Noble Gas Geochemistry in Mantle Dynamics

Noble gas geochemistry offers unique insights into the origin, evolution and present-day dynamics of the Earth’s mantle. Inert by nature, helium, neon, argon, krypton and xenon retain isotopic signatures that record primordial accretion, partial melting, degassing and recycling processes. Variations in radiogenic (for example 4He produced by uranium and thorium decay) and primordial (for example high 3He/4He) isotope ratios distinguish distinct mantle reservoirs such as mid-ocean ridge, plume and lithospheric domains. Noble gases also highlight the role of metasomatism and fluid transport in modifying the subcontinental lithospheric mantle. By coupling noble gas data with major and trace element systematics, geoscientists constrain rates of mantle convection, the longevity of chemical heterogeneities and the mechanisms governing volatile fluxes between deep Earth and surface reservoirs. These findings bear on global heat production, volcanic hazards, geothermal exploration and the evolution of the atmosphere.

Research from Nature Portfolio

Recent studies have refined our understanding of noble gas partitioning and storage under extreme conditions. Advanced computational modelling of helium and neon partitioning between liquid iron and silicate melt under core-forming pressures and temperatures indicates that the very low solubility of neon in metallic iron would produce isotope ratios in the core that are incompatible with those observed in ocean island basalts. This result effectively rules out the core as a major source of plume-derived noble gases, reinforcing the mantle origin of primordial volatiles. Complementary experimental work using transmission electron microscopy with in-situ ion implantation has enabled quantification of xenon solubility and the formation of supercritical xenon precipitates in silicate glasses. These non-equilibrium measurements reveal a high capacity of silicates to store xenon, a mechanism that may reconcile discrepancies between atmospheric and mantle xenon inventories and illuminate the residence time of radiogenic isotopes.

Noble Gas Geochemistry in Mantle Dynamics publication trend

The graph below shows the total number of articles in noble gas geochemistry in mantle dynamics across all publications each year (not limited to Nature Index journals).

Technical terms

Isotopic ratio: The relative abundance of two isotopes of an element, used to trace sources and processes.

Radiogenic: Referring to isotopes produced by radioactive decay within the Earth.

Primordial: Denoting isotopes inherited from the original accretion of the planet.

Partition coefficient: The ratio describing how an element or isotope distributes between two coexisting phases.

Partial melting: The process by which only a portion of a solid is melted, affecting the composition of residual and melt phases.

Metasomatism: Chemical modification of a rock by fluid- or melt-mediated element exchange.

Fluid inclusion: A microscopic pocket of fluid trapped within a mineral, preserving chemical and isotopic information from the time of entrapment.

References

1. Primitive noble gases sampled from ocean island basalts cannot be from the Earth’s core. Nature Communications (2022).
2. Xenon solubility and formation of supercritical xenon precipitates in glasses under non-equilibrium conditions. Scientific Reports (2018).
3. H2-H2O immiscibility in Earth’s upper mantle. Contributions to Mineralogy and Petrology (2023).
4. The heterogeneity of the Mexican lithospheric mantle: Clues from noble gas and CO2 isotopes in fluid inclusions. Frontiers in Earth Science (2022).