Two mathematical models of Mg and Sr partitioning into solution during incongruent calcite dissolution

摘要: Abstract Positive correlation between Sr/Ca and Mg/Ca in cave dripwaters speleothem is often attributed to ‘prior calcite precipitation’ (PCP), where exclusion of Mg Sr from precipitated upstream the dripwater/speleothem site results enrichment ratios residual effluent. Modelling predicts that PCP will produce a straight line graphs ln(Sr/Ca) vs. ln(Mg/Ca) with theoretical slope given by ( Kd  − 1) / (  − 1) (calculated be ∼ 0.88 ± 0.13) regardless rock or absolute dripwater composition Sinclair et al., submitted for publication ). While this makes potentially diagnostic PCP, are also preferentially released during incongruent dissolution (ICD), it possible ICD produces similar ln(Mg/Ca). To examine possibility, mathematical formulations two different mechanisms presented. Model 1 simulates net as dynamic kinetic process forward reverse reactions compete: congruent but ions fractionated simultaneous reaction new forms determined solution . 2 leaching fresh surface tracking thin layer high ion mobility allows maintain homogenous controlled In both models, generalised equations used derivations meaning not specific particular model. models ICD, mathematics predict under conditions may prevail limestone, approximately linear  − 1). Thus, property just PCP. However, universal—expected occur kinetics host rock. A ∼ 0.88 either karst waters therefore calcite–water interaction.