Summary:
NiWest contains one of the highest-grade undeveloped nickel laterite resources in Australia.
NiWest comprises Mt Kilkenny, Hepi, Wanbanna, and Eucalyptus deposits.
The NiWest deposits are all hosted within the Murrin Domain which, from the bottom up, consists of the following formations:
-Welcome Well Formation – andesitic conglomerate, sandstones, and siltstones intercalated with andesiticbasaltic lava flows.
- Minerie Formation – tholeiitic basalts intercalated with lesser amounts of turbiditic sediments and komatiitic basalts.
- Murrin Murrin Formation – ultramafic and komatiitic basalts intercalated with lesser amounts of clastic sedimentary beds (predominantly sandstone).
- Pig Well Formation – conglomerate and feldspathic sandstones.
Elevated nickel and cobalt concentrations occur in the regolith profile that has developed over the serpentinised peridotite cumulates of the Murrin Murrin Formation. The regolith layer, which is typically around 30 m thick, shows distinct grade and textural changes with depth. These changes have resulted from the intense weathering of the serpentinised peridotites. The serpentinised olivines are initially converted to magnesium-rich clays (saponites and chlorites), which in turn are converted to iron-rich, smectitic clays (nontronite), and then to goethite, hematite and kaolinite.
- The deposits in the project area are described as dry climate nickel laterites.
- Elevated nickel and cobalt concentrations occur within the lateritic cappings that formed from the prolonged weathering (serpentinization) of the Archaean ultramafic and komatiitic basalts of the Murrin Murrin Formation.
- The lateritic profile is typically 25 m thick and generally comprises a ferruginous zone, a smectitic clay zone and a saprolitic zone. The saprolitic zone transitions into saprock, and then into unweathered peridotites and dunites.
- Supergene and residual enrichment processes generally result in elevated nickel concentrations developing in the smectite zone and, to a lesser extent, in the saprolite and ferruginous zone. In general, the concentrations in the saprock are only slightly higher than those in the unweathered ultramafics. In many places, the lateritic profile is often covered by a thin layer of recent sediments. The cover is usually only a few metres thick, but can exceed over 50 m in places.
The approximate dimensions of the defined deposits and the average thicknesses of the deposits are summarised below:
1. Mt Kilkenny: Model extent: 8.5 × 0.7 km, Laterite thickness: 25 m, Overburden thickness: 12 m.
2. Hepi: Model extent: 2.4 × 0.5 km, Laterite thickness: 25 m, Overburden thickness: n.d. (not determined).
3. Wanbanna: Model extent: 2.0 × 0.5 km, Laterite thickness: 30 m, Overburden thickness: 16 m.
4. Eucalyptus: Model extent: 14.5 × 3.5 km, Laterite thickness: 35 m, Overburden thickness: n.d. (not determined).