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Extensive melting of ancient depleted oceanic mantle evidenced by decoupled Hf-Nd isotopes in the lowermost oceanic crust

文献类型：期刊论文

作者Zhang, Wei-Qi1,2; Liu, Chuan-Zhou1,2,3; Mitchell, Ross N.1,2; Liu, Tong2; Zhang, Chang2; Zhang, Zhen-Yu1,2
刊名LITHOS
出版日期2022-06-01
卷号418页码:12
关键词

Hf-Nd isotopes

 Lower oceanic crust Ancient depleted mantle Mantle heterogeneity Pengco ophiolite
ISSN号0024-4937
DOI10.1016/j.lithos.2022.106684
英文摘要The upper mantle is highly heterogenous and represents a mixture of depleted peridotites and recycled materials. Isotopic studies (Sm-Nd, Lu-Hf and Re-Os) on abyssal peridotites and oceanic basalts have revealed the recycling of ancient depleted peridotites that record melt extraction as old as 2 Ga. However, the nature, proportions and melting dynamics of these ancient domains are poorly constrained. Here, we present integrated petrological and geochemical data, particularly high-precision clinopyroxene Sm-Nd and Lu-Hf isotopes, on a suite of magnesium-rich and ultra-depleted cumulates in the plume-related Pengco ophiolite from central Tibet. Petrological and geochemical compositions of Pengco cumulates indicate they were derived from a water-poor, magnesium-rich, and ultra-depleted primary melt similar to the low-Ti basalts from Manihiki oceanic plateau. Clinopyroxene in Pengco cumulates exhibit modestly radiogenic Nd isotopes (epsilon Nd (t) = +6.0 to +7.0] but highly radiogenic Hf isotopes (epsilon Hf (t) = +20.2 to +23.3], which deviate from the mantle array by as much as +11.4 epsilon units. Thus, Pengco cumulates represent the most Hf-Nd isotopic decoupling ever documented for oceanic crustal rocks. Based on geochemical models, we argue that the ultra-depleted melt compositions and extremely decoupled Nd-Hf isotopes of Pengco cumulates can be explained by re-melting of a source mainly composed of ancient depleted mantle that were recycled into the upper mantle. This agrees on the idea that ancient depleted peridotites might represent one of the dominant components in Earth's upper mantle. Melts from an ancient depleted mantle contribute prominently to the oceanic basalt compositions, although they have limited leverage on the Nd-Hf isotopic compositions of the fully aggregated melts due to its low incompatible element abundances. The unique Nd-Hf isotopic compositions preserved in the Pengco cumulates demonstrate that the melts preserved in the lowermost oceanic crust exhibit greater isotopic variability than the erupted magmas. Our results are consistent with the idea that full melt aggregation occurred at crustal level. Hf-Nd isotopes of the lowermost oceanic crust thus provide a critical re-evaluation of current models of the heterogeneity and melting dynamics in the upper mantle.
WOS关键词ABYSSAL PERIDOTITES ; RIDGE BASALT ; OS ISOTOPES ; LU-HF ; CONSTRAINTS ; EVOLUTION ; OPHIOLITE ; SM ; EXTRACTION ; SUBDUCTION
资助项目National Science Fund for Distinguished Young Scholars[42025201] ; National Key Research and Development Project of China[2020YFA0714801] ; Strategic Priority Research Program of the Chinese Academy of Sciences[XDB42020301] ; China Postdoctoral Science Foundation[2021M703197]
WOS研究方向Geochemistry & Geophysics ; Mineralogy
语种英语
WOS记录号WOS:000799273100004
出版者ELSEVIER
资助机构National Science Fund for Distinguished Young Scholars ; National Science Fund for Distinguished Young Scholars ; National Science Fund for Distinguished Young Scholars ; National Science Fund for Distinguished Young Scholars ; National Key Research and Development Project of China ; National Key Research and Development Project of China ; National Key Research and Development Project of China ; National Key Research and Development Project of China ; Strategic Priority Research Program of the Chinese Academy of Sciences ; Strategic Priority Research Program of the Chinese Academy of Sciences ; Strategic Priority Research Program of the Chinese Academy of Sciences ; Strategic Priority