地球の核からの貴金属、思ったよりも近い

地球の核から貴金属が漏れ出す仕組み

Contrary to popular belief, the Earth is not very rich in metals, including rare and precious metals like gold. The problem is that most of the heavier elements sank to the core during the planet’s formation from an agglomeration of asteroids.

その結果、地球に存在する金やその他の貴金属の99.999%以上が、3,000km の固体岩石の下に埋まっています。

長い間、これらの鉱物は永遠に地球の核に閉じ込められると考えられてきました。しかし、新しい研究はそれが必ずしも当てはまらない可能性を示しています。

By improving the detection method of another element, ruthenium, researchers of the Georg-August-Universität Göttingen (Germany), University of Bristol (UK), University of Edinburgh (UK), and Colgate University, (USA) have proven that material from the Earth’s core can leak into the mantle and up to the planet’s surface.

“When the first results came in, we realized that we had literally struck gold! Our data confirmed that material from the core, including gold and other precious metals, is leaking into the Earth’s mantle above.”

Dr Nils Messling – 研究者 at Göttingen University
They published their discovery in the prestigious review Nature¹, under the title “Ru and W isotope systematics in ocean island basalts reveals core leakage”.

地球の核とマントルの形成過程

During the early days of the solar system, dust particles aggregated into countless asteroids, which themselves aggregated into bigger and bigger elements, forming the protoplanets that would later on form the 4 rocky planets (Mercury, Venus, Earth, and Mars).

この過程で、惑星は衝突による激しい熱で主に溶融マグマ状態でした。重い元素は重力により徐々に核へ沈み、マントルから分離しました。その後も宇宙からの物質が続いて供給され、マントルが形成されました。

出典: SG Online

Crucially for the study discussed here, the mantle displayed a very different composition for some isotopes of some elements, including ruthenium, due to this later formation using different materials.

科学者が核元素を表層まで追跡する方法

ルテニウム：核の物語を語る同位体

As ruthenium is mostly locked in the core, and with ruthenium-100 more abundant in the core, detection of this isotope can prove that metal came from the core instead of the mantle, normally the source of most surface rocks due to volcanic activities.

A new, more precise method to measure the presence of ruthenium-100 has previously been developed at the University of Göttingen, allowing for this study.

This was confirmed when studying very ancient rock, like samples from Greenland as old as 3.7 billion years, before the definitive separation of core and mantle would change ruthenium-100 composition.

出典: Nature

さらに興味深いことに、少なくともいくつかの火山島では、核由来の添加物を受けた岩石に対してルテニウム-100比率が大きく偏っていることが分かっています。

しかし、ラ・レユニオンやガラパゴス諸島のサンプルのように、すべての火山島が同様というわけではなく、純粋にマントル由来の岩石と変わりません。

“We can now also prove that huge volumes of super-heated mantle material – several hundreds of quadrillion metric tonnes of rock – originate at the core-mantle boundary and rise to the Earth’s surface to form ocean islands like Hawaii.”

教授 Matthias Willbold – Professor at Göttingen University

タングステンが核漏出仮説を支持する理由

Tungsten, or wolfram (hence the W sign for this element), is another heavy metal mostly located in the Earth’s core.

Here the scientists studied a metric called μ182-W (parts-per-million (ppm) deviation of 182W/184W from terrestrial standard. But measuring which type of isotope of tungsten is present in the sample, clarifies how the minerals from the core mixed with the magma of the mantle to form the volcanic rocks of Hawaii islands.

This isotope ratio clearly shows that the tungsten detected is not from the decomposition of hafnium, another potential source of tungsten in the mantle.

新理論が核元素の表層到達を説明する

From the variation of tungsten composition, the scientists deduced a previously unknown mechanism: around the Earth’s core formed an oxygen-rich outer core domain.

Over time, the crystallization of metal-rich oxides through secular core cooling locks in some of the tungsten.

“Whether these processes that we observe today have also been operating in the past remains to be proven. Our findings open up an entirely new perspective on the evolution of the inner dynamics of our home planet.”

