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DOI	10.1016/j.epsl.2021.116989
	Magnesium partitioning into vaterite and its potential role as a precursor phase in foraminiferal Mg/Ca thermometer
	Zhu C.; Chen T.; Zhao L.
发表日期	2021
ISSN	0012821X
卷号	567
英文摘要	The foraminifera shell Mg/Ca thermometer has been extensively used in reconstructing temperature evolution of the past oceans. An important, yet poorly understood observation is the 1-2 orders of magnitude lower Mg/Ca in foraminifera calcite shells than expected from inorganically precipitated calcite. Transient unstable carbonate was long hypothesized as a precursor of foraminiferal calcification, but its potential role in explaining apparent ‘vital effects’ of trace element partitioning is not well understood. In particular, a recent study has identified vaterite as a likely precursor phase during biomineralization of calcite foraminifera shells (Jacob et al., 2017). Here, we explore the possibility of vaterite as a precursor phase in affecting Mg incorporation into foraminifera calcite shells by experimentally calibrating the temperature dependent Mg partition coefficients between carbonate solution and vaterite under different solution Mg concentrations. The experimentally determined sensitivity of Mg incorporation into vaterite as a function of temperature (T in °C) is expressed as: ln⁡(λvateriteMg)=0.022±0.002⋅T−3.65±0.03. It is demonstrated that Mg partitioning is mainly controlled by the strain energy originated from cation substitution in the discontinuous lattices of vaterite particles, without distinct kinetic-controlled effects. We have developed a two-step partition model applying the above experimental results, with the assumption that vaterite is directly precipitated from a seawater-like fluid and later converts to calcite through dissolution-reprecipitation mediated by a second fluid in a localized environment. Within the constrained range of model parameters during phase conversion, the two-step partition model could directly reproduce foraminiferal calcite Mg/Ca temperature dependencies in both magnitude and sensitivity. Our model provides a theoretical framework that could be broadly applied to understand the impact of precursor phase on trace metal partition in biominerals. Overall, our study implies that the energy-consuming biological pumping of Mg outside foraminifera calcifying fluid, as widely believed, might not be a precondition for foraminifera shell mineralization. © 2021 Elsevier B.V.
关键词	foraminifera Mg partition Mg/Ca thermometer vaterite
英文关键词	Biomineralization; Magnesium compounds; Shells (structures); Strain energy; Thermometers; Trace elements; Energy; Foraminifera shells; Foraminifers; Mg incorporation; Mg partition; Mg/ca thermometer; Partition model; Precursor phasis; Temperature evolution; Vaterite; Calcite; concentration (composition); foraminifera; magnesium; mineralization; partitioning; temperature effect; trace metal; vaterite; Foraminifera
语种	英语
来源期刊	Earth and Planetary Science Letters
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/203379
作者单位	Key Laboratory of Surficial Geochemistry, Ministry of Education, School of Earth Sciences and Engineering, Nanjing University, Nanjing, 210023, China; State Key Laboratory for Mineral Deposit Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing, 210023, China
推荐引用方式 GB/T 7714	Zhu C.,Chen T.,Zhao L.. Magnesium partitioning into vaterite and its potential role as a precursor phase in foraminiferal Mg/Ca thermometer[J],2021,567.
APA	Zhu C.,Chen T.,&Zhao L..(2021).Magnesium partitioning into vaterite and its potential role as a precursor phase in foraminiferal Mg/Ca thermometer.Earth and Planetary Science Letters,567.
MLA	Zhu C.,et al."Magnesium partitioning into vaterite and its potential role as a precursor phase in foraminiferal Mg/Ca thermometer".Earth and Planetary Science Letters 567(2021).