Calcium silicate-diorthocarbonate is a missing link in deep-mantle chemistry of silicates and carbonates.
basic_science · Level V
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- Record sourced from PubMed, PMID 42697902.
- Also identified by DOI 10.1038/s41467-026-77204-w.
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Abstract
Interactions between carbonates and silicates play a central role in many industrial and planetary processes. Although current knowledge is largely limited to silicate-carbonate exchange mechanisms, high-pressure compounds incorporating both carbonate and silicate units have long been anticipated. Here we report the synthesis of the high-pressure silicate-diorthocarbonate CaSiC<sub>2</sub>O<sub>7</sub> at 122(2) GPa and 2800(200) K. CaSiC<sub>2</sub>O<sub>7</sub> is based on the framework of vertex-sharing SiO<sub>6</sub> octahedra and CO<sub>4</sub> tetrahedra. Ab initio calculations are consistent with the experimental results and indicate dynamical and mechanical stability of this phase over a wide pressure range. These findings reveal an additional pathway for carbonate-silicate interaction in carbonate-rich deep-mantle environments. CaSiC<sub>2</sub>O<sub>7</sub> has a density lower than that of major mantle minerals and exhibits comparatively low acoustic velocities, suggesting that silicate-carbonates may contribute to seismic anomalies near the core-mantle boundary.