Mineralization of Savannah Operations.

Savannah mineralisation.
The original Savannah sulphide rich nickel, copper and cobalt orebody is hosted by the layered mafic-ultramafic Savannah Intrusion which is enveloped by aluminous metasediments and para-gneisses of the Tickalara Metamorphics. The Savannah Orebody is mostly confined to a marginal norite unit up to 40 metres thick developed above the base of the intrusion. Areas of massive, matrix and disseminated sulphide mineralisation, dominated by pyrrhotite, chalcopyrite, pentlandite and minor pyrite occur throughout the marginal norite unit.

Prior to the development of the Savannah Open Pit, the marginal norite unit outcropped as a prominent 250 metre long limonite-goethite gossan with fresh sulphide mineralisation developing approximately 20 metres below surface. At approximately 500 metres below the surface, a significant sub-horizontal fault, the 500 Fault, cuts the orebody and offsets it 200 metres to the northwest. A similar fault at approximately 900 metres below surface, the 900 Fault, offsets the orebody a further 250 metres to the northwest. Mineralisation above the 500 Fault is referred to as the “Upper Zone”, between the 500 and 900 faults as the “Lower Zone” and below the 900 Fault as the “sub 900 Fault Zone”.

Savannah North mineralisation.
The SNM (Savannah North mineralisation) is based on mining ore associated with the Savannah Intrusion; a palaeo-proterozoic mafic/ultramafic magma conduit. The Ni-Cu-Co rich massive sulphide mineralisation occurs as “classic” magmatic breccias developed about the more primitive, MgO rich basal parts of the conduit.

Magmatic Ni-Cu-Co sulphide Resources hosted by the Savannah North Intrusion (SNI) located to the north of the Savannah Mine.

The Savannah North mineralisation dips moderately (40- 45 degrees) to the north-west and comprises two main zones, the Upper Zone is developed on the basal contact of the North Olivine Gabbro, the second Lower Zone is a consistent remobilised zone of massive sulphide mineralisation, in part associated with the 500 Fault. Both zones are well defined by the drilling and the interpretation is considered sufficiently robust for resource modelling. Additional minor mineralised zones include 5 domains in the hanging wall position to the Upper Zone and a minor mineralized sub-vertical fault.

The Savannah North mineralisation has been defined over a strike length of approximately 1 kilometre with clear indications from geophysics it could extend over 2km. The Resource relates to an area with a strike length of 1,010m from 5,350mE to 6,360mE and extends from 750m to 1,750m below surface with an average domain thickness of approximately 5 metres.

Savannah
Ore production is undertaken via conventional long hole open stoping with remote bogging on retreat. Currently, the long hole drilling is undertaken by a contractor. Savannah purchased a used Cabletec drilling rig for ground support and as a backup production drill, as required. The mine plan requires open stopes to be backfilled with cemented paste fill to maximise recovery of the orebody and to assist geotechnical stability of the mine.

Savannah North.
Mining Method: Long hole open stoping;
Sub-level interval: 20m;
Minimum stope angle: 50 degrees;
Minimum mining width: 2m;
Stope dilution: 10%;
Stope mining recovery: 95%;
Access: Single decline;
Mining Inventory: 6.07Mt;
Mining rate Average: 0.8-1.0Mtpa.

The Savannah Nickel-Copper-Cobalt Operation consists of a number of nickel sulphide orebodies. The Project infrastructure includes an underground mine, 1.0 million tonne per annum processing plant, paste fill plant, a 180 room village, orkshops, office accommodation, tailings and water storage facilities and other associated infrastructure. The Savannah was constructed in 2003 and commissioned in late 2004 initially sourcing ore from an open pit (Copernicus). After 18 months, the operations transitioned to underground mining.

Over an initial twelve-year period, Savannah milled 8.5 million tonnes at an average grade of 1.29% Ni, 0.65% Cu and 0.06% Co to produce 1.22 million tonnes of concentrate containing 94,600t Ni, 53,000t Cu and 5,000t Co. Savannah was placed onto care and maintenance in May 2016 due to the historically low nickel price.

The process plant at Savannah Operation comprises a single stage crusher, SAG mill, flotation, thickening and filtering stages to produce a bulk nickel, copper, cobalt concentrate. Over the 2004 to 2016 initial operating period, metallurgical recoveries averaged 86-89% for nickel, 94-97% for copper and 89-92% for cobalt. The plant was originally designed for a throughput of 750,000 tonnes per annum, but consistently outperformed the design specifications with rates exceeding 1 million tonnes on an annualised basis.

The Processing and Paste Plants were refurbished by MACA Interquip between June 2018 and February 2019 and the Processing Plant was recommissioned in December 2018. The major refurbishment works undertaken included:
- Repair and/or replacement of corroded structural steel and painting throughout;
- ROM orebin refurbishment and replacement of the grizzly;
- Refurbishment of the crusher;
- Refurbishment of the emergency stockpile bin and conveyors;
- Installation or repairs to rubber lining in flotation cells;
- Installation of new lifters and liners in the mill and replacement of trunnion bearings;
- Refurbishment or replacement of most pumps;
- Thickener tanks refurbished;
- Electrical and communication upgrade including replacement of existing PLCs;
- Major refurbishment of the filter press;
- New on-stream analyser.