Identifies New Deep Mineralised Zone
Lefroy Exploration Limited (ASX: LEX) has successfully completed the third and deepest diamond hole to date in its current 3000m diamond drilling programme evaluating the Burns copper, gold prospect.
Burns is located within the Eastern Lefroy tenement package, which is part of the wholly owned greater Lefroy Gold Project (LGP) located 50km south east of Kalgoorlie, in Western Australia.
A 14-hole diamond drill programme commenced on April 20, 2021 to evaluate the Eastern Porphyry over a 200m strike length on 40m spaced drill sections. The first hole of the programme on May 3, 2021. That hole was designed to twin and extend past the high-grade interval found in LEFR260 to determine the width of the Eastern Porphyry.
The host Eastern Porphyry was intersected in LEFD004 from 117m to 304.5m, a down hole interval of 187.5m. The porphyry was interpreted to have a near vertical dip and an estimated true width of approximately 110m bounded by basalt to the west and east.That hole confirmed three distinct variations of the host diorite porphyry were observed in this interval and are interpreted as multi-phase intrusive events.
The second hole of the programme, OBURCD025, commenced at 40m down a pre-existing RC hole and terminated at 396.6m downhole. The collar of that hole is located 35m to the west of LEFD004 and provided further important information to highlight the dimensions and constraints to the porphyry and the sulphide mineralisation on this baseline (0N) section. A 189m interval of the Eastern Porphyry was intersected from 179m, that also includes two narrow intervals of altered basalt. The hole terminated in chlorite biotite altered basalt.
Multiple broad (10m-20m) zones of alteration and mineralisation where intersected in the porphyry in OBURCD025 from 201m to 291m.The observations of the mineralisation in OBURCD025 supported the company’s interpretation that the strength of the Burns Cu-Au mineral system maybe increasing with depth that triggered the decision to adjust the drill program and bring forward the extension of hole LEFR267,.
RC drill Hole LEFR267 was part of the maiden Burns drill programme completed in January 2021 and collared approximately 68m west of LEFR260. The hole was terminated in porphyry at 244m, unaware at the time that this was the commencement of the Eastern Porphyry. The diamond drill extension to LEFR267 terminated at 522.5m down hole, 80m deeper than proposed and is currently the deepest Lefroy drill hole at Burns.
The diamond extension (LEFRD267) intersected a 246m interval of the Eastern Porphyry from 244m downhole. The interval included multiple intervals of basalt up to 25m in length, some of which were deformed, carbonate veined and contain sulphides (chalcopyrite). This is the broadest downhole interval of the Eastern Porphyry intersected at Burns, and although includes intervals of basalt it suggests the porphyry body is becoming wider with depth.
The DD programme at Burns has now:
• confirmed the vertical depth continuity of altered and mineralised porphyry at least100m below the 37m zone of Au/Cu mineralisation in LEFR 260 (38m @ 7.63g/t Au and 0.56% Cu from 134m),
• expanded the Eastern Porphyry body to over 140m true width
• established the broadening with depth of the altered and mineralised zone on the western side of the porphyry, and
• discovered a new mineralised interval on the east side of the porphyry body.
The Burns copper gold prospect is situated on the eastern margin of a large interpreted felsic intrusion, termed the Burns Intrusion. The intrusion does not outcrop but features a distinctive annular aeromagnetic and gravity geophysical signature.
Broad high-grade gold mineralisation is hosted within a newly discovered hematite-pyrite- chalcopyrite-magnetite altered porphyry.
This porphyry, termed the Eastern Porphyry, is open to the north and south and its eastern extent is unknown. The mineralisation is open at depth. The copper and gold mineralisation hosted by both porphyry and basalt is considered by the company to be a new style of mineralisation in the area, a land position dominated by Lefroy
