Yamarna – Mt Venn and Eastern Mafic Complex

The Yamarna project is located approximately 130 kilometres east of Laverton, and approximately 30 kilometres west of the Gruyere gold deposit in the Eastern Goldfields District of Western Australia.

Great Boulder Resources’ Mt Venn Project contains the Mt Venn Ni-Cu-Co discovery and the highly prospective Eastern Mafic Complex. The Mt Venn and Eastern Mafic Complex are interpreted to represent large scale copper-nickel-cobalt magmatic systems with the following key points:

  • Sulphide mineralisation discovered over several kilometres at along the western margin of the Mt Venn complex and remains open in all directions.
  • Multiple, parallel lenses of copper-nickel-cobalt mineralisation have been identified. High grade copper has been intersected along the footwall contact at Mt Venn.
  • The recently identified Eastern Mafic complex resembles a very large ‘pipe-like’ intrusion.
  • Airborne EM flown over the Eastern Mafic Complex have identified multiple late-time conductors, indicative of a bedrock source.
  • Aircore geochemistry confirms a strong correlation between the EM conductors and copper-nickel mineralisation.

Under the Yamarna Joint Venture Agreement, the Company has the right to earn a 75% interest in the Yamarna Project by funding exploration expenditure of $2,000,000 over a 5 year period.

Mt venn 1
Gravity image showing Mt Venn and Eastern Mafic complexes


The Mt Venn Discovery

  • Hosted within the Mt Venn igneous complex
  • Very large magmatic system that has intruded sulphur rich sedimentary country rock
  • Ground EM and aircore geochemistry confirm 9km of prospective strike along the Mt Venn Complex.
  • Primary Copper-Nickel-Cobalt sulphide mineralisation discovered along the western magnetic trend of the Mt Venn Complex
  • Mineralisation is hosted in metamorphosed fractionated gabbro intrusions. Primary Ni-Cu-Co lodes have been remobilised by a bounding footwall shear zone to create secondary Cu-rich lodes along this structure.
  • Two phases of RC (5,185m) and diamond (861m) drilling were completed at Mt Venn in late 2017
  • Multiple, broad lenses of shallow copper-nickel-cobalt mineralisation were intersected over several km’s and open in all directions.  Significant results include:

 - 48m at 0.8% Cu, 0.2% Ni, 0.07% Co from 103m (downhole)

  • including 3m at 1.3% Cu and 5m at 1.0% Cu
  • including 6m at 0.7% Cu, 0.3% Ni and 0.10% Co

 - 61m at 0.5% Cu, 0.1% Ni, 0.05% Co from 86m (downhole)

  • including 2m at 1.12% Cu and 12m at 0.8% Cu

 - 44m at 0.5% Cu, 0.2% Ni, 0.06% Co from 153m (downhole)

  • including 3m at 1.0% Cu and 2m at 1.2% Cu 
  • including 4m at 0.4% Cu, 0.2% Ni, 0.08% Co

 - 27m at 0.6% Cu, 0.2% Ni, 0.05% Co from 43m (downhole)

  • including 5m at 0.9% Cu, 0.2% Ni, 0.07% Co
  • including 5m at 0.9% Cu, 0.1% Ni, 0.02% Co

 - 26.2m at 0.5% Cu, 0.2% Ni, 0.06% Co from 12m (downhole)

 - 18m at 0.8% Cu, 0.1% Ni, 0.02% Co from 187m (downhole)

  • including 2m at 1.0% Cu and 1m at 4.3% Cu

 - 18m at 0.7% Cu, 0.2% Ni, 0.05% Co from 92m (downhole)

  • including 1m at 2.3% Cu and 1m at 1.7% Cu

 - 10.1m at 0.9% Cu from 229.3m (downhole)

  • including 5.9m at 1.1% Cu, 0.1% Ni, 0.02% Co

 - 4.4m at 1.7% Cu from 142.4m (downhole)

  • including 2.5m at 2.2% Cu
Mt Venn Fig 2
Mt Venn RC and Diamond drill program -  Previously reported drill results (yellow), new drill results (red) and pending results (blue) over RTP 1VD magnetics
Mt Venn image 3
IMAGE LEFT: 17MVDD003 - Basal contact with interstitial chalcopyrite and pyrrhotite within very coarse-grained gabbro (108m)
IMAGE RIGHT: 17MVRCD008 - Semi-massive and stringer pyrrhotite with chalcopyrite (113m)


Eastern Mafic Complex

  • Identified in a gravity survey, the Eastern Mafic represents a large intrusive body prospective for copper, nickel and cobalt sulphide mineralisation.
  • Gravity and surface sampling indicates the Eastern Mafic complex is a very large circular body and appears to represent a pipe-like ‘chonolith’ feeder structure.
  • The potential discovery of a feeder structure is significant as many globally-significant magmatic nickel sulphide orebodies occur within these features.
  • Airborne EM was flown in April and identified multiple, strong conductors over a 6km strike length.
  • These conductors are considered highly prospective because of their ‘late-time’ EM response, indicative of a bedrock source.
  • The core of the intrusion has the greatest concentration of strong conductors over 4km strike with more conductors located along the eastern shear zone.
  • In light of the number and strength of these conductors, Great Boulder have commenced  a ground-based MLEM survey to identify drilling targets for testing in mid-2018.
  • Preliminary MLEM results have further confirmed several strong late time conductors.
  • The Strongest response, located close to AEM conductor 22, is very large, approximately 100m below surface and extending over ~400m in strike. The response is interpreted to represent massive sulphide. 
fig 4
Gravity Image (left) and Airborne EM late-time (Channel 30) response (right) overlain with planned MLEM stations. 
Initial MLEM results from the Eastern Mafic Complex showing a strong correlation with AEM conductors.


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