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Sublevel Shrinkage – the Mt Wright Story


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Author D Mackay, S Long and A J Koen


The Mt Wright Underground Mine is located near the town of Ravenswood in North Queensland and is operated by Carpentaria Gold – a wholly owned subsidiary of Resolute Mining Limited. Following the evolution of the mine plan through a number of stages, the ‘sublevel shrinkage (SLS) with continuous fill’ mining method was implemented in 2010 to extract the Mt Wright orebody. The production front in this mining method is similar to a sublevel cave (SLC) operation; however, backfill is placed into the top of the production zone as opposed to requiring the overlying strata to cave.

Continuous fill to replace the void created by extracting the ore was required to manage the potential risks associated with the proximity of infrastructure to the footwall, associated long-term stability and air blast potential due to the limited ‘cavability’ of the material within the cave zone. The available fill material was sourced from a disused waste dump from a previous open pit operation, which introduced further technical and economic risks associated with dilution from ‘no grade’ broken material. Procedures and processes to manage these risks have been incorporated into the operation of the mine.

Despite encountering a number of challenges, the SLS method
has been in use for approximately three years at Mt Wright and has proven to be
viable economically, technically and operationally. This paper will discuss the
challenges encountered and what was done to overcome them, the operational and
financial performance to date, along with the outcomes of some successful
continuous improvement projects that have improved the efficiency of the


Mackay, D, Long, S and Koen, A J,
2014. Sublevel shrinkage – the Mt Wright story, in Proceedings 12th AusIMM
Underground Operators’ Conference 2014
, pp 205–216 (The Australasian Institute of Mining and Metallurgy: Melbourne).