Zásoby zlata v australské dole Olympic Dam jsou o 50 procent větší než se předpokládalo. Podle britského deníku The Guardian to ve středu oznámí vlastník dolu, největší světová důlní společnost BHP Billiton. Olympic Dam by se tak mohl stát největším nalezištěm zlata na světě. Zelení jsou však prý proti rozšíření akvivit a hodlají si stěžovat u zemské vlády.
Located 560 kilometres north of Adelaide, South Australia, Olympic Dam is a multmineral ore body. It is the world's fourth-largest remaining copper deposit and the largest uranium deposit. It also contains significant quantities of gold and silver. Olympic Dam is Australia's largest underground mine. Most of Olympic Dam's employees live in Roxby Downs township, about 16 km south of the operations. The township has a population of about 4 000.
Olympic Dam comprises a large number of discrete ore zones throughout an area of several square kilometres ranging in depth from 350 metres to approximately one kilometre.
The Olympic Dam underground mining operation is highly mechanised, with automated rail transportation and underground crushing. The primary method of ore extraction is long hole open stoping with cemented aggregate fill. This method allows for large equipment to achieve high productivity and maximum ore recovery.
Ore is hoisted to the surface where it is fed to one of two grinding circuits. After grinding, the resultant slurry passes to a flotation circuit where a series of flotation stages and a further regrinding activity produce a copper concentrate. The concentrate then passes through a leaching circuit which is principally designed to extract uranium from the copper minerals. Uranium is extracted in a solvent extraction plant, producing yellow-cake, which is subsequently calcined to produce uranium oxide concentrate and then packaged in drums for export sales.
After drying, copper concentrate is fed to an Outokumpu flash furnace smelter, which produces blister copper and flash furnace slag. Blister copper is transferred to anode furnaces for fire refining. Anode copper is transported to the refinery where the ISA electro-refining process is used to produce copper cathodes. The slimes from this process are treated separately to recover gold and silver.
Olympic Dam has proved and probable ore reserves of 761 million tonnes at 31 December 2004 at 1.5 per cent copper, 0.6 kg/tonne U3O8 and 0.5 g/tonne gold
ZDROJ: Novinky,BHP Billiton,abc.net.au