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Tracing carbonate dissolution in subducting sediments by zinc and magnesium isotopes

文献类型：期刊论文

作者Qu, Yuan-Ru3; Liu, Sheng-Ao3; Wu, Huaichun2; Li, Meng-Lun3; Tian, Heng-Ci1
刊名GEOCHIMICA ET COSMOCHIMICA ACTA
出版日期2022-02-15
卷号319页码:56-72
关键词Zinc isotopes Magnesium isotopes Subducting sediments Carbonate dissolution Subduction
ISSN号0016-7037
DOI10.1016/j.gca.2021.12.020
英文摘要Carbonate dissolution in subduction zones transfers surface carbon to the mantle and plays an important role in regulating global carbon cycles through geologic time. Petrological observations and thermodynamic models predict substantial dissolution of subducting carbonates induced by slab-derived fluids at arc mantle depths, but this dissolution process has rarely been verified by existing geochemical tracers. In this paper we show that zinc and magnesium isotopes can serve as such tracers through a comparative study on carbonate-bearing and carbonate-free sediments from the South China Sea and the Philippine Sea that are going to be subducted. Leaching experiments are further performed to characterize the isotopic difference between dissolved carbonates and silicate components in sediments. Bulk carbonate-bearing sediments and carbonatefree sediments surprisingly have indistinguishable 866Zn (0.26 +/- 0.04% versus 0.25 +/- 0.04%), but the former display systematically lower 826Mg (-0.85% to -0.17%, n = 10) than the latter (-0.26% to +0.13%, n = 13). Leaching experiments show that dissolved carbonates have much higher 866Zn (0.82 +/- 0.26%) and lower 826Mg (-2.70 +/- 0.35%) compared with the silicate residues (866Zn = 0.21 +/- 0.06%; 826Mg = -0.06 +/- 0.14%). These results indicate that the presence of carbonate components has insignificant influence on Zn isotopic compositions of bulk sediments but prominent influence on their Mg isotopic compositions. In this respect, the final fate of carbonates in subducting sediments can be tracked by a combined Mg and Zn isotope analysis on mantle-derived magmas. For instance, bulk carbonate-bearing sediment addition (i.e., no carbonate dissolution) during subduction would produce low 826Mg but normal 866Zn values (i.e., Mg-Zn isotopic "decoupling") in mantle-derived magmas. By contrast, if carbonate dissolution occurs during subduction, the high 866Zn and low 826Mg (i.e., Mg-Zn isotopic "coupling") signals of dissolved carbonates will be transferred to the sources of mantle-derived magmas. We test this application for a Cenozoic subduction-related, arc-like volcanic exposure from Tengchong, Southwestern China and find significant Mg-Zn isotopic coupling, which demonstrates carbonate dissolution during Indian Oceanic slab subduction. Our results also shed constraints on the amount of dissolved carbonates in the sub-arc mantle. Available data reveal the absence of high 866Zn and low 826Mg in global arc lavas, for which we suggest to be the result of a relatively low proportion (c) 2021 Elsevier Ltd. All rights reserved.
WOS关键词DEEP-SEA CARBONATE ; CENOZOIC BASALTS ; 3 GPA ; CHEMICAL-COMPOSITION ; CONTINENTAL-CRUST ; MANTLE SOURCES ; PB ISOTOPE ; FRACTIONATION ; CHINA ; GEOCHEMISTRY
资助项目National Key R&D Program of China[2019YFA0708400] ; National Natural Science Foundation of China[41730214] ; Strategic Priority Research Program (B) of the Chinese Academy of Sciences[XDB18000000]
WOS研究方向Geochemistry & Geophysics
语种英语
WOS记录号WOS:000744157500003
出版者PERGAMON-ELSEVIER SCIENCE LTD
资助机构National Key R&D Program of China ; National Key R&D Program of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; Strategic Priority Research Program (B) of the Chinese Academy of Sciences ; Strategic Priority Research Program (B) of the Chinese Academy of Sciences ; National Key R&D Program of China ; National Key R&D Program of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; Strategic Priority Research Program (B) of the Chinese Academy of Sciences ; Strategic Priority Research Program (B) of the Chinese Academy of Sciences ; National Key R&D Program of China ; National Key R&D Program of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; Strategic Priority Research Program (B) of the Chinese Academy of Sciences ; Strategic Priority Research Program (B) of the Chinese Academy of Sciences ; National Key R&D Program of China ; National Key R&D Program of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; Strategic Priority Research Program (B) of the Chinese Academy of Sciences ; Strategic Priority Research Program (B) of the Chinese Academy of Sciences
源URL[http://ir.iggcas.ac.cn/handle/132A11/104001]  
专题地质与地球物理研究所_中国科学院地球与行星物理重点实验室
通讯作者Liu, Sheng-Ao
作者单位1.Chinese Acad Sci, Inst Geol & Geophys, Key Lab Earth & Planetary Phys, Beijing 100029, Peoples R China
2.China Univ Geosci, Sch Ocean Sci, Beijing 100083, Peoples R China
3.China Univ Geosciences, State Key Lab Geol Proc & Mineral Resources, Beijing 100083, Peoples R China
推荐引用方式
GB/T 7714		 Qu, Yuan-Ru,Liu, Sheng-Ao,Wu, Huaichun,et al. Tracing carbonate dissolution in subducting sediments by zinc and magnesium isotopes[J]. GEOCHIMICA ET COSMOCHIMICA ACTA,2022,319:56-72.
APA Qu, Yuan-Ru,Liu, Sheng-Ao,Wu, Huaichun,Li, Meng-Lun,&Tian, Heng-Ci.(2022).Tracing carbonate dissolution in subducting sediments by zinc and magnesium isotopes.GEOCHIMICA ET COSMOCHIMICA ACTA,319,56-72.
MLA Qu, Yuan-Ru,et al."Tracing carbonate dissolution in subducting sediments by zinc and magnesium isotopes".GEOCHIMICA ET COSMOCHIMICA ACTA 319(2022):56-72.

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来源：地质与地球物理研究所

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