Melting phase relations of the Udachnaya-East Group-I kimberlite at 3.0–6.5 GPa: Experimental evidence for alkali-carbonatite composition of primary kimberlite melts and implications for mantle plumes

Origins of cratonic mantle discontinuities: A view from petrology, geochemistry and thermodynamic models

“…Numerous experimental studies have focused on the formation of melts under cratonic pressure-temperature-composition conditions, with the emerging consensus that both CO 2 and H 2 O are necessary for melting to occur in cratons (Foley, 1989;Foley et al, 2009;Brey et al, 2008Brey et al, , 2009Girnis et al, 2011;Novella and Frost, 2014;Sokol and Kruk, 2015;Sokol et al, 2013Sokol et al, , 2014Sokol et al, , 2015Sharygin et al, 2015). In most cases, experimental melts are low to very low in silica, spanning the compositional range from carbonatites to kimberlites.…”

Carbonate–silicate liquid immiscibility in the mantle propels kimberlite magma ascent

“…Additionally, a number of experimental studies emphasised the role of Na-rich carbonate melts in generation of kimberlites (e.g. Safonov et al, 2009Safonov et al, , 2011Sharygin et al, 2015) and natrocarbonatites (e.g. Sweeney et al, 1995), nucleation and growth of diamonds (e.g.…”

“…The experimental studies dealing with ephemeral alkali-carbonates often report difficulties relating to separating the melt from mantle solids and crystalline products, recognising melt pools large enough for a quantitative analysis, loss of alkali carbonates during sample preparation, degradation of alkali carbonates under the electron beam and uncertainties in mass balance calculations (e.g. Wallace and Green, 1988;Yaxley and Green, 1996;Dasgupta et al, 2004;Ghosh et al, 2009;Litasov et al, 2013;Sharygin et al, 2015;Shatskiy et al, 2015). In other words, the absence or insignificant quantities of Na 2 CO 3 in experiments with carbonated mantle lithologies does not necessarily mean that sodium carbonate melt should be treated as an exotic rather than a common product of mantle melting.…”

Evidence for and consequences of the “hot” subduction model

“…According to the experimental data [15], melting at 1000-1300°C may result in the predominant forma tion of carbonatite melts with a SiO 2 concentration of <5 wt %. The concentration of SiO 2 increases with increasing temperature, and kimberlite magmas are formed.…”