Summary and Techniques

Summary

Mining at Fortescue's first minesite, Cloudbreak, began in 2008 with more than 28 million tonnes of iron ore mined in the first full year of production. Since then, mining and processing at Cloudbreak has increased to more than 100,000 tonnes of ore each day. Fortescue has also established it's second minesite, Christmas Creek, which is 50 kilometres east of Cloudbreak. Together, the two mines make up the Chichester Hub. In 2010, Fortescue will extend its rail line through to Christmas Creek and construct a second ore processing facility at the site.      

Fortescue is building its program around three Marra Mamba products: High Grade Lump (61% Fe) and Fines (60% Fe), and Rocket Fines (59%).  The sinter performance of the Company's unique Rocket Fines is comparable with existing CID deposits such as Yandi for which a very large established market exists.

Mining Breakthroughs

The mining operations will comprise of a mix of proven mining techniques and innovative world-first solutions.

Overburden Removal

The ore at Cloudbreak sits below a layer of overburden with an average thickness of around 20m (starting at 0m and reaching more that 60m in depth).

Initial overburden removal consists of a conventional truck and shovel stripping method. A substantial reduction in the use of conventional methods will occur when the overburden removal system is introduced, however, conventional methods will always form part of the process.

Fortescue has teamed with FLSmidth Rahco to design, engineer and fabricate an overburden removal system that takes existing technology to another level. The revolutionary system, capable of removing 50 million tonnes of overburden per year, will deliver true continuous removal of overburden with costs below other less-efficient methods.

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The system's design affords the mine team exceptional control over the repositioning of overburden, allowing them to mimic the natural form of the landscape and begin the work of environmental restoration almost immediately. Being able to create an extremely flat bench of stripped overburden means that the top soil is far less likely to wash away, making revegetation more successful and allowing cattle to eventually return to the area.

Mining the Ore

The flat lying nature of the deposit has led Fortescue to elect to use a fleet of Wirtgen surface miners rather than traditional drill-blast-excavate mining techniques. Wirtgen 2500 surface miners weigh over 100 tonnes and have over 1000 horsepower, which gives some idea about the size of the operation. Surface miners have been used for a quarter of a century in soft rocks such as coal and salt and in hard rocks such as limestone and granite that are up to 10 times harder than the average ore at Cloudbreak.

Results using this innovative technique have been very encouraging and the benefits of using surface miners on this particular deposit are numerous.

Below: Surface miners at work in the Hayman Pit

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Such benefits include: Elevated grade control Obviation of primary drilling, blasting and crushing Reduced downtime as post-blast remobilisation becomes unnecessary Cleaner pit floors, which leads to reduced damage to vehicles and tyres Multiple pit faces across the flat deposit can be mined simultaneously Increased safety as a by-product of higher predictability Ability to begin environmental rehabilitation work promptly

These benefits will directly translate into better, more cost efficient product.