The Copper Hill deposit of Kharmagtai copper-gold project also hosts high-grade oxide material in addition to sulphide material. Image courtesy of Xanadu Limited.
Kharmagtai project is a high-grade copper-gold project located in the Omnogovi Province of Mongolia. Image courtesy of Xanadu Limited.
Porphyritic intrusive stocks form majority of the copper-gold mineralisation at Kharmagtai. Image courtesy of Xanadu Limited.

Kharmagtai is a high-grade open-pit copper-gold project under development in the Omnogovi Province of Mongolia.

Oyut Ulaan owns the copper-gold project, which is located within the mining licence MV-17387A. The joint venture of Xanadu Mines and Mongol Metals holds a 90% stake in Oyut Ulaan, while Quincunx (BVI) holds the remaining 10%.

The scoping study of the project was completed in April 2019, which focused primarily on open-pit mining at three deposits namely Stockwork Hill, Copper Hill, and White Hill.

Oyut Ulaan also proposes to extend the mine life by undertaking future underground operations at the Stockwork Hill and Copper Hill deposits, in addition to targeting the shallow oxide gold mineralisation at the site.

Kharmagtai copper-gold project location

The Kharmagtai copper-gold property lies approximately 120km north of Rio Tinto’s Oyu Tolgoi copper-gold mine and 440km south-southwest of the town of Ulaanbaatar.

The project is a part of the South Gobi porphyry copper province, which hosts major porphyry deposits, including Oyu Tolgoi, Tsagaan Suvarga, and the Oyut Ulaan porphyry copper-gold exploration project.

Geology and mineralisation at Kharmagtai copper-gold project

The Kharmagtai project comprises multiple co-genetic gold-rich and tourmaline breccia pipes within the carboniferous Kharmagtai Igneous Complex (KIC). The complex hosts intrusive bodies such as diorite through monzodiorite, quartz-monzodiorite to monzonite, and granodiorite compositions.

“The joint venture of Xanadu Mines and Mongol Metals holds a 90% stake in Oyut Ulaan, while Quincunx (BVI) holds the remaining 10%.”

Most of the copper-gold mineralisation is associated with multiple porphyritic intrusive stocks of diorite to monzodiorite. Copper and gold are identified in the chalcopyrite and bornite sulphides and are associated with porphyry style veining.

Three styles of copper-gold mineralisation are identified at the project, namely porphyry style stock work, tourmaline breccia style, and epithermal gold associated with carbonate base metal veins. Porphyry stockwork forms the majority of the mineralisation at the project.

Tourmaline breccia mineralisation consists of chalcopyrite-tourmaline-pyrite as infill to hydrothermal breccia, while epithermal style mineralisation is hosted by carbonate-pyrite-chalcopyrite-sphalerite-galena veins controlled by late north-west trending faults.

Kharmagtai copper-gold project reserves

The Kharmagtai copper-gold project is estimated to hold 129.3Mt of indicated resources, grading 0.36% Cu and 0.36g/t Au. It is estimated to contain 468,000t of copper and 1.48Mt of gold.

Inferred resources are estimated to be 468.9Mt, grading 0.41% Cu and 0.31g/t Au and containing 1.47Mt of copper and 2.83Mt of gold.

Mining and ore processing at Kharmagtai copper-gold project

Conventional open-cut mining method, involving drill-blast-load-haul operations, will be employed at Stockwork Hill, Copper Hill, and White Hill deposits. The initial plan involves mining the three deposits separately, while the Stockwork Hill and White Hill pits are planned to be combined into one large pit during the later part of the mine development.

Initial mining will be conducted at the Copper Hill deposit, which is proposed to be developed in a single phase. The White Hill deposit is proposed to be developed in four phases, while the Stockwork Hill will be developed in two phases.

Ore mined from the Kharmagtai project will be processed at the proposed 20 million tonnes per annum (Mtpa) capacity plant near the mine site.

The processing plant will employ a standard crushing-milling-flotation process to produce a filtered copper-gold concentrate. Ore will be crushed and subjected to two-stage grinding in semi-autogenous grinding (SAG) and ball mills, before being passed through rougher, scavenger, and cleaner flotation cells to produce copper-gold concentrates.

Copper will be recovered at rates of approximately 90.9% and 85.7% from the Copper Hill and White Hill deposits respectively, while the respective gold recovery rates at the two deposits are estimated at 76% and 69.1%.

Infrastructure facilities at Kharmagtai

Access to the project is through the sealed and all-weather unsealed roads connecting the Mongolian road network.

Power supply for the project is proposed to be sourced from the existing transmission lines located nearby. Additional power will be supplied from a new power plant at the Tsogttsetsii coal mine, located approximately 70km from the Kharmagtai mine site.

Contractors involved

CSA Global prepared the scoping study of the Kharmagtai copper-gold project with support from O2 Mining and Xanadu Mines.