Equilibrium mass-dependent fractionation relationships for triple oxygen isotopes

	Equilibrium mass-dependent fractionation relationships for triple oxygen isotopes
	Xiaobin Cao; Yun Liu
通讯作者	Yun Liu
	2011
发表期刊	Geochimica et Cosmochimica Acta
卷号	75 期号:23 页码:7435-7445
摘要	With a growing interest in small 17O-anomaly, there is a pressing need for the precise ratio, ln17a/ln18a, for a particular mass-dependent fractionation process (MDFP) (e.g., for an equilibrium isotope exchange reaction). This ratio (also denoted as “h”) can be determined experimentally, however, such efforts suffer from the demand of well-defined process or a set of processes in addition to high precision analytical capabilities. Here, we present a theoretical approach from which highprecision ratios for MDFPs can be obtained. This approach will complement and serve as a benchmark for experimental studies. We use oxygen isotope exchanges in equilibrium processes as an example. We propose that the ratio at equilibrium, hE ln17a/ln18a, can be calculated through the equation below: hEa b ¼ ja þ ðja jbÞ ln 18bb ln 18aab where 18bb is the fractionation factor between a compound “b” and the mono-atomic ideal reference material “O”, 18aab is the fractionation factor between a and b and it equals to 18ba/18bb and j is a new concept defined in this study as j ln17b/ ln18b. The relationship between h and j is similar to that between a and b. The advantages of using j include the convenience in documenting a large number of h values for MDFPs and in estimating any h values using a small data set due to the fact that j values are similar among O-bearing compounds with similar chemical groups. Frequency scaling factor, anharmonic corrections and clumped isotope effects are found insignificant to the j value calculation. However, the employment of the rule of geometric mean (RGM) can significantly affect the j value. There are only small differences in j values among carbonates and the structural effect is smaller than that of chemical compositions. We provide j values for most O-bearing compounds, and we argue that j values for Mg-bearing and S-bearing compounds should be close to their high temperature limitation (i.e., 0.5210 for Mg and 0.5159 for S). We also provide h values for CO2(g)–water, quartz–water and calcite–water oxygen isotope exchange reactions at temperature from 0 to 100 C.
收录类别	SCI
语种	英语
文献类型	期刊论文
条目标识符	http://ir.gyig.ac.cn/handle/352002/4114
专题	矿床地球化学国家重点实验室_矿床地球化学国家重点实验室_期刊论文
通讯作者	Yun Liu
推荐引用方式 GB/T 7714	Xiaobin Cao,Yun Liu. Equilibrium mass-dependent fractionation relationships for triple oxygen isotopes[J]. Geochimica et Cosmochimica Acta,2011,75(23):7435-7445.
APA	Xiaobin Cao,&Yun Liu.(2011).Equilibrium mass-dependent fractionation relationships for triple oxygen isotopes.Geochimica et Cosmochimica Acta,75(23),7435-7445.
MLA	Xiaobin Cao,et al."Equilibrium mass-dependent fractionation relationships for triple oxygen isotopes".Geochimica et Cosmochimica Acta 75.23(2011):7435-7445.

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