Oxygen and carbon isotope fractionations between CO2 and calcite
Oxygen and carbon isotope fractionations between CO2 and calcite
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DOI：
10.1016/0016-7037(91)90452-b
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发表时间：
1991-10
影响因子：
5
通讯作者：
T. Chacko;T. Mayeda;R. Clayton;J. R. Goldsmith
中科院分区：
文献类型：
--
作者：
T. Chacko;T. Mayeda;R. Clayton;J. R. Goldsmith
氧和碳同位素分馏因子是通过在400-950°C的温度范围和1-13毫巴的压力下二氧化碳和方解石之间的直接交换来测量的。氧交换的平衡常数在400至800°C之间得到了很好的确定，并且与以前的实验和理论估计有很大的不同。碳同位素分馏在所有温度下都有较大的不确定性。氧和碳同位素分馏很好地再现统计力学计算与简单的处理方解石晶格振动。基于方解石配分函数比的新计算重新计算的方解石-石墨分馏曲线表明，该体系非常适合于ValleyandO 'Neil（1981）首次提出的石墨大理岩高温同位素测温。二氧化碳和方解石之间的氧和碳的交换速率是迅速的，并且通过扩散和轻微重结晶的组合进行。
Oxygen and carbon isotopic fractionation factors have been measured by direct exchange between carbon dioxide and calcite over the temperature range 400–950°C at pressures of 1–13 kilobars. Equilibrium constants for oxygen exchange are well determined from 400 to 800°C, and differ substantially from previous experimental and theoretical estimates. Carbon isotopic fractionations have larger uncertainties at all temperatures. Both oxygen and carbon isotopic fractionations are well reproduced by statistical mechanical calculations with simple treatment of the calcite lattice vibrations. A recalculated calcite-graphite fractionation curve based on new calculations of partition functions ratios for calcite suggests that this system is well suited for high-temperature isotopic thermometry of graphitic marbles as first proposed byValleyandO'Neil(1981). The rate of exchange of both oxygen and carbon between carbon dioxide and calcite is rapid, and proceeds by a combination of diffusion and minor recrystallization.