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Australia
Worsley Alumina (Boddington) Operation

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 Location:
127 km SE from Perth, Western Australia, Australia

  Address:

PO Box 344
Collie
Western Australia, Australia
6225
Phone  ...  Subscription required
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Overview

StageProduction
Mine TypeOpen Pit
Commodities
  • Aluminum
  • Bauxite
Mining Method
  • Truck & Shovel / Loader
Processing
  • Calcining
  • Crush & Screen plant
  • Bayer
  • Dissolving & Crystallising
Mine Life15 years (as of Jan 1, 2020)
Worsley Alumina is one of the largest bauxite mining and alumina refining operations in the world.

Bauxite mining takes place near Boddington, 130km south-east of Perth. The bauxite is transported 51km by overland conveyor to our alumina refinery, 15km north-west of Collie, where the red rock is turned into white alumina powder using the Bayer Process. The alumina is then railed 55km to the Bunbury Port for export to aluminium smelters worldwide.
Latest NewsSouth32 hands Worsley Alumina contracts to SRG Global     October 1, 2020


Owners & OPERATOR

Source: p. 44
CompanyInterestOwnershipInvestor's Info
South32 Worsley Alumina Pty Ltd. (operator)
Sojitz Alumina Pty Ltd. 4 % Indirect
Japan Alumina Associates (Australia) Pty Ltd. 10 % Indirect
South32 Limited 86 % Indirect
Worsley Alumina Operation is a joint venture between South32 (86 per cent), Japan Alumina Associates Australia Pty Ltd (10 per cent) and Sojitz Alumina Pty Ltd (4 per cent).

South32 Worsley Alumina Pty Ltd, as manager of the Worsley Joint Venture, acts as agent for and on behalf of the South32 (86%), Japan Alumina Associates (Australia) Pty Ltd (10%) and Sojitz Alumina Pty Ltd (4%).

Deposit Type

  • Laterite


Summary:

The bauxites have developed on the exposed Achaean basement of the Western Gneiss Terrane, which is located on the western edge of the Yilgarn Block. In the project area, the Western Gneiss Terrane is predominantly composed of granitic gneisses and migmatites, as well as the greenstones of the Saddleback Greenstone Belt. The northerly trending greenstone belt is approximately 43 km long and 5 - 12 km wide, and consists of sequences of mafic to felsic volcanics, pyroclastics, and sediments that have undergone greenschist facies metamorphism. The gneisses and greenstones have been intruded by relatively undeformed granites, and subsequently by numerous northerly trending doleritic dykes that range in thickness from 1 to 200 m. The dominant structural feature in the region is the Darling Fault, which forms the western boundary of the Western Gneiss Terrane.

In the project area, bauxite exists as irregular lenses, locally referred to as pods, within the remnant laterite. The pods are generally elongated in the NNW-SSE direction and vary in size from 1 to 200 ha. The majority of the pods contain approximately 2 million tonnes (Mt) of bauxite. The pods are generally confined to slopes where the gradient is between 5° and 10°. In steeper areas, the lateritic cover has often been removed by erosion. In areas where the slope gradients are less than 5°, sub-surface water flow is usually insufficient to promote the removal for the soluble silicate materials. The material in these areas often has a high clay content and is usually not economically viable.

Summary of bauxite deposits:
Brookton. Discontinuous mineralisation over an area covering 20 km northwest / southeast and 12 km northeast / southwest. The total profile depth from surface, varies from 1 m to a maximum of 14 m, but is generally only a few metres thick.

Collie East. Discontinuous mineralisation over an area covering 20 km north / south and 30 km east / west. Total thickness ranges from <1 m up to 16 m with an average thickness of 2.3 m.

Collie (Worsley). Discontinuous mineralisation over an area covering 15 km north / south and 17 km east / west. Total thickness ranges from <1 m up to 10 m with an average thickness of 1.9 m.

Collie South. Discontinuous mineralisation over an area covering 17 km north / south and 15 km east / west. Total thickness ranges from <1m up to 12 m with an average thickness of 2.2 m.

