Name of the Project
Oyu Tolgoi underground mine project.

Location
Mongolia.

Project Owner/s
Rio Tinto (66%) and the government of Mongolia (34%).

Project Description
The Oyu Tolgoi openpit mine was completed on schedule in less than 24 months and production started in 2013. Since then, more than 440 000 t of copper have been sold.

About $6.4-billion was invested to develop the openpit mine, concentrator and associated infrastructure, with an additional $500-million spent on the initial development of the underground mine.

The underground mine is expected to produce more than 500 000 t/y of copper between 2028 and 2036, compared with current openpit production of 175 000 t/y to 200 000 t/y.

The mine also benefits from significant gold by-products, with an average gold grade of 0.35 g/t.

Underground production will come from the Hugo Dummett North deposit, including the North Extension, which contains probable ore reserves of 499-million tonnes with an average grade of 1.66% copper and 0.35 g/t gold.

The material from this brownfield expansion will use the existing concentrator and infrastructure.

The size and quality of this Tier 1 resource provide additional expansion options, which could sustain production for many decades.

Potential Job Creation
Not stated.

Net Present Value/Internal Rate of Return
The project has an expected internal rate of return of more than 20%.

Capital Expenditure
The capital forecast for the project is $7.06-billion, an increase of $300-million against the 2020 definitive estimate, owing largely to Covid-19 disruptions.

Planned Start/End Date
The operation is expected to ramp up to deliver average mined copper production of about 500 000 t/y (100% basis) between 2028 and 2036.

Latest Developments
The ramp-up of copper production continues.

Ventilation shafts 3 and 4 have been commissioned, with fresh air now being drawn into
the underground mine.

Construction work on the conveyor to surface was 98% complete at the end of the quarter ended September 30, 2024, and, after a minor delay to the start of commissioning, Rio Tinto expects first ore on the belt this month.

Construction works for the concentrator conversion is ongoing. Commissioning is expected to be progressively completed from the fourth quarter of 2024 until the second quarter of 2025.

Construction of primary crusher two is progressing to plan and remains on track to be completed by the end of 2025.

Key Contracts, Suppliers and Consultants
Jacobs Engineering (engineering, procurement and construction management) and Cimic Group’s Thiess (underground decline contractor).

Contact Details for Project Information
Rio Tinto (Mongolia) , tel +976 11 331880 or email online@ot.mn.