Mr. Eric Jones reports

THUNDER MOUNTAIN GOLD INTERSECTS NEW CARBONATE REPLACEMENT DEPOSIT SILVER-ZINC MINERALIZATION AND CONFIRMS TWO PORPHYRY CENTERS AT SOUTH MOUNTAIN

Thunder Mountain Gold Inc.'s 2026 core drilling program at the South Mountain project in Owyhee county, Idaho, has intersected new carbonate replacement deposit (CRD) mineralization at Kentucky Ridge, about 250 metres (m) northwest and on strike of the known CRD zone. Drilling also confirmed porphyry-style intrusive rocks and alteration at the Gold Breccia and Birthday targets, which the company believes may be the source of South Mountain's massive sulphide mineralization.

Highlights:

• New CRD stepout at Kentucky Ridge: Hole SM26-062 intersected 22.28 m grading 2.07 per cent zinc (Zn) and 9.00 grams per tonne (g/t) silver (Ag), including 14.81 m grading 2.98 per cent Zn and 11.9 g/t Ag, about 25 m downplunge from a surface gossan that channel sampled 7.6 m at 125 g/t Ag, 1.2 per cent lead (Pb) and 1.7 per cent Zn.
• Known CRD zone extended toward surface: Hole SM26-060 returned 2.38 m grading 29.2 g/t Ag and 0.455 g/t gold (Au), extending DMEA zone mineralization updip.
• Porphyry systems confirmed: At Gold Breccia, SM26-054 returned 55.17 m grading 0.112 g/t Au, including 3.0 m at 0.657 g/t Au. At Birthday, two holes beneath a strong MT anomaly cut five porphyry intrusive phases with intense, widespread sericite alteration and pyrite-biotite, plus or minus quartz veinlets and notable chalcopyrite.
• 2026 program complete: Fourteen core holes were completed totalling 2,670 m (8,760 feet (ft)). Assays have been received for nine holes; results for five holes, including all Birthday drill holes, are pending.

Dr. Steven Osterberg, senior vice-president of exploration, said: "The 2026 program identified new CRD massive sulphide-related mineralization and confirmed two highly altered, sulphide-bearing porphyry centres associated with MT anomalies. These centres, or others not yet drilled, may be the engines driving mineralization at South Mountain. With multiple MT anomalies still untested, we see potential for additional porphyry discoveries in what is now a district-scale opportunity."

Rich Leveille, Thunder Mountain Gold technical committee member, added, "These are very promising results opening up new opportunities at South Mountain and definitely merit follow-up with additional drilling."

CRD drilling: new mineralization at Kentucky Ridge and extensions of the known zone

Drilling began in June, 2026, and was completed in the third quarter. Ten of the 14 holes targeted CRD massive sulphide mineralization. They tested extensions of the known 800 m zone, which hosts several cigar-shaped massive sulphide bodies, and searched for new occurrences beyond it.

Kentucky Ridge (northwest)

The company targeted the downplunge projection of a surface gossan that channel sampled 7.6 m at 125 g/t Ag, 1.2 per cent Pb and 1.7 per cent Zn. Stepout hole SM26-062, drilled to test this zone at depth, intersected 22.28 m grading 9.00 g/t Ag and 2.07 per cent Zn about 25 m downplunge from that channel sample (table 1). Company geologists believe this surface and near-surface mineralization may be the upper expression of a new CRD body, about 250 m from the known 800 m zone. Hole SM26-063 tested beneath this intercept; results are pending.

DMEA zone (known CRD)

Hole SM26-060 returned 2.38 m grading 29.2 g/t Ag and 0.455 g/t Au. Together with SM26-055, SM26-056 and SM26-057 (reported Sept. 7, 2026), these results extend the known DMEA zone mineralization updip toward surface. Nearby, hole SM26-061 intercepted anomalous Ag in two zones (2.28 m at 6.03 g/t and 3.21 m at 8.46 g/t) and is thought to have slightly undercut the plunging Kentucky mineralization.

