REGIONAL PALEOMAGNETIC STUDY OF ARCHEAN ROCKS FROM THE SUPERIOR GEOTRAVERSE AREA, NORTHWESTERN ONTARIO

Preliminary paleomagnetic data are reported for Archean metavolcanics, felsic and mafic intrusives, gneisses, and iron formations from the Quetico, Shebandowan, and Wabigoon belts in the western Superior Structural Province. Eleven of the 23 formations sampled have been studied in detail using stepwise alternating- field demagnetization and, in some cases, thermal demagnetization. Two characteristic components of magnetization are revealed. One is widespread in occurrence and reasonably well grouped. The metamorphism seems to have occurred too early to have been caused by igneous activity ca. 1100 Ma in the nearby Keweenawan basin. About - 2600 Ma, the region was in its present orientation, but at a latitude of 20 to 35oN and probably drifting northward. About - 1250 Ma, the region was equatorial but rotated 90o, so that presently E-W trending greenstone belts were N-S. It is possible, but unproven, that a paleoocean existed between the Wabigoon subprovince and the other belts about - 1250 Ma, the Wabigoon region having since moved more than 500 km westward (present-day direction) to its present location.-Author