The Boorara Gold Project is hosted by the Menzies Boorara Shear Zone in the Eastern Goldfields Province of the Archaean Yilgarn Craton of Western Australia. The Yilgarn Craton is one of the largest gold provinces in the world – the Golden Mile and Mount Charlotte gold deposits have produced 1% of the world’s totally gold production.
The Boorara gold project is located 12 km east of Kalgoorlie and is situated in an Achaean greenstone belt that consisting of a package of rock units including ultramafic, basalt, interflow sediments, sediments and felsic volcanoclastic with the intrusive dolerite known locally as the Boorara dolerite which is the host to gold mineralisation.
Gold was first discovered at Boorara in 1897 and 30,000 oz was produced from the Cataract underground gold mine from 1897–1906. At the Cataract mine, a dominant vein orientation striking 040° and dipping 30° north named the Cross Lode hosted in the Boorara dolerite was a significant source of historical gold production.
Gold mineralisation at Boorara is hosted predominantly within the Boorara dolerite and on the lithological contacts of the Boorara dolerite with other rock types. The Boorara dolerite extends for over 1.5 km and consists of the three deposits, Northern Stockwork (NSW), Southern Stockwork (SSW) and Crown Jewel (CJ) deposits. The overall strike of the Boorara dolerite is 330° with an ultramafic western contact and sediments/felsic volcanoclastic eastern contact.
Gold at Boorara is hosted in quartz veins and quartz vein selvages within the Boorara dolerite and shear zones on the lithological contacts. The three main quartz vein geometries are 020°/48° W, 060°/40° NW and 100°/43° N which form quartz vein arrays. Quartz veining has associated mineralisation assemblage dominated by pyrite and arsenopyrite with hematite, iron carbonate, sericite and chlorite alteration.
Higher grade ore shoots are found within the quartz dolerite unit that dip to the northwest at 35° and consist of quartz vein arrays, see current geological model. This is similar to the Mt Charlotte gold mine at Kalgoorlie.
Within the mineralised Boorara dolerite are high grade localised ore shoots that consist of vein arrays up to 20 metres in width. The true width of the mineralised dolerite indicates that this is potentially a large mineralised system.
In January 2017, a JORC compliant total Mineral Resource Estimate at the Boorara Gold Project was 5.95 Mt @ 1.2 g/t for 232,000 oz Au which is based on a 0.4 g/t Au cut-off grade (previously 0.3 g/t) with a maximum top-cut grade applied of 24 g/t.
Trial Pit Production Summary
In September 2016, MRP commenced four weeks of trial open pit mining operations at the Boorara Gold Project to a pit to a depth of 20 metres and about 100 metres long at the Southern Stockwork deposit.
The aim of the trial pit was to expose the orebody and understand the structural controls on the gold mineralisation providing the basis from which to interpret existing drilling results and undertake future drilling. It also provided valuable mine to mill reconciliation information and metallurgical characteristics of the Boorara oxide ore.
The trial pit ore body consisted of quartz rich granophyric dolerite with stacked sheeted quartz veins. In some areas, the quartz veins graded into quartz stockworks as the quartz vein geometry changed and the intensity increased.
The Boorara trial pit extracted 34,000 t of oxide grading an estimated 1.8 g/t Au.
The head grade of the Boorara oxide ore processed at the carbon-in-pulp (CIP) FMR Pty Ltd mill at Coolgardie in Western Australia was calculated at 1.73 g/t Au for 30,239 dry tonnes for total contained gold ounces of 1,682. The actual gold produced from the trial pit was 1,550 ounces due to a mill recovery of 90.6%.