Hotham North. Discontinuous mineralisation over an area covering 20 km north / south and 14 km east / west Total thickness ranges from <1 m up to 27 m with an average thickness of 5.4 m.

Hotham West. Discontinuous mineralisation over an area covering 6 km north / south and 3 km east / west. Total thickness is up to 25 m but generally is roughly 5-6 m.

Marradong. Discontinuous mineralisation over an area covering 8 km north / south and 8 km east / west. Total thickness ranges from <1 m up to 30 m with an average thickness of 7.4 m.

Mid-Central. Discontinuous mineralisation over an area covering 45 km north / south and 30 km east / west. Total thickness ranges from <1 m up to 13 m with an average thickness of 3 m.

Saddleback. Discontinuous mineralisation over an area covering 19 km northwest / southeast and 10 km northeast / southwest. Total thickness ranges from <1 m up to 32 m with an average thickness of 7.3 m.

Southern MLA258SA. Hotham South covers and area is approximately 14 km north / south and between 5 km and 10 km east /west although mineralisation is discontinuous over this area. Williams South strikes roughly northwest over a distance of approximately 7 km. In the northeast direction, mineralisation stretched up to 2 km. Morgan covers to w areas with dimensions 6 km north / south and 4 km east / west as well as 6 km northwest / southeast and 2 km northeast / southwest. Mineralisation occurs from surface to depths <1 m and up to 11 m but general is only a few metres thick.

Bauxite characteristics
In the project area, bauxites have developed on the meta-basalts that comprise the Saddleback Greenstone Belt as well as on the surrounding granites. The bauxites that have formed on greenstone are usually thicker, higher in iron and sulphate, but lower in silica and organic carbon compared to the bauxites that have formed on granite. However, in general, the bauxite profile is similar across the project area, and typically comprises the horizons described below. Dolerite is not part of the lateritic profile, but it cuts the sequence and is included in the list below for completeness.

• Topsoil. A mix of humus, sandy loam and gravel, which is typically 0.1 m thick.
• Lateritic Gravel. Unconsolidated iron rich pisoliths and gravels in a sandy or silty matrix generally between 0 and 2 m thick.
• Hardcap. A ferruginous and bauxitic indurated laterite consisting of cemented angular fragments and / or pisoliths. The dominant minerals are gibbsite, hematite and goethite, with lesser amounts of quartz, maghemite and kaolinite also present. The hardcap is typically 3 m thick over greenstone and 1 m thick over granite.

• Bauxite Zone. (B zone). A friable, unconsolidated, yellow-brown to red-brown bauxitic layer in which the original rock textures have been destroyed. The dominant minerals are gibbsite, goethite and hematite, with minor kaolinite and trace illite. The horizon is often referred to as the B-zone, and is generally between 1 and 8 m thick.

• Clay Zone. Kaolinite clays with variable degrees of ferruginisation, silicification and kaolinisation. Relict bedrock textures and quartz veins are common. The dominant minerals are kaolinite, mica or illite, kaolinite-halloysite, quartz and phyllosillicates. The Clay Zone is generally 10 - 30 m thick.

• Lower Saprolite. A transitional zone between fresh bedrock and the overlying clay zone. This zone is typified by partially weathered bedrock fragments in a clay matrix. It is often referred to as “basement” in the geological logs.

• Dolerite. The dykes range in breadth from several to over 100 m wide. These are not bauxitised, and in places have acted as impediments to drainage. As a consequence, proximal bauxite on the upslope side of dykes often reports elevated reactive silica concentrations.

With the exception of the top of the Hardcap, most contacts are transitional, although the thickness of the transition zone can vary markedly. The dominant minerals are gibbsite, kaolinite, quartz, hematite and goethite. Elevated concentrations of organic carbon occur in the upper parts of the profile. These are monitored in the feed (expressed as oxalate) because of the adverse effect on refining. In general, boehmite occurs in trace concentrations only. It is thought to have formed from the dehydration of gibbsite during periodic wildfire activity and is typically confined to the upper parts of the profile. Some available alumina is also thought to occur as alumino-goethite, and some partially reactive silica is thought to exist in an amorphous form.

