Natural diamond formation by self-redox of ferromagnesian carbonate

Abstract

Significance The presence of extra reducer was thought to be essential for producing natural diamonds from reduction of carbonates. The present study of the Xiuyan meteoritic crater, however, finds natural diamond formation via a subsolidus self-redox of a ferromagnesian carbonate during shock compression to 25–45 GPa and 800–900 °C without melting, fluid, and another reductant. The ability of carbonate to produce diamond by itself implies that diamond would be a very common mineral in the lower mantle where the carbonates are abundant and pressures and temperatures are sufficiently high.