Research Program of the Chinese Academy of Sciences ; China Postdoctoral Science Foundation ; China Postdoctoral Science Foundation ; China Postdoctoral Science Foundation ; China Postdoctoral Science Foundation ; National Science Fund for Distinguished Young Scholars ; National Science Fund for Distinguished Young Scholars ; National Science Fund for Distinguished Young Scholars ; National Science Fund for Distinguished Young Scholars ; National Key Research and Development Project of China ; National Key Research and Development Project of China ; National Key Research and Development Project of China ; National Key Research and Development Project of China ; Strategic Priority Research Program of the Chinese Academy of Sciences ; Strategic Priority Research Program of the Chinese Academy of Sciences ; Strategic Priority Research Program of the Chinese Academy of Sciences ; Strategic Priority Research Program of the Chinese Academy of Sciences ; China Postdoctoral Science Foundation ; China Postdoctoral Science Foundation ; China Postdoctoral Science Foundation ; China Postdoctoral Science Foundation ; National Science Fund for Distinguished Young Scholars ; National Science Fund for Distinguished Young Scholars ; National Science Fund for Distinguished Young Scholars ; National Science Fund for Distinguished Young Scholars ; National Key Research and Development Project of China ; National Key Research and Development Project of China ; National Key Research and Development Project of China ; National Key Research and Development Project of China ; Strategic Priority Research Program of the Chinese Academy of Sciences ; Strategic Priority Research Program of the Chinese Academy of Sciences ; Strategic Priority Research Program of the Chinese Academy of Sciences ; Strategic Priority Research Program of the Chinese Academy of Sciences ; China Postdoctoral Science Foundation ; China Postdoctoral Science Foundation ; China Postdoctoral Science Foundation ; China Postdoctoral Science Foundation ; National Science Fund for Distinguished Young Scholars ; National Science Fund for Distinguished Young Scholars ; National Science Fund for Distinguished Young Scholars ; National Science Fund for Distinguished Young Scholars ; National Key Research and Development Project of China ; National Key Research and Development Project of China ; National Key Research and Development Project of China ; National Key Research and Development Project of China ; Strategic Priority Research Program of the Chinese Academy of Sciences ; Strategic Priority Research Program of the Chinese Academy of Sciences ; Strategic Priority Research Program of the Chinese Academy of Sciences ; Strategic Priority Research Program of the Chinese Academy of Sciences ; China Postdoctoral Science Foundation ; China Postdoctoral Science Foundation ; China Postdoctoral Science Foundation ; China Postdoctoral Science Foundation
源URL[http://ir.iggcas.ac.cn/handle/132A11/106017]  
专题地质与地球物理研究所_岩石圈演化国家重点实验室
通讯作者Zhang, Wei-Qi
作者单位1.Univ Chinese Acad Sci, Beijing 100049, Peoples R China
2.Chinese Acad Sci, Inst Geol & Geophys, State Key Lab Lithospher Evolut, Beijing 100029, Peoples R China
3.CAS Ctr Excellence Deep Earth Sci, Guangzhou 510640, Peoples R China
推荐引用方式
GB/T 7714		 Zhang, Wei-Qi,Liu, Chuan-Zhou,Mitchell, Ross N.,et al. Extensive melting of ancient depleted oceanic mantle evidenced by decoupled Hf-Nd isotopes in the lowermost oceanic crust[J]. LITHOS,2022,418:12.
APA Zhang, Wei-Qi,Liu, Chuan-Zhou,Mitchell, Ross N.,Liu, Tong,Zhang, Chang,&Zhang, Zhen-Yu.(2022).Extensive melting of ancient depleted oceanic mantle evidenced by decoupled Hf-Nd isotopes in the lowermost oceanic crust.LITHOS,418,12.
MLA Zhang, Wei-Qi,et al."Extensive melting of ancient depleted oceanic mantle evidenced by decoupled Hf-Nd isotopes in the lowermost oceanic crust".LITHOS 418(2022):12.

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来源：地质与地球物理研究所

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