| dc.description.abstract | This thesis presents a detailed investigation of the geology, geochemistry, and
geochronology of the Archean Shebandowan Greenstone Belt (SGB) in the vicinity of the Moss
Lake gold deposit in Northwestern Ontario. The Moss Lake property is located in the western part
of the SGB and consists primarily of rocks belonging to the Greenwater and Burchell assemblages.
The study characterizes the geological attributes, tectonic setting, and timing of magmatism within
the belt and provides regional context for ongoing mineral exploration.
The research involved extensive fieldwork, including detailed lithological descriptions and
structural analysis, supported by petrographic analysis of thin sections. Whole-rock geochemical
analysis was performed on 56 samples to classify rock types, determine magmatic affinities, and
evaluate element mobility, revealing distinct geochemical signatures between the Greenwater and
Burchell assemblages and various intrusive bodies.
The Greenwater assemblage mafic rocks exhibit tholeiitic affinities with flat HREE,
enriched LREE, and negative Nb anomalies. The Burchell assemblage mafic rocks are calcalkaline,
with moderately enriched LREE, flat HREE, and negative Nb-Ti anomalies. Similarly,
the felsic and intermediate metavolcanic rocks show distinct geochemical signatures between
assemblages. Greenwater rocks are more enriched in LREE and display stronger negative Ti
anomalies compared to the less enriched LREE and weaker Ti anomalies observed in Burchell
rocks.
U-Pb zircon geochronology on four key samples yielded new ages: 2716.0 ± 0.45 Ma for
the Moss Lake syenogranite stock, 2718.34 ± 0.14 Ma for the Obadinaw quartz syenite stock,
2711.80 ± 0.14 Ma for an intermediate metavolcanic rock, and 2707.35 ± 0.14 Ma for the Greenwater Lake quartz monzonite stock. These ages complement and refine the existing
geochronological framework of the SGB.
Neodymium isotope analysis of thirteen samples provided insights into the mantle source
and crustal contamination processes. The Greenwater assemblage exhibits consistently positive
εNd(t) values in both mafic and felsic-intermediate rocks (+1.6 to +2.7), indicating a dominantly
juvenile mantle source with limited crustal involvement. In contrast, the Burchell assemblage
shows a broader εNd(t) range (+0.01 to +3.2), suggesting a more heterogeneous source and greater
influence from crustal assimilation, despite an overall juvenile magmatic character.
The integration of geological, geochemical, and geochronological data supports models of
a complex Neoarchean tectonic evolution involving distinct magmatic pulses and settings for the
Greenwater and Burchell assemblages. Geochemical evidence suggested the Greenwater
assemblage originated from an oceanic plateau evolving to a primitive arc, whereas the Burchell
assemblage formed in a primitive arc environment. Intrusive bodies were classified as tonalite
trondjhemite granodiorite, sanukitoids, and Archean hybrid granites, reflecting diverse sources and
conditions of formation. The results confirm independent magmatic histories for the two
assemblages and highlight a protracted crustal evolution involving juvenile mantle input and
crustal assimilation. | en_US |
