The mineral deposits at Oyu Tolgoi lie in a structural corridor where mineralization has been discovered over a 26 km strike length. Four deposits hosting Mineral Resources have been identified: Oyut, Hugo North, Hugo South, and Heruga.

Tolgoi copper-gold deposits currently comprise, from north to south:
• Hugo North – The Hugo Dummett Deposit north of approximately 4766300 N (or the 110 Fault).
• Hugo South - The Hugo Dummett Deposit south the 110 Fault.
• Oyut - The Oyut Deposit includes the Southwest Oyu, South Oyu, Wedge, Central Oyu, Bridge, Western, and Far South zones within mining licence MV-006709.
• Heruga – is within the area governed by the arrangements between Oyu Tolgoi LLC and Entrée LLC except for a small northern portion that lies within the Oyu Tolgoi mining licence MV-006709.

The Oyut deposit is currently being mined as an open pit using conventional drill, blast, load, and haul methods. The Hugo North deposit is currently being developed as an underground mine using the block caving mining method. A staged approach is envisaged for developing the Hugo North deposit, involving mining two block cave lifts (Lift 1 and potentially Lift 2). Mineral Reserves have been estimated for Lift 1, which comprises three panels (Panel 0, Panel 1, and Panel 2).

Hugo South and Hugo North
The Hugo Dummett deposits, Hugo North and Hugo South, contain porphyry-style mineralization associated with quartz-monzodiorite int ........

The initial investment decision to construct Phase 1 of Oyu Tolgoi was made in 2010. Mining of the Oyut deposit started in 2012 using open pit mining methods. The Oyut open pit mine currently has an ore production rate of about 40 Mtpa. Part of the initial investment decision to develop Phase 1, included continued investment into the development of the Hugo North underground mine as a block caving operation (Phase 2 of the Project). Development of Phase 2 commenced in July 2016.

The current production rate from the Oyut open pit continues until 2023, after which it will be progressively reduced as production builds up from underground. Open pit mining will continue in parallel with Hugo North Lift 1 to keep the Oyu Tolgoi concentrator operating at its design capacity. Following depletion of Lift 1, production from the Oyut open pit will be increased to meet mill capacity.

Oyut open pit mining
Open pit mining is carried out using conventional drill, blast, load, and haul methods and is conducted 24 hours per day, 365 days per year.

The slope design criteria which are based on the Golder 2012 Study are summarized as follows:
- Single, 15 m bench height (or batter) in all rock slopes.
- Maximum bench face angle of 65° in weathered zone.
- Average bench face angle of 70° in bedrock zone.
- Minimum berm width of 7.5 m
- Where structural controls are present, berm widths of 9 m, 12 m, and 15 m are applied to be consiste ........

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