IsoEnergy Ltd. press release

IsoEnergy Winter Drilling Intersects Elevated Radioactivity in Multiple Holes, Including 30,050 cps over 1.0 Metre, in a Newly Reinterpreted Fault Zone on the South Trend of the Hurricane Deposit

2026-04-07

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

PR Newswire

TORONTO, April 7, 2026/PRNewswire/ -IsoEnergy Ltd. ("IsoEnergy", or "The Company") (NYSE American: ISOU) (TSX: ISO) is pleased to announce results from its recently completed 2026 winter exploration drilling program at the Larocque East project (the "Project"), home to the high-grade Hurricane deposit ("Hurricane" or the "Deposit"), in the eastern Athabasca Basin, Canada. The program was expanded based on encouraging results, increasing from an initial plan of 13 diamond drill holes totaling 5,200 m to 17 diamond drill holes totaling 6,804 m, targeting potential resource expansion at the Deposit and testing greenfield targets up to three kilometres east along the Larocque Trend ("Larocque Trend").

Hurricane hosts a current Mineral Resource of 48.6 Mlb U3O8at 34.5% U3O8Indicated, and 2.7 Mlb U3O8at 2.2% U3O8Inferred (See "Qualified Person Statement" below). The Project benefits from excellent infrastructure, located approximately 40 km northwest of the McClean Lake mill, and features relatively shallow mineralization at approximately 325 m depth, supporting efficient exploration and future development optionality. The Deposit is located on the Larocque Trend, an important regional structure that also hosts other notable high-grade occurrences including those on Cameco and Orano's Dawn Lake joint venture.

Highlights

Additional mineralized fault strands have been identified across the width of the Hurricane South Trend, highlighting a broader and more prospective corridor than previously interpreted, with potential for additional zones within underexplored areas.

Drill hole LE26-248, drilled within the low-grade resource envelope (Figures 1, 2 and 3), intersected strongly elevated radioactivity returning an average RS-125 spectrometer reading on drill core of 30,050 counts per second ("cps") over 1.0 m (local off-scale readings of >65,500 cps), within a broader zone of 11,275 cps over 3.5 m, in the newly reinterpreted L fault zone within the South Trend.

Mineralization has now been intersected in multiple holes along the South Trend up to 540 m east of the Deposit footprint (Figure 1). Strongly elevated radioactivity intersected in multiple 2026 holes builds on past results in demonstrating the growing scale and prospectivity of this trend: LE26-241 (100 m east of LE26-248): Intersected strongly elevated radioactivity in the lower 8 m of sandstone above the unconformity at 325.9 m, including 3,712 cps over 0.5 m_._ LE26-243 (180 m east of LE26-248): Intersected an average of 10,000 cps over a 0.5 m within an interval of elevated radioactivity in the lower 6 m of sandstone above the unconformity at 328.9 m. LE26-234(560 m east of LE26-248): Intersected two intervals of elevated radioactivity. A 1.5 m interval, including 6,450 cps over 0.5 m, within altered lower sandstone (moderate to strong clay alteration, quartz dissolution, and faults) located 26 m above the unconformity at 358.9 m; and A 2.5 m interval in the basal sandstone immediately above the unconformity, including 1,270 cps over 0.5 m.

Geochemical results are pending as IsoEnergy prepares for summer drilling. All samples from the winter drill program have been submitted to the Saskatchewan Research Council Geoanalytical Laboratory, with assay results anticipated in due course.

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| 1.See Table 2 for a listing of individual 0.5 m mineralized intervals defined as intervals over which average RS-125 handheld spectrometer readings on drill core exceeded 350 cps. | | 2.Radioactivity is total gamma from drill core measured with an RS-125 hand-held spectrometer. | | 3.Individual 0.5 m interval cps values reported throughout this press release are averages of three readings taken over the 0.5 m interval. | | 4.Measurements of total gamma cps on drill core are an indication of uranium content but may not correlate with uranium chemical assays. |

Dan Brisbin, Vice President of Exploration, stated, "The 30,050-cps result in LE26-248, combined with elevated radioactivity confirmed in step-out holes up to 560 metres along strike to the east, continues to highlight the prospectivity of the Hurricane South Trend. Results to date are being used by our Project team to reinterpret the faults that control uranium mineralization along the South Trend and suggest potential for additional mineralization in areas that remain underexplored. We look forward to following up on these results with further drilling."

