- The Boorara Gold Project, completed 34,000 metres of Reverse Circulation (RC) infill pattern drilling and intercepted many near-surface high grade gold hits including:
- 5m at 71.4 g/t Gold (“Au”) from 75 metres downhole, including 1m at 348 g/t , (BORC258 – Crown Jewel)
- 5m at 15.84 g/t from 30 metres depth, including 1m at 39.2 g/t , 1m at 19.7 g/t , (BORC 361 – Northern Stockwork)
- Selected highlights from the Southern Stockwork Deposit include:
- 136m at 1.78 g/t from 26 metres depth (BORC 202)
- 67m at 1.99 g/t from 31 metres (BORC 198)
- 59m at 1.74g/t from 109 metres (BORC 198)
- 99 metres at 2.09 g/t from 98 metres (BORC 206)
- All gold assays will be sent to Independent Geological Group, Cube Consulting, to complete a Gold Resource Estimate by early March 2018.
- Two deep diamond holes intersected the Dolerite mineralised gold host over 620 metres vertically from the surface.
- Definitive Feasibility Studies has started with Updated gold mineral resource work underway, and comprehensive Metallurgical test work commencing.
The Boorara Gold Project is 10 kilometres east of Kalgoorlie’s Super Pit gold mine, Western Australia. The Boorara Project contains over 1.5 kilometres of gold mineralisation striking north-west at 330 degrees. The project is divided into Southern Stockwork (SSW), Crown Jewel (CJ) and Northern Stockwork (NSW) deposits.
The RC drilling program which started on 2 October 2017 of some 34,000 metres was completed on Thursday 18 January 2018. We have reported gold assays available for some 29,726 metres of RC drilling. The two (2) deep hole diamond drill program at the Southern Stockworks was completed on 19 January 2018 and intersected the mineralised dolerite zone below 620 metres from the surface.
MacPhersons has completed a detailed Longitudinal Projection of Southern Stockwork drilling in calendar 2017.
From January to August 2017 using mostly diamond drilling, the company confirmed an extension of the Boorara Southern Stockwork deposit at a vertical depth below 200 metres from the surface and some 500 metres along strike. Within the Southern Stockworks deposit we reported BODH 025 (163m @ 4.29 g/t uncut) and BORC 173 (158m @ 1.6 g/t).
Located about one kilometre to the North West of the Southern Stockworks deposit is the historic Cataract Gold Mine (30,000 oz; 1897-1907) that is hosted within the Northern Stockworks deposit of the Boorara dolerite. The Cataract mine has two major stope geometries, one striking 040° dipping to the North West and the other striking 330°and dipping near vertical. The significance of these stope geometries is that structural controls on historically mined high-grade gold veins is the same as the NW dipping quartz vein arrays encountered in the current drilling program.
A recent reinterpretation of the geometry of mineralisation at Boorara is due to structural mapping and interpretation of the Boorara Gold Project. The new Boorara structural geological model has allowed MacPhersons to make a better estimate of the true gold grade and size of the existing Boorara resource based on an interpretation of mineralised NW-dipping quartz vein arrays. From the structural mapping and the quartz veins exposed within the trial pit completed in October 2016, the drill orientation must be 115 degrees.
The drilling strategy is infill RC drilling continuing to test the geological model and scope out the extent of mineralisation associated with the two styles of gold mineralisation:
- Dolerite hosted NW dipping quartz vein arrays with associated weak to strong pervasive hematite alteration, iron carbonate alteration, with >1% pyrite and >1% arsenopyrite mineralisation, and
- High grade narrow quartz vein gold mineralisation with >1% pyrite and >1% arsenopyrite.
Gold mineralisation is hosted in a series of stacked quartz vein arrays that dip at 40-45° to the North West. The true thickness of the arrays is up to 50 metres vertical that are hosted within the quartz dolerite which dips at 73° to the north east. The mineralised dolerite has a true width of up to 40 metres based on a review of all the historic drilling and MRP drilling. Within the mineralised Boorara dolerite high grade localised ore shoots consist of vein arrays up to 20 metres in width. The increased width of the mineralised dolerite indicates that this is potentially a larger mineralised system.
On 23 January 2017 the company announced a newly estimated Mineral resource based on a 0.4 g/t cut-off grade at the Boorara Gold Project.
