Edah project – Western Australia
The Edah project of Lithium Australia NL (‘LIT’) comprises five contiguous exploration licence applications, all about 70 kilometres (‘km’) west of the gold mining town of Mount Magnet and midway between that town and Yalgoo (see Figure 1). The combined area of the applications is 1027 km2, with the sealed Mt Magnet/Yalgoo road traversing the tenements to the east.
Geology and mineralisation
The Edah project is located in the Archean granite-greenstone terrane of the Murchison Province of the Yilgarn Craton. It overlies large areas of granitic rocks between the Yalgoo and Mount Magnet greenstone belts. The surrounding Murchison region contains scattered occurrences of pegmatites with tantalum, beryl and traces of other rare metals (tin, tungsten, lithium). Some 50 km north of Edah is the now abandoned high-grade Dalgaranga tantalite mine.
Granites in the central part of the project contain a dense network of small pegmatite dykes, with more than 20 dykes per hectare recorded in some areas.
In 1959-60, a small quantity of beryl was extracted from the Rising Fast pegmatite, which has been mapped along strike for 250 metres (‘m’) and varies in width from 20 m to less than 1 m. No other mining activity has been recorded within the area of the tenements.
The project area was identified as a tantalum prospect on the basis of regional geochemical work undertaken by the Geological Survey of Western Australia (‘GSWA’) and published in 2007. Having a nominal sample interval of some 9 km, the GSWA survey is capable of delineating regional scale anomalies only, not individual targets.
One of the largest and most coherent tantalum and multi-element anomalies, with a diameter of about 40 km, lies within the Edah project area (see Figure 2). With values 30 times above background, it is a significant anomaly.
During the period 2013-17, the project was explored for tantalum using mainly stream sediment geochemistry as a tool. Tantalum and tin values were found to be anomalous over wide areas. Lithium was not assayed in all samples but values were low, which may be due to the sampling method – stream geochemistry targets heavy minerals that are resistant to weathering and is not optimised for light, less resistant minerals such as lithium.
No further work was carried out and there has been no drilling for minerals within the project area. Exploration to date has not fully evaluated the potential for lithium mineralisation.
So far, exploration confirms that the Edah anomaly occurs in pegmatite-rich granite terrain and indicates strong and widespread fractionation of a granitic magma. There is little understanding of the origins of the mineralisation, it being confined to the pegmatites or more widely disseminated throughout the granite. The large size of the anomaly is indicative of the fractionated cusp of a granite pluton and as such it presents as an attractive and potentially large-tonnage target.
For LIT, Edah is an early-stage exploration prospect. The project’s large holding presents an ideal opportunity for the use of LIT’s laser-induced breakdown spectroscopy (‘LIBS’) technology, which can produce real-time, in-field soil geochemistry assays for lithium. Used on-ground, LIBS represents a cost-effective exploration tool with the potential to identify lithium-rich target zones and enhance understanding of the style and controls on lithium mineralisation in the area.