Philip Williams, CEO and Director, commented, "I'd like to congratulate the entire Larocque East technical team on a highly successful winter drill program driven by a rigorous geological approach. The team delivered an expanded program, safely and efficiently, producing some of the most encouraging results we've seen along the South Trend and demonstrating the scale of the opportunity in this underexplored corridor. Upon receipt of assay results, the team will design an aggressive follow-up program to further test the South Trend as part of our 2026 summer exploration drilling."

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Resource Expansion Targets at Hurricane

Winter drilling focused on resource expansion targets along the North and South trends that flank the Hurricane deposit (Figure 1). These trends are situated within a low seismic velocity anomaly identified by ambient noise tomography ("ANT"), which is interpreted to map the prospective Hurricane alteration zone. Uranium mineralization was intersected on both trends in 2026 drill holes, building on intersections along these two trends in 2025. Additionally, three drill holes tested targets up to three kilometres along trend to the east of the Hurricane deposit.

South Trend

The Hurricane South Trend is a compelling exploration trend with mineralization intersected in multiple holes over a 540 m strike length to the east of the Deposit. Winter 2026 drilling continued to test the South Trend of the Deposit and along strike to the east, building on positive results from 2025 that intersected mineralization near the unconformity in drill holes LE25-207 and LE25-210, and in previous holes LE21-101 and LE22-115A (see press release dated December 3, 2025). Results from the 2026 winter drilling program continue to demonstrate the potential for a significant unconformity-style uranium discovery along this trend.

Hurricane Footprint on the South Trend

Two holes, LE26-244 and LE26-248, were drilled within the footprint of the low-grade zone in the southwestern portion of the Deposit, with LE26-249 drilled approximately 40 m along strike to the east of LE26-248 to follow up on strongly elevated radioactivity intersected in LE26-248 on the newly redefined L Fault Zone (Figure 3). The L Fault Zone is the southernmost east-striking structure recognized at Hurricane, consisting of one or more fault strands within the South Trend. Exploration on the South Trend has historically focused on the J and K faults that control mineralization in the southern high-grade lens of the Hurricane deposit. The 30,050 cps result in LE26-248 highlights the prospectivity of the L Fault Zone, and future drilling will look to better define its geometry, controls on mineralization, and continuity along strike.

LE26-248returned 30,050 cps over 1.0 m (with local off-scale peak readings >65,500 cps) straddling the unconformity at 330.2 m (Figure 2) within a broader interval that averaged 11,275 cps over 3.5 m. Anomalous radioactivity exceeding 400 cps commences within the sooty pyrite zone in the basal sandstone, extending into the graphitic pelite below.

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The sandstone column from 143.5 m to the unconformity is characterized by strongly pervasive bleaching associated with illitic and kaolinitic clay alteration, indicative of a well-developed hydrothermal system characteristic of unconformity-style uranium deposits in the Athabasca Basin. Two zones of structural disruption were intersected: a 14.3 m (drill width) wide fault zone at 251.7 m characterized by intermittent broken core and quartz dissolution, preceded above by a weak to moderate pervasive hematite overprint from 143.5 m; and a 13.3 m (drill width) wide fault zone at 303.7 m characterized by broken, blocky and friable sandstone with a strong hydrothermal hematite overprint transitioning to a pervasive sooty pyrite overprint at 312.1 m that extends to the unconformity.

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LE26-244returned up to 1,150 cps over 0.5 m within a broader interval averaging 717 cps over 1.5 m, associated with sooty pyrite in the basal sandstone immediately above the unconformity at 332.8 m.

The sandstone column is characterized by progressive bleaching and illitic clay alteration from surface, with three discrete zones of structural disruption: an 8.6 m (drill width) wide fault zone associated with strong pervasive limonite staining at 164.4 m, a 22.7 m (drill width) wide fault zone characterized by quartz dissolution and broken and blocky core from 276.9 to 299.6 m, and a 10.7 m (drill width) wide fault zone from 313.0 to 323.7 m associated with a strong hydrothermal hematite overprint. Below the lowermost fault zone, the sandstone is grey and reduced with a pervasive sooty pyrite overprint, transitioning to very reduced dark grey to black core from 329.8 m to the unconformity. Graphitic pelite was intersected in the basement below.

While the radioactivity returned in LE26-244 is lower grade than the adjacent LE26-248, the well-developed alteration, the degree of structural disruption, and sooty pyrite reduction front at the unconformity contact remain highly prospective and warrant further evaluation.

