocking temperature, T ub , of ∼675°C) carried by hematite is directed shallowly to the east-northeast ( D =59.5°, I =2.4°, α 95 =6.7°, n =47, dip-corrected), and a less stable component B (maximum T ub of ∼580°C) carried by magnetite is directed steeply down to the northeast ( D =52.1°, I =70.3°, α 95 =2.8°, n =75, dip-corrected). Component A is ascribed to a chemical remanent magnetization (CRM) acquired when the hematitic breccia was deposited or soon thereafter. Component B is interpreted as a thermochemical overprint related to the Penokean Orogeny at 1.9–1.8 Ga. Dip-corrected specimen mean directions give the pole positions at latitude = 57.1°N, longitude = 338.3°E (dp = 4.1°, dm = 4.8°) for component B, and latitude = 21.1°S, longitude = 213.1°E (dp = 3.3°, dm = 6.7°) for component A. The more easterly directions for components A and B relative to comparable early and overprint components previously determined for the Lorrain and Gowganda formations at Elliot Lake and Desbarats 260–360 km southwest of Ville-Marie imply relative rotation of ∼30° or more about a vertical axis within the Southern Province since the Penokean Orogeny. The results suggest that the hematitic breccia and the Ville-Marie paleosol formed at a paleolatitude of 1.2°±3.4°, in accord with our earlier inference of equatorial paleolatitudes for the Lorrain and Gowganda formations and Huronian glaciation. Paleomagnetic data from several continents suggest that ferruginous weathering horizons formed over a wide range of paleolatitudes in the Proterozoic.