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Australia
Cloudbreak Mine (Chichester Hub Operation)

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 Location:
87 km SW from Nullagine, Western Australia, Australia

  Regional Office:
Level 2, 87 Adelaide Terrace
East Perth
Western Australia, Australia
6004
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Fax+61-8-6218-8880
WebsiteWeb
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Overview

StageProduction
Mine TypeOpen Pit
Commodities
  • Iron Ore
Mining Method
  • Surface miner
  • Truck & Shovel / Loader
  • Backfill
Processing
  • Wash plant
  • Crush & Screen plant
  • Desand plant
Latest NewsFortescue awards RDG with new Cloudbreak mine contract     June 25, 2020


Owners & OPERATOR

Source: p. 108
CompanyInterestOwnershipInvestor's Info
Fortescue Metals Group Ltd. 100 % Indirect
Chichester Metals Pty Ltd (operator) 100 % Direct

Deposit Type

  • Banded iron formation


Summary:

The Cloudbreak, Christmas Creek and Kutayi deposits lie within the Chichester Ranges, in northern Western Australia. Iron mineralisation is hosted by the Nammuldi Member which is the lowest member of the late Archaean aged Marra Mamba Iron Formation (MMIF). The Nammuldi Member is characterised by extensive, thick and podded iron rich bands, separated by equally extensive units of siliceous and carbonate rich chert and shale. The Nammuldi Member in the Chichester Range is interpreted to be up to 60 metres in true thickness. Underlying the Nammuldi Member rocks are black shales and volcanic rocks belonging to the Jeerinah Formation. Extended periods of tectonic activity have variably folded and faulted these rocks, together with weak metamorphism. Subsequent erosion and hardcapping or lateritic processes have altered these rocks, and present outcrop of Nammuldi Member represents a ridge of lowlying hills (relief up to 30 metres) throughout the prospect areas. These ridges are recognised as the Chichester Ranges.

Drilling within the prospects has proved that the Nammuldi target horizon extends below cover away from the hills. In these regions (recognised mineralisation has been intersected more than 6 kilometres from the outcrop) the target iron formation can be overlain by Tertiary age colluvium and alluvium (younger than 65 Million years). This colluvium can contain both cemented and un- cemented detrital products of iron enriched material, BIF, chert and shale within a matrix of finer grained sediments (including clays). Percolation of groundwater through the weathering profiles has resulted in precipitation of both calcrete and ferricrete creating resistant horizons within the extensive regolith. More proximal to the Fortescue Marsh to the south, the Tertiary sediments become finer grained and more clay dominant, with some recognised calcareous zones.

Structure
The structural geology of the area is predominantly concealed with limited outcrop exposure. However, small scale faulting and folding (metre offsets) can be observed in some outcrops, and larger-scale faults are interpreted from aeromagnetics and regional mapping, plus drilling results. There is currently no evidence to suggest that the faulting or folding crosscuts the mineralisation. In places faults may be the conduit for the mineralisation (hypogene model).

Iron Mineralisation Styles
The mineralisation is characteristically hematite and goethite (with variable degrees of alteration between these minerals). Main gangue minerals are kaolinite, quartz and gibbsite, with minor gangue including carbonates, either calcite or dolomite.

Iron is enriched from the parent rock (Banded Iron Formation, BIF) by processes of supergene and, or hypogene enrichment. In both processes, the original iron is present as magnetite bands within the BIF (iron banded with cherts and lesser carbonates), and oxidation of the magnetite to hematite and goethite occurs. Contemporaneous with the iron enrichment, the original gangue minerals are partially to fully leached out or replaced by iron minerals, giving an overall increasing content of iron minerals depending upon the degree of enrichment. A volume loss of up to 35% can occur with enrichment due to loss of gangue minerals.

Microplaty hematite (MplH) is recognised in varying degrees throughout Fortescue’s Chichester Range deposits. This is interpreted to occur due to hypogene enrichment of the MMIF in proximity to tectonic structures (faults or tight folds), which have allowed upward fluid flow, and low- grade metamorphism of the parent rock, resulting in extensive hematite mineralisation.

The majority of the iron mineralisation is martite-goethite resulting from supergene enrichment of a BIF substantially rich with magnetite (oxidised to martite) in the parent rock.

