Fireweed Metals Corp. has reported significant high-grade zinc-lead-silver mineralization at the Boundary Zone within its Macmillan Pass project in Yukon, Canada. The discovery, confirmed through 2025 drilling, validates anomalies initially identified by a muon tomography survey conducted in 2024, marking a notable advancement in exploration techniques for the sector.
The Macmillan Pass project, located approximately 380 kilometers northeast of Whitehorse, spans 985 square kilometers and hosts multiple zones of sedimentary-hosted sulfide mineralization. The project’s four key deposits—Tom, Jason, Boundary, and End Zone—contain substantial indicated and inferred resources, with recent updates highlighting the district’s potential. The updated calculation in September brought the district-wide total to 56 million metric tons of indicated resources averaging 5.49% zinc, 1.58% lead, and 24.2 grams per metric ton silver, along with 48.49 million metric tons of inferred resources averaging 5.15% zinc, 2.08% lead, and 25.3 g/t silver.
Fireweed’s innovative use of muon tomography, a technique that maps subsurface density variations using cosmic-ray particles, has proven effective in identifying mineralization. The 2024 survey, conducted in collaboration with Ideon Technologies, was the northernmost documented use of this technology and its first application in a greenfield exploration setting. The survey’s success has been confirmed by the 2025 drilling program, which intersected sulfide mineralization within the muon-identified targets.
“The successful intersection of sulphide mineralization within targets generated from the 2024 muon tomography survey confirms the effective use of this exploration technique in the Macpass District,” said Fireweed Metals President and CEO Ian Gibbs. “Our 2025 drilling confirms the density signatures generated from the survey correspond to mineralization, alteration, or denser rock types.”
Fireweed’s 2025 exploration program, the largest to date, involves five active drills across the district. The company is focusing on high-grade step-outs, regional discovery, and technical de-risking. Alongside follow-up drilling at Boundary Zone, Fireweed has initiated resource conversion at Tom, feasibility-supporting studies at Mactung, and early-stage testing at regional targets across the broader Macpass corridor.
The initial drilling at Boundary Zone targeted high-priority density anomalies identified by the muon survey. Step-out holes were designed to test along strike of known mineralization and into previously underexplored areas. The new intercepts cut a range of mineralization styles across multiple targets beyond the current resource. Highlights include:
– 4.4 meters averaging 9.35% zinc, 1.38% lead, and 21.2 g/t silver from a depth of 202.6 meters in hole NB25-004, including 1.2 meters of 23.44% zinc, 4.15% lead, and 55.8 g/t silver.
– 35.34 meters averaging 3.39% zinc and 2.2 g/t silver from 12.8 meters, including 7.97 meters of 8% zinc and 4.1 g/t silver, and 4.31 meters of 3.86% zinc and 12.3 g/t silver.
– 21.72 meters averaging 3.71% zinc and 4.2 g/t silver from 200.9 meters in NB25-002, including 7.48 meters of 4.83% zinc and 3.2 g/t silver, and 7.44 meters of 3.8% zinc and 8.3 g/t silver.
– 11.84 meters averaging 1.58% zinc and 3.4 g/t silver from 108.1 meters in NB25-003, and 6.62 meters of 1.7% zinc and 2.2 g/t silver from 17.8 meters.
– 3.14 meters averaging 5.62% zinc and 4.3 g/t silver from 64 meters in NB25-005.
The new intercepts extended known mineralization beyond the boundaries of the 2024 resource estimate and confirmed multiple sulfide styles across the muon-identified targets. This reinforces the effectiveness of Fireweed’s geophysical modeling and highlights the potential for further discoveries.
With six holes now completed at Boundary Zone and one regional hole drilled west of End Zone, Fire