Erdene to Acquire Up to 80% of Tereg Uul Copper‑Gold Porphyry Prospect

• Erdene enters an agreement to earn up to 80% interest in the 6,694-hectare Tereg Uul copper-gold prospect from Tereg Uul Mines LLC.
• The project lies approximately 10 km southwest of the Oyu Tolgoi deposit, along a mineralized corridor hosting several known porphyry systems.
• Exploration data includes historic mapping and sampling, with untested copper-gold geochemical and geophysical anomalies.
• Erdene can earn its interest through a staged commitment of up to US$28.3 million in exploration and cash payments over eight years.
• Fieldwork is planned to begin in Q3 2025, with early mapping and geophysics ahead of a potential drill program.

Erdene Resource Development Corp. (TSX: ERD | MSE: ERDN) is a Canadian mining company focused on discovering and developing precious and base metal assets in Mongolia. The company’s flagship project is the Bayan Khundii Gold Project, a high-grade open-pit deposit that is advancing towards production this quarter (Q3). Bayan Khundii sits within the broader Khundii Minerals District, a region where Erdene has consolidated a large land position and continues to explore for new resources.

Under the leadership of President and CEO Peter Akerley, Erdene has maintained a steady and technically disciplined exploration strategy over the past two decades. The company has leveraged its deep regional knowledge and strong stakeholder relationships to navigate Mongolia’s operating landscape effectively. With a track record of resource growth, community engagement, and transparent permitting, Erdene is positioning itself to become a leading gold producer in the country.

The Tereg Uul acquisition marks an expansion into copper-gold porphyry systems, a strategic diversification from Erdene’s primarily epithermal gold focus. With copper’s increasing role in electrification and clean energy infrastructure, the company’s move into porphyry exploration adds a layer of commodity balance to its portfolio. This complements ongoing efforts at Bayan Khundii and aims to unlock synergies across southern Mongolia’s mineral belts.

Tereg Uul’s location near Rio Tinto’s world-class Oyu Tolgoi deposit enhances the strategic appeal of this acquisition. By targeting projects along the same mineralized corridor, Erdene is tapping into an area that has already demonstrated the geological potential to host large-scale, long-life copper and gold deposits.

Terms of the Option Agreement

The Tereg Uul license is currently held by Tereg Uul Mines LLC and covers 6,694 hectares within the South Gobi province of Mongolia. The agreement provides Erdene the exclusive right to earn up to an 80% interest in the project through a staged earn-in structure, combining exploration expenditures and direct payments over an eight-year period. This structure minimizes upfront risk while allowing Erdene to progressively de-risk the asset as exploration advances.

Under the agreement, Erdene will make an initial cash payment of US$200,000 and commit to spending US$300,000 on exploration in the first year. In subsequent years, additional payments of US$400,000, US$500,000, and US$900,000 will be required in years two, three, and four respectively, bringing total cash payments to US$2 million. These are complemented by a minimum of US$3 million in cumulative exploration expenditures over the first three years.

To earn a 51% interest, Erdene must make a one-time payment of US$5 million following the third anniversary. If the company elects to move forward toward an 80% interest, it must invest a further US$10 million in exploration and make an additional US$8 million in cash payments by the eighth anniversary. The agreement allows Erdene to exit at any stage prior to vesting, providing flexibility based on exploration outcomes.

This type of agreement structure is typical for early-stage porphyry prospects, where initial surface indicators must be validated through drilling. Erdene’s staged approach ensures that capital is deployed based on the technical merit and evolving understanding of the deposit, while also aligning with its broader risk management principles.

Strategic Importance and Outlook

The acquisition of the Tereg Uul option aligns with Erdene’s broader strategy of consolidating high-potential assets within Mongolia’s premier mineral belts. While the company remains focused on bringing Bayan Khundii into production, it is also positioning for longer-term growth through selective copper-gold exploration. Tereg Uul’s proximity to Oyu Tolgoi and favorable structural setting provide a compelling exploration narrative that complements Erdene’s existing portfolio.

With copper expected to play a central role in the global energy transition, exposure to porphyry systems adds long-term value diversification. Copper-gold deposits are particularly attractive for their dual-commodity economics, often supporting scalable operations and district-level development potential. Tereg Uul offers both standalone discovery potential and strategic optionality in relation to future regional partnerships or infrastructure sharing.

For investors, outside of Bayan Khundii’s march to production, catalysts for Tereg Uul project will include the completion of the transaction, commencement of fieldwork, and eventual drill testing. The staged option terms ensure that capital deployment remains disciplined and milestone-driven. Any early drill success could significantly enhance the asset’s value and shift market perception of Erdene’s growth pipeline.

Ultimately, Tereg Uul strengthens Erdene’s position as a key player in Mongolia’s mineral development landscape. Its acquisition underscores the company’s ability to identify and secure meaningful opportunities in proximity to world-class assets while maintaining financial flexibility and operational focus.

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