A study published in Nature Geoscience has revealed that lavas from volcanic hotspots such as Hawaii, Samoa, and Iceland come from a chemically uniform reservoir in Earth’s mantle composition, challenging prior assumptions about its diversity. Led by Dr. Matthijs Smit of the University of British Columbia and co-authored by Dr. Kooijman from the Swedish Museum of Natural History, the research shows that while lava may appear to have different chemical “flavors” at the surface, these differences arise during its ascent, as the magma interacts with various rocks, rather than from variations within the mantle itself.
This discovery fundamentally changes the way scientists view Earth’s mantle composition and how it influences volcanic activity. Previously, scientists believed that the mantle contained distinct chemical reservoirs, each producing lavas of unique compositions depending on their age and region. This idea was based on trace-element and isotope analysis of lava from oceanic volcanoes. The new study, however, indicates that all hotspot lavas share a common chemical starting point. It is only as the magma rises toward the surface and interacts with different types of rocks that it develops the diverse chemical compositions seen at different volcanic hotspots.
The findings have broad implications for our understanding of Earth’s mantle composition, which makes up about 84% of the planet’s volume, lying between the iron core and the crust. When magma from this layer reaches the surface and erupts as lava, it provides vital clues about the internal workings of the Earth. Understanding the chemical makeup of the mantle is crucial for deciphering the processes behind plate tectonics, volcanic activity, and the global cycle of elements.
The research not only sheds new light on oceanic hotspot lavas but also reveals a surprising connection to basaltic lavas on continents, including those associated with diamond-bearing kimberlites. Although continental lavas are chemically distinct from those at oceanic hotspots, they appear to share the same ancestral magma source, reinforcing the idea of a uniform Earth’s mantle composition.
Dr. Smit described the discovery as a “game-changer” for geochemical models of Earth’s evolution. It challenges the notion of “primordial reservoirs” within the mantle—long thought to explain the differences in lava composition—and instead presents a simpler model where the mantle is much more chemically homogenous than previously believed. The study suggests that mantle convection and the interaction of magma with surrounding rocks during its ascent are sufficient to explain the observed chemical variations.
This groundbreaking research opens up new avenues for exploring Earth’s chemical evolution and the processes that drive volcanic activity. It reshapes how scientists approach the study of Earth’s mantle composition and its influence on the planet’s geology and tectonics.
https://phys.org/news/2024-09-envisions-earth-mantle-uniform-reservoir.html