Interpretation of geological structures is essential at most mine sites because these structures play a key role in controlling mineralisation and determining the properties of the surrounding geology. This importance is generally well understood. The tools used by exploration and mine geologists to interpret geological structures include: geological drill logging, pit mapping, airborne geophysics, downhole geophysics and aerial photography. The structural interpretation is often vital to mitigate issues linked to mineralisation or geotechnical risks, which may present themselves during the life of mine. The risks these same geological structures present in mine closure are sometimes not appreciated.
Numerous geological faults and structures have been interpreted on the Ranger Project Area over the life of mine. Some faults have high hydraulic conductivity and are true representatives of a fractured rock aquifer, whilst others are impermeable and act as barriers to groundwater flow. The misrepresentation of these faults and misunderstanding their importance have resulted in illconceived rehabilitation ideas, which remain as ongoing concerns to regulators and external stakeholders. By addressing and explaining the importance of geological structures in the context of closure strategy, unnecessary delays associated with testing and understanding these faults can be avoided.