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The top ten deepest mines in the world

Eight of the ten deepest mines in the world reside in a particular region of South Africa, while the remaining two - Kidd Creek and Creighton - are both located in Ontario, Canada.

 

1. Mponeng Gold Mine, Gauteng, South Africa

Mponeng_Gold_Mine

On-reef development and thus the start of production, are scheduled for 2013 with full production due in 2015.

"Mponeng is the most recently sunk of the three former Western Deep Levels mines."

AngloGold Ashanti's Mponeng gold mine, located south-west of Johannesburg in South Africa, is AngloGold Ashanti's Mponeng mine is located in Gauteng province of South Africa. It is mined to an average depth of 2,800m-3,400m below surface and is one of the world's deepest and richest gold mines with grades at over 8g/t. It is one of three AngloGold projects in the West Witts area apart from Savuka and TauTona mines. The name means 'look at me' in the local Sotho language.

Formerly the Western Deep Levels South Shaft, or Shaft No 1, Mponeng is the most recently sunk of the three former Western Deep Levels mines. Sinking of Mponeng shafts began in 1981, and the main shaft was completed in 1986, with the subshaft completed in 1993.

Currently all production is sourced from the VCR (Ventersdorp Contact Reef). The mine has been expanded through many deepening projects with the latest one being the extension from 109 to 120 levels. Work is currently in progress to extract the ore from the Carbon Leader Reef (CLR) below it.

The project will facilitate the development of many other smaller projects and extend the mine life. It is yet to be approved by the company board. The other major project, VCR below 120, entails accessing the mineral reserves below 120 level. AngloGold Ashanti estimates that this project will add 2.5Moz to production for 10 years at a cost of R2.03bn ($252m).

The VCR below 120 project is expected to increase the mine's life by eight years to 2024. The project was approved by the board in February 2007, following which construction began. On-reef development and thus the start of production is scheduled for 2013 with full production due in 2015.

Geology and reserves

"The plant conducts electro-winning and smelting (induction furnaces) on products from Savuka and TauTona."

Mponeng is located on the north-western rim of the Witwatersrand Basin. There are seven gold bearing conglomerates within the lease area, of which two are economically viable at present. The VCR is a gold-bearing quartz-pebble conglomerate of intermediate grade, capping the last angular Witwatersrand non-conformity.

The CLR is a 20cm thick tabular auriferous quartz pebble conglomerate.

As of December 2010, proven reserves at the VCR stood at 2.05Mt with an average grade of 9.98g/t Au at 109-120 level and 0.31mt graded at 8.85g/t Au below 120 level.

The yet-to-be-mined CLR below 120 level has probable reserves of 22.52Mt graded at 11.30g/t Au..

Mining

mining

Some 5126 people were employed full time at Mponeng in 2007 with 435 contractors.

The South shaft deepening project commenced in 1996 and as a result Mponeng mines the Ventersdorp Contact Reef (VCR) to the 120 level, which is some 3.4km below datum. Mponeng mines on average at deeper than 2.7km below the surface. The VCR reef that Mponeng mines dips at 22º, and has an average channel width of 78cm.

The deepest operating stope is at a depth of 3.37km below surface. The grade at this operation varies considerably, therefore a sequential grid mining method is used which allows for selective mining and increased flexibility in dealing with changes in grade ahead of the stope. The mine utilises a twin-shaft system housing two vertical shafts and two service shafts.

 
Exploration

Exploration drilling for the CLR below 120 project commenced in early 2008. CLR comprises three economical units. Unit 3 is centrally located and is the oldest of the CLR deposits. Unit 2 is a small size complex channel deposit situated in the east of Unit 3. The unavailability of infrastructure to access these units raised the opportunity of containing additional ounces of gold at the mine.

A series of sub-vertical holes were drilled from underground in 2010 to intersect at the CLR depth. The average length of the hole drilled was 900m with the deepest hole being 1,090m

Ore processing

Ore mined is treated and smelted at Mponeng’s gold plant. The ore is initially ground down by means of semiautogenous milling after which a conventional gold leach process incorporating liquid oxygen injection is applied. The gold is then extracted by means of carbon-in-pulp (CIP) technology. The plant conducts electro-winning and smelting (induction furnaces) on products from Savuka and TauTonaas well.

