The subsurface carbonation potential of basaltic rocks from the Jizan region of Southwest Saudi Arabia

The Jizan region of southwest Saudi Arabia contains large industrial point sources of CO₂ and potentially the capacity to dispose substantial quantities of this gas by the subsurface mineralization of local basaltic rocks. Significant volumes of basaltic magma were erupted within an Oligo-Miocene continental rift valley that preceded the formation of the Red Sea. These igneous rocks consist of lava flows and volcaniclastics intruded by dikes and shallow plutons. The volcanic rocks are densely fractured and variably altered to chlorite-epidote-calcite assemblages. Dissolution rate measurements performed at 25 °C of four variably altered basaltic rock samples from the region demonstrate their ability to increase fluid pH and liberate substantial Ca and Mg to the fluid phase. Reaction path calculations suggest that CO₂-charged water will readily carbonate when interacting with the basaltic rocks at both 25 and 100 °C. Reactive transport calculations, however, suggest that while such carbonation reactions will be slow at 25 °C, these would fix more than 95% of injected water-dissolved CO₂ within five years at 100 °C. Monte Carlo estimates suggest that the total CO₂ mineralization capacity of the Oligocene basaltic rocks is ∼4.2 Gt CO₂, which is sufficient to store all of the carbon emissions from the Jizan region industrial facilities for in excess of one hundred years. Taken together, the results of this study indicate the likely success of large-scale subsurface carbon storage efforts through the subsurface carbonation of basaltic rocks in the Jizan region.