Geotectonics of the Hanson Lake block, Trans-Hudson orogen, central Canada: a preliminary paleomagnetic report

Abstract

We present paleomagnetic results from the Sahli granite in the Hanson Lake block of the Trans-Hudson orogen. Evidence shows that the Sahli granite magnetization was acquired during a metamorphic event which probably peaked in the interval 1840–1800 Ma. The reset nature of the Sahli granite data is partly supported by a negative contact test from a cross-cutting mafic dyke. The Sahli granite results and those from the 1844±2 Ma Hanson Lake pluton and Jan Lake granite in the Hanson Lake block indicate high paleolatitudes compared with the low paleolatitudes found for the Wathaman batholith and other rocks of the Slave–Rae–Hearne cratons of similar ages to the north-west of the Trans-Hudson orogen. Estimates of the `north–south' width of about 4000 km for the Paleoproterozoic Manikewan ocean between the Archean Hearne and Superior cratons using the Hanson Lake pluton and Wathaman batholith poles, for example, are consistent with previous estimates. The angular difference between the Hanson Lake pluton and Sahli granite poles provides an apparent polar wander segment of the geomagnetic field for the Hanson Lake block to compare with the parallel segment given by the poles for the 1851 Ma Reynard Lake pluton and the 1838 Ma Boot Lake–Phantom Lake pluton for the adjacent Flin Flon domain. Both segments indicate a relative north–north-easterly path direction at an apparent polar wander rate within the range 4.3–0.4° per Ma, assuming no large-scale regional tilts of the plutons. The offset between the two apparent polar wander path segments indicates either an `east–west' component of closure of about 1000 km for the Manikewan ocean or vertical-axis counter-clockwise rotation of units within the Trans-Hudson orogen with respect to the Superior craton plus a possible north–south relative translation between the Hanson Lake block and Flin Flon domain.