Production

Production in 2007 fell 2% to 587,000 ounces compared with 2006.

The various planned and unplanned work stoppages and safety initiatives conducted towards the end of the year, combined with a decline in grade and reduced face advance, contributed to the decrease in production.

There was a 4% decline in the area mined in 2007, largely as a result of a 3% decrease in face length. Mponeng undertook extensive cost cutting measures throughout the year. Gold Production at the Mponeng mine in 2010 was 532,000oz.

 

2. TauTona, Anglo Gold, South Africa

TauTona

TauTona I now the world’s deepest mine.

In 2006 AngloGold Ashanti commenced a project to extend its South African TauTona gold mine to 3.9km. This was completed in 2008 making it the world’s deepest mine, surpassing the 3,585m deep East Rand Mine by a good distance. The name TauTona means "great lion" in the Setswana language.

The TauTona mine exists within the West Witts area not so far from Johannesburg in South Africa, near the town of Carletonville. TauTona neighbours the Mponeng and Savukamines, and TauTona and Savuka share processing facilities. All three are owned by AngloGold Ashanti.

Production at TauTona fell to 409,000 ounces in 2007, down from 474,000 ounces in 2006, due to increased seismic activity.

"The plant uses conventional milling to crush the ore and a CIP (carbon in plant) to further treat the ore."

This required a review of the practice of mining of shaft pillars and high-grade remnants, and delays to the build-up in volume caused by opening up of the sequential grid. Capital expenditure in Siguiri was R2.5bn ($US71m) in 2007, with 56% committed to the development of ore reserve.

TauTona accounted for 7% of AngloGold Ashanti’s total 2007 gold production.

The mine was originally built by the Anglo American Corporationwith its 2km deep main shaft being sunk in 1957, with operations starting in 1962.

Since its construction two secondary shafts have been added bringing the mine to its current depth. The mine today has some 800km of tunnels and employs some 5600 miners. It is an extremely dangerous environment, with five workers losing their lives in 2007.

The mine is so deep that temperatures in the mine can rise to dangerous levels. Air conditioning equipment is used to cool the mine from 55°C down to a more tolerable 28°C. The rock face temperature currently reaches 60°C.

The journey to the rock face can take one hour from surface level. The lift cage that transports the workers from the surface to the bottom travels at 16 meters a second. The mine has also been featured on the MegaStructures programme produced by National Geographic.

Geology and reserves

"The mine was originally built by the Anglo American Corporation with its 2km deep main shaft being sunk in 1957, with operations starting in 1962."

The TauTona mine exists within the West Witts area slightly South West of Johannesburg in the North West of South Africa.

Two reef horizons are exploited at the West Wits operations: the Ventersdorp Contact Reef (VCR), located at the top of the Central Rand Group, and the Carbon Leader Reef (CLR) near the base. Owing to nonconformity in the VCR, the separation between the two reefs increases from east to west, from 400m to 900m. TauTona and Savuka exploit both reefs while Mponeng only mines the VCR. The structure is relatively simple with rare instances of faults greater than 70m.

The CLR consists of one or more conglomerate units and varies from several centimetres to more than 3m in thickness. Regionally, the VCR dips at approximately 21°, but may vary between 5° and 50°, accompanied by changes in thickness of the conglomerate units. Where the conglomerate has the attitude of the regional dip, it tends to be thick, well-developed and accompanied by higher gold accumulations.

Where the attitude departs significantly from the regional dip, the reef is thin, varying from several centimetres to more than 3m in thickness.

Total resources 2,615,000 ounces
Measured resources 510,000 ounces
Indicated resources 8,106,000 ounces

Mining and processing

Mining operations are conducted at depths ranging from 1.8km down to 3.9km following the recent expansion.

The mine consists of a main shaft system supported by secondary and tertiary shafts. The main mining method is longwall. TauTona shares a processing plant with Savuka. The plant uses conventional milling to crush the ore and a CIP (carbon in plant) to further treat the ore. Once the carbon has been added to the ore, it is transported to the plant at Mponeng for electro-winning, smelting and the final recovery of the gold.

