Immiscible fluids (CO2-brines) in optical fluorite, Nordvik-Taimyr, Russia

Fluid inclusion investigations in optical fluorite from the Nordvik salt dome caprock (Khatanga Gulf, Taimyr Peninsula, Russia) show that the fluorite has been formed at a temperature of about 300 degrees C, from CO2-brine immiscible hydrothermal fluids. Unmixing occurred at a depth of several kilometres, resulting in the liberation of dense CO2-rich fluids, which played a significant role in helping the diapir to reach its intrusive character. Compared to other optical fluorite deposits in Russia, the exceptional quality of the Nordvik occurrence is due to a relatively high formation temperature, as well as a high salinity (30-35 wt% NaCl eq.) of hydrothermal aqueous fluids.