A 10-hole diamond drilling program is underway at the Bulgera open pit to better understand the geology and controls on the gold mineralisation.
Norwest Minerals Limited plans to test a new high-grade gold lode within the Bulgera Gold Project, north of Meekatharra in Western Australia at around 400m and 700m down dip from the shallow Bulgera open-cut.
The drilling program includes 2,500m of reverse circulation (RC) pre-collars and 1,400m of diamond core tails designed to penetrate below RC drill intersections reported in May.
Schematic cross-section showing RC pre-collars (red) with diamond drill tails (blue) targeting the potential high-grade
gold mineralisation (pink) extending down-dip from the Bulgera open-cut.
Norwest (ASX:NWM) has also conducted preliminary metallurgical tests on three gold bearing composite samples collected from RC holes drilled through the new zone.
Results have demonstrated high gravity leach recoveries, fast leach kinetics and low cyanide and lime consumption.
NWM chief executive officer Charles Schaus said the drilling program is expected to reveal an enormous amount of information concerning the lode-scale geology and controls on the gold mineralisation.
“Importantly, a deep diamond drill intersection similar to those encountered up-dip by RC drilling would be a significant step in understanding the magnitude of this high-grade gold discovery.
“In addition, the preliminary metallurgical work on Bulgera gold RC chips indicates potential for high gold recoveries from a simple low-cost processing circuit.”
RC pre-collar drilling for 10 HQ diamond core tails was completed this week with most of the RC pre-collar holes extended to within 100m of the gold zone target.
The diamond drill rig is now on site and will begin drilling from the base of the RC pre-collared holes down through the interpreted extension of the Bulgera high-grade gold zone.
Phase 1 consists of seven holes with the first two holes set to test the new gold zone close to where RC holes BRC21001, BRC21013 and BRC21015 reported wide, high-grade gold intersections.
The other five holes will test for gold mineralisation at around 400m down dip of the Bulgera open pit, well below any previous drilling undertaken across the project to date.
Map showing diamond drill pad locations (yellow), drill target intercepts (blue circle) and
interpreted gold mineralisation zone dipping 45 degrees to the northwest (pink).
Phase 2 diamond drilling is designed to test the continuation of the gold zone a further 330m down dip from the phase 1 holes.
NWM said the decision to drill the phase 2 holes will ultimately depend on the geological information gathered from the core and gold intersections returned from phase 1 drilling.
Metallurgical test work results
Preliminary metallurgical testing on three Bulgera gold RC samples showed average gold grades of 1.74g/t, 4.43g/t, and 8.66g/t respectively.
Norwest Minerals believes the three samples returned promising flow sheet and processing characteristics, including:
- High gravity separation and mercury amalgamation of the gravity concentrate to yield significant free liberated gravity recoverable gold of 28.80%, 389.08%, and 47.46% for composites 1 to 3 respectively;
- Fast gold leach kinetics for all gravity leach tests with the majority of the gold leaching in the first 2-4 hours;
- Low sodium cyanide and lime consumption rates with Perth tap water for all leach tests;
- Low levels of organic carbon decreasing the likelihood of preg-robbing of gold in solution during cyanidation;
- Low concentrations of base metals decreasing the possibility of excess cyanide consumption through preferential complexing with these metals;
- Low levels of arsenic, decreasing the likelihood of refractory gold deportment;
- Low levels of antimony, thus avoiding high pH which may form passivating oxide layers on the gold surfaces, which can have a detrimental effect on gold cyanidation.
This article was developed in collaboration with Norwest Minerals, a Stockhead advertiser at the time of publishing.