Fig. 5: The Fe³⁺ atomic number (p.f.u.) variation in major silicates of carbonated eclogites.

All garnets and omphacites (or clinopyroxenes) were collected from carbonate-bearing eclogites, including the field survey (natural carbonated eclogites)^{30,31,34,40,47,67,74,75,76}, laboratory simulation experiments (SLEC, EC1, GA1cc, and ATCM1 see Supplementary Table 2)^{43,44,45,46,48}, this study experiments, and garnet-carbonate reaction experiments¹⁵, and then their chemical composition were recalculated (Supplementary Data 2). a Fe²⁺ versus Fe³⁺ in garnet (Grt) of carbonated eclogites. The Fe³⁺ atomic number (p.f.u.) of the grain core, grain mantle, and grain rim of garnets from natural carbonated eclogites in the southwestern Tianshan UHP belt, NW China^{30,31,40,47,67}, the Dabie-Sulu UHPM belt, E China^74,75,76, and the UHPM of Tso-Morari Region, India³⁴ are tracked with black arrows. Using red and pink arrows direct the Fe³⁺ atomic number (p.f.u.) of garnet’s core (initial garnets) and garnet’s rim (garnets reacted with carbonates) in this study and Dasgupta et al.^43,48, respectively. The Fe³⁺ atomic number (p.f.u.) of garnets in other high-temperature and high-pressure simulation experiments serves only as the reference^44,45,46. b Fe²⁺ versus Fe³⁺ in omphacite (Omp or Cpx) of carbonated eclogites. The blue arrow indicate the Fe³⁺ atomic number (p.f.u.) range in the omphacite of carbonated eclogites. The Fe³⁺/ΣFe ratios range is labeled at a specific Fe²⁺ atomic number in garnets and omphacites of carbonated eclogites when the Fe³⁺ atomic number is 0.3.