Ravensthorpe, Western Australia
Lithium Australia NL (‘LIT’) holds 100% equity in the Ravensthorpe lithium project, which lies 420 kilometres (‘km’) southeast of Perth. Consisting of a single Exploration Licence, 74/543, covering a structural corridor 20 km long, it contains the Mt Cattlin lithium and tantalum mining operations of Galaxy Resources Limited (see Figure 1). Recent fieldwork has greatly enhanced the potential of the project through the discovery of additional, substantial pegmatite units.
A 35-hole reverse circulation drill programme, which began in July 2017, will test the Horseshoe pegmatite at depth, as well as other newly generated targets. Horseshoe is estimated to contain an Exploration Target of between 525,000 tonnes (‘t’) and 1,281,000 t at a grade of between 0.8% and 1.2% lithium oxide (‘Li₂O’).
E74/543 covers a belt of Archaean greenstones hosting numerous occurrences of copper, gold and zinc. The greenstones are draped around granitoids, the late-stage, volatile phases of which discordantly intrude the greenstones. These late-stage intrusive phases, which solidified as pegmatites, have concentrated the lithium and rare metals.
The regional mineralisation potential is well demonstrated by the occurrences of lithium pegmatites at Mt Cattlin, as well as sporadic production from other pegmatites within the area, which have been exploited for rare metals. E74/543 contains a significant proportion of the Cocanarup Pegmatite Field, which was discovered in 1900. The licence includes pegmatites named Quarry, Horseshoe and Eastern. Previous exploration has identified lepidolite at Horseshoe (see Figure 2), zinnwaldite at Eastern, and lepidolite, beryl and tantalite at Quarry.
Field mapping and sampling undertaken in February 2016 confirmed the presence of at least seven lithium pegmatites within the project area and immediate surrounds. Assay results for 19 samples of lithium mineralisation from the lithium core-zones of all pegmatites range from 1.26% Li₂O to 4.23% Li₂O, with a mean of 2.96% Li₂O.
Further work in March 2016 resulted in LIT estimating an Exploration Target for the Horseshoe pegmatite zone (ASX: LIT 04 March 2016) of between 525,00 t and 1,281,000 t at a grade of between 0.8% and 1.2% Li₂O.
Ongoing exploration has extended the known pegmatite bodies within E74/543 to at least 12. At the newly discovered Deep Purple prospect, both spodumene and lepidolite pegmatites have been mapped. At Philllips South, outcropping lepidolite mineralisation is indicative of a single large pegmatite extending over some 500 metres.
Analysis of results from the July 2016 soil sampling at the Deep Purple pegmatite are strongly indicative of a continuation of mineralisation under soil cover. Encouragingly, the size of the soil anomaly is more than twice that of the surface expression of the pegmatite.
A 35-hole reverse circulation drill programme commenced in July 2017. The programme will test the Horseshoe pegmatite and other newly generated targets, including the Deep Purple prospect. Drill chip samples from the initial holes have been sent to Perth and submitted for analysis, with results expected in early August 2017.