Helium in Ocean VolcanoesNew study by Manoa's Helge Gonnermann sheds light on Earth’s gasses. Read more
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Photo by Nathan Becker.
Helium in Ocean Volcanoes
A study co-authored by Manoa School of Ocean Earth Sciences and Technology Young Investigator Helge Gonnermann found that helium in lavas from ocean islands, such as Hawai‘i, may be derived from a part of the Earth’s mantle that has retained most of the gases originally incorporated into the Earth during its accretion, 4.5 billion years ago. The study was published in Nature.
“Lavas from submarine volcanic eruptions typically contain gases, predominantly carbon dioxide and water, as well as small amounts of noble gases, such as helium for example,” says Gonnermann. "These gases are derived from the part of the Earth’s mantle that melted to produce the erupted magma. Most magma derived from the Earth’s mantle erupts along the Earth’s mid-ocean ridges, producing mid-ocean ridge basalts (MORBs). However, throughout the oceans there are ocean islands, such as Hawai‘i, whose basalt lavas are commonly called ocean-island basalt (OIB).
It is paradoxical that helium concentrations in OIBs, thought to be derived from the undegassed part of Earth’s mantle, are typically much lower than in MORBs, known to be derived from the degassed upper mantle. This is known as the “helium concentration paradox” and has led to much controversy about the interpretation of 3helium/4helium ratios, as well as about the history and structure of the Earth’s mantle.
“What this study shows us is that there is no helium concentration paradox and that indeed a part of the Earth's mantle probably still contains much of its primordial noble gas content,” says Gonnermann. “This requires us to come up with a geodynamical model that allows for the isolation and preservation of such a primordial mantle component throughout the course of Earth's history. It will also require reconciliation of seismological observations that suggest that the whole of the Earth's mantle appears to be actively convecting, which would make it difficult to isolate such a primordial mantle.”
Read the news release.