Diamond nucleation and growth in sulfide-carbon melts; an experimental study at 6.0-7.1 GPa
Diamond nucleation and growth in sulfide-carbon melts; an experimental study at 6.0-7.1 GPa (in Diamonds, Makoto Arima (editor), Ben Harte (editor) and Nikolay V. Sobolev (editor))
European Journal of Mineralogy (June 2008) 20 (3): 349-355
- boundary conditions
- carbon
- carbonatites
- crystal growth
- crystallization
- diamond
- experimental studies
- genesis
- graphite
- growth rates
- high pressure
- igneous rocks
- melts
- native elements
- nucleation
- P-T conditions
- phase equilibria
- polycrystalline materials
- pressure
- pyrrhotite
- solvents
- sulfides
- sulfide melts
Experimental study of diamond nucleation and growth in pyrrhotite-carbon melts was carried out at 6.0-7.1 GPa. The PT -diagram of diamond crystallization was constructed, and we found that the PT boundary conditions of diamond formation are limited by the diamond-graphite equilibrium line and the PT curve of the pyrrhotite-carbon eutectics. The fields of diamond spontaneous nucleation and mass crystallization as well as of diamond-seeded growth were determined. Diamond nucleation density up to 1.8X10 (super 5) grains in 1 mm (super 3) and growth rate within the range of several mm/min to several mu m/min were estimated. A possibility for formation of both monocrystalline and polycrystalline diamonds in the molten sulfide solvents was also demonstrated. Experimental data are in agreement with the melt-solution model of diamond formation in sulfide solvents of carbon. The experimental and literature data applied to the model of the mantle-derived diamond genesis demonstrate that sulfide melts with dissolved carbon are capable to form a limited mass of diamonds with specific mineralogical and physical properties.
