气候变化领域集成服务门户(CCPortal): Mantle heterogeneity through Zn systematics in oceanic basalts: Evidence for a deep carbon cycling

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DOI	10.1016/j.earscirev.2020.103174
	Mantle heterogeneity through Zn systematics in oceanic basalts: Evidence for a deep carbon cycling
	Beunon H.; Mattielli N.; Doucet L.S.; Moine B.; Debret B.
发表日期	2020
ISSN	00128252
卷号	205
英文摘要	Subduction at convergent margins introduces a range of sedimentary and crustal materials into the mantle, providing the most dominant form of heterogeneity in the source of oceanic basalts. Yet, the relationship between geochemical variability and lithologic heterogeneities in the Earth's mantle remains controversial. In this paper, we comprehensively review Zn, δ66Zn and Sr-Nd isotope systematics in near-primary basalts erupted at mid-ocean ridges (MORB) and ocean islands (OIB) to help constrain the nature and proportion of the carbon (C) bearing slab-derived component in their mantle sources. We show that Zn elemental and isotopic composition of oceanic basalts differs according to their tectonic settings, increasing from MORB (Zn = 62 ± 10 to 73 ± 11 ppm; δ66Zn = +0.24 ± 0.01 to +0.31 ± 0.02‰) to OIB (Zn = 74 ± 9 to 124 ± 7 ppm; δ66Zn = +0.21 ± 0.07 to +0.40 ± 0.04‰). Unlike MORB, the high Zn and δ66Zn recorded in OIB cannot be explained by partial melting of a fertile peridotite mantle source only. Importantly, global correlations between Zn content and Sr-Nd isotopes in oceanic basalts suggest that the Zn enrichment in OIB is inherited from a recycled component in their mantle source rather than melting processes. We demonstrate that involvement of neither typical MORB-like oceanic crust nor subducted sediments can achieve the whole range of Zn composition in OIB. Instead, addition of ≤6% C-bearing oceanic crust to a fertile peridotite mantle fully resolves the Zn heterogeneity of OIB, both in terms of magnitude of Zn enrichment and global trends with Sr-Nd isotopes. Such scenario is corroborated by the elevated δ66Zn of OIB relative to MORB and mantle peridotites, reflecting the contribution of isotopically heavy C-bearing phases (δ66Zn = +0.91 ± 0.24‰) to the mantle source (δ66Zn = +0.16 ± 0.06‰). Our study thus emphasizes the use of Zn and δ66Zn systematics to track the nature and origin of mantle carbon, highlighting the role of subduction in the deep carbon cycle. Finally, the positive correlation between Zn content and temperature of magma generation of oceanic basalts suggests that hotter mantle plumes are more likely to carry a higher proportion of dense C-bearing eclogite. Zinc systematics therefore may provide evidence that the presence of heterogeneous domains in the source of OIB is, at least partly, linked to plume thermal buoyancy, bringing new insights into mantle dynamics. © 2020 Elsevier B.V.
关键词	Deep carbon cycle Mantle heterogeneity MORB OIB Radiogenic isotopes Zinc Zinc isotopes
英文关键词	carbon cycle; heterogeneity; igneous geochemistry; isotopic composition; mantle; mid-ocean ridge basalt; neodymium isotope; ocean island basalt; strontium isotope; zinc
语种	英语
来源期刊	Earth Science Reviews
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/203636
作者单位	Laboratoire G-Time, DGES, ULB, Université Libre de Bruxelles, Av. Roosevelt 50, CP 160/02, Brussels, 1050, Belgium; Earth Dynamics Research Group, TIGeR, Department of Applied Geology, Curtin University PerthWA 6148, Australia; UJM Saint-Etienne, UCA, CNRS, IRD, Laboratoire Magmas et Volcans UMR6524, Université de Lyon, Saint-Etienne, F42023, France; Institut de physique du globe de Paris, CNRS, Université de Paris, Paris, France
推荐引用方式 GB/T 7714	Beunon H.,Mattielli N.,Doucet L.S.,et al. Mantle heterogeneity through Zn systematics in oceanic basalts: Evidence for a deep carbon cycling[J],2020,205.
APA	Beunon H.,Mattielli N.,Doucet L.S.,Moine B.,&Debret B..(2020).Mantle heterogeneity through Zn systematics in oceanic basalts: Evidence for a deep carbon cycling.Earth Science Reviews,205.
MLA	Beunon H.,et al."Mantle heterogeneity through Zn systematics in oceanic basalts: Evidence for a deep carbon cycling".Earth Science Reviews 205(2020).