Effect of sulfate on magnesium incorporation in low-magnesium calcite

摘要: Abstract The incorporation of magnesium and sulfate in calcite is frequently used to characterize trace the environmental conditions occurring during carbonate mineral formation. Although both ions are simultaneously incorporated growing calcite, effect on still under-explored. In this study, we examine Mg low-Mg as a function growth rate at 25 °C 1 bar pCO2 presence absence aqueous sulfate. obtained results suggest that high rates induce significant increase partitioning coefficient between precipitated solution (i.e. D = n / Ca [ 2 + ] ). Obtained DMg values exhibit similar dependence for experiments performed sulfate, however systematic shift lower observed calcites formed sulfate-bearing solutions attributed SO4 which provoke expansion unit cell along c-axis newly calcite. A larger unfavorable substitution by smaller coupled (i) uptake (ii) precipitation can be expressed equation 0.03726 - 0.02345 × l o g r p 7 X S O 4 0.004607 0.002109 ; (−8 ≤ log(rp) ≤ −7; 0 ≤ Xso4 ≤ 2.6; T = 25 °C) valid 0.01 ≤ DMg ≤ 0.04. analogy also inhibiting growth, thus promoting formation aragonite due adsorption phenomena blocking surface sites. These improve our understanding physicochemical parameters controlling CaCO3 composition polymorphism discussed their relevance use proxies natural surroundings.