Accretion history of the Trans-Hudson Orogen in Manitoba and Saskatchewan from paleomagnetism

Lithoprobe's sponsorship has led to the acquisition of paleomagnetic data from approximately 20 units throughout the Paleoproterozoic Trans-Hudson Orogen (THO) of Saskatchewan and Manitoba, essentially the first such data for the region. Discussed summarily in this paper, they provide an initial framework for the THO's tectonic evolution. They show that the Archean Hearne and Superior cratons were at subtropical and subpolar paleolatitudes, respectively, at approximately 1875 Ma, with the Lynn Lake-LaRonge arc midway between them in the Manikewan Ocean. By approximately 1855 Ma, this ocean was still approximately 5500+ or -700 km wide, and its seafloor was subducting northwestward under the Hearne craton and pericratonic Peter Lake domain margin with the coeval development of an Andean-type continental magmatic arc, the Wathaman-Chipewyan batholith. Between approximately 1855 and approximately 1810 Ma, coalescing apparent polar wander path (APWP) segments record closing of the ocean at a rate of approximately 12 cm/a, trapping and accreting the several separate intervening terranes (Flin Flon, Hanson Lake, Lynn Lake-La Ronge, Rottenstone, and presumably also other THO terranes). From approximately 1815 to approximately 1775 Ma, the assembled terranes drifted as a coherent craton, yielding a stillstand and hairpin in the APWP.