Mantle Melting Processes in Volcanic Systems

The generation of magmas in volcanic settings originates in the Earth’s mantle, where variations in temperature, pressure and composition induce partial melting. In mid-ocean ridges, decompression melting of upwelling asthenosphere produces basaltic melts that form new oceanic crust. In subduction zones, fluids released from the subducting slab lower the solidus of the overlying mantle wedge, generating arc magmas enriched in large-ion lithophile elements. Hotspot and continental rift environments exploit thermal anomalies or lithospheric thinning to trigger melting at greater depths. The presence of volatiles such as H₂O and CO₂ plays a critical role in reducing melting temperatures and in dictating melt chemistry. Melts segregate and ascend through porous flow and channel networks, interacting with surrounding peridotite or crustal lithologies and modifying both melt composition and residue mineralogy. The resulting volcanic products record the thermal, chemical and tectonic history of their mantle source regions and underpin hazards assessment, geothermal exploration and mineral resource evaluation worldwide.

Research from Nature Portfolio

High-pressure experiments have demonstrated that partial melting of carbonate-rich sediments at cold, shallow slab-mantle interfaces can produce immiscible carbonatitic and silicic melts. Reaction of these melts with peridotite yields a metasomatic wehrlite assemblage of clinopyroxene, phlogopite, carbonate and amphibole, which constitutes an ideal source for Si-undersaturated ultrapotassic lavas. The physical separation of conjugate melts offers an explanation for canonical trace-element ratios observed in natural ultrapotassic orogenic magmas. Another study has combined geophysical modelling with petrological experiments to show that sediment melts pond trenchwards of volcanic arcs and react with the mantle wedge to form electrically conductive phlogopite-bearing pyroxenites. These reaction zones reproduce magnetotelluric anomalies, account for the origin of potassium-rich volcanics during slab rollback, and constrain regions of diminished seismic coupling in subduction margins.

Mantle Melting Processes in Volcanic Systems publication trend

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

Technical terms

Partial melting: The process by which only a fraction of a solid is melted, producing a melt enriched in incompatible elements. Metasomatism: Chemical modification of a rock by percolating fluids or melts, resulting in new mineral assemblages. Phlogopite: A potassium-rich mica mineral that forms in metasomatised peridotite and serves as a key reservoir of volatile elements. Carbonatitic melt: A carbonate-rich melt with low silica content that can flux the mantle and contribute to alkaline magmatism. Pyroxenite: A coarse-grained ultramafic rock dominated by pyroxene, often produced by reaction between melts and peridotite.

References

1. Experimental production of K-rich metasomes through sediment recycling at the slab-mantle interface in the fore-arc. Scientific Reports (2023).
2. Melting of subducted sediments reconciles geophysical images of subduction zones. Nature Communications (2021).
3. Constraints on crustal recycling from boron isotopes in Italian melt inclusions. Earth and Planetary Science Letters (2023).
4. The multi-component mantle source of Roman province ultrapotassic magmas revealed by melt inclusions. Geochimica et Cosmochimica Acta (2023).