CO3+1 network formation in ultra-high pressure carbonate liquids
2019
Carbonate liquids are an important class of molten salts, not just for industrial applications,
but also in geological processes. Carbonates are generally expected to be simple liquids, in terms of
ionic interactions between the molecular carbonate anions and metal cations, and therefore relatively
structureless compared to more \polymerized" silicate melts. But there is increasing evidence from
phase relations, metal solubility, glass spectroscopy and simulations to suggest the emergence of
carbonate \networks" at length scales longer than the component molecular anions. The stability
of these emergent structures are known to be sensitive to temperature, but are also predicted to be
favoured by pressure. This is important as a recent study suggests that subducted surface carbonate
may melt near the Earth's transition zone (�440 km), representing a barrier to the deep carbon
cycle depending on the buoyancy and viscosity of these liquids. In this study we demonstrate
a major advance in our understanding of carbonate liquids by combining simulations and high
pressure measurements on a carbonate glass, (K2CO3-MgCO3) to pressures in excess of 40 GPa, far
higher than any previous in situ study. We show the clear formation of extended low-dimensional
carbonate networks of close CO2
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