IsoEnergy Provides 2025 Athabasca Basin Exploration Update and Prepares to Launch Winter Exploration Programs Including Drilling at Larocque East

2025-12-03

TSX - Toronto Stock Exchange · Uranium · Silver · Rare Earth Elements · Cobalt · Molybdenum · Gold · Copper · Vanadium · Canada

PR Newswire

TORONTO, Dec. 3, 2025/PRNewswire/ -IsoEnergy Ltd. ("IsoEnergy", or the "Company") (NYSE American: ISOU) (TSX: ISO) is pleased to provide an update on its summer drill programs at the Larocque East and Hawk projects and report uranium geochemistry results received to date from the winter and summer drill programs at Larocque East. Summer drilling at Larocque East totalled 9,561 min 22 holes, bringing the year-to-date total to 15,597 min 39 drill holes (Figure 1). Drilling successfully tested both Hurricane potential resource expansion areas and greenfield exploration targets along the prospective Larocque Trend, returning strongly anomalous radioactivity and uranium geochemistry from multiple holes across both the winter and summer programs. At Hawk, four drill holes were completed for a total of 3,593 m(Figure 2).

Highlights

Resource expansion drilling returned strongly anomalous geochemistry results along the Hurricane Main and South trends that validate previously reported radiometric results (Table1). LE25-194 intersected 0.872% U3O8 over 0.5 mwithin a 3.5 minterval, averaging 0.313% U3O8in the basal sandstone along the Hurricane Main Trend 80 meast of the deposit. LE25-207 intersected 1.61% U3O8over 0.5 min the basal sandstone immediately above the unconformity along the Hurricane South Trend 240 meast of the deposit. A second 0.5 minterval, 4.5 mbelow the unconformity, returned 1.71% U3O8.

Larocque Trend –Area D geochemistry validates best uranium intersection to date outside of the Hurricane Deposit. Geochemical results have confirmed that winter drill hole LE25-202, completed 2.8 km east of the deposit in Target Area D, returned the strongest uranium intersection to date on the Larocque East project outside the Hurricane area. LE25-202 intersected 1.05% U3O8over 0.5 mabout 20 mdown hole from the unconformity in a broader interval that returned 0.583% U3O8over 1.5 m.

Hawk Project – Key elements of prospective unconformity uranium geology continue to be intersected in widely spaced drill holes on this early-stage exploration project. HK25-13 and HK25-16 intersected graphitic gneisses and faults along the previously untested eastern conductor (Figure 2). HK25-14 intersected two significant intervals of structural disruption and prospective alteration in the sandstone in the northern portion of the project where only two other holes have been drilled.

Upcoming winter drilling at Larocque East is expected to build on encouraging results to date – Planning is well advanced, with 5,200 min 13 holes anticipated. Integration of summer exploration results with existing interpretations is underway to finalize 2026 drill targets and the winter work program, with additional details to be provided in due course. Additional work is planned in 2026 to develop drill targets on highly prospective projects –Geophysical surveys and interpretation are planned at the Evergreen, East Rim, Ranger, Trident and Hawk projects (Figure 3). IsoEnergy strengthens its management team with the appointment of Ms. Misty Urbatschas Vice President, Strategy and Commercial, bringing extensive uranium exploration and marketing experience from her years with Cameco and direct experience exploring for uranium in both in the AthabascaBasin and Australia.

Dan Brisbin, Vice President Exploration, commented, "We are pleased that geochemical results received to date have validated the 2025 Larocque East drill program radioactivity results. In particular, the intersection in drill hole LE25-202 nearly three kilometres east of Hurricane is the best uranium intersection on the Larocque East project to date outside of the Hurricane deposit area, highlighting the prospectivity of the Larocque Trend. Hawk is an early-stage project, and we believe that the intersection of key geological elements like graphitic basement rocks, faults in both the sandstone and basement, and indicative alteration in widely spaced drill holes is encouraging. New geochemical data from the 2025 drill holes on both projects will be key information for our exploration team to integrate with geophysical information and drill core structural and alteration information as we develop targets for a 2026 drill program."

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Hurricane Resource Expansion Drilling

Mineralized intervals, defined as zones averaging ≥350 cps over a minimum length of 0.5 mof core, were intersected in nine drill holes from the 2025 drill program (Table 1). Continued testing of potential resource expansion targets at Hurricane will be a focus of the planned winter 2026 drill program (Figure 1). Radioactivity results from six mineralized holes from the winter program were previously reported (see news release dated April 23, 2025). This news release includes radioactivity results from an additional three holes drilled during the summer, along with the corresponding drill core uranium geochemistry results (Table 1). All radioactivity results reported herein are averages over 0.5 mcore intervals, measured with an RS-125 spectrometer unless otherwise noted.