Hardcapping (ferricrete development) of portions of the mineralisation has been identified in mapping and drilling. This process, formed at latter stages of geological development (Tertiary), has changed the physical and geochemical properties of the upper portions of the mineralisation (up to 10 metres thickness). Hardcapped material has a higher density being pervasively cemented by goethite, commonly has vitreous goethite included in the matrix, and can be quite vuggy. An associated increase in gangue content may be seen in hardcap due to the near surface processes of ferricretisation.

Mineralization in the Cloudbreak deposit covers an area approximately 37 kilometers along strike by 5 kilometers in width, from the surface to a depth of 90 meters below surface. Mineralization ranges from 1 to 28 meters thick and is 7 meters thick on average. There are three types of mineralization at Cloudbreak: Nammuldi Member mineralization (50% iron cut-off grade), higher grade Nammuldi Member mineralization (greater than 56% iron cut-off grade) and CID.


Mining Methods

  • Surface miner
  • Truck & Shovel / Loader
  • Backfill


Summary:

The mining methodology proposed is the same as that approved under Statement 721 (Approved Project Statement 721 ), with the exception of increased dewatering. The mining model is based on strip mining.

Pit Sequencing
Fortescue has developed a pit sequence for mining in order to deliver an iron ore product that meets agreed customer specifications. Product is mined and blended to provide the required target ROM ore and product tonnages and grades for each year of the life of mine. The blending optimisation ensures maximum possible resource utilisation.

Overland conveyors is installed over a number of stages as mining moves west to transport ROM ore to the existing OPF. Movement of the mining activities westwards along the ore body will necessitate establishment of satellite hubs to support the mining activities.

Clearing
The total area of disturbance for the Proposal is up to 18 100 ha. Pre-stripping is undertaken to remove the top 100 mm of soil (topsoil) and vegetation as one layer, to reduce the risk of topsoil blowing away. Topsoil and vegetation from pre-stripping operations will be stockpiled and used in progressive rehabilitation activities. Areas subject to weed infestations will be cleared separately and the soil and vegetation from these areas will be buried to prevent further weed infestations.

Removal of Overburden
The term ‘overburden’ is used for the material between the topsoil layer and the ore body, and may include both soil and rock. This includes a thin layer of soil or regrowth material which is important to provide soil chemistry and structure to effectively re-grow vegetation during rehabilitation. The regrowth material will be removed separately and placed in rehabilitation areas.

Following the removal of regrowth material, the rock overburden will be removed through the use of drilling and blasting, shovels, excavators and trucks. Approximately 60 000 tonnes per annum (tpa) of bulk explosives will be used for blasting, which will be undertaken in accordance with current operational procedures.

Mine pits is developed in thin strips generally in the order of 150 m by 700 m, where different mining activities may occur in different strips at the same time. For example while removal of overburden is occurring in one area, mining of ore may be occurring somewhere else in the pit. Once the initial strips have been mined, overburden will be placed in the mined- out sections of the pit and rehabilitation will be undertaken progressively on these areas. The starter pit phase for a new pit will typically last one to two years, as the initial strips are developed. During this period, it will be necessary to place the overburden in a permanent storage area located outside the mine pit area. Once the initial strips have been mined, overburden will be placed in the mined-out sections of the pit.

The volume of overburden and mine waste will exceed the pre-disturbance volume of the mined pits (voids) by approximately 30%. This is because the volume of the overburden when broken and transported is greater than the volume of the overburden plus ore in situ. Excess overburden will be placed in permanent storage areas outside the mine pit area.

An estimated 3150 Mt of overburden will be placed in permanent storage areas near the pits, covering approximately 1160 ha in total. The final design height of the permanent storage areas will be based on the surrounding topography in the specific area. The overburden storage areas will be rehabilitated and revegetated as part of Fortescue’s standard procedures, in line with the Mine Closure Plan.

The Rahco overburden transport system will also be utilised where appropriate. The Rahco comprises of mobile in-pit sizers, mobile conveyor units and a mobile stacker. During mining, overburden will be fed by excavators directly into a mobile sizer, where the material will be crushed to a size that will allow it to be transported by the conveyor units. The conveyor units will transport the crushed overburden over a distance of approximately 500 m where it is placed, by the mobile stacker, in overburden storage areas. The Rahco is capable of transporting up to 50 Mtpa of overburden and is powered by a dedicated mobile 8 MW diesel power station.

Pit Dewatering
The groundwater table at Cloudbreak lies within the alluvium and mineralised Marra Mamba Formation (MMF) above a portion of the available ore. Cloudbreak groundwater chemistry data shows groundwater in the resource area is generally fresh to brackish and becomes increasingly saline towards the Fortescue Marsh and with depth.

