Anhydrous carbonate shortite compressed in the aqueous fluid at high P-T (up to 5 GPa, 350°C) was studied with in situ Raman spectroscopy. The DFT was used to calculate the lattice dynamics and interpret the vibrational spectra. The shortite Raman bands are broadening with pressure and temperature, and signal are decreasing that is caused by gradual structure amorphisation accompanied by an orientational disordering of CO$_3$ triangle units. Despite the aqueous medium presence at high temperature and pressure, shortite did not go hydrated. At 3.2 GPa and 250°C, shortite begins to dissolve followed by crystallisation of aragonite and aragonite’ . A remnant part of shortite crystals was presented in the ex-situ sample. The transition of shortite to aragonite’ was monitored by in situ Raman spectra in the C-O stretching range: strong doublet transforms into singlet at ~4 GPa, 250°C. Additionally, the phases X-phase is characterised by strongest narrow 1358 cm^-1 band. X₁- and X₂-phases are expected to represent organic materials are the most believable Na-formate and some polymorphs of Ca-formate.
The unusual behaviour of aqueous carbonate fluid was observed at 4.8 GPa and 300-350°C. This process is characterised by the active formation of micro-bubbles that are inserted one into another. The existence time of the micro-bubbles is varied within 2-60 seconds. Micro-bubbles are considered to be a result of the two immiscible fluids stratification. This unusual dynamical immiscibility of the fluid promotes the appearance of several crystalline carbonates and organic molecular crystals.