Results from the uranium geochemistry analysis are based on continuous split core samples collected through radioactive zones. The Company is still awaiting a large volume of geochemical data from composite samples taken through the sandstone and basement from the summer drill holes. The interpretation of the pathfinder element geochemistry for the Laroque Trend will be updated once these sample results are received.

Main Trend Highlights

Significantly elevated uranium geochemistry was returned from winter drill holes LE25-194 and LE25-198, as well as summer drill holes LE25-220A and LE25-231, which were drilled on the Hurricane Main Trend east of the deposit. LE25-203, drilled in the winter north of LE25-194, did not intersect significantly elevated radioactivity.

LE25-194, located 80 metres east of the Hurricane deposit, intersected a 3.5 minterval in the basal sandstone immediately above the unconformity at 319.7 min which drill core radioactivity ranged from 480 to 3,100 cps over 0.5 mintervals. Anomalous geochemical results correlate well with the previously reported radioactivity. The best value in a 0.5 msample is 0.872% U3O8, and the broader 3.5 minterval averaged 0.313% U3O8. The spectral mineralogy of the sandstone in LE25-194 is dominated by illite, with lesser kaolinite and dickite, for 90 mup hole of the unconformity. Illite is the dominant clay mineral in alteration zones associated with most AthabascaBasin unconformity uranium deposits, whereas dickite is the regional background clay mineral. Kaolinite, chlorite and dravite are also significant alteration minerals in some deposits.

LE25-198, drilled 110 meast of LE25-194, intersected 0.114% U3O8 over 0.5 min the basal sandstone 1.0 mabove the unconformity at 316.5 m. An average of 625 cps had been measured on core in the same 0.5 minterval. The spectral mineralogy of the sandstone column is dominated by illite, with lesser kaolinite and dickite for 115 mup hole of the unconformity.

LE25-220A intersected the unconformity 150 meast of LE25-194 at a depth of 369.0 m. The sandstone clay mineral spectroscopy is dominated by strong illite, with lesser kaolinite, and an almost complete absence of background dickite for 100 mup hole from the unconformity. Immediately below the unconformity, a 0.5 minterval returned 0.295% U3O8, which correlates with an average of 750 cps, within a zone of strong, pervasive clay alteration.

LE25-231 intersected the unconformity 15 mnorth of LE25-220A. It intersected an average of 313 cps measured on the core over a 1.0 minterval 1.0 mbelow the unconformity at 326.0 m, within a strongly bleached and clay-altered semipelitic gneiss. Geochemistry results are pending.

South Trend Highlights

Intervals of significantly elevated uranium geochemistry returned from winter drill holes LE25-207 and LE25-210 on the Hurricane South Trend correlate with radioactive intervals measured on drill core.

LE25-207 was drilled 240 meast of the deposit and intersected the unconformity at 323.8 m. It returned 1.61% U3O8over a 0.5 minterval in the basal sandstone immediately above the unconformity where drill core radioactivity averaged 4,600 cps over the same interval. Additionally, a second 0.5 minterval 4.5 mbelow the unconformity, returned 1.71% U3O8where drill core radioactivity averaged 8,800 cps.

LE25-210 was drilled 480 meast of Hurricane and intersected the unconformity at 320.6 m. It returned 0.486% U3O8over a 0.5 minterval, located three metres below the unconformity, where drill core radioactivity averaged 3,700 cps over the same interval. This interval is within a 2.5 minterval that extends from 1.5 mabove the unconformity to 1.0 mbelow the unconformity that returned an average of 0.115% U3O8.

An additional ten holes (LE25-195, 197, 199, 200, 201, 208, 211, 212A, 214 and 216) drilled on the South Trend in 2025 intersected prospective alteration and structure. The highest radioactivity measured on drill core was 650 cps over 0.1 massociated with limonitic clay-chlorite alteration immediately below the unconformity at 331.0 min LE25-216. In LE25-197, 360 cps was recorded over 0.5 min the sandstone 1.5 mabove the unconformity at 332.5 m. That interval is within a 1.0 minterval from 330.0 mto 331.0 mthat returned 0.056% U3O8.

