Critical Resources Ltd (ASX:CRR, FRA:9S70) has identified a highly prospective lithium exploration corridor at its 100%-owned Mavis Lake Lithium Project in Ontario, Canada, after geochemical analysis confirmed multiple strongly fractionated pegmatites across the Northern Prospects Area.
Whole-rock sampling returned potassium-to-rubidium ratios as low as 17.4, alongside values of up to 5,510 parts per million rubidium, 221 ppm caesium and 53 ppm tantalum.
The results are consistent with highly evolved lithium-caesium-tantalum pegmatite systems and have established the Northern Prospects as the priority area for follow-up exploration and drill targeting.
Northern corridor emerges as priority target
The 10-day field program covered the Corona Pegmatite Field and adjacent Northern Prospects, about 4 kilometres north of the project’s existing mineral resource.
Critical Resources collected 106 representative rock samples from 14 pegmatite bodies, including six newly identified occurrences. The company also mapped 161 outcrops and recorded 74 structural measurements, significantly improving its understanding of the underexplored northern corridor.
Geochemistry showed the strongest fractionation signatures were concentrated within the northern claim package acquired in August 2025.
In comparison, pegmatites sampled across the Corona field generally displayed slight to moderate fractionation, providing the company with a clearer ranking of exploration priorities.
Critical Resources noted that the low lithium values returned from grab samples were expected because sampling focused on pegmatite margins and non-spodumene-bearing zones. The pathfinder results are being used to assess fertility and guide exploration rather than determine lithium grades, which will require drilling.
Exploration program validates northern claims
The findings support the company’s decision to expand Mavis Lake through the acquisition of the northern claims.
The most prospective pegmatites appear to be associated with granitic host rocks, providing a geological vector for further mapping, surface geochemistry and targeted drilling.
Critical Resources will now integrate the assay results with geological, structural, geophysical and historical datasets to rank drill targets across Gullwing, Tot, Little Wing, Coates, Drope and Corona.
Planned work includes detailed mapping, mechanised stripping where appropriate and scout diamond drilling.
Managing director Tim Wither said the results had “significantly refined” the company’s exploration focus and provided a clear framework for unlocking the broader lithium potential of the northern Mavis Lake corridor.
"These results continue to advance our exploration strategy at Mavis Lake. The 2026 field program was designed to systematically evaluate pegmatites identified during our regional exploration program, and the whole-rock geochemistry has successfully identified the most prospective targets for the next phase of exploration.
"The highly fractionated pegmatites occur within the Northern Prospects Area on the northern claim package acquired by the Company in August 2025, validating the rationale for that acquisition and demonstrating the value of systematic regional exploration in identifying quality growth opportunities beyond our existing Mineral Resource.
"These results have significantly refined our exploration focus, highlighting granitic-hosted pegmatites with geochemical characteristics consistent with highly evolved LCT systems. This provides a clear framework for follow-up prospecting and drill targeting as we continue to unlock the broader lithium potential of the northern Mavis Lake corridor. With an existing Mineral Resource of 8.0 Mt at 1.07% Li₂O and an Exploration Target of 18–29 Mt, our objective remains to build Mavis Lake into a multi-deposit lithium district through disciplined, technically driven exploration."
What's next?
CRR will integrate the assay results with its existing geological, structural and geophysical datasets to rank and refine drill targets across the northern corridor.
The highest-priority targets will then be advanced as part of the 2026 Northern Prospects exploration campaign, supporting the company’s strategy to develop Mavis Lake into a multi-deposit lithium district.
Building a multi-deposit lithium district
Mavis Lake hosts an inferred mineral resource of 8 million tonnes at 1.07% lithium oxide and a project-wide exploration target of 18 million to 29 million tonnes at 0.8% to 1.2% lithium oxide.
The advanced Gullwing target alone has an exploration target of 7 million to 10 million tonnes at 0.3% to 1.2% lithium oxide, supported by a surface pegmatite body measuring up to about 80 metres wide and extending for roughly 500 metres along strike.
Critical Resources is focused on critical minerals. Its portfolio includes Mavis Lake in Canada, the Halls Peak Base Metals Project in New South Wales and gold assets in New Zealand.