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The nature and origin of upper mantle heterogeneity beneath the Mid-Atlantic Ridge 33-25°N: A Sr-Nd-Hf isotopic perspective

Guo, Pengyuan; Niu, Yaoling; Sun, Pu; Zhang, Junjie; Chen, Shuo; Duan, Meng; Gong, Hongmei; Wang, Xiaohong

The nature and origin of upper mantle heterogeneity beneath the Mid-Atlantic Ridge 33-25°N: A Sr-Nd-Hf isotopic perspective Thumbnail


Authors

Pengyuan Guo

Yaoling Niu

Pu Sun

Junjie Zhang

Shuo Chen

Meng Duan

Hongmei Gong

Xiaohong Wang



Abstract

We present new Sr-Nd-Hf isotopic data on mid-ocean ridge basalts from two ridge segments (OH-1, OH-3) between the Oceanographer and Hayes fracture zones at the Mid-Atlantic Ridge 33-35°N to constrain the nature and origin of upper mantle heterogeneity beneath the Mid-Atlantic Ridge. Together with the major and trace elements data (Niu et al., 2001), the new Sr-Nd-Hf isotopic data illustrate that the mantle sources of these lavas comprise three components, i.e., a depleted mantle with high radiogenic Hf isotopic compositions (ADM), an incompatible elemental enriched component with radiogenic Sr and un-radiogenic Nd-Hf isotopic compositions (E-type I), and an incompatible element depleted component with variably enriched Sr-Nd-Hf isotope compositions (i.e., E-type II). The ADM and E-type I components may be understood as representing ancient mantle melting residues and metasomatic veins developed at the base of the thickening oceanic lithosphere, respectively. The unique E-type II component is best explained as recent mantle melting residues of a geochemically enriched mantle, probably associated with the Azores mantle plume to the north. Taking together, we interpret the E-MORB dominated OH-1 lavas as resulting from a relatively higher degree melting of a mantle source composed of ADM matrix and E-type I material, whereas the N-MORB dominated OH-3 lavas resulting from lower degree melting of the mantle source primarily comprising ADM and E-type II components. Such a petrological and geochemical understanding explains the contrast in crustal thickness, ridge morphology and tomography, and mantle Bouguer anomalies between the two ridge segments.

Citation

Guo, P., Niu, Y., Sun, P., Zhang, J., Chen, S., Duan, M., …Wang, X. (2021). The nature and origin of upper mantle heterogeneity beneath the Mid-Atlantic Ridge 33-25°N: A Sr-Nd-Hf isotopic perspective. Geochimica et Cosmochimica Acta, 307, 72-85. https://doi.org/10.1016/j.gca.2021.05.033

Journal Article Type Article
Acceptance Date May 17, 2021
Online Publication Date May 23, 2021
Publication Date Aug 15, 2021
Deposit Date May 17, 2021
Publicly Available Date Mar 28, 2024
Journal Geochimica et Cosmochimica Acta
Print ISSN 0016-7037
Publisher Meteoritical Society
Peer Reviewed Peer Reviewed
Volume 307
Pages 72-85
DOI https://doi.org/10.1016/j.gca.2021.05.033

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