Erdene Confirms Substantial Copper Mineralisation at Khuvyn Khar Porphyry System

• Drill hole ZMD-162 intersected 65 metres averaging 0.63% copper and 2.9 g/t silver, including a higher-grade zone of 30 metres at 1.25% copper and 6.1 g/t silver
• Mineralisation extends from 238 metres downhole to 450 metres, ending in mineralisation and suggesting further potential at depth
• The discovery is located three kilometres from the Zuun Mod molybdenum-copper deposit, indicating connectivity within the same porphyry system
• Strategic location on a wholly owned mining licence, 35 kilometres from the operational Bayan Khundii Gold Mine and approximately 200 kilometres from China
• Exploration programme planned for 2026 to test depth potential across the 20-square-kilometre porphyry footprint

Erdene Resource Development Corp. (TSX: ERD) is a Canada-based resource company producing gold at its Bayan Khundii Gold Mine in Mongolia. The company holds a portfolio of precious and base metal projects in the Khundii Minerals District in southwestern Mongolia, located near the operating Bayan Khundii mine. Projects include gold assets and copper-molybdenum prospects across the district.

High-Grade Copper Intercept in Drill Hole ZMD-162 at Khuvyn Khar

Drill hole ZMD-162 at Khuvyn Khar intersected 65 metres averaging 0.63% copper and 2.9 grams per tonne silver, including 30 metres at 1.25% copper and 6.1 g/t silver. The mineralised interval began at 286 metres downhole and extended to 450 metres, where drilling ceased whilst still in mineralisation. The hole was collared 125 metres from ZMD-121, which in 2010 returned 34 metres of 1.3% copper and 9.2 g/t silver from 308 to 342 metres.

The mineralisation occurs within quartz potassium-feldspar granite showing moderate to intense potassic alteration. Sulphide content in the mineralised zones ranges from 5% to 40%, with chalcopyrite as the dominant copper mineral. The altered and mineralised zone shows magmatic textures typical of the upper portions of porphyry systems.

President and CEO Peter Akerley stated:

"Today's drill results confirm a substantial copper component to the Khuvyn Khar porphyry system beyond the molybdenum-copper deposit defined at the nearby Zuun Mod project. This copper mineralized zone is characteristic of the upper levels of a copper porphyry system."

The northern portion of the Khuvyn Khar porphyry complex hosts disseminated copper mineralisation across a multi-kilometre zone with an approximate 20-square-kilometre footprint. Multiple copper-mineralised intervals have been intersected in wide-spaced drilling, with mineralised zones containing hydrothermally altered intrusive breccias with potassic altered and mineralised fragments.

Porphyry System Characteristics and Exploration Potential to Depth

The Khuvyn Khar copper porphyry system covers approximately 20 square kilometres and shows hydrothermal alteration assemblages and vein systems characteristic of copper-molybdenum porphyries. The presence of cupola textures and associated copper mineralisation indicates the core of the mineralised porphyry system is preserved at depth. Mineralised porphyry systems can extend vertically for considerable distances, as seen at the Oyu Tolgoi deposit 670 kilometres to the east, where mineralisation extends beyond 2,000 metres depth and remains open.

No drilling at the Khuvyn Khar copper target has penetrated below 500 metres. At the adjacent Zuun Mod deposit, drilling has averaged 370 metres in depth, with a single hole extended to 852 metres that ended in mineralisation. Large portions of the 20-square-kilometre footprint remain untested by drilling.

Khuvyn Khar and the Zuun Mod deposit are part of the same porphyry system, based on the three-kilometre separation, alteration patterns, metal ratios, and geological characteristics across the corridor. The Zuun Mod deposit represents a molybdenum-rich zone whilst Khuvyn Khar represents a copper-enriched zone within the system.

2026 Exploration Plans for Copper Porphyry System Expansion

With the Bayan Khundii Gold Mine in production, Erdene has announced plans for exploration in 2026 to test the depth potential of the Khuvyn Khar copper porphyry system. The programme will include advanced geophysical surveys and deeper drilling to test the continuation of copper mineralisation at depth.

The property is located approximately 200 kilometres from China.

CEO Peter Akerley stated:

"Khuvyn Khar and Zuun Mod are located approximately 200 kilometers from China, the world's largest copper and molybdenum consumer. The Khuvyn Khar license lies within a region in Mongolia that has seen significant recent infrastructure investments, supporting development of large-scale projects in the Khundii Minerals District."

A 3,362-metre, 24-hole drill programme was recently completed on the Khuvyn Khar licence. The programme included 18 holes testing the upper 150 metres of the Zuun Mod deposit, three scout holes following up on a gold zone 3.8 kilometres west of Zuun Mod, and two holes testing copper porphyry targets including ZMD-162. Results for the remaining holes are pending and will be incorporated into a preliminary economic assessment for the Zuun Mod deposit, scheduled for mid-2026.

Milestones and Next Steps

Results from the remaining drill holes in the recently completed 24-hole programme are pending. A preliminary economic assessment for the Zuun Mod molybdenum-copper deposit is scheduled for mid-2026. The 2026 exploration programme at Khuvyn Khar will test the depth potential of the copper system. The Bayan Khundii Gold Mine continues production in partnership with Mongolian Mining Corporation.

‍