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Contribution

X-ray structural analysis

Stability of hydrous silicates and carbonates as a part of H2O and CO2 cycle in deep Earth: the high-pressure diffraction studies

Speakers

  • Dr. Anna LIKHACHEVA

Primary authors

  • Dr. Anna LIKHACHEVA (Sobolev Institute of geology and Mineralogy SibD RAS)
  • Dr. Sergey RASHCHENKO (1V.S. Sobolev Institute of Geology and Mineralogy SD RAS, Novosibirsk, 2G.I. Budker Institute of Nuclear Physics SD RAS, Novosibirsk, 3Novosibirsk State University, Novosibirsk)
  • Dr. Sergey GORYAINOV (V.S. Sobolev Institute of Geology and Mineralogy SD RAS, Novosibirsk)
  • Mr. Alexander ROMANENKO (1V.S. Sobolev Institute of Geology and Mineralogy SD RAS, Novosibirsk, 3Novosibirsk State University, Novosibirsk)

Co-authors

  • Prof. Andrey KORSAKOV (1V.S. Sobolev Institute of Geology and Mineralogy SD RAS, Novosibirsk, 3Novosibirsk State University, Novosibirsk)
  • Dr. Sergey DEMENTIEV (1V.S. Sobolev Institute of Geology and Mineralogy SD RAS, Novosibirsk)
  • Dr. Aleksey ANCHAROV (2G.I. Budker Institute of Nuclear Physics SD RAS, Novosibirsk, 4Institute of Solid State Chemistry SD RAS, Novosibirsk)

Content

The global cycle of major volatiles such as H2O and CO2 remains among the key topics of modern petrology. In particular, active interest is taken in water recycling associated with subduction of oceanic plates into the mantle. Mineral serpentine, Mg3Si2O5(OH)4, is shown to be the main water reservoir in oceanic litosphere [1], and therefore its dehydration produces a large impact onto seismic activity and magma generation in subduction zones. Since the dehydration temperature can be effectively decreased in the presence of alkali chlorides [2], we aim to estimate this effect for serpentine dehydration. Here we characterize the decomposition of serpentine in the reference salt-free system, based on in-situ HP-HT diffraction (SSTRC, Novosibirsk) and Raman spectroscopic studies in diamond anvil cell. The global carbon cycle includes, besides outer shells of the Earth, large-scale reservoirs of the Earth’s mantle and core. Earlier the transport of oxidized carbon into the mantle was considered solely within the system CaCO3-MgCO3-FeCO3. Recent findings of Na-Ca carbonates in deep-seated rocks and experiments suggest the participation of these compounds in the formation of deep sodium carbonatite melts and makes them important objects of modern geochemistry. We report on the compressibility of some of the natural (mineral shortite) and synthetic (nyererite) Na-Ca carbonates up to 100-120 kbar as the first step of determination of their PVT equations of state. This work is supported by the state assignment project (0330-2016-0004), Russian Foundation for Basic Research (grant No 18-05-00312) and the Ministry of Education and Science of Russian Federation (project RFMEFI62117X0012). [1] Rüpke et al. (2004) Earth and Planetary Science Letters, 223(1), 17-34. [2] Aranovich and Newton (1997) Contributions to Mineralogy and Petrology, 125(2), 200-212.