Production - Gold production declined by 14% to 12,714kg (409,000oz) (2006: 14,736kg (474,000oz)), owing to a higher-than-expected fall in the volumes of ore mined. This was due to increased seismic activity in the vicinity of the CLR shaft pillar which is being mined, and at several highgrade production panels, where production was halted for limited periods during the course of the year. Both face length and face advance were negatively affected by seismicity during the year. The increased geological risk from this seismic activity necessitated re-planning regarding mine layout and mining methods.

 

3. Savuka Gold Mine, Gauteng, South Africa

Savuka_Gold_Mine

Mining at Savuka is carried out through a three shaft system.
Image courtesy of Karl Schoemaker.

 

AngloGold Ashanti's Savuka gold mine is situated in Gauteng, South Africa. The underground mine is the second deepest mine in the world, at a depth of nearly four kilometres. It produced 49,000oz of gold in 2011 at a cost of $864/oz.

The mine is approaching the end of its productive life with majority of the ore having been exhausted. Minimal mining operations are being carried out at the mine currently.

The mining operations at Savuka are occasionally affected by seismic activities. This has resulted in damage to the shaft and infrastructure, as well as worker fatalities over the years.

The latest earthquake that occurred in January 2012 resulted in the death of an employee. Inspections were carried out and operations halted temporarily following the incident.

Geology, gold reserves and West Wits operations
Savuka is part of AngloGold's West Wits operations in the Gauteng region. The West Wits operations also include the Mponeng and TauTona mines.

The West Wits line is part of the Witwatersrand Basin and is estimated to contain the world's largest gold reserves. The Witwatersrand Basin is of the late Archaean age and is estimated to be 2.8 billion years old.

West Wits operations consist of the Ventersdorp Contact Reef (VCR) and the Carbon Leader Reef (CLR). Savuka and TauTona both mine the CLR while the VCR is mined by Mponeng.

CLR constitutes a major part of the Savuka mine. It is 20cm thick and includes three main stratigraphic units. Unit one is the most economically important of the three units and is spread over the mine in the form of a sheet. Unit two is a channel deposit which is currently being mined. Unit three is the oldest of the three units.

The VCR portion in the Savuka mine is a well-developed deposit and contains higher gold accumulations.

Mineral resources of the mine as of December 2011 are estimated at 5.26 million tons (mt) grading at 17.86g/t. Measured reserves are estimated at 1.51mt grading at 16.67g/t. Indicated reserves are estimated at 2.53mt grading at 17.82g/t.

Mineralisation at Gauteng's Savuka gold mine
Gold mineralisation occurs in two metre thick quartz pebble conglomerates. Gold is accumulated with pyrite and carbon, along with quartz as the gangue material.
Gold processing at the world's second deepest mine

"The mining operations at Savuka are occasionally affected by seismic activities. This has resulted in damage to the shaft and infrastructure."

"Ore recovered from the mine is processed by the Savuka gold processing plant, which also processes ore from the TauTona mine."

Mining is carried out through a three-shaft system including the main, secondary and tertiary shafts. Different mining methods, including longwall, conventional and sequential grid mining, were used to recover the ore. The longwall operation was converted to sequential grid mining recently.

The mine is equipped with various facilities to ensure that the working temperature is bearable for the workers.

In 2009, a seismic event destroyed the shaft and infrastructure at the mine. The aftershocks from the seismic event caused the underground dams to burst. As a result, the mine was flooded and the equipment was damaged. The primary and tertiary shafts were not damaged, but the main supporting structures for the CLR production were.

From the second level, the mine was fully flooded with pumping and ventilation services also affected. A $30m renovation programme was undertaken to restore the operations at the mine.

Completed in 2011, the restoration operations used advanced 3D modelling software including Bentley Systems' MicroStation and Structural Modeler to design the shafts.

Ore processing at AngloGold Ashanti's South African deposit
Ore recovered from the mine is processed by the Savuka gold processing plant, which also processes ore from the TauTona mine.

