气候变化领域集成服务门户(CCPortal): Technical note: Lithium isotopes in dolostone as a palaeo-environmental proxy-An experimental approach

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DOI	10.5194/cp-15-635-2019
	Technical note: Lithium isotopes in dolostone as a palaeo-environmental proxy-An experimental approach
	Taylor H.L.; Kell Duivestein I.J.; Farkas J.; Dietzel M.; Dosseto A.
发表日期	2019
ISSN	18149324
起始页码	635
结束页码	646
卷号	15 期号:2
英文摘要	Lithium (Li) isotopes in marine carbonates have considerable potential as a proxy to constrain past changes in silicate weathering fluxes and improve our understanding of Earth's climate. To date the majority of Li isotope studies on marine carbonates have focussed on calcium carbonates. The determination of the Li isotope fractionation between dolomite and a dolomitizing fluid would allow us to extend investigations to deep times (i.e. Precambrian) when dolostones were the most abundant marine carbonate archives. Dolostones often contain a significant proportion of detrital silicate material, which dominates the Li budget; thus, pretreatment needs to be designed so that only the isotope composition of the carbonate-associated Li is measured. This study aims to serve two main goals: (1) to determine the Li isotope fractionation between Ca-Mg carbonates and solution, and (2) to develop a method for leaching the carbonate-associated Li out of dolostone while not affecting the Li contained within the detrital portion of the rock. We synthesized Ca-Mg carbonates at high temperatures (150 to 220g?C) and measured the Li isotope composition (7Li) of the precipitated solids and their respective reactive solutions. The relationship of the Li isotope fractionation factor with temperature was obtained: 103 in α prec-sol =-((2.56± 0.27)106) Competitive nucleation and growth between dolomite and magnesite were observed during the experiments; however, there was no notable effect of their relative proportion on the apparent Li isotope fractionation. We found that Li isotope fractionation between the precipitated solid and solution is higher for Ca-Mg carbonates than for Ca carbonates. If the temperature of a precipitating solution is known or can be estimated independently, the above equation could be used in conjunction with the Li isotope composition of dolostones to derive the composition of the solution and hence make inferences about the past Li cycle. In addition, we also conducted leaching experiments on a Neoproterozoic dolostone and a Holocene coral. Results show that leaching with 0.05M hydrochloric acid (HCl) or 0.5% acetic acid (HAc) at room temperature for 60min releases Li from the carbonate fraction without a significant contribution of Li from the siliciclastic detrital component. These experimental and analytical developments provide a basis for the use of Li isotopes in dolostones as a palaeo-environmental proxy, which will contribute to further advance our understanding of the evolution of Earth's surface environments.. © 2019 Copernicus GmbH. All Rights Reserved.
语种	英语
scopus关键词	calcium carbonate; coral; dolostone; Holocene; isotopic composition; isotopic fractionation; paleoenvironment; Precambrian; precipitation (chemistry); Proterozoic; proxy climate record; Anthozoa
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/146832
作者单位	Wollongong Isotope Geochronology Laboratory, School of Earth, Atmospheric and Life Sciences, University of Wollongong, Wollongong, NSW, Australia; Institute of Applied Geosciences, Graz University of Technology, Graz, Austria; Department of Earth Sciences, University of Adelaide, Adelaide, SA, Australia; Department of Environmental Geosciences, Czech University of Life Sciences, Prague, Czech Republic
推荐引用方式 GB/T 7714	Taylor H.L.,Kell Duivestein I.J.,Farkas J.,et al. Technical note: Lithium isotopes in dolostone as a palaeo-environmental proxy-An experimental approach[J],2019,15(2).
APA	Taylor H.L.,Kell Duivestein I.J.,Farkas J.,Dietzel M.,&Dosseto A..(2019).Technical note: Lithium isotopes in dolostone as a palaeo-environmental proxy-An experimental approach.Climate of the Past,15(2).
MLA	Taylor H.L.,et al."Technical note: Lithium isotopes in dolostone as a palaeo-environmental proxy-An experimental approach".Climate of the Past 15.2(2019).