Octava Minerals has started its maiden drilling program at its Pinnacle Well prospect in an area in Western Australia’s Pilbara region known as “lithium elephant country”.
Drilling at the prospect, which is part of the company’s Talga project, will test a significant lithium-soil and rock-chip sample anomaly, including a 1.5km pegmatite which is showing visible lithium mineralisation.
Octava has received rock-chip assays from its nearby Nimerry prospect and says they confirm additional lithium-bearing pegmatites. Pinnacle Well sits 10km north of Global Lithium’s Archer deposit that boasts a resource of 18 million tonnes at 1.0 per cent lithium oxide.
The new RC drilling program will test the big anomalous lithium halo at Pinnacle Well, which was identified through mapping, soil and rock-chip sampling and returned up to 0.21 per cent lithium oxide from weathered samples. Multiple pegmatites have been identified at the prospect, including a set of parallel pegmatites with visible lithium minerals.
Octava Minerals managing director Bevan Wakelam said: “We are really pleased to have the drill rig onsite to test the first lithium prospect at Talga. We look forward to the progress of this initial drill campaign which will be followed by additional drill programs throughout the year.”
Pinnacle Well is one of several lithium targets identified within the highly-prospective Talga project. Octava identified Nimerry earlier this year after it discovered multiple outcropping pegmatites up to 30m wide and 60m long at surface.
The Nimerry pegmatites occur as swarms hosted within greenstones close to the granite greenstone contact, which the company says is an important target geology used in the discovery of lithium-mineralised pegmatites in the Pilbara.
At Nimerry, 177 broad-spaced rock-chip samples were collected from weathered outcropping pegmatites in an area extending east of the soil-sampling program which was completed late last year. Octava says potential for additional concealed pegmatites exists beneath colluvium and alluvium. The samples were submitted for analysis by 4-acid digest, with analysis by inductively-coupled plasma mass spectrometry.
The rock chips gave lithium oxide values up to 716 parts per million within pegmatite. Octava says rock chips with lithium oxide values of more than 50ppm are considered encouraging and warrant follow-up work. The company will apply the same systematic approach to exploration at Nimmery as it has conducted at Pinnacle Well.
Management says key indicators of pegmatite fertility include potassium-to-rubidium ratios of less than 150, niobium-to-tantalum ratios of less than five and zirconium-to-hafnium ratios of less than 18. The company says a significant number of samples collected from across Nimerry exhibit the same positive chemical characteristics where pegmatites have intruded into mafic greenstones, away from the Mt Edgar batholith.
Further work is being undertaken around Nimerry to define drill targets.
Talga has about 20km of granite-greenstone contact zones prospective for pegmatites bearing lithium–caesium–tantalum mineralisation. The geology is similar to the massive deposits at Pilgangoora, which has 309 million tonnes at 1.4 per cent lithium oxide, and Wodgina with its 259 million tonnes grading 1.17 per cent lithium oxide. They lie 100km and 120km further west, respectively.
Finding big outcropping pegmatites in arid landscapes is a bit like shooting fish in a barrel. Octava’s plan to use drilling to carefully prove up lithium mineralisation will take a bit more skill than usual and all eyes will be on the results.
But the Pilbara is known to be lithium elephant country and the company will be hoping it can muster a herd.
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By Terry Bates
