Glacial dispersal of indicator minerals from the Brazil Lake lithium–caesium–tantalum pegmatites, SW Nova Scotia, Canada

The Brazil Lake lithium-caesium-tantalum (LCT)-type pegmatites (North, South and Army Road pegmatites) in eastern Canada, were the focus of a detailed till study to document glacial dispersal of LCT pegmatite indicator minerals from bedrock. A total of 84 bulk (7–20 kg) till samples were collected from 77 sites around and down-ice of the three pegmatites. The <2.0 mm fraction of the till samples was processed using shaking table and heavy liquid methods to produce 2.8–3.2 and >3.2 specific gravity (SG) non-ferromagnetic heavy mineral concentrates for visual identification and counting of indicator minerals in the 0.25–0.5, 0.5–1.0 and 1–2 mm fractions. Glacial dispersal from the pegmatites is best defined by spodumene (the primary ore mineral) in the 0.25–0.5 mm fraction of the 2.8–3.2 SG concentrates, and its presence in the till (hundreds to thousands of grains per sample) is visual confirmation of the existence of nearby LCT pegmatites. Glacial dispersal of spodumene forms a fan-shaped exploration target 12 km down-ice that is considerably larger than the pegmatite subcrop areas. Other useful LCT pegmatite indicator minerals in the local till include apatite and tourmaline (tens to hundreds of grains) and lesser amounts of columbite–tantalite, cassiterite and scheelite (single units to tens of grains), however, their abundances and spatial distributions are much less/smaller than that for spodumene. The results clearly demonstrate that indicator mineral methods are useful for lithium exploration in the glaciated terrains of SW Nova Scotia, across Canada and other prospective glaciated terrains globally.