“When the first results came in, we realised 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.” said University of Göttingen’s Dr. Nils Messling, when his researchers confirmed what geochemists have long theorized but never previously demonstrated: the core of our planet is not an impenetrable vault, but a leaky reservoir feeding gold and other precious metals into the mantle and, eventually, onto the surface via volcanic eruptions.
For decades, it was believed by most that the planet’s core nearly 3,000 kilometers below our feet was geochemically isolated, its treasure buried behind an impenetrable wall of rock. But new research in Hawaiian lava geochemistry has turned this idea on its head. The Göttingen group discovered that the key to their insight lay in the identification of a fleeting isotope: ruthenium-100 (^100Ru). This isotope, much more common in the core than in the mantle or crust, serves as a geochemical fingerprint, tracing the path of core-derived metals to the surface.
The technical breakthrough that made it possible was the establishment of sophisticated isotope geochemistry methods at Göttingen. By applying multi-collector inductively coupled plasma mass spectrometry (MC–ICP–MS), scientists were able to separate ruthenium isotopes from the core and indigenous ones for the first time. The process required painstaking sample preparation: volcanic rocks from Hawaii’s Kilauea and Loihi volcanoes were crushed, milled, and subjected to a series of chemical separations and distillations, all designed to isolate and purify ruthenium from trace concentrations as low as 0.25 nanograms per gram with procedural blanks below 8%. The resulting isotopic measurements revealed an unmistakable anomaly elevated ^100Ru signals indicating a source deep within the Earth.
Dr Matthias Willbold, one of the authors of the study, outlined the wider implications: “Our findings not only show that the Earth’s core is not as isolated as previously assumed,” study co-author Matthias Willbold, a professor in the geochemistry department at Göttingen University, said in the statement. “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.”This discovery remodels our concept of the dynamic interaction between the core and mantle, and by implication, the surface distribution of valuable metals.
The geochemical evidence is compelling. The ruthenium signature of the core, with a positive ε100Ru value (a function of isotopic deviation), is different from that of the mantle. By adjusting core–mantle mixing curves to OIB data, the scientists determined that introducing less than 0.25% of a bulk core component with ε100Ru = 0.25–0.35 would explain the measured isotopic variation in both Ru and tungsten (W) isotopes. This tiny amount, while apparently insubstantial, is a geologically important material transfer over millions of years.
The dynamics for this transfer is based on mantle plume processes. Mantle plumes, pipes of superheated rock formed at the core–mantle boundary, are conveyor belts, moving material derived from the core towards the surface. Once these plumes penetrate the lithosphere, they form volcanic islands like Hawaii, with a chemical cargo that includes gold, platinum, iridium, and ruthenium. The occurrence of ^100Ru in Hawaiian lavas is thus not an oddity it is a direct manifestation of core–mantle material transfer.
To dissect the complexity of the processes at deep Earth, the Göttingen researchers also investigated other models. One such model is the creation of an oxygen-rich outer core domain, with metal-rich oxides precipitating via secular cooling. Experimental evidence indicates that tungsten is concentrated in FeO-rich alloys, while highly siderophile elements (HSEs) such as ruthenium are depleted in general. By simulating the partitioning behavior of these elements, the scientists were able to replicate the combined Ru and W isotope systematics of OIBs with the addition of only 0.3% of an oxide-rich outer core layer to the mantle with only a moderate increase in HSE concentrations.
These conclusions have significant ramifications. Firstly, they contradict the supposition that the core is an enclosed system, radically changing theories of Earth’s internal history. Secondly, they offer a new perspective for the interpretation of the surface distribution of precious metals. The geochemical trace of core-type metals in volcanic rocks may guide exploration methodologies for gold and platinum group elements, especially in geologically active terranes associated with deep mantle processes like volcanic island arcs.
The research also highlights the utility of isotope geochemistry as a means to track deep Earth processes. By integrating radiogenic and stable isotope measurements such as Sr, Nd, Pb, Hf, W, and Ru on plume-derived rocks, researchers are able to reconstruct the generation and evolution of mantle plumes, mantle heterogeneities, and core–mantle interactions with unprecedented accuracy.
As Dr. Messling mused,“Our findings open up an entirely new perspective on the evolution of the inner dynamics of our home planet.” It is more than a technical achievement to detect ^100Ru in Hawaiian lavas; it is a glimpse into the continuous, unseen conversation between Earth’s interior and surface, and each volcanic eruption adds another page to the planet’s geochemical history.
