Rubix Resources Limited announced the results of new Ultrafine+ soil geochemistry which support the nickel (Ni) prospectivity of the Lake Johnston project (E63/2091). The new data was collected by Rubix geologists over parts of the Jimberlana Dyke and selected magnetic anomalies interpreted to represent the buried expression of the Lake Johnston Greenstone Belt. The outcrop and exposure of the Jimberlana Dyke and greenstone belt is variable.

In the Lake Johnston area, the topography is flat and outcrops are scarce. An estimated 1m of residual soil covers much of the surface geology, and remnants of a lateritic profile are common over mafic and ultramafic lithologies. However, sub-cropping geology can be found at the surface in the west of the project area and includes weathered granites and foliated amphibolites considered to belong to the greenstone belt.

Cover is relatively thin and the Ultrafine+ soil geochemistry results are considered encouraging, and likely represent the underlying geology. Subdued anomalism in the east of the project area may reflect increased depth of cover. The best lithium assays (up to 121ppm Li) from the Ultrafine+ soil geochemistry are coincident with the best nickel results.

More work is required to expand on these data. Sampling method: Sixty-three samples were collected using hand tools. Approximately 2-3kg samples were collected at each site in a labelled calico bag.

At the end of each day, the samples were then sieved to remove any organic material, larger gravels and coarse sand, and a sample of approximately 300g of the remaining fines was collected in a labelled paper sleeve for assay submission. Ultrafine+ Technique: Soil geochemical exploration has evolved relatively little over the last few decades despite a demonstrable need for innovative techniques in terranes under cover. The Ultrafine+ method was conceived to separate the fine (< 2 µm) soil and sediment fractions collected as part of routine geochemical sampling programs for multi-element analyses and other physico-chemical parameters to aid exploration.

The Ultrafine+ technique is now an established exploration method to identify sensitive geochemical signals at the surface beneath shallow to moderate cover. In transported cover, the soils that host the mobile element signature are the smallest size fractions, so concentrating the clay (< 2 µm) size fraction provides an improved sample medium. Key benefits of the method include reduction of the `nugget effect' (in Au) and the challenges that occur in materials dominated by quartz sands.

Workflow development showed that the < 2 µm fraction was the most effective and cost-efficient sample medium to use and proved that small sample weights (0.2g) are effective. The use of a Na-hexametaphosphate (technical or laboratory grade) dispersant is critical for solid recovery and microwave-assisted aqua regia digestion is the best analytical method for Au detection. Copper and zinc were both consistently and abundantly extracted.

The Ultrafine+ workflow provides significantly more data to assist with mineral exploration. The Ultrafine+ technique was developed as part of a combined CSIRO/MRIWA project (M462 and M462A) led by Dr. Ryan Noble, with LabWest as a project participant and commercial partner. Together with the geological surveys of NSW, Qld, SA, WA and the NT, other commercial sponsors include Newmont, Northern Star, Fortescue and De Grey, highlighting high-level support.

Next Steps: A systematic field sampling campaign is required to better identify anomalism in the western part of the Lake Johnston project area. This may include additional soil grids using the Ultrafine+ technique, deep auger sampling, rock chip sampling and/or structural mapping and potential drill testing.