EXPERIMENTS OF CO2- BASALT- LIQUID INTERACTIONS AND GEOCHEMICAL MODELS: IMPLICATIONS FOR CO2 MINERALIZATION IN BASALTS

Abstract

The rising amount of CO₂ in the atmosphere increased the average temperature of the Earth. The UN made the Paris Agreement in 2015 to significantly mitigate greenhouse gas (GHG) emissions and to try to limit the average global temperature increase to 2°C by the end of the current century. CO₂ constitutes a significant part of the GHG, and carbon capture and storage (CCS) is one of the most promising techniques to achieve these prefixed targets. Several previous studies focused on carbonation of natural sedimentary, mafic and ultramafic rocks, while detailed experimental studies on natural basalts systems are rare in the literature. Here, we carried out a detailed study on interactions between CO₂, liquid and alkali basalts from a young continental lava field in south Saudi Arabia (Al-Birk) coupling scanning electron microscopy (SEM), X‑ray diffraction (XRD), X-ray fluorescence (XRF), Fourier‑transform infrared spectroscopy (FTIR), and Raman spectroscopy. In parallel, liquid products were analyzed via inductively coupled plasma–optical emission spectrometry (ICP‑OES). Laboratory experiments such as ageing tests were carried out through CO₂ injection in grinded basalts to unravel chemical reactions occurring during precipitation/dissolution processes at P-T-X. Eight ageing tests were carried out to evaluate the effects of different parameters on the precipitation of carbonates which are experiment time and fluid sampling method. Experimental observations were tested with geochemical modeling that was used to evaluate carbonate saturation and mineral stability under the investigated conditions. The absence of measurable carbonate precipitation under the investigated experimental conditions indicates that reaction time up to 552 h was insufficient to induce detectable mineral carbonation. Nonetheless, mineral dissolution was observed throughout the experiments, indicating ongoing interaction between CO₂-basalt-liquid and the release of divalent cations. Although these processes did not result in detectable carbonate formation, these findings highlight the importance of the initial alteration state and initial mineralogical composition of basalt in controlling dissolution pathways and the potential for subsequent CO₂ mineralization.