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.

The structural geology of the area is predominantly concealed with limited exposure in outcrop. However, small scale faulting and folding (metre offsets) are observed in some outcrops, and larger-scale faults are interpreted from aero-magnetics and regional mapping, plus drilling results. In places faults may be the conduit for the mineralisation (hypogene model).

Iron mineralisation characteristically comprises hematite, goethite and ocherous goethite, with variable degrees of alteration between these minerals. The main gangue minerals are kaolinite, quartz and gibbsite, with minor amounts of carbonates, either calcite or dolomite.

Iron is enriched in the parent BIF (iron layers banded with cherts and lesser carbonates) by processes of supergene and/or hypogene enrichment. In both processes, the original iron, which is present as magnetite bands within the BIF, is oxidised to hematite and goethite. Contemporaneous with the iron enrichment, the original gangue minerals are partially to fully leached out or may be replaced by iron minerals. These processes increase the iron content of the BIF depending upon the degree of enrichment. A volume loss of up to 35 per cent 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 at the Chichester deposits, is interpreted to be martite-goethite resulting from supergene enrichment of a magnetite-rich BIF (oxidised to martite) parent rock.

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

The majority of the iron mineralisation is hosted by the Nammuldi Member which is the lowest member of the late Archaean aged Marra Mamba Iron Formation (MMIF). The NammuldiMember 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 60m in truethickness. Underlying the Nammuldi Member rocks are black shales and volcanic rocksbelonging to the Jeerinah Formation. Limited iron mineralisation also occurs in the overlying CID and Tertiary alluvial material.

Cloudbreak and Christmas Creek - Up to ~80km along strike and up to 5km plan width. Upper limit of mineralised domain is located between 0m to 125m below the surface. Lower limit of mineralised domain is located between 1m and 130m below the surface. The average thickness of the mineralised domain is 7.0m and the range of thickness is 1m to 28m.

Cloudbreak
The mining model is based on strip 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.

The majority of the ore will be mined using surface miners. Surface miners can cutto 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.

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
Crushing/sizing Facilities
The crushing and sizing facilities consist of a series of crushers designed to handle standard sized ore and large ROM oversize rocks generated in drill and blast operations, pit floor windrow cleanup and pit wall batter scraping at the mine. The crushing and sizing process will size material to less than 250 – 300 mm such that it can be transported by conveyor to the OPF.

Christmas Creek
Remote Crushing
An RCH currently operates approximately 6.5 km east of the main processing facilities at Christmas Creek. The RCH sizes the mined material to prepare it for processing in the OPF (ore processing facilities). The RCH consists of:
- ROM bin
- mineral sizer
- gyratory crusher
- crushed ore vault.
Once material has been crushed, it is transported to OPF2 by an overland conveyor.

Chichester Hub in the Chichester Ranges, comprising the Cloudbreak and Christmas Creek mines, has an annual production capacity of approximately 100mtpa from three Ore Processing Facilities (OPFs). Consistent and sustained performance delivered from the OPFs has allowed us to optimise our product strategy through enhanced blending and beneficiation, supporting iron grades and reducing impurities.

This has contributed to lower mining cut-off grades, as weoptimise ore bodies with sustainably lower strip ratios. To further enhance our ore, the Christmas Creek OPF infrastructure has been upgraded to include a Wet High Intensity Magnetic Separator (WHIMS) to recover high grade iron from the finer ore fed through the plants, helping to improve product yield and reduce total mining volumes.

Cloudbreak utilises relocatable conveyors which can be moved, lengthened or shortened once an area is mined. The conveyors now cover 10km, extended from the initial 5km length due to ........