A down-hole transient electro-magnetic (DHTEM) survey conducted by Estrella Resources (ASX: ESR) at its flagship Carr Boyd discovery in Western Australia has defined massive nickel-copper-platinum group element (PGE) bearing sulphides at the T5 prospect.
The survey was completed on a diamond core hole located approximately 1.1km north-east of the historic Carr Boyd Rocks nickel mine near Kalgoorlie, and showed evidence of a strong conductance body at 438m depth associated with the intersected mineralisation.
Broad moderate-to-strong anomalies were evident off-hole and are believed to support a larger unconstrained body of sulphide extending in all directions away from the hole.
Perth-based Southern Geoscience Consultants modelled the survey using two alternate coupling loop configurations and moderate base frequency readings – providing a moderate-to-high conductance estimate of up to 11,000 Siemens – which will also be used for future surveys to test for high conductance targets beyond the zone of known mineralisation.
The hole was collared 300m south of T5 and intersected the basal contact of the Carr Boyd layered mafic/ultramafic intrusion to return a 15m-wide zone of sulphide mineralisation starting 430.55m downhole and containing a 2.9m-thick core zone of massive nickel-copper sulphide mineralisation from a 435.9m depth.
The anomalism remains open at depth and deeper DHTEM coverage will be required in future diamond holes to investigate extensional sulphide mineralisation which could also be present.
Conditions for the survey were “excellent” with no overburden or stratigraphic geological units present to cause false anomalies or interference, Estrella reported.
Estrella chief executive officer Chris Daws said the DHTEM results are a significant breakthrough in the development of the T5 prospect, which was initially investigated in mid-2019.
“The results of this survey support the mineralised sulphides seen in the drill core, which is currently in the laboratory being cut, sampled and priority assayed,” he said.
“The results have put to rest any of my concerns about scale and we are now eagerly awaiting the assay results to get a clear understanding of the potential of this discovery.”
Mr Daws said scheduling of up to 10 new holes to further test the T5 zone is well underway and will rapidly expand the exploration program at Carr Boyd.
Estrella will also increase the number of drill rigs, personnel and support onsite to enable it to quickly determine the extent of the discovery.
Tier 1 jurisdiction
The Carr Boyd nickel project is a magmatic-hosted sulphide system that comprises the Carr Boyd layered complex in a tier one jurisdiction, approximately 80km north-northeast of Kalgoorlie.
Estrella holds 259sq km of contiguous tenure over the entire magmatic mafic-ultramafic layered complex, which is connected to the Goldfields Highway by an all-weather haul road accessible by the company under a granted miscellaneous licence.
The Carr Boyd layered complex hosts the Carr Boyd Rocks mine, which was the first magmatic-hosted style of nickel deposit mined in WA.
It was discovered in the late 1960s and produced 202,110 tonnes of ore at an average grade of 1.43% nickel and 0.46% copper from 1973 to 1977.
Interest in magmatic nickel-copper deposits have had a resurgence in recent times with the discoveries of this type of mineralisation at the Rockford project, owned by Legend Mining (ASX: LEG) and Chalice Gold Mines’ (ASX: CHN) Julimar project.