Dependence of calcite growth rate and Sr partitioning on solution stoichiometry: Non-Kossel crystal growth

Seeded calcite growth experiments were conducted at fixed pH (10.2) and two degrees of supersaturation (Omega = 5, 16), while varying the Ca2+ to CO32- solution ratio over several orders of magnitude. The calcite growth rate and the incorporation of Sr in the growing crystals strongly depended on the solution stoichiometry. At a constant degree of supersaturation, the growth rate was highest when the solution concentration ratio, r = [Ca2+]/[CO32-], equaled one, and decreased symmetrically with increasing or decreasing values of r. This behavior is consistent with. the kink growth rate theory for non-Kossel crystals, assuming that the frequency factors for attachment to kink sites are the same for the cation and anion. Measured Sr partition coefficients, D-Sr, ranged from 0.02 to 0.12, and correlated positively with the calcite growth rate. (C) 2007 Elsevier Ltd. All rights reserved.