气候变化领域集成服务门户(CCPortal): Experimental evaluation of oxygen isotopic exchange between inclusion water and host calcite in speleothems

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DOI	10.5194/cp-16-17-2020
	Experimental evaluation of oxygen isotopic exchange between inclusion water and host calcite in speleothems
	Uemura R.; Kina Y.; Shen C.-C.; Omine K.
发表日期	2020
ISSN	18149324
起始页码	17
结束页码	27
卷号	16 期号:1
英文摘要	The oxygen and hydrogen isotopic compositions of water in fluid inclusions in speleothems are important hydroclimate proxies because they provide information on the isotopic compositions of rainwater in the past. Moreover, because isotopic differences between fluid inclusion water and the host calcite provide information on the past isotopic fractionation factor, they are also useful for quantitative estimation of past temperature changes. The oxygen isotope ratio of inclusion water (i18Ofi), however, may be affected by isotopic exchange between the water and the host carbonate. Thus, it is necessary to estimate the bias caused by this postdepositional effect for precise reconstruction of paleotemperatures. Here, we evaluate the isotopic exchange reaction between inclusion water and host calcite based on a laboratory experiment involving a natural stalagmite. Multiple stalagmite samples cut from the same depth interval were heated at 105 ĝ'C in the laboratory from 0 to 80 h. Then, the isotopic compositions of the inclusion water were measured. In the 105 ĝ'C heating experiments, the i18Ofi values increased from the initial value by 0.7 ‰ and then remained stable after ca. 20 h. The hydrogen isotope ratio of water showed no trend in response to the heating experiments, suggesting that the hydrogen isotopic composition of fluid inclusion water effectively reflects the composition of past drip water. We then evaluated the process behind the observed isotopic variations using a partial equilibration model. The experimental results are best explained by the assumption that a thin CaCO3 layer surrounding the inclusion reacted with the water. The amount of CaCO3 that reacted with the water is equivalent to 2 % of the water inclusions in molar terms. These results suggest that the magnitude of the isotopic exchange effect has a minor influence on paleotemperature estimates for Quaternary climate reconstructions. © 2020. This work is distributed under the Creative Commons Attribution 4.0 License.
语种	英语
scopus关键词	calcite; calcium carbonate; carbonate; estimation method; experimental study; fluid inclusion; heating; isotopic fractionation; oxygen isotope; paleotemperature; quantitative analysis; reconstruction; speleothem
来源期刊	Climate of the Past
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/146760
作者单位	Graduate School of Environmental Studies, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan; Department of Chemistry Biology, and Marine Science, Faculty of Science, University of the Ryukyus, 1 Senbaru Nishihara, Okinawa, 903-0213, Japan; High-Precision Mass Spectrometry and Environment Change Laboratory (HISPEC), Department of Geosciences, National Taiwan University, Taipei, 10617, Taiwan; Research Center for Future Earth, National Taiwan University, Taipei, 10617, Taiwan; Global Change Research Center, National Taiwan University, Taipei, 10617, Taiwan
推荐引用方式 GB/T 7714	Uemura R.,Kina Y.,Shen C.-C.,et al. Experimental evaluation of oxygen isotopic exchange between inclusion water and host calcite in speleothems[J],2020,16(1).
APA	Uemura R.,Kina Y.,Shen C.-C.,&Omine K..(2020).Experimental evaluation of oxygen isotopic exchange between inclusion water and host calcite in speleothems.Climate of the Past,16(1).
MLA	Uemura R.,et al."Experimental evaluation of oxygen isotopic exchange between inclusion water and host calcite in speleothems".Climate of the Past 16.1(2020).