首页|Strontium isotope fractionation during precipitation of strontianite in aqueous solutions as a function of temperature and reaction rate
Strontium isotope fractionation during precipitation of strontianite in aqueous solutions as a function of temperature and reaction rate
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NSTL
Elsevier
In order to study Strontium (Sr) isotope fractionation during the precipitation of strontianite (SrCO_3) as a function of the specific precipitation rate (R*) and temperature (T), strontianite was precipitated at 12.5, 25.0 and 37.5 ?C by diffusing NH_3 and CO_2 gases into aqueous solutions. The specific precipitation rate R* (mol/ cm~2·h) for every sample was determined by applying the initial rate method. The mean isotope difference between bulk solution and precipitate (Δ~(88/86)Sr_(strontianite-solution)) was found to be-0.279 ± 0.005‰ (2σ_(mean)) independent of both rate and temperature. Hence, Sr isotope fractionation in strontianite is completely different from that in calcite and aragonite, where a strong dependency from both rate and temperature can be observed. The latter is interpreted to reflect the competition between Sr~(2+) and Ca~(2+) ions for incorporation into the calcium carbonate crystal lattice, which is absent during the precipitation of pure strontianite. The isotope difference between strontianite and bulk solution then simply reflects the intermolecular forces in the aqueous solutions as well as the kinetic effect. The difference in the (Δ~(88/86)Sr_(strontianite-solution) between experiments then reflects the dehydration energy of Sr ions in the adsorption layer of SrCO_3.
NSTL
Elsevier