Dewatering is therefore required to lower groundwater levels below the base of each of the pits (in the alluvium and MMF) to enable access to ore required below the water table. The increased mining depth will result in an increase in the volume of groundwater to be abstracted and subsequently reinjected into the aquifer.

The ore body is dewatered ahead of the advancing mining faces using bores, with some sump dewatering in the pit to deal with seepage and rainfall.

Injection
Fresh to brackish and saline waters is abstracted and injected separately. This separation prevents saline groundwater being injected into fresher parts of the aquifer, where it could impact upon vegetation and the future potential use of groundwater for stock watering. Injection occurs into the Marra Mamba Formation.

Excess saline groundwater will be injected into the Oakover Formation, at locations between the mining area and the Fortescue Marsh.

Locations of brackish water injection will change throughout the mine life, as the mine pits move and some earlier mining areas will become injection areas.

Mining
Mining at Cloudbreak will continue to be carried out as open pit strip mining. The pits are developed progressively, where a starter pit is opened (with overburden from the starter pit placed in a small overburden stockpile). As the mining face progresses, the open pit is progressively backfilled and rehabilitated. This option presents a cost-effective method of backfilling the pit with overburden during the life of the mine and reduces the required size of the waste rock dumps placed external to the pits. Progressive rehabilitation practices can be utilised as topsoil is removed ahead of mining and placed directly onto final contoured backfilled areas in one operation, as an integrated mining practice.

Surface Miners
The majority of the ore is mined using surface miners. Surface miners can cut to an accuracy of 0.1 m and can extract ore without the need for drilling, blasting, or primary crushers to crush ore. Ore is loaded from the surface miner into trucks for transfer to the OPF.

Excavator
Small excavators mining is also used to mine from a pit face, which is usually between 3 to 5 m high. Excavators is used to access ore where it is not viable to use a surface miner (e.g. constrained areas requiring small cuts). This method allows selective excavation of narrow bands of material.


Crushing and Grinding


Processing

  • Wash plant
  • Crush & Screen plant
  • Desand plant

Source: Subscription required

Summary:

Ore Transfer
Currently, ore is transferred to the OPF from the ROM pad through the use of trucks. As mining moves west, haul distances to the OPF will become excessive and an overland conveyor system will be installed to transport ore to the OPF. Approximately 27 km of conveyors will be required to convey the ore to the OPF for the Proposal.

The conveyor system extends to the west of the OPF and consists of the following:
- a main services hub;
- two Satellite Crushing Hubs;
- seven delivery conveyors from the crushing stations to the OPF.

Ore Processing
The OPF is able to produce three market products; namely lump, special and rocket fines. Future demand will dictate whether all three products will be produced, however, rocket and special fines are currently the primary products being produced.

The Ore Processing Facility currently includes:
- a screenhouse containing product and scalping screens which are gravity fed; ........


Combined production numbers are reported under Chichester Hub Operation


Reserves at June 30, 2020:
Cut-Off Grade of ore reserve (%Fe) ~ 53.5.

CategoryTonnage CommodityGrade
Proven 266 Mt Iron (hematite) 57.2 %
Probable 294 Mt Iron (hematite) 57.2 %
Proven & Probable 560 Mt Iron (hematite) 57.2 %
Measured 419 Mt Iron (hematite) 56.6 %
Indicated 401 Mt Iron (hematite) 56.2 %
Inferred 117 Mt Iron (hematite) 56.4 %
Total Resource 936 Mt Iron (hematite) 56.4 %


Heavy Mobile Equipment:

Mine Management:

Job TitleNameProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required Aug 28, 2020
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....................... Subscription required ....................... Subscription required Subscription required Jul 29, 2020
....................... Subscription required ....................... Subscription required Subscription required Aug 28, 2020
Subscription required - Subscription is required.


Corporate Filings & Presentations:

DocumentYear
................................... Subscription required 2020
................................... Subscription required 2019
................................... Subscription required 2019
................................... Subscription required 2018
................................... Subscription required 2018
Annual Report 2017
Annual Report 2016
Annual Report 2015
Other 2012
Environmental Assessment 2011
Subscription required - Subscription is required.

News:

NewsDate
Fortescue awards RDG with new Cloudbreak mine contract June 25, 2020
Fortescue extends RCR Mining contract at Cloudbreak October 24, 2019
Fortescue revs up Cloudbreak autonomous truck program May 9, 2019

Aerial view:

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