Overview
Cerro Vanguardia is a gold-silver surface and underground
mine located in Southern Argentina. AngloGold Ashanti has a 92.5% interest
in the mine with Fomicruz (the province of Santa Cruz) owning the remaining
7.5%.
Located to the northwest of Puerto San Julian in the province of Santa Cruz,
Cerro Vanguardia consists of multiple small open pits with high stripping
ratios. The orebodies comprise a series of hydrothermal vein deposits
containing gold and large quantities of silver, which is mined as a
by-product.
Ore is processed at the metallurgical plant which has a capacity of 3,000t
per day and includes a cyanide recovery facility. Technology at the plant is
based on a conventional leaching process in tanks and carbon-in-leach with a
tailings dam incorporated in a closed circuit. The final recovery of gold and
silver is achieved through a Merryl Crowe method with metallic zinc.
In 2011, the mine produced 212 koz gold. As underground mining
operations ramp up future underground production would make up 70% of the
mine's total production.
Location
Cerro Vanguardia mine is located 150 km northwest of Puerto San Julian in
the province of Santa Cruz, Argentina.
Santa Cruz is an Argentine province located in the southern part of the
country in the region known as Patagonia. Oil, gas and mining provide much of
the province's income making it one of the most prosperous Argentine
province.
Geology & Mineralization
Cerro Vanguardia is located in the central portion of the Deseado
Massif stratigrafic and structural unit in Southen Argentina.
Gold and silver mineralisation occurs within a vertical range of about 150
to 200 metres in a series of narrow, banded quartz veins that occupy structures
within the 1,000m thick Chon Aike ignimbrites. These veins form a typical
structural pattern related to major north-south (Concepcion) and east-west
(Vanguardia) shears. Two sets of veins have formed in response to this
shearing; one set strikes about N40W and generally dips 65 to 90° to the east;
the other set strikes about N75W and the veins dip 60 to 80° to the south.
Cerro Vanguardia veins contain quartz, adularia and native gold, silver,
silver sulphides and electrum. Quartz textures are colloform to crustiform
banding, massive to vuggy quartz and breccia. They are typical of epithermal
low-temperature gold-silver deposits.
Mining & Operation
Consists of multiple small deep (up to 200m) open-pits with high
stripping ratios. At one time there are three to five pits operational
depending on the plant feed requirements. Mining uses a doubled bench height of
20m. Average strip ratio for the remaining 10 years mine life (2012) is 26
to 1.Waste dumps and heap-leach stockpiles are located adjacent to
pits.
Cerro Vanguardia orebodies comprise a series of steep hydrothermal
vein deposits containing vast quantities of silver, which is produced as a
by-product. Ore is blended as to smooth out the ore grades.
Due to the high strip ratio mining would move underground and would be
carried in parallel with open pit mining. In the near future open pit
production would decrease to 700,000 tpa - as pits become deeper - while
undergound production would contribute another 300,000 tpa. As of 2012, the
only underground mining operation was carried at the Mangas vein, but more
veins were undergoing underground development.
Processing
Ore is processed at the metallurgical plant which has a capacity of 3,000t
per day and includes a cyanide recovery facility.
Technology at the plant is based on a conventional leaching process in tanks
and carbon-in-leach with a tailings dam incorporated in a closed circuit.
The final recovery of gold and silver is achieved through a Merryl Crowe
method with metallic zinc.
