Geologic Carbon Capture: The Role of Basalt in CO2 Mineralization

By Muhammad OsamaReviewed by Laura ThomsonMay 23 2025

In a recent paper published in Communications Earth & Environment, researchers explored geologic carbon dioxide (CO₂) mineralization in basalt formations, focusing on how complex carbonate phases significantly influence carbon sequestration. By examining the composition and behavior of these minerals after CO₂ injection, they aimed to enhance carbon capture strategies and support sustainable solutions for mitigating climate change.

Advancements in Carbon Capture Technology

The urgency to address climate change has accelerated the development of carbon capture and storage technologies, with geologic carbon sequestration emerging as a leading approach.

This method involves injecting CO₂ into deep geological formations, where it reacts with minerals to form stable carbonates, enabling long-term storage and significantly reducing greenhouse gas emissions.

Mafic and ultramafic rocks, such as basalt, are mainly suitable due to their high iron (Fe), calcium (Ca), and magnesium (Mg) concentrations, promoting rapid mineralization.

The Columbia River Basalt Group in the United States offers significant storage potential. However, a limited understanding of the structural composition and mineralization of carbonates formed during sequestration remains challenging.

Investigating the Mechanisms Behind Carbonation

The authors investigated carbonates recovered from the Wallula Carbon Storage Demonstration site in Washington State, where approximately 977 metric tons of supercritical CO₂ were injected into the Grand Ronde Basalt formation. Two years after injection, core samples were extracted to examine the mineralization outcomes.

The researchers focused on understanding the mineralogical evolution during carbonation, particularly the resulting carbonate phases' composition, structure, and formation conditions. They employed advanced analytical techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), and electron backscatter diffraction (EBSD), allowing for detailed characterization of the microstructure and nanoscale morphology of the formed carbonates.

Key Findings and Insights: Impacts of Injecting Carbon

The outcomes showed that carbonate nodules from the Wallula site contain distinct mineral phases, including ordered and disordered forms of ankerite and siderite. The study highlighted the importance of cation ordering in stabilizing these minerals, which influences predictions of long-term CO₂ storage in geological formations.

A key discovery was a previously unreported ordered ankerite phase formed at near-ambient temperatures (~40 °C) within two years of CO₂ injection, challenging the prevailing view that such structures require extended geological timescales.

The nodules exhibited compositional zonation, featuring a manganese-rich ankerite core and a calcium-rich siderite rim, emphasizing the role of cation availability during carbonation. Micro X-ray fluorescence and bulk compositional analyses confirmed four carbonate phases: manganese-bearing ankerite, calcium-rich ankerite, calcian siderite, and an ordered near-endmember ankerite.

The interiors of the nodules primarily consisted of Ca-manganese (Mn)-Fe carbonates with minimal magnesium, reflecting dynamic carbonation influenced by the local potential of hydrogen ion (pH), temperature, and cation concentrations.

The injection of supercritical CO₂ dissolved host rock minerals, releasing carbonate-forming cations such as Ca²⁺, Mg²⁺, Fe²⁺, and Mn²⁺ into pore fluids, promotes localized mineral growth.

Identifying a highly crystalline, manganese-stabilized, magnesium-free cation-ordered ankerite phase provides new insights into CO₂ mineralization thermodynamics and pathways.

Manganese-bearing ankerite phases constituted over 65% of the analyzed area, underscoring manganese's role in stabilizing the cation-ordered lattice. Additionally, the compositional zonation reflects evolving mineralogy influenced by competitive cation interactions and environmental conditions, indicating the complexity and potential of basalt formations for stable CO₂ storage. Overall, the authors demonstrated that carbonate mineral formation in basalt reservoirs can occur rapidly at relatively low temperatures, suggesting that effective long-term CO₂ sequestration is possible on much shorter timescales.

Practical Applications in Climate Mitigation

This research has significant implications for carbon management and climate change mitigation. It enhances understanding of mineralization pathways and factors influencing carbonate formation, providing insights to optimize carbon sequestration strategies.

The discovery of cation-ordered ankerite phases could improve predictive geochemical models and capacity estimates for CO₂ storage in basalt reservoirs. Given the global abundance of basalt, there is potential for large-scale carbon sequestration, supporting commercial-scale carbon capture technologies and reducing atmospheric CO₂ levels.

The findings inform the design of carbon storage projects by optimizing mineralization conditions and understanding the kinetics and thermodynamics crucial for monitoring. The study supports scalable greenhouse gas mitigation through efficient CO₂ mineralization in basalt, with conditions observed at the Wallula site potentially replicable elsewhere.

Paving the Way for Future Carbon Sequestration

This study enhances understanding of geologic CO₂ mineralization by identifying novel carbonate phases, including a unique cation-ordered ankerite that enables rapid formation in basalt reservoirs. These findings strengthen geochemical models and improve capacity estimates, helping the development of carbon storage technologies.

Leveraging natural mineralization processes in basalt formations supports strategies for reducing greenhouse gas emissions. Future work should examine carbonation mechanisms, environmental factors, and scalability to improve sequestration efforts further. Overall, these results underscore the potential of basalt reservoirs as scalable, sustainable solutions for climate change mitigation and provide a solid basis for future applications.

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