Geology.
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.

Chichester Hub—In the Chichester Range, the Marra Mamba Iron Formation dips less than 5 degrees south and trends west-northwest. In the Christmas Creek area, iron ore outcrops sporadically along with hardcap and detritals. However, further west at Cloudbreak, virtually no iron ore outcrops and surface material is predominately hardcap, unmineralized Nammuldi member rocks and/or detritals.

At the Chichester Hub, the zone of enrichment follows the Nammuldi Member of the Marra Mamba Iron Formation and varies from 5 kilometers to 9 kilometers wide and 80 kilometers long (with a 10 kilometer break where it has been significantly eroded by drainages). Ore grade material can range from about 1 to 25 meters thick with an average approximately 7 meters in thickness. Better mineralized areas average between 8 and 15 meters in thickness. All mineralization dips approximately 2 to 5 degrees south.

Mineralization in the Christmas Creek deposit occurs over an area approximately 39 kilometers along strike and up to 9 kilometers in width, from the surface to a depth of 117 meters. There are four types of mineralization at Christmas Creek: hardcap mineralization, Nammuldi Member mineralization (greater than 50% iron cut-off grade), higher grade Nammuldi Member mineralization (greater than 57% iron cut-off grade) and CID.

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.

Christmas Creek
Drill and blast
Drilling and blasting is used to allow areas of hard rock overburden to be removed. Drilling and blasting is undertaken in accordance with current operational procedures, which generally incorporate the following steps:
1. A series of holes are drilled into the rock.
2. The holes are filled with explosives and detonated.
3. The rock breaks up or collapses after detonation and the rock rubble is then removed.
4. The cleared rock face is ready for drilling and the steps are repeated.

Strip Mining
Mining will continue to be undertaken using the same mining methodology currently in place, consisting of conventional truck and shovel mining and strip mining. Typically, strip mining involves pits being developed in thin strips, around 150-200 m wide by 800 m long. Each mining area is mined to suit a particular set of constraints and requirements.

When mining commences in a new pit, the overburden is removed from the first two adjacent strip and placed just beyond the ore body limits close to the last strip to be mined in the sequence. Ore is then mined from the first strip.

When the ore in the second strip is removed, removal of overburden from fourth strip commences and material is backfilled into the void of second strip, while concurrently mining the ore in the third strip. This process progresses through the mining area.

When the ore from the penultimate strip is removed, waste from the first strip (stockpiled nearby) is backfilled into that void. When the ore from the last strip is removed, the remainder of the stockpiled waste from the first two strip is backfilled into the final void. Completed pits are backfilled at minimum to the pre-mining groundwater level. Waste rock and overburden material are generally removed using a combination of shovels, excavators and trucks. The majority of overburden is used to backfill completed pits.

Cloudbreak
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.

Removal of Overburden
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.

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.

In June 2020, Fortescue rolled out its 100th autonomous haul truck conversion at its Chichester Hub in the Pilbara region of Western Australia.

The Chichester Hub in the Chichester Ranges, comprising Cloudbreak and Christmas Creek mines, has an annual production capacity of 100 million tonnes per annum (mtpa) from three Ore Processing Facilities (OPFs).

Consistent and sustained output delivered from the OPFs has allowed Fortescue to continue optimisation of its product strategy through enhanced blending and beneficiation, increasing iron upgrades and reducing impurities. This has resulted in lower mining cut-off grades, further maximising ore bodies and sustainably reducing strip ratios.

The Company’s Cloudbreak mine site is home to the five-kilometre relocatable conveyor which includes two semi-mobile primary crushing stations and feeds directly into the Cloudbreak OPF. An example of Fortescue’s innovative operations, the infrastructure can be positioned approximate to pits and relocated, extended or shortened once an area is mined.

In order to maximize the quality of mined iron ore product, ........