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. Monte Carlo estimates suggest that the total CO2 mineralization capacity of the mafic igneous rocks in the Jizan area is ~4.2 Gt CO2, which is sufficient to store all of the carbon emissions from the local industrial facilities for four hundred years. Significant volumes of basalt were erupted in the region during the late Oligocene in a continental rift before the opening of the Red Sea. These rocks consist of lava flows and volcaniclastics intruded by dikes and shallow plutons. They are densely fractured and variably altered to chlorite-epidote-calcite assemblages. Dissolution rate measurements performed at 25 oC of four variably altered basaltic rocks 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 water charged CO2 will readily carbonate when interacting with the basaltic rocks at both 25 and 100 oC. Reactive transport calculations, however, suggest that while such carbonation reactions will be slow at 25 oC, these would fix more than 95% of injected water-dissolved CO2 within five years at 100 oC. 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