The Oyu Tolgoi copper-gold project is in the Aimag of Omnogovi, located in the South Gobi desert of Mongolia. The property is approximately 550 km south of the capital city, Ulaanbaatar, and 80 km north of the border with China.
Copper was mined from Oyu Tolgoi outcrops as early as the Bronze Age, but modern recognition had to wait until the 1980s when joint Mongolian and Russian teams identified molybdenum and copper at the Central and South deposits. In 1996, Magma Copper identified porphyry copper mineralization at Oyu Tolgoi; Magma was subsequently bought by BHP. Oyu Tolgoi LLC (an Ivanhoe Mines subsidiary) acquired 100% interest in the property in 1999.
Ivanhoe Mines also entered into an agreement with Entrée Gold Inc and an 80%-20% joint venture had been formed to cover the Heruga Deposit and the Hugo North Extension areas.
A participation agreement had been negotiated with the Mongolian government which acquired a 34% interest in Oyu Tolgoi LLC.
Rio Tinto owns 29.6 per cent of Ivanhoe Mines and has the option to increase this to up to 43.1 per cent of Ivanhoe's shares under fixed price options.
The Integrated Development Plan 2010 presents two complementary development cases that see the development of Southern Oyu open pits 1 through 9 and of the Hugo North, South and Heruga block caving operations. The cases assume the processing of 1.4 billion tonnes of ore over a 27 year period or the processing of 3.01 billion tonnes over 60 years.
Initial production would be derived from the Southern Oyu open pit and it would be followed by the mining of the Hugo North underground block cave deposit. Initial process (concentrator) capacity is designed at 100 kt/d. At the end of the year 5 concentrator capacity would be expanded to 158 kt/d as to be able to meet increased underground production levels of 10 Mt/a to its full production level of 29.5 Mt/a.
The ore is planned to be processed through conventional crushing, grinding and flotation circuits. The concentrate produced will initially be trucked to smelters in China and then in future years transported by the developing Mongolian rail network, expansions to which are already underway.
Currently it has been assumed that first production will occur in Q3 2012.
The Oyu Tolgoi copper-gold project is in the Aimag of Omnogovi, located in the desert South Gobi region of Mongolia.
Mongolia is a landlocked country in Central and East Asia sandwiched between China to the south and Russia to the north. It is the world’s 19th largest country - over 1.5 million square kilometers expanse of land. Tibetan Buddhism is the predominant religion of the 2.9 million people of which approximately 30% are still nomadic. Mongolia’s economy is based on agriculture and mining.
The Oyu Tolgoi project is located in the southern province of Omnogovi. Important sites in the province include the Flaming Cliffs site famous for its dinosaur remains; the Gobi Gurvansaikhan National Park which comprises steppes and famous ‘singing’ sand dunes. The endangered snow leopard inhabits its mountains ranges while its steppes are home to the Gobi Camel.
The Gobi Desert is a cold desert formed as a result of the Himalayas preventing the moisture from reaching the Gobi.
The Oyu Tolgoi topography largely consists of gravel-covered plains, with low hills along the northern and western lease borders. Small, scattered rock outcrops and colluvial talus are widespread within the northern, western, and southern parts of the property.
Four rare plant species occur within the mine licence area. The low population density and isolation of the southern Gobi region of Mongolia has resulted in the survival of several endangered species that no longer exist in neighbouring countries – e.g. the Mongolian wild ass.
The Small Gobi Strictly Protected Area is approximately 80 km south of the mine licence area, on the Mongolia-China border. The access road corridor traverses through 13 km of the protected area.
The land surrounding the mine licence area is predominantly used for nomadic herding of goats, camels, and sheep by small family units.
The South Gobi region has a continental, semi-desert climate. Temperatures range from an extreme maximum of about 50°C to an extreme minimum of about -34°C.
The Umdai River is the most significant hydrological feature of the project area. A tributary of the river passes through the site. Flows after heavy summer rainstorms often result in very turbulent, high-velocity mud flows – i.e. flash floods.
The Oyu Tolgoi area lies within an east-west-trending belt of Devonian-Carboniferous volcanic and sedimentary rocks of continental margin and island arc affinities, constituting the South Mongolia Volcanic Belt.
