Fluid migration in calcite nanopores under salinity gradients: Insights from molecular dynamics

Abstract

The migration mechanisms of ore-forming fluids have long been a focus in the field of ore deposit studies. Calcite is ubiquitously present in various types of rocks in the lithosphere, and the underlying mechanisms of its influence on fluid migration are of crucial importance. While previous studies have revealed that salinity changes can modulate fluid migration, the underlying mechanisms remain poorly understood. We employ molecular dynamics simulations to elucidate how salinity variations in ore-forming fluids modulate the adsorption onto calcite nanopore walls, thereby revealing the microscopic mechanisms governing ore fluid transport through calcite nano-fractures. The results show that the adsorption energy E_int of the solution on the calcite surface increased from −14,948.84 ± 182.48 kcal/mol to −12,144.08 ± 118.2 kcal/mol as salinity increased, which is conducive to the long-range transport of the fluid in the calcite nanopore.