| dc.description.abstract | The Archean komatiites of the Lake of the Woods greenstone belt, Kenora, Ontario
formed on the western extension of the Superior Province southern margin and have not
been studied using modern analytical methods. Although Archean plate tectonic processes
have been the subject of decades of research, the nature of these processes remains the
subject of considerable debate. Recent work has investigated the link between komatiites
and Archean subduction zones. Komatiites are widespread in Archean terranes and together
with spatially associated tholeiitic basalts form an important part of many Late Archean
greenstone belts, therefore a better understanding of Archean geodynamic processes and
comparison to modern day processes is required.
Detailed mapping in the Upper Keewatin Assemblage identified komatiites on the
southern margin of the Long Bay Group. The komatiites are typically metamorphosed to
upper greenschist facies and include a variety of schists that do not show any preserved
primary textures or mineralogy. Polyhedrally jointed flow tops were observed in rare
locations. Mineral assemblages include dominantly anthophyllite-tremolite-chlorite and
serpentine-tremolite-chlorite schists, as well as lesser talc-tremolite-chlorite schists. These
units are moderately to intensely foliated with chlorite and lesser amphibole defining the
foliation and also include randomly oriented bladed amphibole grains that typically have
tremolite cores and anthophyllite rims. The amphiboles show a chemical transition from
core to rim with a loss in Ca as anthophyllite appears. Accessory phases include chromite,
magnetite, ilmenite and apatite. Ultramafic rocks are very fine-grained and mineralogy has
been described using a compilation of petrography, x-ray diffraction and scanning electron
microscope analysis. [...] | en_US |
