Volcanic Rocks Reveal Earth’s Earliest Chemical Secrets
UMD researchers find evidence that deep pockets of primordial material remained undisturbed within Earth’s mantle for billions of years.
Scientists analyzing volcanic rocks from island chains discovered chemical fingerprints dating back 4.5 billion years—evidence that parts of Earth's deep interior remained virtually untouched since our planet's earliest days, long before the cataclysmic impact that formed the moon.
The findings, published in the journal Geochimica et Cosmochimica Acta, challenge popular theories about both the source of these ancient signatures and the violence of the moon-forming collision that scientists believe reshaped Earth roughly 100 million years after its formation.
“We’re seeing chemical signatures that could have only formed really early in Earth history showing up in these comparatively young volcanic rocks,” said the study’s lead author Val Finlayson, an assistant research scientist in the Department of Geological, Environmental, and Planetary Sciences at the University of Maryland. “It’s pretty wild that this differentiation process, or how molten rocks separate into chemically distinct layers as they cool and crystallize, may have somehow stayed preserved throughout the entirety of Earth’s history.”
The research team analyzed basalt samples from three volcanic island chains: Easter Island (Rapa Nui) in the southeastern Pacific, the Bowie-Kodiak seamounts near Alaska and the Louisville seamount chain in the south Pacific region. Through chemical analyses, they measured tiny variations in tungsten isotopes—different forms of the element tungsten that can serve as geological time capsules.
The key isotope, tungsten-182, was created by radioactive decay during Earth’s first 50 to 60 million years, when a parent element called hafnium-182 was still present on the planet. Once hafnium decayed away, new tungsten-182 could not form.
“Any variations in tungsten-182 compared to other tungsten isotopes would then be recording processes from this very early period in Earth’s existence,” Finlayson explained.
These ancient chemical signatures are thought to originate from approximately 2,800 kilometers (1,739 miles) below Earth’s surface, where the base of the mantle meets the Earth’s liquid outer core. Volcanic hot spots like Hawaii and Iceland tap into this deep reservoir. Erupting volcanoes in these regions bring up material deep inside Earth that avoided the recycling process of plate tectonics for billions of years.
“It’s a part of Earth we think has not lost much of its initial primordial, inherited volatile content,” Finlayson said. “It’s probably stayed more or less somewhere in the very deep part of Earth’s interior where it hasn’t really interacted much with anything else.”
The team’s discovery reignites debates about the origin of these primordial chemical signatures. The leading hypothesis is that they result from interactions between Earth’s mantle and its metallic core, which concentrated tungsten and other elements when the core formed early in the planet’s history.
But Finlayson’s team found a crucial clue that challenges this idea: the tungsten anomalies correlate with elevated levels of titanium, tantalum and niobium—elements that behave like tungsten in rocks. While some niobium and tantalum may be present in Earth’s core, titanium shouldn't exist there.
“As far as we know, there’s no titanium in Earth’s core, so it can’t be coming out from there,” Finlayson said. “That means it’s possible that the signatures formed through the differentiation of a basal magma ocean, or this vast layer of molten rock at the base of the mantle during Earth's infancy. As this ocean slowly crystallized, some pockets of material may have developed distinct chemical compositions and might’ve remained isolated ever since.”
Finlayson noted that the team’s findings have implications for understanding how Earth’s moon formed. The prevailing theory suggests a Mars-sized object called Theia collided with an early version of Earth around 100-150 million years after the solar system’s formation. Many models depict this as a catastrophic event that completely vaporized and remixed Earth’s interior.
But if signatures from even earlier times survived into the present day, the impact may not have been as destructive as previously thought.
“If we’re correct about this early differentiation, then maybe we need to rethink how big that giant impact was,” Finlayson explained. “Maybe there was some part of the planet that stayed intact.”
The research team is now investigating other volcanic systems and collaborating with numerical modelers to further test their hypothesis. They hope to examine additional hot spot locations with similar compositions and explore whether other geochemical signatures support the basal magma ocean model.
“We need to broaden the search beyond tungsten to really confirm the theory,” Finlayson said. “We only have part of the picture at the moment.”
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Richard Walker, UMD Distinguished University Professor of Geological, Environmental, and Planetary Sciences, is an additional co-author of the study.
This research was supported by the U.S. National Science Foundation (Award Nos. 2019856, 2220922 and 2051577). This article does not necessarily reflect the views of this organization.
The paper, “A tungsten-182 and trace element perspective on the origin of the FOcal ZOne (FOZO) component,” was published in the journal Geochimica et Cosmochimica Acta on February 5, 2026.
