Dynamical Immiscibility of Aqueous Carbonate Fluid in the Shortite-Water System at High-Pressure-Temperature Conditions

Anhydrous carbonate shortite, Na2Ca2(CO3)3, compressed in water at high pressure–temperature (up to 5 GPa, 350 °C) was studied by Raman spectroscopy. At 3.2 GPa and 250 °C, shortite begins to dissolve, followed by crystallization of aragonite and aragonite’. The unusual behavior of aqueous carbonate fluid was observed at 4.8 GPa and 300–350 °C. This process is characterized by the active formation of microbubbles within 2–60 s that are inserted one into another. Microbubbles are considered to be a result of the two immiscible fluid stratification. This dynamical immiscibility of the fluid accompanies the appearance of several crystalline carbonates and organic molecular crystals. Na-formate and some polymorphs of Ca-formate were observed.

https://doi.org/10.1021/acs.jpcc.1c05077