The effect of pressure, temperature and oxygen fugacity on the stability of subducted carbonates and implications for the deep carbon cycle
Final Report Abstract
We investigated the stability of iron carbonate at high pressure and high temperature using a laserheated diamond anvil cell combined with single crystal X-ray diffraction and Mössbauer spectroscopy (both applied in house and at synchrotrons) as well as Raman and X-ray Absorption. Near Edge Structure spectroscopies. Spin crossover in powder FeCO3 takes place over a broad pressure range (40-47 GPa) during compression at room temperature, while the transition in single crystals is relatively sharp (43-45 GPa), likely due to varying degrees of differential stress. At higher temperatures (> 1800 K), FeCO3 dissociates into diamond and iron oxides. At higher pressures (> 70 GPa), FeCO3 forms new high-pressure carbonates, Fe4C3O12 up to ~ 2200 K, and Fe4C4O13 at higher temperatures. The latter phase is stable at conditions along the entire geotherm to depths of at least 2,500 km, thus demonstrating that self-oxidation-reduction reactions can preserve carbonates in the Earth’s lower mantle. Our results have been reported in the following media channels: http://www.esrf.eu/home/news/general/content-news/general/scientists-shed-light-on-carbonsdescent-into-the-deep-earth.html https://deepcarbon.net/feature/stable-iron-carbonates-survive-journey-earth%E2%80%99sinterior#.WXDoMISGPmE http://www.uni-bayreuth.de/de/universitaet/presse/pressemitteilungen/2017/099-Kohlenstoffkreislauf/index.html
Publications
- (2015) Spectroscopic study of siderite (FeCO3) to Earth’s lower mantle pressures. Amer Mineral 100: 2670-2681
Cerantola V, McCammon C, Kupenko I, Kantor IY, Marini C, Ismailova L, Wilke M, Solopova N, Chumakov A, Pascarelli S, Dubrovinsky LS
(See online at https://doi.org/10.2138/am-2015-5319) - (2017) Stability of iron-bearing carbonates in the deep Earth's interior. Nature Communications 8:15960
Cerantola V, Bykova E, Kupenko I, Merlini M, Ismailova L, McCammon C, Bykov M, Chumakov A, Petitgirard S, Kantor I, Svitlyk V, Jacobs J, Prescher C, Rüffer R, Dubrovinsky L
(See online at https://doi.org/10.1038/ncomms15960)
