Drilling extends the scale of De Grey’s Brolga zone

De Grey Mining Limited (ASX: DEG) has announced a highly encouraging update on the drilling at the Brolga Zone within the Hemi Discovery of its Mallina Gold Project in WA.

The company reported that continuity of gold mineralisation was confirmed at Brolga. DEG said that strong gold zones were defined on four adjacent 80m spaced sections 30,480E, 30,560E, 30,640E, and 30,720E associated with extensive sulphide mineralisation.

Significant new RC gold intercepts at Brolga include 78m @ 1.8g/t Au from 40m; 72m @ 1.6g/t Au from 105m; 21m @ 3.6g/t Au from 45m; 15m @ 5.5g/t Au from 75m; 33m @ 1.6g/t Au from 41m; 76m @ 1.5g/t Au from 42m; and 56m @ 1.1g/t Au from 93m.

The company reported that the gold footprint has increased to +340m strike, +300m width, and +200m depth.

De Grey noted that significant growth potential remains and said that many holes end in mineralisation or have further depth potential. The company said that mineralisation remains open, particularly to south and west.

DEG said that the new broad sulphide intersections increase potential to +420m strike.

The company reported that the recently completed three RC holes have intersected further sulphide mineralisation 80m along strike to west on section 30,400E and 80m to south and down dip on section 30,480E.

Further encouraging aircore results were also reported, which includes 30m @ 1.2g/t Au from 42m, and 12m @ 2.1g/t Au from 44m.

Mallina gold project

De Grey’s Mallina Gold Project is located approx. 60km south of Port Hedland in the Mallina Province of Western Australia.

The 1.7 Moz Mallina project hosts numerous large deposits. Significant gold deposits include Withnell, Mallina, and Toweranna. Other prospects include Hemi, Antwerp, and Scooby prospect.

Withnell is the largest gold resource at Mallina, currently hosting a combined open pit and underground resource of 4.65 million tonnes at 2.9g/t for 429,300oz of gold.

Hemi discovery

Hemi is a new discovery under 30m of transported cover, with two zones of strong, broad sulphide rich alteration with high grade gold mineralisation partially defined in the Aquila and Brolga zones.

The Aquila Zone represents a 30-50m wide high grade gold zone (>5g/t) defined on Section 30,000E (local grid) to 180m below surface. The Brolga Zone is a substantially wider alteration zone, potentially up to 200m wide and is currently defined by RC drilling over 160m of strike.

Hemi prospect comprises of the initial discovery Section A, as well as Section B, Section C, and Section D.

Drilling at Brolga zone

The company had commenced priority RC and diamond drilling programs at Brolga zone to test the scale of the Brolga and Aquila deposits on 80m spaced sections and nominal 80m spaced holes on section.

The aim of the program was to continue defining the lateral and down dip extensions to an initial nominal 400m vertical metres prior to commencing infill resource drilling.

The company announced that highly encouraging gold assays have now been received for all RC drill holes on the four 80m spaced Brolga drill sections, 30480E, 30,560E, 30,640E, and 30720E.

De Grey said that strong and extensive gold mineralisation defined across the four sections defines a robust and large growing volume of mineralised intrusive at Brolga.

Gold footprint increased

DEG said that the gold-sulphide mineralisation is well defined by RC drilling and interpreted to be dipping moderately to the south (local grid) with a large footprint over +340m of strike, up to +300m lateral width, up to 200m depth and remains open along strike and down dip.

It may be noted that the shallower dipping mineralisation is significant, as it has the potential to increase ounces per vertical metre within a future open pit and may reduce the overall strip ratio.

The company said that to date, recent RC drilling has confirmed the sulphide mineralisation in fresh intrusive correlates well with the known gold mineralisation.

Drilling still ongoing

The company reported that the ongoing RC drilling is currently underway on section 30,400E, a further 80m to the west.

DEG said that the geological logging of the initial two RC holes (HERC032 – 033) highlights further wide intersections of strong sulphide mineralisation.


The company said that the drilling on 30,400E extends the strong sulphide mineralisation to +420m of strike and remains open. DEG said that diamond drilling is underway on 30640E and aircore drilling is testing areas north of Aquila.

