Ranger Uranium Mine, Australia
The Ranger Uranium mine is located in Australia's Northern Territory, approximately 260km east of Darwin. Bordered by the Kakadu National park, the mine was discovered in 1969 and began operations in 1980. It attained full production in 1981. The open pit mine consists of three ore bodies and is operated by Energy Resources, a subsidiary of Rio Tinto.
The second largest uranium mine in the world, Ranger produced 5,240t of uranium in 2009. By the end of 1995, the original ore body was exhausted and mining began on a second, Ranger 3, in 1997. In 2009, another significant ore body was discovered. Known as Ranger 3 Deeps, the ore body is adjacent to Ranger 3.
As of 2010, studies of the mineral resources of Ranger 3 Deeps are under-way. Upon completion of the studies, construction of an exploration decline will begin at the pit. A feasibility study to build a heap leach facility will begin at the same time.
The mine consists of an estimated 21.43Mt of proven reserves graded at 0.10% uranium oxide.
As of December 2009, Ranger 3's proven reserves were 3.19Mt graded at 0.24% uranium oxide. Probable reserves hosted are 3.06Mt graded at 0.24%.
The deposit lies within the Pine Creek Inlier mineral province in Australia. Ore bodies, including both first and second, are characterised by palaeoproterozoic age volcanic, carbonate and sedimentary sequences. The folded, faulted and sheared sequences lie unconformably over granitic gneiss belonging to the Archaean age of the Nanambu Complex.
Intruded by east-trending granite, dykes and pegmatite veins besides gradually dipping north-northeast trending mafic dykes, the sequences are regionally metamorphised to greenschist facies. The contact is metamorphised to hornblende-hornfels facies.
Rocks in the Ranger mine have undergone two phases of ductile–brittle deformation and one phase of brittle deformation. The first phase of ductile brittle deformation led to the development of mesoscopic folds and a combination of several thrusts and dextral reverse shears. The second phase led to the development of weakly outlined axial planar cleavage and sinistral reactivation of the phase one shears.
The phase of brittle deformation resulted in normal faults and fault breccias during an east-west extension period. The occurrence of all the deformation phases was preceded by regional diastathermal and the development of an omnipresent bedding-parallel cleavage. During extension in brittle deformation, ore shoots bearing uranium were formed in the first and second pits of Ranger. The uranium mineralisation within the Ranger Mine remains open.
Processing at the mine begins with ore crushing and leaching with sulphuric acid. Kerosene and amine is used to remove the uranium. It is then stripped with gaseous ammonia and ammonium sulphate solution. By increasing the pH level, ammonium diuranate is precipitated and converted to uranium oxide in a furnace. Processing at the pit is scheduled to end in 2020.
Low-grade ores from the mine will be leached in a new heap leach facility. This project is currently in the feasibility stage. Between 15,000t and 20,000t of uranium oxide is expected to be recovered from the proposed heap leach facility. The Environmental Impact Statement of the facility is ongoing and will be submitted in the first half of 2010.
Construction of an exploration decline at Ranger 3 Deeps is scheduled to begin in 2010 after completing studies on the mineral resources in mid 2010.
Exploration decline at Ranger 3 Deeps will allow underground drilling of the Ranger 3 Deeps ore body that hosts an estimated 34,000t of uranium oxide. It will also enable underground exploration drilling towards the north of the ore body, where it is open.
The exploration decline will consist of an entrance and at least one tunnel that will extend between 2,000m and 3,000m. Following the alignment of the known ore body, the tunnel will be extended to approximately 250m and 450m below surface.
Along with the associated infrastructure, the exploration decline will be located within the limits of the existing operations, neighbouring to or within the Ranger 3 pit. During construction and operation of the decline, maximum usage of the existing mine infrastructure will be made. The existing controls, operational and regulatory, will be implemented and increased for water, waste, noise and radiation.