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The Archean Winter Lake greenstone belt (WGB) in the Slave craton, located ~250 km northeast of Yellowknife in the Northwest Territories, has been underexplored relative to other supracrustal belts in the Slave craton, but shows potential for base-metal mineralization. It consists of lower greenschist to upper amphibolite grade mafic to felsic volcanic rocks and sedimentary rocks that are surrounded by ca. 3.3 to 2.9 Ga granitoids of the Central Slave Basement Complex (CSBC). The overall objective of this study is to better understand the origin and geodynamic evolution of the WGB and to evaluate its economic potential. The project will examine the tectonic setting of volcanic and sedimentary rocks of the WGB and their relationships to the CSBC granitoids. In 2019, three weeks were spent bedrock mapping near Newbigging Lake and one week near Big Bear Lake (at 1:5,000 and 1:10,000 scales, respectively) to generate a lithostratigraphic scheme for the southern WGB. This mapping evaluated the nature of contacts, previously interpreted as unconformities, between the CSBC, the ca. 2734-2924 Ma Central Slave Cover Group (CSCG) volcanic and sedimentary rocks, and post-volcanic sedimentary and granitoid rocks (Hrabi et al., 1995). Mapping near Big Bear Lake also allowed the examination of a previously mapped ~ 1.3-1.7 km wide rhyolite interpreted to be part of the ca. 3.3 Ga Newbigging Formation (Hrabi et al., 1995). Based on field observations, the formation does not include a rhyolite sensu stricto but rather a succession of weathered mafic to intermediate volcanic and intrusive rocks. This field season, the first of three, also led to the discovery of several semi-massive to massive sulfide showings within the mafic volcanic sequence, and the identification of sulfides (interpreted as remobilised) and multiple younging indicators within the younger conglomerate unit that are necessary for our lithostratigraphy study. Future U-Pb geochronological analysis of detrital zircon and Sm-Nd isotope geochemistry of metasedimentary rocks will enable us to determine their sources and age. Together with absolute timing of thermotectonic events, an Archean oceanic and continental crust geodynamic evolution model will be produced.  An additional goal of this study is to identify the ore-forming environment for the sulfide mineralization and to generate an ore-deposit model for the mineralisation observed in the WGB. References:Hrabi, H.B., Nelson, M.D., and Helmstaedt, H., 1995: Diverse metavolcanic sequences and late polymictic conglomerate-associated metasedimentary rocks in the Winter Lake supracrustal belt, Slave Province, Northwest Territories; in Current research 1995-E; Geological Survey of Canada, p. 137-148.

Neoarchean volcanic rocks of the Beaulieu River volcanic belt structurally overlie basement rocks of the Sleepy Dragon Complex (ca. 2.85 Ga), approximately 100 km east northeast of Yellowknife. The volcanic belt is comprised of complex lithofacies, including basalt, andesite, rhyolite, and associated volcaniclastic rocks, and hosts the Sunrise volcanogenic massive sulfide deposit. The absolute age of the volcanic strata is not known, nor is the stratigraphy well-defined; therefore, the Beaulieu River volcanic belt cannot be easily correlated to other greenstone belts within the Slave craton. The main objective of this study is to document the litho- and chemo-stratigraphy of the volcanic rocks, and particularly the rhyolite dome, located at the south end  of Sunset Lake to reconstruct their volcanic and petrogenetic evolution, and determine their relationship to the volcanic strata that hosts the Sunrise VMS deposit, located ~6km to the north of the study area. Detailed mapping (1:2000) was completed over two field seasons (2018 and 2019) and shows that the volcanic rocks in the south Sunset Lake area comprise a complex stratigraphy consisting of basaltic, andesitic and rhyolitic lithofacies. This includes massive to pillow basalt and andesite, with lesser amounts of massive to in-situ brecciated, weakly quartz-plagioclase porphyritic rhyolite, heterolithic tuff to lapilli- tuff and felsic tuff to tuff breccia. The felsic clasts within the felsic volcaniclastic rocks are similar in composition to the coherent rhyolite. Units have a trace element geochemical signatures that vary from tholeiitic to calc-alkaline, arc-like rocks. Volumetrically, the volcanic strata in the south Sunset Lake area has a significant amount of volcaniclastic rocks, ranging from tuff to tuff breccia units. The volcaniclastic rocks are interpreted to have been deposited by a series of debris flows and eruption-fed density currents. The stratigraphy of the volcanic rocks in south Sunset Lake is very similar to that of the stratigraphy that hosts the Sunrise VMS deposit. Evidence of a vent proximal environment (e.g. rhyolite dome, peperite, syn-volcanic intrusions) and porous, volcanic debris accumulating on the seafloor highlight conditions favourable for volcanogenic massive sulfide-type mineralization in the south Sunset Lake area.