Metasomatic Processes in Mantle Xenoliths

Metasomatic processes in mantle xenoliths encompass interaction between percolating melts or fluids and the solid peridotitic or pyroxenitic mantle framework. Such interactions modify mineral chemistry, generate new phases and record multistage histories of melt infiltration, often unrelated to the host volcanic event. Common metasomatic agents include alkaline silicate melts, carbonatites and volatile-rich fluids, each imparting distinct trace-element and isotopic signatures to olivine, orthopyroxene, clinopyroxene, amphibole and accessory phases. These signatures reveal cryptic and modal metasomatism, ranging from subtle adjustments in major-element ratios to formation of veins, reaction rims and cumulate assemblages. Metasomatic overprints play a fundamental role in lithospheric fertility, influencing melt generation in subsequent magmatic episodes and controlling volatile budgets in the deep mantle. Comparative studies across diverse tectonic settings—continental rifts, orogenic belts and intraplate volcanic provinces—demonstrate that metasomatism governs lithosphere–asthenosphere differentiation, mantle rheology and the distribution of economically important elements such as rare earth elements (REEs), carbonates and sulphur. By integrating petrographic observation with mineral-scale geochemistry and geochronology, researchers have begun to reconstruct temporal sequences of melt influx, revealing episodic infiltration events separated by tens or hundreds of millions of years. Such insights not only illuminate the dynamic evolution of the subcontinental lithospheric mantle but also underpin exploration for REE-rich deposits and contribute to models of deep CO2 cycling and diamond genesis.

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Metasomatic Processes in Mantle Xenoliths publication trend

The graph below shows the total number of articles in metasomatic processes in mantle xenoliths across all publications each year (not limited to Nature Index journals).

Technical terms

Metasomatism: Chemical alteration of a rock by percolating fluids or melts, leading to the introduction, removal or redistribution of elements and minerals.

Xenolith: A fragment of rock entrained within an igneous host, offering direct samples of deep crustal or mantle lithologies.

Subcontinental lithospheric mantle (SCLM): The rigid, compositionally distinct mantle layer underlying continental crust, susceptible to metasomatic modification.

Peridotite: A coarse-grained ultramafic rock composed mainly of olivine and pyroxenes, dominant in the upper mantle.

Cryptic metasomatism: Subtle mineral-chemical changes in a rock without visible textural overprints, detectable only by detailed geochemical analysis.

Carbonatite melt: A carbonate-rich, silica-undersaturated melt that metasomatizes mantle peridotite, often enriching it in incompatible elements.

Silicate melt: A molten silicate phase whose composition and percolation pathways control the nature and extent of mantle metasomatism.

References

1. Pliocene to Pleistocene REE-P Metasomatism in the Subcontinental Lithosphere beneath Southeast Asia—Evidence from a Monazite- and REE-rich Apatite-bearing Peridotite Xenolith from Central Vietnam. Journal of Petrology (2024).
2. Alkaline Silicate Metasomatism Recorded through Fe-Ti-Rich Mantle Xenoliths from the Calatrava Volcanic Field (Spain). Minerals (2024).
3. Chemical Modification of Lherzolite Xenoliths Due to Interaction with Host Basanite Melt: Evidence from Tumusun Volcano, Baikal Rift Zone. Minerals (2023).