Old Tool, New Purpose: Rock-Eval Analysis for CO₂ Mineralization Screening in Basalts

Rock-Eval (RE) analysis has conventionally been employed as a standard and rapid screening technique in the O&G sector to assess the properties of source rocks. The method relies on thermal decomposition of samples through two heating steps (pyrolysis and combustion), during which released gases (CO, CO₂, HCs, and SO₂) are continuously detected by specific sensors. This study evaluated the applicability of RE as a screening tool for assessing CO₂ conversion into carbonates in the context of carbon mineralization in basalts. For this purpose, after developing a two-step experiment (dissolution and precipitation) using powdered basalt from the Serra Geral Group (Paraná–Etendeka Large Igneous Province), a fraction of the samples was analyzed with the RE instrument to evaluate the CO₂ release profile during heating from 300 °C to 850 °C. The analysis revealed a pattern that is characteristic of carbonates, with decomposition peaks above 650 °C. The amount formed during the experiments was quantified by converting the CO₂ peak into an equivalent calcite mass. This conversion was based on a calibration curve established from known quantities of pure calcite added to a basaltic matrix, allowing for the correlation of the CO₂ signal intensity to the carbonate content. Calculations confirmed that the estimated values were consistent with the CO₂ release observed in the RE profiles. Based on signal intensity, the experimental samples were classified into three groups: G1, with low values (< 500 mV); G2, with moderate values (500–3000 mV); and G3, characterized by high values (> 3000 mV). To complete the workflow, SEM/EDS analyses provided visual confirmation of the carbonate precipitates indicated by RE. The results demonstrate that this approach is a rapid and effective tool for detecting and quantifying mineralized CO₂ in basaltic rocks.