LE26-249was drilled approximately 40 m along strike to the east of LE26-248 to follow up on the strongly elevated radioactivity intersected in that hole. The hole intersected a thick sequence of hydrothermally altered sandstone, with moderate bleaching commencing at 119.0 m and clay alteration predominantly illitic from 100.0 m with minor kaolinite to the unconformity. Strong bleaching with a pervasive interstitial white clay overprint commences at 261.5 m, persisting to the unconformity, associated with a fault zone from 261.7 to 263.4 m characterized by discrete isolated faults with quartz dissolution. A second fault zone from 307.8 to 315.7 m contains multiple clay gouges ranging from 0.2 to 0.5 m in width, associated with a hydrothermal hematite overprint. Trace sooty pyrite alteration was intersected from 326.0 m, intensifying to moderate sooty pyrite from 330.0 to 330.5 m, with associated 2,000 cps over 0.5 m, immediately above the unconformity at 330.8 m. Graphitic pelite was intersected in the basement below the unconformity.

The position of the fault zones within the sandstone column rather than at the unconformity suggests the hole did not intersect the optimal target and was likely drilled slightly into the footwall of the prospective structure. The alteration, structural setting, and weak mineralization at the unconformity are encouraging and indicate that there is still potential and warrant further evaluation.

South Trend Step Out

Drill holes LE26-241, LE26-243, and LE26-247 were drilled to test the South Trend between the southern portion of the Deposit and a zone of mineralization intersected in LE21-101, LE22-115A, and LE25-207 approximately 240 m east of the deposit (Figure 1). LE26-241 intersected strongly elevated radioactivity in the lower eight metres of sandstone above the unconformity at 325.9 m, including an average RS-125 reading over 0.5 m of 3,712 cps. LE26-243 intersected strongly elevated radioactivity in the lower six metres of sandstone above the unconformity at 328.9 m, including a maximum of 10,000 cps over a 0.5 m interval. LE26-247 intersected a well-developed alteration zone and structural setting consistent with the South Trend, however no significant radioactivity was returned, likely reflecting a footwall position relative to the optimal target.

LE26-241intersected elevated radioactivity in two intervals within the lower 8 m of sandstone above the unconformity at 325.9 m, an upper interval between 317.5 m and 321.0 m with 0.5 m average RS-125 values ranging from 297 cps to 3,712 cps within a zone of strong hydrothermal hematite, and a lower interval from 323.0 m to 325.5 m ranging from 342 cps to 862 cps within reduced sandstone immediately above the unconformity. The sandstone column is moderately to strongly bleached with predominantly illitic clay alteration from 128.0 m. A broad zone of structural disruption from 287.0 to 322.0 m is associated with strong hydrothermal hematite and discrete clay gouges to the unconformity. Pegmatite was intersected immediately below the unconformity, contacting graphitic pelite at 330.0 m.

LE26-243intersected strongly elevated radioactivity immediately above the unconformity at 328.9 m, with a peak RS-125 readings averaging 10,000 cps over 0.5 m from 326.5 m to 327.0 m within a zone overprinted by strong hydrothermal hematite, correlating with anomalous readings ranging from 145 to 10,000 cps extending over approximately 6.0 m to the unconformity. The sandstone column is bleached from 263.4 m with predominantly illitic clay alteration, and a zone of structural disruption from 284.0 to 296.2 m characterized by quartz dissolution and clay-infilled fractures. Below this, strong hydrothermal hematite transitions to a sooty pyrite overprint from 327.0 m to the unconformity. A secondary anomaly of 1,800 cps was returned between 333.5 m and 334.0 m within a basement shear zone associated with weak hydrothermal hematite, suggesting uranium mobility extends into the basement.

LE26-247 intersected a well-developed alteration zone with predominantly illitic clay from 130.0 m, bleaching from 165.0 m becoming strongly bleached below 234.3 m, and four fault zones below 228.0 m characterized by quartz dissolution, clay-infilled fractures, and fracture-controlled limonite. Graphitic pelite with several shear zones was intersected below the unconformity at 323.8 m. No significant radioactivity was returned above background. The degree of structural disruption in the lower sandstone column suggests the hole was drilled slightly into the footwall of the prospective structure, however the alteration signature, structural setting, and graphitic basement are consistent with the key elements observed in mineralized holes along the South Trend and warrant further evaluation.

