Basaltic aquifers have the potential to provide secure option for CO
2 sequestration. Because basaltic rocks are widely distributed around the world, their capacity for storage of anthropogenic CO
2 emissions is enormous. In addition, geochemical trapping of CO
2 injected into basaltic aquifers occurs quickly, because basaltic rocks contain many cations that react with CO
2 to form stable carbonate minerals. Two types of large-scale basaltic aquifers may be suitable for sequestering huge amounts of anthropogenic CO
2: continental flood basalt aquifers and deep-sea basalt aquifers. Here, we assess the potential of these two CO
2 sequestration options from geological, geochemical and social-scientific perspectives. From a geological and geochemical viewpoint, both continental flood basalt and deep-sea basalt aquifers have excellent CO
2 storage potential. In deep-sea basalt aquifers, however, storage of injected CO
2 may be more secure than in continental flood basalt aquifers, because leakage of CO
2 to the atmosphere is minimized by geological, geochemical and physical barriers associated with the deep-sea environment. In addition, from a social-scientific point of view, several current CO
2 injection projects in continental flood basalts have encountered problems due to groundwater depletion, and large-scale implementation of CO
2 storage in continental flood basalt aquifers might cause contamination of freshwater resources needed for domestic and agricultural use. In striking contrast to continental flood basalts, deep-sea basalts can be used for CO
2 storage without encountering critical problems, because deep-sea basalt aquifers have no economic value. We conclude, therefore, that deep-sea basalt aquifers are a better option for CO
2 storage than continental flood basalt aquifers.
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