Figure 1
From: Continuous eclogite melting and variable refertilisation in upwelling heterogeneous mantle
(a) Pressure-Temperature-grid of experimentally-determined melting and phase relations of Res2. (b) Comparison of Res2 solidus surface and its (incipient) melting regime with solidii of other experimentally determined mantle lithologies. (a) See explanations within text. Yellow circles – Res2 at 3 GPa, orange circles – Res2 at 4 GPa, red circles – Res2 at 5 GPa. The symbols ‘+’ and ‘-’ indicate the presence of quartz/coesite and absence of clinopyroxene, respectively, as residual phases. Solid and dashed white lines are determined and inferred phase boundaries, respectively. The quartz-coesite transition is taken from Bose & Ganguly44; qtz, quartz; coe, coesite; grt, garnet; cpx, clinopyroxene. (b) The Res2 solidus lies between the ‘dry’ lherzolite solidus29,45 and GA2 eclogite12 and volatile-bearing lherzolite (i.e. peridotite + H2O ± CO2) solidus26,29,30,31,32. The light red shaded area adjacent to Res2 solidus is the incipient melting regime with garnet + clinopyroxene + quartz/coesite residue. Predicted mantle Tp's range from 1280–1600°C46,47,48 but for illustrative purposes, we chose a mantle adiabat of Tp ≈ 1360°C so that the solidus of Res2 intersects the adiabat at 5 GPa at ~1410°C, initiating melting. Using other adiabats will simply shift the pressure of the onset of melting of various lithologies by ~1 GPa per 100°C12. Although such changes would not alter the principles of the scenarios12, they would substantially influence the composition of melts and solid residues of mantle lithologies at the onset of melting and thus, would also influence any associated mantle metasomatism.
