Well-connected basalt sequences as potential reservoirs for large-scale carbon sequestration revealed by strontium isotopes

[Geoengineering News]

https://www.nature.com/articles/s43247-025-03020-7

Authors: Stéphane Polteau, P. Craig Smalley, Vani N. Devegowda, Ingar Johansen, John M. Millett, Marija P. Rosenqvist, Mohamed Mansour Abdelmalak & Sverre Planke 

09 January 2026

Abstract

Permanent storage of gigatons of carbon in basalt requires thick, uncompartmentalized sequences that allow lateral dissipation of CO2 away from injection sites. Here we assess the presence of flow barriers by evaluating the variations in 87Sr/86Sr patterns in pore water, a method used extensively in sedimentary successions. Present-day pore water 87Sr/86Sr was measured from residual salts in core samples, while past water compositions were reconstructed from carbonate cements of different ages. We reveal smooth and uninterrupted trends in strontium isotopes through a 100 m thick basalt section indicating a common fluid reservoir unaffected by low-permeability massive lava flow interiors. The data further indicate that unconsolidated overburden sediments act as a good seal preventing seawater to mix with in situ pore water, and buoyant supercritical CO2 to leak. Finally, basaltic sequences form viable targets for CO2 storage and suggests that fractures may bypass low-permeability units to create a well-connected reservoir system.

Source: Communications Earth & Environment