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.

The mining methods utilised in the LOM plan is in line with the previous operation being a top-down, long hole open stoping mining method utilising paste fill. This mechanised, non-entry method has proven to be a safe, productive mining method at Savannah.

The total global average planned and unplanned stope dilution (i.e. mined material without Resource classification, including fill dilution) proportion within the Mine Plan stope shapes is 22%.

Mining recoveries of 90% were applied to stopes to allow for issues such as local orebody spatial variability and material left behind during remote loading. A mining recovery of 100% was assumed for ore development.

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 North, 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.

Mine scheduling has been adjusted with the objective of ramping up ore production to 960,000t per annum as quickly as possible. Ore sourced from Savannah North underpins the potential restart strategy, with scheduling of ore from Savannah remnants limited to a maximum of 25,000t per month.

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 mine has a long history of concentrate production, sales, recovery, and treatment costs. The assumptions used for the Ore Reserves are based on the recent actuals for these items. No secondary credits have been modelled in the updated Mine Plan, other than from the copper and cobalt included in the NSR calculation. The concentrate produced at the Savannah mine is a “clean concentrate” and does not have any deleterious elements that attract payment penalties.