Seasonal microclimate control of calcite fabrics, stable isotopes and trace elements in modern speleothem from St Michaels Cave, Gibraltar - Tufas and Speleothems: Unravelling the Microbial and Physical Controls - page 327

Fig. 6. (a) Plot of Ca versus Mg/Ca ratios for NSM waters compared with modeled prior calcite precipitation (PCP)
lines. The distribution coefficient for Mg in calcite (K Mg ) used for modeling is 0.02, but the lines are not sensitive
to the exact value. The pCO 2 values correspond to those at equilibrium with calcite for waters of appropriate
Mg/Ca using MIX4 modeling (Fairchild et al. 2000). (b) Similar plot for Sr/Ca; value of K Sr used is 0.3 (Huang
& Fairchild 2001). See text for discussion.