Geology
The Three River Project is located on the fault boundary of the of the Proterozoic Shield and the Tasman Orogenic Belt, which comprise structurally emplaced Proterozoic meta-sedimentary schists and meta-gabbros, Ordovician volcanogenic sediments and granitoids, and Devonian limestone overlain by Neogene basalt. A general northeast structural trend is defined by faulting and foliation in the pre-granitoid sequence.
The Proterozoic meta-sedimentary schists are dominated by micaceous pelite with lesser amounts of micaceous quartzite. The Ordovician volcanogenic sediments occurring on EPM 11223 range from weakly foliated shales to cobble conglomerates, which include some mafic clasts. Fault bounded crystalline, fossiliferous limestone units with minor, thin micaceous bands have been mapped within the meta-gabbro and Ordivician sediments and extend over strike lengths of up to one kilometre and 100m wide. A small Ordovician granitoid intrudes the meta-gabbro and cross cuts a serpentinite unit on the southern boundary of EPM 11223. A late Palaeozoic granitoid pluton has intruded the northern part of the tenement. Narrow porphyritic granitoid dykes are common through-out the pre-granitoid sequence.
In addition to the flat lying Greenvale serpentinite, several other steeply dipping, 50 to 150 metre wide serpentinite units occur on both the eastern and western margin of the Greenvale meta-gabbro. The Lucknow deposit located on EPM 10680 and EPM 10866 has formed on a flat lying serpentinite which is about 50 metres thick. In places the serpentinite is nickel rich and grades into garnierite.
Laterite plateaus are common on high ground and overlie strongly weathered rocks. The nature of the laterite, which are generally less than five metres thick, varies depending on the underlying lithology.
The Greenvale Nickel Laterite Mine began production in 1974 and ceased in 1993. A scoping study conducted by Anaconda Nickel Limited reported a remnant resource of 44 Mt @ 0.9% Ni and 0.1% Co at the Greenvale Nickel Mine.
The Lucknow nickel deposit represents the partial lateritisation of weathered serpentinite associated with shearing of the underlying meta-gabbro. Garnierite-serpentine mineralisation is hosted by the shear and grades between 0.3% to 0.4% nickel. The surface extent of the lateritic nickel anomaly at the Lucknow deposit extends approximately 2500 m by 800 m within a larger lateritic plateau on a northwest trending ridge. The best nickel and cobalt grades are associated with the laterite and the upper parts of the serpentinite.
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