The prospectivity of the Southern Trend remains strong, particularly given that it remains open to the east of LE25-212A. This is supported by mineralization intersected near the unconformity in drill holes LE25-207, LE25-210, LE21-101 and LE22-115A. In addition, clay mineralogy within the sandstone column of the twelve holes drilled in 2025 is dominated by illite, with lesser amounts of kaolinite and chlorite, which is an assemblage consistent with prospective hydrothermal alteration associated with unconformity-related uranium systems. The prospective clay mineralogy extends for 190 mor more up hole from the unconformity in most drill holes. Background dickite is only a component of the lower sandstone spectral mineralogy in LE25-210 and LE25-212.

North Trend Highlights

Drill holes LE25-196 and LE25-205A were drilled in the winter and LE25-218 in the summer to test north of the Hurricane deposit within the prospective ANT seismic velocity low footprint where anomalous uranium geochemistry in historic holes indicates potential for a mineralized trend north of the deposit. Spectral mineralogy results indicate that all three holes intersected prospective illite-chlorite-kaolinite-dickite assemblages over distances between 105 and 130 mup hole of the unconformity intersections in each hole.

LE25-218 was drilled to test the unconformity down-dip of anomalous uranium geochemistry and alteration mineralogy intersected in the sandstone column in 2020 drill hole LE20-56. The lower sandstone interval 190 mup hole from the unconformity at 353.1 min LE20-56 is characterized by spectral clay mineralogy dominated by prospective illite, with lesser kaolinite and dickite, and by > 1 part per million uranium partial values ("ppm U-p").

LE25-218 intersected 1,300 cps over a 0.5 minterval on core 7 mbelow the unconformity at 368.6 m. The same interval returned 0.312% U3O8over 0.5 m. The elevated uranium corresponds with hematite alteration that is flanked by patchy clay and chlorite alteration in a graphitic cordierite pelite. This graphitic basement unit is interpreted to be about 30 mnorth of the graphitic host rocks and faults that underlie the Hurricane deposit.

LE25-205A, which intersected the unconformity approximately 100 meast-southeast of LE25-218, intersected two 0.1 mintervals at 350 cps over in the first 2 mbelow the unconformity at 324.5 m.

Larocque Trend Drilling

Target Area D

Winter drill hole LE25-202 intersected radioactivity with an average RS-125 reading on core of 6,200 cps over 0.5 mon the west end of Target Area D, located 2.8 km from Hurricane. This was the highest radioactivity intersected on the project to date outside of the immediate Hurricane area. Geochemical data for the same interval confirm this result. The same interval returned 1.05% U3O8over 0.5 mapproximately 20 mdown hole from the unconformity at 270.3 min a broader interval that returned 0.583% U3O8over 1.5 m.

LE25-204 and LE25-206 were drilled on section down-dip and up-dip, respectively, of the LE25-202 intersection. Although both drill holes intersected prospective alteration and structure, neither intersected significant radioactivity. To further evaluate the LE25-202 intersection, five drill holes were completed along strike in the summer. Hole LE25-215 was drilled on strike to the northeast; and LE25-222, 225/225c1, 227 and 232 were drilled southwest of LE25-202. The highest radioactivity encountered was 300 cps over 0.1 min graphitic pelite 6 mbelow the unconformity at 257.5 min LE25-232.

Also in Target Area D, drill hole LE25-209 was completed in the winter, and drill holes LE25-213, 217, 219A, 226A, and 229Bwere completed in the summer, all on a parallel trend to the southeast of LE25-202. The highest radioactivity was 260 cps over 0.5 mat the unconformity at 275.5 min LE25-213. This hole was drilled 195 meast-northeast of LE22-116 which intersected 369 ppm U-p over 0.5 min basal sandstone and 2,750 ppm U-p over 0.5 mimmediately below the unconformity in the basement.

Additional testing of this target area is being planned for the 2026 winter drill program (Figure 1).

Additional Target Areas E, F and K

Exploration at Target Areas E, F, and K focused on advancing several untested or lightly explored conductive and structural features east and northeast of the Hurricane deposit.

At Target E, two summer drill holes provided initial tests of a one-by-two-kilometre ANT anomaly interpreted to reflect folded graphitic-pyritic gneisses disrupted by northeast-trending faults. LE25-223, drilled in the north end of Target Area E, did not encounter significant radioactivity. LE25-224 was completed in the southeast end of Target Area E to follow up on LE24-192, drilled in 2024, which intersected 2.0 maveraging 495 ppm U-p straddling the unconformity. LE25-224 intersected 400 cps over 1.0 min the basal sandstone immediately above the unconformity at 226.5 m. This same 1.0 minterval returned 0.35% U3O8.

