Tracing deep Earth volatile heterogeneities with heavy noble gases in Réunion plume-influenced Central Indian Ridge basalts

The initial budgets and subsequent exchange of volatiles ( e.g ., water, carbon, nitrogen, and noble gases) among surface and deep reservoirs govern planetary surface conditions and long-term habitability. Varieties of modern terrestrial basalts—mid-ocean ridge basalts (MORBs), which derive primarily from melting of Earth’s upper mantle, and plume-influenced basalts that sample the lower mantle—provide access to two distinct volatile reservoirs within Earth’s interior. Their heavy noble gas (Ne, Ar, Kr, and Xe) isotope systematics offer powerful insights into volatile accretion, outgassing, and recycling histories of different terrestrial mantle reservoirs. However, existing high-precision heavy noble gas datasets are limited due to challenges related to sample access and analytical methods. Basaltic glasses from the Central Indian Ridge (CIR), influenced by the nearby Réunion hotspot, provide an opportunity to expand the global heavy noble gas record. Here, we present high precision He, Ne, Ar, and Xe elemental and isotopic data measured from four submarine basalts collected from the CIR axis between 16.7°S and 20.6°S. The resulting heavy noble gas dataset confirms Réunion plume influence at the CIR axis near ∼20°S and provides constraints on the origins of the region’s compositional variations. The mantle source Xe composition of the Réunion-influenced CIR basalt D14–1 is consistent with observations from other plume-influenced localities, suggesting globally uniform plume-source volatile origins, with early-formed isotopic signatures preserved from accretion to the present-day.