The copper-gold deposit is part of the Kanmantoo Trough, which is the youngest of a succession of extensional sub-basins developed within the Adelaide Geosyncline. The Kanmantoo orebody comprises three main mineralised zones: Main, O’Neil/Nugent and Emily Star. Each of the ore zones contains an oxide, transition and primary sulphide ore component.

The Main Zone is hosted by a garnet-andalusite-biotite schist within the Cambrian Kanmantoo Group. Copper mineralisation occurs as chalcopyrite within a complex series of northern trending steep northeast plunging pipes and lodes 3 to 80 m wide (Figure 5.4) (Resource Evaluations, 2006). Mineralisation is characterised by chalcopyrite, pyrrhotite and magnetite with lesser pyrite. In the Emily Star Zone, mineralisation is characterised by chalcopyrite and pyrite. Mineralisation in the O’Neil/Nugent Zone is associated with a garnet-chlorite hydrothermal alteration zone with quartz veining. In comparison with the other zones, the O’Neil/Nugent Zone is enriched in gold.

Sulphide becomes less common with distance from the ore zone indicating there is likely to be broad zones of non-sulphidic waste rock outside of the main mineralised blocks. Across the ML area, there is a distinct weathering zone of approximately 15 m depth that appears to be completely oxidised. This oxidised zone is an important source of non-acid-forming (NAF) material suitable for use in encapsulation of the potentially acid-forming (PAF) waste material.

Mining is undertaken using conventional open pit methods, i.e., drilling and blasting where required with truck and excavator for removal from the pit. Ore and waste rock is predominantly blasted using 9 to 12 m high benches and mined over passes or ‘flitches’.

Blasting is undertaken using ammonium nitrate/fuel oil (ANFO) or emulsion-based explosives, which are loaded into blastholes. Hole diameters vary from 89 to 165 mm, with up to 600 holes fired in each shot. Blasting is generally undertaken from 10 am to 3 pm. and is managed to meet the lease conditions, Australian standards (AS 2187.2:2006) and other advanced blasting practices. Blast holes are backfilled with stemming material to contain the explosion on initiation and hence reduce noise, dust and fly rock. Surface and downhole delays are used to minimise ground vibration. Electronic or non-electric (Nonel) signal tube is used for downhole and surface tie-ins to improve blast performance and reduce noise and air blast. Blasts are designed to ensure that there will be no adverse public health and/or nuisance impacts.

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