TY  - JOUR
A1  - Petitgirard, Sylvian
A1  - Sahle, C. J.
A1  - Weis, C.
A1  - Gilmore, K.
A1  - Spiekermann, Georg
A1  - Tse, J. S.
A1  - Wilke, Max
A1  - Cavallari, C.
A1  - Cerantola, V
A1  - Sternemann, Christian
T1  - Magma properties at deep Earth’s conditions from electronic structure of silica
JF  - Geochemical perspectives letters
N2  - SiO(2 )is the main component of silicate melts and thus controls their network structure and physical properties. The compressibility and viscosities of melts at depth are governed by their short range atomic and electronic structure. We measured the O K-edge and the Si L-2,L-3-edge in silica up to 110 GPa using X-ray Raman scattering spectroscopy, and found a striking match to calculated spectra based on structures from molecular dynamic simulations. Between 20 and 27 GPa, Si-[4] species are converted into a mixture of Si-[5] and Si-[6] species and between 60 and 70 GPa, Si-[6] becomes dominant at the expense of Si-[5] with no further increase up to at least 110 GPa. Coordination higher than 6 is only reached beyond 140 GPa, corroborating results from Brillouin scattering. Network modifying elements in silicate melts may shift this change in coordination to lower pressures and thus magmas could be denser than residual solids at the depth of the core-mantle boundary.
Y1  - 2019
U6  - https://doi.org/10.7185/geochemlet.1902
SN  - 2410-339X
SN  - 2410-3403
VL  - 9
SP  - 32
EP  - 37
PB  - Association of Geochemistry
CY  - Paris
ER  -