The objective of this new MRE for Boorara is to establish a solid resource base from which to undertake further mining studies on.
The Mineral Resource Estimate (MRE) at the Boorara Gold Project of 5.95 Million Tonnes @ 1.2 g/t for 232,000 ounces of gold is based on a 0.4 g/t gold cut-off grade (previously used 0.3 g/t) with a maximum top cut grade applied of 24 g/t. The MRE at the Boorara Gold Project is a result of Macpherson drilling 182 holes for 16,974 metres and historical drilling of 937 holes for 74,498 metres.
The MRE for Boorara has been determined using the hard wireframe boundary of 0.4 g/t for mineralisation envelopes that will be used for future mining studies. Approximately 90% of the total MRE is within 120 metres of the surface. The discovery of western contact mineralisation has potential to add significant tonnes to the current MRE and will underpin future organic growth of the Boorara to reach the decision to mine. The location of the western contact zone can be seen on Figure 3 in relation to the existing resource. Total of the MRE Measured and Indicated resources is 4.65 Million Tonnes @ 1.2g/t for 179,000 ounces of gold.
Boorara Trial Pit
The trial pit was completed within budget and 30,000 dry tonnes of ore was treated at the FMR Greenfields treatment plant at Coolgardie at a head grade of 1.73 g/t which produced 1,525 oz of gold that was sold at $1693/oz for gross proceeds of $2.58 million.
The trial open pit was excavated to a final depth of 20 metres. For the first time the orebody was exposed and quartz veining could be measured. A structural mapping project was completed which involved mapping within the trial pit that resulted in a new geological model for the Boorara Gold Project. It was on the basis of the new geological model that a three hole diamond drilling program began in late January 2017.
Boorara - Similarity with Mt Charlotte mine
Previously unrecognised ultramafic and sediment lithologies have been identified adjacent to the Boorara dolerite. The Boorara dolerite can be divided into up to 7 individual units with the quartz granophyric unit being unit 5. It is expected that future diamond drill holes will enable faulting to be better understood. The Boorara faulting is not dissimilar to that seen at the Mt Charlotte gold mine at Kalgoorlie.
Although the Mt Charlotte orebody has a short strike length it extends vertically for over 1200 metres depth and again faulting has resulted in the orebodies being moved considerable distances. The iron enrichment present within the Boorara quartz dolerite provides an oxidised chemical composition favourable to wall rock reaction with reduced gold fluids, this is a well-known host rock setting for major gold deposits in the Eastern Goldfields such as Mt Charlotte (6 Moz) and Darlot-Centenary (3.2 Moz). Reverse fault controlled quartz veins are interpreted for Boorara which is similar to the subhorizontal quartz veins that are controlled by reverse faults at the Darlot-Centenary gold deposit (3.2 Moz).
The Boorara Southern Stockwork gold mineralisation like Mt Charlotte consists of irregular shaped pipelike quartz vein arrays that are hosted in quartz dolerite that are structurally complex and require close spaced systematic drilling to define.
About Mt Charlotte - The Mt Charlotte mine is located close to the original gold discovery at Kalgoorlie by Paddy Hannan in June 1893 and it is most probable that Hannan’s original gold originated from the Mt Charlotte orebody (Haycraft 1979). Mining by open methods at Mt Charlotte from 1893 -1916 produced 71,000 ounces of gold and then mining ceased shortly after reaching the pyritic ores.
It was in 1962 after a detailed evaluation by Western Mining Corporation Ltd (WMC) and its associated company Gold Mines of Kalgoorlie (Australia) Limited that an ore reserve of 2.97 Mt @ 4.9 g/t and a large scale underground mining operation considered viable (Haycraft 1979). The work in 1962 involved dewatering the mine and structural mapping that identified the three principle sets of veins within the quartz dolerite host. Based on this work it was determined by WMC that to estimate the true grade of the orebody close spaced drilling was required using a drill azimuth of 156.5° to intersect all 3 principle vein sets. This strategy has proved to be the only method of accurately determining the grade of the Mt Charlotte orebody to this day.
It took from discovery of gold near Mt Charlotte in 1893 to 1962 - over 69 years - for the Mt Charlotte orebody to be recognised and its gold endowment now is 6 million ounces.