Further Evidence of a High Percentage of Deep-Sourced, Low Nitrogen Diamonds with Ultra-High Pressure Mineral Inclusions
27.06.2024 | The Newswire
A Known Association with Large High-Value Gems. Sequoia Kimberlite, NT
Highlights
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Diamonds retrieved by caustic fusion of drill core from the Sequoia kimberlite show a relatively abundant presence of low nitrogen diamonds
Arctic Star Exploration Corp. ("Arctic Star" or the "Company") (TSXV: ADD) (Frankfurt: 82A2) (WKN: A2DFY5) (OTC: ASDZF) is pleased to announce that it has received results from research carried out at the University of Alberta by Dr. Luisa de Carvalho under the guidance of Thomas Stachel and Graham Pearson. The interpretation of the results are of soley the opinion of the company, however the authors agree it's a possible indication that larger gemstones will be present.The diamonds recovered by caustic fusion from several drill holes were transferred to the University from the SRC laboratories in Saskatoon under an unbroken chain of custody.
Seventy-three (73) of these diamonds were selected for further study based on their size (>700 µm; n = 51) or the presence of visible mineral inclusions (n = 22). The diamonds were analyzed for their nitrogen content and aggregation state and for their C and N isotope compositions. Mineral inclusions from 224 diamonds were also analyzed.
Of the studied diamonds, 27% are fragments, 26% are aggregates/twins, 18% are octahedra, 18% are rounded dodecahedra/resorbed, and 11% are macles.
The colors of monocrystalline diamonds are mainly white (43%), pale yellow (48%), or brown (9%). Six of the diamonds are fibrous, highly resorbed, and black/dark grey (n = 4), white (n = 1), and yellow (n = 1) in color.
Figure 1 shows pie graphs comparing the FTIR results from this study on Sequoia diamonds to published data on diamonds from other Lac de Gras kimberlites.
Figure 1: Distribution of diamond types for the Sequoia kimberlite compared to the Lac De Gras kimberlite field (Central Slave), as determined by micro-Fourier-transform infrared spectroscopy (µ-FTIR). Figure from Carvalho et al. (2024). See reference below.
Study of the mineral inclusions shows that Sequoia kimberlites tapped both lithospheric and sub-lithospheric mantle sources of diamonds beneath the Slave Craton, with peridotite being the principal diamond-bearing substrate. Five of the diamonds belong to the sub-lithospheric suite based on the presence of ferropericlase ± olivine, breyite, or larnite ± olivine, mineral associations that only form under intense pressure. The mineral inclusions were analyzed by Raman Spectroscopy. All of the diamonds classified as sub-lithospheric are either Type IaB or IIa.
For the complete parcel of Sequoia diamonds studied, the analyses have revealed that 37% of the diamonds are sub-lithospheric in source, 26% are Type IIa (no detectable nitrogen), and 11% are Type IaB. Figure 1 compares the population of stones studied from Sequoia with the published distribution of diamond types for the Lac De Gras kimberlite cluster.
Mr. Buddy Doyle, VP Exploration of Arctic Star, commented, "Recent work by the diamond research community has revealed that many of the larger than 10ct diamonds of exceptional quality found around the world are deeply sourced (hundreds of kilometers), nitrogen-free stones, classed as Type IIa. Figure 1 illustrates that Sequoia contains a high proportion of these stones in comparison with other kimberlites in the Central Slave kimberlite province. When compared to the total diamonds mined and studied globally, they are even rarer, making up only a few percent of the total. Also present is a significant population of Type IaB low-nitrogen diamonds which are also relatively rare and sourced from great depths. Studying inclusions in these diamonds reveals minerals that only form under ultra-high pressure, confirming they are coming from great depths."
Mr. Doyle continues, "There are also further layers of evidence that hint that the Sequoia kimberlite complex may harbor large exceptional diamonds. These are: (1) The diamonds liberated by the caustic fusion from the drill core to date demonstrate a population size frequency curve that has a relatively low gradient, meaning the ratio of larger stones to smaller stones is higher than the average. If this relationship holds strong as we increase the sample size, it predicts that larger stones will be encountered.
(2) The relative lack of recovered boart material when compared with caustic fusion diamond results from other kimberlites in the Lac de Gras field. Here, only a few percent are boart, whereas on average the boart dominates at >50 percent.(3) The indicator mineral chemistry presented by Dr. Chuck Fipke, where he reports an abundance of lherzolitic and deep-sourced indicator minerals from Sequoia."
