Genesis of Diamond in Metal–Carbon and Metal–Sulfur–Carbon Melts: Evidence from Experimental Data

The experimental data on diamond growth in the Fe–Ni–S–C and Fe–S–C systems with a sulfur content of 5–14 wt % at 5.5 GPa and 1300–1350°C are reported. Colorless and light yellow diamond crystals with a weight of 0.1–0.8 ct were synthesized. It is shown in the Fe–S–C system that at 5.5. GPa diamond may crystallize in a very narrow temperature range, from 1300 to 1370°C. Based on comparative analysis of the experimental data and the results of the study of native iron inclusions in natural diamonds from kimberlite pipes, it is suggested that diamond genesis may be partly controlled by the pre-eutectic (by the concentration of sulfur in relation to metal) metal–sulfide melt.