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.
An undiluted stope minimum mining width (MMW) of 3.0 m (true width) was applied to the Savannah Nth mining area. This is achievable based on the sub-level interval of 20 m floor to floor as from knowledge gained in the mining of the Savannah orebody.

Drill and blast assumptions have been based on historical performance at Savannah. Long hole size is 89 mm diameter and drill metres are based on 6 t / drill m including slotting.

The existing fill system will be utilised for paste filling of the Savannah North stopes. A new paste fill hole is planned for the Savannah Nth, to be drilled from the surface via 1570DD. Dump valves shall be installed at intervals of 200 vertical metres to protect the paste line in case of paste blockages. Additionally, a backup hole is planned to be drilled to mitigate the risk of downtime due to unexpected blockages. Where opportunities arise, waste rock will be backfilled into stopes either via a dedicated truck fill pass or by loader. When back filling with a loader, truck tipping bays will be mined and loaders will be used to transfer the waste into the stope with an appropriate stop-log. The study assumes that all stopes are paste filled. A cement strength of 2.7% was assumed for all paste placed.

The Savannah mine is accessed through a conventional ramp (decline) of 1:7 gradient and dimensions of 5.2 mW x 5.8 mH. Primary access to Savannah Nth from the Savannah decline is via a splinter decline from the 1452 mRL, consisting of two ramps, one for vehicle access and a second for a return air drive (RAD). The 1570 mRL drill drive also forms part of the access to the Savannah Nth.

Savannah ore has been successfully treated through SAG mill since commissioning in 2004.

Subsequent to the restart further works were completed including the replacement of the Jaw crusher and SAG mill motor. A full set of filters plates is onsite ready for installation.

The Savannah processing plant consists of conventional crushing, grinding, flotation, and concentrate handling, producing a bulk nickel-copper-cobalt concentrate for sale to third-party. The nominal throughput capacity of the Savannah plant is approximately 1.0Mtpa.

The Savannah plant operated continuously from August 2004 to May 2016, with continuous improvements in recoveries and throughput achieved from changes in operating practices and minor circuit modifications.

Prior to restarting in in December 2018, the processing plant was refurbished at a cost of $12M, with work encompassing refurbishment of the ROM bin, apron feeders, conveyors; a SAG mill reline; all pumps; flotation cells including replacement of cleaner cells; refurbishment of thickeners and the concentrate filter; enclosing the courier on stream analyser and replacing key components; installing fusion furnaces and installing an XRF in the laboratory. At the paste plant the paste disc filters were ........