The exciting Burns gold-copper discovery appears to be growing for ASX-listed gold and base metals explorer, Lefroy Exploration as its diamond drilling program continues to probe the recently discovered “eastern porphyry” zone. The company says the first three completed diamond holes of a planned 14-hole program totalling 3,000m at Burns point to the vertical depth continuity of altered and mineralised porphyry rocks at least 100m below the zone of gold-copper mineralisation encountered in the recent reverse circulation discovery hole.
That discovery hole returned 38m at an average grade of 7.63 grams per tonne gold and 0.56 per cent copper from 134m depth in the host eastern porphyry earlier this year.
It included a 27m section grading an average 10.1 g/t gold and 0.74 per cent copper from 141m.
Burns lies within Lefroy’s Eastern Lefroy tenements, which form part of its greater Lefroy gold project about 50km south-east of Kalgoorlie.
Follow-up diamond drilling at the prospect is aimed at testing the eastern porphyry over a 200m strike length on 40m-spaced drill sections.
The high-grade gold mineralisation was unearthed within the newly discovered hematite-pyrite-chalcopyrite-magnetite altered porphyry, while gold and copper mineralisation are hosted by both porphyry and basalt that the company believes is a new style of mineralisation to be identified in the area.
Lefroy says the drilling so far has also expanded the eastern porphyry to more than 140m true width, pointed to the broadening at depth of the altered and mineralised zone on the western side of the porphyry and uncovered a new mineralised interval on the east side of the porphyry area.
Hole number one in the 14-hole program was designed to twin and extend past the high-grade discovery hole interval to help determine the width of the eastern porphyry.
The host eastern porphyry was intersected from 117m to 304.5m, a down-hole interval of 187.5m.
Lefroy interpreted the porphyry to have a near vertical dip and an estimated true width of about 110m bounded by basalt to the west and east.
The second hole of the program started at 40m down a pre-existing RC hole and terminated at 396.6m down-hole.
According to the company, the collar of that hole unveiled further important data highlighting the dimensions and constraints to the porphyry and the sulphide mineralisation.
A 189m interval of the eastern porphyry was intersected from 179m that also includes two narrow intervals of altered basalt.
Multiple broad zones – 10m-20m – of alteration and mineralisation were intersected in the porphyry from 201m to 291m depth.
Lefroy says its appraisal of mineralisation in hole number two supports its interpretation that the strength of the Burns gold-copper mineral system may increase with depth.
The third diamond hole was an extension of RC hole LEFR267 in the maiden Burns drill program completed in January 2021 and collared about 68m west of the discovery RC hole.
LEFR267 came to a halt in porphyry at 244m, which the company was not aware of at the time was the commencement of the eastern porphyry. The diamond drill extension terminated at a whopping 522.5m down-hole, the deepest Lefroy drill hole at Burns to date.
It intersected a massive 246m interval of the eastern porphyry from 244m down-hole, the broadest down-hole interval of the eastern porphyry intersected at Burns.
Interestingly, the interval also included multiple occurrences of basalt up to 25m in length, some of which were deformed, carbonate veined and contain chalcopyrite.
Although the system takes in portions of basalt, Lefroy says its observations of the drill core suggest the porphyry body is becoming wider with depth.
Multiple broad zones of alteration and mineralisation were intersected in both the eastern porphyry and the basalt in hole number three.
Assay results from the three holes are expected next month.
Is your ASX-listed company doing something interesting? Contact: email@example.com