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

The paleomagnetism of a saprolitic paleosol developed on Archean granite an d of an overlying hematitic breccia in the basal Lorrain Formation of the C obalt Group (Huronian Supergroup, similar to 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 t he breccia, whose hematite may be a product of weathering prior to or short ly after deposition, yielded useable results with stepwise thermal demagnet ization. A stable component A (maximum unblocking temperature, T-ub, of sim ilar to 675 degrees C) carried by hematite is directed shallowly to the eas t-northeast (D = 59.5 degrees, I = 2.4 degrees, alpha(95) = 6.7 degrees, n = 47, dip-corrected), and a less stable component B (maximum T-ub of simila r to 580 degrees C) carried by magnetite is directed steeply down to the no rtheast (D = 52.1 degrees, I = 70.3 degrees, alpha(95) = 2.8 degrees n = 75 , dip-corrected). Component A is ascribed to a chemical remanent magnetizat ion (CRM) acquired when the hematitic breccia was deposited or soon thereaf ter. Component B is interpreted as a thermochemical overprint related to th e Penokean Orogeny at 1.9-1.8 Ga. Dip-corrected specimen mean directions gi ve the pole positions at latitude = 57.1 degrees N, longitude = 338.3 degre es E (dp = 4.1 degrees, dm = 4.8 degrees) for component B, and latitude = 2 1.1 degrees S, longitude = 213.1 degrees E (dp = 3.3 degrees, dm = 6.7 degr ees) for component A. The more easterly directions for components A and B r elative to comparable early and overprint components previously determined for the Lorrain and Gowganda formations at Elliot Lake and Desbarats 260-36 0 km southwest of ViIle-Marie imply relative rotation of similar to 30 degr ees or more about a vertical axis within the Southern Province since the Pe nokean Orogeny. The results suggest that the hematitic breccia and the Vill e-Marie paleosol formed at a paleolatitude of 1.2 degrees +/- 3.4 degrees, in accord with our earlier inference of equatorial paleolatitudes for the L orrain and Gowganda formations and Huronian glaciation. Paleomagnetic data from several continents suggest that fermginous weathering horizons formed over a wide range of paleolatitudes in the Proterozoic. (C) 1999 Elsevier S cience B.V. All rights reserved.