“…Through hydrothermal metasomatism, a significant amount of CaCO 3 in the form of calcite enters the oceanic crust to form carbonate-bearing altered oceanic basalt (Alt & Teagle, 1999;Jarrard, 2003;Kelemen & Manning, 2015). Analysis of the inclusions in deep diamonds has revealed evidence of the transportation of CaCO 3 to depths of at least the topmost lower mantle via sinking slabs (Brenker et al, 2007;Kaminsky et al, 2009Kaminsky et al, , 2016Wirth et al, 2009). Previous studies have further shown that CaCO 3 undergoes a series of phase transitions at high pressures (Catalli & Williams, 2005;Gavryushkin et al, 2017;Lobanov et al, 2017;Oganov et al, 2008Oganov et al, , 2006Ono et al, 2005;Pickard & Needs, 2015;Smyth & Ahrens, 1997;Suito et al, 2001).…”