Legacy Minerals pursuing rare opportunity on historical ground within Bauloora Epithermal Gold Project

Legacy Minerals (ASX:LGM) is pursuing an ‘aggressive and systematic’ campaign at its Bauloora Epithermal Gold Project in New South Wales after confirming low-sulphidation epithermal veins on historical ground.

Speaking to Mining.com.au on the sidelines of the Brisbane Mining Investor Conference last week, CEO and Managing Director Chris Byrne says Legacy’s works over the past 18 months includes the first ever diamond drilling into the low sulphidation veining of the project.

According to Byrne, the gold exploration companies of the 1980s and 1990s considered the geological setting Legacy is focused on as a ‘prospectivity downgrade’, with historical viewpoints of the mineralisation at the time being it is not conducive to generating major deposits.

However, Legacy considers the region an overlooked opportunity where it is now applying modern mining techniques to understanding the geology and overprinting systems.

“We’ve pegged what has ended up being the district and a lot of it is centring around a few particular volcanic units around overprinting systems. But it’s a very different geology than what you see elsewhere in New South Wales. There’s no orogenic deformation. In an old district like New South Wales, you see there’s lots of post mineralisation events and cover sequences that get deposited and that hasn’t occurred at Bauloora.

We’re not really quite sure what’s happened, but we’re sort of looking at a perfect window that we’ve got rocks on surface that you would expect to find in Japan, Indonesia, PNG that are half a million to a million and a half years old. So, there’s something there that makes it pretty special and pretty rare.”

The Bauloora Project is located in the Central Lachlan Fold Belt NSW, which is host to ‘world-class’ copper-gold orebodies including the Cadia-Ridgeway, Northparkes, and Cowal mines. It is in a zone which is bounded to the west by the Gilmore Fault Zone and to the east by the Cootamundra Fault. Bauloora contains structural remnants of Early Silurian dominantly dacitic volcanic rocks and related granites, Siluro-Devonian sediments and felsic volcanic rocks deposited on a basement of Late Ordovician turbidites, Late Ordovician to Early Silurian intermediate volcanic rocks and related intrusions and sedimentary rocks.

“So, there’s something there that makes it pretty special and pretty rare”

On 1 March, Legacy updated the market on diamond cored drilling completed at Bauloora. At the Mee Mar prospect, 10 diamond core drillholes have been completed for a total of 1,649.6m testing the 2km-long gold-silver bearing low sulphidation epithermal Mee Mar Vein.

The CEO says gold, silver, and pathfinder anomalism was defined by last year’s soil geochemistry program and extensive rock chip sampling program, which returned gold and silver grades up to 55.5g/t Au and 905g/t Ag. In addition, extensive IP resistivity anomalies underlying the ‘encouraging’ geochemical signatures and coincident with north trending zones of low magnetic responses, interpreted to be the result of magnetite destructive hydrothermal alteration, represented compelling drill targets.

The interpreted position of the mineralised structure has been intersected in all holes. The CEO notes that core processing and logging are in progress and samples are being submitted for assay with results expected in April. Geological observations indicate all drillholes intersected host rocks that are dominantly variably altered quartz-eye and feldspar-phyric dacitic crystal lithic tuffs.

“So, we’re targeting all that and what that means is a fantastic opportunity to see what the mineralisation style is and what those textures are in these types of systems. Grade is important but textures are almost just as important as grade and they give you an understanding of where you sit in the system. And that’s really important. Understanding the zonation. Once you can understand the zonation, you can then narrow your focus into these bonanza grade zone targets that really once you start to find them, you’re talking about some significant potential for world class systems.”

Byrne notes that while a porphyry is certainly related and can be a driver of an epithermal system, Legacy is looking at the top part of such a system, which is close to surface.

“Our mineralisation starts from zero metres at surface, so we’re talking low capex mines. They often have very long mine life, but as soon as they’re in place, they start to weather. So, the erosion, the weathering is a key sort of factor in determining, I guess, those bonanza grade zones are still preserved. The work that we’ve done has confirmed that centre related systems that we are looking at the top of a preserved epithermal system.”

Legacy reported earlier this month that a sedimentary unit of well-bedded sandstone-siltstone-mudstone was intersected in MM003 (170.9 to 176.67m) and MM005 (119.55 to 125.6m). Sericite and hematite alteration are commonly observed in the periphery to the main vein trend with sericite increasing in intensity proximal to more abundant veined zones. The Mee Mar vein trend is dominated by crustiform-colloform quartz-adularia-chalcedony veins and breccia (+/- hematite, galena, low-Fe sphalerite, and chalcopyrite). Common minor quartz-carbonate +/- chalcopyrite, galena, low-Fe sphalerite and chlorite veins are also observed proximal to the main Mee Mar vein trend.

Textural observations and interpretations of the chalcedony-quartz-sulphide veins and breccia intersected to date indicate drillholes have tested the lower chalcedonic superzone to upper crustiform-colloform superzone. This interpretation is based on the observation of abundant chalcedony dominant over crystalline quartz in association locally with amethyst and floating clast breccia.

The CEO adds that the implication of this interpretation is that the boiling zone has been preserved across the vein strike and remains at depth. With increasing depth towards the crystalline crustiform-colloform superzone there is the potential for gold grades to greatly increase. As such, if elevated precious metals and pathfinders are returned within these higher zones then there is great encouragement for further testing at depth, he adds.

The diamond cored drillholes have confirmed low-sulphidation epithermal veins, down dip from gold, silver and pathfinder rock chip and soil geochemistry anomalism, mapped veins and are broadly coincident with north striking magnetic lows and resistivity highs.

Byrne says the low sulphidation epithermal veins and breccias have been encountered in all holes drilled along the Mee Mar vein trend strike length and is open to the north and south along strike, down dip, and to surface.

Legacy Minerals has progressively developed the Bauloora Project through systematic exploration work including geological mapping, rock chip sampling, gradient array IP surveying, detailed ground magnetic surveying, ASTER data acquisition and interpretation, and widespread soil sampling.

The results from this work strongly support the assessment that there is significant potential for a major low sulphidation epithermal-style gold-silver deposit at the Bauloora Project.

Write to Adam Orlando at Mining.com.au

Images: Legacy Minerals Limited
Author Image
Written By Adam Orlando
Mining.com.au Managing Editor Adam Orlando has more than 20 years’ experience in the media having held senior roles at various publications, including as Asia-Pacific Sector Head (Mining) at global newswire Acuris (formerly Mergermarket). Adam has worked in newsrooms around the world including Hong Kong, Singapore, London, and Sydney.