The role of mantle ultrapotassic fluids in diamond formation
- Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, Pr. Koptuyga 3, 630090 Novosibirsk, Russia
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Edited by Ho-kwang Mao, Carnegie Institution of Washington, Washington, DC, and approved January 1, 2007 (received for review September 15, 2006)
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Fig. 1.Degree of graphite-to-diamond transformation [α = MDm/(MDm + MGr)100, where MDm is the mass of obtained diamond and MGr is the mass of residual graphite] as a function of the crystallization media composition (P = 7.5 GPa, τ = 15 h). (a) K2CO3/KCl/C system. (b) K2CO3/H2O/C system. (c) KCl/H2O/C system.
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Fig. 2.Scanning electron micrographs of diamonds. (a) Cubo-octahedral diamonds synthesized in the K2CO3/KCl/C system (run 1053B). (b) Octahedral diamonds synthesized in the KCl/H2O/C system (run 1046A).
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Fig. 3.Effect of the KCl/K2CO3/H2O/C system composition on diamond and graphite crystallization at P = 7.5 GPa and τ = 15 h. (a) 1,500°C. (b) 1,600°C. 1, no diamond nucleation; 2, heterogenous diamond nucleation; 3, homogeneous and heterogenous diamond nucleation; half-filled circles, joint crystallization of diamond and metastable graphite; open circles, only diamond crystallization; filled circles, only graphite crystallization; circles with cross, no crystallization of graphite or diamond.
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Fig. 4.Generalized diagram of the degree of graphite-to-diamond transformation (α) in the KCl/K2CO3/H2O/C system at P = 7.5 GPa, t = 1,500°C, and τ = 15 h. The values of α are given by numbers.
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Fig. 5.High-pressure experimental cell for diamond crystallization in the KCl/K2CO3/H2O/C system. 1, ZrO2 container; 2, cylindrical graphite heater; 3, PtRh6/PtRh30 thermocouple; 4, Pt capsules; 5, CsCl; 6, ZrO2; 7, MgO; 8, Mo leads.
Footnotes
- *To whom correspondence should be addressed. E-mail: palyanov{at}uiggm.nsc.ru
- © 2007 by The National Academy of Sciences of the USA
