Volcanic Stratigraphy and Lithogeochemistry of the Northern Section of the Lynn Lake Greenstone Belt: Implications for Regional Geodynamics and Metallogenesis

The MacLellan Au-Ag deposit, located in the Paleoproterozoic Lynn Lake greenstone belt of the Trans-Hudson Orogen, Manitoba, is hosted by a package of plagioclase-amphibole, chlorite-amphibole, and quartz-plagioclase-biotite schists that are considered to be representative of the geodynamic evolution of the northern section of the Lynn Lake greenstone belt. A combination of field and petrographic observations and high-precision trace element chemistry have identified the protoliths to the host rock sequence as transitional aluminous basalt with subordinate picrite and biotite-altered aluminous basalt, respectively. The Th-Nb-La-REE systematics of these rocks are consistent with a rifted continental margin environment. Volcanic rocks with similar Th-Nb-La-REE systematics to those from the MacLellan host rock sequence have been identified throughout the Lynn Lake region. Therefore, it is proposed that the Lynn Lake greenstone belt represents a rifted continental margin and based on this revised geodynamic model, the mineral potential of the belt should be reassessed.