Southeast of the known CRD zone

Stepout holes SM26-058 and SM26-059 intersected intensely altered Laxey marble and a felsic dike with widespread sericite and pyrite alteration possibly reflecting the fringe of another CRD body. Assays show elevated silver (6.74 m at 4.90 g/t and 0.94 m at 6.32 g/t) in these rocks.

Bay State (northwest of Kentucky and on strike)

Hole SM26-064 also tested a CRD stepout target and intercepted hedenbergite skarn alteration of marble along with carbonate dissolution textures; all assay results are pending.

Porphyry drilling: Gold Breccia and Birthday

Four holes tested intrusive-hosted targets near and farther from the known CRD mineralization. The company followed up on previous exploration at Gold Breccia, a target it first identified in 2009, and made the first tests of a new porphyry target at Birthday. Geological mapping, surface geochemistry and a magnetotelluric (MT) survey by Durango Geophysical Operations defined these targets. The MT survey identified several low-resistivity anomalies, zones that conduct electricity more readily than surrounding rock, at Gold Breccia, Birthday and other untested targets.

Gold Breccia

Hole SM26-054 returned 55.17 m (181 ft) from the surface grading 0.112 g/t Au (table 1), including 3.0 m at 0.657 g/t Au in a heterolithic igneous/hydrothermal breccia. Below the breccia, several porphyry-style features occur in granodiorite, including crowded porphyry textures, sericite alteration, secondary biotite and skarn-related calc-silicate minerals. Sulphides are rare to common and occur dominantly as disseminations and as one-millimetre-to-two-centimetre-wide veinlets of pyrrhotite. Rare sphalerite and arsenopyrite are also present. The core also contains a heterolithic pebble dike with milled fragments. Together, these features support the interpretation that the deeper MT anomaly may reflect porphyry-related sulphides.

Birthday

The company drilled three holes at what its geologists consider the strongest porphyry target to date. Holes SM26-065 and SM26-067 tested a strong MT anomaly and confirmed porphyry-style textures and alteration seen in rare outcrops; a thin cover of younger basalt hides almost the entire area. The two holes cut five quartz-feldspar or feldspar-dacite porphyry phases. The porphyry shows intense, pervasive sericite alteration overprinted by stockwork/hydrofracture-textured biotite-pyrite plus or minus quartz veinlets. Company geologists believe this may be quartz-sericite-pyrite (QSP) alteration, which forms zoned shells around mineralized porphyry systems. Disseminated pyrite and millimetre-scale veinlets of pyrite with trace copper sulphide (chalcopyrite) are common throughout the porphyry (typically 2 to 5 per cent) and are typically associated with quartz and/or biotite. Veins are typically one to five millimetres (mm) in width. A single larger massive sulphide vein of 6.5-centimetre width similarly cuts the porphyry. The vein comprises an estimated 50 per cent pyrite and 15 per cent chalcopyrite with subordinate pyrrhotite, arsenopyrite and quartz. The third hole, SM26-066, was abandoned near surface due to drilling difficulties in basaltic cover rocks. All Birthday assays are pending.

Cautionary statement

The company cautions that CRD-related or porphyry textures, alteration and sulphides as noted do not necessarily indicate that economic type(s) of mineralization will occur at South Mountain, and if present, that the mineralization will occur in sufficient quantity or grade that would be economic to mine. This information is provided for context and as an element of the prospectivity analysis of the company's property.

Next steps

Surface work continues through the end of the 2026 field season to support targeting for the planned 2027 drill program:

• Induced polarization (IP) survey: Durango is running orientation lines over gossan outcrops in the resource area to calibrate survey lines that will extend along covered, untested parts of the Laxey marble. Results are pending.
• Soil geochemistry: The company is expanding its soil sampling grid over targets identified by earlier geophysics and mapping.
• Geological mapping: Continuing mapping is documenting how structure and stratigraphy control CRD and porphyry-style alteration and mineralization.

The company's focus at South Mountain is unchanged: establish the size of the CRD massive sulphide system and determine which of the porphyry centre(s) along the Laxey marble is its source.

