摘要：AbstractThe fluid inclusions in mantle rocks and melt indicated that a large amount of CO2fluid exists in the deep earth, which is of great significance for understanding the deep carbon cycle and the composition of mantle. However, it was also suggested that carbonate minerals were likely to be the main host of mantle carbon. At the same time, the distribution and behavior of carbon in the mantle still remain a puzzle. In this paper, the adsorption behavior and occurrence characteristics of supercritical CO2in magnesite (MgCO3) pores were studied by the Grand Canonical Monte Carlo method (GCMC) under the different conditions of CO2pressures (0–100 MPa), temperatures (350–1500 K) and the pore sizes (7.5–30 Å). The simulated results showed that the adsorption of CO2in magnesite was a physical adsorption, which was mainly controlled by the intermolecular force. The gas adsorption became more stable when the adsorption site shifted from the high energy site to the low energy site with increasing pressure (P) and decreasing temperature (T) and pore size. At the same time, the variations of excess adsorption amounts of CO2in the pores of magnesite (Nexcess) under the different conditions were quantitatively calculated. It was found that the Nexcessdecreased with increasing T, but increased with increasing P and pore size. The results favor understanding the CO2migration, seismic precursor observations, and heat transfer process in the deep earth.Graphical abstractDisplay OmittedHighlights•Simulation proved adsorption of CO2 in magnesite is a physical adsorption and mainly controlled by intermolecular forces.•CO2 adsorption in magnesite pore became more stable with increasing pressure and decreasing temperature and pore size.•The smaller pores of magnesite have a stronger adsorption for CO2 than that bigger size ones.•Excess adsorption amounts of CO2 in magnesite pore decrease with increasing T, but increase with increasing P and pore size.