The deposits are described as lateritic bauxites. Compared to many mined lateritic bauxites, they report relatively low total and available alumina, low reactive silica, high quartz grades and, apart from organic carbon, few contaminant minerals.


Mining Methods

  • Truck & Shovel / Loader


Summary:

There are currently two mining areas at Boddington Bauxite Mine, the Saddleback Mining Envelope and the Marradong Mining Envelope. The crushed bauxite product, after primary crushing (at Marradong or Saddleback) and secondary crushing at the Saddleback area, is transported to the Worsley Refinery near Collie, via a 2-flight cable belt overland bauxite conveyor with a total length of 51 km. The bauxite is stockpiled at the refinery.

The majority of the open pits at Boddington Bauxite Mine are shallow to very shallow, typically less than 10 to 15 m deep. Mining of around 18 Mtpa of (wet) bauxite feed to the Alumina refinery requires large areas to be mined on an annual basis, given the limited thickness (between 1 m and 10 m thick) of the bauxite mineralisation. Typically, an area of around 200 ha is mined on an annual basis.

The primary mining fleet consist out of backhoe excavators, front end loaders, rigid body haul trucks, wheel dozers and track dozers.

Initial overburden is removed by scrapers and secondary overburden is removed by small 30 t backhoe excavators, when it is impractical for the scrapers to remove the remaining overburden.

Drilling and blasting of the hardcap is performed on special prepared drill track roadways.

After drilling and blasting the bauxite is excavated by larger backhoe excavators and loaded into 145 tonne payload capacity rigid haul trucks (CAT 785 trucks).

Ancillary equipment consisting of scrapers (for overburden removal), water carts (for haulroad dust suppression), graders (for haulroad maintenance) and track dozers (for ripping of hardcap material and general maintenance work around mining areas), supplement the primary mining fleet for the various support services.


Crushing and Grinding
Crusher / Mill TypeModelSizePowerQuantity
Jaw crusher ....................... Subscription required 1
Impact crusher ....................... Subscription required 5
Sizer ....................... Subscription required
Ball mill
Rod mill

Summary:

Marradong has primary and secondary crushing facilities. MMD Mineral Sizers are used for the first and second stage crushing of the bauxite ore. Secondary crushing is done using two SBM impact crushers. A 10 km conventional conveyor system with a 3,500 wet tph capacity delivers the crushed ore from Marradong to a stockpile with a 100,000 t capacity at the Saddleback crushing area. The live capacity of the Marradong stockpile at Saddleback is 20,000 t.

Saddleback has primary and secondary crushing facilities. A Weserhütte jaw crusher is used as the primary crusher at Saddleback. Three SBM impact crushers are used for secondary crushing at Saddleback.

The stockpiled bauxite ore is reclaimed by two bucket wheel reclaimers and ground in a two-stage grinding circuit using rod and ball mills. Milling uses caustic liquor to form a bauxite slurry.


Processing

  • Calcining
  • Crush & Screen plant
  • Bayer
  • Dissolving & Crystallising

Flow Sheet: Subscription required

Summary:

Worsley Refinery has been operating since 1984. In the 30 years since operations commenced, the capacity has increased from the original 1 million tonnes per annum (Mtpa) of alumina production to the current nameplate capacity of 4.6 Mtpa through a series of expansions. The most recent expansion in 2012 makes it one of the largest bauxite mining and alumina refinery operations in the world.

Bauxite is refined to alumina using the Bayer process. This process relies on the principal that aluminium is an element with a high solubility in alkaline solution, whereas most of the other elements in bauxite ore (except silica) are not. The process uses sodium hydroxide to digest (leach) alumina from the bauxite. The liquor containing dissolved alumina is separated (clarified) from residual solids before being precipitated as hydrated alumina before being calcined at high temperature to drive off chemically bound “waters of hydration” to produce the final alumina product.

A ........


Production:

CommodityUnits2021202020192018201720162015
Alumina kt  ......  Subscription required ^  ......  Subscription required  ......  Subscription required4,3774,5264,6064,441
All production numbers are expressed as powder. ^ Guidance / Forecast.
Subscription required - Subscription is required.

