Project
Geology
The Windimurra Vanadium deposit lies within the eastern flank of the large (>2,000km2) Windimurra intruded layered gabbro complex, which is part of the regional Murchison granite-greenstone province. The vanadium deposits lie within the lower 200m of a 600m wide structurally discordant section of the layered intrusive, known as the Shephard’s Discordant Zone ("SDZ"), named after the ridge that tracks the strike of the zone. See Figure 1 for an illustration of the Geology.
Figure 1: Windimurra Geology
Since first exploration in 1972 the deposit has undergone extensive geological definition, including drilling, aerial geophysics, ground trenching and mapping. This, together with an extensive geological database from the mining period from 1999-2003, and the relatively simplistic geological framework, provides high confidence in the geological understanding of the deposit.
The vanadium is hosted within a 200m footwall sequence of magnetite rich bands within the gabbro sequence. Vanadium mineralisation is elevated within the bands and also occurs in economic concentrations in the interstitial gabbro material. The layered package dips 35 degrees to the west, with a clearly defined footwall into un-mineralised gabbros. Apart from minor rolling and warping of the layered units, local scaled structural shearing/slumping and emplacement of barren anorthosite rich bands, the package is continuous along the strike length of the existing pit and has been tracked along strike, via drilling, both south and north for a further 5km.
Infill drilling has allowed detailed modelling of vanadium distribution within the 200m footwall gabbro package. The majority of vanadium mineralisation lies within the main zone, which averages 70m in true thickness. Other minor ore zones are located in the upper packages.
The weathering profile, as confirmed by infill drilling and pit exposures, is both regular and also transitional with distinct decreases in weathering down to fresh material below 40m. During the weathering and oxidation processes the vanadium is immobile and thus the concentrations are unaffected, however; the magnetite does vary due to oxidation to various levels of hematite and martite. These changes can be clearly defined by use of magnetic susceptibility probing, resulting in a well defined weathering model.
The level of oxidation directly affects the proportion of magnetite in the ore and thus the recovery of vanadium bearing magnetite to concentrate. Metallurgical test work and experience in the previous operation have indicated that recovery to concentrate increases from 40% near surface to 84% at the 40m fresh interface. The current blending regime of 20% oxide/transitional material to 80% fresh is scheduled to optimise beneficiation performance.