Jesse Halle HBSc thesis abstract

Thesis Title: 
Paleomagnetic Study of the Plateau and Stawson Intrusions of the Quetico Subprovince, Northwestern Ontario

Oriented samples collected from the Plateau Lake Quetico Intrusion (9 km E and 4.5 km S of Atikokan, Ontario) and the Stawson Lake Quetico Intrusion (19 km W and 9 km S of Atikokan) showed NRM vectors in accordance with previously-determined NRM vectors of posttectonic plutons of the Quetico Subprovince.  The strongly anisotropic AMS fabric of oriented samples form the Plateau Quetico Schist country rocks showed strong, east-west magnetic foliation, typical of the study area.  The AMS of the Western sub-area of the Plateau Intrusion revealed an east-west L-fabric resultant from igneous flow concordant with regional structure.  Magnetic fabrics from the Eastern sub-area of Plateau and Stawson are a result of dynamic flow of a 'fluid' magma from the SE (in the direction from their parent, the Quetico Batholithic Complex).

Characteristic remanent magnetism (ChRM) determined from principal component analysis (PCA) of the samples from Plateau East revealed a strong, southwest-directed component of remanence that passed the reversal test.  The ChRM from Plateau West showed little evidence of such geomagnetic reversals.  Despite this evidence, when the site-mean paleopoles from Plateau East and West were plotted on a tentative Precambrian Apparent Polar Wander Path, overlapping confidence ellipses failed to prove significant age differences.  The best age estimation from Plateau West was ~2600 Ma while that at Plateau East is 2550+/-25 Ma.  The limited sampling program at the Stawson Intrusion precluded meaningful age estimations.  In addition, secondary remanences from Plateau East and West were limited in their interpretation.

A first approximation suggests the Ni-,Cu-, and PGE-mineralized core of Plateau may be coeval and comagmatic with its mafic host.  The orientations of L-fabrics of untectonized igneous intrusions reflect the source-direction and may also relate to shape.  As the Stawson Intrusion also hosts economic concentrations of PGE's, it is certain that both concordant and discordant Quetico Intrusions are targets for PGE mineralization.