Lithium Australia identifies potential deposits at Dudley prospect

Energy-metal company Lithium Australia recently identified lithium-anomalous pegmatite dykes at its Dudley prospect at the Kangaroo Island Project.

All data from the recent exploration program indicate the Dudley prospect has potential to host a lithium deposit in a location not previously identified for its lithium potential.

In light of these significant results, the company is planning a geochemical soil-sampling program over the Dudley prospect and surrounding areas.

Lithium Australia however has not renewed the nearby Vivonne lease, EL 5960, in the central portion of Kangaroo Island as its potential was considered low.

The company, listed as LIT, on Thursday, June 20 released a statement to the ASX listing its findings.

"Early results from the Dudley prospect indicate good potential for a new LCT pegmatite field, and we look forward to extending our exploration coverage later in the year," Lithium Australia managing director Adrian Griffin said.

Despite strong weathering of outcrops and exposures in shallow historical tourmaline and tin-mine workings, the host pegmatites exhibit local, anomalous lithium, rubidium and tantalum.

Lithium Australia considers this significant, as lithium, which is very mobile, is usually leached from weathered rocks.

The Dudley pegmatites intrude the Cambrian metasediment Tapanappa Formation and are variably exposed at surface.

Currently, lithium pegmatites in Australia are attracting investment from some of the world's largest lithium companies.

Reconnaissance exploration was undertaken at Dudley in October 2018 and March 2019. The area had not previously been explored for lithium or tantalum.

In all, 66 rock-chip samples were collected from outcrops and another 35 samples from float material, with assays now been received for all samples.

Both the fieldwork and assays confirmed the presence of lithium pegmatites in the shallow, historical Dudley tourmaline mine workings, as well as the broader surrounding prospect area.

The Dudley mine has produced gem-quality elbaite (lithium tourmaline) since 1899, with kaolin also mined after 1906.

"Lithium Australia aspires to 'close the loop' on the energy-metal cycle in an ethical and sustainable manner," the ASX statement reads.

"To that end, it has amassed a portfolio of projects and alliances and developed innovative extraction processes to convert all lithium silicates (including mine waste) to lithium chemicals.

"From these chemicals, the company plans to produce advanced components for the lithium-ion battery industry.

"The final step for Lithium Australia involves the recycling of spent batteries and e-waste. By uniting resources and the best available technology, the company aims to establish a vertically integrated lithium processing business."

Gem-quality elbaite (lithium tourmaline) from the Dudley mine. Photo LIT

Gem-quality elbaite (lithium tourmaline) from the Dudley mine. Photo LIT

Details from the Lithium Australia (LIT) statement to the ASX:

At Dudley, lithium-mineralised pegmatites outcrop intermittently with weathered exposures outcropping through younger limestones, laterite/ferricrete and alluvial cover.

Mineralised float is abundant. The mineralised zone lies within a broader pegmatite field that appears to extend over a strike of 5 km from coastal exposures to the northeast to patchy outcrops in the southwest of EL 6212.

The pegmatite dykes, which vary from tourmaline-rich aplites in the west to coarse- grained pegmatites in the east, are hosted by the Cambrian Tapanappa Group rocks.

Dudley prospect geology and sample locations. Photo LIT

Dudley prospect geology and sample locations. Photo LIT

The central portion is very coarse-grained, with blocky, variably perthitic microcline feldspar, large muscovite 'books', milky quartz and green elbaite; it contains mariolitic cavities and shows intense kaolinisation.

The main known Dudley pegmatite trend strikes northeast-southwest in line with regional foliation, and consists of approximately 30 dykes ranging up to 80 m thick and a strike estimated to be more than 450 m.

Also observed was a new cross-cutting northwest-southeast striking trend of pegmatite dykes up to ~ 40 m thick, which correlates with trends in geophysics images.

This contrasting trend extends about 1 km southeast into LIT's adjacent tenement, EL 6213, where pegmatites were unknown until now.

A previously unreported 'Black Spider' tin mine (name supplied by elderly local farmer) with shallow workings over pegmatites in EL 6213 was also sampled (tin mineralisation is common in lithium-mineralised pegmatites such as the Greenbushes mine in Western Australia).

The two pegmatite trends appear to intersect at the broader Dudley mine area, where variably anomalous chip assays were returned from the LIT samples.

Despite the strong weathering of material sampled by LIT, the outcrop rock-chip assays included results up to 0.43% Li2O, 1,600 ppm rubidium, 770 ppm tantalum, 460 ppm niobium (0.046% assay) and 180 ppm caesium; float samples returned assays up to 0.11% Li2O, 1,100 ppm rubidium and 560 ppm caesium (rounded).

The tantalum values in the outcrop rock chips are also highly significant, as values above 200 ppm are considered economic grades.

Outcrop and float sample results are displayed with SA State 1:100,000 scale GSSA geology in Figure 3. Lithium minerals in the outcrops and float included variably weathered lithium tourmaline (indicolite and rubellite varieties of elbaite), lithium micas (possible poly/trilithionite) and petalite.

As mentioned previously, lithium is extremely soluble during weathering, so highly anomalous results from very weathered samples are uncommon and indicate the potential for high grades in the unweathered bedrock.

The lithium mica lepidolite, which was previously reported from marialitic cavities within the pegmatites (Mindat and specimens in the Sorrell collection), was not observed during the fieldwork programmes.

Data suggest that the workings and outcrops only expose the upper extremities of the pegmatite system, indicating the potential for spodumene mineralisation at depth.

All data from this programme indicate that the Dudley prospect has the potential to host a lithium deposit in a location not previously identified for its lithium potential.

The following factors indicate the potential to delineate a substantial lithium-caesium- tantalum (LCT) pegmatite system (LCT pegmatites host almost all of the world's hard- rock lithium mines):

  • strongly anomalous assays (despite strong weathering and kaolinisation);
  • abundant lithium and pathfinder minerals and elements;
  • multiple dykes with widths up to 80 m occurring over a substantial strike, and
  • relatively shallow cover.

In light of these significant results, LIT is planning a geochemical soil-sampling programme over the Dudley prospect and surrounding areas where anomalous lithium values were obtained from pegmatite float.

Results will assist in locating additional LCT pegmatite dykes under cover and further determining the extent of lithium and tantalum mineralisation of the Dudley and broader area.

Close-spaced costeans in the vicinity of the Dudley mine will improve the geological interpretation. Detailed geological mapping is also required to investigate the nature of the two identified trends, as shown in Figure 3.

Petrological examination and XRD analyses of rock samples are also being considered. The follow-up work programme at Dudley will commence in the fourth quarter of 2019.

LIT has not renewed the nearby Vivonne lease, EL 5960, in the central portion of Kangaroo Island as its potential was considered low.