High-grade results from all 4 sections

The company announced that high-grade results were reported from all four sections, Section 30,480E, Section 30,560E, Section 30,640E, and Section 30,720E.

Section 30,480E

DEG said that at section 30,480E, three RC holes (HERC021-023) show strong gold mineralisation across the drilled section, defining broad gold zones interpreted to dip moderately towards the south (local grid) with a lateral width of approximately 200m and down to 150m depth.

The company said that two new step-out RC hole (HERC034 – 035) have been completed 80m to the south on section, whose assays are pending.

Significant new intercepts on section 30,480E include 34m @ 1.4g/t Au from 65m in HERC021; 11m @ 2.1g/t Au from 44m in HERC022; 76m @ 1.5g/t Au from 42m in HERC023; and 18m @ 1.2g/t Au from 132m in HERC023.

Section 30,560E

In addition to the previously reported results (54m @ 2.2g/t Au) in hole HERC013; the company has reported further high-grade results from section 30,560E.

Highlights include 78m @ 1.8g/t Au from 40m in HERC014; 21m @ 1.2g/t Au from 153m in HERC014; 28m @ 1.4g/t Au from 60m in HERC015; 72m @ 1.6g/t Au from 105m in HERC015; 16m @ 1.3g/t Au from 52m in HERC024; 56m @ 1.1g/t Au from 93m in HERC024; 20m @ 1.4g/t Au from 160m in HERC024; and 16m @ 1.3g/t Au from 194m in HERC024.

Section 30,640E

Previously reported significant RC intercepts on section 30,640E include 97m @ 3.2g/t Au from 35m in HERC001; 43m @ 1.9g/t Au from 34m in HERC002; 51m @ 2.2g/t Au from 98m in HERC002; 13m @ 1.9g/t Au from 36m in HEDD001; 18m @ 2.3g/t Au from 59m in HEDD001; 16m @ 2.6g/t Au from 104m in HEDD001; 43m @ 1.9g/t Au from 99m in HEDD002; and 36m @ 3.2g/t Au from 156m in HEDD002.

Section 30,720E

Significant intercepts on section 30,720E include 21m @ 3.6g/t Au from 45m in HERC016; 15m @ 5.5g/t Au from 75m in HERC016; 33m @ 1.6g/t Au from 41m in HERC017; 17m @ 2.7g/t Au from 121m in HERC017; 17m @ 1.5g/t Au from 107m in HERC018; and 15m @ 1.6g/t Au from 150m in HERC018.

Pending results

The company announced that gold results remain pending for RC holes (HERC019 – 020, HERC032 – 033, HERC034 – 035) on section 30,960E, 30,480E and 30,400E respectively and diamond drilling on section 30,640E.

AC drilling at Aquila

The company announced that encouraging priority aircore drilling results have been received from the Aquila Zone.

Highlights include 30m @ 1.2g/t Au from 42m in BWAC375; 14m @ 1.3g/t Au from 94m in BWAC376; and 12m @ 2.1g/t Au from 44m in BWAC417

Updates and next steps

The company announced that follow up aircore drilling will be undertaken to test for strike extensions to mineralisation.

De Grey said that the programs of follow up RC and diamond drilling aimed at extending resources at depth and laterally are underway.

The Company said that with the support of its various contractors, it plans to continue the drilling program with 1 RC and 2 diamond rigs operating.

DEG said that the plan has been undertaken to maximise the protection of all personnel and reduce potential threats associated with COVID 19 and includes changed rosters to minimize travel and camp management to minimising external third party interaction. The plan is constantly being reviewed and may change at any time.

Management comments

De Grey’s Technical Director, Andy Beckwith said: “Brolga is growing substantially, we continue to increase the overall footprint of the gold-sulphide mineralisation, particularly to the west and down dip where substantial thicknesses of mineralisation remain open.

We have now confirmed the strong correlation between gold and sulphides. The recent four RC holes to the south and west have logged some of the strongest sulphide mineralisation noted to date. Drilling is planned to continue with one RC and two diamond rigs testing the limits of mineralisation at Hemi.”

Written By Jonathan Norris
Jonathan is a founder of Mining.com.au and has been covering the resources industry since 2018. With over 17 years experience in print, broadcast and online media, Jonathan has seen first hand the transformative effect of online niche media.