The processing plant includes a conventional mill circuit which crushes the ore into a suitable size. The crushed ore is fed into the Carbon-In-Pulp circuit.

The processed ore is sent to the Mponeng gold processing plant, where final elution is carried out using electrowinning and smelting. The recovered gold is then moulded into gold bars.

At the Savuka mine, the CLR is mined at depths ranging from 2,600m to 3,500m below the surface, while the VCR is mined at a depth of 1,808m below surface. VCR has been mostly mined out with mining operations ceasing in 2010.

 

4. Driefontein, South Africa

Driefontein_South_Africa

Driefontein lies near the town of Carletonville in South Africa’s Far West Rand goldfield.

Driefontein is located in South Africa’s West Wits Line goldfield, about 60km south west of Johannesburg. Driefontein Consolidated Ltd (Driefontein) was created in 1981 with the merger of the West Driefontein and East Driefontein mines. In January 1998, Gold Fields Ltd assumed management responsibility for the operation, which became a wholly owned subsidiary in May 1999. The mine, which has milled over 222Mt of ore and recovered over 102.5Moz of gold since 1952, employs 16,600 people. The average yield over the mine’s 55-year lifetime has been 14.2g/t.

GEOLOGY AND RESERVES
The goldfield is part of the Witwatersrand Basin. Gold mineralisation occurs at depths between 1,000m and 4,000m below surface and is hosted within two major orebodies; the Carbon Leader Reef (CLR) and the Ventersdorp Contact Reef (VCR). A third body, the Middelvlei Reef (MR), is a minor contributor to the resource base. The CLR comprises various facies from single carbon seam to single and multiple band conglomerates. It is a high-grade reef at the base of the Central Rand Group, and at Driefontein dips at 25°.

As of mid-2006, Driefontein’s proven and probable reserves within the exiting mine infrastructure totalled 55.6Mt at a grade of 5.9g/t gold, containing 14.1Moz of gold. A further 31Mt of probable reserves at 8.2g/t lie below the existing infrastructure (deper than 3,420m below surface), containing an additional 8.3Moz of gold. The mine’s total proven and probable reserves amount to 94.6Mt grading an average 7.4g/t, and containing 21.6Moz of gold.

MINING
Driefontein is a conventional South African underground mine in which opportunities for increasing workplace mechanisation are limited. It comprises eight operating shaft systems which access the VCR and CLR. Shafts 1, 2, 4 and 5 access the eastern part of the mine while shafts 5, 6 and 7 access the west part. As the west part is depleted, production will be maintained by increased use of 1 and 5 shafts.

At present, production comes from a combination of longwall and scattered mining methods. This will continue on the VCR while extraction of the CLR will be based on dip-pillar mining with backfilling of the mined-out areas to facilitate secondary extraction of some 50% of the remaining pillars. The primary layout consists of 40m wide pillars with 140m spans and, after secondary removal, aims to achieve an 87.5% extraction.

The current operations are classed as being at intermediate to deep environments, and are seismically active.

ORE PROCESSING
Driefontein operates three primary metallurgical plants and a secondary recovery plant. New milling facilities have been installed in both the No.1 and No.2 gold-recovery plants, with a two-year programme having taken place to recover gold that had been locked up in the old equipment.

The East Plant processing route consists of three-stage crushing, rod and pebble milling closed by hydrocyclones, pulp thickening, pre-aeration, air agitated leaching, drum filtration, zinc precipitation and smelting to produce doré. The current operating capacity is 240,000t/month. The company aims to incorporate run-of-mine ore milling and to replace filtration with carbon-in-pulp recovery while increasing its capacity to 300,000t/month.

The West Plant consists of the VCR and CLR crushers combined with a central milling and treatment section that is divided into high-grade and low-grade sections. The process route is similar to that of the East Plant. Waste rock comprises approximately 3% of hauled ore and the average throughput is 170,000t/month.

The West Reclaim Plant mills rock-dump (waste and low-grade) material in a circuit consisting of primary crushing, SAG milling, two-stage cycloning and thickening. The product is leached and treated in a pump-cell plant. Loaded carbon is sent to the Leeudoorn metallurgical plant at Kloof for gold recovery and carbon regeneration. The plant is operating below design capacity at 115,000t/month of feed rock.

