Name
Thunderbox Operations (TBO).
Location
The highly prospective Yandal belt and the Agnew-Wiluna belt, in the North Eastern Goldfields of Western Australia.
Mine Owner/s
Northern Star.
Brief Description
TBO forms part of Northern Star’s Yandal Production Centre and includes the Thunderbox, Kailis, Bannockburn and Waterloo projects.
Brief History
Northern Star acquired TBO in 2014 and started commercial gold production in 2016.
Primary Metals/Minerals
Gold.
Secondary Metals/Minerals
None stated.
Geology/Mineralisation
Thunderbox is a mesothermal lode gold deposit at the southern end of the Yandal greenstone belt, in an area where several major shear zones meet and join with the Perseverance fault.
The shear zone dips at 30 ° to 60 ° west-south-west, with the exception in the vicinity of the mineralisation, where the shear is vertical to steeply dipping.
Mineralisation is hosted by strongly deformed, silicified and carbonate-altered albite/quartz porphyry in the hanging wall of the shear zone. The shear juxtaposes foliated basalts and intrusive porphyries in the hanging wall against sedimentary rocks in the footwall. The zone of shearing is more than 200 m wide. An ultramafic unit occurs within the shear, in the footwall of the deposit and is attenuated along the shear.
The main gold-related hydrothermal alteration assemblage comprises quartz/ankerite/arsenopyrite/pyrrhotite/galena and gold. This assemblage has been overprinted by a retrograde chlorite/epidote/white mica/biotite/quartz and pyrite assemblage. Synmineralisation veins have a range of vein textures ranging from laminated to pseudo-breccias.
Throughout the Thunderbox deposit, elevated grades occur within southerly plunging ore shoots that are more evident in the lateral extents of the orebody. While the shoots persist centrally, the gold distribution is far more uniform and ubiquitous than in other areas.
Reserves
Not stated.
Resources
Total measured, indicated and inferred resources as at March 31, 2021, were estimated at 53.81-million tonnes grading 1.8 g/t gold.
Mining Method
Bulk, low-cost openpit and underground methods.
Current openpit mining involves an excavator in backhoe configuration supported by a fleet of rear dump trucks.
The underground operation is a modern mechanised trackless mine using a combination of longhole open stoping methods based on ore zone widths. Paste fill has recently been introduced to maximise recovery of the orebody and ensure the stability of the mining areas.
Major Infrastructure and Equipment
Thunderbox has processing circuit comprising a conventional carbon-in-leach plant, with a hard-rock processing capacity of about three-million tonnes a year. The process consists of a double toggle-jaw crusher followed by a semiautogenous grinding and ball milling circuit, incorporating gravity recovery and carbon-in-pulp processing achieving 94% recoveries.
Prospects
None stated.
Contact Details
Northern Star, tel +61 8 6188 2100 or email info@nsrltd.com
Sources
Northern Star. https://www.nsrltd.com/ (accessed August 12, 2021).