The Berkshire Valley Project lies within the western gneiss belt of the South West Province of the Yilgarn Craton and consists of meta-sedimentary and igneous rocks, including parallel trends of mafic and ultramafic intrusions that can be clearly seen in magnetic imagery (Figure 1).
Previous investigations by the Co-operative Research Centre for Landscape Environments and Mineral Exploration (CRC LEME) identified the region as having anomalous chrome, copper and nickel associated with mafic and ultramafic units in a 2006 report on laterite geochemistry, and subsequent exploration by IGO from 2006-2008 reaffirmed this.
Although exploration by IGO was primarily targeting gold mineralisation and focussed on the southern tenement at Berkshire Valley, they recognised the presence of the mafic and ultramafic intrusions and routinely assayed their auger geochemical samples and shallow aircore drill samples for a suite of minerals including nickel and copper, however there was no assaying for platinum group elements which are critical in vectoring towards potential sulphide occurrences.
Following routine wide spaced auger sampling, further infill and extensional work was concentrated over 8 kilometres of strike of the western greenstone package that includes several magnetic features which correspond to mafic and ultramafic intrusions. A number of nickel and copper hot spots were identified in this work with gridded results shown in Figure 2.
Very limited and incomplete aircore drilling to follow up low level gold anomalism coincidently reaffirmed the presence of mafic and ultramafic rocks both through geological logging of the drill samples and assay results where values up to 0.48% Ni and 0.2% Cu were recorded close to the northern edge of E70/5204.
The remaining >34 kilometres of interpreted strike remains largely untested.