The Oyu Tolgoi deposits display copper–gold porphyry and related high-sulfidation copper–gold deposit styles. Its porphyry copper deposits display a range of mineralization styles, alteration characteristics, and deposit morphologies despite having formed in close spatial and temporal association.
The project area is underlain by complex networks of faults, folds, and shear zones.
Five deposits have been identified in the Mineral Resource at Oyu Tolgoi:
• Hugo South
• Hugo North
Copper mineralization in the South Oyu deposit (Southwest and Central) is associated with stockworks of thin (usually <10 cm) quartz–sulfide veins. Copper–gold porphyry style mineralization at the Southwest deposit consists of a cylindrical high-grade core roughly 250 m in diameter enclosed within a broad zone of lower-grade mineralization.
The Wedge deposit contains a zone of high-sulfidation mineralization hosted principally in basaltic tuff and breccia, grading downward and southward into chalcopyrite mineralization in basalt and quartz monzodiorite host rocks.
Mineralized veins within the Central deposit show a range in orientations, the most common including southwest-, west-, and northwest-dipping attitudes. Mineralization is characterized by an upward-flaring, high-sulfidation zone that overprints and overlies porphyry-style chalcopyrite–gold mineralization. A secondary-enriched supergene chalcocite blanket tens of metres in thickness overlies the high-sulfidation covellite–pyrite zone.
Copper mineralization at the Hugo South deposit is centered on a high-grade (typically >2% Cu) zone of intense quartz stockwork veining, which in much of the deposit is localized within narrow quartz monzodiorite intrusions and extends into the enclosing basalt and dacite tuff. The highest-grade copper mineralization in the Hugo North deposit is related to a zone of intensely stockworked to sheeted quartz veins.
The Heruga deposit is a Cu, Au, Mo porphyry deposit with overlapping zones of mineralization consisting of a Mo-rich carapace at higher elevation with increasing Au-rich mineralization at depth.
The New Discovery Zone occurs in the 3 km gap between Heruga and SW Oyu. Mineralization consists of strong chalcopyrite-pyrite mineralization with trace molybdenite occurring in veinlets and disseminated.
The recent Heruga and Far South discoveries have again highlighted the exploration potential of the Oyu Tolgoi region.
The series of deposits contain a currently identified resource of almost 40 billion pounds of contained copper in concentrate and 20 million ounces of contained gold in concentrate in the Measured and Indicated categories and another 40 billion pounds of contained copper and 25 million oz of contained gold in the Inferred category. The Oyu Tolgoi trend is still open to the north and south and the deposits have not been closed off at depth.
Mining & Operations
The Integrated Development Plan 2010 presents two complementary development cases:
• Reserve Case, based strictly on Proven and Probable Mineral Reserves proposes the development of theSouthern Oyu pits 1 through 9 and Hugo North Lift 1 underground block cave. The Reserve Case assumes processing of 1.4 billion tonnes of ore over a 27 year period.
• Life of Mine (Sensitivity) Case, which adds a large base of Inferred resources to the Reserve Case assumes that later phases of development would include underground block caving operations at the Heruga, Hugo South and the second lift of Hugo North that would result in the processing of 3.01 billion tonnes over 60 years.
Open pit mining at Oyu Tolgoi is planned to be a conventional shovel-truck operation. The Owner’s workforce will carry out drilling, loading, hauling, and dumping. Equipment maintenance will be undertaken by a Maintenance and Repair Contract arrangement.
Open pit equipment include three (3) 42m3 Diesel Shovels; five (5) 42m3 Electric Shovels; 73 220 t Class Trucks; six (6) 39R Electric Production Drills; four (4) 39R Diesel Production Drills; eleven (11) 390kW Dozers; six (6) Graders; two (2) 18m3 Front End Loader; three (3) Wheel Dozers; nine (9) 50t Watercarts; three (3) 15m3 excavators; two cranes; five (5) Cable trucks; nine (9) 8t trucks; pumps and trailer pumps.
Blast holes for ore and waste production drilling will be 17 m deep x 305 mm diameter. A contractor will carry out blasting activities including supply and storage. It is assumed that ammonium nitrate fuel oil (ANFO) will be used in dry holes and heavy ANFO in wet holes.
Underground mining would be carried out by using the block-caving method.
