The World's Largest ...
Iron Mine
An ore body 4km long, 80m thick and up to 2km deep, LKAB's Kiruna is the world's largest and most modern underground iron ore mine.
Since mining began here a hundred years ago, LKAB has produced 1000Mt of ore, yet only a third of the ore body has been extracted.
Since mid 1999, Kiruna's haulage level at 775m has been replaced by the next level down at 1045m, to support production until 2018. The operation employs 1800 people, of whom 400 work underground.
In 2006, Kiruna produced some two thirds of LKAB's output of 23.3Mt, of which 16.9Mt were pellets. The company's sales of iron ore products totalled 23.3Mt, of which 15.9Mt were pellets.
Reserves
Kiruna orebody was formed around 1600 Ma following intense volcanic activity with the precipitation of iron rich solutions on a syenite porphyry footwall. The ore bed was then covered by further volcanic deposits of quartz porphyry and sedimetary rocks before being tilted to its current dip of 50 to 60°.
The ore contains a very pure magnetite-apatite mix, containing more than 60% iron and an average of 0.9% phosphorus. Black ore contains less apatite than grey ore.
The original reserve at Kiruna was some 1800Mt. At the end of 2004, LKAB estimated that the current proven reserve was 657Mt at 48.3% iron grading, with probable reserves of 140Mt at 46.5% iron.
Measured, indicated and inferred resources add a further 500Mt to the inventory, with exploration continuing to identify further resources at depth.
Mining
The mine is divided into eight production areas, each containing its own group of ore passes and ventilation systems. Mining the ventilation shafts for the current production level was carried out by SIAB using Indau 500 raise borers, while Skanska Raise Drilling developed a total of 32 ore passes between the 775 and 1045m levels using Tamrock and Robbins raise borers.
Alimak developed two special units based on its RCM-6 system to reinforce the ore passes with cable bolts and shotcrete where necessary.
Ore is mined using sublevel caving, with sublevels spaced 28.5m vertically. With a burden of 3.0 to 3.5m per ring, this yields around 8500t for each blast. LKAB subsidiary Kimit AB supplies the explosives and prepares holes for blasting.
The main haulage level at Kiruna lies at 1045m, with the mine's ore handling systems capable of handling 26Mt/y of run-of-mine rock.
Seven 500t capacity shuttle trains, controlled from 775m level, collect ore from ten groups of ore passes and deliver it to one of four crushing stations. Ore below 100mm size is then skip hoisted in two stages to 775m level, then to surface.
Electric powered, remote controlled drilling and ore handling equipment supplied by Atlas Copco and Tamrock is widely used.
After blasting, load-haul-dump machines, some fully automated, carry the run-of-mine ore to the nearest ore pass, from which it is loaded automatically onto one of the trains operating on 1045m level.
After primary crushing, sampling by a Morgårdshammer automatic sampler to obtain apatite and magnetite contents, and hoisting to surface, the ore is processed in Kiruna's complex sorting plant, including two concentrators and two pellet plants to pellet and sinter fines products.
Some ore is moved by rail to LKAB's Svappavaara plant for pelletisation. Products are hauled by rail to the ports of Narvik (Norway) or Luleå for shipment.
