Figure 5
Diagram of δ18O versus Δ18ODol-Cc in dolomite for calcitic and dolomitic carbonatite dykes and ore bodies of the Bayan Obo deposit.
The “positive correlation” between Δ18ODol-Cc and δ18O in dolomite and lack of correlation in calcite (Supplementary Fig. S4) indicates that the oxygen isotope disequilibrium between dolomite and calcite is controlled by dolomite. The lowest δ18O in dolomite is much lower than the mantle value, the most likely candidate for which is subduction released fluids. Also shown is a bar illustrating the equilibrium Δ18ODol-Cc at temperatures between 200 and 480°C60.
