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Dart Mining homes in on Victorian lithium pegmatites

Dart Mining drilling for lithium at Fergusson’s Dyke on Dorchap Track in Victoria. Credit: File

Dart Mining has ploughed through 2200m of a 3000m diamond drilling program at its lithium-caesium-tantalum (LCT) pegmatite project in Victoria’s Dorchap Range.

Drilling has been completed at the company’s Eagle, Fergusson’s and Blair’s dykes, while a 10th hole is being drilled at Boone’s dyke and the final three holes of the 13-hole program will soon begin at the Rhoda Creek dyke. All dykes being drilled have previously returned lithium in surface rock-chip samples, including 10m at 1.0 per cent lithium oxide from Eagle.

Dart has identified more than 1500 pegmatite dykes in its Dorchap Range tenements and confirmed many as being LCT-type. Many of them have been previously-worked for tin, although Dart was the first to recognise the ground’s potential for lithium and the LCT character of the dykes.

Drilling has focused on dykes where previous surface sampling has confirmed lithium mineralisation. In addition to Eagle, Fergusson’s dyke recorded 5.6m going 0.5 per cent lithium oxide, Boone’s dyke returned 5.5m at 0.5 per cent and Rhoda Creek gave 5m at 0.4 per cent lithium oxide.

All holes to date have intersected pegmatites and core from the first three holes have been logged and samples have been sent for assay. Dart said its drilling is providing considerable information on the dyke system mineralogy, structural setting and geological emplacement.

Aside from the LCT pegmatite dykes, a separate set of quartz-porphyry and diorite dykes is known to be associated with rich gold in quartz shoots – for example, at the Warrnambool mine. But it is not the company’s current focus.

The Dorchap lithium project exploration work is fully funded by an earn-in joint venture (JV) agreement with leading Chilean lithium miner, Sociedad Química y Minera (SQM). SQM has the right to sole-fund exploration expenditure to the tune of $12m in the next six years. It can earn an initial 30 per cent interest in the Dorchap project by sole-funding $3m in exploration expenditure.

Previous extensive regional sampling by Dart resolved a 20km-long and 12km-wide zone of highly-fractionated pegmatites bearing enriched lithium, caesium, tantalum, beryllium and tin mineralisation. The company completed grab and channel samples returning rock-chip results of up to 1.57 per cent lithium oxide near Glen Wills in the south and Dorchap Range channel samples with 10m grading 1.38 per cent lithium oxide and 10m going 1.22 per cent lithium oxide. One grab sample returned an incredibly-high tin assay of 9.98 per cent.

The detailed geological map accompanying Victorian Geological Survey Bulletin 37 from 1915, shows tin-bearing pegmatite and greisen dykes of up to 40m in width and continuous over several kilometres in some instances. Tin mining from the period discovered that the dykes were plentiful and often close together in swarms and it was believed they represented the upper levels of the Mount Wills granite.

What was not known back then, was that the pegmatite dykes contained lithium mineralisation, which Dart is proving up in its JV with SQM.

Blair’s dyke was described in Bulletin 37 as standing 3m high at the northern end and 9m wide, before gradually reducing in width to the south. Fair tin values were observed along the outcrop of Blair’s and one sample assayed 6.6 per cent tin.

Dart and SQM are keenly testing the known lithium-bearing pegmatites and their program will only just scratch the surface of the extensive dyke swarms in a huge area. The assay results should only be a pointer to things to come.

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