PRODUCTION AND COST
In the 2005-06 financial year, Driefontein produced 1,150,000oz of gold from 6.87Mt of ore milled. Of this amount, 3Mt of low-grade ore were sourced from surface material, with 3.87Mt being hoisted. This was marginally lower than the output the previous year, with some higher-grade areas having been affected by increased seismicity, while the overall yield from underground decreased from 8.3g/t to 8.1g/t. The combined yield was 5.2g/t, down from 5.4g/t the year before. As a result, total cash costs rose from US$330/oz in 2004–05 to US$355/oz in 2005–06, with total production costs of US$392/oz.

THE FUTURE
Gold Fields has been carrying out a feasibility study into ways of accessing the 8.8Moz of gold that lie below the mine’s existing infrastructure. Involving deepening the existing No.9 sub-vertical shaft, this would extend Driefontein’s life by at least 13 years to around 2035. The company has also been evaluating the recovery of high-grade Carbon Leader reef pillars from the No.10 Shaft complex.

 

5. Kusasalethu Mine Project, Far West Rand, South Africa

Kusasalethu_Mine_Project

The Elandsrand project has required an entirely new mine to be equipped beneath the existing infrastructure which has been operating continuously, seven-days-a-week throughout.

The Kusasalethu mine, formerly known as Elandsrand, is a project being developed beneath the existing mine, adding a further 18 years of life to the operation and allowing 9.8Moz of reserves to be exploited. The deepening project is almost complete.

The mine was renamed in February 2010. Kusasalethu mine employed 5,756 employees and contractors and produced 180,334oz of gold in 2011. The production output will be 450,000oz of gold a year, with full production set to be achieved by 2013.

Located in Far West Rand, 1km south-west of Carletonville, Mpumalanga, Harmony acquired Elandsrand in February 2001, along with the adjacent Deelkraal mine - known collectively as Kusasalethu - from AngloGold for a cash price of R1bn.

"Production output will be 450,000oz of gold a year."
"Witwatersrand is home to the world's richest gold deposits."
"The work calls for the sinking of two settling dams."

 
Geology

The Witwatersrand is home to the world's richest gold deposits and three identified main reef groupings – the Ventersdorp Contact Reef (VCR), the Carbon Leader Reef (CLR) and the Mondeor Reef – are contained in Elandskraal. Of these, only the VCR is economic and has been mined between 1,600–2,800m below surface; future production at the Elandsrand mine will be down to 3,600m.

Both the VCR and CLR are narrow, tabular ore bodies, 0.2–2m thick, consisting of quartz pebble conglomerates hosting gold, with extreme lateral continuity.

Mine project
mine_project

Schematic of the Elandsrand mine. The mine is being built below the existing infrastructure and will add 18 years to the workings life.

 

During the period when Elandsrand was managed by AngloGold, production came mainly from the workings between 73 and 98 levels, though over time these reserves were progressively mined out.

Based on a feasibility study undertaken in 1990, AngloGold decided to extend the life of the mine by exploiting the western high grade VCR block, below the limit of the then existing infrastructure, at depths from 3,000m to 3,500m below datum. The plan was to deepen both the sub-vertical and sub-ventilation shafts by around 500m apiece and then develop the reef on four new levels – 102, 105, 109 and 113 respectively.

After acquisition, Harmony have continued with the deepening project – now termed the 'new mine' – making a capital investment of over R600m to counter Elandsrand’s declining production profile.

Apart from deepening the sub-shafts and developing access for the mine, a variety of other aspects have had to be addressed, including raising the reef and waste ore pass system, installing new rock hoisting facilities and integrating the two mines’ ore pass systems.

In addition, the work calls for the sinking of two settling dams, together with the provision of underground pumping stations, a refrigeration chamber, two service shafts and a turbine chamber and dam.

Kusasalethu progress

Project delivery has not been without its setbacks – most notably in November 2002 when a high-pressure gas pocket was released with the blast on 109 level as a result of intersecting the Cobra Dyke. Although the dyke was intersected in the upper levels of the mine, it is not associated with much gas there. As a result, the work on 109 and 113 levels was put roughly two years behind schedule, with development on the upper levels to give access to the Deelkraal reserve being accelerated to offset the delay.