Shaft 1 has been successfully sunk to about 1300m depth at Hugo North and lateral development assumes building a characterization drift that is planned to transect the orebody and provide valuable information for the geotechnical assessment and analyses.
A total of four shafts would be constructed and would be used for transporting personnel, materials and equipment, for hoisting out ore, and ventilation.
Orepasses discharge through chutes to 50 t trucks on the haulage level. The trucks will transport ore to the primary gyratory crushers through one way haulage loops. The haulage level is all one way travel to reduce congestion. Haulage drifts are located 40 m below the extraction level.
Three gyratory crushers are located along the west side of the footprint. Each crusher discharges to a 700 t bin and apron feeder. The feeders discharge to a transfer conveyor that moves ore to the main inclined conveyors. The gyratory crushers are located according to geotechnical and haulage requirements.
The inclined conveyors transfer ore to the large bins located near the shafts. Each bin at the shafts feed a set of high speed measuring conveyors which directly load the skips. Skips are hoisted to surface to discharge into bins from which ore is transferred to the main overland conveyor and on to the mill facilities.
Underground mobile equipment include thirty (30) 3 m3 to 7 m3 LHDs; six (6) 30 t Haulage Trucks; seventeen (17) 50 t Haulage Trucks; Jumbo Drills, etc.
The mine has several refuge stations for use in case of emergency, which are designed to be sealed and pressurized from the compressed air line in Shaft No. 2. Emergency drinking water and oxygen supplies are maintained in each station.
Communications will be a vital part of Oyu Tolgoi’s infrastructure and operational capabilities. A state of-the-art information, security, data and voice communications system will be installed to ensure that operational needs will be adequately provided.
The flow sheet consists of primary crushing and coarse ore stockpiling followed by SAG and ball milling with pebble crushing. Rougher flotation is followed by concentrate regrinding and two stages of cleaning, the second stage being column flotation. Final concentrate is thickened and filtered before being transported by truck or rail. Rougher and cleaner scavenger tails are thickened and disposed of in a tailings impoundment.
IDP10 outlines the initial construction of a concentrator and infrastructure to support production at a nominal capacity of 100 kt/d. The predominant source of ore at start up is the Southern Oyu Open Pit.
The initial concentrator design is based on processing 35 Mt/a (96,000tpd) of ore from the Southwest open pit and Hugo North block cave underground deposits followed by an expansion to bring capacity to 58 Mt/a.
Underground ore is designated the priority feed. After available underground ore is fed to the plant the additional capacity is met with open pit ore.
Flow sheet include two Primary Crushers (1.52 m x 2.87 m gyratory, 746 kW); three SAG Mills (11.6 m dia x 6.9m, 20 MW); five Pebble Crushers (MP1000; 746 kW); six Ball Mills (7.3m dia x 11m, 11.4 MW); 6 x 8 160 m3 Tank Cells (rougher flotation); 8 – 14 Vertimill VTM 1500, 1119 kW (Regrind Mill); 4 – 6 x 4 (160 m3 Tank Cell); 4 – 6 x 4 160 m3 Tank Cell (Cleaner Scavenger Flotation); twelve 5.5m dia x 16m Column Cell (Column Flotation); four 20m dia High Rate Concentrate Thickeners; six 144 m2 Pressure Filter (Concentrate Filters); and, four 85 m dia High Compression Tail Thickeners.
During the initial 5 years of operation, the transport of bulk supplies and the delivery of copper concentrate will be by access road to the railhead which is locate din China. However, direct rail transport is considered a long term transportation solution after this initial development period.
To support the development of the Oyu Tolgoi and its ongoing operation, the existing access road from China to Oyu Tolgoi will be upgraded using the self perform fleet. Two road routes south from the Mongolian border are under consideration to link up with existing infrastructure and railroads in China. They would be 260 km to 280 km in length.
Water demand will be supplied from the Gunii Hooloi basin which extends 35-75 km north of the Oyu Tolgoi site and can meet average demand for 40 years.
A permanent water treatment facility and bottling plant will be constructed to treat raw water from the Gunii Hooloi borefield to drinking (potable) and domestic water standards.
Initial power for the Project is to be sourced from Inner Mongolia, China. By the fourth year power must be sourced from a power station within Mongolia.