Ardea Resources Limited (ASX:ARL) has made a significant rare earths discovery while undertaking Sterilisation Drilling results for the Kalgoorlie Nickel Project’s Prefeasibility Study (PFS) in Western Australia.
The Sterilisation Drilling programme was designed for finalising the site layout General Arrangement Plan for the Kalgoorlie Nickel Project (KNP) – Goongarrie Hub. Additionally, the drilling was used to test Rare Earth Element (REE) targets previously generated by the company’s Critical Mineral Research and Development (R&D) in rocks adjoining the nickel laterite mineralisation.
One of two proposed infrastructure sites was at Goongarrie West adjoining the Goongarrie South Nickel Laterite mineralisation southwest of the Elsie Tynan pit. Three single hole traverses were designed at Goongarrie West as broad-spaced aircore drilling over a three km NNW strike in a location containing no previous drilling.
Intercepts of Total Rare-Earth Oxides (TREO) at a 1,000ppm TREO cut-off for the three hole Goongarrie West programme were received, with highlights including:
- AGSA0224, 7m at 3,506ppm TREO from 64m
- AGSA0225, 12m at 2,487ppm TREO from 40m
- AGSA0226, 4m at 1,181ppm TREO from 56m
These are considered significant intercepts, particularly based on such consistent mineralisation occurring in one km spaced reconnaissance drill holes.
Mineralisation in the three holes, based on drill-chip logging and associated geochemistry, is controlled by regolith contacts, specifically hosted by Saprolite Lower clay at its regolith contact with the underlying clay-weathered Saprock.
Interpretation of results indicates the system is an Ionic Adsorption Clay (IAC) Rare Earth occurrence. As such, the drill intercept grades are considered particularly significant, precluding Goongarrie West as an infrastructure site option.
In view of the drill results at Goongarrie West and as required by the WA Mines Act 1978, the Department of Mines, Industry Regulation and Safety (DMIRS) has been notified that a discovery of economic interest has been made.
The Feasibility Study for the Kalgoorlie Nickel Project – Goongarrie Hub has completed pit optimisations and confirmed the production pit locations and thus likely infrastructure site requirements. The two main infrastructure alternatives were east of the Pamela Jean pit, or southwest of Elsie Tynan at Goongarrie West. Requisite drilling was completed in September 2022,” Managing Director, Andrew Penkethman, said.
“With the high-grade TREO results returned for the three holes at Goongarrie West, it has been an easy decision to instruct the Consulting Engineer to site the key production infrastructure at Pamela Jean East.
“The Goongarrie West REE Prospect will have confirmatory reverse circulation drill traverses completed as soon as possible, followed by bench-scale metallurgy designed to quantify the IAC REE potential.
“This additional drilling is an unexpected variation for the PFS work programs, being an unavoidable if not valuable outcome from the PFS. We trust that KNP stakeholders are as excited as the Ardea Team with these REE drill results.”
The Prefeasibility Study (PFS) for the KNP – Goongarrie Hub is designing a three Mtpa High Pressure Acid Leach (HPAL) and 0.5Mtpa Atmospheric Leach (AL) circuit, with onsite Mineralised Neutraliser (MN) for hydrometallurgical solution neutralisation. This is a well understood and proven flowsheet, so minimising any flowsheet technical risk.
Strip ratio is approximately 2:1. In order to have a uniform plant feed and to coordinate exhausted pit void space for tailings storage, the earthmoving schedule exceeds the theoretical 10.5Mtpa and is up to 18.7Mtpa, necessitating both waste rock dumps and temporary ore feed laydown areas adjacent each and every pit.
The “centre of gravity” for the Mineral Resource Estimate (MRE) is the Pamela Jean and Elsie Tynan pits at Goongarrie South, with the processing plant as close as practical to this location.
This then leads to two preferred alternatives for location of the laydown areas and Processing Infrastructure, being east to southeast of the Pamela Jean pit extending to the eastern mining lease boundary or southwest of the Elsie Tynan pit extending to the Goldfields Highway in the west.
In order to confirm no non-outcropping mineralisation is present and that foundation conditions are suitable, Sterilisation Drilling is required. In view of the extensive historical exploration drilling for both nickel laterite and gold associated with the Bardoc Tectonic Zone (BTZ), Aircore drilling on a broad 320m x 160m pattern was utilised as a supplement to historic drill data.
Ardea’s KNP Research and Development (R&D) commenced in 2017 with the systematic re-assay of archived KNP drill assay pulps for a multi-element suite including Rare Earth Elements (REE). This means that in addition to the pay-metals nickel and cobalt, all drill samples have been systematically assayed for REEs.
Forward Programme
The five identified mineralised intercepts at four sites are to be followed up with a 160 x 80m pattern Reverse Circulation (RC) drilling program once a rig can be secured.
If as expected, a flat-lying mineralised sheet is confirmed, RC drilling on four of the lines will be extended east at a 160m hole spacing to the WWF nickel laterite drilling areas centred on the proposed Big Four pit areas.
The exploration objective is to evaluate the effectively undrilled areas between the WWF pit areas which have only sporadic REE assays in historic nickel laterite resource drilling and the Goongarrie West discovery drill-holes.
Drill material from the RC drilling will be used for initial bench-scale hydrometallurgical studies.
