The Quetico subprovince; which consists of metasedimentary rocks, gneisses, and migmatites, is a east-to-west trending linear belt in the Superior Province of the Canadian Shield. This subprovince has been subjected to extensive periods of metamorphism and deformation throughout its evolution. Hosted within this subprovince are a number of igneous intrusions that are granitic to quartz monzonitic in composition, and show little evidence of a complex geological history. Emplacement of these plutons have resulted in the development of contact metamorphic aureoles in the regionally metamorphosed host country rock. The objective of this study was to find evidence of such an aureole in the host rock, and to describe the mineralogical and textural features that are commonly developed in this type of aureole.
The study area under consideration is located northwest of Thunder Bay, Ontario. In this area, a late-stage pluton, the Barnum Lake pluton is hosted in metagreywackes. A series of samples were taken and studied for evidence of contact metamorphic overprinting. These studies revealed features characteristic of contact metamorphic aureoles, such as the presence of hornfelsic texture and the growth of second generations of minerals such as biotite. Mineral assemblages found in the host rock, were consistent with those described in the literature as typical of contact metamorphic aureoles.
Oriented samples were also taken directly from the Barnum Lake pluton, and were the object of anisotropy of magnetic susceptibility studies. AMS studies revealed that the pluton was emplaced, and that the emplacement of the pluton was responsible for the contact metamorphic features observable in the host rocks of the Quetico subprovince.