Critical Resources (ASX:CRR) has identified granitic-hosted pegmatites in the northern corridor of its Mavis Lake Project in Ontario, Canada, as priorities for follow-up lithium exploration.
Critical Resources reports whole-rock geochemistry returned potassium-to-rubidium ratios as low as 17.4, alongside elevated lithium pathfinder elements, from pegmatites around 4km north of the project’s existing mineral resource estimate (MRE).
The most fractionated sample returned 5,510 parts per million (ppm) rubidium (Rb), 221ppm caesium (Cs), and 22.9ppm tantalum (Ta). Other samples returned potassium-to-rubidium ratios below 40, more than 2,000ppm Rb, and up to 53ppm Ta.
Critical Resources says the results are consistent with highly evolved lithium-caesium-tantalum (LCT) pegmatite systems and will help direct further exploration. However, lithium oxide values were low across all samples, and the company says drilling will be required to confirm lithium mineralisation.
The 10-day field program collected 106 rock samples across the surveyed area, including from 14 pegmatite bodies, six of which were newly identified. Critical Resources also mapped 161 outcrops and collected 74 structural measurements.
The company says the strongest fractionation signatures occurred within the Northern prospects claim package acquired in August 2025. Pegmatites sampled at the Corona field generally returned higher potassium-to-rubidium ratios and lower enrichment in pathfinder elements, indicating less magmatic fractionation.
Managing Director Tim Wither says the results have refined the company’s exploration focus towards granitic-hosted pegmatites.
“These results have significantly refined our exploration focus, highlighting granitic-hosted pegmatites with geochemical characteristics consistent with highly evolved LCT systems,” Wither says.
The company says it will integrate the results with geological, structural, geophysical, and historical datasets to rank targets. Planned work includes further mapping, surface geochemistry, mechanised stripping, and scout diamond drilling.
Mavis Lake hosts an Inferred MRE of 8 million tonnes (Mt) @ 1.07% lithium oxide. The project lies approximately 19km east-northeast of Dryden in northwestern Ontario.
Write to France Pinzon at Mining.com.au
Images: Critical Resources
