Timmothy Lemmetty HBSc thesis abstract

Thesis Title: 
Paleomagnetism and magnetic fabrics of late Archean lamprophyres, Shebandowan, northwestern Ontario

Late Archean lamprophyre dikes are common throughout the Superior Province of the Canadian Shield, and are associated with the late stages of Archean deformation in the Canadian Shield.  Accurate age constraints on the timing of this late metamorphism would benefit both the economic and the academic fields of study in this area.  Limited geochronology suggests an approximate age of 2696"2Ma (Corfu and Stott, 1986), for the shoshonitic volcanism in the Superior Province.

Oriented samples taken from dikes outcropping between Thunder Bay and Atikokan were used to make 60 oriented core samples.  These samples underwent anisotropy of magnetic susceptibility measurements (AMS) to determine the origin of the internal fabric and define the cryptic metamorphic fabric.

Subsequently, the samples underwent low temperature demagnetization (LTD), to minimize domain-wall effects on the remnant magnetism contained within each sample.  The samples were then treated to ten steps of thermal demagnetization (100°C - 550°C) with the remnant magnetization measured between each step.  The data acquired from the thermal demagnetization was examined and A-and B-components of magnetization were isolated by Principal Component Analysis (PCA).  The principle components of magnetization were then used to determine the paleopole positions on a geographical map and compared with the best known apparent polar wander paths (APWP) for the Archean and the Proterozoic.  From this, the ages of magnetization may be estimated as 2500 Ma for the A-component and 2400-2300 Ma for the B-component.