The venture will reduce the partners' reliance on third-party smelters to process their ore and make blister, a partially purified form of copper.

The 500,000-tonne-per-year direct-to-blister plant will be the largest copper smelter in Africa and one of the largest single-line smelters in the world, Ivanhoe said last week when announcing the award of the basic engineering contract to China Nerin Engineering Co.

The $769 million, which includes $699 million for construction, will come from the Kamoa-Kamula joint venture's (JV) own cash flows, Zijin said in a filing.

Known as Kamoa Copper, Ivanhoe and Zijin will own 39.6% each, the DRC government 20% and Crystal River Global Limited 0.8%.

Construction of the plant is expected to take three years, Zijin added.

Around 35% of current copper concentrate output from Kamoa-Kakula, which started producing in May, is treated at the nearby Lualaba smelter, majority-owned by China Nonferrous Mining Corp Ltd (CNMC), while the rest is transported to international smelters.

Kamoa-Kamula's first phase is expected to produce around 200,000 tonnes of copper per year, while Phase 2 expansion to 400,000 tonnes per year is on track to be completed in the second quarter of 2022, Ivanhoe said last week.

The Canada-based company says Kamoa-Kakula has the potential to reach peak annual copper production of more than 800,000 tonnes, which would make it the world's second-largest copper mining complex, after the Escondida mine in Chile.

(Reporting by Tom Daly; Editing by Bernadette Baum)