Other corporate news

The company announces that pursuant to its corporate stock option plan, the company has granted Ron Clayton, newly appointed director of the board, 400,000 stock options to purchase common shares in the capital stock of the company. The 400,000 options are exercisable on or before 5 p.m. Pacific Time on oct. 14, 2031, at a price of 75 cents per share.

About the South Mountain project

South Mountain is a polymetallic silver, zinc, gold, copper and lead project on private land about 70 miles southwest of Boise, Idaho. Mining began in the 1860s with high-grade silver from surface exposures of the polymetallic chimneys in the Laxey marble. Historic mining began during the Second World War and continued intermittently into the late 1960s, most notably under Anaconda Copper, developing more than 8,000 feet of drifts, shafts, raises and stopes. Historical smelter records show about 53,642 tons were shipped at average grades of 14.5 per cent Zn, 10.6 ounces per ton (oz/t) Ag (363 g/t), 0.058 oz/t Au (1.99 g/t), 1.4 per cent Cu and 2.4 per cent Pb.

The company acquired the mine in 2007 and has invested over $25-million (U.S.) in the project. It has rehabilitated about 4,000 feet of underground workings to MSHA-compliant condition and outlined significant massive sulphide mineralization through underground core drilling. The high-grade CRD zones remain open at depth and along strike. Through recent land purchases, staking and leases, including 113 acres of private land adjoining the historic mine and Gold Breccia, 423 lode claims (about 8,200 acres) on adjoining BLM land, a 1,073-acre private lease, and a State of Idaho lease, the company has added 13,061 acres, or about 20 square miles, to its property position. The company completed a mineral resource estimate in 2023 (table 2).

Refer to S-K 1300 technical resource statement and National Instrument 43-101 technical report: "Updated Mineral Resource Estimate for the South Mountain Project," dated Dec. 31, 2023, and Dec. 15, 2023, respectively, available on EDGAR and SEDAR+.

Sampling methodology, chain of custody, quality control and quality assurance

Cutting and sampling of drill core were directed by Thunder Mountain Gold geologists. The drilling contractors transported the core samples to the company's secure facility in nearby Jordan Valley, Ore. An independent contractor delivered these and additional surface samples collected by geologists to MSA Labs for sample preparation in Elko, Nev. The sample prep process included drying, crushing one kilogram (kg) to two millimetres (mm), splitting 250 grams and pulverizing rock material to 85 per cent at minus 75 microns. Quality control was monitored by the insertion of numerous blind certified standard reference materials, duplicates and blanks into each sample shipment. Drill samples were assayed by MSA Labs for gold by fire assay of a 30-gram charge with an AA (atomic absorption) finish (code FAS-111). Satisfactory results were achieved for all quality control samples related to the data reported herein. In addition, samples were submitted for multielement analysis (48 elements) by 0.25 g four-acid digestion and ICP-MS (inductively coupled plasma mass spectroscopy) ultratrace finish (code IMS-230).

Qualified person

The technical information in this news release was reviewed and approved by Steven A. Osterberg, PhD, PG, the company's senior vice-president of exploration, a qualified person as defined by S-K 1300 and National Instrument 43-101. Dr. Osterberg is not independent of the company as he is an officer.

Cautionary statement

The opinions expressed regarding the potential of the exploration results should not be relied upon as an indication of future economic viability of the targets at the South Mountain project. Characterization of certain targets as discoveries will require additional geologic studies and exploration drilling.

About Thunder Mountain Gold Inc.

Founded in 1935, Thunder Mountain Gold is a junior exploration company developing base and precious metals assets in the Western United States. Its principal asset is the South Mountain project, a historic former Anaconda Copper Company development on private and state land in Owyhee County, Idaho, containing zinc, silver, gold, lead and copper. The company also owns 100 per cent of the Trout Creek project, a gold exploration property in Nevada surrounded by Nevada Gold Mines, a Barrick-Newmont joint venture.