Dr Nils Messling – Researcher at Göttingen University

この発見が採鉱・産業にとって重要な理由

This is not just an academic pursuit. Many of the elements present in the core are either of very high value, like gold, or very useful in modern society, like, for example, tungsten, an ultra-hard metal used in semiconductors, industrial tools, aerospace, weapons, and engines.

これらの金属の一部が地球の核から来ていることが判明すれば、地質学者は鉱床の形成過程や、地球最深部と表層がどのように相互作用するかについての見方が根本的に変わります。

結果として、鉱業会社が希少元素を探査する方法も変わる可能性があります。たとえば、ある地域の岩石中のルテニウム含有量を分析すれば、そこに地球核の侵入があることが分かり、同じ場所で他の重元素を見つける確率が大幅に上がります。

最終的考察：核・マントル科学が重要な理由

This sort of study might sound a little abstract and only of scientific interest at first. However, understanding how our planet formed and how some parts of the Earth’s core can resurface can help us find more of these important metals.

この知見は他の惑星、特に火星や金星の地質学を理解する上でも重要です。もし地球で核元素の再浮上が可能なら、他の惑星でも同様のプロセスが起こり得ます。

今後数十年で火星へのコロニー建設が検討される中、火星の核に含まれる金属資源が予想以上にアクセスしやすいかどうかは大きな関心事です。特に火星は太陽系最大の火山を有し、ハワイ諸島に似た火山プロファイルを持っています。

地球の核元素への投資

Almonty Industries

Among Earth’s core elements, one of the most useful and least known to investors is tungsten. This very resistant metal is important for a wide array of high-tech industries. It is also currently produced almost exclusively in China and Russia.

We covered in more detail the investment case for tungsten in detail in the 2024年10月 report “Tungsten – The Secret High-Tech Metal”.

Almonty Industries is a tungsten miner that is currently mostly produced from a mine in Portugal, in operation for the last 125 years.

The company has been working on expanding the Portuguese mine and owns undeveloped deposits in Spain.

出典: Almonty

The company’s most important project is the ongoing development of a new mine in Sangdong, South Korea. The mine contains more inferred resources than all of its other deposits combined.

出典: Almonty

As one of the only active and producing tungsten miners in Western countries, Almonty is a key strategic supplier for the defense industry. So it is an important company for reducing dependence on Chinese supply.

The Sangdong mine’s location makes it a perfect supplier to the defense industry, with South Korea a new giant in mass production of “low tech” military gear like tanks, artillery, and ammunition (compared to less tungsten-demanding fighter jets, aircraft carriers, etc.).

While China prepares to open a huge tungsten mine in Kazakhstan, Almonty is poised to “substantially shift the politics involved with securing tungsten” when the Almonty Korea Tungsten Project’s Sangdong mine comes online within a few months. When it begins production, it will be one of the world’s largest tungsten mines, accounting for 30% of the non-Chinese supply.

Lewis Black, director, president, and CEO of Almonty Industries

Almonty should start producing tungsten from the Korean mine in early to mid-2025.

Because of its strategic position as essentially the sole large supplier in the West, Almonty was offered a guaranteed price by Plansee. Plansee is a high-performance metal manufacturer and one of Almonty’s larger clients, as well as the owner of 15% of the company.

The minimum guaranteed price was $235/MTU (metric ton unit), with no upper threshold. As Sangdong Mine is aiming for cash costs of $110/mtu, this should virtually ensure a high profit margin for the project.

With a luckily almost perfect timing between the upcoming opening of Sangdong and a new trade war between Trump’s America and China, the stock price has reacted strongly and rose by 40% in just 2 days following the announcement of tungsten export restriction from China.

参照文献：

^{1. Messling, N., Willbold, M., Kallas, L. et al. Ru and W isotope systematics in ocean island basalts reveals core leakage. Nature (2025). https://doi.org/10.1038/s41586-025-09003-0}