Structural Controls on Gold Mineralization at the Burnt Timber Mine, Lynn Lake Greenstone Belt, Trans-Hudson Orogen, Manitoba

摘要

The Burnt Timber gold deposit is located in the Paleoproterozoic Lynn Lake greenstone belt of the Trans-Hudson Orogen, Manitoba. The deposit occurs along the Johnson shear zone, and is hosted by enriched and depleted tholeiitic volcanic arc basalts cut by feldspar porphyry dikes. The Johnson shear zone is a regional, belt-parallel structure characterized by the intensification of the regional S₂ foliation. At the Burnt Timber deposit, S₂ is folded by centimeter- to meter-scale, Z-shaped, F₃ chevron folds that have an axial planar S3 crenulation cleavage. Within the 20 to 30 m-wide core zone of the shear zone, S₂ and F₃ are transposed parallel to S₃ and the volcanic rocks are strongly sheared parallel to S₃. The presence of a steeply plunging stretching lineation, together with dextral shear sense indicators along both S₂ and S₃ on horizontal surfaces, suggest that the Johnson shear zone is a dextral transpression zone.