At Target F, one summer reconnaissance hole, LE25-221, evaluated coincident conductor, resistivity, and ANT anomalies within a structurally complex corridor. Clay mineralogy in the sandstone 25 mup hole of the unconformity at 263.1 mis characterized by a prospective mix of illite, kaolinite and chlorite.

At Target K, a newly defined 2.5 km conductive trend located 800 mnorth of the main Hurricane conductor trend was tested through electromagnetic surveying and two reconnaissance summer drill holes, LE25-228 and LE25-230. Although the source of the conductivity was not intersected, the data collected will support ongoing refinements to the geophysical model and future targeting in this emerging area.

Hawk Project

The Hawk Project encompasses more than 15 km of prospective conductive strike, with depths to the unconformity interpreted between 600 and 750 m. Summer exploration activities, designed to build on 2023 and 2024 programs, included four drill holes totaling 3,593 m, ambient noise tomography (ANT) surveys in the northern portion to extend 2023 coverage, and stepwise moving loop (SWML) electromagnetic surveys in the south to refine conductor interpretations based on previous fixed loop (FL) data (Figure 2).

HK25-13 and H25-16 were the first tests of the eastern conductor. They intersected the unconformity 674.5 mand 688 mdown hole, respectively. Encouragingly, both intersected graphitic gneiss units in the basement, and brittle faults and structural disruption in both the sandstone and basement. Though preliminary interpretation of spectral mineralogy results indicates that dickite dominates the sandstone column clay mineralogy, prospective alteration is present in the basal sandstone of both holes – chlorite in HK25-13 and mixed illite-chlorite in HK25-16.

HK25-14 was drilled to test a conductor in the northern portion of the project, where only two previous holes have been drilled. HK25-14 intersected the unconformity at 726.5 mdownhole. A conductive source was not intersected in the basement. However, two significant intervals of structural disruption and prospective bleached and desilicified sandstone were intersected in the middle and basal sandstone. The structural disruption observed in the sandstone suggests that the drill hole overshot the targeted conductive basement structure. Prospective spectral mineralogy mixtures of illite, chlorite, kaolinite and dickite are associated with both these structurally disrupted, bleached, and desilicified intervals.

HK25-15 was drilled to test a strong conductor plate interpreted from the 2025 SWML EM survey. It intersected the unconformity 727.8 mdown hole. The conductive source was not intersected. Although preliminary mineral spectroscopy data indicate that dickite, with lesser kaolinite, dominates the sandstone column, three 10 mlong chloritic intervals were intersected in the middle sandstone, and the basal sandstone is characterized by a mix of illite-chlorite-dickite.

Once geochemical results have been received, the interpretation for this sparsely drilled prospective project will be updated utilizing drill hole geology, spectral mineralogy and chemistry along with available geophysical survey information. Additional ground electromagnetic surveys to refine drill targets will be evaluated in conjunction with the updated project interpretation.

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Additional AthabascaBasin Exploration

Winter geophysical surveys and interpretation are being planned for four projects to further develop a pipeline of drill-ready targets on the Company's projects in the Eastern AthabascaBasin (Figure 3). These surveys will add to airborne, and selective ground, conductivity, magnetic, radiometric and gravity data acquired on the Evergreen, East Rim, Ranger, and Trident projects since 2022 to evaluate unconformity and basement-hosted deposit potential along multiple prospective corridors under shallow cover near the basin margin.

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Corporate Update

IsoEnergy is pleased to announce the appointment of Misty Urbatschas Vice President, Strategy and Commercial. Ms. Urbatsch brings over fifteen years of diverse experience in the mining sector, combining a strong technical foundation in uranium exploration with commercial expertise in global uranium marketing and trading. Her career spans both field and corporate roles, providing her with a comprehensive understanding of the metals industry from discovery through to sales.

Ms. Urbatsch began her career with Cameco Australia Pty Ltd., where she explored for unconformity-type uranium deposits in the East Alligator River Uranium Field in the Northern Territory. She also managed exploration programs focused on sandstone-hosted uranium systems in South Australia'sFrome Basin. In 2012, she relocated to Canadato join Cameco's Saskatchewan-based exploration team, leading projects near some of the highest-grade uranium deposits in the AthabascaBasin.

Following the completion of her Executive MBA, Ms. Urbatsch transitioned to Cameco's Marketing division, where she played a key role in international uranium sales and oversaw the company's uranium trading activities.

She holds a Bachelor of Science in Geology and Geography (2008) and an Executive Master of Business Administration (2019) and is a registered member of the Association of Professional Engineers and Geoscientists of Saskatchewan.