Fig. 6: Modelled magnesium partition coefficients from CD3.
From: Magnesium in subaqueous speleothems as a potential palaeotemperature proxy
a CD3 Mg concentrations derived from a range of Mg partition coefficients (DMg) and four hypothetic pool-water Mg/Ca ratios (values in mol/mol displayed next to each line). The modern DMg (0.042) is shown by the long-dash vertical line. The black diamond shows the mean modern calcite concentration value (~11,750 p.p.m.) and the mean pool-water Mg/Ca value (1.175 mol/mol)33. The short-dash horizontal line is the minimum measured Mg concentration (8000 p.p.m.) from Fig. 5d. Each coloured solid vertical line gives the DMg value for the corresponding pool-water Mg/Ca at 8000 p.p.m. The grey panel shows the range of DMg values for 0–10 °C from previously published studies33. b Published experimentally derived DMg–temperature relationships (coloured symbols) compared to CD3 (black diamonds). Open and closed coloured symbols are from cave-analogue and seawater-analogue experiments respectively (green solid circles, Burton and Walter77; red solid triangles, Oomori et al.78; solid brown squares, Mucci79; open blue circles, Day and Henderson80; open orange diamonds, Huang and Fairchild81). The modern CD3 value is based on Drysdale et al.33; the glacial CD3 value is the maximum possible DMg assuming a MIS 6 glacial cave temperature of 6 °C below present (i.e., 2 °C) and a pool-water Mg/Ca value (1.175 mol/mol) equivalent to modern.
