Precious metal mineralization related to the Falcon Lake Intrusive Complex, southeastern Manitoba

Abstract

The Falcon Lake Intrusive Complex (FLIC) is a composite pluton located in the Lake of the Woods greenstone belt of the Western Wabigoon Subprovince. Gold occurrences in the area are concentrated within the complex, itself, and in the country rock bordering the pluton to the north. Relationships between host rocks, structure, alteration, and mineralization suggest that the occurrences in the study area were formed during at least two mineralizing events. An early, pre-FLIC event localized low grade gold in zones of deformation in the country rocks. The intrusion of a diorite phase of the complex served to generate new structures, and remobilize and concentrate the gold precipitated during the early event. A later mineralization event giving rise to the interior occurrences is related to the final consolidation of quartz monzonite. Late stage magmatism coincident with tectonism produced structural traps such as breccia pipes, and may have been the source for the gold bearing fluids. FLIC had multiple roles in the development of the occurrences in the study area: as a host, the generation of structures during emplacement and consolidation, the initiation of orthomagmatic and convective hydrothermal systems, and as a source of mineralization. The interior occurrences can be considered as porphyry deposits in most aspects, except size. These occurrences may represent a small scale, gold dominated analogue of plutonic-type porphyry deposits.