Lefroy’s Burns porphyry system is looking bigger and better than ever

Lefroy has secured further evidence of a large mineral system at its Burns project with drilling returning multiple thick intervals of copper, gold and silver porphyry-style mineralisation.

Gold and multiple-element assays from a further 24 holes from the 67-hole reverse circulation drill program completed in December 2022 cover 240m of strike south of the Baseline Discovery Section and returned tasty hits in the Western Basalt host rock such as:

78m grading 0.64% copper, 0.35 grams per tonne (g/t) gold and 1.08g/t silver from a downhole depth of 24m including 8m at 1.2% copper, 0.19g/t gold and 1.69g/t silver from 29m and 6m at 4% copper, 1.85g/t gold and 7.17g/t silver from 78m (LEFR349); and
69m at 0.68% copper, 0.41g/t gold and 2.06g/t silver from 24m including 6m at 4.03% copper, 2.12g/t gold and 11.17g/t silver from 79m (LEFR347); and
66m at 0.85% copper, 0.40g/t gold and 2.15g/t silver from 27m including 8m at 3.77% copper, 1.97g/t gold and 10.39g/t silver from 56m (LEFR355).

Importantly for Lefroy Exploration (ASX:LEX), the results significantly expand the known copper-gold mineralisation within the Western Basalt, which remains open along strike and at depth, and defined key areas for follow-up extensional drilling after the maiden resource is defined.

Adding to this prospectivity, final assays from the EFD006 and LEFD007a deep diamond holes have confirmed continuity to the mineralised system to at least 1000m from surface and reinforced the company’s view that Burns is a alkalic copper-gold porphyry system.

Better results from these holes are:

17m at 0.47% copper, 0.23g/t gold and 2.21g/t silver from 80m including 1m at 4.18% copper, 2.78g/t gold, 15g/t silver and 175 parts per million (ppm) molybdenum from 96m in hole LEFD007a
20.4m at 0.18g/t gold from 748.5m including 1.5m at 0.88g/t gold, 65.8ppm molybdenum and a surprise 0.15% cobalt from 759.5m in hole LEFD006.

Managing director Wade Johnson said the drilling generated multiple “outstanding” +100m downhole thicknesses of total copper-gold mineralisation that in many cases, continued at the end of hole, which indicates that mineralisation continues at depth.

“The thickness of the mineralisation is outstanding and the fact that much of the mineralisation starts at around 25m depth means that a mineral resource defined at this shallow depth will likely be amenable to be mined via open cut methods and have a low strip ratio, he added.

“We are excited by these results, which continue to reinforce the growing scale of the Burns Central system and especially the continuity of the shallow part of the system.

“We are further encouraged by the implications of these results for finding more mineralisation associated with the other six currently identified magnetic anomalies to the north and south of the Burns Central area.”

RC drilling

The 67-hole RC drill program totalling 16,635m was designed to evaluate the Burns Central system to a vertical depth of 200m from surface over a 700m north-south and 450 east-west extent.

Data from this program will be combined with previous drilling data to support the compilation of a maiden resource estimate for Burns Central in the first quarter of this year.

Mineralisation within the epidote-magnetite altered Western Basalt is considered by the company to be part of an outer alteration halo around the Central porphyry that consists primarily of chalcocite (copper sulphide).

The chalcocite occurs as fine disseminations and fracture fill in the basalt resulting in the consistent broad downhole intervals that start just below surface and include discrete, very high-grade copper zones.

Lefroy noted that the high-grade copper zones appear to be structurally controlled and coincide with shallow west dipping magnetite breccia structures identified from diamond drilling, which provide a clear target for follow-up drilling.

Mineralisation is open at depth and is untested to the south of the 240S drill section, the most southerly drill traverse drilled to date.

Additionally, multi-element assays have highlighted significant zones of cobalt and molybdenum which are further evidence for an alkalic porphyry style of mineralisation and are of potential economic interest.

Deep hole LEFD006, which was co-funded by Western Australia’s Exploration Incentive Scheme, intersected multiple zones of gold and copper mineralisation, confirming that the geometry and continuity of the diorite porphyry intrusions and major structures in the
Burns system extends more than 300m below existing drilling.

Likewise, LEFD007a has confirmed the structural interpretation and continuity of the high-grade mineralisation which remains open to the south.

Future activity

Work is now underway on the resource estimate with final delivery expected towards the end of the quarter subject to pending assays from the remaining 39 RC holes.

Interrogation and interpretation of the geological model is ongoing along with targeting of initial metallurgical holes to complement the resource estimate.

Planning is also underway for resource extension drilling as well as the development and identification of additional targets within the Burns Intrusive Complex.

This article was developed in collaboration with Lefroy Exploration, a Stockhead advertiser at the time of publishing.

This article does not constitute financial product advice. You should consider obtaining independent advice before making any financial decisions.