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First-Principles Determination of Oxygen and Silicon β-Factors for Zircon
Petrology ( IF 1.5 ) Pub Date : 2019-08-08 , DOI: 10.1134/s0869591119040052
D. P. Krylov

Abstract

The temperature dependence of the β-factors of zircon was determined for 18O/16O and 30Si/28Si isotopic substitutions. Calculations were performed on the basis of the density functional theory (DFT) using the frozen phonon approach. The obtained geometric parameters of the zircon crystal lattice and vibrational frequencies are in good agreement with experimental data. The results were approximated by the following cubic polynomials in x = 106/T(K)2: 1000 ln βzrn(18O/16O) = 9.83055x – 0.19499x2 + 0.00388x3 and 1000 ln βzrn(30Si/28Si) = 7.89907x – 0.17978x2 + 0.00377x3. The obtained relations can be used in combination with the β-factors of other phases for the construction of geothermometers. New calibrations of the quartz–zircon isotope geothermometer were proposed. The obtained 1000 ln βzrn values and isotope fractionation factors between quartz and zircon (1000 ln βqtz – 1000 ln βzrn) are significantly different from those obtained by previous experimental, empirical, and semiempirical calibrations of isotope equilibria.


中文翻译:

锆石中氧和硅β因子的第一性原理测定

摘要

确定了18 O / 16 O和30 Si / 28 Si同位素取代的锆石β因子的温度依赖性。使用冻结声子方法,根据密度泛函理论(DFT)进行计算。所获得的锆石晶格的几何参数和振动频率与实验数据吻合良好。通过以下三次多项式近似结果为x = 10 6 / T(K)2:1000 lnβzrn18 O / 16 O)= 9.83055 x – 0.19499 x 2+ 0.00388 x 3和1000 lnβzrn30 Si / 28 Si)= 7.89907 x – 0.17978 x 2 + 0.00377 x 3。可以将获得的关系与其他相的β因子结合使用来构造地热仪。提出了石英-锆石同位素地热仪的新校准方法。将得到的1000个LNβ ZRN石英和锆石之间的值和同位素分馏因子(1000 LNβ QTZ - 1000 LNβ ZRN)是从由以前的实验,经验,以及同位素平衡半经验校准获得的那些不同显著。
更新日期:2019-08-08
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