Summary:
Natural carbonation of ultramafic rocks in Oman occurred during shallow crustal extension rather than deep subduction processes, according to research published in Geological Society of America Bulletin. The study focuses on listwaenite, a rock formed when carbon-rich fluids react with ultramafic mantle rocks, effectively locking carbon into solid minerals.
Researchers mapped about 200 km² of terrain in the Fanja area of the Eastern Oman Mountains at a detailed scale of 1:10,000 to examine how this transformation occurred within the Samail Ophiolite. Their results show that brittle faulting in the upper crust created pathways that allowed carbon-bearing fluids to circulate through reactive ultramafic rocks.
The team identified two generations of listwaenite. The older formed along low-angle normal faults that overprinted earlier thrust structures after the ophiolite was emplaced. A younger generation developed later along steep extensional and strike-slip faults associated with regional tectonic activity and uplift.
These findings suggest that large-scale natural carbonation in the region developed during periods of crustal stretching. The work also highlights the role of fault systems in enabling fluid flow and mineral reactions, offering a natural example of long-term carbon storage in rocks.
— Press Release —
New Insights into natural carbonation of ultramafic rocks in the Sultanate of Oman
New research published in the GSA Bulletin reveals how fluids naturally carbonate ultramafic rocks formed within Oman’s Samail Ophiolite, providing new insight into tectonic processes and natural carbon sequestration.
The study focuses on listwaenite, a carbonate-altered ultramafic rock formed when carbon-bearing fluids react with mantle rocks. Through detailed geological mapping in the Fanja area of the Eastern Oman Mountains (including a detailed geological map at a scale of 1:10,000), researchers examined the structural controls that enabled large-scale carbonation.
Results show that carbonation occurred during shallow crustal extension, when brittle faulting created pathways for carbon-rich fluids to circulate through ultramafic rocks. This finding challenges earlier interpretations that linked these rocks primarily to deep subduction environments.
The team identified two generations of listwaenite. The older generation formed along low-angle normal faults that overprinted earlier thrust structures, while the younger generation developed along later steep-dipping extensional and strike-slip faults. These structures reflect a complex tectonic history involving post-obduction extension, plate interactions, and regional uplift.
Beyond reconstructing Oman’s geological evolution, the study highlights the importance of fault systems in facilitating mineral carbonation. Naturally carbonated ultramafic rocks provide a valuable natural analogue for long-term carbon storage in solid minerals, offering insights relevant to future geological carbon sequestration strategies.
The findings underscore the role of tectonics in controlling fluid flow and mineral transformation within Earth’s crust.
Journal Reference:
Andreas Scharf, Ivan Callegari, Christopher M. Bailey, Frank Mattern, Thomas Zack, Reuben Hansman, Muhammed Qasim, Uwe Ring, ‘Tectonic setting of naturally carbonated ultramafic rocks from the Samail Ophiolite (Sultanate of Oman)’, GSA Bulletin 138 (1-2): 232–252 (2025). DOI: 10.1130/B38384.1
Article Source:
Press Release/Material by Ruqaiah AlAraimi | Sultan Qaboos University
Featured image credit: Dr. Andreas Scharf
