Pengyuan Guo
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
Authors
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.
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 | Aug 13, 2021 |
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 |
Public URL | https://durham-repository.worktribe.com/output/1247902 |
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Copyright Statement
© 2021 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)
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