Anthill – Au


Intermin acquired the Anthill project in early 2017 which is 54km northwest of Kalgoorlie-Boulder in Western Australia and favourably located on the highly prospective Zuleika Shear.

The geology is dominated by a variolitic basalt with lesser amounts of porphyry and ultramafic rocks observed. At least two mineralised trends are evident and add to the geological complexity at Anthill. The gold mineralisation is pervasive and occurs in a number of settings, the most important being a quartz stock work of thin veins with carbonate-sericite-silica-sulphide alteration. Some of the gold is coarse and is easily visible in panned RC chips.

The host rock is intensely weathered to 70 to 80m depth and there is a surface layer of soil and lateritic mineralisation 1 to 8m thick. Mineralisation is continuous from around 20m depth to the depth limit of drilling at around 250m.

Over 6,500m of infill, validation and extensional diamond and RC drilling was completed in 2017 and generated a Maiden (JORC 2012) Mineral Resource Estimate.  This program included excellent results including:

  • 41m @ 2.63 g/t Au from 69m (AHRC17027)
  • 17m @ 5.37g/t Au from 137m (AHRC17043)
  • 11m @ 3.72 g/t Au from 46m, 11m @ 6.22g/t Au from 157m and 3m @ 6.48 g/t from 187m (AHRC17039)
  • 15m @ 2.26g/t Au from 32m and 6m @ 11.15 g/t Au from 110m (AHRC17032)
  • 30m @ 2.98 g/t Au from 73m (AHRC17024)
  • 7m @ 4.58g/t Au from 37m and 43m @ 1.46g/t Au from 54m (AHRC17028)
  • 19m @ 2.22g/t Au from 39m and 27m @ 2.17g/t Au from 98m (AHRC17031)
  • 19m @ 1.50g/t Au from 32m and 38m @ 1.48g/t Au from 86m (AHRC17029)
  • 18m @ 2.80 g/t Au from 48m and 11m @ 4.91 g/t Au from 90m (AHRC17020)
  • 29m @ 1.84g/t Au from 41m (AHRC17035)
  • 19m @ 1.40g/t Au from 33m, 16m @ 3.23g/t Au from 70m and 1m @ 30.70 g/t Au from 91m (AHRC17017)
  • 9m @ 3.08g/t Au from 36m, 21m @ 1.38g/t Au from 52m and 34m @ 1.31g/t Au from 104m (AHRC17036)
  • 19m @ 2.22g/t Au from 36m (AHRC17031)
  • 21m @ 1.83g/t Au from 49m (AHRC17013)
  • 9m @ 3.87 g/t Au from 150m (AHRC17034)

Following on from this initial successful program, drilling at Anthill commenced in the June Quarter of 2018 with 122 resource holes (mostly RC) completed for 15,118m to an average depth of 120m and maximum depth of 284m.

New results have extended the known strike length from approximately 100m on acquisition, to more than 400m with significant mineralisation intersected, including:

  • 31m @ 3.28 g/t Au from 112m including 1m @ 31.7 g/t Au from 130m (AHRC18079)
  • 19m @ 2.70 g/t Au from 57m (AHRC18092)
  • 10m @ 2.79 g/t Au from 80m (AHRC18051)
  • 12m @ 2.00 g/t Au from 36m (AHRC18043)3
  • 4m @ 8.13 g/t Au from 60m (AHRC18119)3
  • 8m @ 1.92 g/t Au from 96m and 4m @ 7.67 g/t Au from 112m (AHRC180116)3
  • 13m @ 1.44 g/t Au from 43m, 6m @ 1.00 g/t Au from 66m, 3m @ 2.70 g/t Au from 112m (AHRC18079)

Mineral Resource Estimate (JORC 2012) of 2.28Mt @ 1.71 g/t Au for 125,000oz at a 1.0g/t Au lower grade cut-off.

Mineralisation intercepted to the north, south and east beyond the current resource envelope and remains open in all directions.

