Abstract
The influence of metal cations on 13C-18O bonds in carbonates is still under debate. This paper used ab initio method to investigate this kind of influence of Mg2+, Fe2+ and Zn2+ cations on 13C-18O bonds in precipitated aragonite, calcite and dolomite. The polynomials of Δ47 and reduced partition function ratios (RPFRs) for 13/12C, 14/12C and 18/16O of these minerals were given within temperatures ranging from 260 to 1500 K. We found that these cations significantly decreased the Δ47 values at the level of 10-3 - 10-2 per mil, comparing with pure crystals; and that if the Δ47 values were used to reconstruct the temperatures Ts, the deviation of T was about 7.2°C for, for instance, zinc-enriched aragonite, as discussed in our paper. It was suggested that due to such influence, researchers would better use a proper thermometer according to the main impurity metal cations in carbonates. We also found that according to the probability theory, the theoretical value of the influence of phosphoric acid on Δ47 of CO2 degassed from different carbonates was zero.
Highlights
13C-18O clumping effects [1]-[3] in carbonates play significant roles in reconstructing the temperatures in geological research [4]-[9]
This paper studied the effects of Mg2+, Fe2+ and Zn2+ cations on the 13C-18O bonds in aragonite, calcite and dolomite
The metal cations in precipitated carbonates cause the decrease of ∆47 values from pure carbonates
Summary
13C-18O clumping effects [1]-[3] in carbonates play significant roles in reconstructing the temperatures in geological research [4]-[9]. The majority of data points of 13C-18O signals of CO2 extracted from carbonate minerals is explained by the equilibrium isotope reactions on the growth surfaces of crystals during their formation [10]. There still exist some measured data points which deviate from our predicted ∆47 polynomials of pure. (2015) Influence of Mg2+, Fe2+ and Zn2+ Cations on 13C-18O Bonds in Precipitated Aragonite, Calcite and Dolomite: An ab Initio Study. J. Yuan aragonite and calcite [10]. One hypothesis for solving this problem was that during the crystallization of minerals, the carbonates captured the metal cations (M2+) from solutions and these cations influenced the 13C-18O isotope signals in turn
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