Latest news with #volcanism
Forbes
6 days ago
- Science
- Forbes
Superplume Beneath Continent Is Splitting Africa Apart
Aerial view of Suguta River in the Great Rift Valley. Kenya. Sophisticated chemical analysis of volcanic gases from Kenya have provided the first evidence that a superplume lies beneath East Africa driving active tectonics and slowly separating the Somali plate and the Horn of Africa from the rest of the continent. An international team of scientists led by Professor Fin Stuart from the University of Glasgow, working in partnership with the Kenya Geothermal Development Company, has discovered surprising results in a new study of gases from the Menengai geothermal field in central Kenya. The rift valleys of East Africa are some of the largest and most spectacular topographic features on Earth. They extend for 3,500 kilometers through Ethiopia, Kenya, Uganda and Malawi, and host extensive volcanic fields. The rifts are the manifestation of the African tectonic plate being split apart driven by forces in the Earth's interior. However, scientists are uncertain whether the volcanism and rifting is due to shallow processes or whether it is driven by up-welling hot material from Earth's mantle. As countries along the rift zone are tapping into geothermal energy, scientists get access to new sampling sites. The researchers used gases collected from the Menengai geothermal field (started in 2009 and still in development) in central Kenya to reconstruct the source in Earth's mantle feeding the geothermal activity. The team notes that the gases are chemically indistinguishable from gases present in volcanic rocks from Hawaiʻi', where volcanism is fueled by a mantle plume. Together with the common chemical 'fingerprint' between different geothermal fields— the researchers compared their results with gas samples coming from the Red Sea to the north and from Malawi to the south — this discovery supports the theory that a single "superplume" is the main source. 'Our research suggests that a giant hot blob of rock from the core-mantle boundary is present beneath East Africa," summarizes Stuart. The plume not only drives the tectonic plates apart, but also pushes up the African continent preventing the rift zone to be flooded by the Red Sea (forming the geologically spectacular landscapes of the Afar Depression). Map of East Africa showing some of the historically active volcanoes (red triangles) and the Afar ... More Depression (shaded, center). Seismic surveys indicate the presence of a large anomaly beneath the southern tip of the African continent. Such "Large Low Shear Velocity Provinces" are composed of hot and weak mantle material, and the only other similar anomaly lies beneath the Pacific Plate. They may be the primary source feeding the mantle plume of Hawai'i and the plume beneath Africa, explaining the identical chemical signatures as described by the researchers. The study,"Neon Isotopes in Geothermal Gases From the Kenya Rift Reveal a Common Deep Mantle Source Beneath East Africa," was published in the journal Geophysical Research Letters. Additional material and interviews provided by the University of Glasgow.
Forbes
23-05-2025
- Science
- Forbes
Volcanic Rocks Reveal How Gold Reaches Earth's Surface
Crystallized gold in rocky matrix. getty Gold is a surprisingly common metal (it is more common than lead if we consider the bulk composition of Earth), but more than 99.999 percent of Earth's stores of gold and other precious metals lie buried under 3,000 kilometers of solid rock, locked away within Earth's mantle and metallic core and far beyond the reaches of humankind. A new study published by researchers from the University of Göttingen suggests that at least some of the supplies of gold and other precious metals that we rely on for their value and applications in modern technology may have come from Earth's core. Compared to Earth's rocky mantle, the metallic core contains a slightly higher abundance of a particular isotope known as rubidium-100. When Earth formed around 4.5 billion years ago the rubidium was locked in the core together with gold and other precious metals. Standard rock analysis methods aren't sensitive enough to identify and quantify rubidium isotopes. The researchers were able to amplify the signal by first dissolving rocks in hot acid, condense the resulting steam back to a liquid, and finally measuring the rubidium signal in the concentrated samples. Analyzing lava from Hawaiʻi, the researchers found an unusually high rubidium-100 signal in the samples. Hawaiʻi's active volcanism is feed by large plumes of molten rock rising up in Earth's mantle. The origin, dynamics and composition of such mantle plumes is still debated among geologists. The rubidium signal suggests that these rocks ultimately originated from the core-mantle boundary. "Our findings not only show that Earth's core is not as isolated as previously assumed. We can now also prove that huge volumes of super-heated mantle material—several hundreds of quadrillion metric tons of rock—originate at the core-mantle boundary and rise to Earth's surface to form ocean islands like Hawaiʻi," explains study coauthor Professor Matthias Willbold, researcher at Göttingen University's Department of Geochemistry and Isotope Geology. '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 Earth's mantle above, ' explains study author Dr. Nils Messling, a geochemist working at the same department, the Pure gold is inert in Earth's mantle and tends to stay there. However, gold atoms can bound with three sulfur atoms forming a gold-trisulfur complex. This complex is highly mobile in the molten sections of the mantle called magma. Where material from Earth's core-mantle zone has the opportunity to rise to the surface, like along subduction zones or in a mantle plume, it can mix with sulfur-rich fluids and form gold-bearing magmas. As the magma rises to the surface, degassing and circulation of hydrothermal fluids further concentrate the gold in veins and clusters, forming a deposit that can be mined. The study,"Ru and W isotope systematics in ocean island basalts reveals core leakage," was published in the journal Nature. Additional material and interviews provided by the University of Göttingen.
