Ben Ellis

B.Sc. (Honours) Thesis

GEOCHRONOLOGY OF THE CHICOUTIMI GNEISS BELT, ST. FULGENCE, QUEBEC

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The Grenvillian Orogeny was a drawn-out mountain building event occurring in the Mesoproterozoic Era induced by the formation of the supercontinent Rodinia. This event produced several distinguishable waves of metamorphism preserved throughout the Grenville Province. Although a significant portion of the Grenville province located in North America has been precisely dated, the Chicoutimi Gneiss Belt within the St. Fulgence region of Quebec is one region in which precise metamorphic dates have not been obtained. The aim of this project is to use the well-known Monazite dating method, in order to discover the metamorphic age(s) that are preserved in this particular suite of rocks. In the study, the monazite grains selected are analysed in situ, to allow for easier interpretation of their relationship to the metamorphic fabric seen throughout the terranes. Samples from the Cap a l’Est Gneiss Complex are also examined in this study. Metamorphic age peaks at 1060 ± 7.3 Ma and ~1145Ma ± 16 Ma were found in the Chicoutimi Gneiss samples, and age peaks of 969 ± 13 Ma and 1029.1 ± 8 Ma were found for the Cap a l’Est Gneiss samples. These metamorphic ages obtained are consistent with the ages of the orogenic events occurring in the area, as well as the plutonism, and show that there are several pulses of metamorphism preserved in these rocks, along with relict ages of the basement rock and xenocrysts.

Keywords: Grenville, Gneiss, Monazite, U-Th-Pb Dating, Electron Microprobe
Pages: 72
Supervisor: Richard Cox