Janek Urbanksi, MSc

The Troilus deposit is hosted in the eastern Frotet-Troilus segment of the Frotet-Evans Greenstone Belt, part of the Opatica Subprovince of the Superior Province of Canada. Located approximately 120km north of the town of Chibougamau, Quebec, the deposit produced gold and copper as an open pit mining operation between 1996 and 2010. New ownership and revived exploration efforts led by Troilus Gold Corp, since 2018 has led to resource growth of over 12 Moz AuEq between 4 main mineralized zones. While the deposit is understood to be structurally controlled, observed structural features question the current deformation sequence for the deposit and the genesis and evolution of these features is poorly understood.

This research employs a traditional structural geology field mapping approach which integrates detailed structural analysis at regional, outcrop, and microscopic scales to establish a comprehensive structural framework. Through the integration of geometric and kinematic analysis of features observed at multiple scales, the geological history and structurally controlled nature of the Troilus deposit can be better constrained.

Field mapping has shown that the Troilus deposit is hosted within a broad mylonite zone characterized by a dominant WSW-ESE striking transposition foliation (S₁) which is the earliest recognizable fabric in the study area and defines a major regional lineament. This mylonite zone is interpreted to have formed during regional dextral transpression and overprints an earlier mineralizing event, leading to reworking and zone refining. Features indicating a post-mineralization tectonic overprint include stretched semi-massive sulphide clasts and lenses within mylonites, and aggregate lineations of sulphide minerals on foliation surfaces in pit walls and around the deposit which control high grade ore shoots. Post-mylonite kinking, crenulations, shear zones, and veins are observed in the vicinity of the deposit.

Rocks are dominantly S-tectonites with poorly developed mineral lineations except in the vicinity of the deposit where lineations are more recognizable and are approximately down-dip. Mineral lineations shallow to approximately sub-horizontal away from the deposit towards the northeast. Similar metamorphic grades of upper greenschist to lower amphibolite are observed across the deposit and suggest a dominant horizontal shortening component. Shear sense indicators include asymmetric porphyroclasts, flanking folds and S/C fabrics on horizontal surfaces which are consistent with a dextral sense. Shear sense determinations from quartz LPO are currently ongoing.