Raw data of manuscript Miscible saline–silicic fluids prior to the growth of fibrous diamonds from DRC
Description
SiO2 and Cl-rich HDFs with compositions along the saline–silicic series were identified precisely at the diamond core–coat boundaries of coated diamonds from the Democratic Republic of the Congo (DRC) in this study. HDFs in these diamonds show consistent transition from intermediate saline–silicic compositions at the boundary, to more silicic ones in the inner dark layer, and then to more carbonatitic ones in the outer gray layer. Nitrogen-aggregation thermochronology, combined with diamond–inclusion isomekes and orthopyroxene thermobarometries, yields P–T ranges of 4.9–6.6 GPa and 1059–1198 ℃ for the cores, and 4.1–6.5 GPa and 970–1020 ℃ for the coats and included HDFs, which correspond respectively to the higher and lower parts of the P–T range for octahedral diamonds from DRC. Compositional characters of these HDFs and diamond growth features of corresponding positions indicate that the evolution spanning nearly the whole spectrum of saline–silicic–carbonatitic compositions and the growth of fibrous diamonds are controlled by source H2O/CO2 ratios. Miscible saline–silicic fluids are possible to form in the mantle under high source H2O/CO2 ratios, which are not conducive to diamond crystallization. This study validates the miscibility between saline and silicic fluids and connects the evolution of HDFs with the crystallization of fibrous diamonds.