Critical Resources Identifies Highly Fractionated Lithium Pegmatites in Mavis Lake Northern Corridor, Ontario

2026 Field Exploration Program and Methodology at Mavis Lake Northern Corridor

Critical Resources conducted a focused 10-day systematic field exploration across the northern corridor of the Mavis Lake Lithium Project, approximately 4 kilometres north of its existing 8.0 million tonnes at 1.07% Li2O mineral resource. The program aimed to assess pegmatite fertility and magmatic fractionation within the Corona Pegmatite Field and adjacent Northern Prospects Area, with the goal of refining exploration priorities and identifying new drill targets aligned with the company’s district-scale strategy.

The exploration team carried out detailed prospecting, geological mapping, structural measurements, and representative rock sampling in the underexplored northern sector. A total of 106 rock samples were collected from 14 pegmatite bodies, including six newly identified pegmatites. Additionally, 74 structural measurements and mapping of 161 outcrops enhanced geological understanding of this area. This comprehensive approach generated essential baseline data for geochemical analysis and drill target prioritisation.

Whole-Rock Geochemical Analysis Validates Highly Evolved LCT Pegmatite System

Whole-rock lithogeochemical testing employed sodium peroxide fusion followed by ICP-OES and ICP-MS to evaluate pegmatite fertility and magmatic fractionation via major and trace element geochemistry. The study focused on potassium-to-rubidium (K/Rb) ratios and concentrations of lithium pathfinder elements across northern corridor samples.

Results delineated varying degrees of pegmatite fractionation and pinpointed key exploration targets. The Northern Prospects Area yielded the strongest fractionation signatures, with multiple samples showing very low K/Rb ratios and significant enrichment in lithium pathfinder elements. The most fractionated sample recorded a K/Rb ratio of 17.4, with 5,510 ppm rubidium, 221 ppm caesium, 53 ppm tantalum, and notable beryllium enrichment. These geochemical indicators align with highly evolved lithium-caesium-tantalum (LCT) pegmatite systems, the primary target for lithium mineralisation in the region.

Northern Prospects Confirmed as Top Exploration Priority

The August 2025 acquisition of the northern claim package has been validated by the 2026 field results, which show the strongest fractionation signatures concentrated in this area. Geochemical data clearly distinguish highly evolved LCT pegmatites from less fractionated ones, establishing a focused target for continued exploration. Granitic-hosted pegmatites in the Northern Prospects presented the most promising geochemical signatures, supporting the strategic rationale behind the acquisition.

Conversely, pegmatites in the Corona Pegmatite Field exhibited only slight to moderate magmatic fractionation. Although Corona remains prospective, the 2026 findings indicate the northern claim package hosts the most fertile pegmatites, enabling Critical Resources to prioritize exploration investment there. This prioritisation aligns with the company’s district-scale exploration strategy at Mavis Lake.

Multi-Disciplinary Data Integration to Enhance Drill Targeting

The 2026 geochemical outcomes will be combined with geological, structural, geophysical, and historical datasets to guide follow-up prospecting and refine high-confidence drill targets. This integrated approach aims to advance exploration across the Northern Prospects and supports Critical Resources’ systematic evaluation of regional pegmatite targets beyond the current resource estimate. The objective is to develop Mavis Lake into a multi-deposit lithium district through science-driven exploration.

Integration will include geological mapping, structural data, lithogeochemical signatures from 2026, and geophysical information to build a comprehensive targeting model. This model will help identify drill targets with the highest likelihood of economic lithium mineralisation. The company notes these results underpin its exploration strategy and provide a geochemical foundation for upcoming drilling decisions within the Northern Prospects.

Expanding Beyond Existing Mavis Lake Lithium Resource

Critical Resources’ Mavis Lake Lithium Project currently holds an 8.0 million tonne mineral resource at 1.07% Li2O, defined through prior exploration. The company aims to grow lithium resources beyond this through systematic evaluation of multiple district-scale targets. The 2026 field program and geochemical analyses represent the initial phase of this expanded strategy to identify additional lithium-bearing pegmatite systems across the property.

The company has identified six major district-scale pegmatite targets: Gullwing, Tot, Little Wing, Coates, Drope, and Corona. These underpin Critical Resources’ growth potential at Mavis Lake. The geochemical framework from the 2026 program offers a systematic method to assess pegmatite fertility and prioritize drilling locations. By establishing clear geochemical markers for fractionation and lithium potential, the company has developed a replicable evaluation approach applicable across its Mavis Lake prospects.

Discovery of Six New Pegmatite Bodies Enhances Exploration Potential

During the northern corridor mapping and prospecting, six previously unknown pegmatite bodies were discovered, expanding lithium exploration targets and enhancing understanding of pegmatite-hosted lithium systems at Mavis Lake. The discovery within a focused 10-day program suggests further undiscovered pegmatites may exist across the broader project area.

The systematic geological and geochemical approach used in 2026 provides a template for pegmatite identification and evaluation throughout the district. The identification of six pegmatites in a single season supports the effectiveness of combining prospecting with targeted geochemical analysis. As exploration continues across Gullwing, Tot, Little Wing, Coates, Drope, and Corona, similar discoveries may emerge.

Geochemical Benchmarks for Lithium Mineralisation Assessment

The 2026 program established clear geochemical criteria to differentiate pegmatite fertility across Mavis Lake. K/Rb ratios serve as a key indicator of fractionation, with highly evolved LCT pegmatites showing ratios as low as 17.4. Enrichment in rubidium, caesium, tantalum, and beryllium further signals fertile pegmatites with lithium potential. These benchmarks provide an objective framework for evaluating prospects and guiding exploration priorities.

Top samples showed 5,510 ppm rubidium, 221 ppm caesium, and 53 ppm tantalum, setting reference signatures for the most fractionated and prospective pegmatites. This geochemical characterization enables consistent evaluation across Mavis Lake targets and rapid prioritization of new discoveries during future prospecting.

Validation of August 2025 Northern Claim Acquisition

The August 2025 acquisition of the northern claim package is validated by 2026 results, which confirm the highest fractionation and fertility pegmatites reside there. The strongest signatures concentrated in this area establish it as the top exploration focus within Mavis Lake’s portfolio. This outcome confirms the company’s due diligence and geological rationale behind the acquisition.

The 2026 program provided the first systematic geological and geochemical assessment of the northern claims, quantifying their lithium potential relative to other areas. Findings show the northern corridor hosts pegmatites with stronger magmatic fractionation and higher lithium pathfinder element concentrations than the Corona Pegmatite Field, home to the existing resource. This supports a multi-deposit exploration approach and suggests the northern claims may contain complementary lithium systems.

Upcoming Exploration and Drilling Plans

Critical Resources plans to integrate geological, structural, lithogeochemical, and geophysical data to prioritize the next exploration phase aimed at expanding lithium resources beyond the current 8.0 million tonne mineral resource at 1.07% Li2O. While specific drill targets and timelines have not been disclosed, the company states that the results refine drill targeting within the Northern Prospects and support its district-scale strategy. Key upcoming milestones include completing data integration and identifying priority drill targets.

The 2026 program’s systematic approach—combining mapping, structural analysis, whole-rock geochemistry, and targeted sampling—lays a solid foundation for future exploration. As drilling decisions approach, the geochemical framework will guide prioritization of targets with the greatest economic lithium potential. Critical Resources aims to develop Mavis Lake into a multi-deposit lithium district, anticipating multiple drilling campaigns as district-scale evaluation progresses.