Two areas of significant mineralisation outside of the current resource envelope have now been discovered. Anthill South is dominated by the NW “Zuleika Shear” structure and appears to be the strike extension of Anthill. Anthill East looks to be more controlled by a NE cross structure and lacks significant primary ore at depth. The bulk of the ore being supergene/transitional ore.

Drilling to the south of Anthill delineated another 140m of strike length to Anthill. The mineralisation is similar to Anthill, but appears to be more patchy, possibly the result of structural complexity. All the westernmost holes appear to warrant further “up dip” drilling to the west. Best results at Anthill South include:

  • 31m @ 3.28 g/t Au from 112m including 1m @ 31.7 g/t Au from 130m (AHRC18079)
  • 19m @ 2.70 g/t Au from 57m (AHRC18092)
  • 10m @ 2.79 g/t Au from 80m (AHRC18051)
  • 8m @ 1.92 g/t Au from 96m and 4m @ 7.67 g/t Au from 112m (AHRC180116)3
  • 4m @ 15.50 g/t Au from 56m (AHRC18057)
  • 13m @ 1.44 g/t Au from 43m and 3m @ 2.70 g/t Au from 112m (AHRC18079)
  • 1m @ 24.10 g/t Au from 79m (AHRC18038)

At Anthill East, the mineralisation spans about 160m in length. Anthill East has a pronounced cross structure orientation (NE/SW) and has recorded significant lengths of supergene or oxide ore along the main trend. Better results include1:

  • 10m @ 2.77 g/t Au from 80m (AHRC18051)
  • 4m @ 7.65 g/t Au from 52m (AHRC18090)
  • 8m @ 2.33 g/t Au from 68m (AHRC18091)
  • 12m @ 2.00 g/t Au from 36m (AHRC18043)
  • 4m @ 8.13 g/t Au from 60m (AHRC18119)
  • 6m @ 2.56 g/t Au from 49m (AHRC18046)

Regionally, a total of six targets were tested in an area about 2.5km north of Anthill.  Several of these targets were drilled beneath historic holes that had been terminated in mildly anomalous mineralisation (>0.1 g/t Au) or had anomalous surface Au geochemistry. These targets were later confirmed in sampling conducted by Intermin.  A total of 24 holes for 1,666m were drilled. The drilling was highly successful in delineating two new prospects at Fire Ant and Tree Ant.   These are the best results to date outside of the Anthill area on M16/531 and included:

  • 5m @ 2.45 g/t Au from 33m and 1m @ 0.91 g/t Au from 44m (ARAC1808, Tree Ant)
  • 4m @ 0.69 g/t from 32m and 8m @ 1.37 g/t Au from 80m (ARRC1815, Tree Ant)
  • 4m @ 1.08 g/t Au from 72m (ARRC1822, Tree Ant)
  • 4m @ 1.36 g/t Au from 64m (ARRC1821, Tree Ant)
  • 2m @ 1.32 g/t Au from 40m (ARAC 1803, Fire Ant)

Intermin believes the mineralisation at Anthill is significant with potential for further resources to be delineated with further drilling beyond the current mineralised envelope. The proximity and influence of the Zuleika shear zone together with high grade intersections returned during 2017/2018 indicate the potential for a larger size resource at depth and extensions to be tested.

Further resource drilling is planned for the Anthill South and Anthill East areas in 2019, together with further resource extension drilling to the north and at depth.  The high grade intercept at Anthill South (AHRC18079 – 31m @ 3.28 g/t Au) will be investigated in more detail via diamond drilling to further increase structural knowledge of the area.

Exploration drilling is also planned for the regional prospects in 2019. Tree Ant and Fire Ant both offer potential for significant mineralisation beneath a highly depleted weathering profile. Further refinements in the drill direction are anticipated.

Open pit mine development studies have also commenced with initial optimisation and design work underway. Additional metallurgical testwork will also be completed on new representative samples to confirm previous results where recoveries ranged from 93% to 99% with a high gravity recoverable component (17% to 78%)2. The statutory approvals process has also commenced ahead of Feasibility Study release planned for 2019.