Date of Award
1996
Degree Type
Dissertation
Degree Name
Doctor of Philosophy
Abstract
This thesis is divided into two major parts: paleomagnetism of the Hanson Lake block of the Trans-Hudson orogen and paleomagnetism of Paleozoic and Mesozoic strata from Stikinia of the western Canadian Cordillera.;Paleomagnetic results from a total of 71 sites are presented from the Hanson Lake pluton (HP), the Sahli granite (SG) and the Jan Lake granite (JG) in the Hanson Lake block. Whereas the HP magnetization is inferred to be primary and it is estimated to be about 1844 Ma old by U-Pb zircon methods, evidence shows that the SG magnetization was acquired during a metamorphic event which probably peaked in the interval 1831-1805 Ma. The reset nature of the SG data is partly supported by a negative contact test from a cross-cutting diabase dyke. The JG apparently records two components of magnetization with one probably being older than 1844 Ma and the other being about 1770 Ma, the age of massive Jan Lake granite pegmatites. All these Hanson Lake block data provide high paleolatitudes. In contrast previous paleomagnetic studies of equivalent rocks of the Wathaman batholith (WB) and of the Slave-Kae-Hearne cratons to the northwest of the Trans-Hudson orogen suture yield low paleolatitudes. Estimates of the "north-south" width of about 4000 km for the Paleoproterozoic Manikewan ocean using the HP and WB poles, for example, are consistent with previous estimates by other workers. The angular difference between the HP and SG poles suggests apparent polar wander (APW) of the geomagnetic field, especially when compared with the angular difference between the poles for the 1851 Ma Reynard Lake pluton (RE) and the 1838 Ma Boot Lake-Phantom Lake pluton (BP) in the adjacent Flin Flon domain. The offset between the HP-SG APW path and the RE-BP APW path indicate either an "east-west" component of closure of about 1000 km for the Manikewan ocean or vertical-axis counterclockwise rotation of units within the Reindeer zone with respect to the Superior craton plus a possible "north-south" relative translation between the Hanson Lake block and Flin Flon domain.;In the Iskut River area of Stikinia, the Paleozoic Stikine assemblage and Mesozoic volcanic rocks, volcaniclastics and minor limestone each provide characteristic remanence magnetization (ChRM) with very low intensities and generally poor within-site precision. This is due to low grade metamorphism as evidenced by replacement of primary minerals with secondary equivalents. Data from the Paleozoic strata provide two dominant modes one of which has a steep downward direction and is likely a Cretaceous remagnetization. The other has a direction that is generally southwest and moderately upward inclined and is interpreted to have resulted from a Norian to Toarcian contraction/thermal event. This implies that the Paleozoic rocks were to the south of their present location by between 6{dollar}\sp\circ{dollar} and 15{dollar}\sp\circ{dollar} at the time of remagnetization and have been rotated about a vertical axis by more than 90{dollar}\sp\circ{dollar} since then. The paleomagnetic signature from the Mesozoic strata is less clear. The ChRM directions have inclinations that span the range of inclination for the Triassic to Cretaceous expected directions for the Iskut River area calculated from the North America reference pole.
Recommended Citation
Gala, Monday Gang, "Paleomagnetism And Geotectonic Implications Of Terrane History Within The Trans-hudson Orogen And The Western Canadian Cordillera" (1996). Digitized Theses. 2695.
https://ir.lib.uwo.ca/digitizedtheses/2695