Announcement • Sep 17

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Cosa Resources Announces Summer Drilling Results for Murphy Lake North Uranium Joint Venture with Denison Mines

Cosa Resources Corp. announced results of the summer drilling program at the Company's Murphy Lake North project. MLN is a joint venture between Cosa and Denison Mines Corp. and is located three kilometres east of IsoEnergy's Hurricane Deposit. Cosa is the project operator and holds a 70% interest with Denison holding a 30% interest. Multiple zones of structurally controlled alteration and elevated radioactivity remain open along strike for several hundred meters and on multiple sections. Drilling evaluated multiple structures over 650 metres of strike length with all 13 drill holes intersecting strong structure and/or alteration. Summer 2026 drilling prioritized unconformity targets with significant room for basement-hosted mineralization remaining. Drilling at Cyclone has confirmed that the mineralization intersected during the winter drill program is contained within a much larger zone of structure and alteration than previously recognized that remains open for at least several hundred meters along strike in both directions. Drill holes testing unconformity targets over a 650-metre strike length intersected structure and/or alteration in all drill holes, with several targets that remain to be tested in the immediate area. The 13-hole, 6,752 metre drill program followed up winter results at the Cyclone trend highlighted by 5.0 metres averaging 0.55% U3O8 (308.5-313.5 metres) in MLN26-013 including a 0.5 metre subinterval of 1.70% U3O8 (310.5-311.0 metres). Summer drilling targeted the Cyclone trend over a 650-metre strike length extending 400 metres west and 250 metres east of MLN26-013. All 13 summer drill holes intersected moderate to strong alteration and/or structure, and several drill holes intersected intervals of elevated radioactivity. Drilling identified two prominent faults, the N- and S-faults, which are generally located along the northern and southern edges of the Cyclone graphitic basement unit. The N-fault is the most prominent basement structure intersected on the project and hosts the zone of strong basement alteration intersected by winter 2026 drill hole MLN26-017. Drill holes MLN26-023, -024, -25A, -026, and -028 targeted the N-fault at the unconformity and intersected moderate to strong alteration and faulting in the sandstone and/or basement including intervals of hydrothermal hematite. Most of these drill holes also intersected alteration and faulting above the interpreted location of the S-fault. Pending assay results will guide further exploration. The N-fault remains untested at the unconformity west of MLN26-028 and east of MLN26-025. Drill holes MLN26-019 and -027 targeted the S-fault at the unconformity. Both holes undershot the target and intersected the fault in the basement. The S-fault remains untested at the unconformity and is interpreted to join the N-fault west of the 2026 drilling area. Drill hole MLN26-020C1 targeted the zone of strong basement alteration intersected by MLN26-017. Assay results received after the start of summer drilling indicate the zone is strongly enriched in uranium pathfinder elements including Ni and Co, similar to the MLN26-013 mineralization. MLN26-020C1 extended the basement alteration zone 36 m to the east and intersected enrichment of a similar suite of pathfinder elements. This zone remains open down dip and down plunge of MLN26-017. Immediate follow up targets include the uranium pathfinder element enriched basement alteration zone intersected by MLN26-017 and MLN26-020C1, the S-fault, and the strike extensions of the N-fault. The 13-hole, 6,752 metre drill program included radioactive intersections such as MLN26-018A (351.0-351.2m, 0.2m, 315 CPS, Hematitic/chloritic fault), MLN26-024 (327.4-327.5m, 0.1m, 250 CPS, Strongly altered basal sandstone), MLN26-026 (336.5-337.0m, 0.5m, 340 CPS, Argillized/hematitic basement), MLN26-026 (379.2-379.6m, 0.4m, 340 CPS, Hematitic basement structure), MLN26-027 (348.2-348.3m, 0.1m, 320 CPS, Argillized/hematitic basal sandstone), MLN26-029 (360.9-361.0m, 0.1m, 275 CPS, Argillized upper basement), and MLN26-030 (348.7-349.0m, 0.3m, 300 CPS, Hematitic/limonitic fracture). Radioactivity is total gamma from drill core measured with an RS-125 hand-held spectrometer. Measurements of total gamma from drill core are an indication of uranium content but may not correlate with chemical assays. MLN covers a portion of the Larocque Lake trend and is located 3 kilometres east of the Hurricane deposit. Hurricane is the world's highest-grade indicated uranium resource and was discovered and delineated for IsoEnergy Ltd. by current members of Cosa's team. The Larocque Lake trend also hosts the high-grade Larocque Lake Zone, Yelka Prospect, and Alligator Lake Zone. MLN contains the along-strike extension of basement geology underlying the Hurricane deposit (the Hurricane trend), as well as a parallel conductive trend to the south (the Cyclone trend). Cosa's winter 2026 drill program intersected several metres of basement hosted uranium mineralization within a broader zone of strong structure and alteration at the Cyclone trend. Historical drilling and geophysical results for MLN were sourced from the Saskatchewan Mineral Assessment Database (SMAD). Verification of historical drilling results included confirming historical drill hole collar locations from air photos and ground checking selected collars with a handheld GPS unit. Basement and lower sandstone sections from most historical drill holes were relogged in 2024 and 2025 by Cosa. Verification of historical geophysical results included confirming the locations of geophysical survey grids from air photos, compiling survey data and interpretations, and evaluating whether interpreted geophysical results could be reasonably explained by historical and current drilling results. For MLN, Cosa engaged a consultant to re-interpret historical geophysical surveys to validate selected previous interpretations. Anomalous radioactivity in drill core was measured by removing intervals of drill core to an area of background radioactivity and scanning it with an RS-125 handheld spectrometer to determine average CPS. Sampling of mineralized zones was completed by collecting half-core splits with intervals that align with radioactive measurement intervals. Samples were transported to SRC Geoanalytical Laboratories (SRC) in Saskatoon, Saskatchewan (ISO/IEC 17025:2005 accredited) for U3O8 assay and multielement analysis. Cosa inserts certified reference material (CRM) blanks and standards into the split core sample series as a QA/QC measure. SRC conducts a QA/QC programme which includes repeat analyses and insertion of CRM standards CAR218, BL4A, and BL2A. SRC's CRM results are verified by Cosa staff. U3O8 assay results are compared to RS-125 handheld scintillometer readings and downhole gamma probe results to verify chemical assays and measured radioactivity align.

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