Havilah Resources Limited (ASX: HAV) has announced a positive update from the re-assaying of selected retained drill samples from its several deposits and prospects in South Australia.
The company reported that elevated levels of rare earth elements (REE) were returned in re-assaying of Havilah drill samples.
HAV said that two drill samples from West Kalkaroo contained elevated levels of higher value REE, with up to 1,355 ppm Neodymium (Nd) and 366 ppm Praseodymium (Pr).
The company reported that 11 drill samples from the Croziers copper prospect were also similarly elevated in REE, with up to 953 ppm Nd, 425 ppm Pr, 5,443 ppm Lanthanum (La) and 6,104 ppm Cerium (Ce).
It may be noted that REE are of relevance and strategic importance given the Australian Government’s recent efforts in promoting international investment in the development of critical minerals resources within Australia.
Havilah controls more than 16,000 square kilometres of mineral tenements in the Curnamona Craton in northeastern South Australia.
Important projects include Kalkaroo, Mutooroo, Maldorky, Grants, and Oban.
Most historic exploration in the region focused on base metals, uranium and gold, which means that REE were not routinely assayed.
Kalkaroo is Havilah’s flagship mineral project and is the largest undeveloped open pit copper deposit in Australia on a CuEq ore reserve basis, with a 0.74% CuEq grade.
It contains 1.1 million tonnes of copper, 3.15 million ounces of gold and 23,200 tonnes of cobalt in Measured, Indicated and Inferred JORC Mineral Resources.
Historic limited REE data reviewed
The company had reviewed a limited amount of REE data from older drilling late last year. Limited REE data that was available from earlier MMG joint venture diamond drillholes on several Havilah prospects, along with compilation of La and Nd data from a limited number of Havilah drillholes.
MMG had reported some elevated REE results from both the Eurinilla and Birksgate prospect areas, generally associated with copper-gold mineralisation. These available limited REE results were promising.
Re-assaying of samples
Prompted by Havilah’s new management team’s recent technical review of limited REE data, the company had recently re-assayed selected retained drill samples from the Kalkaroo copper-gold-cobalt deposit and the Croziers copper prospect.
Given the current strategic importance of REE, study of the REE distribution and grade across Havilah’s deposits and prospects is warranted due to the potential opportunity to enhance the deposit and/or project economics.
HAV said that the re-assaying has confirmed elevated levels of REE. The table below shows REE assays from re-assaying of selected retained drill samples from West Kalkaroo and the Croziers copper prospect; as well as the earlier MMG joint venture drilling at the Eurinilla and Birksgate prospects.
The company reported that two copper-gold mineralised reconnaissance aircore drillhole samples, recently re-assayed from West Kalkaroo, show elevated levels of higher value REE, namely Nd, Pr, Dysprosium (Dy) and Terbium (Tb).
These four REE make up approximately 80% of the potential value of REE in the two drill samples, which are from the soft clayey saprolite gold ore at West Kalkaroo.
HAV said that the levels of these REE in the underlying copper ore types (e.g. native copper, chalcocite and chalcopyrite) is yet to be determined, although it is noted that previous limited La assay values were generally elevated.
Croziers copper prospect
HAV said that the composites of eleven drill samples also recently re-assayed from two Havilah reverse circulation drillholes at the Croziers copper prospect returned similarly elevated REE, although with higher relative proportions of the light-REE, namely La and Ce.
The REE analyses reported earlier by MMG Limited from diamond drillhole BNG13DD001 at Croziers compare favourably with Havilah’s new assays.
In all cases the higher value REE (namely Dy, Nd, Pr and Tb) on average make up approximately 75% of the potential value of REE. At Croziers, higher REE are spatially associated with the copper skarn mineralisation in both the fresh and oxidised zones.
The company said that exploration drilling planned for the first calendar quarter of 2020 will primarily target copper and tungsten mineralisation at the Croziers copper prospect, but will also be designed to search for extensions of the associated untested REE mineralisation.
Further exploration drilling and assaying required
The company said that while the available limited REE results are promising, considerably more exploration drilling and assaying is required to determine the full extent of REE mineralisation associated with the stratabound replacement and vein style copper-gold mineralisation across Havilah’s mineral tenements in the Curnamona Craton.
Potential revenue stream
It may be noted that the value upside for Havilah is that if REE can be economically recovered in a mineral concentrate as a by-product of the standard copper and gold recovery processes, it potentially provides a further revenue stream for the Kalkaroo copper-gold project.
Havilah announced that studies have commenced on the Kalkaroo copper-gold project to investigate the potential for economic recovery of a REE concentrate as a by-product.
The company announced that additional drilling may be carried out in the future to explore strike and depth extensions and for resource delineation.
Havilah said that over the next few months, it plans to initially focus its effort on the geologically better understood Kalkaroo copper-gold-cobalt deposit to determine the distribution and grade of REE mineralisation, especially at West Kalkaroo; the host mineral(s) for the REE; and whether the host mineral(s) can be concentrated by standard recovery processes as a by-product.
The company said that this will be in addition to milestone completion of the updated Kalkaroo project pre-feasibility study, which is currently well advanced.
Havilah’s Technical Director, Chris Giles, said: “The elevated REE levels in fairly typical West Kalkaroo saprolite gold ore drill samples clearly warrant careful follow up studies.
The critical questions for Havilah are what mineral(s) host the REE and can the REE be recovered and concentrated to produce a saleable, direct shipping by-product along with copper concentrates?
We plan to initiate some strategic metallurgical testwork to investigate these questions due to the potential opportunity to enhance the Kalkaroo project economics.
While the Kalkaroo project will be the initial focus for REE testwork, in due course exploration drilling of the stratabound copper-gold mineralisation will also follow up the associated elevated REE at several other locations in the Curnamona Craton such as Croziers and Eurinilla.”