Overall, good progress has been made, with capital access development being completed on levels 105 and 109 by the first half of 2007 and cash operating cost development taking place in easterly and westerly directions on 102, 105 and 109 levels.

Arrangements for the clear water and mud handling are also well advanced. A series of annex holes have been drilled from level 102 down to level 113, where the water will enter two 10m-diameter high flow settlers installed on top of the clear water dams between 113 and 115 levels.

A new pump station on 115 level completed in March 2011 is equipped with four seven-stage 2.4MW pumps. It delivers clear water from here up to existing clear water dams on 98 level, with settled mud being pumped to the existing mud dams on 100 level.

Re-engineering the closed loop chilled water system has allowed the project to make significant reductions in high-pressure piping. Having service water fed to the workings on each level from the discharge side of the air coolers, enabling surplus ‘cool’ water to be returned to the 98/100 level dam, results in fewer chilled water columns being needed.

The cooling for the mine is supplied by two 3.5MW Bulk Air Coolers (BACs) located on 100 level, which receive a water feed from three 3.5MW refrigeration plants installed on the same level - air for the BACs was supplied by two Axial AFN Booster fans.

A 22kV sub-station equipped with two 10MVA transformers, completed in early 2011, feeds the refrigeration complex in operation. Developing the refrigeration chambers themselves proved challenging, since the work had to be done behind the existing mid-shaft loading arrangement on 100 level; all the production from the original mine - above 100 level - had to be subsequently hoisted.

Mine fatalities

During January 2009, production at the mine was halted for two days because of a fatal accident caused by a seismic event. The mishap occurred in the 95/10 W4 panel, around 2,780m below surface. Another mine fatality occurred in May 2011. The mining operations were temporarily suspended again in November 2011 due to another mine fatality.

 

6. Moab Khotsong Gold Mine

Moab_Khotsong_Gold_Mine

Moab Khotsong gold mine is one of AngloGold Ashanti's Vaal River operations in the South Africa. The mine is located around 180km south-west of Johannesburg near the towns of Orkney and Klerksdorp. The mine is in production since 2003. It currently ranks as the sixth deepest mine in the world, with its mining depth ranging between 2.6km and 3.054km below surface.

The mine exploits the Vaal Reef (VR) through three mining layers, namely the Top, Middle and Lower Mines. Moab Khotsong employs a scattered mining method with an integrated backfill support system.

The mine produced 162,000 ounces of gold grading 0.238oz/t in 2012. The ore reserve stood at 6.61Moz grading 10.02g/t as of December 2012. AngloGold Ashanti engaged 19 underground drilling machines at Moab Khotsong in 2012, to increase the mineral resource base and extend the mine's life up to 2040.

 

7. South Deep Gold Mine

South_Deep_Gold_Mine

The South Deep gold mine, owned and operated by Gold Fields, is the seventh deepest mine in the world. The South African gold mine extends up to 2,995m below surface. The mine, covering an area of 4,268ha, is located 45km south-west of Johannesburg.

The deep underground mine comprises of two shaft systems known as the South Shaft complex and the Twin Shaft complex. The mine switched from conventional mining to fully mechanised mining in 2008. The extracted ore is processed at a central metallurgical plant.

The managed mineral reserve at South Deep as of December 2012 was estimated to be 39.1Moz. The mine produced 270,000oz of gold in 2012. It is undergoing a major development project to increase its annual production to about 700,000oz by 2016. The mine life of South Deep is expected to be extended up to 2092.

8. Kidd Creek Copper and Zinc Mine, Ontario, Canada

Kidd_Creek

Drillers underground at Kidd Creek.

The Kidd Creek copper/zinc mine is located near Timmins, Ontario, Canada. Along with copper and zinc it produces indium, silver-bearing slimes, nickel-copper carbonate, liquid SO2 and sulphuric acid. Kidd Creek is 100% owned and operated by Xstrata plc, which acquired the complex through its take-over of the former owner, Falconbridge Ltd, in 2006. The operations incorporate two business units: Kidd Mining Division and Kidd Metallurgical Division.