Operational Metrics:

Metrics201920182017201620152014
Annual production capacity  ......  Subscription required4.6 Mt of alumina powder4.6 Mt of alumina powder4.6 Mt of alumina powder
Ore tonnes mined  ......  Subscription required18.1 M wmt18.5 M wmt18.4 M wmt17,484 kwmt
Stripping / waste ratio  ......  Subscription required0.51
Subscription required - Subscription is required.

Reserves at June 30, 2020:
Cut-off grade
Mineral Resources: Variable ranging from 22-28% A.Al2O3 and >1m thickness;
Ore Reserves: Variable ranging from 22.5-28% A.Al2O3 and >1m thickness (except Marradong West >2m thickness).

Ore delivered to process plant. Metallurgical recovery - 94.1%

CategoryOreTypeTonnage CommodityGrade
Proven Laterite 241 Mt Al2O3 27.6 %
Probable Laterite 15 Mt Al2O3 28.8 %
Proven & Probable Laterite 257 Mt Al2O3 27.7 %
Measured Laterite 331 Mt Al2O3 28.3 %
Indicated Laterite 405 Mt Al2O3 29.2 %
Inferred Laterite 406 Mt Al2O3 28.7 %
Total Resource Laterite 1,140 Mt Al2O3 28.8 %

Commodity Production Costs:

CommodityUnits2021202020192018201720162015
Cash costs (sold) Alumina USD  ......  Subscription required ^  ......  Subscription required  ......  Subscription required 235 / t 203 / t 210 / t 250 / t
^ Guidance / Forecast.
Subscription required - Subscription is required.

Operating Costs:

Units20142013
OP mining costs ($/t milled) AUD 9.967.95

Financials:

Units2021202020192018201720162015
Capital expenditures (planned) M USD  ......  Subscription required
Sustaining costs M USD  ......  Subscription required  ......  Subscription required60.5  50   51.2   72.1  
Revenue M USD  ......  Subscription required  ......  Subscription required1,713  1,286   1,776   1,501  
EBIT M USD  ......  Subscription required  ......  Subscription required490.7  184.9   48.8   202.3  
EBITDA M USD  ......  Subscription required  ......  Subscription required683.7  379.1   231.4   377.9  
Subscription required - Subscription is required


Heavy Mobile Equipment:
HME TypeModelSizeQuantityRef. Date
Dozer (crawler) 3 Dec 6, 2017
Loader (FEL) ....................... Subscription required 4 Mar 16, 2015
Shovel (hydraulic) ....................... Subscription required 2 Mar 16, 2015
Shovel (hydraulic) ....................... Subscription required 1 Mar 16, 2015
Shovel (hydraulic) ....................... Subscription required 1 Mar 16, 2015
Truck (haul) ....................... Subscription required 145 t 15 Mar 16, 2015
Subscription required - Subscription is required.

Mine Management:

Job TitleNamePhoneEmailProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required Mar 5, 2021
....................... Subscription required ....................... Subscription required Subscription required Mar 5, 2021
....................... Subscription required ....................... Subscription required Subscription required Mar 5, 2021
....................... Subscription required ....................... Subscription required Subscription required Mar 5, 2021
....................... Subscription required ....................... Subscription required ....................... Subscription required ....................... Subscription required Mar 5, 2021
Subscription required - Subscription is required.

Staff:

EmployeesContractorsTotal WorkforceYear
Subscription required Subscription required Subscription required 2020
Subscription required Subscription required Subscription required 2017
Subscription required Subscription required Subscription required 2016
Subscription required Subscription required Subscription required 2015

Corporate Filings & Presentations:

DocumentYear
................................... Subscription required 2020
................................... Subscription required 2019
................................... Subscription required 2019
................................... Subscription required 2019
Annual Report 2018
Year-end Mineral Reserves 2018
Annual Report 2017
Corporate Presentation 2017
Fact Sheet 2017
Annual Report 2016
Other 2015
Subscription required - Subscription is required.

News:

NewsDate
South32 hands Worsley Alumina contracts to SRG Global October 1, 2020
South32 updates Worsley mine expansion plan July 9, 2019

Aerial view:

Subscription required - Subscription is required.

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