LE26-246was drilled to test for the potential extension of the southwestern boundary of the Hurricane deposit south of where currently interpreted as mineralization in the southernmost previous drill hole, LE21-103. Elevated radioactivity was not intersected but mineral spectrometry results indicate that the entire sandstone column is strongly illitic, with lesser, localized dickite. This prospective clay mineralogy corresponds to the observation that bleached intervals with desilicification and clay alteration focused along numerous fault and fracture zones are present throughout the sandstone column. This degree of structural disruption and alteration is consistent with LE26-246 traversing the up-dip expression of the Hurricane alteration zone and intersecting the unconformity only about 20 m south of the interpreted resource boundary.

LE25-210 Follow Up on South Trend

Drill holes LE26-234, LE26-236, and LE26-245 were drilled to test for extensions to mineralization intersected in LE25-210, located 480 metres east of the Deposit, which returned 0.486% U3O8over 0.5 m located three metres below the unconformity, within a 2.5 m interval averaging 0.115% U3O8extending from 1.5 m above to 1.0 m below the unconformity.

LE26-234returned the strongest result in this corridor, with a peak RS-125 reading over 0.5 m of 6,450 cps approximately 26 m above the unconformity within a broad zone of structural disruption, and a second interval of 1,270 cps immediately above the unconformity contact in a fault gouge. The sandstone column is moderately bleached from 157.6 m, becoming strongly bleached with pervasive interstitial white clay from 200.0 m, with predominantly illitic clay alteration and minor kaolinite below 210.0 m. A broad zone of structural disruption extends from 301.6 m to the unconformity, characterized by multiple centimetre-scale clay gouges, quartz dissolution, broken and blocky core, and metre-scale zones of unconsolidated core, with limonite staining intensifying in clay-rich intervals and sooty pyrite present in more competent intervals. Semipelite and pelite were intersected in the basement below the unconformity.

LE26-236 and LE26-245 intersected well-developed hydrothermal strongly bleached, illitic clay alteration in the sandstone, and graphitic pelite in the basement, consistent with a prospective setting, however no significant radioactivity was returned above background in either hole.

LE26-236intersected a thick sequence of hydrothermally altered sandstone with predominantly illitic clay alteration and lesser kaolinite from 120.0 m, becoming strongly bleached with pervasive interstitial white clay from 242.0 m to the unconformity at 329.4 m. Intermittent centimetre-scale zones of quartz dissolution were intersected from 296.3 m to the unconformity, comprising less than 5% of the unit. Pelite to graphitic pelite was intersected in the basement below the unconformity. No significant radioactivity was returned above background.

LE26-245intersected a thick sequence of hydrothermally altered sandstone, strongly bleached from 141.0 m, with predominantly illitic clay alteration and lesser kaolinite from 130.0 m to the unconformity. Two zones of structural disruption were intersected: the first from 217.1 to 253.7 m, characterized by increased desilicification on fracture and fault surfaces with limonite staining; and the second commencing at 272.4 m and extending to the unconformity at 324.5 m, characterized by clay gouge-dominated faults, limonite-stained fractures, and pervasive interstitial white clay throughout. Limonite staining intensifies from 320.1 m to the unconformity. Graphitic pelite was intersected in the basement below the unconformity, with bleaching extending 2.0 m below the unconformity contact and a 20 cm zone of hydrothermal hematite at the base of the bleached basement zone. No significant radioactivity was returned above background.

The winter drilling results, combined with the previously reported mineralization in LE25-210, highlight the potential for uranium mineralization along this eastern extension of the South Trend and warrant further drill testing.

North Trend

The North Trend is characterized by discontinuous faults in sandstone and basement, associated with a northern graphitic pelite basement unit and anomalous uranium geochemistry up to 50 metres north of the Hurricane deposit.

LE26-239was completed on the North Trend as a cross-strike test between drill holes LE25-218 and LE20-56 (Figure 1), both of which returned strongly anomalous uranium geochemistry. (see news release dated December 3, 2025). LE26-239 intersected 2,747 cps over 1.0 m from 336.8 m to 337.8 m, within a 1.5 m interval of >350 cps, three metres below the unconformity at 334.2 m. This interval included 0.5 m with an average RS-125 value of 3,203 cps. The sandstone column has a mixed illite-dickite-kaolinite spectral mineralogy signature with illite dominant from 310 m to the unconformity where a chlorite component is also present. Minor faults with associated clay alteration and desilicification are abundant between 133.2 m and 170.5 m, and from 264.9 m to 343.8 m. A third interval of minor clay-coated faults is present in the basement from 359.9 m to 363.9 m. Pelite and semi-pelite were intersected in the basement.