Saracen Mineral Holdings acquired TBO in 2014 and commenced commercial production in 2016. TBO includes the Thunderbox Project (comprised of the Thunderbox, Rainbow and Otto Bore gold deposits), the Kailis Project (comprised of the Kailis Stage 1 & 2 gold deposits), the Bannockburn Project (comprised of the Bannockburn and North Well gold deposits) and the Waterloo Project (comprised of the Waterloo and Amorac nickel deposits).

The Thunderbox processing facility has an annual capacity of 2.5 Mtpa and incorporates a single-stage crusher, a SAG mill and a ball mill as well as conventional CIL leaching and elution circuits.


TBO is located in the highly prospective Yandal Belt and the Agnew-Wiluna Belt in the North Eastern Goldfields of Western Australia. The Thunderbox Operations are centred on the Thunderbox Open Pit and CIL gold treatment plant; located 45km south of the town of Leinster in Western Australia and immediately adjacent to the sealed Goldfields Highway.

Deposit Geology

The Thunderbox deposit comprises three main mineralised zones, termed A, C, and D, over a strike length of 1.5km. Thunderbox mineralisation is hosted in an intermediate intrusive porphyry, in the hangingwall of the Thunderbox Shear Zone. The shear zone is over 200m wide and the mineralisation is predominantly confined to the intrusive porphyry, which is up to 80m in width.

Production and Growth
Gold production in the near term will be principally sourced from the Thunderbox C Zone open pit; As production in C Zone comes to completion, production in D Zone will increase. Production will also be sourced from the developing Thunderbox underground mine and various stockpiles.

Saracen’s business plan for TBO over the next 2 years includes:

  • Delivery aligned to meet or exceed the 7 year production outlook;
  • Maintaining base load production from the Thunderbox C Zone open pit whilst assessing opportunities for higher grade satellite top up feed;
  • Continuing to mine the Kailis Stage 2 open pit contributing higher grade ore feed to optimise ore blending opportunities at the Thunderbox mill;
  • Further development of the Thunderbox underground mine;
  • Commencing operations at the nearby Otto Bore satellite open pit;
  • Commencing pre-strip at the D Zone open pit cutback;
  • Pursuing the optimal operation of the Thunderbox mill to maximise production and cash flow generation;
  • Funding all project development through internal cash flow generation;
  • Commencing major exploration focus on near mine extensions – the best spot to find a new mine is at an existing mine;
  • Growing the Reserve base;
  • Continuing the trajectory of reduced AISC; and
  • Generating sustaining cash flows.