Due to their exceptional value, even getting one +10ct 'special' stone per 100,000 tonnes of kimberlite can significantly affect mine economics. Arctic plans to take a bulk sample of approximately 3000t, timed for winter 2026. Even at this size of sample, some luck would have to be involved to "see" such large stones. This size sample, limited by cost and logistics, is designed to give a good first estimate of the average value of the "run of mine" stones. If the economics from this sample prove robust on the run of mine stones alone, then every time a larger stone reports, it would be welcome bonus. The size distribution of the diamonds from the proposed bulk sample, and any variation in the quality of the stones compared from different size classes, will allow us to gain a greater understanding.
Sequoia is part of the large Lac de Gras kimberlite cluster (Central Slave group), a geographic grouping of over 200 separate kimberlites that all erupted in a 20-million-year time period, centered around 55 million years before present. Of these, about a dozen are mined or considered for mining, and there is public information on their economics. They vary in their realized average run of mine aggregate diamond values, with prices ranging from $US 70/ct to $US 420/ct (2014 prices). Assuming the Sequoia kimberlite complex has an average grade of circa 0.3 ct/t (estimated by projecting the size distribution of the caustic fusion recovered small stones into commercial stone space, an estimate that will be refined and become more certain as we take more samples). Sequoia would need to demonstrate it contains diamonds averaging >$US 200/ct in value to trigger a feasibility study. There are kimberlites in the cluster with these grades and valuations, so it is not unreasonable to consider Sequoia may have this potential.
The next planned step is to complete the first pass delineation of the Sequoia kimberlite complex with HQ size drilling to further understand the diamond distribution and geology. Approximately fifteen, 200m holes are planned for spring 2025. The delineation work so far (8 holes) has revealed several different kimberlite varieties, each with the potential to have different diamond populations. Completion of this work will help in the design of the bulk sample.
Of note, in a previous news release, Arctic reported a sample containing 51% Type IIa diamonds, a higher percentage than reported here. This may be due to a number of reasons. First, the original study looked at diamonds down to 0.3mm in size, and second, only looked at diamonds from the first two holes. This study looked at material from all drill holes and only stones >0.7mm. Third, the first two holes had a different mix of kimberlites to the other drill holes; there might be a kimberlite type that has an enhanced Type IIa population. This requires further work to gain understanding.
Mr. Doyle concludes, "Diamonds are the ultimate sampling challenge in the mining industry. Taking a bulk sample is an expensive hurdle; however, once that hurdle is crossed, the pathway to production is usually less capital-intensive than that of other commodities, especially if we can leverage the existing mining infrastructure in this world-class diamond district."
Dr. Carvalho will present the work reported here at the Quadrennial Kimberlite Conference, being held in Yellowknife, this July 2024. At which core from the Sequoia Kimberlite complex will be on display. The reference for the extended abstract is given below.
Carvalho, L.D.V., Doyle, B., Stachel, T., Pearson, G. (2024). A first look at diamonds and their inclusions from the Sequoia Kimberlite Complex, Northwest Territories, Canada. Extended Abstract (150), 12th International Kimberlite Conference, Yellowknife.
Arctic Star thanks the University of Alberta for this interesting contribution and looks forward to continuing studies and further collaboration.
About Arctic Star
Arctic Star is predominantly a diamond explorer, recently discovering 5 new kimberlites in the prolific Lac De Gras kimberlite field that supports 2 multi-billion dollar kimberlite mining complexes. The Company also has a 958 Ha Exploration permit containing several diamond-bearing kimberlites on its Timantti project, Kuusamo Finland. The Company continues to look for appropriate diamond opportunities elsewhere.
ON BEHALF OF THE BOARD OF DIRECTORS OF
ARCTIC STAR EXPLORATION CORP."Patrick Power"
Patrick Power, President & CEO
+1 (604) 218-8772
ppower@arcticstar.caThis news release contains "forward-looking statements" including but not limited to statements with respect to the Diagras Joint Venture. Forward-looking statements, while based on management's best estimates and assumptions, are subject to risks and uncertainties that may cause actual results to be materially different from those expressed or implied by such forward-looking statements. There can be no assurance that such statements will prove to be accurate, as actual results and future events could differ materially from those anticipated in such statements. Accordingly, readers should not place undue reliance on forward-looking statements. Arctic Star undertakes no obligation or responsibility to update forward-looking statements, except as required by law.
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