Ranger is a uranium mining operation located within one of the most
environmentally sensitive regions of Australia. Geology has played an
important role in mine planning, operations and rehabilitation since
discovery of the deposits 25 years ago. The Ranger orebodies have a
reserve total of 166 300 tonnes of U308 including 90 400 tonnes of U308
at North Ranger. At current milling rates these reserves give a mine life
greater than 40 years. The uranium is hosted in Lower Proterozoic rocks of the Cahill
I ormation and is associated with strong chlorite alteration. In pit grade
control involves the use of calibrated probes and a radiometric truck
discriminator allowing fast, accurate grade determination of material.
Ore is defined at a cut-off grade of 0.2 per cent U308. Mineralised
material is defined by the Uranium Mining (Environmental Control) Act
1979 (UMEC Act) at a grade of 0.02 per cent U30s. Natural water levels
in the #1 Pit area vary as much as 7.5 metres between wet and dry
seasons. Ground water inflow into the pit during the dry season is
600 m3/day. No significant slope failures have occurred in the pit. The
environmental impact of mining operations is constantly monitored.
Rehabilitation of non-mineralised stockpiles is ongoing. This paper discusses the interaction between geology, hydrogeology,
rock mechanics and grade control with the present mining operation.