Placer deposits occur in unusual geological settings in the Mayo Mining District, where gold is mined from Reid-age glacial till and glaciofluvial gravel and from more recent (McConnell and post-McConnell-age) alluvial fans and fan-deltas. In other districts these types of deposits are not generally explored or prospected for placers. In the Mayo area, placer deposits are best preserved near the maximum limit of glacial ice where ice-scouring is minimal and depositional processes dominate. Pre-existing alluvial gold deposits were likely buried in this region where the ice limits of the Reid and McConnell glaciations exist in close proximity.
Initial studies of the geomorphology of the region's known placer deposits show that they occur in three main types of landforms of different ages. Alluvial fans and fan-deltas contain placer deposits that are McConnell and younger in age while valley-bottomplacers are likely interglacial, glacial or glaciofluvial deposits of Reid age or older. A number of drainages have not been extensively explored or prospected; however, given similarities with known placer occurrences in the area, the potential for discovery of new placer deposits is good for many sites in the Mayo map area.
