- Names
-
- Sergey Goryainov
- Alexander Krylov
- Ulyana Borodina
- Anna Likhacheva
- Svetlana Krylova
- Yurii Seryotkin
- Nikita Bogdanov
- Alexander Vtyurin
- Svetlana Grishina
- Title
- Raman study of decomposition of Na-bearing carbonates in water fluid at high P\textendashT parameters
- Abstract
- The study of Na-carbonates stability and their transformations in aqueous carbonate fluid under high P\textendashT conditions is relevant from the point of view of the understanding geochemical processes of the Na-assisted carbon circulation in the Earth's crust and subduction zones. In situ Raman study of Na-bearing carbonate-water-Fe-metal system in diamond anvil cell (DAC) at high P\textendashT conditions revealed that carbonates decompose with abiogenic formation of formates and other organic compounds that differs from behavior of carbonates in dry system. XRD and FTIR methods have been used additionally to determine the phase composition. Na-bearing carbonates (nahcolite $NaHCO_3$, shortite $Na_2Ca_2(CO_3)_3$ and cancrinite $Na_7Ca[(CO_3)_{1.5}Al_6Si_6O_{24}].2H_2O$) in aqueous fluid decompose to form simple carbonates and formates (as dominant organic molecules) at moderate P-T parameters (above $\sim$0.2 GPa, 200°C). Our experimental results directly confirm the hypothesis of Horita and Berndt (Science, 1999) about possible yield of organic formates in the carbonate-water-metal system. Nahcolite $NaHCO_3$ in aqueous fluid in the presence of Fe metal decomposes into anhydrous phases: natrite $γ-Na_2CO_3$, siderite, magnetite (due to dissolution of Fe steel gasket), Na-formate and likely organic molecular crystalline solvate of Na-formate and methyl formate. Shortite decays into anhydrous phases: aragonite CaCO3, Na-Ca-formates and an amorphous phase. Cancrinite decomposes to unidentified carbonate-alumonosilicate phases, Na-Ca-formates and unknown organic molecular crystal. Magnetite is also formed in this system due to dissolution of Fe steel gasket used in DAC. The present study provides a new insight in processes of abiogenic formation of organic matter from carbonates in the crust and upper mantle.
- Keywords
- spectroscopy, Raman spectroscopy, FIR, MIR, band position, High pressure, High temperature, aqueous fluid, organics formation, Organic formates, Organic molecular crystals, minerals, carbonate, nahcolite, shortite, cancrinite, magnetite, siderite, natrite, NaHCO3, Na2Ca2(CO3)3, Na7Ca[(CO3)1.5Al6Si6O24].2H2O, Fe3O4, FeCO3, Na2CO3
- Content
- spectral data, experimental physics, chemistry
- Year
- 2024
- Journal
- Spectrochimica Acta, Part A
- Volume
- 322
- Pages
- 124801
- Pages number
- 12
- Document type
- article
- Publication state
- published
- Doi
- 10.1016/j.saa.2024.124801
- Identifiers
-
- bibcode: 2024AcSpA.32224801G