Home – Home – Jornals – Russian Geology and Geophysics 2018 number Неопубликованное

The first experimental data on the relationship between the carbon dioxide content in minerals of the lazurite-type minerals (LTM) and its partial pressure in the gas phase and temperature in the range corresponding to the lazurite formation process at deposits in the Southern Baikal region have been obtained. The content of structural CO₂ species was determined by IR- Fourier spectroscopy. It depends more on temperature than on the partial pressure of CO₂ and is maximum for cubic lazurites at 500 °C (0.05-0.07 formula units, f.u.), decreasing to 0.01-0.03 f.u. both when the temperature decreases (460 °C) and when it increases (560 °C). A positive dependence of CO₂ content on O₂ fugacity in the system has been noted. LTM with an orthorhombic structure (vladimirivanovite) retains CO₂ less effectively, with its content decreasing from the initial (natural) 0.08 to 0.01-0.02 f.u. in the specified temperature range of 460-560 °C. The experiments with exposure at 560 ^oC and subsequent cooling to 460 or 360 ^oC show the lack of retrograde CO₂ solubility in LTM under saturation from gas phase. According to data on CO₂ content, cubic lazurites with incommensurate 3D modulation of the structure could have formed at a temperature of about 500 °C, a partial CO₂ pressure of ~1.4-2.2 bar, and fO₂ at the level of the magnetite-hematite buffer. The high CO₂ contents (0.15-0.3 f.u.) recorded in some LTMs may not be related to the direct absorption of CO₂ from the gas (fluid) phase, but are the product of relatively low-temperature (<400 °C) transformations of carbon forms, leading to the association of CO₂ and molecular forms of sulphur. This temperature range and the fugacity of volatile compounds corresponding to such forms of sulphur should be considered as possible conditions for the synthesis or modification of materials based on sodalite, nosaean and LTMs, which are promising as carbon dioxide absorbers or indicators.