Experimental modeling of diamond dissolution in kimberlite within crustal cumulative centers

The main stages within the chemically active history of diamond genesis are proposed, from the upper-mantle chambers to the explosive ejections of diamonds and kimberlite material from cumulative centers to the surface. The paper focuses on the pre-final episode of diamond deposit genesis – the interaction of diamonds with carbonate-silicate kimberlite magmas in a crustal cumulate chamber. Such interactions are possible when the transport of diamonds by these magmas from the depths of the mantle primary chambers to the surface is stopped within crustal rock complexes with a strong roof. The cooling and solidification time of kimberlite melts in such cumulative centers is long enough to cause a significant mass loss of dissolving diamonds. The interaction of carbonate-silicate kimberlite melts with varying carbonate content with natural single-crystal diamonds was studied experimentally at a pressure of 0.15 GPa and a temperature of 1200 °C. Model carbonate, carbonate-fluid, natural kimberlite, and kimberlite-fluid systems were used as solvents. At experimental conditions, the solvents melted, and diamond crystals surface were underwent by dissolution. It was established that etching patterns are recorded on the growth planes, and diamonds lose mass: from 3-4.5 % after 2-hour exposure (the order of kimberlite transport time from the upper-mantle diamond-forming centers to the crustal cumulative centers) to 47.6 % after 10-day exposure (at the crustal cumulative center conditions). The results demonstrate that the dissolving ability of carbonate-silicate transport magmas is a factor that effectively reduces the diamond potential of kimberlite deposits.