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Title: Jurassic metasomatised lithospheric mantle beneath South China and its implications: Geochemical and Sr-Nd isotope evidence from the Late Jurassic shoshonitic rocks
Authors: Gan, C
Zhang, Y
Barry, TL
He, J
Wang, Y
First Published: 15-Sep-2018
Publisher: Elsevier
Citation: LITHOS, 2018, 320, pp. 236-249 (14)
Abstract: It is well established that the Late Jurassic magmatism in the southeastern area of the South China Block (SCB) was associated with an extensional event. However, the triggering mechanism for this event remains unclear, with models commonly invoking either back-arc extension or intra-continental extension in response to slab roll-back of the Pacific plate or asthenospheric upwelling. The key issue about these models revolves around whether the subducted Pacific slab contributed to the mantle source beneath the SCB during the Jurassic, or not. Basalts erupted during the Late Jurassic can provide significant clues for probing the nature of the lithospheric mantle and underlying convective mantle. In this study, we present detailed zircon U-Pb geochronological, whole-rock element and Sr-Nd isotope data for Late Jurassic trachybasalt and trachyandesite from the Mashan Complex, and provide new constraints on the condition of the lithospheric mantle and mantle dynamicsof the SCB during that time. LA-ICP-MS zircon U-Pb dating suggests that these volcanic rocks erupted in the Late Jurassic (~158 Ma). All volcanic samples have shoshonitic geochemical affinities with high K2O (2.03–4.89 wt%) and K2O/Na2O (0.55–2.50). They are strongly enriched in LILE and LREE with positive K anomalies, positive εNd(t) values (from +0.8 to +3.0), moderate Dy/Yb (1.98–2.36) and low Ba/La (11.1–30.7), Th/Yb (2.29–5.77), U/Th (0.18–0.35), Th/Nb (0.16–0.27) and Th/Ce (0.08–0.15) ratios. Such geochemical signatures suggest that the Mashan volcanic rocks were derived from low-degree (1–5%) partial melting of a metasomatised lithospheric mantle with little evidence supporting the involvement of the Pacific slab in the genesis of the magmas. The synthesis of the available data shows that the Jurassic shoshonitic and mafic rocks have higher εNd(t) values than the Triassic shoshonitic and mafic rocks (εNd(t) b 0), reflecting source transformation from a Triassic enriched lithospheric mantle to a Jurassic depleted source. The metasomatism of the lithospheric mantle is likely to be associated with asthenospheric upwelling prior to the Late Jurassic. The asthenosphere-lithosphere interaction might have produced a newly metasomatised zone within the lowermost lithospheric mantle. It is inferred that the Jurassic magmatism in the southeast of the SCB might be associated with asthenospheric upwelling in an intracontinental extension setting.
DOI Link: 10.1016/j.lithos.2018.09.007
ISSN: 0024-4937
eISSN: 1872-6143
Embargo on file until: 15-Sep-2019
Version: Post-print
Status: Peer-reviewed
Type: Journal Article
Rights: Copyright © Elsevier, 2018. After an embargo period this version of the paper will be an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License (, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
Description: The file associated with this record is under embargo until 12 months after publication, in accordance with the publisher's self-archiving policy. The full text may be available through the publisher links provided above.
Appears in Collections:Published Articles, College of Science and Engineering

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