Thunder Mountain Gold advances Ag-Au-Cu-Pb-Zn massive sulfide targets at South Mountain

Confirmed near-resource expansion potential: Four holes tested the previously undrilled up-dip extension of the DMEA massive-sulfide chimney and intersected intense skarn alteration with copper, zinc, and lead sulfides.

Delivered strong initial assay results: Drilling returned broad silver-enriched intervals, including 22.47 meters grading 86 g/t silver, with higher-grade subintervals and associated gold, copper, lead, and zinc values.

Identified new massive sulfide mineralization at the Kentucky target approximately 250m westward of resource area: Three step-out holes demonstrated approximately 80 meters of down-plunge continuity, intersected about 15 meters of intense gossan, and left the mineralized zone open at depth.

Advanced district-scale discovery targets: Drilling at the Bay State to the northwest, and on private claims to the southeast along trend intersected strongly altered, pyrite-rich schist and marble with localized skarn, improving the geological model and supporting additional exploration along the Laxey Marble trend.

Boise, Idaho--(Newsfile Corp. - September 17, 2026) - Thunder Mountain Gold, Inc. (OTCQB: THMG) (TSXV: THM) ("Thunder Mountain Gold" or the "Company") is pleased to report successful results from its 2026 exploration program at the South Mountain Project in southern Idaho, where drilling has successfully advanced multiple high-priority targets across the Company's expanding silver-zinc-gold-copper-lead district.

The Company's 8,500-foot diamond core program was designed to expand the established carbonate replacement deposit (CRD) massive sulfide resource while also testing compelling district-scale copper-gold porphyry targets identified through integrated geological and geophysical work. To date, ten drill holes have intersected mineralogic alteration with associated iron, copper, zinc, and lead sulfide mineralization