GEOLOGY AND RESERVES
Kidd Creek is based on a rich, steeply dipping volcanogenic sulphide deposit located in the Archaean Abitibi greenstone belt. There are two major orebodies, with associated smaller lenses. The ore is hosted in felsic rocks of the Kidd Volcanic Complex and is cut by mafic sills and dykes. Structural deformation resulting from several phases of folding and faulting affects the distribution of sulphide lenses.

Three ore types predominate: massive, banded and bedded (MBB) ores (pyrite, sphalerite, chalcopyrite, galena and pyrrhotite); breccia ores containing fragments of the MBB ores; and stringer ores consisting of irregular chalcopyrite stringers cutting a siliceous volcaniclastic host.

At the end of 2005, Kidd Creek’s proven and probable reserves were stated as being 19Mt grading 1.8% copper, 5.5% zinc, 0.18% lead and 53g/t silver. Measured and indicated resources totalled 2.6Mt at 2.2% copper, 6.3% zinc, 0.2% lead and 48 g/t silver, with a further 11.9Mt in inferred resources at 2.7% copper, 4.8% zinc, 0.3% lead and 81g/t silver.

UNDERGROUND MINING
The mine started production in 1966 from an open pit. The orebody is now mined at depth through three shafts as the No.1, No.2 and No.3 Mines. Phase 2 of No.3 Mine is currently being developed. Mine D will extend Kidd Creek below No 3, from a depth of 2,100m to 3,100m.

Blasthole stoping with cemented backfill is used to extract the ore underground, Kidd Creek being the world’s second-largest user of cemented backfill (after Mt Isa in Australia). Blastholes are drilled using Ingersoll Rand, Mission and Cubex drills and broken ore is hauled underground by Tamrock load-haul-dump units. The hoisting shafts are equipped with an ABB Hoist Automation System, which has significantly increased the efficiency of raising ore from depth.

PROCESSING
The run-of mine ore is shipped to the Metallurgical Division, 27km southeast of the mine. This division consists of a concentrator, copper smelter and refinery, zinc refinery, cadmium plant, indium plant and two sulphuric acid plants.

The Kidd concentrator crushes and grinds the ore before flotation. Zinc concentrates are roasted, and the sulphur oxides and trioxides are passed to the sulphuric acid plant. The zinc calcine is leached, the zinc-rich solution then being processed in a purification stage where cadmium is extracted. The purified zinc-rich solution is sent to the electrolysis plant where zinc is plated onto aluminium cathodes. Indium, zinc and copper are recovered from smelter dusts processed in the indium plant.

The smelter has a capacity of 150,000t/y of blister copper, which is then refined at the company's 147,000t/y-capacity refinery. Silver-bearing slimes are also produced and shipped to other facilities for processing.

The zinc plant has a capacity to produce 147,000t/y of zinc metal, with the Kidd Mining Division supplying 61% of the feed and the rest coming from outside sources. In 2004, the Kidd smelter produced 121,557t of zinc and 115,578t of copper.

CUSTOM FEED
Kidd Metallurgical Division’s Custom Feed Business processes concentrates from outside Kidd Mining in order to ensure that the smelters and refineries run at full capacity. Outside imports include concentrates from Sudbury, Collahuasi, Minera Escondida Ltda and others, while zinc comes from Billiton Metals Canada and other sources.

PRODUCTION AND COSTS
Kidd Creek processed 2.3Mt of ore in 2005, at head grades of 2.0% copper and 6.2% zinc, from which it produced 42,738t of copper, 119,960t of zinc and 3.7Moz of silver. Smelter and refinery production totalled 118,973t of smelted copper, 111,231t of refined copper and 113,711t of refined zinc.

DEVELOPMENTS
By the end of 2005, Kidd Creek had spent C$518m on the development of its Mine D area, below the existing mines. Commissioning began in 2004, with Mine D scheduled to increase the operation's capacity to 2.4Mt/yr of ore. Transition to the new mine area was 90% complete by the end of 2005, with a total project budget of C$68m.

