Greenhills Dunite Subsurface Reaction Kinetics in a Global Mafic-Ultramafic Context

Area of Science:

• Geochemistry
• Mineralogy
• Environmental Science

Background:

• Growing need for carbon emission reduction drives development of carbon storage technologies.
• In situ carbon storage via mineralization in mafic and ultramafic rocks is a promising abatement strategy.
• Limited field-scale studies exist for ultramafic rock carbonation compared to basaltic reservoirs.

Purpose of the Study:

• Evaluate the potential of Greenhills Dunite in New Zealand for in situ carbon storage via mineralization.
• Investigate the carbonation extent and reaction products under simulated subsurface conditions.
• Compare the reaction kinetics with existing data for other mafic-ultramafic rocks.

Main Methods:

• Experimental matrix of batch reactions at subsurface temperatures and pressures.
• 10-day high-pressure in situ X-ray diffraction experiment.
• Comparative analysis with literature data on mafic and ultramafic rock carbonation.

Main Results:

• High carbonation extent observed across various conditions and size fractions of Greenhills Dunite.
• Reaction products primarily magnesite with evidence of iron incorporation.
• Brucite carbonation is rapid, followed by slower olivine carbonation kinetics.

Conclusions:

• Greenhills Dunite shows significant potential for field-scale in situ carbon mineralization.
• The findings support the broader application of mafic-ultramafic rocks for global CO2 storage.
• Further research into reaction kinetics can optimize deployment strategies.