More Nickel in Updated Black Swan Disseminated Mineral Resource Poseidon Nickel reported an updated Mineral Resource Estimate (MRE) for the Black Swan disseminated sulphide deposit at Black Swan.
Managing Director and CEO, Peter Harold, commented, “The update of the Black Swan Disseminated Resource is an important milestone for our Fill the Mill Strategy. Black Swan has a 2.2Mtpa process plant (mill) and our strategy is to “Fill the Mill” to leverage off the existing infrastructure and large resource base at Black Swan. The latest MRE incorporates the results from the recent underground drill programs undertaken from the Gosling drill drive. We are pleased the update has resulted in both an increase in the overall tonnes of contained nickel together with an increase in the inventory of the Measured and Indicated Resources.
Most importantly, the recent drilling has provided an improved understanding of the disseminated grade distribution within the metallurgically important serpentinite and talc-carbonate hosted ores below the existing Black Swan open pit. The improved metallurgical understanding is key to further de-risking the restart of Black Swan. Work is well advanced on optimising the pit shell designs from the new MRE and from the underground mining studies at Silver Swan and Golden Swan. Once completed, this work will allow the updating of Ore Reserves for the Black Swan Project to underpin the Bankable Feasibility Study.”
Overview
The MRE was prepared for Poseidon by independent resource consultants Golder Associates Pty Ltd (Golder) using all available assay data as at June 2022. The updated MRE now totals 28.9 Mt @ 0.63% Ni for 181kt of nickel metal contained. The MRE replaces the previous Black Swan MRE completed by Golder in 2014 (refer to Company announcement “Black Swan Mineral Resource” dated 4 August 2014) which reported 29.1 Mt @ 0.59% Ni for 170.9kt of nickel metal contained excluding stockpiles which have not been updated at this time.
The updated 2022 Black Swan MRE is classified in accordance with the Australasian Code for Reporting of
Exploration Results, Mineral Resources and Ore Reserves (JORC 2012) and are reported herein above a 0.4% Ni cut-off grade in Tables 1 and 2.
Competent Persons for this updated 2022 MRE are Poseidon’s in-house geology team for providing the
validated drill hole database and the lithological and mineralisation domains for the Black Swan deposit. Golder’s personnel were responsible for the estimation, reporting and classification of the MRE.
New Data
The updated MRE incorporates 5,144 metres of new drilling from 24 diamond drill holes (DDH) completed by Poseidon between October 2021 and March 2022 (refer to Table 2) and 14 RC holes (2,481 metres) completed in 2019 (refer to Company announcement “Black Swan underground RC Drilling – Final Assay Results” dated 27 November 2019). Both drill programs were completed from underground using the Gosling access drive. The recent 24-hole drill program was specifically undertaken to increase the confidence in the Black Swan MRE, by infilling the area extending approximately 125 metres immediately below the existing Black Swan open pit with the objective of better delineating the metallurgically important serpentinite and talccarbonate hosted resources in this area. Below this area, the MRE is based on the same historical drill hole data that was used in the August 2014 MRE.
Mineral Resource Summary
Poseidon engaged Golder in March 2022 to update the Black Swan MRE with the aim to quantify the current resource following recent drilling and create a block model for ongoing mine planning studies as part of a Black Swan Project Bankable Feasibility Study (BFS).
Geology and Geological Interpretation
The Black Swan Komatiite Complex (BSKC) is a 3.5km long by 0.6km thick arcuate lens of olivine cumulate and spinifex textured flows. The complex is enclosed by a broad sequence of proximal facies intermediate felsic lavas and associated volcanoclastic rocks situated on the NE dipping, NE facing limb of the Kanowna-Scotia anticline. The anticline is located in the upper greenschist – lower amphibolite facies of the Boorara Domain, one of six tectono-stratigraphic domains making up the Kalgoorlie Terrane.
The complex evolved as a series of episodically emplaced komatiite flows. The flows were channelised within a dynamic, coevally erupting calc-alkaline submarine environment, which resulted in the formation of several large felsic bodies (extrusive and intrusive) at various levels within the complex. Early during its evolution, massive and disseminated nickel sulphides accumulated in favourable locations on and adjacent to the basal contact of the complex. Post emplacement serpentinization and talc-carbonate alteration, metamorphism and deformation, was moderate to extreme and was responsible for the destruction of primary igneous textures throughout much of the complex, but without significant modification of the nickel sulphides.
The host lithologies to the Black Swan disseminated sulphide deposit comprise a core area of serpentinite
(dominantly as antigorite) enclosed by broad areas of talc magnesite and dolomite altered komatiites. The disseminated sulphides form between 2-10% of the host rock. They generally consist of composite grains of pyrite-millerite-magnetite±violarite in serpentinite areas with vaesite-polydymite becoming significant in the surrounding talc-carbonate altered rocks.
Two textural sulphide types are recognised:
– fine grained interstitial composite grains between olivine pseudomorphs; and
– coarse grained blebby or droplet composites similar in size to the olivine pseudomorphs.
The fine-grained composites are more widely distributed, defining a broad, low grade mineralised horizon
consisting of several discrete lenses (Figure 1). The coarser grained composites are much less widely
distributed, forming small discrete, higher-grade zones within the sulphide rich lenses. They are also unique to the Black Swan deposit and are generally restricted to the disseminated sulphide lenses developed between 11 200 N -11 450 N (Black Swan local grid).
The majority of the Black Swan disseminated sulphide mineralisation is contained within a central ‘main” lens which is up to 50 metres thick and contains most of the coarser grained blebby sulphides. Consequently, the main lens is typically higher grade with a S/Ni ratio > 1. Up to five much thinner discrete “hanging wall” sulphide lenses are recognised to the east on the main lens. The hanging wall lenses are typically millerite dominant with a characteristic S/Ni ratio of <1 when hosted by serpentinite. To the west of the main lens two footwall sulphide lenses are recognised. Consisting dominantly of the finer grained interstitial sulphide composites, the footwall lenses are mostly hosted within talc-carbonate altered komatiites and are typically lower grade that the main and hanging wall lenses.
(Source: Press Releases – www.wcsecure.weblink.com.au/pdf/POS/02538190.pdf)
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