Kidd Creek is also processing ore from from the company’s Montcalm nickel-copper mine, which began production in 2004.

 

9. Great Noligwa Gold Mine, South Africa

Great_Noligwa_Gold_Mine

The gold plant situated next to the mine.
AngloGold Ashanti’s Great Noligwa underground gold mine is situated close to the town of Orkney, on the free state side of the Vaal River in South Africa.

It adjoins Kopanang and Moab Khotsong as part of AngloGold’s extensive Vaal River operations, which comprise four gold plants, one uranium plant and a sulphuric acid plant.

In 2008, the Vaal River operations (including surface operations) produced 34,785kg (1,119,000oz) of gold, equivalent to 22% of group production.

Production at Great Noligwa fell significantly in 2008 because of a transfer of the SV4 section to Moab Khotsong from where it is more easily accessible.

Geology and reserves
The reefs mined at Great Noligwa are the Vaal Reef and the Crystalkop Reef, with the Vaal Reef accounting for over 90% of the gold produced in the mine. The Vaal Reef consists of 85% of the ore reserve tonnage with mining grades between 10g/t and 20g/t.

Mining and processing
The complexity of the ore at Great Noligwa has necessitated a scattered mining strategy comprising a twin-shaft system serving eight main levels at an average depth of 2,400m.

The reef is accessed from the footwall haulage and return airway development, with cross-cuts spaced every 180m to the reef horizon.

 

"The reefs mined at Great Noligwa are the Vaal Reef and the Crystalkop Reef, with the Vaal Reef accounting for over 90% of the gold produced in the mine."

Raises are then developed on-reef to the level above and the reef is stoped out on strike with an average stope width of 150cm. Approximately 4,000m of development is completed each quarter.

The orebody is narrow and tabular and averages 35,000m² a month. Panels are on average 26m long.

Great Noligwa has its own dedicated milling and treatment plant which applies conventional crushing, screening, semi-autogenous grinding and carbon-in-leach processes to treat the ore and extract the gold. The plant has a nominal throughput capacity of 230,000tpm.

Production and costs
Production fell by 32% to (330,000oz) in 2008, compared to 483,000oz in 2007. The decline was due to the transfer of the high-grade SV4 section of the Great Noligwa mine to Moab Khotsong.

Safety stoppages and power-saving initiatives also contributed to the decline. The mine saw a decline in tonnes mined by about 34%.

Total cash costs for the year rose by 31% due to production volumes and higher input costs of power, labour and support.

The increase in costs was offset by an increase in uranium by-product credits resulting out of improved production and the cancellation of loss-making uranium contracts. Capital expenditure came to R213m ($26m).

AngloGold Ashanti is expecting a further 30% fall in production in 2009 to 7,000kg (220,000oz) at a total cash cost of between $460/oz and $480/oz. Capital expenditure of R198m ($20m) is planned.

The future
As the operation ages, mining methods are converting from conventional scattered mining to pillar or remnant mining. Until now the Vaal Reef has been the most economically viable reef to mine. However, as this reef is mined out, the less economical Crystalkop Reef is being increasingly exploited as are economically viable pillars within the mine boundaries.

10. Creighton Mine

Creighton_Mine

Creighton, an underground nickel mine located in the City of Greater Sudbury, Ontario, Canada, is the tenth deepest mine in the world. It is also the world's deepest nickel mine, with its mining depth extending up to 2.5km. The mine is owned and operated by Vale. The mine was discovered in 1991.

The first production from the Creighton open pit started in 1901. Underground operation commenced in 1906. Current mining methods include shrinkage mining and mechanised undercut-and-fill mining. The large-diameter blasthole method combined with vertical retreat mining has also been introduced recently. Extracted ore is crushed underground and sent by rail to the Clarabelle Mill for processing.

The mine produced 797,000t of ore grading 1.80% copper and 1.84% nickel in 2012. Exploration drilling carried out at Creighton in 2007 confirmed mineralisation at depth. The Creighton Deep exploration Project is believed to have almost doubled the proven and probable reserve to 32Mt grading 1.9% to 2.2% nickel and two percent to 2.3% copper.
 
 
 
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