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Tracing carbonate dissolution in subducting sediments by zinc and magnesium isotopes
Qu, Yuan-Ru1; Liu, Sheng-Ao1; Wu, Huaichun2; Li, Meng-Lun1; Tian, Heng-Ci3
2022-02-15
Source PublicationGEOCHIMICA ET COSMOCHIMICA ACTA
ISSN0016-7037
Volume319Pages:56-72
AbstractCarbonate 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.
KeywordZinc isotopes Magnesium isotopes Subducting sediments Carbonate dissolution Subduction
DOI10.1016/j.gca.2021.12.020
Funding OrganizationNational 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
WOS KeywordDEEP-SEA CARBONATE ; CENOZOIC BASALTS ; 3 GPA ; CHEMICAL-COMPOSITION ; CONTINENTAL-CRUST ; MANTLE SOURCES ; PB ISOTOPE ; FRACTIONATION ; CHINA ; GEOCHEMISTRY
Language英语
Funding ProjectNational 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]
Funding OrganizationNational 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
WOS Research AreaGeochemistry & Geophysics
WOS SubjectGeochemistry & Geophysics
WOS IDWOS:000744157500003
PublisherPERGAMON-ELSEVIER SCIENCE LTD
Citation statistics
Document Type期刊论文
Identifierhttp://ir.iggcas.ac.cn/handle/132A11/104001
Collection地球与行星物理院重点实验室
Corresponding AuthorLiu, Sheng-Ao
Affiliation1.China Univ Geosciences, State Key Lab Geol Proc & Mineral Resources, Beijing 100083, Peoples R China
2.China Univ Geosci, Sch Ocean Sci, Beijing 100083, Peoples R China
3.Chinese Acad Sci, Inst Geol & Geophys, Key Lab Earth & Planetary Phys, Beijing 100029, Peoples R China
Recommended Citation
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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