The first occurrence of metamorphic diamond.
UHP dolomite marbles and pelitic gneisses (subduction zone : 250 km deep).
Three types of marbles are known : diamond-bearing dolomite marbles, Ti-clinohumite-bearing dolomitic marbles and titanite-bearing calcite marbles.
Presence of lamproites.
In pelitic gneisses, diamonds formed from carbon dissolved into aqueous fluids.
In marbles, diamond precipitated from fluids (C-O-H).
