Litchfield Minerals confirms wider spread of NT polymetallic mineralisation
- Rowena Duckworth
- Oct 3
- 3 min read
Field mapping by emerging explorer Litchfield Minerals (ASX: LMS) has identified continuous outcrop of the Northern Territory’s polymetallic mineralised Oonagalabi Formation all the way from the company’s Silverado prospect to Bomb Diggity, encompassing an area along about 3 kilometres of strike.
Mapping and rock chip sampling found that outcrop between Silverado and Oonagalabi is strongly mineralised. Portable XRF spectrometer analysis of rock chips recorded values up to 21.5 per cent copper, 2.47 per cent zinc and a striking 25 grams per tonne (g/t) silver.
The Oonagalabi copper, zinc, gold and silver deposit sits 120km northeast of Alice Springs and is hosted within metamorphosed Paleoproterozoic sedimentary rocks of the Strangways Metamorphic Complex in the well-endowed Aileron Province. The project spans about 3km by 0.5km, and geophysics suggests that mineralisation extends to at least 500m depth.
Litchfield finalised its acquisition of a strategic copper-gold-base metals portfolio, including Oonagalabi, in October last year as part of a strategy to invest fresh capital into the NT.
Oonagalabi was first explored in the 1970s, with Russgar Minerals completing 14 percussion holes plus extensive mapping and geophysics. Amoco Minerals Australia followed this work up with six reverse circulation drill holes in the early 1980s. That historical work was not followed up by more recent exploration, leaving Litchfield with a tantalising opportunity to discover further base metal riches in the territory’s highly prospective Arunta region.
Litchfield interprets the Oonagalabi deposit to have formed within an epigenetic carbonate-replacement or skarn-type environment. The company acknowledges the data may also support a Mt Isa-type syn-sedimentary model of mineralisation. It is kicking off an 11-hole reverse circulation drilling program this weekend, which may shed more light on the mode of formation.
The project area shares geological similarities with KGL Resources’ Jervois project, about 150km east-northeast of Oonagalabi, which has total proven and probable 14.38-million-tonne reserves at 1.77 per cent copper for a contained 265,000 tonnes of copper, 9.4 million ounces of silver and 761,000 ounces of gold.
The two areas have a similar metamorphic and structural evolution, potential for contained metal and a possible genetic link. Mineralisation at Jervois is structurally controlled and is characterised by copper sulphides, such as chalcopyrite, occurring in quartz veins, fractures, or disseminated within host rocks. Oonagalabi may be a geological analogue of the Jervois zone, which is the NT’s largest base metals deposit hosting more than 10 prospects.
Litchfield’s recently completed field mapping program has linked mineralised Oonagalabi Formation exposures from Silverado to the main Oonagalabi outcrops, confirming continuous outcrop and also local thickening. Structural and sedimentary features support a southeast dipping geometry consistent with observations in the main zone and suggests the mineralised Oonagalabi Formation extends southeast under cover.
Mapping of four new zones confirmed that the mineralised Oonagalabi Formation is decidedly more extensive than previously thought. Litchfield sees potential for depth extensions over significant parts of the system. Additionally, base metal soil anomalism southwest of the company’s Silverado and Bomb Diggity prospects indicate that the system is probably open to the northeast and southwest.
Drill testing of the main zone and a possible Bomb Diggity extension begins in the next few days. Litchfield says it will release the results as assays are received and validated. It expects to receive the first assays in mid to late November.
Litchfield plans to conduct further induced polarisation (IP) surveys early next year to further define the full extent of the subsurface Oonagalabi Formation within the system.
The new VTEM data showing increased conductivity prompted follow-up checks in several areas. Mapping has now identified four new areas and, importantly, now links outcrop from Silverado through to the Main Oonagalabi zone, which is about three kilometres end-to-end, with several new areas where the formation thickens and dips steeply to the southeast.
Litchfield Minerals Managing Director Matthew Pustahya
Pustahya said IP surveys conducted earlier this year didn’t just frame the main corridor but also picked up a second, parallel structure right where new mapping said it should be.
“With VTEM indicating conductivity trends to the northeast and southwest, we have further clear, testable targets over a broader area that has not been rigorously examined to date,” he said.
The company also says geophysical chargeability and resistivity IP responses limit the lateral extent of sulphide-bearing horizons within the tested corridor and define a second, sub-parallel structure coincident with the newly mapped Oonagalabi horizon in the central corridor.
With drilling planned and high-priority sulphide targets in sight, Litchfield could be on the cusp of unlocking the full potential of its flagship Oonagalabi polymetallic project in the Territory’s Harts Range.
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