Overview
The Rosebel mine is located in Suriname, South America, some 80 kilometres from the capital city of Paramaribo. The concession covers 170 square kilometres and holds six major deposits and numerous gold prospects divided between two distinct limbs. Rosebel is Cambior's most important asset.
The Rosebel mine began production in 2004. Cambior has invested $176 million in the project, including $143 million for construction and production start-up. A significant portion of the processing facilities and mobile equipment from Omai were transferred to Rosebel in 2003.
In 2008 and 2009 major expansion to increase both mine and mill capacity were successful.
Proven and probable reserves at Rosebel rose by 37% or 1.4 million ounces in 2009. This increase was driven by the successful infill and exploration drilling, grade reconciliation, and increase in gold price. Major increases were achieved at the currently producing Royal Hill pit (where higher grade material was encountered at depth) and from the Mayo deposit that expanded at depth and on the western extension.
With the mill expansion complete in 2009 attention in 2010 was placed on resource delineation, near-mine exploration and additional leach tanks to improve recoveries. A 81,000 metre near-mine drill program is designed to upgrade additional resources to reserves and pursue targets in close proximity to existing resources.
Rosebel employs 1260 people and has a projected mine life of 12 years (until 2022). However, the exploration potential is still high and it is expected that new mineral reserves will be added in the future.
Location
The mine is located in the Brokopondo district of Suriname, South America, approximately 2.5 hours by paved road from the airport at Paramaribo. The mine also has an air strip for emergencies.
Geology
The Rosebel concession lies within the Lower Proterozoic Guiana Shield. The Suriname portion of the Shield consists of three distinct belts of metamorphic rocks separated by large areas underlain by granitoids and gneisses. The concession, excluding Headley's Reef and Thunder Mountain, covers 170 square kilometres, with the Suriname River to the east, the Saramacca River to the west and the Brokopondo reserve to the south.
There are six major deposits and numerous gold prospects divided between two distinct limbs. The northern limb holds the Pay Caro, East Pay Caro and Koolhoven/Bigi reserves as well as the "J" zone, Spin and Mama Creek anomalies. The southern limb holds the Rosebel, Mayo, Roma and Royal Hill deposits as well as the Eriaan Hill and Monsanto Hill anomalies. Mineralized lateritic blankets typically between 3 and 10 m thick cap all target areas.
Proterozoic metasedimentary and metavolcanic greenstone formations are intruded by a large tonalite stock near the southern boundary of the property, which resulted in the doming of the adjacent metasediments and the development of steep reverse faults. The greenstones are folded into a broad E-W trending, west plunging, synform.
Mineralization
Mineralization is associated with at least five generations of hydrothermal quartz veins over large areas in both the south and north limbs of the synform, crossed by W-NW trending shear zones. Mineralization is controlled by zones of dilation along the shear planes and by drag folding. Weathering has developed surface laterite and saprolite up to 50 m thick over the bedrock.
Mining & Operations
Mining is taking place at six pits: Pay Caro (2009: 1.95 Mt @ 1.23g/t), East Pay Caro (2009: 81,260t @ 0.80 g/t), Royal Hill NW and SE (2009: 3.60Mt @ 1.27g/t), Koolhoven (3.61Mt @ 1.08 g/t), and Mayo (3.13Mt @ 1.32 g/t).
Mining operations employ conventional open pit methods using a 5-meter bench interval and CAT 777 haul trucks with seven CAT 5130 (in both shovel and backhoe configurations) and two CAT 993K wheel-loaders.
Production drilling is accomplished by a fleet of 10 drills drilling 6-inch diameter holes creating a 3.9m x 4.5m grid pattern. The soft rock does not require blasting and is drilled using rotary bits. Transition ore and hard rock are drilled using down-the-hole hammer bits and loaded with explosives.
Loading and hauling are controlled by a computerized truck dispatch system.
Excavating equipment consists of 4-cubic metre backhoes, 10-cubic metre hydraulic shovels and a 10-cubic metre front end loader. Hydraulic backhoes are used to excavate soft and transition ore, hydraulic shovels excavate ore and waste, front end loaders stockpile material and move blasted rock. Additional small backhoes are used for ditching and related tasks.
Twelve to fifteen 85-tonne trucks haul waste rock to stockpiles located near each pit. Ore is trucked directly to the mill or stockpiles.
The tailings facility has storage capacity for 46 million tonnes of material. It is possible to increase storage to 80 million tonnes by raising the dam by 10 metres to 30 metres.
Processing
The process flowsheet consists of a crushing and grinding circuit followed by a conventional gravity circuit, cyanidation circuit and carbon-in-leach (CIL) plant. Omai's A grinding circuit processed both hard rock and saprolite at a rate of 12,000 tonnes per day. In 2002 circuit A was dismantled, transported, and installed at Rosebel.
Processing extracts 95% of the gold. The material is crushed to powder in a mill; heavier gold particles, 25% to 30% of the gold, is recovered in a gravity circuit. The remaining gold is recovered using reagents -- cyanide solutions which dissolve the gold and recovery is done by electrowinning. Water that has been contaminated with reagents is kept separate and recirculated.
Early phases of production are producing soft sticky ore; over time this will change and the plant will need to treat harder material from the transition zone and hard rock zone. The amenability of the ore to gravity concentration and cyanide leaching for gold extraction are the reasons for the choice of wet processes. Over 30% of the gold is recovered through a gravity circuit. A new primary crusher plant was added in 2005 allowing Rosebel to process hard rock.
The original mining plan called for selective mining of higher-grade ore and stockpiling low-grade material for milling later in the mine life. Now all the ore is being fed to the processing plant, resulting in lower grade than originally planned.
Gold is sent to the Royal Canadian Mint for further processing and sale. The RCM deducts the royalty, in kind, immediately after final refining and deposits the gold in an account for Suriname.
